summaryrefslogtreecommitdiff
path: root/samples/kprobes/kprobe_example.c
blob: d693c23a85e8a0f21df776d48463950ab13cedaa (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
// SPDX-License-Identifier: GPL-2.0-only
/*
 * NOTE: This example is works on x86 and powerpc.
 * Here's a sample kernel module showing the use of kprobes to dump a
 * stack trace and selected registers when _do_fork() is called.
 *
 * For more information on theory of operation of kprobes, see
 * Documentation/kprobes.txt
 *
 * You will see the trace data in /var/log/messages and on the console
 * whenever _do_fork() is invoked to create a new process.
 */

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

#define MAX_SYMBOL_LEN	64
static char symbol[MAX_SYMBOL_LEN] = "_do_fork";
module_param_string(symbol, symbol, sizeof(symbol), 0644);

/* For each probe you need to allocate a kprobe structure */
static struct kprobe kp = {
	.symbol_name	= symbol,
};

/* kprobe pre_handler: called just before the probed instruction is executed */
static int handler_pre(struct kprobe *p, struct pt_regs *regs)
{
#ifdef CONFIG_X86
	pr_info("<%s> pre_handler: p->addr = 0x%p, ip = %lx, flags = 0x%lx\n",
		p->symbol_name, p->addr, regs->ip, regs->flags);
#endif
#ifdef CONFIG_PPC
	pr_info("<%s> pre_handler: p->addr = 0x%p, nip = 0x%lx, msr = 0x%lx\n",
		p->symbol_name, p->addr, regs->nip, regs->msr);
#endif
#ifdef CONFIG_MIPS
	pr_info("<%s> pre_handler: p->addr = 0x%p, epc = 0x%lx, status = 0x%lx\n",
		p->symbol_name, p->addr, regs->cp0_epc, regs->cp0_status);
#endif
#ifdef CONFIG_ARM64
	pr_info("<%s> pre_handler: p->addr = 0x%p, pc = 0x%lx,"
			" pstate = 0x%lx\n",
		p->symbol_name, p->addr, (long)regs->pc, (long)regs->pstate);
#endif
#ifdef CONFIG_S390
	pr_info("<%s> pre_handler: p->addr, 0x%p, ip = 0x%lx, flags = 0x%lx\n",
		p->symbol_name, p->addr, regs->psw.addr, regs->flags);
#endif

	/* A dump_stack() here will give a stack backtrace */
	return 0;
}

/* kprobe post_handler: called after the probed instruction is executed */
static void handler_post(struct kprobe *p, struct pt_regs *regs,
				unsigned long flags)
{
#ifdef CONFIG_X86
	pr_info("<%s> post_handler: p->addr = 0x%p, flags = 0x%lx\n",
		p->symbol_name, p->addr, regs->flags);
#endif
#ifdef CONFIG_PPC
	pr_info("<%s> post_handler: p->addr = 0x%p, msr = 0x%lx\n",
		p->symbol_name, p->addr, regs->msr);
#endif
#ifdef CONFIG_MIPS
	pr_info("<%s> post_handler: p->addr = 0x%p, status = 0x%lx\n",
		p->symbol_name, p->addr, regs->cp0_status);
#endif
#ifdef CONFIG_ARM64
	pr_info("<%s> post_handler: p->addr = 0x%p, pstate = 0x%lx\n",
		p->symbol_name, p->addr, (long)regs->pstate);
#endif
#ifdef CONFIG_S390
	pr_info("<%s> pre_handler: p->addr, 0x%p, flags = 0x%lx\n",
		p->symbol_name, p->addr, regs->flags);
#endif
}

/*
 * fault_handler: this is called if an exception is generated for any
 * instruction within the pre- or post-handler, or when Kprobes
 * single-steps the probed instruction.
 */
static int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr)
{
	pr_info("fault_handler: p->addr = 0x%p, trap #%dn", p->addr, trapnr);
	/* Return 0 because we don't handle the fault. */
	return 0;
}

static int __init kprobe_init(void)
{
	int ret;
	kp.pre_handler = handler_pre;
	kp.post_handler = handler_post;
	kp.fault_handler = handler_fault;

	ret = register_kprobe(&kp);
	if (ret < 0) {
		pr_err("register_kprobe failed, returned %d\n", ret);
		return ret;
	}
	pr_info("Planted kprobe at %p\n", kp.addr);
	return 0;
}

static void __exit kprobe_exit(void)
{
	unregister_kprobe(&kp);
	pr_info("kprobe at %p unregistered\n", kp.addr);
}

module_init(kprobe_init)
module_exit(kprobe_exit)
MODULE_LICENSE("GPL");