---

AT&T

• mov_test.s

mov $0,%r8d

• gcc -c mov_test.s 输出 mov_test.o,
• objdump -D mov_test.o 查看 mov_test.o:

mov_test.o:     file format elf64-x86-64


Disassembly of section .text:

0000000000000000 <.text>:
   0:   41 b8 00 00 00 00       mov    $0x0,%r8d

• mov_.S

mov %r8d,0
nop

• 执行命令： gcc -c mov_.S 会输出 mov_.o 文件：
• objdump -D mov_.o :

mov_.o：     文件格式 elf64-x86-64

Disassembly of section .text:

0000000000000000 <.text>:
   0:   44 89 04 25 00 00 00    mov    %r8d,0x0
   7:   00 
   8:   90                      nop

• main.c:

void main() {
}

• 执行命令： gcc -S main.c 输出文件 main.s
• main.s:

       .file   "main.c"
        .text
        .globl  main
        .type   main, @function
main:
.LFB0:
        .cfi_startproc
        pushq   %rbp
        .cfi_def_cfa_offset 16
        .cfi_offset 6, -16
        movq    %rsp, %rbp
        .cfi_def_cfa_register 6
        nop
        popq    %rbp
        .cfi_def_cfa 7, 8
        ret
        .cfi_endproc
.LFE0:
        .size   main, .-main
        .ident  "GCC: (Uos 8.3.0.3-3+rebuild) 8.3.0"
        .section        .note.GNU-stack,"",@progbits

• doubao.s:

section .text
    global _start

_start:
    ; 将 0 存入 r8d 寄存器
    mov r8d, 0

    ; 退出程序
    mov eax, 1
    xor ebx, ebx
    int 0x80    

asm

• asm_test.c:

#include <stdio.h>

int main() {
    int num = 10;
    __asm__ (
        "movl %1, %%eax\n\t"
        "movl %%eax, %0\n\t"
        : "=m" (num)
        : "r" (num)
        : "%eax"
    );
    printf("The value of num is: %d\n", num);
    return 0;
}

Intel

• Intel 语法 mov_test.s 应改为

mov  r8d,0

• asm_test.c , 指定使用 Intel 语法，需要执行 gcc -masm=intel -S asm_test.c