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如何禁止地址空间布局随机化对调试带来的影响

 2 years ago
source link: https://www.lujun9972.win/blog/2018/10/27/%E5%A6%82%E4%BD%95%E7%A6%81%E6%AD%A2%E5%9C%B0%E5%9D%80%E7%A9%BA%E9%97%B4%E5%B8%83%E5%B1%80%E9%9A%8F%E6%9C%BA%E5%8C%96%E5%AF%B9%E8%B0%83%E8%AF%95%E5%B8%A6%E6%9D%A5%E7%9A%84%E5%BD%B1%E5%93%8D/index.html
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如何禁止地址空间布局随机化对调试带来的影响

从 《Effective Debugging》中学来的，记录一下。

现代linux内核每次加载程序时会将程序加载到内存的随机位置，以防止缓冲区益处的代码注入攻击。

比如下面程序可以输出自身的栈、堆、代码及数据相关的内存地址: 

#include <stdio.h>
#include <stdlib.h>

int z;
int i=1;
const int c=1;

int main(int argc, char *argv[])
{
  printf("Stack:\t%p\n", (void*)&argc);
  printf("heap:\t%p\n", (void*) malloc(1));
  printf("code:\t%p\n", (void*) main);
  printf("data:\t%p (zero)\n", (void*) &z);
  printf("data:\t%p (initialized)\n", (void*) &i);
  printf("data:\t%p (constant)\n", (void*) &c);
  return 0;
}

第一次执行结果: 

Stack:  0x7ffde6f8cf9c
heap:   0x55ca3fd9d270
code:   0x55ca3ee95149
data:   0x55ca3ee98040 (zero)
data:   0x55ca3ee98038 (initialized)
data:   0x55ca3ee96004 (constant)

第二次执行结果: 

Stack:  0x7ffebd2eb6ec
heap:   0x55a72ae36270
code:   0x55a72ae04149
data:   0x55a72ae07040 (zero)
data:   0x55a72ae07038 (initialized)
data:   0x55a72ae05004 (constant)

然而这种地址空间布局随机化措施(address space layout randomization, ASLR)可能干扰调试工作，比如会使我们记录下来的指针指变得无效。

要禁止ASLR,可以采用下面方法来运行程序 

setarch $(uname -m) -R myprogram
# 这里 -R 表示 --addr-no-randomize
              # Disables randomization of the virtual address space.  Turns on ADDR_NO_RANDOMIZE.

report

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