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15 Commits

Author SHA1 Message Date
Bob Lee
d1d2a2b031
Fix a weird behavior of a function 
The procfile_write prints the content what user writes into. However,
when the content size is greater than or equal to PROCFS_MAX_SIZE,
procfile_write will print nothing, because the index for appending the
tail NULL character will be modulo to 0, which is an off-by-one error.

This fixes the problem by changing the upper bound of procfs_buffer_size
to (PROCFS_MAX_SIZE - 1), leaving one byte for NULL character. After
the change, we can discard the modulo because the range of
procfs_buffer_size is already between 0 and (PROCFS_MAX_SIZE - 1).
 2024-10-07 12:05:43 +08:00
keytouch
5e2b7aa2e3 procfs: Remove unnecessary cleanup on proc_create failure 2023-07-23 18:41:46 +08:00
Chih-En Lin
23c0a73c78 procfs: Enforce Linux naming style 2023-03-24 11:36:33 +08:00
linD026
39a313dc20 procfs{2, 3}: Change to use offset parameter 
To make sure the behavior of the read and write operations are correct
with offset, update it each time. Also, since it is using the offset,
modify the part of read for removing unnecessary variable.
 2022-09-08 12:53:29 +08:00
linD026
6b6b6635cf
CI: Introduce Smatch for static analysis (#125) 
Smatch[1][2] is a pluggable static analysis for C. It may help us find
out the potential problem of the example code.

Doing with smatch, if set the --file-output flag, it will generate the
{}.c.smatch report for each c file. This will make a little bit
complicated to collect all the report messages. So, here we stay at the
default setting, stdout for the smatch messages.

For more information, see:
- https://lwn.net/Articles/696624/
- https://elinux.org/images/d/d3/Bargmann.pdf

Also, fix the warning from Smatch:

Smatch failed: 1 warning(s), 1 error(s)
lkmpg/examples/procfs2.c:57 procfile_write() error: buffer overflow 'procfs_buffer' 1024 <= 1024
lkmpg/examples/kbleds.c:58 kbleds_init() warn: argument 5 to %lx specifier is cast from pointer

Furthermore, the effect of the write operation in procfs2.c is too
implied. So after writing, print the buffer every time.

Close #122

[1] https://github.com/error27/smatch
[2] https://repo.or.cz/w/smatch.git
 2021-11-01 08:20:41 +08:00
linD026
9289bfe59c
Fix the warnings raised by Sparse (#92) 
Sparse[1] is a semantic parser, capable of finding out the potential
problems of Linux kernel code. This patch fixed the warnings.

[1] https://www.kernel.org/doc/html/latest/dev-tools/sparse.html
 2021-09-04 17:53:29 +08:00
linD026
eef2bc4395
Enforce Linux kernel coding style (#88) 
The only exception is to indent with four spaces rather than tabs
for sticking to compact layout of source listing.

Close #87
 2021-09-02 15:15:07 +08:00
Jim Huang
10c7a9433a Apply editorial changes 
This patch makes source listing shorter and more compact, that helps
when browsing.
 2021-08-08 01:24:59 +08:00
Jim Huang
d43259c553 Drop the deprecated init_module() and cleanup_module() 2021-08-08 00:29:24 +08:00
Jim Huang
a26d93037e Enforce consistent style 
Execute "make indent" before submitting patches.
 2021-08-07 23:33:37 +08:00
linD026
c7a7a667cf
Avoid strlen by assigning explicit length of string for proc_read (#18) 
Since the address of buffer is userspace address, it may trigger an unexpected fault on strlen(buffer).

On Ubuntu 20.04.2 LTS ( 5.8.0-63-generic ), using strlen(buffer) will result in the following:
[ 2168.010930] /proc/buffer1k created
[ 2177.014347] BUG: unable to handle page fault for address: 00007fbbc2a17000
[ 2177.014355] #PF: supervisor read access in kernel mode
[ 2177.014358] #PF: error_code(0x0000) - not-present page
[ 2177.014361] PGD 80000003c61d0067 P4D 80000003c61d0067 PUD 3ee6c5067 PMD 40e1ff067 PTE 0
[ 2177.014369] Oops: 0000 [#1] SMP PTI
[ 2177.014376] CPU: 7 PID: 4750 Comm: cat Tainted: P        W  OE     5.8.0-63-generic #71~20.04.1-Ubuntu

[ 2177.014387] RIP: 0010:procfile_read+0xb/0x20 [procfs2]
[ 2177.014393] Code: Unable to access opcode bytes at RIP 0xffffffffc1253fe1.
[ 2177.014396] RSP: 0018:ffffbc84412cbe78 EFLAGS: 00010286
[ 2177.014400] RAX: ffffffffc1254000 RBX: 0000000000020000 RCX: ffffbc84412cbef0
[ 2177.014403] RDX: 0000000000020000 RSI: 00007fbbc2a17000 RDI: ffffa057d2708f00
[ 2177.014406] RBP: ffffbc84412cbe80 R08: 0000000000000001 R09: 0000000000000000
[ 2177.014409] R10: 0000000000000000 R11: 0000000000000000 R12: ffffa0581de8ccc0
[ 2177.014411] R13: ffffa057d2708f00 R14: ffffbc84412cbef0 R15: 00007fbbc2a17000
[ 2177.014415] FS:  00007fbbc3bfa580(0000) GS:ffffa0582dbc0000(0000) knlGS:0000000000000000
[ 2177.014418] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 2177.014421] CR2: ffffffffc1253fe1 CR3: 00000003c611c004 CR4: 00000000003606e0
[ 2177.014424] Call Trace:
[ 2177.014435]  proc_reg_read+0x66/0x90
[ 2177.014441]  vfs_read+0xaa/0x190
[ 2177.014446]  ksys_read+0x67/0xe0
[ 2177.014451]  __x64_sys_read+0x1a/0x20
[ 2177.014458]  do_syscall_64+0x49/0xc0
[ 2177.014464]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 2177.014467] RIP: 0033:0x7fbbc3b18142
[ 2177.014472] Code: c0 e9 c2 fe ff ff 50 48 8d 3d 3a ca 0a 00 e8 f5 19 02 00 0f 1f 44 00 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 0f 05 <48> 3d 00 f0 ff ff 77 56 c3 0f 1f 44 00 00 48 83 ec 28 48 89 54 24
[ 2177.014476] RSP: 002b:00007ffcf2d20d78 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
[ 2177.014479] RAX: ffffffffffffffda RBX: 0000000000020000 RCX: 00007fbbc3b18142
[ 2177.014482] RDX: 0000000000020000 RSI: 00007fbbc2a17000 RDI: 0000000000000003
[ 2177.014485] RBP: 00007fbbc2a17000 R08: 00007fbbc2a16010 R09: 0000000000000000
[ 2177.014487] R10: 0000000000000022 R11: 0000000000000246 R12: 0000560f8ff081f0
[ 2177.014490] R13: 0000000000000003 R14: 0000000000020000 R15: 0000000000020000

[ 2177.014635] CR2: 00007fbbc2a17000
[ 2177.014639] ---[ end trace b71ff05c1b0a10f6 ]---
[ 2177.184174] RIP: 0010:procfile_read+0xb/0x20 [procfs2]
[ 2177.184176] Code: Unable to access opcode bytes at RIP 0xffffffffc1253fe1.
[ 2177.184177] RSP: 0018:ffffbc84412cbe78 EFLAGS: 00010286
[ 2177.184178] RAX: ffffffffc1254000 RBX: 0000000000020000 RCX: ffffbc84412cbef0
[ 2177.184179] RDX: 0000000000020000 RSI: 00007fbbc2a17000 RDI: ffffa057d2708f00
[ 2177.184180] RBP: ffffbc84412cbe80 R08: 0000000000000001 R09: 0000000000000000
[ 2177.184180] R10: 0000000000000000 R11: 0000000000000000 R12: ffffa0581de8ccc0
[ 2177.184181] R13: ffffa057d2708f00 R14: ffffbc84412cbef0 R15: 00007fbbc2a17000
[ 2177.184182] FS:  00007fbbc3bfa580(0000) GS:ffffa0582dbc0000(0000) knlGS:0000000000000000
[ 2177.184182] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 2177.184183] CR2: ffffffffc1253fe1 CR3: 00000003c611c004 CR4: 00000000003606e0
 2021-07-29 16:10:52 +08:00
Jim Huang
faf3aa7c22 Make each source file more consistent 
It is vital to denote the file name and summary for each source,
otherwise readers could not figure out the corresponding files.
 2021-07-22 11:25:32 +08:00
Jim Huang
64f791f274 Improve the compatibility with kernel version < 5.6 2021-07-22 07:17:31 +08:00
Jim Huang
50b8dfe6c2 Enforce the customized style for example code 
Instead of using tab for indention, the style defaults to 4 spaces for
the sake of compact layout.
 2021-07-22 06:58:13 +08:00
Jim Huang
2246e20809 Add LaTeX script and sample code 2021-07-22 06:35:24 +08:00