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 import java.lang.reflect.*;

    30 import java.net.MalformedURLException;

    31 import java.net.URL;

    32 import java.net.URLClassLoader;

    33 import java.nio.file.Paths;

    34 

    35 public class Agent implements ClassFileTransformer {

    36     public static ClassLoader newClassLoader() {

    37         try {

    38             return new URLClassLoader(new URL[] {

    39                     Paths.get(System.getProperty("test.classes",".")).toUri().toURL(),

    40             }, null);

    41         } catch (MalformedURLException e){

    42             throw new RuntimeException("Unexpected URL conversion failure", e);

    43         }

    44     }

    45 

    46     static public Class Test_class;

    47 

    48     static public void main(String[] args) throws Exception {

    49 

    50         // loader2 must be first on the list so loader 1 must be used first

    51         ClassLoader loader1 = newClassLoader();

    52         Class dummy = loader1.loadClass("Test");

    53 

    54         ClassLoader loader2 = newClassLoader();

    55 

    56         Test_class = loader2.loadClass("Test");

    57         Method m3 = Test_class.getMethod("m3", ClassLoader.class);

    58         // Add speculative trap in m2() (loaded by loader1) that

    59         // references m4() (loaded by loader2).

    60         m3.invoke(Test_class.newInstance(), loader1);

    61 

    62         String nameOfRunningVM = ManagementFactory.getRuntimeMXBean().getName();

    63         int p = nameOfRunningVM.indexOf('@');

    64         String pid = nameOfRunningVM.substring(0, p);

    65 

    66         // Make the nmethod go away

    67         for (int i = 0; i < 10; i++) {

    68             System.gc();

    69         }

    70 

    71         // Redefine class Test loaded by loader2

    72         for (int i = 0; i < 2; i++) {

    73             try {

    74                 VirtualMachine vm = VirtualMachine.attach(pid);

    75                 vm.loadAgent(System.getProperty("test.classes",".") + "/agent.jar", "");

    76                 vm.detach();

    77             } catch (Exception e) {

    78                 throw new RuntimeException(e);

    79             }

    80         }

    81         // Will process loader2 first, find m4() is redefined and

    82         // needs to be freed then process loader1, check the

    83         // speculative trap in m2() and try to access m4() which was

    84         // freed already.

    85         for (int i = 0; i < 10; i++) {

    86             System.gc();

    87         }

    88     }

    89 

    90     public synchronized byte[] transform(final ClassLoader classLoader,

    91                                          final String className,

    92                                          Class<?> classBeingRedefined,

    93                                          ProtectionDomain protectionDomain,

    94                                          byte[] classfileBuffer) {

    95         System.out.println("Transforming class " + className + " "+ classLoader);

    96         return classfileBuffer;

    97     }

    98 

    99     public static void redefine(String agentArgs, Instrumentation instrumentation, Class to_redefine) {

   100 

   101         try {

   102             instrumentation.retransformClasses(to_redefine);

   103         } catch (Exception e) {

   104             e.printStackTrace();

   105         }

   106 

   107     }

   108 

   109     public static void agentmain(String agentArgs, Instrumentation instrumentation) throws Exception {

   110         Agent transformer = new Agent();

   111         instrumentation.addTransformer(transformer, true);

   112 

   113         redefine(agentArgs, instrumentation, Test_class);

   114     }

   115 }