From 47032a209517ccdc50bbcc27b2f4e5bbaaf28552 Mon Sep 17 00:00:00 2001
From: Tim Murray <timmurray@google.com>
Date: Mon, 11 Apr 2022 21:44:01 -0700
Subject: [PATCH] Icon: make Icon's Bitmaps immutable

Because Bitmap mutability is propagated across Parcel and Binder, the
following problem can happen when sending an Icon containing a Bitmap
as part of a Notification:

1. App creates Icon with a mutable Bitmap (1 alloc)
2. App sends Icon to system_server, often creating ashmem Bitmap (2 allocs)
3. system_server converts ashmem Bitmap back to heap Bitmap (3 allocs)
4. system_server sends heap Bitmap to each NotificationListener individually,
converting the heap Bitmap to ashmem each time (3+N allocs)
5. NotificationListener converts ashmem Bitmap to heap Bitmap (3+2N allocs)

This is inefficient. This is especially bad because the API to update
a Notification involves sending a full Notification object, including
Icons, repeatedly, and some apps do that several times per second.

Instead, ensure that all Bitmaps transmitted as part of Icons are
immutable. Instead, we get:

1. App creates Icon, which may copy to immutable Bitamp (1 or 2 allocs)
2. App sends Icon to system_server over ashmem (still 1 or 2 allocs)
3. system_server uses received ashmem Bitmap directly (still 1 or 2 allocs)
4. system_server sends same ashmem Bitmap to NotificationListeners (1 or 2)
5. Each NotificationListener uses the same ashmem Bitmap (1 or 2)

This solves the per-NotificationListener amplification, but it does
not solve sending what is likely the same Bitmap N times per second
when apps update Notifications. That will require either app changes
or Notification API changes to avoid bytewise comparisons for all
Bitmaps.

Test: boot, notifications work, memory in maps/gearhead remains good
Bug: 227920378

Change-Id: If92835f647a76da599f358c7c02888e3e2f59235
---
 .../java/android/graphics/drawable/Icon.java  | 23 +++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/graphics/java/android/graphics/drawable/Icon.java b/graphics/java/android/graphics/drawable/Icon.java
index b04b82629b921..a76d74edc0f4d 100644
--- a/graphics/java/android/graphics/drawable/Icon.java
+++ b/graphics/java/android/graphics/drawable/Icon.java
@@ -128,6 +128,7 @@ public final class Icon implements Parcelable {
     // TYPE_RESOURCE: Resources
     // TYPE_DATA: DataBytes
     private Object          mObj1;
+    private boolean mCachedAshmem = false;
 
     // TYPE_RESOURCE: package name
     // TYPE_URI: uri string
@@ -156,6 +157,8 @@ public final class Icon implements Parcelable {
     /**
      * @return The {@link android.graphics.Bitmap} held by this {@link #TYPE_BITMAP} or
      * {@link #TYPE_ADAPTIVE_BITMAP} Icon.
+     *
+     * Note that this will always return an immutable Bitmap.
      * @hide
      */
     @UnsupportedAppUsage
@@ -166,8 +169,20 @@ public final class Icon implements Parcelable {
         return (Bitmap) mObj1;
     }
 
+    /**
+     * Sets the Icon's contents to a particular Bitmap. Note that this may make a copy of the Bitmap
+     * if the supplied Bitmap is mutable. In that case, the value returned by getBitmap() may not
+     * equal the Bitmap passed to setBitmap().
+     *
+     * @hide
+     */
     private void setBitmap(Bitmap b) {
-        mObj1 = b;
+        if (b.isMutable()) {
+            mObj1 = b.copy(b.getConfig(), false);
+        } else {
+            mObj1 = b;
+        }
+        mCachedAshmem = false;
     }
 
     /**
@@ -488,6 +503,7 @@ public final class Icon implements Parcelable {
             getBitmap().getAllocationByteCount() >= MIN_ASHMEM_ICON_SIZE) {
             setBitmap(getBitmap().asShared());
         }
+        mCachedAshmem = true;
     }
 
     /**
@@ -913,7 +929,10 @@ public final class Icon implements Parcelable {
         switch (mType) {
             case TYPE_BITMAP:
             case TYPE_ADAPTIVE_BITMAP:
-                final Bitmap bits = getBitmap();
+                if (!mCachedAshmem) {
+                    mObj1 = ((Bitmap) mObj1).asShared();
+                    mCachedAshmem = true;
+                }
                 getBitmap().writeToParcel(dest, flags);
                 break;
             case TYPE_RESOURCE: