1 // SPDX-License-Identifier: GPL-2.0-only
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.
6 * For more information on theory of operation of kprobes, see
7 * Documentation/trace/kprobes.rst
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.
13 #define pr_fmt(fmt) "%s: " fmt, __func__
15 #include <linux/kernel.h>
16 #include <linux/module.h>
17 #include <linux/kprobes.h>
19 #define MAX_SYMBOL_LEN 64
20 static char symbol[MAX_SYMBOL_LEN] = "kernel_clone";
21 module_param_string(symbol, symbol, sizeof(symbol), 0644);
23 /* For each probe you need to allocate a kprobe structure */
24 static struct kprobe kp = {
25 .symbol_name = symbol,
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)
32 pr_info("<%s> p->addr = 0x%p, ip = %lx, flags = 0x%lx\n",
33 p->symbol_name, p->addr, regs->ip, regs->flags);
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);
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);
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);
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);
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);
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);
60 /* A dump_stack() here will give a stack backtrace */
64 /* kprobe post_handler: called after the probed instruction is executed */
65 static void __kprobes handler_post(struct kprobe *p, struct pt_regs *regs,
69 pr_info("<%s> p->addr = 0x%p, flags = 0x%lx\n",
70 p->symbol_name, p->addr, regs->flags);
73 pr_info("<%s> p->addr = 0x%p, msr = 0x%lx\n",
74 p->symbol_name, p->addr, regs->msr);
77 pr_info("<%s> p->addr = 0x%p, status = 0x%lx\n",
78 p->symbol_name, p->addr, regs->cp0_status);
81 pr_info("<%s> p->addr = 0x%p, pstate = 0x%lx\n",
82 p->symbol_name, p->addr, (long)regs->pstate);
85 pr_info("<%s> p->addr = 0x%p, cpsr = 0x%lx\n",
86 p->symbol_name, p->addr, (long)regs->ARM_cpsr);
89 pr_info("<%s> p->addr = 0x%p, status = 0x%lx\n",
90 p->symbol_name, p->addr, regs->status);
93 pr_info("<%s> p->addr, 0x%p, flags = 0x%lx\n",
94 p->symbol_name, p->addr, regs->flags);
99 * fault_handler: this is called if an exception is generated for any
100 * instruction within the pre- or post-handler, or when Kprobes
101 * single-steps the probed instruction.
103 static int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr)
105 pr_info("p->addr = 0x%p, trap #%d\n", p->addr, trapnr);
106 /* Return 0 because we don't handle the fault. */
109 /* NOKPROBE_SYMBOL() is also available */
110 NOKPROBE_SYMBOL(handler_fault);
112 static int __init kprobe_init(void)
115 kp.pre_handler = handler_pre;
116 kp.post_handler = handler_post;
117 kp.fault_handler = handler_fault;
119 ret = register_kprobe(&kp);
121 pr_err("register_kprobe failed, returned %d\n", ret);
124 pr_info("Planted kprobe at %p\n", kp.addr);
128 static void __exit kprobe_exit(void)
130 unregister_kprobe(&kp);
131 pr_info("kprobe at %p unregistered\n", kp.addr);
134 module_init(kprobe_init)
135 module_exit(kprobe_exit)
136 MODULE_LICENSE("GPL");