1 /*
  2  * Copyright (c) 1997, 2025, 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 #include "cds/cdsConfig.hpp"
 26 #include "classfile/classFileParser.hpp"
 27 #include "classfile/javaClasses.hpp"
 28 #include "classfile/vmClasses.hpp"
 29 #include "classfile/vmSymbols.hpp"
 30 #include "oops/instanceRefKlass.inline.hpp"
 31 #include "oops/oop.inline.hpp"
 32 
 33 InstanceRefKlass::InstanceRefKlass() {
 34   assert(CDSConfig::is_dumping_static_archive() || CDSConfig::is_using_archive(), "only for CDS");
 35 }
 36 
 37 static ReferenceType reference_subclass_name_to_type(const Symbol* name) {
 38   if (       name == vmSymbols::java_lang_ref_SoftReference()) {
 39     return REF_SOFT;
 40   } else if (name == vmSymbols::java_lang_ref_WeakReference()) {
 41     return REF_WEAK;
 42   } else if (name == vmSymbols::java_lang_ref_FinalReference()) {
 43     return REF_FINAL;
 44   } else if (name == vmSymbols::java_lang_ref_PhantomReference()) {
 45     return REF_PHANTOM;
 46   } else {
 47     ShouldNotReachHere();
 48     return REF_NONE;
 49   }
 50 }
 51 
 52 static ReferenceType determine_reference_type(const ClassFileParser& parser) {
 53   const ReferenceType rt = parser.super_reference_type();
 54   if (rt != REF_NONE) {
 55     // Inherit type from super class
 56     return rt;
 57   }
 58 
 59   // Bootstrapping: this is one of the direct subclasses of java.lang.ref.Reference
 60   const Symbol* const name = parser.class_name();
 61   return reference_subclass_name_to_type(name);
 62 }
 63 
 64 InstanceRefKlass::InstanceRefKlass(const ClassFileParser& parser)
 65   : InstanceKlass(parser, Kind, determine_reference_type(parser)) {}
 66 
 67 void InstanceRefKlass::update_nonstatic_oop_maps(Klass* k) {
 68   // Clear the nonstatic oop-map entries corresponding to referent
 69   // and discovered fields.  They are treated specially by the
 70   // garbage collector.
 71   InstanceKlass* ik = InstanceKlass::cast(k);
 72 
 73   // Check that we have the right class
 74   debug_only(static bool first_time = true);
 75   assert(k == vmClasses::Reference_klass() && first_time,
 76          "Invalid update of maps");
 77   debug_only(first_time = false);
 78   assert(ik->nonstatic_oop_map_count() == 1, "just checking");
 79 
 80   OopMapBlock* map = ik->start_of_nonstatic_oop_maps();
 81 
 82 #ifdef ASSERT
 83   // Verify fields are in the expected places.
 84   int referent_offset = java_lang_ref_Reference::referent_offset();
 85   int queue_offset = java_lang_ref_Reference::queue_offset();
 86   int next_offset = java_lang_ref_Reference::next_offset();
 87   int discovered_offset = java_lang_ref_Reference::discovered_offset();
 88   assert(referent_offset < queue_offset, "just checking");
 89   assert(queue_offset < next_offset, "just checking");
 90   assert(next_offset < discovered_offset, "just checking");
 91   const unsigned int count =
 92     1 + ((discovered_offset - referent_offset) / heapOopSize);
 93   assert(count == 4, "just checking");
 94 #endif // ASSERT
 95 
 96   // Updated map starts at "queue", covers "queue" and "next".
 97   const int new_offset = java_lang_ref_Reference::queue_offset();
 98   const unsigned int new_count = 2; // queue and next
 99 
100   // Verify existing map is as expected, and update if needed.
101   if (CDSConfig::is_using_archive()) {
102     assert(map->offset() == new_offset, "just checking");
103     assert(map->count() == new_count, "just checking");
104   } else {
105     assert(map->offset() == referent_offset, "just checking");
106     assert(map->count() == count, "just checking");
107     map->set_offset(new_offset);
108     map->set_count(new_count);
109   }
110 }
111 
112 
113 // Verification
114 
115 void InstanceRefKlass::oop_verify_on(oop obj, outputStream* st) {
116   InstanceKlass::oop_verify_on(obj, st);
117   // Verify referent field
118   oop referent = java_lang_ref_Reference::unknown_referent_no_keepalive(obj);
119   if (referent != nullptr) {
120     guarantee(oopDesc::is_oop(referent), "referent field heap failed");
121   }
122   // Additional verification for next field, which must be a Reference or null
123   oop next = java_lang_ref_Reference::next(obj);
124   if (next != nullptr) {
125     guarantee(oopDesc::is_oop(next), "next field should be an oop");
126     guarantee(next->is_instanceRef(), "next field verify failed");
127   }
128 }