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5148 lines
700 KiB
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<head> <title>The Linux Kernel Module Programming Guide</title>
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<div class='maketitle'>
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<h2 class='titleHead'>The Linux Kernel Module Programming Guide</h2>
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<div class='author'><span class='ecrm-1200'>Peter Jay Salzman, Michael Burian, Ori Pomerantz, Bob Mottram, Jim Huang</span></div><br />
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<div class='date'><span class='ecrm-1200'>August 5, 2021</span></div>
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</div>
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<div class='tableofcontents'>
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<span class='sectionToc'>0.1 <a href='#introduction' id='QQ2-1-1'>Introduction</a></span>
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<br /> <span class='subsectionToc'>0.1.1 <a href='#authorship' id='QQ2-1-2'>Authorship</a></span>
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<br /> <span class='subsectionToc'>0.1.2 <a href='#acknowledgements' id='QQ2-1-3'>Acknowledgements</a></span>
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<br /> <span class='subsectionToc'>0.1.3 <a href='#what-is-a-kernel-module' id='QQ2-1-4'>What Is A Kernel Module?</a></span>
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<br /> <span class='subsectionToc'>0.1.4 <a href='#kernel-module-package' id='QQ2-1-5'>Kernel module package</a></span>
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<br /> <span class='subsectionToc'>0.1.5 <a href='#what-modules-are-in-my-kernel' id='QQ2-1-6'>What Modules are in my Kernel?</a></span>
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<br /> <span class='subsectionToc'>0.1.6 <a href='#do-i-need-to-download-and-compile-the-kernel' id='QQ2-1-7'>Do I need to download and compile the kernel?</a></span>
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<br /> <span class='subsectionToc'>0.1.7 <a href='#before-we-begin' id='QQ2-1-8'>Before We Begin</a></span>
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<br /> <span class='sectionToc'>0.2 <a href='#headers' id='QQ2-1-9'>Headers</a></span>
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<br /> <span class='sectionToc'>0.3 <a href='#examples' id='QQ2-1-10'>Examples</a></span>
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<br /> <span class='sectionToc'>0.4 <a href='#hello-world' id='QQ2-1-11'>Hello World</a></span>
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<br /> <span class='subsectionToc'>0.4.1 <a href='#the-simplest-module' id='QQ2-1-12'>The Simplest Module</a></span>
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<br /> <span class='subsectionToc'>0.4.2 <a href='#hello-and-goodbye' id='QQ2-1-13'>Hello and Goodbye</a></span>
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<br /> <span class='subsectionToc'>0.4.3 <a href='#the-init-and-exit-macros' id='QQ2-1-14'>The __init and __exit Macros</a></span>
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<br /> <span class='subsectionToc'>0.4.4 <a href='#licensing-and-module-documentation' id='QQ2-1-15'>Licensing and Module Documentation</a></span>
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<br /> <span class='subsectionToc'>0.4.5 <a href='#passing-command-line-arguments-to-a-module' id='QQ2-1-16'>Passing Command Line Arguments to a Module</a></span>
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<br /> <span class='subsectionToc'>0.4.6 <a href='#modules-spanning-multiple-files' id='QQ2-1-17'>Modules Spanning Multiple Files</a></span>
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<br /> <span class='subsectionToc'>0.4.7 <a href='#building-modules-for-a-precompiled-kernel' id='QQ2-1-18'>Building modules for a precompiled kernel</a></span>
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<br /> <span class='sectionToc'>0.5 <a href='#preliminaries' id='QQ2-1-19'>Preliminaries</a></span>
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<br /> <span class='subsectionToc'>0.5.1 <a href='#how-modules-begin-and-end' id='QQ2-1-20'>How modules begin and end</a></span>
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<br /> <span class='subsectionToc'>0.5.2 <a href='#functions-available-to-modules' id='QQ2-1-21'>Functions available to modules</a></span>
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<br /> <span class='subsectionToc'>0.5.3 <a href='#user-space-vs-kernel-space' id='QQ2-1-22'>User Space vs Kernel Space</a></span>
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<br /> <span class='subsectionToc'>0.5.4 <a href='#name-space' id='QQ2-1-23'>Name Space</a></span>
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<br /> <span class='subsectionToc'>0.5.5 <a href='#code-space' id='QQ2-1-24'>Code space</a></span>
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<br /> <span class='subsectionToc'>0.5.6 <a href='#device-drivers' id='QQ2-1-25'>Device Drivers</a></span>
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<br /> <span class='sectionToc'>0.6 <a href='#character-device-drivers' id='QQ2-1-26'>Character Device drivers</a></span>
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<br /> <span class='subsectionToc'>0.6.1 <a href='#the-procops-structure' id='QQ2-1-27'>The proc_ops Structure</a></span>
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<br /> <span class='subsectionToc'>0.6.2 <a href='#the-file-structure' id='QQ2-1-28'>The file structure</a></span>
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<br /> <span class='subsectionToc'>0.6.3 <a href='#registering-a-device' id='QQ2-1-29'>Registering A Device</a></span>
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<br /> <span class='subsectionToc'>0.6.4 <a href='#unregistering-a-device' id='QQ2-1-30'>Unregistering A Device</a></span>
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<br /> <span class='subsectionToc'>0.6.5 <a href='#chardevc' id='QQ2-1-31'>chardev.c</a></span>
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<br /> <span class='subsectionToc'>0.6.6 <a href='#writing-modules-for-multiple-kernel-versions' id='QQ2-1-32'>Writing Modules for Multiple Kernel Versions</a></span>
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<br /> <span class='sectionToc'>0.7 <a href='#the-proc-file-system' id='QQ2-1-33'>The /proc File System</a></span>
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<br /> <span class='subsectionToc'>0.7.1 <a href='#read-and-write-a-proc-file' id='QQ2-1-34'>Read and Write a /proc File</a></span>
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<br /> <span class='subsectionToc'>0.7.2 <a href='#manage-proc-file-with-standard-filesystem' id='QQ2-1-35'>Manage /proc file with standard filesystem</a></span>
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<br /> <span class='subsectionToc'>0.7.3 <a href='#manage-proc-file-with-seqfile' id='QQ2-1-36'>Manage /proc file with seq_file</a></span>
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<br /> <span class='sectionToc'>0.8 <a href='#sysfs-interacting-with-your-module' id='QQ2-1-38'>sysfs: Interacting with your module</a></span>
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<br /> <span class='sectionToc'>0.9 <a href='#talking-to-device-files' id='QQ2-1-39'>Talking To Device Files</a></span>
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<br /> <span class='sectionToc'>0.10 <a href='#system-calls' id='QQ2-1-40'>System Calls</a></span>
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<br /> <span class='sectionToc'>0.11 <a href='#blocking-processes-and-threads' id='QQ2-1-41'>Blocking Processes and threads</a></span>
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<br /> <span class='subsectionToc'>0.11.1 <a href='#sleep' id='QQ2-1-42'>Sleep</a></span>
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<br /> <span class='subsectionToc'>0.11.2 <a href='#completions' id='QQ2-1-43'>Completions</a></span>
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<br /> <span class='sectionToc'>0.12 <a href='#avoiding-collisions-and-deadlocks' id='QQ2-1-44'>Avoiding Collisions and Deadlocks</a></span>
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<br /> <span class='subsectionToc'>0.12.1 <a href='#mutex' id='QQ2-1-45'>Mutex</a></span>
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<br /> <span class='subsectionToc'>0.12.2 <a href='#spinlocks' id='QQ2-1-46'>Spinlocks</a></span>
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<br /> <span class='subsectionToc'>0.12.3 <a href='#read-and-write-locks' id='QQ2-1-47'>Read and write locks</a></span>
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<br /> <span class='subsectionToc'>0.12.4 <a href='#atomic-operations' id='QQ2-1-48'>Atomic operations</a></span>
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<br /> <span class='sectionToc'>0.13 <a href='#replacing-print-macros' id='QQ2-1-49'>Replacing Print Macros</a></span>
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<br /> <span class='subsectionToc'>0.13.1 <a href='#replacement' id='QQ2-1-50'>Replacement</a></span>
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<br /> <span class='subsectionToc'>0.13.2 <a href='#flashing-keyboard-leds' id='QQ2-1-51'>Flashing keyboard LEDs</a></span>
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<br /> <span class='sectionToc'>0.14 <a href='#scheduling-tasks' id='QQ2-1-52'>Scheduling Tasks</a></span>
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<br /> <span class='subsectionToc'>0.14.1 <a href='#tasklets' id='QQ2-1-53'>Tasklets</a></span>
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<br /> <span class='subsectionToc'>0.14.2 <a href='#work-queues' id='QQ2-1-54'>Work queues</a></span>
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<br /> <span class='sectionToc'>0.15 <a href='#interrupt-handlers' id='QQ2-1-55'>Interrupt Handlers</a></span>
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<br /> <span class='subsectionToc'>0.15.1 <a href='#interrupt-handlers1' id='QQ2-1-56'>Interrupt Handlers</a></span>
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<br /> <span class='subsectionToc'>0.15.2 <a href='#detecting-button-presses' id='QQ2-1-57'>Detecting button presses</a></span>
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<br /> <span class='subsectionToc'>0.15.3 <a href='#bottom-half' id='QQ2-1-58'>Bottom Half</a></span>
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<br /> <span class='sectionToc'>0.16 <a href='#crypto' id='QQ2-1-59'>Crypto</a></span>
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<br /> <span class='subsectionToc'>0.16.1 <a href='#hash-functions' id='QQ2-1-60'>Hash functions</a></span>
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<br /> <span class='subsectionToc'>0.16.2 <a href='#symmetric-key-encryption' id='QQ2-1-61'>Symmetric key encryption</a></span>
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<br /> <span class='sectionToc'>0.17 <a href='#standardising-the-interfaces-the-device-model' id='QQ2-1-62'>Standardising the interfaces: The Device Model</a></span>
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<br /> <span class='sectionToc'>0.18 <a href='#optimizations' id='QQ2-1-63'>Optimizations</a></span>
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<br /> <span class='subsectionToc'>0.18.1 <a href='#likely-and-unlikely-conditions' id='QQ2-1-64'>Likely and Unlikely conditions</a></span>
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<br /> <span class='sectionToc'>0.19 <a href='#common-pitfalls' id='QQ2-1-65'>Common Pitfalls</a></span>
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<br /> <span class='subsectionToc'>0.19.1 <a href='#using-standard-libraries' id='QQ2-1-66'>Using standard libraries</a></span>
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<br /> <span class='subsectionToc'>0.19.2 <a href='#disabling-interrupts' id='QQ2-1-67'>Disabling interrupts</a></span>
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<br /> <span class='subsectionToc'>0.19.3 <a href='#sticking-your-head-inside-a-large-carnivore' id='QQ2-1-68'>Sticking your head inside a large carnivore</a></span>
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<br /> <span class='sectionToc'>0.20 <a href='#where-to-go-from-here' id='QQ2-1-69'>Where To Go From Here?</a></span>
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</div>
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<h3 class='sectionHead' id='introduction'><span class='titlemark'>0.1 </span> <a id='x1-10000.1'></a>Introduction</h3>
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<!-- l. 51 --><p class='noindent'>The Linux Kernel Module Programming Guide is a free book; you may reproduce
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and/or modify it under the terms of the <a href='https://opensource.org/licenses/OSL-3.0'>Open Software License</a>, version
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3.0.
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</p><!-- l. 53 --><p class='indent'> This book is distributed in the hope it will be useful, but without any warranty,
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without even the implied warranty of merchantability or fitness for a particular
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purpose.
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</p><!-- l. 55 --><p class='indent'> The author encourages wide distribution of this book for personal or commercial
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use, provided the above copyright notice remains intact and the method adheres to
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the provisions of the <a href='https://opensource.org/licenses/OSL-3.0'>Open Software License</a>. In summary, you may copy and
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distribute this book free of charge or for a profit. No explicit permission is required
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from the author for reproduction of this book in any medium, physical or
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electronic.
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</p><!-- l. 58 --><p class='indent'> Derivative works and translations of this document must be placed under the
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Open Software License, and the original copyright notice must remain intact. If you
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have contributed new material to this book, you must make the material and source
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code available for your revisions. Please make revisions and updates available directly
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to the document maintainer, Peter Jay Salzman <p@dirac.org>. This will allow
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for the merging of updates and provide consistent revisions to the Linux
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community.
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</p><!-- l. 63 --><p class='indent'> If you publish or distribute this book commercially, donations, royalties, and/or
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printed copies are greatly appreciated by the author and the <a href='http://www.tldp.org'>Linux Documentation
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Project</a> (LDP). Contributing in this way shows your support for free software and
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the LDP. If you have questions or comments, please contact the address
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above.
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</p><!-- l. 66 --><p class='noindent'>
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</p>
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<h4 class='subsectionHead' id='authorship'><span class='titlemark'>0.1.1 </span> <a id='x1-20000.1.1'></a>Authorship</h4>
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<!-- l. 69 --><p class='noindent'>The Linux Kernel Module Programming Guide was originally written for
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the 2.2 kernels by Ori Pomerantz. Eventually, Ori no longer had time to
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maintain the document. After all, the Linux kernel is a fast moving target.
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Peter Jay Salzman took over maintenance and updated it for the 2.4 kernels.
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Eventually, Peter no longer had time to follow developments with the 2.6
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kernel, so Michael Burian became a co-maintainer to update the document
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for the 2.6 kernels. Bob Mottram updated the examples for 3.8+ kernels.
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Jim Huang upgraded to recent kernel versions (v5.x) and revised LaTeX
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scripts.
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</p><!-- l. 77 --><p class='noindent'>
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</p>
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<h4 class='subsectionHead' id='acknowledgements'><span class='titlemark'>0.1.2 </span> <a id='x1-30000.1.2'></a>Acknowledgements</h4>
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<!-- l. 80 --><p class='noindent'>The following people have contributed corrections or good suggestions: Ignacio
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Martin, David Porter, Daniele Paolo Scarpazza, Dimo Velev, Francois Audeon, Horst
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Schirmeier, and Roman Lakeev.
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</p><!-- l. 82 --><p class='noindent'>
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</p>
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<h4 class='subsectionHead' id='what-is-a-kernel-module'><span class='titlemark'>0.1.3 </span> <a id='x1-40000.1.3'></a>What Is A Kernel Module?</h4>
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<!-- l. 85 --><p class='noindent'>So, you want to write a kernel module. You know C, you have written a few normal
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programs to run as processes, and now you want to get to where the real action is, to
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where a single wild pointer can wipe out your file system and a core dump means a
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reboot.
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</p><!-- l. 88 --><p class='indent'> What exactly is a kernel module? Modules are pieces of code that can be loaded
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and unloaded into the kernel upon demand. They extend the functionality of the
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kernel without the need to reboot the system. For example, one type of module is the
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device driver, which allows the kernel to access hardware connected to the system.
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Without modules, we would have to build monolithic kernels and add new
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functionality directly into the kernel image. Besides having larger kernels, this has
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the disadvantage of requiring us to rebuild and reboot the kernel every time we want
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new functionality.
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</p><!-- l. 95 --><p class='noindent'>
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</p>
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<h4 class='subsectionHead' id='kernel-module-package'><span class='titlemark'>0.1.4 </span> <a id='x1-50000.1.4'></a>Kernel module package</h4>
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<!-- l. 98 --><p class='noindent'>Linux distributions provide the commands <span class='ecti-1000'>modprobe</span>, <span class='ecti-1000'>insmod </span>and <span class='ecti-1000'>depmod </span>within a
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package.
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</p><!-- l. 100 --><p class='indent'> On Ubuntu/Debian:
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</p>
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<pre class='fancyvrb' id='fancyvrb1'><a id='x1-5003r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>sudo apt-get install build-essential kmod</span></pre>
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<!-- l. 105 --><p class='indent'> On Arch Linux:
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</p>
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<pre class='fancyvrb' id='fancyvrb2'><a id='x1-5006r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>sudo pacman -S gcc kmod</span></pre>
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<!-- l. 110 --><p class='noindent'>
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</p>
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<h4 class='subsectionHead' id='what-modules-are-in-my-kernel'><span class='titlemark'>0.1.5 </span> <a id='x1-60000.1.5'></a>What Modules are in my Kernel?</h4>
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<!-- l. 113 --><p class='noindent'>To discover what modules are already loaded within your current kernel use the
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command <span class='ecbx-1000'>lsmod</span>.
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</p>
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<pre class='fancyvrb' id='fancyvrb3'><a id='x1-6003r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>sudo lsmod</span></pre>
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<!-- l. 118 --><p class='indent'> Modules are stored within the file /proc/modules, so you can also see them with:
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</p>
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<pre class='fancyvrb' id='fancyvrb4'><a id='x1-6006r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>sudo cat /proc/modules</span></pre>
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<!-- l. 123 --><p class='indent'> This can be a long list, and you might prefer to search for something particular.
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To search for the <span class='ecti-1000'>fat </span>module:
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</p>
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<pre class='fancyvrb' id='fancyvrb5'><a id='x1-6009r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>sudo lsmod | grep fat</span></pre>
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<!-- l. 129 --><p class='noindent'>
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</p>
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<h4 class='subsectionHead' id='do-i-need-to-download-and-compile-the-kernel'><span class='titlemark'>0.1.6 </span> <a id='x1-70000.1.6'></a>Do I need to download and compile the kernel?</h4>
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<!-- l. 131 --><p class='noindent'>For the purposes of following this guide you don’t necessarily need to do that.
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However, it would be wise to run the examples within a test distribution running
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on a virtual machine in order to avoid any possibility of messing up your
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system.
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</p><!-- l. 134 --><p class='noindent'>
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</p>
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<h4 class='subsectionHead' id='before-we-begin'><span class='titlemark'>0.1.7 </span> <a id='x1-80000.1.7'></a>Before We Begin</h4>
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<!-- l. 136 --><p class='noindent'>Before we delve into code, there are a few issues we need to cover. Everyone’s system
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is different and everyone has their own groove. Getting your first "hello world"
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program to compile and load correctly can sometimes be a trick. Rest assured, after
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you get over the initial hurdle of doing it for the first time, it will be smooth sailing
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thereafter.
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</p><!-- l. 141 --><p class='indent'>
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</p><ol class='enumerate1'>
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<li class='enumerate' id='x1-8002x1'>Modversioning. A module compiled for one kernel will not load if you boot
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a different kernel unless you enable <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>CONFIG_MODVERSIONS</span></span></span> in the kernel.
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We will not go into module versioning until later in this guide. Until
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we cover modversions, the examples in the guide may not work if you
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are running a kernel with modversioning turned on. However, most stock
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Linux distribution kernels come with it turned on. If you are having trouble
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loading the modules because of versioning errors, compile a kernel with
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modversioning turned off.
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</li>
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<li class='enumerate' id='x1-8004x2'>
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<!-- l. 149 --><p class='noindent'>Using X Window System. It is highly recommended that you extract,
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compile and load all the examples this guide discusses. It is also highly
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recommended you do this from a console. You should not be working on
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this stuff in X Window System.
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</p><!-- l. 154 --><p class='noindent'>Modules can not print to the screen like <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>printf()</span></span></span> can, but they can log
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information and warnings, which ends up being printed on your screen, but
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only on a console. If you insmod a module from an xterm, the information
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and warnings will be logged, but only to your systemd journal. You will
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not see it unless you look through your <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>journalctl</span></span></span>. See <a href='#hello-world'>0.4<!-- tex4ht:ref: sec:helloworld --></a> for details.
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To have immediate access to this information, do all your work from the
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console.</p></li></ol>
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<!-- l. 161 --><p class='noindent'>
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</p>
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<h3 class='sectionHead' id='headers'><span class='titlemark'>0.2 </span> <a id='x1-90000.2'></a>Headers</h3>
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<!-- l. 163 --><p class='noindent'>Before you can build anything you’ll need to install the header files for your
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kernel.
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</p><!-- l. 165 --><p class='indent'> On Ubuntu/Debian:
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</p>
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<pre class='fancyvrb' id='fancyvrb6'><a id='x1-9004r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>sudo apt-get update</span>
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<a id='x1-9006r2'></a><span class='ecrm-0500'>2</span><span class='ectt-1000'>apt-cache search linux-headers-</span><span id='textcolor1'><span class='tctt-1000'>`</span></span><span class='ectt-1000'>uname -r</span><span id='textcolor2'><span class='tctt-1000'>`</span></span></pre>
|
|
<!-- l. 171 --><p class='indent'> On Arch Linux:
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb7'><a id='x1-9009r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>sudo pacman -S linux-libre-headers</span></pre>
|
|
<!-- l. 176 --><p class='indent'> This will tell you what kernel header files are available. Then for example:
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb8'><a id='x1-9012r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>sudo apt-get install kmod linux-headers-5.4.0-80-generic</span></pre>
|
|
<!-- l. 182 --><p class='noindent'>
|
|
</p>
|
|
<h3 class='sectionHead' id='examples'><span class='titlemark'>0.3 </span> <a id='x1-100000.3'></a>Examples</h3>
|
|
<!-- l. 184 --><p class='noindent'>All the examples from this document are available within the <span class='ecti-1000'>examples </span>subdirectory.
|
|
</p><!-- l. 186 --><p class='indent'> If there are any compile errors then you might have a more recent kernel version
|
|
or need to install the corresponding kernel header files.
|
|
</p><!-- l. 188 --><p class='noindent'>
|
|
</p>
|
|
<h3 class='sectionHead' id='hello-world'><span class='titlemark'>0.4 </span> <a id='x1-110000.4'></a>Hello World</h3>
|
|
|
|
|
|
|
|
<!-- l. 190 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='the-simplest-module'><span class='titlemark'>0.4.1 </span> <a id='x1-120000.4.1'></a>The Simplest Module</h4>
|
|
<!-- l. 192 --><p class='noindent'>Most people learning programming start out with some sort of "<span class='ecti-1000'>hello world</span>"
|
|
example. I don’t know what happens to people who break with this tradition, but I
|
|
think it is safer not to find out. We will start with a series of hello world
|
|
programs that demonstrate the different aspects of the basics of writing a kernel
|
|
module.
|
|
</p><!-- l. 196 --><p class='indent'> Here is the simplest module possible.
|
|
</p><!-- l. 198 --><p class='indent'> Make a test directory:
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb9'><a id='x1-12004r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>mkdir -p ~/develop/kernel/hello-1</span>
|
|
<a id='x1-12006r2'></a><span class='ecrm-0500'>2</span><span class='ectt-1000'>cd ~/develop/kernel/hello-1</span></pre>
|
|
<!-- l. 204 --><p class='indent'> Paste this into you favorite editor and save it as <span class='ecbx-1000'>hello-1.c</span>:
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb10'><a id='x1-12008r1'></a><span class='ecrm-0500'>1</span><span id='textcolor3'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-12010r2'></a><span class='ecrm-0500'>2</span><span id='textcolor4'><span class='ectt-0800'> * hello-1.c - The simplest kernel module.</span></span>
|
|
<a id='x1-12012r3'></a><span class='ecrm-0500'>3</span><span id='textcolor5'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-12014r4'></a><span class='ecrm-0500'>4</span><span id='textcolor6'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor7'><span class='ectt-0800'><linux/kernel.h> /* Needed for KERN_INFO */</span></span>
|
|
<a id='x1-12016r5'></a><span class='ecrm-0500'>5</span><span id='textcolor8'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor9'><span class='ectt-0800'><linux/module.h> /* Needed by all modules */</span></span>
|
|
<a id='x1-12018r6'></a><span class='ecrm-0500'>6</span>
|
|
<a id='x1-12020r7'></a><span class='ecrm-0500'>7</span><span id='textcolor10'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> init_module(</span><span id='textcolor11'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-12022r8'></a><span class='ecrm-0500'>8</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-12024r9'></a><span class='ecrm-0500'>9</span><span class='ectt-0800'> pr_info(</span><span id='textcolor12'><span class='ectt-0800'>"Hello world 1.</span></span><span id='textcolor13'><span class='ectt-0800'>\n</span></span><span id='textcolor14'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-12026r10'></a><span class='ecrm-0500'>10</span>
|
|
<a id='x1-12028r11'></a><span class='ecrm-0500'>11</span><span class='ectt-0800'> </span><span id='textcolor15'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-12030r12'></a><span class='ecrm-0500'>12</span><span id='textcolor16'><span class='ectt-0800'> * A non 0 return means init_module failed; module can</span><span class='tctt-0800'>'</span><span class='ectt-0800'>t be loaded.</span></span>
|
|
<a id='x1-12032r13'></a><span class='ecrm-0500'>13</span><span id='textcolor17'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-12034r14'></a><span class='ecrm-0500'>14</span><span class='ectt-0800'> </span><span id='textcolor18'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-12036r15'></a><span class='ecrm-0500'>15</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-12038r16'></a><span class='ecrm-0500'>16</span>
|
|
<a id='x1-12040r17'></a><span class='ecrm-0500'>17</span><span id='textcolor19'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> cleanup_module(</span><span id='textcolor20'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-12042r18'></a><span class='ecrm-0500'>18</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-12044r19'></a><span class='ecrm-0500'>19</span><span class='ectt-0800'> pr_info(</span><span id='textcolor21'><span class='ectt-0800'>"Goodbye world 1.</span></span><span id='textcolor22'><span class='ectt-0800'>\n</span></span><span id='textcolor23'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-12046r20'></a><span class='ecrm-0500'>20</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-12048r21'></a><span class='ecrm-0500'>21</span>
|
|
<a id='x1-12050r22'></a><span class='ecrm-0500'>22</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor24'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
|
|
<!-- l. 208 --><p class='indent'> Now you will need a Makefile. If you copy and paste this, change the indentation
|
|
to use <span class='ecti-1000'>tabs</span>, not spaces.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb11'><a id='x1-12059r1'></a><span class='ecrm-0500'>1</span><span class='ectt-0800'>obj-m += hello-1.o</span>
|
|
<a id='x1-12061r2'></a><span class='ecrm-0500'>2</span>
|
|
<a id='x1-12063r3'></a><span class='ecrm-0500'>3</span><span class='ectt-0800'>all:</span>
|
|
<a id='x1-12065r4'></a><span class='ecrm-0500'>4 </span><span class='ectt-0800'>make -C /lib/modules/</span><span class='colorbox' id='colorbox25'><span class='ectt-0800'>$</span></span><span class='ectt-0800'>(shell uname -r)/build M=</span><span class='colorbox' id='colorbox26'><span class='ectt-0800'>$</span></span><span class='ectt-0800'>(PWD) modules</span>
|
|
<a id='x1-12067r5'></a><span class='ecrm-0500'>5</span>
|
|
<a id='x1-12069r6'></a><span class='ecrm-0500'>6</span><span class='ectt-0800'>clean:</span>
|
|
<a id='x1-12071r7'></a><span class='ecrm-0500'>7 </span><span class='ectt-0800'>make -C /lib/modules/</span><span class='colorbox' id='colorbox27'><span class='ectt-0800'>$</span></span><span class='ectt-0800'>(shell uname -r)/build M=</span><span class='colorbox' id='colorbox28'><span class='ectt-0800'>$</span></span><span class='ectt-0800'>(PWD) clean</span></pre>
|
|
<!-- l. 220 --><p class='indent'> And finally just:
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb12'><a id='x1-12074r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>make</span></pre>
|
|
<!-- l. 225 --><p class='indent'> If all goes smoothly you should then find that you have a compiled <span class='ecbx-1000'>hello-1.ko</span>
|
|
module. You can find info on it with the command:
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb13'><a id='x1-12077r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>sudo modinfo hello-1.ko</span></pre>
|
|
<!-- l. 231 --><p class='indent'> At this point the command:
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb14'><a id='x1-12080r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>sudo lsmod | grep hello</span></pre>
|
|
<!-- l. 236 --><p class='indent'> should return nothing. You can try loading your shiny new module with:
|
|
|
|
|
|
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb15'><a id='x1-12083r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>sudo insmod hello-1.ko</span></pre>
|
|
<!-- l. 242 --><p class='indent'> The dash character will get converted to an underscore, so when you again try:
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb16'><a id='x1-12086r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>sudo lsmod | grep hello</span></pre>
|
|
<!-- l. 247 --><p class='indent'> you should now see your loaded module. It can be removed again with:
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb17'><a id='x1-12089r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>sudo rmmod hello_1</span></pre>
|
|
<!-- l. 252 --><p class='indent'> Notice that the dash was replaced by an underscore. To see what just happened in
|
|
the logs:
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb18'><a id='x1-12092r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>journalctl --since </span><span id='textcolor29'><span class='ectt-1000'>"1 hour ago"</span></span><span class='ectt-1000'> | grep kernel</span></pre>
|
|
<!-- l. 258 --><p class='indent'> You now know the basics of creating, compiling, installing and removing modules.
|
|
Now for more of a description of how this module works.
|
|
</p><!-- l. 261 --><p class='indent'> Kernel modules must have at least two functions: a "start" (initialization)
|
|
function called <span class='ecbx-1000'>init_module() </span>which is called when the module is insmoded into
|
|
the kernel, and an "end" (cleanup) function called <span class='ecbx-1000'>cleanup_module() </span>which is
|
|
called just before it is removed from the kernel. Actually, things have changed
|
|
starting with kernel 2.3.13. You can now use whatever name you like for the start and
|
|
end functions of a module, and you will learn how to do this in Section 2.3.
|
|
In fact, the new method is the preferred method. However, many people
|
|
still use <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>init_module()</span></span></span> and <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>cleanup_module()</span></span></span> for their start and end
|
|
functions.
|
|
</p><!-- l. 268 --><p class='indent'> Typically, init_module() either registers a handler for something with the kernel,
|
|
or it replaces one of the kernel functions with its own code (usually code to do
|
|
something and then call the original function). The <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>cleanup_module()</span></span></span> function is
|
|
supposed to undo whatever <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>init_module()</span></span></span> did, so the module can be unloaded
|
|
safely.
|
|
</p><!-- l. 271 --><p class='indent'> Lastly, every kernel module needs to include <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>linux/module.h</span></span></span>. We needed to
|
|
include <span class='ecbx-1000'>linux/kernel.h </span>only for the macro expansion for the pr_alert() log level,
|
|
which you’ll learn about in Section 2.1.1.
|
|
</p><!-- l. 275 --><p class='indent'>
|
|
</p><ol class='enumerate1'>
|
|
|
|
|
|
|
|
<li class='enumerate' id='x1-12094x1'>A point about coding style. Another thing which may not be immediately
|
|
obvious to anyone getting started with kernel programming is that
|
|
indentation within your code should be using <span class='ecbx-1000'>tabs </span>and <span class='ecbx-1000'>not spaces</span>. It is
|
|
one of the coding conventions of the kernel. You may not like it, but you’ll
|
|
need to get used to it if you ever submit a patch upstream.
|
|
</li>
|
|
<li class='enumerate' id='x1-12096x2'>Introducing print macros. In the beginning there was <span class='ecbx-1000'>printk</span>, usually
|
|
followed by a priority such as <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>KERN_INFO</span></span></span> or <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>KERN_DEBUG</span></span></span>. More recently
|
|
this can also be expressed in abbreviated form using a set of print macros,
|
|
such as <span class='ecbx-1000'>pr_info </span>and <span class='ecbx-1000'>pr_debug</span>. This just saves some mindless keyboard
|
|
bashing and looks a bit neater. They can be found within <span class='ecbx-1000'>linux/printk.h</span>.
|
|
Take time to read through the available priority macros.
|
|
</li>
|
|
<li class='enumerate' id='x1-12098x3'>
|
|
<!-- l. 288 --><p class='noindent'>About Compiling. Kernel modules need to be compiled a bit differently
|
|
from regular userspace apps. Former kernel versions required us to
|
|
care much about these settings, which are usually stored in Makefiles.
|
|
Although hierarchically organized, many redundant settings accumulated
|
|
in sublevel Makefiles and made them large and rather difficult to maintain.
|
|
Fortunately, there is a new way of doing these things, called kbuild, and
|
|
the build process for external loadable modules is now fully integrated into
|
|
the standard kernel build mechanism. To learn more on how to compile
|
|
modules which are not part of the official kernel (such as all the examples
|
|
you will find in this guide), see file <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>Documentation/kbuild/modules.rst</span></span></span>.
|
|
</p><!-- l. 295 --><p class='noindent'>Additional details about Makefiles for kernel modules are available in
|
|
<span class='obeylines-h'><span class='verb'><span class='ectt-1000'>Documentation/kbuild/makefiles.rst</span></span></span>. Be sure to read this and the
|
|
related files before starting to hack Makefiles. It will probably save you
|
|
lots of work.
|
|
</p><!-- l. 297 --><p class='noindent'>
|
|
</p><blockquote class='quote'>
|
|
<!-- l. 298 --><p class='noindent'>Here is another exercise for the reader. See that comment above
|
|
the return statement in <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>init_module()</span></span></span>? Change the return
|
|
value to something negative, recompile and load the module
|
|
again. What happens?</p></blockquote>
|
|
</li></ol>
|
|
|
|
|
|
|
|
<!-- l. 305 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='hello-and-goodbye'><span class='titlemark'>0.4.2 </span> <a id='x1-130000.4.2'></a>Hello and Goodbye</h4>
|
|
<!-- l. 307 --><p class='noindent'>In early kernel versions you had to use the <span class='ecbx-1000'>init_module </span>and <span class='ecbx-1000'>cleanup_module</span>
|
|
functions, as in the first hello world example, but these days you can name those
|
|
anything you want by using the <span class='ecbx-1000'>module_init </span>and <span class='ecbx-1000'>module_exit </span>macros.
|
|
These macros are defined in <span class='ecbx-1000'>linux/init.h</span>. The only requirement is that
|
|
your init and cleanup functions must be defined before calling the those
|
|
macros, otherwise you’ll get compilation errors. Here is an example of this
|
|
technique:
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb19'><a id='x1-13002r1'></a><span class='ecrm-0500'>1</span><span id='textcolor30'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-13004r2'></a><span class='ecrm-0500'>2</span><span id='textcolor31'><span class='ectt-0800'> * hello-2.c - Demonstrating the module_init() and module_exit() macros.</span></span>
|
|
<a id='x1-13006r3'></a><span class='ecrm-0500'>3</span><span id='textcolor32'><span class='ectt-0800'> * This is preferred over using init_module() and cleanup_module().</span></span>
|
|
<a id='x1-13008r4'></a><span class='ecrm-0500'>4</span><span id='textcolor33'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-13010r5'></a><span class='ecrm-0500'>5</span><span id='textcolor34'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor35'><span class='ectt-0800'><linux/init.h> /* Needed for the macros */</span></span>
|
|
<a id='x1-13012r6'></a><span class='ecrm-0500'>6</span><span id='textcolor36'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor37'><span class='ectt-0800'><linux/kernel.h> /* Needed for KERN_INFO */</span></span>
|
|
<a id='x1-13014r7'></a><span class='ecrm-0500'>7</span><span id='textcolor38'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor39'><span class='ectt-0800'><linux/module.h> /* Needed by all modules */</span></span>
|
|
<a id='x1-13016r8'></a><span class='ecrm-0500'>8</span>
|
|
<a id='x1-13018r9'></a><span class='ecrm-0500'>9</span><span id='textcolor40'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor41'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> __init hello_2_init(</span><span id='textcolor42'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-13020r10'></a><span class='ecrm-0500'>10</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-13022r11'></a><span class='ecrm-0500'>11</span><span class='ectt-0800'> pr_info(</span><span id='textcolor43'><span class='ectt-0800'>"Hello, world 2</span></span><span id='textcolor44'><span class='ectt-0800'>\n</span></span><span id='textcolor45'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-13024r12'></a><span class='ecrm-0500'>12</span><span class='ectt-0800'> </span><span id='textcolor46'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-13026r13'></a><span class='ecrm-0500'>13</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-13028r14'></a><span class='ecrm-0500'>14</span>
|
|
<a id='x1-13030r15'></a><span class='ecrm-0500'>15</span><span id='textcolor47'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor48'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> __exit hello_2_exit(</span><span id='textcolor49'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-13032r16'></a><span class='ecrm-0500'>16</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-13034r17'></a><span class='ecrm-0500'>17</span><span class='ectt-0800'> pr_info(</span><span id='textcolor50'><span class='ectt-0800'>"Goodbye, world 2</span></span><span id='textcolor51'><span class='ectt-0800'>\n</span></span><span id='textcolor52'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-13036r18'></a><span class='ecrm-0500'>18</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-13038r19'></a><span class='ecrm-0500'>19</span>
|
|
<a id='x1-13040r20'></a><span class='ecrm-0500'>20</span><span class='ectt-0800'>module_init(hello_2_init);</span>
|
|
<a id='x1-13042r21'></a><span class='ecrm-0500'>21</span><span class='ectt-0800'>module_exit(hello_2_exit);</span>
|
|
<a id='x1-13044r22'></a><span class='ecrm-0500'>22</span>
|
|
<a id='x1-13046r23'></a><span class='ecrm-0500'>23</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor53'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
|
|
<!-- l. 313 --><p class='indent'> So now we have two real kernel modules under our belt. Adding another module
|
|
is as simple as this:
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb20'><a id='x1-13056r1'></a><span class='ecrm-0500'>1</span><span class='ectt-0800'>obj-m += hello-1.o</span>
|
|
<a id='x1-13058r2'></a><span class='ecrm-0500'>2</span><span class='ectt-0800'>obj-m += hello-2.o</span>
|
|
<a id='x1-13060r3'></a><span class='ecrm-0500'>3</span>
|
|
<a id='x1-13062r4'></a><span class='ecrm-0500'>4</span><span class='ectt-0800'>all:</span>
|
|
<a id='x1-13064r5'></a><span class='ecrm-0500'>5 </span><span class='ectt-0800'>make -C /lib/modules/</span><span class='colorbox' id='colorbox54'><span class='ectt-0800'>$</span></span><span class='ectt-0800'>(shell uname -r)/build M=</span><span class='colorbox' id='colorbox55'><span class='ectt-0800'>$</span></span><span class='ectt-0800'>(PWD) modules</span>
|
|
<a id='x1-13066r6'></a><span class='ecrm-0500'>6</span>
|
|
<a id='x1-13068r7'></a><span class='ecrm-0500'>7</span><span class='ectt-0800'>clean:</span>
|
|
<a id='x1-13070r8'></a><span class='ecrm-0500'>8 </span><span class='ectt-0800'>make -C /lib/modules/</span><span class='colorbox' id='colorbox56'><span class='ectt-0800'>$</span></span><span class='ectt-0800'>(shell uname -r)/build M=</span><span class='colorbox' id='colorbox57'><span class='ectt-0800'>$</span></span><span class='ectt-0800'>(PWD) clean</span></pre>
|
|
<!-- l. 326 --><p class='indent'> Now have a look at <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>linux/drivers/char/Makefile</span></span></span> for a real world example. As
|
|
you can see, some things get hardwired into the kernel (<span class='obeylines-h'><span class='verb'><span class='ectt-1000'>obj-y</span></span></span>) but where are all
|
|
those <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>obj-m</span></span></span> gone? Those familiar with shell scripts will easily be able to spot them.
|
|
For those not, the <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>obj-$(CONFIG_FOO)</span></span></span> entries you see everywhere expand into <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>obj-y</span></span></span>
|
|
or <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>obj-m</span></span></span>, depending on whether the <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>CONFIG_FOO</span></span></span> variable has been set to y or m.
|
|
While we are at it, those were exactly the kind of variables that you have set in the
|
|
<span class='obeylines-h'><span class='verb'><span class='ectt-1000'>linux/.confi</span></span></span>g file, the last time when you said make menuconfig or something like
|
|
that.
|
|
</p><!-- l. 332 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='the-init-and-exit-macros'><span class='titlemark'>0.4.3 </span> <a id='x1-140000.4.3'></a>The __init and __exit Macros</h4>
|
|
<!-- l. 334 --><p class='noindent'>This demonstrates a feature of kernel 2.2 and later. Notice the change in the
|
|
definitions of the init and cleanup functions. The <span class='ecbx-1000'>__init </span>macro causes the init
|
|
function to be discarded and its memory freed once the init function finishes for
|
|
built-in drivers, but not loadable modules. If you think about when the init function
|
|
is invoked, this makes perfect sense.
|
|
</p><!-- l. 339 --><p class='indent'> There is also an <span class='ecbx-1000'>__initdata </span>which works similarly to <span class='ecbx-1000'>__init </span>but for init
|
|
variables rather than functions.
|
|
</p><!-- l. 341 --><p class='indent'> The <span class='ecbx-1000'>__exit </span>macro causes the omission of the function when the module is
|
|
built into the kernel, and like __init, has no effect for loadable modules.
|
|
Again, if you consider when the cleanup function runs, this makes complete
|
|
sense; built-in drivers do not need a cleanup function, while loadable modules
|
|
do.
|
|
|
|
|
|
|
|
</p><!-- l. 344 --><p class='indent'> These macros are defined in <span class='ecbx-1000'>linux/init.h </span>and serve to free up kernel memory.
|
|
When you boot your kernel and see something like Freeing unused kernel memory:
|
|
236k freed, this is precisely what the kernel is freeing.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb21'><a id='x1-14002r1'></a><span class='ecrm-0500'>1</span><span id='textcolor58'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-14004r2'></a><span class='ecrm-0500'>2</span><span id='textcolor59'><span class='ectt-0800'> * hello-3.c - Illustrating the __init, __initdata and __exit macros.</span></span>
|
|
<a id='x1-14006r3'></a><span class='ecrm-0500'>3</span><span id='textcolor60'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-14008r4'></a><span class='ecrm-0500'>4</span><span id='textcolor61'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor62'><span class='ectt-0800'><linux/init.h> /* Needed for the macros */</span></span>
|
|
<a id='x1-14010r5'></a><span class='ecrm-0500'>5</span><span id='textcolor63'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor64'><span class='ectt-0800'><linux/kernel.h> /* Needed for KERN_INFO */</span></span>
|
|
<a id='x1-14012r6'></a><span class='ecrm-0500'>6</span><span id='textcolor65'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor66'><span class='ectt-0800'><linux/module.h> /* Needed by all modules */</span></span>
|
|
<a id='x1-14014r7'></a><span class='ecrm-0500'>7</span>
|
|
<a id='x1-14016r8'></a><span class='ecrm-0500'>8</span><span id='textcolor67'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor68'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> hello3_data __initdata = 3;</span>
|
|
<a id='x1-14018r9'></a><span class='ecrm-0500'>9</span>
|
|
<a id='x1-14020r10'></a><span class='ecrm-0500'>10</span><span id='textcolor69'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor70'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> __init hello_3_init(</span><span id='textcolor71'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-14022r11'></a><span class='ecrm-0500'>11</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-14024r12'></a><span class='ecrm-0500'>12</span><span class='ectt-0800'> pr_info(</span><span id='textcolor72'><span class='ectt-0800'>"Hello, world %d</span></span><span id='textcolor73'><span class='ectt-0800'>\n</span></span><span id='textcolor74'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, hello3_data);</span>
|
|
<a id='x1-14026r13'></a><span class='ecrm-0500'>13</span><span class='ectt-0800'> </span><span id='textcolor75'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-14028r14'></a><span class='ecrm-0500'>14</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-14030r15'></a><span class='ecrm-0500'>15</span>
|
|
<a id='x1-14032r16'></a><span class='ecrm-0500'>16</span><span id='textcolor76'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor77'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> __exit hello_3_exit(</span><span id='textcolor78'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-14034r17'></a><span class='ecrm-0500'>17</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-14036r18'></a><span class='ecrm-0500'>18</span><span class='ectt-0800'> pr_info(</span><span id='textcolor79'><span class='ectt-0800'>"Goodbye, world 3</span></span><span id='textcolor80'><span class='ectt-0800'>\n</span></span><span id='textcolor81'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-14038r19'></a><span class='ecrm-0500'>19</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-14040r20'></a><span class='ecrm-0500'>20</span>
|
|
<a id='x1-14042r21'></a><span class='ecrm-0500'>21</span><span class='ectt-0800'>module_init(hello_3_init);</span>
|
|
<a id='x1-14044r22'></a><span class='ecrm-0500'>22</span><span class='ectt-0800'>module_exit(hello_3_exit);</span>
|
|
<a id='x1-14046r23'></a><span class='ecrm-0500'>23</span>
|
|
<a id='x1-14048r24'></a><span class='ecrm-0500'>24</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor82'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
|
|
<!-- l. 349 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='licensing-and-module-documentation'><span class='titlemark'>0.4.4 </span> <a id='x1-150000.4.4'></a>Licensing and Module Documentation</h4>
|
|
<!-- l. 351 --><p class='noindent'>Honestly, who loads or even cares about proprietary modules? If you do then you
|
|
might have seen something like this:
|
|
|
|
|
|
|
|
</p>
|
|
<pre class='verbatim' id='verbatim-1'>
|
|
$ sudo insmod xxxxxx.ko
|
|
loading out-of-tree module taints kernel.
|
|
module license 'unspecified' taints kernel.
|
|
</pre>
|
|
<!-- l. 357 --><p class='nopar'>
|
|
</p><!-- l. 359 --><p class='indent'> You can use a few macros to indicate the license for your module. Some examples
|
|
are "GPL", "GPL v2", "GPL and additional rights", "Dual BSD/GPL", "Dual
|
|
MIT/GPL", "Dual MPL/GPL" and "Proprietary". They are defined within
|
|
<span class='ecbx-1000'>linux/module.h</span>.
|
|
</p><!-- l. 363 --><p class='indent'> To reference what license you’re using a macro is available called
|
|
<span class='ecbx-1000'>MODULE_LICENSE</span>. This and a few other macros describing the module are
|
|
illustrated in the below example.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb22'><a id='x1-15002r1'></a><span class='ecrm-0500'>1</span><span id='textcolor83'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-15004r2'></a><span class='ecrm-0500'>2</span><span id='textcolor84'><span class='ectt-0800'> * hello-4.c - Demonstrates module documentation.</span></span>
|
|
<a id='x1-15006r3'></a><span class='ecrm-0500'>3</span><span id='textcolor85'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-15008r4'></a><span class='ecrm-0500'>4</span><span id='textcolor86'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor87'><span class='ectt-0800'><linux/init.h> /* Needed for the macros */</span></span>
|
|
<a id='x1-15010r5'></a><span class='ecrm-0500'>5</span><span id='textcolor88'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor89'><span class='ectt-0800'><linux/kernel.h> /* Needed for KERN_INFO */</span></span>
|
|
<a id='x1-15012r6'></a><span class='ecrm-0500'>6</span><span id='textcolor90'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor91'><span class='ectt-0800'><linux/module.h> /* Needed by all modules */</span></span>
|
|
<a id='x1-15014r7'></a><span class='ecrm-0500'>7</span>
|
|
<a id='x1-15016r8'></a><span class='ecrm-0500'>8</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor92'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-15018r9'></a><span class='ecrm-0500'>9</span><span class='ectt-0800'>MODULE_AUTHOR(</span><span id='textcolor93'><span class='ectt-0800'>"LKMPG"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-15020r10'></a><span class='ecrm-0500'>10</span><span class='ectt-0800'>MODULE_DESCRIPTION(</span><span id='textcolor94'><span class='ectt-0800'>"A sample driver"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-15022r11'></a><span class='ecrm-0500'>11</span><span class='ectt-0800'>MODULE_SUPPORTED_DEVICE(</span><span id='textcolor95'><span class='ectt-0800'>"testdevice"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-15024r12'></a><span class='ecrm-0500'>12</span>
|
|
<a id='x1-15026r13'></a><span class='ecrm-0500'>13</span><span id='textcolor96'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor97'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> __init init_hello_4(</span><span id='textcolor98'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-15028r14'></a><span class='ecrm-0500'>14</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-15030r15'></a><span class='ecrm-0500'>15</span><span class='ectt-0800'> pr_info(</span><span id='textcolor99'><span class='ectt-0800'>"Hello, world 4</span></span><span id='textcolor100'><span class='ectt-0800'>\n</span></span><span id='textcolor101'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-15032r16'></a><span class='ecrm-0500'>16</span><span class='ectt-0800'> </span><span id='textcolor102'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-15034r17'></a><span class='ecrm-0500'>17</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-15036r18'></a><span class='ecrm-0500'>18</span>
|
|
<a id='x1-15038r19'></a><span class='ecrm-0500'>19</span><span id='textcolor103'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor104'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> __exit cleanup_hello_4(</span><span id='textcolor105'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-15040r20'></a><span class='ecrm-0500'>20</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-15042r21'></a><span class='ecrm-0500'>21</span><span class='ectt-0800'> pr_info(</span><span id='textcolor106'><span class='ectt-0800'>"Goodbye, world 4</span></span><span id='textcolor107'><span class='ectt-0800'>\n</span></span><span id='textcolor108'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-15044r22'></a><span class='ecrm-0500'>22</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-15046r23'></a><span class='ecrm-0500'>23</span>
|
|
<a id='x1-15048r24'></a><span class='ecrm-0500'>24</span><span class='ectt-0800'>module_init(init_hello_4);</span>
|
|
<a id='x1-15050r25'></a><span class='ecrm-0500'>25</span><span class='ectt-0800'>module_exit(cleanup_hello_4);</span></pre>
|
|
<!-- l. 368 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='passing-command-line-arguments-to-a-module'><span class='titlemark'>0.4.5 </span> <a id='x1-160000.4.5'></a>Passing Command Line Arguments to a Module</h4>
|
|
<!-- l. 370 --><p class='noindent'>Modules can take command line arguments, but not with the argc/argv you might be
|
|
used to.
|
|
</p><!-- l. 372 --><p class='indent'> To allow arguments to be passed to your module, declare the variables that
|
|
will take the values of the command line arguments as global and then use
|
|
the module_param() macro, (defined in linux/moduleparam.h) to set the
|
|
mechanism up. At runtime, insmod will fill the variables with any command line
|
|
arguments that are given, like insmod ./mymodule.ko myvariable=5. The
|
|
variable declarations and macros should be placed at the beginning of the
|
|
module for clarity. The example code should clear up my admittedly lousy
|
|
explanation.
|
|
</p><!-- l. 377 --><p class='indent'> The module_param() macro takes 3 arguments: the name of the variable, its type
|
|
and permissions for the corresponding file in sysfs. Integer types can be signed
|
|
as usual or unsigned. If you’d like to use arrays of integers or strings see
|
|
<span class='obeylines-h'><span class='verb'><span class='ectt-1000'>module_param_array()</span></span></span> and <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>module_param_string()</span></span></span>.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb23'><a id='x1-16004r1'></a><span class='ecrm-0500'>1</span><span id='textcolor109'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> myint = 3;</span>
|
|
<a id='x1-16006r2'></a><span class='ecrm-0500'>2</span><span class='ectt-0800'>module_param(myint, </span><span id='textcolor110'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>, 0);</span></pre>
|
|
<!-- l. 385 --><p class='indent'> Arrays are supported too, but things are a bit different now than they were in the
|
|
olden days. To keep track of the number of parameters you need to pass a
|
|
|
|
|
|
|
|
pointer to a count variable as third parameter. At your option, you could
|
|
also ignore the count and pass NULL instead. We show both possibilities
|
|
here:
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb24'><a id='x1-16014r1'></a><span class='ecrm-0500'>1</span><span id='textcolor111'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> myintarray[2];</span>
|
|
<a id='x1-16016r2'></a><span class='ecrm-0500'>2</span><span class='ectt-0800'>module_param_array(myintarray, </span><span id='textcolor112'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>, NULL, 0); </span><span id='textcolor113'><span class='ectt-0800'>/* not interested in count */</span></span>
|
|
<a id='x1-16018r3'></a><span class='ecrm-0500'>3</span>
|
|
<a id='x1-16020r4'></a><span class='ecrm-0500'>4</span><span id='textcolor114'><span class='ectt-0800'>short</span></span><span class='ectt-0800'> myshortarray[4];</span>
|
|
<a id='x1-16022r5'></a><span class='ecrm-0500'>5</span><span id='textcolor115'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> count;</span>
|
|
<a id='x1-16024r6'></a><span class='ecrm-0500'>6</span><span class='ectt-0800'>module_param_array(myshortarray, </span><span id='textcolor116'><span class='ectt-0800'>short</span></span><span class='ectt-0800'>, &count, 0); </span><span id='textcolor117'><span class='ectt-0800'>/* put count into "count" variable */</span></span></pre>
|
|
<!-- l. 398 --><p class='indent'> A good use for this is to have the module variable’s default values set, like an port
|
|
or IO address. If the variables contain the default values, then perform autodetection
|
|
(explained elsewhere). Otherwise, keep the current value. This will be made clear
|
|
later on.
|
|
</p><!-- l. 402 --><p class='indent'> Lastly, there’s a macro function, <span class='ecbx-1000'>MODULE_PARM_DESC()</span>, that is used to
|
|
document arguments that the module can take. It takes two parameters: a variable
|
|
name and a free form string describing that variable.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb25'><a id='x1-16026r1'></a><span class='ecrm-0500'>1</span><span id='textcolor118'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-16028r2'></a><span class='ecrm-0500'>2</span><span id='textcolor119'><span class='ectt-0800'> * hello-5.c - Demonstrates command line argument passing to a module.</span></span>
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<a id='x1-16030r3'></a><span class='ecrm-0500'>3</span><span id='textcolor120'><span class='ectt-0800'> */</span></span>
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<a id='x1-16032r4'></a><span class='ecrm-0500'>4</span><span id='textcolor121'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor122'><span class='ectt-0800'><linux/init.h></span></span>
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<a id='x1-16034r5'></a><span class='ecrm-0500'>5</span><span id='textcolor123'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor124'><span class='ectt-0800'><linux/kernel.h></span></span>
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<a id='x1-16036r6'></a><span class='ecrm-0500'>6</span><span id='textcolor125'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor126'><span class='ectt-0800'><linux/module.h></span></span>
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<a id='x1-16038r7'></a><span class='ecrm-0500'>7</span><span id='textcolor127'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor128'><span class='ectt-0800'><linux/moduleparam.h></span></span>
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<a id='x1-16040r8'></a><span class='ecrm-0500'>8</span><span id='textcolor129'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor130'><span class='ectt-0800'><linux/stat.h></span></span>
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<a id='x1-16042r9'></a><span class='ecrm-0500'>9</span>
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<a id='x1-16044r10'></a><span class='ecrm-0500'>10</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor131'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span>
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<a id='x1-16046r11'></a><span class='ecrm-0500'>11</span>
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<a id='x1-16048r12'></a><span class='ecrm-0500'>12</span><span id='textcolor132'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor133'><span class='ectt-0800'>short</span></span><span class='ectt-0800'> </span><span id='textcolor134'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> myshort = 1;</span>
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<a id='x1-16050r13'></a><span class='ecrm-0500'>13</span><span id='textcolor135'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor136'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> myint = 420;</span>
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<a id='x1-16052r14'></a><span class='ecrm-0500'>14</span><span id='textcolor137'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor138'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> </span><span id='textcolor139'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> mylong = 9999;</span>
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<a id='x1-16054r15'></a><span class='ecrm-0500'>15</span><span id='textcolor140'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor141'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *mystring = </span><span id='textcolor142'><span class='ectt-0800'>"blah"</span></span><span class='ectt-0800'>;</span>
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<a id='x1-16056r16'></a><span class='ecrm-0500'>16</span><span id='textcolor143'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor144'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> myintArray[2] = {420, 420};</span>
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<a id='x1-16058r17'></a><span class='ecrm-0500'>17</span><span id='textcolor145'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor146'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> arr_argc = 0;</span>
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<a id='x1-16060r18'></a><span class='ecrm-0500'>18</span>
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<a id='x1-16062r19'></a><span class='ecrm-0500'>19</span><span id='textcolor147'><span class='ectt-0800'>/*</span></span>
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<a id='x1-16064r20'></a><span class='ecrm-0500'>20</span><span id='textcolor148'><span class='ectt-0800'> * module_param(foo, int, 0000)</span></span>
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<a id='x1-16066r21'></a><span class='ecrm-0500'>21</span><span id='textcolor149'><span class='ectt-0800'> * The first param is the parameters name</span></span>
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<a id='x1-16068r22'></a><span class='ecrm-0500'>22</span><span id='textcolor150'><span class='ectt-0800'> * The second param is it</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s data type</span></span>
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<a id='x1-16070r23'></a><span class='ecrm-0500'>23</span><span id='textcolor151'><span class='ectt-0800'> * The final argument is the permissions bits,</span></span>
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<a id='x1-16072r24'></a><span class='ecrm-0500'>24</span><span id='textcolor152'><span class='ectt-0800'> * for exposing parameters in sysfs (if non-zero) at a later stage.</span></span>
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<a id='x1-16074r25'></a><span class='ecrm-0500'>25</span><span id='textcolor153'><span class='ectt-0800'> */</span></span>
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<a id='x1-16076r26'></a><span class='ecrm-0500'>26</span>
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<a id='x1-16078r27'></a><span class='ecrm-0500'>27</span><span class='ectt-0800'>module_param(myshort, </span><span id='textcolor154'><span class='ectt-0800'>short</span></span><span class='ectt-0800'>, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);</span>
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<a id='x1-16080r28'></a><span class='ecrm-0500'>28</span><span class='ectt-0800'>MODULE_PARM_DESC(myshort, </span><span id='textcolor155'><span class='ectt-0800'>"A short integer"</span></span><span class='ectt-0800'>);</span>
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<a id='x1-16082r29'></a><span class='ecrm-0500'>29</span><span class='ectt-0800'>module_param(myint, </span><span id='textcolor156'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);</span>
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<a id='x1-16084r30'></a><span class='ecrm-0500'>30</span><span class='ectt-0800'>MODULE_PARM_DESC(myint, </span><span id='textcolor157'><span class='ectt-0800'>"An integer"</span></span><span class='ectt-0800'>);</span>
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<a id='x1-16086r31'></a><span class='ecrm-0500'>31</span><span class='ectt-0800'>module_param(mylong, </span><span id='textcolor158'><span class='ectt-0800'>long</span></span><span class='ectt-0800'>, S_IRUSR);</span>
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<a id='x1-16088r32'></a><span class='ecrm-0500'>32</span><span class='ectt-0800'>MODULE_PARM_DESC(mylong, </span><span id='textcolor159'><span class='ectt-0800'>"A long integer"</span></span><span class='ectt-0800'>);</span>
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<a id='x1-16090r33'></a><span class='ecrm-0500'>33</span><span class='ectt-0800'>module_param(mystring, charp, 0000);</span>
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<a id='x1-16092r34'></a><span class='ecrm-0500'>34</span><span class='ectt-0800'>MODULE_PARM_DESC(mystring, </span><span id='textcolor160'><span class='ectt-0800'>"A character string"</span></span><span class='ectt-0800'>);</span>
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<a id='x1-16094r35'></a><span class='ecrm-0500'>35</span>
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<a id='x1-16096r36'></a><span class='ecrm-0500'>36</span><span id='textcolor161'><span class='ectt-0800'>/*</span></span>
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<a id='x1-16098r37'></a><span class='ecrm-0500'>37</span><span id='textcolor162'><span class='ectt-0800'> * module_param_array(name, type, num, perm);</span></span>
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<a id='x1-16100r38'></a><span class='ecrm-0500'>38</span><span id='textcolor163'><span class='ectt-0800'> * The first param is the parameter</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s (in this case the array</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s) name</span></span>
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<a id='x1-16102r39'></a><span class='ecrm-0500'>39</span><span id='textcolor164'><span class='ectt-0800'> * The second param is the data type of the elements of the array</span></span>
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<a id='x1-16104r40'></a><span class='ecrm-0500'>40</span><span id='textcolor165'><span class='ectt-0800'> * The third argument is a pointer to the variable that will store the number</span></span>
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<a id='x1-16106r41'></a><span class='ecrm-0500'>41</span><span id='textcolor166'><span class='ectt-0800'> * of elements of the array initialized by the user at module loading time</span></span>
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<a id='x1-16108r42'></a><span class='ecrm-0500'>42</span><span id='textcolor167'><span class='ectt-0800'> * The fourth argument is the permission bits</span></span>
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<a id='x1-16110r43'></a><span class='ecrm-0500'>43</span><span id='textcolor168'><span class='ectt-0800'> */</span></span>
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<a id='x1-16112r44'></a><span class='ecrm-0500'>44</span><span class='ectt-0800'>module_param_array(myintArray, </span><span id='textcolor169'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>, &arr_argc, 0000);</span>
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<a id='x1-16114r45'></a><span class='ecrm-0500'>45</span><span class='ectt-0800'>MODULE_PARM_DESC(myintArray, </span><span id='textcolor170'><span class='ectt-0800'>"An array of integers"</span></span><span class='ectt-0800'>);</span>
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<a id='x1-16116r46'></a><span class='ecrm-0500'>46</span>
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<a id='x1-16118r47'></a><span class='ecrm-0500'>47</span><span id='textcolor171'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor172'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> __init hello_5_init(</span><span id='textcolor173'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
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<a id='x1-16120r48'></a><span class='ecrm-0500'>48</span><span class='ectt-0800'>{</span>
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<a id='x1-16122r49'></a><span class='ecrm-0500'>49</span><span class='ectt-0800'> </span><span id='textcolor174'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> i;</span>
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<a id='x1-16124r50'></a><span class='ecrm-0500'>50</span><span class='ectt-0800'> pr_info(</span><span id='textcolor175'><span class='ectt-0800'>"Hello, world 5</span></span><span id='textcolor176'><span class='ectt-0800'>\n</span></span><span id='textcolor177'><span class='ectt-0800'>=============</span></span><span id='textcolor178'><span class='ectt-0800'>\n</span></span><span id='textcolor179'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
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<a id='x1-16126r51'></a><span class='ecrm-0500'>51</span><span class='ectt-0800'> pr_info(</span><span id='textcolor180'><span class='ectt-0800'>"myshort is a short integer: %hd</span></span><span id='textcolor181'><span class='ectt-0800'>\n</span></span><span id='textcolor182'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, myshort);</span>
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<a id='x1-16128r52'></a><span class='ecrm-0500'>52</span><span class='ectt-0800'> pr_info(</span><span id='textcolor183'><span class='ectt-0800'>"myint is an integer: %d</span></span><span id='textcolor184'><span class='ectt-0800'>\n</span></span><span id='textcolor185'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, myint);</span>
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<a id='x1-16130r53'></a><span class='ecrm-0500'>53</span><span class='ectt-0800'> pr_info(</span><span id='textcolor186'><span class='ectt-0800'>"mylong is a long integer: %ld</span></span><span id='textcolor187'><span class='ectt-0800'>\n</span></span><span id='textcolor188'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, mylong);</span>
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<a id='x1-16132r54'></a><span class='ecrm-0500'>54</span><span class='ectt-0800'> pr_info(</span><span id='textcolor189'><span class='ectt-0800'>"mystring is a string: %s</span></span><span id='textcolor190'><span class='ectt-0800'>\n</span></span><span id='textcolor191'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, mystring);</span>
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<a id='x1-16134r55'></a><span class='ecrm-0500'>55</span>
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<a id='x1-16136r56'></a><span class='ecrm-0500'>56</span><span class='ectt-0800'> </span><span id='textcolor192'><span class='ectt-0800'>for</span></span><span class='ectt-0800'> (i = 0; i < (</span><span id='textcolor193'><span class='ectt-0800'>sizeof</span></span><span class='ectt-0800'> myintArray / </span><span id='textcolor194'><span class='ectt-0800'>sizeof</span></span><span class='ectt-0800'>(</span><span id='textcolor195'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>)); i++)</span>
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<a id='x1-16138r57'></a><span class='ecrm-0500'>57</span><span class='ectt-0800'> pr_info(</span><span id='textcolor196'><span class='ectt-0800'>"myintArray[%d] = %d</span></span><span id='textcolor197'><span class='ectt-0800'>\n</span></span><span id='textcolor198'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, i, myintArray[i]);</span>
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<a id='x1-16140r58'></a><span class='ecrm-0500'>58</span>
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<a id='x1-16142r59'></a><span class='ecrm-0500'>59</span><span class='ectt-0800'> pr_info(</span><span id='textcolor199'><span class='ectt-0800'>"got %d arguments for myintArray.</span></span><span id='textcolor200'><span class='ectt-0800'>\n</span></span><span id='textcolor201'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, arr_argc);</span>
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<a id='x1-16144r60'></a><span class='ecrm-0500'>60</span><span class='ectt-0800'> </span><span id='textcolor202'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
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<a id='x1-16146r61'></a><span class='ecrm-0500'>61</span><span class='ectt-0800'>}</span>
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<a id='x1-16148r62'></a><span class='ecrm-0500'>62</span>
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<a id='x1-16150r63'></a><span class='ecrm-0500'>63</span><span id='textcolor203'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor204'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> __exit hello_5_exit(</span><span id='textcolor205'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
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<a id='x1-16152r64'></a><span class='ecrm-0500'>64</span><span class='ectt-0800'>{</span>
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<a id='x1-16154r65'></a><span class='ecrm-0500'>65</span><span class='ectt-0800'> pr_info(</span><span id='textcolor206'><span class='ectt-0800'>"Goodbye, world 5</span></span><span id='textcolor207'><span class='ectt-0800'>\n</span></span><span id='textcolor208'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
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<a id='x1-16156r66'></a><span class='ecrm-0500'>66</span><span class='ectt-0800'>}</span>
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<a id='x1-16158r67'></a><span class='ecrm-0500'>67</span>
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<a id='x1-16160r68'></a><span class='ecrm-0500'>68</span><span class='ectt-0800'>module_init(hello_5_init);</span>
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<a id='x1-16162r69'></a><span class='ecrm-0500'>69</span><span class='ectt-0800'>module_exit(hello_5_exit);</span></pre>
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<!-- l. 407 --><p class='indent'> I would recommend playing around with this code:
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</p>
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<pre class='fancyvrb' id='fancyvrb26'><a id='x1-16190r1'></a><span class='ecrm-0500'>1</span><span class='colorbox' id='colorbox209'><span class='ectt-0800'>$</span></span><span class='ectt-0800'> sudo insmod hello-5.ko mystring=</span><span id='textcolor210'><span class='ectt-0800'>"bebop"</span></span><span class='ectt-0800'> myintArray=-1</span>
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<a id='x1-16192r2'></a><span class='ecrm-0500'>2</span><span class='ectt-0800'>myshort is a </span><span id='textcolor211'><span class='ectt-0800'>short</span></span><span class='ectt-0800'> integer: 1</span>
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<a id='x1-16194r3'></a><span class='ecrm-0500'>3</span><span class='ectt-0800'>myint is an integer: 420</span>
|
|
<a id='x1-16196r4'></a><span class='ecrm-0500'>4</span><span class='ectt-0800'>mylong is a </span><span id='textcolor212'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> integer: 9999</span>
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<a id='x1-16198r5'></a><span class='ecrm-0500'>5</span><span class='ectt-0800'>mystring is a string: bebop</span>
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|
<a id='x1-16200r6'></a><span class='ecrm-0500'>6</span><span class='ectt-0800'>myintArray[0] = -1</span>
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|
<a id='x1-16202r7'></a><span class='ecrm-0500'>7</span><span class='ectt-0800'>myintArray[1] = 420</span>
|
|
<a id='x1-16204r8'></a><span class='ecrm-0500'>8</span><span class='ectt-0800'>got 1 arguments </span><span id='textcolor213'><span class='ectt-0800'>for</span></span><span class='ectt-0800'> myintArray.</span>
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<a id='x1-16206r9'></a><span class='ecrm-0500'>9</span>
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<a id='x1-16208r10'></a><span class='ecrm-0500'>10</span><span class='colorbox' id='colorbox214'><span class='ectt-0800'>$</span></span><span class='ectt-0800'> sudo rmmod hello-5</span>
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<a id='x1-16210r11'></a><span class='ecrm-0500'>11</span><span class='ectt-0800'>Goodbye, world 5</span>
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<a id='x1-16212r12'></a><span class='ecrm-0500'>12</span>
|
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<a id='x1-16214r13'></a><span class='ecrm-0500'>13</span><span class='colorbox' id='colorbox215'><span class='ectt-0800'>$</span></span><span class='ectt-0800'> sudo insmod hello-5.ko mystring=</span><span id='textcolor216'><span class='ectt-0800'>"supercalifragilisticexpialidocious"</span></span><span class='ectt-0800'> myintArray=-1,-1</span>
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|
<a id='x1-16216r14'></a><span class='ecrm-0500'>14</span><span class='ectt-0800'>myshort is a </span><span id='textcolor217'><span class='ectt-0800'>short</span></span><span class='ectt-0800'> integer: 1</span>
|
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<a id='x1-16218r15'></a><span class='ecrm-0500'>15</span><span class='ectt-0800'>myint is an integer: 420</span>
|
|
<a id='x1-16220r16'></a><span class='ecrm-0500'>16</span><span class='ectt-0800'>mylong is a </span><span id='textcolor218'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> integer: 9999</span>
|
|
<a id='x1-16222r17'></a><span class='ecrm-0500'>17</span><span class='ectt-0800'>mystring is a string: supercalifragilisticexpialidocious</span>
|
|
<a id='x1-16224r18'></a><span class='ecrm-0500'>18</span><span class='ectt-0800'>myintArray[0] = -1</span>
|
|
<a id='x1-16226r19'></a><span class='ecrm-0500'>19</span><span class='ectt-0800'>myintArray[1] = -1</span>
|
|
<a id='x1-16228r20'></a><span class='ecrm-0500'>20</span><span class='ectt-0800'>got 2 arguments </span><span id='textcolor219'><span class='ectt-0800'>for</span></span><span class='ectt-0800'> myintArray.</span>
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<a id='x1-16230r21'></a><span class='ecrm-0500'>21</span>
|
|
<a id='x1-16232r22'></a><span class='ecrm-0500'>22</span><span class='colorbox' id='colorbox220'><span class='ectt-0800'>$</span></span><span class='ectt-0800'> sudo rmmod hello-5</span>
|
|
<a id='x1-16234r23'></a><span class='ecrm-0500'>23</span><span class='ectt-0800'>Goodbye, world 5</span>
|
|
<a id='x1-16236r24'></a><span class='ecrm-0500'>24</span>
|
|
<a id='x1-16238r25'></a><span class='ecrm-0500'>25</span><span class='colorbox' id='colorbox221'><span class='ectt-0800'>$</span></span><span class='ectt-0800'> sudo insmod hello-5.ko mylong=hello</span>
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|
<a id='x1-16240r26'></a><span class='ecrm-0500'>26</span><span class='ectt-0800'>hello-5.o: invalid argument syntax </span><span id='textcolor222'><span class='ectt-0800'>for</span></span><span class='ectt-0800'> mylong: </span><span id='textcolor223'><span class='tctt-0800'>'</span><span class='ectt-0800'>h</span><span class='tctt-0800'>'</span></span></pre>
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<!-- l. 437 --><p class='noindent'>
|
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</p>
|
|
<h4 class='subsectionHead' id='modules-spanning-multiple-files'><span class='titlemark'>0.4.6 </span> <a id='x1-170000.4.6'></a>Modules Spanning Multiple Files</h4>
|
|
<!-- l. 439 --><p class='noindent'>Sometimes it makes sense to divide a kernel module between several source
|
|
files.
|
|
</p><!-- l. 441 --><p class='indent'> Here is an example of such a kernel module.
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb27'><a id='x1-17002r1'></a><span class='ecrm-0500'>1</span><span id='textcolor224'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-17004r2'></a><span class='ecrm-0500'>2</span><span id='textcolor225'><span class='ectt-0800'> * start.c - Illustration of multi filed modules</span></span>
|
|
<a id='x1-17006r3'></a><span class='ecrm-0500'>3</span><span id='textcolor226'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-17008r4'></a><span class='ecrm-0500'>4</span>
|
|
<a id='x1-17010r5'></a><span class='ecrm-0500'>5</span><span id='textcolor227'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor228'><span class='ectt-0800'><linux/kernel.h> /* We</span><span class='tctt-0800'>'</span><span class='ectt-0800'>re doing kernel work */</span></span>
|
|
<a id='x1-17012r6'></a><span class='ecrm-0500'>6</span><span id='textcolor229'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor230'><span class='ectt-0800'><linux/module.h> /* Specifically, a module */</span></span>
|
|
<a id='x1-17014r7'></a><span class='ecrm-0500'>7</span>
|
|
<a id='x1-17016r8'></a><span class='ecrm-0500'>8</span><span id='textcolor231'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> init_module(</span><span id='textcolor232'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-17018r9'></a><span class='ecrm-0500'>9</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-17020r10'></a><span class='ecrm-0500'>10</span><span class='ectt-0800'> pr_info(</span><span id='textcolor233'><span class='ectt-0800'>"Hello, world - this is the kernel speaking</span></span><span id='textcolor234'><span class='ectt-0800'>\n</span></span><span id='textcolor235'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-17022r11'></a><span class='ecrm-0500'>11</span><span class='ectt-0800'> </span><span id='textcolor236'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-17024r12'></a><span class='ecrm-0500'>12</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-17026r13'></a><span class='ecrm-0500'>13</span>
|
|
<a id='x1-17028r14'></a><span class='ecrm-0500'>14</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor237'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
|
|
<!-- l. 444 --><p class='indent'> The next file:
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb28'><a id='x1-17030r1'></a><span class='ecrm-0500'>1</span><span id='textcolor238'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-17032r2'></a><span class='ecrm-0500'>2</span><span id='textcolor239'><span class='ectt-0800'> * stop.c - Illustration of multi filed modules</span></span>
|
|
<a id='x1-17034r3'></a><span class='ecrm-0500'>3</span><span id='textcolor240'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-17036r4'></a><span class='ecrm-0500'>4</span>
|
|
<a id='x1-17038r5'></a><span class='ecrm-0500'>5</span><span id='textcolor241'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor242'><span class='ectt-0800'><linux/kernel.h> /* We</span><span class='tctt-0800'>'</span><span class='ectt-0800'>re doing kernel work */</span></span>
|
|
<a id='x1-17040r6'></a><span class='ecrm-0500'>6</span><span id='textcolor243'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor244'><span class='ectt-0800'><linux/module.h> /* Specifically, a module */</span></span>
|
|
<a id='x1-17042r7'></a><span class='ecrm-0500'>7</span>
|
|
<a id='x1-17044r8'></a><span class='ecrm-0500'>8</span><span id='textcolor245'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> cleanup_module()</span>
|
|
<a id='x1-17046r9'></a><span class='ecrm-0500'>9</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-17048r10'></a><span class='ecrm-0500'>10</span><span class='ectt-0800'> pr_info(</span><span id='textcolor246'><span class='ectt-0800'>"Short is the life of a kernel module</span></span><span id='textcolor247'><span class='ectt-0800'>\n</span></span><span id='textcolor248'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-17050r11'></a><span class='ecrm-0500'>11</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-17052r12'></a><span class='ecrm-0500'>12</span>
|
|
<a id='x1-17054r13'></a><span class='ecrm-0500'>13</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor249'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
|
|
<!-- l. 447 --><p class='indent'> And finally, the makefile:
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb29'><a id='x1-17069r1'></a><span class='ecrm-0500'>1</span><span class='ectt-0800'>obj-m += hello-1.o</span>
|
|
<a id='x1-17071r2'></a><span class='ecrm-0500'>2</span><span class='ectt-0800'>obj-m += hello-2.o</span>
|
|
<a id='x1-17073r3'></a><span class='ecrm-0500'>3</span><span class='ectt-0800'>obj-m += hello-3.o</span>
|
|
<a id='x1-17075r4'></a><span class='ecrm-0500'>4</span><span class='ectt-0800'>obj-m += hello-4.o</span>
|
|
<a id='x1-17077r5'></a><span class='ecrm-0500'>5</span><span class='ectt-0800'>obj-m += hello-5.o</span>
|
|
<a id='x1-17079r6'></a><span class='ecrm-0500'>6</span><span class='ectt-0800'>obj-m += startstop.o</span>
|
|
<a id='x1-17081r7'></a><span class='ecrm-0500'>7</span><span class='ectt-0800'>startstop-objs := start.o stop.o</span>
|
|
<a id='x1-17083r8'></a><span class='ecrm-0500'>8</span>
|
|
<a id='x1-17085r9'></a><span class='ecrm-0500'>9</span><span class='ectt-0800'>all:</span>
|
|
<a id='x1-17087r10'></a><span class='ecrm-0500'>10 </span><span class='ectt-0800'>make -C /lib/modules/</span><span class='colorbox' id='colorbox250'><span class='ectt-0800'>$</span></span><span class='ectt-0800'>(shell uname -r)/build M=</span><span class='colorbox' id='colorbox251'><span class='ectt-0800'>$</span></span><span class='ectt-0800'>(PWD) modules</span>
|
|
<a id='x1-17089r11'></a><span class='ecrm-0500'>11</span>
|
|
<a id='x1-17091r12'></a><span class='ecrm-0500'>12</span><span class='ectt-0800'>clean:</span>
|
|
<a id='x1-17093r13'></a><span class='ecrm-0500'>13 </span><span class='ectt-0800'>make -C /lib/modules/</span><span class='colorbox' id='colorbox252'><span class='ectt-0800'>$</span></span><span class='ectt-0800'>(shell uname -r)/build M=</span><span class='colorbox' id='colorbox253'><span class='ectt-0800'>$</span></span><span class='ectt-0800'>(PWD) clean</span></pre>
|
|
<!-- l. 465 --><p class='indent'> This is the complete makefile for all the examples we have seen so far. The first
|
|
five lines are nothing special, but for the last example we will need two lines. First we
|
|
invent an object name for our combined module, second we tell make what object
|
|
files are part of that module.
|
|
|
|
|
|
|
|
</p><!-- l. 469 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='building-modules-for-a-precompiled-kernel'><span class='titlemark'>0.4.7 </span> <a id='x1-180000.4.7'></a>Building modules for a precompiled kernel</h4>
|
|
<!-- l. 471 --><p class='noindent'>Obviously, we strongly suggest you to recompile your kernel, so that you can enable
|
|
a number of useful debugging features, such as forced module unloading
|
|
(<span class='ecbx-1000'>MODULE_FORCE_UNLOAD</span>): when this option is enabled, you can force the
|
|
kernel to unload a module even when it believes it is unsafe, via a <span class='ecbx-1000'>sudo rmmod -f
|
|
</span><span class='ecbx-1000'>module </span>command. This option can save you a lot of time and a number of reboots
|
|
during the development of a module. If you do not want to recompile your kernel
|
|
then you should consider running the examples within a test distribution on a virtual
|
|
machine. If you mess anything up then you can easily reboot or restore the virtual
|
|
machine (VM).
|
|
</p><!-- l. 476 --><p class='indent'> There are a number of cases in which you may want to load your module into a
|
|
precompiled running kernel, such as the ones shipped with common Linux
|
|
distributions, or a kernel you have compiled in the past. In certain circumstances you
|
|
could require to compile and insert a module into a running kernel which you are not
|
|
allowed to recompile, or on a machine that you prefer not to reboot. If you
|
|
can’t think of a case that will force you to use modules for a precompiled
|
|
kernel you might want to skip this and treat the rest of this chapter as a big
|
|
footnote.
|
|
</p><!-- l. 480 --><p class='indent'> Now, if you just install a kernel source tree, use it to compile your kernel module
|
|
and you try to insert your module into the kernel, in most cases you would obtain an
|
|
error as follows:
|
|
|
|
|
|
|
|
</p>
|
|
<pre class='verbatim' id='verbatim-2'>
|
|
insmod: error inserting 'poet_atkm.ko': -1 Invalid module format
|
|
</pre>
|
|
<!-- l. 484 --><p class='nopar'>
|
|
</p><!-- l. 486 --><p class='indent'> Less cryptical information are logged to the systemd journal:
|
|
|
|
|
|
|
|
</p>
|
|
<pre class='verbatim' id='verbatim-3'>
|
|
Jun 4 22:07:54 localhost kernel: poet_atkm: version magic '2.6.5-1.358custom 686
|
|
REGPARM 4KSTACKS gcc-3.3' should be '2.6.5-1.358 686 REGPARM 4KSTACKS gcc-3.3'
|
|
</pre>
|
|
<!-- l. 491 --><p class='nopar'>
|
|
</p><!-- l. 493 --><p class='indent'> In other words, your kernel refuses to accept your module because version strings
|
|
(more precisely, version magics) do not match. Incidentally, version magics are stored
|
|
in the module object in the form of a static string, starting with vermagic:. Version
|
|
data are inserted in your module when it is linked against the <span class='ecbx-1000'>init/vermagic.o </span>file.
|
|
To inspect version magics and other strings stored in a given module, issue the
|
|
modinfo module.ko command:
|
|
|
|
|
|
|
|
</p>
|
|
<pre class='verbatim' id='verbatim-4'>
|
|
$ modinfo hello-4.ko
|
|
description: A sample driver
|
|
author: LKMPG
|
|
license: GPL
|
|
srcversion: B2AA7FBFCC2C39AED665382
|
|
depends:
|
|
retpoline: Y
|
|
name: hello_4
|
|
vermagic: 5.4.0-70-generic SMP mod_unload modversions
|
|
</pre>
|
|
<!-- l. 508 --><p class='nopar'>
|
|
</p><!-- l. 510 --><p class='indent'> To overcome this problem we could resort to the <span class='ecbx-1000'>–force-vermagic </span>option, but
|
|
this solution is potentially unsafe, and unquestionably inacceptable in production
|
|
modules. Consequently, we want to compile our module in an environment which was
|
|
identical to the one in which our precompiled kernel was built. How to do this, is the
|
|
subject of the remainder of this chapter.
|
|
</p><!-- l. 514 --><p class='indent'> First of all, make sure that a kernel source tree is available, having exactly the
|
|
same version as your current kernel. Then, find the configuration file which was used
|
|
to compile your precompiled kernel. Usually, this is available in your current <span class='ecti-1000'>boot</span>
|
|
directory, under a name like config-2.6.x. You may just want to copy it to your kernel
|
|
source tree: <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>cp /boot/config-</span><span class='tctt-1000'>`</span><span class='ectt-1000'>uname -r</span><span class='tctt-1000'>`</span><span class='ectt-1000'> .config</span></span></span>.
|
|
</p><!-- l. 519 --><p class='indent'> Let’s focus again on the previous error message: a closer look at the version magic
|
|
strings suggests that, even with two configuration files which are exactly the same, a
|
|
slight difference in the version magic could be possible, and it is sufficient to prevent
|
|
insertion of the module into the kernel. That slight difference, namely the custom
|
|
string which appears in the module’s version magic and not in the kernel’s one,
|
|
is due to a modification with respect to the original, in the makefile that
|
|
some distribution include. Then, examine your <span class='ecbx-1000'>/usr/src/linux/Makefile</span>,
|
|
and make sure that the specified version information matches exactly the
|
|
one used for your current kernel. For example, you makefile could start as
|
|
follows:
|
|
|
|
|
|
|
|
</p>
|
|
<pre class='verbatim' id='verbatim-5'>
|
|
VERSION = 5
|
|
PATCHLEVEL = 14
|
|
SUBLEVEL = 0
|
|
EXTRAVERSION = -rc2
|
|
</pre>
|
|
<!-- l. 528 --><p class='nopar'>
|
|
</p><!-- l. 530 --><p class='indent'> In this case, you need to restore the value of symbol <span class='ecbx-1000'>EXTRAVERSION </span>to
|
|
<span class='ecbx-1000'>-rc2</span>. We suggest to keep a backup copy of the makefile used to compile
|
|
your kernel available in <span class='ecbx-1000'>/lib/modules/5.14.0-rc2/build</span>. A simple <span class='ecbx-1000'>cp
|
|
</span><span class='ecbx-1000'>/lib/modules/‘uname-r‘/build/Makefile /usr/src/linux-‘uname -r‘ </span>should
|
|
suffice. Additionally, if you already started a kernel build with the previous (wrong)
|
|
Makefile, you should also rerun make, or directly modify symbol UTS_RELEASE in
|
|
file <span class='ecbx-1000'>/usr/src/linux-5.14.0/include/linux/version.h </span>according to contents of file
|
|
<span class='ecbx-1000'>/lib/modules/5.14.0/build/include/linux/version.h</span>, or overwrite the latter
|
|
with the first.
|
|
</p><!-- l. 536 --><p class='indent'> Now, please run make to update configuration and version headers and
|
|
objects:
|
|
|
|
|
|
|
|
</p>
|
|
<pre class='verbatim' id='verbatim-6'>
|
|
$ make
|
|
CHK include/linux/version.h
|
|
UPD include/linux/version.h
|
|
SYMLINK include/asm -> include/asm-i386
|
|
SPLIT include/linux/autoconf.h -> include/config/*
|
|
HOSTCC scripts/basic/fixdep
|
|
HOSTCC scripts/basic/split-include
|
|
HOSTCC scripts/basic/docproc
|
|
HOSTCC scripts/conmakehash
|
|
HOSTCC scripts/kallsyms
|
|
CC scripts/empty.o
|
|
</pre>
|
|
<!-- l. 550 --><p class='nopar'>
|
|
</p><!-- l. 552 --><p class='indent'> If you do not desire to actually compile the kernel, you can interrupt the build
|
|
process (CTRL-C) just after the SPLIT line, because at that time, the files you need
|
|
will be are ready. Now you can turn back to the directory of your module and
|
|
compile it: It will be built exactly according to your current kernel settings, and it
|
|
will load into it without any errors.
|
|
</p><!-- l. 555 --><p class='noindent'>
|
|
</p>
|
|
<h3 class='sectionHead' id='preliminaries'><span class='titlemark'>0.5 </span> <a id='x1-190000.5'></a>Preliminaries</h3>
|
|
<!-- l. 556 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='how-modules-begin-and-end'><span class='titlemark'>0.5.1 </span> <a id='x1-200000.5.1'></a>How modules begin and end</h4>
|
|
<!-- l. 558 --><p class='noindent'>A program usually begins with a <span class='ecbx-1000'>main() </span>function, executes a bunch of instructions
|
|
and terminates upon completion of those instructions. Kernel modules work a bit
|
|
differently. A module always begin with either the init_module or the function you
|
|
specify with module_init call. This is the entry function for modules; it tells the
|
|
kernel what functionality the module provides and sets up the kernel to run the
|
|
module’s functions when they are needed. Once it does this, entry function returns
|
|
and the module does nothing until the kernel wants to do something with the code
|
|
that the module provides.
|
|
</p><!-- l. 563 --><p class='indent'> All modules end by calling either <span class='ecbx-1000'>cleanup_module </span>or the function you specify
|
|
with the <span class='ecbx-1000'>module_exit </span>call. This is the exit function for modules; it undoes
|
|
whatever entry function did. It unregisters the functionality that the entry function
|
|
registered.
|
|
|
|
|
|
|
|
</p><!-- l. 567 --><p class='indent'> Every module must have an entry function and an exit function. Since there’s
|
|
more than one way to specify entry and exit functions, I’ll try my best to use the
|
|
terms “entry function” and “exit function”, but if I slip and simply refer
|
|
to them as init_module and cleanup_module, I think you’ll know what I
|
|
mean.
|
|
</p><!-- l. 570 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='functions-available-to-modules'><span class='titlemark'>0.5.2 </span> <a id='x1-210000.5.2'></a>Functions available to modules</h4>
|
|
<!-- l. 572 --><p class='noindent'>Programmers use functions they do not define all the time. A prime example of
|
|
this is <span class='ecbx-1000'>printf()</span>. You use these library functions which are provided by the
|
|
standard C library, libc. The definitions for these functions do not actually
|
|
enter your program until the linking stage, which insures that the code (for
|
|
printf() for example) is available, and fixes the call instruction to point to that
|
|
code.
|
|
</p><!-- l. 576 --><p class='indent'> Kernel modules are different here, too. In the hello world example, you might
|
|
have noticed that we used a function, <span class='ecbx-1000'>pr_info() </span>but did not include a standard I/O
|
|
library. That is because modules are object files whose symbols get resolved upon
|
|
insmod’ing. The definition for the symbols comes from the kernel itself; the only
|
|
external functions you can use are the ones provided by the kernel. If you’re
|
|
curious about what symbols have been exported by your kernel, take a look at
|
|
<span class='ecbx-1000'>/proc/kallsyms</span>.
|
|
</p><!-- l. 581 --><p class='indent'> One point to keep in mind is the difference between library functions
|
|
and system calls. Library functions are higher level, run completely in user
|
|
space and provide a more convenient interface for the programmer to the
|
|
functions that do the real work — system calls. System calls run in kernel
|
|
mode on the user’s behalf and are provided by the kernel itself. The library
|
|
function printf() may look like a very general printing function, but all it
|
|
really does is format the data into strings and write the string data using
|
|
the low-level system call write(), which then sends the data to standard
|
|
output.
|
|
</p><!-- l. 585 --><p class='indent'> Would you like to see what system calls are made by printf()? It is easy! Compile
|
|
the following program:
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb30'><a id='x1-21009r1'></a><span class='ecrm-0500'>1</span><span id='textcolor254'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor255'><span class='ectt-0800'><stdio.h></span></span>
|
|
<a id='x1-21011r2'></a><span class='ecrm-0500'>2</span>
|
|
<a id='x1-21013r3'></a><span class='ecrm-0500'>3</span><span id='textcolor256'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> main(</span><span id='textcolor257'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-21015r4'></a><span class='ecrm-0500'>4</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-21017r5'></a><span class='ecrm-0500'>5</span><span class='ectt-0800'> printf(</span><span id='textcolor258'><span class='ectt-0800'>"hello"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-21019r6'></a><span class='ecrm-0500'>6</span><span class='ectt-0800'> </span><span id='textcolor259'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-21021r7'></a><span class='ecrm-0500'>7</span><span class='ectt-0800'>}</span></pre>
|
|
<!-- l. 599 --><p class='indent'> with <span class='ecbx-1000'>gcc -Wall -o hello hello.c</span>. Run the exectable with <span class='ecbx-1000'>strace ./hello</span>. Are
|
|
you impressed? Every line you see corresponds to a system call. <a href='https://strace.io/'>strace</a> is a handy
|
|
program that gives you details about what system calls a program is making,
|
|
including which call is made, what its arguments are and what it returns. It is an
|
|
invaluable tool for figuring out things like what files a program is trying to access.
|
|
Towards the end, you will see a line which looks like <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>write(1, "hello", 5hello)</span></span></span>.
|
|
There it is. The face behind the printf() mask. You may not be familiar with write,
|
|
since most people use library functions for file I/O (like fopen, fputs, fclose). If that
|
|
|
|
|
|
|
|
is the case, try looking at man 2 write. The 2nd man section is devoted
|
|
to system calls (like kill() and read()). The 3rd man section is devoted to
|
|
library calls, which you would probably be more familiar with (like cosh() and
|
|
random()).
|
|
</p><!-- l. 613 --><p class='indent'> You can even write modules to replace the kernel’s system calls, which we will do
|
|
shortly. Crackers often make use of this sort of thing for backdoors or trojans, but
|
|
you can write your own modules to do more benign things, like have the kernel
|
|
write Tee hee, that tickles! everytime someone tries to delete a file on your
|
|
system.
|
|
</p><!-- l. 616 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='user-space-vs-kernel-space'><span class='titlemark'>0.5.3 </span> <a id='x1-220000.5.3'></a>User Space vs Kernel Space</h4>
|
|
<!-- l. 618 --><p class='noindent'>A kernel is all about access to resources, whether the resource in question happens to
|
|
be a video card, a hard drive or even memory. Programs often compete for the same
|
|
resource. As I just saved this document, updatedb started updating the locate
|
|
database. My vim session and updatedb are both using the hard drive concurrently.
|
|
The kernel needs to keep things orderly, and not give users access to resources
|
|
whenever they feel like it. To this end, a CPU can run in different modes. Each mode
|
|
gives a different level of freedom to do what you want on the system. The Intel 80386
|
|
architecture had 4 of these modes, which were called rings. Unix uses only
|
|
two rings; the highest ring (ring 0, also known as “supervisor mode” where
|
|
everything is allowed to happen) and the lowest ring, which is called “user
|
|
mode”.
|
|
</p><!-- l. 626 --><p class='indent'> Recall the discussion about library functions vs system calls. Typically, you use a
|
|
library function in user mode. The library function calls one or more system calls,
|
|
and these system calls execute on the library function’s behalf, but do so in
|
|
supervisor mode since they are part of the kernel itself. Once the system call
|
|
completes its task, it returns and execution gets transfered back to user
|
|
mode.
|
|
</p><!-- l. 631 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='name-space'><span class='titlemark'>0.5.4 </span> <a id='x1-230000.5.4'></a>Name Space</h4>
|
|
<!-- l. 633 --><p class='noindent'>When you write a small C program, you use variables which are convenient and make
|
|
sense to the reader. If, on the other hand, you are writing routines which will be part
|
|
of a bigger problem, any global variables you have are part of a community of other
|
|
peoples’ global variables; some of the variable names can clash. When a program has
|
|
lots of global variables which aren’t meaningful enough to be distinguished, you get
|
|
namespace pollution. In large projects, effort must be made to remember reserved
|
|
names, and to find ways to develop a scheme for naming unique variable names and
|
|
symbols.
|
|
</p><!-- l. 638 --><p class='indent'> When writing kernel code, even the smallest module will be linked against the
|
|
|
|
|
|
|
|
entire kernel, so this is definitely an issue. The best way to deal with this is to declare
|
|
all your variables as static and to use a well-defined prefix for your symbols. By
|
|
convention, all kernel prefixes are lowercase. If you do not want to declare everything
|
|
as static, another option is to declare a symbol table and register it with a kernel. We
|
|
will get to this later.
|
|
</p><!-- l. 643 --><p class='indent'> The file <span class='ecbx-1000'>/proc/kallsyms </span>holds all the symbols that the kernel knows about and
|
|
which are therefore accessible to your modules since they share the kernel’s
|
|
codespace.
|
|
</p><!-- l. 645 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='code-space'><span class='titlemark'>0.5.5 </span> <a id='x1-240000.5.5'></a>Code space</h4>
|
|
<!-- l. 647 --><p class='noindent'>Memory management is a very complicated subject and the majority of O’Reilly’s
|
|
"<span class='ecti-1000'>Understanding The Linux Kernel</span>" exclusively covers memory management!
|
|
We are not setting out to be experts on memory managements, but we do
|
|
need to know a couple of facts to even begin worrying about writing real
|
|
modules.
|
|
</p><!-- l. 650 --><p class='indent'> If you have not thought about what a segfault really means, you may be surprised
|
|
to hear that pointers do not actually point to memory locations. Not real
|
|
ones, anyway. When a process is created, the kernel sets aside a portion of
|
|
real physical memory and hands it to the process to use for its executing
|
|
code, variables, stack, heap and other things which a computer scientist
|
|
would know about. This memory begins with 0x00000000 and extends up to
|
|
whatever it needs to be. Since the memory space for any two processes do not
|
|
overlap, every process that can access a memory address, say 0xbffff978, would
|
|
be accessing a different location in real physical memory! The processes
|
|
would be accessing an index named 0xbffff978 which points to some kind of
|
|
offset into the region of memory set aside for that particular process. For
|
|
the most part, a process like our Hello, World program can’t access the
|
|
space of another process, although there are ways which we will talk about
|
|
later.
|
|
</p><!-- l. 657 --><p class='indent'> The kernel has its own space of memory as well. Since a module is code which
|
|
can be dynamically inserted and removed in the kernel (as opposed to a
|
|
semi-autonomous object), it shares the kernel’s codespace rather than having its own.
|
|
Therefore, if your module segfaults, the kernel segfaults. And if you start writing
|
|
over data because of an off-by-one error, then you’re trampling on kernel
|
|
data (or code). This is even worse than it sounds, so try your best to be
|
|
careful.
|
|
</p><!-- l. 662 --><p class='indent'> By the way, I would like to point out that the above discussion is true for any
|
|
operating system which uses a monolithic kernel. This is not quite the same thing as
|
|
<span class='ecti-1000'>"building all your modules into the kernel"</span>, although the idea is the same. There are
|
|
things called microkernels which have modules which get their own codespace. The
|
|
GNU Hurd and the Zircon kernel of Google Fuchsia are two examples of a
|
|
microkernel.
|
|
|
|
|
|
|
|
</p><!-- l. 667 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='device-drivers'><span class='titlemark'>0.5.6 </span> <a id='x1-250000.5.6'></a>Device Drivers</h4>
|
|
<!-- l. 669 --><p class='noindent'>One class of module is the device driver, which provides functionality for hardware
|
|
like a serial port. On Unix, each piece of hardware is represented by a file located in
|
|
/dev named a device file which provides the means to communicate with the
|
|
hardware. The device driver provides the communication on behalf of a
|
|
user program. So the es1370.ko sound card device driver might connect the
|
|
/dev/sound device file to the Ensoniq IS1370 sound card. A userspace program like
|
|
mp3blaster can use /dev/sound without ever knowing what kind of sound card is
|
|
installed.
|
|
</p><!-- l. 675 --><p class='indent'> Let’s look at some device files. Here are device files which represent the first three
|
|
partitions on the primary master IDE hard drive:
|
|
|
|
|
|
|
|
</p>
|
|
<pre class='verbatim' id='verbatim-7'>
|
|
$ ls -l /dev/hda[1-3]
|
|
brw-rw---- 1 root disk 3, 1 Jul 5 2000 /dev/hda1
|
|
brw-rw---- 1 root disk 3, 2 Jul 5 2000 /dev/hda2
|
|
brw-rw---- 1 root disk 3, 3 Jul 5 2000 /dev/hda3
|
|
</pre>
|
|
<!-- l. 684 --><p class='nopar'>
|
|
</p><!-- l. 686 --><p class='indent'> Notice the column of numbers separated by a comma. The first number is called
|
|
the device’s major number. The second number is the minor number. The major
|
|
number tells you which driver is used to access the hardware. Each driver is assigned
|
|
a unique major number; all device files with the same major number are controlled
|
|
by the same driver. All the above major numbers are 3, because they’re all controlled
|
|
by the same driver.
|
|
</p><!-- l. 692 --><p class='indent'> The minor number is used by the driver to distinguish between the various
|
|
hardware it controls. Returning to the example above, although all three devices are
|
|
handled by the same driver they have unique minor numbers because the driver sees
|
|
them as being different pieces of hardware.
|
|
</p><!-- l. 695 --><p class='indent'> Devices are divided into two types: character devices and block devices. The
|
|
difference is that block devices have a buffer for requests, so they can choose the best
|
|
order in which to respond to the requests. This is important in the case of storage
|
|
devices, where it is faster to read or write sectors which are close to each other,
|
|
rather than those which are further apart. Another difference is that block devices
|
|
can only accept input and return output in blocks (whose size can vary according to
|
|
the device), whereas character devices are allowed to use as many or as few bytes
|
|
as they like. Most devices in the world are character, because they don’t
|
|
need this type of buffering, and they don’t operate with a fixed block size.
|
|
You can tell whether a device file is for a block device or a character device
|
|
by looking at the first character in the output of ls -l. If it is ‘b’ then it
|
|
is a block device, and if it is ‘c’ then it is a character device. The devices
|
|
you see above are block devices. Here are some character devices (the serial
|
|
ports):
|
|
|
|
|
|
|
|
</p>
|
|
<pre class='verbatim' id='verbatim-8'>
|
|
crw-rw---- 1 root dial 4, 64 Feb 18 23:34 /dev/ttyS0
|
|
crw-r----- 1 root dial 4, 65 Nov 17 10:26 /dev/ttyS1
|
|
crw-rw---- 1 root dial 4, 66 Jul 5 2000 /dev/ttyS2
|
|
crw-rw---- 1 root dial 4, 67 Jul 5 2000 /dev/ttyS3
|
|
</pre>
|
|
<!-- l. 709 --><p class='nopar'>
|
|
</p><!-- l. 712 --><p class='indent'> If you want to see which major numbers have been assigned, you can look at
|
|
<span class='obeylines-h'><span class='verb'><span class='ectt-1000'>Documentation/devices.txt</span></span></span>.
|
|
</p><!-- l. 714 --><p class='indent'> When the system was installed, all of those device files were created by the
|
|
mknod command. To create a new char device named ‘coffee’ with major/minor
|
|
number 12 and 2, simply do mknod /dev/coffee c 12 2. You do not have to put your
|
|
device files into /dev, but it is done by convention. Linus put his device files in /dev,
|
|
and so should you. However, when creating a device file for testing purposes, it is
|
|
probably OK to place it in your working directory where you compile the kernel
|
|
module. Just be sure to put it in the right place when you’re done writing the device
|
|
driver.
|
|
</p><!-- l. 721 --><p class='indent'> I would like to make a few last points which are implicit from the above
|
|
discussion, but I would like to make them explicit just in case. When a device file is
|
|
accessed, the kernel uses the major number of the file to determine which driver
|
|
should be used to handle the access. This means that the kernel doesn’t really need
|
|
to use or even know about the minor number. The driver itself is the only thing that
|
|
cares about the minor number. It uses the minor number to distinguish between
|
|
different pieces of hardware.
|
|
</p><!-- l. 727 --><p class='indent'> By the way, when I say <span class='ecti-1000'>"hardware"</span>, I mean something a bit more abstract
|
|
than a PCI card that you can hold in your hand. Look at these two device
|
|
files:
|
|
|
|
|
|
|
|
</p>
|
|
<pre class='verbatim' id='verbatim-9'>
|
|
$ ls -l /dev/sda /dev/sdb
|
|
brw-rw---- 1 root disk 8, 0 Jan 3 09:02 /dev/sda
|
|
brw-rw---- 1 root disk 8, 16 Jan 3 09:02 /dev/sdb
|
|
</pre>
|
|
<!-- l. 734 --><p class='nopar'>
|
|
</p><!-- l. 736 --><p class='indent'> By now you can look at these two device files and know instantly that they are
|
|
block devices and are handled by same driver (block major 8). Sometimes two device
|
|
files with the same major but different minor number can actually represent the same
|
|
piece of physical hardware. So just be aware that the word “hardware” in our
|
|
discussion can mean something very abstract.
|
|
</p><!-- l. 740 --><p class='noindent'>
|
|
</p>
|
|
<h3 class='sectionHead' id='character-device-drivers'><span class='titlemark'>0.6 </span> <a id='x1-260000.6'></a>Character Device drivers</h3>
|
|
<!-- l. 742 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='the-procops-structure'><span class='titlemark'>0.6.1 </span> <a id='x1-270000.6.1'></a>The proc_ops Structure</h4>
|
|
<!-- l. 744 --><p class='noindent'>The <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>proc_ops</span></span></span> structure is defined in <span class='ecbx-1000'>/usr/include/linux/fs.h</span>, and holds pointers
|
|
to functions defined by the driver that perform various operations on the device.
|
|
Each field of the structure corresponds to the address of some function defined by the
|
|
driver to handle a requested operation.
|
|
</p><!-- l. 747 --><p class='indent'> For example, every character driver needs to define a function that reads from the
|
|
device. The <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>proc_ops</span></span></span> structure holds the address of the module’s function that
|
|
performs that operation. Here is what the definition looks like for kernel
|
|
3.0:
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb31'><a id='x1-27032r1'></a><span class='ecrm-0500'>1</span><span id='textcolor260'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> proc_ops {</span>
|
|
<a id='x1-27034r2'></a><span class='ecrm-0500'>2</span><span class='ectt-0800'> </span><span id='textcolor261'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> module *owner;</span>
|
|
<a id='x1-27036r3'></a><span class='ecrm-0500'>3</span><span class='ectt-0800'> loff_t (*llseek) (</span><span id='textcolor262'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *, loff_t, </span><span id='textcolor263'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-27038r4'></a><span class='ecrm-0500'>4</span><span class='ectt-0800'> </span><span id='textcolor264'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> (*read) (</span><span id='textcolor265'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *, </span><span id='textcolor266'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> __user *, </span><span id='textcolor267'><span class='ectt-0800'>size_t</span></span><span class='ectt-0800'>, loff_t *);</span>
|
|
<a id='x1-27040r5'></a><span class='ecrm-0500'>5</span><span class='ectt-0800'> </span><span id='textcolor268'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> (*write) (</span><span id='textcolor269'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *, </span><span id='textcolor270'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor271'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> __user *, </span><span id='textcolor272'><span class='ectt-0800'>size_t</span></span><span class='ectt-0800'>, loff_t *);</span>
|
|
<a id='x1-27042r6'></a><span class='ecrm-0500'>6</span><span class='ectt-0800'> </span><span id='textcolor273'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> (*aio_read) (</span><span id='textcolor274'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> kiocb *, </span><span id='textcolor275'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor276'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> iovec *, </span><span id='textcolor277'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor278'><span class='ectt-0800'>long</span></span><span class='ectt-0800'>, loff_t);</span>
|
|
<a id='x1-27044r7'></a><span class='ecrm-0500'>7</span><span class='ectt-0800'> </span><span id='textcolor279'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> (*aio_write) (</span><span id='textcolor280'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> kiocb *, </span><span id='textcolor281'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor282'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> iovec *, </span><span id='textcolor283'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor284'><span class='ectt-0800'>long</span></span><span class='ectt-0800'>, loff_t);</span>
|
|
<a id='x1-27046r8'></a><span class='ecrm-0500'>8</span><span class='ectt-0800'> </span><span id='textcolor285'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> (*iterate) (</span><span id='textcolor286'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *, </span><span id='textcolor287'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> dir_context *);</span>
|
|
<a id='x1-27048r9'></a><span class='ecrm-0500'>9</span><span class='ectt-0800'> </span><span id='textcolor288'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> int (*poll) (</span><span id='textcolor289'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *, </span><span id='textcolor290'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> poll_table_struct *);</span>
|
|
<a id='x1-27050r10'></a><span class='ecrm-0500'>10</span><span class='ectt-0800'> </span><span id='textcolor291'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> (*unlocked_ioctl) (</span><span id='textcolor292'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *, </span><span id='textcolor293'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor294'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>, </span><span id='textcolor295'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor296'><span class='ectt-0800'>long</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-27052r11'></a><span class='ecrm-0500'>11</span><span class='ectt-0800'> </span><span id='textcolor297'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> (*compat_ioctl) (</span><span id='textcolor298'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *, </span><span id='textcolor299'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor300'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>, </span><span id='textcolor301'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor302'><span class='ectt-0800'>long</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-27054r12'></a><span class='ecrm-0500'>12</span><span class='ectt-0800'> </span><span id='textcolor303'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> (*mmap) (</span><span id='textcolor304'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *, </span><span id='textcolor305'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> vm_area_struct *);</span>
|
|
<a id='x1-27056r13'></a><span class='ecrm-0500'>13</span><span class='ectt-0800'> </span><span id='textcolor306'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> (*open) (</span><span id='textcolor307'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> inode *, </span><span id='textcolor308'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *);</span>
|
|
<a id='x1-27058r14'></a><span class='ecrm-0500'>14</span><span class='ectt-0800'> </span><span id='textcolor309'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> (*flush) (</span><span id='textcolor310'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *, fl_owner_t id);</span>
|
|
<a id='x1-27060r15'></a><span class='ecrm-0500'>15</span><span class='ectt-0800'> </span><span id='textcolor311'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> (*release) (</span><span id='textcolor312'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> inode *, </span><span id='textcolor313'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *);</span>
|
|
<a id='x1-27062r16'></a><span class='ecrm-0500'>16</span><span class='ectt-0800'> </span><span id='textcolor314'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> (*fsync) (</span><span id='textcolor315'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *, loff_t, loff_t, </span><span id='textcolor316'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> datasync);</span>
|
|
<a id='x1-27064r17'></a><span class='ecrm-0500'>17</span><span class='ectt-0800'> </span><span id='textcolor317'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> (*aio_fsync) (</span><span id='textcolor318'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> kiocb *, </span><span id='textcolor319'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> datasync);</span>
|
|
<a id='x1-27066r18'></a><span class='ecrm-0500'>18</span><span class='ectt-0800'> </span><span id='textcolor320'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> (*fasync) (</span><span id='textcolor321'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>, </span><span id='textcolor322'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *, </span><span id='textcolor323'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-27068r19'></a><span class='ecrm-0500'>19</span><span class='ectt-0800'> </span><span id='textcolor324'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> (*lock) (</span><span id='textcolor325'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *, </span><span id='textcolor326'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>, </span><span id='textcolor327'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file_lock *);</span>
|
|
<a id='x1-27070r20'></a><span class='ecrm-0500'>20</span><span class='ectt-0800'> </span><span id='textcolor328'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> (*sendpage) (</span><span id='textcolor329'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *, </span><span id='textcolor330'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> page *, </span><span id='textcolor331'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>, </span><span id='textcolor332'><span class='ectt-0800'>size_t</span></span><span class='ectt-0800'>, loff_t *, </span><span id='textcolor333'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-27072r21'></a><span class='ecrm-0500'>21</span><span class='ectt-0800'> </span><span id='textcolor334'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> long (*get_unmapped_area)(</span><span id='textcolor335'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *, </span><span id='textcolor336'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor337'><span class='ectt-0800'>long</span></span><span class='ectt-0800'>, </span><span id='textcolor338'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor339'><span class='ectt-0800'>long</span></span><span class='ectt-0800'>, </span><span id='textcolor340'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor341'><span class='ectt-0800'>long</span></span><span class='ectt-0800'>, </span><span id='textcolor342'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor343'><span class='ectt-0800'>long</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-27074r22'></a><span class='ecrm-0500'>22</span><span class='ectt-0800'> </span><span id='textcolor344'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> (*check_flags)(</span><span id='textcolor345'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-27076r23'></a><span class='ecrm-0500'>23</span><span class='ectt-0800'> </span><span id='textcolor346'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> (*flock) (</span><span id='textcolor347'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *, </span><span id='textcolor348'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>, </span><span id='textcolor349'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file_lock *);</span>
|
|
<a id='x1-27078r24'></a><span class='ecrm-0500'>24</span><span class='ectt-0800'> </span><span id='textcolor350'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> (*splice_write)(</span><span id='textcolor351'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> pipe_inode_info *, </span><span id='textcolor352'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *, loff_t *, </span><span id='textcolor353'><span class='ectt-0800'>size_t</span></span><span class='ectt-0800'>, </span><span id='textcolor354'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor355'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-27080r25'></a><span class='ecrm-0500'>25</span><span class='ectt-0800'> </span><span id='textcolor356'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> (*splice_read)(</span><span id='textcolor357'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *, loff_t *, </span><span id='textcolor358'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> pipe_inode_info *, </span><span id='textcolor359'><span class='ectt-0800'>size_t</span></span><span class='ectt-0800'>, </span><span id='textcolor360'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor361'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-27082r26'></a><span class='ecrm-0500'>26</span><span class='ectt-0800'> </span><span id='textcolor362'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> (*setlease)(</span><span id='textcolor363'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *, </span><span id='textcolor364'><span class='ectt-0800'>long</span></span><span class='ectt-0800'>, </span><span id='textcolor365'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file_lock **);</span>
|
|
<a id='x1-27084r27'></a><span class='ecrm-0500'>27</span><span class='ectt-0800'> </span><span id='textcolor366'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> (*fallocate)(</span><span id='textcolor367'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *file, </span><span id='textcolor368'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> mode, loff_t offset,</span>
|
|
<a id='x1-27086r28'></a><span class='ecrm-0500'>28 </span><span class='ectt-0800'> loff_t len);</span>
|
|
<a id='x1-27088r29'></a><span class='ecrm-0500'>29</span><span class='ectt-0800'> </span><span id='textcolor369'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> (*show_fdinfo)(</span><span id='textcolor370'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> seq_file *m, </span><span id='textcolor371'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *f);</span>
|
|
<a id='x1-27090r30'></a><span class='ecrm-0500'>30</span><span class='ectt-0800'>};</span></pre>
|
|
<!-- l. 784 --><p class='indent'> Some operations are not implemented by a driver. For example, a driver that
|
|
handles a video card will not need to read from a directory structure. The
|
|
corresponding entries in the <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>proc_ops</span></span></span> structure should be set to NULL.
|
|
</p><!-- l. 788 --><p class='indent'> There is a gcc extension that makes assigning to this structure more convenient.
|
|
You will see it in modern drivers, and may catch you by surprise. This is what the
|
|
new way of assigning to the structure looks like:
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb32'><a id='x1-27098r1'></a><span class='ecrm-0500'>1</span><span id='textcolor372'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> proc_ops fops = {</span>
|
|
<a id='x1-27100r2'></a><span class='ecrm-0500'>2 </span><span class='ectt-0800'>proc_read: device_read,</span>
|
|
<a id='x1-27102r3'></a><span class='ecrm-0500'>3 </span><span class='ectt-0800'>proc_write: device_write,</span>
|
|
<a id='x1-27104r4'></a><span class='ecrm-0500'>4 </span><span class='ectt-0800'>proc_open: device_open,</span>
|
|
<a id='x1-27106r5'></a><span class='ecrm-0500'>5 </span><span class='ectt-0800'>proc_release: device_release</span>
|
|
<a id='x1-27108r6'></a><span class='ecrm-0500'>6</span><span class='ectt-0800'>};</span></pre>
|
|
|
|
|
|
|
|
<!-- l. 801 --><p class='indent'> However, there is also a C99 way of assigning to elements of a structure,
|
|
<a href='https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html'>designated initializers</a>, and this is definitely preferred over using the GNU extension.
|
|
You should use this syntax in case someone wants to port your driver. It will help
|
|
with compatibility:
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb33'><a id='x1-27116r1'></a><span class='ecrm-0500'>1</span><span id='textcolor373'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> proc_ops fops = {</span>
|
|
<a id='x1-27118r2'></a><span class='ecrm-0500'>2 </span><span class='ectt-0800'>.proc_read = device_read,</span>
|
|
<a id='x1-27120r3'></a><span class='ecrm-0500'>3 </span><span class='ectt-0800'>.proc_write = device_write,</span>
|
|
<a id='x1-27122r4'></a><span class='ecrm-0500'>4 </span><span class='ectt-0800'>.proc_open = device_open,</span>
|
|
<a id='x1-27124r5'></a><span class='ecrm-0500'>5 </span><span class='ectt-0800'>.proc_release = device_release</span>
|
|
<a id='x1-27126r6'></a><span class='ecrm-0500'>6</span><span class='ectt-0800'>};</span></pre>
|
|
<!-- l. 814 --><p class='indent'> The meaning is clear, and you should be aware that any member of the
|
|
structure which you do not explicitly assign will be initialized to NULL by
|
|
gcc.
|
|
</p><!-- l. 816 --><p class='indent'> An instance of struct proc_ops containing pointers to functions that are used to
|
|
implement read, write, open, … syscalls is commonly named fops.
|
|
</p><!-- l. 818 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='the-file-structure'><span class='titlemark'>0.6.2 </span> <a id='x1-280000.6.2'></a>The file structure</h4>
|
|
<!-- l. 821 --><p class='noindent'>Each device is represented in the kernel by a file structure, which is defined in
|
|
<span class='ecbx-1000'>linux/fs.h</span>. Be aware that a file is a kernel level structure and never appears in a
|
|
user space program. It is not the same thing as a <span class='ecbx-1000'>FILE</span>, which is defined by glibc and
|
|
would never appear in a kernel space function. Also, its name is a bit misleading; it
|
|
represents an abstract open ‘file’, not a file on a disk, which is represented by a
|
|
structure named inode.
|
|
</p><!-- l. 826 --><p class='indent'> An instance of struct file is commonly named filp. You’ll also see it refered to as
|
|
struct file file. Resist the temptation.
|
|
</p><!-- l. 829 --><p class='indent'> Go ahead and look at the definition of file. Most of the entries you see, like struct
|
|
dentry are not used by device drivers, and you can ignore them. This is because
|
|
drivers do not fill file directly; they only use structures contained in file which are
|
|
created elsewhere.
|
|
</p><!-- l. 833 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='registering-a-device'><span class='titlemark'>0.6.3 </span> <a id='x1-290000.6.3'></a>Registering A Device</h4>
|
|
<!-- l. 835 --><p class='noindent'>As discussed earlier, char devices are accessed through device files, usually located in
|
|
/dev. This is by convention. When writing a driver, it is OK to put the
|
|
device file in your current directory. Just make sure you place it in /dev for a
|
|
production driver. The major number tells you which driver handles which
|
|
device file. The minor number is used only by the driver itself to differentiate
|
|
which device it is operating on, just in case the driver handles more than one
|
|
device.
|
|
</p><!-- l. 841 --><p class='indent'> Adding a driver to your system means registering it with the kernel.
|
|
This is synonymous with assigning it a major number during the module’s
|
|
initialization. You do this by using the <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>register_chrdev</span></span></span> function, defined by
|
|
|
|
|
|
|
|
linux/fs.h.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb34'><a id='x1-29003r1'></a><span class='ecrm-0500'>1</span><span id='textcolor374'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> register_chrdev(</span><span id='textcolor375'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor376'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> major, </span><span id='textcolor377'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor378'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *name, </span><span id='textcolor379'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> proc_ops *fops);</span></pre>
|
|
<!-- l. 849 --><p class='indent'> where unsigned int major is the major number you want to request, <span class='ecti-1000'>const char
|
|
</span><span class='ecti-1000'>*name </span>is the name of the device as it will appear in <span class='ecbx-1000'>/proc/devices </span>and <span class='ecti-1000'>struct
|
|
</span><span class='ecti-1000'>proc_ops *fops </span>is a pointer to the proc_ops table for your driver. A negative return
|
|
value means the registration failed. Note that we didn’t pass the minor number to
|
|
register_chrdev. That is because the kernel doesn’t care about the minor number;
|
|
only our driver uses it.
|
|
</p><!-- l. 853 --><p class='indent'> Now the question is, how do you get a major number without hijacking one that’s
|
|
already in use? The easiest way would be to look through Documentation
|
|
/devices.txt and pick an unused one. That is a bad way of doing things
|
|
because you will never be sure if the number you picked will be assigned later.
|
|
The answer is that you can ask the kernel to assign you a dynamic major
|
|
number.
|
|
</p><!-- l. 859 --><p class='indent'> If you pass a major number of 0 to <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>register_chrdev</span></span></span>, the return value will be the
|
|
dynamically allocated major number. The downside is that you can not make a
|
|
device file in advance, since you don’t know what the major number will be. There
|
|
are a couple of ways to do this. First, the driver itself can print the newly assigned
|
|
number and we can make the device file by hand. Second, the newly registered device
|
|
will have an entry in <span class='ecbx-1000'>/proc/devices</span>, and we can either make the device file by hand
|
|
or write a shell script to read the file in and make the device file. The third method is
|
|
we can have our driver make the the device file using the <span class='ecbx-1000'>device_create</span>
|
|
function after a successful registration and <span class='ecbx-1000'>device_destroy </span>during the call to
|
|
cleanup_module.
|
|
</p><!-- l. 866 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='unregistering-a-device'><span class='titlemark'>0.6.4 </span> <a id='x1-300000.6.4'></a>Unregistering A Device</h4>
|
|
<!-- l. 868 --><p class='noindent'>We can not allow the kernel module to be rmmod’ed whenever root feels like it. If the
|
|
device file is opened by a process and then we remove the kernel module, using the
|
|
file would cause a call to the memory location where the appropriate function
|
|
(read/write) used to be. If we are lucky, no other code was loaded there, and we’ll get
|
|
an ugly error message. If we are unlucky, another kernel module was loaded into the
|
|
same location, which means a jump into the middle of another function within the
|
|
kernel. The results of this would be impossible to predict, but they can not be very
|
|
positive.
|
|
</p><!-- l. 874 --><p class='indent'> Normally, when you don’t want to allow something, you return an error code
|
|
(a negative number) from the function which is supposed to do it. With
|
|
cleanup_module that’s impossible because it is a void function. However, there is a
|
|
counter which keeps track of how many processes are using your module. You can see
|
|
what its value is by looking at the 3rd field of <span class='ecbx-1000'>/proc/modules</span>. If this number isn’t
|
|
zero, rmmod will fail. Note that you don’t have to check the counter from within
|
|
|
|
|
|
|
|
cleanup_module because the check will be performed for you by the system call
|
|
sys_delete_module, defined in <span class='ecbx-1000'>linux/module.c</span>. You should not use this counter
|
|
directly, but there are functions defined in <span class='ecbx-1000'>linux/module.h </span>which let you increase,
|
|
decrease and display this counter:
|
|
</p>
|
|
<ul class='itemize1'>
|
|
<li class='itemize'>try_module_get(THIS_MODULE): Increment the use count.
|
|
</li>
|
|
<li class='itemize'>module_put(THIS_MODULE): Decrement the use count.</li></ul>
|
|
<!-- l. 886 --><p class='indent'> It is important to keep the counter accurate; if you ever do lose track of the
|
|
correct usage count, you will never be able to unload the module; it’s now reboot
|
|
time, boys and girls. This is bound to happen to you sooner or later during a
|
|
module’s development.
|
|
</p><!-- l. 889 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='chardevc'><span class='titlemark'>0.6.5 </span> <a id='x1-310000.6.5'></a>chardev.c</h4>
|
|
<!-- l. 891 --><p class='noindent'>The next code sample creates a char driver named chardev. You can cat its device
|
|
file.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb35'><a id='x1-31003r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>cat /proc/devices</span></pre>
|
|
<!-- l. 898 --><p class='indent'> (or open the file with a program) and the driver will put the number of times the
|
|
device file has been read from into the file. We do not support writing to the file
|
|
(like <span class='ecbx-1000'>echo "hi" > /dev/hello</span>), but catch these attempts and tell the user
|
|
that the operation is not supported. Don’t worry if you don’t see what we
|
|
do with the data we read into the buffer; we don’t do much with it. We
|
|
simply read in the data and print a message acknowledging that we received
|
|
it.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb36'><a id='x1-31005r1'></a><span class='ecrm-0500'>1</span><span id='textcolor380'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-31007r2'></a><span class='ecrm-0500'>2</span><span id='textcolor381'><span class='ectt-0800'> * chardev.c: Creates a read-only char device that says how many times</span></span>
|
|
<a id='x1-31009r3'></a><span class='ecrm-0500'>3</span><span id='textcolor382'><span class='ectt-0800'> * you</span><span class='tctt-0800'>'</span><span class='ectt-0800'>ve read from the dev file</span></span>
|
|
<a id='x1-31011r4'></a><span class='ecrm-0500'>4</span><span id='textcolor383'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-31013r5'></a><span class='ecrm-0500'>5</span>
|
|
<a id='x1-31015r6'></a><span class='ecrm-0500'>6</span><span id='textcolor384'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor385'><span class='ectt-0800'><linux/cdev.h></span></span>
|
|
<a id='x1-31017r7'></a><span class='ecrm-0500'>7</span><span id='textcolor386'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor387'><span class='ectt-0800'><linux/delay.h></span></span>
|
|
<a id='x1-31019r8'></a><span class='ecrm-0500'>8</span><span id='textcolor388'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor389'><span class='ectt-0800'><linux/device.h></span></span>
|
|
<a id='x1-31021r9'></a><span class='ecrm-0500'>9</span><span id='textcolor390'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor391'><span class='ectt-0800'><linux/fs.h></span></span>
|
|
<a id='x1-31023r10'></a><span class='ecrm-0500'>10</span><span id='textcolor392'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor393'><span class='ectt-0800'><linux/init.h></span></span>
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<a id='x1-31025r11'></a><span class='ecrm-0500'>11</span><span id='textcolor394'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor395'><span class='ectt-0800'><linux/irq.h></span></span>
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<a id='x1-31027r12'></a><span class='ecrm-0500'>12</span><span id='textcolor396'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor397'><span class='ectt-0800'><linux/kernel.h></span></span>
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<a id='x1-31029r13'></a><span class='ecrm-0500'>13</span><span id='textcolor398'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor399'><span class='ectt-0800'><linux/module.h></span></span>
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<a id='x1-31031r14'></a><span class='ecrm-0500'>14</span><span id='textcolor400'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor401'><span class='ectt-0800'><linux/poll.h></span></span>
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<a id='x1-31033r15'></a><span class='ecrm-0500'>15</span>
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<a id='x1-31035r16'></a><span class='ecrm-0500'>16</span><span id='textcolor402'><span class='ectt-0800'>/*</span></span>
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<a id='x1-31037r17'></a><span class='ecrm-0500'>17</span><span id='textcolor403'><span class='ectt-0800'> * Prototypes - this would normally go in a .h file</span></span>
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<a id='x1-31039r18'></a><span class='ecrm-0500'>18</span><span id='textcolor404'><span class='ectt-0800'> */</span></span>
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<a id='x1-31041r19'></a><span class='ecrm-0500'>19</span><span id='textcolor405'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> init_module(</span><span id='textcolor406'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>);</span>
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<a id='x1-31043r20'></a><span class='ecrm-0500'>20</span><span id='textcolor407'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> cleanup_module(</span><span id='textcolor408'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>);</span>
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<a id='x1-31045r21'></a><span class='ecrm-0500'>21</span><span id='textcolor409'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor410'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> device_open(</span><span id='textcolor411'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> inode *, </span><span id='textcolor412'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *);</span>
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<a id='x1-31047r22'></a><span class='ecrm-0500'>22</span><span id='textcolor413'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor414'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> device_release(</span><span id='textcolor415'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> inode *, </span><span id='textcolor416'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *);</span>
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<a id='x1-31049r23'></a><span class='ecrm-0500'>23</span><span id='textcolor417'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor418'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> device_read(</span><span id='textcolor419'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *, </span><span id='textcolor420'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *, </span><span id='textcolor421'><span class='ectt-0800'>size_t</span></span><span class='ectt-0800'>, loff_t *);</span>
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<a id='x1-31051r24'></a><span class='ecrm-0500'>24</span><span id='textcolor422'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor423'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> device_write(</span><span id='textcolor424'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *, </span><span id='textcolor425'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor426'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *, </span><span id='textcolor427'><span class='ectt-0800'>size_t</span></span><span class='ectt-0800'>, loff_t *);</span>
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<a id='x1-31053r25'></a><span class='ecrm-0500'>25</span>
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<a id='x1-31055r26'></a><span class='ecrm-0500'>26</span><span id='textcolor428'><span class='ectt-0800'>#define SUCCESS 0</span></span>
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<a id='x1-31057r27'></a><span class='ecrm-0500'>27</span><span id='textcolor429'><span class='ectt-0800'>#define DEVICE_NAME "chardev" </span></span><span id='textcolor430'><span class='ectt-0800'>/* Dev name as it appears in /proc/devices */</span></span>
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<a id='x1-31059r28'></a><span class='ecrm-0500'>28</span><span id='textcolor431'><span class='ectt-0800'>#define BUF_LEN 80 </span></span><span id='textcolor432'><span class='ectt-0800'>/* Max length of the message from the device */</span></span>
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<a id='x1-31061r29'></a><span class='ecrm-0500'>29</span>
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<a id='x1-31063r30'></a><span class='ecrm-0500'>30</span><span id='textcolor433'><span class='ectt-0800'>/*</span></span>
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<a id='x1-31065r31'></a><span class='ecrm-0500'>31</span><span id='textcolor434'><span class='ectt-0800'> * Global variables are declared as static, so are global within the file.</span></span>
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<a id='x1-31067r32'></a><span class='ecrm-0500'>32</span><span id='textcolor435'><span class='ectt-0800'> */</span></span>
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<a id='x1-31069r33'></a><span class='ecrm-0500'>33</span>
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<a id='x1-31071r34'></a><span class='ecrm-0500'>34</span><span id='textcolor436'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor437'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> Major; </span><span id='textcolor438'><span class='ectt-0800'>/* Major number assigned to our device driver */</span></span>
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<a id='x1-31073r35'></a><span class='ecrm-0500'>35</span><span id='textcolor439'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor440'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> Device_Open = 0; </span><span id='textcolor441'><span class='ectt-0800'>/* Is device open?</span></span>
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<a id='x1-31075r36'></a><span class='ecrm-0500'>36</span><span id='textcolor442'><span class='ectt-0800'> * Used to prevent multiple access to device */</span></span>
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<a id='x1-31077r37'></a><span class='ecrm-0500'>37</span><span id='textcolor443'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor444'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> msg[BUF_LEN]; </span><span id='textcolor445'><span class='ectt-0800'>/* The msg the device will give when asked */</span></span>
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<a id='x1-31079r38'></a><span class='ecrm-0500'>38</span><span id='textcolor446'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor447'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *msg_Ptr;</span>
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<a id='x1-31081r39'></a><span class='ecrm-0500'>39</span>
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<a id='x1-31083r40'></a><span class='ecrm-0500'>40</span><span id='textcolor448'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor449'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> class *cls;</span>
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<a id='x1-31085r41'></a><span class='ecrm-0500'>41</span>
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<a id='x1-31087r42'></a><span class='ecrm-0500'>42</span><span id='textcolor450'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor451'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file_operations chardev_fops = {.read = device_read,</span>
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<a id='x1-31089r43'></a><span class='ecrm-0500'>43</span><span class='ectt-0800'> .write = device_write,</span>
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<a id='x1-31091r44'></a><span class='ecrm-0500'>44</span><span class='ectt-0800'> .open = device_open,</span>
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<a id='x1-31093r45'></a><span class='ecrm-0500'>45</span><span class='ectt-0800'> .release = device_release};</span>
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<a id='x1-31095r46'></a><span class='ecrm-0500'>46</span>
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<a id='x1-31097r47'></a><span class='ecrm-0500'>47</span><span id='textcolor452'><span class='ectt-0800'>/*</span></span>
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<a id='x1-31099r48'></a><span class='ecrm-0500'>48</span><span id='textcolor453'><span class='ectt-0800'> * This function is called when the module is loaded</span></span>
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<a id='x1-31101r49'></a><span class='ecrm-0500'>49</span><span id='textcolor454'><span class='ectt-0800'> */</span></span>
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<a id='x1-31103r50'></a><span class='ecrm-0500'>50</span><span id='textcolor455'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> init_module(</span><span id='textcolor456'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
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<a id='x1-31105r51'></a><span class='ecrm-0500'>51</span><span class='ectt-0800'>{</span>
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<a id='x1-31107r52'></a><span class='ecrm-0500'>52</span><span class='ectt-0800'> Major = register_chrdev(0, DEVICE_NAME, &chardev_fops);</span>
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<a id='x1-31109r53'></a><span class='ecrm-0500'>53</span>
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<a id='x1-31111r54'></a><span class='ecrm-0500'>54</span><span class='ectt-0800'> </span><span id='textcolor457'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (Major < 0) {</span>
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<a id='x1-31113r55'></a><span class='ecrm-0500'>55</span><span class='ectt-0800'> pr_alert(</span><span id='textcolor458'><span class='ectt-0800'>"Registering char device failed with %d</span></span><span id='textcolor459'><span class='ectt-0800'>\n</span></span><span id='textcolor460'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, Major);</span>
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<a id='x1-31115r56'></a><span class='ecrm-0500'>56</span><span class='ectt-0800'> </span><span id='textcolor461'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> Major;</span>
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<a id='x1-31117r57'></a><span class='ecrm-0500'>57</span><span class='ectt-0800'> }</span>
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<a id='x1-31119r58'></a><span class='ecrm-0500'>58</span>
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<a id='x1-31121r59'></a><span class='ecrm-0500'>59</span><span class='ectt-0800'> pr_info(</span><span id='textcolor462'><span class='ectt-0800'>"I was assigned major number %d.</span></span><span id='textcolor463'><span class='ectt-0800'>\n</span></span><span id='textcolor464'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, Major);</span>
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<a id='x1-31123r60'></a><span class='ecrm-0500'>60</span>
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<a id='x1-31125r61'></a><span class='ecrm-0500'>61</span><span class='ectt-0800'> cls = class_create(THIS_MODULE, DEVICE_NAME);</span>
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<a id='x1-31127r62'></a><span class='ecrm-0500'>62</span><span class='ectt-0800'> device_create(cls, NULL, MKDEV(Major, 0), NULL, DEVICE_NAME);</span>
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<a id='x1-31129r63'></a><span class='ecrm-0500'>63</span>
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<a id='x1-31131r64'></a><span class='ecrm-0500'>64</span><span class='ectt-0800'> pr_info(</span><span id='textcolor465'><span class='ectt-0800'>"Device created on /dev/%s</span></span><span id='textcolor466'><span class='ectt-0800'>\n</span></span><span id='textcolor467'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, DEVICE_NAME);</span>
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<a id='x1-31133r65'></a><span class='ecrm-0500'>65</span>
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<a id='x1-31135r66'></a><span class='ecrm-0500'>66</span><span class='ectt-0800'> </span><span id='textcolor468'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> SUCCESS;</span>
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<a id='x1-31137r67'></a><span class='ecrm-0500'>67</span><span class='ectt-0800'>}</span>
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<a id='x1-31139r68'></a><span class='ecrm-0500'>68</span>
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<a id='x1-31141r69'></a><span class='ecrm-0500'>69</span><span id='textcolor469'><span class='ectt-0800'>/*</span></span>
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<a id='x1-31143r70'></a><span class='ecrm-0500'>70</span><span id='textcolor470'><span class='ectt-0800'> * This function is called when the module is unloaded</span></span>
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<a id='x1-31145r71'></a><span class='ecrm-0500'>71</span><span id='textcolor471'><span class='ectt-0800'> */</span></span>
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<a id='x1-31147r72'></a><span class='ecrm-0500'>72</span><span id='textcolor472'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> cleanup_module(</span><span id='textcolor473'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
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<a id='x1-31149r73'></a><span class='ecrm-0500'>73</span><span class='ectt-0800'>{</span>
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<a id='x1-31151r74'></a><span class='ecrm-0500'>74</span><span class='ectt-0800'> device_destroy(cls, MKDEV(Major, 0));</span>
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<a id='x1-31153r75'></a><span class='ecrm-0500'>75</span><span class='ectt-0800'> class_destroy(cls);</span>
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<a id='x1-31155r76'></a><span class='ecrm-0500'>76</span>
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<a id='x1-31157r77'></a><span class='ecrm-0500'>77</span><span class='ectt-0800'> </span><span id='textcolor474'><span class='ectt-0800'>/*</span></span>
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<a id='x1-31159r78'></a><span class='ecrm-0500'>78</span><span id='textcolor475'><span class='ectt-0800'> * Unregister the device</span></span>
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<a id='x1-31161r79'></a><span class='ecrm-0500'>79</span><span id='textcolor476'><span class='ectt-0800'> */</span></span>
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<a id='x1-31163r80'></a><span class='ecrm-0500'>80</span><span class='ectt-0800'> unregister_chrdev(Major, DEVICE_NAME);</span>
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<a id='x1-31165r81'></a><span class='ecrm-0500'>81</span><span class='ectt-0800'>}</span>
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<a id='x1-31167r82'></a><span class='ecrm-0500'>82</span>
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<a id='x1-31169r83'></a><span class='ecrm-0500'>83</span><span id='textcolor477'><span class='ectt-0800'>/*</span></span>
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<a id='x1-31171r84'></a><span class='ecrm-0500'>84</span><span id='textcolor478'><span class='ectt-0800'> * Methods</span></span>
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<a id='x1-31173r85'></a><span class='ecrm-0500'>85</span><span id='textcolor479'><span class='ectt-0800'> */</span></span>
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<a id='x1-31175r86'></a><span class='ecrm-0500'>86</span>
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<a id='x1-31177r87'></a><span class='ecrm-0500'>87</span><span id='textcolor480'><span class='ectt-0800'>/*</span></span>
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<a id='x1-31179r88'></a><span class='ecrm-0500'>88</span><span id='textcolor481'><span class='ectt-0800'> * Called when a process tries to open the device file, like</span></span>
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<a id='x1-31181r89'></a><span class='ecrm-0500'>89</span><span id='textcolor482'><span class='ectt-0800'> * "sudo cat /dev/chardev"</span></span>
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<a id='x1-31183r90'></a><span class='ecrm-0500'>90</span><span id='textcolor483'><span class='ectt-0800'> */</span></span>
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<a id='x1-31185r91'></a><span class='ecrm-0500'>91</span><span id='textcolor484'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor485'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> device_open(</span><span id='textcolor486'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> inode *inode, </span><span id='textcolor487'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *file)</span>
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<a id='x1-31187r92'></a><span class='ecrm-0500'>92</span><span class='ectt-0800'>{</span>
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<a id='x1-31189r93'></a><span class='ecrm-0500'>93</span><span class='ectt-0800'> </span><span id='textcolor488'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor489'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> counter = 0;</span>
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<a id='x1-31191r94'></a><span class='ecrm-0500'>94</span>
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<a id='x1-31193r95'></a><span class='ecrm-0500'>95</span><span class='ectt-0800'> </span><span id='textcolor490'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (Device_Open)</span>
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<a id='x1-31195r96'></a><span class='ecrm-0500'>96</span><span class='ectt-0800'> </span><span id='textcolor491'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -EBUSY;</span>
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<a id='x1-31197r97'></a><span class='ecrm-0500'>97</span>
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<a id='x1-31199r98'></a><span class='ecrm-0500'>98</span><span class='ectt-0800'> Device_Open++;</span>
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<a id='x1-31201r99'></a><span class='ecrm-0500'>99</span><span class='ectt-0800'> sprintf(msg, </span><span id='textcolor492'><span class='ectt-0800'>"I already told you %d times Hello world!</span></span><span id='textcolor493'><span class='ectt-0800'>\n</span></span><span id='textcolor494'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, counter++);</span>
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<a id='x1-31203r100'></a><span class='ecrm-0500'>100</span><span class='ectt-0800'> msg_Ptr = msg;</span>
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<a id='x1-31205r101'></a><span class='ecrm-0500'>101</span><span class='ectt-0800'> try_module_get(THIS_MODULE);</span>
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<a id='x1-31207r102'></a><span class='ecrm-0500'>102</span>
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<a id='x1-31209r103'></a><span class='ecrm-0500'>103</span><span class='ectt-0800'> </span><span id='textcolor495'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> SUCCESS;</span>
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<a id='x1-31211r104'></a><span class='ecrm-0500'>104</span><span class='ectt-0800'>}</span>
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<a id='x1-31213r105'></a><span class='ecrm-0500'>105</span>
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<a id='x1-31215r106'></a><span class='ecrm-0500'>106</span><span id='textcolor496'><span class='ectt-0800'>/*</span></span>
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<a id='x1-31217r107'></a><span class='ecrm-0500'>107</span><span id='textcolor497'><span class='ectt-0800'> * Called when a process closes the device file.</span></span>
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<a id='x1-31219r108'></a><span class='ecrm-0500'>108</span><span id='textcolor498'><span class='ectt-0800'> */</span></span>
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|
<a id='x1-31221r109'></a><span class='ecrm-0500'>109</span><span id='textcolor499'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor500'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> device_release(</span><span id='textcolor501'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> inode *inode, </span><span id='textcolor502'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *file)</span>
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|
<a id='x1-31223r110'></a><span class='ecrm-0500'>110</span><span class='ectt-0800'>{</span>
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<a id='x1-31225r111'></a><span class='ecrm-0500'>111</span><span class='ectt-0800'> Device_Open--; </span><span id='textcolor503'><span class='ectt-0800'>/* We</span><span class='tctt-0800'>'</span><span class='ectt-0800'>re now ready for our next caller */</span></span>
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<a id='x1-31227r112'></a><span class='ecrm-0500'>112</span>
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<a id='x1-31229r113'></a><span class='ecrm-0500'>113</span><span class='ectt-0800'> </span><span id='textcolor504'><span class='ectt-0800'>/*</span></span>
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<a id='x1-31231r114'></a><span class='ecrm-0500'>114</span><span id='textcolor505'><span class='ectt-0800'> * Decrement the usage count, or else once you opened the file, you</span><span class='tctt-0800'>'</span><span class='ectt-0800'>ll</span></span>
|
|
<a id='x1-31233r115'></a><span class='ecrm-0500'>115</span><span id='textcolor506'><span class='ectt-0800'> * never get get rid of the module.</span></span>
|
|
<a id='x1-31235r116'></a><span class='ecrm-0500'>116</span><span id='textcolor507'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-31237r117'></a><span class='ecrm-0500'>117</span><span class='ectt-0800'> module_put(THIS_MODULE);</span>
|
|
<a id='x1-31239r118'></a><span class='ecrm-0500'>118</span>
|
|
<a id='x1-31241r119'></a><span class='ecrm-0500'>119</span><span class='ectt-0800'> </span><span id='textcolor508'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> SUCCESS;</span>
|
|
<a id='x1-31243r120'></a><span class='ecrm-0500'>120</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-31245r121'></a><span class='ecrm-0500'>121</span>
|
|
<a id='x1-31247r122'></a><span class='ecrm-0500'>122</span><span id='textcolor509'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-31249r123'></a><span class='ecrm-0500'>123</span><span id='textcolor510'><span class='ectt-0800'> * Called when a process, which already opened the dev file, attempts to</span></span>
|
|
<a id='x1-31251r124'></a><span class='ecrm-0500'>124</span><span id='textcolor511'><span class='ectt-0800'> * read from it.</span></span>
|
|
<a id='x1-31253r125'></a><span class='ecrm-0500'>125</span><span id='textcolor512'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-31255r126'></a><span class='ecrm-0500'>126</span><span id='textcolor513'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor514'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> device_read(</span><span id='textcolor515'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *filp, </span><span id='textcolor516'><span class='ectt-0800'>/* see include/linux/fs.h */</span></span>
|
|
<a id='x1-31257r127'></a><span class='ecrm-0500'>127</span><span class='ectt-0800'> </span><span id='textcolor517'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *buffer, </span><span id='textcolor518'><span class='ectt-0800'>/* buffer to fill with data */</span></span>
|
|
<a id='x1-31259r128'></a><span class='ecrm-0500'>128</span><span class='ectt-0800'> </span><span id='textcolor519'><span class='ectt-0800'>size_t</span></span><span class='ectt-0800'> length, </span><span id='textcolor520'><span class='ectt-0800'>/* length of the buffer */</span></span>
|
|
<a id='x1-31261r129'></a><span class='ecrm-0500'>129</span><span class='ectt-0800'> loff_t *offset)</span>
|
|
<a id='x1-31263r130'></a><span class='ecrm-0500'>130</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-31265r131'></a><span class='ecrm-0500'>131</span><span class='ectt-0800'> </span><span id='textcolor521'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-31267r132'></a><span class='ecrm-0500'>132</span><span id='textcolor522'><span class='ectt-0800'> * Number of bytes actually written to the buffer</span></span>
|
|
<a id='x1-31269r133'></a><span class='ecrm-0500'>133</span><span id='textcolor523'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-31271r134'></a><span class='ecrm-0500'>134</span><span class='ectt-0800'> </span><span id='textcolor524'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> bytes_read = 0;</span>
|
|
<a id='x1-31273r135'></a><span class='ecrm-0500'>135</span>
|
|
<a id='x1-31275r136'></a><span class='ecrm-0500'>136</span><span class='ectt-0800'> </span><span id='textcolor525'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-31277r137'></a><span class='ecrm-0500'>137</span><span id='textcolor526'><span class='ectt-0800'> * If we</span><span class='tctt-0800'>'</span><span class='ectt-0800'>re at the end of the message,</span></span>
|
|
<a id='x1-31279r138'></a><span class='ecrm-0500'>138</span><span id='textcolor527'><span class='ectt-0800'> * return 0 signifying end of file</span></span>
|
|
<a id='x1-31281r139'></a><span class='ecrm-0500'>139</span><span id='textcolor528'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-31283r140'></a><span class='ecrm-0500'>140</span><span class='ectt-0800'> </span><span id='textcolor529'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (*msg_Ptr == 0)</span>
|
|
<a id='x1-31285r141'></a><span class='ecrm-0500'>141</span><span class='ectt-0800'> </span><span id='textcolor530'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-31287r142'></a><span class='ecrm-0500'>142</span>
|
|
<a id='x1-31289r143'></a><span class='ecrm-0500'>143</span><span class='ectt-0800'> </span><span id='textcolor531'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-31291r144'></a><span class='ecrm-0500'>144</span><span id='textcolor532'><span class='ectt-0800'> * Actually put the data into the buffer</span></span>
|
|
<a id='x1-31293r145'></a><span class='ecrm-0500'>145</span><span id='textcolor533'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-31295r146'></a><span class='ecrm-0500'>146</span><span class='ectt-0800'> </span><span id='textcolor534'><span class='ectt-0800'>while</span></span><span class='ectt-0800'> (length && *msg_Ptr) {</span>
|
|
<a id='x1-31297r147'></a><span class='ecrm-0500'>147</span><span class='ectt-0800'> </span><span id='textcolor535'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-31299r148'></a><span class='ecrm-0500'>148</span><span id='textcolor536'><span class='ectt-0800'> * The buffer is in the user data segment, not the kernel</span></span>
|
|
<a id='x1-31301r149'></a><span class='ecrm-0500'>149</span><span id='textcolor537'><span class='ectt-0800'> * segment so "*" assignment won</span><span class='tctt-0800'>'</span><span class='ectt-0800'>t work. We have to use</span></span>
|
|
<a id='x1-31303r150'></a><span class='ecrm-0500'>150</span><span id='textcolor538'><span class='ectt-0800'> * put_user which copies data from the kernel data segment to</span></span>
|
|
<a id='x1-31305r151'></a><span class='ecrm-0500'>151</span><span id='textcolor539'><span class='ectt-0800'> * the user data segment.</span></span>
|
|
<a id='x1-31307r152'></a><span class='ecrm-0500'>152</span><span id='textcolor540'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-31309r153'></a><span class='ecrm-0500'>153</span><span class='ectt-0800'> put_user(*(msg_Ptr++), buffer++);</span>
|
|
<a id='x1-31311r154'></a><span class='ecrm-0500'>154</span>
|
|
<a id='x1-31313r155'></a><span class='ecrm-0500'>155</span><span class='ectt-0800'> length--;</span>
|
|
<a id='x1-31315r156'></a><span class='ecrm-0500'>156</span><span class='ectt-0800'> bytes_read++;</span>
|
|
<a id='x1-31317r157'></a><span class='ecrm-0500'>157</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-31319r158'></a><span class='ecrm-0500'>158</span>
|
|
<a id='x1-31321r159'></a><span class='ecrm-0500'>159</span><span class='ectt-0800'> </span><span id='textcolor541'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-31323r160'></a><span class='ecrm-0500'>160</span><span id='textcolor542'><span class='ectt-0800'> * Most read functions return the number of bytes put into the buffer</span></span>
|
|
<a id='x1-31325r161'></a><span class='ecrm-0500'>161</span><span id='textcolor543'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-31327r162'></a><span class='ecrm-0500'>162</span><span class='ectt-0800'> </span><span id='textcolor544'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> bytes_read;</span>
|
|
<a id='x1-31329r163'></a><span class='ecrm-0500'>163</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-31331r164'></a><span class='ecrm-0500'>164</span>
|
|
<a id='x1-31333r165'></a><span class='ecrm-0500'>165</span><span id='textcolor545'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-31335r166'></a><span class='ecrm-0500'>166</span><span id='textcolor546'><span class='ectt-0800'> * Called when a process writes to dev file: echo "hi" > /dev/hello</span></span>
|
|
<a id='x1-31337r167'></a><span class='ecrm-0500'>167</span><span id='textcolor547'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-31339r168'></a><span class='ecrm-0500'>168</span><span id='textcolor548'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor549'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> device_write(</span><span id='textcolor550'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *filp,</span>
|
|
<a id='x1-31341r169'></a><span class='ecrm-0500'>169</span><span class='ectt-0800'> </span><span id='textcolor551'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor552'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *buff,</span>
|
|
<a id='x1-31343r170'></a><span class='ecrm-0500'>170</span><span class='ectt-0800'> </span><span id='textcolor553'><span class='ectt-0800'>size_t</span></span><span class='ectt-0800'> len,</span>
|
|
<a id='x1-31345r171'></a><span class='ecrm-0500'>171</span><span class='ectt-0800'> loff_t *off)</span>
|
|
<a id='x1-31347r172'></a><span class='ecrm-0500'>172</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-31349r173'></a><span class='ecrm-0500'>173</span><span class='ectt-0800'> pr_alert(</span><span id='textcolor554'><span class='ectt-0800'>"Sorry, this operation isn</span><span class='tctt-0800'>'</span><span class='ectt-0800'>t supported.</span></span><span id='textcolor555'><span class='ectt-0800'>\n</span></span><span id='textcolor556'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-31351r174'></a><span class='ecrm-0500'>174</span><span class='ectt-0800'> </span><span id='textcolor557'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -EINVAL;</span>
|
|
<a id='x1-31353r175'></a><span class='ecrm-0500'>175</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-31355r176'></a><span class='ecrm-0500'>176</span>
|
|
<a id='x1-31357r177'></a><span class='ecrm-0500'>177</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor558'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
|
|
|
|
|
|
|
|
<!-- l. 905 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='writing-modules-for-multiple-kernel-versions'><span class='titlemark'>0.6.6 </span> <a id='x1-320000.6.6'></a>Writing Modules for Multiple Kernel Versions</h4>
|
|
<!-- l. 907 --><p class='noindent'>The system calls, which are the major interface the kernel shows to the processes,
|
|
generally stay the same across versions. A new system call may be added, but
|
|
usually the old ones will behave exactly like they used to. This is necessary for
|
|
backward compatibility – a new kernel version is not supposed to break regular
|
|
processes. In most cases, the device files will also remain the same. On the other
|
|
hand, the internal interfaces within the kernel can and do change between
|
|
versions.
|
|
</p><!-- l. 912 --><p class='indent'> There are differences between different kernel versions, and if you want to support
|
|
multiple kernel versions, you will find yourself having to code conditional compilation
|
|
directives. The way to do this to compare the macro <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>LINUX_VERSION_CODE</span></span></span> to the
|
|
macro <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>KERNEL_VERSION</span></span></span>. In version a.b.c of the kernel, the value of this macro would
|
|
be <img alt='216a + 28b+ c ' class='math' src='lkmpg0x.svg' />.
|
|
</p><!-- l. 916 --><p class='indent'> While previous versions of this guide showed how you can write backward
|
|
compatible code with such constructs in great detail, we decided to break with this
|
|
tradition for the better. People interested in doing such might now use a LKMPG
|
|
with a version matching to their kernel.
|
|
</p><!-- l. 919 --><p class='noindent'>
|
|
</p>
|
|
<h3 class='sectionHead' id='the-proc-file-system'><span class='titlemark'>0.7 </span> <a id='x1-330000.7'></a>The /proc File System</h3>
|
|
<!-- l. 921 --><p class='noindent'>In Linux, there is an additional mechanism for the kernel and kernel modules to send
|
|
information to processes — the <span class='ecbx-1000'>/proc </span>file system. Originally designed to allow easy
|
|
access to information about processes (hence the name), it is now used by every bit
|
|
of the kernel which has something interesting to report, such as <span class='ecbx-1000'>/proc/modules</span>
|
|
which provides the list of modules and <span class='ecbx-1000'>/proc/meminfo </span>which stats memory usage
|
|
statistics.
|
|
</p><!-- l. 924 --><p class='indent'> The method to use the proc file system is very similar to the one used with device
|
|
drivers — a structure is created with all the information needed for the <span class='ecbx-1000'>/proc </span>file,
|
|
including pointers to any handler functions (in our case there is only one, the
|
|
one called when somebody attempts to read from the <span class='ecbx-1000'>/proc </span>file). Then,
|
|
init_module registers the structure with the kernel and cleanup_module unregisters
|
|
it.
|
|
</p><!-- l. 927 --><p class='indent'> Normal file systems are located on a disk, rather than just in memory (which is
|
|
where <span class='ecbx-1000'>/proc </span>is), and in that case the inode number is a pointer to a disk
|
|
location where the file’s index-node (inode for short) is located. The inode
|
|
contains information about the file, for example the file’s permissions, together
|
|
with a pointer to the disk location or locations where the file’s data can be
|
|
found.
|
|
</p><!-- l. 930 --><p class='indent'> Because we don’t get called when the file is opened or closed, there’s nowhere for
|
|
us to put try_module_get and try_module_put in this module, and if the
|
|
file is opened and then the module is removed, there’s no way to avoid the
|
|
|
|
|
|
|
|
consequences.
|
|
</p><!-- l. 932 --><p class='indent'> Here a simple example showing how to use a <span class='ecbx-1000'>/proc </span>file. This is the HelloWorld
|
|
for the <span class='ecbx-1000'>/proc </span>filesystem. There are three parts: create the file <span class='ecbx-1000'>/proc/helloworld</span>
|
|
in the function init_module, return a value (and a buffer) when the file
|
|
<span class='ecbx-1000'>/proc/helloworld </span>is read in the callback function <span class='ecbx-1000'>procfile_read</span>, and delete the
|
|
file <span class='ecbx-1000'>/proc/helloworld </span>in the function cleanup_module.
|
|
</p><!-- l. 936 --><p class='indent'> The <span class='ecbx-1000'>/proc/helloworld </span>is created when the module is loaded with the function
|
|
<span class='ecbx-1000'>proc_create</span>. The return value is a <span class='ecbx-1000'>struct proc_dir_entry </span>, and it will be used
|
|
to configure the file <span class='ecbx-1000'>/proc/helloworld </span>(for example, the owner of this file). A null
|
|
return value means that the creation has failed.
|
|
</p><!-- l. 940 --><p class='indent'> Each time, everytime the file <span class='ecbx-1000'>/proc/helloworld </span>is read, the function
|
|
<span class='ecbx-1000'>procfile_read </span>is called. Two parameters of this function are very important: the
|
|
buffer (the second parameter) and the offset (the fourth one). The content of the
|
|
buffer will be returned to the application which read it (for example the
|
|
cat command). The offset is the current position in the file. If the return
|
|
value of the function is not null, then this function is called again. So be
|
|
careful with this function, if it never returns zero, the read function is called
|
|
endlessly.
|
|
|
|
|
|
|
|
</p>
|
|
<pre class='verbatim' id='verbatim-10'>
|
|
$ cat /proc/helloworld
|
|
HelloWorld!
|
|
</pre>
|
|
<!-- l. 950 --><p class='nopar'>
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb37'><a id='x1-33002r1'></a><span class='ecrm-0500'>1</span><span id='textcolor559'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-33004r2'></a><span class='ecrm-0500'>2</span><span id='textcolor560'><span class='ectt-0800'> * procfs1.c</span></span>
|
|
<a id='x1-33006r3'></a><span class='ecrm-0500'>3</span><span id='textcolor561'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-33008r4'></a><span class='ecrm-0500'>4</span>
|
|
<a id='x1-33010r5'></a><span class='ecrm-0500'>5</span><span id='textcolor562'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor563'><span class='ectt-0800'><linux/kernel.h></span></span>
|
|
<a id='x1-33012r6'></a><span class='ecrm-0500'>6</span><span id='textcolor564'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor565'><span class='ectt-0800'><linux/module.h></span></span>
|
|
<a id='x1-33014r7'></a><span class='ecrm-0500'>7</span><span id='textcolor566'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor567'><span class='ectt-0800'><linux/proc_fs.h></span></span>
|
|
<a id='x1-33016r8'></a><span class='ecrm-0500'>8</span><span id='textcolor568'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor569'><span class='ectt-0800'><linux/uaccess.h></span></span>
|
|
<a id='x1-33018r9'></a><span class='ecrm-0500'>9</span><span id='textcolor570'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor571'><span class='ectt-0800'><linux/version.h></span></span>
|
|
<a id='x1-33020r10'></a><span class='ecrm-0500'>10</span>
|
|
<a id='x1-33022r11'></a><span class='ecrm-0500'>11</span><span id='textcolor572'><span class='ectt-0800'>#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 6, 0)</span></span>
|
|
<a id='x1-33024r12'></a><span class='ecrm-0500'>12</span><span id='textcolor573'><span class='ectt-0800'>#define HAVE_PROC_OPS</span></span>
|
|
<a id='x1-33026r13'></a><span class='ecrm-0500'>13</span><span id='textcolor574'><span class='ectt-0800'>#endif</span></span>
|
|
<a id='x1-33028r14'></a><span class='ecrm-0500'>14</span>
|
|
<a id='x1-33030r15'></a><span class='ecrm-0500'>15</span><span id='textcolor575'><span class='ectt-0800'>#define procfs_name "helloworld"</span></span>
|
|
<a id='x1-33032r16'></a><span class='ecrm-0500'>16</span>
|
|
<a id='x1-33034r17'></a><span class='ecrm-0500'>17</span><span id='textcolor576'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> proc_dir_entry *Our_Proc_File;</span>
|
|
<a id='x1-33036r18'></a><span class='ecrm-0500'>18</span>
|
|
<a id='x1-33038r19'></a><span class='ecrm-0500'>19</span>
|
|
<a id='x1-33040r20'></a><span class='ecrm-0500'>20</span><span id='textcolor577'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> procfile_read(</span><span id='textcolor578'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *filePointer,</span>
|
|
<a id='x1-33042r21'></a><span class='ecrm-0500'>21</span><span class='ectt-0800'> </span><span id='textcolor579'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *buffer,</span>
|
|
<a id='x1-33044r22'></a><span class='ecrm-0500'>22</span><span class='ectt-0800'> </span><span id='textcolor580'><span class='ectt-0800'>size_t</span></span><span class='ectt-0800'> buffer_length,</span>
|
|
<a id='x1-33046r23'></a><span class='ecrm-0500'>23</span><span class='ectt-0800'> loff_t *offset)</span>
|
|
<a id='x1-33048r24'></a><span class='ecrm-0500'>24</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-33050r25'></a><span class='ecrm-0500'>25</span><span class='ectt-0800'> </span><span id='textcolor581'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> s[13] = </span><span id='textcolor582'><span class='ectt-0800'>"HelloWorld!</span></span><span id='textcolor583'><span class='ectt-0800'>\n</span></span><span id='textcolor584'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>;</span>
|
|
<a id='x1-33052r26'></a><span class='ecrm-0500'>26</span><span class='ectt-0800'> </span><span id='textcolor585'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> len = </span><span id='textcolor586'><span class='ectt-0800'>sizeof</span></span><span class='ectt-0800'>(s);</span>
|
|
<a id='x1-33054r27'></a><span class='ecrm-0500'>27</span><span class='ectt-0800'> </span><span id='textcolor587'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> ret = len;</span>
|
|
<a id='x1-33056r28'></a><span class='ecrm-0500'>28</span>
|
|
<a id='x1-33058r29'></a><span class='ecrm-0500'>29</span><span class='ectt-0800'> </span><span id='textcolor588'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (*offset >= len || copy_to_user(buffer, s, len)) {</span>
|
|
<a id='x1-33060r30'></a><span class='ecrm-0500'>30 </span><span class='ectt-0800'> pr_info(</span><span id='textcolor589'><span class='ectt-0800'>"copy_to_user failed</span></span><span id='textcolor590'><span class='ectt-0800'>\n</span></span><span id='textcolor591'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-33062r31'></a><span class='ecrm-0500'>31 </span><span class='ectt-0800'> ret = 0;</span>
|
|
<a id='x1-33064r32'></a><span class='ecrm-0500'>32</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-33066r33'></a><span class='ecrm-0500'>33</span><span class='ectt-0800'> </span><span id='textcolor592'><span class='ectt-0800'>else</span></span><span class='ectt-0800'> {</span>
|
|
<a id='x1-33068r34'></a><span class='ecrm-0500'>34</span><span class='ectt-0800'> pr_info(</span><span id='textcolor593'><span class='ectt-0800'>"procfile read %s</span></span><span id='textcolor594'><span class='ectt-0800'>\n</span></span><span id='textcolor595'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, filePointer->f_path.dentry->d_name.name);</span>
|
|
<a id='x1-33070r35'></a><span class='ecrm-0500'>35</span><span class='ectt-0800'> *offset += len;</span>
|
|
<a id='x1-33072r36'></a><span class='ecrm-0500'>36</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-33074r37'></a><span class='ecrm-0500'>37</span>
|
|
<a id='x1-33076r38'></a><span class='ecrm-0500'>38</span><span class='ectt-0800'> </span><span id='textcolor596'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> ret;</span>
|
|
<a id='x1-33078r39'></a><span class='ecrm-0500'>39</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-33080r40'></a><span class='ecrm-0500'>40</span>
|
|
<a id='x1-33082r41'></a><span class='ecrm-0500'>41</span><span id='textcolor597'><span class='ectt-0800'>#ifdef HAVE_PROC_OPS</span></span>
|
|
<a id='x1-33084r42'></a><span class='ecrm-0500'>42</span><span id='textcolor598'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor599'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor600'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> proc_ops proc_file_fops = {</span>
|
|
<a id='x1-33086r43'></a><span class='ecrm-0500'>43</span><span class='ectt-0800'> .proc_read = procfile_read,</span>
|
|
<a id='x1-33088r44'></a><span class='ecrm-0500'>44</span><span class='ectt-0800'>};</span>
|
|
<a id='x1-33090r45'></a><span class='ecrm-0500'>45</span><span id='textcolor601'><span class='ectt-0800'>#else</span></span>
|
|
<a id='x1-33092r46'></a><span class='ecrm-0500'>46</span><span id='textcolor602'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor603'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor604'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file_operations proc_file_fops = {</span>
|
|
<a id='x1-33094r47'></a><span class='ecrm-0500'>47</span><span class='ectt-0800'> .read = procfile_read,</span>
|
|
<a id='x1-33096r48'></a><span class='ecrm-0500'>48</span><span class='ectt-0800'>};</span>
|
|
<a id='x1-33098r49'></a><span class='ecrm-0500'>49</span><span id='textcolor605'><span class='ectt-0800'>#endif</span></span>
|
|
<a id='x1-33100r50'></a><span class='ecrm-0500'>50</span>
|
|
<a id='x1-33102r51'></a><span class='ecrm-0500'>51</span><span id='textcolor606'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> init_module()</span>
|
|
<a id='x1-33104r52'></a><span class='ecrm-0500'>52</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-33106r53'></a><span class='ecrm-0500'>53</span><span class='ectt-0800'> Our_Proc_File = proc_create(procfs_name, 0644, NULL, &proc_file_fops);</span>
|
|
<a id='x1-33108r54'></a><span class='ecrm-0500'>54</span><span class='ectt-0800'> </span><span id='textcolor607'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (NULL == Our_Proc_File) {</span>
|
|
<a id='x1-33110r55'></a><span class='ecrm-0500'>55</span><span class='ectt-0800'> proc_remove(Our_Proc_File);</span>
|
|
<a id='x1-33112r56'></a><span class='ecrm-0500'>56</span><span class='ectt-0800'> pr_alert(</span><span id='textcolor608'><span class='ectt-0800'>"Error:Could not initialize /proc/%s</span></span><span id='textcolor609'><span class='ectt-0800'>\n</span></span><span id='textcolor610'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, procfs_name);</span>
|
|
<a id='x1-33114r57'></a><span class='ecrm-0500'>57</span><span class='ectt-0800'> </span><span id='textcolor611'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -ENOMEM;</span>
|
|
<a id='x1-33116r58'></a><span class='ecrm-0500'>58</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-33118r59'></a><span class='ecrm-0500'>59</span>
|
|
<a id='x1-33120r60'></a><span class='ecrm-0500'>60</span><span class='ectt-0800'> pr_info(</span><span id='textcolor612'><span class='ectt-0800'>"/proc/%s created</span></span><span id='textcolor613'><span class='ectt-0800'>\n</span></span><span id='textcolor614'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, procfs_name);</span>
|
|
<a id='x1-33122r61'></a><span class='ecrm-0500'>61</span><span class='ectt-0800'> </span><span id='textcolor615'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-33124r62'></a><span class='ecrm-0500'>62</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-33126r63'></a><span class='ecrm-0500'>63</span>
|
|
<a id='x1-33128r64'></a><span class='ecrm-0500'>64</span><span id='textcolor616'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> cleanup_module()</span>
|
|
<a id='x1-33130r65'></a><span class='ecrm-0500'>65</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-33132r66'></a><span class='ecrm-0500'>66</span><span class='ectt-0800'> proc_remove(Our_Proc_File);</span>
|
|
<a id='x1-33134r67'></a><span class='ecrm-0500'>67</span><span class='ectt-0800'> pr_info(</span><span id='textcolor617'><span class='ectt-0800'>"/proc/%s removed</span></span><span id='textcolor618'><span class='ectt-0800'>\n</span></span><span id='textcolor619'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, procfs_name);</span>
|
|
<a id='x1-33136r68'></a><span class='ecrm-0500'>68</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-33138r69'></a><span class='ecrm-0500'>69</span>
|
|
<a id='x1-33140r70'></a><span class='ecrm-0500'>70</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor620'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
|
|
<!-- l. 954 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='read-and-write-a-proc-file'><span class='titlemark'>0.7.1 </span> <a id='x1-340000.7.1'></a>Read and Write a /proc File</h4>
|
|
<!-- l. 956 --><p class='noindent'>We have seen a very simple example for a /proc file where we only read the
|
|
file /proc/helloworld. It is also possible to write in a /proc file. It works
|
|
the same way as read, a function is called when the /proc file is written.
|
|
But there is a little difference with read, data comes from user, so you have
|
|
to import data from user space to kernel space (with copy_from_user or
|
|
get_user)
|
|
</p><!-- l. 961 --><p class='indent'> The reason for copy_from_user or get_user is that Linux memory (on Intel
|
|
architecture, it may be different under some other processors) is segmented. This
|
|
means that a pointer, by itself, does not reference a unique location in memory, only
|
|
a location in a memory segment, and you need to know which memory segment it is
|
|
to be able to use it. There is one memory segment for the kernel, and one for each of
|
|
the processes.
|
|
</p><!-- l. 965 --><p class='indent'> The only memory segment accessible to a process is its own, so when
|
|
writing regular programs to run as processes, there is no need to worry about
|
|
segments. When you write a kernel module, normally you want to access
|
|
the kernel memory segment, which is handled automatically by the system.
|
|
However, when the content of a memory buffer needs to be passed between the
|
|
currently running process and the kernel, the kernel function receives a pointer
|
|
to the memory buffer which is in the process segment. The put_user and
|
|
get_user macros allow you to access that memory. These functions handle
|
|
only one character, you can handle several characters with copy_to_user
|
|
and copy_from_user. As the buffer (in read or write function) is in kernel
|
|
space, for write function you need to import data because it comes from
|
|
user space, but not for the read function because data is already in kernel
|
|
space.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb38'><a id='x1-34002r1'></a><span class='ecrm-0500'>1</span><span id='textcolor621'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-34004r2'></a><span class='ecrm-0500'>2</span><span id='textcolor622'><span class='ectt-0800'> * procfs2.c - create a "file" in /proc</span></span>
|
|
<a id='x1-34006r3'></a><span class='ecrm-0500'>3</span><span id='textcolor623'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-34008r4'></a><span class='ecrm-0500'>4</span>
|
|
<a id='x1-34010r5'></a><span class='ecrm-0500'>5</span><span id='textcolor624'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor625'><span class='ectt-0800'><linux/kernel.h> /* We</span><span class='tctt-0800'>'</span><span class='ectt-0800'>re doing kernel work */</span></span>
|
|
<a id='x1-34012r6'></a><span class='ecrm-0500'>6</span><span id='textcolor626'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor627'><span class='ectt-0800'><linux/module.h> /* Specifically, a module */</span></span>
|
|
<a id='x1-34014r7'></a><span class='ecrm-0500'>7</span><span id='textcolor628'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor629'><span class='ectt-0800'><linux/proc_fs.h> /* Necessary because we use the proc fs */</span></span>
|
|
<a id='x1-34016r8'></a><span class='ecrm-0500'>8</span><span id='textcolor630'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor631'><span class='ectt-0800'><linux/uaccess.h> /* for copy_from_user */</span></span>
|
|
<a id='x1-34018r9'></a><span class='ecrm-0500'>9</span><span id='textcolor632'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor633'><span class='ectt-0800'><linux/version.h></span></span>
|
|
<a id='x1-34020r10'></a><span class='ecrm-0500'>10</span>
|
|
<a id='x1-34022r11'></a><span class='ecrm-0500'>11</span><span id='textcolor634'><span class='ectt-0800'>#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 6, 0)</span></span>
|
|
<a id='x1-34024r12'></a><span class='ecrm-0500'>12</span><span id='textcolor635'><span class='ectt-0800'>#define HAVE_PROC_OPS</span></span>
|
|
<a id='x1-34026r13'></a><span class='ecrm-0500'>13</span><span id='textcolor636'><span class='ectt-0800'>#endif</span></span>
|
|
<a id='x1-34028r14'></a><span class='ecrm-0500'>14</span>
|
|
<a id='x1-34030r15'></a><span class='ecrm-0500'>15</span><span id='textcolor637'><span class='ectt-0800'>#define PROCFS_MAX_SIZE 1024</span></span>
|
|
<a id='x1-34032r16'></a><span class='ecrm-0500'>16</span><span id='textcolor638'><span class='ectt-0800'>#define PROCFS_NAME "buffer1k"</span></span>
|
|
<a id='x1-34034r17'></a><span class='ecrm-0500'>17</span>
|
|
<a id='x1-34036r18'></a><span class='ecrm-0500'>18</span><span id='textcolor639'><span class='ectt-0800'>/**</span></span>
|
|
<a id='x1-34038r19'></a><span class='ecrm-0500'>19</span><span id='textcolor640'><span class='ectt-0800'> * This structure hold information about the /proc file</span></span>
|
|
<a id='x1-34040r20'></a><span class='ecrm-0500'>20</span><span id='textcolor641'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-34042r21'></a><span class='ecrm-0500'>21</span><span id='textcolor642'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-34044r22'></a><span class='ecrm-0500'>22</span><span id='textcolor643'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor644'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> proc_dir_entry *Our_Proc_File;</span>
|
|
<a id='x1-34046r23'></a><span class='ecrm-0500'>23</span>
|
|
<a id='x1-34048r24'></a><span class='ecrm-0500'>24</span><span id='textcolor645'><span class='ectt-0800'>/**</span></span>
|
|
<a id='x1-34050r25'></a><span class='ecrm-0500'>25</span><span id='textcolor646'><span class='ectt-0800'> * The buffer used to store character for this module</span></span>
|
|
<a id='x1-34052r26'></a><span class='ecrm-0500'>26</span><span id='textcolor647'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-34054r27'></a><span class='ecrm-0500'>27</span><span id='textcolor648'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-34056r28'></a><span class='ecrm-0500'>28</span><span id='textcolor649'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor650'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> procfs_buffer[PROCFS_MAX_SIZE];</span>
|
|
<a id='x1-34058r29'></a><span class='ecrm-0500'>29</span>
|
|
<a id='x1-34060r30'></a><span class='ecrm-0500'>30</span><span id='textcolor651'><span class='ectt-0800'>/**</span></span>
|
|
<a id='x1-34062r31'></a><span class='ecrm-0500'>31</span><span id='textcolor652'><span class='ectt-0800'> * The size of the buffer</span></span>
|
|
<a id='x1-34064r32'></a><span class='ecrm-0500'>32</span><span id='textcolor653'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-34066r33'></a><span class='ecrm-0500'>33</span><span id='textcolor654'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-34068r34'></a><span class='ecrm-0500'>34</span><span id='textcolor655'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor656'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor657'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> procfs_buffer_size = 0;</span>
|
|
<a id='x1-34070r35'></a><span class='ecrm-0500'>35</span>
|
|
<a id='x1-34072r36'></a><span class='ecrm-0500'>36</span><span id='textcolor658'><span class='ectt-0800'>/**</span></span>
|
|
<a id='x1-34074r37'></a><span class='ecrm-0500'>37</span><span id='textcolor659'><span class='ectt-0800'> * This function is called then the /proc file is read</span></span>
|
|
<a id='x1-34076r38'></a><span class='ecrm-0500'>38</span><span id='textcolor660'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-34078r39'></a><span class='ecrm-0500'>39</span><span id='textcolor661'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-34080r40'></a><span class='ecrm-0500'>40</span><span id='textcolor662'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> procfile_read(</span><span id='textcolor663'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *filePointer,</span>
|
|
<a id='x1-34082r41'></a><span class='ecrm-0500'>41</span><span class='ectt-0800'> </span><span id='textcolor664'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *buffer,</span>
|
|
<a id='x1-34084r42'></a><span class='ecrm-0500'>42</span><span class='ectt-0800'> </span><span id='textcolor665'><span class='ectt-0800'>size_t</span></span><span class='ectt-0800'> buffer_length,</span>
|
|
<a id='x1-34086r43'></a><span class='ecrm-0500'>43</span><span class='ectt-0800'> loff_t *offset)</span>
|
|
<a id='x1-34088r44'></a><span class='ecrm-0500'>44</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-34090r45'></a><span class='ecrm-0500'>45</span><span class='ectt-0800'> </span><span id='textcolor666'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> s[13] = </span><span id='textcolor667'><span class='ectt-0800'>"HelloWorld!</span></span><span id='textcolor668'><span class='ectt-0800'>\n</span></span><span id='textcolor669'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>;</span>
|
|
<a id='x1-34092r46'></a><span class='ecrm-0500'>46</span><span class='ectt-0800'> </span><span id='textcolor670'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> len = </span><span id='textcolor671'><span class='ectt-0800'>sizeof</span></span><span class='ectt-0800'>(s);</span>
|
|
<a id='x1-34094r47'></a><span class='ecrm-0500'>47</span><span class='ectt-0800'> </span><span id='textcolor672'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> ret = len;</span>
|
|
<a id='x1-34096r48'></a><span class='ecrm-0500'>48</span>
|
|
<a id='x1-34098r49'></a><span class='ecrm-0500'>49</span><span class='ectt-0800'> </span><span id='textcolor673'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (*offset >= len || copy_to_user(buffer, s, len)) {</span>
|
|
<a id='x1-34100r50'></a><span class='ecrm-0500'>50 </span><span class='ectt-0800'> pr_info(</span><span id='textcolor674'><span class='ectt-0800'>"copy_to_user failed</span></span><span id='textcolor675'><span class='ectt-0800'>\n</span></span><span id='textcolor676'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-34102r51'></a><span class='ecrm-0500'>51 </span><span class='ectt-0800'> ret = 0;</span>
|
|
<a id='x1-34104r52'></a><span class='ecrm-0500'>52</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-34106r53'></a><span class='ecrm-0500'>53</span><span class='ectt-0800'> </span><span id='textcolor677'><span class='ectt-0800'>else</span></span><span class='ectt-0800'> {</span>
|
|
<a id='x1-34108r54'></a><span class='ecrm-0500'>54</span><span class='ectt-0800'> pr_info(</span><span id='textcolor678'><span class='ectt-0800'>"procfile read %s</span></span><span id='textcolor679'><span class='ectt-0800'>\n</span></span><span id='textcolor680'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, filePointer->f_path.dentry->d_name.name);</span>
|
|
<a id='x1-34110r55'></a><span class='ecrm-0500'>55</span><span class='ectt-0800'> *offset += len;</span>
|
|
<a id='x1-34112r56'></a><span class='ecrm-0500'>56</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-34114r57'></a><span class='ecrm-0500'>57</span>
|
|
<a id='x1-34116r58'></a><span class='ecrm-0500'>58</span><span class='ectt-0800'> </span><span id='textcolor681'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> ret;</span>
|
|
<a id='x1-34118r59'></a><span class='ecrm-0500'>59</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-34120r60'></a><span class='ecrm-0500'>60</span>
|
|
<a id='x1-34122r61'></a><span class='ecrm-0500'>61</span>
|
|
<a id='x1-34124r62'></a><span class='ecrm-0500'>62</span><span id='textcolor682'><span class='ectt-0800'>/**</span></span>
|
|
<a id='x1-34126r63'></a><span class='ecrm-0500'>63</span><span id='textcolor683'><span class='ectt-0800'> * This function is called with the /proc file is written</span></span>
|
|
<a id='x1-34128r64'></a><span class='ecrm-0500'>64</span><span id='textcolor684'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-34130r65'></a><span class='ecrm-0500'>65</span><span id='textcolor685'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-34132r66'></a><span class='ecrm-0500'>66</span><span id='textcolor686'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor687'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> procfile_write(</span><span id='textcolor688'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *file,</span>
|
|
<a id='x1-34134r67'></a><span class='ecrm-0500'>67</span><span class='ectt-0800'> </span><span id='textcolor689'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor690'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *buff,</span>
|
|
<a id='x1-34136r68'></a><span class='ecrm-0500'>68</span><span class='ectt-0800'> </span><span id='textcolor691'><span class='ectt-0800'>size_t</span></span><span class='ectt-0800'> len,</span>
|
|
<a id='x1-34138r69'></a><span class='ecrm-0500'>69</span><span class='ectt-0800'> loff_t *off)</span>
|
|
<a id='x1-34140r70'></a><span class='ecrm-0500'>70</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-34142r71'></a><span class='ecrm-0500'>71</span><span class='ectt-0800'> procfs_buffer_size = len;</span>
|
|
<a id='x1-34144r72'></a><span class='ecrm-0500'>72</span><span class='ectt-0800'> </span><span id='textcolor692'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (procfs_buffer_size > PROCFS_MAX_SIZE)</span>
|
|
<a id='x1-34146r73'></a><span class='ecrm-0500'>73</span><span class='ectt-0800'> procfs_buffer_size = PROCFS_MAX_SIZE;</span>
|
|
<a id='x1-34148r74'></a><span class='ecrm-0500'>74</span>
|
|
<a id='x1-34150r75'></a><span class='ecrm-0500'>75</span><span class='ectt-0800'> </span><span id='textcolor693'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (copy_from_user(procfs_buffer, buff, procfs_buffer_size))</span>
|
|
<a id='x1-34152r76'></a><span class='ecrm-0500'>76</span><span class='ectt-0800'> </span><span id='textcolor694'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -EFAULT;</span>
|
|
<a id='x1-34154r77'></a><span class='ecrm-0500'>77</span>
|
|
<a id='x1-34156r78'></a><span class='ecrm-0500'>78</span><span class='ectt-0800'> procfs_buffer[procfs_buffer_size] = </span><span id='textcolor695'><span class='tctt-0800'>'</span><span class='ectt-0800'>\0</span><span class='tctt-0800'>'</span></span><span class='ectt-0800'>;</span>
|
|
<a id='x1-34158r79'></a><span class='ecrm-0500'>79</span><span class='ectt-0800'> </span><span id='textcolor696'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> procfs_buffer_size;</span>
|
|
<a id='x1-34160r80'></a><span class='ecrm-0500'>80</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-34162r81'></a><span class='ecrm-0500'>81</span>
|
|
<a id='x1-34164r82'></a><span class='ecrm-0500'>82</span><span id='textcolor697'><span class='ectt-0800'>#ifdef HAVE_PROC_OPS</span></span>
|
|
<a id='x1-34166r83'></a><span class='ecrm-0500'>83</span><span id='textcolor698'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor699'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor700'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> proc_ops proc_file_fops = {</span>
|
|
<a id='x1-34168r84'></a><span class='ecrm-0500'>84</span><span class='ectt-0800'> .proc_read = procfile_read,</span>
|
|
<a id='x1-34170r85'></a><span class='ecrm-0500'>85</span><span class='ectt-0800'> .proc_write = procfile_write,</span>
|
|
<a id='x1-34172r86'></a><span class='ecrm-0500'>86</span><span class='ectt-0800'>};</span>
|
|
<a id='x1-34174r87'></a><span class='ecrm-0500'>87</span><span id='textcolor701'><span class='ectt-0800'>#else</span></span>
|
|
<a id='x1-34176r88'></a><span class='ecrm-0500'>88</span><span id='textcolor702'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor703'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor704'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file_operations proc_file_fops = {</span>
|
|
<a id='x1-34178r89'></a><span class='ecrm-0500'>89</span><span class='ectt-0800'> .read = procfile_read,</span>
|
|
<a id='x1-34180r90'></a><span class='ecrm-0500'>90</span><span class='ectt-0800'> .write = procfile_write,</span>
|
|
<a id='x1-34182r91'></a><span class='ecrm-0500'>91</span><span class='ectt-0800'>};</span>
|
|
<a id='x1-34184r92'></a><span class='ecrm-0500'>92</span><span id='textcolor705'><span class='ectt-0800'>#endif</span></span>
|
|
<a id='x1-34186r93'></a><span class='ecrm-0500'>93</span>
|
|
<a id='x1-34188r94'></a><span class='ecrm-0500'>94</span><span id='textcolor706'><span class='ectt-0800'>/**</span></span>
|
|
<a id='x1-34190r95'></a><span class='ecrm-0500'>95</span><span id='textcolor707'><span class='ectt-0800'> *This function is called when the module is loaded</span></span>
|
|
<a id='x1-34192r96'></a><span class='ecrm-0500'>96</span><span id='textcolor708'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-34194r97'></a><span class='ecrm-0500'>97</span><span id='textcolor709'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-34196r98'></a><span class='ecrm-0500'>98</span><span id='textcolor710'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> init_module()</span>
|
|
<a id='x1-34198r99'></a><span class='ecrm-0500'>99</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-34200r100'></a><span class='ecrm-0500'>100</span><span class='ectt-0800'> Our_Proc_File = proc_create(PROCFS_NAME, 0644, NULL, &proc_file_fops);</span>
|
|
<a id='x1-34202r101'></a><span class='ecrm-0500'>101</span><span class='ectt-0800'> </span><span id='textcolor711'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (NULL == Our_Proc_File) {</span>
|
|
<a id='x1-34204r102'></a><span class='ecrm-0500'>102</span><span class='ectt-0800'> proc_remove(Our_Proc_File);</span>
|
|
<a id='x1-34206r103'></a><span class='ecrm-0500'>103</span><span class='ectt-0800'> pr_alert(</span><span id='textcolor712'><span class='ectt-0800'>"Error:Could not initialize /proc/%s</span></span><span id='textcolor713'><span class='ectt-0800'>\n</span></span><span id='textcolor714'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, PROCFS_NAME);</span>
|
|
<a id='x1-34208r104'></a><span class='ecrm-0500'>104</span><span class='ectt-0800'> </span><span id='textcolor715'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -ENOMEM;</span>
|
|
<a id='x1-34210r105'></a><span class='ecrm-0500'>105</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-34212r106'></a><span class='ecrm-0500'>106</span>
|
|
<a id='x1-34214r107'></a><span class='ecrm-0500'>107</span><span class='ectt-0800'> pr_info(</span><span id='textcolor716'><span class='ectt-0800'>"/proc/%s created</span></span><span id='textcolor717'><span class='ectt-0800'>\n</span></span><span id='textcolor718'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, PROCFS_NAME);</span>
|
|
<a id='x1-34216r108'></a><span class='ecrm-0500'>108</span><span class='ectt-0800'> </span><span id='textcolor719'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-34218r109'></a><span class='ecrm-0500'>109</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-34220r110'></a><span class='ecrm-0500'>110</span>
|
|
<a id='x1-34222r111'></a><span class='ecrm-0500'>111</span><span id='textcolor720'><span class='ectt-0800'>/**</span></span>
|
|
<a id='x1-34224r112'></a><span class='ecrm-0500'>112</span><span id='textcolor721'><span class='ectt-0800'> *This function is called when the module is unloaded</span></span>
|
|
<a id='x1-34226r113'></a><span class='ecrm-0500'>113</span><span id='textcolor722'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-34228r114'></a><span class='ecrm-0500'>114</span><span id='textcolor723'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-34230r115'></a><span class='ecrm-0500'>115</span><span id='textcolor724'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> cleanup_module()</span>
|
|
<a id='x1-34232r116'></a><span class='ecrm-0500'>116</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-34234r117'></a><span class='ecrm-0500'>117</span><span class='ectt-0800'> proc_remove(Our_Proc_File);</span>
|
|
<a id='x1-34236r118'></a><span class='ecrm-0500'>118</span><span class='ectt-0800'> pr_info(</span><span id='textcolor725'><span class='ectt-0800'>"/proc/%s removed</span></span><span id='textcolor726'><span class='ectt-0800'>\n</span></span><span id='textcolor727'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, PROCFS_NAME);</span>
|
|
<a id='x1-34238r119'></a><span class='ecrm-0500'>119</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-34240r120'></a><span class='ecrm-0500'>120</span>
|
|
<a id='x1-34242r121'></a><span class='ecrm-0500'>121</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor728'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
|
|
|
|
|
|
|
|
<!-- l. 974 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='manage-proc-file-with-standard-filesystem'><span class='titlemark'>0.7.2 </span> <a id='x1-350000.7.2'></a>Manage /proc file with standard filesystem</h4>
|
|
<!-- l. 976 --><p class='noindent'>We have seen how to read and write a /proc file with the /proc interface. But it is
|
|
also possible to manage /proc file with inodes. The main concern is to use advanced
|
|
functions, like permissions.
|
|
</p><!-- l. 980 --><p class='indent'> In Linux, there is a standard mechanism for file system registration. Since every
|
|
file system has to have its own functions to handle inode and file operations, there is
|
|
a special structure to hold pointers to all those functions, struct <span class='ecbx-1000'>inode_operations</span>,
|
|
which includes a pointer to struct proc_ops.
|
|
</p><!-- l. 983 --><p class='indent'> The difference between file and inode operations is that file operations deal with
|
|
the file itself whereas inode operations deal with ways of referencing the file, such as
|
|
creating links to it.
|
|
</p><!-- l. 985 --><p class='indent'> In /proc, whenever we register a new file, we’re allowed to specify which struct
|
|
inode_operations will be used to access to it. This is the mechanism we use, a struct
|
|
inode_operations which includes a pointer to a struct proc_ops which includes
|
|
pointers to our procfs_read and procfs_write functions.
|
|
</p><!-- l. 988 --><p class='indent'> Another interesting point here is the <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>module_permission</span></span></span> function. This function
|
|
is called whenever a process tries to do something with the /proc file, and it
|
|
can decide whether to allow access or not. Right now it is only based on
|
|
the operation and the uid of the current user (as available in current, a
|
|
pointer to a structure which includes information on the currently running
|
|
process), but it could be based on anything we like, such as what other
|
|
processes are doing with the same file, the time of day, or the last input we
|
|
received.
|
|
</p><!-- l. 992 --><p class='indent'> It is important to note that the standard roles of read and write are reversed in
|
|
the kernel. Read functions are used for output, whereas write functions are used for
|
|
input. The reason for that is that read and write refer to the user’s point of view — if
|
|
a process reads something from the kernel, then the kernel needs to output it, and
|
|
if a process writes something to the kernel, then the kernel receives it as
|
|
input.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb39'><a id='x1-35002r1'></a><span class='ecrm-0500'>1</span><span id='textcolor729'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-35004r2'></a><span class='ecrm-0500'>2</span><span id='textcolor730'><span class='ectt-0800'> * procfs3.c</span></span>
|
|
<a id='x1-35006r3'></a><span class='ecrm-0500'>3</span><span id='textcolor731'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-35008r4'></a><span class='ecrm-0500'>4</span>
|
|
<a id='x1-35010r5'></a><span class='ecrm-0500'>5</span><span id='textcolor732'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor733'><span class='ectt-0800'><linux/kernel.h></span></span>
|
|
<a id='x1-35012r6'></a><span class='ecrm-0500'>6</span><span id='textcolor734'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor735'><span class='ectt-0800'><linux/module.h></span></span>
|
|
<a id='x1-35014r7'></a><span class='ecrm-0500'>7</span><span id='textcolor736'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor737'><span class='ectt-0800'><linux/proc_fs.h></span></span>
|
|
<a id='x1-35016r8'></a><span class='ecrm-0500'>8</span><span id='textcolor738'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor739'><span class='ectt-0800'><linux/sched.h></span></span>
|
|
<a id='x1-35018r9'></a><span class='ecrm-0500'>9</span><span id='textcolor740'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor741'><span class='ectt-0800'><linux/uaccess.h></span></span>
|
|
<a id='x1-35020r10'></a><span class='ecrm-0500'>10</span><span id='textcolor742'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor743'><span class='ectt-0800'><linux/version.h></span></span>
|
|
<a id='x1-35022r11'></a><span class='ecrm-0500'>11</span>
|
|
<a id='x1-35024r12'></a><span class='ecrm-0500'>12</span><span id='textcolor744'><span class='ectt-0800'>#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 6, 0)</span></span>
|
|
<a id='x1-35026r13'></a><span class='ecrm-0500'>13</span><span id='textcolor745'><span class='ectt-0800'>#define HAVE_PROC_OPS</span></span>
|
|
<a id='x1-35028r14'></a><span class='ecrm-0500'>14</span><span id='textcolor746'><span class='ectt-0800'>#endif</span></span>
|
|
<a id='x1-35030r15'></a><span class='ecrm-0500'>15</span>
|
|
<a id='x1-35032r16'></a><span class='ecrm-0500'>16</span><span id='textcolor747'><span class='ectt-0800'>#define PROCFS_MAX_SIZE 2048</span></span>
|
|
<a id='x1-35034r17'></a><span class='ecrm-0500'>17</span><span id='textcolor748'><span class='ectt-0800'>#define PROCFS_ENTRY_FILENAME "buffer2k"</span></span>
|
|
<a id='x1-35036r18'></a><span class='ecrm-0500'>18</span>
|
|
<a id='x1-35038r19'></a><span class='ecrm-0500'>19</span><span id='textcolor749'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> proc_dir_entry *Our_Proc_File;</span>
|
|
<a id='x1-35040r20'></a><span class='ecrm-0500'>20</span><span id='textcolor750'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor751'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> procfs_buffer[PROCFS_MAX_SIZE];</span>
|
|
<a id='x1-35042r21'></a><span class='ecrm-0500'>21</span><span id='textcolor752'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor753'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor754'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> procfs_buffer_size = 0;</span>
|
|
<a id='x1-35044r22'></a><span class='ecrm-0500'>22</span>
|
|
<a id='x1-35046r23'></a><span class='ecrm-0500'>23</span><span id='textcolor755'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor756'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> procfs_read(</span><span id='textcolor757'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *filp,</span>
|
|
<a id='x1-35048r24'></a><span class='ecrm-0500'>24</span><span class='ectt-0800'> </span><span id='textcolor758'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *buffer,</span>
|
|
<a id='x1-35050r25'></a><span class='ecrm-0500'>25</span><span class='ectt-0800'> </span><span id='textcolor759'><span class='ectt-0800'>size_t</span></span><span class='ectt-0800'> length,</span>
|
|
<a id='x1-35052r26'></a><span class='ecrm-0500'>26</span><span class='ectt-0800'> loff_t *offset)</span>
|
|
<a id='x1-35054r27'></a><span class='ecrm-0500'>27</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-35056r28'></a><span class='ecrm-0500'>28</span><span class='ectt-0800'> </span><span id='textcolor760'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor761'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> finished = 0;</span>
|
|
<a id='x1-35058r29'></a><span class='ecrm-0500'>29</span><span class='ectt-0800'> </span><span id='textcolor762'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (finished) {</span>
|
|
<a id='x1-35060r30'></a><span class='ecrm-0500'>30</span><span class='ectt-0800'> pr_debug(</span><span id='textcolor763'><span class='ectt-0800'>"procfs_read: END</span></span><span id='textcolor764'><span class='ectt-0800'>\n</span></span><span id='textcolor765'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-35062r31'></a><span class='ecrm-0500'>31</span><span class='ectt-0800'> finished = 0;</span>
|
|
<a id='x1-35064r32'></a><span class='ecrm-0500'>32</span><span class='ectt-0800'> </span><span id='textcolor766'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-35066r33'></a><span class='ecrm-0500'>33</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-35068r34'></a><span class='ecrm-0500'>34</span><span class='ectt-0800'> finished = 1;</span>
|
|
<a id='x1-35070r35'></a><span class='ecrm-0500'>35</span><span class='ectt-0800'> </span><span id='textcolor767'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (copy_to_user(buffer, procfs_buffer, procfs_buffer_size))</span>
|
|
<a id='x1-35072r36'></a><span class='ecrm-0500'>36</span><span class='ectt-0800'> </span><span id='textcolor768'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -EFAULT;</span>
|
|
<a id='x1-35074r37'></a><span class='ecrm-0500'>37</span><span class='ectt-0800'> pr_debug(</span><span id='textcolor769'><span class='ectt-0800'>"procfs_read: read %lu bytes</span></span><span id='textcolor770'><span class='ectt-0800'>\n</span></span><span id='textcolor771'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, procfs_buffer_size);</span>
|
|
<a id='x1-35076r38'></a><span class='ecrm-0500'>38</span><span class='ectt-0800'> </span><span id='textcolor772'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> procfs_buffer_size;</span>
|
|
<a id='x1-35078r39'></a><span class='ecrm-0500'>39</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-35080r40'></a><span class='ecrm-0500'>40</span><span id='textcolor773'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor774'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> procfs_write(</span><span id='textcolor775'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *file,</span>
|
|
<a id='x1-35082r41'></a><span class='ecrm-0500'>41</span><span class='ectt-0800'> </span><span id='textcolor776'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor777'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *buffer,</span>
|
|
<a id='x1-35084r42'></a><span class='ecrm-0500'>42</span><span class='ectt-0800'> </span><span id='textcolor778'><span class='ectt-0800'>size_t</span></span><span class='ectt-0800'> len,</span>
|
|
<a id='x1-35086r43'></a><span class='ecrm-0500'>43</span><span class='ectt-0800'> loff_t *off)</span>
|
|
<a id='x1-35088r44'></a><span class='ecrm-0500'>44</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-35090r45'></a><span class='ecrm-0500'>45</span><span class='ectt-0800'> </span><span id='textcolor779'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (len > PROCFS_MAX_SIZE)</span>
|
|
<a id='x1-35092r46'></a><span class='ecrm-0500'>46</span><span class='ectt-0800'> procfs_buffer_size = PROCFS_MAX_SIZE;</span>
|
|
<a id='x1-35094r47'></a><span class='ecrm-0500'>47</span><span class='ectt-0800'> </span><span id='textcolor780'><span class='ectt-0800'>else</span></span>
|
|
<a id='x1-35096r48'></a><span class='ecrm-0500'>48</span><span class='ectt-0800'> procfs_buffer_size = len;</span>
|
|
<a id='x1-35098r49'></a><span class='ecrm-0500'>49</span><span class='ectt-0800'> </span><span id='textcolor781'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (copy_from_user(procfs_buffer, buffer, procfs_buffer_size))</span>
|
|
<a id='x1-35100r50'></a><span class='ecrm-0500'>50</span><span class='ectt-0800'> </span><span id='textcolor782'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -EFAULT;</span>
|
|
<a id='x1-35102r51'></a><span class='ecrm-0500'>51</span><span class='ectt-0800'> pr_debug(</span><span id='textcolor783'><span class='ectt-0800'>"procfs_write: write %lu bytes</span></span><span id='textcolor784'><span class='ectt-0800'>\n</span></span><span id='textcolor785'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, procfs_buffer_size);</span>
|
|
<a id='x1-35104r52'></a><span class='ecrm-0500'>52</span><span class='ectt-0800'> </span><span id='textcolor786'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> procfs_buffer_size;</span>
|
|
<a id='x1-35106r53'></a><span class='ecrm-0500'>53</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-35108r54'></a><span class='ecrm-0500'>54</span><span id='textcolor787'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> procfs_open(</span><span id='textcolor788'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> inode *inode, </span><span id='textcolor789'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *file)</span>
|
|
<a id='x1-35110r55'></a><span class='ecrm-0500'>55</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-35112r56'></a><span class='ecrm-0500'>56</span><span class='ectt-0800'> try_module_get(THIS_MODULE);</span>
|
|
<a id='x1-35114r57'></a><span class='ecrm-0500'>57</span><span class='ectt-0800'> </span><span id='textcolor790'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-35116r58'></a><span class='ecrm-0500'>58</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-35118r59'></a><span class='ecrm-0500'>59</span><span id='textcolor791'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> procfs_close(</span><span id='textcolor792'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> inode *inode, </span><span id='textcolor793'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *file)</span>
|
|
<a id='x1-35120r60'></a><span class='ecrm-0500'>60</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-35122r61'></a><span class='ecrm-0500'>61</span><span class='ectt-0800'> module_put(THIS_MODULE);</span>
|
|
<a id='x1-35124r62'></a><span class='ecrm-0500'>62</span><span class='ectt-0800'> </span><span id='textcolor794'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-35126r63'></a><span class='ecrm-0500'>63</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-35128r64'></a><span class='ecrm-0500'>64</span>
|
|
<a id='x1-35130r65'></a><span class='ecrm-0500'>65</span><span id='textcolor795'><span class='ectt-0800'>#ifdef HAVE_PROC_OPS</span></span>
|
|
<a id='x1-35132r66'></a><span class='ecrm-0500'>66</span><span id='textcolor796'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor797'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> proc_ops File_Ops_4_Our_Proc_File = {</span>
|
|
<a id='x1-35134r67'></a><span class='ecrm-0500'>67</span><span class='ectt-0800'> .proc_read = procfs_read,</span>
|
|
<a id='x1-35136r68'></a><span class='ecrm-0500'>68</span><span class='ectt-0800'> .proc_write = procfs_write,</span>
|
|
<a id='x1-35138r69'></a><span class='ecrm-0500'>69</span><span class='ectt-0800'> .proc_open = procfs_open,</span>
|
|
<a id='x1-35140r70'></a><span class='ecrm-0500'>70</span><span class='ectt-0800'> .proc_release = procfs_close,</span>
|
|
<a id='x1-35142r71'></a><span class='ecrm-0500'>71</span><span class='ectt-0800'>};</span>
|
|
<a id='x1-35144r72'></a><span class='ecrm-0500'>72</span><span id='textcolor798'><span class='ectt-0800'>#else</span></span>
|
|
<a id='x1-35146r73'></a><span class='ecrm-0500'>73</span><span id='textcolor799'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor800'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor801'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file_operations File_Ops_4_Our_Proc_File = {</span>
|
|
<a id='x1-35148r74'></a><span class='ecrm-0500'>74</span><span class='ectt-0800'> .read = procfs_read,</span>
|
|
<a id='x1-35150r75'></a><span class='ecrm-0500'>75</span><span class='ectt-0800'> .write = procfs_write,</span>
|
|
<a id='x1-35152r76'></a><span class='ecrm-0500'>76</span><span class='ectt-0800'> .open = procfs_open,</span>
|
|
<a id='x1-35154r77'></a><span class='ecrm-0500'>77</span><span class='ectt-0800'> .release = procfs_close,</span>
|
|
<a id='x1-35156r78'></a><span class='ecrm-0500'>78</span><span class='ectt-0800'>};</span>
|
|
<a id='x1-35158r79'></a><span class='ecrm-0500'>79</span><span id='textcolor802'><span class='ectt-0800'>#endif</span></span>
|
|
<a id='x1-35160r80'></a><span class='ecrm-0500'>80</span>
|
|
<a id='x1-35162r81'></a><span class='ecrm-0500'>81</span><span id='textcolor803'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> init_module()</span>
|
|
<a id='x1-35164r82'></a><span class='ecrm-0500'>82</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-35166r83'></a><span class='ecrm-0500'>83</span><span class='ectt-0800'> Our_Proc_File = proc_create(PROCFS_ENTRY_FILENAME, 0644, NULL,</span>
|
|
<a id='x1-35168r84'></a><span class='ecrm-0500'>84</span><span class='ectt-0800'> &File_Ops_4_Our_Proc_File);</span>
|
|
<a id='x1-35170r85'></a><span class='ecrm-0500'>85</span><span class='ectt-0800'> </span><span id='textcolor804'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (Our_Proc_File == NULL) {</span>
|
|
<a id='x1-35172r86'></a><span class='ecrm-0500'>86</span><span class='ectt-0800'> remove_proc_entry(PROCFS_ENTRY_FILENAME, NULL);</span>
|
|
<a id='x1-35174r87'></a><span class='ecrm-0500'>87</span><span class='ectt-0800'> pr_debug(</span><span id='textcolor805'><span class='ectt-0800'>"Error: Could not initialize /proc/%s</span></span><span id='textcolor806'><span class='ectt-0800'>\n</span></span><span id='textcolor807'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>,</span>
|
|
<a id='x1-35176r88'></a><span class='ecrm-0500'>88</span><span class='ectt-0800'> PROCFS_ENTRY_FILENAME);</span>
|
|
<a id='x1-35178r89'></a><span class='ecrm-0500'>89</span><span class='ectt-0800'> </span><span id='textcolor808'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -ENOMEM;</span>
|
|
<a id='x1-35180r90'></a><span class='ecrm-0500'>90</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-35182r91'></a><span class='ecrm-0500'>91</span><span class='ectt-0800'> proc_set_size(Our_Proc_File, 80);</span>
|
|
<a id='x1-35184r92'></a><span class='ecrm-0500'>92</span><span class='ectt-0800'> proc_set_user(Our_Proc_File, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID);</span>
|
|
<a id='x1-35186r93'></a><span class='ecrm-0500'>93</span>
|
|
<a id='x1-35188r94'></a><span class='ecrm-0500'>94</span><span class='ectt-0800'> pr_debug(</span><span id='textcolor809'><span class='ectt-0800'>"/proc/%s created</span></span><span id='textcolor810'><span class='ectt-0800'>\n</span></span><span id='textcolor811'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, PROCFS_ENTRY_FILENAME);</span>
|
|
<a id='x1-35190r95'></a><span class='ecrm-0500'>95</span><span class='ectt-0800'> </span><span id='textcolor812'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-35192r96'></a><span class='ecrm-0500'>96</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-35194r97'></a><span class='ecrm-0500'>97</span><span id='textcolor813'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> cleanup_module()</span>
|
|
<a id='x1-35196r98'></a><span class='ecrm-0500'>98</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-35198r99'></a><span class='ecrm-0500'>99</span><span class='ectt-0800'> remove_proc_entry(PROCFS_ENTRY_FILENAME, NULL);</span>
|
|
<a id='x1-35200r100'></a><span class='ecrm-0500'>100</span><span class='ectt-0800'> pr_debug(</span><span id='textcolor814'><span class='ectt-0800'>"/proc/%s removed</span></span><span id='textcolor815'><span class='ectt-0800'>\n</span></span><span id='textcolor816'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, PROCFS_ENTRY_FILENAME);</span>
|
|
<a id='x1-35202r101'></a><span class='ecrm-0500'>101</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-35204r102'></a><span class='ecrm-0500'>102</span>
|
|
<a id='x1-35206r103'></a><span class='ecrm-0500'>103</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor817'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
|
|
<!-- l. 998 --><p class='indent'> Still hungry for procfs examples? Well, first of all keep in mind, there are rumors
|
|
around, claiming that procfs is on its way out, consider using <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>sysfs</span></span></span> instead. Consider
|
|
using this mechanism, in case you want to document something kernel related
|
|
yourself.
|
|
</p><!-- l. 1002 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='manage-proc-file-with-seqfile'><span class='titlemark'>0.7.3 </span> <a id='x1-360000.7.3'></a>Manage /proc file with seq_file</h4>
|
|
<!-- l. 1004 --><p class='noindent'>As we have seen, writing a /proc file may be quite “complex”. So to help people
|
|
writting /proc file, there is an API named <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>seq_file</span></span></span> that helps formating a /proc file
|
|
|
|
|
|
|
|
for output. It is based on sequence, which is composed of 3 functions: start(), next(),
|
|
and stop(). The <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>seq_file</span></span></span> API starts a sequence when a user read the /proc
|
|
file.
|
|
</p><!-- l. 1009 --><p class='indent'> A sequence begins with the call of the function start(). If the return is a non
|
|
NULL value, the function next() is called. This function is an iterator, the goal is to
|
|
go through all the data. Each time next() is called, the function show() is also called.
|
|
It writes data values in the buffer read by the user. The function next() is called until
|
|
it returns NULL. The sequence ends when next() returns NULL, then the function
|
|
stop() is called.
|
|
</p><!-- l. 1017 --><p class='indent'> BE CAREFUL: when a sequence is finished, another one starts. That means that
|
|
at the end of function stop(), the function start() is called again. This loop finishes
|
|
when the function start() returns NULL. You can see a scheme of this in the
|
|
Figure <a href='#ignorespaces-how-seqfile-works'>1<!-- tex4ht:ref: img:seqfile --></a>.
|
|
</p>
|
|
<figure class='figure' id='ignorespaces-how-seqfile-works'>
|
|
|
|
|
|
|
|
|
|
<a id='x1-36001r1'></a>
|
|
|
|
|
|
|
|
<!-- l. 1024 --><p class='noindent'><img alt='srYrsNNYtaeenetoooertusetupstrxr((ntn))( tis)istrr teeaNreNatUaUtmLtLmeLmLen?e?ntntt ' src='lkmpg1x.svg' />
|
|
</p>
|
|
<figcaption class='caption'><span class='id'>Figure 1:</span><span class='content'>How seq_file works</span></figcaption><!-- tex4ht:label?: x1-36001r1 -->
|
|
|
|
|
|
|
|
</figure>
|
|
<!-- l. 1044 --><p class='indent'> The <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>seq_file</span></span></span> provides basic functions for <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>proc_ops</span></span></span>, such as seq_read,
|
|
seq_lseek, and some others. But nothing to write in the /proc file. Of course, you can
|
|
still use the same way as in the previous example.
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb40'><a id='x1-36003r1'></a><span class='ecrm-0500'>1</span><span id='textcolor818'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-36005r2'></a><span class='ecrm-0500'>2</span><span id='textcolor819'><span class='ectt-0800'> * procfs4.c - create a "file" in /proc</span></span>
|
|
<a id='x1-36007r3'></a><span class='ecrm-0500'>3</span><span id='textcolor820'><span class='ectt-0800'> * This program uses the seq_file library to manage the /proc file.</span></span>
|
|
<a id='x1-36009r4'></a><span class='ecrm-0500'>4</span><span id='textcolor821'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-36011r5'></a><span class='ecrm-0500'>5</span><span id='textcolor822'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-36013r6'></a><span class='ecrm-0500'>6</span>
|
|
<a id='x1-36015r7'></a><span class='ecrm-0500'>7</span><span id='textcolor823'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor824'><span class='ectt-0800'><linux/kernel.h> /* We</span><span class='tctt-0800'>'</span><span class='ectt-0800'>re doing kernel work */</span></span>
|
|
<a id='x1-36017r8'></a><span class='ecrm-0500'>8</span><span id='textcolor825'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor826'><span class='ectt-0800'><linux/module.h> /* Specifically, a module */</span></span>
|
|
<a id='x1-36019r9'></a><span class='ecrm-0500'>9</span><span id='textcolor827'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor828'><span class='ectt-0800'><linux/proc_fs.h> /* Necessary because we use proc fs */</span></span>
|
|
<a id='x1-36021r10'></a><span class='ecrm-0500'>10</span><span id='textcolor829'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor830'><span class='ectt-0800'><linux/seq_file.h> /* for seq_file */</span></span>
|
|
<a id='x1-36023r11'></a><span class='ecrm-0500'>11</span><span id='textcolor831'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor832'><span class='ectt-0800'><linux/version.h></span></span>
|
|
<a id='x1-36025r12'></a><span class='ecrm-0500'>12</span>
|
|
<a id='x1-36027r13'></a><span class='ecrm-0500'>13</span><span id='textcolor833'><span class='ectt-0800'>#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 6, 0)</span></span>
|
|
<a id='x1-36029r14'></a><span class='ecrm-0500'>14</span><span id='textcolor834'><span class='ectt-0800'>#define HAVE_PROC_OPS</span></span>
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<a id='x1-36031r15'></a><span class='ecrm-0500'>15</span><span id='textcolor835'><span class='ectt-0800'>#endif</span></span>
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<a id='x1-36033r16'></a><span class='ecrm-0500'>16</span>
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<a id='x1-36035r17'></a><span class='ecrm-0500'>17</span><span id='textcolor836'><span class='ectt-0800'>#define PROC_NAME "iter"</span></span>
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<a id='x1-36037r18'></a><span class='ecrm-0500'>18</span>
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<a id='x1-36039r19'></a><span class='ecrm-0500'>19</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor837'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span>
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<a id='x1-36041r20'></a><span class='ecrm-0500'>20</span>
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<a id='x1-36043r21'></a><span class='ecrm-0500'>21</span><span id='textcolor838'><span class='ectt-0800'>/**</span></span>
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<a id='x1-36045r22'></a><span class='ecrm-0500'>22</span><span id='textcolor839'><span class='ectt-0800'> * This function is called at the beginning of a sequence.</span></span>
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<a id='x1-36047r23'></a><span class='ecrm-0500'>23</span><span id='textcolor840'><span class='ectt-0800'> * ie, when:</span></span>
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<a id='x1-36049r24'></a><span class='ecrm-0500'>24</span><span id='textcolor841'><span class='ectt-0800'> * - the /proc file is read (first time)</span></span>
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<a id='x1-36051r25'></a><span class='ecrm-0500'>25</span><span id='textcolor842'><span class='ectt-0800'> * - after the function stop (end of sequence)</span></span>
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<a id='x1-36053r26'></a><span class='ecrm-0500'>26</span><span id='textcolor843'><span class='ectt-0800'> *</span></span>
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<a id='x1-36055r27'></a><span class='ecrm-0500'>27</span><span id='textcolor844'><span class='ectt-0800'> */</span></span>
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<a id='x1-36057r28'></a><span class='ecrm-0500'>28</span><span id='textcolor845'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor846'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *my_seq_start(</span><span id='textcolor847'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> seq_file *s, loff_t *pos)</span>
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<a id='x1-36059r29'></a><span class='ecrm-0500'>29</span><span class='ectt-0800'>{</span>
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<a id='x1-36061r30'></a><span class='ecrm-0500'>30</span><span class='ectt-0800'> </span><span id='textcolor848'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor849'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor850'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> counter = 0;</span>
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<a id='x1-36063r31'></a><span class='ecrm-0500'>31</span>
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<a id='x1-36065r32'></a><span class='ecrm-0500'>32</span><span class='ectt-0800'> </span><span id='textcolor851'><span class='ectt-0800'>/* beginning a new sequence ? */</span></span>
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<a id='x1-36067r33'></a><span class='ecrm-0500'>33</span><span class='ectt-0800'> </span><span id='textcolor852'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (*pos == 0) {</span>
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<a id='x1-36069r34'></a><span class='ecrm-0500'>34</span><span class='ectt-0800'> </span><span id='textcolor853'><span class='ectt-0800'>/* yes => return a non null value to begin the sequence */</span></span>
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<a id='x1-36071r35'></a><span class='ecrm-0500'>35</span><span class='ectt-0800'> </span><span id='textcolor854'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> &counter;</span>
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<a id='x1-36073r36'></a><span class='ecrm-0500'>36</span><span class='ectt-0800'> } </span><span id='textcolor855'><span class='ectt-0800'>else</span></span><span class='ectt-0800'> {</span>
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|
<a id='x1-36075r37'></a><span class='ecrm-0500'>37</span><span class='ectt-0800'> </span><span id='textcolor856'><span class='ectt-0800'>/* no => it</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s the end of the sequence, return end to stop reading */</span></span>
|
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<a id='x1-36077r38'></a><span class='ecrm-0500'>38</span><span class='ectt-0800'> *pos = 0;</span>
|
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<a id='x1-36079r39'></a><span class='ecrm-0500'>39</span><span class='ectt-0800'> </span><span id='textcolor857'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> NULL;</span>
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<a id='x1-36081r40'></a><span class='ecrm-0500'>40</span><span class='ectt-0800'> }</span>
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<a id='x1-36083r41'></a><span class='ecrm-0500'>41</span><span class='ectt-0800'>}</span>
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<a id='x1-36085r42'></a><span class='ecrm-0500'>42</span>
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<a id='x1-36087r43'></a><span class='ecrm-0500'>43</span><span id='textcolor858'><span class='ectt-0800'>/**</span></span>
|
|
<a id='x1-36089r44'></a><span class='ecrm-0500'>44</span><span id='textcolor859'><span class='ectt-0800'> * This function is called after the beginning of a sequence.</span></span>
|
|
<a id='x1-36091r45'></a><span class='ecrm-0500'>45</span><span id='textcolor860'><span class='ectt-0800'> * It</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s called untill the return is NULL (this ends the sequence).</span></span>
|
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<a id='x1-36093r46'></a><span class='ecrm-0500'>46</span><span id='textcolor861'><span class='ectt-0800'> *</span></span>
|
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<a id='x1-36095r47'></a><span class='ecrm-0500'>47</span><span id='textcolor862'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-36097r48'></a><span class='ecrm-0500'>48</span><span id='textcolor863'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor864'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *my_seq_next(</span><span id='textcolor865'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> seq_file *s, </span><span id='textcolor866'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *v, loff_t *pos)</span>
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|
<a id='x1-36099r49'></a><span class='ecrm-0500'>49</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-36101r50'></a><span class='ecrm-0500'>50</span><span class='ectt-0800'> </span><span id='textcolor867'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor868'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> *tmp_v = (</span><span id='textcolor869'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor870'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> *) v;</span>
|
|
<a id='x1-36103r51'></a><span class='ecrm-0500'>51</span><span class='ectt-0800'> (*tmp_v)++;</span>
|
|
<a id='x1-36105r52'></a><span class='ecrm-0500'>52</span><span class='ectt-0800'> (*pos)++;</span>
|
|
<a id='x1-36107r53'></a><span class='ecrm-0500'>53</span><span class='ectt-0800'> </span><span id='textcolor871'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> NULL;</span>
|
|
<a id='x1-36109r54'></a><span class='ecrm-0500'>54</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-36111r55'></a><span class='ecrm-0500'>55</span>
|
|
<a id='x1-36113r56'></a><span class='ecrm-0500'>56</span><span id='textcolor872'><span class='ectt-0800'>/**</span></span>
|
|
<a id='x1-36115r57'></a><span class='ecrm-0500'>57</span><span id='textcolor873'><span class='ectt-0800'> * This function is called at the end of a sequence</span></span>
|
|
<a id='x1-36117r58'></a><span class='ecrm-0500'>58</span><span id='textcolor874'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-36119r59'></a><span class='ecrm-0500'>59</span><span id='textcolor875'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-36121r60'></a><span class='ecrm-0500'>60</span><span id='textcolor876'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor877'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> my_seq_stop(</span><span id='textcolor878'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> seq_file *s, </span><span id='textcolor879'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *v)</span>
|
|
<a id='x1-36123r61'></a><span class='ecrm-0500'>61</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-36125r62'></a><span class='ecrm-0500'>62</span><span class='ectt-0800'> </span><span id='textcolor880'><span class='ectt-0800'>/* nothing to do, we use a static value in start() */</span></span>
|
|
<a id='x1-36127r63'></a><span class='ecrm-0500'>63</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-36129r64'></a><span class='ecrm-0500'>64</span>
|
|
<a id='x1-36131r65'></a><span class='ecrm-0500'>65</span><span id='textcolor881'><span class='ectt-0800'>/**</span></span>
|
|
<a id='x1-36133r66'></a><span class='ecrm-0500'>66</span><span id='textcolor882'><span class='ectt-0800'> * This function is called for each "step" of a sequence</span></span>
|
|
<a id='x1-36135r67'></a><span class='ecrm-0500'>67</span><span id='textcolor883'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-36137r68'></a><span class='ecrm-0500'>68</span><span id='textcolor884'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-36139r69'></a><span class='ecrm-0500'>69</span><span id='textcolor885'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor886'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> my_seq_show(</span><span id='textcolor887'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> seq_file *s, </span><span id='textcolor888'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *v)</span>
|
|
<a id='x1-36141r70'></a><span class='ecrm-0500'>70</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-36143r71'></a><span class='ecrm-0500'>71</span><span class='ectt-0800'> loff_t *spos = (loff_t *) v;</span>
|
|
<a id='x1-36145r72'></a><span class='ecrm-0500'>72</span>
|
|
<a id='x1-36147r73'></a><span class='ecrm-0500'>73</span><span class='ectt-0800'> seq_printf(s, </span><span id='textcolor889'><span class='ectt-0800'>"%Ld</span></span><span id='textcolor890'><span class='ectt-0800'>\n</span></span><span id='textcolor891'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, *spos);</span>
|
|
<a id='x1-36149r74'></a><span class='ecrm-0500'>74</span><span class='ectt-0800'> </span><span id='textcolor892'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-36151r75'></a><span class='ecrm-0500'>75</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-36153r76'></a><span class='ecrm-0500'>76</span>
|
|
<a id='x1-36155r77'></a><span class='ecrm-0500'>77</span><span id='textcolor893'><span class='ectt-0800'>/**</span></span>
|
|
<a id='x1-36157r78'></a><span class='ecrm-0500'>78</span><span id='textcolor894'><span class='ectt-0800'> * This structure gather "function" to manage the sequence</span></span>
|
|
<a id='x1-36159r79'></a><span class='ecrm-0500'>79</span><span id='textcolor895'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-36161r80'></a><span class='ecrm-0500'>80</span><span id='textcolor896'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-36163r81'></a><span class='ecrm-0500'>81</span><span id='textcolor897'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor898'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> seq_operations my_seq_ops = {.start = my_seq_start,</span>
|
|
<a id='x1-36165r82'></a><span class='ecrm-0500'>82</span><span class='ectt-0800'> .next = my_seq_next,</span>
|
|
<a id='x1-36167r83'></a><span class='ecrm-0500'>83</span><span class='ectt-0800'> .stop = my_seq_stop,</span>
|
|
<a id='x1-36169r84'></a><span class='ecrm-0500'>84</span><span class='ectt-0800'> .show = my_seq_show};</span>
|
|
<a id='x1-36171r85'></a><span class='ecrm-0500'>85</span>
|
|
<a id='x1-36173r86'></a><span class='ecrm-0500'>86</span><span id='textcolor899'><span class='ectt-0800'>/**</span></span>
|
|
<a id='x1-36175r87'></a><span class='ecrm-0500'>87</span><span id='textcolor900'><span class='ectt-0800'> * This function is called when the /proc file is open.</span></span>
|
|
<a id='x1-36177r88'></a><span class='ecrm-0500'>88</span><span id='textcolor901'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-36179r89'></a><span class='ecrm-0500'>89</span><span id='textcolor902'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-36181r90'></a><span class='ecrm-0500'>90</span><span id='textcolor903'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor904'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> my_open(</span><span id='textcolor905'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> inode *inode, </span><span id='textcolor906'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *file)</span>
|
|
<a id='x1-36183r91'></a><span class='ecrm-0500'>91</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-36185r92'></a><span class='ecrm-0500'>92</span><span class='ectt-0800'> </span><span id='textcolor907'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> seq_open(file, &my_seq_ops);</span>
|
|
<a id='x1-36187r93'></a><span class='ecrm-0500'>93</span><span class='ectt-0800'>};</span>
|
|
<a id='x1-36189r94'></a><span class='ecrm-0500'>94</span>
|
|
<a id='x1-36191r95'></a><span class='ecrm-0500'>95</span><span id='textcolor908'><span class='ectt-0800'>/**</span></span>
|
|
<a id='x1-36193r96'></a><span class='ecrm-0500'>96</span><span id='textcolor909'><span class='ectt-0800'> * This structure gather "function" that manage the /proc file</span></span>
|
|
<a id='x1-36195r97'></a><span class='ecrm-0500'>97</span><span id='textcolor910'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-36197r98'></a><span class='ecrm-0500'>98</span><span id='textcolor911'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-36199r99'></a><span class='ecrm-0500'>99</span><span id='textcolor912'><span class='ectt-0800'>#ifdef HAVE_PROC_OPS</span></span>
|
|
<a id='x1-36201r100'></a><span class='ecrm-0500'>100</span><span id='textcolor913'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor914'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor915'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> proc_ops my_file_ops = {</span>
|
|
<a id='x1-36203r101'></a><span class='ecrm-0500'>101</span><span class='ectt-0800'> .proc_open = my_open,</span>
|
|
<a id='x1-36205r102'></a><span class='ecrm-0500'>102</span><span class='ectt-0800'> .proc_read = seq_read,</span>
|
|
<a id='x1-36207r103'></a><span class='ecrm-0500'>103</span><span class='ectt-0800'> .proc_lseek = seq_lseek,</span>
|
|
<a id='x1-36209r104'></a><span class='ecrm-0500'>104</span><span class='ectt-0800'> .proc_release = seq_release,</span>
|
|
<a id='x1-36211r105'></a><span class='ecrm-0500'>105</span><span class='ectt-0800'>};</span>
|
|
<a id='x1-36213r106'></a><span class='ecrm-0500'>106</span><span id='textcolor916'><span class='ectt-0800'>#else</span></span>
|
|
<a id='x1-36215r107'></a><span class='ecrm-0500'>107</span><span id='textcolor917'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor918'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor919'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file_operations my_file_ops = {</span>
|
|
<a id='x1-36217r108'></a><span class='ecrm-0500'>108</span><span class='ectt-0800'> .open = my_open,</span>
|
|
<a id='x1-36219r109'></a><span class='ecrm-0500'>109</span><span class='ectt-0800'> .read = seq_read,</span>
|
|
<a id='x1-36221r110'></a><span class='ecrm-0500'>110</span><span class='ectt-0800'> .llseek = seq_lseek,</span>
|
|
<a id='x1-36223r111'></a><span class='ecrm-0500'>111</span><span class='ectt-0800'> .release = seq_release,</span>
|
|
<a id='x1-36225r112'></a><span class='ecrm-0500'>112</span><span class='ectt-0800'>};</span>
|
|
<a id='x1-36227r113'></a><span class='ecrm-0500'>113</span><span id='textcolor920'><span class='ectt-0800'>#endif</span></span>
|
|
<a id='x1-36229r114'></a><span class='ecrm-0500'>114</span>
|
|
<a id='x1-36231r115'></a><span class='ecrm-0500'>115</span><span id='textcolor921'><span class='ectt-0800'>/**</span></span>
|
|
<a id='x1-36233r116'></a><span class='ecrm-0500'>116</span><span id='textcolor922'><span class='ectt-0800'> * This function is called when the module is loaded</span></span>
|
|
<a id='x1-36235r117'></a><span class='ecrm-0500'>117</span><span id='textcolor923'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-36237r118'></a><span class='ecrm-0500'>118</span><span id='textcolor924'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-36239r119'></a><span class='ecrm-0500'>119</span><span id='textcolor925'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> init_module(</span><span id='textcolor926'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-36241r120'></a><span class='ecrm-0500'>120</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-36243r121'></a><span class='ecrm-0500'>121</span><span class='ectt-0800'> </span><span id='textcolor927'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> proc_dir_entry *entry;</span>
|
|
<a id='x1-36245r122'></a><span class='ecrm-0500'>122</span>
|
|
<a id='x1-36247r123'></a><span class='ecrm-0500'>123</span><span class='ectt-0800'> entry = proc_create(PROC_NAME, 0, NULL, &my_file_ops);</span>
|
|
<a id='x1-36249r124'></a><span class='ecrm-0500'>124</span><span class='ectt-0800'> </span><span id='textcolor928'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (entry == NULL) {</span>
|
|
<a id='x1-36251r125'></a><span class='ecrm-0500'>125</span><span class='ectt-0800'> remove_proc_entry(PROC_NAME, NULL);</span>
|
|
<a id='x1-36253r126'></a><span class='ecrm-0500'>126</span><span class='ectt-0800'> pr_debug(</span><span id='textcolor929'><span class='ectt-0800'>"Error: Could not initialize /proc/%s</span></span><span id='textcolor930'><span class='ectt-0800'>\n</span></span><span id='textcolor931'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, PROC_NAME);</span>
|
|
<a id='x1-36255r127'></a><span class='ecrm-0500'>127</span><span class='ectt-0800'> </span><span id='textcolor932'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -ENOMEM;</span>
|
|
<a id='x1-36257r128'></a><span class='ecrm-0500'>128</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-36259r129'></a><span class='ecrm-0500'>129</span>
|
|
<a id='x1-36261r130'></a><span class='ecrm-0500'>130</span><span class='ectt-0800'> </span><span id='textcolor933'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-36263r131'></a><span class='ecrm-0500'>131</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-36265r132'></a><span class='ecrm-0500'>132</span>
|
|
<a id='x1-36267r133'></a><span class='ecrm-0500'>133</span><span id='textcolor934'><span class='ectt-0800'>/**</span></span>
|
|
<a id='x1-36269r134'></a><span class='ecrm-0500'>134</span><span id='textcolor935'><span class='ectt-0800'> * This function is called when the module is unloaded.</span></span>
|
|
<a id='x1-36271r135'></a><span class='ecrm-0500'>135</span><span id='textcolor936'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-36273r136'></a><span class='ecrm-0500'>136</span><span id='textcolor937'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-36275r137'></a><span class='ecrm-0500'>137</span><span id='textcolor938'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> cleanup_module(</span><span id='textcolor939'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-36277r138'></a><span class='ecrm-0500'>138</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-36279r139'></a><span class='ecrm-0500'>139</span><span class='ectt-0800'> remove_proc_entry(PROC_NAME, NULL);</span>
|
|
<a id='x1-36281r140'></a><span class='ecrm-0500'>140</span><span class='ectt-0800'> pr_debug(</span><span id='textcolor940'><span class='ectt-0800'>"/proc/%s removed</span></span><span id='textcolor941'><span class='ectt-0800'>\n</span></span><span id='textcolor942'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, PROC_NAME);</span>
|
|
<a id='x1-36283r141'></a><span class='ecrm-0500'>141</span><span class='ectt-0800'>}</span></pre>
|
|
<!-- l. 1050 --><p class='indent'> If you want more information, you can read this web page:
|
|
</p>
|
|
<ul class='itemize1'>
|
|
<li class='itemize'><a class='url' href='http://lwn.net/Articles/22355/'><span class='ectt-1000'>http://lwn.net/Articles/22355/</span></a>
|
|
</li>
|
|
<li class='itemize'><a class='url' href='https://kernelnewbies.org/Documents/SeqFileHowTo'><span class='ectt-1000'>https://kernelnewbies.org/Documents/SeqFileHowTo</span></a></li></ul>
|
|
<!-- l. 1057 --><p class='indent'> You can also read the code of fs/seq_file.c in the linux kernel.
|
|
</p>
|
|
<h3 class='sectionHead' id='sysfs-interacting-with-your-module'><span class='titlemark'>0.8 </span> <a id='x1-370000.8'></a>sysfs: Interacting with your module</h3>
|
|
<!-- l. 1061 --><p class='noindent'><span class='ecti-1000'>sysfs </span>allows you to interact with the running kernel from userspace by reading or
|
|
setting variables inside of modules. This can be useful for debugging purposes, or just
|
|
as an interface for applications or scripts. You can find sysfs directories and files
|
|
under the <span class='ecti-1000'>sys </span>directory on your system.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb41'><a id='x1-37003r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>ls -l /sys</span></pre>
|
|
<!-- l. 1069 --><p class='indent'> An example of a hello world module which includes the creation of a variable
|
|
accessible via sysfs is given below.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb42'><a id='x1-37005r1'></a><span class='ecrm-0500'>1</span><span id='textcolor943'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-37007r2'></a><span class='ecrm-0500'>2</span><span id='textcolor944'><span class='ectt-0800'> * hello-sysfs.c sysfs example</span></span>
|
|
<a id='x1-37009r3'></a><span class='ecrm-0500'>3</span><span id='textcolor945'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-37011r4'></a><span class='ecrm-0500'>4</span><span id='textcolor946'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor947'><span class='ectt-0800'><linux/fs.h></span></span>
|
|
<a id='x1-37013r5'></a><span class='ecrm-0500'>5</span><span id='textcolor948'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor949'><span class='ectt-0800'><linux/init.h></span></span>
|
|
<a id='x1-37015r6'></a><span class='ecrm-0500'>6</span><span id='textcolor950'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor951'><span class='ectt-0800'><linux/kobject.h></span></span>
|
|
<a id='x1-37017r7'></a><span class='ecrm-0500'>7</span><span id='textcolor952'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor953'><span class='ectt-0800'><linux/module.h></span></span>
|
|
<a id='x1-37019r8'></a><span class='ecrm-0500'>8</span><span id='textcolor954'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor955'><span class='ectt-0800'><linux/string.h></span></span>
|
|
<a id='x1-37021r9'></a><span class='ecrm-0500'>9</span><span id='textcolor956'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor957'><span class='ectt-0800'><linux/sysfs.h></span></span>
|
|
<a id='x1-37023r10'></a><span class='ecrm-0500'>10</span>
|
|
<a id='x1-37025r11'></a><span class='ecrm-0500'>11</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor958'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-37027r12'></a><span class='ecrm-0500'>12</span>
|
|
<a id='x1-37029r13'></a><span class='ecrm-0500'>13</span><span id='textcolor959'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor960'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> kobject *mymodule;</span>
|
|
<a id='x1-37031r14'></a><span class='ecrm-0500'>14</span>
|
|
<a id='x1-37033r15'></a><span class='ecrm-0500'>15</span><span id='textcolor961'><span class='ectt-0800'>/* the variable you want to be able to change */</span></span>
|
|
<a id='x1-37035r16'></a><span class='ecrm-0500'>16</span><span id='textcolor962'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor963'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> myvariable = 0;</span>
|
|
<a id='x1-37037r17'></a><span class='ecrm-0500'>17</span>
|
|
<a id='x1-37039r18'></a><span class='ecrm-0500'>18</span><span id='textcolor964'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor965'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> myvariable_show(</span><span id='textcolor966'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> kobject *kobj,</span>
|
|
<a id='x1-37041r19'></a><span class='ecrm-0500'>19</span><span class='ectt-0800'> </span><span id='textcolor967'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> kobj_attribute *attr,</span>
|
|
<a id='x1-37043r20'></a><span class='ecrm-0500'>20</span><span class='ectt-0800'> </span><span id='textcolor968'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *buf)</span>
|
|
<a id='x1-37045r21'></a><span class='ecrm-0500'>21</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-37047r22'></a><span class='ecrm-0500'>22</span><span class='ectt-0800'> </span><span id='textcolor969'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> sprintf(buf, </span><span id='textcolor970'><span class='ectt-0800'>"%d</span></span><span id='textcolor971'><span class='ectt-0800'>\n</span></span><span id='textcolor972'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, myvariable);</span>
|
|
<a id='x1-37049r23'></a><span class='ecrm-0500'>23</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-37051r24'></a><span class='ecrm-0500'>24</span>
|
|
<a id='x1-37053r25'></a><span class='ecrm-0500'>25</span><span id='textcolor973'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor974'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> myvariable_store(</span><span id='textcolor975'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> kobject *kobj,</span>
|
|
<a id='x1-37055r26'></a><span class='ecrm-0500'>26</span><span class='ectt-0800'> </span><span id='textcolor976'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> kobj_attribute *attr,</span>
|
|
<a id='x1-37057r27'></a><span class='ecrm-0500'>27</span><span class='ectt-0800'> </span><span id='textcolor977'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *buf,</span>
|
|
<a id='x1-37059r28'></a><span class='ecrm-0500'>28</span><span class='ectt-0800'> </span><span id='textcolor978'><span class='ectt-0800'>size_t</span></span><span class='ectt-0800'> count)</span>
|
|
<a id='x1-37061r29'></a><span class='ecrm-0500'>29</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-37063r30'></a><span class='ecrm-0500'>30</span><span class='ectt-0800'> sscanf(buf, </span><span id='textcolor979'><span class='ectt-0800'>"%du"</span></span><span class='ectt-0800'>, &myvariable);</span>
|
|
<a id='x1-37065r31'></a><span class='ecrm-0500'>31</span><span class='ectt-0800'> </span><span id='textcolor980'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> count;</span>
|
|
<a id='x1-37067r32'></a><span class='ecrm-0500'>32</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-37069r33'></a><span class='ecrm-0500'>33</span>
|
|
<a id='x1-37071r34'></a><span class='ecrm-0500'>34</span>
|
|
<a id='x1-37073r35'></a><span class='ecrm-0500'>35</span><span id='textcolor981'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor982'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> kobj_attribute myvariable_attribute =</span>
|
|
<a id='x1-37075r36'></a><span class='ecrm-0500'>36</span><span class='ectt-0800'> __ATTR(myvariable, 0660, myvariable_show, (</span><span id='textcolor983'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *) myvariable_store);</span>
|
|
<a id='x1-37077r37'></a><span class='ecrm-0500'>37</span>
|
|
<a id='x1-37079r38'></a><span class='ecrm-0500'>38</span><span id='textcolor984'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor985'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> __init mymodule_init(</span><span id='textcolor986'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-37081r39'></a><span class='ecrm-0500'>39</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-37083r40'></a><span class='ecrm-0500'>40</span><span class='ectt-0800'> </span><span id='textcolor987'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> error = 0;</span>
|
|
<a id='x1-37085r41'></a><span class='ecrm-0500'>41</span>
|
|
<a id='x1-37087r42'></a><span class='ecrm-0500'>42</span><span class='ectt-0800'> pr_info(</span><span id='textcolor988'><span class='ectt-0800'>"mymodule: initialised</span></span><span id='textcolor989'><span class='ectt-0800'>\n</span></span><span id='textcolor990'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-37089r43'></a><span class='ecrm-0500'>43</span>
|
|
<a id='x1-37091r44'></a><span class='ecrm-0500'>44</span><span class='ectt-0800'> mymodule = kobject_create_and_add(</span><span id='textcolor991'><span class='ectt-0800'>"mymodule"</span></span><span class='ectt-0800'>, kernel_kobj);</span>
|
|
<a id='x1-37093r45'></a><span class='ecrm-0500'>45</span><span class='ectt-0800'> </span><span id='textcolor992'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (!mymodule)</span>
|
|
<a id='x1-37095r46'></a><span class='ecrm-0500'>46</span><span class='ectt-0800'> </span><span id='textcolor993'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -ENOMEM;</span>
|
|
<a id='x1-37097r47'></a><span class='ecrm-0500'>47</span>
|
|
<a id='x1-37099r48'></a><span class='ecrm-0500'>48</span><span class='ectt-0800'> error = sysfs_create_file(mymodule, &myvariable_attribute.attr);</span>
|
|
<a id='x1-37101r49'></a><span class='ecrm-0500'>49</span><span class='ectt-0800'> </span><span id='textcolor994'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (error) {</span>
|
|
<a id='x1-37103r50'></a><span class='ecrm-0500'>50</span><span class='ectt-0800'> pr_info(</span>
|
|
<a id='x1-37105r51'></a><span class='ecrm-0500'>51</span><span class='ectt-0800'> </span><span id='textcolor995'><span class='ectt-0800'>"failed to create the myvariable file "</span></span>
|
|
<a id='x1-37107r52'></a><span class='ecrm-0500'>52</span><span class='ectt-0800'> </span><span id='textcolor996'><span class='ectt-0800'>"in /sys/kernel/mymodule</span></span><span id='textcolor997'><span class='ectt-0800'>\n</span></span><span id='textcolor998'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-37109r53'></a><span class='ecrm-0500'>53</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-37111r54'></a><span class='ecrm-0500'>54</span>
|
|
<a id='x1-37113r55'></a><span class='ecrm-0500'>55</span><span class='ectt-0800'> </span><span id='textcolor999'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> error;</span>
|
|
<a id='x1-37115r56'></a><span class='ecrm-0500'>56</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-37117r57'></a><span class='ecrm-0500'>57</span>
|
|
<a id='x1-37119r58'></a><span class='ecrm-0500'>58</span><span id='textcolor1000'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1001'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> __exit mymodule_exit(</span><span id='textcolor1002'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-37121r59'></a><span class='ecrm-0500'>59</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-37123r60'></a><span class='ecrm-0500'>60</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1003'><span class='ectt-0800'>"mymodule: Exit success</span></span><span id='textcolor1004'><span class='ectt-0800'>\n</span></span><span id='textcolor1005'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-37125r61'></a><span class='ecrm-0500'>61</span><span class='ectt-0800'> kobject_put(mymodule);</span>
|
|
<a id='x1-37127r62'></a><span class='ecrm-0500'>62</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-37129r63'></a><span class='ecrm-0500'>63</span>
|
|
<a id='x1-37131r64'></a><span class='ecrm-0500'>64</span><span class='ectt-0800'>module_init(mymodule_init);</span>
|
|
<a id='x1-37133r65'></a><span class='ecrm-0500'>65</span><span class='ectt-0800'>module_exit(mymodule_exit);</span></pre>
|
|
<!-- l. 1073 --><p class='indent'> Make and install the module:
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb43'><a id='x1-37137r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>make</span>
|
|
<a id='x1-37139r2'></a><span class='ecrm-0500'>2</span><span class='ectt-1000'>sudo insmod hello-sysfs.ko</span></pre>
|
|
<!-- l. 1080 --><p class='indent'> Check that it exists:
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
|
|
|
|
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb44'><a id='x1-37142r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>sudo lsmod | grep hello_sysfs</span></pre>
|
|
<!-- l. 1086 --><p class='indent'> What is the current value of <span class='ecti-1000'>myvariable </span>?
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb45'><a id='x1-37145r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>cat /sys/kernel/mymodule/myvariable</span></pre>
|
|
<!-- l. 1092 --><p class='indent'> Set the value of <span class='ecti-1000'>myvariable </span>and check that it changed.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb46'><a id='x1-37149r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>echo </span><span id='textcolor1006'><span class='ectt-1000'>"32"</span></span><span class='ectt-1000'> > /sys/kernel/mymodule/myvariable</span>
|
|
<a id='x1-37151r2'></a><span class='ecrm-0500'>2</span><span class='ectt-1000'>cat /sys/kernel/mymodule/myvariable</span></pre>
|
|
<!-- l. 1099 --><p class='indent'> Finally, remove the test module:
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb47'><a id='x1-37154r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>sudo rmmod hello_sysfs</span></pre>
|
|
<!-- l. 1105 --><p class='noindent'>
|
|
</p>
|
|
<h3 class='sectionHead' id='talking-to-device-files'><span class='titlemark'>0.9 </span> <a id='x1-380000.9'></a>Talking To Device Files</h3>
|
|
<!-- l. 1107 --><p class='noindent'>Device files are supposed to represent physical devices. Most physical devices are
|
|
used for output as well as input, so there has to be some mechanism for
|
|
device drivers in the kernel to get the output to send to the device from
|
|
processes. This is done by opening the device file for output and writing to it,
|
|
just like writing to a file. In the following example, this is implemented by
|
|
device_write.
|
|
</p><!-- l. 1112 --><p class='indent'> This is not always enough. Imagine you had a serial port connected to a modem
|
|
(even if you have an internal modem, it is still implemented from the CPU’s
|
|
perspective as a serial port connected to a modem, so you don’t have to tax
|
|
your imagination too hard). The natural thing to do would be to use the
|
|
device file to write things to the modem (either modem commands or data to
|
|
be sent through the phone line) and read things from the modem (either
|
|
responses for commands or the data received through the phone line). However,
|
|
this leaves open the question of what to do when you need to talk to the
|
|
serial port itself, for example to send the rate at which data is sent and
|
|
received.
|
|
</p><!-- l. 1117 --><p class='indent'> The answer in Unix is to use a special function called <span class='ecbx-1000'>ioctl </span>(short for
|
|
Input Output ConTroL). Every device can have its own ioctl commands,
|
|
which can be read ioctl’s (to send information from a process to the kernel),
|
|
write ioctl’s (to return information to a process), both or neither. Notice
|
|
|
|
|
|
|
|
here the roles of read and write are reversed again, so in ioctl’s read is to
|
|
send information to the kernel and write is to receive information from the
|
|
kernel.
|
|
</p><!-- l. 1121 --><p class='indent'> The ioctl function is called with three parameters: the file descriptor of the
|
|
appropriate device file, the ioctl number, and a parameter, which is of type
|
|
long so you can use a cast to use it to pass anything. You will not be able
|
|
to pass a structure this way, but you will be able to pass a pointer to the
|
|
structure.
|
|
</p><!-- l. 1124 --><p class='indent'> The ioctl number encodes the major device number, the type of the ioctl, the
|
|
command, and the type of the parameter. This ioctl number is usually created by a
|
|
macro call (_IO, _IOR, _IOW or _IOWR — depending on the type) in a header
|
|
file. This header file should then be included both by the programs which will use
|
|
ioctl (so they can generate the appropriate ioctl’s) and by the kernel module (so it
|
|
can understand it). In the example below, the header file is chardev.h and the
|
|
program which uses it is ioctl.c.
|
|
</p><!-- l. 1129 --><p class='indent'> If you want to use ioctls in your own kernel modules, it is best to receive an
|
|
official ioctl assignment, so if you accidentally get somebody else’s ioctls, or if they
|
|
get yours, you’ll know something is wrong. For more information, consult the kernel
|
|
source tree at Documentation/ioctl-number.txt.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb48'><a id='x1-38002r1'></a><span class='ecrm-0500'>1</span><span id='textcolor1007'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38004r2'></a><span class='ecrm-0500'>2</span><span id='textcolor1008'><span class='ectt-0800'> * chardev2.c - Create an input/output character device</span></span>
|
|
<a id='x1-38006r3'></a><span class='ecrm-0500'>3</span><span id='textcolor1009'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38008r4'></a><span class='ecrm-0500'>4</span>
|
|
<a id='x1-38010r5'></a><span class='ecrm-0500'>5</span><span id='textcolor1010'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1011'><span class='ectt-0800'><linux/cdev.h></span></span>
|
|
<a id='x1-38012r6'></a><span class='ecrm-0500'>6</span><span id='textcolor1012'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1013'><span class='ectt-0800'><linux/delay.h></span></span>
|
|
<a id='x1-38014r7'></a><span class='ecrm-0500'>7</span><span id='textcolor1014'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1015'><span class='ectt-0800'><linux/device.h></span></span>
|
|
<a id='x1-38016r8'></a><span class='ecrm-0500'>8</span><span id='textcolor1016'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1017'><span class='ectt-0800'><linux/fs.h></span></span>
|
|
<a id='x1-38018r9'></a><span class='ecrm-0500'>9</span><span id='textcolor1018'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1019'><span class='ectt-0800'><linux/init.h></span></span>
|
|
<a id='x1-38020r10'></a><span class='ecrm-0500'>10</span><span id='textcolor1020'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1021'><span class='ectt-0800'><linux/irq.h></span></span>
|
|
<a id='x1-38022r11'></a><span class='ecrm-0500'>11</span><span id='textcolor1022'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1023'><span class='ectt-0800'><linux/kernel.h> /* We</span><span class='tctt-0800'>'</span><span class='ectt-0800'>re doing kernel work */</span></span>
|
|
<a id='x1-38024r12'></a><span class='ecrm-0500'>12</span><span id='textcolor1024'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1025'><span class='ectt-0800'><linux/module.h> /* Specifically, a module */</span></span>
|
|
<a id='x1-38026r13'></a><span class='ecrm-0500'>13</span><span id='textcolor1026'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1027'><span class='ectt-0800'><linux/poll.h></span></span>
|
|
<a id='x1-38028r14'></a><span class='ecrm-0500'>14</span>
|
|
<a id='x1-38030r15'></a><span class='ecrm-0500'>15</span><span id='textcolor1028'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1029'><span class='ectt-0800'>"chardev.h"</span></span>
|
|
<a id='x1-38032r16'></a><span class='ecrm-0500'>16</span><span id='textcolor1030'><span class='ectt-0800'>#define SUCCESS 0</span></span>
|
|
<a id='x1-38034r17'></a><span class='ecrm-0500'>17</span><span id='textcolor1031'><span class='ectt-0800'>#define DEVICE_NAME "char_dev"</span></span>
|
|
<a id='x1-38036r18'></a><span class='ecrm-0500'>18</span><span id='textcolor1032'><span class='ectt-0800'>#define BUF_LEN 80</span></span>
|
|
<a id='x1-38038r19'></a><span class='ecrm-0500'>19</span>
|
|
<a id='x1-38040r20'></a><span class='ecrm-0500'>20</span><span id='textcolor1033'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38042r21'></a><span class='ecrm-0500'>21</span><span id='textcolor1034'><span class='ectt-0800'> * Is the device open right now? Used to prevent</span></span>
|
|
<a id='x1-38044r22'></a><span class='ecrm-0500'>22</span><span id='textcolor1035'><span class='ectt-0800'> * concurent access into the same device</span></span>
|
|
<a id='x1-38046r23'></a><span class='ecrm-0500'>23</span><span id='textcolor1036'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38048r24'></a><span class='ecrm-0500'>24</span><span id='textcolor1037'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1038'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> Device_Open = 0;</span>
|
|
<a id='x1-38050r25'></a><span class='ecrm-0500'>25</span>
|
|
<a id='x1-38052r26'></a><span class='ecrm-0500'>26</span><span id='textcolor1039'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38054r27'></a><span class='ecrm-0500'>27</span><span id='textcolor1040'><span class='ectt-0800'> * The message the device will give when asked</span></span>
|
|
<a id='x1-38056r28'></a><span class='ecrm-0500'>28</span><span id='textcolor1041'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38058r29'></a><span class='ecrm-0500'>29</span><span id='textcolor1042'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1043'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> Message[BUF_LEN];</span>
|
|
<a id='x1-38060r30'></a><span class='ecrm-0500'>30</span>
|
|
<a id='x1-38062r31'></a><span class='ecrm-0500'>31</span><span id='textcolor1044'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38064r32'></a><span class='ecrm-0500'>32</span><span id='textcolor1045'><span class='ectt-0800'> * How far did the process reading the message get?</span></span>
|
|
<a id='x1-38066r33'></a><span class='ecrm-0500'>33</span><span id='textcolor1046'><span class='ectt-0800'> * Useful if the message is larger than the size of the</span></span>
|
|
<a id='x1-38068r34'></a><span class='ecrm-0500'>34</span><span id='textcolor1047'><span class='ectt-0800'> * buffer we get to fill in device_read.</span></span>
|
|
<a id='x1-38070r35'></a><span class='ecrm-0500'>35</span><span id='textcolor1048'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38072r36'></a><span class='ecrm-0500'>36</span><span id='textcolor1049'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1050'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *Message_Ptr;</span>
|
|
<a id='x1-38074r37'></a><span class='ecrm-0500'>37</span>
|
|
<a id='x1-38076r38'></a><span class='ecrm-0500'>38</span><span id='textcolor1051'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1052'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> Major; </span><span id='textcolor1053'><span class='ectt-0800'>/* Major number assigned to our device driver */</span></span>
|
|
<a id='x1-38078r39'></a><span class='ecrm-0500'>39</span><span id='textcolor1054'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1055'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> class *cls;</span>
|
|
<a id='x1-38080r40'></a><span class='ecrm-0500'>40</span>
|
|
<a id='x1-38082r41'></a><span class='ecrm-0500'>41</span><span id='textcolor1056'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38084r42'></a><span class='ecrm-0500'>42</span><span id='textcolor1057'><span class='ectt-0800'> * This is called whenever a process attempts to open the device file</span></span>
|
|
<a id='x1-38086r43'></a><span class='ecrm-0500'>43</span><span id='textcolor1058'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38088r44'></a><span class='ecrm-0500'>44</span><span id='textcolor1059'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1060'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> device_open(</span><span id='textcolor1061'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> inode *inode, </span><span id='textcolor1062'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *file)</span>
|
|
<a id='x1-38090r45'></a><span class='ecrm-0500'>45</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-38092r46'></a><span class='ecrm-0500'>46</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1063'><span class='ectt-0800'>"device_open(%p)</span></span><span id='textcolor1064'><span class='ectt-0800'>\n</span></span><span id='textcolor1065'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, file);</span>
|
|
<a id='x1-38094r47'></a><span class='ecrm-0500'>47</span>
|
|
<a id='x1-38096r48'></a><span class='ecrm-0500'>48</span><span class='ectt-0800'> </span><span id='textcolor1066'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38098r49'></a><span class='ecrm-0500'>49</span><span id='textcolor1067'><span class='ectt-0800'> * We don</span><span class='tctt-0800'>'</span><span class='ectt-0800'>t want to talk to two processes at the same time</span></span>
|
|
<a id='x1-38100r50'></a><span class='ecrm-0500'>50</span><span id='textcolor1068'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38102r51'></a><span class='ecrm-0500'>51</span><span class='ectt-0800'> </span><span id='textcolor1069'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (Device_Open)</span>
|
|
<a id='x1-38104r52'></a><span class='ecrm-0500'>52</span><span class='ectt-0800'> </span><span id='textcolor1070'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -EBUSY;</span>
|
|
<a id='x1-38106r53'></a><span class='ecrm-0500'>53</span>
|
|
<a id='x1-38108r54'></a><span class='ecrm-0500'>54</span><span class='ectt-0800'> Device_Open++;</span>
|
|
<a id='x1-38110r55'></a><span class='ecrm-0500'>55</span><span class='ectt-0800'> </span><span id='textcolor1071'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38112r56'></a><span class='ecrm-0500'>56</span><span id='textcolor1072'><span class='ectt-0800'> * Initialize the message</span></span>
|
|
<a id='x1-38114r57'></a><span class='ecrm-0500'>57</span><span id='textcolor1073'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38116r58'></a><span class='ecrm-0500'>58</span><span class='ectt-0800'> Message_Ptr = Message;</span>
|
|
<a id='x1-38118r59'></a><span class='ecrm-0500'>59</span><span class='ectt-0800'> try_module_get(THIS_MODULE);</span>
|
|
<a id='x1-38120r60'></a><span class='ecrm-0500'>60</span><span class='ectt-0800'> </span><span id='textcolor1074'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> SUCCESS;</span>
|
|
<a id='x1-38122r61'></a><span class='ecrm-0500'>61</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-38124r62'></a><span class='ecrm-0500'>62</span>
|
|
<a id='x1-38126r63'></a><span class='ecrm-0500'>63</span><span id='textcolor1075'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1076'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> device_release(</span><span id='textcolor1077'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> inode *inode, </span><span id='textcolor1078'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *file)</span>
|
|
<a id='x1-38128r64'></a><span class='ecrm-0500'>64</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-38130r65'></a><span class='ecrm-0500'>65</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1079'><span class='ectt-0800'>"device_release(%p,%p)</span></span><span id='textcolor1080'><span class='ectt-0800'>\n</span></span><span id='textcolor1081'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, inode, file);</span>
|
|
<a id='x1-38132r66'></a><span class='ecrm-0500'>66</span>
|
|
<a id='x1-38134r67'></a><span class='ecrm-0500'>67</span><span class='ectt-0800'> </span><span id='textcolor1082'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38136r68'></a><span class='ecrm-0500'>68</span><span id='textcolor1083'><span class='ectt-0800'> * We</span><span class='tctt-0800'>'</span><span class='ectt-0800'>re now ready for our next caller</span></span>
|
|
<a id='x1-38138r69'></a><span class='ecrm-0500'>69</span><span id='textcolor1084'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38140r70'></a><span class='ecrm-0500'>70</span><span class='ectt-0800'> Device_Open--;</span>
|
|
<a id='x1-38142r71'></a><span class='ecrm-0500'>71</span>
|
|
<a id='x1-38144r72'></a><span class='ecrm-0500'>72</span><span class='ectt-0800'> module_put(THIS_MODULE);</span>
|
|
<a id='x1-38146r73'></a><span class='ecrm-0500'>73</span><span class='ectt-0800'> </span><span id='textcolor1085'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> SUCCESS;</span>
|
|
<a id='x1-38148r74'></a><span class='ecrm-0500'>74</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-38150r75'></a><span class='ecrm-0500'>75</span>
|
|
<a id='x1-38152r76'></a><span class='ecrm-0500'>76</span><span id='textcolor1086'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38154r77'></a><span class='ecrm-0500'>77</span><span id='textcolor1087'><span class='ectt-0800'> * This function is called whenever a process which has already opened the</span></span>
|
|
<a id='x1-38156r78'></a><span class='ecrm-0500'>78</span><span id='textcolor1088'><span class='ectt-0800'> * device file attempts to read from it.</span></span>
|
|
<a id='x1-38158r79'></a><span class='ecrm-0500'>79</span><span id='textcolor1089'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38160r80'></a><span class='ecrm-0500'>80</span><span id='textcolor1090'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1091'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> device_read(</span><span id='textcolor1092'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *file, </span><span id='textcolor1093'><span class='ectt-0800'>/* see include/linux/fs.h */</span></span>
|
|
<a id='x1-38162r81'></a><span class='ecrm-0500'>81</span><span class='ectt-0800'> </span><span id='textcolor1094'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> __user *buffer, </span><span id='textcolor1095'><span class='ectt-0800'>/* buffer to be</span></span>
|
|
<a id='x1-38164r82'></a><span class='ecrm-0500'>82</span><span id='textcolor1096'><span class='ectt-0800'> * filled with data */</span></span>
|
|
<a id='x1-38166r83'></a><span class='ecrm-0500'>83</span><span class='ectt-0800'> </span><span id='textcolor1097'><span class='ectt-0800'>size_t</span></span><span class='ectt-0800'> length, </span><span id='textcolor1098'><span class='ectt-0800'>/* length of the buffer */</span></span>
|
|
<a id='x1-38168r84'></a><span class='ecrm-0500'>84</span><span class='ectt-0800'> loff_t *offset)</span>
|
|
<a id='x1-38170r85'></a><span class='ecrm-0500'>85</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-38172r86'></a><span class='ecrm-0500'>86</span><span class='ectt-0800'> </span><span id='textcolor1099'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38174r87'></a><span class='ecrm-0500'>87</span><span id='textcolor1100'><span class='ectt-0800'> * Number of bytes actually written to the buffer</span></span>
|
|
<a id='x1-38176r88'></a><span class='ecrm-0500'>88</span><span id='textcolor1101'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38178r89'></a><span class='ecrm-0500'>89</span><span class='ectt-0800'> </span><span id='textcolor1102'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> bytes_read = 0;</span>
|
|
<a id='x1-38180r90'></a><span class='ecrm-0500'>90</span>
|
|
<a id='x1-38182r91'></a><span class='ecrm-0500'>91</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1103'><span class='ectt-0800'>"device_read(%p,%p,%ld)</span></span><span id='textcolor1104'><span class='ectt-0800'>\n</span></span><span id='textcolor1105'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, file, buffer, length);</span>
|
|
<a id='x1-38184r92'></a><span class='ecrm-0500'>92</span>
|
|
<a id='x1-38186r93'></a><span class='ecrm-0500'>93</span><span class='ectt-0800'> </span><span id='textcolor1106'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38188r94'></a><span class='ecrm-0500'>94</span><span id='textcolor1107'><span class='ectt-0800'> * If we</span><span class='tctt-0800'>'</span><span class='ectt-0800'>re at the end of the message, return 0</span></span>
|
|
<a id='x1-38190r95'></a><span class='ecrm-0500'>95</span><span id='textcolor1108'><span class='ectt-0800'> * (which signifies end of file)</span></span>
|
|
<a id='x1-38192r96'></a><span class='ecrm-0500'>96</span><span id='textcolor1109'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38194r97'></a><span class='ecrm-0500'>97</span><span class='ectt-0800'> </span><span id='textcolor1110'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (*Message_Ptr == 0)</span>
|
|
<a id='x1-38196r98'></a><span class='ecrm-0500'>98</span><span class='ectt-0800'> </span><span id='textcolor1111'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-38198r99'></a><span class='ecrm-0500'>99</span>
|
|
<a id='x1-38200r100'></a><span class='ecrm-0500'>100</span><span class='ectt-0800'> </span><span id='textcolor1112'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38202r101'></a><span class='ecrm-0500'>101</span><span id='textcolor1113'><span class='ectt-0800'> * Actually put the data into the buffer</span></span>
|
|
<a id='x1-38204r102'></a><span class='ecrm-0500'>102</span><span id='textcolor1114'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38206r103'></a><span class='ecrm-0500'>103</span><span class='ectt-0800'> </span><span id='textcolor1115'><span class='ectt-0800'>while</span></span><span class='ectt-0800'> (length && *Message_Ptr) {</span>
|
|
<a id='x1-38208r104'></a><span class='ecrm-0500'>104</span><span class='ectt-0800'> </span><span id='textcolor1116'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38210r105'></a><span class='ecrm-0500'>105</span><span id='textcolor1117'><span class='ectt-0800'> * Because the buffer is in the user data segment,</span></span>
|
|
<a id='x1-38212r106'></a><span class='ecrm-0500'>106</span><span id='textcolor1118'><span class='ectt-0800'> * not the kernel data segment, assignment wouldn</span><span class='tctt-0800'>'</span><span class='ectt-0800'>t</span></span>
|
|
<a id='x1-38214r107'></a><span class='ecrm-0500'>107</span><span id='textcolor1119'><span class='ectt-0800'> * work. Instead, we have to use put_user which</span></span>
|
|
<a id='x1-38216r108'></a><span class='ecrm-0500'>108</span><span id='textcolor1120'><span class='ectt-0800'> * copies data from the kernel data segment to the</span></span>
|
|
<a id='x1-38218r109'></a><span class='ecrm-0500'>109</span><span id='textcolor1121'><span class='ectt-0800'> * user data segment.</span></span>
|
|
<a id='x1-38220r110'></a><span class='ecrm-0500'>110</span><span id='textcolor1122'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38222r111'></a><span class='ecrm-0500'>111</span><span class='ectt-0800'> put_user(*(Message_Ptr++), buffer++);</span>
|
|
<a id='x1-38224r112'></a><span class='ecrm-0500'>112</span><span class='ectt-0800'> length--;</span>
|
|
<a id='x1-38226r113'></a><span class='ecrm-0500'>113</span><span class='ectt-0800'> bytes_read++;</span>
|
|
<a id='x1-38228r114'></a><span class='ecrm-0500'>114</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-38230r115'></a><span class='ecrm-0500'>115</span>
|
|
<a id='x1-38232r116'></a><span class='ecrm-0500'>116</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1123'><span class='ectt-0800'>"Read %d bytes, %ld left</span></span><span id='textcolor1124'><span class='ectt-0800'>\n</span></span><span id='textcolor1125'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, bytes_read, length);</span>
|
|
<a id='x1-38234r117'></a><span class='ecrm-0500'>117</span>
|
|
<a id='x1-38236r118'></a><span class='ecrm-0500'>118</span><span class='ectt-0800'> </span><span id='textcolor1126'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38238r119'></a><span class='ecrm-0500'>119</span><span id='textcolor1127'><span class='ectt-0800'> * Read functions are supposed to return the number</span></span>
|
|
<a id='x1-38240r120'></a><span class='ecrm-0500'>120</span><span id='textcolor1128'><span class='ectt-0800'> * of bytes actually inserted into the buffer</span></span>
|
|
<a id='x1-38242r121'></a><span class='ecrm-0500'>121</span><span id='textcolor1129'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38244r122'></a><span class='ecrm-0500'>122</span><span class='ectt-0800'> </span><span id='textcolor1130'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> bytes_read;</span>
|
|
<a id='x1-38246r123'></a><span class='ecrm-0500'>123</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-38248r124'></a><span class='ecrm-0500'>124</span>
|
|
<a id='x1-38250r125'></a><span class='ecrm-0500'>125</span><span id='textcolor1131'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38252r126'></a><span class='ecrm-0500'>126</span><span id='textcolor1132'><span class='ectt-0800'> * This function is called when somebody tries to</span></span>
|
|
<a id='x1-38254r127'></a><span class='ecrm-0500'>127</span><span id='textcolor1133'><span class='ectt-0800'> * write into our device file.</span></span>
|
|
<a id='x1-38256r128'></a><span class='ecrm-0500'>128</span><span id='textcolor1134'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38258r129'></a><span class='ecrm-0500'>129</span><span id='textcolor1135'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1136'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> device_write(</span><span id='textcolor1137'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *file,</span>
|
|
<a id='x1-38260r130'></a><span class='ecrm-0500'>130</span><span class='ectt-0800'> </span><span id='textcolor1138'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor1139'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> __user *buffer,</span>
|
|
<a id='x1-38262r131'></a><span class='ecrm-0500'>131</span><span class='ectt-0800'> </span><span id='textcolor1140'><span class='ectt-0800'>size_t</span></span><span class='ectt-0800'> length,</span>
|
|
<a id='x1-38264r132'></a><span class='ecrm-0500'>132</span><span class='ectt-0800'> loff_t *offset)</span>
|
|
<a id='x1-38266r133'></a><span class='ecrm-0500'>133</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-38268r134'></a><span class='ecrm-0500'>134</span><span class='ectt-0800'> </span><span id='textcolor1141'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> i;</span>
|
|
<a id='x1-38270r135'></a><span class='ecrm-0500'>135</span>
|
|
<a id='x1-38272r136'></a><span class='ecrm-0500'>136</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1142'><span class='ectt-0800'>"device_write(%p,%s,%ld)"</span></span><span class='ectt-0800'>, file, buffer, length);</span>
|
|
<a id='x1-38274r137'></a><span class='ecrm-0500'>137</span>
|
|
<a id='x1-38276r138'></a><span class='ecrm-0500'>138</span><span class='ectt-0800'> </span><span id='textcolor1143'><span class='ectt-0800'>for</span></span><span class='ectt-0800'> (i = 0; i < length && i < BUF_LEN; i++)</span>
|
|
<a id='x1-38278r139'></a><span class='ecrm-0500'>139</span><span class='ectt-0800'> get_user(Message[i], buffer + i);</span>
|
|
<a id='x1-38280r140'></a><span class='ecrm-0500'>140</span>
|
|
<a id='x1-38282r141'></a><span class='ecrm-0500'>141</span><span class='ectt-0800'> Message_Ptr = Message;</span>
|
|
<a id='x1-38284r142'></a><span class='ecrm-0500'>142</span>
|
|
<a id='x1-38286r143'></a><span class='ecrm-0500'>143</span><span class='ectt-0800'> </span><span id='textcolor1144'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38288r144'></a><span class='ecrm-0500'>144</span><span id='textcolor1145'><span class='ectt-0800'> * Again, return the number of input characters used</span></span>
|
|
<a id='x1-38290r145'></a><span class='ecrm-0500'>145</span><span id='textcolor1146'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38292r146'></a><span class='ecrm-0500'>146</span><span class='ectt-0800'> </span><span id='textcolor1147'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> i;</span>
|
|
<a id='x1-38294r147'></a><span class='ecrm-0500'>147</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-38296r148'></a><span class='ecrm-0500'>148</span>
|
|
<a id='x1-38298r149'></a><span class='ecrm-0500'>149</span><span id='textcolor1148'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38300r150'></a><span class='ecrm-0500'>150</span><span id='textcolor1149'><span class='ectt-0800'> * This function is called whenever a process tries to do an ioctl on our</span></span>
|
|
<a id='x1-38302r151'></a><span class='ecrm-0500'>151</span><span id='textcolor1150'><span class='ectt-0800'> * device file. We get two extra parameters (additional to the inode and file</span></span>
|
|
<a id='x1-38304r152'></a><span class='ecrm-0500'>152</span><span id='textcolor1151'><span class='ectt-0800'> * structures, which all device functions get): the number of the ioctl called</span></span>
|
|
<a id='x1-38306r153'></a><span class='ecrm-0500'>153</span><span id='textcolor1152'><span class='ectt-0800'> * and the parameter given to the ioctl function.</span></span>
|
|
<a id='x1-38308r154'></a><span class='ecrm-0500'>154</span><span id='textcolor1153'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-38310r155'></a><span class='ecrm-0500'>155</span><span id='textcolor1154'><span class='ectt-0800'> * If the ioctl is write or read/write (meaning output is returned to the</span></span>
|
|
<a id='x1-38312r156'></a><span class='ecrm-0500'>156</span><span id='textcolor1155'><span class='ectt-0800'> * calling process), the ioctl call returns the output of this function.</span></span>
|
|
<a id='x1-38314r157'></a><span class='ecrm-0500'>157</span><span id='textcolor1156'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-38316r158'></a><span class='ecrm-0500'>158</span><span id='textcolor1157'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38318r159'></a><span class='ecrm-0500'>159</span><span id='textcolor1158'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> device_ioctl(</span><span id='textcolor1159'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *file, </span><span id='textcolor1160'><span class='ectt-0800'>/* ditto */</span></span>
|
|
<a id='x1-38320r160'></a><span class='ecrm-0500'>160</span><span class='ectt-0800'> </span><span id='textcolor1161'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1162'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> ioctl_num, </span><span id='textcolor1163'><span class='ectt-0800'>/* number and param for ioctl */</span></span>
|
|
<a id='x1-38322r161'></a><span class='ecrm-0500'>161</span><span class='ectt-0800'> </span><span id='textcolor1164'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1165'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> ioctl_param)</span>
|
|
<a id='x1-38324r162'></a><span class='ecrm-0500'>162</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-38326r163'></a><span class='ecrm-0500'>163</span><span class='ectt-0800'> </span><span id='textcolor1166'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> i;</span>
|
|
<a id='x1-38328r164'></a><span class='ecrm-0500'>164</span><span class='ectt-0800'> </span><span id='textcolor1167'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *temp;</span>
|
|
<a id='x1-38330r165'></a><span class='ecrm-0500'>165</span><span class='ectt-0800'> </span><span id='textcolor1168'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> ch;</span>
|
|
<a id='x1-38332r166'></a><span class='ecrm-0500'>166</span>
|
|
<a id='x1-38334r167'></a><span class='ecrm-0500'>167</span><span class='ectt-0800'> </span><span id='textcolor1169'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38336r168'></a><span class='ecrm-0500'>168</span><span id='textcolor1170'><span class='ectt-0800'> * Switch according to the ioctl called</span></span>
|
|
<a id='x1-38338r169'></a><span class='ecrm-0500'>169</span><span id='textcolor1171'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38340r170'></a><span class='ecrm-0500'>170</span><span class='ectt-0800'> </span><span id='textcolor1172'><span class='ectt-0800'>switch</span></span><span class='ectt-0800'> (ioctl_num) {</span>
|
|
<a id='x1-38342r171'></a><span class='ecrm-0500'>171</span><span class='ectt-0800'> </span><span id='textcolor1173'><span class='ectt-0800'>case</span></span><span class='ectt-0800'> IOCTL_SET_MSG:</span>
|
|
<a id='x1-38344r172'></a><span class='ecrm-0500'>172</span><span class='ectt-0800'> </span><span id='textcolor1174'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38346r173'></a><span class='ecrm-0500'>173</span><span id='textcolor1175'><span class='ectt-0800'> * Receive a pointer to a message (in user space) and set that</span></span>
|
|
<a id='x1-38348r174'></a><span class='ecrm-0500'>174</span><span id='textcolor1176'><span class='ectt-0800'> * to be the device</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s message. Get the parameter given to</span></span>
|
|
<a id='x1-38350r175'></a><span class='ecrm-0500'>175</span><span id='textcolor1177'><span class='ectt-0800'> * ioctl by the process.</span></span>
|
|
<a id='x1-38352r176'></a><span class='ecrm-0500'>176</span><span id='textcolor1178'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38354r177'></a><span class='ecrm-0500'>177</span><span class='ectt-0800'> temp = (</span><span id='textcolor1179'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *) ioctl_param;</span>
|
|
<a id='x1-38356r178'></a><span class='ecrm-0500'>178</span>
|
|
<a id='x1-38358r179'></a><span class='ecrm-0500'>179</span><span class='ectt-0800'> </span><span id='textcolor1180'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38360r180'></a><span class='ecrm-0500'>180</span><span id='textcolor1181'><span class='ectt-0800'> * Find the length of the message</span></span>
|
|
<a id='x1-38362r181'></a><span class='ecrm-0500'>181</span><span id='textcolor1182'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38364r182'></a><span class='ecrm-0500'>182</span><span class='ectt-0800'> get_user(ch, temp);</span>
|
|
<a id='x1-38366r183'></a><span class='ecrm-0500'>183</span><span class='ectt-0800'> </span><span id='textcolor1183'><span class='ectt-0800'>for</span></span><span class='ectt-0800'> (i = 0; ch && i < BUF_LEN; i++, temp++)</span>
|
|
<a id='x1-38368r184'></a><span class='ecrm-0500'>184</span><span class='ectt-0800'> get_user(ch, temp);</span>
|
|
<a id='x1-38370r185'></a><span class='ecrm-0500'>185</span>
|
|
<a id='x1-38372r186'></a><span class='ecrm-0500'>186</span><span class='ectt-0800'> device_write(file, (</span><span id='textcolor1184'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *) ioctl_param, i, 0);</span>
|
|
<a id='x1-38374r187'></a><span class='ecrm-0500'>187</span><span class='ectt-0800'> </span><span id='textcolor1185'><span class='ectt-0800'>break</span></span><span class='ectt-0800'>;</span>
|
|
<a id='x1-38376r188'></a><span class='ecrm-0500'>188</span>
|
|
<a id='x1-38378r189'></a><span class='ecrm-0500'>189</span><span class='ectt-0800'> </span><span id='textcolor1186'><span class='ectt-0800'>case</span></span><span class='ectt-0800'> IOCTL_GET_MSG:</span>
|
|
<a id='x1-38380r190'></a><span class='ecrm-0500'>190</span><span class='ectt-0800'> </span><span id='textcolor1187'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38382r191'></a><span class='ecrm-0500'>191</span><span id='textcolor1188'><span class='ectt-0800'> * Give the current message to the calling process -</span></span>
|
|
<a id='x1-38384r192'></a><span class='ecrm-0500'>192</span><span id='textcolor1189'><span class='ectt-0800'> * the parameter we got is a pointer, fill it.</span></span>
|
|
<a id='x1-38386r193'></a><span class='ecrm-0500'>193</span><span id='textcolor1190'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38388r194'></a><span class='ecrm-0500'>194</span><span class='ectt-0800'> i = device_read(file, (</span><span id='textcolor1191'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *) ioctl_param, 99, 0);</span>
|
|
<a id='x1-38390r195'></a><span class='ecrm-0500'>195</span>
|
|
<a id='x1-38392r196'></a><span class='ecrm-0500'>196</span><span class='ectt-0800'> </span><span id='textcolor1192'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38394r197'></a><span class='ecrm-0500'>197</span><span id='textcolor1193'><span class='ectt-0800'> * Put a zero at the end of the buffer, so it will be</span></span>
|
|
<a id='x1-38396r198'></a><span class='ecrm-0500'>198</span><span id='textcolor1194'><span class='ectt-0800'> * properly terminated</span></span>
|
|
<a id='x1-38398r199'></a><span class='ecrm-0500'>199</span><span id='textcolor1195'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38400r200'></a><span class='ecrm-0500'>200</span><span class='ectt-0800'> put_user(</span><span id='textcolor1196'><span class='tctt-0800'>'</span><span class='ectt-0800'>\0</span><span class='tctt-0800'>'</span></span><span class='ectt-0800'>, (</span><span id='textcolor1197'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *) ioctl_param + i);</span>
|
|
<a id='x1-38402r201'></a><span class='ecrm-0500'>201</span><span class='ectt-0800'> </span><span id='textcolor1198'><span class='ectt-0800'>break</span></span><span class='ectt-0800'>;</span>
|
|
<a id='x1-38404r202'></a><span class='ecrm-0500'>202</span>
|
|
<a id='x1-38406r203'></a><span class='ecrm-0500'>203</span><span class='ectt-0800'> </span><span id='textcolor1199'><span class='ectt-0800'>case</span></span><span class='ectt-0800'> IOCTL_GET_NTH_BYTE:</span>
|
|
<a id='x1-38408r204'></a><span class='ecrm-0500'>204</span><span class='ectt-0800'> </span><span id='textcolor1200'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38410r205'></a><span class='ecrm-0500'>205</span><span id='textcolor1201'><span class='ectt-0800'> * This ioctl is both input (ioctl_param) and</span></span>
|
|
<a id='x1-38412r206'></a><span class='ecrm-0500'>206</span><span id='textcolor1202'><span class='ectt-0800'> * output (the return value of this function)</span></span>
|
|
<a id='x1-38414r207'></a><span class='ecrm-0500'>207</span><span id='textcolor1203'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38416r208'></a><span class='ecrm-0500'>208</span><span class='ectt-0800'> </span><span id='textcolor1204'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> Message[ioctl_param];</span>
|
|
<a id='x1-38418r209'></a><span class='ecrm-0500'>209</span><span class='ectt-0800'> </span><span id='textcolor1205'><span class='ectt-0800'>break</span></span><span class='ectt-0800'>;</span>
|
|
<a id='x1-38420r210'></a><span class='ecrm-0500'>210</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-38422r211'></a><span class='ecrm-0500'>211</span>
|
|
<a id='x1-38424r212'></a><span class='ecrm-0500'>212</span><span class='ectt-0800'> </span><span id='textcolor1206'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> SUCCESS;</span>
|
|
<a id='x1-38426r213'></a><span class='ecrm-0500'>213</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-38428r214'></a><span class='ecrm-0500'>214</span>
|
|
<a id='x1-38430r215'></a><span class='ecrm-0500'>215</span><span id='textcolor1207'><span class='ectt-0800'>/* Module Declarations */</span></span>
|
|
<a id='x1-38432r216'></a><span class='ecrm-0500'>216</span>
|
|
<a id='x1-38434r217'></a><span class='ecrm-0500'>217</span><span id='textcolor1208'><span class='ectt-0800'>/*</span></span>
|
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<a id='x1-38436r218'></a><span class='ecrm-0500'>218</span><span id='textcolor1209'><span class='ectt-0800'> * This structure will hold the functions to be called</span></span>
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<a id='x1-38438r219'></a><span class='ecrm-0500'>219</span><span id='textcolor1210'><span class='ectt-0800'> * when a process does something to the device we</span></span>
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<a id='x1-38440r220'></a><span class='ecrm-0500'>220</span><span id='textcolor1211'><span class='ectt-0800'> * created. Since a pointer to this structure is kept in</span></span>
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<a id='x1-38442r221'></a><span class='ecrm-0500'>221</span><span id='textcolor1212'><span class='ectt-0800'> * the devices table, it can</span><span class='tctt-0800'>'</span><span class='ectt-0800'>t be local to</span></span>
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<a id='x1-38444r222'></a><span class='ecrm-0500'>222</span><span id='textcolor1213'><span class='ectt-0800'> * init_module. NULL is for unimplemented functions.</span></span>
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<a id='x1-38446r223'></a><span class='ecrm-0500'>223</span><span id='textcolor1214'><span class='ectt-0800'> */</span></span>
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<a id='x1-38448r224'></a><span class='ecrm-0500'>224</span><span id='textcolor1215'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file_operations Fops = {</span>
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<a id='x1-38450r225'></a><span class='ecrm-0500'>225</span><span class='ectt-0800'> .read = device_read,</span>
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<a id='x1-38452r226'></a><span class='ecrm-0500'>226</span><span class='ectt-0800'> .write = device_write,</span>
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|
<a id='x1-38454r227'></a><span class='ecrm-0500'>227</span><span class='ectt-0800'> .unlocked_ioctl = device_ioctl,</span>
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<a id='x1-38456r228'></a><span class='ecrm-0500'>228</span><span class='ectt-0800'> .open = device_open,</span>
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<a id='x1-38458r229'></a><span class='ecrm-0500'>229</span><span class='ectt-0800'> .release = device_release, </span><span id='textcolor1216'><span class='ectt-0800'>/* a.k.a. close */</span></span>
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<a id='x1-38460r230'></a><span class='ecrm-0500'>230</span><span class='ectt-0800'>};</span>
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<a id='x1-38462r231'></a><span class='ecrm-0500'>231</span>
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<a id='x1-38464r232'></a><span class='ecrm-0500'>232</span><span id='textcolor1217'><span class='ectt-0800'>/*</span></span>
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<a id='x1-38466r233'></a><span class='ecrm-0500'>233</span><span id='textcolor1218'><span class='ectt-0800'> * Initialize the module - Register the character device</span></span>
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<a id='x1-38468r234'></a><span class='ecrm-0500'>234</span><span id='textcolor1219'><span class='ectt-0800'> */</span></span>
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|
<a id='x1-38470r235'></a><span class='ecrm-0500'>235</span><span id='textcolor1220'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> init_module()</span>
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<a id='x1-38472r236'></a><span class='ecrm-0500'>236</span><span class='ectt-0800'>{</span>
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<a id='x1-38474r237'></a><span class='ecrm-0500'>237</span><span class='ectt-0800'> </span><span id='textcolor1221'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> ret_val;</span>
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|
<a id='x1-38476r238'></a><span class='ecrm-0500'>238</span><span class='ectt-0800'> </span><span id='textcolor1222'><span class='ectt-0800'>/*</span></span>
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<a id='x1-38478r239'></a><span class='ecrm-0500'>239</span><span id='textcolor1223'><span class='ectt-0800'> * Register the character device (atleast try)</span></span>
|
|
<a id='x1-38480r240'></a><span class='ecrm-0500'>240</span><span id='textcolor1224'><span class='ectt-0800'> */</span></span>
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<a id='x1-38482r241'></a><span class='ecrm-0500'>241</span><span class='ectt-0800'> ret_val = register_chrdev(MAJOR_NUM, DEVICE_NAME, &Fops);</span>
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<a id='x1-38484r242'></a><span class='ecrm-0500'>242</span>
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<a id='x1-38486r243'></a><span class='ecrm-0500'>243</span><span class='ectt-0800'> </span><span id='textcolor1225'><span class='ectt-0800'>/*</span></span>
|
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<a id='x1-38488r244'></a><span class='ecrm-0500'>244</span><span id='textcolor1226'><span class='ectt-0800'> * Negative values signify an error</span></span>
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<a id='x1-38490r245'></a><span class='ecrm-0500'>245</span><span id='textcolor1227'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38492r246'></a><span class='ecrm-0500'>246</span><span class='ectt-0800'> </span><span id='textcolor1228'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (ret_val < 0) {</span>
|
|
<a id='x1-38494r247'></a><span class='ecrm-0500'>247</span><span class='ectt-0800'> pr_alert(</span><span id='textcolor1229'><span class='ectt-0800'>"%s failed with %d</span></span><span id='textcolor1230'><span class='ectt-0800'>\n</span></span><span id='textcolor1231'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>,</span>
|
|
<a id='x1-38496r248'></a><span class='ecrm-0500'>248</span><span class='ectt-0800'> </span><span id='textcolor1232'><span class='ectt-0800'>"Sorry, registering the character device "</span></span><span class='ectt-0800'>, ret_val);</span>
|
|
<a id='x1-38498r249'></a><span class='ecrm-0500'>249</span><span class='ectt-0800'> </span><span id='textcolor1233'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> ret_val;</span>
|
|
<a id='x1-38500r250'></a><span class='ecrm-0500'>250</span><span class='ectt-0800'> }</span>
|
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<a id='x1-38502r251'></a><span class='ecrm-0500'>251</span>
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<a id='x1-38504r252'></a><span class='ecrm-0500'>252</span><span class='ectt-0800'> Major = ret_val;</span>
|
|
<a id='x1-38506r253'></a><span class='ecrm-0500'>253</span>
|
|
<a id='x1-38508r254'></a><span class='ecrm-0500'>254</span><span class='ectt-0800'> cls = class_create(THIS_MODULE, DEVICE_FILE_NAME);</span>
|
|
<a id='x1-38510r255'></a><span class='ecrm-0500'>255</span><span class='ectt-0800'> device_create(cls, NULL, MKDEV(Major, MAJOR_NUM), NULL, DEVICE_FILE_NAME);</span>
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|
<a id='x1-38512r256'></a><span class='ecrm-0500'>256</span>
|
|
<a id='x1-38514r257'></a><span class='ecrm-0500'>257</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1234'><span class='ectt-0800'>"Device created on /dev/%s</span></span><span id='textcolor1235'><span class='ectt-0800'>\n</span></span><span id='textcolor1236'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, DEVICE_FILE_NAME);</span>
|
|
<a id='x1-38516r258'></a><span class='ecrm-0500'>258</span>
|
|
<a id='x1-38518r259'></a><span class='ecrm-0500'>259</span><span class='ectt-0800'> </span><span id='textcolor1237'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-38520r260'></a><span class='ecrm-0500'>260</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-38522r261'></a><span class='ecrm-0500'>261</span>
|
|
<a id='x1-38524r262'></a><span class='ecrm-0500'>262</span><span id='textcolor1238'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38526r263'></a><span class='ecrm-0500'>263</span><span id='textcolor1239'><span class='ectt-0800'> * Cleanup - unregister the appropriate file from /proc</span></span>
|
|
<a id='x1-38528r264'></a><span class='ecrm-0500'>264</span><span id='textcolor1240'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38530r265'></a><span class='ecrm-0500'>265</span><span id='textcolor1241'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> cleanup_module()</span>
|
|
<a id='x1-38532r266'></a><span class='ecrm-0500'>266</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-38534r267'></a><span class='ecrm-0500'>267</span><span class='ectt-0800'> device_destroy(cls, MKDEV(Major, 0));</span>
|
|
<a id='x1-38536r268'></a><span class='ecrm-0500'>268</span><span class='ectt-0800'> class_destroy(cls);</span>
|
|
<a id='x1-38538r269'></a><span class='ecrm-0500'>269</span>
|
|
<a id='x1-38540r270'></a><span class='ecrm-0500'>270</span><span class='ectt-0800'> </span><span id='textcolor1242'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38542r271'></a><span class='ecrm-0500'>271</span><span id='textcolor1243'><span class='ectt-0800'> * Unregister the device</span></span>
|
|
<a id='x1-38544r272'></a><span class='ecrm-0500'>272</span><span id='textcolor1244'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38546r273'></a><span class='ecrm-0500'>273</span><span class='ectt-0800'> unregister_chrdev(Major, DEVICE_NAME);</span>
|
|
<a id='x1-38548r274'></a><span class='ecrm-0500'>274</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-38550r275'></a><span class='ecrm-0500'>275</span>
|
|
<a id='x1-38552r276'></a><span class='ecrm-0500'>276</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor1245'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
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|
|
|
<!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb49'><a id='x1-38554r1'></a><span class='ecrm-0500'>1</span><span id='textcolor1246'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38556r2'></a><span class='ecrm-0500'>2</span><span id='textcolor1247'><span class='ectt-0800'> * chardev.h - the header file with the ioctl definitions.</span></span>
|
|
<a id='x1-38558r3'></a><span class='ecrm-0500'>3</span><span id='textcolor1248'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-38560r4'></a><span class='ecrm-0500'>4</span><span id='textcolor1249'><span class='ectt-0800'> * The declarations here have to be in a header file, because</span></span>
|
|
<a id='x1-38562r5'></a><span class='ecrm-0500'>5</span><span id='textcolor1250'><span class='ectt-0800'> * they need to be known both to the kernel module</span></span>
|
|
<a id='x1-38564r6'></a><span class='ecrm-0500'>6</span><span id='textcolor1251'><span class='ectt-0800'> * (in chardev.c) and the process calling ioctl (ioctl.c)</span></span>
|
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<a id='x1-38566r7'></a><span class='ecrm-0500'>7</span><span id='textcolor1252'><span class='ectt-0800'> */</span></span>
|
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<a id='x1-38568r8'></a><span class='ecrm-0500'>8</span>
|
|
<a id='x1-38570r9'></a><span class='ecrm-0500'>9</span><span id='textcolor1253'><span class='ectt-0800'>#ifndef CHARDEV_H</span></span>
|
|
<a id='x1-38572r10'></a><span class='ecrm-0500'>10</span><span id='textcolor1254'><span class='ectt-0800'>#define CHARDEV_H</span></span>
|
|
<a id='x1-38574r11'></a><span class='ecrm-0500'>11</span>
|
|
<a id='x1-38576r12'></a><span class='ecrm-0500'>12</span><span id='textcolor1255'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1256'><span class='ectt-0800'><linux/ioctl.h></span></span>
|
|
<a id='x1-38578r13'></a><span class='ecrm-0500'>13</span>
|
|
<a id='x1-38580r14'></a><span class='ecrm-0500'>14</span><span id='textcolor1257'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38582r15'></a><span class='ecrm-0500'>15</span><span id='textcolor1258'><span class='ectt-0800'> * The major device number. We can</span><span class='tctt-0800'>'</span><span class='ectt-0800'>t rely on dynamic</span></span>
|
|
<a id='x1-38584r16'></a><span class='ecrm-0500'>16</span><span id='textcolor1259'><span class='ectt-0800'> * registration any more, because ioctls need to know</span></span>
|
|
<a id='x1-38586r17'></a><span class='ecrm-0500'>17</span><span id='textcolor1260'><span class='ectt-0800'> * it.</span></span>
|
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<a id='x1-38588r18'></a><span class='ecrm-0500'>18</span><span id='textcolor1261'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38590r19'></a><span class='ecrm-0500'>19</span><span id='textcolor1262'><span class='ectt-0800'>#define MAJOR_NUM 100</span></span>
|
|
<a id='x1-38592r20'></a><span class='ecrm-0500'>20</span>
|
|
<a id='x1-38594r21'></a><span class='ecrm-0500'>21</span><span id='textcolor1263'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38596r22'></a><span class='ecrm-0500'>22</span><span id='textcolor1264'><span class='ectt-0800'> * Set the message of the device driver</span></span>
|
|
<a id='x1-38598r23'></a><span class='ecrm-0500'>23</span><span id='textcolor1265'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38600r24'></a><span class='ecrm-0500'>24</span><span id='textcolor1266'><span class='ectt-0800'>#define IOCTL_SET_MSG _IOW(MAJOR_NUM, 0, char *)</span></span>
|
|
<a id='x1-38602r25'></a><span class='ecrm-0500'>25</span><span id='textcolor1267'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38604r26'></a><span class='ecrm-0500'>26</span><span id='textcolor1268'><span class='ectt-0800'> * _IOW means that we</span><span class='tctt-0800'>'</span><span class='ectt-0800'>re creating an ioctl command</span></span>
|
|
<a id='x1-38606r27'></a><span class='ecrm-0500'>27</span><span id='textcolor1269'><span class='ectt-0800'> * number for passing information from a user process</span></span>
|
|
<a id='x1-38608r28'></a><span class='ecrm-0500'>28</span><span id='textcolor1270'><span class='ectt-0800'> * to the kernel module.</span></span>
|
|
<a id='x1-38610r29'></a><span class='ecrm-0500'>29</span><span id='textcolor1271'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-38612r30'></a><span class='ecrm-0500'>30</span><span id='textcolor1272'><span class='ectt-0800'> * The first arguments, MAJOR_NUM, is the major device</span></span>
|
|
<a id='x1-38614r31'></a><span class='ecrm-0500'>31</span><span id='textcolor1273'><span class='ectt-0800'> * number we</span><span class='tctt-0800'>'</span><span class='ectt-0800'>re using.</span></span>
|
|
<a id='x1-38616r32'></a><span class='ecrm-0500'>32</span><span id='textcolor1274'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-38618r33'></a><span class='ecrm-0500'>33</span><span id='textcolor1275'><span class='ectt-0800'> * The second argument is the number of the command</span></span>
|
|
<a id='x1-38620r34'></a><span class='ecrm-0500'>34</span><span id='textcolor1276'><span class='ectt-0800'> * (there could be several with different meanings).</span></span>
|
|
<a id='x1-38622r35'></a><span class='ecrm-0500'>35</span><span id='textcolor1277'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-38624r36'></a><span class='ecrm-0500'>36</span><span id='textcolor1278'><span class='ectt-0800'> * The third argument is the type we want to get from</span></span>
|
|
<a id='x1-38626r37'></a><span class='ecrm-0500'>37</span><span id='textcolor1279'><span class='ectt-0800'> * the process to the kernel.</span></span>
|
|
<a id='x1-38628r38'></a><span class='ecrm-0500'>38</span><span id='textcolor1280'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38630r39'></a><span class='ecrm-0500'>39</span>
|
|
<a id='x1-38632r40'></a><span class='ecrm-0500'>40</span><span id='textcolor1281'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38634r41'></a><span class='ecrm-0500'>41</span><span id='textcolor1282'><span class='ectt-0800'> * Get the message of the device driver</span></span>
|
|
<a id='x1-38636r42'></a><span class='ecrm-0500'>42</span><span id='textcolor1283'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38638r43'></a><span class='ecrm-0500'>43</span><span id='textcolor1284'><span class='ectt-0800'>#define IOCTL_GET_MSG _IOR(MAJOR_NUM, 1, char *)</span></span>
|
|
<a id='x1-38640r44'></a><span class='ecrm-0500'>44</span><span id='textcolor1285'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38642r45'></a><span class='ecrm-0500'>45</span><span id='textcolor1286'><span class='ectt-0800'> * This IOCTL is used for output, to get the message</span></span>
|
|
<a id='x1-38644r46'></a><span class='ecrm-0500'>46</span><span id='textcolor1287'><span class='ectt-0800'> * of the device driver. However, we still need the</span></span>
|
|
<a id='x1-38646r47'></a><span class='ecrm-0500'>47</span><span id='textcolor1288'><span class='ectt-0800'> * buffer to place the message in to be input,</span></span>
|
|
<a id='x1-38648r48'></a><span class='ecrm-0500'>48</span><span id='textcolor1289'><span class='ectt-0800'> * as it is allocated by the process.</span></span>
|
|
<a id='x1-38650r49'></a><span class='ecrm-0500'>49</span><span id='textcolor1290'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38652r50'></a><span class='ecrm-0500'>50</span>
|
|
<a id='x1-38654r51'></a><span class='ecrm-0500'>51</span><span id='textcolor1291'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38656r52'></a><span class='ecrm-0500'>52</span><span id='textcolor1292'><span class='ectt-0800'> * Get the n</span><span class='tctt-0800'>'</span><span class='ectt-0800'>th byte of the message</span></span>
|
|
<a id='x1-38658r53'></a><span class='ecrm-0500'>53</span><span id='textcolor1293'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38660r54'></a><span class='ecrm-0500'>54</span><span id='textcolor1294'><span class='ectt-0800'>#define IOCTL_GET_NTH_BYTE _IOWR(MAJOR_NUM, 2, int)</span></span>
|
|
<a id='x1-38662r55'></a><span class='ecrm-0500'>55</span><span id='textcolor1295'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38664r56'></a><span class='ecrm-0500'>56</span><span id='textcolor1296'><span class='ectt-0800'> * The IOCTL is used for both input and output. It</span></span>
|
|
<a id='x1-38666r57'></a><span class='ecrm-0500'>57</span><span id='textcolor1297'><span class='ectt-0800'> * receives from the user a number, n, and returns</span></span>
|
|
<a id='x1-38668r58'></a><span class='ecrm-0500'>58</span><span id='textcolor1298'><span class='ectt-0800'> * Message[n].</span></span>
|
|
<a id='x1-38670r59'></a><span class='ecrm-0500'>59</span><span id='textcolor1299'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38672r60'></a><span class='ecrm-0500'>60</span>
|
|
<a id='x1-38674r61'></a><span class='ecrm-0500'>61</span><span id='textcolor1300'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38676r62'></a><span class='ecrm-0500'>62</span><span id='textcolor1301'><span class='ectt-0800'> * The name of the device file</span></span>
|
|
<a id='x1-38678r63'></a><span class='ecrm-0500'>63</span><span id='textcolor1302'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38680r64'></a><span class='ecrm-0500'>64</span><span id='textcolor1303'><span class='ectt-0800'>#define DEVICE_FILE_NAME "char_dev"</span></span>
|
|
<a id='x1-38682r65'></a><span class='ecrm-0500'>65</span>
|
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<a id='x1-38684r66'></a><span class='ecrm-0500'>66</span><span id='textcolor1304'><span class='ectt-0800'>#endif</span></span></pre>
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<!-- l. 1 --><p class='indent'>
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</p>
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<pre class='fancyvrb' id='fancyvrb50'><a id='x1-38686r1'></a><span class='ecrm-0500'>1</span><span id='textcolor1305'><span class='ectt-0800'>/*</span></span>
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<a id='x1-38688r2'></a><span class='ecrm-0500'>2</span><span id='textcolor1306'><span class='ectt-0800'> * ioctl.c</span></span>
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<a id='x1-38690r3'></a><span class='ecrm-0500'>3</span><span id='textcolor1307'><span class='ectt-0800'> */</span></span>
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<a id='x1-38692r4'></a><span class='ecrm-0500'>4</span><span id='textcolor1308'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1309'><span class='ectt-0800'><linux/cdev.h></span></span>
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<a id='x1-38694r5'></a><span class='ecrm-0500'>5</span><span id='textcolor1310'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1311'><span class='ectt-0800'><linux/fs.h></span></span>
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<a id='x1-38696r6'></a><span class='ecrm-0500'>6</span><span id='textcolor1312'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1313'><span class='ectt-0800'><linux/init.h></span></span>
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<a id='x1-38698r7'></a><span class='ecrm-0500'>7</span><span id='textcolor1314'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1315'><span class='ectt-0800'><linux/ioctl.h></span></span>
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<a id='x1-38700r8'></a><span class='ecrm-0500'>8</span><span id='textcolor1316'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1317'><span class='ectt-0800'><linux/module.h></span></span>
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<a id='x1-38702r9'></a><span class='ecrm-0500'>9</span><span id='textcolor1318'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1319'><span class='ectt-0800'><linux/slab.h></span></span>
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<a id='x1-38704r10'></a><span class='ecrm-0500'>10</span><span id='textcolor1320'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1321'><span class='ectt-0800'><linux/uaccess.h></span></span>
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<a id='x1-38706r11'></a><span class='ecrm-0500'>11</span>
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<a id='x1-38708r12'></a><span class='ecrm-0500'>12</span><span id='textcolor1322'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> ioctl_arg {</span>
|
|
<a id='x1-38710r13'></a><span class='ecrm-0500'>13</span><span class='ectt-0800'> </span><span id='textcolor1323'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1324'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> reg;</span>
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<a id='x1-38712r14'></a><span class='ecrm-0500'>14</span><span class='ectt-0800'> </span><span id='textcolor1325'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1326'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> val;</span>
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<a id='x1-38714r15'></a><span class='ecrm-0500'>15</span><span class='ectt-0800'>};</span>
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<a id='x1-38716r16'></a><span class='ecrm-0500'>16</span>
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<a id='x1-38718r17'></a><span class='ecrm-0500'>17</span><span id='textcolor1327'><span class='ectt-0800'>/* Documentation/ioctl/ioctl-number.txt */</span></span>
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|
<a id='x1-38720r18'></a><span class='ecrm-0500'>18</span><span id='textcolor1328'><span class='ectt-0800'>#define IOC_MAGIC </span><span class='tctt-0800'>'</span><span class='ectt-0800'>\x66</span><span class='tctt-0800'>'</span></span>
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<a id='x1-38722r19'></a><span class='ecrm-0500'>19</span>
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|
<a id='x1-38724r20'></a><span class='ecrm-0500'>20</span><span id='textcolor1329'><span class='ectt-0800'>#define IOCTL_VALSET _IOW(IOC_MAGIC, 0, struct ioctl_arg)</span></span>
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<a id='x1-38726r21'></a><span class='ecrm-0500'>21</span><span id='textcolor1330'><span class='ectt-0800'>#define IOCTL_VALGET _IOR(IOC_MAGIC, 1, struct ioctl_arg)</span></span>
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|
<a id='x1-38728r22'></a><span class='ecrm-0500'>22</span><span id='textcolor1331'><span class='ectt-0800'>#define IOCTL_VALGET_NUM _IOR(IOC_MAGIC, 2, int)</span></span>
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|
<a id='x1-38730r23'></a><span class='ecrm-0500'>23</span><span id='textcolor1332'><span class='ectt-0800'>#define IOCTL_VALSET_NUM _IOW(IOC_MAGIC, 3, int)</span></span>
|
|
<a id='x1-38732r24'></a><span class='ecrm-0500'>24</span>
|
|
<a id='x1-38734r25'></a><span class='ecrm-0500'>25</span><span id='textcolor1333'><span class='ectt-0800'>#define IOCTL_VAL_MAXNR 3</span></span>
|
|
<a id='x1-38736r26'></a><span class='ecrm-0500'>26</span><span id='textcolor1334'><span class='ectt-0800'>#define DRIVER_NAME "ioctltest"</span></span>
|
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<a id='x1-38738r27'></a><span class='ecrm-0500'>27</span>
|
|
<a id='x1-38740r28'></a><span class='ecrm-0500'>28</span><span id='textcolor1335'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1336'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1337'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> test_ioctl_major = 0;</span>
|
|
<a id='x1-38742r29'></a><span class='ecrm-0500'>29</span><span id='textcolor1338'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1339'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1340'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> num_of_dev = 1;</span>
|
|
<a id='x1-38744r30'></a><span class='ecrm-0500'>30</span><span id='textcolor1341'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1342'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> cdev test_ioctl_cdev;</span>
|
|
<a id='x1-38746r31'></a><span class='ecrm-0500'>31</span><span id='textcolor1343'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1344'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> ioctl_num = 0;</span>
|
|
<a id='x1-38748r32'></a><span class='ecrm-0500'>32</span>
|
|
<a id='x1-38750r33'></a><span class='ecrm-0500'>33</span><span id='textcolor1345'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> test_ioctl_data {</span>
|
|
<a id='x1-38752r34'></a><span class='ecrm-0500'>34</span><span class='ectt-0800'> </span><span id='textcolor1346'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1347'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> val;</span>
|
|
<a id='x1-38754r35'></a><span class='ecrm-0500'>35</span><span class='ectt-0800'> rwlock_t lock;</span>
|
|
<a id='x1-38756r36'></a><span class='ecrm-0500'>36</span><span class='ectt-0800'>};</span>
|
|
<a id='x1-38758r37'></a><span class='ecrm-0500'>37</span>
|
|
<a id='x1-38760r38'></a><span class='ecrm-0500'>38</span><span id='textcolor1348'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1349'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> test_ioctl_ioctl(</span><span id='textcolor1350'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *filp,</span>
|
|
<a id='x1-38762r39'></a><span class='ecrm-0500'>39</span><span class='ectt-0800'> </span><span id='textcolor1351'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1352'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> cmd,</span>
|
|
<a id='x1-38764r40'></a><span class='ecrm-0500'>40</span><span class='ectt-0800'> </span><span id='textcolor1353'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1354'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> arg)</span>
|
|
<a id='x1-38766r41'></a><span class='ecrm-0500'>41</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-38768r42'></a><span class='ecrm-0500'>42</span><span class='ectt-0800'> </span><span id='textcolor1355'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> test_ioctl_data *ioctl_data = filp->private_data;</span>
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|
<a id='x1-38770r43'></a><span class='ecrm-0500'>43</span><span class='ectt-0800'> </span><span id='textcolor1356'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> retval = 0;</span>
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|
<a id='x1-38772r44'></a><span class='ecrm-0500'>44</span><span class='ectt-0800'> </span><span id='textcolor1357'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1358'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> val;</span>
|
|
<a id='x1-38774r45'></a><span class='ecrm-0500'>45</span><span class='ectt-0800'> </span><span id='textcolor1359'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> ioctl_arg data;</span>
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|
<a id='x1-38776r46'></a><span class='ecrm-0500'>46</span><span class='ectt-0800'> memset(&data, 0, </span><span id='textcolor1360'><span class='ectt-0800'>sizeof</span></span><span class='ectt-0800'>(data));</span>
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<a id='x1-38778r47'></a><span class='ecrm-0500'>47</span>
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<a id='x1-38780r48'></a><span class='ecrm-0500'>48</span><span class='ectt-0800'> </span><span id='textcolor1361'><span class='ectt-0800'>switch</span></span><span class='ectt-0800'> (cmd) {</span>
|
|
<a id='x1-38782r49'></a><span class='ecrm-0500'>49</span><span class='ectt-0800'> </span><span id='textcolor1362'><span class='ectt-0800'>case</span></span><span class='ectt-0800'> IOCTL_VALSET:</span>
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<a id='x1-38784r50'></a><span class='ecrm-0500'>50</span>
|
|
<a id='x1-38786r51'></a><span class='ecrm-0500'>51</span><span class='ectt-0800'> </span><span id='textcolor1363'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38788r52'></a><span class='ecrm-0500'>52</span><span id='textcolor1364'><span class='ectt-0800'> if (!capable(CAP_SYS_ADMIN)) {</span></span>
|
|
<a id='x1-38790r53'></a><span class='ecrm-0500'>53</span><span id='textcolor1365'><span class='ectt-0800'> retval = -EPERM;</span></span>
|
|
<a id='x1-38792r54'></a><span class='ecrm-0500'>54</span><span id='textcolor1366'><span class='ectt-0800'> goto done;</span></span>
|
|
<a id='x1-38794r55'></a><span class='ecrm-0500'>55</span><span id='textcolor1367'><span class='ectt-0800'> }</span></span>
|
|
<a id='x1-38796r56'></a><span class='ecrm-0500'>56</span><span id='textcolor1368'><span class='ectt-0800'> if (!access_ok(VERIFY_READ, (void __user *)arg, _IOC_SIZE(cmd))) {</span></span>
|
|
<a id='x1-38798r57'></a><span class='ecrm-0500'>57</span><span id='textcolor1369'><span class='ectt-0800'> retval = -EFAULT;</span></span>
|
|
<a id='x1-38800r58'></a><span class='ecrm-0500'>58</span><span id='textcolor1370'><span class='ectt-0800'> goto done;</span></span>
|
|
<a id='x1-38802r59'></a><span class='ecrm-0500'>59</span><span id='textcolor1371'><span class='ectt-0800'> }</span></span>
|
|
<a id='x1-38804r60'></a><span class='ecrm-0500'>60</span><span id='textcolor1372'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38806r61'></a><span class='ecrm-0500'>61</span><span class='ectt-0800'> </span><span id='textcolor1373'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (copy_from_user(&data, (</span><span id='textcolor1374'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> __user *) arg, </span><span id='textcolor1375'><span class='ectt-0800'>sizeof</span></span><span class='ectt-0800'>(data))) {</span>
|
|
<a id='x1-38808r62'></a><span class='ecrm-0500'>62</span><span class='ectt-0800'> retval = -EFAULT;</span>
|
|
<a id='x1-38810r63'></a><span class='ecrm-0500'>63</span><span class='ectt-0800'> </span><span id='textcolor1376'><span class='ectt-0800'>goto</span></span><span class='ectt-0800'> done;</span>
|
|
<a id='x1-38812r64'></a><span class='ecrm-0500'>64</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-38814r65'></a><span class='ecrm-0500'>65</span>
|
|
<a id='x1-38816r66'></a><span class='ecrm-0500'>66</span><span class='ectt-0800'> pr_alert(</span><span id='textcolor1377'><span class='ectt-0800'>"IOCTL set val:%x .</span></span><span id='textcolor1378'><span class='ectt-0800'>\n</span></span><span id='textcolor1379'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, data.val);</span>
|
|
<a id='x1-38818r67'></a><span class='ecrm-0500'>67</span><span class='ectt-0800'> write_lock(&ioctl_data->lock);</span>
|
|
<a id='x1-38820r68'></a><span class='ecrm-0500'>68</span><span class='ectt-0800'> ioctl_data->val = data.val;</span>
|
|
<a id='x1-38822r69'></a><span class='ecrm-0500'>69</span><span class='ectt-0800'> write_unlock(&ioctl_data->lock);</span>
|
|
<a id='x1-38824r70'></a><span class='ecrm-0500'>70</span><span class='ectt-0800'> </span><span id='textcolor1380'><span class='ectt-0800'>break</span></span><span class='ectt-0800'>;</span>
|
|
<a id='x1-38826r71'></a><span class='ecrm-0500'>71</span>
|
|
<a id='x1-38828r72'></a><span class='ecrm-0500'>72</span><span class='ectt-0800'> </span><span id='textcolor1381'><span class='ectt-0800'>case</span></span><span class='ectt-0800'> IOCTL_VALGET:</span>
|
|
<a id='x1-38830r73'></a><span class='ecrm-0500'>73</span><span class='ectt-0800'> </span><span id='textcolor1382'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38832r74'></a><span class='ecrm-0500'>74</span><span id='textcolor1383'><span class='ectt-0800'> if (!access_ok(VERIFY_WRITE, (void __user *)arg, _IOC_SIZE(cmd))) {</span></span>
|
|
<a id='x1-38834r75'></a><span class='ecrm-0500'>75</span><span id='textcolor1384'><span class='ectt-0800'> retval = -EFAULT;</span></span>
|
|
<a id='x1-38836r76'></a><span class='ecrm-0500'>76</span><span id='textcolor1385'><span class='ectt-0800'> goto done;</span></span>
|
|
<a id='x1-38838r77'></a><span class='ecrm-0500'>77</span><span id='textcolor1386'><span class='ectt-0800'> }</span></span>
|
|
<a id='x1-38840r78'></a><span class='ecrm-0500'>78</span><span id='textcolor1387'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38842r79'></a><span class='ecrm-0500'>79</span><span class='ectt-0800'> read_lock(&ioctl_data->lock);</span>
|
|
<a id='x1-38844r80'></a><span class='ecrm-0500'>80</span><span class='ectt-0800'> val = ioctl_data->val;</span>
|
|
<a id='x1-38846r81'></a><span class='ecrm-0500'>81</span><span class='ectt-0800'> read_unlock(&ioctl_data->lock);</span>
|
|
<a id='x1-38848r82'></a><span class='ecrm-0500'>82</span><span class='ectt-0800'> data.val = val;</span>
|
|
<a id='x1-38850r83'></a><span class='ecrm-0500'>83</span>
|
|
<a id='x1-38852r84'></a><span class='ecrm-0500'>84</span><span class='ectt-0800'> </span><span id='textcolor1388'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (copy_to_user((</span><span id='textcolor1389'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> __user *) arg, &data, </span><span id='textcolor1390'><span class='ectt-0800'>sizeof</span></span><span class='ectt-0800'>(data))) {</span>
|
|
<a id='x1-38854r85'></a><span class='ecrm-0500'>85</span><span class='ectt-0800'> retval = -EFAULT;</span>
|
|
<a id='x1-38856r86'></a><span class='ecrm-0500'>86</span><span class='ectt-0800'> </span><span id='textcolor1391'><span class='ectt-0800'>goto</span></span><span class='ectt-0800'> done;</span>
|
|
<a id='x1-38858r87'></a><span class='ecrm-0500'>87</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-38860r88'></a><span class='ecrm-0500'>88</span>
|
|
<a id='x1-38862r89'></a><span class='ecrm-0500'>89</span><span class='ectt-0800'> </span><span id='textcolor1392'><span class='ectt-0800'>break</span></span><span class='ectt-0800'>;</span>
|
|
<a id='x1-38864r90'></a><span class='ecrm-0500'>90</span>
|
|
<a id='x1-38866r91'></a><span class='ecrm-0500'>91</span><span class='ectt-0800'> </span><span id='textcolor1393'><span class='ectt-0800'>case</span></span><span class='ectt-0800'> IOCTL_VALGET_NUM:</span>
|
|
<a id='x1-38868r92'></a><span class='ecrm-0500'>92</span><span class='ectt-0800'> retval = __put_user(ioctl_num, (</span><span id='textcolor1394'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> __user *) arg);</span>
|
|
<a id='x1-38870r93'></a><span class='ecrm-0500'>93</span><span class='ectt-0800'> </span><span id='textcolor1395'><span class='ectt-0800'>break</span></span><span class='ectt-0800'>;</span>
|
|
<a id='x1-38872r94'></a><span class='ecrm-0500'>94</span>
|
|
<a id='x1-38874r95'></a><span class='ecrm-0500'>95</span><span class='ectt-0800'> </span><span id='textcolor1396'><span class='ectt-0800'>case</span></span><span class='ectt-0800'> IOCTL_VALSET_NUM:</span>
|
|
<a id='x1-38876r96'></a><span class='ecrm-0500'>96</span><span class='ectt-0800'> </span><span id='textcolor1397'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-38878r97'></a><span class='ecrm-0500'>97</span><span id='textcolor1398'><span class='ectt-0800'> if (!capable(CAP_SYS_ADMIN))</span></span>
|
|
<a id='x1-38880r98'></a><span class='ecrm-0500'>98</span><span id='textcolor1399'><span class='ectt-0800'> return -EPERM;</span></span>
|
|
<a id='x1-38882r99'></a><span class='ecrm-0500'>99</span><span id='textcolor1400'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-38884r100'></a><span class='ecrm-0500'>100</span><span class='ectt-0800'> ioctl_num = arg;</span>
|
|
<a id='x1-38886r101'></a><span class='ecrm-0500'>101</span><span class='ectt-0800'> </span><span id='textcolor1401'><span class='ectt-0800'>break</span></span><span class='ectt-0800'>;</span>
|
|
<a id='x1-38888r102'></a><span class='ecrm-0500'>102</span>
|
|
<a id='x1-38890r103'></a><span class='ecrm-0500'>103</span><span class='ectt-0800'> </span><span id='textcolor1402'><span class='ectt-0800'>default</span></span><span class='ectt-0800'>:</span>
|
|
<a id='x1-38892r104'></a><span class='ecrm-0500'>104</span><span class='ectt-0800'> retval = -ENOTTY;</span>
|
|
<a id='x1-38894r105'></a><span class='ecrm-0500'>105</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-38896r106'></a><span class='ecrm-0500'>106</span>
|
|
<a id='x1-38898r107'></a><span class='ecrm-0500'>107</span><span class='ectt-0800'>done:</span>
|
|
<a id='x1-38900r108'></a><span class='ecrm-0500'>108</span><span class='ectt-0800'> </span><span id='textcolor1403'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> retval;</span>
|
|
<a id='x1-38902r109'></a><span class='ecrm-0500'>109</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-38904r110'></a><span class='ecrm-0500'>110</span>
|
|
<a id='x1-38906r111'></a><span class='ecrm-0500'>111</span><span id='textcolor1404'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> test_ioctl_read(</span><span id='textcolor1405'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *filp,</span>
|
|
<a id='x1-38908r112'></a><span class='ecrm-0500'>112</span><span class='ectt-0800'> </span><span id='textcolor1406'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> __user *buf,</span>
|
|
<a id='x1-38910r113'></a><span class='ecrm-0500'>113</span><span class='ectt-0800'> </span><span id='textcolor1407'><span class='ectt-0800'>size_t</span></span><span class='ectt-0800'> count,</span>
|
|
<a id='x1-38912r114'></a><span class='ecrm-0500'>114</span><span class='ectt-0800'> loff_t *f_pos)</span>
|
|
<a id='x1-38914r115'></a><span class='ecrm-0500'>115</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-38916r116'></a><span class='ecrm-0500'>116</span><span class='ectt-0800'> </span><span id='textcolor1408'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> test_ioctl_data *ioctl_data = filp->private_data;</span>
|
|
<a id='x1-38918r117'></a><span class='ecrm-0500'>117</span><span class='ectt-0800'> </span><span id='textcolor1409'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1410'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> val;</span>
|
|
<a id='x1-38920r118'></a><span class='ecrm-0500'>118</span><span class='ectt-0800'> </span><span id='textcolor1411'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> retval;</span>
|
|
<a id='x1-38922r119'></a><span class='ecrm-0500'>119</span><span class='ectt-0800'> </span><span id='textcolor1412'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> i = 0;</span>
|
|
<a id='x1-38924r120'></a><span class='ecrm-0500'>120</span><span class='ectt-0800'> read_lock(&ioctl_data->lock);</span>
|
|
<a id='x1-38926r121'></a><span class='ecrm-0500'>121</span><span class='ectt-0800'> val = ioctl_data->val;</span>
|
|
<a id='x1-38928r122'></a><span class='ecrm-0500'>122</span><span class='ectt-0800'> read_unlock(&ioctl_data->lock);</span>
|
|
<a id='x1-38930r123'></a><span class='ecrm-0500'>123</span>
|
|
<a id='x1-38932r124'></a><span class='ecrm-0500'>124</span><span class='ectt-0800'> </span><span id='textcolor1413'><span class='ectt-0800'>for</span></span><span class='ectt-0800'> (; i < count; i++) {</span>
|
|
<a id='x1-38934r125'></a><span class='ecrm-0500'>125</span><span class='ectt-0800'> </span><span id='textcolor1414'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (copy_to_user(&buf[i], &val, 1)) {</span>
|
|
<a id='x1-38936r126'></a><span class='ecrm-0500'>126</span><span class='ectt-0800'> retval = -EFAULT;</span>
|
|
<a id='x1-38938r127'></a><span class='ecrm-0500'>127</span><span class='ectt-0800'> </span><span id='textcolor1415'><span class='ectt-0800'>goto</span></span><span class='ectt-0800'> out;</span>
|
|
<a id='x1-38940r128'></a><span class='ecrm-0500'>128</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-38942r129'></a><span class='ecrm-0500'>129</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-38944r130'></a><span class='ecrm-0500'>130</span>
|
|
<a id='x1-38946r131'></a><span class='ecrm-0500'>131</span><span class='ectt-0800'> retval = count;</span>
|
|
<a id='x1-38948r132'></a><span class='ecrm-0500'>132</span><span class='ectt-0800'>out:</span>
|
|
<a id='x1-38950r133'></a><span class='ecrm-0500'>133</span><span class='ectt-0800'> </span><span id='textcolor1416'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> retval;</span>
|
|
<a id='x1-38952r134'></a><span class='ecrm-0500'>134</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-38954r135'></a><span class='ecrm-0500'>135</span>
|
|
<a id='x1-38956r136'></a><span class='ecrm-0500'>136</span><span id='textcolor1417'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1418'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> test_ioctl_close(</span><span id='textcolor1419'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> inode *inode, </span><span id='textcolor1420'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *filp)</span>
|
|
<a id='x1-38958r137'></a><span class='ecrm-0500'>137</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-38960r138'></a><span class='ecrm-0500'>138</span><span class='ectt-0800'> pr_alert(</span><span id='textcolor1421'><span class='ectt-0800'>"%s call.</span></span><span id='textcolor1422'><span class='ectt-0800'>\n</span></span><span id='textcolor1423'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, __func__);</span>
|
|
<a id='x1-38962r139'></a><span class='ecrm-0500'>139</span>
|
|
<a id='x1-38964r140'></a><span class='ecrm-0500'>140</span><span class='ectt-0800'> </span><span id='textcolor1424'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (filp->private_data) {</span>
|
|
<a id='x1-38966r141'></a><span class='ecrm-0500'>141</span><span class='ectt-0800'> kfree(filp->private_data);</span>
|
|
<a id='x1-38968r142'></a><span class='ecrm-0500'>142</span><span class='ectt-0800'> filp->private_data = NULL;</span>
|
|
<a id='x1-38970r143'></a><span class='ecrm-0500'>143</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-38972r144'></a><span class='ecrm-0500'>144</span>
|
|
<a id='x1-38974r145'></a><span class='ecrm-0500'>145</span><span class='ectt-0800'> </span><span id='textcolor1425'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-38976r146'></a><span class='ecrm-0500'>146</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-38978r147'></a><span class='ecrm-0500'>147</span>
|
|
<a id='x1-38980r148'></a><span class='ecrm-0500'>148</span><span id='textcolor1426'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1427'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> test_ioctl_open(</span><span id='textcolor1428'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> inode *inode, </span><span id='textcolor1429'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *filp)</span>
|
|
<a id='x1-38982r149'></a><span class='ecrm-0500'>149</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-38984r150'></a><span class='ecrm-0500'>150</span><span class='ectt-0800'> </span><span id='textcolor1430'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> test_ioctl_data *ioctl_data;</span>
|
|
<a id='x1-38986r151'></a><span class='ecrm-0500'>151</span><span class='ectt-0800'> pr_alert(</span><span id='textcolor1431'><span class='ectt-0800'>"%s call.</span></span><span id='textcolor1432'><span class='ectt-0800'>\n</span></span><span id='textcolor1433'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, __func__);</span>
|
|
<a id='x1-38988r152'></a><span class='ecrm-0500'>152</span><span class='ectt-0800'> ioctl_data = kmalloc(</span><span id='textcolor1434'><span class='ectt-0800'>sizeof</span></span><span class='ectt-0800'>(</span><span id='textcolor1435'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> test_ioctl_data), GFP_KERNEL);</span>
|
|
<a id='x1-38990r153'></a><span class='ecrm-0500'>153</span>
|
|
<a id='x1-38992r154'></a><span class='ecrm-0500'>154</span><span class='ectt-0800'> </span><span id='textcolor1436'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (ioctl_data == NULL) {</span>
|
|
<a id='x1-38994r155'></a><span class='ecrm-0500'>155</span><span class='ectt-0800'> </span><span id='textcolor1437'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -ENOMEM;</span>
|
|
<a id='x1-38996r156'></a><span class='ecrm-0500'>156</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-38998r157'></a><span class='ecrm-0500'>157</span>
|
|
<a id='x1-39000r158'></a><span class='ecrm-0500'>158</span><span class='ectt-0800'> rwlock_init(&ioctl_data->lock);</span>
|
|
<a id='x1-39002r159'></a><span class='ecrm-0500'>159</span><span class='ectt-0800'> ioctl_data->val = 0xFF;</span>
|
|
<a id='x1-39004r160'></a><span class='ecrm-0500'>160</span><span class='ectt-0800'> filp->private_data = ioctl_data;</span>
|
|
<a id='x1-39006r161'></a><span class='ecrm-0500'>161</span><span class='ectt-0800'> </span><span id='textcolor1438'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-39008r162'></a><span class='ecrm-0500'>162</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-39010r163'></a><span class='ecrm-0500'>163</span>
|
|
<a id='x1-39012r164'></a><span class='ecrm-0500'>164</span><span id='textcolor1439'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file_operations fops = {</span>
|
|
<a id='x1-39014r165'></a><span class='ecrm-0500'>165</span><span class='ectt-0800'> .owner = THIS_MODULE,</span>
|
|
<a id='x1-39016r166'></a><span class='ecrm-0500'>166</span><span class='ectt-0800'> .open = test_ioctl_open,</span>
|
|
<a id='x1-39018r167'></a><span class='ecrm-0500'>167</span><span class='ectt-0800'> .release = test_ioctl_close,</span>
|
|
<a id='x1-39020r168'></a><span class='ecrm-0500'>168</span><span class='ectt-0800'> .read = test_ioctl_read,</span>
|
|
<a id='x1-39022r169'></a><span class='ecrm-0500'>169</span><span class='ectt-0800'> .unlocked_ioctl = test_ioctl_ioctl,</span>
|
|
<a id='x1-39024r170'></a><span class='ecrm-0500'>170</span><span class='ectt-0800'>};</span>
|
|
<a id='x1-39026r171'></a><span class='ecrm-0500'>171</span>
|
|
<a id='x1-39028r172'></a><span class='ecrm-0500'>172</span><span id='textcolor1440'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1441'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> ioctl_init(</span><span id='textcolor1442'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-39030r173'></a><span class='ecrm-0500'>173</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-39032r174'></a><span class='ecrm-0500'>174</span><span class='ectt-0800'> </span><span id='textcolor1443'><span class='ectt-0800'>dev_t</span></span><span class='ectt-0800'> dev = MKDEV(test_ioctl_major, 0);</span>
|
|
<a id='x1-39034r175'></a><span class='ecrm-0500'>175</span><span class='ectt-0800'> </span><span id='textcolor1444'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> alloc_ret = 0;</span>
|
|
<a id='x1-39036r176'></a><span class='ecrm-0500'>176</span><span class='ectt-0800'> </span><span id='textcolor1445'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> cdev_ret = 0;</span>
|
|
<a id='x1-39038r177'></a><span class='ecrm-0500'>177</span><span class='ectt-0800'> alloc_ret = alloc_chrdev_region(&dev, 0, num_of_dev, DRIVER_NAME);</span>
|
|
<a id='x1-39040r178'></a><span class='ecrm-0500'>178</span>
|
|
<a id='x1-39042r179'></a><span class='ecrm-0500'>179</span><span class='ectt-0800'> </span><span id='textcolor1446'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (alloc_ret) {</span>
|
|
<a id='x1-39044r180'></a><span class='ecrm-0500'>180</span><span class='ectt-0800'> </span><span id='textcolor1447'><span class='ectt-0800'>goto</span></span><span class='ectt-0800'> error;</span>
|
|
<a id='x1-39046r181'></a><span class='ecrm-0500'>181</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-39048r182'></a><span class='ecrm-0500'>182</span>
|
|
<a id='x1-39050r183'></a><span class='ecrm-0500'>183</span><span class='ectt-0800'> test_ioctl_major = MAJOR(dev);</span>
|
|
<a id='x1-39052r184'></a><span class='ecrm-0500'>184</span><span class='ectt-0800'> cdev_init(&test_ioctl_cdev, &fops);</span>
|
|
<a id='x1-39054r185'></a><span class='ecrm-0500'>185</span><span class='ectt-0800'> cdev_ret = cdev_add(&test_ioctl_cdev, dev, num_of_dev);</span>
|
|
<a id='x1-39056r186'></a><span class='ecrm-0500'>186</span>
|
|
<a id='x1-39058r187'></a><span class='ecrm-0500'>187</span><span class='ectt-0800'> </span><span id='textcolor1448'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (cdev_ret) {</span>
|
|
<a id='x1-39060r188'></a><span class='ecrm-0500'>188</span><span class='ectt-0800'> </span><span id='textcolor1449'><span class='ectt-0800'>goto</span></span><span class='ectt-0800'> error;</span>
|
|
<a id='x1-39062r189'></a><span class='ecrm-0500'>189</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-39064r190'></a><span class='ecrm-0500'>190</span>
|
|
<a id='x1-39066r191'></a><span class='ecrm-0500'>191</span><span class='ectt-0800'> pr_alert(</span><span id='textcolor1450'><span class='ectt-0800'>"%s driver(major: %d) installed.</span></span><span id='textcolor1451'><span class='ectt-0800'>\n</span></span><span id='textcolor1452'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, DRIVER_NAME,</span>
|
|
<a id='x1-39068r192'></a><span class='ecrm-0500'>192</span><span class='ectt-0800'> test_ioctl_major);</span>
|
|
<a id='x1-39070r193'></a><span class='ecrm-0500'>193</span><span class='ectt-0800'> </span><span id='textcolor1453'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-39072r194'></a><span class='ecrm-0500'>194</span><span class='ectt-0800'>error:</span>
|
|
<a id='x1-39074r195'></a><span class='ecrm-0500'>195</span>
|
|
<a id='x1-39076r196'></a><span class='ecrm-0500'>196</span><span class='ectt-0800'> </span><span id='textcolor1454'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (cdev_ret == 0) {</span>
|
|
<a id='x1-39078r197'></a><span class='ecrm-0500'>197</span><span class='ectt-0800'> cdev_del(&test_ioctl_cdev);</span>
|
|
<a id='x1-39080r198'></a><span class='ecrm-0500'>198</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-39082r199'></a><span class='ecrm-0500'>199</span>
|
|
<a id='x1-39084r200'></a><span class='ecrm-0500'>200</span><span class='ectt-0800'> </span><span id='textcolor1455'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (alloc_ret == 0) {</span>
|
|
<a id='x1-39086r201'></a><span class='ecrm-0500'>201</span><span class='ectt-0800'> unregister_chrdev_region(dev, num_of_dev);</span>
|
|
<a id='x1-39088r202'></a><span class='ecrm-0500'>202</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-39090r203'></a><span class='ecrm-0500'>203</span>
|
|
<a id='x1-39092r204'></a><span class='ecrm-0500'>204</span><span class='ectt-0800'> </span><span id='textcolor1456'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -1;</span>
|
|
<a id='x1-39094r205'></a><span class='ecrm-0500'>205</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-39096r206'></a><span class='ecrm-0500'>206</span>
|
|
<a id='x1-39098r207'></a><span class='ecrm-0500'>207</span><span id='textcolor1457'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1458'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> ioctl_exit(</span><span id='textcolor1459'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-39100r208'></a><span class='ecrm-0500'>208</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-39102r209'></a><span class='ecrm-0500'>209</span><span class='ectt-0800'> </span><span id='textcolor1460'><span class='ectt-0800'>dev_t</span></span><span class='ectt-0800'> dev = MKDEV(test_ioctl_major, 0);</span>
|
|
<a id='x1-39104r210'></a><span class='ecrm-0500'>210</span><span class='ectt-0800'> cdev_del(&test_ioctl_cdev);</span>
|
|
<a id='x1-39106r211'></a><span class='ecrm-0500'>211</span><span class='ectt-0800'> unregister_chrdev_region(dev, num_of_dev);</span>
|
|
<a id='x1-39108r212'></a><span class='ecrm-0500'>212</span><span class='ectt-0800'> pr_alert(</span><span id='textcolor1461'><span class='ectt-0800'>"%s driver removed.</span></span><span id='textcolor1462'><span class='ectt-0800'>\n</span></span><span id='textcolor1463'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, DRIVER_NAME);</span>
|
|
<a id='x1-39110r213'></a><span class='ecrm-0500'>213</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-39112r214'></a><span class='ecrm-0500'>214</span>
|
|
<a id='x1-39114r215'></a><span class='ecrm-0500'>215</span><span class='ectt-0800'>module_init(ioctl_init);</span>
|
|
<a id='x1-39116r216'></a><span class='ecrm-0500'>216</span><span class='ectt-0800'>module_exit(ioctl_exit);</span>
|
|
<a id='x1-39118r217'></a><span class='ecrm-0500'>217</span>
|
|
<a id='x1-39120r218'></a><span class='ecrm-0500'>218</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor1464'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-39122r219'></a><span class='ecrm-0500'>219</span><span class='ectt-0800'>MODULE_DESCRIPTION(</span><span id='textcolor1465'><span class='ectt-0800'>"This is test_ioctl module"</span></span><span class='ectt-0800'>);</span></pre>
|
|
<!-- l. 1139 --><p class='noindent'>
|
|
</p>
|
|
<h3 class='sectionHead' id='system-calls'><span class='titlemark'>0.10 </span> <a id='x1-400000.10'></a>System Calls</h3>
|
|
<!-- l. 1141 --><p class='noindent'>So far, the only thing we’ve done was to use well defined kernel mechanisms to
|
|
register <span class='ecbx-1000'>/proc </span>files and device handlers. This is fine if you want to do something the
|
|
kernel programmers thought you’d want, such as write a device driver. But what if
|
|
you want to do something unusual, to change the behavior of the system in some
|
|
way? Then, you are mostly on your own.
|
|
</p><!-- l. 1146 --><p class='indent'> If you are not being sensible and using a virtual machine then this is where kernel
|
|
programming can become hazardous. While writing the example below,
|
|
I killed the <span class='ecbx-1000'>open() </span>system call. This meant I could not open any files, I
|
|
could not run any programs, and I could not shutdown the system. I had
|
|
to restart the virtual machine. No important files got anihilated, but if I
|
|
|
|
|
|
|
|
was doing this on some live mission critical system then that could have
|
|
been a possible outcome. To ensure you do not lose any files, even within a
|
|
test environment, please run <span class='ecbx-1000'>sync </span>right before you do the <span class='ecbx-1000'>insmod </span>and the
|
|
<span class='ecbx-1000'>rmmod</span>.
|
|
</p><!-- l. 1153 --><p class='indent'> Forget about <span class='ecbx-1000'>/proc </span>files, forget about device files. They are just minor details.
|
|
Minutiae in the vast expanse of the universe. The real process to kernel
|
|
communication mechanism, the one used by all processes, is <span class='ecti-1000'>system calls</span>. When a
|
|
process requests a service from the kernel (such as opening a file, forking to a new
|
|
process, or requesting more memory), this is the mechanism used. If you want to
|
|
change the behaviour of the kernel in interesting ways, this is the place to do
|
|
it. By the way, if you want to see which system calls a program uses, run
|
|
<span class='obeylines-h'><span class='verb'><span class='ectt-1000'>strace <arguments></span></span></span>.
|
|
</p><!-- l. 1161 --><p class='indent'> In general, a process is not supposed to be able to access the kernel. It can not
|
|
access kernel memory and it can’t call kernel functions. The hardware of the CPU
|
|
enforces this (that is the reason why it is called “protected mode” or “page
|
|
protection”).
|
|
</p><!-- l. 1165 --><p class='indent'> System calls are an exception to this general rule. What happens is that the
|
|
process fills the registers with the appropriate values and then calls a special
|
|
instruction which jumps to a previously defined location in the kernel (of course, that
|
|
location is readable by user processes, it is not writable by them). Under Intel CPUs,
|
|
this is done by means of interrupt 0x80. The hardware knows that once you jump to
|
|
this location, you are no longer running in restricted user mode, but as the
|
|
operating system kernel — and therefore you’re allowed to do whatever you
|
|
want.
|
|
</p><!-- l. 1170 --><p class='indent'> The location in the kernel a process can jump to is called <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>system_call</span></span></span>. The
|
|
procedure at that location checks the system call number, which tells the kernel what
|
|
service the process requested. Then, it looks at the table of system calls
|
|
(<span class='obeylines-h'><span class='verb'><span class='ectt-1000'>sys_call_table</span></span></span>) to see the address of the kernel function to call. Then it calls the
|
|
function, and after it returns, does a few system checks and then return back to the
|
|
process (or to a different process, if the process time ran out). If you want to read
|
|
this code, it is at the source file <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>arch/$(architecture)/kernel/entry.S</span></span></span>, after the
|
|
line <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>ENTRY(system_call)</span></span></span>.
|
|
</p><!-- l. 1176 --><p class='indent'> So, if we want to change the way a certain system call works, what we need to do
|
|
is to write our own function to implement it (usually by adding a bit of our own
|
|
code, and then calling the original function) and then change the pointer at
|
|
sys_call_table to point to our function. Because we might be removed later and
|
|
we don’t want to leave the system in an unstable state, it’s important for
|
|
cleanup_module to restore the table to its original state.
|
|
</p><!-- l. 1179 --><p class='indent'> The source code here is an example of such a kernel module. We want to “spy” on
|
|
a certain user, and to <span class='ecbx-1000'>pr_info() </span>a message whenever that user opens a file.
|
|
Towards this end, we replace the system call to open a file with our own
|
|
function, called <span class='ecbx-1000'>our_sys_open</span>. This function checks the uid (user’s id) of the
|
|
current process, and if it is equal to the uid we spy on, it calls pr_info()
|
|
to display the name of the file to be opened. Then, either way, it calls the
|
|
original open() function with the same parameters, to actually open the
|
|
file.
|
|
|
|
|
|
|
|
</p><!-- l. 1185 --><p class='indent'> The <span class='ecbx-1000'>init_module </span>function replaces the appropriate location in <span class='ecbx-1000'>sys_call_table</span>
|
|
and keeps the original pointer in a variable. The cleanup_module function uses that
|
|
variable to restore everything back to normal. This approach is dangerous, because of
|
|
the possibility of two kernel modules changing the same system call. Imagine we have
|
|
two kernel modules, A and B. A’s open system call will be A_open and B’s will be
|
|
B_open. Now, when A is inserted into the kernel, the system call is replaced with
|
|
A_open, which will call the original sys_open when it is done. Next, B
|
|
is inserted into the kernel, which replaces the system call with B_open,
|
|
which will call what it thinks is the original system call, A_open, when it’s
|
|
done.
|
|
</p><!-- l. 1192 --><p class='indent'> Now, if B is removed first, everything will be well — it will simply restore the
|
|
system call to A_open, which calls the original. However, if A is removed and then B
|
|
is removed, the system will crash. A’s removal will restore the system call to the
|
|
original, sys_open, cutting B out of the loop. Then, when B is removed, it will
|
|
restore the system call to what it thinks is the original, <span class='ecbx-1000'>A_open</span>, which is no
|
|
longer in memory. At first glance, it appears we could solve this particular
|
|
problem by checking if the system call is equal to our open function and if so
|
|
not changing it at all (so that B won’t change the system call when it is
|
|
removed), but that will cause an even worse problem. When A is removed, it
|
|
sees that the system call was changed to <span class='ecbx-1000'>B_open </span>so that it is no longer
|
|
pointing to <span class='ecbx-1000'>A_open</span>, so it will not restore it to <span class='ecbx-1000'>sys_open </span>before it is
|
|
removed from memory. Unfortunately, <span class='ecbx-1000'>B_open </span>will still try to call <span class='ecbx-1000'>A_open</span>
|
|
which is no longer there, so that even without removing B the system would
|
|
crash.
|
|
</p><!-- l. 1200 --><p class='indent'> Note that all the related problems make syscall stealing unfeasiable for production
|
|
use. In order to keep people from doing potential harmful things <span class='ecbx-1000'>sys_call_table </span>is
|
|
no longer exported. This means, if you want to do something more than a mere dry
|
|
run of this example, you will have to patch your current kernel in order to
|
|
have <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>sys_call_table</span></span></span> exported. In the example directory you will find a
|
|
README and the patch. As you can imagine, such modifications are not to be
|
|
taken lightly. Do not try this on valueable systems (ie systems that you
|
|
do not own - or cannot restore easily). You will need to get the complete
|
|
sourcecode of this guide as a tarball in order to get the patch and the README.
|
|
Depending on your kernel version, you might even need to hand apply the
|
|
patch.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb51'><a id='x1-40002r1'></a><span class='ecrm-0500'>1</span><span id='textcolor1466'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-40004r2'></a><span class='ecrm-0500'>2</span><span id='textcolor1467'><span class='ectt-0800'> * syscall.c</span></span>
|
|
<a id='x1-40006r3'></a><span class='ecrm-0500'>3</span><span id='textcolor1468'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-40008r4'></a><span class='ecrm-0500'>4</span><span id='textcolor1469'><span class='ectt-0800'> * System call "stealing" sample.</span></span>
|
|
<a id='x1-40010r5'></a><span class='ecrm-0500'>5</span><span id='textcolor1470'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-40012r6'></a><span class='ecrm-0500'>6</span><span id='textcolor1471'><span class='ectt-0800'> * Disables page protection at a processor level by</span></span>
|
|
<a id='x1-40014r7'></a><span class='ecrm-0500'>7</span><span id='textcolor1472'><span class='ectt-0800'> * changing the 16th bit in the cr0 register (could be Intel specific)</span></span>
|
|
<a id='x1-40016r8'></a><span class='ecrm-0500'>8</span><span id='textcolor1473'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-40018r9'></a><span class='ecrm-0500'>9</span><span id='textcolor1474'><span class='ectt-0800'> * Based on example by Peter Jay Salzman and</span></span>
|
|
<a id='x1-40020r10'></a><span class='ecrm-0500'>10</span><span id='textcolor1475'><span class='ectt-0800'> * https://bbs.archlinux.org/viewtopic.php?id=139406</span></span>
|
|
<a id='x1-40022r11'></a><span class='ecrm-0500'>11</span><span id='textcolor1476'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-40024r12'></a><span class='ecrm-0500'>12</span>
|
|
<a id='x1-40026r13'></a><span class='ecrm-0500'>13</span><span id='textcolor1477'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1478'><span class='ectt-0800'><linux/delay.h></span></span>
|
|
<a id='x1-40028r14'></a><span class='ecrm-0500'>14</span><span id='textcolor1479'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1480'><span class='ectt-0800'><linux/kernel.h></span></span>
|
|
<a id='x1-40030r15'></a><span class='ecrm-0500'>15</span><span id='textcolor1481'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1482'><span class='ectt-0800'><linux/module.h></span></span>
|
|
<a id='x1-40032r16'></a><span class='ecrm-0500'>16</span><span id='textcolor1483'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1484'><span class='ectt-0800'><linux/moduleparam.h> /* which will have params */</span></span>
|
|
<a id='x1-40034r17'></a><span class='ecrm-0500'>17</span><span id='textcolor1485'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1486'><span class='ectt-0800'><linux/syscalls.h></span></span>
|
|
<a id='x1-40036r18'></a><span class='ecrm-0500'>18</span><span id='textcolor1487'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1488'><span class='ectt-0800'><linux/unistd.h> /* The list of system calls */</span></span>
|
|
<a id='x1-40038r19'></a><span class='ecrm-0500'>19</span>
|
|
<a id='x1-40040r20'></a><span class='ecrm-0500'>20</span><span id='textcolor1489'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-40042r21'></a><span class='ecrm-0500'>21</span><span id='textcolor1490'><span class='ectt-0800'> * For the current (process) structure, we need</span></span>
|
|
<a id='x1-40044r22'></a><span class='ecrm-0500'>22</span><span id='textcolor1491'><span class='ectt-0800'> * this to know who the current user is.</span></span>
|
|
<a id='x1-40046r23'></a><span class='ecrm-0500'>23</span><span id='textcolor1492'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-40048r24'></a><span class='ecrm-0500'>24</span><span id='textcolor1493'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1494'><span class='ectt-0800'><linux/sched.h></span></span>
|
|
<a id='x1-40050r25'></a><span class='ecrm-0500'>25</span><span id='textcolor1495'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1496'><span class='ectt-0800'><linux/uaccess.h></span></span>
|
|
<a id='x1-40052r26'></a><span class='ecrm-0500'>26</span>
|
|
<a id='x1-40054r27'></a><span class='ecrm-0500'>27</span><span id='textcolor1497'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1498'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> **sys_call_table;</span>
|
|
<a id='x1-40056r28'></a><span class='ecrm-0500'>28</span><span id='textcolor1499'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1500'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> original_cr0;</span>
|
|
<a id='x1-40058r29'></a><span class='ecrm-0500'>29</span>
|
|
<a id='x1-40060r30'></a><span class='ecrm-0500'>30</span><span id='textcolor1501'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-40062r31'></a><span class='ecrm-0500'>31</span><span id='textcolor1502'><span class='ectt-0800'> * UID we want to spy on - will be filled from the</span></span>
|
|
<a id='x1-40064r32'></a><span class='ecrm-0500'>32</span><span id='textcolor1503'><span class='ectt-0800'> * command line</span></span>
|
|
<a id='x1-40066r33'></a><span class='ecrm-0500'>33</span><span id='textcolor1504'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-40068r34'></a><span class='ecrm-0500'>34</span><span id='textcolor1505'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1506'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> uid;</span>
|
|
<a id='x1-40070r35'></a><span class='ecrm-0500'>35</span><span class='ectt-0800'>module_param(uid, </span><span id='textcolor1507'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>, 0644);</span>
|
|
<a id='x1-40072r36'></a><span class='ecrm-0500'>36</span>
|
|
<a id='x1-40074r37'></a><span class='ecrm-0500'>37</span><span id='textcolor1508'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-40076r38'></a><span class='ecrm-0500'>38</span><span id='textcolor1509'><span class='ectt-0800'> * A pointer to the original system call. The reason</span></span>
|
|
<a id='x1-40078r39'></a><span class='ecrm-0500'>39</span><span id='textcolor1510'><span class='ectt-0800'> * we keep this, rather than call the original function</span></span>
|
|
<a id='x1-40080r40'></a><span class='ecrm-0500'>40</span><span id='textcolor1511'><span class='ectt-0800'> * (sys_open), is because somebody else might have</span></span>
|
|
<a id='x1-40082r41'></a><span class='ecrm-0500'>41</span><span id='textcolor1512'><span class='ectt-0800'> * replaced the system call before us. Note that this</span></span>
|
|
<a id='x1-40084r42'></a><span class='ecrm-0500'>42</span><span id='textcolor1513'><span class='ectt-0800'> * is not 100% safe, because if another module</span></span>
|
|
<a id='x1-40086r43'></a><span class='ecrm-0500'>43</span><span id='textcolor1514'><span class='ectt-0800'> * replaced sys_open before us, then when we</span><span class='tctt-0800'>'</span><span class='ectt-0800'>re inserted</span></span>
|
|
<a id='x1-40088r44'></a><span class='ecrm-0500'>44</span><span id='textcolor1515'><span class='ectt-0800'> * we</span><span class='tctt-0800'>'</span><span class='ectt-0800'>ll call the function in that module - and it</span></span>
|
|
<a id='x1-40090r45'></a><span class='ecrm-0500'>45</span><span id='textcolor1516'><span class='ectt-0800'> * might be removed before we are.</span></span>
|
|
<a id='x1-40092r46'></a><span class='ecrm-0500'>46</span><span id='textcolor1517'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-40094r47'></a><span class='ecrm-0500'>47</span><span id='textcolor1518'><span class='ectt-0800'> * Another reason for this is that we can</span><span class='tctt-0800'>'</span><span class='ectt-0800'>t get sys_open.</span></span>
|
|
<a id='x1-40096r48'></a><span class='ecrm-0500'>48</span><span id='textcolor1519'><span class='ectt-0800'> * It</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s a static variable, so it is not exported.</span></span>
|
|
<a id='x1-40098r49'></a><span class='ecrm-0500'>49</span><span id='textcolor1520'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-40100r50'></a><span class='ecrm-0500'>50</span><span class='ectt-0800'>asmlinkage int (*original_call)(</span><span id='textcolor1521'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor1522'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *, </span><span id='textcolor1523'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>, </span><span id='textcolor1524'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-40102r51'></a><span class='ecrm-0500'>51</span>
|
|
<a id='x1-40104r52'></a><span class='ecrm-0500'>52</span><span id='textcolor1525'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-40106r53'></a><span class='ecrm-0500'>53</span><span id='textcolor1526'><span class='ectt-0800'> * The function we</span><span class='tctt-0800'>'</span><span class='ectt-0800'>ll replace sys_open (the function</span></span>
|
|
<a id='x1-40108r54'></a><span class='ecrm-0500'>54</span><span id='textcolor1527'><span class='ectt-0800'> * called when you call the open system call) with. To</span></span>
|
|
<a id='x1-40110r55'></a><span class='ecrm-0500'>55</span><span id='textcolor1528'><span class='ectt-0800'> * find the exact prototype, with the number and type</span></span>
|
|
<a id='x1-40112r56'></a><span class='ecrm-0500'>56</span><span id='textcolor1529'><span class='ectt-0800'> * of arguments, we find the original function first</span></span>
|
|
<a id='x1-40114r57'></a><span class='ecrm-0500'>57</span><span id='textcolor1530'><span class='ectt-0800'> * (it</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s at fs/open.c).</span></span>
|
|
<a id='x1-40116r58'></a><span class='ecrm-0500'>58</span><span id='textcolor1531'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-40118r59'></a><span class='ecrm-0500'>59</span><span id='textcolor1532'><span class='ectt-0800'> * In theory, this means that we</span><span class='tctt-0800'>'</span><span class='ectt-0800'>re tied to the</span></span>
|
|
<a id='x1-40120r60'></a><span class='ecrm-0500'>60</span><span id='textcolor1533'><span class='ectt-0800'> * current version of the kernel. In practice, the</span></span>
|
|
<a id='x1-40122r61'></a><span class='ecrm-0500'>61</span><span id='textcolor1534'><span class='ectt-0800'> * system calls almost never change (it would wreck havoc</span></span>
|
|
<a id='x1-40124r62'></a><span class='ecrm-0500'>62</span><span id='textcolor1535'><span class='ectt-0800'> * and require programs to be recompiled, since the system</span></span>
|
|
<a id='x1-40126r63'></a><span class='ecrm-0500'>63</span><span id='textcolor1536'><span class='ectt-0800'> * calls are the interface between the kernel and the</span></span>
|
|
<a id='x1-40128r64'></a><span class='ecrm-0500'>64</span><span id='textcolor1537'><span class='ectt-0800'> * processes).</span></span>
|
|
<a id='x1-40130r65'></a><span class='ecrm-0500'>65</span><span id='textcolor1538'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-40132r66'></a><span class='ecrm-0500'>66</span><span class='ectt-0800'>asmlinkage </span><span id='textcolor1539'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> our_sys_open(</span><span id='textcolor1540'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor1541'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *filename, </span><span id='textcolor1542'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> flags, </span><span id='textcolor1543'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> mode)</span>
|
|
<a id='x1-40134r67'></a><span class='ecrm-0500'>67</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-40136r68'></a><span class='ecrm-0500'>68</span><span class='ectt-0800'> </span><span id='textcolor1544'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> i = 0;</span>
|
|
<a id='x1-40138r69'></a><span class='ecrm-0500'>69</span><span class='ectt-0800'> </span><span id='textcolor1545'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> ch;</span>
|
|
<a id='x1-40140r70'></a><span class='ecrm-0500'>70</span>
|
|
<a id='x1-40142r71'></a><span class='ecrm-0500'>71</span><span class='ectt-0800'> </span><span id='textcolor1546'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-40144r72'></a><span class='ecrm-0500'>72</span><span id='textcolor1547'><span class='ectt-0800'> * Report the file, if relevant</span></span>
|
|
<a id='x1-40146r73'></a><span class='ecrm-0500'>73</span><span id='textcolor1548'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-40148r74'></a><span class='ecrm-0500'>74</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1549'><span class='ectt-0800'>"Opened file by %d: "</span></span><span class='ectt-0800'>, uid);</span>
|
|
<a id='x1-40150r75'></a><span class='ecrm-0500'>75</span><span class='ectt-0800'> </span><span id='textcolor1550'><span class='ectt-0800'>do</span></span><span class='ectt-0800'> {</span>
|
|
<a id='x1-40152r76'></a><span class='ecrm-0500'>76</span><span class='ectt-0800'> get_user(ch, filename + i);</span>
|
|
<a id='x1-40154r77'></a><span class='ecrm-0500'>77</span><span class='ectt-0800'> i++;</span>
|
|
<a id='x1-40156r78'></a><span class='ecrm-0500'>78</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1551'><span class='ectt-0800'>"%c"</span></span><span class='ectt-0800'>, ch);</span>
|
|
<a id='x1-40158r79'></a><span class='ecrm-0500'>79</span><span class='ectt-0800'> } </span><span id='textcolor1552'><span class='ectt-0800'>while</span></span><span class='ectt-0800'> (ch != 0);</span>
|
|
<a id='x1-40160r80'></a><span class='ecrm-0500'>80</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1553'><span class='ectt-0800'>"</span></span><span id='textcolor1554'><span class='ectt-0800'>\n</span></span><span id='textcolor1555'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-40162r81'></a><span class='ecrm-0500'>81</span>
|
|
<a id='x1-40164r82'></a><span class='ecrm-0500'>82</span><span class='ectt-0800'> </span><span id='textcolor1556'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-40166r83'></a><span class='ecrm-0500'>83</span><span id='textcolor1557'><span class='ectt-0800'> * Call the original sys_open - otherwise, we lose</span></span>
|
|
<a id='x1-40168r84'></a><span class='ecrm-0500'>84</span><span id='textcolor1558'><span class='ectt-0800'> * the ability to open files</span></span>
|
|
<a id='x1-40170r85'></a><span class='ecrm-0500'>85</span><span id='textcolor1559'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-40172r86'></a><span class='ecrm-0500'>86</span><span class='ectt-0800'> </span><span id='textcolor1560'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> original_call(filename, flags, mode);</span>
|
|
<a id='x1-40174r87'></a><span class='ecrm-0500'>87</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-40176r88'></a><span class='ecrm-0500'>88</span>
|
|
<a id='x1-40178r89'></a><span class='ecrm-0500'>89</span><span id='textcolor1561'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1562'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1563'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> **aquire_sys_call_table(</span><span id='textcolor1564'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-40180r90'></a><span class='ecrm-0500'>90</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-40182r91'></a><span class='ecrm-0500'>91</span><span class='ectt-0800'> </span><span id='textcolor1565'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1566'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> </span><span id='textcolor1567'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> offset = PAGE_OFFSET;</span>
|
|
<a id='x1-40184r92'></a><span class='ecrm-0500'>92</span><span class='ectt-0800'> </span><span id='textcolor1568'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1569'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> **sct;</span>
|
|
<a id='x1-40186r93'></a><span class='ecrm-0500'>93</span>
|
|
<a id='x1-40188r94'></a><span class='ecrm-0500'>94</span><span class='ectt-0800'> </span><span id='textcolor1570'><span class='ectt-0800'>while</span></span><span class='ectt-0800'> (offset < ULLONG_MAX) {</span>
|
|
<a id='x1-40190r95'></a><span class='ecrm-0500'>95</span><span class='ectt-0800'> sct = (</span><span id='textcolor1571'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1572'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> **) offset;</span>
|
|
<a id='x1-40192r96'></a><span class='ecrm-0500'>96</span>
|
|
<a id='x1-40194r97'></a><span class='ecrm-0500'>97</span><span class='ectt-0800'> </span><span id='textcolor1573'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (sct[__NR_close] == (</span><span id='textcolor1574'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1575'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> *) ksys_close)</span>
|
|
<a id='x1-40196r98'></a><span class='ecrm-0500'>98</span><span class='ectt-0800'> </span><span id='textcolor1576'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> sct;</span>
|
|
<a id='x1-40198r99'></a><span class='ecrm-0500'>99</span>
|
|
<a id='x1-40200r100'></a><span class='ecrm-0500'>100</span><span class='ectt-0800'> offset += </span><span id='textcolor1577'><span class='ectt-0800'>sizeof</span></span><span class='ectt-0800'>(</span><span id='textcolor1578'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *);</span>
|
|
<a id='x1-40202r101'></a><span class='ecrm-0500'>101</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-40204r102'></a><span class='ecrm-0500'>102</span>
|
|
<a id='x1-40206r103'></a><span class='ecrm-0500'>103</span><span class='ectt-0800'> </span><span id='textcolor1579'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> NULL;</span>
|
|
<a id='x1-40208r104'></a><span class='ecrm-0500'>104</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-40210r105'></a><span class='ecrm-0500'>105</span>
|
|
<a id='x1-40212r106'></a><span class='ecrm-0500'>106</span><span id='textcolor1580'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1581'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> __init syscall_start(</span><span id='textcolor1582'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-40214r107'></a><span class='ecrm-0500'>107</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-40216r108'></a><span class='ecrm-0500'>108</span><span class='ectt-0800'> </span><span id='textcolor1583'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (!(sys_call_table = aquire_sys_call_table()))</span>
|
|
<a id='x1-40218r109'></a><span class='ecrm-0500'>109</span><span class='ectt-0800'> </span><span id='textcolor1584'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -1;</span>
|
|
<a id='x1-40220r110'></a><span class='ecrm-0500'>110</span>
|
|
<a id='x1-40222r111'></a><span class='ecrm-0500'>111</span><span class='ectt-0800'> original_cr0 = read_cr0();</span>
|
|
<a id='x1-40224r112'></a><span class='ecrm-0500'>112</span>
|
|
<a id='x1-40226r113'></a><span class='ecrm-0500'>113</span><span class='ectt-0800'> write_cr0(original_cr0 & ~0x00010000);</span>
|
|
<a id='x1-40228r114'></a><span class='ecrm-0500'>114</span>
|
|
<a id='x1-40230r115'></a><span class='ecrm-0500'>115</span><span class='ectt-0800'> </span><span id='textcolor1585'><span class='ectt-0800'>/* keep track of the original open function */</span></span>
|
|
<a id='x1-40232r116'></a><span class='ecrm-0500'>116</span><span class='ectt-0800'> original_call = (</span><span id='textcolor1586'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *) sys_call_table[__NR_open];</span>
|
|
<a id='x1-40234r117'></a><span class='ecrm-0500'>117</span>
|
|
<a id='x1-40236r118'></a><span class='ecrm-0500'>118</span><span class='ectt-0800'> </span><span id='textcolor1587'><span class='ectt-0800'>/* use our open function instead */</span></span>
|
|
<a id='x1-40238r119'></a><span class='ecrm-0500'>119</span><span class='ectt-0800'> sys_call_table[__NR_open] = (</span><span id='textcolor1588'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1589'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> *) our_sys_open;</span>
|
|
<a id='x1-40240r120'></a><span class='ecrm-0500'>120</span>
|
|
<a id='x1-40242r121'></a><span class='ecrm-0500'>121</span><span class='ectt-0800'> write_cr0(original_cr0);</span>
|
|
<a id='x1-40244r122'></a><span class='ecrm-0500'>122</span>
|
|
<a id='x1-40246r123'></a><span class='ecrm-0500'>123</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1590'><span class='ectt-0800'>"Spying on UID:%d</span></span><span id='textcolor1591'><span class='ectt-0800'>\n</span></span><span id='textcolor1592'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, uid);</span>
|
|
<a id='x1-40248r124'></a><span class='ecrm-0500'>124</span>
|
|
<a id='x1-40250r125'></a><span class='ecrm-0500'>125</span><span class='ectt-0800'> </span><span id='textcolor1593'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-40252r126'></a><span class='ecrm-0500'>126</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-40254r127'></a><span class='ecrm-0500'>127</span>
|
|
<a id='x1-40256r128'></a><span class='ecrm-0500'>128</span><span id='textcolor1594'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1595'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> __exit syscall_end(</span><span id='textcolor1596'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-40258r129'></a><span class='ecrm-0500'>129</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-40260r130'></a><span class='ecrm-0500'>130</span><span class='ectt-0800'> </span><span id='textcolor1597'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (!sys_call_table) {</span>
|
|
<a id='x1-40262r131'></a><span class='ecrm-0500'>131</span><span class='ectt-0800'> </span><span id='textcolor1598'><span class='ectt-0800'>return</span></span><span class='ectt-0800'>;</span>
|
|
<a id='x1-40264r132'></a><span class='ecrm-0500'>132</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-40266r133'></a><span class='ecrm-0500'>133</span>
|
|
<a id='x1-40268r134'></a><span class='ecrm-0500'>134</span><span class='ectt-0800'> </span><span id='textcolor1599'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-40270r135'></a><span class='ecrm-0500'>135</span><span id='textcolor1600'><span class='ectt-0800'> * Return the system call back to normal</span></span>
|
|
<a id='x1-40272r136'></a><span class='ecrm-0500'>136</span><span id='textcolor1601'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-40274r137'></a><span class='ecrm-0500'>137</span><span class='ectt-0800'> </span><span id='textcolor1602'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (sys_call_table[__NR_open] != (</span><span id='textcolor1603'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1604'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> *) our_sys_open) {</span>
|
|
<a id='x1-40276r138'></a><span class='ecrm-0500'>138</span><span class='ectt-0800'> pr_alert(</span><span id='textcolor1605'><span class='ectt-0800'>"Somebody else also played with the "</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-40278r139'></a><span class='ecrm-0500'>139</span><span class='ectt-0800'> pr_alert(</span><span id='textcolor1606'><span class='ectt-0800'>"open system call</span></span><span id='textcolor1607'><span class='ectt-0800'>\n</span></span><span id='textcolor1608'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-40280r140'></a><span class='ecrm-0500'>140</span><span class='ectt-0800'> pr_alert(</span><span id='textcolor1609'><span class='ectt-0800'>"The system may be left in "</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-40282r141'></a><span class='ecrm-0500'>141</span><span class='ectt-0800'> pr_alert(</span><span id='textcolor1610'><span class='ectt-0800'>"an unstable state.</span></span><span id='textcolor1611'><span class='ectt-0800'>\n</span></span><span id='textcolor1612'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-40284r142'></a><span class='ecrm-0500'>142</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-40286r143'></a><span class='ecrm-0500'>143</span>
|
|
<a id='x1-40288r144'></a><span class='ecrm-0500'>144</span><span class='ectt-0800'> write_cr0(original_cr0 & ~0x00010000);</span>
|
|
<a id='x1-40290r145'></a><span class='ecrm-0500'>145</span><span class='ectt-0800'> sys_call_table[__NR_open] = (</span><span id='textcolor1613'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1614'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> *) original_call;</span>
|
|
<a id='x1-40292r146'></a><span class='ecrm-0500'>146</span><span class='ectt-0800'> write_cr0(original_cr0);</span>
|
|
<a id='x1-40294r147'></a><span class='ecrm-0500'>147</span>
|
|
<a id='x1-40296r148'></a><span class='ecrm-0500'>148</span><span class='ectt-0800'> msleep(2000);</span>
|
|
<a id='x1-40298r149'></a><span class='ecrm-0500'>149</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-40300r150'></a><span class='ecrm-0500'>150</span>
|
|
<a id='x1-40302r151'></a><span class='ecrm-0500'>151</span><span class='ectt-0800'>module_init(syscall_start);</span>
|
|
<a id='x1-40304r152'></a><span class='ecrm-0500'>152</span><span class='ectt-0800'>module_exit(syscall_end);</span>
|
|
<a id='x1-40306r153'></a><span class='ecrm-0500'>153</span>
|
|
<a id='x1-40308r154'></a><span class='ecrm-0500'>154</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor1615'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
|
|
<!-- l. 1211 --><p class='noindent'>
|
|
</p>
|
|
<h3 class='sectionHead' id='blocking-processes-and-threads'><span class='titlemark'>0.11 </span> <a id='x1-410000.11'></a>Blocking Processes and threads</h3>
|
|
|
|
|
|
|
|
<!-- l. 1213 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='sleep'><span class='titlemark'>0.11.1 </span> <a id='x1-420000.11.1'></a>Sleep</h4>
|
|
<!-- l. 1215 --><p class='noindent'>What do you do when somebody asks you for something you can’t do right away? If
|
|
you’re a human being and you’re bothered by a human being, the only thing you can
|
|
say is: "<span class='ecti-1000'>Not right now, I’m busy. Go away!</span>". But if you’re a kernel module and
|
|
you’re bothered by a process, you have another possibility. You can put the process
|
|
to sleep until you can service it. After all, processes are being put to sleep by the
|
|
kernel and woken up all the time (that’s the way multiple processes appear to run on
|
|
the same time on a single CPU).
|
|
</p><!-- l. 1217 --><p class='indent'> This kernel module is an example of this. The file (called <span class='ecbx-1000'>/proc/sleep</span>) can only
|
|
be opened by a single process at a time. If the file is already open, the kernel module
|
|
calls wait_event_interruptible. The easiest way to keep a file open is to open it
|
|
with:
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb52'><a id='x1-42003r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>tail -f</span></pre>
|
|
<!-- l. 1223 --><p class='indent'> This function changes the status of the task (a task is the kernel data
|
|
structure which holds information about a process and the system call it’s in, if
|
|
any) to <span class='ecbx-1000'>TASK_INTERRUPTIBLE</span>, which means that the task will
|
|
not run until it is woken up somehow, and adds it to WaitQ, the queue
|
|
of tasks waiting to access the file. Then, the function calls the scheduler
|
|
to context switch to a different process, one which has some use for the
|
|
CPU.
|
|
</p><!-- l. 1225 --><p class='indent'> When a process is done with the file, it closes it, and module_close is called. That
|
|
function wakes up all the processes in the queue (there’s no mechanism
|
|
to only wake up one of them). It then returns and the process which just
|
|
closed the file can continue to run. In time, the scheduler decides that that
|
|
process has had enough and gives control of the CPU to another process.
|
|
Eventually, one of the processes which was in the queue will be given control
|
|
of the CPU by the scheduler. It starts at the point right after the call to
|
|
<span class='ecbx-1000'>module_interruptible_sleep_on</span>.
|
|
</p><!-- l. 1227 --><p class='indent'> This means that the process is still in kernel mode - as far as the process is
|
|
concerned, it issued the open system call and the system call hasn’t returned yet.
|
|
The process doesn’t know somebody else used the CPU for most of the time between
|
|
the moment it issued the call and the moment it returned.
|
|
</p><!-- l. 1229 --><p class='indent'> It can then proceed to set a global variable to tell all the other processes that the
|
|
file is still open and go on with its life. When the other processes get a piece of the
|
|
CPU, they’ll see that global variable and go back to sleep.
|
|
</p><!-- l. 1231 --><p class='indent'> So we’ll use tail -f to keep the file open in the background, while trying to
|
|
access it with another process (again in the background, so that we need not
|
|
switch to a different vt). As soon as the first background process is killed
|
|
with kill %1 , the second is woken up, is able to access the file and finally
|
|
terminates.
|
|
|
|
|
|
|
|
</p><!-- l. 1233 --><p class='indent'> To make our life more interesting, <span class='ecbx-1000'>module_close </span>doesn’t have a monopoly
|
|
on waking up the processes which wait to access the file. A signal, such as
|
|
<span class='ecti-1000'>Ctrl +c </span>(<span class='ecbx-1000'>SIGINT</span>) can also wake up a process. This is because we used
|
|
<span class='ecbx-1000'>module_interruptible_sleep_on</span>. We could have used <span class='ecbx-1000'>module_sleep_on</span>
|
|
instead, but that would have resulted in extremely angry users whose <span class='ecti-1000'>Ctrl+c</span>’s are
|
|
ignored.
|
|
</p><!-- l. 1235 --><p class='indent'> In that case, we want to return with <span class='ecbx-1000'>-EINTR </span>immediately. This is important so
|
|
users can, for example, kill the process before it receives the file.
|
|
</p><!-- l. 1237 --><p class='indent'> There is one more point to remember. Some times processes don’t want to sleep,
|
|
they want either to get what they want immediately, or to be told it cannot be done.
|
|
Such processes use the <span class='ecbx-1000'>O_NONBLOCK </span>flag when opening the file. The kernel is
|
|
supposed to respond by returning with the error code <span class='ecbx-1000'>-EAGAIN </span>from operations
|
|
which would otherwise block, such as opening the file in this example. The program
|
|
cat_noblock, available in the source directory for this chapter, can be used to open a
|
|
file with <span class='ecbx-1000'>O_NONBLOCK</span>.
|
|
|
|
|
|
|
|
</p>
|
|
<pre class='verbatim' id='verbatim-11'>
|
|
$ sudo insmod sleep.ko
|
|
$ cat_nonblock /proc/sleep
|
|
Last input:
|
|
$ tail -f /proc/sleep &
|
|
Last input:
|
|
Last input:
|
|
Last input:
|
|
Last input:
|
|
Last input:
|
|
Last input:
|
|
Last input:
|
|
tail: /proc/sleep: file truncated
|
|
[1] 6540
|
|
$ cat_nonblock /proc/sleep
|
|
Open would block
|
|
$ kill %1
|
|
[1]+ Terminated tail -f /proc/sleep
|
|
$ cat_nonblock /proc/sleep
|
|
Last input:
|
|
$
|
|
</pre>
|
|
<!-- l. 1260 --><p class='nopar'>
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb53'><a id='x1-42005r1'></a><span class='ecrm-0500'>1</span><span id='textcolor1616'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42007r2'></a><span class='ecrm-0500'>2</span><span id='textcolor1617'><span class='ectt-0800'> * sleep.c - create a /proc file, and if several processes try to open it at</span></span>
|
|
<a id='x1-42009r3'></a><span class='ecrm-0500'>3</span><span id='textcolor1618'><span class='ectt-0800'> * the same time, put all but one to sleep</span></span>
|
|
<a id='x1-42011r4'></a><span class='ecrm-0500'>4</span><span id='textcolor1619'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42013r5'></a><span class='ecrm-0500'>5</span>
|
|
<a id='x1-42015r6'></a><span class='ecrm-0500'>6</span><span id='textcolor1620'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1621'><span class='ectt-0800'><linux/kernel.h> /* We</span><span class='tctt-0800'>'</span><span class='ectt-0800'>re doing kernel work */</span></span>
|
|
<a id='x1-42017r7'></a><span class='ecrm-0500'>7</span><span id='textcolor1622'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1623'><span class='ectt-0800'><linux/module.h> /* Specifically, a module */</span></span>
|
|
<a id='x1-42019r8'></a><span class='ecrm-0500'>8</span><span id='textcolor1624'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1625'><span class='ectt-0800'><linux/proc_fs.h> /* Necessary because we use proc fs */</span></span>
|
|
<a id='x1-42021r9'></a><span class='ecrm-0500'>9</span><span id='textcolor1626'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1627'><span class='ectt-0800'><linux/sched.h> /* For putting processes to sleep and</span></span>
|
|
<a id='x1-42023r10'></a><span class='ecrm-0500'>10</span><span class='ectt-0800'> waking them up </span><span class='colorbox' id='colorbox1628'><span class='ectt-0800'>*/</span></span>
|
|
<a id='x1-42025r11'></a><span class='ecrm-0500'>11</span><span id='textcolor1629'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1630'><span class='ectt-0800'><linux/uaccess.h> /* for get_user and put_user */</span></span>
|
|
<a id='x1-42027r12'></a><span class='ecrm-0500'>12</span><span id='textcolor1631'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1632'><span class='ectt-0800'><linux/version.h></span></span>
|
|
<a id='x1-42029r13'></a><span class='ecrm-0500'>13</span>
|
|
<a id='x1-42031r14'></a><span class='ecrm-0500'>14</span><span id='textcolor1633'><span class='ectt-0800'>#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 6, 0)</span></span>
|
|
<a id='x1-42033r15'></a><span class='ecrm-0500'>15</span><span id='textcolor1634'><span class='ectt-0800'>#define HAVE_PROC_OPS</span></span>
|
|
<a id='x1-42035r16'></a><span class='ecrm-0500'>16</span><span id='textcolor1635'><span class='ectt-0800'>#endif</span></span>
|
|
<a id='x1-42037r17'></a><span class='ecrm-0500'>17</span>
|
|
<a id='x1-42039r18'></a><span class='ecrm-0500'>18</span><span id='textcolor1636'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42041r19'></a><span class='ecrm-0500'>19</span><span id='textcolor1637'><span class='ectt-0800'> * The module</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s file functions</span></span>
|
|
<a id='x1-42043r20'></a><span class='ecrm-0500'>20</span><span id='textcolor1638'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42045r21'></a><span class='ecrm-0500'>21</span>
|
|
<a id='x1-42047r22'></a><span class='ecrm-0500'>22</span><span id='textcolor1639'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42049r23'></a><span class='ecrm-0500'>23</span><span id='textcolor1640'><span class='ectt-0800'> * Here we keep the last message received, to prove that we can process our</span></span>
|
|
<a id='x1-42051r24'></a><span class='ecrm-0500'>24</span><span id='textcolor1641'><span class='ectt-0800'> * input</span></span>
|
|
<a id='x1-42053r25'></a><span class='ecrm-0500'>25</span><span id='textcolor1642'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42055r26'></a><span class='ecrm-0500'>26</span><span id='textcolor1643'><span class='ectt-0800'>#define MESSAGE_LENGTH 80</span></span>
|
|
<a id='x1-42057r27'></a><span class='ecrm-0500'>27</span><span id='textcolor1644'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1645'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> Message[MESSAGE_LENGTH];</span>
|
|
<a id='x1-42059r28'></a><span class='ecrm-0500'>28</span>
|
|
<a id='x1-42061r29'></a><span class='ecrm-0500'>29</span><span id='textcolor1646'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1647'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> proc_dir_entry *Our_Proc_File;</span>
|
|
<a id='x1-42063r30'></a><span class='ecrm-0500'>30</span><span id='textcolor1648'><span class='ectt-0800'>#define PROC_ENTRY_FILENAME "sleep"</span></span>
|
|
<a id='x1-42065r31'></a><span class='ecrm-0500'>31</span>
|
|
<a id='x1-42067r32'></a><span class='ecrm-0500'>32</span><span id='textcolor1649'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42069r33'></a><span class='ecrm-0500'>33</span><span id='textcolor1650'><span class='ectt-0800'> * Since we use the file operations struct, we can</span><span class='tctt-0800'>'</span><span class='ectt-0800'>t use the special proc</span></span>
|
|
<a id='x1-42071r34'></a><span class='ecrm-0500'>34</span><span id='textcolor1651'><span class='ectt-0800'> * output provisions - we have to use a standard read function, which is this</span></span>
|
|
<a id='x1-42073r35'></a><span class='ecrm-0500'>35</span><span id='textcolor1652'><span class='ectt-0800'> * function</span></span>
|
|
<a id='x1-42075r36'></a><span class='ecrm-0500'>36</span><span id='textcolor1653'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42077r37'></a><span class='ecrm-0500'>37</span><span id='textcolor1654'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1655'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> module_output(</span><span id='textcolor1656'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *file, </span><span id='textcolor1657'><span class='ectt-0800'>/* see include/linux/fs.h */</span></span>
|
|
<a id='x1-42079r38'></a><span class='ecrm-0500'>38</span><span class='ectt-0800'> </span><span id='textcolor1658'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *buf, </span><span id='textcolor1659'><span class='ectt-0800'>/* The buffer to put data to</span></span>
|
|
<a id='x1-42081r39'></a><span class='ecrm-0500'>39</span><span id='textcolor1660'><span class='ectt-0800'> (in the user segment)</span></span><span class='ectt-0800'> </span><span class='colorbox' id='colorbox1661'><span class='ectt-0800'>*/</span></span>
|
|
<a id='x1-42083r40'></a><span class='ecrm-0500'>40</span><span class='ectt-0800'> </span><span id='textcolor1662'><span class='ectt-0800'>size_t</span></span><span class='ectt-0800'> len, </span><span id='textcolor1663'><span class='ectt-0800'>/* The length of the buffer */</span></span>
|
|
<a id='x1-42085r41'></a><span class='ecrm-0500'>41</span><span class='ectt-0800'> loff_t *offset)</span>
|
|
<a id='x1-42087r42'></a><span class='ecrm-0500'>42</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-42089r43'></a><span class='ecrm-0500'>43</span><span class='ectt-0800'> </span><span id='textcolor1664'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1665'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> finished = 0;</span>
|
|
<a id='x1-42091r44'></a><span class='ecrm-0500'>44</span><span class='ectt-0800'> </span><span id='textcolor1666'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> i;</span>
|
|
<a id='x1-42093r45'></a><span class='ecrm-0500'>45</span><span class='ectt-0800'> </span><span id='textcolor1667'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> message[MESSAGE_LENGTH + 30];</span>
|
|
<a id='x1-42095r46'></a><span class='ecrm-0500'>46</span>
|
|
<a id='x1-42097r47'></a><span class='ecrm-0500'>47</span><span class='ectt-0800'> </span><span id='textcolor1668'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42099r48'></a><span class='ecrm-0500'>48</span><span id='textcolor1669'><span class='ectt-0800'> * Return 0 to signify end of file - that we have nothing</span></span>
|
|
<a id='x1-42101r49'></a><span class='ecrm-0500'>49</span><span id='textcolor1670'><span class='ectt-0800'> * more to say at this point.</span></span>
|
|
<a id='x1-42103r50'></a><span class='ecrm-0500'>50</span><span id='textcolor1671'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42105r51'></a><span class='ecrm-0500'>51</span><span class='ectt-0800'> </span><span id='textcolor1672'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (finished) {</span>
|
|
<a id='x1-42107r52'></a><span class='ecrm-0500'>52</span><span class='ectt-0800'> finished = 0;</span>
|
|
<a id='x1-42109r53'></a><span class='ecrm-0500'>53</span><span class='ectt-0800'> </span><span id='textcolor1673'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-42111r54'></a><span class='ecrm-0500'>54</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-42113r55'></a><span class='ecrm-0500'>55</span>
|
|
<a id='x1-42115r56'></a><span class='ecrm-0500'>56</span><span class='ectt-0800'> </span><span id='textcolor1674'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42117r57'></a><span class='ecrm-0500'>57</span><span id='textcolor1675'><span class='ectt-0800'> * If you don</span><span class='tctt-0800'>'</span><span class='ectt-0800'>t understand this by now, you</span><span class='tctt-0800'>'</span><span class='ectt-0800'>re hopeless as a kernel</span></span>
|
|
<a id='x1-42119r58'></a><span class='ecrm-0500'>58</span><span id='textcolor1676'><span class='ectt-0800'> * programmer.</span></span>
|
|
<a id='x1-42121r59'></a><span class='ecrm-0500'>59</span><span id='textcolor1677'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42123r60'></a><span class='ecrm-0500'>60</span><span class='ectt-0800'> sprintf(message, </span><span id='textcolor1678'><span class='ectt-0800'>"Last input:%s</span></span><span id='textcolor1679'><span class='ectt-0800'>\n</span></span><span id='textcolor1680'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, Message);</span>
|
|
<a id='x1-42125r61'></a><span class='ecrm-0500'>61</span><span class='ectt-0800'> </span><span id='textcolor1681'><span class='ectt-0800'>for</span></span><span class='ectt-0800'> (i = 0; i < len && message[i]; i++)</span>
|
|
<a id='x1-42127r62'></a><span class='ecrm-0500'>62</span><span class='ectt-0800'> put_user(message[i], buf + i);</span>
|
|
<a id='x1-42129r63'></a><span class='ecrm-0500'>63</span>
|
|
<a id='x1-42131r64'></a><span class='ecrm-0500'>64</span><span class='ectt-0800'> finished = 1;</span>
|
|
<a id='x1-42133r65'></a><span class='ecrm-0500'>65</span><span class='ectt-0800'> </span><span id='textcolor1682'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> i; </span><span id='textcolor1683'><span class='ectt-0800'>/* Return the number of bytes "read" */</span></span>
|
|
<a id='x1-42135r66'></a><span class='ecrm-0500'>66</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-42137r67'></a><span class='ecrm-0500'>67</span>
|
|
<a id='x1-42139r68'></a><span class='ecrm-0500'>68</span><span id='textcolor1684'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42141r69'></a><span class='ecrm-0500'>69</span><span id='textcolor1685'><span class='ectt-0800'> * This function receives input from the user when the user writes to the /proc</span></span>
|
|
<a id='x1-42143r70'></a><span class='ecrm-0500'>70</span><span id='textcolor1686'><span class='ectt-0800'> * file.</span></span>
|
|
<a id='x1-42145r71'></a><span class='ecrm-0500'>71</span><span id='textcolor1687'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42147r72'></a><span class='ecrm-0500'>72</span><span id='textcolor1688'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1689'><span class='ectt-0800'>ssize_t</span></span><span class='ectt-0800'> module_input(</span><span id='textcolor1690'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *file, </span><span id='textcolor1691'><span class='ectt-0800'>/* The file itself */</span></span>
|
|
<a id='x1-42149r73'></a><span class='ecrm-0500'>73</span><span class='ectt-0800'> </span><span id='textcolor1692'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor1693'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *buf, </span><span id='textcolor1694'><span class='ectt-0800'>/* The buffer with input */</span></span>
|
|
<a id='x1-42151r74'></a><span class='ecrm-0500'>74</span><span class='ectt-0800'> </span><span id='textcolor1695'><span class='ectt-0800'>size_t</span></span><span class='ectt-0800'> length, </span><span id='textcolor1696'><span class='ectt-0800'>/* The buffer</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s length */</span></span>
|
|
<a id='x1-42153r75'></a><span class='ecrm-0500'>75</span><span class='ectt-0800'> loff_t *offset) </span><span id='textcolor1697'><span class='ectt-0800'>/* offset to file - ignore */</span></span>
|
|
<a id='x1-42155r76'></a><span class='ecrm-0500'>76</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-42157r77'></a><span class='ecrm-0500'>77</span><span class='ectt-0800'> </span><span id='textcolor1698'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> i;</span>
|
|
<a id='x1-42159r78'></a><span class='ecrm-0500'>78</span>
|
|
<a id='x1-42161r79'></a><span class='ecrm-0500'>79</span><span class='ectt-0800'> </span><span id='textcolor1699'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42163r80'></a><span class='ecrm-0500'>80</span><span id='textcolor1700'><span class='ectt-0800'> * Put the input into Message, where module_output will later be</span></span>
|
|
<a id='x1-42165r81'></a><span class='ecrm-0500'>81</span><span id='textcolor1701'><span class='ectt-0800'> * able to use it</span></span>
|
|
<a id='x1-42167r82'></a><span class='ecrm-0500'>82</span><span id='textcolor1702'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42169r83'></a><span class='ecrm-0500'>83</span><span class='ectt-0800'> </span><span id='textcolor1703'><span class='ectt-0800'>for</span></span><span class='ectt-0800'> (i = 0; i < MESSAGE_LENGTH - 1 && i < length; i++)</span>
|
|
<a id='x1-42171r84'></a><span class='ecrm-0500'>84</span><span class='ectt-0800'> get_user(Message[i], buf + i);</span>
|
|
<a id='x1-42173r85'></a><span class='ecrm-0500'>85</span><span class='ectt-0800'> </span><span id='textcolor1704'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42175r86'></a><span class='ecrm-0500'>86</span><span id='textcolor1705'><span class='ectt-0800'> * we want a standard, zero terminated string</span></span>
|
|
<a id='x1-42177r87'></a><span class='ecrm-0500'>87</span><span id='textcolor1706'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42179r88'></a><span class='ecrm-0500'>88</span><span class='ectt-0800'> Message[i] = </span><span id='textcolor1707'><span class='tctt-0800'>'</span><span class='ectt-0800'>\0</span><span class='tctt-0800'>'</span></span><span class='ectt-0800'>;</span>
|
|
<a id='x1-42181r89'></a><span class='ecrm-0500'>89</span>
|
|
<a id='x1-42183r90'></a><span class='ecrm-0500'>90</span><span class='ectt-0800'> </span><span id='textcolor1708'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42185r91'></a><span class='ecrm-0500'>91</span><span id='textcolor1709'><span class='ectt-0800'> * We need to return the number of input characters used</span></span>
|
|
<a id='x1-42187r92'></a><span class='ecrm-0500'>92</span><span id='textcolor1710'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42189r93'></a><span class='ecrm-0500'>93</span><span class='ectt-0800'> </span><span id='textcolor1711'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> i;</span>
|
|
<a id='x1-42191r94'></a><span class='ecrm-0500'>94</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-42193r95'></a><span class='ecrm-0500'>95</span>
|
|
<a id='x1-42195r96'></a><span class='ecrm-0500'>96</span><span id='textcolor1712'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42197r97'></a><span class='ecrm-0500'>97</span><span id='textcolor1713'><span class='ectt-0800'> * 1 if the file is currently open by somebody</span></span>
|
|
<a id='x1-42199r98'></a><span class='ecrm-0500'>98</span><span id='textcolor1714'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42201r99'></a><span class='ecrm-0500'>99</span><span id='textcolor1715'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> Already_Open = 0;</span>
|
|
<a id='x1-42203r100'></a><span class='ecrm-0500'>100</span>
|
|
<a id='x1-42205r101'></a><span class='ecrm-0500'>101</span><span id='textcolor1716'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42207r102'></a><span class='ecrm-0500'>102</span><span id='textcolor1717'><span class='ectt-0800'> * Queue of processes who want our file</span></span>
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<a id='x1-42209r103'></a><span class='ecrm-0500'>103</span><span id='textcolor1718'><span class='ectt-0800'> */</span></span>
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<a id='x1-42211r104'></a><span class='ecrm-0500'>104</span><span class='ectt-0800'>DECLARE_WAIT_QUEUE_HEAD(WaitQ);</span>
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<a id='x1-42213r105'></a><span class='ecrm-0500'>105</span><span id='textcolor1719'><span class='ectt-0800'>/*</span></span>
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<a id='x1-42215r106'></a><span class='ecrm-0500'>106</span><span id='textcolor1720'><span class='ectt-0800'> * Called when the /proc file is opened</span></span>
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<a id='x1-42217r107'></a><span class='ecrm-0500'>107</span><span id='textcolor1721'><span class='ectt-0800'> */</span></span>
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<a id='x1-42219r108'></a><span class='ecrm-0500'>108</span><span id='textcolor1722'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1723'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> module_open(</span><span id='textcolor1724'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> inode *inode, </span><span id='textcolor1725'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *file)</span>
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<a id='x1-42221r109'></a><span class='ecrm-0500'>109</span><span class='ectt-0800'>{</span>
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<a id='x1-42223r110'></a><span class='ecrm-0500'>110</span><span class='ectt-0800'> </span><span id='textcolor1726'><span class='ectt-0800'>/*</span></span>
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|
<a id='x1-42225r111'></a><span class='ecrm-0500'>111</span><span id='textcolor1727'><span class='ectt-0800'> * If the file</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s flags include O_NONBLOCK, it means the process doesn</span><span class='tctt-0800'>'</span><span class='ectt-0800'>t</span></span>
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<a id='x1-42227r112'></a><span class='ecrm-0500'>112</span><span id='textcolor1728'><span class='ectt-0800'> * want to wait for the file. In this case, if the file is already</span></span>
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<a id='x1-42229r113'></a><span class='ecrm-0500'>113</span><span id='textcolor1729'><span class='ectt-0800'> * open, we should fail with -EAGAIN, meaning "you</span><span class='tctt-0800'>'</span><span class='ectt-0800'>ll have to try</span></span>
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<a id='x1-42231r114'></a><span class='ecrm-0500'>114</span><span id='textcolor1730'><span class='ectt-0800'> * again", instead of blocking a process which would rather stay awake.</span></span>
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<a id='x1-42233r115'></a><span class='ecrm-0500'>115</span><span id='textcolor1731'><span class='ectt-0800'> */</span></span>
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<a id='x1-42235r116'></a><span class='ecrm-0500'>116</span><span class='ectt-0800'> </span><span id='textcolor1732'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> ((file->f_flags & O_NONBLOCK) && Already_Open)</span>
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<a id='x1-42237r117'></a><span class='ecrm-0500'>117</span><span class='ectt-0800'> </span><span id='textcolor1733'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -EAGAIN;</span>
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<a id='x1-42239r118'></a><span class='ecrm-0500'>118</span>
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<a id='x1-42241r119'></a><span class='ecrm-0500'>119</span><span class='ectt-0800'> </span><span id='textcolor1734'><span class='ectt-0800'>/*</span></span>
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<a id='x1-42243r120'></a><span class='ecrm-0500'>120</span><span id='textcolor1735'><span class='ectt-0800'> * This is the correct place for try_module_get(THIS_MODULE) because</span></span>
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<a id='x1-42245r121'></a><span class='ecrm-0500'>121</span><span id='textcolor1736'><span class='ectt-0800'> * if a process is in the loop, which is within the kernel module,</span></span>
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<a id='x1-42247r122'></a><span class='ecrm-0500'>122</span><span id='textcolor1737'><span class='ectt-0800'> * the kernel module must not be removed.</span></span>
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<a id='x1-42249r123'></a><span class='ecrm-0500'>123</span><span id='textcolor1738'><span class='ectt-0800'> */</span></span>
|
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<a id='x1-42251r124'></a><span class='ecrm-0500'>124</span><span class='ectt-0800'> try_module_get(THIS_MODULE);</span>
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<a id='x1-42253r125'></a><span class='ecrm-0500'>125</span>
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<a id='x1-42255r126'></a><span class='ecrm-0500'>126</span><span class='ectt-0800'> </span><span id='textcolor1739'><span class='ectt-0800'>/*</span></span>
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<a id='x1-42257r127'></a><span class='ecrm-0500'>127</span><span id='textcolor1740'><span class='ectt-0800'> * If the file is already open, wait until it isn</span><span class='tctt-0800'>'</span><span class='ectt-0800'>t</span></span>
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<a id='x1-42259r128'></a><span class='ecrm-0500'>128</span><span id='textcolor1741'><span class='ectt-0800'> */</span></span>
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<a id='x1-42261r129'></a><span class='ecrm-0500'>129</span>
|
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<a id='x1-42263r130'></a><span class='ecrm-0500'>130</span><span class='ectt-0800'> </span><span id='textcolor1742'><span class='ectt-0800'>while</span></span><span class='ectt-0800'> (Already_Open) {</span>
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|
<a id='x1-42265r131'></a><span class='ecrm-0500'>131</span><span class='ectt-0800'> </span><span id='textcolor1743'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> i, is_sig = 0;</span>
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|
<a id='x1-42267r132'></a><span class='ecrm-0500'>132</span>
|
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<a id='x1-42269r133'></a><span class='ecrm-0500'>133</span><span class='ectt-0800'> </span><span id='textcolor1744'><span class='ectt-0800'>/*</span></span>
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|
<a id='x1-42271r134'></a><span class='ecrm-0500'>134</span><span id='textcolor1745'><span class='ectt-0800'> * This function puts the current process, including any system</span></span>
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|
<a id='x1-42273r135'></a><span class='ecrm-0500'>135</span><span id='textcolor1746'><span class='ectt-0800'> * calls, such as us, to sleep. Execution will be resumed right</span></span>
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|
<a id='x1-42275r136'></a><span class='ecrm-0500'>136</span><span id='textcolor1747'><span class='ectt-0800'> * after the function call, either because somebody called</span></span>
|
|
<a id='x1-42277r137'></a><span class='ecrm-0500'>137</span><span id='textcolor1748'><span class='ectt-0800'> * wake_up(&WaitQ) (only module_close does that, when the file</span></span>
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|
<a id='x1-42279r138'></a><span class='ecrm-0500'>138</span><span id='textcolor1749'><span class='ectt-0800'> * is closed) or when a signal, such as Ctrl-C, is sent</span></span>
|
|
<a id='x1-42281r139'></a><span class='ecrm-0500'>139</span><span id='textcolor1750'><span class='ectt-0800'> * to the process</span></span>
|
|
<a id='x1-42283r140'></a><span class='ecrm-0500'>140</span><span id='textcolor1751'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42285r141'></a><span class='ecrm-0500'>141</span><span class='ectt-0800'> wait_event_interruptible(WaitQ, !Already_Open);</span>
|
|
<a id='x1-42287r142'></a><span class='ecrm-0500'>142</span>
|
|
<a id='x1-42289r143'></a><span class='ecrm-0500'>143</span><span class='ectt-0800'> </span><span id='textcolor1752'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42291r144'></a><span class='ecrm-0500'>144</span><span id='textcolor1753'><span class='ectt-0800'> * If we woke up because we got a signal we</span><span class='tctt-0800'>'</span><span class='ectt-0800'>re not blocking,</span></span>
|
|
<a id='x1-42293r145'></a><span class='ecrm-0500'>145</span><span id='textcolor1754'><span class='ectt-0800'> * return -EINTR (fail the system call). This allows processes</span></span>
|
|
<a id='x1-42295r146'></a><span class='ecrm-0500'>146</span><span id='textcolor1755'><span class='ectt-0800'> * to be killed or stopped.</span></span>
|
|
<a id='x1-42297r147'></a><span class='ecrm-0500'>147</span><span id='textcolor1756'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42299r148'></a><span class='ecrm-0500'>148</span>
|
|
<a id='x1-42301r149'></a><span class='ecrm-0500'>149</span><span class='ectt-0800'> </span><span id='textcolor1757'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42303r150'></a><span class='ecrm-0500'>150</span><span id='textcolor1758'><span class='ectt-0800'> * Emmanuel Papirakis:</span></span>
|
|
<a id='x1-42305r151'></a><span class='ecrm-0500'>151</span><span id='textcolor1759'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-42307r152'></a><span class='ecrm-0500'>152</span><span id='textcolor1760'><span class='ectt-0800'> * This is a little update to work with 2.2.*. Signals now are</span></span>
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|
<a id='x1-42309r153'></a><span class='ecrm-0500'>153</span><span id='textcolor1761'><span class='ectt-0800'> * contained in two words (64 bits) and are stored in a structure that</span></span>
|
|
<a id='x1-42311r154'></a><span class='ecrm-0500'>154</span><span id='textcolor1762'><span class='ectt-0800'> * contains an array of two unsigned longs. We now have to make 2</span></span>
|
|
<a id='x1-42313r155'></a><span class='ecrm-0500'>155</span><span id='textcolor1763'><span class='ectt-0800'> * checks in our if.</span></span>
|
|
<a id='x1-42315r156'></a><span class='ecrm-0500'>156</span><span id='textcolor1764'><span class='ectt-0800'> *</span></span>
|
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<a id='x1-42317r157'></a><span class='ecrm-0500'>157</span><span id='textcolor1765'><span class='ectt-0800'> * Ori Pomerantz:</span></span>
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|
<a id='x1-42319r158'></a><span class='ecrm-0500'>158</span><span id='textcolor1766'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-42321r159'></a><span class='ecrm-0500'>159</span><span id='textcolor1767'><span class='ectt-0800'> * Nobody promised me they</span><span class='tctt-0800'>'</span><span class='ectt-0800'>ll never use more than 64 bits, or that this</span></span>
|
|
<a id='x1-42323r160'></a><span class='ecrm-0500'>160</span><span id='textcolor1768'><span class='ectt-0800'> * book won</span><span class='tctt-0800'>'</span><span class='ectt-0800'>t be used for a version of Linux with a word size of 16</span></span>
|
|
<a id='x1-42325r161'></a><span class='ecrm-0500'>161</span><span id='textcolor1769'><span class='ectt-0800'> * bits. This code would work in any case.</span></span>
|
|
<a id='x1-42327r162'></a><span class='ecrm-0500'>162</span><span id='textcolor1770'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42329r163'></a><span class='ecrm-0500'>163</span><span class='ectt-0800'> </span><span id='textcolor1771'><span class='ectt-0800'>for</span></span><span class='ectt-0800'> (i = 0; i < _NSIG_WORDS && !is_sig; i++)</span>
|
|
<a id='x1-42331r164'></a><span class='ecrm-0500'>164</span><span class='ectt-0800'> is_sig = current->pending.signal.sig[i] & ~current->blocked.sig[i];</span>
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<a id='x1-42333r165'></a><span class='ecrm-0500'>165</span>
|
|
<a id='x1-42335r166'></a><span class='ecrm-0500'>166</span><span class='ectt-0800'> </span><span id='textcolor1772'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (is_sig) {</span>
|
|
<a id='x1-42337r167'></a><span class='ecrm-0500'>167</span><span class='ectt-0800'> </span><span id='textcolor1773'><span class='ectt-0800'>/*</span></span>
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|
<a id='x1-42339r168'></a><span class='ecrm-0500'>168</span><span id='textcolor1774'><span class='ectt-0800'> * It</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s important to put module_put(THIS_MODULE) here,</span></span>
|
|
<a id='x1-42341r169'></a><span class='ecrm-0500'>169</span><span id='textcolor1775'><span class='ectt-0800'> * because for processes where the open is interrupted</span></span>
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|
<a id='x1-42343r170'></a><span class='ecrm-0500'>170</span><span id='textcolor1776'><span class='ectt-0800'> * there will never be a corresponding close. If we</span></span>
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|
<a id='x1-42345r171'></a><span class='ecrm-0500'>171</span><span id='textcolor1777'><span class='ectt-0800'> * don</span><span class='tctt-0800'>'</span><span class='ectt-0800'>t decrement the usage count here, we will be</span></span>
|
|
<a id='x1-42347r172'></a><span class='ecrm-0500'>172</span><span id='textcolor1778'><span class='ectt-0800'> * left with a positive usage count which we</span><span class='tctt-0800'>'</span><span class='ectt-0800'>ll have no</span></span>
|
|
<a id='x1-42349r173'></a><span class='ecrm-0500'>173</span><span id='textcolor1779'><span class='ectt-0800'> * way to bring down to zero, giving us an immortal</span></span>
|
|
<a id='x1-42351r174'></a><span class='ecrm-0500'>174</span><span id='textcolor1780'><span class='ectt-0800'> * module, which can only be killed by rebooting</span></span>
|
|
<a id='x1-42353r175'></a><span class='ecrm-0500'>175</span><span id='textcolor1781'><span class='ectt-0800'> * the machine.</span></span>
|
|
<a id='x1-42355r176'></a><span class='ecrm-0500'>176</span><span id='textcolor1782'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42357r177'></a><span class='ecrm-0500'>177</span><span class='ectt-0800'> module_put(THIS_MODULE);</span>
|
|
<a id='x1-42359r178'></a><span class='ecrm-0500'>178</span><span class='ectt-0800'> </span><span id='textcolor1783'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -EINTR;</span>
|
|
<a id='x1-42361r179'></a><span class='ecrm-0500'>179</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-42363r180'></a><span class='ecrm-0500'>180</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-42365r181'></a><span class='ecrm-0500'>181</span>
|
|
<a id='x1-42367r182'></a><span class='ecrm-0500'>182</span><span class='ectt-0800'> </span><span id='textcolor1784'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42369r183'></a><span class='ecrm-0500'>183</span><span id='textcolor1785'><span class='ectt-0800'> * If we got here, Already_Open must be zero</span></span>
|
|
<a id='x1-42371r184'></a><span class='ecrm-0500'>184</span><span id='textcolor1786'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42373r185'></a><span class='ecrm-0500'>185</span>
|
|
<a id='x1-42375r186'></a><span class='ecrm-0500'>186</span><span class='ectt-0800'> </span><span id='textcolor1787'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42377r187'></a><span class='ecrm-0500'>187</span><span id='textcolor1788'><span class='ectt-0800'> * Open the file</span></span>
|
|
<a id='x1-42379r188'></a><span class='ecrm-0500'>188</span><span id='textcolor1789'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42381r189'></a><span class='ecrm-0500'>189</span><span class='ectt-0800'> Already_Open = 1;</span>
|
|
<a id='x1-42383r190'></a><span class='ecrm-0500'>190</span><span class='ectt-0800'> </span><span id='textcolor1790'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0; </span><span id='textcolor1791'><span class='ectt-0800'>/* Allow the access */</span></span>
|
|
<a id='x1-42385r191'></a><span class='ecrm-0500'>191</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-42387r192'></a><span class='ecrm-0500'>192</span>
|
|
<a id='x1-42389r193'></a><span class='ecrm-0500'>193</span><span id='textcolor1792'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42391r194'></a><span class='ecrm-0500'>194</span><span id='textcolor1793'><span class='ectt-0800'> * Called when the /proc file is closed</span></span>
|
|
<a id='x1-42393r195'></a><span class='ecrm-0500'>195</span><span id='textcolor1794'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42395r196'></a><span class='ecrm-0500'>196</span><span id='textcolor1795'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> module_close(</span><span id='textcolor1796'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> inode *inode, </span><span id='textcolor1797'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *file)</span>
|
|
<a id='x1-42397r197'></a><span class='ecrm-0500'>197</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-42399r198'></a><span class='ecrm-0500'>198</span><span class='ectt-0800'> </span><span id='textcolor1798'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42401r199'></a><span class='ecrm-0500'>199</span><span id='textcolor1799'><span class='ectt-0800'> * Set Already_Open to zero, so one of the processes in the WaitQ will</span></span>
|
|
<a id='x1-42403r200'></a><span class='ecrm-0500'>200</span><span id='textcolor1800'><span class='ectt-0800'> * be able to set Already_Open back to one and to open the file. All</span></span>
|
|
<a id='x1-42405r201'></a><span class='ecrm-0500'>201</span><span id='textcolor1801'><span class='ectt-0800'> * the other processes will be called when Already_Open is back to one,</span></span>
|
|
<a id='x1-42407r202'></a><span class='ecrm-0500'>202</span><span id='textcolor1802'><span class='ectt-0800'> * so they</span><span class='tctt-0800'>'</span><span class='ectt-0800'>ll go back to sleep.</span></span>
|
|
<a id='x1-42409r203'></a><span class='ecrm-0500'>203</span><span id='textcolor1803'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42411r204'></a><span class='ecrm-0500'>204</span><span class='ectt-0800'> Already_Open = 0;</span>
|
|
<a id='x1-42413r205'></a><span class='ecrm-0500'>205</span>
|
|
<a id='x1-42415r206'></a><span class='ecrm-0500'>206</span><span class='ectt-0800'> </span><span id='textcolor1804'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42417r207'></a><span class='ecrm-0500'>207</span><span id='textcolor1805'><span class='ectt-0800'> * Wake up all the processes in WaitQ, so if anybody is waiting for the</span></span>
|
|
<a id='x1-42419r208'></a><span class='ecrm-0500'>208</span><span id='textcolor1806'><span class='ectt-0800'> * file, they can have it.</span></span>
|
|
<a id='x1-42421r209'></a><span class='ecrm-0500'>209</span><span id='textcolor1807'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42423r210'></a><span class='ecrm-0500'>210</span><span class='ectt-0800'> wake_up(&WaitQ);</span>
|
|
<a id='x1-42425r211'></a><span class='ecrm-0500'>211</span>
|
|
<a id='x1-42427r212'></a><span class='ecrm-0500'>212</span><span class='ectt-0800'> module_put(THIS_MODULE);</span>
|
|
<a id='x1-42429r213'></a><span class='ecrm-0500'>213</span>
|
|
<a id='x1-42431r214'></a><span class='ecrm-0500'>214</span><span class='ectt-0800'> </span><span id='textcolor1808'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0; </span><span id='textcolor1809'><span class='ectt-0800'>/* success */</span></span>
|
|
<a id='x1-42433r215'></a><span class='ecrm-0500'>215</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-42435r216'></a><span class='ecrm-0500'>216</span>
|
|
<a id='x1-42437r217'></a><span class='ecrm-0500'>217</span><span id='textcolor1810'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42439r218'></a><span class='ecrm-0500'>218</span><span id='textcolor1811'><span class='ectt-0800'> * Structures to register as the /proc file, with pointers to all the relevant</span></span>
|
|
<a id='x1-42441r219'></a><span class='ecrm-0500'>219</span><span id='textcolor1812'><span class='ectt-0800'> * functions.</span></span>
|
|
<a id='x1-42443r220'></a><span class='ecrm-0500'>220</span><span id='textcolor1813'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42445r221'></a><span class='ecrm-0500'>221</span>
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<a id='x1-42447r222'></a><span class='ecrm-0500'>222</span><span id='textcolor1814'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42449r223'></a><span class='ecrm-0500'>223</span><span id='textcolor1815'><span class='ectt-0800'> * File operations for our proc file. This is where we place pointers to all</span></span>
|
|
<a id='x1-42451r224'></a><span class='ecrm-0500'>224</span><span id='textcolor1816'><span class='ectt-0800'> * the functions called when somebody tries to do something to our file. NULL</span></span>
|
|
<a id='x1-42453r225'></a><span class='ecrm-0500'>225</span><span id='textcolor1817'><span class='ectt-0800'> * means we don</span><span class='tctt-0800'>'</span><span class='ectt-0800'>t want to deal with something.</span></span>
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|
<a id='x1-42455r226'></a><span class='ecrm-0500'>226</span><span id='textcolor1818'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42457r227'></a><span class='ecrm-0500'>227</span><span id='textcolor1819'><span class='ectt-0800'>#ifdef HAVE_PROC_OPS</span></span>
|
|
<a id='x1-42459r228'></a><span class='ecrm-0500'>228</span><span id='textcolor1820'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1821'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor1822'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> proc_ops File_Ops_4_Our_Proc_File = {</span>
|
|
<a id='x1-42461r229'></a><span class='ecrm-0500'>229</span><span class='ectt-0800'> .proc_read = module_output, </span><span id='textcolor1823'><span class='ectt-0800'>/* "read" from the file */</span></span>
|
|
<a id='x1-42463r230'></a><span class='ecrm-0500'>230</span><span class='ectt-0800'> .proc_write = module_input, </span><span id='textcolor1824'><span class='ectt-0800'>/* "write" to the file */</span></span>
|
|
<a id='x1-42465r231'></a><span class='ecrm-0500'>231</span><span class='ectt-0800'> .proc_open = module_open, </span><span id='textcolor1825'><span class='ectt-0800'>/* called when the /proc file is opened */</span></span>
|
|
<a id='x1-42467r232'></a><span class='ecrm-0500'>232</span><span class='ectt-0800'> .proc_release = module_close, </span><span id='textcolor1826'><span class='ectt-0800'>/* called when it</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s closed */</span></span>
|
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<a id='x1-42469r233'></a><span class='ecrm-0500'>233</span><span class='ectt-0800'>};</span>
|
|
<a id='x1-42471r234'></a><span class='ecrm-0500'>234</span><span id='textcolor1827'><span class='ectt-0800'>#else</span></span>
|
|
<a id='x1-42473r235'></a><span class='ecrm-0500'>235</span><span id='textcolor1828'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1829'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor1830'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file_operations File_Ops_4_Our_Proc_File = {</span>
|
|
<a id='x1-42475r236'></a><span class='ecrm-0500'>236</span><span class='ectt-0800'> .read = module_output,</span>
|
|
<a id='x1-42477r237'></a><span class='ecrm-0500'>237</span><span class='ectt-0800'> .write = module_input,</span>
|
|
<a id='x1-42479r238'></a><span class='ecrm-0500'>238</span><span class='ectt-0800'> .open = module_open,</span>
|
|
<a id='x1-42481r239'></a><span class='ecrm-0500'>239</span><span class='ectt-0800'> .release = module_close,</span>
|
|
<a id='x1-42483r240'></a><span class='ecrm-0500'>240</span><span class='ectt-0800'>};</span>
|
|
<a id='x1-42485r241'></a><span class='ecrm-0500'>241</span><span id='textcolor1831'><span class='ectt-0800'>#endif</span></span>
|
|
<a id='x1-42487r242'></a><span class='ecrm-0500'>242</span>
|
|
<a id='x1-42489r243'></a><span class='ecrm-0500'>243</span><span id='textcolor1832'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42491r244'></a><span class='ecrm-0500'>244</span><span id='textcolor1833'><span class='ectt-0800'> * Module initialization and cleanup</span></span>
|
|
<a id='x1-42493r245'></a><span class='ecrm-0500'>245</span><span id='textcolor1834'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42495r246'></a><span class='ecrm-0500'>246</span>
|
|
<a id='x1-42497r247'></a><span class='ecrm-0500'>247</span><span id='textcolor1835'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42499r248'></a><span class='ecrm-0500'>248</span><span id='textcolor1836'><span class='ectt-0800'> * Initialize the module - register the proc file</span></span>
|
|
<a id='x1-42501r249'></a><span class='ecrm-0500'>249</span><span id='textcolor1837'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42503r250'></a><span class='ecrm-0500'>250</span>
|
|
<a id='x1-42505r251'></a><span class='ecrm-0500'>251</span><span id='textcolor1838'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> init_module()</span>
|
|
<a id='x1-42507r252'></a><span class='ecrm-0500'>252</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-42509r253'></a><span class='ecrm-0500'>253</span><span class='ectt-0800'> Our_Proc_File =</span>
|
|
<a id='x1-42511r254'></a><span class='ecrm-0500'>254</span><span class='ectt-0800'> proc_create(PROC_ENTRY_FILENAME, 0644, NULL, &File_Ops_4_Our_Proc_File);</span>
|
|
<a id='x1-42513r255'></a><span class='ecrm-0500'>255</span><span class='ectt-0800'> </span><span id='textcolor1839'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (Our_Proc_File == NULL) {</span>
|
|
<a id='x1-42515r256'></a><span class='ecrm-0500'>256</span><span class='ectt-0800'> remove_proc_entry(PROC_ENTRY_FILENAME, NULL);</span>
|
|
<a id='x1-42517r257'></a><span class='ecrm-0500'>257</span><span class='ectt-0800'> pr_debug(</span><span id='textcolor1840'><span class='ectt-0800'>"Error: Could not initialize /proc/%s</span></span><span id='textcolor1841'><span class='ectt-0800'>\n</span></span><span id='textcolor1842'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, PROC_ENTRY_FILENAME);</span>
|
|
<a id='x1-42519r258'></a><span class='ecrm-0500'>258</span><span class='ectt-0800'> </span><span id='textcolor1843'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -ENOMEM;</span>
|
|
<a id='x1-42521r259'></a><span class='ecrm-0500'>259</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-42523r260'></a><span class='ecrm-0500'>260</span><span class='ectt-0800'> proc_set_size(Our_Proc_File, 80);</span>
|
|
<a id='x1-42525r261'></a><span class='ecrm-0500'>261</span><span class='ectt-0800'> proc_set_user(Our_Proc_File, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID);</span>
|
|
<a id='x1-42527r262'></a><span class='ecrm-0500'>262</span>
|
|
<a id='x1-42529r263'></a><span class='ecrm-0500'>263</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1844'><span class='ectt-0800'>"/proc/test created</span></span><span id='textcolor1845'><span class='ectt-0800'>\n</span></span><span id='textcolor1846'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-42531r264'></a><span class='ecrm-0500'>264</span>
|
|
<a id='x1-42533r265'></a><span class='ecrm-0500'>265</span><span class='ectt-0800'> </span><span id='textcolor1847'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-42535r266'></a><span class='ecrm-0500'>266</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-42537r267'></a><span class='ecrm-0500'>267</span>
|
|
<a id='x1-42539r268'></a><span class='ecrm-0500'>268</span><span id='textcolor1848'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42541r269'></a><span class='ecrm-0500'>269</span><span id='textcolor1849'><span class='ectt-0800'> * Cleanup - unregister our file from /proc. This could get dangerous if</span></span>
|
|
<a id='x1-42543r270'></a><span class='ecrm-0500'>270</span><span id='textcolor1850'><span class='ectt-0800'> * there are still processes waiting in WaitQ, because they are inside our</span></span>
|
|
<a id='x1-42545r271'></a><span class='ecrm-0500'>271</span><span id='textcolor1851'><span class='ectt-0800'> * open function, which will get unloaded. I</span><span class='tctt-0800'>'</span><span class='ectt-0800'>ll explain how to avoid removal</span></span>
|
|
<a id='x1-42547r272'></a><span class='ecrm-0500'>272</span><span id='textcolor1852'><span class='ectt-0800'> * of a kernel module in such a case in chapter 10.</span></span>
|
|
<a id='x1-42549r273'></a><span class='ecrm-0500'>273</span><span id='textcolor1853'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42551r274'></a><span class='ecrm-0500'>274</span><span id='textcolor1854'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> cleanup_module()</span>
|
|
<a id='x1-42553r275'></a><span class='ecrm-0500'>275</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-42555r276'></a><span class='ecrm-0500'>276</span><span class='ectt-0800'> remove_proc_entry(PROC_ENTRY_FILENAME, NULL);</span>
|
|
<a id='x1-42557r277'></a><span class='ecrm-0500'>277</span><span class='ectt-0800'> pr_debug(</span><span id='textcolor1855'><span class='ectt-0800'>"/proc/%s removed</span></span><span id='textcolor1856'><span class='ectt-0800'>\n</span></span><span id='textcolor1857'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, PROC_ENTRY_FILENAME);</span>
|
|
<a id='x1-42559r278'></a><span class='ecrm-0500'>278</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-42561r279'></a><span class='ecrm-0500'>279</span>
|
|
<a id='x1-42563r280'></a><span class='ecrm-0500'>280</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor1858'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
|
|
|
|
<!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb54'><a id='x1-42565r1'></a><span class='ecrm-0500'>1</span><span id='textcolor1859'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-42567r2'></a><span class='ecrm-0500'>2</span><span id='textcolor1860'><span class='ectt-0800'> * cat_nonblock.c - open a file and display its contents, but exit rather than</span></span>
|
|
<a id='x1-42569r3'></a><span class='ecrm-0500'>3</span><span id='textcolor1861'><span class='ectt-0800'> * wait for input.</span></span>
|
|
<a id='x1-42571r4'></a><span class='ecrm-0500'>4</span><span id='textcolor1862'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-42573r5'></a><span class='ecrm-0500'>5</span><span id='textcolor1863'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1864'><span class='ectt-0800'><errno.h> /* for errno */</span></span>
|
|
<a id='x1-42575r6'></a><span class='ecrm-0500'>6</span><span id='textcolor1865'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1866'><span class='ectt-0800'><fcntl.h> /* for open */</span></span>
|
|
<a id='x1-42577r7'></a><span class='ecrm-0500'>7</span><span id='textcolor1867'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1868'><span class='ectt-0800'><stdio.h> /* standard I/O */</span></span>
|
|
<a id='x1-42579r8'></a><span class='ecrm-0500'>8</span><span id='textcolor1869'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1870'><span class='ectt-0800'><stdlib.h> /* for exit */</span></span>
|
|
<a id='x1-42581r9'></a><span class='ecrm-0500'>9</span><span id='textcolor1871'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1872'><span class='ectt-0800'><unistd.h> /* for read */</span></span>
|
|
<a id='x1-42583r10'></a><span class='ecrm-0500'>10</span>
|
|
<a id='x1-42585r11'></a><span class='ecrm-0500'>11</span><span id='textcolor1873'><span class='ectt-0800'>#define MAX_BYTES 1024 * 4</span></span>
|
|
<a id='x1-42587r12'></a><span class='ecrm-0500'>12</span>
|
|
<a id='x1-42589r13'></a><span class='ecrm-0500'>13</span><span id='textcolor1874'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> main(</span><span id='textcolor1875'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> argc, </span><span id='textcolor1876'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *argv[])</span>
|
|
<a id='x1-42591r14'></a><span class='ecrm-0500'>14</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-42593r15'></a><span class='ecrm-0500'>15</span><span class='ectt-0800'> </span><span id='textcolor1877'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> fd; </span><span id='textcolor1878'><span class='ectt-0800'>/* The file descriptor for the file to read */</span></span>
|
|
<a id='x1-42595r16'></a><span class='ecrm-0500'>16</span><span class='ectt-0800'> </span><span id='textcolor1879'><span class='ectt-0800'>size_t</span></span><span class='ectt-0800'> bytes; </span><span id='textcolor1880'><span class='ectt-0800'>/* The number of bytes read */</span></span>
|
|
<a id='x1-42597r17'></a><span class='ecrm-0500'>17</span><span class='ectt-0800'> </span><span id='textcolor1881'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> buffer[MAX_BYTES]; </span><span id='textcolor1882'><span class='ectt-0800'>/* The buffer for the bytes */</span></span>
|
|
<a id='x1-42599r18'></a><span class='ecrm-0500'>18</span>
|
|
<a id='x1-42601r19'></a><span class='ecrm-0500'>19</span><span class='ectt-0800'> </span><span id='textcolor1883'><span class='ectt-0800'>/* Usage */</span></span>
|
|
<a id='x1-42603r20'></a><span class='ecrm-0500'>20</span><span class='ectt-0800'> </span><span id='textcolor1884'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (argc != 2) {</span>
|
|
<a id='x1-42605r21'></a><span class='ecrm-0500'>21</span><span class='ectt-0800'> printf(</span><span id='textcolor1885'><span class='ectt-0800'>"Usage: %s <filename></span></span><span id='textcolor1886'><span class='ectt-0800'>\n</span></span><span id='textcolor1887'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, argv[0]);</span>
|
|
<a id='x1-42607r22'></a><span class='ecrm-0500'>22</span><span class='ectt-0800'> puts(</span><span id='textcolor1888'><span class='ectt-0800'>"Reads the content of a file, but doesn</span><span class='tctt-0800'>'</span><span class='ectt-0800'>t wait for input"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-42609r23'></a><span class='ecrm-0500'>23</span><span class='ectt-0800'> exit(-1);</span>
|
|
<a id='x1-42611r24'></a><span class='ecrm-0500'>24</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-42613r25'></a><span class='ecrm-0500'>25</span>
|
|
<a id='x1-42615r26'></a><span class='ecrm-0500'>26</span><span class='ectt-0800'> </span><span id='textcolor1889'><span class='ectt-0800'>/* Open the file for reading in non blocking mode */</span></span>
|
|
<a id='x1-42617r27'></a><span class='ecrm-0500'>27</span><span class='ectt-0800'> fd = open(argv[1], O_RDONLY | O_NONBLOCK);</span>
|
|
<a id='x1-42619r28'></a><span class='ecrm-0500'>28</span>
|
|
<a id='x1-42621r29'></a><span class='ecrm-0500'>29</span><span class='ectt-0800'> </span><span id='textcolor1890'><span class='ectt-0800'>/* If open failed */</span></span>
|
|
<a id='x1-42623r30'></a><span class='ecrm-0500'>30</span><span class='ectt-0800'> </span><span id='textcolor1891'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (fd == -1) {</span>
|
|
<a id='x1-42625r31'></a><span class='ecrm-0500'>31</span><span class='ectt-0800'> puts(errno == EAGAIN ? </span><span id='textcolor1892'><span class='ectt-0800'>"Open would block"</span></span><span class='ectt-0800'> : </span><span id='textcolor1893'><span class='ectt-0800'>"Open failed"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-42627r32'></a><span class='ecrm-0500'>32</span><span class='ectt-0800'> exit(-1);</span>
|
|
<a id='x1-42629r33'></a><span class='ecrm-0500'>33</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-42631r34'></a><span class='ecrm-0500'>34</span>
|
|
<a id='x1-42633r35'></a><span class='ecrm-0500'>35</span><span class='ectt-0800'> </span><span id='textcolor1894'><span class='ectt-0800'>/* Read the file and output its contents */</span></span>
|
|
<a id='x1-42635r36'></a><span class='ecrm-0500'>36</span><span class='ectt-0800'> </span><span id='textcolor1895'><span class='ectt-0800'>do</span></span><span class='ectt-0800'> {</span>
|
|
<a id='x1-42637r37'></a><span class='ecrm-0500'>37</span><span class='ectt-0800'> </span><span id='textcolor1896'><span class='ectt-0800'>/* Read characters from the file */</span></span>
|
|
<a id='x1-42639r38'></a><span class='ecrm-0500'>38</span><span class='ectt-0800'> bytes = read(fd, buffer, MAX_BYTES);</span>
|
|
<a id='x1-42641r39'></a><span class='ecrm-0500'>39</span>
|
|
<a id='x1-42643r40'></a><span class='ecrm-0500'>40</span><span class='ectt-0800'> </span><span id='textcolor1897'><span class='ectt-0800'>/* If there</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s an error, report it and die */</span></span>
|
|
<a id='x1-42645r41'></a><span class='ecrm-0500'>41</span><span class='ectt-0800'> </span><span id='textcolor1898'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (bytes == -1) {</span>
|
|
<a id='x1-42647r42'></a><span class='ecrm-0500'>42</span><span class='ectt-0800'> </span><span id='textcolor1899'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (errno = EAGAIN)</span>
|
|
<a id='x1-42649r43'></a><span class='ecrm-0500'>43</span><span class='ectt-0800'> puts(</span><span id='textcolor1900'><span class='ectt-0800'>"Normally I</span><span class='tctt-0800'>'</span><span class='ectt-0800'>d block, but you told me not to"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-42651r44'></a><span class='ecrm-0500'>44</span><span class='ectt-0800'> </span><span id='textcolor1901'><span class='ectt-0800'>else</span></span>
|
|
<a id='x1-42653r45'></a><span class='ecrm-0500'>45</span><span class='ectt-0800'> puts(</span><span id='textcolor1902'><span class='ectt-0800'>"Another read error"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-42655r46'></a><span class='ecrm-0500'>46</span><span class='ectt-0800'> exit(-1);</span>
|
|
<a id='x1-42657r47'></a><span class='ecrm-0500'>47</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-42659r48'></a><span class='ecrm-0500'>48</span>
|
|
<a id='x1-42661r49'></a><span class='ecrm-0500'>49</span><span class='ectt-0800'> </span><span id='textcolor1903'><span class='ectt-0800'>/* Print the characters */</span></span>
|
|
<a id='x1-42663r50'></a><span class='ecrm-0500'>50</span><span class='ectt-0800'> </span><span id='textcolor1904'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (bytes > 0) {</span>
|
|
<a id='x1-42665r51'></a><span class='ecrm-0500'>51</span><span class='ectt-0800'> </span><span id='textcolor1905'><span class='ectt-0800'>for</span></span><span class='ectt-0800'> (</span><span id='textcolor1906'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> i = 0; i < bytes; i++)</span>
|
|
<a id='x1-42667r52'></a><span class='ecrm-0500'>52</span><span class='ectt-0800'> putchar(buffer[i]);</span>
|
|
<a id='x1-42669r53'></a><span class='ecrm-0500'>53</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-42671r54'></a><span class='ecrm-0500'>54</span>
|
|
<a id='x1-42673r55'></a><span class='ecrm-0500'>55</span><span class='ectt-0800'> </span><span id='textcolor1907'><span class='ectt-0800'>/* While there are no errors and the file isn</span><span class='tctt-0800'>'</span><span class='ectt-0800'>t over */</span></span>
|
|
<a id='x1-42675r56'></a><span class='ecrm-0500'>56</span><span class='ectt-0800'> } </span><span id='textcolor1908'><span class='ectt-0800'>while</span></span><span class='ectt-0800'> (bytes > 0);</span>
|
|
<a id='x1-42677r57'></a><span class='ecrm-0500'>57</span>
|
|
<a id='x1-42679r58'></a><span class='ecrm-0500'>58</span><span class='ectt-0800'> </span><span id='textcolor1909'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-42681r59'></a><span class='ecrm-0500'>59</span><span class='ectt-0800'>}</span></pre>
|
|
<!-- l. 1266 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='completions'><span class='titlemark'>0.11.2 </span> <a id='x1-430000.11.2'></a>Completions</h4>
|
|
<!-- l. 1268 --><p class='noindent'>Sometimes one thing should happen before another within a module having multiple
|
|
threads. Rather than using <span class='ecbx-1000'>/proc/sleep </span>commands the kernel has another way to
|
|
do this which allows timeouts or interrupts to also happen.
|
|
</p><!-- l. 1270 --><p class='indent'> In the following example two threads are started, but one needs to start before
|
|
another.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
|
|
|
|
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb55'><a id='x1-43002r1'></a><span class='ecrm-0500'>1</span><span id='textcolor1910'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-43004r2'></a><span class='ecrm-0500'>2</span><span id='textcolor1911'><span class='ectt-0800'> * completions.c</span></span>
|
|
<a id='x1-43006r3'></a><span class='ecrm-0500'>3</span><span id='textcolor1912'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-43008r4'></a><span class='ecrm-0500'>4</span><span id='textcolor1913'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1914'><span class='ectt-0800'><linux/completion.h></span></span>
|
|
<a id='x1-43010r5'></a><span class='ecrm-0500'>5</span><span id='textcolor1915'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1916'><span class='ectt-0800'><linux/init.h></span></span>
|
|
<a id='x1-43012r6'></a><span class='ecrm-0500'>6</span><span id='textcolor1917'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1918'><span class='ectt-0800'><linux/kernel.h></span></span>
|
|
<a id='x1-43014r7'></a><span class='ecrm-0500'>7</span><span id='textcolor1919'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1920'><span class='ectt-0800'><linux/kthread.h></span></span>
|
|
<a id='x1-43016r8'></a><span class='ecrm-0500'>8</span><span id='textcolor1921'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1922'><span class='ectt-0800'><linux/module.h></span></span>
|
|
<a id='x1-43018r9'></a><span class='ecrm-0500'>9</span>
|
|
<a id='x1-43020r10'></a><span class='ecrm-0500'>10</span><span id='textcolor1923'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1924'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> {</span>
|
|
<a id='x1-43022r11'></a><span class='ecrm-0500'>11</span><span class='ectt-0800'> </span><span id='textcolor1925'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> completion crank_comp;</span>
|
|
<a id='x1-43024r12'></a><span class='ecrm-0500'>12</span><span class='ectt-0800'> </span><span id='textcolor1926'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> completion flywheel_comp;</span>
|
|
<a id='x1-43026r13'></a><span class='ecrm-0500'>13</span><span class='ectt-0800'>} machine;</span>
|
|
<a id='x1-43028r14'></a><span class='ecrm-0500'>14</span>
|
|
<a id='x1-43030r15'></a><span class='ecrm-0500'>15</span><span id='textcolor1927'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1928'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> machine_crank_thread(</span><span id='textcolor1929'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *arg)</span>
|
|
<a id='x1-43032r16'></a><span class='ecrm-0500'>16</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-43034r17'></a><span class='ecrm-0500'>17</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1930'><span class='ectt-0800'>"Turn the crank</span></span><span id='textcolor1931'><span class='ectt-0800'>\n</span></span><span id='textcolor1932'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-43036r18'></a><span class='ecrm-0500'>18</span>
|
|
<a id='x1-43038r19'></a><span class='ecrm-0500'>19</span><span class='ectt-0800'> complete_all(&machine.crank_comp);</span>
|
|
<a id='x1-43040r20'></a><span class='ecrm-0500'>20</span><span class='ectt-0800'> complete_and_exit(&machine.crank_comp, 0);</span>
|
|
<a id='x1-43042r21'></a><span class='ecrm-0500'>21</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-43044r22'></a><span class='ecrm-0500'>22</span>
|
|
<a id='x1-43046r23'></a><span class='ecrm-0500'>23</span><span id='textcolor1933'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1934'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> machine_flywheel_spinup_thread(</span><span id='textcolor1935'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *arg)</span>
|
|
<a id='x1-43048r24'></a><span class='ecrm-0500'>24</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-43050r25'></a><span class='ecrm-0500'>25</span><span class='ectt-0800'> wait_for_completion(&machine.crank_comp);</span>
|
|
<a id='x1-43052r26'></a><span class='ecrm-0500'>26</span>
|
|
<a id='x1-43054r27'></a><span class='ecrm-0500'>27</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1936'><span class='ectt-0800'>"Flywheel spins up</span></span><span id='textcolor1937'><span class='ectt-0800'>\n</span></span><span id='textcolor1938'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-43056r28'></a><span class='ecrm-0500'>28</span>
|
|
<a id='x1-43058r29'></a><span class='ecrm-0500'>29</span><span class='ectt-0800'> complete_all(&machine.flywheel_comp);</span>
|
|
<a id='x1-43060r30'></a><span class='ecrm-0500'>30</span><span class='ectt-0800'> complete_and_exit(&machine.flywheel_comp, 0);</span>
|
|
<a id='x1-43062r31'></a><span class='ecrm-0500'>31</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-43064r32'></a><span class='ecrm-0500'>32</span>
|
|
<a id='x1-43066r33'></a><span class='ecrm-0500'>33</span><span id='textcolor1939'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1940'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> completions_init(</span><span id='textcolor1941'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-43068r34'></a><span class='ecrm-0500'>34</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-43070r35'></a><span class='ecrm-0500'>35</span><span class='ectt-0800'> </span><span id='textcolor1942'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> task_struct *crank_thread;</span>
|
|
<a id='x1-43072r36'></a><span class='ecrm-0500'>36</span><span class='ectt-0800'> </span><span id='textcolor1943'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> task_struct *flywheel_thread;</span>
|
|
<a id='x1-43074r37'></a><span class='ecrm-0500'>37</span>
|
|
<a id='x1-43076r38'></a><span class='ecrm-0500'>38</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1944'><span class='ectt-0800'>"completions example</span></span><span id='textcolor1945'><span class='ectt-0800'>\n</span></span><span id='textcolor1946'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-43078r39'></a><span class='ecrm-0500'>39</span>
|
|
<a id='x1-43080r40'></a><span class='ecrm-0500'>40</span><span class='ectt-0800'> init_completion(&machine.crank_comp);</span>
|
|
<a id='x1-43082r41'></a><span class='ecrm-0500'>41</span><span class='ectt-0800'> init_completion(&machine.flywheel_comp);</span>
|
|
<a id='x1-43084r42'></a><span class='ecrm-0500'>42</span>
|
|
<a id='x1-43086r43'></a><span class='ecrm-0500'>43</span><span class='ectt-0800'> crank_thread = kthread_create(machine_crank_thread, NULL, </span><span id='textcolor1947'><span class='ectt-0800'>"KThread Crank"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-43088r44'></a><span class='ecrm-0500'>44</span><span class='ectt-0800'> </span><span id='textcolor1948'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (IS_ERR(crank_thread))</span>
|
|
<a id='x1-43090r45'></a><span class='ecrm-0500'>45</span><span class='ectt-0800'> </span><span id='textcolor1949'><span class='ectt-0800'>goto</span></span><span class='ectt-0800'> ERROR_THREAD_1;</span>
|
|
<a id='x1-43092r46'></a><span class='ecrm-0500'>46</span>
|
|
<a id='x1-43094r47'></a><span class='ecrm-0500'>47</span><span class='ectt-0800'> flywheel_thread = kthread_create(machine_flywheel_spinup_thread, NULL,</span>
|
|
<a id='x1-43096r48'></a><span class='ecrm-0500'>48</span><span class='ectt-0800'> </span><span id='textcolor1950'><span class='ectt-0800'>"KThread Flywheel"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-43098r49'></a><span class='ecrm-0500'>49</span><span class='ectt-0800'> </span><span id='textcolor1951'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (IS_ERR(flywheel_thread))</span>
|
|
<a id='x1-43100r50'></a><span class='ecrm-0500'>50</span><span class='ectt-0800'> </span><span id='textcolor1952'><span class='ectt-0800'>goto</span></span><span class='ectt-0800'> ERROR_THREAD_2;</span>
|
|
<a id='x1-43102r51'></a><span class='ecrm-0500'>51</span>
|
|
<a id='x1-43104r52'></a><span class='ecrm-0500'>52</span><span class='ectt-0800'> wake_up_process(flywheel_thread);</span>
|
|
<a id='x1-43106r53'></a><span class='ecrm-0500'>53</span><span class='ectt-0800'> wake_up_process(crank_thread);</span>
|
|
<a id='x1-43108r54'></a><span class='ecrm-0500'>54</span>
|
|
<a id='x1-43110r55'></a><span class='ecrm-0500'>55</span><span class='ectt-0800'> </span><span id='textcolor1953'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-43112r56'></a><span class='ecrm-0500'>56</span>
|
|
<a id='x1-43114r57'></a><span class='ecrm-0500'>57</span><span class='ectt-0800'>ERROR_THREAD_2:</span>
|
|
<a id='x1-43116r58'></a><span class='ecrm-0500'>58</span><span class='ectt-0800'> kthread_stop(crank_thread);</span>
|
|
<a id='x1-43118r59'></a><span class='ecrm-0500'>59</span><span class='ectt-0800'>ERROR_THREAD_1:</span>
|
|
<a id='x1-43120r60'></a><span class='ecrm-0500'>60</span>
|
|
<a id='x1-43122r61'></a><span class='ecrm-0500'>61</span><span class='ectt-0800'> </span><span id='textcolor1954'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -1;</span>
|
|
<a id='x1-43124r62'></a><span class='ecrm-0500'>62</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-43126r63'></a><span class='ecrm-0500'>63</span>
|
|
<a id='x1-43128r64'></a><span class='ecrm-0500'>64</span><span id='textcolor1955'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> completions_exit(</span><span id='textcolor1956'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-43130r65'></a><span class='ecrm-0500'>65</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-43132r66'></a><span class='ecrm-0500'>66</span><span class='ectt-0800'> wait_for_completion(&machine.crank_comp);</span>
|
|
<a id='x1-43134r67'></a><span class='ecrm-0500'>67</span><span class='ectt-0800'> wait_for_completion(&machine.flywheel_comp);</span>
|
|
<a id='x1-43136r68'></a><span class='ecrm-0500'>68</span>
|
|
<a id='x1-43138r69'></a><span class='ecrm-0500'>69</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1957'><span class='ectt-0800'>"completions exit</span></span><span id='textcolor1958'><span class='ectt-0800'>\n</span></span><span id='textcolor1959'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-43140r70'></a><span class='ecrm-0500'>70</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-43142r71'></a><span class='ecrm-0500'>71</span>
|
|
<a id='x1-43144r72'></a><span class='ecrm-0500'>72</span><span class='ectt-0800'>module_init(completions_init);</span>
|
|
<a id='x1-43146r73'></a><span class='ecrm-0500'>73</span><span class='ectt-0800'>module_exit(completions_exit);</span>
|
|
<a id='x1-43148r74'></a><span class='ecrm-0500'>74</span>
|
|
<a id='x1-43150r75'></a><span class='ecrm-0500'>75</span><span class='ectt-0800'>MODULE_DESCRIPTION(</span><span id='textcolor1960'><span class='ectt-0800'>"Completions example"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-43152r76'></a><span class='ecrm-0500'>76</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor1961'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
|
|
<!-- l. 1274 --><p class='indent'> The <span class='ecti-1000'>machine </span>structure stores the completion states for the two threads. At the
|
|
exit point of each thread the respective completion state is updated, and
|
|
<span class='ecti-1000'>wait_for_completion </span>is used by the flywheel thread to ensure that it doesn’t begin
|
|
prematurely.
|
|
</p><!-- l. 1276 --><p class='indent'> So even though <span class='ecti-1000'>flywheel_thread </span>is started first you should notice if you load this
|
|
module and run <span class='ecti-1000'>dmesg </span>that turning the crank always happens first because the
|
|
flywheel thread waits for it to complete.
|
|
</p><!-- l. 1278 --><p class='indent'> There are other variations upon the <span class='ecti-1000'>wait_for_completion </span>function, which include
|
|
timeouts or being interrupted, but this basic mechanism is enough for many common
|
|
situations without adding a lot of complexity.
|
|
</p><!-- l. 1280 --><p class='noindent'>
|
|
</p>
|
|
<h3 class='sectionHead' id='avoiding-collisions-and-deadlocks'><span class='titlemark'>0.12 </span> <a id='x1-440000.12'></a>Avoiding Collisions and Deadlocks</h3>
|
|
<!-- l. 1282 --><p class='noindent'>If processes running on different CPUs or in different threads try to access the same
|
|
memory then it’s possible that strange things can happen or your system can lock
|
|
up. To avoid this various types of mutual exclusion kernel functions are available.
|
|
These indicate if a section of code is "locked" or "unlocked" so that simultaneous
|
|
attempts to run it can’t happen.
|
|
</p>
|
|
<h4 class='subsectionHead' id='mutex'><span class='titlemark'>0.12.1 </span> <a id='x1-450000.12.1'></a>Mutex</h4>
|
|
<!-- l. 1285 --><p class='noindent'>You can use kernel mutexes (mutual exclusions) in much the same manner that you
|
|
might deploy them in userland. This may be all that’s needed to avoid collisions in
|
|
most cases.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb56'><a id='x1-45002r1'></a><span class='ecrm-0500'>1</span><span id='textcolor1962'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-45004r2'></a><span class='ecrm-0500'>2</span><span id='textcolor1963'><span class='ectt-0800'> * example_mutex.c</span></span>
|
|
<a id='x1-45006r3'></a><span class='ecrm-0500'>3</span><span id='textcolor1964'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-45008r4'></a><span class='ecrm-0500'>4</span><span id='textcolor1965'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1966'><span class='ectt-0800'><linux/init.h></span></span>
|
|
<a id='x1-45010r5'></a><span class='ecrm-0500'>5</span><span id='textcolor1967'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1968'><span class='ectt-0800'><linux/kernel.h></span></span>
|
|
<a id='x1-45012r6'></a><span class='ecrm-0500'>6</span><span id='textcolor1969'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1970'><span class='ectt-0800'><linux/module.h></span></span>
|
|
<a id='x1-45014r7'></a><span class='ecrm-0500'>7</span><span id='textcolor1971'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1972'><span class='ectt-0800'><linux/mutex.h></span></span>
|
|
<a id='x1-45016r8'></a><span class='ecrm-0500'>8</span>
|
|
<a id='x1-45018r9'></a><span class='ecrm-0500'>9</span><span class='ectt-0800'>DEFINE_MUTEX(mymutex);</span>
|
|
<a id='x1-45020r10'></a><span class='ecrm-0500'>10</span>
|
|
<a id='x1-45022r11'></a><span class='ecrm-0500'>11</span><span id='textcolor1973'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1974'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> example_mutex_init(</span><span id='textcolor1975'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-45024r12'></a><span class='ecrm-0500'>12</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-45026r13'></a><span class='ecrm-0500'>13</span><span class='ectt-0800'> </span><span id='textcolor1976'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> ret;</span>
|
|
<a id='x1-45028r14'></a><span class='ecrm-0500'>14</span>
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<a id='x1-45030r15'></a><span class='ecrm-0500'>15</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1977'><span class='ectt-0800'>"example_mutex init</span></span><span id='textcolor1978'><span class='ectt-0800'>\n</span></span><span id='textcolor1979'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
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<a id='x1-45032r16'></a><span class='ecrm-0500'>16</span>
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<a id='x1-45034r17'></a><span class='ecrm-0500'>17</span><span class='ectt-0800'> ret = mutex_trylock(&mymutex);</span>
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<a id='x1-45036r18'></a><span class='ecrm-0500'>18</span><span class='ectt-0800'> </span><span id='textcolor1980'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (ret != 0) {</span>
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<a id='x1-45038r19'></a><span class='ecrm-0500'>19</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1981'><span class='ectt-0800'>"mutex is locked</span></span><span id='textcolor1982'><span class='ectt-0800'>\n</span></span><span id='textcolor1983'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
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<a id='x1-45040r20'></a><span class='ecrm-0500'>20</span>
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<a id='x1-45042r21'></a><span class='ecrm-0500'>21</span><span class='ectt-0800'> </span><span id='textcolor1984'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (mutex_is_locked(&mymutex) == 0)</span>
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<a id='x1-45044r22'></a><span class='ecrm-0500'>22</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1985'><span class='ectt-0800'>"The mutex failed to lock!</span></span><span id='textcolor1986'><span class='ectt-0800'>\n</span></span><span id='textcolor1987'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
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<a id='x1-45046r23'></a><span class='ecrm-0500'>23</span>
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<a id='x1-45048r24'></a><span class='ecrm-0500'>24</span><span class='ectt-0800'> mutex_unlock(&mymutex);</span>
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|
<a id='x1-45050r25'></a><span class='ecrm-0500'>25</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1988'><span class='ectt-0800'>"mutex is unlocked</span></span><span id='textcolor1989'><span class='ectt-0800'>\n</span></span><span id='textcolor1990'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
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<a id='x1-45052r26'></a><span class='ecrm-0500'>26</span><span class='ectt-0800'> } </span><span id='textcolor1991'><span class='ectt-0800'>else</span></span>
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<a id='x1-45054r27'></a><span class='ecrm-0500'>27</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1992'><span class='ectt-0800'>"Failed to lock</span></span><span id='textcolor1993'><span class='ectt-0800'>\n</span></span><span id='textcolor1994'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
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<a id='x1-45056r28'></a><span class='ecrm-0500'>28</span>
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<a id='x1-45058r29'></a><span class='ecrm-0500'>29</span><span class='ectt-0800'> </span><span id='textcolor1995'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
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<a id='x1-45060r30'></a><span class='ecrm-0500'>30</span><span class='ectt-0800'>}</span>
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<a id='x1-45062r31'></a><span class='ecrm-0500'>31</span>
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<a id='x1-45064r32'></a><span class='ecrm-0500'>32</span><span id='textcolor1996'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1997'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> example_mutex_exit(</span><span id='textcolor1998'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
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<a id='x1-45066r33'></a><span class='ecrm-0500'>33</span><span class='ectt-0800'>{</span>
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<a id='x1-45068r34'></a><span class='ecrm-0500'>34</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1999'><span class='ectt-0800'>"example_mutex exit</span></span><span id='textcolor2000'><span class='ectt-0800'>\n</span></span><span id='textcolor2001'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
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<a id='x1-45070r35'></a><span class='ecrm-0500'>35</span><span class='ectt-0800'>}</span>
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<a id='x1-45072r36'></a><span class='ecrm-0500'>36</span>
|
|
<a id='x1-45074r37'></a><span class='ecrm-0500'>37</span><span class='ectt-0800'>module_init(example_mutex_init);</span>
|
|
<a id='x1-45076r38'></a><span class='ecrm-0500'>38</span><span class='ectt-0800'>module_exit(example_mutex_exit);</span>
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<a id='x1-45078r39'></a><span class='ecrm-0500'>39</span>
|
|
<a id='x1-45080r40'></a><span class='ecrm-0500'>40</span><span class='ectt-0800'>MODULE_DESCRIPTION(</span><span id='textcolor2002'><span class='ectt-0800'>"Mutex example"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-45082r41'></a><span class='ecrm-0500'>41</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor2003'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
|
|
<!-- l. 1289 --><p class='noindent'>
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|
</p>
|
|
<h4 class='subsectionHead' id='spinlocks'><span class='titlemark'>0.12.2 </span> <a id='x1-460000.12.2'></a>Spinlocks</h4>
|
|
<!-- l. 1291 --><p class='noindent'>As the name suggests, spinlocks lock up the CPU that the code is running on,
|
|
taking 100% of its resources. Because of this you should only use the spinlock
|
|
mechanism around code which is likely to take no more than a few milliseconds to
|
|
run and so won’t noticably slow anything down from the user’s point of
|
|
view.
|
|
|
|
|
|
|
|
</p><!-- l. 1293 --><p class='indent'> The example here is <span class='ecti-1000'>"irq safe" </span>in that if interrupts happen during the lock then
|
|
they won’t be forgotten and will activate when the unlock happens, using the <span class='ecti-1000'>flags</span>
|
|
variable to retain their state.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb57'><a id='x1-46002r1'></a><span class='ecrm-0500'>1</span><span id='textcolor2004'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-46004r2'></a><span class='ecrm-0500'>2</span><span id='textcolor2005'><span class='ectt-0800'> * example_spinlock.c</span></span>
|
|
<a id='x1-46006r3'></a><span class='ecrm-0500'>3</span><span id='textcolor2006'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-46008r4'></a><span class='ecrm-0500'>4</span><span id='textcolor2007'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2008'><span class='ectt-0800'><linux/init.h></span></span>
|
|
<a id='x1-46010r5'></a><span class='ecrm-0500'>5</span><span id='textcolor2009'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2010'><span class='ectt-0800'><linux/interrupt.h></span></span>
|
|
<a id='x1-46012r6'></a><span class='ecrm-0500'>6</span><span id='textcolor2011'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2012'><span class='ectt-0800'><linux/kernel.h></span></span>
|
|
<a id='x1-46014r7'></a><span class='ecrm-0500'>7</span><span id='textcolor2013'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2014'><span class='ectt-0800'><linux/module.h></span></span>
|
|
<a id='x1-46016r8'></a><span class='ecrm-0500'>8</span><span id='textcolor2015'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2016'><span class='ectt-0800'><linux/spinlock.h></span></span>
|
|
<a id='x1-46018r9'></a><span class='ecrm-0500'>9</span>
|
|
<a id='x1-46020r10'></a><span class='ecrm-0500'>10</span><span class='ectt-0800'>DEFINE_SPINLOCK(sl_static);</span>
|
|
<a id='x1-46022r11'></a><span class='ecrm-0500'>11</span><span class='ectt-0800'>spinlock_t sl_dynamic;</span>
|
|
<a id='x1-46024r12'></a><span class='ecrm-0500'>12</span>
|
|
<a id='x1-46026r13'></a><span class='ecrm-0500'>13</span><span id='textcolor2017'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2018'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> example_spinlock_static(</span><span id='textcolor2019'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-46028r14'></a><span class='ecrm-0500'>14</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-46030r15'></a><span class='ecrm-0500'>15</span><span class='ectt-0800'> </span><span id='textcolor2020'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor2021'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> flags;</span>
|
|
<a id='x1-46032r16'></a><span class='ecrm-0500'>16</span>
|
|
<a id='x1-46034r17'></a><span class='ecrm-0500'>17</span><span class='ectt-0800'> spin_lock_irqsave(&sl_static, flags);</span>
|
|
<a id='x1-46036r18'></a><span class='ecrm-0500'>18</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2022'><span class='ectt-0800'>"Locked static spinlock</span></span><span id='textcolor2023'><span class='ectt-0800'>\n</span></span><span id='textcolor2024'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-46038r19'></a><span class='ecrm-0500'>19</span>
|
|
<a id='x1-46040r20'></a><span class='ecrm-0500'>20</span><span class='ectt-0800'> </span><span id='textcolor2025'><span class='ectt-0800'>/* Do something or other safely.</span></span>
|
|
<a id='x1-46042r21'></a><span class='ecrm-0500'>21</span><span id='textcolor2026'><span class='ectt-0800'> Because this uses 100% CPU time this</span></span>
|
|
<a id='x1-46044r22'></a><span class='ecrm-0500'>22</span><span id='textcolor2027'><span class='ectt-0800'> code should take no more than a few</span></span>
|
|
<a id='x1-46046r23'></a><span class='ecrm-0500'>23</span><span id='textcolor2028'><span class='ectt-0800'> milliseconds to run */</span></span>
|
|
<a id='x1-46048r24'></a><span class='ecrm-0500'>24</span>
|
|
<a id='x1-46050r25'></a><span class='ecrm-0500'>25</span><span class='ectt-0800'> spin_unlock_irqrestore(&sl_static, flags);</span>
|
|
<a id='x1-46052r26'></a><span class='ecrm-0500'>26</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2029'><span class='ectt-0800'>"Unlocked static spinlock</span></span><span id='textcolor2030'><span class='ectt-0800'>\n</span></span><span id='textcolor2031'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-46054r27'></a><span class='ecrm-0500'>27</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-46056r28'></a><span class='ecrm-0500'>28</span>
|
|
<a id='x1-46058r29'></a><span class='ecrm-0500'>29</span><span id='textcolor2032'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2033'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> example_spinlock_dynamic(</span><span id='textcolor2034'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-46060r30'></a><span class='ecrm-0500'>30</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-46062r31'></a><span class='ecrm-0500'>31</span><span class='ectt-0800'> </span><span id='textcolor2035'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor2036'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> flags;</span>
|
|
<a id='x1-46064r32'></a><span class='ecrm-0500'>32</span>
|
|
<a id='x1-46066r33'></a><span class='ecrm-0500'>33</span><span class='ectt-0800'> spin_lock_init(&sl_dynamic);</span>
|
|
<a id='x1-46068r34'></a><span class='ecrm-0500'>34</span><span class='ectt-0800'> spin_lock_irqsave(&sl_dynamic, flags);</span>
|
|
<a id='x1-46070r35'></a><span class='ecrm-0500'>35</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2037'><span class='ectt-0800'>"Locked dynamic spinlock</span></span><span id='textcolor2038'><span class='ectt-0800'>\n</span></span><span id='textcolor2039'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-46072r36'></a><span class='ecrm-0500'>36</span>
|
|
<a id='x1-46074r37'></a><span class='ecrm-0500'>37</span><span class='ectt-0800'> </span><span id='textcolor2040'><span class='ectt-0800'>/* Do something or other safely.</span></span>
|
|
<a id='x1-46076r38'></a><span class='ecrm-0500'>38</span><span id='textcolor2041'><span class='ectt-0800'> Because this uses 100% CPU time this</span></span>
|
|
<a id='x1-46078r39'></a><span class='ecrm-0500'>39</span><span id='textcolor2042'><span class='ectt-0800'> code should take no more than a few</span></span>
|
|
<a id='x1-46080r40'></a><span class='ecrm-0500'>40</span><span id='textcolor2043'><span class='ectt-0800'> milliseconds to run */</span></span>
|
|
<a id='x1-46082r41'></a><span class='ecrm-0500'>41</span>
|
|
<a id='x1-46084r42'></a><span class='ecrm-0500'>42</span><span class='ectt-0800'> spin_unlock_irqrestore(&sl_dynamic, flags);</span>
|
|
<a id='x1-46086r43'></a><span class='ecrm-0500'>43</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2044'><span class='ectt-0800'>"Unlocked dynamic spinlock</span></span><span id='textcolor2045'><span class='ectt-0800'>\n</span></span><span id='textcolor2046'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-46088r44'></a><span class='ecrm-0500'>44</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-46090r45'></a><span class='ecrm-0500'>45</span>
|
|
<a id='x1-46092r46'></a><span class='ecrm-0500'>46</span><span id='textcolor2047'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2048'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> example_spinlock_init(</span><span id='textcolor2049'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-46094r47'></a><span class='ecrm-0500'>47</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-46096r48'></a><span class='ecrm-0500'>48</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2050'><span class='ectt-0800'>"example spinlock started</span></span><span id='textcolor2051'><span class='ectt-0800'>\n</span></span><span id='textcolor2052'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-46098r49'></a><span class='ecrm-0500'>49</span>
|
|
<a id='x1-46100r50'></a><span class='ecrm-0500'>50</span><span class='ectt-0800'> example_spinlock_static();</span>
|
|
<a id='x1-46102r51'></a><span class='ecrm-0500'>51</span><span class='ectt-0800'> example_spinlock_dynamic();</span>
|
|
<a id='x1-46104r52'></a><span class='ecrm-0500'>52</span>
|
|
<a id='x1-46106r53'></a><span class='ecrm-0500'>53</span><span class='ectt-0800'> </span><span id='textcolor2053'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-46108r54'></a><span class='ecrm-0500'>54</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-46110r55'></a><span class='ecrm-0500'>55</span>
|
|
<a id='x1-46112r56'></a><span class='ecrm-0500'>56</span><span id='textcolor2054'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2055'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> example_spinlock_exit(</span><span id='textcolor2056'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-46114r57'></a><span class='ecrm-0500'>57</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-46116r58'></a><span class='ecrm-0500'>58</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2057'><span class='ectt-0800'>"example spinlock exit</span></span><span id='textcolor2058'><span class='ectt-0800'>\n</span></span><span id='textcolor2059'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-46118r59'></a><span class='ecrm-0500'>59</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-46120r60'></a><span class='ecrm-0500'>60</span>
|
|
<a id='x1-46122r61'></a><span class='ecrm-0500'>61</span><span class='ectt-0800'>module_init(example_spinlock_init);</span>
|
|
<a id='x1-46124r62'></a><span class='ecrm-0500'>62</span><span class='ectt-0800'>module_exit(example_spinlock_exit);</span>
|
|
<a id='x1-46126r63'></a><span class='ecrm-0500'>63</span>
|
|
<a id='x1-46128r64'></a><span class='ecrm-0500'>64</span><span class='ectt-0800'>MODULE_DESCRIPTION(</span><span id='textcolor2060'><span class='ectt-0800'>"Spinlock example"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-46130r65'></a><span class='ecrm-0500'>65</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor2061'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
|
|
<!-- l. 1297 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='read-and-write-locks'><span class='titlemark'>0.12.3 </span> <a id='x1-470000.12.3'></a>Read and write locks</h4>
|
|
<!-- l. 1299 --><p class='noindent'>Read and write locks are specialised kinds of spinlocks so that you can exclusively
|
|
read from something or write to something. Like the earlier spinlocks example the
|
|
one below shows an "irq safe" situation in which if other functions were triggered
|
|
from irqs which might also read and write to whatever you are concerned
|
|
with then they wouldn’t disrupt the logic. As before it’s a good idea to keep
|
|
anything done within the lock as short as possible so that it doesn’t hang up
|
|
the system and cause users to start revolting against the tyranny of your
|
|
module.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb58'><a id='x1-47002r1'></a><span class='ecrm-0500'>1</span><span id='textcolor2062'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-47004r2'></a><span class='ecrm-0500'>2</span><span id='textcolor2063'><span class='ectt-0800'> * example_rwlock.c</span></span>
|
|
<a id='x1-47006r3'></a><span class='ecrm-0500'>3</span><span id='textcolor2064'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-47008r4'></a><span class='ecrm-0500'>4</span><span id='textcolor2065'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2066'><span class='ectt-0800'><linux/interrupt.h></span></span>
|
|
<a id='x1-47010r5'></a><span class='ecrm-0500'>5</span><span id='textcolor2067'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2068'><span class='ectt-0800'><linux/kernel.h></span></span>
|
|
<a id='x1-47012r6'></a><span class='ecrm-0500'>6</span><span id='textcolor2069'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2070'><span class='ectt-0800'><linux/module.h></span></span>
|
|
<a id='x1-47014r7'></a><span class='ecrm-0500'>7</span>
|
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<a id='x1-47016r8'></a><span class='ecrm-0500'>8</span><span class='ectt-0800'>DEFINE_RWLOCK(myrwlock);</span>
|
|
<a id='x1-47018r9'></a><span class='ecrm-0500'>9</span>
|
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<a id='x1-47020r10'></a><span class='ecrm-0500'>10</span><span id='textcolor2071'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2072'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> example_read_lock(</span><span id='textcolor2073'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-47022r11'></a><span class='ecrm-0500'>11</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-47024r12'></a><span class='ecrm-0500'>12</span><span class='ectt-0800'> </span><span id='textcolor2074'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor2075'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> flags;</span>
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<a id='x1-47026r13'></a><span class='ecrm-0500'>13</span>
|
|
<a id='x1-47028r14'></a><span class='ecrm-0500'>14</span><span class='ectt-0800'> read_lock_irqsave(&myrwlock, flags);</span>
|
|
<a id='x1-47030r15'></a><span class='ecrm-0500'>15</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2076'><span class='ectt-0800'>"Read Locked</span></span><span id='textcolor2077'><span class='ectt-0800'>\n</span></span><span id='textcolor2078'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-47032r16'></a><span class='ecrm-0500'>16</span>
|
|
<a id='x1-47034r17'></a><span class='ecrm-0500'>17</span><span class='ectt-0800'> </span><span id='textcolor2079'><span class='ectt-0800'>/* Read from something */</span></span>
|
|
<a id='x1-47036r18'></a><span class='ecrm-0500'>18</span>
|
|
<a id='x1-47038r19'></a><span class='ecrm-0500'>19</span><span class='ectt-0800'> read_unlock_irqrestore(&myrwlock, flags);</span>
|
|
<a id='x1-47040r20'></a><span class='ecrm-0500'>20</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2080'><span class='ectt-0800'>"Read Unlocked</span></span><span id='textcolor2081'><span class='ectt-0800'>\n</span></span><span id='textcolor2082'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-47042r21'></a><span class='ecrm-0500'>21</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-47044r22'></a><span class='ecrm-0500'>22</span>
|
|
<a id='x1-47046r23'></a><span class='ecrm-0500'>23</span><span id='textcolor2083'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2084'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> example_write_lock(</span><span id='textcolor2085'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-47048r24'></a><span class='ecrm-0500'>24</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-47050r25'></a><span class='ecrm-0500'>25</span><span class='ectt-0800'> </span><span id='textcolor2086'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor2087'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> flags;</span>
|
|
<a id='x1-47052r26'></a><span class='ecrm-0500'>26</span>
|
|
<a id='x1-47054r27'></a><span class='ecrm-0500'>27</span><span class='ectt-0800'> write_lock_irqsave(&myrwlock, flags);</span>
|
|
<a id='x1-47056r28'></a><span class='ecrm-0500'>28</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2088'><span class='ectt-0800'>"Write Locked</span></span><span id='textcolor2089'><span class='ectt-0800'>\n</span></span><span id='textcolor2090'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-47058r29'></a><span class='ecrm-0500'>29</span>
|
|
<a id='x1-47060r30'></a><span class='ecrm-0500'>30</span><span class='ectt-0800'> </span><span id='textcolor2091'><span class='ectt-0800'>/* Write to something */</span></span>
|
|
<a id='x1-47062r31'></a><span class='ecrm-0500'>31</span>
|
|
<a id='x1-47064r32'></a><span class='ecrm-0500'>32</span><span class='ectt-0800'> write_unlock_irqrestore(&myrwlock, flags);</span>
|
|
<a id='x1-47066r33'></a><span class='ecrm-0500'>33</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2092'><span class='ectt-0800'>"Write Unlocked</span></span><span id='textcolor2093'><span class='ectt-0800'>\n</span></span><span id='textcolor2094'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-47068r34'></a><span class='ecrm-0500'>34</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-47070r35'></a><span class='ecrm-0500'>35</span>
|
|
<a id='x1-47072r36'></a><span class='ecrm-0500'>36</span><span id='textcolor2095'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2096'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> example_rwlock_init(</span><span id='textcolor2097'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-47074r37'></a><span class='ecrm-0500'>37</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-47076r38'></a><span class='ecrm-0500'>38</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2098'><span class='ectt-0800'>"example_rwlock started</span></span><span id='textcolor2099'><span class='ectt-0800'>\n</span></span><span id='textcolor2100'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-47078r39'></a><span class='ecrm-0500'>39</span>
|
|
<a id='x1-47080r40'></a><span class='ecrm-0500'>40</span><span class='ectt-0800'> example_read_lock();</span>
|
|
<a id='x1-47082r41'></a><span class='ecrm-0500'>41</span><span class='ectt-0800'> example_write_lock();</span>
|
|
<a id='x1-47084r42'></a><span class='ecrm-0500'>42</span>
|
|
<a id='x1-47086r43'></a><span class='ecrm-0500'>43</span><span class='ectt-0800'> </span><span id='textcolor2101'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-47088r44'></a><span class='ecrm-0500'>44</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-47090r45'></a><span class='ecrm-0500'>45</span>
|
|
<a id='x1-47092r46'></a><span class='ecrm-0500'>46</span><span id='textcolor2102'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2103'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> example_rwlock_exit(</span><span id='textcolor2104'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-47094r47'></a><span class='ecrm-0500'>47</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-47096r48'></a><span class='ecrm-0500'>48</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2105'><span class='ectt-0800'>"example_rwlock exit</span></span><span id='textcolor2106'><span class='ectt-0800'>\n</span></span><span id='textcolor2107'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-47098r49'></a><span class='ecrm-0500'>49</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-47100r50'></a><span class='ecrm-0500'>50</span>
|
|
<a id='x1-47102r51'></a><span class='ecrm-0500'>51</span><span class='ectt-0800'>module_init(example_rwlock_init);</span>
|
|
<a id='x1-47104r52'></a><span class='ecrm-0500'>52</span><span class='ectt-0800'>module_exit(example_rwlock_exit);</span>
|
|
<a id='x1-47106r53'></a><span class='ecrm-0500'>53</span>
|
|
<a id='x1-47108r54'></a><span class='ecrm-0500'>54</span><span class='ectt-0800'>MODULE_DESCRIPTION(</span><span id='textcolor2108'><span class='ectt-0800'>"Read/Write locks example"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-47110r55'></a><span class='ecrm-0500'>55</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor2109'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
|
|
<!-- l. 1303 --><p class='indent'> Of course if you know for sure that there are no functions triggered by irqs
|
|
which could possibly interfere with your logic then you can use the simpler
|
|
<span class='ecti-1000'>read_lock(&myrwlock) </span>and <span class='ecti-1000'>read_unlock(&myrwlock) </span>or the corresponding write
|
|
functions.
|
|
</p>
|
|
<h4 class='subsectionHead' id='atomic-operations'><span class='titlemark'>0.12.4 </span> <a id='x1-480000.12.4'></a>Atomic operations</h4>
|
|
<!-- l. 1306 --><p class='noindent'>If you’re doing simple arithmetic: adding, subtracting or bitwise operations then
|
|
there’s another way in the multi-CPU and multi-hyperthreaded world to stop other
|
|
parts of the system from messing with your mojo. By using atomic operations you
|
|
can be confident that your addition, subtraction or bit flip did actually happen
|
|
and wasn’t overwritten by some other shenanigans. An example is shown
|
|
below.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb59'><a id='x1-48002r1'></a><span class='ecrm-0500'>1</span><span id='textcolor2110'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-48004r2'></a><span class='ecrm-0500'>2</span><span id='textcolor2111'><span class='ectt-0800'> * example_atomic.c</span></span>
|
|
<a id='x1-48006r3'></a><span class='ecrm-0500'>3</span><span id='textcolor2112'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-48008r4'></a><span class='ecrm-0500'>4</span><span id='textcolor2113'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2114'><span class='ectt-0800'><linux/interrupt.h></span></span>
|
|
<a id='x1-48010r5'></a><span class='ecrm-0500'>5</span><span id='textcolor2115'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2116'><span class='ectt-0800'><linux/kernel.h></span></span>
|
|
<a id='x1-48012r6'></a><span class='ecrm-0500'>6</span><span id='textcolor2117'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2118'><span class='ectt-0800'><linux/module.h></span></span>
|
|
<a id='x1-48014r7'></a><span class='ecrm-0500'>7</span>
|
|
<a id='x1-48016r8'></a><span class='ecrm-0500'>8</span><span id='textcolor2119'><span class='ectt-0800'>#define BYTE_TO_BINARY_PATTERN "%c%c%c%c%c%c%c%c"</span></span>
|
|
<a id='x1-48018r9'></a><span class='ecrm-0500'>9</span><span id='textcolor2120'><span class='ectt-0800'>#define BYTE_TO_BINARY(byte) \</span></span>
|
|
<a id='x1-48020r10'></a><span class='ecrm-0500'>10</span><span id='textcolor2121'><span class='ectt-0800'> (byte & 0x80 ? </span><span class='tctt-0800'>'</span><span class='ectt-0800'>1</span><span class='tctt-0800'>'</span><span class='ectt-0800'> : </span><span class='tctt-0800'>'</span><span class='ectt-0800'>0</span><span class='tctt-0800'>'</span><span class='ectt-0800'>), (byte & 0x40 ? </span><span class='tctt-0800'>'</span><span class='ectt-0800'>1</span><span class='tctt-0800'>'</span><span class='ectt-0800'> : </span><span class='tctt-0800'>'</span><span class='ectt-0800'>0</span><span class='tctt-0800'>'</span><span class='ectt-0800'>), \</span></span>
|
|
<a id='x1-48022r11'></a><span class='ecrm-0500'>11</span><span id='textcolor2122'><span class='ectt-0800'> (byte & 0x20 ? </span><span class='tctt-0800'>'</span><span class='ectt-0800'>1</span><span class='tctt-0800'>'</span><span class='ectt-0800'> : </span><span class='tctt-0800'>'</span><span class='ectt-0800'>0</span><span class='tctt-0800'>'</span><span class='ectt-0800'>), (byte & 0x10 ? </span><span class='tctt-0800'>'</span><span class='ectt-0800'>1</span><span class='tctt-0800'>'</span><span class='ectt-0800'> : </span><span class='tctt-0800'>'</span><span class='ectt-0800'>0</span><span class='tctt-0800'>'</span><span class='ectt-0800'>), \</span></span>
|
|
<a id='x1-48024r12'></a><span class='ecrm-0500'>12</span><span id='textcolor2123'><span class='ectt-0800'> (byte & 0x08 ? </span><span class='tctt-0800'>'</span><span class='ectt-0800'>1</span><span class='tctt-0800'>'</span><span class='ectt-0800'> : </span><span class='tctt-0800'>'</span><span class='ectt-0800'>0</span><span class='tctt-0800'>'</span><span class='ectt-0800'>), (byte & 0x04 ? </span><span class='tctt-0800'>'</span><span class='ectt-0800'>1</span><span class='tctt-0800'>'</span><span class='ectt-0800'> : </span><span class='tctt-0800'>'</span><span class='ectt-0800'>0</span><span class='tctt-0800'>'</span><span class='ectt-0800'>), \</span></span>
|
|
<a id='x1-48026r13'></a><span class='ecrm-0500'>13</span><span id='textcolor2124'><span class='ectt-0800'> (byte & 0x02 ? </span><span class='tctt-0800'>'</span><span class='ectt-0800'>1</span><span class='tctt-0800'>'</span><span class='ectt-0800'> : </span><span class='tctt-0800'>'</span><span class='ectt-0800'>0</span><span class='tctt-0800'>'</span><span class='ectt-0800'>), (byte & 0x01 ? </span><span class='tctt-0800'>'</span><span class='ectt-0800'>1</span><span class='tctt-0800'>'</span><span class='ectt-0800'> : </span><span class='tctt-0800'>'</span><span class='ectt-0800'>0</span><span class='tctt-0800'>'</span><span class='ectt-0800'>)</span></span>
|
|
<a id='x1-48028r14'></a><span class='ecrm-0500'>14</span>
|
|
<a id='x1-48030r15'></a><span class='ecrm-0500'>15</span><span id='textcolor2125'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2126'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> atomic_add_subtract(</span><span id='textcolor2127'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-48032r16'></a><span class='ecrm-0500'>16</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-48034r17'></a><span class='ecrm-0500'>17</span><span class='ectt-0800'> atomic_t debbie;</span>
|
|
<a id='x1-48036r18'></a><span class='ecrm-0500'>18</span><span class='ectt-0800'> atomic_t chris = ATOMIC_INIT(50);</span>
|
|
<a id='x1-48038r19'></a><span class='ecrm-0500'>19</span>
|
|
<a id='x1-48040r20'></a><span class='ecrm-0500'>20</span><span class='ectt-0800'> atomic_set(&debbie, 45);</span>
|
|
<a id='x1-48042r21'></a><span class='ecrm-0500'>21</span>
|
|
<a id='x1-48044r22'></a><span class='ecrm-0500'>22</span><span class='ectt-0800'> </span><span id='textcolor2128'><span class='ectt-0800'>/* subtract one */</span></span>
|
|
<a id='x1-48046r23'></a><span class='ecrm-0500'>23</span><span class='ectt-0800'> atomic_dec(&debbie);</span>
|
|
<a id='x1-48048r24'></a><span class='ecrm-0500'>24</span>
|
|
<a id='x1-48050r25'></a><span class='ecrm-0500'>25</span><span class='ectt-0800'> atomic_add(7, &debbie);</span>
|
|
<a id='x1-48052r26'></a><span class='ecrm-0500'>26</span>
|
|
<a id='x1-48054r27'></a><span class='ecrm-0500'>27</span><span class='ectt-0800'> </span><span id='textcolor2129'><span class='ectt-0800'>/* add one */</span></span>
|
|
<a id='x1-48056r28'></a><span class='ecrm-0500'>28</span><span class='ectt-0800'> atomic_inc(&debbie);</span>
|
|
<a id='x1-48058r29'></a><span class='ecrm-0500'>29</span>
|
|
<a id='x1-48060r30'></a><span class='ecrm-0500'>30</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2130'><span class='ectt-0800'>"chris: %d, debbie: %d</span></span><span id='textcolor2131'><span class='ectt-0800'>\n</span></span><span id='textcolor2132'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, atomic_read(&chris),</span>
|
|
<a id='x1-48062r31'></a><span class='ecrm-0500'>31</span><span class='ectt-0800'> atomic_read(&debbie));</span>
|
|
<a id='x1-48064r32'></a><span class='ecrm-0500'>32</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-48066r33'></a><span class='ecrm-0500'>33</span>
|
|
<a id='x1-48068r34'></a><span class='ecrm-0500'>34</span><span id='textcolor2133'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2134'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> atomic_bitwise(</span><span id='textcolor2135'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-48070r35'></a><span class='ecrm-0500'>35</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-48072r36'></a><span class='ecrm-0500'>36</span><span class='ectt-0800'> </span><span id='textcolor2136'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor2137'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> word = 0;</span>
|
|
<a id='x1-48074r37'></a><span class='ecrm-0500'>37</span>
|
|
<a id='x1-48076r38'></a><span class='ecrm-0500'>38</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2138'><span class='ectt-0800'>"Bits 0: "</span></span><span class='ectt-0800'> BYTE_TO_BINARY_PATTERN, BYTE_TO_BINARY(word));</span>
|
|
<a id='x1-48078r39'></a><span class='ecrm-0500'>39</span><span class='ectt-0800'> set_bit(3, &word);</span>
|
|
<a id='x1-48080r40'></a><span class='ecrm-0500'>40</span><span class='ectt-0800'> set_bit(5, &word);</span>
|
|
<a id='x1-48082r41'></a><span class='ecrm-0500'>41</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2139'><span class='ectt-0800'>"Bits 1: "</span></span><span class='ectt-0800'> BYTE_TO_BINARY_PATTERN, BYTE_TO_BINARY(word));</span>
|
|
<a id='x1-48084r42'></a><span class='ecrm-0500'>42</span><span class='ectt-0800'> clear_bit(5, &word);</span>
|
|
<a id='x1-48086r43'></a><span class='ecrm-0500'>43</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2140'><span class='ectt-0800'>"Bits 2: "</span></span><span class='ectt-0800'> BYTE_TO_BINARY_PATTERN, BYTE_TO_BINARY(word));</span>
|
|
<a id='x1-48088r44'></a><span class='ecrm-0500'>44</span><span class='ectt-0800'> change_bit(3, &word);</span>
|
|
<a id='x1-48090r45'></a><span class='ecrm-0500'>45</span>
|
|
<a id='x1-48092r46'></a><span class='ecrm-0500'>46</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2141'><span class='ectt-0800'>"Bits 3: "</span></span><span class='ectt-0800'> BYTE_TO_BINARY_PATTERN, BYTE_TO_BINARY(word));</span>
|
|
<a id='x1-48094r47'></a><span class='ecrm-0500'>47</span><span class='ectt-0800'> </span><span id='textcolor2142'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (test_and_set_bit(3, &word))</span>
|
|
<a id='x1-48096r48'></a><span class='ecrm-0500'>48</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2143'><span class='ectt-0800'>"wrong</span></span><span id='textcolor2144'><span class='ectt-0800'>\n</span></span><span id='textcolor2145'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-48098r49'></a><span class='ecrm-0500'>49</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2146'><span class='ectt-0800'>"Bits 4: "</span></span><span class='ectt-0800'> BYTE_TO_BINARY_PATTERN, BYTE_TO_BINARY(word));</span>
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<a id='x1-48100r50'></a><span class='ecrm-0500'>50</span>
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<a id='x1-48102r51'></a><span class='ecrm-0500'>51</span><span class='ectt-0800'> word = 255;</span>
|
|
<a id='x1-48104r52'></a><span class='ecrm-0500'>52</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2147'><span class='ectt-0800'>"Bits 5: "</span></span><span class='ectt-0800'> BYTE_TO_BINARY_PATTERN, BYTE_TO_BINARY(word));</span>
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<a id='x1-48106r53'></a><span class='ecrm-0500'>53</span><span class='ectt-0800'>}</span>
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<a id='x1-48108r54'></a><span class='ecrm-0500'>54</span>
|
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<a id='x1-48110r55'></a><span class='ecrm-0500'>55</span><span id='textcolor2148'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2149'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> example_atomic_init(</span><span id='textcolor2150'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
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<a id='x1-48112r56'></a><span class='ecrm-0500'>56</span><span class='ectt-0800'>{</span>
|
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<a id='x1-48114r57'></a><span class='ecrm-0500'>57</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2151'><span class='ectt-0800'>"example_atomic started</span></span><span id='textcolor2152'><span class='ectt-0800'>\n</span></span><span id='textcolor2153'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
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<a id='x1-48116r58'></a><span class='ecrm-0500'>58</span>
|
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<a id='x1-48118r59'></a><span class='ecrm-0500'>59</span><span class='ectt-0800'> atomic_add_subtract();</span>
|
|
<a id='x1-48120r60'></a><span class='ecrm-0500'>60</span><span class='ectt-0800'> atomic_bitwise();</span>
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<a id='x1-48122r61'></a><span class='ecrm-0500'>61</span>
|
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<a id='x1-48124r62'></a><span class='ecrm-0500'>62</span><span class='ectt-0800'> </span><span id='textcolor2154'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
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<a id='x1-48126r63'></a><span class='ecrm-0500'>63</span><span class='ectt-0800'>}</span>
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<a id='x1-48128r64'></a><span class='ecrm-0500'>64</span>
|
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<a id='x1-48130r65'></a><span class='ecrm-0500'>65</span><span id='textcolor2155'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2156'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> example_atomic_exit(</span><span id='textcolor2157'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-48132r66'></a><span class='ecrm-0500'>66</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-48134r67'></a><span class='ecrm-0500'>67</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2158'><span class='ectt-0800'>"example_atomic exit</span></span><span id='textcolor2159'><span class='ectt-0800'>\n</span></span><span id='textcolor2160'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
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<a id='x1-48136r68'></a><span class='ecrm-0500'>68</span><span class='ectt-0800'>}</span>
|
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<a id='x1-48138r69'></a><span class='ecrm-0500'>69</span>
|
|
<a id='x1-48140r70'></a><span class='ecrm-0500'>70</span><span class='ectt-0800'>module_init(example_atomic_init);</span>
|
|
<a id='x1-48142r71'></a><span class='ecrm-0500'>71</span><span class='ectt-0800'>module_exit(example_atomic_exit);</span>
|
|
<a id='x1-48144r72'></a><span class='ecrm-0500'>72</span>
|
|
<a id='x1-48146r73'></a><span class='ecrm-0500'>73</span><span class='ectt-0800'>MODULE_DESCRIPTION(</span><span id='textcolor2161'><span class='ectt-0800'>"Atomic operations example"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-48148r74'></a><span class='ecrm-0500'>74</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor2162'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
|
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|
|
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<!-- l. 1310 --><p class='noindent'>
|
|
</p>
|
|
<h3 class='sectionHead' id='replacing-print-macros'><span class='titlemark'>0.13 </span> <a id='x1-490000.13'></a>Replacing Print Macros</h3>
|
|
<!-- l. 1312 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='replacement'><span class='titlemark'>0.13.1 </span> <a id='x1-500000.13.1'></a>Replacement</h4>
|
|
<!-- l. 1314 --><p class='noindent'>In Section 1.2.1.2, I said that X and kernel module programming don’t mix. That’s
|
|
true for developing kernel modules, but in actual use, you want to be able
|
|
to send messages to whichever tty the command to load the module came
|
|
from.
|
|
</p><!-- l. 1316 --><p class='indent'> "tty" is an abbreviation of <span class='ecti-1000'>teletype</span>: originally a combination keyboard-printer
|
|
used to communicate with a Unix system, and today an abstraction for the text
|
|
stream used for a Unix program, whether it’s a physical terminal, an xterm on an X
|
|
display, a network connection used with ssh, etc.
|
|
</p><!-- l. 1318 --><p class='indent'> The way this is done is by using current, a pointer to the currently running task,
|
|
to get the current task’s tty structure. Then, we look inside that tty structure to find
|
|
a pointer to a string write function, which we use to write a string to the
|
|
tty.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb60'><a id='x1-50002r1'></a><span class='ecrm-0500'>1</span><span id='textcolor2163'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-50004r2'></a><span class='ecrm-0500'>2</span><span id='textcolor2164'><span class='ectt-0800'> * print_string.c - Send output to the tty we</span><span class='tctt-0800'>'</span><span class='ectt-0800'>re running on, regardless if it</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s</span></span>
|
|
<a id='x1-50006r3'></a><span class='ecrm-0500'>3</span><span id='textcolor2165'><span class='ectt-0800'> * through X11, telnet, etc. We do this by printing the string to the tty</span></span>
|
|
<a id='x1-50008r4'></a><span class='ecrm-0500'>4</span><span id='textcolor2166'><span class='ectt-0800'> * associated with the current task.</span></span>
|
|
<a id='x1-50010r5'></a><span class='ecrm-0500'>5</span><span id='textcolor2167'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-50012r6'></a><span class='ecrm-0500'>6</span><span id='textcolor2168'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2169'><span class='ectt-0800'><linux/init.h></span></span>
|
|
<a id='x1-50014r7'></a><span class='ecrm-0500'>7</span><span id='textcolor2170'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2171'><span class='ectt-0800'><linux/kernel.h></span></span>
|
|
<a id='x1-50016r8'></a><span class='ecrm-0500'>8</span><span id='textcolor2172'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2173'><span class='ectt-0800'><linux/module.h></span></span>
|
|
<a id='x1-50018r9'></a><span class='ecrm-0500'>9</span><span id='textcolor2174'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2175'><span class='ectt-0800'><linux/sched.h> /* For current */</span></span>
|
|
<a id='x1-50020r10'></a><span class='ecrm-0500'>10</span><span id='textcolor2176'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2177'><span class='ectt-0800'><linux/tty.h> /* For the tty declarations */</span></span>
|
|
<a id='x1-50022r11'></a><span class='ecrm-0500'>11</span>
|
|
<a id='x1-50024r12'></a><span class='ecrm-0500'>12</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor2178'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-50026r13'></a><span class='ecrm-0500'>13</span>
|
|
<a id='x1-50028r14'></a><span class='ecrm-0500'>14</span><span id='textcolor2179'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2180'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> print_string(</span><span id='textcolor2181'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *str)</span>
|
|
<a id='x1-50030r15'></a><span class='ecrm-0500'>15</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-50032r16'></a><span class='ecrm-0500'>16</span><span class='ectt-0800'> </span><span id='textcolor2182'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> tty_struct *my_tty;</span>
|
|
<a id='x1-50034r17'></a><span class='ecrm-0500'>17</span><span class='ectt-0800'> </span><span id='textcolor2183'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor2184'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> tty_operations *ttyops;</span>
|
|
<a id='x1-50036r18'></a><span class='ecrm-0500'>18</span>
|
|
<a id='x1-50038r19'></a><span class='ecrm-0500'>19</span><span class='ectt-0800'> </span><span id='textcolor2185'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-50040r20'></a><span class='ecrm-0500'>20</span><span id='textcolor2186'><span class='ectt-0800'> * The tty for the current task, for 2.6.6+ kernels</span></span>
|
|
<a id='x1-50042r21'></a><span class='ecrm-0500'>21</span><span id='textcolor2187'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-50044r22'></a><span class='ecrm-0500'>22</span><span class='ectt-0800'> my_tty = get_current_tty();</span>
|
|
<a id='x1-50046r23'></a><span class='ecrm-0500'>23</span><span class='ectt-0800'> ttyops = my_tty->driver->ops;</span>
|
|
<a id='x1-50048r24'></a><span class='ecrm-0500'>24</span>
|
|
<a id='x1-50050r25'></a><span class='ecrm-0500'>25</span><span class='ectt-0800'> </span><span id='textcolor2188'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-50052r26'></a><span class='ecrm-0500'>26</span><span id='textcolor2189'><span class='ectt-0800'> * If my_tty is NULL, the current task has no tty you can print to</span></span>
|
|
<a id='x1-50054r27'></a><span class='ecrm-0500'>27</span><span id='textcolor2190'><span class='ectt-0800'> * (ie, if it</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s a daemon). If so, there</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s nothing we can do.</span></span>
|
|
<a id='x1-50056r28'></a><span class='ecrm-0500'>28</span><span id='textcolor2191'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-50058r29'></a><span class='ecrm-0500'>29</span><span class='ectt-0800'> </span><span id='textcolor2192'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (my_tty != NULL) {</span>
|
|
<a id='x1-50060r30'></a><span class='ecrm-0500'>30</span><span class='ectt-0800'> </span><span id='textcolor2193'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-50062r31'></a><span class='ecrm-0500'>31</span><span id='textcolor2194'><span class='ectt-0800'> * my_tty->driver is a struct which holds the tty</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s functions,</span></span>
|
|
<a id='x1-50064r32'></a><span class='ecrm-0500'>32</span><span id='textcolor2195'><span class='ectt-0800'> * one of which (write) is used to write strings to the tty.</span></span>
|
|
<a id='x1-50066r33'></a><span class='ecrm-0500'>33</span><span id='textcolor2196'><span class='ectt-0800'> * It can be used to take a string either from the user</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s or</span></span>
|
|
<a id='x1-50068r34'></a><span class='ecrm-0500'>34</span><span id='textcolor2197'><span class='ectt-0800'> * kernel</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s memory segment.</span></span>
|
|
<a id='x1-50070r35'></a><span class='ecrm-0500'>35</span><span id='textcolor2198'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-50072r36'></a><span class='ecrm-0500'>36</span><span id='textcolor2199'><span class='ectt-0800'> * The function</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s 1st parameter is the tty to write to,</span></span>
|
|
<a id='x1-50074r37'></a><span class='ecrm-0500'>37</span><span id='textcolor2200'><span class='ectt-0800'> * because the same function would normally be used for all</span></span>
|
|
<a id='x1-50076r38'></a><span class='ecrm-0500'>38</span><span id='textcolor2201'><span class='ectt-0800'> * tty</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s of a certain type.</span></span>
|
|
<a id='x1-50078r39'></a><span class='ecrm-0500'>39</span><span id='textcolor2202'><span class='ectt-0800'> * The 2nd parameter is a pointer to a string.</span></span>
|
|
<a id='x1-50080r40'></a><span class='ecrm-0500'>40</span><span id='textcolor2203'><span class='ectt-0800'> * The 3rd parameter is the length of the string.</span></span>
|
|
<a id='x1-50082r41'></a><span class='ecrm-0500'>41</span><span id='textcolor2204'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-50084r42'></a><span class='ecrm-0500'>42</span><span id='textcolor2205'><span class='ectt-0800'> * As you will see below, sometimes it</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s necessary to use</span></span>
|
|
<a id='x1-50086r43'></a><span class='ecrm-0500'>43</span><span id='textcolor2206'><span class='ectt-0800'> * preprocessor stuff to create code that works for different</span></span>
|
|
<a id='x1-50088r44'></a><span class='ecrm-0500'>44</span><span id='textcolor2207'><span class='ectt-0800'> * kernel versions. The (naive) approach we</span><span class='tctt-0800'>'</span><span class='ectt-0800'>ve taken here</span></span>
|
|
<a id='x1-50090r45'></a><span class='ecrm-0500'>45</span><span id='textcolor2208'><span class='ectt-0800'> * does not scale well. The right way to deal with this</span></span>
|
|
<a id='x1-50092r46'></a><span class='ecrm-0500'>46</span><span id='textcolor2209'><span class='ectt-0800'> * is described in section 2 of</span></span>
|
|
<a id='x1-50094r47'></a><span class='ecrm-0500'>47</span><span id='textcolor2210'><span class='ectt-0800'> * linux/Documentation/SubmittingPatches</span></span>
|
|
<a id='x1-50096r48'></a><span class='ecrm-0500'>48</span><span id='textcolor2211'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-50098r49'></a><span class='ecrm-0500'>49</span><span class='ectt-0800'> (ttyops->write)(my_tty, </span><span id='textcolor2212'><span class='ectt-0800'>/* The tty itself */</span></span>
|
|
<a id='x1-50100r50'></a><span class='ecrm-0500'>50</span><span class='ectt-0800'> str, </span><span id='textcolor2213'><span class='ectt-0800'>/* String */</span></span>
|
|
<a id='x1-50102r51'></a><span class='ecrm-0500'>51</span><span class='ectt-0800'> strlen(str)); </span><span id='textcolor2214'><span class='ectt-0800'>/* Length */</span></span>
|
|
<a id='x1-50104r52'></a><span class='ecrm-0500'>52</span>
|
|
<a id='x1-50106r53'></a><span class='ecrm-0500'>53</span><span class='ectt-0800'> </span><span id='textcolor2215'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-50108r54'></a><span class='ecrm-0500'>54</span><span id='textcolor2216'><span class='ectt-0800'> * ttys were originally hardware devices, which (usually)</span></span>
|
|
<a id='x1-50110r55'></a><span class='ecrm-0500'>55</span><span id='textcolor2217'><span class='ectt-0800'> * strictly followed the ASCII standard. In ASCII, to move to</span></span>
|
|
<a id='x1-50112r56'></a><span class='ecrm-0500'>56</span><span id='textcolor2218'><span class='ectt-0800'> * a new line you need two characters, a carriage return and a</span></span>
|
|
<a id='x1-50114r57'></a><span class='ecrm-0500'>57</span><span id='textcolor2219'><span class='ectt-0800'> * line feed. On Unix, the ASCII line feed is used for both</span></span>
|
|
<a id='x1-50116r58'></a><span class='ecrm-0500'>58</span><span id='textcolor2220'><span class='ectt-0800'> * purposes - so we can</span><span class='tctt-0800'>'</span><span class='ectt-0800'>t just use \n, because it wouldn</span><span class='tctt-0800'>'</span><span class='ectt-0800'>t have</span></span>
|
|
<a id='x1-50118r59'></a><span class='ecrm-0500'>59</span><span id='textcolor2221'><span class='ectt-0800'> * a carriage return and the next line will start at the</span></span>
|
|
<a id='x1-50120r60'></a><span class='ecrm-0500'>60</span><span id='textcolor2222'><span class='ectt-0800'> * column right after the line feed.</span></span>
|
|
<a id='x1-50122r61'></a><span class='ecrm-0500'>61</span><span id='textcolor2223'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-50124r62'></a><span class='ecrm-0500'>62</span><span id='textcolor2224'><span class='ectt-0800'> * This is why text files are different between Unix and</span></span>
|
|
<a id='x1-50126r63'></a><span class='ecrm-0500'>63</span><span id='textcolor2225'><span class='ectt-0800'> * MS Windows. In CP/M and derivatives, like MS-DOS and</span></span>
|
|
<a id='x1-50128r64'></a><span class='ecrm-0500'>64</span><span id='textcolor2226'><span class='ectt-0800'> * MS Windows, the ASCII standard was strictly adhered to,</span></span>
|
|
<a id='x1-50130r65'></a><span class='ecrm-0500'>65</span><span id='textcolor2227'><span class='ectt-0800'> * and therefore a newline requirs both a LF and a CR.</span></span>
|
|
<a id='x1-50132r66'></a><span class='ecrm-0500'>66</span><span id='textcolor2228'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-50134r67'></a><span class='ecrm-0500'>67</span><span class='ectt-0800'> (ttyops->write)(my_tty, </span><span id='textcolor2229'><span class='ectt-0800'>"</span></span><span id='textcolor2230'><span class='ectt-0800'>\015\012</span></span><span id='textcolor2231'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, 2);</span>
|
|
<a id='x1-50136r68'></a><span class='ecrm-0500'>68</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-50138r69'></a><span class='ecrm-0500'>69</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-50140r70'></a><span class='ecrm-0500'>70</span>
|
|
<a id='x1-50142r71'></a><span class='ecrm-0500'>71</span><span id='textcolor2232'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2233'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> __init print_string_init(</span><span id='textcolor2234'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-50144r72'></a><span class='ecrm-0500'>72</span><span class='ectt-0800'>{</span>
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<a id='x1-50146r73'></a><span class='ecrm-0500'>73</span><span class='ectt-0800'> print_string(</span><span id='textcolor2235'><span class='ectt-0800'>"The module has been inserted. Hello world!"</span></span><span class='ectt-0800'>);</span>
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<a id='x1-50148r74'></a><span class='ecrm-0500'>74</span><span class='ectt-0800'> </span><span id='textcolor2236'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
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<a id='x1-50150r75'></a><span class='ecrm-0500'>75</span><span class='ectt-0800'>}</span>
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<a id='x1-50152r76'></a><span class='ecrm-0500'>76</span>
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<a id='x1-50154r77'></a><span class='ecrm-0500'>77</span><span id='textcolor2237'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2238'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> __exit print_string_exit(</span><span id='textcolor2239'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
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<a id='x1-50156r78'></a><span class='ecrm-0500'>78</span><span class='ectt-0800'>{</span>
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<a id='x1-50158r79'></a><span class='ecrm-0500'>79</span><span class='ectt-0800'> print_string(</span><span id='textcolor2240'><span class='ectt-0800'>"The module has been removed. Farewell world!"</span></span><span class='ectt-0800'>);</span>
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<a id='x1-50160r80'></a><span class='ecrm-0500'>80</span><span class='ectt-0800'>}</span>
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<a id='x1-50162r81'></a><span class='ecrm-0500'>81</span>
|
|
<a id='x1-50164r82'></a><span class='ecrm-0500'>82</span><span class='ectt-0800'>module_init(print_string_init);</span>
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<a id='x1-50166r83'></a><span class='ecrm-0500'>83</span><span class='ectt-0800'>module_exit(print_string_exit);</span></pre>
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<!-- l. 1322 --><p class='noindent'>
|
|
</p>
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|
<h4 class='subsectionHead' id='flashing-keyboard-leds'><span class='titlemark'>0.13.2 </span> <a id='x1-510000.13.2'></a>Flashing keyboard LEDs</h4>
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<!-- l. 1324 --><p class='noindent'>In certain conditions, you may desire a simpler and more direct way to communicate
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to the external world. Flashing keyboard LEDs can be such a solution: It is an
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|
immediate way to attract attention or to display a status condition. Keyboard LEDs
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|
are present on every hardware, they are always visible, they do not need any setup,
|
|
and their use is rather simple and non-intrusive, compared to writing to a tty or a
|
|
file.
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|
</p><!-- l. 1326 --><p class='indent'> The following source code illustrates a minimal kernel module which, when
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loaded, starts blinking the keyboard LEDs until it is unloaded.
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|
</p><!-- l. 1 --><p class='indent'>
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|
</p>
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|
<pre class='fancyvrb' id='fancyvrb61'><a id='x1-51002r1'></a><span class='ecrm-0500'>1</span><span id='textcolor2241'><span class='ectt-0800'>/*</span></span>
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|
<a id='x1-51004r2'></a><span class='ecrm-0500'>2</span><span id='textcolor2242'><span class='ectt-0800'> * kbleds.c - Blink keyboard leds until the module is unloaded.</span></span>
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<a id='x1-51006r3'></a><span class='ecrm-0500'>3</span><span id='textcolor2243'><span class='ectt-0800'> */</span></span>
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<a id='x1-51008r4'></a><span class='ecrm-0500'>4</span>
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|
<a id='x1-51010r5'></a><span class='ecrm-0500'>5</span><span id='textcolor2244'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2245'><span class='ectt-0800'><linux/init.h></span></span>
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|
<a id='x1-51012r6'></a><span class='ecrm-0500'>6</span><span id='textcolor2246'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2247'><span class='ectt-0800'><linux/kd.h> /* For KDSETLED */</span></span>
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<a id='x1-51014r7'></a><span class='ecrm-0500'>7</span><span id='textcolor2248'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2249'><span class='ectt-0800'><linux/module.h></span></span>
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|
<a id='x1-51016r8'></a><span class='ecrm-0500'>8</span><span id='textcolor2250'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2251'><span class='ectt-0800'><linux/tty.h> /* For fg_console, MAX_NR_CONSOLES */</span></span>
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|
<a id='x1-51018r9'></a><span class='ecrm-0500'>9</span><span id='textcolor2252'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2253'><span class='ectt-0800'><linux/vt.h></span></span>
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|
<a id='x1-51020r10'></a><span class='ecrm-0500'>10</span><span id='textcolor2254'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2255'><span class='ectt-0800'><linux/vt_kern.h> /* for fg_console */</span></span>
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|
<a id='x1-51022r11'></a><span class='ecrm-0500'>11</span>
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|
<a id='x1-51024r12'></a><span class='ecrm-0500'>12</span><span id='textcolor2256'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2257'><span class='ectt-0800'><linux/console_struct.h> /* For vc_cons */</span></span>
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|
<a id='x1-51026r13'></a><span class='ecrm-0500'>13</span>
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|
<a id='x1-51028r14'></a><span class='ecrm-0500'>14</span><span class='ectt-0800'>MODULE_DESCRIPTION(</span><span id='textcolor2258'><span class='ectt-0800'>"Example module illustrating the use of Keyboard LEDs."</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-51030r15'></a><span class='ecrm-0500'>15</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor2259'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span>
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<a id='x1-51032r16'></a><span class='ecrm-0500'>16</span>
|
|
<a id='x1-51034r17'></a><span class='ecrm-0500'>17</span><span id='textcolor2260'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> timer_list my_timer;</span>
|
|
<a id='x1-51036r18'></a><span class='ecrm-0500'>18</span><span id='textcolor2261'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> tty_driver *my_driver;</span>
|
|
<a id='x1-51038r19'></a><span class='ecrm-0500'>19</span><span id='textcolor2262'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> kbledstatus = 0;</span>
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|
<a id='x1-51040r20'></a><span class='ecrm-0500'>20</span>
|
|
<a id='x1-51042r21'></a><span class='ecrm-0500'>21</span><span id='textcolor2263'><span class='ectt-0800'>#define BLINK_DELAY HZ / 5</span></span>
|
|
<a id='x1-51044r22'></a><span class='ecrm-0500'>22</span><span id='textcolor2264'><span class='ectt-0800'>#define ALL_LEDS_ON 0x07</span></span>
|
|
<a id='x1-51046r23'></a><span class='ecrm-0500'>23</span><span id='textcolor2265'><span class='ectt-0800'>#define RESTORE_LEDS 0xFF</span></span>
|
|
<a id='x1-51048r24'></a><span class='ecrm-0500'>24</span>
|
|
<a id='x1-51050r25'></a><span class='ecrm-0500'>25</span><span id='textcolor2266'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-51052r26'></a><span class='ecrm-0500'>26</span><span id='textcolor2267'><span class='ectt-0800'> * Function my_timer_func blinks the keyboard LEDs periodically by invoking</span></span>
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|
<a id='x1-51054r27'></a><span class='ecrm-0500'>27</span><span id='textcolor2268'><span class='ectt-0800'> * command KDSETLED of ioctl() on the keyboard driver. To learn more on virtual</span></span>
|
|
<a id='x1-51056r28'></a><span class='ecrm-0500'>28</span><span id='textcolor2269'><span class='ectt-0800'> * terminal ioctl operations, please see file:</span></span>
|
|
<a id='x1-51058r29'></a><span class='ecrm-0500'>29</span><span id='textcolor2270'><span class='ectt-0800'> * /usr/src/linux/drivers/char/vt_ioctl.c, function vt_ioctl().</span></span>
|
|
<a id='x1-51060r30'></a><span class='ecrm-0500'>30</span><span id='textcolor2271'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-51062r31'></a><span class='ecrm-0500'>31</span><span id='textcolor2272'><span class='ectt-0800'> * The argument to KDSETLED is alternatively set to 7 (thus causing the led</span></span>
|
|
<a id='x1-51064r32'></a><span class='ecrm-0500'>32</span><span id='textcolor2273'><span class='ectt-0800'> * mode to be set to LED_SHOW_IOCTL, and all the leds are lit) and to 0xFF</span></span>
|
|
<a id='x1-51066r33'></a><span class='ecrm-0500'>33</span><span id='textcolor2274'><span class='ectt-0800'> * (any value above 7 switches back the led mode to LED_SHOW_FLAGS, thus</span></span>
|
|
<a id='x1-51068r34'></a><span class='ecrm-0500'>34</span><span id='textcolor2275'><span class='ectt-0800'> * the LEDs reflect the actual keyboard status). To learn more on this,</span></span>
|
|
<a id='x1-51070r35'></a><span class='ecrm-0500'>35</span><span id='textcolor2276'><span class='ectt-0800'> * please see file:</span></span>
|
|
<a id='x1-51072r36'></a><span class='ecrm-0500'>36</span><span id='textcolor2277'><span class='ectt-0800'> * /usr/src/linux/drivers/char/keyboard.c, function setledstate().</span></span>
|
|
<a id='x1-51074r37'></a><span class='ecrm-0500'>37</span><span id='textcolor2278'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-51076r38'></a><span class='ecrm-0500'>38</span><span id='textcolor2279'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-51078r39'></a><span class='ecrm-0500'>39</span>
|
|
<a id='x1-51080r40'></a><span class='ecrm-0500'>40</span><span id='textcolor2280'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2281'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> my_timer_func(</span><span id='textcolor2282'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor2283'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> ptr)</span>
|
|
<a id='x1-51082r41'></a><span class='ecrm-0500'>41</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-51084r42'></a><span class='ecrm-0500'>42</span><span class='ectt-0800'> </span><span id='textcolor2284'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor2285'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> *pstatus = (</span><span id='textcolor2286'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor2287'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> *) ptr;</span>
|
|
<a id='x1-51086r43'></a><span class='ecrm-0500'>43</span><span class='ectt-0800'> </span><span id='textcolor2288'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> tty_struct *t = vc_cons[fg_console].d->port.tty;</span>
|
|
<a id='x1-51088r44'></a><span class='ecrm-0500'>44</span>
|
|
<a id='x1-51090r45'></a><span class='ecrm-0500'>45</span><span class='ectt-0800'> </span><span id='textcolor2289'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (*pstatus == ALL_LEDS_ON)</span>
|
|
<a id='x1-51092r46'></a><span class='ecrm-0500'>46</span><span class='ectt-0800'> *pstatus = RESTORE_LEDS;</span>
|
|
<a id='x1-51094r47'></a><span class='ecrm-0500'>47</span><span class='ectt-0800'> </span><span id='textcolor2290'><span class='ectt-0800'>else</span></span>
|
|
<a id='x1-51096r48'></a><span class='ecrm-0500'>48</span><span class='ectt-0800'> *pstatus = ALL_LEDS_ON;</span>
|
|
<a id='x1-51098r49'></a><span class='ecrm-0500'>49</span>
|
|
<a id='x1-51100r50'></a><span class='ecrm-0500'>50</span><span class='ectt-0800'> (my_driver->ops->ioctl)(t, KDSETLED, *pstatus);</span>
|
|
<a id='x1-51102r51'></a><span class='ecrm-0500'>51</span>
|
|
<a id='x1-51104r52'></a><span class='ecrm-0500'>52</span><span class='ectt-0800'> my_timer.expires = jiffies + BLINK_DELAY;</span>
|
|
<a id='x1-51106r53'></a><span class='ecrm-0500'>53</span><span class='ectt-0800'> add_timer(&my_timer);</span>
|
|
<a id='x1-51108r54'></a><span class='ecrm-0500'>54</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-51110r55'></a><span class='ecrm-0500'>55</span>
|
|
<a id='x1-51112r56'></a><span class='ecrm-0500'>56</span><span id='textcolor2291'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2292'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> __init kbleds_init(</span><span id='textcolor2293'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-51114r57'></a><span class='ecrm-0500'>57</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-51116r58'></a><span class='ecrm-0500'>58</span><span class='ectt-0800'> </span><span id='textcolor2294'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> i;</span>
|
|
<a id='x1-51118r59'></a><span class='ecrm-0500'>59</span>
|
|
<a id='x1-51120r60'></a><span class='ecrm-0500'>60</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2295'><span class='ectt-0800'>"kbleds: loading</span></span><span id='textcolor2296'><span class='ectt-0800'>\n</span></span><span id='textcolor2297'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-51122r61'></a><span class='ecrm-0500'>61</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2298'><span class='ectt-0800'>"kbleds: fgconsole is %x</span></span><span id='textcolor2299'><span class='ectt-0800'>\n</span></span><span id='textcolor2300'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, fg_console);</span>
|
|
<a id='x1-51124r62'></a><span class='ecrm-0500'>62</span><span class='ectt-0800'> </span><span id='textcolor2301'><span class='ectt-0800'>for</span></span><span class='ectt-0800'> (i = 0; i < MAX_NR_CONSOLES; i++) {</span>
|
|
<a id='x1-51126r63'></a><span class='ecrm-0500'>63</span><span class='ectt-0800'> </span><span id='textcolor2302'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (!vc_cons[i].d)</span>
|
|
<a id='x1-51128r64'></a><span class='ecrm-0500'>64</span><span class='ectt-0800'> </span><span id='textcolor2303'><span class='ectt-0800'>break</span></span><span class='ectt-0800'>;</span>
|
|
<a id='x1-51130r65'></a><span class='ecrm-0500'>65</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2304'><span class='ectt-0800'>"poet_atkm: console[%i/%i] #%i, tty %lx</span></span><span id='textcolor2305'><span class='ectt-0800'>\n</span></span><span id='textcolor2306'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, i, MAX_NR_CONSOLES,</span>
|
|
<a id='x1-51132r66'></a><span class='ecrm-0500'>66</span><span class='ectt-0800'> vc_cons[i].d->vc_num, (</span><span id='textcolor2307'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor2308'><span class='ectt-0800'>long</span></span><span class='ectt-0800'>) vc_cons[i].d->port.tty);</span>
|
|
<a id='x1-51134r67'></a><span class='ecrm-0500'>67</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-51136r68'></a><span class='ecrm-0500'>68</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2309'><span class='ectt-0800'>"kbleds: finished scanning consoles</span></span><span id='textcolor2310'><span class='ectt-0800'>\n</span></span><span id='textcolor2311'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-51138r69'></a><span class='ecrm-0500'>69</span>
|
|
<a id='x1-51140r70'></a><span class='ecrm-0500'>70</span><span class='ectt-0800'> my_driver = vc_cons[fg_console].d->port.tty->driver;</span>
|
|
<a id='x1-51142r71'></a><span class='ecrm-0500'>71</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2312'><span class='ectt-0800'>"kbleds: tty driver magic %x</span></span><span id='textcolor2313'><span class='ectt-0800'>\n</span></span><span id='textcolor2314'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, my_driver->magic);</span>
|
|
<a id='x1-51144r72'></a><span class='ecrm-0500'>72</span>
|
|
<a id='x1-51146r73'></a><span class='ecrm-0500'>73</span><span class='ectt-0800'> </span><span id='textcolor2315'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-51148r74'></a><span class='ecrm-0500'>74</span><span id='textcolor2316'><span class='ectt-0800'> * Set up the LED blink timer the first time</span></span>
|
|
<a id='x1-51150r75'></a><span class='ecrm-0500'>75</span><span id='textcolor2317'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-51152r76'></a><span class='ecrm-0500'>76</span><span class='ectt-0800'> timer_setup(&my_timer, (</span><span id='textcolor2318'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *) &my_timer_func,</span>
|
|
<a id='x1-51154r77'></a><span class='ecrm-0500'>77</span><span class='ectt-0800'> (</span><span id='textcolor2319'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor2320'><span class='ectt-0800'>long</span></span><span class='ectt-0800'>) &kbledstatus);</span>
|
|
<a id='x1-51156r78'></a><span class='ecrm-0500'>78</span><span class='ectt-0800'> my_timer.expires = jiffies + BLINK_DELAY;</span>
|
|
<a id='x1-51158r79'></a><span class='ecrm-0500'>79</span><span class='ectt-0800'> add_timer(&my_timer);</span>
|
|
<a id='x1-51160r80'></a><span class='ecrm-0500'>80</span>
|
|
<a id='x1-51162r81'></a><span class='ecrm-0500'>81</span><span class='ectt-0800'> </span><span id='textcolor2321'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-51164r82'></a><span class='ecrm-0500'>82</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-51166r83'></a><span class='ecrm-0500'>83</span>
|
|
<a id='x1-51168r84'></a><span class='ecrm-0500'>84</span><span id='textcolor2322'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2323'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> __exit kbleds_cleanup(</span><span id='textcolor2324'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-51170r85'></a><span class='ecrm-0500'>85</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-51172r86'></a><span class='ecrm-0500'>86</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2325'><span class='ectt-0800'>"kbleds: unloading...</span></span><span id='textcolor2326'><span class='ectt-0800'>\n</span></span><span id='textcolor2327'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-51174r87'></a><span class='ecrm-0500'>87</span><span class='ectt-0800'> del_timer(&my_timer);</span>
|
|
<a id='x1-51176r88'></a><span class='ecrm-0500'>88</span><span class='ectt-0800'> (my_driver->ops->ioctl)(vc_cons[fg_console].d->port.tty, KDSETLED,</span>
|
|
<a id='x1-51178r89'></a><span class='ecrm-0500'>89</span><span class='ectt-0800'> RESTORE_LEDS);</span>
|
|
<a id='x1-51180r90'></a><span class='ecrm-0500'>90</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-51182r91'></a><span class='ecrm-0500'>91</span>
|
|
<a id='x1-51184r92'></a><span class='ecrm-0500'>92</span><span class='ectt-0800'>module_init(kbleds_init);</span>
|
|
<a id='x1-51186r93'></a><span class='ecrm-0500'>93</span><span class='ectt-0800'>module_exit(kbleds_cleanup);</span></pre>
|
|
<!-- l. 1330 --><p class='indent'> If none of the examples in this chapter fit your debugging needs there might yet
|
|
be some other tricks to try. Ever wondered what CONFIG_LL_DEBUG in
|
|
make menuconfig is good for? If you activate that you get low level access
|
|
to the serial port. While this might not sound very powerful by itself, you
|
|
|
|
|
|
|
|
can patch <span class='ecbx-1000'>kernel/printk.c </span>or any other essential syscall to use printascii,
|
|
thus makeing it possible to trace virtually everything what your code does
|
|
over a serial line. If you find yourself porting the kernel to some new and
|
|
former unsupported architecture this is usually amongst the first things that
|
|
should be implemented. Logging over a netconsole might also be worth a
|
|
try.
|
|
</p><!-- l. 1332 --><p class='indent'> While you have seen lots of stuff that can be used to aid debugging here, there are
|
|
some things to be aware of. Debugging is almost always intrusive. Adding debug code
|
|
can change the situation enough to make the bug seem to dissappear. Thus you
|
|
should try to keep debug code to a minimum and make sure it does not show up in
|
|
production code.
|
|
</p><!-- l. 1334 --><p class='noindent'>
|
|
</p>
|
|
<h3 class='sectionHead' id='scheduling-tasks'><span class='titlemark'>0.14 </span> <a id='x1-520000.14'></a>Scheduling Tasks</h3>
|
|
<!-- l. 1336 --><p class='noindent'>There are two main ways of running tasks: tasklets and work queues. Tasklets are a
|
|
quick and easy way of scheduling a single function to be run, for example when
|
|
triggered from an interrupt, whereas work queues are more complicated but also
|
|
better suited to running multiple things in a sequence.
|
|
</p><!-- l. 1338 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='tasklets'><span class='titlemark'>0.14.1 </span> <a id='x1-530000.14.1'></a>Tasklets</h4>
|
|
<!-- l. 1340 --><p class='noindent'>Here’s an example tasklet module. The <span class='ecti-1000'>tasklet_fn </span>function runs for a few seconds
|
|
and in the mean time execution of the <span class='ecti-1000'>example_tasklet_init </span>function continues to
|
|
the exit point.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb62'><a id='x1-53002r1'></a><span class='ecrm-0500'>1</span><span id='textcolor2328'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-53004r2'></a><span class='ecrm-0500'>2</span><span id='textcolor2329'><span class='ectt-0800'> * example_tasklet.c</span></span>
|
|
<a id='x1-53006r3'></a><span class='ecrm-0500'>3</span><span id='textcolor2330'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-53008r4'></a><span class='ecrm-0500'>4</span><span id='textcolor2331'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2332'><span class='ectt-0800'><linux/delay.h></span></span>
|
|
<a id='x1-53010r5'></a><span class='ecrm-0500'>5</span><span id='textcolor2333'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2334'><span class='ectt-0800'><linux/interrupt.h></span></span>
|
|
<a id='x1-53012r6'></a><span class='ecrm-0500'>6</span><span id='textcolor2335'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2336'><span class='ectt-0800'><linux/kernel.h></span></span>
|
|
<a id='x1-53014r7'></a><span class='ecrm-0500'>7</span><span id='textcolor2337'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2338'><span class='ectt-0800'><linux/module.h></span></span>
|
|
<a id='x1-53016r8'></a><span class='ecrm-0500'>8</span>
|
|
<a id='x1-53018r9'></a><span class='ecrm-0500'>9</span><span id='textcolor2339'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2340'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> tasklet_fn(</span><span id='textcolor2341'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor2342'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> data)</span>
|
|
<a id='x1-53020r10'></a><span class='ecrm-0500'>10</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-53022r11'></a><span class='ecrm-0500'>11</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2343'><span class='ectt-0800'>"Example tasklet starts</span></span><span id='textcolor2344'><span class='ectt-0800'>\n</span></span><span id='textcolor2345'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-53024r12'></a><span class='ecrm-0500'>12</span><span class='ectt-0800'> mdelay(5000);</span>
|
|
<a id='x1-53026r13'></a><span class='ecrm-0500'>13</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2346'><span class='ectt-0800'>"Example tasklet ends</span></span><span id='textcolor2347'><span class='ectt-0800'>\n</span></span><span id='textcolor2348'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-53028r14'></a><span class='ecrm-0500'>14</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-53030r15'></a><span class='ecrm-0500'>15</span>
|
|
<a id='x1-53032r16'></a><span class='ecrm-0500'>16</span><span class='ectt-0800'>DECLARE_TASKLET(mytask, tasklet_fn, 0L);</span>
|
|
<a id='x1-53034r17'></a><span class='ecrm-0500'>17</span>
|
|
<a id='x1-53036r18'></a><span class='ecrm-0500'>18</span><span id='textcolor2349'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2350'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> example_tasklet_init(</span><span id='textcolor2351'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-53038r19'></a><span class='ecrm-0500'>19</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-53040r20'></a><span class='ecrm-0500'>20</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2352'><span class='ectt-0800'>"tasklet example init</span></span><span id='textcolor2353'><span class='ectt-0800'>\n</span></span><span id='textcolor2354'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-53042r21'></a><span class='ecrm-0500'>21</span><span class='ectt-0800'> tasklet_schedule(&mytask);</span>
|
|
<a id='x1-53044r22'></a><span class='ecrm-0500'>22</span><span class='ectt-0800'> mdelay(200);</span>
|
|
<a id='x1-53046r23'></a><span class='ecrm-0500'>23</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2355'><span class='ectt-0800'>"Example tasklet init continues...</span></span><span id='textcolor2356'><span class='ectt-0800'>\n</span></span><span id='textcolor2357'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-53048r24'></a><span class='ecrm-0500'>24</span><span class='ectt-0800'> </span><span id='textcolor2358'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-53050r25'></a><span class='ecrm-0500'>25</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-53052r26'></a><span class='ecrm-0500'>26</span>
|
|
<a id='x1-53054r27'></a><span class='ecrm-0500'>27</span><span id='textcolor2359'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2360'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> example_tasklet_exit(</span><span id='textcolor2361'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-53056r28'></a><span class='ecrm-0500'>28</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-53058r29'></a><span class='ecrm-0500'>29</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2362'><span class='ectt-0800'>"tasklet example exit</span></span><span id='textcolor2363'><span class='ectt-0800'>\n</span></span><span id='textcolor2364'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-53060r30'></a><span class='ecrm-0500'>30</span><span class='ectt-0800'> tasklet_kill(&mytask);</span>
|
|
<a id='x1-53062r31'></a><span class='ecrm-0500'>31</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-53064r32'></a><span class='ecrm-0500'>32</span>
|
|
<a id='x1-53066r33'></a><span class='ecrm-0500'>33</span><span class='ectt-0800'>module_init(example_tasklet_init);</span>
|
|
<a id='x1-53068r34'></a><span class='ecrm-0500'>34</span><span class='ectt-0800'>module_exit(example_tasklet_exit);</span>
|
|
<a id='x1-53070r35'></a><span class='ecrm-0500'>35</span>
|
|
<a id='x1-53072r36'></a><span class='ecrm-0500'>36</span><span class='ectt-0800'>MODULE_DESCRIPTION(</span><span id='textcolor2365'><span class='ectt-0800'>"Tasklet example"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-53074r37'></a><span class='ecrm-0500'>37</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor2366'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
|
|
<!-- l. 1344 --><p class='indent'> So with this example loaded <span class='ecti-1000'>dmesg </span>should show:
|
|
|
|
|
|
|
|
</p>
|
|
<pre class='verbatim' id='verbatim-12'>
|
|
tasklet example init
|
|
Example tasklet starts
|
|
Example tasklet init continues...
|
|
Example tasklet ends
|
|
</pre>
|
|
<!-- l. 1351 --><p class='nopar'>
|
|
</p><!-- l. 1353 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='work-queues'><span class='titlemark'>0.14.2 </span> <a id='x1-540000.14.2'></a>Work queues</h4>
|
|
<!-- l. 1355 --><p class='noindent'>To add a task to the scheduler we can use a workqueue. The kernel then uses the
|
|
Completely Fair Scheduler (CFS) to execute work within the queue.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb63'><a id='x1-54002r1'></a><span class='ecrm-0500'>1</span><span id='textcolor2367'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-54004r2'></a><span class='ecrm-0500'>2</span><span id='textcolor2368'><span class='ectt-0800'> * sched.c</span></span>
|
|
<a id='x1-54006r3'></a><span class='ecrm-0500'>3</span><span id='textcolor2369'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-54008r4'></a><span class='ecrm-0500'>4</span><span id='textcolor2370'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2371'><span class='ectt-0800'><linux/init.h></span></span>
|
|
<a id='x1-54010r5'></a><span class='ecrm-0500'>5</span><span id='textcolor2372'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2373'><span class='ectt-0800'><linux/module.h></span></span>
|
|
<a id='x1-54012r6'></a><span class='ecrm-0500'>6</span><span id='textcolor2374'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2375'><span class='ectt-0800'><linux/workqueue.h></span></span>
|
|
<a id='x1-54014r7'></a><span class='ecrm-0500'>7</span>
|
|
<a id='x1-54016r8'></a><span class='ecrm-0500'>8</span><span id='textcolor2376'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2377'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> workqueue_struct *queue = NULL;</span>
|
|
<a id='x1-54018r9'></a><span class='ecrm-0500'>9</span><span id='textcolor2378'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2379'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> work_struct work;</span>
|
|
<a id='x1-54020r10'></a><span class='ecrm-0500'>10</span>
|
|
<a id='x1-54022r11'></a><span class='ecrm-0500'>11</span><span id='textcolor2380'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2381'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> work_handler(</span><span id='textcolor2382'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> work_struct *data)</span>
|
|
<a id='x1-54024r12'></a><span class='ecrm-0500'>12</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-54026r13'></a><span class='ecrm-0500'>13</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2383'><span class='ectt-0800'>"work handler function.</span></span><span id='textcolor2384'><span class='ectt-0800'>\n</span></span><span id='textcolor2385'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-54028r14'></a><span class='ecrm-0500'>14</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-54030r15'></a><span class='ecrm-0500'>15</span>
|
|
<a id='x1-54032r16'></a><span class='ecrm-0500'>16</span><span id='textcolor2386'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> init_module()</span>
|
|
<a id='x1-54034r17'></a><span class='ecrm-0500'>17</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-54036r18'></a><span class='ecrm-0500'>18</span><span class='ectt-0800'> queue = alloc_workqueue(</span><span id='textcolor2387'><span class='ectt-0800'>"HELLOWORLD"</span></span><span class='ectt-0800'>, WQ_UNBOUND, 1);</span>
|
|
<a id='x1-54038r19'></a><span class='ecrm-0500'>19</span><span class='ectt-0800'> INIT_WORK(&work, work_handler);</span>
|
|
<a id='x1-54040r20'></a><span class='ecrm-0500'>20</span><span class='ectt-0800'> schedule_work(&work);</span>
|
|
<a id='x1-54042r21'></a><span class='ecrm-0500'>21</span>
|
|
<a id='x1-54044r22'></a><span class='ecrm-0500'>22</span><span class='ectt-0800'> </span><span id='textcolor2388'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-54046r23'></a><span class='ecrm-0500'>23</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-54048r24'></a><span class='ecrm-0500'>24</span>
|
|
<a id='x1-54050r25'></a><span class='ecrm-0500'>25</span><span id='textcolor2389'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> cleanup_module()</span>
|
|
<a id='x1-54052r26'></a><span class='ecrm-0500'>26</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-54054r27'></a><span class='ecrm-0500'>27</span><span class='ectt-0800'> destroy_workqueue(queue);</span>
|
|
<a id='x1-54056r28'></a><span class='ecrm-0500'>28</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-54058r29'></a><span class='ecrm-0500'>29</span>
|
|
<a id='x1-54060r30'></a><span class='ecrm-0500'>30</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor2390'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-54062r31'></a><span class='ecrm-0500'>31</span><span class='ectt-0800'>MODULE_DESCRIPTION(</span><span id='textcolor2391'><span class='ectt-0800'>"Workqueue example"</span></span><span class='ectt-0800'>);</span></pre>
|
|
<!-- l. 1359 --><p class='noindent'>
|
|
</p>
|
|
<h3 class='sectionHead' id='interrupt-handlers'><span class='titlemark'>0.15 </span> <a id='x1-550000.15'></a>Interrupt Handlers</h3>
|
|
<!-- l. 1361 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='interrupt-handlers1'><span class='titlemark'>0.15.1 </span> <a id='x1-560000.15.1'></a>Interrupt Handlers</h4>
|
|
<!-- l. 1363 --><p class='noindent'>Except for the last chapter, everything we did in the kernel so far we’ve done as a
|
|
response to a process asking for it, either by dealing with a special file, sending an
|
|
ioctl(), or issuing a system call. But the job of the kernel isn’t just to respond to
|
|
process requests. Another job, which is every bit as important, is to speak to the
|
|
hardware connected to the machine.
|
|
</p><!-- l. 1365 --><p class='indent'> There are two types of interaction between the CPU and the rest of the
|
|
computer’s hardware. The first type is when the CPU gives orders to the hardware,
|
|
the other is when the hardware needs to tell the CPU something. The second, called
|
|
interrupts, is much harder to implement because it has to be dealt with when
|
|
convenient for the hardware, not the CPU. Hardware devices typically have a very
|
|
small amount of RAM, and if you don’t read their information when available, it is
|
|
lost.
|
|
|
|
|
|
|
|
</p><!-- l. 1367 --><p class='indent'> Under Linux, hardware interrupts are called IRQ’s (Interrupt ReQuests). There
|
|
are two types of IRQ’s, short and long. A short IRQ is one which is expected to take
|
|
a very short period of time, during which the rest of the machine will be blocked and
|
|
no other interrupts will be handled. A long IRQ is one which can take longer, and
|
|
during which other interrupts may occur (but not interrupts from the same
|
|
device). If at all possible, it’s better to declare an interrupt handler to be
|
|
long.
|
|
</p><!-- l. 1369 --><p class='indent'> When the CPU receives an interrupt, it stops whatever it’s doing (unless it’s
|
|
processing a more important interrupt, in which case it will deal with this one
|
|
only when the more important one is done), saves certain parameters on
|
|
the stack and calls the interrupt handler. This means that certain things
|
|
are not allowed in the interrupt handler itself, because the system is in an
|
|
unknown state. The solution to this problem is for the interrupt handler to
|
|
do what needs to be done immediately, usually read something from the
|
|
hardware or send something to the hardware, and then schedule the handling of
|
|
the new information at a later time (this is called the "bottom half") and
|
|
return. The kernel is then guaranteed to call the bottom half as soon as
|
|
possible – and when it does, everything allowed in kernel modules will be
|
|
allowed.
|
|
</p><!-- l. 1371 --><p class='indent'> The way to implement this is to call <span class='ecbx-1000'>request_irq() </span>to get your interrupt handler
|
|
called when the relevant IRQ is received.
|
|
</p><!-- l. 1373 --><p class='indent'> In practice IRQ handling can be a bit more complex. Hardware is often
|
|
designed in a way that chains two interrupt controllers, so that all the IRQs
|
|
from interrupt controller B are cascaded to a certain IRQ from interrupt
|
|
controller A. Of course that requires that the kernel finds out which IRQ it
|
|
really was afterwards and that adds overhead. Other architectures offer some
|
|
special, very low overhead, so called "fast IRQ" or FIQs. To take advantage of
|
|
them requires handlers to be written in assembler, so they do not really fit
|
|
into the kernel. They can be made to work similar to the others, but after
|
|
that procedure, they’re no longer any faster than "common" IRQs. SMP
|
|
enabled kernels running on systems with more than one processor need to solve
|
|
another truckload of problems. It’s not enough to know if a certain IRQs
|
|
has happend, it’s also important for what CPU(s) it was for. People still
|
|
interested in more details, might want to do a web search for "APIC" now
|
|
;)
|
|
</p><!-- l. 1375 --><p class='indent'> This function receives the IRQ number, the name of the function, flags, a name
|
|
for /proc/interrupts and a parameter to pass to the interrupt handler. Usually
|
|
there is a certain number of IRQs available. How many IRQs there are is
|
|
hardware-dependent. The flags can include SA_SHIRQ to indicate you’re willing to
|
|
share the IRQ with other interrupt handlers (usually because a number of hardware
|
|
devices sit on the same IRQ) and SA_INTERRUPT to indicate this is a fast
|
|
interrupt. This function will only succeed if there isn’t already a handler on this IRQ,
|
|
or if you’re both willing to share.
|
|
|
|
|
|
|
|
</p><!-- l. 1377 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='detecting-button-presses'><span class='titlemark'>0.15.2 </span> <a id='x1-570000.15.2'></a>Detecting button presses</h4>
|
|
<!-- l. 1379 --><p class='noindent'>Many popular single board computers, such as Raspberry Pis or Beagleboards, have
|
|
a bunch of GPIO pins. Attaching buttons to those and then having a button press do
|
|
something is a classic case in which you might need to use interrupts so that instead
|
|
of having the CPU waste time and battery power polling for a change in input state
|
|
it’s better for the input to trigger the CPU to then run a particular handling
|
|
function.
|
|
</p><!-- l. 1381 --><p class='indent'> Here’s an example where buttons are connected to GPIO numbers 17 and 18 and
|
|
an LED is connected to GPIO 4. You can change those numbers to whatever is
|
|
appropriate for your board.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb64'><a id='x1-57002r1'></a><span class='ecrm-0500'>1</span><span id='textcolor2392'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-57004r2'></a><span class='ecrm-0500'>2</span><span id='textcolor2393'><span class='ectt-0800'> * intrpt.c - Handling GPIO with interrupts</span></span>
|
|
<a id='x1-57006r3'></a><span class='ecrm-0500'>3</span><span id='textcolor2394'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-57008r4'></a><span class='ecrm-0500'>4</span><span id='textcolor2395'><span class='ectt-0800'> * Based upon the RPi example by Stefan Wendler (devnull@kaltpost.de)</span></span>
|
|
<a id='x1-57010r5'></a><span class='ecrm-0500'>5</span><span id='textcolor2396'><span class='ectt-0800'> * from:</span></span>
|
|
<a id='x1-57012r6'></a><span class='ecrm-0500'>6</span><span id='textcolor2397'><span class='ectt-0800'> * https://github.com/wendlers/rpi-kmod-samples</span></span>
|
|
<a id='x1-57014r7'></a><span class='ecrm-0500'>7</span><span id='textcolor2398'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-57016r8'></a><span class='ecrm-0500'>8</span><span id='textcolor2399'><span class='ectt-0800'> * Press one button to turn on a LED and another to turn it off</span></span>
|
|
<a id='x1-57018r9'></a><span class='ecrm-0500'>9</span><span id='textcolor2400'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-57020r10'></a><span class='ecrm-0500'>10</span>
|
|
<a id='x1-57022r11'></a><span class='ecrm-0500'>11</span><span id='textcolor2401'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2402'><span class='ectt-0800'><linux/gpio.h></span></span>
|
|
<a id='x1-57024r12'></a><span class='ecrm-0500'>12</span><span id='textcolor2403'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2404'><span class='ectt-0800'><linux/interrupt.h></span></span>
|
|
<a id='x1-57026r13'></a><span class='ecrm-0500'>13</span><span id='textcolor2405'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2406'><span class='ectt-0800'><linux/kernel.h></span></span>
|
|
<a id='x1-57028r14'></a><span class='ecrm-0500'>14</span><span id='textcolor2407'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2408'><span class='ectt-0800'><linux/module.h></span></span>
|
|
<a id='x1-57030r15'></a><span class='ecrm-0500'>15</span>
|
|
<a id='x1-57032r16'></a><span class='ecrm-0500'>16</span><span id='textcolor2409'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2410'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> button_irqs[] = {-1, -1};</span>
|
|
<a id='x1-57034r17'></a><span class='ecrm-0500'>17</span>
|
|
<a id='x1-57036r18'></a><span class='ecrm-0500'>18</span><span id='textcolor2411'><span class='ectt-0800'>/* Define GPIOs for LEDs.</span></span>
|
|
<a id='x1-57038r19'></a><span class='ecrm-0500'>19</span><span id='textcolor2412'><span class='ectt-0800'> Change the numbers for the GPIO on your board. */</span></span>
|
|
<a id='x1-57040r20'></a><span class='ecrm-0500'>20</span><span id='textcolor2413'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2414'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> gpio leds[] = {{4, GPIOF_OUT_INIT_LOW, </span><span id='textcolor2415'><span class='ectt-0800'>"LED 1"</span></span><span class='ectt-0800'>}};</span>
|
|
<a id='x1-57042r21'></a><span class='ecrm-0500'>21</span>
|
|
<a id='x1-57044r22'></a><span class='ecrm-0500'>22</span><span id='textcolor2416'><span class='ectt-0800'>/* Define GPIOs for BUTTONS</span></span>
|
|
<a id='x1-57046r23'></a><span class='ecrm-0500'>23</span><span id='textcolor2417'><span class='ectt-0800'> Change the numbers for the GPIO on your board. */</span></span>
|
|
<a id='x1-57048r24'></a><span class='ecrm-0500'>24</span><span id='textcolor2418'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2419'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> gpio buttons[] = {{17, GPIOF_IN, </span><span id='textcolor2420'><span class='ectt-0800'>"LED 1 ON BUTTON"</span></span><span class='ectt-0800'>},</span>
|
|
<a id='x1-57050r25'></a><span class='ecrm-0500'>25</span><span class='ectt-0800'> {18, GPIOF_IN, </span><span id='textcolor2421'><span class='ectt-0800'>"LED 1 OFF BUTTON"</span></span><span class='ectt-0800'>}};</span>
|
|
<a id='x1-57052r26'></a><span class='ecrm-0500'>26</span>
|
|
<a id='x1-57054r27'></a><span class='ecrm-0500'>27</span><span id='textcolor2422'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-57056r28'></a><span class='ecrm-0500'>28</span><span id='textcolor2423'><span class='ectt-0800'> * interrupt function triggered when a button is pressed</span></span>
|
|
<a id='x1-57058r29'></a><span class='ecrm-0500'>29</span><span id='textcolor2424'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-57060r30'></a><span class='ecrm-0500'>30</span><span id='textcolor2425'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> irqreturn_t button_isr(</span><span id='textcolor2426'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> irq, </span><span id='textcolor2427'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *data)</span>
|
|
<a id='x1-57062r31'></a><span class='ecrm-0500'>31</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-57064r32'></a><span class='ecrm-0500'>32</span><span class='ectt-0800'> </span><span id='textcolor2428'><span class='ectt-0800'>/* first button */</span></span>
|
|
<a id='x1-57066r33'></a><span class='ecrm-0500'>33</span><span class='ectt-0800'> </span><span id='textcolor2429'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (irq == button_irqs[0] && !gpio_get_value(leds[0].gpio))</span>
|
|
<a id='x1-57068r34'></a><span class='ecrm-0500'>34</span><span class='ectt-0800'> gpio_set_value(leds[0].gpio, 1);</span>
|
|
<a id='x1-57070r35'></a><span class='ecrm-0500'>35</span><span class='ectt-0800'> </span><span id='textcolor2430'><span class='ectt-0800'>/* second button */</span></span>
|
|
<a id='x1-57072r36'></a><span class='ecrm-0500'>36</span><span class='ectt-0800'> </span><span id='textcolor2431'><span class='ectt-0800'>else</span></span><span class='ectt-0800'> </span><span id='textcolor2432'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (irq == button_irqs[1] && gpio_get_value(leds[0].gpio))</span>
|
|
<a id='x1-57074r37'></a><span class='ecrm-0500'>37</span><span class='ectt-0800'> gpio_set_value(leds[0].gpio, 0);</span>
|
|
<a id='x1-57076r38'></a><span class='ecrm-0500'>38</span>
|
|
<a id='x1-57078r39'></a><span class='ecrm-0500'>39</span><span class='ectt-0800'> </span><span id='textcolor2433'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> IRQ_HANDLED;</span>
|
|
<a id='x1-57080r40'></a><span class='ecrm-0500'>40</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-57082r41'></a><span class='ecrm-0500'>41</span>
|
|
<a id='x1-57084r42'></a><span class='ecrm-0500'>42</span><span id='textcolor2434'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> init_module()</span>
|
|
<a id='x1-57086r43'></a><span class='ecrm-0500'>43</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-57088r44'></a><span class='ecrm-0500'>44</span><span class='ectt-0800'> </span><span id='textcolor2435'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> ret = 0;</span>
|
|
<a id='x1-57090r45'></a><span class='ecrm-0500'>45</span>
|
|
<a id='x1-57092r46'></a><span class='ecrm-0500'>46</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2436'><span class='ectt-0800'>"%s</span></span><span id='textcolor2437'><span class='ectt-0800'>\n</span></span><span id='textcolor2438'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, __func__);</span>
|
|
<a id='x1-57094r47'></a><span class='ecrm-0500'>47</span>
|
|
<a id='x1-57096r48'></a><span class='ecrm-0500'>48</span><span class='ectt-0800'> </span><span id='textcolor2439'><span class='ectt-0800'>/* register LED gpios */</span></span>
|
|
<a id='x1-57098r49'></a><span class='ecrm-0500'>49</span><span class='ectt-0800'> ret = gpio_request_array(leds, ARRAY_SIZE(leds));</span>
|
|
<a id='x1-57100r50'></a><span class='ecrm-0500'>50</span>
|
|
<a id='x1-57102r51'></a><span class='ecrm-0500'>51</span><span class='ectt-0800'> </span><span id='textcolor2440'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (ret) {</span>
|
|
<a id='x1-57104r52'></a><span class='ecrm-0500'>52</span><span class='ectt-0800'> pr_err(</span><span id='textcolor2441'><span class='ectt-0800'>"Unable to request GPIOs for LEDs: %d</span></span><span id='textcolor2442'><span class='ectt-0800'>\n</span></span><span id='textcolor2443'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, ret);</span>
|
|
<a id='x1-57106r53'></a><span class='ecrm-0500'>53</span><span class='ectt-0800'> </span><span id='textcolor2444'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> ret;</span>
|
|
<a id='x1-57108r54'></a><span class='ecrm-0500'>54</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-57110r55'></a><span class='ecrm-0500'>55</span>
|
|
<a id='x1-57112r56'></a><span class='ecrm-0500'>56</span><span class='ectt-0800'> </span><span id='textcolor2445'><span class='ectt-0800'>/* register BUTTON gpios */</span></span>
|
|
<a id='x1-57114r57'></a><span class='ecrm-0500'>57</span><span class='ectt-0800'> ret = gpio_request_array(buttons, ARRAY_SIZE(buttons));</span>
|
|
<a id='x1-57116r58'></a><span class='ecrm-0500'>58</span>
|
|
<a id='x1-57118r59'></a><span class='ecrm-0500'>59</span><span class='ectt-0800'> </span><span id='textcolor2446'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (ret) {</span>
|
|
<a id='x1-57120r60'></a><span class='ecrm-0500'>60</span><span class='ectt-0800'> pr_err(</span><span id='textcolor2447'><span class='ectt-0800'>"Unable to request GPIOs for BUTTONs: %d</span></span><span id='textcolor2448'><span class='ectt-0800'>\n</span></span><span id='textcolor2449'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, ret);</span>
|
|
<a id='x1-57122r61'></a><span class='ecrm-0500'>61</span><span class='ectt-0800'> </span><span id='textcolor2450'><span class='ectt-0800'>goto</span></span><span class='ectt-0800'> fail1;</span>
|
|
<a id='x1-57124r62'></a><span class='ecrm-0500'>62</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-57126r63'></a><span class='ecrm-0500'>63</span>
|
|
<a id='x1-57128r64'></a><span class='ecrm-0500'>64</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2451'><span class='ectt-0800'>"Current button1 value: %d</span></span><span id='textcolor2452'><span class='ectt-0800'>\n</span></span><span id='textcolor2453'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, gpio_get_value(buttons[0].gpio));</span>
|
|
<a id='x1-57130r65'></a><span class='ecrm-0500'>65</span>
|
|
<a id='x1-57132r66'></a><span class='ecrm-0500'>66</span><span class='ectt-0800'> ret = gpio_to_irq(buttons[0].gpio);</span>
|
|
<a id='x1-57134r67'></a><span class='ecrm-0500'>67</span>
|
|
<a id='x1-57136r68'></a><span class='ecrm-0500'>68</span><span class='ectt-0800'> </span><span id='textcolor2454'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (ret < 0) {</span>
|
|
<a id='x1-57138r69'></a><span class='ecrm-0500'>69</span><span class='ectt-0800'> pr_err(</span><span id='textcolor2455'><span class='ectt-0800'>"Unable to request IRQ: %d</span></span><span id='textcolor2456'><span class='ectt-0800'>\n</span></span><span id='textcolor2457'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, ret);</span>
|
|
<a id='x1-57140r70'></a><span class='ecrm-0500'>70</span><span class='ectt-0800'> </span><span id='textcolor2458'><span class='ectt-0800'>goto</span></span><span class='ectt-0800'> fail2;</span>
|
|
<a id='x1-57142r71'></a><span class='ecrm-0500'>71</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-57144r72'></a><span class='ecrm-0500'>72</span>
|
|
<a id='x1-57146r73'></a><span class='ecrm-0500'>73</span><span class='ectt-0800'> button_irqs[0] = ret;</span>
|
|
<a id='x1-57148r74'></a><span class='ecrm-0500'>74</span>
|
|
<a id='x1-57150r75'></a><span class='ecrm-0500'>75</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2459'><span class='ectt-0800'>"Successfully requested BUTTON1 IRQ # %d</span></span><span id='textcolor2460'><span class='ectt-0800'>\n</span></span><span id='textcolor2461'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, button_irqs[0]);</span>
|
|
<a id='x1-57152r76'></a><span class='ecrm-0500'>76</span>
|
|
<a id='x1-57154r77'></a><span class='ecrm-0500'>77</span><span class='ectt-0800'> ret = request_irq(button_irqs[0], button_isr,</span>
|
|
<a id='x1-57156r78'></a><span class='ecrm-0500'>78</span><span class='ectt-0800'> IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,</span>
|
|
<a id='x1-57158r79'></a><span class='ecrm-0500'>79</span><span class='ectt-0800'> </span><span id='textcolor2462'><span class='ectt-0800'>"gpiomod#button1"</span></span><span class='ectt-0800'>, NULL);</span>
|
|
<a id='x1-57160r80'></a><span class='ecrm-0500'>80</span>
|
|
<a id='x1-57162r81'></a><span class='ecrm-0500'>81</span><span class='ectt-0800'> </span><span id='textcolor2463'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (ret) {</span>
|
|
<a id='x1-57164r82'></a><span class='ecrm-0500'>82</span><span class='ectt-0800'> pr_err(</span><span id='textcolor2464'><span class='ectt-0800'>"Unable to request IRQ: %d</span></span><span id='textcolor2465'><span class='ectt-0800'>\n</span></span><span id='textcolor2466'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, ret);</span>
|
|
<a id='x1-57166r83'></a><span class='ecrm-0500'>83</span><span class='ectt-0800'> </span><span id='textcolor2467'><span class='ectt-0800'>goto</span></span><span class='ectt-0800'> fail2;</span>
|
|
<a id='x1-57168r84'></a><span class='ecrm-0500'>84</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-57170r85'></a><span class='ecrm-0500'>85</span>
|
|
<a id='x1-57172r86'></a><span class='ecrm-0500'>86</span>
|
|
<a id='x1-57174r87'></a><span class='ecrm-0500'>87</span><span class='ectt-0800'> ret = gpio_to_irq(buttons[1].gpio);</span>
|
|
<a id='x1-57176r88'></a><span class='ecrm-0500'>88</span>
|
|
<a id='x1-57178r89'></a><span class='ecrm-0500'>89</span><span class='ectt-0800'> </span><span id='textcolor2468'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (ret < 0) {</span>
|
|
<a id='x1-57180r90'></a><span class='ecrm-0500'>90</span><span class='ectt-0800'> pr_err(</span><span id='textcolor2469'><span class='ectt-0800'>"Unable to request IRQ: %d</span></span><span id='textcolor2470'><span class='ectt-0800'>\n</span></span><span id='textcolor2471'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, ret);</span>
|
|
<a id='x1-57182r91'></a><span class='ecrm-0500'>91</span><span class='ectt-0800'> </span><span id='textcolor2472'><span class='ectt-0800'>goto</span></span><span class='ectt-0800'> fail2;</span>
|
|
<a id='x1-57184r92'></a><span class='ecrm-0500'>92</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-57186r93'></a><span class='ecrm-0500'>93</span>
|
|
<a id='x1-57188r94'></a><span class='ecrm-0500'>94</span><span class='ectt-0800'> button_irqs[1] = ret;</span>
|
|
<a id='x1-57190r95'></a><span class='ecrm-0500'>95</span>
|
|
<a id='x1-57192r96'></a><span class='ecrm-0500'>96</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2473'><span class='ectt-0800'>"Successfully requested BUTTON2 IRQ # %d</span></span><span id='textcolor2474'><span class='ectt-0800'>\n</span></span><span id='textcolor2475'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, button_irqs[1]);</span>
|
|
<a id='x1-57194r97'></a><span class='ecrm-0500'>97</span>
|
|
<a id='x1-57196r98'></a><span class='ecrm-0500'>98</span><span class='ectt-0800'> ret = request_irq(button_irqs[1], button_isr,</span>
|
|
<a id='x1-57198r99'></a><span class='ecrm-0500'>99</span><span class='ectt-0800'> IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,</span>
|
|
<a id='x1-57200r100'></a><span class='ecrm-0500'>100</span><span class='ectt-0800'> </span><span id='textcolor2476'><span class='ectt-0800'>"gpiomod#button2"</span></span><span class='ectt-0800'>, NULL);</span>
|
|
<a id='x1-57202r101'></a><span class='ecrm-0500'>101</span>
|
|
<a id='x1-57204r102'></a><span class='ecrm-0500'>102</span><span class='ectt-0800'> </span><span id='textcolor2477'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (ret) {</span>
|
|
<a id='x1-57206r103'></a><span class='ecrm-0500'>103</span><span class='ectt-0800'> pr_err(</span><span id='textcolor2478'><span class='ectt-0800'>"Unable to request IRQ: %d</span></span><span id='textcolor2479'><span class='ectt-0800'>\n</span></span><span id='textcolor2480'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, ret);</span>
|
|
<a id='x1-57208r104'></a><span class='ecrm-0500'>104</span><span class='ectt-0800'> </span><span id='textcolor2481'><span class='ectt-0800'>goto</span></span><span class='ectt-0800'> fail3;</span>
|
|
<a id='x1-57210r105'></a><span class='ecrm-0500'>105</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-57212r106'></a><span class='ecrm-0500'>106</span>
|
|
<a id='x1-57214r107'></a><span class='ecrm-0500'>107</span><span class='ectt-0800'> </span><span id='textcolor2482'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-57216r108'></a><span class='ecrm-0500'>108</span>
|
|
<a id='x1-57218r109'></a><span class='ecrm-0500'>109</span><span id='textcolor2483'><span class='ectt-0800'>/* cleanup what has been setup so far */</span></span>
|
|
<a id='x1-57220r110'></a><span class='ecrm-0500'>110</span><span class='ectt-0800'>fail3:</span>
|
|
<a id='x1-57222r111'></a><span class='ecrm-0500'>111</span><span class='ectt-0800'> free_irq(button_irqs[0], NULL);</span>
|
|
<a id='x1-57224r112'></a><span class='ecrm-0500'>112</span>
|
|
<a id='x1-57226r113'></a><span class='ecrm-0500'>113</span><span class='ectt-0800'>fail2:</span>
|
|
<a id='x1-57228r114'></a><span class='ecrm-0500'>114</span><span class='ectt-0800'> gpio_free_array(buttons, ARRAY_SIZE(leds));</span>
|
|
<a id='x1-57230r115'></a><span class='ecrm-0500'>115</span>
|
|
<a id='x1-57232r116'></a><span class='ecrm-0500'>116</span><span class='ectt-0800'>fail1:</span>
|
|
<a id='x1-57234r117'></a><span class='ecrm-0500'>117</span><span class='ectt-0800'> gpio_free_array(leds, ARRAY_SIZE(leds));</span>
|
|
<a id='x1-57236r118'></a><span class='ecrm-0500'>118</span>
|
|
<a id='x1-57238r119'></a><span class='ecrm-0500'>119</span><span class='ectt-0800'> </span><span id='textcolor2484'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> ret;</span>
|
|
<a id='x1-57240r120'></a><span class='ecrm-0500'>120</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-57242r121'></a><span class='ecrm-0500'>121</span>
|
|
<a id='x1-57244r122'></a><span class='ecrm-0500'>122</span><span id='textcolor2485'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> cleanup_module()</span>
|
|
<a id='x1-57246r123'></a><span class='ecrm-0500'>123</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-57248r124'></a><span class='ecrm-0500'>124</span><span class='ectt-0800'> </span><span id='textcolor2486'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> i;</span>
|
|
<a id='x1-57250r125'></a><span class='ecrm-0500'>125</span>
|
|
<a id='x1-57252r126'></a><span class='ecrm-0500'>126</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2487'><span class='ectt-0800'>"%s</span></span><span id='textcolor2488'><span class='ectt-0800'>\n</span></span><span id='textcolor2489'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, __func__);</span>
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|
<a id='x1-57254r127'></a><span class='ecrm-0500'>127</span>
|
|
<a id='x1-57256r128'></a><span class='ecrm-0500'>128</span><span class='ectt-0800'> </span><span id='textcolor2490'><span class='ectt-0800'>/* free irqs */</span></span>
|
|
<a id='x1-57258r129'></a><span class='ecrm-0500'>129</span><span class='ectt-0800'> free_irq(button_irqs[0], NULL);</span>
|
|
<a id='x1-57260r130'></a><span class='ecrm-0500'>130</span><span class='ectt-0800'> free_irq(button_irqs[1], NULL);</span>
|
|
<a id='x1-57262r131'></a><span class='ecrm-0500'>131</span>
|
|
<a id='x1-57264r132'></a><span class='ecrm-0500'>132</span><span class='ectt-0800'> </span><span id='textcolor2491'><span class='ectt-0800'>/* turn all LEDs off */</span></span>
|
|
<a id='x1-57266r133'></a><span class='ecrm-0500'>133</span><span class='ectt-0800'> </span><span id='textcolor2492'><span class='ectt-0800'>for</span></span><span class='ectt-0800'> (i = 0; i < ARRAY_SIZE(leds); i++)</span>
|
|
<a id='x1-57268r134'></a><span class='ecrm-0500'>134</span><span class='ectt-0800'> gpio_set_value(leds[i].gpio, 0);</span>
|
|
<a id='x1-57270r135'></a><span class='ecrm-0500'>135</span>
|
|
<a id='x1-57272r136'></a><span class='ecrm-0500'>136</span><span class='ectt-0800'> </span><span id='textcolor2493'><span class='ectt-0800'>/* unregister */</span></span>
|
|
<a id='x1-57274r137'></a><span class='ecrm-0500'>137</span><span class='ectt-0800'> gpio_free_array(leds, ARRAY_SIZE(leds));</span>
|
|
<a id='x1-57276r138'></a><span class='ecrm-0500'>138</span><span class='ectt-0800'> gpio_free_array(buttons, ARRAY_SIZE(buttons));</span>
|
|
<a id='x1-57278r139'></a><span class='ecrm-0500'>139</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-57280r140'></a><span class='ecrm-0500'>140</span>
|
|
<a id='x1-57282r141'></a><span class='ecrm-0500'>141</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor2494'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-57284r142'></a><span class='ecrm-0500'>142</span><span class='ectt-0800'>MODULE_DESCRIPTION(</span><span id='textcolor2495'><span class='ectt-0800'>"Handle some GPIO interrupts"</span></span><span class='ectt-0800'>);</span></pre>
|
|
<!-- l. 1385 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='bottom-half'><span class='titlemark'>0.15.3 </span> <a id='x1-580000.15.3'></a>Bottom Half</h4>
|
|
<!-- l. 1387 --><p class='noindent'>Suppose you want to do a bunch of stuff inside of an interrupt routine. A common
|
|
way to do that without rendering the interrupt unavailable for a significant duration
|
|
is to combine it with a tasklet. This pushes the bulk of the work off into the
|
|
scheduler.
|
|
</p><!-- l. 1389 --><p class='indent'> The example below modifies the previous example to also run an additional task
|
|
when an interrupt is triggered.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb65'><a id='x1-58002r1'></a><span class='ecrm-0500'>1</span><span id='textcolor2496'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-58004r2'></a><span class='ecrm-0500'>2</span><span id='textcolor2497'><span class='ectt-0800'> * bottomhalf.c - Top and bottom half interrupt handling</span></span>
|
|
<a id='x1-58006r3'></a><span class='ecrm-0500'>3</span><span id='textcolor2498'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-58008r4'></a><span class='ecrm-0500'>4</span><span id='textcolor2499'><span class='ectt-0800'> * Based upon the RPi example by Stefan Wendler (devnull@kaltpost.de)</span></span>
|
|
<a id='x1-58010r5'></a><span class='ecrm-0500'>5</span><span id='textcolor2500'><span class='ectt-0800'> * from:</span></span>
|
|
<a id='x1-58012r6'></a><span class='ecrm-0500'>6</span><span id='textcolor2501'><span class='ectt-0800'> * https://github.com/wendlers/rpi-kmod-samples</span></span>
|
|
<a id='x1-58014r7'></a><span class='ecrm-0500'>7</span><span id='textcolor2502'><span class='ectt-0800'> *</span></span>
|
|
<a id='x1-58016r8'></a><span class='ecrm-0500'>8</span><span id='textcolor2503'><span class='ectt-0800'> * Press one button to turn on a LED and another to turn it off</span></span>
|
|
<a id='x1-58018r9'></a><span class='ecrm-0500'>9</span><span id='textcolor2504'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-58020r10'></a><span class='ecrm-0500'>10</span>
|
|
<a id='x1-58022r11'></a><span class='ecrm-0500'>11</span><span id='textcolor2505'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2506'><span class='ectt-0800'><linux/delay.h></span></span>
|
|
<a id='x1-58024r12'></a><span class='ecrm-0500'>12</span><span id='textcolor2507'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2508'><span class='ectt-0800'><linux/gpio.h></span></span>
|
|
<a id='x1-58026r13'></a><span class='ecrm-0500'>13</span><span id='textcolor2509'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2510'><span class='ectt-0800'><linux/interrupt.h></span></span>
|
|
<a id='x1-58028r14'></a><span class='ecrm-0500'>14</span><span id='textcolor2511'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2512'><span class='ectt-0800'><linux/kernel.h></span></span>
|
|
<a id='x1-58030r15'></a><span class='ecrm-0500'>15</span><span id='textcolor2513'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2514'><span class='ectt-0800'><linux/module.h></span></span>
|
|
<a id='x1-58032r16'></a><span class='ecrm-0500'>16</span>
|
|
<a id='x1-58034r17'></a><span class='ecrm-0500'>17</span><span id='textcolor2515'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2516'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> button_irqs[] = {-1, -1};</span>
|
|
<a id='x1-58036r18'></a><span class='ecrm-0500'>18</span>
|
|
<a id='x1-58038r19'></a><span class='ecrm-0500'>19</span><span id='textcolor2517'><span class='ectt-0800'>/* Define GPIOs for LEDs.</span></span>
|
|
<a id='x1-58040r20'></a><span class='ecrm-0500'>20</span><span id='textcolor2518'><span class='ectt-0800'> Change the numbers for the GPIO on your board. */</span></span>
|
|
<a id='x1-58042r21'></a><span class='ecrm-0500'>21</span><span id='textcolor2519'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2520'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> gpio leds[] = {{4, GPIOF_OUT_INIT_LOW, </span><span id='textcolor2521'><span class='ectt-0800'>"LED 1"</span></span><span class='ectt-0800'>}};</span>
|
|
<a id='x1-58044r22'></a><span class='ecrm-0500'>22</span>
|
|
<a id='x1-58046r23'></a><span class='ecrm-0500'>23</span><span id='textcolor2522'><span class='ectt-0800'>/* Define GPIOs for BUTTONS</span></span>
|
|
<a id='x1-58048r24'></a><span class='ecrm-0500'>24</span><span id='textcolor2523'><span class='ectt-0800'> Change the numbers for the GPIO on your board. */</span></span>
|
|
<a id='x1-58050r25'></a><span class='ecrm-0500'>25</span><span id='textcolor2524'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2525'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> gpio buttons[] = {{17, GPIOF_IN, </span><span id='textcolor2526'><span class='ectt-0800'>"LED 1 ON BUTTON"</span></span><span class='ectt-0800'>},</span>
|
|
<a id='x1-58052r26'></a><span class='ecrm-0500'>26</span><span class='ectt-0800'> {18, GPIOF_IN, </span><span id='textcolor2527'><span class='ectt-0800'>"LED 1 OFF BUTTON"</span></span><span class='ectt-0800'>}};</span>
|
|
<a id='x1-58054r27'></a><span class='ecrm-0500'>27</span>
|
|
<a id='x1-58056r28'></a><span class='ecrm-0500'>28</span><span id='textcolor2528'><span class='ectt-0800'>/* Tasklet containing some non-trivial amount of processing */</span></span>
|
|
<a id='x1-58058r29'></a><span class='ecrm-0500'>29</span><span id='textcolor2529'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2530'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> bottomhalf_tasklet_fn(</span><span id='textcolor2531'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor2532'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> data)</span>
|
|
<a id='x1-58060r30'></a><span class='ecrm-0500'>30</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-58062r31'></a><span class='ecrm-0500'>31</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2533'><span class='ectt-0800'>"Bottom half tasklet starts</span></span><span id='textcolor2534'><span class='ectt-0800'>\n</span></span><span id='textcolor2535'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-58064r32'></a><span class='ecrm-0500'>32</span><span class='ectt-0800'> </span><span id='textcolor2536'><span class='ectt-0800'>/* do something which takes a while */</span></span>
|
|
<a id='x1-58066r33'></a><span class='ecrm-0500'>33</span><span class='ectt-0800'> mdelay(500);</span>
|
|
<a id='x1-58068r34'></a><span class='ecrm-0500'>34</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2537'><span class='ectt-0800'>"Bottom half tasklet ends</span></span><span id='textcolor2538'><span class='ectt-0800'>\n</span></span><span id='textcolor2539'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-58070r35'></a><span class='ecrm-0500'>35</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-58072r36'></a><span class='ecrm-0500'>36</span>
|
|
<a id='x1-58074r37'></a><span class='ecrm-0500'>37</span><span class='ectt-0800'>DECLARE_TASKLET(buttontask, bottomhalf_tasklet_fn, 0L);</span>
|
|
<a id='x1-58076r38'></a><span class='ecrm-0500'>38</span>
|
|
<a id='x1-58078r39'></a><span class='ecrm-0500'>39</span><span id='textcolor2540'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-58080r40'></a><span class='ecrm-0500'>40</span><span id='textcolor2541'><span class='ectt-0800'> * interrupt function triggered when a button is pressed</span></span>
|
|
<a id='x1-58082r41'></a><span class='ecrm-0500'>41</span><span id='textcolor2542'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-58084r42'></a><span class='ecrm-0500'>42</span><span id='textcolor2543'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> irqreturn_t button_isr(</span><span id='textcolor2544'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> irq, </span><span id='textcolor2545'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *data)</span>
|
|
<a id='x1-58086r43'></a><span class='ecrm-0500'>43</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-58088r44'></a><span class='ecrm-0500'>44</span><span class='ectt-0800'> </span><span id='textcolor2546'><span class='ectt-0800'>/* Do something quickly right now */</span></span>
|
|
<a id='x1-58090r45'></a><span class='ecrm-0500'>45</span><span class='ectt-0800'> </span><span id='textcolor2547'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (irq == button_irqs[0] && !gpio_get_value(leds[0].gpio))</span>
|
|
<a id='x1-58092r46'></a><span class='ecrm-0500'>46</span><span class='ectt-0800'> gpio_set_value(leds[0].gpio, 1);</span>
|
|
<a id='x1-58094r47'></a><span class='ecrm-0500'>47</span><span class='ectt-0800'> </span><span id='textcolor2548'><span class='ectt-0800'>else</span></span><span class='ectt-0800'> </span><span id='textcolor2549'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (irq == button_irqs[1] && gpio_get_value(leds[0].gpio))</span>
|
|
<a id='x1-58096r48'></a><span class='ecrm-0500'>48</span><span class='ectt-0800'> gpio_set_value(leds[0].gpio, 0);</span>
|
|
<a id='x1-58098r49'></a><span class='ecrm-0500'>49</span>
|
|
<a id='x1-58100r50'></a><span class='ecrm-0500'>50</span><span class='ectt-0800'> </span><span id='textcolor2550'><span class='ectt-0800'>/* Do the rest at leisure via the scheduler */</span></span>
|
|
<a id='x1-58102r51'></a><span class='ecrm-0500'>51</span><span class='ectt-0800'> tasklet_schedule(&buttontask);</span>
|
|
<a id='x1-58104r52'></a><span class='ecrm-0500'>52</span>
|
|
<a id='x1-58106r53'></a><span class='ecrm-0500'>53</span><span class='ectt-0800'> </span><span id='textcolor2551'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> IRQ_HANDLED;</span>
|
|
<a id='x1-58108r54'></a><span class='ecrm-0500'>54</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-58110r55'></a><span class='ecrm-0500'>55</span>
|
|
<a id='x1-58112r56'></a><span class='ecrm-0500'>56</span><span id='textcolor2552'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> init_module()</span>
|
|
<a id='x1-58114r57'></a><span class='ecrm-0500'>57</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-58116r58'></a><span class='ecrm-0500'>58</span><span class='ectt-0800'> </span><span id='textcolor2553'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> ret = 0;</span>
|
|
<a id='x1-58118r59'></a><span class='ecrm-0500'>59</span>
|
|
<a id='x1-58120r60'></a><span class='ecrm-0500'>60</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2554'><span class='ectt-0800'>"%s</span></span><span id='textcolor2555'><span class='ectt-0800'>\n</span></span><span id='textcolor2556'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, __func__);</span>
|
|
<a id='x1-58122r61'></a><span class='ecrm-0500'>61</span>
|
|
<a id='x1-58124r62'></a><span class='ecrm-0500'>62</span><span class='ectt-0800'> </span><span id='textcolor2557'><span class='ectt-0800'>/* register LED gpios */</span></span>
|
|
<a id='x1-58126r63'></a><span class='ecrm-0500'>63</span><span class='ectt-0800'> ret = gpio_request_array(leds, ARRAY_SIZE(leds));</span>
|
|
<a id='x1-58128r64'></a><span class='ecrm-0500'>64</span>
|
|
<a id='x1-58130r65'></a><span class='ecrm-0500'>65</span><span class='ectt-0800'> </span><span id='textcolor2558'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (ret) {</span>
|
|
<a id='x1-58132r66'></a><span class='ecrm-0500'>66</span><span class='ectt-0800'> pr_err(</span><span id='textcolor2559'><span class='ectt-0800'>"Unable to request GPIOs for LEDs: %d</span></span><span id='textcolor2560'><span class='ectt-0800'>\n</span></span><span id='textcolor2561'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, ret);</span>
|
|
<a id='x1-58134r67'></a><span class='ecrm-0500'>67</span><span class='ectt-0800'> </span><span id='textcolor2562'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> ret;</span>
|
|
<a id='x1-58136r68'></a><span class='ecrm-0500'>68</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-58138r69'></a><span class='ecrm-0500'>69</span>
|
|
<a id='x1-58140r70'></a><span class='ecrm-0500'>70</span><span class='ectt-0800'> </span><span id='textcolor2563'><span class='ectt-0800'>/* register BUTTON gpios */</span></span>
|
|
<a id='x1-58142r71'></a><span class='ecrm-0500'>71</span><span class='ectt-0800'> ret = gpio_request_array(buttons, ARRAY_SIZE(buttons));</span>
|
|
<a id='x1-58144r72'></a><span class='ecrm-0500'>72</span>
|
|
<a id='x1-58146r73'></a><span class='ecrm-0500'>73</span><span class='ectt-0800'> </span><span id='textcolor2564'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (ret) {</span>
|
|
<a id='x1-58148r74'></a><span class='ecrm-0500'>74</span><span class='ectt-0800'> pr_err(</span><span id='textcolor2565'><span class='ectt-0800'>"Unable to request GPIOs for BUTTONs: %d</span></span><span id='textcolor2566'><span class='ectt-0800'>\n</span></span><span id='textcolor2567'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, ret);</span>
|
|
<a id='x1-58150r75'></a><span class='ecrm-0500'>75</span><span class='ectt-0800'> </span><span id='textcolor2568'><span class='ectt-0800'>goto</span></span><span class='ectt-0800'> fail1;</span>
|
|
<a id='x1-58152r76'></a><span class='ecrm-0500'>76</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-58154r77'></a><span class='ecrm-0500'>77</span>
|
|
<a id='x1-58156r78'></a><span class='ecrm-0500'>78</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2569'><span class='ectt-0800'>"Current button1 value: %d</span></span><span id='textcolor2570'><span class='ectt-0800'>\n</span></span><span id='textcolor2571'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, gpio_get_value(buttons[0].gpio));</span>
|
|
<a id='x1-58158r79'></a><span class='ecrm-0500'>79</span>
|
|
<a id='x1-58160r80'></a><span class='ecrm-0500'>80</span><span class='ectt-0800'> ret = gpio_to_irq(buttons[0].gpio);</span>
|
|
<a id='x1-58162r81'></a><span class='ecrm-0500'>81</span>
|
|
<a id='x1-58164r82'></a><span class='ecrm-0500'>82</span><span class='ectt-0800'> </span><span id='textcolor2572'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (ret < 0) {</span>
|
|
<a id='x1-58166r83'></a><span class='ecrm-0500'>83</span><span class='ectt-0800'> pr_err(</span><span id='textcolor2573'><span class='ectt-0800'>"Unable to request IRQ: %d</span></span><span id='textcolor2574'><span class='ectt-0800'>\n</span></span><span id='textcolor2575'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, ret);</span>
|
|
<a id='x1-58168r84'></a><span class='ecrm-0500'>84</span><span class='ectt-0800'> </span><span id='textcolor2576'><span class='ectt-0800'>goto</span></span><span class='ectt-0800'> fail2;</span>
|
|
<a id='x1-58170r85'></a><span class='ecrm-0500'>85</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-58172r86'></a><span class='ecrm-0500'>86</span>
|
|
<a id='x1-58174r87'></a><span class='ecrm-0500'>87</span><span class='ectt-0800'> button_irqs[0] = ret;</span>
|
|
<a id='x1-58176r88'></a><span class='ecrm-0500'>88</span>
|
|
<a id='x1-58178r89'></a><span class='ecrm-0500'>89</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2577'><span class='ectt-0800'>"Successfully requested BUTTON1 IRQ # %d</span></span><span id='textcolor2578'><span class='ectt-0800'>\n</span></span><span id='textcolor2579'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, button_irqs[0]);</span>
|
|
<a id='x1-58180r90'></a><span class='ecrm-0500'>90</span>
|
|
<a id='x1-58182r91'></a><span class='ecrm-0500'>91</span><span class='ectt-0800'> ret = request_irq(button_irqs[0], button_isr,</span>
|
|
<a id='x1-58184r92'></a><span class='ecrm-0500'>92</span><span class='ectt-0800'> IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,</span>
|
|
<a id='x1-58186r93'></a><span class='ecrm-0500'>93</span><span class='ectt-0800'> </span><span id='textcolor2580'><span class='ectt-0800'>"gpiomod#button1"</span></span><span class='ectt-0800'>, NULL);</span>
|
|
<a id='x1-58188r94'></a><span class='ecrm-0500'>94</span>
|
|
<a id='x1-58190r95'></a><span class='ecrm-0500'>95</span><span class='ectt-0800'> </span><span id='textcolor2581'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (ret) {</span>
|
|
<a id='x1-58192r96'></a><span class='ecrm-0500'>96</span><span class='ectt-0800'> pr_err(</span><span id='textcolor2582'><span class='ectt-0800'>"Unable to request IRQ: %d</span></span><span id='textcolor2583'><span class='ectt-0800'>\n</span></span><span id='textcolor2584'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, ret);</span>
|
|
<a id='x1-58194r97'></a><span class='ecrm-0500'>97</span><span class='ectt-0800'> </span><span id='textcolor2585'><span class='ectt-0800'>goto</span></span><span class='ectt-0800'> fail2;</span>
|
|
<a id='x1-58196r98'></a><span class='ecrm-0500'>98</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-58198r99'></a><span class='ecrm-0500'>99</span>
|
|
<a id='x1-58200r100'></a><span class='ecrm-0500'>100</span>
|
|
<a id='x1-58202r101'></a><span class='ecrm-0500'>101</span><span class='ectt-0800'> ret = gpio_to_irq(buttons[1].gpio);</span>
|
|
<a id='x1-58204r102'></a><span class='ecrm-0500'>102</span>
|
|
<a id='x1-58206r103'></a><span class='ecrm-0500'>103</span><span class='ectt-0800'> </span><span id='textcolor2586'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (ret < 0) {</span>
|
|
<a id='x1-58208r104'></a><span class='ecrm-0500'>104</span><span class='ectt-0800'> pr_err(</span><span id='textcolor2587'><span class='ectt-0800'>"Unable to request IRQ: %d</span></span><span id='textcolor2588'><span class='ectt-0800'>\n</span></span><span id='textcolor2589'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, ret);</span>
|
|
<a id='x1-58210r105'></a><span class='ecrm-0500'>105</span><span class='ectt-0800'> </span><span id='textcolor2590'><span class='ectt-0800'>goto</span></span><span class='ectt-0800'> fail2;</span>
|
|
<a id='x1-58212r106'></a><span class='ecrm-0500'>106</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-58214r107'></a><span class='ecrm-0500'>107</span>
|
|
<a id='x1-58216r108'></a><span class='ecrm-0500'>108</span><span class='ectt-0800'> button_irqs[1] = ret;</span>
|
|
<a id='x1-58218r109'></a><span class='ecrm-0500'>109</span>
|
|
<a id='x1-58220r110'></a><span class='ecrm-0500'>110</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2591'><span class='ectt-0800'>"Successfully requested BUTTON2 IRQ # %d</span></span><span id='textcolor2592'><span class='ectt-0800'>\n</span></span><span id='textcolor2593'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, button_irqs[1]);</span>
|
|
<a id='x1-58222r111'></a><span class='ecrm-0500'>111</span>
|
|
<a id='x1-58224r112'></a><span class='ecrm-0500'>112</span><span class='ectt-0800'> ret = request_irq(button_irqs[1], button_isr,</span>
|
|
<a id='x1-58226r113'></a><span class='ecrm-0500'>113</span><span class='ectt-0800'> IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,</span>
|
|
<a id='x1-58228r114'></a><span class='ecrm-0500'>114</span><span class='ectt-0800'> </span><span id='textcolor2594'><span class='ectt-0800'>"gpiomod#button2"</span></span><span class='ectt-0800'>, NULL);</span>
|
|
<a id='x1-58230r115'></a><span class='ecrm-0500'>115</span>
|
|
<a id='x1-58232r116'></a><span class='ecrm-0500'>116</span><span class='ectt-0800'> </span><span id='textcolor2595'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (ret) {</span>
|
|
<a id='x1-58234r117'></a><span class='ecrm-0500'>117</span><span class='ectt-0800'> pr_err(</span><span id='textcolor2596'><span class='ectt-0800'>"Unable to request IRQ: %d</span></span><span id='textcolor2597'><span class='ectt-0800'>\n</span></span><span id='textcolor2598'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, ret);</span>
|
|
<a id='x1-58236r118'></a><span class='ecrm-0500'>118</span><span class='ectt-0800'> </span><span id='textcolor2599'><span class='ectt-0800'>goto</span></span><span class='ectt-0800'> fail3;</span>
|
|
<a id='x1-58238r119'></a><span class='ecrm-0500'>119</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-58240r120'></a><span class='ecrm-0500'>120</span>
|
|
<a id='x1-58242r121'></a><span class='ecrm-0500'>121</span><span class='ectt-0800'> </span><span id='textcolor2600'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-58244r122'></a><span class='ecrm-0500'>122</span>
|
|
<a id='x1-58246r123'></a><span class='ecrm-0500'>123</span><span id='textcolor2601'><span class='ectt-0800'>/* cleanup what has been setup so far */</span></span>
|
|
<a id='x1-58248r124'></a><span class='ecrm-0500'>124</span><span class='ectt-0800'>fail3:</span>
|
|
<a id='x1-58250r125'></a><span class='ecrm-0500'>125</span><span class='ectt-0800'> free_irq(button_irqs[0], NULL);</span>
|
|
<a id='x1-58252r126'></a><span class='ecrm-0500'>126</span>
|
|
<a id='x1-58254r127'></a><span class='ecrm-0500'>127</span><span class='ectt-0800'>fail2:</span>
|
|
<a id='x1-58256r128'></a><span class='ecrm-0500'>128</span><span class='ectt-0800'> gpio_free_array(buttons, ARRAY_SIZE(leds));</span>
|
|
<a id='x1-58258r129'></a><span class='ecrm-0500'>129</span>
|
|
<a id='x1-58260r130'></a><span class='ecrm-0500'>130</span><span class='ectt-0800'>fail1:</span>
|
|
<a id='x1-58262r131'></a><span class='ecrm-0500'>131</span><span class='ectt-0800'> gpio_free_array(leds, ARRAY_SIZE(leds));</span>
|
|
<a id='x1-58264r132'></a><span class='ecrm-0500'>132</span>
|
|
<a id='x1-58266r133'></a><span class='ecrm-0500'>133</span><span class='ectt-0800'> </span><span id='textcolor2602'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> ret;</span>
|
|
<a id='x1-58268r134'></a><span class='ecrm-0500'>134</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-58270r135'></a><span class='ecrm-0500'>135</span>
|
|
<a id='x1-58272r136'></a><span class='ecrm-0500'>136</span><span id='textcolor2603'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> cleanup_module()</span>
|
|
<a id='x1-58274r137'></a><span class='ecrm-0500'>137</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-58276r138'></a><span class='ecrm-0500'>138</span><span class='ectt-0800'> </span><span id='textcolor2604'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> i;</span>
|
|
<a id='x1-58278r139'></a><span class='ecrm-0500'>139</span>
|
|
<a id='x1-58280r140'></a><span class='ecrm-0500'>140</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2605'><span class='ectt-0800'>"%s</span></span><span id='textcolor2606'><span class='ectt-0800'>\n</span></span><span id='textcolor2607'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, __func__);</span>
|
|
<a id='x1-58282r141'></a><span class='ecrm-0500'>141</span>
|
|
<a id='x1-58284r142'></a><span class='ecrm-0500'>142</span><span class='ectt-0800'> </span><span id='textcolor2608'><span class='ectt-0800'>/* free irqs */</span></span>
|
|
<a id='x1-58286r143'></a><span class='ecrm-0500'>143</span><span class='ectt-0800'> free_irq(button_irqs[0], NULL);</span>
|
|
<a id='x1-58288r144'></a><span class='ecrm-0500'>144</span><span class='ectt-0800'> free_irq(button_irqs[1], NULL);</span>
|
|
<a id='x1-58290r145'></a><span class='ecrm-0500'>145</span>
|
|
<a id='x1-58292r146'></a><span class='ecrm-0500'>146</span><span class='ectt-0800'> </span><span id='textcolor2609'><span class='ectt-0800'>/* turn all LEDs off */</span></span>
|
|
<a id='x1-58294r147'></a><span class='ecrm-0500'>147</span><span class='ectt-0800'> </span><span id='textcolor2610'><span class='ectt-0800'>for</span></span><span class='ectt-0800'> (i = 0; i < ARRAY_SIZE(leds); i++)</span>
|
|
<a id='x1-58296r148'></a><span class='ecrm-0500'>148</span><span class='ectt-0800'> gpio_set_value(leds[i].gpio, 0);</span>
|
|
<a id='x1-58298r149'></a><span class='ecrm-0500'>149</span>
|
|
<a id='x1-58300r150'></a><span class='ecrm-0500'>150</span><span class='ectt-0800'> </span><span id='textcolor2611'><span class='ectt-0800'>/* unregister */</span></span>
|
|
<a id='x1-58302r151'></a><span class='ecrm-0500'>151</span><span class='ectt-0800'> gpio_free_array(leds, ARRAY_SIZE(leds));</span>
|
|
<a id='x1-58304r152'></a><span class='ecrm-0500'>152</span><span class='ectt-0800'> gpio_free_array(buttons, ARRAY_SIZE(buttons));</span>
|
|
<a id='x1-58306r153'></a><span class='ecrm-0500'>153</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-58308r154'></a><span class='ecrm-0500'>154</span>
|
|
<a id='x1-58310r155'></a><span class='ecrm-0500'>155</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor2612'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-58312r156'></a><span class='ecrm-0500'>156</span><span class='ectt-0800'>MODULE_DESCRIPTION(</span><span id='textcolor2613'><span class='ectt-0800'>"Interrupt with top and bottom half"</span></span><span class='ectt-0800'>);</span></pre>
|
|
<!-- l. 1393 --><p class='noindent'>
|
|
</p>
|
|
<h3 class='sectionHead' id='crypto'><span class='titlemark'>0.16 </span> <a id='x1-590000.16'></a>Crypto</h3>
|
|
<!-- l. 1395 --><p class='noindent'>At the dawn of the internet everybody trusted everybody completely…but that didn’t
|
|
work out so well. When this guide was originally written it was a more innocent era
|
|
in which almost nobody actually gave a damn about crypto - least of all kernel
|
|
developers. That’s certainly no longer the case now. To handle crypto stuff the kernel
|
|
has its own API enabling common methods of encryption, decryption and your
|
|
favourite hash functions.
|
|
|
|
|
|
|
|
</p><!-- l. 1397 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='hash-functions'><span class='titlemark'>0.16.1 </span> <a id='x1-600000.16.1'></a>Hash functions</h4>
|
|
<!-- l. 1400 --><p class='noindent'>Calculating and checking the hashes of things is a common operation. Here is a
|
|
demonstration of how to calculate a sha256 hash within a kernel module.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb66'><a id='x1-60002r1'></a><span class='ecrm-0500'>1</span><span id='textcolor2614'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-60004r2'></a><span class='ecrm-0500'>2</span><span id='textcolor2615'><span class='ectt-0800'> * cryptosha256.c</span></span>
|
|
<a id='x1-60006r3'></a><span class='ecrm-0500'>3</span><span id='textcolor2616'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-60008r4'></a><span class='ecrm-0500'>4</span><span id='textcolor2617'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2618'><span class='ectt-0800'><crypto/internal/hash.h></span></span>
|
|
<a id='x1-60010r5'></a><span class='ecrm-0500'>5</span><span id='textcolor2619'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2620'><span class='ectt-0800'><linux/module.h></span></span>
|
|
<a id='x1-60012r6'></a><span class='ecrm-0500'>6</span>
|
|
<a id='x1-60014r7'></a><span class='ecrm-0500'>7</span><span id='textcolor2621'><span class='ectt-0800'>#define SHA256_LENGTH 32</span></span>
|
|
<a id='x1-60016r8'></a><span class='ecrm-0500'>8</span>
|
|
<a id='x1-60018r9'></a><span class='ecrm-0500'>9</span><span id='textcolor2622'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2623'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> show_hash_result(</span><span id='textcolor2624'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *plaintext, </span><span id='textcolor2625'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *hash_sha256)</span>
|
|
<a id='x1-60020r10'></a><span class='ecrm-0500'>10</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-60022r11'></a><span class='ecrm-0500'>11</span><span class='ectt-0800'> </span><span id='textcolor2626'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> i;</span>
|
|
<a id='x1-60024r12'></a><span class='ecrm-0500'>12</span><span class='ectt-0800'> </span><span id='textcolor2627'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> str[SHA256_LENGTH * 2 + 1];</span>
|
|
<a id='x1-60026r13'></a><span class='ecrm-0500'>13</span>
|
|
<a id='x1-60028r14'></a><span class='ecrm-0500'>14</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2628'><span class='ectt-0800'>"sha256 test for string: </span></span><span id='textcolor2629'><span class='ectt-0800'>\"</span></span><span id='textcolor2630'><span class='ectt-0800'>%s</span></span><span id='textcolor2631'><span class='ectt-0800'>\"\n</span></span><span id='textcolor2632'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, plaintext);</span>
|
|
<a id='x1-60030r15'></a><span class='ecrm-0500'>15</span><span class='ectt-0800'> </span><span id='textcolor2633'><span class='ectt-0800'>for</span></span><span class='ectt-0800'> (i = 0; i < SHA256_LENGTH; i++)</span>
|
|
<a id='x1-60032r16'></a><span class='ecrm-0500'>16</span><span class='ectt-0800'> sprintf(&str[i * 2], </span><span id='textcolor2634'><span class='ectt-0800'>"%02x"</span></span><span class='ectt-0800'>, (</span><span id='textcolor2635'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor2636'><span class='ectt-0800'>char</span></span><span class='ectt-0800'>) hash_sha256[i]);</span>
|
|
<a id='x1-60034r17'></a><span class='ecrm-0500'>17</span><span class='ectt-0800'> str[i * 2] = 0;</span>
|
|
<a id='x1-60036r18'></a><span class='ecrm-0500'>18</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2637'><span class='ectt-0800'>"%s</span></span><span id='textcolor2638'><span class='ectt-0800'>\n</span></span><span id='textcolor2639'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, str);</span>
|
|
<a id='x1-60038r19'></a><span class='ecrm-0500'>19</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-60040r20'></a><span class='ecrm-0500'>20</span>
|
|
<a id='x1-60042r21'></a><span class='ecrm-0500'>21</span><span id='textcolor2640'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> cryptosha256_init(</span><span id='textcolor2641'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-60044r22'></a><span class='ecrm-0500'>22</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-60046r23'></a><span class='ecrm-0500'>23</span><span class='ectt-0800'> </span><span id='textcolor2642'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *plaintext = </span><span id='textcolor2643'><span class='ectt-0800'>"This is a test"</span></span><span class='ectt-0800'>;</span>
|
|
<a id='x1-60048r24'></a><span class='ecrm-0500'>24</span><span class='ectt-0800'> </span><span id='textcolor2644'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> hash_sha256[SHA256_LENGTH];</span>
|
|
<a id='x1-60050r25'></a><span class='ecrm-0500'>25</span><span class='ectt-0800'> </span><span id='textcolor2645'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> crypto_shash *sha256;</span>
|
|
<a id='x1-60052r26'></a><span class='ecrm-0500'>26</span><span class='ectt-0800'> </span><span id='textcolor2646'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> shash_desc *shash;</span>
|
|
<a id='x1-60054r27'></a><span class='ecrm-0500'>27</span>
|
|
<a id='x1-60056r28'></a><span class='ecrm-0500'>28</span><span class='ectt-0800'> sha256 = crypto_alloc_shash(</span><span id='textcolor2647'><span class='ectt-0800'>"sha256"</span></span><span class='ectt-0800'>, 0, 0);</span>
|
|
<a id='x1-60058r29'></a><span class='ecrm-0500'>29</span><span class='ectt-0800'> </span><span id='textcolor2648'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (IS_ERR(sha256))</span>
|
|
<a id='x1-60060r30'></a><span class='ecrm-0500'>30</span><span class='ectt-0800'> </span><span id='textcolor2649'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -1;</span>
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|
<a id='x1-60062r31'></a><span class='ecrm-0500'>31</span>
|
|
<a id='x1-60064r32'></a><span class='ecrm-0500'>32</span><span class='ectt-0800'> shash = kmalloc(</span><span id='textcolor2650'><span class='ectt-0800'>sizeof</span></span><span class='ectt-0800'>(</span><span id='textcolor2651'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> shash_desc) + crypto_shash_descsize(sha256),</span>
|
|
<a id='x1-60066r33'></a><span class='ecrm-0500'>33</span><span class='ectt-0800'> GFP_KERNEL);</span>
|
|
<a id='x1-60068r34'></a><span class='ecrm-0500'>34</span><span class='ectt-0800'> </span><span id='textcolor2652'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (!shash)</span>
|
|
<a id='x1-60070r35'></a><span class='ecrm-0500'>35</span><span class='ectt-0800'> </span><span id='textcolor2653'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -ENOMEM;</span>
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|
<a id='x1-60072r36'></a><span class='ecrm-0500'>36</span>
|
|
<a id='x1-60074r37'></a><span class='ecrm-0500'>37</span><span class='ectt-0800'> shash->tfm = sha256;</span>
|
|
<a id='x1-60076r38'></a><span class='ecrm-0500'>38</span>
|
|
<a id='x1-60078r39'></a><span class='ecrm-0500'>39</span><span class='ectt-0800'> </span><span id='textcolor2654'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (crypto_shash_init(shash))</span>
|
|
<a id='x1-60080r40'></a><span class='ecrm-0500'>40</span><span class='ectt-0800'> </span><span id='textcolor2655'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -1;</span>
|
|
<a id='x1-60082r41'></a><span class='ecrm-0500'>41</span>
|
|
<a id='x1-60084r42'></a><span class='ecrm-0500'>42</span><span class='ectt-0800'> </span><span id='textcolor2656'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (crypto_shash_update(shash, plaintext, strlen(plaintext)))</span>
|
|
<a id='x1-60086r43'></a><span class='ecrm-0500'>43</span><span class='ectt-0800'> </span><span id='textcolor2657'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -1;</span>
|
|
<a id='x1-60088r44'></a><span class='ecrm-0500'>44</span>
|
|
<a id='x1-60090r45'></a><span class='ecrm-0500'>45</span><span class='ectt-0800'> </span><span id='textcolor2658'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (crypto_shash_final(shash, hash_sha256))</span>
|
|
<a id='x1-60092r46'></a><span class='ecrm-0500'>46</span><span class='ectt-0800'> </span><span id='textcolor2659'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -1;</span>
|
|
<a id='x1-60094r47'></a><span class='ecrm-0500'>47</span>
|
|
<a id='x1-60096r48'></a><span class='ecrm-0500'>48</span><span class='ectt-0800'> kfree(shash);</span>
|
|
<a id='x1-60098r49'></a><span class='ecrm-0500'>49</span><span class='ectt-0800'> crypto_free_shash(sha256);</span>
|
|
<a id='x1-60100r50'></a><span class='ecrm-0500'>50</span>
|
|
<a id='x1-60102r51'></a><span class='ecrm-0500'>51</span><span class='ectt-0800'> show_hash_result(plaintext, hash_sha256);</span>
|
|
<a id='x1-60104r52'></a><span class='ecrm-0500'>52</span>
|
|
<a id='x1-60106r53'></a><span class='ecrm-0500'>53</span><span class='ectt-0800'> </span><span id='textcolor2660'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-60108r54'></a><span class='ecrm-0500'>54</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-60110r55'></a><span class='ecrm-0500'>55</span>
|
|
<a id='x1-60112r56'></a><span class='ecrm-0500'>56</span><span id='textcolor2661'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> cryptosha256_exit(</span><span id='textcolor2662'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>) {}</span>
|
|
<a id='x1-60114r57'></a><span class='ecrm-0500'>57</span>
|
|
<a id='x1-60116r58'></a><span class='ecrm-0500'>58</span><span class='ectt-0800'>module_init(cryptosha256_init);</span>
|
|
<a id='x1-60118r59'></a><span class='ecrm-0500'>59</span><span class='ectt-0800'>module_exit(cryptosha256_exit);</span>
|
|
<a id='x1-60120r60'></a><span class='ecrm-0500'>60</span>
|
|
<a id='x1-60122r61'></a><span class='ecrm-0500'>61</span><span class='ectt-0800'>MODULE_DESCRIPTION(</span><span id='textcolor2663'><span class='ectt-0800'>"sha256 hash test"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-60124r62'></a><span class='ecrm-0500'>62</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor2664'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
|
|
<!-- l. 1404 --><p class='indent'> Make and install the module:
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb67'><a id='x1-60129r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>make</span>
|
|
<a id='x1-60131r2'></a><span class='ecrm-0500'>2</span><span class='ectt-1000'>sudo insmod cryptosha256.ko</span>
|
|
<a id='x1-60133r3'></a><span class='ecrm-0500'>3</span><span class='ectt-1000'>dmesg</span></pre>
|
|
<!-- l. 1412 --><p class='indent'> And you should see that the hash was calculated for the test string.
|
|
</p><!-- l. 1414 --><p class='indent'> Finally, remove the test module:
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb68'><a id='x1-60136r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>sudo rmmod cryptosha256</span></pre>
|
|
<!-- l. 1420 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='symmetric-key-encryption'><span class='titlemark'>0.16.2 </span> <a id='x1-610000.16.2'></a>Symmetric key encryption</h4>
|
|
<!-- l. 1422 --><p class='noindent'>Here is an example of symmetrically encrypting a string using the AES algorithm
|
|
and a password.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb69'><a id='x1-61002r1'></a><span class='ecrm-0500'>1</span><span id='textcolor2665'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-61004r2'></a><span class='ecrm-0500'>2</span><span id='textcolor2666'><span class='ectt-0800'> * cryptosk.c</span></span>
|
|
<a id='x1-61006r3'></a><span class='ecrm-0500'>3</span><span id='textcolor2667'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-61008r4'></a><span class='ecrm-0500'>4</span><span id='textcolor2668'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2669'><span class='ectt-0800'><crypto/internal/skcipher.h></span></span>
|
|
<a id='x1-61010r5'></a><span class='ecrm-0500'>5</span><span id='textcolor2670'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2671'><span class='ectt-0800'><linux/crypto.h></span></span>
|
|
<a id='x1-61012r6'></a><span class='ecrm-0500'>6</span><span id='textcolor2672'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2673'><span class='ectt-0800'><linux/module.h></span></span>
|
|
<a id='x1-61014r7'></a><span class='ecrm-0500'>7</span>
|
|
<a id='x1-61016r8'></a><span class='ecrm-0500'>8</span><span id='textcolor2674'><span class='ectt-0800'>#define SYMMETRIC_KEY_LENGTH 32</span></span>
|
|
<a id='x1-61018r9'></a><span class='ecrm-0500'>9</span><span id='textcolor2675'><span class='ectt-0800'>#define CIPHER_BLOCK_SIZE 16</span></span>
|
|
<a id='x1-61020r10'></a><span class='ecrm-0500'>10</span>
|
|
<a id='x1-61022r11'></a><span class='ecrm-0500'>11</span><span id='textcolor2676'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> tcrypt_result {</span>
|
|
<a id='x1-61024r12'></a><span class='ecrm-0500'>12</span><span class='ectt-0800'> </span><span id='textcolor2677'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> completion completion;</span>
|
|
<a id='x1-61026r13'></a><span class='ecrm-0500'>13</span><span class='ectt-0800'> </span><span id='textcolor2678'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> err;</span>
|
|
<a id='x1-61028r14'></a><span class='ecrm-0500'>14</span><span class='ectt-0800'>};</span>
|
|
<a id='x1-61030r15'></a><span class='ecrm-0500'>15</span>
|
|
<a id='x1-61032r16'></a><span class='ecrm-0500'>16</span><span id='textcolor2679'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> skcipher_def {</span>
|
|
<a id='x1-61034r17'></a><span class='ecrm-0500'>17</span><span class='ectt-0800'> </span><span id='textcolor2680'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> scatterlist sg;</span>
|
|
<a id='x1-61036r18'></a><span class='ecrm-0500'>18</span><span class='ectt-0800'> </span><span id='textcolor2681'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> crypto_skcipher *tfm;</span>
|
|
<a id='x1-61038r19'></a><span class='ecrm-0500'>19</span><span class='ectt-0800'> </span><span id='textcolor2682'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> skcipher_request *req;</span>
|
|
<a id='x1-61040r20'></a><span class='ecrm-0500'>20</span><span class='ectt-0800'> </span><span id='textcolor2683'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> tcrypt_result result;</span>
|
|
<a id='x1-61042r21'></a><span class='ecrm-0500'>21</span><span class='ectt-0800'> </span><span id='textcolor2684'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *scratchpad;</span>
|
|
<a id='x1-61044r22'></a><span class='ecrm-0500'>22</span><span class='ectt-0800'> </span><span id='textcolor2685'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *ciphertext;</span>
|
|
<a id='x1-61046r23'></a><span class='ecrm-0500'>23</span><span class='ectt-0800'> </span><span id='textcolor2686'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *ivdata;</span>
|
|
<a id='x1-61048r24'></a><span class='ecrm-0500'>24</span><span class='ectt-0800'>};</span>
|
|
<a id='x1-61050r25'></a><span class='ecrm-0500'>25</span>
|
|
<a id='x1-61052r26'></a><span class='ecrm-0500'>26</span><span id='textcolor2687'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2688'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> skcipher_def sk;</span>
|
|
<a id='x1-61054r27'></a><span class='ecrm-0500'>27</span>
|
|
<a id='x1-61056r28'></a><span class='ecrm-0500'>28</span><span id='textcolor2689'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2690'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> test_skcipher_finish(</span><span id='textcolor2691'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> skcipher_def *sk)</span>
|
|
<a id='x1-61058r29'></a><span class='ecrm-0500'>29</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-61060r30'></a><span class='ecrm-0500'>30</span><span class='ectt-0800'> </span><span id='textcolor2692'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (sk->tfm)</span>
|
|
<a id='x1-61062r31'></a><span class='ecrm-0500'>31</span><span class='ectt-0800'> crypto_free_skcipher(sk->tfm);</span>
|
|
<a id='x1-61064r32'></a><span class='ecrm-0500'>32</span><span class='ectt-0800'> </span><span id='textcolor2693'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (sk->req)</span>
|
|
<a id='x1-61066r33'></a><span class='ecrm-0500'>33</span><span class='ectt-0800'> skcipher_request_free(sk->req);</span>
|
|
<a id='x1-61068r34'></a><span class='ecrm-0500'>34</span><span class='ectt-0800'> </span><span id='textcolor2694'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (sk->ivdata)</span>
|
|
<a id='x1-61070r35'></a><span class='ecrm-0500'>35</span><span class='ectt-0800'> kfree(sk->ivdata);</span>
|
|
<a id='x1-61072r36'></a><span class='ecrm-0500'>36</span><span class='ectt-0800'> </span><span id='textcolor2695'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (sk->scratchpad)</span>
|
|
<a id='x1-61074r37'></a><span class='ecrm-0500'>37</span><span class='ectt-0800'> kfree(sk->scratchpad);</span>
|
|
<a id='x1-61076r38'></a><span class='ecrm-0500'>38</span><span class='ectt-0800'> </span><span id='textcolor2696'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (sk->ciphertext)</span>
|
|
<a id='x1-61078r39'></a><span class='ecrm-0500'>39</span><span class='ectt-0800'> kfree(sk->ciphertext);</span>
|
|
<a id='x1-61080r40'></a><span class='ecrm-0500'>40</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-61082r41'></a><span class='ecrm-0500'>41</span>
|
|
<a id='x1-61084r42'></a><span class='ecrm-0500'>42</span><span id='textcolor2697'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2698'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> test_skcipher_result(</span><span id='textcolor2699'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> skcipher_def *sk, </span><span id='textcolor2700'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> rc)</span>
|
|
<a id='x1-61086r43'></a><span class='ecrm-0500'>43</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-61088r44'></a><span class='ecrm-0500'>44</span><span class='ectt-0800'> </span><span id='textcolor2701'><span class='ectt-0800'>switch</span></span><span class='ectt-0800'> (rc) {</span>
|
|
<a id='x1-61090r45'></a><span class='ecrm-0500'>45</span><span class='ectt-0800'> </span><span id='textcolor2702'><span class='ectt-0800'>case</span></span><span class='ectt-0800'> 0:</span>
|
|
<a id='x1-61092r46'></a><span class='ecrm-0500'>46</span><span class='ectt-0800'> </span><span id='textcolor2703'><span class='ectt-0800'>break</span></span><span class='ectt-0800'>;</span>
|
|
<a id='x1-61094r47'></a><span class='ecrm-0500'>47</span><span class='ectt-0800'> </span><span id='textcolor2704'><span class='ectt-0800'>case</span></span><span class='ectt-0800'> -EINPROGRESS || -EBUSY:</span>
|
|
<a id='x1-61096r48'></a><span class='ecrm-0500'>48</span><span class='ectt-0800'> rc = wait_for_completion_interruptible(&sk->result.completion);</span>
|
|
<a id='x1-61098r49'></a><span class='ecrm-0500'>49</span><span class='ectt-0800'> </span><span id='textcolor2705'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (!rc && !sk->result.err) {</span>
|
|
<a id='x1-61100r50'></a><span class='ecrm-0500'>50</span><span class='ectt-0800'> reinit_completion(&sk->result.completion);</span>
|
|
<a id='x1-61102r51'></a><span class='ecrm-0500'>51</span><span class='ectt-0800'> </span><span id='textcolor2706'><span class='ectt-0800'>break</span></span><span class='ectt-0800'>;</span>
|
|
<a id='x1-61104r52'></a><span class='ecrm-0500'>52</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-61106r53'></a><span class='ecrm-0500'>53</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2707'><span class='ectt-0800'>"skcipher encrypt returned with %d result %d</span></span><span id='textcolor2708'><span class='ectt-0800'>\n</span></span><span id='textcolor2709'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, rc,</span>
|
|
<a id='x1-61108r54'></a><span class='ecrm-0500'>54</span><span class='ectt-0800'> sk->result.err);</span>
|
|
<a id='x1-61110r55'></a><span class='ecrm-0500'>55</span><span class='ectt-0800'> </span><span id='textcolor2710'><span class='ectt-0800'>break</span></span><span class='ectt-0800'>;</span>
|
|
<a id='x1-61112r56'></a><span class='ecrm-0500'>56</span><span class='ectt-0800'> </span><span id='textcolor2711'><span class='ectt-0800'>default</span></span><span class='ectt-0800'>:</span>
|
|
<a id='x1-61114r57'></a><span class='ecrm-0500'>57</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2712'><span class='ectt-0800'>"skcipher encrypt returned with %d result %d</span></span><span id='textcolor2713'><span class='ectt-0800'>\n</span></span><span id='textcolor2714'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, rc,</span>
|
|
<a id='x1-61116r58'></a><span class='ecrm-0500'>58</span><span class='ectt-0800'> sk->result.err);</span>
|
|
<a id='x1-61118r59'></a><span class='ecrm-0500'>59</span><span class='ectt-0800'> </span><span id='textcolor2715'><span class='ectt-0800'>break</span></span><span class='ectt-0800'>;</span>
|
|
<a id='x1-61120r60'></a><span class='ecrm-0500'>60</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-61122r61'></a><span class='ecrm-0500'>61</span>
|
|
<a id='x1-61124r62'></a><span class='ecrm-0500'>62</span><span class='ectt-0800'> init_completion(&sk->result.completion);</span>
|
|
<a id='x1-61126r63'></a><span class='ecrm-0500'>63</span>
|
|
<a id='x1-61128r64'></a><span class='ecrm-0500'>64</span><span class='ectt-0800'> </span><span id='textcolor2716'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> rc;</span>
|
|
<a id='x1-61130r65'></a><span class='ecrm-0500'>65</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-61132r66'></a><span class='ecrm-0500'>66</span>
|
|
<a id='x1-61134r67'></a><span class='ecrm-0500'>67</span><span id='textcolor2717'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2718'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> test_skcipher_callback(</span><span id='textcolor2719'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> crypto_async_request *req, </span><span id='textcolor2720'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> error)</span>
|
|
<a id='x1-61136r68'></a><span class='ecrm-0500'>68</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-61138r69'></a><span class='ecrm-0500'>69</span><span class='ectt-0800'> </span><span id='textcolor2721'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> tcrypt_result *result = req->data;</span>
|
|
<a id='x1-61140r70'></a><span class='ecrm-0500'>70</span><span class='ectt-0800'> </span><span id='textcolor2722'><span class='ectt-0800'>/* int ret; */</span></span>
|
|
<a id='x1-61142r71'></a><span class='ecrm-0500'>71</span>
|
|
<a id='x1-61144r72'></a><span class='ecrm-0500'>72</span><span class='ectt-0800'> </span><span id='textcolor2723'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (error == -EINPROGRESS)</span>
|
|
<a id='x1-61146r73'></a><span class='ecrm-0500'>73</span><span class='ectt-0800'> </span><span id='textcolor2724'><span class='ectt-0800'>return</span></span><span class='ectt-0800'>;</span>
|
|
<a id='x1-61148r74'></a><span class='ecrm-0500'>74</span>
|
|
<a id='x1-61150r75'></a><span class='ecrm-0500'>75</span><span class='ectt-0800'> result->err = error;</span>
|
|
<a id='x1-61152r76'></a><span class='ecrm-0500'>76</span><span class='ectt-0800'> complete(&result->completion);</span>
|
|
<a id='x1-61154r77'></a><span class='ecrm-0500'>77</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2725'><span class='ectt-0800'>"Encryption finished successfully</span></span><span id='textcolor2726'><span class='ectt-0800'>\n</span></span><span id='textcolor2727'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-61156r78'></a><span class='ecrm-0500'>78</span>
|
|
<a id='x1-61158r79'></a><span class='ecrm-0500'>79</span><span class='ectt-0800'> </span><span id='textcolor2728'><span class='ectt-0800'>/* decrypt data */</span></span>
|
|
<a id='x1-61160r80'></a><span class='ecrm-0500'>80</span><span class='ectt-0800'> </span><span id='textcolor2729'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-61162r81'></a><span class='ecrm-0500'>81</span><span id='textcolor2730'><span class='ectt-0800'> memset((void*)sk.scratchpad, </span><span class='tctt-0800'>'</span><span class='ectt-0800'>-</span><span class='tctt-0800'>'</span><span class='ectt-0800'>, CIPHER_BLOCK_SIZE);</span></span>
|
|
<a id='x1-61164r82'></a><span class='ecrm-0500'>82</span><span id='textcolor2731'><span class='ectt-0800'> ret = crypto_skcipher_decrypt(sk.req);</span></span>
|
|
<a id='x1-61166r83'></a><span class='ecrm-0500'>83</span><span id='textcolor2732'><span class='ectt-0800'> ret = test_skcipher_result(&sk, ret);</span></span>
|
|
<a id='x1-61168r84'></a><span class='ecrm-0500'>84</span><span id='textcolor2733'><span class='ectt-0800'> if (ret)</span></span>
|
|
<a id='x1-61170r85'></a><span class='ecrm-0500'>85</span><span id='textcolor2734'><span class='ectt-0800'> return;</span></span>
|
|
<a id='x1-61172r86'></a><span class='ecrm-0500'>86</span>
|
|
<a id='x1-61174r87'></a><span class='ecrm-0500'>87</span><span id='textcolor2735'><span class='ectt-0800'> sg_copy_from_buffer(&sk.sg, 1, sk.scratchpad, CIPHER_BLOCK_SIZE);</span></span>
|
|
<a id='x1-61176r88'></a><span class='ecrm-0500'>88</span><span id='textcolor2736'><span class='ectt-0800'> sk.scratchpad[CIPHER_BLOCK_SIZE-1] = 0;</span></span>
|
|
<a id='x1-61178r89'></a><span class='ecrm-0500'>89</span>
|
|
<a id='x1-61180r90'></a><span class='ecrm-0500'>90</span><span id='textcolor2737'><span class='ectt-0800'> pr_info("Decryption request successful\n");</span></span>
|
|
<a id='x1-61182r91'></a><span class='ecrm-0500'>91</span><span id='textcolor2738'><span class='ectt-0800'> pr_info("Decrypted: %s\n", sk.scratchpad);</span></span>
|
|
<a id='x1-61184r92'></a><span class='ecrm-0500'>92</span><span id='textcolor2739'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-61186r93'></a><span class='ecrm-0500'>93</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-61188r94'></a><span class='ecrm-0500'>94</span>
|
|
<a id='x1-61190r95'></a><span class='ecrm-0500'>95</span><span id='textcolor2740'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2741'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> test_skcipher_encrypt(</span><span id='textcolor2742'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *plaintext,</span>
|
|
<a id='x1-61192r96'></a><span class='ecrm-0500'>96</span><span class='ectt-0800'> </span><span id='textcolor2743'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *password,</span>
|
|
<a id='x1-61194r97'></a><span class='ecrm-0500'>97</span><span class='ectt-0800'> </span><span id='textcolor2744'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> skcipher_def *sk)</span>
|
|
<a id='x1-61196r98'></a><span class='ecrm-0500'>98</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-61198r99'></a><span class='ecrm-0500'>99</span><span class='ectt-0800'> </span><span id='textcolor2745'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> ret = -EFAULT;</span>
|
|
<a id='x1-61200r100'></a><span class='ecrm-0500'>100</span><span class='ectt-0800'> </span><span id='textcolor2746'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor2747'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> key[SYMMETRIC_KEY_LENGTH];</span>
|
|
<a id='x1-61202r101'></a><span class='ecrm-0500'>101</span>
|
|
<a id='x1-61204r102'></a><span class='ecrm-0500'>102</span><span class='ectt-0800'> </span><span id='textcolor2748'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (!sk->tfm) {</span>
|
|
<a id='x1-61206r103'></a><span class='ecrm-0500'>103</span><span class='ectt-0800'> sk->tfm = crypto_alloc_skcipher(</span><span id='textcolor2749'><span class='ectt-0800'>"cbc-aes-aesni"</span></span><span class='ectt-0800'>, 0, 0);</span>
|
|
<a id='x1-61208r104'></a><span class='ecrm-0500'>104</span><span class='ectt-0800'> </span><span id='textcolor2750'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (IS_ERR(sk->tfm)) {</span>
|
|
<a id='x1-61210r105'></a><span class='ecrm-0500'>105</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2751'><span class='ectt-0800'>"could not allocate skcipher handle</span></span><span id='textcolor2752'><span class='ectt-0800'>\n</span></span><span id='textcolor2753'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-61212r106'></a><span class='ecrm-0500'>106</span><span class='ectt-0800'> </span><span id='textcolor2754'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> PTR_ERR(sk->tfm);</span>
|
|
<a id='x1-61214r107'></a><span class='ecrm-0500'>107</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-61216r108'></a><span class='ecrm-0500'>108</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-61218r109'></a><span class='ecrm-0500'>109</span>
|
|
<a id='x1-61220r110'></a><span class='ecrm-0500'>110</span><span class='ectt-0800'> </span><span id='textcolor2755'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (!sk->req) {</span>
|
|
<a id='x1-61222r111'></a><span class='ecrm-0500'>111</span><span class='ectt-0800'> sk->req = skcipher_request_alloc(sk->tfm, GFP_KERNEL);</span>
|
|
<a id='x1-61224r112'></a><span class='ecrm-0500'>112</span><span class='ectt-0800'> </span><span id='textcolor2756'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (!sk->req) {</span>
|
|
<a id='x1-61226r113'></a><span class='ecrm-0500'>113</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2757'><span class='ectt-0800'>"could not allocate skcipher request</span></span><span id='textcolor2758'><span class='ectt-0800'>\n</span></span><span id='textcolor2759'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-61228r114'></a><span class='ecrm-0500'>114</span><span class='ectt-0800'> ret = -ENOMEM;</span>
|
|
<a id='x1-61230r115'></a><span class='ecrm-0500'>115</span><span class='ectt-0800'> </span><span id='textcolor2760'><span class='ectt-0800'>goto</span></span><span class='ectt-0800'> out;</span>
|
|
<a id='x1-61232r116'></a><span class='ecrm-0500'>116</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-61234r117'></a><span class='ecrm-0500'>117</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-61236r118'></a><span class='ecrm-0500'>118</span>
|
|
<a id='x1-61238r119'></a><span class='ecrm-0500'>119</span><span class='ectt-0800'> skcipher_request_set_callback(sk->req, CRYPTO_TFM_REQ_MAY_BACKLOG,</span>
|
|
<a id='x1-61240r120'></a><span class='ecrm-0500'>120</span><span class='ectt-0800'> test_skcipher_callback, &sk->result);</span>
|
|
<a id='x1-61242r121'></a><span class='ecrm-0500'>121</span>
|
|
<a id='x1-61244r122'></a><span class='ecrm-0500'>122</span><span class='ectt-0800'> </span><span id='textcolor2761'><span class='ectt-0800'>/* clear the key */</span></span>
|
|
<a id='x1-61246r123'></a><span class='ecrm-0500'>123</span><span class='ectt-0800'> memset((</span><span id='textcolor2762'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *) key, </span><span id='textcolor2763'><span class='tctt-0800'>'</span><span class='ectt-0800'>\0</span><span class='tctt-0800'>'</span></span><span class='ectt-0800'>, SYMMETRIC_KEY_LENGTH);</span>
|
|
<a id='x1-61248r124'></a><span class='ecrm-0500'>124</span>
|
|
<a id='x1-61250r125'></a><span class='ecrm-0500'>125</span><span class='ectt-0800'> </span><span id='textcolor2764'><span class='ectt-0800'>/* Use the world</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s favourite password */</span></span>
|
|
<a id='x1-61252r126'></a><span class='ecrm-0500'>126</span><span class='ectt-0800'> sprintf((</span><span id='textcolor2765'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *) key, </span><span id='textcolor2766'><span class='ectt-0800'>"%s"</span></span><span class='ectt-0800'>, password);</span>
|
|
<a id='x1-61254r127'></a><span class='ecrm-0500'>127</span>
|
|
<a id='x1-61256r128'></a><span class='ecrm-0500'>128</span><span class='ectt-0800'> </span><span id='textcolor2767'><span class='ectt-0800'>/* AES 256 with given symmetric key */</span></span>
|
|
<a id='x1-61258r129'></a><span class='ecrm-0500'>129</span><span class='ectt-0800'> </span><span id='textcolor2768'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (crypto_skcipher_setkey(sk->tfm, key, SYMMETRIC_KEY_LENGTH)) {</span>
|
|
<a id='x1-61260r130'></a><span class='ecrm-0500'>130</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2769'><span class='ectt-0800'>"key could not be set</span></span><span id='textcolor2770'><span class='ectt-0800'>\n</span></span><span id='textcolor2771'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-61262r131'></a><span class='ecrm-0500'>131</span><span class='ectt-0800'> ret = -EAGAIN;</span>
|
|
<a id='x1-61264r132'></a><span class='ecrm-0500'>132</span><span class='ectt-0800'> </span><span id='textcolor2772'><span class='ectt-0800'>goto</span></span><span class='ectt-0800'> out;</span>
|
|
<a id='x1-61266r133'></a><span class='ecrm-0500'>133</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-61268r134'></a><span class='ecrm-0500'>134</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2773'><span class='ectt-0800'>"Symmetric key: %s</span></span><span id='textcolor2774'><span class='ectt-0800'>\n</span></span><span id='textcolor2775'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, key);</span>
|
|
<a id='x1-61270r135'></a><span class='ecrm-0500'>135</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2776'><span class='ectt-0800'>"Plaintext: %s</span></span><span id='textcolor2777'><span class='ectt-0800'>\n</span></span><span id='textcolor2778'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, plaintext);</span>
|
|
<a id='x1-61272r136'></a><span class='ecrm-0500'>136</span>
|
|
<a id='x1-61274r137'></a><span class='ecrm-0500'>137</span><span class='ectt-0800'> </span><span id='textcolor2779'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (!sk->ivdata) {</span>
|
|
<a id='x1-61276r138'></a><span class='ecrm-0500'>138</span><span class='ectt-0800'> </span><span id='textcolor2780'><span class='ectt-0800'>/* see https://en.wikipedia.org/wiki/Initialization_vector */</span></span>
|
|
<a id='x1-61278r139'></a><span class='ecrm-0500'>139</span><span class='ectt-0800'> sk->ivdata = kmalloc(CIPHER_BLOCK_SIZE, GFP_KERNEL);</span>
|
|
<a id='x1-61280r140'></a><span class='ecrm-0500'>140</span><span class='ectt-0800'> </span><span id='textcolor2781'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (!sk->ivdata) {</span>
|
|
<a id='x1-61282r141'></a><span class='ecrm-0500'>141</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2782'><span class='ectt-0800'>"could not allocate ivdata</span></span><span id='textcolor2783'><span class='ectt-0800'>\n</span></span><span id='textcolor2784'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-61284r142'></a><span class='ecrm-0500'>142</span><span class='ectt-0800'> </span><span id='textcolor2785'><span class='ectt-0800'>goto</span></span><span class='ectt-0800'> out;</span>
|
|
<a id='x1-61286r143'></a><span class='ecrm-0500'>143</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-61288r144'></a><span class='ecrm-0500'>144</span><span class='ectt-0800'> get_random_bytes(sk->ivdata, CIPHER_BLOCK_SIZE);</span>
|
|
<a id='x1-61290r145'></a><span class='ecrm-0500'>145</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-61292r146'></a><span class='ecrm-0500'>146</span>
|
|
<a id='x1-61294r147'></a><span class='ecrm-0500'>147</span><span class='ectt-0800'> </span><span id='textcolor2786'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (!sk->scratchpad) {</span>
|
|
<a id='x1-61296r148'></a><span class='ecrm-0500'>148</span><span class='ectt-0800'> </span><span id='textcolor2787'><span class='ectt-0800'>/* The text to be encrypted */</span></span>
|
|
<a id='x1-61298r149'></a><span class='ecrm-0500'>149</span><span class='ectt-0800'> sk->scratchpad = kmalloc(CIPHER_BLOCK_SIZE, GFP_KERNEL);</span>
|
|
<a id='x1-61300r150'></a><span class='ecrm-0500'>150</span><span class='ectt-0800'> </span><span id='textcolor2788'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (!sk->scratchpad) {</span>
|
|
<a id='x1-61302r151'></a><span class='ecrm-0500'>151</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2789'><span class='ectt-0800'>"could not allocate scratchpad</span></span><span id='textcolor2790'><span class='ectt-0800'>\n</span></span><span id='textcolor2791'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-61304r152'></a><span class='ecrm-0500'>152</span><span class='ectt-0800'> </span><span id='textcolor2792'><span class='ectt-0800'>goto</span></span><span class='ectt-0800'> out;</span>
|
|
<a id='x1-61306r153'></a><span class='ecrm-0500'>153</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-61308r154'></a><span class='ecrm-0500'>154</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-61310r155'></a><span class='ecrm-0500'>155</span><span class='ectt-0800'> sprintf((</span><span id='textcolor2793'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *) sk->scratchpad, </span><span id='textcolor2794'><span class='ectt-0800'>"%s"</span></span><span class='ectt-0800'>, plaintext);</span>
|
|
<a id='x1-61312r156'></a><span class='ecrm-0500'>156</span>
|
|
<a id='x1-61314r157'></a><span class='ecrm-0500'>157</span><span class='ectt-0800'> sg_init_one(&sk->sg, sk->scratchpad, CIPHER_BLOCK_SIZE);</span>
|
|
<a id='x1-61316r158'></a><span class='ecrm-0500'>158</span><span class='ectt-0800'> skcipher_request_set_crypt(sk->req, &sk->sg, &sk->sg, CIPHER_BLOCK_SIZE,</span>
|
|
<a id='x1-61318r159'></a><span class='ecrm-0500'>159</span><span class='ectt-0800'> sk->ivdata);</span>
|
|
<a id='x1-61320r160'></a><span class='ecrm-0500'>160</span><span class='ectt-0800'> init_completion(&sk->result.completion);</span>
|
|
<a id='x1-61322r161'></a><span class='ecrm-0500'>161</span>
|
|
<a id='x1-61324r162'></a><span class='ecrm-0500'>162</span><span class='ectt-0800'> </span><span id='textcolor2795'><span class='ectt-0800'>/* encrypt data */</span></span>
|
|
<a id='x1-61326r163'></a><span class='ecrm-0500'>163</span><span class='ectt-0800'> ret = crypto_skcipher_encrypt(sk->req);</span>
|
|
<a id='x1-61328r164'></a><span class='ecrm-0500'>164</span><span class='ectt-0800'> ret = test_skcipher_result(sk, ret);</span>
|
|
<a id='x1-61330r165'></a><span class='ecrm-0500'>165</span><span class='ectt-0800'> </span><span id='textcolor2796'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (ret)</span>
|
|
<a id='x1-61332r166'></a><span class='ecrm-0500'>166</span><span class='ectt-0800'> </span><span id='textcolor2797'><span class='ectt-0800'>goto</span></span><span class='ectt-0800'> out;</span>
|
|
<a id='x1-61334r167'></a><span class='ecrm-0500'>167</span>
|
|
<a id='x1-61336r168'></a><span class='ecrm-0500'>168</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2798'><span class='ectt-0800'>"Encryption request successful</span></span><span id='textcolor2799'><span class='ectt-0800'>\n</span></span><span id='textcolor2800'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-61338r169'></a><span class='ecrm-0500'>169</span>
|
|
<a id='x1-61340r170'></a><span class='ecrm-0500'>170</span><span class='ectt-0800'>out:</span>
|
|
<a id='x1-61342r171'></a><span class='ecrm-0500'>171</span><span class='ectt-0800'> </span><span id='textcolor2801'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> ret;</span>
|
|
<a id='x1-61344r172'></a><span class='ecrm-0500'>172</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-61346r173'></a><span class='ecrm-0500'>173</span>
|
|
<a id='x1-61348r174'></a><span class='ecrm-0500'>174</span><span id='textcolor2802'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> cryptoapi_init(</span><span id='textcolor2803'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-61350r175'></a><span class='ecrm-0500'>175</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-61352r176'></a><span class='ecrm-0500'>176</span><span class='ectt-0800'> </span><span id='textcolor2804'><span class='ectt-0800'>/* The world</span><span class='tctt-0800'>'</span><span class='ectt-0800'>s favorite password */</span></span>
|
|
<a id='x1-61354r177'></a><span class='ecrm-0500'>177</span><span class='ectt-0800'> </span><span id='textcolor2805'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *password = </span><span id='textcolor2806'><span class='ectt-0800'>"password123"</span></span><span class='ectt-0800'>;</span>
|
|
<a id='x1-61356r178'></a><span class='ecrm-0500'>178</span>
|
|
<a id='x1-61358r179'></a><span class='ecrm-0500'>179</span><span class='ectt-0800'> sk.tfm = NULL;</span>
|
|
<a id='x1-61360r180'></a><span class='ecrm-0500'>180</span><span class='ectt-0800'> sk.req = NULL;</span>
|
|
<a id='x1-61362r181'></a><span class='ecrm-0500'>181</span><span class='ectt-0800'> sk.scratchpad = NULL;</span>
|
|
<a id='x1-61364r182'></a><span class='ecrm-0500'>182</span><span class='ectt-0800'> sk.ciphertext = NULL;</span>
|
|
<a id='x1-61366r183'></a><span class='ecrm-0500'>183</span><span class='ectt-0800'> sk.ivdata = NULL;</span>
|
|
<a id='x1-61368r184'></a><span class='ecrm-0500'>184</span>
|
|
<a id='x1-61370r185'></a><span class='ecrm-0500'>185</span><span class='ectt-0800'> test_skcipher_encrypt(</span><span id='textcolor2807'><span class='ectt-0800'>"Testing"</span></span><span class='ectt-0800'>, password, &sk);</span>
|
|
<a id='x1-61372r186'></a><span class='ecrm-0500'>186</span><span class='ectt-0800'> </span><span id='textcolor2808'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-61374r187'></a><span class='ecrm-0500'>187</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-61376r188'></a><span class='ecrm-0500'>188</span>
|
|
<a id='x1-61378r189'></a><span class='ecrm-0500'>189</span><span id='textcolor2809'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> cryptoapi_exit(</span><span id='textcolor2810'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-61380r190'></a><span class='ecrm-0500'>190</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-61382r191'></a><span class='ecrm-0500'>191</span><span class='ectt-0800'> test_skcipher_finish(&sk);</span>
|
|
<a id='x1-61384r192'></a><span class='ecrm-0500'>192</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-61386r193'></a><span class='ecrm-0500'>193</span>
|
|
<a id='x1-61388r194'></a><span class='ecrm-0500'>194</span><span class='ectt-0800'>module_init(cryptoapi_init);</span>
|
|
<a id='x1-61390r195'></a><span class='ecrm-0500'>195</span><span class='ectt-0800'>module_exit(cryptoapi_exit);</span>
|
|
<a id='x1-61392r196'></a><span class='ecrm-0500'>196</span>
|
|
<a id='x1-61394r197'></a><span class='ecrm-0500'>197</span><span class='ectt-0800'>MODULE_DESCRIPTION(</span><span id='textcolor2811'><span class='ectt-0800'>"Symmetric key encryption example"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-61396r198'></a><span class='ecrm-0500'>198</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor2812'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
|
|
<!-- l. 1426 --><p class='noindent'>
|
|
</p>
|
|
<h3 class='sectionHead' id='standardising-the-interfaces-the-device-model'><span class='titlemark'>0.17 </span> <a id='x1-620000.17'></a>Standardising the interfaces: The Device Model</h3>
|
|
<!-- l. 1428 --><p class='noindent'>Up to this point we’ve seen all kinds of modules doing all kinds of things, but there
|
|
was no consistency in their interfaces with the rest of the kernel. To impose some
|
|
consistency such that there is at minimum a standardised way to start, suspend and
|
|
resume a device a device model was added. An example is show below, and you can
|
|
use this as a template to add your own suspend, resume or other interface
|
|
functions.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb70'><a id='x1-62002r1'></a><span class='ecrm-0500'>1</span><span id='textcolor2813'><span class='ectt-0800'>/*</span></span>
|
|
<a id='x1-62004r2'></a><span class='ecrm-0500'>2</span><span id='textcolor2814'><span class='ectt-0800'> * devicemodel.c</span></span>
|
|
<a id='x1-62006r3'></a><span class='ecrm-0500'>3</span><span id='textcolor2815'><span class='ectt-0800'> */</span></span>
|
|
<a id='x1-62008r4'></a><span class='ecrm-0500'>4</span><span id='textcolor2816'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2817'><span class='ectt-0800'><linux/kernel.h></span></span>
|
|
<a id='x1-62010r5'></a><span class='ecrm-0500'>5</span><span id='textcolor2818'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2819'><span class='ectt-0800'><linux/module.h></span></span>
|
|
<a id='x1-62012r6'></a><span class='ecrm-0500'>6</span><span id='textcolor2820'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor2821'><span class='ectt-0800'><linux/platform_device.h></span></span>
|
|
<a id='x1-62014r7'></a><span class='ecrm-0500'>7</span>
|
|
<a id='x1-62016r8'></a><span class='ecrm-0500'>8</span><span id='textcolor2822'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> devicemodel_data {</span>
|
|
<a id='x1-62018r9'></a><span class='ecrm-0500'>9</span><span class='ectt-0800'> </span><span id='textcolor2823'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *greeting;</span>
|
|
<a id='x1-62020r10'></a><span class='ecrm-0500'>10</span><span class='ectt-0800'> </span><span id='textcolor2824'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> number;</span>
|
|
<a id='x1-62022r11'></a><span class='ecrm-0500'>11</span><span class='ectt-0800'>};</span>
|
|
<a id='x1-62024r12'></a><span class='ecrm-0500'>12</span>
|
|
<a id='x1-62026r13'></a><span class='ecrm-0500'>13</span><span id='textcolor2825'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2826'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> devicemodel_probe(</span><span id='textcolor2827'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> platform_device *dev)</span>
|
|
<a id='x1-62028r14'></a><span class='ecrm-0500'>14</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-62030r15'></a><span class='ecrm-0500'>15</span><span class='ectt-0800'> </span><span id='textcolor2828'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> devicemodel_data *pd =</span>
|
|
<a id='x1-62032r16'></a><span class='ecrm-0500'>16</span><span class='ectt-0800'> (</span><span id='textcolor2829'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> devicemodel_data *) (dev->dev.platform_data);</span>
|
|
<a id='x1-62034r17'></a><span class='ecrm-0500'>17</span>
|
|
<a id='x1-62036r18'></a><span class='ecrm-0500'>18</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2830'><span class='ectt-0800'>"devicemodel probe</span></span><span id='textcolor2831'><span class='ectt-0800'>\n</span></span><span id='textcolor2832'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-62038r19'></a><span class='ecrm-0500'>19</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2833'><span class='ectt-0800'>"devicemodel greeting: %s; %d</span></span><span id='textcolor2834'><span class='ectt-0800'>\n</span></span><span id='textcolor2835'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, pd->greeting, pd->number);</span>
|
|
<a id='x1-62040r20'></a><span class='ecrm-0500'>20</span>
|
|
<a id='x1-62042r21'></a><span class='ecrm-0500'>21</span><span class='ectt-0800'> </span><span id='textcolor2836'><span class='ectt-0800'>/* Your device initialisation code */</span></span>
|
|
<a id='x1-62044r22'></a><span class='ecrm-0500'>22</span>
|
|
<a id='x1-62046r23'></a><span class='ecrm-0500'>23</span><span class='ectt-0800'> </span><span id='textcolor2837'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-62048r24'></a><span class='ecrm-0500'>24</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-62050r25'></a><span class='ecrm-0500'>25</span>
|
|
<a id='x1-62052r26'></a><span class='ecrm-0500'>26</span><span id='textcolor2838'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2839'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> devicemodel_remove(</span><span id='textcolor2840'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> platform_device *dev)</span>
|
|
<a id='x1-62054r27'></a><span class='ecrm-0500'>27</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-62056r28'></a><span class='ecrm-0500'>28</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2841'><span class='ectt-0800'>"devicemodel example removed</span></span><span id='textcolor2842'><span class='ectt-0800'>\n</span></span><span id='textcolor2843'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-62058r29'></a><span class='ecrm-0500'>29</span>
|
|
<a id='x1-62060r30'></a><span class='ecrm-0500'>30</span><span class='ectt-0800'> </span><span id='textcolor2844'><span class='ectt-0800'>/* Your device removal code */</span></span>
|
|
<a id='x1-62062r31'></a><span class='ecrm-0500'>31</span>
|
|
<a id='x1-62064r32'></a><span class='ecrm-0500'>32</span><span class='ectt-0800'> </span><span id='textcolor2845'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-62066r33'></a><span class='ecrm-0500'>33</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-62068r34'></a><span class='ecrm-0500'>34</span>
|
|
<a id='x1-62070r35'></a><span class='ecrm-0500'>35</span><span id='textcolor2846'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2847'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> devicemodel_suspend(</span><span id='textcolor2848'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> device *dev)</span>
|
|
<a id='x1-62072r36'></a><span class='ecrm-0500'>36</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-62074r37'></a><span class='ecrm-0500'>37</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2849'><span class='ectt-0800'>"devicemodel example suspend</span></span><span id='textcolor2850'><span class='ectt-0800'>\n</span></span><span id='textcolor2851'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-62076r38'></a><span class='ecrm-0500'>38</span>
|
|
<a id='x1-62078r39'></a><span class='ecrm-0500'>39</span><span class='ectt-0800'> </span><span id='textcolor2852'><span class='ectt-0800'>/* Your device suspend code */</span></span>
|
|
<a id='x1-62080r40'></a><span class='ecrm-0500'>40</span>
|
|
<a id='x1-62082r41'></a><span class='ecrm-0500'>41</span><span class='ectt-0800'> </span><span id='textcolor2853'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-62084r42'></a><span class='ecrm-0500'>42</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-62086r43'></a><span class='ecrm-0500'>43</span>
|
|
<a id='x1-62088r44'></a><span class='ecrm-0500'>44</span><span id='textcolor2854'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2855'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> devicemodel_resume(</span><span id='textcolor2856'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> device *dev)</span>
|
|
<a id='x1-62090r45'></a><span class='ecrm-0500'>45</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-62092r46'></a><span class='ecrm-0500'>46</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2857'><span class='ectt-0800'>"devicemodel example resume</span></span><span id='textcolor2858'><span class='ectt-0800'>\n</span></span><span id='textcolor2859'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-62094r47'></a><span class='ecrm-0500'>47</span>
|
|
<a id='x1-62096r48'></a><span class='ecrm-0500'>48</span><span class='ectt-0800'> </span><span id='textcolor2860'><span class='ectt-0800'>/* Your device resume code */</span></span>
|
|
<a id='x1-62098r49'></a><span class='ecrm-0500'>49</span>
|
|
<a id='x1-62100r50'></a><span class='ecrm-0500'>50</span><span class='ectt-0800'> </span><span id='textcolor2861'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-62102r51'></a><span class='ecrm-0500'>51</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-62104r52'></a><span class='ecrm-0500'>52</span>
|
|
<a id='x1-62106r53'></a><span class='ecrm-0500'>53</span><span id='textcolor2862'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2863'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor2864'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> dev_pm_ops devicemodel_pm_ops = {</span>
|
|
<a id='x1-62108r54'></a><span class='ecrm-0500'>54</span><span class='ectt-0800'> .suspend = devicemodel_suspend,</span>
|
|
<a id='x1-62110r55'></a><span class='ecrm-0500'>55</span><span class='ectt-0800'> .resume = devicemodel_resume,</span>
|
|
<a id='x1-62112r56'></a><span class='ecrm-0500'>56</span><span class='ectt-0800'> .poweroff = devicemodel_suspend,</span>
|
|
<a id='x1-62114r57'></a><span class='ecrm-0500'>57</span><span class='ectt-0800'> .freeze = devicemodel_suspend,</span>
|
|
<a id='x1-62116r58'></a><span class='ecrm-0500'>58</span><span class='ectt-0800'> .thaw = devicemodel_resume,</span>
|
|
<a id='x1-62118r59'></a><span class='ecrm-0500'>59</span><span class='ectt-0800'> .restore = devicemodel_resume,</span>
|
|
<a id='x1-62120r60'></a><span class='ecrm-0500'>60</span><span class='ectt-0800'>};</span>
|
|
<a id='x1-62122r61'></a><span class='ecrm-0500'>61</span>
|
|
<a id='x1-62124r62'></a><span class='ecrm-0500'>62</span><span id='textcolor2865'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2866'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> platform_driver devicemodel_driver = {</span>
|
|
<a id='x1-62126r63'></a><span class='ecrm-0500'>63</span><span class='ectt-0800'> .driver =</span>
|
|
<a id='x1-62128r64'></a><span class='ecrm-0500'>64</span><span class='ectt-0800'> {</span>
|
|
<a id='x1-62130r65'></a><span class='ecrm-0500'>65</span><span class='ectt-0800'> .name = </span><span id='textcolor2867'><span class='ectt-0800'>"devicemodel_example"</span></span><span class='ectt-0800'>,</span>
|
|
<a id='x1-62132r66'></a><span class='ecrm-0500'>66</span><span class='ectt-0800'> .owner = THIS_MODULE,</span>
|
|
<a id='x1-62134r67'></a><span class='ecrm-0500'>67</span><span class='ectt-0800'> .pm = &devicemodel_pm_ops,</span>
|
|
<a id='x1-62136r68'></a><span class='ecrm-0500'>68</span><span class='ectt-0800'> },</span>
|
|
<a id='x1-62138r69'></a><span class='ecrm-0500'>69</span><span class='ectt-0800'> .probe = devicemodel_probe,</span>
|
|
<a id='x1-62140r70'></a><span class='ecrm-0500'>70</span><span class='ectt-0800'> .remove = devicemodel_remove,</span>
|
|
<a id='x1-62142r71'></a><span class='ecrm-0500'>71</span><span class='ectt-0800'>};</span>
|
|
<a id='x1-62144r72'></a><span class='ecrm-0500'>72</span>
|
|
<a id='x1-62146r73'></a><span class='ecrm-0500'>73</span><span id='textcolor2868'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2869'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> devicemodel_init(</span><span id='textcolor2870'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-62148r74'></a><span class='ecrm-0500'>74</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-62150r75'></a><span class='ecrm-0500'>75</span><span class='ectt-0800'> </span><span id='textcolor2871'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> ret;</span>
|
|
<a id='x1-62152r76'></a><span class='ecrm-0500'>76</span>
|
|
<a id='x1-62154r77'></a><span class='ecrm-0500'>77</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2872'><span class='ectt-0800'>"devicemodel init</span></span><span id='textcolor2873'><span class='ectt-0800'>\n</span></span><span id='textcolor2874'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-62156r78'></a><span class='ecrm-0500'>78</span>
|
|
<a id='x1-62158r79'></a><span class='ecrm-0500'>79</span><span class='ectt-0800'> ret = platform_driver_register(&devicemodel_driver);</span>
|
|
<a id='x1-62160r80'></a><span class='ecrm-0500'>80</span>
|
|
<a id='x1-62162r81'></a><span class='ecrm-0500'>81</span><span class='ectt-0800'> </span><span id='textcolor2875'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (ret) {</span>
|
|
<a id='x1-62164r82'></a><span class='ecrm-0500'>82</span><span class='ectt-0800'> pr_err(</span><span id='textcolor2876'><span class='ectt-0800'>"Unable to register driver</span></span><span id='textcolor2877'><span class='ectt-0800'>\n</span></span><span id='textcolor2878'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-62166r83'></a><span class='ecrm-0500'>83</span><span class='ectt-0800'> </span><span id='textcolor2879'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> ret;</span>
|
|
<a id='x1-62168r84'></a><span class='ecrm-0500'>84</span><span class='ectt-0800'> }</span>
|
|
<a id='x1-62170r85'></a><span class='ecrm-0500'>85</span>
|
|
<a id='x1-62172r86'></a><span class='ecrm-0500'>86</span><span class='ectt-0800'> </span><span id='textcolor2880'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
<a id='x1-62174r87'></a><span class='ecrm-0500'>87</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-62176r88'></a><span class='ecrm-0500'>88</span>
|
|
<a id='x1-62178r89'></a><span class='ecrm-0500'>89</span><span id='textcolor2881'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor2882'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> devicemodel_exit(</span><span id='textcolor2883'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
<a id='x1-62180r90'></a><span class='ecrm-0500'>90</span><span class='ectt-0800'>{</span>
|
|
<a id='x1-62182r91'></a><span class='ecrm-0500'>91</span><span class='ectt-0800'> pr_info(</span><span id='textcolor2884'><span class='ectt-0800'>"devicemodel exit</span></span><span id='textcolor2885'><span class='ectt-0800'>\n</span></span><span id='textcolor2886'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-62184r92'></a><span class='ecrm-0500'>92</span><span class='ectt-0800'> platform_driver_unregister(&devicemodel_driver);</span>
|
|
<a id='x1-62186r93'></a><span class='ecrm-0500'>93</span><span class='ectt-0800'>}</span>
|
|
<a id='x1-62188r94'></a><span class='ecrm-0500'>94</span>
|
|
<a id='x1-62190r95'></a><span class='ecrm-0500'>95</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor2887'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-62192r96'></a><span class='ecrm-0500'>96</span><span class='ectt-0800'>MODULE_DESCRIPTION(</span><span id='textcolor2888'><span class='ectt-0800'>"Linux Device Model example"</span></span><span class='ectt-0800'>);</span>
|
|
<a id='x1-62194r97'></a><span class='ecrm-0500'>97</span>
|
|
<a id='x1-62196r98'></a><span class='ecrm-0500'>98</span><span class='ectt-0800'>module_init(devicemodel_init);</span>
|
|
<a id='x1-62198r99'></a><span class='ecrm-0500'>99</span><span class='ectt-0800'>module_exit(devicemodel_exit);</span></pre>
|
|
|
|
|
|
|
|
<!-- l. 1432 --><p class='noindent'>
|
|
</p>
|
|
<h3 class='sectionHead' id='optimizations'><span class='titlemark'>0.18 </span> <a id='x1-630000.18'></a>Optimizations</h3>
|
|
<!-- l. 1434 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='likely-and-unlikely-conditions'><span class='titlemark'>0.18.1 </span> <a id='x1-640000.18.1'></a>Likely and Unlikely conditions</h4>
|
|
<!-- l. 1436 --><p class='noindent'>Sometimes you might want your code to run as quickly as possible, especially if
|
|
it’s handling an interrupt or doing something which might cause noticible
|
|
latency. If your code contains boolean conditions and if you know that the
|
|
conditions are almost always likely to evaluate as either <span class='ecti-1000'>true </span>or <span class='ecti-1000'>false</span>, then
|
|
you can allow the compiler to optimise for this using the <span class='ecti-1000'>likely </span>and <span class='ecti-1000'>unlikely</span>
|
|
macros.
|
|
</p><!-- l. 1438 --><p class='indent'> For example, when allocating memory you’re almost always expecting this to
|
|
succeed.
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
</p>
|
|
<pre class='fancyvrb' id='fancyvrb71'><a id='x1-64008r1'></a><span class='ecrm-0500'>1</span><span class='ectt-0800'>bvl = bvec_alloc(gfp_mask, nr_iovecs, &idx);</span>
|
|
<a id='x1-64010r2'></a><span class='ecrm-0500'>2</span><span id='textcolor2889'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (unlikely(!bvl)) {</span>
|
|
<a id='x1-64012r3'></a><span class='ecrm-0500'>3</span><span class='ectt-0800'> mempool_free(bio, bio_pool);</span>
|
|
<a id='x1-64014r4'></a><span class='ecrm-0500'>4</span><span class='ectt-0800'> bio = NULL;</span>
|
|
<a id='x1-64016r5'></a><span class='ecrm-0500'>5</span><span class='ectt-0800'> </span><span id='textcolor2890'><span class='ectt-0800'>goto</span></span><span class='ectt-0800'> out;</span>
|
|
<a id='x1-64018r6'></a><span class='ecrm-0500'>6</span><span class='ectt-0800'>}</span></pre>
|
|
<!-- l. 1449 --><p class='indent'> When the <span class='ecti-1000'>unlikely </span>macro is used the compiler alters its machine instruction
|
|
output so that it continues along the false branch and only jumps if the condition is
|
|
true. That avoids flushing the processor pipeline. The opposite happens if you use the
|
|
<span class='ecti-1000'>likely </span>macro.
|
|
</p>
|
|
<h3 class='sectionHead' id='common-pitfalls'><span class='titlemark'>0.19 </span> <a id='x1-650000.19'></a>Common Pitfalls</h3>
|
|
<!-- l. 1452 --><p class='noindent'>Before I send you on your way to go out into the world and write kernel modules,
|
|
there are a few things I need to warn you about. If I fail to warn you and something
|
|
bad happens, please report the problem to me for a full refund of the amount I was
|
|
paid for your copy of the book.
|
|
</p><!-- l. 1454 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='using-standard-libraries'><span class='titlemark'>0.19.1 </span> <a id='x1-660000.19.1'></a>Using standard libraries</h4>
|
|
<!-- l. 1456 --><p class='noindent'>You can’t do that. In a kernel module you can only use kernel functions, which are
|
|
the functions you can see in /proc/kallsyms.
|
|
</p><!-- l. 1458 --><p class='noindent'>
|
|
</p>
|
|
|
|
|
|
|
|
<h4 class='subsectionHead' id='disabling-interrupts'><span class='titlemark'>0.19.2 </span> <a id='x1-670000.19.2'></a>Disabling interrupts</h4>
|
|
<!-- l. 1460 --><p class='noindent'>You might need to do this for a short time and that is OK, but if you don’t
|
|
enable them afterwards, your system will be stuck and you’ll have to power it
|
|
off.
|
|
</p><!-- l. 1462 --><p class='noindent'>
|
|
</p>
|
|
<h4 class='subsectionHead' id='sticking-your-head-inside-a-large-carnivore'><span class='titlemark'>0.19.3 </span> <a id='x1-680000.19.3'></a>Sticking your head inside a large carnivore</h4>
|
|
<!-- l. 1464 --><p class='noindent'>I probably don’t have to warn you about this, but I figured I will anyway, just in
|
|
case.
|
|
</p><!-- l. 1466 --><p class='noindent'>
|
|
</p>
|
|
<h3 class='sectionHead' id='where-to-go-from-here'><span class='titlemark'>0.20 </span> <a id='x1-690000.20'></a>Where To Go From Here?</h3>
|
|
<!-- l. 1468 --><p class='noindent'>I could easily have squeezed a few more chapters into this book. I could have added a
|
|
chapter about creating new file systems, or about adding new protocol stacks (as if
|
|
there’s a need for that – you’d have to dig underground to find a protocol stack
|
|
not supported by Linux). I could have added explanations of the kernel
|
|
mechanisms we haven’t touched upon, such as bootstrapping or the disk
|
|
interface.
|
|
</p><!-- l. 1470 --><p class='indent'> However, I chose not to. My purpose in writing this book was to provide initiation
|
|
into the mysteries of kernel module programming and to teach the common
|
|
techniques for that purpose. For people seriously interested in kernel programming, I
|
|
recommend <a href='https://kernelnewbies.org'>kernelnewbies.org</a> and the <span class='ecti-1000'>Documentation </span>subdirectory within the kernel
|
|
source code which isn’t always easy to understand but can be a starting point for
|
|
further investigation. Also, as Linus said, the best way to learn the kernel is to read
|
|
the source code yourself.
|
|
</p><!-- l. 1472 --><p class='indent'> If you’re interested in more examples of short kernel modules then searching on
|
|
sites such as Github and Gitlab is a good way to start, although there is a lot of
|
|
duplication of older LKMPG examples which may not compile with newer kernel
|
|
versions. You will also be able to find examples of the use of kernel modules to attack
|
|
or compromise systems or exfiltrate data and those can be useful for thinking about
|
|
how to defend systems and learning about existing security mechanisms within the
|
|
kernel.
|
|
</p><!-- l. 1474 --><p class='indent'> I hope I have helped you in your quest to become a better programmer, or at
|
|
least to have fun through technology. And, if you do write useful kernel modules, I
|
|
hope you publish them under the GPL, so I can use them too.
|
|
</p><!-- l. 1476 --><p class='indent'> If you’d like to contribute to this guide or notice anything glaringly wrong, please
|
|
create an issue at <a class='url' href='https://github.com/sysprog21/lkmpg'><span class='ectt-1000'>https://github.com/sysprog21/lkmpg</span></a>.
|
|
</p><!-- l. 1478 --><p class='indent'> Happy hacking.
|
|
</p>
|
|
|
|
</body>
|
|
</html> |