C++与汇编

1: int myTransform(int nInput){ 00401000 push ebp ; 保护现场原先的EBP指针

00401001 mov ebp,esp

2: return (nInput*2 + 3) % 7; 00401003 mov eax,dword ptr [nInput] ; 取参数

00401006 lea eax,[eax+eax+3] ; LEA比ADD加法更快

0040100A cdq ; DWORD->QWORD(扩展字长)

0040100B mov ecx,7 ; 除数

00401010 idiv eax,ecx ; 除

00401012 mov eax,edx ; 商->eax(eax中保存返回值)

3: } 00401014 pop ebp ; 恢复现场的ebp指针

00401015 ret ; 返回

; 此处删除10条int 3指令，它们是方便调试用的，并不影响程序行为。

4: 5: int main(int argc, char* argv[]) 6: { 00401020 push ebp ; 保护现场原先的EBP指针

00401021 mov ebp,esp

00401023 sub esp,10h ; 为取argc, argv修正堆栈指针。

7: int a[3]; 8: for(register int i=0; i<3; i++){ 00401026 mov dword ptr [i],0 ; 0->i

0040102D jmp main+18h (00401038) ; 判断循环条件

0040102F mov eax,dword ptr [i] ; i->eax

00401032 add eax,1 ; eax ++

00401035 mov dword ptr [i],eax ; eax->i

00401038 cmp dword ptr [i],3 ; 循环条件: i与3比较

0040103C jge main+33h (00401053) ; 如果不符合条件，则应结束循环

9: a[i] = myTransform(i); 0040103E mov ecx,dword ptr [i] ; i->ecx

00401041 push ecx ; ecx (i) -> 堆栈

00401042 call myTransform (00401000); 调用myTransform

00401047 add esp,4 ; esp+=4: 在堆中的新单元

; 准备存放返回结果

0040104A mov edx,dword ptr [i] ; i->edx

0040104D mov dword ptr a[edx*4],eax ; 将eax(myTransform返回值)

; 放回a[i]

10: } 00401051 jmp main+0Fh (0040102f) ; 计算i++，并继续循环

11: return 0; 00401053 xor eax,eax ; 返回值应该是0

12: } 00401055 mov esp,ebp ; 恢复堆栈指针

00401057 pop ebp ; 恢复BP

00401058 ret ; 返回调用者(C++运行环境)

void myTransform1(int nCount, char* sBytes){

for(register int i=1; isBytes[i] += sBytes[i-1];

for(i=0; isBytes[i] <<= 1;

}

void myTransform2(int nCount, char* sBytes){

for(register int i=0; isBytes[i] <<= 1;

}

1: void myTransform1(int nCount, char* sBytes){ 00401000 push ebp

00401001 mov ebp,esp

00401003 push ecx

2: for(register int i=1; i0040100B jmp myTransform1+16h (00401016)

0040100D mov eax,dword ptr [i]

00401010 add eax,1

00401013 mov dword ptr [i],eax

00401016 mov ecx,dword ptr [i]

00401019 cmp ecx,dword ptr [nCount]

0040101C jge myTransform1+3Dh (0040103d)

3: sBytes[i] += sBytes[i-1];

0040101E mov edx,dword ptr [sBytes]

00401021 add edx,dword ptr [i]

00401024 movsx eax,byte ptr [edx-1]

00401028 mov ecx,dword ptr [sBytes]

0040102B add ecx,dword ptr [i]

0040102E movsx edx,byte ptr [ecx]

00401031 add edx,eax

00401033 mov eax,dword ptr [sBytes]

00401036 add eax,dword ptr [i]

00401039 mov byte ptr [eax],dl

0040103B jmp myTransform1+0Dh (0040100d)

4: for(i=0; i00401044 jmp myTransform1+4Fh (0040104f)

00401046 mov ecx,dword ptr [i]

00401049 add ecx,1

0040104C mov dword ptr [i],ecx

0040104F mov edx,dword ptr [i]

00401052 cmp edx,dword ptr [nCount]

00401055 jge myTransform1+6Bh (0040106b)

5: sBytes[i] <<= 1; 00401057 mov eax,dword ptr [sBytes]

0040105A add eax,dword ptr [i]

0040105D mov cl,byte ptr [eax]

0040105F shl cl,1

00401061 mov edx,dword ptr [sBytes]

00401064 add edx,dword ptr [i]

00401067 mov byte ptr [edx],cl

00401069 jmp myTransform1+46h (00401046)

6: } 0040106B mov esp,ebp

0040106D pop ebp

0040106E ret

7: 8: void myTransform2(int nCount, char* sBytes){ 00401070 push ebp

00401071 mov ebp,esp

00401073 push ecx

9: for(register int i=0; i0040107B jmp myTransform2+16h (00401086)

0040107D mov eax,dword ptr [i]

00401080 add eax,1

00401083 mov dword ptr [i],eax

00401086 mov ecx,dword ptr [i]

00401089 cmp ecx,dword ptr [nCount]

0040108C jge myTransform2+32h (004010a2)

10: sBytes[i] <<= 1;

0040108E mov edx,dword ptr [sBytes]

00401091 add edx,dword ptr [i]

00401094 mov al,byte ptr [edx]

00401096 shl al,1

00401098 mov ecx,dword ptr [sBytes]

0040109B add ecx,dword ptr [i]

0040109E mov byte ptr [ecx],al

004010A0 jmp myTransform2+0Dh (0040107d)

11: } 004010A2 mov esp,ebp

004010A4 pop ebp

004010A5 ret

12: 13: int main(int argc, char* argv[]) 14: { 004010B0 push ebp

004010B1 mov ebp,esp

004010B3 sub esp,0CCh

15: char a[200]; 16: for(register int i=0; i<200; i++)a[i]=i; 004010B9 mov dword ptr [i],0

004010C3 jmp main+24h (004010d4)

004010C5 mov eax,dword ptr [i]

004010CB add eax,1

004010CE mov dword ptr [i],eax

004010D4 cmp dword ptr [i],0C8h

004010DE jge main+45h (004010f5)

004010E0 mov ecx,dword ptr [i]

004010E6 mov dl,byte ptr [i]

004010EC mov byte ptr a[ecx],dl

004010F3 jmp main+15h (004010c5)

17: myTransform1(200, a); 004010F5 lea eax,[a]

004010FB push eax

004010FC push 0C8h

00401101 call myTransform1 (00401000)

00401106 add esp,8

18: myTransform2(200, a); 00401109 lea ecx,[a]

0040110F push ecx

00401110 push 0C8h

00401115 call myTransform2 (00401070)

0040111A add esp,8

19: return 0; 0040111D xor eax,eax

20: }

0040111F mov esp,ebp

00401121 pop ebp

00401122 ret