--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/gc/z/ZPage.java	Tue Jun 12 17:40:28 2018 +0200
@@ -0,0 +1,108 @@
+/*
+ * 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.gc.z;
+
+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.CIntegerField;
+import sun.jvm.hotspot.types.Type;
+import sun.jvm.hotspot.types.TypeDataBase;
+
+public class ZPage extends VMObject {
+    private static CIntegerField typeField;
+    private static long virtualFieldOffset;
+    private static long forwardingFieldOffset;
+
+    static {
+        VM.registerVMInitializedObserver((o, d) -> initialize(VM.getVM().getTypeDataBase()));
+    }
+
+    static private synchronized void initialize(TypeDataBase db) {
+        Type type = db.lookupType("ZPage");
+
+        typeField = type.getCIntegerField("_type");
+        virtualFieldOffset = type.getField("_virtual").getOffset();
+        forwardingFieldOffset = type.getField("_forwarding").getOffset();
+    }
+
+    public ZPage(Address addr) {
+        super(addr);
+    }
+
+    private byte type() {
+        return typeField.getJByte(addr);
+    }
+
+    private ZVirtualMemory virtual() {
+        return (ZVirtualMemory)VMObjectFactory.newObject(ZVirtualMemory.class, addr.addOffsetTo(virtualFieldOffset));
+    }
+
+    private ZForwardingTable forwarding() {
+        return (ZForwardingTable)VMObjectFactory.newObject(ZForwardingTable.class, addr.addOffsetTo(forwardingFieldOffset));
+    }
+
+    private long start() {
+        return virtual().start();
+    }
+
+    Address forward_object(Address from) {
+        // Lookup address in forwarding table
+        long from_offset = ZAddress.offset(from);
+        long from_index = (from_offset - start()) >> object_alignment_shift();
+        ZForwardingTableEntry entry = forwarding().find(from_index);
+        assert(!entry.is_empty());
+        assert(entry.from_index() == from_index);
+
+        return ZAddress.good(entry.to_offset());
+    }
+
+    Address relocate_object(Address from) {
+        // Lookup address in forwarding table
+        long from_offset = ZAddress.offset(from);
+        long from_index = (from_offset - start()) >> object_alignment_shift();
+        ZForwardingTableEntry entry = forwarding().find(from_index);
+        if (!entry.is_empty() && entry.from_index() == from_index) {
+          return ZAddress.good(entry.to_offset());
+        }
+
+        // There's no relocate operation in the SA.
+        // Mimic object pinning and return the good view of the from object.
+        return ZAddress.good(from);
+    }
+
+
+    long object_alignment_shift() {
+        if (type() == ZGlobals.ZPageTypeSmall) {
+            return ZGlobals.ZObjectAlignmentSmallShift();
+        } else if (type() == ZGlobals.ZPageTypeMedium) {
+            return ZGlobals.ZObjectAlignmentMediumShift;
+        } else {
+            assert(type() == ZGlobals.ZPageTypeLarge);
+            return ZGlobals.ZObjectAlignmentLargeShift;
+        }
+    }
+}