64位linux下玩32位汇编编程

　　利用下假期，打算把linux下的汇编语言给熟悉下，结果是以32位为版本的，只能在办公室的机器上跑了个opensuse的32位版本，家里的suse挂了，无法输入中文。打算再安装下32位系统，今天找到了个解决方法，记录如下：

代码如下，文件名位test32.s：　　

 .section .data

 .section .text

 .globl _start
 _start:
     pushl $
     pushl $
     call sumer
     addl $, %esp
     movl %eax, %ebx
     movl $, %eax
     int $0x80

 .type sumer, @function

 sumer:
     pushl %ebp
     movl %esp, %ebp
     movl (%ebp), %eax
     movl (%ebp), %ecx
     addl %ecx, %eax
     popl %ebp
     ret

　　无法按照原来的方式，直接用as  test32.s  -o  test32.o汇编

　　　　　　　　　　　　直接用ld  test32.o -o test32链接

　　直接报错，由于我的linux是64位，解决方法就是在两个命令选项中加上适当的选项即可。

　　正确的命令是这样的，直接用as  test32.s  -o  test32.o  --32 汇编

　　　　　　　　　　　　直接用ld -m  elf_i386  test32.o -o test32链接　　

其中：-m参数是让ld模仿后面跟的连接器，也就是elf_i386格式的连接器，

--32参数是使用32位个是的汇编进行代码汇编，

如果有以下代码test321.c

 #include <stdio.h>

 int factorial(int num){
     if( == num){
         return ;
     }
     return num * factorial(num - );
 }                                                                               

 int main(int argc, char **argv)
 {
     printf("factorial(5): %d\n", factorial());

     return ;
 }

在64位系统中，直接使用gcc test321.c  -S  test321.s，64位汇编代码如下

       .file   "test321.c"
       .text
       .globl  factorial
       .type   factorial, @function
   factorial:
   .LFB0:
       .cfi_startproc
       pushq   %rbp
       .cfi_def_cfa_offset
      .cfi_offset , -
      movq    %rsp, %rbp
      .cfi_def_cfa_register
      subq    $, %rsp
      movl    %edi, -(%rbp)
      cmpl    $, -(%rbp)
      jne .L2
      movl    $, %eax
      jmp .L3
  .L2:
      movl    -(%rbp), %eax
      subl    $, %eax
      movl    %eax, %edi
      call    factorial
      imull   -(%rbp), %eax
  .L3:
      leave
      .cfi_def_cfa ,
      ret
      .cfi_endproc
  .LFE0:
      .size   factorial, .-factorial
      .section    .rodata
  .LC0:
      .string "factorial(5): %d\n"
      .text
      .globl  main
      .type   main, @function
  main:
  .LFB1:
      .cfi_startproc
      pushq   %rbp
      .cfi_def_cfa_offset
      .cfi_offset , -
      movq    %rsp, %rbp
      .cfi_def_cfa_register
      subq    $, %rsp
      movl    %edi, -(%rbp)
      movq    %rsi, -(%rbp)
      movl    $, %edi
      call    factorial
      movl    %eax, %esi
      leaq    .LC0(%rip), %rdi
      movl    $, %eax
      call    printf@PLT
      movl    $, %eax
      leave
      .cfi_def_cfa ,
      ret
      .cfi_endproc
  .LFE1:
      .size   main, .-main
      .ident  "GCC: (GNU) 9.1.0"
      .section    .note.GNU-stack,"",@progbits
~                                                 

在64位系统中，使用gcc test321.c  -S  -m32  test321.s，32位汇编代码如下

  .file   "test321.c"
     .text
     .globl  factorial
     .type   factorial, @function
 factorial:
 .LFB0:
     .cfi_startproc
     pushl   %ebp
     .cfi_def_cfa_offset
     .cfi_offset , -
     movl    %esp, %ebp
     .cfi_def_cfa_register
     subl    $, %esp
     call    __x86.get_pc_thunk.ax
     addl    $_GLOBAL_OFFSET_TABLE_, %eax
     cmpl    $, (%ebp)
     jne .L2
     movl    $, %eax
     jmp .L3
 .L2:
     movl    (%ebp), %eax
     subl    $, %eax
     subl    $, %esp
     pushl   %eax
     call    factorial
     addl    $, %esp
     imull   (%ebp), %eax
 .L3:
     leave
     .cfi_restore
     .cfi_def_cfa ,
     ret
     .cfi_endproc
 .LFE0:
     .size   factorial, .-factorial
     .section    .rodata
 .LC0:
     .string "factorial(5): %d\n"
     .text
     .globl  main
     .type   main, @function
 main:
 .LFB1:
     .cfi_startproc
     leal    (%esp), %ecx
     .cfi_def_cfa ,
     andl    $-, %esp
     pushl   -(%ecx)
     pushl   %ebp
     .cfi_escape 0x10,0x5,0x2,0x75,
     movl    %esp, %ebp
     pushl   %ebx
     pushl   %ecx
     .cfi_escape 0xf,0x3,0x75,0x78,0x6
     .cfi_escape 0x10,0x3,0x2,0x75,0x7c
     call    __x86.get_pc_thunk.bx
     addl    $_GLOBAL_OFFSET_TABLE_, %ebx
     subl    $, %esp
     pushl   $
     call    factorial
     addl    $, %esp
     subl    $, %esp
     pushl   %eax
     leal    .LC0@GOTOFF(%ebx), %eax
     pushl   %eax
     call    printf@PLT
     addl    $, %esp
     movl    $, %eax
     leal    -(%ebp), %esp
     popl    %ecx
     .cfi_restore
     .cfi_def_cfa ,
     popl    %ebx
     .cfi_restore
     popl    %ebp
     .cfi_restore
     leal    -(%ecx), %esp
     .cfi_def_cfa ,
     ret
     .cfi_endproc
 .LFE1:
     .size   main, .-main
     .section    .text.__x86.get_pc_thunk.ax,"axG",@progbits,__x86.get_pc_thunk.ax,comdat
     .globl  __x86.get_pc_thunk.ax
     .hidden __x86.get_pc_thunk.ax
     .type   __x86.get_pc_thunk.ax, @function
 __x86.get_pc_thunk.ax:
 .LFB2:
     .cfi_startproc
     movl    (%esp), %eax
     ret
     .cfi_endproc
 .LFE2:
     .section    .text.__x86.get_pc_thunk.bx,"axG",@progbits,__x86.get_pc_thunk.bx,comdat
     .globl  __x86.get_pc_thunk.bx
     .hidden __x86.get_pc_thunk.bx
     .type   __x86.get_pc_thunk.bx, @function
 __x86.get_pc_thunk.bx:
 .LFB3:
     .cfi_startproc
     movl    (%esp), %ebx
     ret
     .cfi_endproc
 .LFE3:
     .ident  "GCC: (GNU) 9.1.0"
     .section    .note.GNU-stack,"",@progbits   

　　linux下命令的选项比命令更重要