最近在学堂在线上重温汇编语言课程，整理了用gcc将helloworld.c程序生成汇编代码，并将汇编代码进行编译和连接生成可执行ELF文件的过程。方法和操作步骤记录如下以做备忘，同时也供各位感兴趣的同学学习参考。

    整个过程是在ubuntu1604下进行的。（uname -srvio: Linux 4.4.0-83-generic #106-Ubuntu SMP Mon Jun 26 17:54:43 UTC 2017 x86_64 GNU/Linux）

#include <stdlib.h>

#include <stdio.h>

int add(int x, int y) {

        return x + y;

}

void main() {

        char *msg = "hello world \n";

        printf("%s", msg);

        int x = 12;

        int y = 8;

        printf("%d + %d = %d \n", x, y, add(x, y));

        return;

}

        .file   "helloworld.c"
        .text
        .globl  add
        .type   add, @function
add:
.LFB2:
        .cfi_startproc
        pushq   %rbp
        .cfi_def_cfa_offset 16
        .cfi_offset 6, -16
        movq    %rsp, %rbp
        .cfi_def_cfa_register 6
        movl    %edi, -4(%rbp)
        movl    %esi, -8(%rbp)
        movl    -4(%rbp), %edx
        movl    -8(%rbp), %eax
        addl    %edx, %eax
        popq    %rbp
        .cfi_def_cfa 7, 8
        ret
        .cfi_endproc
.LFE2:
        .size   add, .-add
        .section        .rodata
.LC0:
        .string "hello world \n"
.LC1:
        .string "%s"
.LC2:
        .string "%d + %d = %d \n"
        .text
        .globl  main
        .type   main, @function
main:
.LFB3:
        .cfi_startproc
        pushq   %rbp
        .cfi_def_cfa_offset 16
        .cfi_offset 6, -16
        movq    %rsp, %rbp
        .cfi_def_cfa_register 6
        subq    $16, %rsp
        movq    $.LC0, -8(%rbp)
        movq    -8(%rbp), %rax
        movq    %rax, %rsi
        movl    $.LC1, %edi
        movl    $0, %eax
        call    printf
        movl    $12, -16(%rbp)
        movl    $8, -12(%rbp)
        movl    -12(%rbp), %edx
        movl    -16(%rbp), %eax
        movl    %edx, %esi
        movl    %eax, %edi
        call    add
        movl    %eax, %ecx
        movl    -12(%rbp), %edx
        movl    -16(%rbp), %eax
        movl    %eax, %esi
        movl    $.LC2, %edi
        movl    $0, %eax
        call    printf
        nop
        leave
        .cfi_def_cfa 7, 8
        ret
        .cfi_endproc
.LFE3:
        .size   main, .-main
        .ident  "GCC: (Ubuntu 5.4.0-6ubuntu1~16.04.4) 5.4.0 20160609"
        .section        .note.GNU-stack,"",@progbits

        .file   "helloworld.c"
        .text
        .globl  add
        .type   add, @function
add:
.LFB2:
        .cfi_startproc
        pushl   %ebp
        .cfi_def_cfa_offset 8
        .cfi_offset 5, -8
        movl    %esp, %ebp
        .cfi_def_cfa_register 5
        movl    8(%ebp), %edx
        movl    12(%ebp), %eax
        addl    %edx, %eax
        popl    %ebp
        .cfi_restore 5
        .cfi_def_cfa 4, 4
        ret
        .cfi_endproc
.LFE2:
        .size   add, .-add
        .section        .rodata
.LC0:
        .string "hello world \n"
.LC1:
        .string "%s"
.LC2:
        .string "%d + %d = %d \n"
        .text
        .globl  main
        .type   main, @function
main:
.LFB3:
        .cfi_startproc
        leal    4(%esp), %ecx
        .cfi_def_cfa 1, 0
        andl    $-16, %esp
        pushl   -4(%ecx)
        pushl   %ebp
        .cfi_escape 0x10,0x5,0x2,0x75,0
        movl    %esp, %ebp
        pushl   %ecx
        .cfi_escape 0xf,0x3,0x75,0x7c,0x6
        subl    $20, %esp
        movl    $.LC0, -20(%ebp)
        subl    $8, %esp
        pushl   -20(%ebp)
        pushl   $.LC1
        call    printf

        addl    $16, %esp
        movl    $12, -16(%ebp)
        movl    $8, -12(%ebp)
        subl    $8, %esp
        pushl   -12(%ebp)
        pushl   -16(%ebp)
        call    add
        addl    $16, %esp
        pushl   %eax
        pushl   -12(%ebp)
        pushl   -16(%ebp)
        pushl   $.LC2
        call    printf
        addl    $16, %esp
        nop
        movl    -4(%ebp), %ecx
        .cfi_def_cfa 1, 0
        leave
        .cfi_restore 5
        leal    -4(%ecx), %esp
        .cfi_def_cfa 4, 4
        ret
        .cfi_endproc
.LFE3:
        .size   main, .-main
        .ident  "GCC: (Ubuntu 5.4.0-6ubuntu1~16.04.4) 5.4.0 20160609"
        .section        .note.GNU-stack,"",@progbits