I have the following assembly program
asm2:
<+0>: push ebp
<+1>: mov ebp,esp
<+3>: sub esp,0x10
<+6>: mov eax,DWORD PTR [ebp+0xc]
<+9>: mov DWORD PTR [ebp-0x4],eax
<+12>: mov eax,DWORD PTR [ebp+0x8]
<+15>: mov DWORD PTR [ebp-0x8],eax
<+18>: jmp 0x50c <asm2+31>
<+20>: add DWORD PTR [ebp-0x4],0x1
<+24>: add DWORD PTR [ebp-0x8],0xcc
<+31>: cmp DWORD PTR [ebp-0x8],0x3937
<+38>: jle 0x501 <asm2+20>
<+40>: mov eax,DWORD PTR [ebp-0x4]
<+43>: leave
<+44>: ret
From what I know, this runs a loop that checks if the second parameter is equal to 0x3937 (14647). If it's less than, then it adds 204 to the second parameter and adds 1 to the first parameter. I wrote a C program that does this, which is below, however when I take either of the parameters, convert them to hex, then submit it, it says it's wrong.
#include <stdio.h>
int main() {
int i = 0;
int a = 7;
int b = 24;
while(b < 14647) {
a += 1;
b += 204;
}
printf("%d %d", a, b);
return 0;
}
asm2
does not print anything, it just writes the final value of b
(in the program below) into eax
and stops, which means that it returns b
:
int asm2(int a1, int b1)
{
int a; //DWORD PTR [ebp-0x8]
int b; //DWORD PTR [ebp-0x4]
a = a1; // (a = b1 if arguments are pushed from left to right)
b = b1; // (b = a1 if arguments are pushed from left to right)
while(a <= 14647) {
b += 1;
a += 204;
}
return b;
}
So if you invoke asm2(0x7, 0x18)
and
-if arguments are pushed from right to left, it returns 96
-if arguments are pushed from left to right, it returns 79