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
98 lines
2.5 KiB
C
98 lines
2.5 KiB
C
/* https://cirosantilli.com/linux-kernel-module-cheat#poll */
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#include <linux/debugfs.h>
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#include <linux/delay.h> /* usleep_range */
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#include <linux/errno.h> /* EFAULT */
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#include <linux/fs.h>
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#include <linux/jiffies.h>
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#include <linux/kernel.h> /* min */
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#include <linux/kthread.h>
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#include <linux/module.h>
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#include <linux/poll.h>
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#include <linux/printk.h> /* printk */
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#include <linux/uaccess.h> /* copy_from_user, copy_to_user */
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#include <linux/wait.h> /* wait_queue_head_t, wait_event_interruptible, wake_up_interruptible */
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#include <uapi/linux/stat.h> /* S_IRUSR */
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static int ret0 = 0;
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module_param(ret0, int, S_IRUSR | S_IWUSR);
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MODULE_PARM_DESC(i, "if 1, always return 0 from poll");
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static char readbuf[1024];
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static size_t readbuflen;
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static struct dentry *debugfs_file;
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static struct task_struct *kthread;
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static wait_queue_head_t waitqueue;
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static ssize_t read(struct file *filp, char __user *buf, size_t len, loff_t *off)
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{
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ssize_t ret;
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if (copy_to_user(buf, readbuf, readbuflen)) {
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ret = -EFAULT;
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} else {
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ret = readbuflen;
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}
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/* This is normal pipe behaviour: data gets drained once a reader reads from it. */
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/* https://stackoverflow.com/questions/1634580/named-pipes-fifos-on-unix-with-multiple-readers */
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readbuflen = 0;
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return ret;
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}
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/* If you return 0 here, then the kernel will sleep until an event
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* happens in the queue. and then call this again, because of the call to poll_wait. */
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unsigned int poll(struct file *filp, struct poll_table_struct *wait)
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{
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pr_info("poll\n");
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/* This doesn't sleep. It just makes the kernel call poll again if we return 0. */
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poll_wait(filp, &waitqueue, wait);
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if (readbuflen && !ret0) {
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pr_info("return POLLIN\n");
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return POLLIN;
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} else {
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pr_info("return 0\n");
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return 0;
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}
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}
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static int lkmc_kthread_func(void *data)
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{
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while (!kthread_should_stop()) {
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readbuflen = snprintf(
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readbuf,
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sizeof(readbuf),
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"%llu",
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(unsigned long long)jiffies
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);
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usleep_range(1000000, 1000001);
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pr_info("wake_up\n");
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wake_up(&waitqueue);
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}
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return 0;
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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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.read = read,
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.poll = poll
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};
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static int myinit(void)
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{
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debugfs_file = debugfs_create_file(
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"lkmc_poll", S_IRUSR | S_IWUSR, NULL, NULL, &fops);
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init_waitqueue_head(&waitqueue);
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kthread = kthread_create(lkmc_kthread_func, NULL, "mykthread");
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wake_up_process(kthread);
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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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kthread_stop(kthread);
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debugfs_remove(debugfs_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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