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.AccessController; 30 import java.security.ProtectionDomain; 31 import java.security.PrivilegedAction; 32 import java.util.concurrent.atomic.AtomicInteger; 33 34 /** 35 * A thread that has no permissions, is not a member of any user-defined 36 * ThreadGroup and supports the ability to erase ThreadLocals. 37 */ 38 public final class InnocuousThread extends ManagedLocalsThread { 39 private static final Unsafe UNSAFE; 40 private static final ThreadGroup INNOCUOUSTHREADGROUP; 41 private static final AccessControlContext ACC; 42 private static final long INHERITEDACCESSCONTROLCONTEXT; 43 private static final long CONTEXTCLASSLOADER; 44 45 private static final AtomicInteger threadNumber = new AtomicInteger(1); 46 47 public InnocuousThread(Runnable target) { 48 this(INNOCUOUSTHREADGROUP, target, 49 "InnocuousThread-" + threadNumber.getAndIncrement()); 50 } 51 52 public InnocuousThread(Runnable target, String name) { 53 this(INNOCUOUSTHREADGROUP, target, name); 54 } 55 56 public InnocuousThread(ThreadGroup group, Runnable target, String name) { 57 super(group, target, name); 58 UNSAFE.putOrderedObject(this, INHERITEDACCESSCONTROLCONTEXT, ACC); 59 UNSAFE.putOrderedObject(this, CONTEXTCLASSLOADER, ClassLoader.getSystemClassLoader()); 60 } 61 62 @Override 63 public void setUncaughtExceptionHandler(UncaughtExceptionHandler x) { 64 // silently fail 65 } 66 67 @Override 68 public void setContextClassLoader(ClassLoader cl) { 69 // Allow clearing of the TCCL to remove the reference to the system classloader. 70 if (cl == null) 71 super.setContextClassLoader(null); 72 else 73 throw new SecurityException("setContextClassLoader"); 74 } 75 76 // ensure run method is run only once 77 private volatile boolean hasRun; 78 79 @Override 80 public void run() { 81 if (Thread.currentThread() == this && !hasRun) { 82 hasRun = true; 83 super.run(); 84 } 85 } 86 87 // Use Unsafe to access Thread group and ThreadGroup parent fields 88 static { 89 try { 90 ACC = new AccessControlContext(new ProtectionDomain[] { 91 new ProtectionDomain(null, null) 92 }); 93 94 // Find and use topmost ThreadGroup as parent of new group 95 UNSAFE = Unsafe.getUnsafe(); 96 Class<?> tk = Thread.class; 97 Class<?> gk = ThreadGroup.class; 98 99 INHERITEDACCESSCONTROLCONTEXT = UNSAFE.objectFieldOffset 100 (tk.getDeclaredField("inheritedAccessControlContext")); 101 CONTEXTCLASSLOADER = UNSAFE.objectFieldOffset 102 (tk.getDeclaredField("contextClassLoader")); 103 104 long tg = UNSAFE.objectFieldOffset(tk.getDeclaredField("group")); 105 long gp = UNSAFE.objectFieldOffset(gk.getDeclaredField("parent")); 106 ThreadGroup group = (ThreadGroup) 107 UNSAFE.getObject(Thread.currentThread(), tg); 108 109 while (group != null) { 110 ThreadGroup parent = (ThreadGroup)UNSAFE.getObject(group, gp); 111 if (parent == null) 112 break; 113 group = parent; 114 } 115 final ThreadGroup root = group; 116 INNOCUOUSTHREADGROUP = AccessController.doPrivileged( 117 (PrivilegedAction<ThreadGroup>) () -> 118 { return new ThreadGroup(root, "InnocuousThreadGroup"); }); 119 } catch (Exception e) { 120 throw new Error(e); 121 } 122 } 123 }