Add property to force restorecon to run.

As an optimization, we typically only run restorecon when
seapp_contexts changes.  This CL checks a property that can be used
to always force a restorecon to help investigate boot timing.

Bug: 30213213
Change-Id: I4d65c1a4e4a0830ef4a32cd2fae1d3ab188b65cc

services/core/java/com/android/server/pm/SELinuxMMAC.java

@@ -19,6 +19,7 @@ package com.android.server.pm;
 import android.content.pm.PackageParser;
 import android.content.pm.Signature;
 import android.os.Environment;
+import android.os.SystemProperties;
 import android.system.ErrnoException;
 import android.system.Os;
 import android.system.OsConstants;
@@ -64,6 +65,8 @@ public final class SELinuxMMAC {
     // to synchronize access during policy load and access attempts.
     private static List<Policy> sPolicies = new ArrayList<>();
 
+    private static final String PROP_FORCE_RESTORECON = "sys.force_restorecon";
+
     /** Path to version on rootfs */
     private static final File VERSION_FILE = new File("/selinux_version");
 
@@ -322,6 +325,11 @@ public final class SELinuxMMAC {
      * @return Returns true if the restorecon should occur or false otherwise.
      */
     public static boolean isRestoreconNeeded(File file) {
+        // To investigate boot timing, allow a property to always force restorecon
+        if (SystemProperties.getBoolean(PROP_FORCE_RESTORECON, false)) {
+            return true;
+        }
+
         try {
             final byte[] buf = new byte[20];
             final int len = Os.getxattr(file.getAbsolutePath(), XATTR_SEAPP_HASH, buf);