1 /*
   2  * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 package sun.hotspot;
  26 import java.security.BasicPermission;
  27 
  28 public class WhiteBox {
  29 
  30   @SuppressWarnings("serial")
  31   public static class WhiteBoxPermission extends BasicPermission {
  32     public WhiteBoxPermission(String s) {
  33       super(s);
  34     }
  35   }
  36 
  37   private WhiteBox() {}
  38   private static final WhiteBox instance = new WhiteBox();
  39   private static native void registerNatives();
  40 
  41   /**
  42    * Returns the singleton WhiteBox instance.
  43    *
  44    * The returned WhiteBox object should be carefully guarded
  45    * by the caller, since it can be used to read and write data
  46    * at arbitrary memory addresses. It must never be passed to
  47    * untrusted code.
  48    */
  49   public synchronized static WhiteBox getWhiteBox() {
  50     SecurityManager sm = System.getSecurityManager();
  51     if (sm != null) {
  52       sm.checkPermission(new WhiteBoxPermission("getInstance"));
  53     }
  54     return instance;
  55   }
  56 
  57   static {
  58     registerNatives();
  59   }
  60 
  61   // Memory
  62   public native long getObjectAddress(Object o);
  63   public native int  getHeapOopSize();
  64 
  65   // G1
  66   public native boolean g1InConcurrentMark();
  67   public native boolean g1IsHumongous(Object o);
  68   public native long    g1NumFreeRegions();
  69   public native int     g1RegionSize();
  70 }