Parcel: lift 'isForRpc' here from native

Platform API, in order to fix bugs like b/254835230 where
certain utilities call getCallingUid, which doesn't make
sense for RPC calls.

Bug: 254835230
Test: android.os.ParcelTest
Change-Id: If2dd13d8edd515c945ccde2a2554f6f2b7b87b26

core/java/android/os/Parcel.java

@@ -368,6 +368,8 @@ public final class Parcel {
     @FastNative
     private static native void nativeMarkForBinder(long nativePtr, IBinder binder);
     @CriticalNative
+    private static native boolean nativeIsForRpc(long nativePtr);
+    @CriticalNative
     private static native int nativeDataSize(long nativePtr);
     @CriticalNative
     private static native int nativeDataAvail(long nativePtr);
@@ -645,6 +647,15 @@ public final class Parcel {
         nativeMarkForBinder(mNativePtr, binder);
     }
 
+    /**
+     * Whether this Parcel is written for an RPC transaction.
+     *
+     * @hide
+     */
+    public final boolean isForRpc() {
+        return nativeIsForRpc(mNativePtr);
+    }
+
     /** @hide */
     @ParcelFlags
     @TestApi

core/jni/android_os_Parcel.cpp

@@ -116,6 +116,11 @@ static void android_os_Parcel_markForBinder(JNIEnv* env, jclass clazz, jlong nat
     }
 }
 
+static jboolean android_os_Parcel_isForRpc(jlong nativePtr) {
+    Parcel* parcel = reinterpret_cast<Parcel*>(nativePtr);
+    return parcel ? parcel->isForRpc() : false;
+}
+
 static jint android_os_Parcel_dataSize(jlong nativePtr)
 {
     Parcel* parcel = reinterpret_cast<Parcel*>(nativePtr);
@@ -808,6 +813,8 @@ static const JNINativeMethod gParcelMethods[] = {
     // @FastNative
     {"nativeMarkForBinder",       "(JLandroid/os/IBinder;)V", (void*)android_os_Parcel_markForBinder},
     // @CriticalNative
+    {"nativeIsForRpc",            "(J)Z", (void*)android_os_Parcel_isForRpc},
+    // @CriticalNative
     {"nativeDataSize",            "(J)I", (void*)android_os_Parcel_dataSize},
     // @CriticalNative
     {"nativeDataAvail",           "(J)I", (void*)android_os_Parcel_dataAvail},

core/tests/coretests/src/android/os/ParcelTest.java

@@ -36,6 +36,13 @@ public class ParcelTest {
     private static final String INTERFACE_TOKEN_1 = "IBinder interface token";
     private static final String INTERFACE_TOKEN_2 = "Another IBinder interface token";
 
+    @Test
+    public void testIsForRpc() {
+        Parcel p = Parcel.obtain();
+        assertEquals(false, p.isForRpc());
+        p.recycle();
+    }
+
     @Test
     public void testCallingWorkSourceUidAfterWrite() {
         Parcel p = Parcel.obtain();