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

常见汇编指令及范例解释

悦读