Question

I am writing a program in C and i use inline asm. In the inline assembler code is have some addresses where i want to patch them at runtime.

A quick sample of the code is this:

void __declspec(naked) inline(void)
{
      mov eax, 0xAABBCCDD
      call 0xAABBCCDD
}

An say i want to modify the 0xAABBCCDD value from the main C program.
What i tried to do is to Call VirtualProtect an is the pointer of the function in order to make it Writeable, and then call memcpy to add the appropriate values to the code.

DWORD old;
VirtualProtect(inline, len, PAGE_EXECUTE_READWRITE, &old);

However VirtualProtect fails and GetLastError() returns 487 which means accessing invalid address. Anyone have a clue about this problem??
Thanks

Answer 1

Doesn’t this work?

int X = 0xAABBCCDD;

void __declspec(naked) inline(void)
{
      mov eax, [X]
      call [X]
}