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 /* For each probe you need to allocate a kprobe structure */
18 static struct kprobe kp = {
19 .symbol_name = "_do_fork",
22 /* kprobe pre_handler: called just before the probed instruction is executed */
23 static int handler_pre(struct kprobe *p, struct pt_regs *regs)
26 printk(KERN_INFO "pre_handler: p->addr = 0x%p, ip = %lx,"
28 p->addr, regs->ip, regs->flags);
31 printk(KERN_INFO "pre_handler: p->addr = 0x%p, nip = 0x%lx,"
33 p->addr, regs->nip, regs->msr);
36 printk(KERN_INFO "pre_handler: p->addr = 0x%p, epc = 0x%lx,"
38 p->addr, regs->cp0_epc, regs->cp0_status);
41 printk(KERN_INFO "pre_handler: p->addr = 0x%p, pc = 0x%lx,"
43 p->addr, regs->pc, regs->ex1);
46 pr_info("<%s> pre_handler: p->addr = 0x%p, pc = 0x%lx,"
48 p->symbol_name, p->addr, (long)regs->pc, (long)regs->pstate);
51 /* A dump_stack() here will give a stack backtrace */
55 /* kprobe post_handler: called after the probed instruction is executed */
56 static void handler_post(struct kprobe *p, struct pt_regs *regs,
60 printk(KERN_INFO "post_handler: p->addr = 0x%p, flags = 0x%lx\n",
61 p->addr, regs->flags);
64 printk(KERN_INFO "post_handler: p->addr = 0x%p, msr = 0x%lx\n",
68 printk(KERN_INFO "post_handler: p->addr = 0x%p, status = 0x%lx\n",
69 p->addr, regs->cp0_status);
72 printk(KERN_INFO "post_handler: p->addr = 0x%p, ex1 = 0x%lx\n",
76 pr_info("<%s> post_handler: p->addr = 0x%p, pstate = 0x%lx\n",
77 p->symbol_name, p->addr, (long)regs->pstate);
82 * fault_handler: this is called if an exception is generated for any
83 * instruction within the pre- or post-handler, or when Kprobes
84 * single-steps the probed instruction.
86 static int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr)
88 printk(KERN_INFO "fault_handler: p->addr = 0x%p, trap #%dn",
90 /* Return 0 because we don't handle the fault. */
94 static int __init kprobe_init(void)
97 kp.pre_handler = handler_pre;
98 kp.post_handler = handler_post;
99 kp.fault_handler = handler_fault;
101 ret = register_kprobe(&kp);
103 printk(KERN_INFO "register_kprobe failed, returned %d\n", ret);
106 printk(KERN_INFO "Planted kprobe at %p\n", kp.addr);
110 static void __exit kprobe_exit(void)
112 unregister_kprobe(&kp);
113 printk(KERN_INFO "kprobe at %p unregistered\n", kp.addr);
116 module_init(kprobe_init)
117 module_exit(kprobe_exit)
118 MODULE_LICENSE("GPL");