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Win32下AT&T汇编Hello world教程

pingf posted @ Tue, 08 Mar 2011 18:50:26 -1100 in 未分类 , 4141 readers

因为复试的需要,学习了下和汇编相关的东西,

虽然当年学过微机原理,不过没下功夫[其实是老师水,教材水啊....]

现在只能恶补了

这两天玩了下masm,nasm,gas,当然只是搭建了基本的环境,跑了下基本的实例

因为gas相关文档比较稀缺,所以本篇日志记录一些和其相关的

主要目的是备份一下,省的以后忘了

顺便说一下,我用的是和谐的WinXP系统

1.环境搭建,从sf下MinGW套件,这一步不在赘述

2.基本的程序

先来一个最简单的hello world,不过用到了c运行时,

当然也可以写那种纯粹的保护模式的,不过比较麻烦,现在也没深入研究,故暂不讨论

.section .data
out_text:
    .asciz "hello world"
.section .text
.globl _main
_main:
    pushl $out_text
    call _printf
    pushl $0
    call _exit
这里用到了c运行时的main,exit,printf函数,因为win32的原因多加了个下划线
3.编译
as test_win.s -o test_win.o -gstabs 
ld test_win.o -o test_win.exe -Le:/mingw/lib -lcrtdll
-gstabs保留了调试相关的符号表
-Le:/mingw/lib -lcrtdll链接了c运行时,注意mingw路径是我机器上的
4.运行

上面那个是带有调试信息的,可以看到strip后只有2K了
5.调试
注意不要strip

这里面要注意的是设置断点时的*号,以及main和_main的区别
另外查看寄存器可用"i r"指令
6.com版本的hello world
这个不管怎样还是大了点,想想当年学习微机原理的伪dos程序貌似是按字节论的,
下面就来个com版的hello world
(1)代码test.s
.code16
.text
    movw %cs, %ax
    movw %ax, %ds
    movw %ax, %es
    movw %ax, %ss
     
    movw $11, %cx
    movw $0x1301,%ax
    movb $0x07,%bl
    movw $0,%dx
    movw $outstring,%bp
    int $0x10
    jmp .
outstring:
    .asciz "hello world"
注意.code16是很有必要的
(2)编译
as test.s -o test.o 
ld test.o -Ttext 0x0100 -o test.exe
objcopy.exe -R .pdr -R .comment -R .note -S -O binary test.exe test.com
最后的objcopy将编译后的按binary输出成.com格式的
[另外如果跳过第二部exe生成,直接从.o生成.com也是可以运行的,不过对比发现有1bit的异常引起了输出字符的乱码
具体原因我就不去纠结的探索了,如果修改了那一比特,字符显示就正常了]
另外链接时的-Ttext 0x0100也可以用如下lds文件来控制
SECTIONS
{
. = 0x0100;
.text : {*(.text)}
}
同时链接时的选项应该为-Ttest.lds
(3)输出

(4)修改
此时如果ls -l一下会发现有将近4k之巨,这是因为填充了很多的0,用HxD这样的软件把结尾的0
给干掉再看其大小

看看最后的那个文件52字节,终于瘦身成功了!


Avatar_small
纵横天下 said:
Fri, 11 Mar 2011 02:32:38 -1100

在Win32下还是用NASM/MASM这类Intel风格吧。。。

Avatar_small
pingf said:
Fri, 11 Mar 2011 19:40:30 -1100

风格其实无所谓,因为最后都是二进制的
不过GAS汇编有其方便的地方,
无论*nix,windows还有avr单片机,arm单片机都可以采用这种汇编
另外调试也比较方便,可以配合SlickEdit等工具进行可视化的调试
并且也可以通过选项转换为Intel格式的
并且GAS语义上更为明确,不像masm那般从16位到32位连寄存器关键字都可能要改动
另外nasm虽号称跨平台,但无论*nix还是win32都不够普及,调试起来也较为不便
另外从学习的角度,gas汇编并没有过分隐藏细节,当然这会带来很多麻烦,但学到的东西更多

Avatar_small
Garfileo said:
Wed, 16 Mar 2011 15:03:39 -1100

Richard Blum 写的《汇编语言程序设计》(机械工业出版社)是 gas 的,内容很翔实。

Avatar_small
pingf said:
Fri, 18 Mar 2011 16:36:33 -1100

@Garfileo:
是那本wrox的红皮书么?Professional Assembly Language
早先被某本wrox的关于vs的红皮书伤过[低级错误连篇],然后养成了不看wrox红皮的习惯
这本大致看了下,还不错,不过貌似还是没有关于gas跨平台应用的讲解

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