gumjs: Preserve thread's system error over NativeCallback invocations

Though JavaScript function wrapped as a NativeCallback allows both
inspecting and altering the current thread's system error, it wasn't
possible to leave the system error as-is. Unless replaced by a value
unequal to the original, the system error was being forced to 0 upon
return from the NativeCallback.

bindings/gumjs/gumquickcore.c

@@ -4433,6 +4433,7 @@ gum_quick_native_callback_invoke (ffi_cif * cif,
 {
   GumQuickNativeCallback * self = user_data;
   GumQuickCore * core = self->core;
+  gint saved_system_error;
   guintptr return_address = 0;
   guintptr stack_pointer = 0;
   guintptr frame_pointer = 0;
@@ -4448,6 +4449,8 @@ gum_quick_native_callback_invoke (ffi_cif * cif,
   JSValue * argv;
   JSValue result;
 
+  saved_system_error = gum_thread_get_system_error ();
+
 #if defined (HAVE_I386) && defined (_MSC_VER)
   return_address = GPOINTER_TO_SIZE (_ReturnAddress ());
   stack_pointer = GPOINTER_TO_SIZE (_AddressOfReturnAddress ());
@@ -4556,6 +4559,8 @@ gum_quick_native_callback_invoke (ffi_cif * cif,
   JS_FreeValue (ctx, self->wrapper);
 
   _gum_quick_scope_leave (&scope);
+
+  gum_thread_set_system_error (saved_system_error);
 }
 
 GUMJS_DEFINE_FINALIZER (gumjs_callback_context_finalize)

bindings/gumjs/gumv8core.cpp

@@ -3434,6 +3434,7 @@ gum_v8_native_callback_invoke (ffi_cif * cif,
                                void ** args,
                                void * user_data)
 {
+  GumV8SystemErrorPreservationScope error_scope;
   guintptr return_address = 0;
   guintptr stack_pointer = 0;
   guintptr frame_pointer = 0;

bindings/gumjs/gumv8core.h

@@ -159,6 +159,23 @@ struct GumV8NativeCallback
   GumV8Core * core;
 };
 
+class GumV8SystemErrorPreservationScope
+{
+public:
+  GumV8SystemErrorPreservationScope ()
+    : saved_error (gum_thread_get_system_error ())
+  {
+  }
+
+  ~GumV8SystemErrorPreservationScope ()
+  {
+    gum_thread_set_system_error (saved_error);
+  }
+
+private:
+  gint saved_error;
+};
+
 G_GNUC_INTERNAL void _gum_v8_core_init (GumV8Core * self,
     GumV8Script * script, const gchar * runtime_source_map,
     GumV8MessageEmitter message_emitter, GumScriptScheduler * scheduler,

bindings/gumjs/gumv8stalker.cpp

@@ -70,23 +70,6 @@ struct GumV8CallProbe
   GumV8Stalker * module;
 };
 
-class GumV8SystemErrorPreservationScope
-{
-public:
-  GumV8SystemErrorPreservationScope ()
-    : saved_error (gum_thread_get_system_error ())
-  {
-  }
-
-  ~GumV8SystemErrorPreservationScope ()
-  {
-    gum_thread_set_system_error (saved_error);
-  }
-
-private:
-  gint saved_error;
-};
-
 static gboolean gum_v8_stalker_on_flush_timer_tick (GumV8Stalker * self);
 
 GUMJS_DECLARE_GETTER (gumjs_stalker_get_trust_threshold)

tests/gumjs/script.c

@@ -67,6 +67,8 @@ TESTLIST_BEGIN (script)
     TESTENTRY (system_error_can_be_read_from_replacement_function)
     TESTENTRY (system_error_can_be_replaced_from_interceptor_listener)
     TESTENTRY (system_error_can_be_replaced_from_replacement_function)
+    TESTENTRY (system_error_unaffected_by_replacement_if_set_to_original_value)
+    TESTENTRY (system_error_unaffected_by_replacement_if_untouched)
     TESTENTRY (invocations_are_bound_on_tls_object)
     TESTENTRY (invocations_provide_thread_id)
     TESTENTRY (invocations_provide_call_depth)
@@ -368,6 +370,7 @@ TESTLIST_BEGIN (script)
     TESTENTRY (cmodule_should_support_global_callbacks)
     TESTENTRY (cmodule_should_provide_access_to_cpu_registers)
     TESTENTRY (cmodule_should_provide_access_to_system_error)
+    TESTENTRY (system_error_unaffected_by_native_callback_from_cmodule)
 #else
     TESTENTRY (cmodule_constructor_should_throw_not_available)
 #endif
@@ -6988,6 +6991,52 @@ TESTCASE (system_error_can_be_replaced_from_replacement_function)
 #endif
 }
 
+TESTCASE (system_error_unaffected_by_replacement_if_set_to_original_value)
+{
+#ifdef HAVE_WINDOWS
+  COMPILE_AND_LOAD_SCRIPT (
+      "Interceptor.replace(" GUM_PTR_CONST ","
+      "    new NativeCallback(function (arg) {"
+      "  this.lastError = 1337;"
+      "  return 0;"
+      "}, 'int', ['int']));", target_function_int);
+
+  SetLastError (1337);
+  target_function_int (7);
+  g_assert_cmpint (GetLastError (), ==, 1337);
+#else
+  COMPILE_AND_LOAD_SCRIPT (
+      "Interceptor.replace(" GUM_PTR_CONST ","
+      "    new NativeCallback(function (arg) {"
+      "  this.errno = 1337;"
+      "  return 0;"
+      "}, 'int', ['int']));", target_function_int);
+
+  errno = 1337;
+  target_function_int (7);
+  g_assert_cmpint (errno, ==, 1337);
+#endif
+}
+
+TESTCASE (system_error_unaffected_by_replacement_if_untouched)
+{
+  COMPILE_AND_LOAD_SCRIPT (
+      "Interceptor.replace(" GUM_PTR_CONST ","
+      "    new NativeCallback(function (arg) {"
+      "  return 0;"
+      "}, 'int', ['int']));", target_function_int);
+
+#ifdef HAVE_WINDOWS
+  SetLastError (1337);
+  target_function_int (7);
+  g_assert_cmpint (GetLastError (), ==, 1337);
+#else
+  errno = 1337;
+  target_function_int (7);
+  g_assert_cmpint (errno, ==, 1337);
+#endif
+}
+
 TESTCASE (invocations_are_bound_on_tls_object)
 {
   COMPILE_AND_LOAD_SCRIPT (
@@ -10195,6 +10244,36 @@ TESTCASE (cmodule_should_provide_access_to_system_error)
   g_assert_cmpint (gum_thread_get_system_error (), ==, 2);
 }
 
+TESTCASE (system_error_unaffected_by_native_callback_from_cmodule)
+{
+  COMPILE_AND_LOAD_SCRIPT (
+      "const cm = new CModule(`\\n"
+      "  #include <gum/guminterceptor.h>\\n"
+      "\\n"
+      "  extern void nativeCallback (void);\\n"
+      "\\n"
+      "  void\\n"
+      "  replacement (GumInvocationContext * ic)\\n"
+      "  {\\n"
+      "    nativeCallback ();\\n"
+      "  }\\n"
+      "`, {\n"
+      "  nativeCallback: new NativeCallback(() => {}, 'void', [])\n"
+      "});\n"
+      "Interceptor.replace(" GUM_PTR_CONST ", cm.replacement);",
+      target_function_int);
+
+#ifdef HAVE_WINDOWS
+  SetLastError (1337);
+  target_function_int (7);
+  g_assert_cmpint (GetLastError (), ==, 1337);
+#else
+  errno = 1337;
+  target_function_int (7);
+  g_assert_cmpint (errno, ==, 1337);
+#endif
+}
+
 #else /* !HAVE_TINYCC */
 
 TESTCASE (cmodule_constructor_should_throw_not_available)