Made libbinder's waitForService accessible in java

waitForService is used to lazily start AIDL services

Bug: 138756857
Test: Manual (tested starting gsiservice with this function)
Change-Id: I7ff16b014052d3845bd4b1baa8fc9843e7975a16

2 files changed, 36 insertions, 1 deletions

diff --git a/core/java/android/os/Binder.java b/core/java/android/os/Binder.java
index 6178b2bf5817..357c0c97b22c 100644
--- a/core/java/android/os/Binder.java
+++ b/core/java/android/os/Binder.java
@@ -1063,4 +1063,13 @@ public class Binder implements IBinder {
         StrictMode.clearGatheredViolations();
         return res;
     }
+
+    /**
+     * Returns the specified service from servicemanager. If the service is not running,
+     * servicemanager will attempt to start it, and this function will wait for it to be ready.
+     * Returns nullptr only if there are permission problems or fatal errors.
+     * @hide
+     */
+    public static final native @Nullable IBinder waitForService(@NonNull String serviceName)
+            throws RemoteException;
 }
diff --git a/core/jni/android_util_Binder.cpp b/core/jni/android_util_Binder.cpp
index 0afbaa0e174c..fe7e508872ab 100644
--- a/core/jni/android_util_Binder.cpp
+++ b/core/jni/android_util_Binder.cpp
@@ -989,6 +989,31 @@ static void android_os_Binder_blockUntilThreadAvailable(JNIEnv* env, jobject cla
     return IPCThreadState::self()->blockUntilThreadAvailable();
 }
 
+static jobject android_os_Binder_waitForService(
+        JNIEnv *env,
+        jclass /* clazzObj */,
+        jstring serviceNameObj) {
+
+    const jchar* serviceName = env->GetStringCritical(serviceNameObj, nullptr);
+    if (!serviceName) {
+        signalExceptionForError(env, nullptr, BAD_VALUE, true /*canThrowRemoteException*/);
+        return nullptr;
+    }
+    String16 nameCopy = String16(reinterpret_cast<const char16_t *>(serviceName),
+            env->GetStringLength(serviceNameObj));
+    env->ReleaseStringCritical(serviceNameObj, serviceName);
+
+    auto sm = android::defaultServiceManager();
+    sp<IBinder> service = sm->waitForService(nameCopy);
+
+    if (!service) {
+        signalExceptionForError(env, nullptr, NAME_NOT_FOUND, true /*canThrowRemoteException*/);
+        return nullptr;
+    }
+
+    return javaObjectForIBinder(env, service);
+}
+
 // ----------------------------------------------------------------------------
 
 static const JNINativeMethod gBinderMethods[] = {
@@ -1016,7 +1041,8 @@ static const JNINativeMethod gBinderMethods[] = {
     { "flushPendingCommands", "()V", (void*)android_os_Binder_flushPendingCommands },
     { "getNativeBBinderHolder", "()J", (void*)android_os_Binder_getNativeBBinderHolder },
     { "getNativeFinalizer", "()J", (void*)android_os_Binder_getNativeFinalizer },
-    { "blockUntilThreadAvailable", "()V", (void*)android_os_Binder_blockUntilThreadAvailable }
+    { "blockUntilThreadAvailable", "()V", (void*)android_os_Binder_blockUntilThreadAvailable },
+    { "waitForService", "(Ljava/lang/String;)Landroid/os/IBinder;", (void*)android_os_Binder_waitForService }
 };
 
 const char* const kBinderPathName = "android/os/Binder";