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");
122