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#ifdef CONFIG_S390
51 pr_info("<%s> pre_handler: p->addr, 0x%p, ip = 0x%lx, flags = 0x%lx\n",
52 p->symbol_name, p->addr, regs->psw.addr, regs->flags);
53#endif
54
55 /* A dump_stack() here will give a stack backtrace */
56 return 0;
57}
58
59/* kprobe post_handler: called after the probed instruction is executed */
60static void handler_post(struct kprobe *p, struct pt_regs *regs,
61 unsigned long flags)
62{
63#ifdef CONFIG_X86
64 pr_info("<%s> post_handler: p->addr = 0x%p, flags = 0x%lx\n",
65 p->symbol_name, p->addr, regs->flags);
66#endif
67#ifdef CONFIG_PPC
68 pr_info("<%s> post_handler: p->addr = 0x%p, msr = 0x%lx\n",
69 p->symbol_name, p->addr, regs->msr);
70#endif
71#ifdef CONFIG_MIPS
72 pr_info("<%s> post_handler: p->addr = 0x%p, status = 0x%lx\n",
73 p->symbol_name, p->addr, regs->cp0_status);
74#endif
75#ifdef CONFIG_TILEGX
76 pr_info("<%s> post_handler: p->addr = 0x%p, ex1 = 0x%lx\n",
77 p->symbol_name, p->addr, regs->ex1);
78#endif
79#ifdef CONFIG_ARM64
80 pr_info("<%s> post_handler: p->addr = 0x%p, pstate = 0x%lx\n",
81 p->symbol_name, p->addr, (long)regs->pstate);
82#endif
83#ifdef CONFIG_S390
84 pr_info("<%s> pre_handler: p->addr, 0x%p, flags = 0x%lx\n",
85 p->symbol_name, p->addr, regs->flags);
86#endif
87}
88
89/*
90 * fault_handler: this is called if an exception is generated for any
91 * instruction within the pre- or post-handler, or when Kprobes
92 * single-steps the probed instruction.
93 */
94static int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr)
95{
96 pr_info("fault_handler: p->addr = 0x%p, trap #%dn", p->addr, trapnr);
97 /* Return 0 because we don't handle the fault. */
98 return 0;
99}
100
101static int __init kprobe_init(void)
102{
103 int ret;
104 kp.pre_handler = handler_pre;
105 kp.post_handler = handler_post;
106 kp.fault_handler = handler_fault;
107
108 ret = register_kprobe(&kp);
109 if (ret < 0) {
110 pr_err("register_kprobe failed, returned %d\n", ret);
111 return ret;
112 }
113 pr_info("Planted kprobe at %p\n", kp.addr);
114 return 0;
115}
116
117static void __exit kprobe_exit(void)
118{
119 unregister_kprobe(&kp);
120 pr_info("kprobe at %p unregistered\n", kp.addr);
121}
122
123module_init(kprobe_init)
124module_exit(kprobe_exit)
125MODULE_LICENSE("GPL");