mirror of
https://github.com/cirosantilli/linux-kernel-module-cheat.git
synced 2026-01-13 20:12:26 +00:00
50570326d4
- `dep.c` and `dep2.c`: `debugfs_create_u32` does not return anymore, not sure why: https://unix.stackexchange.com/questions/593983/creating-a-debugfs-file-that-is-used-to-read-write-u32-value/621282#621282 So just doing `debugfs_lookup` for now - vermagic.c:51161bfc66prevents its usage in v5.8. Just migrating to `init_utsname` for now - procfs.c: `struct file_operations` moved to a new `struct proc_ops` at:b567e07513- myprintk.c: `pr_warning` dropped for `pr_warn`:61ff72f401- `poll.c`: `kthread_func` is not defined in kernel, prefix with lkmc to avoid conflict Fix https://github.com/cirosantilli/linux-kernel-module-cheat/issues/136 Fix https://github.com/cirosantilli/linux-kernel-module-cheat/issues/137
63 lines
1.4 KiB
C
63 lines
1.4 KiB
C
/* https://cirosantilli.com/linux-kernel-module-cheat#debugfs */
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#include <linux/debugfs.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <uapi/linux/stat.h> /* S_IRUSR */
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static struct dentry *dir, *toplevel_file;
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static u32 value = 42;
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/* This basically re-implents the write operation of debugfs_create_u32,
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* it is just an excuse to illustrate a fop. */
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static ssize_t write(struct file *filp, const char __user *buf, size_t len, loff_t *off)
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{
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int ret;
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unsigned long long res;
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/* https://stackoverflow.com/questions/6139493/how-convert-char-to-int-in-linux-kernel */
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ret = kstrtoull_from_user(buf, len, 10, &res);
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if (ret) {
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/* Negative error code. */
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return ret;
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} else {
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value = res;
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*off= len;
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return len;
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}
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}
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static const struct file_operations fops = {
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.owner = THIS_MODULE,
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.write = write,
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};
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static int myinit(void)
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{
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dir = debugfs_create_dir("lkmc_debugfs", 0);
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if (!dir) {
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pr_alert("debugfs_create_dir failed");
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return -1;
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}
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debugfs_create_u32("myfile", S_IRUSR | S_IWUSR, dir, &value);
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/* Created on the toplevel of the debugfs mount,
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* and with explicit fops instead of a fixed integer value.
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*/
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toplevel_file = debugfs_create_file(
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"lkmc_debugfs_file", S_IWUSR, NULL, NULL, &fops);
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if (!toplevel_file) {
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return -1;
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}
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return 0;
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}
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static void myexit(void)
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{
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debugfs_remove_recursive(dir);
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debugfs_remove(toplevel_file);
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}
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module_init(myinit)
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module_exit(myexit)
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MODULE_LICENSE("GPL");
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