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annotate agent/src/share/classes/sun/jvm/hotspot/utilities/RobustOopDeterminator.java @ 3945:8ed53447f690
Merge
author | iveresov |
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date | Thu, 15 Sep 2011 12:44:09 -0700 |
parents | c18cbe5936b8 |
children | da91efe96a93 |
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0 | 1 /* |
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2 * Copyright (c) 2000, 2008, Oracle and/or its affiliates. All rights reserved. |
0 | 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 * | |
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
0 | 22 * |
23 */ | |
24 | |
25 package sun.jvm.hotspot.utilities; | |
26 | |
27 import java.util.*; | |
28 import sun.jvm.hotspot.debugger.*; | |
29 import sun.jvm.hotspot.memory.*; | |
30 import sun.jvm.hotspot.runtime.*; | |
31 import sun.jvm.hotspot.types.*; | |
32 | |
33 /** This class determines to the best of its ability, and in a | |
34 reasonably robust fashion, whether a given pointer is an intact | |
35 oop or not. It does this by checking the integrity of the | |
36 metaclass hierarchy. This is only intended for use in the | |
37 debugging system. It may provide more resilience to unexpected VM | |
38 states than the ObjectHeap code. */ | |
39 | |
40 public class RobustOopDeterminator { | |
41 private static OopField klassField; | |
42 | |
43 static { | |
44 VM.registerVMInitializedObserver(new Observer() { | |
45 public void update(Observable o, Object data) { | |
46 initialize(VM.getVM().getTypeDataBase()); | |
47 } | |
48 }); | |
49 } | |
50 | |
51 private static void initialize(TypeDataBase db) { | |
52 Type type = db.lookupType("oopDesc"); | |
53 | |
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54 if (VM.getVM().isCompressedOopsEnabled()) { |
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55 klassField = type.getNarrowOopField("_metadata._compressed_klass"); |
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56 } else { |
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57 klassField = type.getOopField("_metadata._klass"); |
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58 } |
0 | 59 } |
60 | |
61 public static boolean oopLooksValid(OopHandle oop) { | |
62 if (oop == null) { | |
63 return false; | |
64 } | |
65 if (!VM.getVM().getUniverse().isIn(oop)) { | |
66 return false; | |
67 } | |
68 try { | |
69 for (int i = 0; i < 4; ++i) { | |
70 OopHandle next = klassField.getValue(oop); | |
71 if (next == null) { | |
72 return false; | |
73 } | |
74 if (next.equals(oop)) { | |
75 return true; | |
76 } | |
77 oop = next; | |
78 } | |
79 return false; | |
80 } | |
81 catch (AddressException e) { | |
82 return false; | |
83 } | |
84 } | |
85 } |