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