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 #include <linux/kernel.h>
14 #include <linux/module.h>
15 #include <linux/kprobes.h>
17 #define MAX_SYMBOL_LEN 64
18 static char symbol[MAX_SYMBOL_LEN] = "kernel_clone";
19 module_param_string(symbol, symbol, sizeof(symbol), 0644);
21 /* For each probe you need to allocate a kprobe structure */
22 static struct kprobe kp = {
23 .symbol_name = symbol,
26 /* kprobe pre_handler: called just before the probed instruction is executed */
27 static int __kprobes handler_pre(struct kprobe *p, struct pt_regs *regs)
30 pr_info("<%s> pre_handler: p->addr = 0x%p, ip = %lx, flags = 0x%lx\n",
31 p->symbol_name, p->addr, regs->ip, regs->flags);
34 pr_info("<%s> pre_handler: p->addr = 0x%p, nip = 0x%lx, msr = 0x%lx\n",
35 p->symbol_name, p->addr, regs->nip, regs->msr);
38 pr_info("<%s> pre_handler: p->addr = 0x%p, epc = 0x%lx, status = 0x%lx\n",
39 p->symbol_name, p->addr, regs->cp0_epc, regs->cp0_status);
42 pr_info("<%s> pre_handler: p->addr = 0x%p, pc = 0x%lx,"
44 p->symbol_name, p->addr, (long)regs->pc, (long)regs->pstate);
47 pr_info("<%s> pre_handler: 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);
51 pr_info("<%s> pre_handler: p->addr = 0x%p, pc = 0x%lx, status = 0x%lx\n",
52 p->symbol_name, p->addr, regs->epc, regs->status);
55 pr_info("<%s> pre_handler: p->addr, 0x%p, ip = 0x%lx, flags = 0x%lx\n",
56 p->symbol_name, p->addr, regs->psw.addr, regs->flags);
59 /* A dump_stack() here will give a stack backtrace */
63 /* kprobe post_handler: called after the probed instruction is executed */
64 static void __kprobes handler_post(struct kprobe *p, struct pt_regs *regs,
68 pr_info("<%s> post_handler: p->addr = 0x%p, flags = 0x%lx\n",
69 p->symbol_name, p->addr, regs->flags);
72 pr_info("<%s> post_handler: p->addr = 0x%p, msr = 0x%lx\n",
73 p->symbol_name, p->addr, regs->msr);
76 pr_info("<%s> post_handler: p->addr = 0x%p, status = 0x%lx\n",
77 p->symbol_name, p->addr, regs->cp0_status);
80 pr_info("<%s> post_handler: p->addr = 0x%p, pstate = 0x%lx\n",
81 p->symbol_name, p->addr, (long)regs->pstate);
84 pr_info("<%s> post_handler: p->addr = 0x%p, cpsr = 0x%lx\n",
85 p->symbol_name, p->addr, (long)regs->ARM_cpsr);
88 pr_info("<%s> post_handler: p->addr = 0x%p, status = 0x%lx\n",
89 p->symbol_name, p->addr, regs->status);
92 pr_info("<%s> pre_handler: p->addr, 0x%p, flags = 0x%lx\n",
93 p->symbol_name, p->addr, regs->flags);
98 * fault_handler: this is called if an exception is generated for any
99 * instruction within the pre- or post-handler, or when Kprobes
100 * single-steps the probed instruction.
102 static int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr)
104 pr_info("fault_handler: p->addr = 0x%p, trap #%dn", p->addr, trapnr);
105 /* Return 0 because we don't handle the fault. */
108 /* NOKPROBE_SYMBOL() is also available */
109 NOKPROBE_SYMBOL(handler_fault);
111 static int __init kprobe_init(void)
114 kp.pre_handler = handler_pre;
115 kp.post_handler = handler_post;
116 kp.fault_handler = handler_fault;
118 ret = register_kprobe(&kp);
120 pr_err("register_kprobe failed, returned %d\n", ret);
123 pr_info("Planted kprobe at %p\n", kp.addr);
127 static void __exit kprobe_exit(void)
129 unregister_kprobe(&kp);
130 pr_info("kprobe at %p unregistered\n", kp.addr);
133 module_init(kprobe_init)
134 module_exit(kprobe_exit)
135 MODULE_LICENSE("GPL");