标签：处理 style call 寄存器 汇编代码 转换 c语言 嵌入式 两数交换
编写一个两数交换函数swap，具体代码如下：
#include<stdio.h> void swap(int *a,int *b) { int temp; temp = *a; *a = *b; *b= temp; //printf("a=%d,b=%d,temp=%d\n",a,b,temp); } void main(){ int a=0; int b=0; char *str1="a=%d,b=%d\n"; printf("++++++\n"); a=2; b=3; printf(str1,a,b); swap(&a,&b); printf(str1,a,b); }
首先对main函数进行汇编转换：
#include<stdio.h> void swap(int *a,int *b) { int temp; temp = *a; *a = *b; *b= temp; //printf("a=%d,b=%d,temp=%d\n",a,b,temp); } main(){ int a=0; int b=0; char *str1="a=%d,b=%d\n"; printf("++++++\n"); _asm{ //a=2 mov a,2 //b=3 mov b,3 //printf(str1,a,b); mov ecx,b push ecx mov eax,a push eax mov edx,str1 push edx call printf add esp,12 //swap(&a,&b); lea eax,b push eax lea ecx,a push ecx call swap add esp,8 //printf(str1,a,b); mov ecx,b push ecx mov eax,a push eax mov edx,str1 push edx call printf add esp,12 } }
现在需要将swap也转化为汇编，并放入main函数中，具体思路如下：
1、先对swap函数反汇编，并删除ret指令，
注明：swap函数大致处理过程为：把下个地址压入堆栈，然后参数入栈，然后把所有寄存器压入堆栈，分配空间，空间清C然后变量赋值开始程序然后做堆栈平衡清理堆栈
void swap(int *a,int *b) { int temp; temp = *a; *a = *b; *b= temp; } swap: push ebp mov ebp,esp sub esp,44h push ebx push esi push edi lea edi,[ebp-44h] mov ecx,11h mov eax,0CCCCCCCCh rep stos dword ptr [edi] mov eax,dword ptr [ebp+8] mov ecx,dword ptr [eax] mov dword ptr [ebp-4],ecx mov edx,dword ptr [ebp+8] mov eax,dword ptr [ebp+0Ch] mov ecx,dword ptr [eax] mov dword ptr [edx],ecx mov edx,dword ptr [ebp+0Ch] mov eax,dword ptr [ebp-4] mov dword ptr [edx],eax pop edi pop esi pop ebx mov esp,ebp pop ebp ret
2、将1中的汇编代码替换掉call swap，
#include<stdio.h> main(){ int a=0; int b=0; char *str1="a=%d,b=%d\n"; printf("++++++\n"); _asm{ //a=2 mov a,2 //b=3 mov b,3 //printf(str1,a,b); mov ecx,b push ecx mov eax,a push eax mov edx,str1 push edx call printf add esp,12 //swap(&a,&b); lea eax,b push eax lea ecx,a push ecx //call swap push ebp mov ebp,esp sub esp,44h push ebx push esi push edi lea edi,[ebp-44h] mov ecx,11h mov eax,0CCCCCCCCh rep stos dword ptr [edi] mov eax,dword ptr [ebp+8] mov ecx,dword ptr [eax] mov dword ptr [ebp-4],ecx mov edx,dword ptr [ebp+8] mov eax,dword ptr [ebp+0Ch] mov ecx,dword ptr [eax] mov dword ptr [edx],ecx mov edx,dword ptr [ebp+0Ch] mov eax,dword ptr [ebp-4] mov dword ptr [edx],eax pop edi pop esi pop ebx mov esp,ebp pop ebp add esp,8 //printf(str1,a,b); mov ecx,b push ecx mov eax,a push eax mov edx,str1 push edx call printf add esp,12 } }
3、调整替换的swap汇编
#include<stdio.h> main(){ int a=0; int b=0; char *str1="a=%d,b=%d\n"; printf("++++++\n"); _asm{ //a=2 mov a,2 //b=3 mov b,3 //printf(str1,a,b); mov ecx,b push ecx mov eax,a push eax mov edx,str1 push edx call printf add esp,12 //swap(&a,&b); lea eax,b push eax lea ecx,a push ecx //call swap push ebp mov ebp,esp sub esp,44h push ebx push esi push edi lea edi,[ebp-44h] mov ecx,11h mov eax,0CCCCCCCCh rep stos dword ptr [edi] mov eax,a //取a地址 mov ecx,dword ptr [eax] //将a的值赋给ecx mov dword ptr [ebp-4],ecx //temp=*a=2 mov edx,a //取a地址 mov eax,b //取b地址 mov ecx,dword ptr [eax] //取b的值3 mov dword ptr [edx],ecx //a=b=3 mov edx,b //取b地址 mov eax,dword ptr [ebp-4] //取temp的值2 mov dword ptr [edx],eax //b=temp=2 pop edi pop esi pop ebx mov esp,ebp pop ebp //add esp,8 //printf(str1,a,b); mov ecx,b push ecx mov eax,a push eax mov edx,str1 push edx call printf add esp,12 } }
标签：处理 style call 寄存器 汇编代码 转换 c语言 嵌入式 两数交换
原文地址：https://www.cnblogs.com/little-kwy/p/12267261.html
