From 22b1fea96d6ef9d9ae7710da93630b8882d5c0e9 Mon Sep 17 00:00:00 2001
From: Billy Laws <blaws05@gmail.com>
Date: Thu, 10 Aug 2023 11:42:20 -0700
Subject: [PATCH] WOW64: Handle unaligned atomic accesses

This is done in EnsureConsistentState rather than as a VEH to avoid needing to
go through all of wine's exception handling logic for such a hot path.
---
 Source/Windows/WOW64/Module.cpp | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/Source/Windows/WOW64/Module.cpp b/Source/Windows/WOW64/Module.cpp
index 890712c1f..42b803aa3 100644
--- a/Source/Windows/WOW64/Module.cpp
+++ b/Source/Windows/WOW64/Module.cpp
@@ -204,6 +204,21 @@ namespace Context {
     Context::StoreWowContextFromState(TLS.ThreadState(), &TmpWowContext);
     return RtlWow64SetThreadContext(Thread, &TmpWowContext);
   }
+
+  bool HandleUnalignedAccess(CONTEXT *Context) {
+    if (!GetTLS().ThreadState()->CPUBackend->IsAddressInCodeBuffer(Context->Pc)) {
+      return false;
+    }
+
+    FEX_CONFIG_OPT(ParanoidTSO, PARANOIDTSO);
+    const auto Result = FEXCore::ArchHelpers::Arm64::HandleUnalignedAccess(ParanoidTSO(), Context->Pc, &Context->X0);
+    if (!Result.first) {
+      return false;
+    }
+
+    Context->Pc += Result.second;
+    return true;
+  }
 }
 
 namespace Logging {
@@ -423,6 +438,18 @@ void BTCpuSimulate() {
   }
 }
 
+NTSTATUS BTCpuResetToConsistentState(EXCEPTION_POINTERS *Ptrs) {
+  auto *Context = Ptrs->ContextRecord;
+  const auto *Exception = Ptrs->ExceptionRecord;
+
+  if (Exception->ExceptionCode == EXCEPTION_DATATYPE_MISALIGNMENT && Context::HandleUnalignedAccess(Context)) {
+    LogMan::Msg::DFmt("Handled unaligned atomic: new pc: {:X}", Context->Pc);
+    NtContinue(Context, FALSE);
+  }
+
+  return STATUS_SUCCESS;
+}
+
 BOOLEAN WINAPI BTCpuIsProcessorFeaturePresent(UINT Feature) {
   switch (Feature) {
     case PF_FLOATING_POINT_PRECISION_ERRATA: