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patch lld-link's tailMerge to almost fix xmm registers

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see: https://github.com/llvm/llvm-project/issues/51941
This commit is contained in:
matcool 2024-06-02 14:22:32 -03:00
parent a7bf4ef5ae
commit 6b79cb2b6e
1 changed files with 65 additions and 0 deletions

65
loader/src/platform/windows/main.cpp
View file

@ -27,6 +27,69 @@ void updateGeode() {
utils::game::restart();
}
void patchDelayLoad() {
#ifdef GEODE_IS_WINDOWS64
// clang has a stupid issue where its tailmerge does not allocate
// the correct space for xmm registers, causing them to be overwritten by the delayLoadHelper2 function
// See: https://github.com/llvm/llvm-project/issues/51941
// based off addresser.cpp followThunkFunction
// get some function thats not virtual
auto address = geode::cast::reference_cast<uintptr_t>(&cocos2d::CCNode::convertToNodeSpace);
static constexpr auto checkByteSequence = [](uintptr_t address, const std::initializer_list<uint8_t>& bytes) {
for (auto byte : bytes) {
if (*reinterpret_cast<uint8_t*>(address++) != byte) {
return false;
}
}
return true;
};
// check if first instruction is a jmp qword ptr [rip + ...], i.e. if the func is a thunk
// FF 25 xxxxxxxx
if (address && checkByteSequence(address, {0xFF, 0x25})) {
const auto offset = *reinterpret_cast<int32_t*>(address + 2);
// rip is at address + 6 (size of the instruction)
address = *reinterpret_cast<uintptr_t*>(address + 6 + offset);
}
// if it starts with lea eax,..., it's a delay loaded func
// 48 8D 05 xxxxxxxx
if (address && checkByteSequence(address, {0x48, 0x8d, 0x05})) {
// follow the jmp to the tailMerge func and grab the ImgDelayDescr pointer from there
// do it this way instead of grabbing it from the NT header ourselves because
// we don't know the dll name
auto leaAddress = address + 7 + *reinterpret_cast<int32_t*>(address + 3);
auto jmpOffset = *reinterpret_cast<int32_t*>(address + 7 + 1);
auto tailMergeAddr = address + 7 + jmpOffset + 5;
// see https://github.com/llvm/llvm-project/blob/main/lld/COFF/DLL.cpp#L207
if (checkByteSequence(tailMergeAddr, {0x51, 0x52, 0x41, 0x50, 0x41, 0x51, 0x48, 0x83, 0xEC, 0x48})) {
// ok we are probably in the broken lld-link tailMerge, time to patch it
// TODO:
// FIXME: xmm0 is still wrong, dont have enough space to fix it,
// gotta allocate space somewhere else
static constexpr uint8_t patch1[] = {
0x48, 0x83, 0xEC, 0x68, // sub rsp, 68h
0x66, 0x0F, 0x7F, 0x04, 0x24, // movdqa xmmword ptr [rsp], xmm0
0x66, 0x0F, 0x7F, 0x4C, 0x24, 0x30, // movdqa xmmword ptr [rsp+30h], xmm1
0x66, 0x0F, 0x7F, 0x54, 0x24, 0x40, // movdqa xmmword ptr [rsp+40h], xmm2
0x66, 0x0F, 0x7F, 0x5C, 0x24, 0x50, // movdqa xmmword ptr [rsp+50h], xmm3
};
(void) tulip::hook::writeMemory(reinterpret_cast<void*>(tailMergeAddr + 6), patch1, sizeof(patch1));
static constexpr uint8_t patch2[] = {
0x66, 0x0F, 0x6F, 0x04, 0x24, // movdqa xmm0, xmmword ptr [rsp]
0x66, 0x0F, 0x6F, 0x4C, 0x24, 0x30, // movdqa xmm1, xmmword ptr [rsp+30h]
0x66, 0x0F, 0x6F, 0x54, 0x24, 0x40, // movdqa xmm2, xmmword ptr [rsp+40h]
0x66, 0x0F, 0x6F, 0x5C, 0x24, 0x50, // movdqa xmm3, xmmword ptr [rsp+50h]
0x48, 0x83, 0xC4, 0x68, // add rsp, 68h
};
(void) tulip::hook::writeMemory(reinterpret_cast<void*>(tailMergeAddr + 48), patch2, sizeof(patch2));
}
}
#endif
}
void* mainTrampolineAddr;
#include "gdTimestampMap.hpp"
@ -50,6 +113,8 @@ int WINAPI gdMainHook(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPWSTR lpCmd
);
// TODO: should geode FreeLibrary itself here?
} else {
patchDelayLoad();
int exitCode = geodeEntry(hInstance);
if (exitCode != 0)
return exitCode;