blob: a681998a871cae548eb05f741ed6533daa17d238 [file] [log] [blame]
Ananth N Mavinakayanahalli804defe2008-03-04 14:28:38 -08001/*
2 * NOTE: This example is works on x86 and powerpc.
3 * Here's a sample kernel module showing the use of kprobes to dump a
4 * stack trace and selected registers when do_fork() is called.
5 *
6 * For more information on theory of operation of kprobes, see
7 * Documentation/kprobes.txt
8 *
9 * You will see the trace data in /var/log/messages and on the console
10 * whenever do_fork() is invoked to create a new process.
11 */
12
13#include <linux/kernel.h>
14#include <linux/module.h>
15#include <linux/kprobes.h>
16
17/* For each probe you need to allocate a kprobe structure */
18static struct kprobe kp = {
19 .symbol_name = "do_fork",
20};
21
22/* kprobe pre_handler: called just before the probed instruction is executed */
23static int handler_pre(struct kprobe *p, struct pt_regs *regs)
24{
25#ifdef CONFIG_X86
26 printk(KERN_INFO "pre_handler: p->addr = 0x%p, ip = %lx,"
27 " flags = 0x%lx\n",
28 p->addr, regs->ip, regs->flags);
29#endif
30#ifdef CONFIG_PPC
31 printk(KERN_INFO "pre_handler: p->addr = 0x%p, nip = 0x%lx,"
32 " msr = 0x%lx\n",
33 p->addr, regs->nip, regs->msr);
34#endif
35
36 /* A dump_stack() here will give a stack backtrace */
37 return 0;
38}
39
40/* kprobe post_handler: called after the probed instruction is executed */
41static void handler_post(struct kprobe *p, struct pt_regs *regs,
42 unsigned long flags)
43{
44#ifdef CONFIG_X86
45 printk(KERN_INFO "post_handler: p->addr = 0x%p, flags = 0x%lx\n",
46 p->addr, regs->flags);
47#endif
48#ifdef CONFIG_PPC
49 printk(KERN_INFO "post_handler: p->addr = 0x%p, msr = 0x%lx\n",
50 p->addr, regs->msr);
51#endif
52}
53
54/*
55 * fault_handler: this is called if an exception is generated for any
56 * instruction within the pre- or post-handler, or when Kprobes
57 * single-steps the probed instruction.
58 */
59static int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr)
60{
61 printk(KERN_INFO "fault_handler: p->addr = 0x%p, trap #%dn",
62 p->addr, trapnr);
63 /* Return 0 because we don't handle the fault. */
64 return 0;
65}
66
67static int __init kprobe_init(void)
68{
69 int ret;
70 kp.pre_handler = handler_pre;
71 kp.post_handler = handler_post;
72 kp.fault_handler = handler_fault;
73
74 ret = register_kprobe(&kp);
75 if (ret < 0) {
76 printk(KERN_INFO "register_kprobe failed, returned %d\n", ret);
77 return ret;
78 }
79 printk(KERN_INFO "Planted kprobe at %p\n", kp.addr);
80 return 0;
81}
82
83static void __exit kprobe_exit(void)
84{
85 unregister_kprobe(&kp);
86 printk(KERN_INFO "kprobe at %p unregistered\n", kp.addr);
87}
88
89module_init(kprobe_init)
90module_exit(kprobe_exit)
91MODULE_LICENSE("GPL");