1 /* 2 * Copyright (c) 2013, 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. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package sun.misc; 27 28 import java.security.AccessControlContext; 29 import java.security.ProtectionDomain; 30 31 /** 32 * A thread that has no permissions, is not a member of any user-defined 33 * ThreadGroup and supports the ability to erase ThreadLocals. 34 * 35 * @implNote Based on the implementation of InnocuousForkJoinWorkerThread. 36 */ 37 public final class InnocuousThread extends Thread { 38 private static final Unsafe UNSAFE; 39 private static final ThreadGroup THREADGROUP; 40 private static final AccessControlContext ACC; 41 private static final long THREADLOCALS; 42 private static final long INHERITABLETHREADLOCALS; 43 private static final long INHERITEDACCESSCONTROLCONTEXT; 44 45 public InnocuousThread(Runnable target) { 46 super(THREADGROUP, target, "anInnocuousThread"); 47 UNSAFE.putOrderedObject(this, INHERITEDACCESSCONTROLCONTEXT, ACC); 48 eraseThreadLocals(); 49 } 50 51 @Override 52 public ClassLoader getContextClassLoader() { 53 // always report system class loader 54 return ClassLoader.getSystemClassLoader(); 55 } 56 57 @Override 58 public void setUncaughtExceptionHandler(UncaughtExceptionHandler x) { 59 // silently fail 60 } 61 62 @Override 63 public void setContextClassLoader(ClassLoader cl) { 64 throw new SecurityException("setContextClassLoader"); 65 } 66 67 // ensure run method is run only once 68 private volatile boolean hasRun; 69 70 @Override 71 public void run() { 72 if (Thread.currentThread() == this && !hasRun) { 73 hasRun = true; 74 super.run(); 75 } 76 } 77 78 /** 79 * Drops all thread locals (and inherited thread locals). 80 */ 81 public void eraseThreadLocals() { 82 UNSAFE.putObject(this, THREADLOCALS, null); 83 UNSAFE.putObject(this, INHERITABLETHREADLOCALS, null); 84 } 85 86 // Use Unsafe to access Thread group and ThreadGroup parent fields 87 static { 88 try { 89 ACC = new AccessControlContext(new ProtectionDomain[] { 90 new ProtectionDomain(null, null) 91 }); 92 93 // Find and use topmost ThreadGroup as parent of new group 94 UNSAFE = Unsafe.getUnsafe(); 95 Class<?> tk = Thread.class; 96 Class<?> gk = ThreadGroup.class; 97 98 THREADLOCALS = UNSAFE.objectFieldOffset 99 (tk.getDeclaredField("threadLocals")); 100 INHERITABLETHREADLOCALS = UNSAFE.objectFieldOffset 101 (tk.getDeclaredField("inheritableThreadLocals")); 102 INHERITEDACCESSCONTROLCONTEXT = UNSAFE.objectFieldOffset 103 (tk.getDeclaredField("inheritedAccessControlContext")); 104 105 long tg = UNSAFE.objectFieldOffset(tk.getDeclaredField("group")); 106 long gp = UNSAFE.objectFieldOffset(gk.getDeclaredField("parent")); 107 ThreadGroup group = (ThreadGroup) 108 UNSAFE.getObject(Thread.currentThread(), tg); 109 110 while (group != null) { 111 ThreadGroup parent = (ThreadGroup)UNSAFE.getObject(group, gp); 112 if (parent == null) 113 break; 114 group = parent; 115 } 116 THREADGROUP = new ThreadGroup(group, "InnocuousThreadGroup"); 117 } catch (Exception e) { 118 throw new Error(e); 119 } 120 } 121 }