3rd-party/linux-kernel-module-cheat
1
0
Fork 0
mirror of https://github.com/cirosantilli/linux-kernel-module-cheat.git synced 2026-01-23 02:05:57 +01:00
Code Issues Releases Wiki Activity

poll kernel module: overhaul with prints everywhere

Browse Source
This commit is contained in:
Ciro Santilli 六四事件 法轮功
2020-07-11 02:00:01 +00:00
parent f9f6c557cc
commit 8cbf47265f
6 changed files with 90 additions and 22 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
kernel_modules/kprobe_example.c
View File

@@ -3,8 +3,7 @@
* Adapted from: https://github.com/torvalds/linux/blob/v4.17/samples/kprobes/kprobe_example.c
*/
/*
* NOTE: This example is works on x86 and powerpc.
/* NOTE: This example is works on x86 and powerpc.
* Here's a sample kernel module showing the use of kprobes to dump a
* stack trace and selected registers when _do_fork() is called.
*

4
kernel_modules/params.c
View File

@@ -7,8 +7,8 @@
#include <linux/seq_file.h> /* seq_read, seq_lseek, single_release */
#include <uapi/linux/stat.h> /* S_IRUSR | S_IWUSR */
static u32 i = 0;
static u32 j = 0;
static int i = 0;
static int j = 0;
module_param(i, int, S_IRUSR | S_IWUSR);
module_param(j, int, S_IRUSR | S_IWUSR);
MODULE_PARM_DESC(i, "my favorite int");

27
kernel_modules/poll.c
View File

@@ -14,6 +14,10 @@
#include <linux/wait.h> /* wait_queue_head_t, wait_event_interruptible, wake_up_interruptible */
#include <uapi/linux/stat.h> /* S_IRUSR */
static int ret0 = 0;
module_param(ret0, int, S_IRUSR | S_IWUSR);
MODULE_PARM_DESC(i, "if 1, always return 0 from poll");
static char readbuf[1024];
static size_t readbuflen;
static struct dentry *debugfs_file;
@@ -34,24 +38,33 @@ static ssize_t read(struct file *filp, char __user *buf, size_t len, loff_t *off
return ret;
}
/* If you return 0 here, then the kernel will sleep until an event happens in the queue.
*
* This gets called again every time an event happens in the wait queue.
*/
/* If you return 0 here, then the kernel will sleep until an event
* happens in the queue. and then call this again, because of the call to poll_wait. */
unsigned int poll(struct file *filp, struct poll_table_struct *wait)
{
pr_info("poll\n");
/* This doesn't sleep. It just makes the kernel call poll again if we return 0. */
poll_wait(filp, &waitqueue, wait);
if (readbuflen)
if (readbuflen && !ret0) {
pr_info("return POLLIN\n");
return POLLIN;
else
} else {
pr_info("return 0\n");
return 0;
}
}
static int kthread_func(void *data)
{
while (!kthread_should_stop()) {
readbuflen = snprintf(readbuf, sizeof(readbuf), "%llu", (unsigned long long)jiffies);
readbuflen = snprintf(
readbuf,
sizeof(readbuf),
"%llu",
(unsigned long long)jiffies
);
usleep_range(1000000, 1000001);
pr_info("wake_up\n");
wake_up(&waitqueue);
}
return 0;