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CodeCache: Support reverse application of relocations

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This allows code to be serialized consistently across runs.
This commit is contained in:
Tony Wasserka committed 2025-12-02 22:27:53 +01:00
1 parent 1430fa8220
commit 994613260c
2 files changed
+9 -4
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FEXCore/Source/Interface/Context/Context.h
+5 -1
View File
@@ -88,14 +88,18 @@ public:
* When loading a code cache, they are used to move cached code to the
* dynamically chosen base address of the guest binary.
*
* Conversely, relocations are applied in reverse when writing code caches
* to ensure consistency across generation runs.
*
* Note that FEX relocations are unrelated to ELF/PE relocations.
*
* @param GuestDelta Guest address offset to apply to RIP-relative data
* @param ForStorage True for serializing data (producing deterministic output); false for de-serializing it (resolving dynamic symbols)
*
* @return Returns true on success
*/
[[nodiscard]]
bool ApplyCodeRelocations(uint64_t GuestDelta, std::span<std::byte> Code, std::span<const CPU::Relocation> Relocations);
bool ApplyCodeRelocations(uint64_t GuestDelta, std::span<std::byte> Code, std::span<const CPU::Relocation> Relocations, bool ForStorage);
};
class ContextImpl final : public FEXCore::Context::Context, public CPU::CodeBufferManager {
FEXCore/Source/Interface/Core/CodeCache.cpp
+4 -3
View File
@@ -229,7 +229,8 @@ bool CodeCache::SaveData(Core::InternalThreadState& Thread, int fd, const Execut
return true;
}
bool CodeCache::ApplyCodeRelocations(uint64_t GuestEntry, std::span<std::byte> Code, std::span<const FEXCore::CPU::Relocation> EntryRelocations) {
bool CodeCache::ApplyCodeRelocations(uint64_t GuestEntry, std::span<std::byte> Code,
std::span<const FEXCore::CPU::Relocation> EntryRelocations, bool ForStorage) {
CPU::Arm64Emitter Emitter(&CTX, Code.data(), Code.size_bytes());
for (size_t j = 0; j < EntryRelocations.size(); ++j) {
const FEXCore::CPU::Relocation& Reloc = EntryRelocations[j];
@@ -238,12 +239,12 @@ bool CodeCache::ApplyCodeRelocations(uint64_t GuestEntry, std::span<std::byte> C
switch (Reloc.Header.Type) {
case FEXCore::CPU::RelocationTypes::RELOC_NAMED_SYMBOL_LITERAL: {
// Generate a literal so we can place it
uint64_t Pointer = GetNamedSymbolLiteral(CTX, Reloc.NamedSymbolLiteral.Symbol);
uint64_t Pointer = ForStorage ? 0 : GetNamedSymbolLiteral(CTX, Reloc.NamedSymbolLiteral.Symbol);
Emitter.dc64(Pointer);
break;
}
case FEXCore::CPU::RelocationTypes::RELOC_NAMED_THUNK_MOVE: {
uint64_t Pointer = reinterpret_cast<uint64_t>(CTX.ThunkHandler->LookupThunk(Reloc.NamedThunkMove.Symbol));
uint64_t Pointer = ForStorage ? 0 : reinterpret_cast<uint64_t>(CTX.ThunkHandler->LookupThunk(Reloc.NamedThunkMove.Symbol));
if (Pointer == ~0ULL) {
return false;
}