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| 1 | +/* | |
| 2 | + * Copyright (c) 2001, 2008, 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.reflect; | |
| 27 | + | |
| 28 | +import java.security.AccessController; | |
| 29 | +import java.security.PrivilegedAction; | |
| 30 | +import sun.misc.Unsafe; | |
| 31 | + | |
| 32 | +/** Utility class which assists in calling Unsafe.defineClass() by | |
| 33 | + creating a new class loader which delegates to the one needed in | |
| 34 | + order for proper resolution of the given bytecodes to occur. */ | |
| 35 | + | |
| 36 | +class ClassDefiner { | |
| 37 | + static final Unsafe unsafe = Unsafe.getUnsafe(); | |
| 38 | + | |
| 39 | + /** <P> We define generated code into a new class loader which | |
| 40 | + delegates to the defining loader of the target class. It is | |
| 41 | + necessary for the VM to be able to resolve references to the | |
| 42 | + target class from the generated bytecodes, which could not occur | |
| 43 | + if the generated code was loaded into the bootstrap class | |
| 44 | + loader. </P> | |
| 45 | + | |
| 46 | + <P> There are two primary reasons for creating a new loader | |
| 47 | + instead of defining these bytecodes directly into the defining | |
| 48 | + loader of the target class: first, it avoids any possible | |
| 49 | + security risk of having these bytecodes in the same loader. | |
| 50 | + Second, it allows the generated bytecodes to be unloaded earlier | |
| 51 | + than would otherwise be possible, decreasing run-time | |
| 52 | + footprint. </P> | |
| 53 | + */ | |
| 54 | + static Class defineClass(String name, byte[] bytes, int off, int len, | |
| 55 | + final ClassLoader parentClassLoader) | |
| 56 | + { | |
| 57 | + ClassLoader newLoader = AccessController.doPrivileged( | |
| 58 | + new PrivilegedAction<ClassLoader>() { | |
| 59 | + public ClassLoader run() { | |
| 60 | + return new DelegatingClassLoader(parentClassLoader); | |
| 61 | + } | |
| 62 | + }); | |
| 63 | + return unsafe.defineClass(name, bytes, off, len, newLoader, null); | |
| 64 | + } | |
| 65 | +} | |
| 66 | + | |
| 67 | + | |
| 68 | +// NOTE: this class's name and presence are known to the virtual | |
| 69 | +// machine as of the fix for 4474172. | |
| 70 | +class DelegatingClassLoader extends ClassLoader { | |
| 71 | + DelegatingClassLoader(ClassLoader parent) { | |
| 72 | + super(parent); | |
| 73 | + } | |
| 74 | +} | |