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6b6b6635cf
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
98 lines
2.6 KiB
C
98 lines
2.6 KiB
C
/*
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* procfs2.c - create a "file" in /proc
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*/
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#include <linux/kernel.h> /* We're doing kernel work */
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#include <linux/module.h> /* Specifically, a module */
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#include <linux/proc_fs.h> /* Necessary because we use the proc fs */
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#include <linux/uaccess.h> /* for copy_from_user */
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#include <linux/version.h>
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#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 6, 0)
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#define HAVE_PROC_OPS
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#endif
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#define PROCFS_MAX_SIZE 1024
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#define PROCFS_NAME "buffer1k"
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/* This structure hold information about the /proc file */
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static struct proc_dir_entry *our_proc_file;
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/* The buffer used to store character for this module */
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static char procfs_buffer[PROCFS_MAX_SIZE];
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/* The size of the buffer */
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static unsigned long procfs_buffer_size = 0;
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/* This function is called then the /proc file is read */
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static ssize_t procfile_read(struct file *filePointer, char __user *buffer,
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size_t buffer_length, loff_t *offset)
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{
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char s[13] = "HelloWorld!\n";
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int len = sizeof(s);
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ssize_t ret = len;
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if (*offset >= len || copy_to_user(buffer, s, len)) {
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pr_info("copy_to_user failed\n");
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ret = 0;
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} else {
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pr_info("procfile read %s\n", filePointer->f_path.dentry->d_name.name);
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*offset += len;
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}
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return ret;
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}
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/* This function is called with the /proc file is written. */
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static ssize_t procfile_write(struct file *file, const char __user *buff,
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size_t len, loff_t *off)
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{
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procfs_buffer_size = len;
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if (procfs_buffer_size > PROCFS_MAX_SIZE)
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procfs_buffer_size = PROCFS_MAX_SIZE;
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if (copy_from_user(procfs_buffer, buff, procfs_buffer_size))
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return -EFAULT;
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procfs_buffer[procfs_buffer_size & (PROCFS_MAX_SIZE - 1)] = '\0';
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pr_info("procfile write %s\n", procfs_buffer);
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return procfs_buffer_size;
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}
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#ifdef HAVE_PROC_OPS
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static const struct proc_ops proc_file_fops = {
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.proc_read = procfile_read,
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.proc_write = procfile_write,
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};
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#else
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static const struct file_operations proc_file_fops = {
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.read = procfile_read,
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.write = procfile_write,
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};
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#endif
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static int __init procfs2_init(void)
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{
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our_proc_file = proc_create(PROCFS_NAME, 0644, NULL, &proc_file_fops);
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if (NULL == our_proc_file) {
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proc_remove(our_proc_file);
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pr_alert("Error:Could not initialize /proc/%s\n", PROCFS_NAME);
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return -ENOMEM;
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}
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pr_info("/proc/%s created\n", PROCFS_NAME);
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return 0;
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}
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static void __exit procfs2_exit(void)
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{
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proc_remove(our_proc_file);
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pr_info("/proc/%s removed\n", PROCFS_NAME);
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}
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module_init(procfs2_init);
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module_exit(procfs2_exit);
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MODULE_LICENSE("GPL");
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