c++ - 函数指针 - DInput8.dll Hook 代码参数的用途

Question

我一直在努力弄清楚 DirectInput8 Hook 项目中一个参数的用途。我正在制作 opensource 的一部分代码在这里。为了简洁起见，我只发布了一些功能。

ULONG oldCreateDevice;
HRESULT WINAPI xCreateDevice(DWORD d1, DWORD d2, DWORD d3, DWORD d4)
{
    HRESULT hr = ((HRESULT(WINAPI*)(DWORD,DWORD,DWORD,DWORD))oldCreateDevice)(d1,d2,d3,d4);

    // hook only if keyboard requested
    if(*(DWORD*)d2 != GUID_SysKeyboard)
        return hr;

    DWORD dwKeybTable = *(DWORD*)(*(DWORD*)d3);

    DWORD oldprot;
    VirtualProtect((LPVOID)dwKeybTable, 0x2C, PAGE_EXECUTE_READWRITE, &oldprot);

    // already hooked?
    if((DWORD)xGetDeviceState == *((DWORD*)(dwKeybTable+0x24))) goto ex1;
    // hook it!
    oldGetDeviceState = *((DWORD*)(dwKeybTable+0x24));
    *((DWORD*)(dwKeybTable+0x24)) = (DWORD)xGetDeviceState;

ex1:
    // already hooked?
    if((DWORD)xGetDeviceData == *((DWORD*)(dwKeybTable+0x28))) goto ex2;
    // hook it!
    oldGetDeviceData = *((DWORD*)(dwKeybTable+0x28));
    *((DWORD*)(dwKeybTable+0x28)) = (DWORD)xGetDeviceData;

ex2:

    return hr;

}


ULONG oldDirectInput8Create;
HRESULT WINAPI xDirectInput8Create(HINSTANCE hinst, DWORD dwVersion, REFIID riidltf, VOID **ppvOut, LPUNKNOWN punkOuter)
{
    HRESULT ret = ((HRESULT(WINAPI*)(HINSTANCE,DWORD,REFIID,VOID**,LPUNKNOWN))oldDirectInput8Create)(hinst,dwVersion,riidltf,ppvOut,punkOuter);

    DWORD dwFuncTable = (DWORD)*((DWORD*)*ppvOut);

    DWORD oldprot;
    VirtualProtect((LPVOID)dwFuncTable, 0x10, PAGE_EXECUTE_READWRITE, &oldprot);

    //already hooked?
    if((DWORD)xCreateDevice == *((DWORD*)(dwFuncTable + 0x0C))) goto ex;
    //hook it
    oldCreateDevice = *((DWORD*)(dwFuncTable + 0x0C));
    *((DWORD*)(dwFuncTable + 0x0C)) = (DWORD)xCreateDevice;

ex:
    return ret;
}


DWORD WINAPI RemoteMain(LPVOID lpParam)
{

    LoadLibrary("user32.dll");
    LoadLibrary("advapi32.dll");

    Splice_Init();

    Splice((ULONG)GetProcAddress(LoadLibrary("dinput8.dll"),"DirectInput8Create"), xDirectInput8Create, &oldDirectInput8Create);

    ThreadControl(FALSE); // resume all
    return 0;
}

正如您可能注意到的那样，代码正在用重定向的( Hook 的)函数替换函数。我的问题是关于 xCreateDevice 函数中的第一个参数对于 DirectInput8，CreateDevice 函数根据我理解的文档占用 3 个参数。但我不确定为什么在这里使用 4 个参数。它是否指向原来的“oldCreateDevice”？还是其他原因？

我希望有人能指导我解决这个问题。谢谢

Answer 1

它是一个接口(interface)(类)非静态方法，所以第一个参数是this指针(指向类实例的指针)。

this (Wikipedia)

this (MSDN)