--- /dev/null	2018-04-24 16:10:17.224000000 +0530
+++ new/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/memory/FileMapInfo.java	2018-04-25 08:29:44.401931000 +0530
@@ -0,0 +1,148 @@
+/*
+ * Copyright (c) 2018, Oracle and/or its affiliates. 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.
+ *
+ */
+
+package sun.jvm.hotspot.memory;
+
+import java.util.*;
+import sun.jvm.hotspot.debugger.Address;
+import sun.jvm.hotspot.runtime.VM;
+import sun.jvm.hotspot.runtime.VMObject;
+import sun.jvm.hotspot.runtime.VMObjectFactory;
+import sun.jvm.hotspot.types.*;
+
+public class FileMapInfo {
+  private static FileMapHeader header;
+  private static Address headerValue;
+
+  // Fields for class FileMapHeader
+  private static Address mdSpaceValue;
+  private static Address mdRegionBaseAddress;
+  private static Address mdRegionEndAddress;
+
+  // HashMap created by mapping the vTable addresses in the md region with
+  // the corresponding metadata type.
+  private static Map<Address, Type> vTableTypeMap;
+
+  private static Type metadataTypeArray[];
+
+  static {
+    VM.registerVMInitializedObserver(new Observer() {
+        public void update(Observable o, Object data) {
+          initialize(VM.getVM().getTypeDataBase());
+        }
+      });
+  }
+
+  private static void initialize(TypeDataBase db) {
+    // FileMapInfo
+    Type type = db.lookupType("FileMapInfo");
+    AddressField currentInfoField = type.getAddressField("_current_info");
+    long headerFieldOffset = type.getField("_header").getOffset();
+    Address headerAddress = currentInfoField.getValue().addOffsetTo(headerFieldOffset);
+    headerValue = headerAddress.getAddressAt(0);
+
+    // FileMapHeader
+    type = db.lookupType("FileMapInfo::FileMapHeader");
+    AddressField spaceField = type.getAddressField("_space[0]");
+    Address spaceValue = headerValue.addOffsetTo(type.getField("_space[0]").getOffset());
+    mdSpaceValue = spaceValue.addOffsetTo(3 * spaceField.getSize());
+
+    // SpaceInfo
+    type = db.lookupType("FileMapInfo::FileMapHeader::space_info");
+    long mdRegionBaseAddressOffset = type.getField("_addr._base").getOffset();
+    mdRegionBaseAddress = (mdSpaceValue.addOffsetTo(mdRegionBaseAddressOffset)).getAddressAt(0);
+    long mdRegionSizeOffset = type.getField("_used").getOffset();
+    long mdRegionSize = (mdSpaceValue.addOffsetTo(mdRegionSizeOffset)).getAddressAt(0).asLongValue();
+    mdRegionEndAddress = mdRegionBaseAddress.addOffsetTo(mdRegionSize);
+
+    populateMetadataTypeArray(db);
+  }
+
+  private static void populateMetadataTypeArray(TypeDataBase db) {
+    metadataTypeArray = new Type[8];
+
+    metadataTypeArray[0] = db.lookupType("ConstantPool");
+    metadataTypeArray[1] = db.lookupType("InstanceKlass");
+    metadataTypeArray[2] = db.lookupType("InstanceClassLoaderKlass");
+    metadataTypeArray[3] = db.lookupType("InstanceMirrorKlass");
+    metadataTypeArray[4] = db.lookupType("InstanceRefKlass");
+    metadataTypeArray[5] = db.lookupType("Method");
+    metadataTypeArray[6] = db.lookupType("ObjArrayKlass");
+    metadataTypeArray[7] = db.lookupType("TypeArrayKlass");
+  }
+
+  public FileMapHeader getHeader() {
+    if (header == null) {
+      header = (FileMapHeader) VMObjectFactory.newObject(FileMapInfo.FileMapHeader.class, headerValue);
+    }
+    return header;
+  }
+
+  public boolean inCopiedVtableSpace(Address vptrAddress) {
+    FileMapHeader fmHeader = getHeader();
+    return fmHeader.inCopiedVtableSpace(vptrAddress);
+  }
+
+  public Type getTypeForVptrAddress(Address vptrAddress) {
+    if (vTableTypeMap == null) {
+      getHeader().createVtableTypeMapping();
+    }
+    return vTableTypeMap.get(vptrAddress);
+  }
+
+
+  //------------------------------------------------------------------------------------------
+
+  public static class FileMapHeader extends VMObject {
+
+    public FileMapHeader(Address addr) {
+      super(addr);
+    }
+
+    public boolean inCopiedVtableSpace(Address vptrAddress) {
+      if (vptrAddress.greaterThan(mdRegionBaseAddress) &&
+          vptrAddress.lessThanOrEqual(mdRegionEndAddress)) {
+        return true;
+      }
+      return false;
+    }
+
+    public void createVtableTypeMapping() {
+      vTableTypeMap = new HashMap<Address, Type>();
+      long metadataVTableSize = 0;
+      long addressSize = VM.getVM().getAddressSize();
+
+      Address copiedVtableAddress = mdRegionBaseAddress;
+      for (int i=0; i < metadataTypeArray.length; i++) {
+        // The first entry denotes the vtable size.
+        metadataVTableSize = copiedVtableAddress.getAddressAt(0).asLongValue();
+        vTableTypeMap.put(copiedVtableAddress.addOffsetTo(addressSize), metadataTypeArray[i]);
+
+        // The '+ 1' below is to skip the entry containing the size of this metadata's vtable.
+        copiedVtableAddress =
+          copiedVtableAddress.addOffsetTo((metadataVTableSize + 1) * addressSize);
+      }
+    }
+  }
+}