常见汇编指令及范例解释

有两种汇编格式：Intel汇编和AT&T汇编，前者常用于Windows，后者常用于Unix，是GNU汇编器的缺省格式，本文介绍后者(AT&T汇编格式)。

1，常用指令及解释

movl %eax, %edx  ---   数据传递，%eax地址传递给%edx

pushl %eax  --- 入栈，分两步：subl $4, %esp(栈向低地址方向增长) + movl %eax, (%esp)

popl %eax --- 出栈，分两步：movl (%esp), %eax + addl $4, %esp 

addl $8, %eax --- 

subl $4, %esp --- 

enter --- 进入函数，分两步：pushl %ebp + movl %esp, %ebp(将栈顶地址复制给栈基址，当前栈变为空)

leave --- 退出函数，分两步：movl %ebp, %esp + popl %ebp

call 0x12345 --- push %eip + movl 0x12345, %eip(%eip存放下一条执行指令)

ret --- call的逆操作，相当于popl %eip

2，传输字节数

movb         8bit

movw        16bit

movl          32bit

movq         64bit

3，程序实例

int g(int x){
return x + 10;
}

int f(int x){
return g(x);
}

int main(){
return f(20) + 8;
}执行汇编命令：
gcc -S -o main.s main.c -m32生成32位汇编代码main.s；

.file	"main.c"
.text
.globl	g
.type	g, @function
g:
.LFB0:
.cfi_startproc
pushl	%ebp
.cfi_def_cfa_offset 8
.cfi_offset 5, -8
movl	%esp, %ebp
.cfi_def_cfa_register 5
movl	8(%ebp), %eax
addl	$10, %eax
popl	%ebp
.cfi_restore 5
.cfi_def_cfa 4, 4
ret
.cfi_endproc
.LFE0:
.size	g, .-g
.globl	f
.type	f, @function
f:
.LFB1:
.cfi_startproc
pushl	%ebp
.cfi_def_cfa_offset 8
.cfi_offset 5, -8
movl	%esp, %ebp
.cfi_def_cfa_register 5
subl	$4, %esp
movl	8(%ebp), %eax
movl	%eax, (%esp)
call	g
leave
.cfi_restore 5
.cfi_def_cfa 4, 4
ret
.cfi_endproc
.LFE1:
.size	f, .-f
.globl	main
.type	main, @function
main:
.LFB2:
.cfi_startproc
pushl	%ebp
.cfi_def_cfa_offset 8
.cfi_offset 5, -8
movl	%esp, %ebp
.cfi_def_cfa_register 5
subl	$4, %esp
movl	$20, (%esp)
call	f
addl	$8, %eax
leave
.cfi_restore 5
.cfi_def_cfa 4, 4
ret
.cfi_endproc
.LFE2:
.size	main, .-main
.ident	"GCC: (GNU) 4.8.5 20150623 (Red Hat 4.8.5-11)"
.section	.note.GNU-stack,"",@progbits

剔除无关精要的部分，核心汇编代码如下：
1 g:
2 pushl %ebp
3 movl %esp, %ebp
4 movl 8(%ebp), %eax
5 addl $10, %eax
6 popl %ebp
7 ret
8 f:
9 pushl %ebp
10 movl %esp, %ebp
11 subl $4, %esp
12 movl 8(%ebp), %eax
13 movl %eax, (%esp)
14 call g
15 leave
16 ret
17 main:
18 pushl %ebp
19 movl %esp, %ebp
20 subl $4, %esp
21 movl $20, (%esp)
22 call f
23 addl $8, %eax
24 leave
25 ret