Support "Parcel.propagateAllowBlocking" for AIDL

Bug: 216685683
Test: atest android.os.cts.ParcelTest
Change-Id: I9299632c8c4fd88afc6b539270c097b9c00188b3

core/api/current.txt

@@ -31699,6 +31699,7 @@ package android.os {
     method public void setDataCapacity(int);
     method public void setDataPosition(int);
     method public void setDataSize(int);
+    method public void setPropagateAllowBlocking();
     method public void unmarshall(@NonNull byte[], int, int);
     method public void writeArray(@Nullable Object[]);
     method public void writeBinderArray(@Nullable android.os.IBinder[]);

core/api/test-current.txt

@@ -1715,8 +1715,11 @@ package android.os {
 
   public final class Parcel {
     method public boolean allowSquashing();
+    method public int getFlags();
     method public int readExceptionCode();
     method public void restoreAllowSquashing(boolean);
+    field public static final int FLAG_IS_REPLY_FROM_BLOCKING_ALLOWED_OBJECT = 1; // 0x1
+    field public static final int FLAG_PROPAGATE_ALLOW_BLOCKING = 2; // 0x2
   }
 
   public class ParcelFileDescriptor implements java.io.Closeable android.os.Parcelable {

core/java/android/os/BinderProxy.java

@@ -516,12 +516,15 @@ public final class BinderProxy implements IBinder {
     public boolean transact(int code, Parcel data, Parcel reply, int flags) throws RemoteException {
         Binder.checkParcel(this, code, data, "Unreasonably large binder buffer");
 
-        if (mWarnOnBlocking && ((flags & FLAG_ONEWAY) == 0)
+        boolean warnOnBlocking = mWarnOnBlocking; // Cache it to reduce volatile access.
+
+        if (warnOnBlocking && ((flags & FLAG_ONEWAY) == 0)
                 && Binder.sWarnOnBlockingOnCurrentThread.get()) {
 
             // For now, avoid spamming the log by disabling after we've logged
             // about this interface at least once
             mWarnOnBlocking = false;
+            warnOnBlocking = false;
 
             if (Build.IS_USERDEBUG) {
                 // Log this as a WTF on userdebug builds.
@@ -568,7 +571,13 @@ public final class BinderProxy implements IBinder {
         }
 
         try {
-            return transactNative(code, data, reply, flags);
+            final boolean result = transactNative(code, data, reply, flags);
+
+            if (reply != null && !warnOnBlocking) {
+                reply.addFlags(Parcel.FLAG_IS_REPLY_FROM_BLOCKING_ALLOWED_OBJECT);
+            }
+
+            return result;
         } finally {
             AppOpsManager.resumeNotedAppOpsCollection(prevCollection);
 

core/java/android/os/Parcel.java

@@ -18,6 +18,7 @@ package android.os;
 
 import static java.util.Objects.requireNonNull;
 
+import android.annotation.IntDef;
 import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.annotation.SuppressLint;
@@ -53,6 +54,8 @@ import java.io.ObjectInputStream;
 import java.io.ObjectOutputStream;
 import java.io.ObjectStreamClass;
 import java.io.Serializable;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
 import java.lang.reflect.Array;
 import java.lang.reflect.Field;
 import java.lang.reflect.Modifier;
@@ -229,6 +232,25 @@ public final class Parcel {
 
     private RuntimeException mStack;
 
+    /** @hide */
+    @TestApi
+    public static final int FLAG_IS_REPLY_FROM_BLOCKING_ALLOWED_OBJECT = 1 << 0;
+
+    /** @hide */
+    @TestApi
+    public static final int FLAG_PROPAGATE_ALLOW_BLOCKING = 1 << 1;
+
+    /** @hide */
+    @IntDef(flag = true, prefix = { "FLAG_" }, value = {
+            FLAG_IS_REPLY_FROM_BLOCKING_ALLOWED_OBJECT,
+            FLAG_PROPAGATE_ALLOW_BLOCKING,
+    })
+    @Retention(RetentionPolicy.SOURCE)
+    public @interface ParcelFlags {}
+
+    @ParcelFlags
+    private int mFlags;
+
     /**
      * Whether or not to parcel the stack trace of an exception. This has a performance
      * impact, so should only be included in specific processes and only on debug builds.
@@ -585,6 +607,40 @@ public final class Parcel {
         nativeMarkForBinder(mNativePtr, binder);
     }
 
+    /** @hide */
+    @ParcelFlags
+    @TestApi
+    public int getFlags() {
+        return mFlags;
+    }
+
+    /** @hide */
+    public void setFlags(@ParcelFlags int flags) {
+        mFlags = flags;
+    }
+
+    /** @hide */
+    public void addFlags(@ParcelFlags int flags) {
+        mFlags |= flags;
+    }
+
+    /** @hide */
+    private boolean hasFlags(@ParcelFlags int flags) {
+        return (mFlags & flags) == flags;
+    }
+
+    /**
+     * This method is used by the AIDL compiler for system components. Not intended to be
+     * used by non-system apps.
+     */
+    // Note: Ideally this method should be @SystemApi(client = SystemApi.Client.MODULE_LIBRARIES),
+    // but we need to make this method public due to the way the aidl compiler is compiled.
+    // We don't really need to protect it; even if 3p / non-system apps, nothing would happen.
+    // This would only work when used on a reply parcel by a binder object that's allowed-blocking.
+    public void setPropagateAllowBlocking() {
+        addFlags(FLAG_PROPAGATE_ALLOW_BLOCKING);
+    }
+
     /**
      * Returns the total amount of data contained in the parcel.
      */
@@ -2940,7 +2996,15 @@ public final class Parcel {
      * Read an object from the parcel at the current dataPosition().
      */
     public final IBinder readStrongBinder() {
-        return nativeReadStrongBinder(mNativePtr);
+        final IBinder result = nativeReadStrongBinder(mNativePtr);
+
+        // If it's a reply from a method with @PropagateAllowBlocking, then inherit allow-blocking
+        // from the object that returned it.
+        if (result != null && hasFlags(
+                FLAG_IS_REPLY_FROM_BLOCKING_ALLOWED_OBJECT | FLAG_PROPAGATE_ALLOW_BLOCKING)) {
+            Binder.allowBlocking(result);
+        }
+        return result;
     }
 
     /**
@@ -4584,6 +4648,7 @@ public final class Parcel {
     }
 
     private void freeBuffer() {
+        mFlags = 0;
         resetSqaushingState();
         if (mOwnsNativeParcelObject) {
             nativeFreeBuffer(mNativePtr);