Loading...
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * NOTE: This example is works on x86 and powerpc.
4 * Here's a sample kernel module showing the use of kprobes to dump a
5 * stack trace and selected registers when _do_fork() is called.
6 *
7 * For more information on theory of operation of kprobes, see
8 * Documentation/staging/kprobes.rst
9 *
10 * You will see the trace data in /var/log/messages and on the console
11 * whenever _do_fork() is invoked to create a new process.
12 */
13
14#include <linux/kernel.h>
15#include <linux/module.h>
16#include <linux/kprobes.h>
17
18#define MAX_SYMBOL_LEN 64
19static char symbol[MAX_SYMBOL_LEN] = "_do_fork";
20module_param_string(symbol, symbol, sizeof(symbol), 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> pre_handler: 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> pre_handler: 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> pre_handler: 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> pre_handler: p->addr = 0x%p, pc = 0x%lx,"
44 " pstate = 0x%lx\n",
45 p->symbol_name, p->addr, (long)regs->pc, (long)regs->pstate);
46#endif
47#ifdef CONFIG_S390
48 pr_info("<%s> pre_handler: p->addr, 0x%p, ip = 0x%lx, flags = 0x%lx\n",
49 p->symbol_name, p->addr, regs->psw.addr, regs->flags);
50#endif
51
52 /* A dump_stack() here will give a stack backtrace */
53 return 0;
54}
55
56/* kprobe post_handler: called after the probed instruction is executed */
57static void __kprobes handler_post(struct kprobe *p, struct pt_regs *regs,
58 unsigned long flags)
59{
60#ifdef CONFIG_X86
61 pr_info("<%s> post_handler: p->addr = 0x%p, flags = 0x%lx\n",
62 p->symbol_name, p->addr, regs->flags);
63#endif
64#ifdef CONFIG_PPC
65 pr_info("<%s> post_handler: p->addr = 0x%p, msr = 0x%lx\n",
66 p->symbol_name, p->addr, regs->msr);
67#endif
68#ifdef CONFIG_MIPS
69 pr_info("<%s> post_handler: p->addr = 0x%p, status = 0x%lx\n",
70 p->symbol_name, p->addr, regs->cp0_status);
71#endif
72#ifdef CONFIG_ARM64
73 pr_info("<%s> post_handler: p->addr = 0x%p, pstate = 0x%lx\n",
74 p->symbol_name, p->addr, (long)regs->pstate);
75#endif
76#ifdef CONFIG_S390
77 pr_info("<%s> pre_handler: p->addr, 0x%p, flags = 0x%lx\n",
78 p->symbol_name, p->addr, regs->flags);
79#endif
80}
81
82/*
83 * fault_handler: this is called if an exception is generated for any
84 * instruction within the pre- or post-handler, or when Kprobes
85 * single-steps the probed instruction.
86 */
87static int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr)
88{
89 pr_info("fault_handler: p->addr = 0x%p, trap #%dn", p->addr, trapnr);
90 /* Return 0 because we don't handle the fault. */
91 return 0;
92}
93/* NOKPROBE_SYMBOL() is also available */
94NOKPROBE_SYMBOL(handler_fault);
95
96static int __init kprobe_init(void)
97{
98 int ret;
99 kp.pre_handler = handler_pre;
100 kp.post_handler = handler_post;
101 kp.fault_handler = handler_fault;
102
103 ret = register_kprobe(&kp);
104 if (ret < 0) {
105 pr_err("register_kprobe failed, returned %d\n", ret);
106 return ret;
107 }
108 pr_info("Planted kprobe at %p\n", kp.addr);
109 return 0;
110}
111
112static void __exit kprobe_exit(void)
113{
114 unregister_kprobe(&kp);
115 pr_info("kprobe at %p unregistered\n", kp.addr);
116}
117
118module_init(kprobe_init)
119module_exit(kprobe_exit)
120MODULE_LICENSE("GPL");
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");