Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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kernel
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linux
1/*
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#define MAX_SYMBOL_LEN 64
18static char symbol[MAX_SYMBOL_LEN] = "_do_fork";
19module_param_string(symbol, symbol, sizeof(symbol), 0644);
20
21/* For each probe you need to allocate a kprobe structure */
22static struct kprobe kp = {
23 .symbol_name = symbol,
24};
25
26/* kprobe pre_handler: called just before the probed instruction is executed */
27static int handler_pre(struct kprobe *p, struct pt_regs *regs)
28{
29#ifdef CONFIG_X86
30 pr_info("<%s> pre_handler: p->addr = 0x%p, ip = %lx, flags = 0x%lx\n",
31 p->symbol_name, p->addr, regs->ip, regs->flags);
32#endif
33#ifdef CONFIG_PPC
34 pr_info("<%s> pre_handler: p->addr = 0x%p, nip = 0x%lx, msr = 0x%lx\n",
35 p->symbol_name, p->addr, regs->nip, regs->msr);
36#endif
37#ifdef CONFIG_MIPS
38 pr_info("<%s> pre_handler: p->addr = 0x%p, epc = 0x%lx, status = 0x%lx\n",
39 p->symbol_name, p->addr, regs->cp0_epc, regs->cp0_status);
40#endif
41#ifdef CONFIG_TILEGX
42 pr_info("<%s> pre_handler: p->addr = 0x%p, pc = 0x%lx, ex1 = 0x%lx\n",
43 p->symbol_name, p->addr, regs->pc, regs->ex1);
44#endif
45#ifdef CONFIG_ARM64
46 pr_info("<%s> pre_handler: p->addr = 0x%p, pc = 0x%lx,"
47 " pstate = 0x%lx\n",
48 p->symbol_name, p->addr, (long)regs->pc, (long)regs->pstate);
49#endif
50
51 /* A dump_stack() here will give a stack backtrace */
52 return 0;
53}
54
55/* kprobe post_handler: called after the probed instruction is executed */
56static void handler_post(struct kprobe *p, struct pt_regs *regs,
57 unsigned long flags)
58{
59#ifdef CONFIG_X86
60 pr_info("<%s> post_handler: p->addr = 0x%p, flags = 0x%lx\n",
61 p->symbol_name, p->addr, regs->flags);
62#endif
63#ifdef CONFIG_PPC
64 pr_info("<%s> post_handler: p->addr = 0x%p, msr = 0x%lx\n",
65 p->symbol_name, p->addr, regs->msr);
66#endif
67#ifdef CONFIG_MIPS
68 pr_info("<%s> post_handler: p->addr = 0x%p, status = 0x%lx\n",
69 p->symbol_name, p->addr, regs->cp0_status);
70#endif
71#ifdef CONFIG_TILEGX
72 pr_info("<%s> post_handler: p->addr = 0x%p, ex1 = 0x%lx\n",
73 p->symbol_name, p->addr, regs->ex1);
74#endif
75#ifdef CONFIG_ARM64
76 pr_info("<%s> post_handler: p->addr = 0x%p, pstate = 0x%lx\n",
77 p->symbol_name, p->addr, (long)regs->pstate);
78#endif
79}
80
81/*
82 * fault_handler: this is called if an exception is generated for any
83 * instruction within the pre- or post-handler, or when Kprobes
84 * single-steps the probed instruction.
85 */
86static int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr)
87{
88 pr_info("fault_handler: p->addr = 0x%p, trap #%dn", p->addr, trapnr);
89 /* Return 0 because we don't handle the fault. */
90 return 0;
91}
92
93static int __init kprobe_init(void)
94{
95 int ret;
96 kp.pre_handler = handler_pre;
97 kp.post_handler = handler_post;
98 kp.fault_handler = handler_fault;
99
100 ret = register_kprobe(&kp);
101 if (ret < 0) {
102 pr_err("register_kprobe failed, returned %d\n", ret);
103 return ret;
104 }
105 pr_info("Planted kprobe at %p\n", kp.addr);
106 return 0;
107}
108
109static void __exit kprobe_exit(void)
110{
111 unregister_kprobe(&kp);
112 pr_info("kprobe at %p unregistered\n", kp.addr);
113}
114
115module_init(kprobe_init)
116module_exit(kprobe_exit)
117MODULE_LICENSE("GPL");