| Ananth N Mavinakayanahalli | 804defe | 2008-03-04 14:28:38 -0800 | [diff] [blame] | 1 | /* |
| 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. |
| 5 | * |
| 6 | * For more information on theory of operation of kprobes, see |
| 7 | * Documentation/kprobes.txt |
| 8 | * |
| 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. |
| 11 | */ |
| 12 | |
| 13 | #include <linux/kernel.h> |
| 14 | #include <linux/module.h> |
| 15 | #include <linux/kprobes.h> |
| 16 | |
| 17 | /* For each probe you need to allocate a kprobe structure */ |
| 18 | static struct kprobe kp = { |
| 19 | .symbol_name = "do_fork", |
| 20 | }; |
| 21 | |
| 22 | /* kprobe pre_handler: called just before the probed instruction is executed */ |
| 23 | static int handler_pre(struct kprobe *p, struct pt_regs *regs) |
| 24 | { |
| 25 | #ifdef CONFIG_X86 |
| 26 | printk(KERN_INFO "pre_handler: p->addr = 0x%p, ip = %lx," |
| 27 | " flags = 0x%lx\n", |
| 28 | p->addr, regs->ip, regs->flags); |
| 29 | #endif |
| 30 | #ifdef CONFIG_PPC |
| 31 | printk(KERN_INFO "pre_handler: p->addr = 0x%p, nip = 0x%lx," |
| 32 | " msr = 0x%lx\n", |
| 33 | p->addr, regs->nip, regs->msr); |
| 34 | #endif |
| 35 | |
| 36 | /* A dump_stack() here will give a stack backtrace */ |
| 37 | return 0; |
| 38 | } |
| 39 | |
| 40 | /* kprobe post_handler: called after the probed instruction is executed */ |
| 41 | static void handler_post(struct kprobe *p, struct pt_regs *regs, |
| 42 | unsigned long flags) |
| 43 | { |
| 44 | #ifdef CONFIG_X86 |
| 45 | printk(KERN_INFO "post_handler: p->addr = 0x%p, flags = 0x%lx\n", |
| 46 | p->addr, regs->flags); |
| 47 | #endif |
| 48 | #ifdef CONFIG_PPC |
| 49 | printk(KERN_INFO "post_handler: p->addr = 0x%p, msr = 0x%lx\n", |
| 50 | p->addr, regs->msr); |
| 51 | #endif |
| 52 | } |
| 53 | |
| 54 | /* |
| 55 | * fault_handler: this is called if an exception is generated for any |
| 56 | * instruction within the pre- or post-handler, or when Kprobes |
| 57 | * single-steps the probed instruction. |
| 58 | */ |
| 59 | static int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr) |
| 60 | { |
| 61 | printk(KERN_INFO "fault_handler: p->addr = 0x%p, trap #%dn", |
| 62 | p->addr, trapnr); |
| 63 | /* Return 0 because we don't handle the fault. */ |
| 64 | return 0; |
| 65 | } |
| 66 | |
| 67 | static int __init kprobe_init(void) |
| 68 | { |
| 69 | int ret; |
| 70 | kp.pre_handler = handler_pre; |
| 71 | kp.post_handler = handler_post; |
| 72 | kp.fault_handler = handler_fault; |
| 73 | |
| 74 | ret = register_kprobe(&kp); |
| 75 | if (ret < 0) { |
| 76 | printk(KERN_INFO "register_kprobe failed, returned %d\n", ret); |
| 77 | return ret; |
| 78 | } |
| 79 | printk(KERN_INFO "Planted kprobe at %p\n", kp.addr); |
| 80 | return 0; |
| 81 | } |
| 82 | |
| 83 | static void __exit kprobe_exit(void) |
| 84 | { |
| 85 | unregister_kprobe(&kp); |
| 86 | printk(KERN_INFO "kprobe at %p unregistered\n", kp.addr); |
| 87 | } |
| 88 | |
| 89 | module_init(kprobe_init) |
| 90 | module_exit(kprobe_exit) |
| 91 | MODULE_LICENSE("GPL"); |