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 class MemoryChunk {
  70         MemoryChunk other;
  71         long[] array;
  72         MemoryChunk(MemoryChunk other) {
  73             other = other;
  74             array = new long[1024 * 1024 * 1024];
  75         }
  76     }
  77 
  78     static public boolean m2(A a) {
  79         boolean res = false;
  80         if (a.getClass() == B.class) {
  81             a.m();
  82         } else {
  83             res = true;
  84         }
  85         return res;
  86     }
  87 
  88     static public void main(String[] args) throws Exception {
  89         // Create speculative trap entries
  90         Test.m();
  91 
  92         String nameOfRunningVM = ManagementFactory.getRuntimeMXBean().getName();
  93         int p = nameOfRunningVM.indexOf('@');
  94         String pid = nameOfRunningVM.substring(0, p);
  95 
  96         // Make the nmethod go away
  97         for (int i = 0; i < 10; i++) {
  98             System.gc();
  99         }
 100 
 101         // Redefine class
 102         try {
 103             VirtualMachine vm = VirtualMachine.attach(pid);
 104             vm.loadAgent(System.getProperty("test.classes",".") + "/agent.jar", "");
 105             vm.detach();
 106         } catch (Exception e) {
 107             throw new RuntimeException(e);
 108         }
 109 
 110         Test.m();
 111         // GC will hit dead method pointer
 112         for (int i = 0; i < 10; i++) {
 113             System.gc();
 114         }
 115     }
 116 
 117     public synchronized byte[] transform(final ClassLoader classLoader,
 118                                          final String className,
 119                                          Class<?> classBeingRedefined,
 120                                          ProtectionDomain protectionDomain,
 121                                          byte[] classfileBuffer) {
 122         System.out.println("Transforming class " + className);
 123         return classfileBuffer;
 124     }
 125 
 126     public static void redefine(String agentArgs, Instrumentation instrumentation, Class to_redefine) {
 127 
 128         try {
 129             instrumentation.retransformClasses(to_redefine);
 130         } catch (Exception e) {
 131             e.printStackTrace();
 132         }
 133 
 134     }
 135 
 136     public static void agentmain(String agentArgs, Instrumentation instrumentation) throws Exception {
 137         Agent transformer = new Agent();
 138         instrumentation.addTransformer(transformer, true);
 139 
 140         redefine(agentArgs, instrumentation, Test.class);
 141     }
 142 }