1 /* 2 * Copyright (c) 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 24 import java.security.*; 25 import java.lang.instrument.*; 26 import java.lang.reflect.*; 27 import java.lang.management.ManagementFactory; 28 import com.sun.tools.attach.VirtualMachine; 29 30 class A { 31 void m() { 32 } 33 } 34 35 class B extends A { 36 void m() { 37 } 38 } 39 40 class C extends A { 41 void m() { 42 } 43 } 44 45 class Test { 46 47 static public void m() throws Exception { 48 for (int i = 0; i < 20000; i++) { 49 m1(a); 50 } 51 for (int i = 0; i < 4; i++) { 52 m1(b); 53 } 54 } 55 56 static boolean m1(A a) { 57 boolean res = Agent.m2(a); 58 return res; 59 } 60 61 static public A a = new A(); 62 static public B b = new B(); 63 static public C c = new C(); 64 } 65 66 public class Agent implements ClassFileTransformer { 67 68 69 static public boolean m2(A a) { 70 boolean res = false; 71 if (a.getClass() == B.class) { 72 a.m(); 73 } else { 74 res = true; 75 } 76 return res; 77 } 78 79 static public void main(String[] args) throws Exception { 80 // Create speculative trap entries 81 Test.m(); 82 83 String nameOfRunningVM = ManagementFactory.getRuntimeMXBean().getName(); 84 int p = nameOfRunningVM.indexOf('@'); 85 String pid = nameOfRunningVM.substring(0, p); 86 87 // Make the nmethod go away 88 for (int i = 0; i < 10; i++) { 89 System.gc(); 90 } 91 92 // Redefine class 93 try { 94 VirtualMachine vm = VirtualMachine.attach(pid); 95 vm.loadAgent(System.getProperty("test.classes",".") + "/agent.jar", ""); 96 vm.detach(); 97 } catch (Exception e) { 98 throw new RuntimeException(e); 99 } 100 101 Test.m(); 102 // GC will hit dead method pointer 103 for (int i = 0; i < 10; i++) { 104 System.gc(); 105 } 106 } 107 108 public synchronized byte[] transform(final ClassLoader classLoader, 109 final String className, 110 Class<?> classBeingRedefined, 111 ProtectionDomain protectionDomain, 112 byte[] classfileBuffer) { 113 System.out.println("Transforming class " + className); 114 return classfileBuffer; 115 } 116 117 public static void redefine(String agentArgs, Instrumentation instrumentation, Class to_redefine) { 118 119 try { 120 instrumentation.retransformClasses(to_redefine); 121 } catch (Exception e) { 122 e.printStackTrace(); 123 } 124 125 } 126 127 public static void agentmain(String agentArgs, Instrumentation instrumentation) throws Exception { 128 Agent transformer = new Agent(); 129 instrumentation.addTransformer(transformer, true); 130 131 redefine(agentArgs, instrumentation, Test.class); 132 } 133 }