Linux Kernel  3.7.1
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jprobe_example.c
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1 /*
2  * Here's a sample kernel module showing the use of jprobes to dump
3  * the arguments of do_fork().
4  *
5  * For more information on theory of operation of jprobes, see
6  * Documentation/kprobes.txt
7  *
8  * Build and insert the kernel module as done in the kprobe example.
9  * You will see the trace data in /var/log/messages and on the
10  * console whenever do_fork() is invoked to create a new process.
11  * (Some messages may be suppressed if syslogd is configured to
12  * eliminate duplicate messages.)
13  */
14 
15 #include <linux/kernel.h>
16 #include <linux/module.h>
17 #include <linux/kprobes.h>
18 
19 /*
20  * Jumper probe for do_fork.
21  * Mirror principle enables access to arguments of the probed routine
22  * from the probe handler.
23  */
24 
25 /* Proxy routine having the same arguments as actual do_fork() routine */
26 static long jdo_fork(unsigned long clone_flags, unsigned long stack_start,
27  struct pt_regs *regs, unsigned long stack_size,
28  int __user *parent_tidptr, int __user *child_tidptr)
29 {
30  printk(KERN_INFO "jprobe: clone_flags = 0x%lx, stack_size = 0x%lx,"
31  " regs = 0x%p\n",
32  clone_flags, stack_size, regs);
33 
34  /* Always end with a call to jprobe_return(). */
35  jprobe_return();
36  return 0;
37 }
38 
39 static struct jprobe my_jprobe = {
40  .entry = jdo_fork,
41  .kp = {
42  .symbol_name = "do_fork",
43  },
44 };
45 
46 static int __init jprobe_init(void)
47 {
48  int ret;
49 
50  ret = register_jprobe(&my_jprobe);
51  if (ret < 0) {
52  printk(KERN_INFO "register_jprobe failed, returned %d\n", ret);
53  return -1;
54  }
55  printk(KERN_INFO "Planted jprobe at %p, handler addr %p\n",
56  my_jprobe.kp.addr, my_jprobe.entry);
57  return 0;
58 }
59 
60 static void __exit jprobe_exit(void)
61 {
62  unregister_jprobe(&my_jprobe);
63  printk(KERN_INFO "jprobe at %p unregistered\n", my_jprobe.kp.addr);
64 }
65 
66 module_init(jprobe_init)
67 module_exit(jprobe_exit)
68 MODULE_LICENSE("GPL");