Reverse Assembly _ while statement Disassembly

Reverse Assembly _ while statement Disassembly

By: for example

Chapter 4, while statement Disassembly
Sample Code:

 

 1 #include"stdio.h" 2 int function(int a,int b) 3 { 4     int c=a+b; 5     int i=0; 6     while(i<50) 7     { 8         c=c+i; 9     }10     return c;11 }12 void main()13 {14     function(1,2);15 } 

 

Disassembly code:

 

1 #include "stdio.h"2 3 int function(int a,int b)4 5 {

 

00ae1a40 push EBP 00ae1a41 mov EBP, ESP 00ae1a43 sub ESP, 0d8h  00ae1a49 push EBX 00ae1a4a push ESI 00ae1a4b push EDI  00ae1a4c Lea EDI, [ebp-0D8h] 00ae1a52 mov ECx, 36 h 00ae1a57 mov eax, 0 cccccccch 00ae1a5c rep STOs dword ptr es: [EDI]; Start allocating 36 4-byte space, locate to EDI, EDI is from [ebp-od8h], locate to buffer header and initialize to CC,

 

1 int c=a+b;

00ae1a5e mov eax, dword ptr [A]; Variable A is put into eax,

00ae1a61 add eax, dword ptr [B]; Add variable A to variable B and put the result to eax. 00ae1a64 mov dword ptr [c], eax; Variable C is equal to variable A + variable B, equal to C = A + B;

1  int i=0;

00ae1a67 mov dword ptr [I], 0; variable d equals 0

 

1    while(i<50)    

00ae1a6e cmp dword ptr [I], 32 h; compare whether variable D is greater than or equal to 0x32 h (hexadecimal)  00ae1a72 jge Function + 3fh (0ae1a7fh); if not greater than or equal to, point to the following statement; otherwise, jump 0x00ae1a7f

1 {                                                                       2         c=c+i;

00ae1a74 mov eax, dword ptr [c]; C = C + I 00ae1a77 add eax, dword ptr [I] 00ae1a7a mov dword ptr [c], eax

 

    }

00ae1a7d JMP Function + 2EH (0ae1a6eh) can be restored to IF and else statements if this is the next hop

00ae1a7f mov eax, dword ptr [c]; put the result of C into eax. eax is the return value of the function, so the result is return C;

 

}

 

00ae1a82 pop EDI 00ae1a83 pop ESI 00ae1a84 pop EBX

 

00ae1a85 mov ESP, EBP 00ae1a87 pop EBP

00ae1a88 RET

Damn typographical, annoying