[Kernel] Make XexUnloadImage fully release the image

Previously XexUnloadImage did not cleanup the image fully,
and if XexLoadImage was to be called again on the same module,
it was not initialized fully, leading to a crash when using it.

src/xenia/kernel/kernel_state.cc

@@ -405,6 +405,39 @@ object_ref<UserModule> KernelState::LoadUserModule(const char* raw_name,
   return module;
 }
 
+void KernelState::UnloadUserModule(const object_ref<UserModule>& module,
+                                   bool call_entry) {
+  auto global_lock = global_critical_region_.Acquire();
+
+  if (module->is_dll_module() && module->entry_point() && call_entry) {
+    // Call DllMain(DLL_PROCESS_DETACH):
+    // https://msdn.microsoft.com/en-us/library/windows/desktop/ms682583%28v=vs.85%29.aspx
+    uint64_t args[] = {
+        module->handle(),
+        0,  // DLL_PROCESS_DETACH
+        0,  // 0 for now, assume XexUnloadImage is like FreeLibrary
+    };
+    auto thread_state = XThread::GetCurrentThread()->thread_state();
+    processor()->Execute(thread_state, module->entry_point(), args,
+                         xe::countof(args));
+  }
+
+  auto iter = std::find_if(
+      user_modules_.begin(), user_modules_.end(),
+      [&module](const auto& e) { return e->path() == module->path(); });
+  assert_true(iter != user_modules_.end());  // Unloading an unregistered module
+                                             // is probably really bad
+  user_modules_.erase(iter);
+
+  // Ensure this module was not somehow registered twice
+  assert_true(std::find_if(user_modules_.begin(), user_modules_.end(),
+                           [&module](const auto& e) {
+                             return e->path() == module->path();
+                           }) == user_modules_.end());
+
+  object_table()->ReleaseHandle(module->handle());
+}
+
 void KernelState::TerminateTitle() {
   XELOGD("KernelState::TerminateTitle");
   auto global_lock = global_critical_region_.Acquire();

src/xenia/kernel/kernel_state.h

@@ -131,6 +131,8 @@ class KernelState {
   void SetExecutableModule(object_ref<UserModule> module);
   object_ref<UserModule> LoadUserModule(const char* name,
                                         bool call_entry = true);
+  void UnloadUserModule(const object_ref<UserModule>& module,
+                        bool call_entry = true);
 
   object_ref<KernelModule> GetKernelModule(const char* name);
   template <typename T>

src/xenia/kernel/xboxkrnl/xboxkrnl_modules.cc

@@ -129,7 +129,8 @@ dword_result_t XexUnloadImage(lpvoid_t hmodule) {
     if (--ldr_data->load_count == 0) {
       // No more references, free it.
       module->Release();
-      kernel_state()->object_table()->RemoveHandle(module->handle());
+      kernel_state()->UnloadUserModule(object_ref<UserModule>(
+          reinterpret_cast<UserModule*>(module.release())));
     }
   }