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May 5th, 2009

Asm help .Please

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For Example .I have a function that code in C++ :

Assembly Syntax (Toggle Plain Text)
void MyFunc(int s) {
	struct itemRec {
		int code;
		int index;
	} bItem;
	bItem.code = 0x0000000B;
	bItem.index = s;
	__asm {
		push	eax
  		push	edx
  		mov	ecx,0x00625388
  		push	00000000h
  		lea	edx,bItem
  		push	edx
  		push	00000016h
  		mov	eax,0x00487273
  		call	eax
  		pop	edx
  		pop	eax
	}
}
void MyFunc(int s) {
	struct itemRec {
		int code;
		int index;
	} bItem;
	bItem.code = 0x0000000B;
	bItem.index = s;
	__asm {
		push	eax
  		push	edx
  		mov	ecx,0x00625388
  		push	00000000h
  		lea	edx,bItem
  		push	edx
  		push	00000016h
  		mov	eax,0x00487273
  		call	eax
  		pop	edx
  		pop	eax
	}
}

and when I compile that function,so I found in asm that code :

Assembly Syntax (Toggle Plain Text)
  		push	ebp
  		mov	ebp,esp
  		sub	esp,00000008h
  		mov	eax,[ebp+08h]
  		mov	dword ptr [ebp-08h],0000000Bh
  		mov	[ebp-04h],eax
  		push	eax
  		push	edx
  		mov	ecx,00625388h
  		push	00000000h
  		lea	edx,[ebp-08h]
  		push	edx
  		push	00000016h
  		mov	eax,0x00487273h
  		call	eax
  		pop	edx
  		pop	eax
  		mov	esp,ebp
  		pop	ebp
  		retn
  		push	ebp
  		mov	ebp,esp
  		sub	esp,00000008h
  		mov	eax,[ebp+08h]
  		mov	dword ptr [ebp-08h],0000000Bh
  		mov	[ebp-04h],eax
  		push	eax
  		push	edx
  		mov	ecx,00625388h
  		push	00000000h
  		lea	edx,[ebp-08h]
  		push	edx
  		push	00000016h
  		mov	eax,0x00487273h
  		call	eax
  		pop	edx
  		pop	eax
  		mov	esp,ebp
  		pop	ebp
  		retn

It's my example.So when I search in other asm file,I found that asm code :

Assembly Syntax (Toggle Plain Text)
  		push	ebp
  		mov	ebp,esp
  		sub	esp,00000008h
  		mov	eax,[ebp+08h]
  		add	eax,eax
  		mov	ecx,[eax+eax+L1000D004]
  		add	eax,eax
  		lea	edx,[ebp+08h]
  		mov	[ebp+08h],ecx
  		mov	[ebp-04h],eax
  		mov	[ebp-08h],edx
  		push	eax
  		push	ecx
  		mov	ecx,ds:[00838344h]
  		add	ecx,0000843Ch
  		add	ecx,00007EBCh
  		push	ecx
  		add	ecx,0000054Ch
  		mov	eax,[ebp-08h]
  		push	eax
  		mov	eax,0051F900h
  		call	eax
  		mov	ecx,[eax+0Ch]
  		cmp	ecx,[ebp+08h]
  		pop	ecx
  		jnz	L100010A8
  		add	eax,00000010h
  		add	ecx,[ebp-04h]
  		mov	[ecx],eax
 L100010A8:
  		pop	ecx
  		pop	eax
  		mov	esp,ebp
  		pop	ebp
  		retn
  		push	ebp
  		mov	ebp,esp
  		sub	esp,00000008h
  		mov	eax,[ebp+08h]
  		add	eax,eax
  		mov	ecx,[eax+eax+L1000D004]
  		add	eax,eax
  		lea	edx,[ebp+08h]
  		mov	[ebp+08h],ecx
  		mov	[ebp-04h],eax
  		mov	[ebp-08h],edx
  		push	eax
  		push	ecx
  		mov	ecx,ds:[00838344h]
  		add	ecx,0000843Ch
  		add	ecx,00007EBCh
  		push	ecx
  		add	ecx,0000054Ch
  		mov	eax,[ebp-08h]
  		push	eax
  		mov	eax,0051F900h
  		call	eax
  		mov	ecx,[eax+0Ch]
  		cmp	ecx,[ebp+08h]
  		pop	ecx
  		jnz	L100010A8
  		add	eax,00000010h
  		add	ecx,[ebp-04h]
  		mov	[ecx],eax
 L100010A8:
  		pop	ecx
  		pop	eax
  		mov	esp,ebp
  		pop	ebp
  		retn

Please help me and tell me know what the real code in C++ (same my example) .And parameter to function that has address 0051F900h .Please help me

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LangTuHaoHoa

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since May 2009

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May 5th, 2009

Re: Asm help .Please

Either I don't know what you're asking for or this smells like homework.

Anyway the param to the function you were asking about

Assembly Syntax (Toggle Plain Text)
 
		mov	eax,[ebp-08h]
  		push	eax
  		mov	eax,0051F900h
  		call	eax
  
		mov	eax,[ebp-08h]
  		push	eax
  		mov	eax,0051F900h
  		call	eax

The C calling convention is to push arguments on the stack from right to left. So what do you think the argument passed is?

sysop_fb

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May 5th, 2009

Re: Asm help .Please

SO,I want to know how many arguments in that function,and How to use that function

for example:

void MyFunc(int s) {
struct itemRec {
int code;
int index;
} bItem;
bItem.code = 0x0000000B;
bItem.index = s;
__asm {
push eax
push edx
mov ecx,0x00625388
push 00000000h
lea edx,bItem
push edx
push 00000016h
mov eax,0x00487273
call eax
pop edx
pop eax
}
}

I really want to know how use that function ( 0x0051F900) .So because I don't know how many arguments that push to that function and code for use that function .Please help me.

In your post.You say :

Quote ...

mov eax,[ebp-08h]
push eax
mov eax,0051F900h
call eax

So [ebp-08h] is?I don't know type of that argument.

LangTuHaoHoa

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since May 2009

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May 5th, 2009

Re: Asm help .Please

Click to Expand / Collapse Quote originally posted by sysop_fb ...

Either I don't know what you're asking for or this smells like homework.

Anyway the param to the function you were asking about
Assembly Syntax (Toggle Plain Text)
 
		mov	eax,[ebp-08h]
  		push	eax
  		mov	eax,0051F900h
  		call	eax
mov eax,[ebp-08h] push eax mov eax,0051F900h call eax
The C calling convention is to push arguments on the stack from right to left. So what do you think the argument passed is?

If possible,please help me decompile that asm code to real code in C++ .Please see my example to understand what I say .Thanks u

LangTuHaoHoa

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May 7th, 2009

Re: Asm help .Please

No one can help me how to use function 0x51F900 and what is arguments pass to that function ?

Please help me

LangTuHaoHoa

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