Hooking address (GCC)

Hello,



I'm trying to hook a function, I know the address, but the problem is
I'm using GCC now, I used to be using VS and my method does not work
anymore,

Code:

void Hooks::EnableHooks () { *(char*)ulSend = 0xE9; *(long*)ulSend + 1 = NewSendFun - ulSend - 5; // error line } /* New functions for hooked Functions */ void Hooks::NewSendFun() { __asm__ ( "mov [ppSendPacket],%espnt" "pushant" "call SendPacketCallbacknt" "popant" "jmp *%ulSendRet]nt" ); }

The error line gives this error:

invalid use of member(did you forget the '&'?)



Hope someone can help me.



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Jani wrote:

You don't have to make the whole class static. Only the member receiving the callback. This is because the compiler can't just run a method of a class, which doesn't have an instance. The other way would be to tell the compiler which instance of the object to use and then call the member: ((class).*(member))(args). But seeing the case, using a static member is much more easier.

I'm not sure what you mean by "((class).*(member))(args)", because dot
is used with class instance - objects, not class, you should've used ::
instead. and by member I assumed you meant the function, and then I
don't understand what's the dereference operator for... get the
function's... value? and the call it with the arguments?

I think you meant:

((return_type (call_convention*)(void*))class::member)(&object)

for example:

((int (__cdecl*)(void*, other_params))class::member)(&object, other_param)

because "this" pointer is passed as a paramater.



Unfortunatly, the compiler didn't like me converting a class method to a
pointer (int*, char*, void*, nothing...) even though it worked
perfectly fine with functions that didn't belong to a class, so I had to
write a warper, nothing too complicated, just a few lines of inline
assembly.

Here's an example:

Code:

#include class Class { public: void* __stdcall GetThisPointer() { return (void*)this; } }; //This is how the compiler implements the function //"this" pointer is passed as a paramater void* GetThisPointer_Implementation(Class* object) { return (void*)object; } //Proof of Concept int __declspec(naked) GetThisPointer_PoC(Class* object) { __asm { PUSH EBP //since we specified __declspec(naked) MOV EBP, ESP //fix stack //if GetThisPointer was __cdecl (by default) then //you should've used "MOV ECX, object" instead of "PUSH object" PUSH object //Pass "this" pointer as a parameter LEA EAX, [Class::GetThisPointer] CALL EAX POP EBP RETN 4 } } int main() { Class Object; printf("Object (%p) = this (%p)n", &Object, Object.GetThisPointer()); printf("Implementation: %pn", GetThisPointer_Implementation(&Object)); printf("Proof of Concept: %pn", GetThisPointer_PoC(&Object)); return 0; }