GB: Fixed stack overflow crash when 2 halt instructions are executed …

…in a row with halt bug
SourMesen · Jul 9, 2023 · 4cb89a2 · 4cb89a2
1 parent 3e36c39
commit 4cb89a2
Show file tree

Hide file tree

Showing 5 changed files with 37 additions and 14 deletions.
diff --git a/Core/Gameboy/Debugger/DummyGbCpu.cpp b/Core/Gameboy/Debugger/DummyGbCpu.cpp
@@ -12,6 +12,7 @@ void DummyGbCpu::SetDummyState(GbCpuState& state)
 	_memOpCounter = 0;
 	_state = state;
 	_state.HaltCounter = 0;
+	_state.HaltBug = false;
 }
 
 uint32_t DummyGbCpu::GetOperationCount()

diff --git a/Core/Gameboy/GbCpu.cpp b/Core/Gameboy/GbCpu.cpp
@@ -40,7 +40,7 @@ void GbCpu::Exec()
 {
 #ifndef DUMMYCPU
 	uint8_t irqVector = _memoryManager->ProcessIrqRequests();
-	if(irqVector) {
+	if(irqVector && !_state.HaltBug) {
 		if(_state.IME) {
 			uint16_t oldPc = _state.PC;
 			IncCycleCount();
@@ -81,14 +81,17 @@ void GbCpu::Exec()
 #endif
 
 	if(_state.HaltCounter) {
+		if(_state.HaltBug) {
+			ProcessHaltBug();
+		} else {
 #ifndef DUMMYCPU
-		_emu->ProcessHaltedCpu<CpuType::Gameboy>();
-		IncCycleCount();
-
-		if(_state.HaltCounter > 1) {
-			ProcessCgbSpeedSwitch();
-		}
+			_emu->ProcessHaltedCpu<CpuType::Gameboy>();
+			IncCycleCount();
+			if(_state.HaltCounter > 1) {
+				ProcessCgbSpeedSwitch();
+			}
 #endif
+		}
 		return;
 	}
 
@@ -103,6 +106,25 @@ void GbCpu::Exec()
 	ExecOpCode(ReadOpCode());
 }
 
+void GbCpu::ProcessHaltBug()
+{
+	if(_state.EiPending) {
+		_state.EiPending = false;
+		_state.IME = true;
+	}
+
+#ifndef DUMMYCPU
+	_emu->ProcessInstruction<CpuType::Gameboy>();
+#endif
+
+	//HALT bug, execution continues, but PC isn't incremented for the first byte
+	uint8_t opCode = ReadOpCode();
+	_state.PC--;
+	_state.HaltCounter = 0;
+	_state.HaltBug = false;
+	ExecOpCode(opCode);
+}
+
 void GbCpu::ExecOpCode(uint8_t opCode)
 {
 	switch(opCode) {
@@ -805,12 +827,8 @@ void GbCpu::HALT()
 		_state.HaltCounter = 1;
 	} else {
 		//HALT bug, execution continues, but PC isn't incremented for the first byte
-#ifndef DUMMYCPU
-		HalfCycle();
-		uint8_t opCode = ReadMemory<MemoryOperationType::ExecOpCode, GbOamCorruptionType::Read>(_state.PC);
-		HalfCycle();
-		ExecOpCode(opCode);
-#endif
+		_state.HaltCounter = 1;
+		_state.HaltBug = true;
 	}
 }
 
@@ -1463,4 +1481,5 @@ void GbCpu::Serialize(Serializer& s)
 	SV(_state.C); SV(_state.D); SV(_state.E); SV(_state.H); SV(_state.L); SV(_state.IME); SV(_state.HaltCounter);
 	SV(_state.EiPending);
 	SV(_state.CycleCount);
+	SV(_state.HaltBug);
 }
diff --git a/Core/Gameboy/GbCpu.h b/Core/Gameboy/GbCpu.h
@@ -32,6 +32,7 @@ class GbCpu : public ISerializable
 	void ExecOpCode(uint8_t opCode);
 
 	void ProcessCgbSpeedSwitch();
+	__noinline void ProcessHaltBug();
 
 	__forceinline void IncCycleCount();
 	__forceinline void HalfCycle();
@@ -166,7 +167,7 @@ class GbCpu : public ISerializable
 	uint64_t GetCycleCount() { return _state.CycleCount; }
 
 	void Exec();
-	
+
 	void Serialize(Serializer& s) override;
 
 #ifdef DUMMYCPU

diff --git a/Core/Gameboy/GbTypes.h b/Core/Gameboy/GbTypes.h
@@ -23,6 +23,7 @@ struct GbCpuState : BaseState
 
 	bool EiPending;
 	bool IME;
+	bool HaltBug;
 };
 
 namespace GbCpuFlags

diff --git a/UI/Interop/DebugState.cs b/UI/Interop/DebugState.cs
@@ -804,6 +804,7 @@ public struct GbCpuState : BaseState
 
 		[MarshalAs(UnmanagedType.I1)] public bool EiPending;
 		[MarshalAs(UnmanagedType.I1)] public bool IME;
+		[MarshalAs(UnmanagedType.I1)] public bool HaltBug;
 	}
 
 	public enum PpuMode