nativebridge: Add PreZygoteFork callback

It's required to clean-up the emulated enviroment (e.g. close file
descriptors) after emulated execution in doPreload() in app-zygote.

Test: NativeBridge6PreZygoteFork_test
Test: CtsSeccompHostTestCases
android.seccomp.cts.SeccompHostJUnit4DeviceTest
testAppZygoteSyscalls
both for Q.sdk_gphone_x86_arm.armeabi-v7a
Bug: 146904103

Change-Id: Id192a1647c2f405570bf196daf65b3f2a9faca42
diff --git a/libnativebridge/tests/DummyNativeBridge6.cpp b/libnativebridge/tests/DummyNativeBridge6.cpp
new file mode 100644
index 0000000..ce27e67
--- /dev/null
+++ b/libnativebridge/tests/DummyNativeBridge6.cpp
@@ -0,0 +1,133 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// A dummy implementation of the native-bridge interface.
+
+#include "nativebridge/native_bridge.h"
+
+#include "NativeBridge6PreZygoteFork_lib.h"
+
+// NativeBridgeCallbacks implementations
+extern "C" bool native_bridge6_initialize(
+                      const android::NativeBridgeRuntimeCallbacks* /* art_cbs */,
+                      const char* /* app_code_cache_dir */,
+                      const char* /* isa */) {
+  return true;
+}
+
+extern "C" void* native_bridge6_loadLibrary(const char* /* libpath */, int /* flag */) {
+  return nullptr;
+}
+
+extern "C" void* native_bridge6_getTrampoline(void* /* handle */, const char* /* name */,
+                                             const char* /* shorty */, uint32_t /* len */) {
+  return nullptr;
+}
+
+extern "C" bool native_bridge6_isSupported(const char* /* libpath */) {
+  return false;
+}
+
+extern "C" const struct android::NativeBridgeRuntimeValues* native_bridge6_getAppEnv(
+    const char* /* abi */) {
+  return nullptr;
+}
+
+extern "C" bool native_bridge6_isCompatibleWith(uint32_t version) {
+  // For testing, allow 1-6, but disallow 7+.
+  return version <= 6;
+}
+
+extern "C" android::NativeBridgeSignalHandlerFn native_bridge6_getSignalHandler(int /* signal */) {
+  return nullptr;
+}
+
+extern "C" int native_bridge6_unloadLibrary(void* /* handle */) {
+  return 0;
+}
+
+extern "C" const char* native_bridge6_getError() {
+  return nullptr;
+}
+
+extern "C" bool native_bridge6_isPathSupported(const char* /* path */) {
+  return true;
+}
+
+extern "C" bool native_bridge6_initAnonymousNamespace(const char* /* public_ns_sonames */,
+                                                      const char* /* anon_ns_library_path */) {
+  return true;
+}
+
+extern "C" android::native_bridge_namespace_t*
+native_bridge6_createNamespace(const char* /* name */,
+                               const char* /* ld_library_path */,
+                               const char* /* default_library_path */,
+                               uint64_t /* type */,
+                               const char* /* permitted_when_isolated_path */,
+                               android::native_bridge_namespace_t* /* parent_ns */) {
+  return nullptr;
+}
+
+extern "C" bool native_bridge6_linkNamespaces(android::native_bridge_namespace_t* /* from */,
+                                              android::native_bridge_namespace_t* /* to */,
+                                              const char* /* shared_libs_soname */) {
+  return true;
+}
+
+extern "C" void* native_bridge6_loadLibraryExt(const char* /* libpath */,
+                                               int /* flag */,
+                                               android::native_bridge_namespace_t* /* ns */) {
+  return nullptr;
+}
+
+extern "C" android::native_bridge_namespace_t* native_bridge6_getVendorNamespace() {
+  return nullptr;
+}
+
+extern "C" android::native_bridge_namespace_t* native_bridge6_getExportedNamespace(const char* /* name */) {
+  return nullptr;
+}
+
+extern "C" void native_bridge6_preZygoteFork() {
+  android::SetPreZygoteForkDone();
+}
+
+android::NativeBridgeCallbacks NativeBridgeItf{
+    // v1
+    .version = 6,
+    .initialize = &native_bridge6_initialize,
+    .loadLibrary = &native_bridge6_loadLibrary,
+    .getTrampoline = &native_bridge6_getTrampoline,
+    .isSupported = &native_bridge6_isSupported,
+    .getAppEnv = &native_bridge6_getAppEnv,
+    // v2
+    .isCompatibleWith = &native_bridge6_isCompatibleWith,
+    .getSignalHandler = &native_bridge6_getSignalHandler,
+    // v3
+    .unloadLibrary = &native_bridge6_unloadLibrary,
+    .getError = &native_bridge6_getError,
+    .isPathSupported = &native_bridge6_isPathSupported,
+    .initAnonymousNamespace = &native_bridge6_initAnonymousNamespace,
+    .createNamespace = &native_bridge6_createNamespace,
+    .linkNamespaces = &native_bridge6_linkNamespaces,
+    .loadLibraryExt = &native_bridge6_loadLibraryExt,
+    // v4
+    &native_bridge6_getVendorNamespace,
+    // v5
+    &native_bridge6_getExportedNamespace,
+    // v6
+    &native_bridge6_preZygoteFork};