Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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linux
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 kernel_clone() is called.
6 *
7 * For more information on theory of operation of kprobes, see
8 * Documentation/trace/kprobes.rst
9 *
10 * You will see the trace data in /var/log/messages and on the console
11 * whenever kernel_clone() 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] = "kernel_clone";
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");