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 }