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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 | } | ||