1 /* 2 * Copyright (c) 2013, 2014, 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. 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 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 */ 23 import java.security.*; 24 import java.lang.instrument.*; 25 import java.lang.reflect.*; 26 27 public class Agent implements ClassFileTransformer { 28 public synchronized byte[] transform(final ClassLoader classLoader, 29 final String className, 30 Class<?> classBeingRedefined, 31 ProtectionDomain protectionDomain, 32 byte[] classfileBuffer) { 33 System.out.println("Transforming class " + className); 34 return classfileBuffer; 35 } 36 37 public static void redefine(String agentArgs, Instrumentation instrumentation, Class to_redefine) { 38 39 try { 40 instrumentation.retransformClasses(to_redefine); 41 } catch (Exception e) { 42 e.printStackTrace(); 43 } 44 45 } 46 47 public static void premain(String agentArgs, Instrumentation instrumentation) { 48 Agent transformer = new Agent(); 49 instrumentation.addTransformer(transformer, true); 50 51 // Redefine java/lang/Object and java/lang/reflect/Method.invoke and 52 // java/lang/ClassLoader 53 Class object_class = Object.class; 54 redefine(agentArgs, instrumentation, object_class); 55 56 Class method_class = Method.class; 57 redefine(agentArgs, instrumentation, method_class); 58 59 Class loader_class = ClassLoader.class; 60 redefine(agentArgs, instrumentation, loader_class); 61 62 instrumentation.removeTransformer(transformer); 63 } 64 65 public static void main(String[] args) { 66 byte[] ba = new byte[0]; 67 68 // If it survives 100 GC's, it's good. 69 for (int i = 0; i < 100 ; i++) { 70 System.gc(); 71 ba.clone(); 72 } 73 try { 74 // Use java/lang/reflect/Method.invoke to call 75 WalkThroughInvoke a = new WalkThroughInvoke(); 76 Class aclass = WalkThroughInvoke.class; 77 Method m = aclass.getMethod("stackWalk"); 78 m.invoke(a); 79 } catch (Exception x) { 80 x.printStackTrace(); 81 } 82 } 83 }