7158988: jvm crashes while debugging on x86_32 and x86_64

Summary: Object pointer is pushed more than once on stack, where GC doesn't expect it.
Reviewed-by: coleenp, kvn
Contributed-by: axel.siebenborn@sap.com

src/cpu/x86/vm/templateTable_x86_32.cpp

@@ -2651,56 +2651,49 @@ void TemplateTable::jvmti_post_fast_field_mod() {
     // Check to see if a field modification watch has been set before we take
     // the time to call into the VM.
     Label L2;
-    __ mov32(rcx, ExternalAddress((address)JvmtiExport::get_field_modification_count_addr()));
-    __ testl(rcx,rcx);
-    __ jcc(Assembler::zero, L2);
-    __ pop_ptr(rbx);               // copy the object pointer from tos
-    __ verify_oop(rbx);
-    __ push_ptr(rbx);              // put the object pointer back on tos
-    __ subptr(rsp, sizeof(jvalue));  // add space for a jvalue object
-    __ mov(rcx, rsp);
-    __ push_ptr(rbx);                 // save object pointer so we can steal rbx,
-    __ xorptr(rbx, rbx);
-    const Address lo_value(rcx, rbx, Address::times_1, 0*wordSize);
-    const Address hi_value(rcx, rbx, Address::times_1, 1*wordSize);
-    switch (bytecode()) {          // load values into the jvalue object
-    case Bytecodes::_fast_bputfield: __ movb(lo_value, rax); break;
-    case Bytecodes::_fast_sputfield: __ movw(lo_value, rax); break;
-    case Bytecodes::_fast_cputfield: __ movw(lo_value, rax); break;
-    case Bytecodes::_fast_iputfield: __ movl(lo_value, rax);                         break;
-    case Bytecodes::_fast_lputfield:
-      NOT_LP64(__ movptr(hi_value, rdx));
-      __ movptr(lo_value, rax);
-      break;
-
-    // need to call fld_s() after fstp_s() to restore the value for below
-    case Bytecodes::_fast_fputfield: __ fstp_s(lo_value); __ fld_s(lo_value);        break;
-
-    // need to call fld_d() after fstp_d() to restore the value for below
-    case Bytecodes::_fast_dputfield: __ fstp_d(lo_value); __ fld_d(lo_value);        break;
-
-    // since rcx is not an object we don't call store_check() here
-    case Bytecodes::_fast_aputfield: __ movptr(lo_value, rax);                       break;
-
-    default:  ShouldNotReachHere();
-    }
-    __ pop_ptr(rbx);  // restore copy of object pointer
-
-    // Save rax, and sometimes rdx because call_VM() will clobber them,
-    // then use them for JVM/DI purposes
-    __ push(rax);
-    if (bytecode() == Bytecodes::_fast_lputfield) __ push(rdx);
-    // access constant pool cache entry
-    __ get_cache_entry_pointer_at_bcp(rax, rdx, 1);
-    __ verify_oop(rbx);
-    // rbx,: object pointer copied above
-    // rax,: cache entry pointer
-    // rcx: jvalue object on the stack
-    __ call_VM(noreg, CAST_FROM_FN_PTR(address, InterpreterRuntime::post_field_modification), rbx, rax, rcx);
-    if (bytecode() == Bytecodes::_fast_lputfield) __ pop(rdx);  // restore high value
-    __ pop(rax);     // restore lower value
-    __ addptr(rsp, sizeof(jvalue));  // release jvalue object space
-    __ bind(L2);
+     __ mov32(rcx, ExternalAddress((address)JvmtiExport::get_field_modification_count_addr()));
+     __ testl(rcx,rcx);
+     __ jcc(Assembler::zero, L2);
+     __ pop_ptr(rbx);               // copy the object pointer from tos
+     __ verify_oop(rbx);
+     __ push_ptr(rbx);              // put the object pointer back on tos
+
+     // Save tos values before call_VM() clobbers them. Since we have
+     // to do it for every data type, we use the saved values as the
+     // jvalue object.
+     switch (bytecode()) {          // load values into the jvalue object
+     case Bytecodes::_fast_aputfield: __ push_ptr(rax); break;
+     case Bytecodes::_fast_bputfield: // fall through
+     case Bytecodes::_fast_sputfield: // fall through
+     case Bytecodes::_fast_cputfield: // fall through
+     case Bytecodes::_fast_iputfield: __ push_i(rax); break;
+     case Bytecodes::_fast_dputfield: __ push_d(); break;
+     case Bytecodes::_fast_fputfield: __ push_f(); break;
+     case Bytecodes::_fast_lputfield: __ push_l(rax); break;
+
+     default:
+       ShouldNotReachHere();
+     }
+     __ mov(rcx, rsp);              // points to jvalue on the stack
+     // access constant pool cache entry
+     __ get_cache_entry_pointer_at_bcp(rax, rdx, 1);
+     __ verify_oop(rbx);
+     // rbx,: object pointer copied above
+     // rax,: cache entry pointer
+     // rcx: jvalue object on the stack
+     __ call_VM(noreg, CAST_FROM_FN_PTR(address, InterpreterRuntime::post_field_modification), rbx, rax, rcx);
+
+     switch (bytecode()) {             // restore tos values
+     case Bytecodes::_fast_aputfield: __ pop_ptr(rax); break;
+     case Bytecodes::_fast_bputfield: // fall through
+     case Bytecodes::_fast_sputfield: // fall through
+     case Bytecodes::_fast_cputfield: // fall through
+     case Bytecodes::_fast_iputfield: __ pop_i(rax); break;
+     case Bytecodes::_fast_dputfield: __ pop_d(); break;
+     case Bytecodes::_fast_fputfield: __ pop_f(); break;
+     case Bytecodes::_fast_lputfield: __ pop_l(rax); break;
+     }
+     __ bind(L2);
   }
 }
 

src/cpu/x86/vm/templateTable_x86_64.cpp

@@ -2685,26 +2685,23 @@ void TemplateTable::jvmti_post_fast_field_mod() {
     __ pop_ptr(rbx);                  // copy the object pointer from tos
     __ verify_oop(rbx);
     __ push_ptr(rbx);                 // put the object pointer back on tos
-    __ subptr(rsp, sizeof(jvalue));  // add space for a jvalue object
-    __ mov(c_rarg3, rsp);
-    const Address field(c_rarg3, 0);
-
+    // Save tos values before call_VM() clobbers them. Since we have
+    // to do it for every data type, we use the saved values as the
+    // jvalue object.
     switch (bytecode()) {          // load values into the jvalue object
-    case Bytecodes::_fast_aputfield: __ movq(field, rax); break;
-    case Bytecodes::_fast_lputfield: __ movq(field, rax); break;
-    case Bytecodes::_fast_iputfield: __ movl(field, rax); break;
-    case Bytecodes::_fast_bputfield: __ movb(field, rax); break;
+    case Bytecodes::_fast_aputfield: __ push_ptr(rax); break;
+    case Bytecodes::_fast_bputfield: // fall through
     case Bytecodes::_fast_sputfield: // fall through
-    case Bytecodes::_fast_cputfield: __ movw(field, rax); break;
-    case Bytecodes::_fast_fputfield: __ movflt(field, xmm0); break;
-    case Bytecodes::_fast_dputfield: __ movdbl(field, xmm0); break;
+    case Bytecodes::_fast_cputfield: // fall through
+    case Bytecodes::_fast_iputfield: __ push_i(rax); break;
+    case Bytecodes::_fast_dputfield: __ push_d(); break;
+    case Bytecodes::_fast_fputfield: __ push_f(); break;
+    case Bytecodes::_fast_lputfield: __ push_l(rax); break;
+
     default:
       ShouldNotReachHere();
     }
-
-    // Save rax because call_VM() will clobber it, then use it for
-    // JVMTI purposes
-    __ push(rax);
+    __ mov(c_rarg3, rsp);             // points to jvalue on the stack
     // access constant pool cache entry
     __ get_cache_entry_pointer_at_bcp(c_rarg2, rax, 1);
     __ verify_oop(rbx);
@@ -2715,8 +2712,17 @@ void TemplateTable::jvmti_post_fast_field_mod() {
                CAST_FROM_FN_PTR(address,
                                 InterpreterRuntime::post_field_modification),
                rbx, c_rarg2, c_rarg3);
-    __ pop(rax);     // restore lower value
-    __ addptr(rsp, sizeof(jvalue));  // release jvalue object space
+
+    switch (bytecode()) {             // restore tos values
+    case Bytecodes::_fast_aputfield: __ pop_ptr(rax); break;
+    case Bytecodes::_fast_bputfield: // fall through
+    case Bytecodes::_fast_sputfield: // fall through
+    case Bytecodes::_fast_cputfield: // fall through
+    case Bytecodes::_fast_iputfield: __ pop_i(rax); break;
+    case Bytecodes::_fast_dputfield: __ pop_d(); break;
+    case Bytecodes::_fast_fputfield: __ pop_f(); break;
+    case Bytecodes::_fast_lputfield: __ pop_l(rax); break;
+    }
     __ bind(L2);
   }
 }

test/runtime/7158988/FieldMonitor.java

+/*
+ * Copyright 2012 SAP AG.  All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test FieldMonitor.java
+ * @bug 7158988
+ * @summary verify jvm does not crash while debugging
+ * @run shell TestFieldMonitor.sh
+ * @author axel.siebenborn@sap.com
+ */
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.OutputStream;
+import java.io.OutputStreamWriter;
+import java.io.Reader;
+import java.io.Writer;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+
+import com.sun.jdi.Bootstrap;
+import com.sun.jdi.Field;
+import com.sun.jdi.ReferenceType;
+import com.sun.jdi.VirtualMachine;
+import com.sun.jdi.connect.Connector;
+import com.sun.jdi.connect.IllegalConnectorArgumentsException;
+import com.sun.jdi.connect.LaunchingConnector;
+import com.sun.jdi.connect.VMStartException;
+import com.sun.jdi.event.ClassPrepareEvent;
+import com.sun.jdi.event.Event;
+import com.sun.jdi.event.EventQueue;
+import com.sun.jdi.event.EventSet;
+import com.sun.jdi.event.ModificationWatchpointEvent;
+import com.sun.jdi.event.VMDeathEvent;
+import com.sun.jdi.event.VMDisconnectEvent;
+import com.sun.jdi.request.ClassPrepareRequest;
+import com.sun.jdi.request.EventRequest;
+import com.sun.jdi.request.EventRequestManager;
+import com.sun.jdi.request.ModificationWatchpointRequest;
+
+public class FieldMonitor {
+
+  public static final String CLASS_NAME = "TestPostFieldModification";
+  public static final String FIELD_NAME = "value";
+  public static final String ARGUMENTS = "-Xshare:off -XX:+PrintGC";
+
+  public static void main(String[] args)
+      throws IOException, InterruptedException {
+
+    StringBuffer sb = new StringBuffer();
+
+    for (int i=0; i < args.length; i++) {
+        sb.append(' ');
+        sb.append(args[i]);
+    }
+    //VirtualMachine vm = launchTarget(sb.toString());
+    VirtualMachine vm = launchTarget(CLASS_NAME);
+
+    System.out.println("Vm launched");
+    // set watch field on already loaded classes
+    List<ReferenceType> referenceTypes = vm
+        .classesByName(CLASS_NAME);
+    for (ReferenceType refType : referenceTypes) {
+      addFieldWatch(vm, refType);
+    }
+    // watch for loaded classes
+    addClassWatch(vm);
+
+    // process events
+    EventQueue eventQueue = vm.eventQueue();
+    // resume the vm
+
+    Process process = vm.process();
+
+
+    // Copy target's output and error to our output and error.
+    Thread outThread = new StreamRedirectThread("out reader", process.getInputStream());
+    Thread errThread = new StreamRedirectThread("error reader", process.getErrorStream());
+
+    errThread.start();
+    outThread.start();
+
+
+    vm.resume();
+    boolean connected = true;
+    while (connected) {
+      EventSet eventSet = eventQueue.remove();
+      for (Event event : eventSet) {
+        if (event instanceof VMDeathEvent
+            || event instanceof VMDisconnectEvent) {
+          // exit
+          connected = false;
+        } else if (event instanceof ClassPrepareEvent) {
+          // watch field on loaded class
+          System.out.println("ClassPrepareEvent");
+          ClassPrepareEvent classPrepEvent = (ClassPrepareEvent) event;
+          ReferenceType refType = classPrepEvent
+              .referenceType();
+          addFieldWatch(vm, refType);
+        } else if (event instanceof ModificationWatchpointEvent) {
+          System.out.println("sleep for 500 ms");
+          Thread.sleep(500);
+          System.out.println("resume...");
+
+          ModificationWatchpointEvent modEvent = (ModificationWatchpointEvent) event;
+          System.out.println("old="
+              + modEvent.valueCurrent());
+          System.out.println("new=" + modEvent.valueToBe());
+          System.out.println();
+        }
+      }
+      eventSet.resume();
+    }
+    // Shutdown begins when event thread terminates
+    try {
+        errThread.join(); // Make sure output is forwarded
+        outThread.join();
+    } catch (InterruptedException exc) {
+        // we don't interrupt
+    }
+  }
+
+  /**
+   * Find a com.sun.jdi.CommandLineLaunch connector
+   */
+  static LaunchingConnector findLaunchingConnector() {
+    List <Connector> connectors = Bootstrap.virtualMachineManager().allConnectors();
+    Iterator <Connector> iter = connectors.iterator();
+    while (iter.hasNext()) {
+      Connector connector = iter.next();
+      if (connector.name().equals("com.sun.jdi.CommandLineLaunch")) {
+        return (LaunchingConnector)connector;
+      }
+    }
+    throw new Error("No launching connector");
+  }
+  /**
+   * Return the launching connector's arguments.
+   */
+ static Map <String,Connector.Argument> connectorArguments(LaunchingConnector connector, String mainArgs) {
+      Map<String,Connector.Argument> arguments = connector.defaultArguments();
+      for (String key : arguments.keySet()) {
+        System.out.println(key);
+      }
+
+      Connector.Argument mainArg = (Connector.Argument)arguments.get("main");
+      if (mainArg == null) {
+          throw new Error("Bad launching connector");
+      }
+      mainArg.setValue(mainArgs);
+
+      Connector.Argument optionsArg = (Connector.Argument)arguments.get("options");
+      if (optionsArg == null) {
+        throw new Error("Bad launching connector");
+      }
+      optionsArg.setValue(ARGUMENTS);
+      return arguments;
+  }
+
+ static VirtualMachine launchTarget(String mainArgs) {
+    LaunchingConnector connector = findLaunchingConnector();
+    Map  arguments = connectorArguments(connector, mainArgs);
+    try {
+        return (VirtualMachine) connector.launch(arguments);
+    } catch (IOException exc) {
+        throw new Error("Unable to launch target VM: " + exc);
+    } catch (IllegalConnectorArgumentsException exc) {
+        throw new Error("Internal error: " + exc);
+    } catch (VMStartException exc) {
+        throw new Error("Target VM failed to initialize: " +
+                        exc.getMessage());
+    }
+}
+
+
+  private static void addClassWatch(VirtualMachine vm) {
+    EventRequestManager erm = vm.eventRequestManager();
+    ClassPrepareRequest classPrepareRequest = erm
+        .createClassPrepareRequest();
+    classPrepareRequest.addClassFilter(CLASS_NAME);
+    classPrepareRequest.setEnabled(true);
+  }
+
+
+  private static void addFieldWatch(VirtualMachine vm,
+      ReferenceType refType) {
+    EventRequestManager erm = vm.eventRequestManager();
+    Field field = refType.fieldByName(FIELD_NAME);
+    ModificationWatchpointRequest modificationWatchpointRequest = erm
+        .createModificationWatchpointRequest(field);
+    modificationWatchpointRequest.setSuspendPolicy(EventRequest.SUSPEND_EVENT_THREAD);
+    modificationWatchpointRequest.setEnabled(true);
+  }
+}
+
+class StreamRedirectThread extends Thread {
+
+  private final BufferedReader in;
+
+  private static final int BUFFER_SIZE = 2048;
+
+  /**
+   * Set up for copy.
+   * @param name  Name of the thread
+   * @param in    Stream to copy from
+   * @param out   Stream to copy to
+   */
+  StreamRedirectThread(String name, InputStream in) {
+    super(name);
+    this.in = new BufferedReader(new InputStreamReader(in));
+  }
+
+  /**
+   * Copy.
+   */
+  public void run() {
+    try {
+      String line;
+        while ((line = in.readLine ()) != null) {
+          System.out.println ("testvm: " + line);
+      }
+     System.out.flush();
+    } catch(IOException exc) {
+      System.err.println("Child I/O Transfer - " + exc);
+    }
+  }
+}

test/runtime/7158988/TestFieldMonitor.sh

+#!/bin/sh
+
+if [ "${TESTSRC}" = "" ]
+then TESTSRC=.
+fi
+
+if [ "${TESTJAVA}" = "" ]
+then
+  PARENT=`dirname \`which java\``
+  TESTJAVA=`dirname ${PARENT}`
+  echo "TESTJAVA not set, selecting " ${TESTJAVA}
+  echo "If this is incorrect, try setting the variable manually."
+fi
+
+if [ "${TESTCLASSES}" = "" ]
+then
+  echo "TESTCLASSES not set.  Test cannot execute.  Failed."
+  exit 1
+fi
+
+BIT_FLAG=""
+
+# set platform-dependent variables
+OS=`uname -s`
+case "$OS" in
+  SunOS | Linux )
+    NULL=/dev/null
+    PS=":"
+    FS="/"
+    ## for solaris, linux it's HOME
+    FILE_LOCATION=$HOME
+    if [ -f ${FILE_LOCATION}${FS}JDK64BIT -a ${OS} = "SunOS" -a `uname -p`='sparc' ]
+    then
+        BIT_FLAG="-d64"
+    fi
+    ;;
+  Windows_95 | Windows_98 | Windows_ME )
+    NULL=NUL
+    PS=";"
+    FS="\\"
+    echo "Test skipped, only for WinNT"
+    exit 0
+    ;;
+  Windows_NT )
+    NULL=NUL
+    PS=";"
+    FS="\\"
+    ;;
+  * )
+    echo "Unrecognized system!"
+    exit 1;
+    ;;
+esac
+
+#CLASSPATH=.${PS}${TESTCLASSES} ; export CLASSPATH
+
+cp ${TESTSRC}${FS}*.java .
+
+${TESTJAVA}${FS}bin${FS}java ${BIT_FLAG} -fullversion
+
+${TESTJAVA}${FS}bin${FS}javac -classpath .${PS}$TESTJAVA${FS}lib${FS}tools.jar *.java
+
+${TESTJAVA}${FS}bin${FS}java ${BIT_FLAG} -classpath .${PS}$TESTJAVA${FS}lib${FS}tools.jar FieldMonitor > test.out 2>&1 &
+
+P_PID=$!
+
+sleep 60
+STATUS=0
+
+case "$OS" in
+    SunOS | Linux )
+        ps -ef | grep $P_PID | grep -v grep > ${NULL}
+        if [ $? = 0 ]; then
+            kill -9 $P_PID
+            STATUS=1
+        fi
+        ;;
+      * )
+        ps | grep -i "FieldMonitor" | grep -v grep > ${NULL}
+        if [ $? = 0 ]; then
+            C_PID=`ps | grep -i "FieldMonitor" | awk '{print $1}'`
+            kill -s 9 $C_PID
+            STATUS=1
+        fi
+        ;;
+esac
+
+grep "A fatal error has been detected" test.out > ${NULL}
+if [ $? = 0 ]; then
+    cat test.out
+    STATUS=1
+fi
+
+exit $STATUS

test/runtime/7158988/TestPostFieldModification.java

+/*
+ * Copyright 2012 SAP AG.  All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test FieldMonitor.java
+ * @bug 7158988
+ * @summary verify jvm does not crash while debugging
+ * @run shell TestFieldMonitor.sh
+ * @author axel.siebenborn@sap.com
+ */
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.OutputStream;
+import java.io.OutputStreamWriter;
+import java.io.Reader;
+import java.io.Writer;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+
+import com.sun.jdi.Bootstrap;
+import com.sun.jdi.Field;
+import com.sun.jdi.ReferenceType;
+import com.sun.jdi.VirtualMachine;
+import com.sun.jdi.connect.Connector;
+import com.sun.jdi.connect.IllegalConnectorArgumentsException;
+import com.sun.jdi.connect.LaunchingConnector;
+import com.sun.jdi.connect.VMStartException;
+import com.sun.jdi.event.ClassPrepareEvent;
+import com.sun.jdi.event.Event;
+import com.sun.jdi.event.EventQueue;
+import com.sun.jdi.event.EventSet;
+import com.sun.jdi.event.ModificationWatchpointEvent;
+import com.sun.jdi.event.VMDeathEvent;
+import com.sun.jdi.event.VMDisconnectEvent;
+import com.sun.jdi.request.ClassPrepareRequest;
+import com.sun.jdi.request.EventRequest;
+import com.sun.jdi.request.EventRequestManager;
+import com.sun.jdi.request.ModificationWatchpointRequest;
+
+public class FieldMonitor {
+
+  public static final String CLASS_NAME = "TestPostFieldModification";
+  public static final String FIELD_NAME = "value";
+  public static final String ARGUMENTS = "-Xshare:off -XX:+PrintGC";
+
+  public static void main(String[] args)
+      throws IOException, InterruptedException {
+
+    StringBuffer sb = new StringBuffer();
+
+    for (int i=0; i < args.length; i++) {
+        sb.append(' ');
+        sb.append(args[i]);
+    }
+    //VirtualMachine vm = launchTarget(sb.toString());
+    VirtualMachine vm = launchTarget(CLASS_NAME);
+
+    System.out.println("Vm launched");
+    // set watch field on already loaded classes
+    List<ReferenceType> referenceTypes = vm
+        .classesByName(CLASS_NAME);
+    for (ReferenceType refType : referenceTypes) {
+      addFieldWatch(vm, refType);
+    }
+    // watch for loaded classes
+    addClassWatch(vm);
+
+    // process events
+    EventQueue eventQueue = vm.eventQueue();
+    // resume the vm
+
+    Process process = vm.process();
+
+
+    // Copy target's output and error to our output and error.
+    Thread outThread = new StreamRedirectThread("out reader", process.getInputStream());
+    Thread errThread = new StreamRedirectThread("error reader", process.getErrorStream());
+
+    errThread.start();
+    outThread.start();
+
+
+    vm.resume();
+    boolean connected = true;
+    while (connected) {
+      EventSet eventSet = eventQueue.remove();
+      for (Event event : eventSet) {
+        if (event instanceof VMDeathEvent
+            || event instanceof VMDisconnectEvent) {
+          // exit
+          connected = false;
+        } else if (event instanceof ClassPrepareEvent) {
+          // watch field on loaded class
+          System.out.println("ClassPrepareEvent");
+          ClassPrepareEvent classPrepEvent = (ClassPrepareEvent) event;
+          ReferenceType refType = classPrepEvent
+              .referenceType();
+          addFieldWatch(vm, refType);
+        } else if (event instanceof ModificationWatchpointEvent) {
+          System.out.println("sleep for 500 ms");
+          Thread.sleep(500);
+          System.out.println("resume...");
+
+          ModificationWatchpointEvent modEvent = (ModificationWatchpointEvent) event;
+          System.out.println("old="
+              + modEvent.valueCurrent());
+          System.out.println("new=" + modEvent.valueToBe());
+          System.out.println();
+        }
+      }
+      eventSet.resume();
+    }
+    // Shutdown begins when event thread terminates
+    try {
+        errThread.join(); // Make sure output is forwarded
+        outThread.join();
+    } catch (InterruptedException exc) {
+        // we don't interrupt
+    }
+  }
+
+  /**
+   * Find a com.sun.jdi.CommandLineLaunch connector
+   */
+  static LaunchingConnector findLaunchingConnector() {
+    List <Connector> connectors = Bootstrap.virtualMachineManager().allConnectors();
+    Iterator <Connector> iter = connectors.iterator();
+    while (iter.hasNext()) {
+      Connector connector = iter.next();
+      if (connector.name().equals("com.sun.jdi.CommandLineLaunch")) {
+        return (LaunchingConnector)connector;
+      }
+    }
+    throw new Error("No launching connector");
+  }
+  /**
+   * Return the launching connector's arguments.
+   */
+ static Map <String,Connector.Argument> connectorArguments(LaunchingConnector connector, String mainArgs) {
+      Map<String,Connector.Argument> arguments = connector.defaultArguments();
+      for (String key : arguments.keySet()) {
+        System.out.println(key);
+      }
+
+      Connector.Argument mainArg = (Connector.Argument)arguments.get("main");
+      if (mainArg == null) {
+          throw new Error("Bad launching connector");
+      }
+      mainArg.setValue(mainArgs);
+
+      Connector.Argument optionsArg = (Connector.Argument)arguments.get("options");
+      if (optionsArg == null) {
+        throw new Error("Bad launching connector");
+      }
+      optionsArg.setValue(ARGUMENTS);
+      return arguments;
+  }
+
+ static VirtualMachine launchTarget(String mainArgs) {
+    LaunchingConnector connector = findLaunchingConnector();
+    Map  arguments = connectorArguments(connector, mainArgs);
+    try {
+        return (VirtualMachine) connector.launch(arguments);
+    } catch (IOException exc) {
+        throw new Error("Unable to launch target VM: " + exc);
+    } catch (IllegalConnectorArgumentsException exc) {
+        throw new Error("Internal error: " + exc);
+    } catch (VMStartException exc) {
+        throw new Error("Target VM failed to initialize: " +
+                        exc.getMessage());
+    }
+}
+
+
+  private static void addClassWatch(VirtualMachine vm) {
+    EventRequestManager erm = vm.eventRequestManager();
+    ClassPrepareRequest classPrepareRequest = erm
+        .createClassPrepareRequest();
+    classPrepareRequest.addClassFilter(CLASS_NAME);
+    classPrepareRequest.setEnabled(true);
+  }
+
+
+  private static void addFieldWatch(VirtualMachine vm,
+      ReferenceType refType) {
+    EventRequestManager erm = vm.eventRequestManager();
+    Field field = refType.fieldByName(FIELD_NAME);
+    ModificationWatchpointRequest modificationWatchpointRequest = erm
+        .createModificationWatchpointRequest(field);
+    modificationWatchpointRequest.setSuspendPolicy(EventRequest.SUSPEND_EVENT_THREAD);
+    modificationWatchpointRequest.setEnabled(true);
+  }
+}
+
+class StreamRedirectThread extends Thread {
+
+  private final BufferedReader in;
+
+  private static final int BUFFER_SIZE = 2048;
+
+  /**
+   * Set up for copy.
+   * @param name  Name of the thread
+   * @param in    Stream to copy from
+   * @param out   Stream to copy to
+   */
+  StreamRedirectThread(String name, InputStream in) {
+    super(name);
+    this.in = new BufferedReader(new InputStreamReader(in));
+  }
+
+  /**
+   * Copy.
+   */
+  public void run() {
+    try {
+      String line;
+        while ((line = in.readLine ()) != null) {
+          System.out.println ("testvm: " + line);
+      }
+     System.out.flush();
+    } catch(IOException exc) {
+      System.err.println("Child I/O Transfer - " + exc);
+    }
+  }
+}