汇编 if else

知识点：
if else
逆向还原代码

一、了解if else结构
sub esp,8
00401029  |.  8B45 FC       MOV EAX,DWORD PTR SS:[EBP-4]
0040102C  |.  3B45 F8       CMP EAX,DWORD PTR SS:[EBP-8]
0040102F  |.  7E 10         JLE SHORT ifelse01.00401041 //表示 else部分的开始
00401031  |.  68 FC204000   PUSH ifelse01.004020FC                   ; /format = "a>b"
00401036  |.  FF15 A0204000 CALL DWORD PTR DS:[<&MSVCR90.printf>]    ; \printf
0040103C  |.  83C4 04       ADD ESP,4
0040103F  |.  EB 0E        JMP SHORT ifelse01.0040104F //结合前边的 jle 401041 判断是否有else部分
00401041  |>  68 00214000   PUSH ifelse01.00402100                   ; /format = "b>=a"
00401046  |.  FF15 A0204000 CALL DWORD PTR DS:[<&MSVCR90.printf>]    ; \printf
0040104C  |.  83C4 04       ADD ESP,4

二、逆向还原代码
 int a,b,c;
//00401006  |.  68 F4204000   PUSH ifelse01.004020F4                   ; /format = "begin"
//0040100B  |.  FF15 A0204000 CALL DWORD PTR DS:[<&MSVCR90.printf>]    ; \printf
//00401011  |.  83C4 04       ADD ESP,4
 printf("begin");
//00401014  |.  C745 FC 01000>MOV DWORD PTR SS:[EBP-4],1
//0040101B  |.  C745 F8 02000>MOV DWORD PTR SS:[EBP-8],2
//00401022  |.  C745 F4 03000>MOV DWORD PTR SS:[EBP-C],3 a=1,b=2,c=3;
//00401029  |.  8B45 FC       MOV EAX,DWORD PTR SS:[EBP-4]
//0040102C  |.  3B45 F8       CMP EAX,DWORD PTR SS:[EBP-8]
//0040102F  |.  7E 10         JLE SHORT ifelse01.00401041
if (a>b)
{    //00401031  |.  68 FC204000   PUSH ifelse01.004020FC                   ; /format = "a>b"
    //00401036  |.  FF15 A0204000 CALL DWORD PTR DS:[<&MSVCR90.printf>]    ; \printf
    //0040103C  |.  83C4 04       ADD ESP,4
    //0040103F  |.  EB 0E         JMP SHORT ifelse01.0040104F
    printf("a>b");
}else
{    //00401041  |>  68 00214000   PUSH ifelse01.00402100                   ; /format = "b>=a"
    //00401046  |.  FF15 A0204000 CALL DWORD PTR DS:[<&MSVCR90.printf>]    ; \printf
    //0040104C  |.  83C4 04       ADD ESP,4
   printf("b>=a");
}
//0040104F  |> \8B4D F4       MOV ECX,DWORD PTR SS:[EBP-C]             ;  c
//00401052  |.  3B4D F8       CMP ECX,DWORD PTR SS:[EBP-8]             ;  b
//00401055  |.  7E 46         JLE SHORT ifelse01.0040109D              ;  if (c>b)
if (c>b)
{
//00401057  |.  8B55 F4       MOV EDX,DWORD PTR SS:[EBP-C] c
//0040105A  |.  3B55 FC       CMP EDX,DWORD PTR SS:[EBP-4] a
//0040105D  |.  7E 20         JLE SHORT ifelse01.0040107F
    if (c>a)
    {    
//0040105F  |.  8B45 FC       MOV EAX,DWORD PTR SS:[EBP-4]
//00401062  |.  50            PUSH EAX                                 ; /<%d>
//00401063  |.  8B4D F4       MOV ECX,DWORD PTR SS:[EBP-C]             ; |
//00401066  |.  51            PUSH ECX                                 ; |<%d>
//00401067  |.  8B55 F8       MOV EDX,DWORD PTR SS:[EBP-8]             ; |
//0040106A  |.  52            PUSH EDX                                 ; |<%d>
//0040106B  |.  8B45 F4       MOV EAX,DWORD PTR SS:[EBP-C]             ; |
//0040106E  |.  50            PUSH EAX                                 ; |<%d>
//0040106F  |.  68 08214000   PUSH ifelse01.00402108                   ; |format = "%d>%d,%d>%d"
//00401074  |.  FF15 A0204000 CALL DWORD PTR DS:[<&MSVCR90.printf>]    ; \printf
//0040107A  |.  83C4 14       ADD ESP,14
        printf("%d>%d,%d>%d",c,b,c,a);
//0040107D  |.  EB 1E         JMP SHORT ifelse01.0040109D
        }else
    {        
//0040107F  |>  8B4D FC       MOV ECX,DWORD PTR SS:[EBP-4]
//00401082  |.  51            PUSH ECX                                 ; /<%d>
//00401083  |.  8B55 F4       MOV EDX,DWORD PTR SS:[EBP-C]             ; |
//00401086  |.  52            PUSH EDX                                 ; |<%d>
//00401087  |.  8B45 F8       MOV EAX,DWORD PTR SS:[EBP-8]             ; |
//0040108A  |.  50            PUSH EAX                                 ; |<%d>
//0040108B  |.  8B4D F4       MOV ECX,DWORD PTR SS:[EBP-C]             ; |
//0040108E  |.  51            PUSH ECX                                 ; |<%d>
//0040108F  |.  68 14214000   PUSH ifelse01.00402114                   ; |format = "%d>%d,%d<=%d"
//00401094  |.  FF15 A0204000 CALL DWORD PTR DS:[<&MSVCR90.printf>]    ; \printf
//0040109A  |.  83C4 14       ADD ESP,14
        printf("%d>%d,%d<=%d",c,b,c,a);
        }
}
//0040109D  |>  33C0          XOR EAX,EAX