获取总​​线错误在大会在线编程86 [英] Getting a bus error in Assembly in-line programming x86

问题描述

我偶然发现了一个汇编语言编程的挑战，我需要找到原因如下code试图运行它时，给出了一个总线错误。很多谷歌搜索后，我仍然无法弄清楚，为什么..我的集会86不是很​​大的了解，在寻找解决任何提示将是非常美联社preciated。

下面是code：

 的#include＆LT;＆stdlib.h中GT;
诠释主要（无效）{
  ASM（PUSHF \\ n
      ORL $ 0x40000（％ESP）\\ n
      POPF \\ n）;  *（为（int *）（（（字符*）malloc的（5））+ 1））= 23; //此行会导致总线错误
  返回0;
}
 

解决方案

从本质上讲要设置在标志一个标志寄存器。标志0x40000，又名位18而根据 http://en.wikipedia.org/wiki/ FLAGS_register_％28computing％29 是

18 AC对齐检查（486SX +专用）X

如果你搜索标志对齐检查你发现除其他：

http://forum.soft32.com/linux2/打开86校准 - 检查 - ftopict12003.html

我希望这台你在正确的轨道上。但你真的有一个486SX？

I stumbled upon an assembly programming challenge where I need to find why the following code gives a Bus Error when trying to run it. After much googling, I still can't figure out why.. My understanding of assembly x86 not great, any tips on finding the solution would be very appreciated.

Here is the code:

#include <stdlib.h>
int main(void) {
  asm("pushf\n"
      "orl $ 0x40000, (%esp)\n"
      "popf\n");

  *((int*) (((char*) malloc(5)) + 1)) = 23; // This line causes the Bus Error


  return 0;
}

解决方案

Essentially you are setting a flag in the flags register. Flag 0x40000, aka bit 18 which according to http://en.wikipedia.org/wiki/FLAGS_register_%28computing%29 is

18 AC Alignment check (486SX+ only) X

If you search for "flag alignment check" you find amongst others:

http://forum.soft32.com/linux2/Turn-x86-Alignment-Check-ftopict12003.html

I hope this sets you on the right track. But do you really have a 486SX?

这篇关于获取总​​线错误在大会在线编程86的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！