Hello World - 更小code size(2)

來trace 上一篇中用write()寫的Hello World程式吧:)

$ gcc fn.c -g -static -o fn
$ objdump -S fn
.... 省略 ....
int main(void)
{
 80481f4:       55                      push   %ebp
 80481f5:       89 e5                   mov    %esp,%ebp
 80481f7:       83 ec 18                sub    $0x18,%esp
 80481fa:       83 e4 f0                and    $0xfffffff0,%esp
 80481fd:       b8 00 00 00 00          mov    $0x0,%eax
 8048202:       83 c0 0f                add    $0xf,%eax
 8048205:       83 c0 0f                add    $0xf,%eax
 8048208:       c1 e8 04                shr    $0x4,%eax
 804820b:       c1 e0 04                shl    $0x4,%eax
 804820e:       29 c4                   sub    %eax,%esp
    write(STDOUT_FILENO, HELLO_WORLD, sizeof(HELLO_WORLD));
 8048210:       c7 44 24 08 0d 00 00    movl   $0xd,0x8(%esp)
 8048217:       00 
 8048218:       c7 44 24 04 c8 64 0a    movl   $0x80a64c8,0x4(%esp)
 804821f:       08 
 8048220:       c7 04 24 01 00 00 00    movl   $0x1,(%esp)
 8048227:       e8 34 66 00 00          call   804e860 <__libc_write>

    return 0;
 804822c:       b8 00 00 00 00          mov    $0x0,%eax
}
 8048231:       c9                      leave  
 8048232:       c3                      ret    
 8048233:       90                      nop    
.... 省略 ....
0804e860 <__libc_write>:
.... 省略 ....
 804e86a:       53                      push   %ebx
 804e86b:       8b 54 24 10             mov    0x10(%esp),%edx
 804e86f:       8b 4c 24 0c             mov    0xc(%esp),%ecx
 804e873:       8b 5c 24 08             mov    0x8(%esp),%ebx
 804e877:       b8 04 00 00 00          mov    $0x4,%eax
 804e87c:       cd 80                   int    $0x80
.... 省略 ....

所以...他的順序... main() -> write -> __libc_write
那之後的？？？？
注意！！！有一個

int 0x80

這是一個Linux kernel的進入點(學名稱做system call)
所以到這邊先一個總結...(接下一篇)