1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Here's a sample kernel module showing the use of kprobes to dump a
4 * stack trace and selected registers when kernel_clone() is called.
5 *
6 * For more information on theory of operation of kprobes, see
7 * Documentation/trace/kprobes.rst
8 *
9 * You will see the trace data in /var/log/messages and on the console
10 * whenever kernel_clone() is invoked to create a new process.
11 */
12
13#define pr_fmt(fmt) "%s: " fmt, __func__
14
15#include <linux/kernel.h>
16#include <linux/module.h>
17#include <linux/kprobes.h>
18
19static char symbol[KSYM_NAME_LEN] = "kernel_clone";
20module_param_string(symbol, symbol, KSYM_NAME_LEN, 0644);
21
22/* For each probe you need to allocate a kprobe structure */
23static struct kprobe kp = {
24 .symbol_name = symbol,
25};
26
27/* kprobe pre_handler: called just before the probed instruction is executed */
28static int __kprobes handler_pre(struct kprobe *p, struct pt_regs *regs)
29{
30#ifdef CONFIG_X86
31 pr_info("<%s> p->addr = 0x%p, ip = %lx, flags = 0x%lx\n",
32 p->symbol_name, p->addr, regs->ip, regs->flags);
33#endif
34#ifdef CONFIG_PPC
35 pr_info("<%s> p->addr = 0x%p, nip = 0x%lx, msr = 0x%lx\n",
36 p->symbol_name, p->addr, regs->nip, regs->msr);
37#endif
38#ifdef CONFIG_MIPS
39 pr_info("<%s> p->addr = 0x%p, epc = 0x%lx, status = 0x%lx\n",
40 p->symbol_name, p->addr, regs->cp0_epc, regs->cp0_status);
41#endif
42#ifdef CONFIG_ARM64
43 pr_info("<%s> p->addr = 0x%p, pc = 0x%lx, pstate = 0x%lx\n",
44 p->symbol_name, p->addr, (long)regs->pc, (long)regs->pstate);
45#endif
46#ifdef CONFIG_ARM
47 pr_info("<%s> p->addr = 0x%p, pc = 0x%lx, cpsr = 0x%lx\n",
48 p->symbol_name, p->addr, (long)regs->ARM_pc, (long)regs->ARM_cpsr);
49#endif
50#ifdef CONFIG_RISCV
51 pr_info("<%s> p->addr = 0x%p, pc = 0x%lx, status = 0x%lx\n",
52 p->symbol_name, p->addr, regs->epc, regs->status);
53#endif
54#ifdef CONFIG_S390
55 pr_info("<%s> p->addr, 0x%p, ip = 0x%lx, flags = 0x%lx\n",
56 p->symbol_name, p->addr, regs->psw.addr, regs->flags);
57#endif
58#ifdef CONFIG_LOONGARCH
59 pr_info("<%s> p->addr = 0x%p, era = 0x%lx, estat = 0x%lx\n",
60 p->symbol_name, p->addr, regs->csr_era, regs->csr_estat);
61#endif
62
63 /* A dump_stack() here will give a stack backtrace */
64 return 0;
65}
66
67/* kprobe post_handler: called after the probed instruction is executed */
68static void __kprobes handler_post(struct kprobe *p, struct pt_regs *regs,
69 unsigned long flags)
70{
71#ifdef CONFIG_X86
72 pr_info("<%s> p->addr = 0x%p, flags = 0x%lx\n",
73 p->symbol_name, p->addr, regs->flags);
74#endif
75#ifdef CONFIG_PPC
76 pr_info("<%s> p->addr = 0x%p, msr = 0x%lx\n",
77 p->symbol_name, p->addr, regs->msr);
78#endif
79#ifdef CONFIG_MIPS
80 pr_info("<%s> p->addr = 0x%p, status = 0x%lx\n",
81 p->symbol_name, p->addr, regs->cp0_status);
82#endif
83#ifdef CONFIG_ARM64
84 pr_info("<%s> p->addr = 0x%p, pstate = 0x%lx\n",
85 p->symbol_name, p->addr, (long)regs->pstate);
86#endif
87#ifdef CONFIG_ARM
88 pr_info("<%s> p->addr = 0x%p, cpsr = 0x%lx\n",
89 p->symbol_name, p->addr, (long)regs->ARM_cpsr);
90#endif
91#ifdef CONFIG_RISCV
92 pr_info("<%s> p->addr = 0x%p, status = 0x%lx\n",
93 p->symbol_name, p->addr, regs->status);
94#endif
95#ifdef CONFIG_S390
96 pr_info("<%s> p->addr, 0x%p, flags = 0x%lx\n",
97 p->symbol_name, p->addr, regs->flags);
98#endif
99#ifdef CONFIG_LOONGARCH
100 pr_info("<%s> p->addr = 0x%p, estat = 0x%lx\n",
101 p->symbol_name, p->addr, regs->csr_estat);
102#endif
103}
104
105static int __init kprobe_init(void)
106{
107 int ret;
108 kp.pre_handler = handler_pre;
109 kp.post_handler = handler_post;
110
111 ret = register_kprobe(p: &kp);
112 if (ret < 0) {
113 pr_err("register_kprobe failed, returned %d\n", ret);
114 return ret;
115 }
116 pr_info("Planted kprobe at %p\n", kp.addr);
117 return 0;
118}
119
120static void __exit kprobe_exit(void)
121{
122 unregister_kprobe(p: &kp);
123 pr_info("kprobe at %p unregistered\n", kp.addr);
124}
125
126module_init(kprobe_init)
127module_exit(kprobe_exit)
128MODULE_DESCRIPTION("sample kernel module showing the use of kprobes");
129MODULE_LICENSE("GPL");
130

source code of linux/samples/kprobes/kprobe_example.c