jprobes example

jprobe_etn_io.c

/*
 * Here's a sample kernel module showing the use of jprobes to dump
 * the arguments of third-party network driver for Bercut ETN.
 *
 * 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.)
 */
#define pr_fmt(fmt) "ETN JPROBE: %s:%d: " fmt, __FUNCTION__, __LINE__

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

static ssize_t trace_etn_write(struct file *filp, const char __user *buf, 
                               size_t count, loff_t *f_pos)
{
	pr_info("Writing %zu bytes at offset %lld\n", count, *f_pos);
	/* Always end with a call to jprobe_return(). */
	jprobe_return();
	return 0;
}

static struct jprobe etn_write_jprobe = {
	.entry			= trace_etn_write,
	.kp = {
		.symbol_name	= "etn_write",
	},
};

static int __init jprobe_init(void)
{
	int ret;

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

static void __exit jprobe_exit(void)
{
	unregister_jprobe(&etn_write_jprobe);
	pr_info("jprobe at %p unregistered\n", etn_write_jprobe.kp.addr);
}

module_init(jprobe_init)
module_exit(jprobe_exit)
MODULE_LICENSE("GPL");