Kprobe的使用方法

 

/* For each probe you need to allocate a kprobe structure */
static struct kprobe kp = {
    .symbol_name    = "do_fork",
};
 
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 < 0) {
        printk(KERN_INFO "register_kprobe failed, returned %d\n", ret);
        return ret;
    }
    printk(KERN_INFO "Planted kprobe at %p\n", kp.addr);
    return 0;
}
 
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");

 

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
#ifdef CONFIG_TILEGX
    printk(KERN_INFO "pre_handler: p->addr = 0x%p, pc = 0x%lx,"
            " ex1 = 0x%lx\n",
        p->addr, regs->pc, regs->ex1);
#endif
 
    /* A dump_stack() here will give a stack backtrace */
    return 0;
}

/* 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
#ifdef CONFIG_TILEGX
    printk(KERN_INFO "post_handler: p->addr = 0x%p, ex1 = 0x%lx\n",
        p->addr, regs->ex1);
#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 0;
}

 

测试结果：

加载到内核中后，随便在终端上敲一个命令，可以看到dmesg中打印如下信息：

 

<6>pre_handler: p->addr = 0xc0439cc0, ip = c0439cc1, flags = 0x246
<6>post_handler: p->addr = 0xc0439cc0, flags = 0x246
<6>pre_handler: p->addr = 0xc0439cc0, ip = c0439cc1, flags = 0x246
<6>post_handler: p->addr = 0xc0439cc0, flags = 0x246
<6>pre_handler: p->addr = 0xc0439cc0, ip = c0439cc1, flags = 0x246
<6>post_handler: p->addr = 0xc0439cc0, flags = 0x246

可以看到被探测点的地址为0xc0439cc0，用以下命令确定这个地址就是do_fork的入口地址。

[root@apple kprobes]# cat /proc/kallsyms | grep do_fork
c0439cc0 T do_fork

 

来源：https://blog.csdn.net/luckyapple1028/article/details/52972315