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 #ifdef CONFIG_MIPS 36 printk(KERN_INFO "pre_handler: p->addr = 0x%p, epc = 0x%lx," 37 " status = 0x%lx\n", 38 p->addr, regs->cp0_epc, regs->cp0_status); 39 #endif 40 #ifdef CONFIG_TILEGX 41 printk(KERN_INFO "pre_handler: p->addr = 0x%p, pc = 0x%lx," 42 " ex1 = 0x%lx\n", 43 p->addr, regs->pc, regs->ex1); 44 #endif 45 46 /* A dump_stack() here will give a stack backtrace */ 47 return 0; 48 } 49 50 /* kprobe post_handler: called after the probed instruction is executed */ 51 static void handler_post(struct kprobe *p, struct pt_regs *regs, 52 unsigned long flags) 53 { 54 #ifdef CONFIG_X86 55 printk(KERN_INFO "post_handler: p->addr = 0x%p, flags = 0x%lx\n", 56 p->addr, regs->flags); 57 #endif 58 #ifdef CONFIG_PPC 59 printk(KERN_INFO "post_handler: p->addr = 0x%p, msr = 0x%lx\n", 60 p->addr, regs->msr); 61 #endif 62 #ifdef CONFIG_MIPS 63 printk(KERN_INFO "post_handler: p->addr = 0x%p, status = 0x%lx\n", 64 p->addr, regs->cp0_status); 65 #endif 66 #ifdef CONFIG_TILEGX 67 printk(KERN_INFO "post_handler: p->addr = 0x%p, ex1 = 0x%lx\n", 68 p->addr, regs->ex1); 69 #endif 70 } 71 72 /* 73 * fault_handler: this is called if an exception is generated for any 74 * instruction within the pre- or post-handler, or when Kprobes 75 * single-steps the probed instruction. 76 */ 77 static int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr) 78 { 79 printk(KERN_INFO "fault_handler: p->addr = 0x%p, trap #%dn", 80 p->addr, trapnr); 81 /* Return 0 because we don't handle the fault. */ 82 return 0; 83 } 84 85 static int __init kprobe_init(void) 86 { 87 int ret; 88 kp.pre_handler = handler_pre; 89 kp.post_handler = handler_post; 90 kp.fault_handler = handler_fault; 91 92 ret = register_kprobe(&kp); 93 if (ret < 0) { 94 printk(KERN_INFO "register_kprobe failed, returned %d\n", ret); 95 return ret; 96 } 97 printk(KERN_INFO "Planted kprobe at %p\n", kp.addr); 98 return 0; 99 } 100 101 static void __exit kprobe_exit(void) 102 { 103 unregister_kprobe(&kp); 104 printk(KERN_INFO "kprobe at %p unregistered\n", kp.addr); 105 } 106 107 module_init(kprobe_init) 108 module_exit(kprobe_exit) 109 MODULE_LICENSE("GPL"); 110