blob: b7541355b92bd547c27faa21ac6a01a2b96cbc85 (plain) (tree)

 * Here's a sample kernel module showing the use of jprobes to dump
 * the arguments of do_fork().
 * For more information on theory of operation of jprobes, see
 * Documentation/kprobes.txt
 * Build and insert the kernel module as done in the kprobe example.
 * You will see the trace data in /var/log/messages and on the
 * console whenever do_fork() is invoked to create a new process.
 * (Some messages may be suppressed if syslogd is configured to
 * eliminate duplicate messages.)

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/kprobes.h>

 * Jumper probe for do_fork.
 * Mirror principle enables access to arguments of the probed routine
 * from the probe handler.

/* Proxy routine having the same arguments as actual do_fork() routine */
static long jdo_fork(unsigned long clone_flags, unsigned long stack_start,
	      struct pt_regs *regs, unsigned long stack_size,
	      int __user *parent_tidptr, int __user *child_tidptr)
	printk(KERN_INFO "jprobe: clone_flags = 0x%lx, stack_size = 0x%lx,"
			" regs = 0x%p\n",
	       clone_flags, stack_size, regs);

	/* Always end with a call to jprobe_return(). */
	return 0;

static struct jprobe my_jprobe = {
	.entry			= jdo_fork,
	.kp = {
		.symbol_name	= "do_fork",

static int __init jprobe_init(void)
	int ret;

	ret = register_jprobe(&my_jprobe);
	if (ret < 0) {
		printk(KERN_INFO "register_jprobe failed, returned %d\n", ret);
		return -1;
	printk(KERN_INFO "Planted jprobe at %p, handler addr %p\n",
	       my_jprobe.kp.addr, my_jprobe.entry);
	return 0;

static void __exit jprobe_exit(void)
	printk(KERN_INFO "jprobe at %p unregistered\n", my_jprobe.kp.addr);