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 static char symbol[KSYM_NAME_LEN] = "kernel_clone";
20 module_param_string(symbol, symbol, KSYM_NAME_LEN, 0644);
21 
22 /* For each probe you need to allocate a kprobe structure */
23 static struct kprobe kp = {
24 	.symbol_name	= symbol,
25 };
26 
27 /* kprobe pre_handler: called just before the probed instruction is executed */
28 static 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 
59 	/* A dump_stack() here will give a stack backtrace */
60 	return 0;
61 }
62 
63 /* kprobe post_handler: called after the probed instruction is executed */
64 static void __kprobes handler_post(struct kprobe *p, struct pt_regs *regs,
65 				unsigned long flags)
66 {
67 #ifdef CONFIG_X86
68 	pr_info("<%s> p->addr = 0x%p, flags = 0x%lx\n",
69 		p->symbol_name, p->addr, regs->flags);
70 #endif
71 #ifdef CONFIG_PPC
72 	pr_info("<%s> p->addr = 0x%p, msr = 0x%lx\n",
73 		p->symbol_name, p->addr, regs->msr);
74 #endif
75 #ifdef CONFIG_MIPS
76 	pr_info("<%s> p->addr = 0x%p, status = 0x%lx\n",
77 		p->symbol_name, p->addr, regs->cp0_status);
78 #endif
79 #ifdef CONFIG_ARM64
80 	pr_info("<%s> p->addr = 0x%p, pstate = 0x%lx\n",
81 		p->symbol_name, p->addr, (long)regs->pstate);
82 #endif
83 #ifdef CONFIG_ARM
84 	pr_info("<%s> p->addr = 0x%p, cpsr = 0x%lx\n",
85 		p->symbol_name, p->addr, (long)regs->ARM_cpsr);
86 #endif
87 #ifdef CONFIG_RISCV
88 	pr_info("<%s> p->addr = 0x%p, status = 0x%lx\n",
89 		p->symbol_name, p->addr, regs->status);
90 #endif
91 #ifdef CONFIG_S390
92 	pr_info("<%s> p->addr, 0x%p, flags = 0x%lx\n",
93 		p->symbol_name, p->addr, regs->flags);
94 #endif
95 }
96 
97 static int __init kprobe_init(void)
98 {
99 	int ret;
100 	kp.pre_handler = handler_pre;
101 	kp.post_handler = handler_post;
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 
112 static void __exit kprobe_exit(void)
113 {
114 	unregister_kprobe(&kp);
115 	pr_info("kprobe at %p unregistered\n", kp.addr);
116 }
117 
118 module_init(kprobe_init)
119 module_exit(kprobe_exit)
120 MODULE_LICENSE("GPL");
121