kprobe 内核模块

代码来自于linux内核sample/kprobe

kprobe_example.c

 /*
  * NOTE: This example is works on x86 and powerpc.
  * Here's a sample kernel module showing the use of kprobes to dump a
  * stack trace and selected registers when do_fork() is called.
  *
  * For more information on theory of operation of kprobes, see
  * Documentation/kprobes.txt
  *
  * You will see the trace data in /var/log/messages and on the console
  * whenever do_fork() is invoked to create a new process.
  */

 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/kprobes.h>

 /* For each probe you need to allocate a kprobe structure */
 static struct kprobe kp = {
     .symbol_name    = "do_fork",
 };

 /* kprobe pre_handler: called just before the probed instruction is executed */
 static int handler_pre(struct kprobe *p, struct pt_regs *regs)
 {
 #ifdef CONFIG_X86
     printk(KERN_INFO "pre_handler: p->addr = 0x%p, ip = %lx,"
             " flags = 0x%lx\n",
         p->addr, regs->ip, regs->flags);
 #endif
 #ifdef CONFIG_PPC
     printk(KERN_INFO "pre_handler: p->addr = 0x%p, nip = 0x%lx,"
             " msr = 0x%lx\n",
         p->addr, regs->nip, regs->msr);
 #endif
 #ifdef CONFIG_MIPS
     printk(KERN_INFO "pre_handler: p->addr = 0x%p, epc = 0x%lx,"
             " status = 0x%lx\n",
         p->addr, regs->cp0_epc, regs->cp0_status);
 #endif

     /* A dump_stack() here will give a stack backtrace */
     return ;
 }

 /* kprobe post_handler: called after the probed instruction is executed */
 static void handler_post(struct kprobe *p, struct pt_regs *regs,
                 unsigned long flags)
 {
 #ifdef CONFIG_X86
     printk(KERN_INFO "post_handler: p->addr = 0x%p, flags = 0x%lx\n",
         p->addr, regs->flags);
 #endif
 #ifdef CONFIG_PPC
     printk(KERN_INFO "post_handler: p->addr = 0x%p, msr = 0x%lx\n",
         p->addr, regs->msr);
 #endif
 #ifdef CONFIG_MIPS
     printk(KERN_INFO "post_handler: p->addr = 0x%p, status = 0x%lx\n",
         p->addr, regs->cp0_status);
 #endif
 }

 /*
  * fault_handler: this is called if an exception is generated for any
  * instruction within the pre- or post-handler, or when Kprobes
  * single-steps the probed instruction.
  */
 static int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr)
 {
     printk(KERN_INFO "fault_handler: p->addr = 0x%p, trap #%dn",
         p->addr, trapnr);
     /* Return 0 because we don't handle the fault. */
     return ;
 }

 static int __init kprobe_init(void)
 {
     int ret;
     kp.pre_handler = handler_pre;
     kp.post_handler = handler_post;
     kp.fault_handler = handler_fault;

     ret = register_kprobe(&kp);
     if (ret < ) {
         printk(KERN_INFO "register_kprobe failed, returned %d\n", ret);
         return ret;
     }
     printk(KERN_INFO "Planted kprobe at %p\n", kp.addr);
     return ;
 }

 static void __exit kprobe_exit(void)
 {
     unregister_kprobe(&kp);
     printk(KERN_INFO "kprobe at %p unregistered\n", kp.addr);
 }

 module_init(kprobe_init)
 module_exit(kprobe_exit)
 MODULE_LICENSE("GPL");

makefile 如下：

obj-m := kprobe-example.o 
KDIR := /lib/modules/$(shell uname -r)/build
PWD := $(shell pwd)
default:
    $(MAKE) -C $(KDIR) SUBDIRS=$(PWD) modules
clean:
    rm -f *.mod.c *.ko *.o

su root

insmod kprobe-example.ko

cat /var/log/messages 查看消息

lsmod | grep krpobe

rm kprobe-example.ko