From 064a6e96c78713c7985aaaee61ffd9ed25cda3d4 Mon Sep 17 00:00:00 2001
From: Jacek Caban <jacek@codeweavers.com>
Date: Sun, 6 Sep 2026 15:09:18 +0200
Subject: [PATCH] ARM64EC: Use NtRaiseException to raise guest exception

Instead of returning to KiUserExceptionDispatcher, which doesn't send a debug event.
---
 Source/Windows/ARM64EC/Module.cpp | 23 ++++++++---------------
 1 file changed, 8 insertions(+), 15 deletions(-)

diff --git a/Source/Windows/ARM64EC/Module.cpp b/Source/Windows/ARM64EC/Module.cpp
index fa3a994bc..7b0469257 100644
--- a/Source/Windows/ARM64EC/Module.cpp
+++ b/Source/Windows/ARM64EC/Module.cpp
@@ -484,18 +484,15 @@ static ARM64_NT_CONTEXT StoreStateToPackedECContext(FEXCore::Core::InternalThrea
 }
 
 static void RethrowGuestException(const EXCEPTION_RECORD& Rec, ARM64_NT_CONTEXT& Context) {
-  const auto& Config = SignalDelegator->GetConfig();
   auto* Thread = GetCPUArea().ThreadState();
   auto& Fault = Thread->CurrentFrame->SynchronousFaultData;
-  uint64_t GuestSp = Context.X[Config.SRAGPRMapping[static_cast<size_t>(FEXCore::X86State::REG_RSP)]];
-  auto* Args = reinterpret_cast<KiUserExceptionDispatcherStackLayout*>(FEXCore::AlignDown(GuestSp, 64)) - 1;
 
   LogMan::Msg::DFmt("Reconstructing context");
   if (!IsDispatcherAddress(Context.Pc)) {
     ReconstructThreadState(Thread, Context);
   }
-  Args->Context = StoreStateToPackedECContext(Thread, Context.Fpcr, Context.Fpsr);
-  LogMan::Msg::DFmt("pc: {:X} rip: {:X}", Context.Pc, Args->Context.Pc);
+  ARM64_NT_CONTEXT GuestContext = StoreStateToPackedECContext(Thread, Context.Fpcr, Context.Fpsr);
+  LogMan::Msg::DFmt("pc: {:X} rip: {:X}", Context.Pc, GuestContext.Pc);
 
   // X64 Windows always clears TF, DF and AF when handling an exception, restoring after.
   // Current ARM64EC windows can only restore NZCV+SS when returning from an exception and other flags are left untouched from the handler context.
@@ -505,19 +502,15 @@ static void RethrowGuestException(const EXCEPTION_RECORD& Rec, ARM64_NT_CONTEXT&
   CTX->SetFlagsFromCompactedEFLAGS(Thread, EFlags);
 
   BOOL FirstChance = TRUE;
-  Args->Rec = FEX::Windows::HandleGuestException(Fault, Rec, Args->Context.Pc, Args->Context.X8, Args->Context.X0, FirstChance);
-  if (Args->Rec.ExceptionCode == EXCEPTION_SINGLE_STEP) {
-    Args->Context.Cpsr &= ~(1 << 21); // PSTATE.SS
-  } else if (Args->Rec.ExceptionCode == EXCEPTION_BREAKPOINT) {
+  EXCEPTION_RECORD GuestRec = FEX::Windows::HandleGuestException(Fault, Rec, GuestContext.Pc, GuestContext.X8, GuestContext.X0, FirstChance);
+  if (GuestRec.ExceptionCode == EXCEPTION_SINGLE_STEP) {
+    GuestContext.Cpsr &= ~(1 << 21); // PSTATE.SS
+  } else if (GuestRec.ExceptionCode == EXCEPTION_BREAKPOINT) {
     // INT3 will set RIP to the instruction following it, undo this (any edge cases with multibyte instructions that trigger breakpoints are bugs present in Windows also)
-    Args->Context.Pc -= 1;
+    GuestContext.Pc -= 1;
   }
 
-  if (!FirstChance) {
-    NtRaiseExceptionNative(&Args->Rec, &Args->Context, FirstChance);
-  }
-  Context.Sp = reinterpret_cast<uint64_t>(Args);
-  Context.Pc = KiUserExceptionDispatcher;
+  NtRaiseExceptionNative(&GuestRec, &GuestContext, FirstChance);
 }
 
 class ECSyscallHandler : public FEXCore::HLE::SyscallHandler, public FEXCore::Allocator::FEXAllocOperators {