Merge "Don't ask libc for PT feature w/o kernel support."

core/java/com/android/internal/os/Zygote.java

@@ -1065,4 +1065,11 @@ public final class Zygote {
      * Returns whether the hardware supports memory tagging (ARM MTE).
      */
     public static native boolean nativeSupportsMemoryTagging();
+
+    /**
+     * Returns whether the kernel supports tagged pointers. Present in the
+     * Android Common Kernel from 4.14 and up. By default, you should prefer
+     * fully-feature Memory Tagging, rather than the static Tagged Pointers.
+     */
+    public static native boolean nativeSupportsTaggedPointers();
 }

core/java/com/android/internal/os/ZygoteInit.java

@@ -754,9 +754,9 @@ public class ZygoteInit {
                 /* The system server is more privileged than regular app processes, so it has async
                  * tag checks enabled on hardware that supports memory tagging. */
                 parsedArgs.mRuntimeFlags |= Zygote.MEMORY_TAG_LEVEL_ASYNC;
-            } else {
+            } else if (Zygote.nativeSupportsTaggedPointers()) {
                 /* Enable pointer tagging in the system server. Hardware support for this is present
-                 * in all ARMv8 CPUs; this flag has no effect on other platforms. */
+                 * in all ARMv8 CPUs. */
                 parsedArgs.mRuntimeFlags |= Zygote.MEMORY_TAG_LEVEL_TBI;
             }