Add libandroid_runtime_lazy

Extract lazy loading of libandroid_runtime from libbinder_ndk
into its own library.

This lib loads libandroid_runtime on demand, so the clients
which don't use this can benefit.

Do not over-use this lib to mock the build system and pretend not
depending on libandroid_runtime.

Bug: 125550121
Test: m -j
Test: readelf -d $OUT/system/lib64/libbinder_ndk.so | grep NEED
        # see if there is not libandroid_runtime
Test: atest android.binder.cts

Change-Id: I4b120686ba34f45e060594641ffc74bc1496c8c9

1 files changed, 98 insertions, 0 deletions

diff --git a/libs/android_runtime_lazy/android_runtime_lazy.cpp b/libs/android_runtime_lazy/android_runtime_lazy.cpp
new file mode 100644
index 0000000000..98d8e8a511
--- /dev/null
+++ b/libs/android_runtime_lazy/android_runtime_lazy.cpp
@@ -0,0 +1,98 @@
+/*
+ * Copyright (C) 2019 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.
+ */
+#define LOG_TAG "ANDROID_RUNTIME_LAZY"
+#include "android_runtime/AndroidRuntime.h"
+#include "android_util_Binder.h"
+
+#include <dlfcn.h>
+#include <mutex>
+
+#include <log/log.h>
+
+namespace android {
+namespace {
+
+std::once_flag loadFlag;
+
+typedef JNIEnv* (*getJNIEnv_t)();
+typedef sp<IBinder> (*ibinderForJavaObject_t)(JNIEnv* env, jobject obj);
+typedef jobject (*javaObjectForIBinder_t)(JNIEnv* env, const sp<IBinder>& val);
+
+getJNIEnv_t _getJNIEnv;
+ibinderForJavaObject_t _ibinderForJavaObject;
+javaObjectForIBinder_t _javaObjectForIBinder;
+
+void load() {
+    std::call_once(loadFlag, []() {
+        void* handle = dlopen("libandroid_runtime.so", RTLD_LAZY);
+        if (handle == nullptr) {
+            ALOGE("Could not open libandroid_runtime.");
+            return;
+        }
+
+        _getJNIEnv = reinterpret_cast<getJNIEnv_t>(
+                dlsym(handle, "_ZN7android14AndroidRuntime9getJNIEnvEv"));
+        if (_getJNIEnv == nullptr) {
+            ALOGW("Could not find getJNIEnv.");
+            // no return
+        }
+
+        _ibinderForJavaObject = reinterpret_cast<ibinderForJavaObject_t>(
+                dlsym(handle, "_ZN7android20ibinderForJavaObjectEP7_JNIEnvP8_jobject"));
+        if (_ibinderForJavaObject == nullptr) {
+            ALOGW("Could not find ibinderForJavaObject.");
+            // no return
+        }
+
+        _javaObjectForIBinder = reinterpret_cast<javaObjectForIBinder_t>(
+                dlsym(handle,
+                      "_ZN7android20javaObjectForIBinderEP7_JNIEnvRKNS_2spINS_7IBinderEEE"));
+        if (_javaObjectForIBinder == nullptr) {
+            ALOGW("Could not find javaObjectForIBinder.");
+            // no return
+        }
+    });
+}
+
+} // namespace
+
+// exports delegate functions
+
+JNIEnv* AndroidRuntime::getJNIEnv() {
+    load();
+    if (_getJNIEnv == nullptr) {
+        return nullptr;
+    }
+    return _getJNIEnv();
+}
+
+sp<IBinder> ibinderForJavaObject(JNIEnv* env, jobject obj) {
+    load();
+    if (_ibinderForJavaObject == nullptr) {
+        return nullptr;
+    }
+    return _ibinderForJavaObject(env, obj);
+}
+
+jobject javaObjectForIBinder(JNIEnv* env, const sp<IBinder>& val) {
+    load();
+    if (_javaObjectForIBinder == nullptr) {
+        return nullptr;
+    }
+    return _javaObjectForIBinder(env, val);
+}
+
+} // namespace android