1 /*
   2  * Copyright (c) 2018, 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 
  25 package sun.jvm.hotspot.gc.z;
  26 
  27 import sun.jvm.hotspot.debugger.Address;
  28 import sun.jvm.hotspot.runtime.VM;
  29 import sun.jvm.hotspot.runtime.VMObject;
  30 import sun.jvm.hotspot.types.CIntegerField;
  31 import sun.jvm.hotspot.types.Type;
  32 import sun.jvm.hotspot.types.TypeDataBase;
  33 
  34 class ZPage extends VMObject {
  35     private static CIntegerField typeField;
  36     private static long virtualFieldOffset;
  37     private static long forwardingFieldOffset;
  38 
  39     static {
  40         VM.registerVMInitializedObserver((o, d) -> initialize(VM.getVM().getTypeDataBase()));
  41     }
  42 
  43     static private synchronized void initialize(TypeDataBase db) {
  44         Type type = db.lookupType("ZPage");
  45 
  46         typeField = type.getCIntegerField("_type");
  47         virtualFieldOffset = type.getField("_virtual").getOffset();
  48         forwardingFieldOffset = type.getField("_forwarding").getOffset();
  49     }
  50 
  51     ZPage(Address addr) {
  52         super(addr);
  53     }
  54 
  55     private byte type() {
  56         return typeField.getJByte(addr);
  57     }
  58 
  59     private ZVirtualMemory virtual() {
  60         return new ZVirtualMemory(addr.addOffsetTo(virtualFieldOffset));
  61     }
  62 
  63     private ZForwardingTable forwarding() {
  64         return new ZForwardingTable(addr.addOffsetTo(forwardingFieldOffset));
  65     }
  66 
  67     private long start() {
  68         return virtual().start();
  69     }
  70 
  71     Address forward_object(Address from) {
  72         // Lookup address in forwarding table
  73         long from_offset = ZAddress.offset(from);
  74         long from_index = (from_offset - start()) >> object_alignment_shift();
  75         ZForwardingTableEntry entry = forwarding().find(from_index);
  76         assert(!entry.is_empty());
  77         assert(entry.from_index() == from_index);
  78 
  79         return ZAddress.good(entry.to_offset());
  80     }
  81 
  82     Address relocate_object(Address from) {
  83         // Lookup address in forwarding table
  84         long from_offset = ZAddress.offset(from);
  85         long from_index = (from_offset - start()) >> object_alignment_shift();
  86         ZForwardingTableEntry entry = forwarding().find(from_index);
  87         if (!entry.is_empty() && entry.from_index() == from_index) {
  88           return ZAddress.good(entry.to_offset());
  89         }
  90 
  91         // There's no relocate operation in the SA. Simply use the from address and hope for the best.
  92         return from;
  93     }
  94 
  95 
  96     long object_alignment_shift() {
  97         switch (type()) {
  98         case ZGlobals.ZPageTypeSmall:
  99             return ZGlobals.ZObjectAlignmentSmallShift();
 100 
 101         case ZGlobals.ZPageTypeMedium:
 102             return ZGlobals.ZObjectAlignmentMediumShift;
 103 
 104         default:
 105             assert(type() == ZGlobals.ZPageTypeLarge);
 106             return ZGlobals.ZObjectAlignmentLargeShift;
 107         }
 108     }
 109 }