Clear stack before executing guest code (#2877)

* Clear stack before executing guest code

* clang, don't optimize me 🚨

avoid ClearStack function being optimized in release builds

src/core/tls.h

@@ -5,6 +5,8 @@
 
 #include "common/types.h"
 
+void* memset(void* ptr, int value, size_t num);
+
 namespace Xbyak {
 class CodeGenerator;
 }
@@ -41,9 +43,18 @@ Tcb* GetTcbBase();
 /// Makes sure TLS is initialized for the thread before entering guest.
 void EnsureThreadInitialized();
 
+template <size_t size>
+__attribute__((optnone)) void ClearStack() {
+    volatile void* buf = alloca(size);
+    memset(const_cast<void*>(buf), 0, size);
+    buf = nullptr;
+}
+
 template <class ReturnType, class... FuncArgs, class... CallArgs>
 ReturnType ExecuteGuest(PS4_SYSV_ABI ReturnType (*func)(FuncArgs...), CallArgs&&... args) {
     EnsureThreadInitialized();
+    // clear stack to avoid trash from EnsureThreadInitialized
+    ClearStack<13_KB>();
     return func(std::forward<CallArgs>(args)...);
 }