Merge branch 'akpm' (patches from Andrew)
[sfrench/cifs-2.6.git] / samples / kprobes / kprobe_example.c
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
19 #define MAX_SYMBOL_LEN  64
20 static char symbol[MAX_SYMBOL_LEN] = "kernel_clone";
21 module_param_string(symbol, symbol, sizeof(symbol), 0644);
22
23 /* For each probe you need to allocate a kprobe structure */
24 static struct kprobe kp = {
25         .symbol_name    = symbol,
26 };
27
28 /* kprobe pre_handler: called just before the probed instruction is executed */
29 static int __kprobes handler_pre(struct kprobe *p, struct pt_regs *regs)
30 {
31 #ifdef CONFIG_X86
32         pr_info("<%s> p->addr = 0x%p, ip = %lx, flags = 0x%lx\n",
33                 p->symbol_name, p->addr, regs->ip, regs->flags);
34 #endif
35 #ifdef CONFIG_PPC
36         pr_info("<%s> p->addr = 0x%p, nip = 0x%lx, msr = 0x%lx\n",
37                 p->symbol_name, p->addr, regs->nip, regs->msr);
38 #endif
39 #ifdef CONFIG_MIPS
40         pr_info("<%s> p->addr = 0x%p, epc = 0x%lx, status = 0x%lx\n",
41                 p->symbol_name, p->addr, regs->cp0_epc, regs->cp0_status);
42 #endif
43 #ifdef CONFIG_ARM64
44         pr_info("<%s> p->addr = 0x%p, pc = 0x%lx, pstate = 0x%lx\n",
45                 p->symbol_name, p->addr, (long)regs->pc, (long)regs->pstate);
46 #endif
47 #ifdef CONFIG_ARM
48         pr_info("<%s> p->addr = 0x%p, pc = 0x%lx, cpsr = 0x%lx\n",
49                 p->symbol_name, p->addr, (long)regs->ARM_pc, (long)regs->ARM_cpsr);
50 #endif
51 #ifdef CONFIG_RISCV
52         pr_info("<%s> p->addr = 0x%p, pc = 0x%lx, status = 0x%lx\n",
53                 p->symbol_name, p->addr, regs->epc, regs->status);
54 #endif
55 #ifdef CONFIG_S390
56         pr_info("<%s> p->addr, 0x%p, ip = 0x%lx, flags = 0x%lx\n",
57                 p->symbol_name, p->addr, regs->psw.addr, regs->flags);
58 #endif
59
60         /* A dump_stack() here will give a stack backtrace */
61         return 0;
62 }
63
64 /* kprobe post_handler: called after the probed instruction is executed */
65 static void __kprobes handler_post(struct kprobe *p, struct pt_regs *regs,
66                                 unsigned long flags)
67 {
68 #ifdef CONFIG_X86
69         pr_info("<%s> p->addr = 0x%p, flags = 0x%lx\n",
70                 p->symbol_name, p->addr, regs->flags);
71 #endif
72 #ifdef CONFIG_PPC
73         pr_info("<%s> p->addr = 0x%p, msr = 0x%lx\n",
74                 p->symbol_name, p->addr, regs->msr);
75 #endif
76 #ifdef CONFIG_MIPS
77         pr_info("<%s> p->addr = 0x%p, status = 0x%lx\n",
78                 p->symbol_name, p->addr, regs->cp0_status);
79 #endif
80 #ifdef CONFIG_ARM64
81         pr_info("<%s> p->addr = 0x%p, pstate = 0x%lx\n",
82                 p->symbol_name, p->addr, (long)regs->pstate);
83 #endif
84 #ifdef CONFIG_ARM
85         pr_info("<%s> p->addr = 0x%p, cpsr = 0x%lx\n",
86                 p->symbol_name, p->addr, (long)regs->ARM_cpsr);
87 #endif
88 #ifdef CONFIG_RISCV
89         pr_info("<%s> p->addr = 0x%p, status = 0x%lx\n",
90                 p->symbol_name, p->addr, regs->status);
91 #endif
92 #ifdef CONFIG_S390
93         pr_info("<%s> p->addr, 0x%p, flags = 0x%lx\n",
94                 p->symbol_name, p->addr, regs->flags);
95 #endif
96 }
97
98 static int __init kprobe_init(void)
99 {
100         int ret;
101         kp.pre_handler = handler_pre;
102         kp.post_handler = handler_post;
103
104         ret = register_kprobe(&kp);
105         if (ret < 0) {
106                 pr_err("register_kprobe failed, returned %d\n", ret);
107                 return ret;
108         }
109         pr_info("Planted kprobe at %p\n", kp.addr);
110         return 0;
111 }
112
113 static void __exit kprobe_exit(void)
114 {
115         unregister_kprobe(&kp);
116         pr_info("kprobe at %p unregistered\n", kp.addr);
117 }
118
119 module_init(kprobe_init)
120 module_exit(kprobe_exit)
121 MODULE_LICENSE("GPL");