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update main hook, probably

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i havent tested this yet because bindings dont build, but it probably
workd :-)
This commit is contained in:
matcool 2023-12-20 14:55:26 -03:00
parent bb2dbc91b1
commit b6b20b0bd3
1 changed files with 43 additions and 12 deletions
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55
loader/src/platform/windows/main.cpp
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@ -27,37 +27,68 @@ void updateGeode() {
utils::game::restart();
}
void* mainTrampolineAddr;
int WINAPI gdMainHook(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPWSTR lpCmdLine, int nCmdShow) {
MessageBoxA(NULL, "Hello from gdMainHook!", "Hi", 0);
updateGeode();
int exitCode = geodeEntry(hInstance);
if (exitCode != 0)
return exitCode;
return reinterpret_cast<decltype(&wWinMain)>(geode::base::get() + 0x260ff8)(hInstance, hPrevInstance, lpCmdLine, nCmdShow);
return reinterpret_cast<decltype(&wWinMain)>(mainTrampolineAddr)(hInstance, hPrevInstance, lpCmdLine, nCmdShow);
}
bool loadGeode() {
// TODO: add version check or something
auto process = GetCurrentProcess();
auto patchAddr = reinterpret_cast<void*>(geode::base::get() + 0x260ff8);
constexpr size_t patchLength = 13;
auto detourAddr = reinterpret_cast<uintptr_t>(&gdMainHook) - geode::base::get() - 0x261005;
auto detourAddrPtr = reinterpret_cast<uint8_t*>(&detourAddr);
constexpr size_t trampolineSize = 12;
mainTrampolineAddr = VirtualAlloc(
nullptr, trampolineSize,
MEM_COMMIT | MEM_RESERVE, PAGE_EXECUTE_READWRITE
);
uint8_t patchBytes[patchLength] = {
static constexpr uintptr_t MAIN_OFFSET = 0x3ba7d0;
auto patchAddr = geode::base::get() + MAIN_OFFSET;
constexpr size_t patchSize = 6;
#define JMP_ADDR(from, to) (std::bit_cast<uintptr_t>(to) - std::bit_cast<uintptr_t>(from) - 5)
#define JMP_BYTES(from, to) \
((JMP_ADDR(from, to) >> 0) & 0xFF), \
((JMP_ADDR(from, to) >> 8) & 0xFF), \
((JMP_ADDR(from, to) >> 16) & 0xFF), \
((JMP_ADDR(from, to) >> 24) & 0xFF)
uint8_t trampolineBytes[trampolineSize] = {
// push ebp
0x55,
// mov ebp, esp
0x8b, 0xec,
0x83, 0xe4, 0xf8,
0xeb, 0x06,
0xe9, detourAddrPtr[0], detourAddrPtr[1], detourAddrPtr[2], detourAddrPtr[3]
// and esp, ...
0x83, 0xe4, 0xf8,
// jmp main + 6 (after our jmp detour)
0xe9, JMP_BYTES(reinterpret_cast<uintptr_t>(mainTrampolineAddr) + 6, patchAddr + patchSize)
};
std::memcpy(mainTrampolineAddr, trampolineBytes, trampolineSize);
uint8_t patchBytes[patchSize] = {
// jmp gdMainHook
0xe9, JMP_BYTES(patchAddr, &gdMainHook),
// nop to pad it out, helps the asm to show up properly on debuggers
0x90
};
DWORD oldProtect;
if (!VirtualProtectEx(process, patchAddr, patchLength, PAGE_EXECUTE_READWRITE, &oldProtect))
if (!VirtualProtectEx(process, reinterpret_cast<void*>(patchAddr), patchSize, PAGE_EXECUTE_READWRITE, &oldProtect))
return false;
std::memcpy(patchAddr, patchBytes, patchLength);
VirtualProtectEx(process, patchAddr, patchLength, oldProtect, &oldProtect);
std::memcpy(reinterpret_cast<void*>(patchAddr), patchBytes, patchSize);
VirtualProtectEx(process, reinterpret_cast<void*>(patchAddr), patchSize, oldProtect, &oldProtect);
return true;
}