2 * NOTE: This example is works on x86 and powerpc.
3 * Here's a sample kernel module showing the use of kprobes to dump a
4 * stack trace and selected registers when _do_fork() is called.
6 * For more information on theory of operation of kprobes, see
7 * Documentation/kprobes.txt
9 * You will see the trace data in /var/log/messages and on the console
10 * whenever _do_fork() 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] = "_do_fork";
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 handler_pre(struct kprobe *p, struct pt_regs *regs)
30 printk(KERN_INFO "<%s> pre_handler: p->addr = 0x%p, ip = %lx,"
32 p->symbol_name, p->addr, regs->ip, regs->flags);
35 printk(KERN_INFO "<%s> pre_handler: p->addr = 0x%p, nip = 0x%lx,"
37 p->symbol_name, p->addr, regs->nip, regs->msr);
40 printk(KERN_INFO "<%s> pre_handler: p->addr = 0x%p, epc = 0x%lx,"
42 p->symbol_name, p->addr, regs->cp0_epc, regs->cp0_status);
45 printk(KERN_INFO "<%s> pre_handler: p->addr = 0x%p, pc = 0x%lx,"
47 p->symbol_name, p->addr, regs->pc, regs->ex1);
50 pr_info("<%s> pre_handler: p->addr = 0x%p, pc = 0x%lx,"
52 p->symbol_name, p->addr, (long)regs->pc, (long)regs->pstate);
55 /* A dump_stack() here will give a stack backtrace */
59 /* kprobe post_handler: called after the probed instruction is executed */
60 static void handler_post(struct kprobe *p, struct pt_regs *regs,
64 printk(KERN_INFO "<%s> post_handler: p->addr = 0x%p, flags = 0x%lx\n",
65 p->symbol_name, p->addr, regs->flags);
68 printk(KERN_INFO "<%s> post_handler: p->addr = 0x%p, msr = 0x%lx\n",
69 p->symbol_name, p->addr, regs->msr);
72 printk(KERN_INFO "<%s> post_handler: p->addr = 0x%p, status = 0x%lx\n",
73 p->symbol_name, p->addr, regs->cp0_status);
76 printk(KERN_INFO "<%s> post_handler: p->addr = 0x%p, ex1 = 0x%lx\n",
77 p->symbol_name, p->addr, regs->ex1);
80 pr_info("<%s> post_handler: p->addr = 0x%p, pstate = 0x%lx\n",
81 p->symbol_name, p->addr, (long)regs->pstate);
86 * fault_handler: this is called if an exception is generated for any
87 * instruction within the pre- or post-handler, or when Kprobes
88 * single-steps the probed instruction.
90 static int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr)
92 printk(KERN_INFO "fault_handler: p->addr = 0x%p, trap #%dn",
94 /* Return 0 because we don't handle the fault. */
98 static int __init kprobe_init(void)
101 kp.pre_handler = handler_pre;
102 kp.post_handler = handler_post;
103 kp.fault_handler = handler_fault;
105 ret = register_kprobe(&kp);
107 printk(KERN_INFO "register_kprobe failed, returned %d\n", ret);
110 printk(KERN_INFO "Planted kprobe at %p\n", kp.addr);
114 static void __exit kprobe_exit(void)
116 unregister_kprobe(&kp);
117 printk(KERN_INFO "kprobe at %p unregistered\n", kp.addr);
120 module_init(kprobe_init)
121 module_exit(kprobe_exit)
122 MODULE_LICENSE("GPL");