在Linux下写汇编总是会出现段错误是什么情况？

我这里是ubuntu x86-64，照着抄你的代码运行非常正常。

编译运行：

as run.s -o run.o

ld run.o -o run

./run

GDB调试也没问题

GNU gdb (Ubuntu 8.1.1-0ubuntu1) 8.1.1

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License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

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Type "show configuration" for configuration details.

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<http://www.gnu.org/software/gdb/bugs/>.

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For help, type "help".

Type "apropos word" to search for commands related to "word"...

Reading symbols from run...done.

(gdb) b _start

Breakpoint 1 at 0x400078: file run.s, line 6.

(gdb) r

Starting program: /home/×××××××/Desktop/run

Breakpoint 1, _start () at run.s:6

6movl $1, %eax

(gdb) ni

7movl $0, %ebx

(gdb) ni

8int $0x80

(gdb) ni

[Inferior 1 (process 10617) exited normally]

(gdb) b _start

Linux 下调试汇编代码既可以用 GDB、DDD 这类通用的调试器，也可以使用专门用来调试汇编代码的 ALD(Assembly Language Debugger)。

从调试的角度来看，使用 GAS 的好处是可以在生成的目标代码中包含符号表(symbol table)，这样就可以使用 GDB 和 DDD 来进行源码级的调试了。要在生成的可执行程序中包含符号表，可以采用下面的方式进行编译和链接：

[xiaowp@gary code]$ as --gstabs -o hello.o hello.s

[xiaowp@gary code]$ ld -o hello hello.o

执行 as 命令时带上参数 --gstabs 可以告诉汇编器在生成的目标代码中加上符号表，同时需要注意的是，在用 ld 命令进行链接时不要加上 -s 参数，否则目标代码中的符号表在链接时将被删去。

汇编程序员通常面对的都是一些比较苛刻的软硬件环境，短小精悍的ALD可能更能符合实际的需要，因此下面主要介绍一下如何用ALD来调试汇编程序。首先在命令行方式下执行ald命令来启动调试器，该命令的参数是将要被调试的可执行程序：

[xiaowp@gary doc]$ ald hello

Assembly Language Debugger 0.1.3Copyright (C) 2000-2002 Patrick Alken

hell ELF Intel 80386 (32 bit), LSB, Executable, Version 1 (current)

Loading debugging symbols...(15 symbols loaded)

ald>

当 ALD 的提示符出现之后，用 disassemble 命令对代码段进行反汇编：

ald>disassemble -s .text

Disassembling section .text (0x08048074 - 0x08048096)

08048074 BA0F000000 mov edx, 0xf

08048079 B998900408 mov ecx, 0x8049098

0804807E BB01000000 mov ebx, 0x1

08048083 B804000000 mov eax, 0x4

08048088 CD80 int 0x80

0804808A BB00000000 mov ebx, 0x0

0804808F B801000000 mov eax, 0x1

08048094 CD80 int 0x80

上述输出信息的第一列是指令对应的地址码，利用它可以设置在程序执行时的断点：

ald>break 0x08048088

Breakpoint 1 set for 0x08048088

断点设置好后，使用 run 命令开始执行程序。ALD 在遇到断点时将自动暂停程序的运行，同时会显示所有寄存器的当前值：

ald>run

Starting program: hello

Breakpoint 1 encountered at 0x08048088

eax = 0x00000004 ebx = 0x00000001 ecx = 0x08049098 edx = 0x0000000Fesp = 0xBFFFF6C0 ebp = 0x00000000 esi = 0x00000000 edi = 0x00000000

ds = 0x0000002B es = 0x0000002B fs = 0x00000000 gs = 0x00000000

ss = 0x0000002B cs = 0x00000023 eip = 0x08048088 eflags = 0x00000246

Flags: PF ZF IF

08048088 CD80 int 0x80

如果需要对汇编代码进行单步调试，可以使用 next 命令：

ald>next

Hello, world!

eax = 0x0000000F ebx = 0x00000000 ecx = 0x08049098 edx = 0x0000000Fesp = 0xBFFFF6C0 ebp = 0x00000000 esi = 0x00000000 edi = 0x00000000

ds = 0x0000002B es = 0x0000002B fs = 0x00000000 gs = 0x00000000

ss = 0x0000002B cs = 0x00000023 eip = 0x0804808F eflags = 0x00000346

Flags: PF ZF TF IF

0804808F B801000000 mov eax, 0x1

若想获得 ALD 支持的所有调试命令的详细列表，可以使用 help 命令：

ald>help

Commands may be abbreviated.

If a blank command is entered, the last command is repeated.

Type `help <command>'' for more specific information on <command>.

General commands

attach clear continue detach disassemble

enter examine file help load

next quit register run set

step unload window write

Breakpoint related commands

break delete disable enable ignore

lbreak tbreak

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