1 /*
   2  * Copyright (c) 2018, 2024, 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 "precompiled.hpp"
  26 #include "cds/archiveBuilder.hpp"
  27 #include "cds/archiveHeapLoader.hpp"
  28 #include "cds/archiveHeapWriter.hpp"
  29 #include "cds/archiveUtils.hpp"
  30 #include "cds/cdsConfig.hpp"
  31 #include "cds/cdsHeapVerifier.hpp"
  32 #include "cds/heapShared.hpp"
  33 #include "cds/metaspaceShared.hpp"
  34 #include "classfile/classLoaderData.hpp"
  35 #include "classfile/javaClasses.inline.hpp"
  36 #include "classfile/modules.hpp"
  37 #include "classfile/stringTable.hpp"
  38 #include "classfile/symbolTable.hpp"
  39 #include "classfile/systemDictionary.hpp"
  40 #include "classfile/systemDictionaryShared.hpp"
  41 #include "classfile/vmClasses.hpp"
  42 #include "classfile/vmSymbols.hpp"
  43 #include "gc/shared/collectedHeap.hpp"
  44 #include "gc/shared/gcLocker.hpp"
  45 #include "gc/shared/gcVMOperations.hpp"
  46 #include "logging/log.hpp"
  47 #include "logging/logStream.hpp"
  48 #include "memory/iterator.inline.hpp"
  49 #include "memory/resourceArea.hpp"
  50 #include "memory/universe.hpp"
  51 #include "oops/compressedOops.inline.hpp"
  52 #include "oops/fieldStreams.inline.hpp"
  53 #include "oops/objArrayOop.inline.hpp"
  54 #include "oops/oop.inline.hpp"
  55 #include "oops/typeArrayOop.inline.hpp"
  56 #include "prims/jvmtiExport.hpp"
  57 #include "runtime/fieldDescriptor.inline.hpp"
  58 #include "runtime/init.hpp"
  59 #include "runtime/javaCalls.hpp"
  60 #include "runtime/mutexLocker.hpp"
  61 #include "runtime/safepointVerifiers.hpp"
  62 #include "utilities/bitMap.inline.hpp"
  63 #include "utilities/copy.hpp"
  64 #if INCLUDE_G1GC
  65 #include "gc/g1/g1CollectedHeap.hpp"
  66 #endif
  67 
  68 #if INCLUDE_CDS_JAVA_HEAP
  69 
  70 struct ArchivableStaticFieldInfo {
  71   const char* klass_name;
  72   const char* field_name;
  73   InstanceKlass* klass;
  74   int offset;
  75   BasicType type;
  76 
  77   ArchivableStaticFieldInfo(const char* k, const char* f)
  78   : klass_name(k), field_name(f), klass(nullptr), offset(0), type(T_ILLEGAL) {}
  79 
  80   bool valid() {
  81     return klass_name != nullptr;
  82   }
  83 };
  84 
  85 bool HeapShared::_disable_writing = false;
  86 DumpedInternedStrings *HeapShared::_dumped_interned_strings = nullptr;
  87 
  88 size_t HeapShared::_alloc_count[HeapShared::ALLOC_STAT_SLOTS];
  89 size_t HeapShared::_alloc_size[HeapShared::ALLOC_STAT_SLOTS];
  90 size_t HeapShared::_total_obj_count;
  91 size_t HeapShared::_total_obj_size;
  92 
  93 #ifndef PRODUCT
  94 #define ARCHIVE_TEST_FIELD_NAME "archivedObjects"
  95 static Array<char>* _archived_ArchiveHeapTestClass = nullptr;
  96 static const char* _test_class_name = nullptr;
  97 static const Klass* _test_class = nullptr;
  98 static const ArchivedKlassSubGraphInfoRecord* _test_class_record = nullptr;
  99 #endif
 100 
 101 
 102 //
 103 // If you add new entries to the following tables, you should know what you're doing!
 104 //
 105 
 106 static ArchivableStaticFieldInfo archive_subgraph_entry_fields[] = {
 107   {"java/lang/Integer$IntegerCache",              "archivedCache"},
 108   {"java/lang/Long$LongCache",                    "archivedCache"},
 109   {"java/lang/Byte$ByteCache",                    "archivedCache"},
 110   {"java/lang/Short$ShortCache",                  "archivedCache"},
 111   {"java/lang/Character$CharacterCache",          "archivedCache"},
 112   {"java/util/jar/Attributes$Name",               "KNOWN_NAMES"},
 113   {"sun/util/locale/BaseLocale",                  "constantBaseLocales"},
 114   {"jdk/internal/module/ArchivedModuleGraph",     "archivedModuleGraph"},
 115   {"java/util/ImmutableCollections",              "archivedObjects"},
 116   {"java/lang/ModuleLayer",                       "EMPTY_LAYER"},
 117   {"java/lang/module/Configuration",              "EMPTY_CONFIGURATION"},
 118   {"jdk/internal/math/FDBigInteger",              "archivedCaches"},
 119 #ifndef PRODUCT
 120   {nullptr, nullptr}, // Extra slot for -XX:ArchiveHeapTestClass
 121 #endif
 122   {nullptr, nullptr},
 123 };
 124 
 125 // full module graph
 126 static ArchivableStaticFieldInfo fmg_archive_subgraph_entry_fields[] = {
 127   {"jdk/internal/loader/ArchivedClassLoaders",    "archivedClassLoaders"},
 128   {ARCHIVED_BOOT_LAYER_CLASS,                     ARCHIVED_BOOT_LAYER_FIELD},
 129   {"java/lang/Module$ArchivedData",               "archivedData"},
 130   {nullptr, nullptr},
 131 };
 132 
 133 KlassSubGraphInfo* HeapShared::_default_subgraph_info;
 134 GrowableArrayCHeap<oop, mtClassShared>* HeapShared::_pending_roots = nullptr;
 135 OopHandle HeapShared::_roots;
 136 OopHandle HeapShared::_scratch_basic_type_mirrors[T_VOID+1];
 137 MetaspaceObjToOopHandleTable* HeapShared::_scratch_java_mirror_table = nullptr;
 138 MetaspaceObjToOopHandleTable* HeapShared::_scratch_references_table = nullptr;
 139 
 140 static bool is_subgraph_root_class_of(ArchivableStaticFieldInfo fields[], InstanceKlass* ik) {
 141   for (int i = 0; fields[i].valid(); i++) {
 142     if (fields[i].klass == ik) {
 143       return true;
 144     }
 145   }
 146   return false;
 147 }
 148 
 149 bool HeapShared::is_subgraph_root_class(InstanceKlass* ik) {
 150   return is_subgraph_root_class_of(archive_subgraph_entry_fields, ik) ||
 151          is_subgraph_root_class_of(fmg_archive_subgraph_entry_fields, ik);
 152 }
 153 
 154 unsigned HeapShared::oop_hash(oop const& p) {
 155   // Do not call p->identity_hash() as that will update the
 156   // object header.
 157   return primitive_hash(cast_from_oop<intptr_t>(p));
 158 }
 159 
 160 static void reset_states(oop obj, TRAPS) {
 161   Handle h_obj(THREAD, obj);
 162   InstanceKlass* klass = InstanceKlass::cast(obj->klass());
 163   TempNewSymbol method_name = SymbolTable::new_symbol("resetArchivedStates");
 164   Symbol* method_sig = vmSymbols::void_method_signature();
 165 
 166   while (klass != nullptr) {
 167     Method* method = klass->find_method(method_name, method_sig);
 168     if (method != nullptr) {
 169       assert(method->is_private(), "must be");
 170       if (log_is_enabled(Debug, cds)) {
 171         ResourceMark rm(THREAD);
 172         log_debug(cds)("  calling %s", method->name_and_sig_as_C_string());
 173       }
 174       JavaValue result(T_VOID);
 175       JavaCalls::call_special(&result, h_obj, klass,
 176                               method_name, method_sig, CHECK);
 177     }
 178     klass = klass->java_super();
 179   }
 180 }
 181 
 182 void HeapShared::reset_archived_object_states(TRAPS) {
 183   assert(CDSConfig::is_dumping_heap(), "dump-time only");
 184   log_debug(cds)("Resetting platform loader");
 185   reset_states(SystemDictionary::java_platform_loader(), CHECK);
 186   log_debug(cds)("Resetting system loader");
 187   reset_states(SystemDictionary::java_system_loader(), CHECK);
 188 
 189   // Clean up jdk.internal.loader.ClassLoaders::bootLoader(), which is not
 190   // directly used for class loading, but rather is used by the core library
 191   // to keep track of resources, etc, loaded by the null class loader.
 192   //
 193   // Note, this object is non-null, and is not the same as
 194   // ClassLoaderData::the_null_class_loader_data()->class_loader(),
 195   // which is null.
 196   log_debug(cds)("Resetting boot loader");
 197   JavaValue result(T_OBJECT);
 198   JavaCalls::call_static(&result,
 199                          vmClasses::jdk_internal_loader_ClassLoaders_klass(),
 200                          vmSymbols::bootLoader_name(),
 201                          vmSymbols::void_BuiltinClassLoader_signature(),
 202                          CHECK);
 203   Handle boot_loader(THREAD, result.get_oop());
 204   reset_states(boot_loader(), CHECK);
 205 }
 206 
 207 HeapShared::ArchivedObjectCache* HeapShared::_archived_object_cache = nullptr;
 208 
 209 bool HeapShared::has_been_archived(oop obj) {
 210   assert(CDSConfig::is_dumping_heap(), "dump-time only");
 211   return archived_object_cache()->get(obj) != nullptr;
 212 }
 213 
 214 int HeapShared::append_root(oop obj) {
 215   assert(CDSConfig::is_dumping_heap(), "dump-time only");
 216 
 217   // No GC should happen since we aren't scanning _pending_roots.
 218   assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
 219 
 220   if (_pending_roots == nullptr) {
 221     _pending_roots = new GrowableArrayCHeap<oop, mtClassShared>(500);
 222   }
 223 
 224   return _pending_roots->append(obj);
 225 }
 226 
 227 objArrayOop HeapShared::roots() {
 228   if (CDSConfig::is_dumping_heap()) {
 229     assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
 230     if (!HeapShared::can_write()) {
 231       return nullptr;
 232     }
 233   } else {
 234     assert(CDSConfig::is_using_archive(), "must be");
 235   }
 236 
 237   objArrayOop roots = (objArrayOop)_roots.resolve();
 238   assert(roots != nullptr, "should have been initialized");
 239   return roots;
 240 }
 241 
 242 // Returns an objArray that contains all the roots of the archived objects
 243 oop HeapShared::get_root(int index, bool clear) {
 244   assert(index >= 0, "sanity");
 245   assert(!CDSConfig::is_dumping_heap() && CDSConfig::is_using_archive(), "runtime only");
 246   assert(!_roots.is_empty(), "must have loaded shared heap");
 247   oop result = roots()->obj_at(index);
 248   if (clear) {
 249     clear_root(index);
 250   }
 251   return result;
 252 }
 253 
 254 void HeapShared::clear_root(int index) {
 255   assert(index >= 0, "sanity");
 256   assert(CDSConfig::is_using_archive(), "must be");
 257   if (ArchiveHeapLoader::is_in_use()) {
 258     if (log_is_enabled(Debug, cds, heap)) {
 259       oop old = roots()->obj_at(index);
 260       log_debug(cds, heap)("Clearing root %d: was " PTR_FORMAT, index, p2i(old));
 261     }
 262     roots()->obj_at_put(index, nullptr);
 263   }
 264 }
 265 
 266 bool HeapShared::archive_object(oop obj) {
 267   assert(CDSConfig::is_dumping_heap(), "dump-time only");
 268 
 269   assert(!obj->is_stackChunk(), "do not archive stack chunks");
 270   if (has_been_archived(obj)) {
 271     return true;
 272   }
 273 
 274   if (ArchiveHeapWriter::is_too_large_to_archive(obj->size())) {
 275     log_debug(cds, heap)("Cannot archive, object (" PTR_FORMAT ") is too large: " SIZE_FORMAT,
 276                          p2i(obj), obj->size());
 277     return false;
 278   } else {
 279     count_allocation(obj->size());
 280     ArchiveHeapWriter::add_source_obj(obj);
 281     CachedOopInfo info = make_cached_oop_info(obj);
 282     archived_object_cache()->put_when_absent(obj, info);
 283     archived_object_cache()->maybe_grow();
 284     mark_native_pointers(obj);
 285 
 286     if (log_is_enabled(Debug, cds, heap)) {
 287       ResourceMark rm;
 288       log_debug(cds, heap)("Archived heap object " PTR_FORMAT " : %s",
 289                            p2i(obj), obj->klass()->external_name());
 290     }
 291 
 292     if (java_lang_Module::is_instance(obj) && Modules::check_archived_module_oop(obj)) {
 293       Modules::update_oops_in_archived_module(obj, append_root(obj));
 294     }
 295 
 296     return true;
 297   }
 298 }
 299 
 300 class MetaspaceObjToOopHandleTable: public ResourceHashtable<MetaspaceObj*, OopHandle,
 301     36137, // prime number
 302     AnyObj::C_HEAP,
 303     mtClassShared> {
 304 public:
 305   oop get_oop(MetaspaceObj* ptr) {
 306     MutexLocker ml(ScratchObjects_lock, Mutex::_no_safepoint_check_flag);
 307     OopHandle* handle = get(ptr);
 308     if (handle != nullptr) {
 309       return handle->resolve();
 310     } else {
 311       return nullptr;
 312     }
 313   }
 314   void set_oop(MetaspaceObj* ptr, oop o) {
 315     MutexLocker ml(ScratchObjects_lock, Mutex::_no_safepoint_check_flag);
 316     OopHandle handle(Universe::vm_global(), o);
 317     bool is_new = put(ptr, handle);
 318     assert(is_new, "cannot set twice");
 319   }
 320   void remove_oop(MetaspaceObj* ptr) {
 321     MutexLocker ml(ScratchObjects_lock, Mutex::_no_safepoint_check_flag);
 322     OopHandle* handle = get(ptr);
 323     if (handle != nullptr) {
 324       handle->release(Universe::vm_global());
 325       remove(ptr);
 326     }
 327   }
 328 };
 329 
 330 void HeapShared::add_scratch_resolved_references(ConstantPool* src, objArrayOop dest) {
 331   _scratch_references_table->set_oop(src, dest);
 332 }
 333 
 334 objArrayOop HeapShared::scratch_resolved_references(ConstantPool* src) {
 335   return (objArrayOop)_scratch_references_table->get_oop(src);
 336 }
 337 
 338 void HeapShared::init_scratch_objects(TRAPS) {
 339   for (int i = T_BOOLEAN; i < T_VOID+1; i++) {
 340     BasicType bt = (BasicType)i;
 341     if (!is_reference_type(bt)) {
 342       oop m = java_lang_Class::create_basic_type_mirror(type2name(bt), bt, CHECK);
 343       _scratch_basic_type_mirrors[i] = OopHandle(Universe::vm_global(), m);
 344     }
 345   }
 346   _scratch_java_mirror_table = new (mtClass)MetaspaceObjToOopHandleTable();
 347   _scratch_references_table = new (mtClass)MetaspaceObjToOopHandleTable();
 348 }
 349 
 350 oop HeapShared::scratch_java_mirror(BasicType t) {
 351   assert((uint)t < T_VOID+1, "range check");
 352   assert(!is_reference_type(t), "sanity");
 353   return _scratch_basic_type_mirrors[t].resolve();
 354 }
 355 
 356 oop HeapShared::scratch_java_mirror(Klass* k) {
 357   return _scratch_java_mirror_table->get_oop(k);
 358 }
 359 
 360 void HeapShared::set_scratch_java_mirror(Klass* k, oop mirror) {
 361   _scratch_java_mirror_table->set_oop(k, mirror);
 362 }
 363 
 364 void HeapShared::remove_scratch_objects(Klass* k) {
 365   _scratch_java_mirror_table->remove_oop(k);
 366   if (k->is_instance_klass()) {
 367     _scratch_references_table->remove(InstanceKlass::cast(k)->constants());
 368   }
 369 }
 370 
 371 void HeapShared::archive_java_mirrors() {
 372   for (int i = T_BOOLEAN; i < T_VOID+1; i++) {
 373     BasicType bt = (BasicType)i;
 374     if (!is_reference_type(bt)) {
 375       oop m = _scratch_basic_type_mirrors[i].resolve();
 376       assert(m != nullptr, "sanity");
 377       bool success = archive_reachable_objects_from(1, _default_subgraph_info, m);
 378       assert(success, "sanity");
 379 
 380       log_trace(cds, heap, mirror)(
 381         "Archived %s mirror object from " PTR_FORMAT,
 382         type2name(bt), p2i(m));
 383 
 384       Universe::set_archived_basic_type_mirror_index(bt, append_root(m));
 385     }
 386   }
 387 
 388   GrowableArray<Klass*>* klasses = ArchiveBuilder::current()->klasses();
 389   assert(klasses != nullptr, "sanity");
 390   for (int i = 0; i < klasses->length(); i++) {
 391     Klass* orig_k = klasses->at(i);
 392     oop m = scratch_java_mirror(orig_k);
 393     if (m != nullptr) {
 394       Klass* buffered_k = ArchiveBuilder::get_buffered_klass(orig_k);
 395       bool success = archive_reachable_objects_from(1, _default_subgraph_info, m);
 396       guarantee(success, "scratch mirrors must point to only archivable objects");
 397       buffered_k->set_archived_java_mirror(append_root(m));
 398       ResourceMark rm;
 399       log_trace(cds, heap, mirror)(
 400         "Archived %s mirror object from " PTR_FORMAT,
 401         buffered_k->external_name(), p2i(m));
 402 
 403       // archive the resolved_referenes array
 404       if (buffered_k->is_instance_klass()) {
 405         InstanceKlass* ik = InstanceKlass::cast(buffered_k);
 406         oop rr = ik->constants()->prepare_resolved_references_for_archiving();
 407         if (rr != nullptr && !ArchiveHeapWriter::is_too_large_to_archive(rr)) {
 408           bool success = HeapShared::archive_reachable_objects_from(1, _default_subgraph_info, rr);
 409           assert(success, "must be");
 410           int root_index = append_root(rr);
 411           ik->constants()->cache()->set_archived_references(root_index);
 412         }
 413       }
 414     }
 415   }
 416 }
 417 
 418 void HeapShared::archive_strings() {
 419   oop shared_strings_array = StringTable::init_shared_table(_dumped_interned_strings);
 420   bool success = archive_reachable_objects_from(1, _default_subgraph_info, shared_strings_array);
 421   // We must succeed because:
 422   // - _dumped_interned_strings do not contain any large strings.
 423   // - StringTable::init_shared_table() doesn't create any large arrays.
 424   assert(success, "shared strings array must not point to arrays or strings that are too large to archive");
 425   StringTable::set_shared_strings_array_index(append_root(shared_strings_array));
 426 }
 427 
 428 int HeapShared::archive_exception_instance(oop exception) {
 429   bool success = archive_reachable_objects_from(1, _default_subgraph_info, exception);
 430   assert(success, "sanity");
 431   return append_root(exception);
 432 }
 433 
 434 void HeapShared::mark_native_pointers(oop orig_obj) {
 435   if (java_lang_Class::is_instance(orig_obj)) {
 436     ArchiveHeapWriter::mark_native_pointer(orig_obj, java_lang_Class::klass_offset());
 437     ArchiveHeapWriter::mark_native_pointer(orig_obj, java_lang_Class::array_klass_offset());
 438   }
 439 }
 440 
 441 void HeapShared::get_pointer_info(oop src_obj, bool& has_oop_pointers, bool& has_native_pointers) {
 442   CachedOopInfo* info = archived_object_cache()->get(src_obj);
 443   assert(info != nullptr, "must be");
 444   has_oop_pointers = info->has_oop_pointers();
 445   has_native_pointers = info->has_native_pointers();
 446 }
 447 
 448 void HeapShared::set_has_native_pointers(oop src_obj) {
 449   CachedOopInfo* info = archived_object_cache()->get(src_obj);
 450   assert(info != nullptr, "must be");
 451   info->set_has_native_pointers();
 452 }
 453 
 454 // -- Handling of Enum objects
 455 // Java Enum classes have synthetic <clinit> methods that look like this
 456 //     enum MyEnum {FOO, BAR}
 457 //     MyEnum::<clinint> {
 458 //        /*static final MyEnum*/ MyEnum::FOO = new MyEnum("FOO");
 459 //        /*static final MyEnum*/ MyEnum::BAR = new MyEnum("BAR");
 460 //     }
 461 //
 462 // If MyEnum::FOO object is referenced by any of the archived subgraphs, we must
 463 // ensure the archived value equals (in object address) to the runtime value of
 464 // MyEnum::FOO.
 465 //
 466 // However, since MyEnum::<clinint> is synthetically generated by javac, there's
 467 // no way of programmatically handling this inside the Java code (as you would handle
 468 // ModuleLayer::EMPTY_LAYER, for example).
 469 //
 470 // Instead, we archive all static field of such Enum classes. At runtime,
 471 // HeapShared::initialize_enum_klass() will skip the <clinit> method and pull
 472 // the static fields out of the archived heap.
 473 void HeapShared::check_enum_obj(int level,
 474                                 KlassSubGraphInfo* subgraph_info,
 475                                 oop orig_obj) {
 476   assert(level > 1, "must never be called at the first (outermost) level");
 477   Klass* k = orig_obj->klass();
 478   Klass* buffered_k = ArchiveBuilder::get_buffered_klass(k);
 479   if (!k->is_instance_klass()) {
 480     return;
 481   }
 482   InstanceKlass* ik = InstanceKlass::cast(k);
 483   if (ik->java_super() == vmClasses::Enum_klass() && !ik->has_archived_enum_objs()) {
 484     ResourceMark rm;
 485     ik->set_has_archived_enum_objs();
 486     buffered_k->set_has_archived_enum_objs();
 487     oop mirror = ik->java_mirror();
 488 
 489     for (JavaFieldStream fs(ik); !fs.done(); fs.next()) {
 490       if (fs.access_flags().is_static()) {
 491         fieldDescriptor& fd = fs.field_descriptor();
 492         if (fd.field_type() != T_OBJECT && fd.field_type() != T_ARRAY) {
 493           guarantee(false, "static field %s::%s must be T_OBJECT or T_ARRAY",
 494                     ik->external_name(), fd.name()->as_C_string());
 495         }
 496         oop oop_field = mirror->obj_field(fd.offset());
 497         if (oop_field == nullptr) {
 498           guarantee(false, "static field %s::%s must not be null",
 499                     ik->external_name(), fd.name()->as_C_string());
 500         } else if (oop_field->klass() != ik && oop_field->klass() != ik->array_klass_or_null()) {
 501           guarantee(false, "static field %s::%s is of the wrong type",
 502                     ik->external_name(), fd.name()->as_C_string());
 503         }
 504         bool success = archive_reachable_objects_from(level, subgraph_info, oop_field);
 505         assert(success, "VM should have exited with unarchivable objects for _level > 1");
 506         int root_index = append_root(oop_field);
 507         log_info(cds, heap)("Archived enum obj @%d %s::%s (" INTPTR_FORMAT ")",
 508                             root_index, ik->external_name(), fd.name()->as_C_string(),
 509                             p2i((oopDesc*)oop_field));
 510         SystemDictionaryShared::add_enum_klass_static_field(ik, root_index);
 511       }
 512     }
 513   }
 514 }
 515 
 516 // See comments in HeapShared::check_enum_obj()
 517 bool HeapShared::initialize_enum_klass(InstanceKlass* k, TRAPS) {
 518   if (!ArchiveHeapLoader::is_in_use()) {
 519     return false;
 520   }
 521 
 522   RunTimeClassInfo* info = RunTimeClassInfo::get_for(k);
 523   assert(info != nullptr, "sanity");
 524 
 525   if (log_is_enabled(Info, cds, heap)) {
 526     ResourceMark rm;
 527     log_info(cds, heap)("Initializing Enum class: %s", k->external_name());
 528   }
 529 
 530   oop mirror = k->java_mirror();
 531   int i = 0;
 532   for (JavaFieldStream fs(k); !fs.done(); fs.next()) {
 533     if (fs.access_flags().is_static()) {
 534       int root_index = info->enum_klass_static_field_root_index_at(i++);
 535       fieldDescriptor& fd = fs.field_descriptor();
 536       assert(fd.field_type() == T_OBJECT || fd.field_type() == T_ARRAY, "must be");
 537       mirror->obj_field_put(fd.offset(), get_root(root_index, /*clear=*/true));
 538     }
 539   }
 540   return true;
 541 }
 542 
 543 void HeapShared::archive_objects(ArchiveHeapInfo *heap_info) {
 544   {
 545     NoSafepointVerifier nsv;
 546 
 547     _default_subgraph_info = init_subgraph_info(vmClasses::Object_klass(), false);
 548 
 549     // Cache for recording where the archived objects are copied to
 550     create_archived_object_cache();
 551 
 552     log_info(cds)("Heap range = [" PTR_FORMAT " - "  PTR_FORMAT "]",
 553                    UseCompressedOops ? p2i(CompressedOops::begin()) :
 554                                        p2i((address)G1CollectedHeap::heap()->reserved().start()),
 555                    UseCompressedOops ? p2i(CompressedOops::end()) :
 556                                        p2i((address)G1CollectedHeap::heap()->reserved().end()));
 557     copy_objects();
 558 
 559     CDSHeapVerifier::verify();
 560     check_default_subgraph_classes();
 561   }
 562 
 563   ArchiveHeapWriter::write(_pending_roots, heap_info);
 564 }
 565 
 566 void HeapShared::copy_interned_strings() {
 567   init_seen_objects_table();
 568 
 569   auto copier = [&] (oop s, bool value_ignored) {
 570     assert(s != nullptr, "sanity");
 571     assert(!ArchiveHeapWriter::is_string_too_large_to_archive(s), "large strings must have been filtered");
 572     bool success = archive_reachable_objects_from(1, _default_subgraph_info, s);
 573     assert(success, "must be");
 574     // Prevent string deduplication from changing the value field to
 575     // something not in the archive.
 576     java_lang_String::set_deduplication_forbidden(s);
 577   };
 578   _dumped_interned_strings->iterate_all(copier);
 579 
 580   delete_seen_objects_table();
 581 }
 582 
 583 void HeapShared::copy_special_objects() {
 584   // Archive special objects that do not belong to any subgraphs
 585   init_seen_objects_table();
 586   archive_java_mirrors();
 587   archive_strings();
 588   Universe::archive_exception_instances();
 589   delete_seen_objects_table();
 590 }
 591 
 592 void HeapShared::copy_objects() {
 593   assert(HeapShared::can_write(), "must be");
 594 
 595   copy_interned_strings();
 596   copy_special_objects();
 597 
 598   archive_object_subgraphs(archive_subgraph_entry_fields,
 599                            false /* is_full_module_graph */);
 600 
 601   if (CDSConfig::is_dumping_full_module_graph()) {
 602     archive_object_subgraphs(fmg_archive_subgraph_entry_fields,
 603                              true /* is_full_module_graph */);
 604     Modules::verify_archived_modules();
 605   }
 606 }
 607 
 608 //
 609 // Subgraph archiving support
 610 //
 611 HeapShared::DumpTimeKlassSubGraphInfoTable* HeapShared::_dump_time_subgraph_info_table = nullptr;
 612 HeapShared::RunTimeKlassSubGraphInfoTable   HeapShared::_run_time_subgraph_info_table;
 613 
 614 // Get the subgraph_info for Klass k. A new subgraph_info is created if
 615 // there is no existing one for k. The subgraph_info records the "buffered"
 616 // address of the class.
 617 KlassSubGraphInfo* HeapShared::init_subgraph_info(Klass* k, bool is_full_module_graph) {
 618   assert(CDSConfig::is_dumping_heap(), "dump time only");
 619   bool created;
 620   Klass* buffered_k = ArchiveBuilder::get_buffered_klass(k);
 621   KlassSubGraphInfo* info =
 622     _dump_time_subgraph_info_table->put_if_absent(k, KlassSubGraphInfo(buffered_k, is_full_module_graph),
 623                                                   &created);
 624   assert(created, "must not initialize twice");
 625   return info;
 626 }
 627 
 628 KlassSubGraphInfo* HeapShared::get_subgraph_info(Klass* k) {
 629   assert(CDSConfig::is_dumping_heap(), "dump time only");
 630   KlassSubGraphInfo* info = _dump_time_subgraph_info_table->get(k);
 631   assert(info != nullptr, "must have been initialized");
 632   return info;
 633 }
 634 
 635 // Add an entry field to the current KlassSubGraphInfo.
 636 void KlassSubGraphInfo::add_subgraph_entry_field(int static_field_offset, oop v) {
 637   assert(CDSConfig::is_dumping_heap(), "dump time only");
 638   if (_subgraph_entry_fields == nullptr) {
 639     _subgraph_entry_fields =
 640       new (mtClass) GrowableArray<int>(10, mtClass);
 641   }
 642   _subgraph_entry_fields->append(static_field_offset);
 643   _subgraph_entry_fields->append(HeapShared::append_root(v));
 644 }
 645 
 646 // Add the Klass* for an object in the current KlassSubGraphInfo's subgraphs.
 647 // Only objects of boot classes can be included in sub-graph.
 648 void KlassSubGraphInfo::add_subgraph_object_klass(Klass* orig_k) {
 649   assert(CDSConfig::is_dumping_heap(), "dump time only");
 650   Klass* buffered_k = ArchiveBuilder::get_buffered_klass(orig_k);
 651 
 652   if (_subgraph_object_klasses == nullptr) {
 653     _subgraph_object_klasses =
 654       new (mtClass) GrowableArray<Klass*>(50, mtClass);
 655   }
 656 
 657   assert(ArchiveBuilder::current()->is_in_buffer_space(buffered_k), "must be a shared class");
 658 
 659   if (_k == buffered_k) {
 660     // Don't add the Klass containing the sub-graph to it's own klass
 661     // initialization list.
 662     return;
 663   }
 664 
 665   if (buffered_k->is_instance_klass()) {
 666     assert(InstanceKlass::cast(buffered_k)->is_shared_boot_class(),
 667           "must be boot class");
 668     // vmClasses::xxx_klass() are not updated, need to check
 669     // the original Klass*
 670     if (orig_k == vmClasses::String_klass() ||
 671         orig_k == vmClasses::Object_klass()) {
 672       // Initialized early during VM initialization. No need to be added
 673       // to the sub-graph object class list.
 674       return;
 675     }
 676     check_allowed_klass(InstanceKlass::cast(orig_k));
 677   } else if (buffered_k->is_objArray_klass()) {
 678     Klass* abk = ObjArrayKlass::cast(buffered_k)->bottom_klass();
 679     if (abk->is_instance_klass()) {
 680       assert(InstanceKlass::cast(abk)->is_shared_boot_class(),
 681             "must be boot class");
 682       check_allowed_klass(InstanceKlass::cast(ObjArrayKlass::cast(orig_k)->bottom_klass()));
 683     }
 684     if (buffered_k == Universe::objectArrayKlass()) {
 685       // Initialized early during Universe::genesis. No need to be added
 686       // to the list.
 687       return;
 688     }
 689   } else {
 690     assert(buffered_k->is_typeArray_klass(), "must be");
 691     // Primitive type arrays are created early during Universe::genesis.
 692     return;
 693   }
 694 
 695   if (log_is_enabled(Debug, cds, heap)) {
 696     if (!_subgraph_object_klasses->contains(buffered_k)) {
 697       ResourceMark rm;
 698       log_debug(cds, heap)("Adding klass %s", orig_k->external_name());
 699     }
 700   }
 701 
 702   _subgraph_object_klasses->append_if_missing(buffered_k);
 703   _has_non_early_klasses |= is_non_early_klass(orig_k);
 704 }
 705 
 706 void KlassSubGraphInfo::check_allowed_klass(InstanceKlass* ik) {
 707   if (ik->module()->name() == vmSymbols::java_base()) {
 708     assert(ik->package() != nullptr, "classes in java.base cannot be in unnamed package");
 709     return;
 710   }
 711 
 712 #ifndef PRODUCT
 713   if (!ik->module()->is_named() && ik->package() == nullptr) {
 714     // This class is loaded by ArchiveHeapTestClass
 715     return;
 716   }
 717   const char* extra_msg = ", or in an unnamed package of an unnamed module";
 718 #else
 719   const char* extra_msg = "";
 720 #endif
 721 
 722   ResourceMark rm;
 723   log_error(cds, heap)("Class %s not allowed in archive heap. Must be in java.base%s",
 724                        ik->external_name(), extra_msg);
 725   MetaspaceShared::unrecoverable_writing_error();
 726 }
 727 
 728 bool KlassSubGraphInfo::is_non_early_klass(Klass* k) {
 729   if (k->is_objArray_klass()) {
 730     k = ObjArrayKlass::cast(k)->bottom_klass();
 731   }
 732   if (k->is_instance_klass()) {
 733     if (!SystemDictionaryShared::is_early_klass(InstanceKlass::cast(k))) {
 734       ResourceMark rm;
 735       log_info(cds, heap)("non-early: %s", k->external_name());
 736       return true;
 737     } else {
 738       return false;
 739     }
 740   } else {
 741     return false;
 742   }
 743 }
 744 
 745 // Initialize an archived subgraph_info_record from the given KlassSubGraphInfo.
 746 void ArchivedKlassSubGraphInfoRecord::init(KlassSubGraphInfo* info) {
 747   _k = info->klass();
 748   _entry_field_records = nullptr;
 749   _subgraph_object_klasses = nullptr;
 750   _is_full_module_graph = info->is_full_module_graph();
 751 
 752   if (_is_full_module_graph) {
 753     // Consider all classes referenced by the full module graph as early -- we will be
 754     // allocating objects of these classes during JVMTI early phase, so they cannot
 755     // be processed by (non-early) JVMTI ClassFileLoadHook
 756     _has_non_early_klasses = false;
 757   } else {
 758     _has_non_early_klasses = info->has_non_early_klasses();
 759   }
 760 
 761   if (_has_non_early_klasses) {
 762     ResourceMark rm;
 763     log_info(cds, heap)(
 764           "Subgraph of klass %s has non-early klasses and cannot be used when JVMTI ClassFileLoadHook is enabled",
 765           _k->external_name());
 766   }
 767 
 768   // populate the entry fields
 769   GrowableArray<int>* entry_fields = info->subgraph_entry_fields();
 770   if (entry_fields != nullptr) {
 771     int num_entry_fields = entry_fields->length();
 772     assert(num_entry_fields % 2 == 0, "sanity");
 773     _entry_field_records =
 774       ArchiveBuilder::new_ro_array<int>(num_entry_fields);
 775     for (int i = 0 ; i < num_entry_fields; i++) {
 776       _entry_field_records->at_put(i, entry_fields->at(i));
 777     }
 778   }
 779 
 780   // the Klasses of the objects in the sub-graphs
 781   GrowableArray<Klass*>* subgraph_object_klasses = info->subgraph_object_klasses();
 782   if (subgraph_object_klasses != nullptr) {
 783     int num_subgraphs_klasses = subgraph_object_klasses->length();
 784     _subgraph_object_klasses =
 785       ArchiveBuilder::new_ro_array<Klass*>(num_subgraphs_klasses);
 786     for (int i = 0; i < num_subgraphs_klasses; i++) {
 787       Klass* subgraph_k = subgraph_object_klasses->at(i);
 788       if (log_is_enabled(Info, cds, heap)) {
 789         ResourceMark rm;
 790         log_info(cds, heap)(
 791           "Archived object klass %s (%2d) => %s",
 792           _k->external_name(), i, subgraph_k->external_name());
 793       }
 794       _subgraph_object_klasses->at_put(i, subgraph_k);
 795       ArchivePtrMarker::mark_pointer(_subgraph_object_klasses->adr_at(i));
 796     }
 797   }
 798 
 799   ArchivePtrMarker::mark_pointer(&_k);
 800   ArchivePtrMarker::mark_pointer(&_entry_field_records);
 801   ArchivePtrMarker::mark_pointer(&_subgraph_object_klasses);
 802 }
 803 
 804 struct CopyKlassSubGraphInfoToArchive : StackObj {
 805   CompactHashtableWriter* _writer;
 806   CopyKlassSubGraphInfoToArchive(CompactHashtableWriter* writer) : _writer(writer) {}
 807 
 808   bool do_entry(Klass* klass, KlassSubGraphInfo& info) {
 809     if (info.subgraph_object_klasses() != nullptr || info.subgraph_entry_fields() != nullptr) {
 810       ArchivedKlassSubGraphInfoRecord* record =
 811         (ArchivedKlassSubGraphInfoRecord*)ArchiveBuilder::ro_region_alloc(sizeof(ArchivedKlassSubGraphInfoRecord));
 812       record->init(&info);
 813 
 814       Klass* buffered_k = ArchiveBuilder::get_buffered_klass(klass);
 815       unsigned int hash = SystemDictionaryShared::hash_for_shared_dictionary((address)buffered_k);
 816       u4 delta = ArchiveBuilder::current()->any_to_offset_u4(record);
 817       _writer->add(hash, delta);
 818     }
 819     return true; // keep on iterating
 820   }
 821 };
 822 
 823 // Build the records of archived subgraph infos, which include:
 824 // - Entry points to all subgraphs from the containing class mirror. The entry
 825 //   points are static fields in the mirror. For each entry point, the field
 826 //   offset, and value are recorded in the sub-graph
 827 //   info. The value is stored back to the corresponding field at runtime.
 828 // - A list of klasses that need to be loaded/initialized before archived
 829 //   java object sub-graph can be accessed at runtime.
 830 void HeapShared::write_subgraph_info_table() {
 831   // Allocate the contents of the hashtable(s) inside the RO region of the CDS archive.
 832   DumpTimeKlassSubGraphInfoTable* d_table = _dump_time_subgraph_info_table;
 833   CompactHashtableStats stats;
 834 
 835   _run_time_subgraph_info_table.reset();
 836 
 837   CompactHashtableWriter writer(d_table->_count, &stats);
 838   CopyKlassSubGraphInfoToArchive copy(&writer);
 839   d_table->iterate(&copy);
 840   writer.dump(&_run_time_subgraph_info_table, "subgraphs");
 841 
 842 #ifndef PRODUCT
 843   if (ArchiveHeapTestClass != nullptr) {
 844     size_t len = strlen(ArchiveHeapTestClass) + 1;
 845     Array<char>* array = ArchiveBuilder::new_ro_array<char>((int)len);
 846     strncpy(array->adr_at(0), ArchiveHeapTestClass, len);
 847     _archived_ArchiveHeapTestClass = array;
 848   }
 849 #endif
 850   if (log_is_enabled(Info, cds, heap)) {
 851     print_stats();
 852   }
 853 }
 854 
 855 void HeapShared::init_roots(oop roots_oop) {
 856   if (roots_oop != nullptr) {
 857     assert(ArchiveHeapLoader::is_in_use(), "must be");
 858     _roots = OopHandle(Universe::vm_global(), roots_oop);
 859   }
 860 }
 861 
 862 void HeapShared::serialize_tables(SerializeClosure* soc) {
 863 
 864 #ifndef PRODUCT
 865   soc->do_ptr(&_archived_ArchiveHeapTestClass);
 866   if (soc->reading() && _archived_ArchiveHeapTestClass != nullptr) {
 867     _test_class_name = _archived_ArchiveHeapTestClass->adr_at(0);
 868     setup_test_class(_test_class_name);
 869   }
 870 #endif
 871 
 872   _run_time_subgraph_info_table.serialize_header(soc);
 873 }
 874 
 875 static void verify_the_heap(Klass* k, const char* which) {
 876   if (VerifyArchivedFields > 0) {
 877     ResourceMark rm;
 878     log_info(cds, heap)("Verify heap %s initializing static field(s) in %s",
 879                         which, k->external_name());
 880 
 881     VM_Verify verify_op;
 882     VMThread::execute(&verify_op);
 883 
 884     if (VerifyArchivedFields > 1 && is_init_completed()) {
 885       // At this time, the oop->klass() of some archived objects in the heap may not
 886       // have been loaded into the system dictionary yet. Nevertheless, oop->klass() should
 887       // have enough information (object size, oop maps, etc) so that a GC can be safely
 888       // performed.
 889       //
 890       // -XX:VerifyArchivedFields=2 force a GC to happen in such an early stage
 891       // to check for GC safety.
 892       log_info(cds, heap)("Trigger GC %s initializing static field(s) in %s",
 893                           which, k->external_name());
 894       FlagSetting fs1(VerifyBeforeGC, true);
 895       FlagSetting fs2(VerifyDuringGC, true);
 896       FlagSetting fs3(VerifyAfterGC,  true);
 897       Universe::heap()->collect(GCCause::_java_lang_system_gc);
 898     }
 899   }
 900 }
 901 
 902 // Before GC can execute, we must ensure that all oops reachable from HeapShared::roots()
 903 // have a valid klass. I.e., oopDesc::klass() must have already been resolved.
 904 //
 905 // Note: if a ArchivedKlassSubGraphInfoRecord contains non-early classes, and JVMTI
 906 // ClassFileLoadHook is enabled, it's possible for this class to be dynamically replaced. In
 907 // this case, we will not load the ArchivedKlassSubGraphInfoRecord and will clear its roots.
 908 void HeapShared::resolve_classes(JavaThread* current) {
 909   assert(CDSConfig::is_using_archive(), "runtime only!");
 910   if (!ArchiveHeapLoader::is_in_use()) {
 911     return; // nothing to do
 912   }
 913   resolve_classes_for_subgraphs(current, archive_subgraph_entry_fields);
 914   resolve_classes_for_subgraphs(current, fmg_archive_subgraph_entry_fields);
 915 }
 916 
 917 void HeapShared::resolve_classes_for_subgraphs(JavaThread* current, ArchivableStaticFieldInfo fields[]) {
 918   for (int i = 0; fields[i].valid(); i++) {
 919     ArchivableStaticFieldInfo* info = &fields[i];
 920     TempNewSymbol klass_name = SymbolTable::new_symbol(info->klass_name);
 921     InstanceKlass* k = SystemDictionaryShared::find_builtin_class(klass_name);
 922     assert(k != nullptr && k->is_shared_boot_class(), "sanity");
 923     resolve_classes_for_subgraph_of(current, k);
 924   }
 925 }
 926 
 927 void HeapShared::resolve_classes_for_subgraph_of(JavaThread* current, Klass* k) {
 928   JavaThread* THREAD = current;
 929   ExceptionMark em(THREAD);
 930   const ArchivedKlassSubGraphInfoRecord* record =
 931    resolve_or_init_classes_for_subgraph_of(k, /*do_init=*/false, THREAD);
 932   if (HAS_PENDING_EXCEPTION) {
 933    CLEAR_PENDING_EXCEPTION;
 934   }
 935   if (record == nullptr) {
 936    clear_archived_roots_of(k);
 937   }
 938 }
 939 
 940 void HeapShared::initialize_from_archived_subgraph(JavaThread* current, Klass* k) {
 941   JavaThread* THREAD = current;
 942   if (!ArchiveHeapLoader::is_in_use()) {
 943     return; // nothing to do
 944   }
 945 
 946   ExceptionMark em(THREAD);
 947   const ArchivedKlassSubGraphInfoRecord* record =
 948     resolve_or_init_classes_for_subgraph_of(k, /*do_init=*/true, THREAD);
 949 
 950   if (HAS_PENDING_EXCEPTION) {
 951     CLEAR_PENDING_EXCEPTION;
 952     // None of the field value will be set if there was an exception when initializing the classes.
 953     // The java code will not see any of the archived objects in the
 954     // subgraphs referenced from k in this case.
 955     return;
 956   }
 957 
 958   if (record != nullptr) {
 959     init_archived_fields_for(k, record);
 960   }
 961 }
 962 
 963 const ArchivedKlassSubGraphInfoRecord*
 964 HeapShared::resolve_or_init_classes_for_subgraph_of(Klass* k, bool do_init, TRAPS) {
 965   assert(!CDSConfig::is_dumping_heap(), "Should not be called when dumping heap");
 966 
 967   if (!k->is_shared()) {
 968     return nullptr;
 969   }
 970   unsigned int hash = SystemDictionaryShared::hash_for_shared_dictionary_quick(k);
 971   const ArchivedKlassSubGraphInfoRecord* record = _run_time_subgraph_info_table.lookup(k, hash, 0);
 972 
 973 #ifndef PRODUCT
 974   if (_test_class_name != nullptr && k->name()->equals(_test_class_name) && record != nullptr) {
 975     _test_class = k;
 976     _test_class_record = record;
 977   }
 978 #endif
 979 
 980   // Initialize from archived data. Currently this is done only
 981   // during VM initialization time. No lock is needed.
 982   if (record == nullptr) {
 983     if (log_is_enabled(Info, cds, heap)) {
 984       ResourceMark rm(THREAD);
 985       log_info(cds, heap)("subgraph %s is not recorded",
 986                           k->external_name());
 987     }
 988     return nullptr;
 989   } else {
 990     if (record->is_full_module_graph() && !CDSConfig::is_using_full_module_graph()) {
 991       if (log_is_enabled(Info, cds, heap)) {
 992         ResourceMark rm(THREAD);
 993         log_info(cds, heap)("subgraph %s cannot be used because full module graph is disabled",
 994                             k->external_name());
 995       }
 996       return nullptr;
 997     }
 998 
 999     if (record->has_non_early_klasses() && JvmtiExport::should_post_class_file_load_hook()) {
1000       if (log_is_enabled(Info, cds, heap)) {
1001         ResourceMark rm(THREAD);
1002         log_info(cds, heap)("subgraph %s cannot be used because JVMTI ClassFileLoadHook is enabled",
1003                             k->external_name());
1004       }
1005       return nullptr;
1006     }
1007 
1008     if (log_is_enabled(Info, cds, heap)) {
1009       ResourceMark rm;
1010       log_info(cds, heap)("%s subgraph %s ", do_init ? "init" : "resolve", k->external_name());
1011     }
1012 
1013     resolve_or_init(k, do_init, CHECK_NULL);
1014 
1015     // Load/link/initialize the klasses of the objects in the subgraph.
1016     // nullptr class loader is used.
1017     Array<Klass*>* klasses = record->subgraph_object_klasses();
1018     if (klasses != nullptr) {
1019       for (int i = 0; i < klasses->length(); i++) {
1020         Klass* klass = klasses->at(i);
1021         if (!klass->is_shared()) {
1022           return nullptr;
1023         }
1024         resolve_or_init(klass, do_init, CHECK_NULL);
1025       }
1026     }
1027   }
1028 
1029   return record;
1030 }
1031 
1032 void HeapShared::resolve_or_init(Klass* k, bool do_init, TRAPS) {
1033   if (!do_init) {
1034     if (k->class_loader_data() == nullptr) {
1035       Klass* resolved_k = SystemDictionary::resolve_or_null(k->name(), CHECK);
1036       assert(resolved_k == k, "classes used by archived heap must not be replaced by JVMTI ClassFileLoadHook");
1037     }
1038   } else {
1039     assert(k->class_loader_data() != nullptr, "must have been resolved by HeapShared::resolve_classes");
1040     if (k->is_instance_klass()) {
1041       InstanceKlass* ik = InstanceKlass::cast(k);
1042       ik->initialize(CHECK);
1043     } else if (k->is_objArray_klass()) {
1044       ObjArrayKlass* oak = ObjArrayKlass::cast(k);
1045       oak->initialize(CHECK);
1046     }
1047   }
1048 }
1049 
1050 void HeapShared::init_archived_fields_for(Klass* k, const ArchivedKlassSubGraphInfoRecord* record) {
1051   verify_the_heap(k, "before");
1052 
1053   // Load the subgraph entry fields from the record and store them back to
1054   // the corresponding fields within the mirror.
1055   oop m = k->java_mirror();
1056   Array<int>* entry_field_records = record->entry_field_records();
1057   if (entry_field_records != nullptr) {
1058     int efr_len = entry_field_records->length();
1059     assert(efr_len % 2 == 0, "sanity");
1060     for (int i = 0; i < efr_len; i += 2) {
1061       int field_offset = entry_field_records->at(i);
1062       int root_index = entry_field_records->at(i+1);
1063       oop v = get_root(root_index, /*clear=*/true);
1064       m->obj_field_put(field_offset, v);
1065       log_debug(cds, heap)("  " PTR_FORMAT " init field @ %2d = " PTR_FORMAT, p2i(k), field_offset, p2i(v));
1066     }
1067 
1068     // Done. Java code can see the archived sub-graphs referenced from k's
1069     // mirror after this point.
1070     if (log_is_enabled(Info, cds, heap)) {
1071       ResourceMark rm;
1072       log_info(cds, heap)("initialize_from_archived_subgraph %s " PTR_FORMAT "%s",
1073                           k->external_name(), p2i(k), JvmtiExport::is_early_phase() ? " (early)" : "");
1074     }
1075   }
1076 
1077   verify_the_heap(k, "after ");
1078 }
1079 
1080 void HeapShared::clear_archived_roots_of(Klass* k) {
1081   unsigned int hash = SystemDictionaryShared::hash_for_shared_dictionary_quick(k);
1082   const ArchivedKlassSubGraphInfoRecord* record = _run_time_subgraph_info_table.lookup(k, hash, 0);
1083   if (record != nullptr) {
1084     Array<int>* entry_field_records = record->entry_field_records();
1085     if (entry_field_records != nullptr) {
1086       int efr_len = entry_field_records->length();
1087       assert(efr_len % 2 == 0, "sanity");
1088       for (int i = 0; i < efr_len; i += 2) {
1089         int root_index = entry_field_records->at(i+1);
1090         clear_root(root_index);
1091       }
1092     }
1093   }
1094 }
1095 
1096 class WalkOopAndArchiveClosure: public BasicOopIterateClosure {
1097   int _level;
1098   bool _record_klasses_only;
1099   KlassSubGraphInfo* _subgraph_info;
1100   oop _referencing_obj;
1101 
1102   // The following are for maintaining a stack for determining
1103   // CachedOopInfo::_referrer
1104   static WalkOopAndArchiveClosure* _current;
1105   WalkOopAndArchiveClosure* _last;
1106  public:
1107   WalkOopAndArchiveClosure(int level,
1108                            bool record_klasses_only,
1109                            KlassSubGraphInfo* subgraph_info,
1110                            oop orig) :
1111     _level(level),
1112     _record_klasses_only(record_klasses_only),
1113     _subgraph_info(subgraph_info),
1114     _referencing_obj(orig) {
1115     _last = _current;
1116     _current = this;
1117   }
1118   ~WalkOopAndArchiveClosure() {
1119     _current = _last;
1120   }
1121   void do_oop(narrowOop *p) { WalkOopAndArchiveClosure::do_oop_work(p); }
1122   void do_oop(      oop *p) { WalkOopAndArchiveClosure::do_oop_work(p); }
1123 
1124  protected:
1125   template <class T> void do_oop_work(T *p) {
1126     oop obj = RawAccess<>::oop_load(p);
1127     if (!CompressedOops::is_null(obj)) {
1128       size_t field_delta = pointer_delta(p, _referencing_obj, sizeof(char));
1129 
1130       if (!_record_klasses_only && log_is_enabled(Debug, cds, heap)) {
1131         ResourceMark rm;
1132         log_debug(cds, heap)("(%d) %s[" SIZE_FORMAT "] ==> " PTR_FORMAT " size " SIZE_FORMAT " %s", _level,
1133                              _referencing_obj->klass()->external_name(), field_delta,
1134                              p2i(obj), obj->size() * HeapWordSize, obj->klass()->external_name());
1135         if (log_is_enabled(Trace, cds, heap)) {
1136           LogTarget(Trace, cds, heap) log;
1137           LogStream out(log);
1138           obj->print_on(&out);
1139         }
1140       }
1141 
1142       bool success = HeapShared::archive_reachable_objects_from(
1143           _level + 1, _subgraph_info, obj);
1144       assert(success, "VM should have exited with unarchivable objects for _level > 1");
1145     }
1146   }
1147 
1148  public:
1149   static WalkOopAndArchiveClosure* current()  { return _current;              }
1150   oop referencing_obj()                       { return _referencing_obj;      }
1151   KlassSubGraphInfo* subgraph_info()          { return _subgraph_info;        }
1152 };
1153 
1154 WalkOopAndArchiveClosure* WalkOopAndArchiveClosure::_current = nullptr;
1155 
1156 // Checks if an oop has any non-null oop fields
1157 class PointsToOopsChecker : public BasicOopIterateClosure {
1158   bool _result;
1159 
1160   template <class T> void check(T *p) {
1161     _result |= (HeapAccess<>::oop_load(p) != nullptr);
1162   }
1163 
1164 public:
1165   PointsToOopsChecker() : _result(false) {}
1166   void do_oop(narrowOop *p) { check(p); }
1167   void do_oop(      oop *p) { check(p); }
1168   bool result() { return _result; }
1169 };
1170 
1171 HeapShared::CachedOopInfo HeapShared::make_cached_oop_info(oop obj) {
1172   WalkOopAndArchiveClosure* walker = WalkOopAndArchiveClosure::current();
1173   oop referrer = (walker == nullptr) ? nullptr : walker->referencing_obj();
1174   PointsToOopsChecker points_to_oops_checker;
1175   obj->oop_iterate(&points_to_oops_checker);
1176   return CachedOopInfo(referrer, points_to_oops_checker.result());
1177 }
1178 
1179 // (1) If orig_obj has not been archived yet, archive it.
1180 // (2) If orig_obj has not been seen yet (since start_recording_subgraph() was called),
1181 //     trace all  objects that are reachable from it, and make sure these objects are archived.
1182 // (3) Record the klasses of all orig_obj and all reachable objects.
1183 bool HeapShared::archive_reachable_objects_from(int level,
1184                                                 KlassSubGraphInfo* subgraph_info,
1185                                                 oop orig_obj) {
1186   assert(orig_obj != nullptr, "must be");
1187 
1188   if (!JavaClasses::is_supported_for_archiving(orig_obj)) {
1189     // This object has injected fields that cannot be supported easily, so we disallow them for now.
1190     // If you get an error here, you probably made a change in the JDK library that has added
1191     // these objects that are referenced (directly or indirectly) by static fields.
1192     ResourceMark rm;
1193     log_error(cds, heap)("Cannot archive object of class %s", orig_obj->klass()->external_name());
1194     MetaspaceShared::unrecoverable_writing_error();
1195   }
1196 
1197   // java.lang.Class instances cannot be included in an archived object sub-graph. We only support
1198   // them as Klass::_archived_mirror because they need to be specially restored at run time.
1199   //
1200   // If you get an error here, you probably made a change in the JDK library that has added a Class
1201   // object that is referenced (directly or indirectly) by static fields.
1202   if (java_lang_Class::is_instance(orig_obj) && subgraph_info != _default_subgraph_info) {
1203     log_error(cds, heap)("(%d) Unknown java.lang.Class object is in the archived sub-graph", level);
1204     MetaspaceShared::unrecoverable_writing_error();
1205   }
1206 
1207   if (has_been_seen_during_subgraph_recording(orig_obj)) {
1208     // orig_obj has already been archived and traced. Nothing more to do.
1209     return true;
1210   } else {
1211     set_has_been_seen_during_subgraph_recording(orig_obj);
1212   }
1213 
1214   bool already_archived = has_been_archived(orig_obj);
1215   bool record_klasses_only = already_archived;
1216   if (!already_archived) {
1217     ++_num_new_archived_objs;
1218     if (!archive_object(orig_obj)) {
1219       // Skip archiving the sub-graph referenced from the current entry field.
1220       ResourceMark rm;
1221       log_error(cds, heap)(
1222         "Cannot archive the sub-graph referenced from %s object ("
1223         PTR_FORMAT ") size " SIZE_FORMAT ", skipped.",
1224         orig_obj->klass()->external_name(), p2i(orig_obj), orig_obj->size() * HeapWordSize);
1225       if (level == 1) {
1226         // Don't archive a subgraph root that's too big. For archives static fields, that's OK
1227         // as the Java code will take care of initializing this field dynamically.
1228         return false;
1229       } else {
1230         // We don't know how to handle an object that has been archived, but some of its reachable
1231         // objects cannot be archived. Bail out for now. We might need to fix this in the future if
1232         // we have a real use case.
1233         MetaspaceShared::unrecoverable_writing_error();
1234       }
1235     }
1236   }
1237 
1238   Klass *orig_k = orig_obj->klass();
1239   subgraph_info->add_subgraph_object_klass(orig_k);
1240 
1241   WalkOopAndArchiveClosure walker(level, record_klasses_only, subgraph_info, orig_obj);
1242   orig_obj->oop_iterate(&walker);
1243 
1244   check_enum_obj(level + 1, subgraph_info, orig_obj);
1245   return true;
1246 }
1247 
1248 //
1249 // Start from the given static field in a java mirror and archive the
1250 // complete sub-graph of java heap objects that are reached directly
1251 // or indirectly from the starting object by following references.
1252 // Sub-graph archiving restrictions (current):
1253 //
1254 // - All classes of objects in the archived sub-graph (including the
1255 //   entry class) must be boot class only.
1256 // - No java.lang.Class instance (java mirror) can be included inside
1257 //   an archived sub-graph. Mirror can only be the sub-graph entry object.
1258 //
1259 // The Java heap object sub-graph archiving process (see
1260 // WalkOopAndArchiveClosure):
1261 //
1262 // 1) Java object sub-graph archiving starts from a given static field
1263 // within a Class instance (java mirror). If the static field is a
1264 // reference field and points to a non-null java object, proceed to
1265 // the next step.
1266 //
1267 // 2) Archives the referenced java object. If an archived copy of the
1268 // current object already exists, updates the pointer in the archived
1269 // copy of the referencing object to point to the current archived object.
1270 // Otherwise, proceed to the next step.
1271 //
1272 // 3) Follows all references within the current java object and recursively
1273 // archive the sub-graph of objects starting from each reference.
1274 //
1275 // 4) Updates the pointer in the archived copy of referencing object to
1276 // point to the current archived object.
1277 //
1278 // 5) The Klass of the current java object is added to the list of Klasses
1279 // for loading and initializing before any object in the archived graph can
1280 // be accessed at runtime.
1281 //
1282 void HeapShared::archive_reachable_objects_from_static_field(InstanceKlass *k,
1283                                                              const char* klass_name,
1284                                                              int field_offset,
1285                                                              const char* field_name) {
1286   assert(CDSConfig::is_dumping_heap(), "dump time only");
1287   assert(k->is_shared_boot_class(), "must be boot class");
1288 
1289   oop m = k->java_mirror();
1290 
1291   KlassSubGraphInfo* subgraph_info = get_subgraph_info(k);
1292   oop f = m->obj_field(field_offset);
1293 
1294   log_debug(cds, heap)("Start archiving from: %s::%s (" PTR_FORMAT ")", klass_name, field_name, p2i(f));
1295 
1296   if (!CompressedOops::is_null(f)) {
1297     if (log_is_enabled(Trace, cds, heap)) {
1298       LogTarget(Trace, cds, heap) log;
1299       LogStream out(log);
1300       f->print_on(&out);
1301     }
1302 
1303     bool success = archive_reachable_objects_from(1, subgraph_info, f);
1304     if (!success) {
1305       log_error(cds, heap)("Archiving failed %s::%s (some reachable objects cannot be archived)",
1306                            klass_name, field_name);
1307     } else {
1308       // Note: the field value is not preserved in the archived mirror.
1309       // Record the field as a new subGraph entry point. The recorded
1310       // information is restored from the archive at runtime.
1311       subgraph_info->add_subgraph_entry_field(field_offset, f);
1312       log_info(cds, heap)("Archived field %s::%s => " PTR_FORMAT, klass_name, field_name, p2i(f));
1313     }
1314   } else {
1315     // The field contains null, we still need to record the entry point,
1316     // so it can be restored at runtime.
1317     subgraph_info->add_subgraph_entry_field(field_offset, nullptr);
1318   }
1319 }
1320 
1321 #ifndef PRODUCT
1322 class VerifySharedOopClosure: public BasicOopIterateClosure {
1323  public:
1324   void do_oop(narrowOop *p) { VerifySharedOopClosure::do_oop_work(p); }
1325   void do_oop(      oop *p) { VerifySharedOopClosure::do_oop_work(p); }
1326 
1327  protected:
1328   template <class T> void do_oop_work(T *p) {
1329     oop obj = RawAccess<>::oop_load(p);
1330     if (!CompressedOops::is_null(obj)) {
1331       HeapShared::verify_reachable_objects_from(obj);
1332     }
1333   }
1334 };
1335 
1336 void HeapShared::verify_subgraph_from_static_field(InstanceKlass* k, int field_offset) {
1337   assert(CDSConfig::is_dumping_heap(), "dump time only");
1338   assert(k->is_shared_boot_class(), "must be boot class");
1339 
1340   oop m = k->java_mirror();
1341   oop f = m->obj_field(field_offset);
1342   if (!CompressedOops::is_null(f)) {
1343     verify_subgraph_from(f);
1344   }
1345 }
1346 
1347 void HeapShared::verify_subgraph_from(oop orig_obj) {
1348   if (!has_been_archived(orig_obj)) {
1349     // It's OK for the root of a subgraph to be not archived. See comments in
1350     // archive_reachable_objects_from().
1351     return;
1352   }
1353 
1354   // Verify that all objects reachable from orig_obj are archived.
1355   init_seen_objects_table();
1356   verify_reachable_objects_from(orig_obj);
1357   delete_seen_objects_table();
1358 }
1359 
1360 void HeapShared::verify_reachable_objects_from(oop obj) {
1361   _num_total_verifications ++;
1362   if (!has_been_seen_during_subgraph_recording(obj)) {
1363     set_has_been_seen_during_subgraph_recording(obj);
1364     assert(has_been_archived(obj), "must be");
1365     VerifySharedOopClosure walker;
1366     obj->oop_iterate(&walker);
1367   }
1368 }
1369 #endif
1370 
1371 // The "default subgraph" contains special objects (see heapShared.hpp) that
1372 // can be accessed before we load any Java classes (including java/lang/Class).
1373 // Make sure that these are only instances of the very few specific types
1374 // that we can handle.
1375 void HeapShared::check_default_subgraph_classes() {
1376   GrowableArray<Klass*>* klasses = _default_subgraph_info->subgraph_object_klasses();
1377   int num = klasses->length();
1378   for (int i = 0; i < num; i++) {
1379     Klass* subgraph_k = klasses->at(i);
1380     if (log_is_enabled(Info, cds, heap)) {
1381       ResourceMark rm;
1382       log_info(cds, heap)(
1383           "Archived object klass (default subgraph %d) => %s",
1384           i, subgraph_k->external_name());
1385     }
1386 
1387     Symbol* name = ArchiveBuilder::current()->get_source_addr(subgraph_k->name());
1388     guarantee(name == vmSymbols::java_lang_Class() ||
1389               name == vmSymbols::java_lang_String() ||
1390               name == vmSymbols::java_lang_ArithmeticException() ||
1391               name == vmSymbols::java_lang_NullPointerException() ||
1392               name == vmSymbols::java_lang_InternalError() ||
1393               name == vmSymbols::object_array_signature() ||
1394               name == vmSymbols::byte_array_signature() ||
1395               name == vmSymbols::char_array_signature(),
1396               "default subgraph can have only these objects");
1397   }
1398 }
1399 
1400 HeapShared::SeenObjectsTable* HeapShared::_seen_objects_table = nullptr;
1401 int HeapShared::_num_new_walked_objs;
1402 int HeapShared::_num_new_archived_objs;
1403 int HeapShared::_num_old_recorded_klasses;
1404 
1405 int HeapShared::_num_total_subgraph_recordings = 0;
1406 int HeapShared::_num_total_walked_objs = 0;
1407 int HeapShared::_num_total_archived_objs = 0;
1408 int HeapShared::_num_total_recorded_klasses = 0;
1409 int HeapShared::_num_total_verifications = 0;
1410 
1411 bool HeapShared::has_been_seen_during_subgraph_recording(oop obj) {
1412   return _seen_objects_table->get(obj) != nullptr;
1413 }
1414 
1415 void HeapShared::set_has_been_seen_during_subgraph_recording(oop obj) {
1416   assert(!has_been_seen_during_subgraph_recording(obj), "sanity");
1417   _seen_objects_table->put_when_absent(obj, true);
1418   _seen_objects_table->maybe_grow();
1419   ++ _num_new_walked_objs;
1420 }
1421 
1422 void HeapShared::start_recording_subgraph(InstanceKlass *k, const char* class_name, bool is_full_module_graph) {
1423   log_info(cds, heap)("Start recording subgraph(s) for archived fields in %s", class_name);
1424   init_subgraph_info(k, is_full_module_graph);
1425   init_seen_objects_table();
1426   _num_new_walked_objs = 0;
1427   _num_new_archived_objs = 0;
1428   _num_old_recorded_klasses = get_subgraph_info(k)->num_subgraph_object_klasses();
1429 }
1430 
1431 void HeapShared::done_recording_subgraph(InstanceKlass *k, const char* class_name) {
1432   int num_new_recorded_klasses = get_subgraph_info(k)->num_subgraph_object_klasses() -
1433     _num_old_recorded_klasses;
1434   log_info(cds, heap)("Done recording subgraph(s) for archived fields in %s: "
1435                       "walked %d objs, archived %d new objs, recorded %d classes",
1436                       class_name, _num_new_walked_objs, _num_new_archived_objs,
1437                       num_new_recorded_klasses);
1438 
1439   delete_seen_objects_table();
1440 
1441   _num_total_subgraph_recordings ++;
1442   _num_total_walked_objs      += _num_new_walked_objs;
1443   _num_total_archived_objs    += _num_new_archived_objs;
1444   _num_total_recorded_klasses +=  num_new_recorded_klasses;
1445 }
1446 
1447 class ArchivableStaticFieldFinder: public FieldClosure {
1448   InstanceKlass* _ik;
1449   Symbol* _field_name;
1450   bool _found;
1451   int _offset;
1452 public:
1453   ArchivableStaticFieldFinder(InstanceKlass* ik, Symbol* field_name) :
1454     _ik(ik), _field_name(field_name), _found(false), _offset(-1) {}
1455 
1456   virtual void do_field(fieldDescriptor* fd) {
1457     if (fd->name() == _field_name) {
1458       assert(!_found, "fields can never be overloaded");
1459       if (is_reference_type(fd->field_type())) {
1460         _found = true;
1461         _offset = fd->offset();
1462       }
1463     }
1464   }
1465   bool found()     { return _found;  }
1466   int offset()     { return _offset; }
1467 };
1468 
1469 void HeapShared::init_subgraph_entry_fields(ArchivableStaticFieldInfo fields[],
1470                                             TRAPS) {
1471   for (int i = 0; fields[i].valid(); i++) {
1472     ArchivableStaticFieldInfo* info = &fields[i];
1473     TempNewSymbol klass_name =  SymbolTable::new_symbol(info->klass_name);
1474     TempNewSymbol field_name =  SymbolTable::new_symbol(info->field_name);
1475     ResourceMark rm; // for stringStream::as_string() etc.
1476 
1477 #ifndef PRODUCT
1478     bool is_test_class = (ArchiveHeapTestClass != nullptr) && (strcmp(info->klass_name, ArchiveHeapTestClass) == 0);
1479     const char* test_class_name = ArchiveHeapTestClass;
1480 #else
1481     bool is_test_class = false;
1482     const char* test_class_name = ""; // avoid C++ printf checks warnings.
1483 #endif
1484 
1485     if (is_test_class) {
1486       log_warning(cds)("Loading ArchiveHeapTestClass %s ...", test_class_name);
1487     }
1488 
1489     Klass* k = SystemDictionary::resolve_or_fail(klass_name, true, THREAD);
1490     if (HAS_PENDING_EXCEPTION) {
1491       CLEAR_PENDING_EXCEPTION;
1492       stringStream st;
1493       st.print("Fail to initialize archive heap: %s cannot be loaded by the boot loader", info->klass_name);
1494       THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), st.as_string());
1495     }
1496 
1497     if (!k->is_instance_klass()) {
1498       stringStream st;
1499       st.print("Fail to initialize archive heap: %s is not an instance class", info->klass_name);
1500       THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), st.as_string());
1501     }
1502 
1503     InstanceKlass* ik = InstanceKlass::cast(k);
1504     assert(InstanceKlass::cast(ik)->is_shared_boot_class(),
1505            "Only support boot classes");
1506 
1507     if (is_test_class) {
1508       if (ik->module()->is_named()) {
1509         // We don't want ArchiveHeapTestClass to be abused to easily load/initialize arbitrary
1510         // core-lib classes. You need to at least append to the bootclasspath.
1511         stringStream st;
1512         st.print("ArchiveHeapTestClass %s is not in unnamed module", test_class_name);
1513         THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), st.as_string());
1514       }
1515 
1516       if (ik->package() != nullptr) {
1517         // This restriction makes HeapShared::is_a_test_class_in_unnamed_module() easy.
1518         stringStream st;
1519         st.print("ArchiveHeapTestClass %s is not in unnamed package", test_class_name);
1520         THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), st.as_string());
1521       }
1522     } else {
1523       if (ik->module()->name() != vmSymbols::java_base()) {
1524         // We don't want to deal with cases when a module is unavailable at runtime.
1525         // FUTURE -- load from archived heap only when module graph has not changed
1526         //           between dump and runtime.
1527         stringStream st;
1528         st.print("%s is not in java.base module", info->klass_name);
1529         THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), st.as_string());
1530       }
1531     }
1532 
1533     if (is_test_class) {
1534       log_warning(cds)("Initializing ArchiveHeapTestClass %s ...", test_class_name);
1535     }
1536     ik->initialize(CHECK);
1537 
1538     ArchivableStaticFieldFinder finder(ik, field_name);
1539     ik->do_local_static_fields(&finder);
1540     if (!finder.found()) {
1541       stringStream st;
1542       st.print("Unable to find the static T_OBJECT field %s::%s", info->klass_name, info->field_name);
1543       THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), st.as_string());
1544     }
1545 
1546     info->klass = ik;
1547     info->offset = finder.offset();
1548   }
1549 }
1550 
1551 void HeapShared::init_subgraph_entry_fields(TRAPS) {
1552   assert(HeapShared::can_write(), "must be");
1553   _dump_time_subgraph_info_table = new (mtClass)DumpTimeKlassSubGraphInfoTable();
1554   init_subgraph_entry_fields(archive_subgraph_entry_fields, CHECK);
1555   if (CDSConfig::is_dumping_full_module_graph()) {
1556     init_subgraph_entry_fields(fmg_archive_subgraph_entry_fields, CHECK);
1557   }
1558 }
1559 
1560 #ifndef PRODUCT
1561 void HeapShared::setup_test_class(const char* test_class_name) {
1562   ArchivableStaticFieldInfo* p = archive_subgraph_entry_fields;
1563   int num_slots = sizeof(archive_subgraph_entry_fields) / sizeof(ArchivableStaticFieldInfo);
1564   assert(p[num_slots - 2].klass_name == nullptr, "must have empty slot that's patched below");
1565   assert(p[num_slots - 1].klass_name == nullptr, "must have empty slot that marks the end of the list");
1566 
1567   if (test_class_name != nullptr) {
1568     p[num_slots - 2].klass_name = test_class_name;
1569     p[num_slots - 2].field_name = ARCHIVE_TEST_FIELD_NAME;
1570   }
1571 }
1572 
1573 // See if ik is one of the test classes that are pulled in by -XX:ArchiveHeapTestClass
1574 // during runtime. This may be called before the module system is initialized so
1575 // we cannot rely on InstanceKlass::module(), etc.
1576 bool HeapShared::is_a_test_class_in_unnamed_module(Klass* ik) {
1577   if (_test_class != nullptr) {
1578     if (ik == _test_class) {
1579       return true;
1580     }
1581     Array<Klass*>* klasses = _test_class_record->subgraph_object_klasses();
1582     if (klasses == nullptr) {
1583       return false;
1584     }
1585 
1586     for (int i = 0; i < klasses->length(); i++) {
1587       Klass* k = klasses->at(i);
1588       if (k == ik) {
1589         Symbol* name;
1590         if (k->is_instance_klass()) {
1591           name = InstanceKlass::cast(k)->name();
1592         } else if (k->is_objArray_klass()) {
1593           Klass* bk = ObjArrayKlass::cast(k)->bottom_klass();
1594           if (!bk->is_instance_klass()) {
1595             return false;
1596           }
1597           name = bk->name();
1598         } else {
1599           return false;
1600         }
1601 
1602         // See KlassSubGraphInfo::check_allowed_klass() - only two types of
1603         // classes are allowed:
1604         //   (A) java.base classes (which must not be in the unnamed module)
1605         //   (B) test classes which must be in the unnamed package of the unnamed module.
1606         // So if we see a '/' character in the class name, it must be in (A);
1607         // otherwise it must be in (B).
1608         if (name->index_of_at(0, "/", 1)  >= 0) {
1609           return false; // (A)
1610         }
1611 
1612         return true; // (B)
1613       }
1614     }
1615   }
1616 
1617   return false;
1618 }
1619 #endif
1620 
1621 void HeapShared::init_for_dumping(TRAPS) {
1622   if (HeapShared::can_write()) {
1623     setup_test_class(ArchiveHeapTestClass);
1624     _dumped_interned_strings = new (mtClass)DumpedInternedStrings(INITIAL_TABLE_SIZE, MAX_TABLE_SIZE);
1625     init_subgraph_entry_fields(CHECK);
1626   }
1627 }
1628 
1629 void HeapShared::archive_object_subgraphs(ArchivableStaticFieldInfo fields[],
1630                                           bool is_full_module_graph) {
1631   _num_total_subgraph_recordings = 0;
1632   _num_total_walked_objs = 0;
1633   _num_total_archived_objs = 0;
1634   _num_total_recorded_klasses = 0;
1635   _num_total_verifications = 0;
1636 
1637   // For each class X that has one or more archived fields:
1638   // [1] Dump the subgraph of each archived field
1639   // [2] Create a list of all the class of the objects that can be reached
1640   //     by any of these static fields.
1641   //     At runtime, these classes are initialized before X's archived fields
1642   //     are restored by HeapShared::initialize_from_archived_subgraph().
1643   int i;
1644   for (int i = 0; fields[i].valid(); ) {
1645     ArchivableStaticFieldInfo* info = &fields[i];
1646     const char* klass_name = info->klass_name;
1647     start_recording_subgraph(info->klass, klass_name, is_full_module_graph);
1648 
1649     // If you have specified consecutive fields of the same klass in
1650     // fields[], these will be archived in the same
1651     // {start_recording_subgraph ... done_recording_subgraph} pass to
1652     // save time.
1653     for (; fields[i].valid(); i++) {
1654       ArchivableStaticFieldInfo* f = &fields[i];
1655       if (f->klass_name != klass_name) {
1656         break;
1657       }
1658 
1659       archive_reachable_objects_from_static_field(f->klass, f->klass_name,
1660                                                   f->offset, f->field_name);
1661     }
1662     done_recording_subgraph(info->klass, klass_name);
1663   }
1664 
1665   log_info(cds, heap)("Archived subgraph records = %d",
1666                       _num_total_subgraph_recordings);
1667   log_info(cds, heap)("  Walked %d objects", _num_total_walked_objs);
1668   log_info(cds, heap)("  Archived %d objects", _num_total_archived_objs);
1669   log_info(cds, heap)("  Recorded %d klasses", _num_total_recorded_klasses);
1670 
1671 #ifndef PRODUCT
1672   for (int i = 0; fields[i].valid(); i++) {
1673     ArchivableStaticFieldInfo* f = &fields[i];
1674     verify_subgraph_from_static_field(f->klass, f->offset);
1675   }
1676   log_info(cds, heap)("  Verified %d references", _num_total_verifications);
1677 #endif
1678 }
1679 
1680 // Not all the strings in the global StringTable are dumped into the archive, because
1681 // some of those strings may be only referenced by classes that are excluded from
1682 // the archive. We need to explicitly mark the strings that are:
1683 //   [1] used by classes that WILL be archived;
1684 //   [2] included in the SharedArchiveConfigFile.
1685 void HeapShared::add_to_dumped_interned_strings(oop string) {
1686   assert_at_safepoint(); // DumpedInternedStrings uses raw oops
1687   assert(!ArchiveHeapWriter::is_string_too_large_to_archive(string), "must be");
1688   bool created;
1689   _dumped_interned_strings->put_if_absent(string, true, &created);
1690   if (created) {
1691     _dumped_interned_strings->maybe_grow();
1692   }
1693 }
1694 
1695 #ifndef PRODUCT
1696 // At dump-time, find the location of all the non-null oop pointers in an archived heap
1697 // region. This way we can quickly relocate all the pointers without using
1698 // BasicOopIterateClosure at runtime.
1699 class FindEmbeddedNonNullPointers: public BasicOopIterateClosure {
1700   void* _start;
1701   BitMap *_oopmap;
1702   int _num_total_oops;
1703   int _num_null_oops;
1704  public:
1705   FindEmbeddedNonNullPointers(void* start, BitMap* oopmap)
1706     : _start(start), _oopmap(oopmap), _num_total_oops(0),  _num_null_oops(0) {}
1707 
1708   virtual void do_oop(narrowOop* p) {
1709     assert(UseCompressedOops, "sanity");
1710     _num_total_oops ++;
1711     narrowOop v = *p;
1712     if (!CompressedOops::is_null(v)) {
1713       size_t idx = p - (narrowOop*)_start;
1714       _oopmap->set_bit(idx);
1715     } else {
1716       _num_null_oops ++;
1717     }
1718   }
1719   virtual void do_oop(oop* p) {
1720     assert(!UseCompressedOops, "sanity");
1721     _num_total_oops ++;
1722     if ((*p) != nullptr) {
1723       size_t idx = p - (oop*)_start;
1724       _oopmap->set_bit(idx);
1725     } else {
1726       _num_null_oops ++;
1727     }
1728   }
1729   int num_total_oops() const { return _num_total_oops; }
1730   int num_null_oops()  const { return _num_null_oops; }
1731 };
1732 #endif
1733 
1734 #ifndef PRODUCT
1735 ResourceBitMap HeapShared::calculate_oopmap(MemRegion region) {
1736   size_t num_bits = region.byte_size() / (UseCompressedOops ? sizeof(narrowOop) : sizeof(oop));
1737   ResourceBitMap oopmap(num_bits);
1738 
1739   HeapWord* p   = region.start();
1740   HeapWord* end = region.end();
1741   FindEmbeddedNonNullPointers finder((void*)p, &oopmap);
1742 
1743   int num_objs = 0;
1744   while (p < end) {
1745     oop o = cast_to_oop(p);
1746     o->oop_iterate(&finder);
1747     p += o->size();
1748     ++ num_objs;
1749   }
1750 
1751   log_info(cds, heap)("calculate_oopmap: objects = %6d, oop fields = %7d (nulls = %7d)",
1752                       num_objs, finder.num_total_oops(), finder.num_null_oops());
1753   return oopmap;
1754 }
1755 
1756 #endif // !PRODUCT
1757 
1758 void HeapShared::count_allocation(size_t size) {
1759   _total_obj_count ++;
1760   _total_obj_size += size;
1761   for (int i = 0; i < ALLOC_STAT_SLOTS; i++) {
1762     if (size <= (size_t(1) << i)) {
1763       _alloc_count[i] ++;
1764       _alloc_size[i] += size;
1765       return;
1766     }
1767   }
1768 }
1769 
1770 static double avg_size(size_t size, size_t count) {
1771   double avg = 0;
1772   if (count > 0) {
1773     avg = double(size * HeapWordSize) / double(count);
1774   }
1775   return avg;
1776 }
1777 
1778 void HeapShared::print_stats() {
1779   size_t huge_count = _total_obj_count;
1780   size_t huge_size = _total_obj_size;
1781 
1782   for (int i = 0; i < ALLOC_STAT_SLOTS; i++) {
1783     size_t byte_size_limit = (size_t(1) << i) * HeapWordSize;
1784     size_t count = _alloc_count[i];
1785     size_t size = _alloc_size[i];
1786     log_info(cds, heap)(SIZE_FORMAT_W(8) " objects are <= " SIZE_FORMAT_W(-6)
1787                         " bytes (total " SIZE_FORMAT_W(8) " bytes, avg %8.1f bytes)",
1788                         count, byte_size_limit, size * HeapWordSize, avg_size(size, count));
1789     huge_count -= count;
1790     huge_size -= size;
1791   }
1792 
1793   log_info(cds, heap)(SIZE_FORMAT_W(8) " huge  objects               (total "  SIZE_FORMAT_W(8) " bytes"
1794                       ", avg %8.1f bytes)",
1795                       huge_count, huge_size * HeapWordSize,
1796                       avg_size(huge_size, huge_count));
1797   log_info(cds, heap)(SIZE_FORMAT_W(8) " total objects               (total "  SIZE_FORMAT_W(8) " bytes"
1798                       ", avg %8.1f bytes)",
1799                       _total_obj_count, _total_obj_size * HeapWordSize,
1800                       avg_size(_total_obj_size, _total_obj_count));
1801 }
1802 
1803 bool HeapShared::is_archived_boot_layer_available(JavaThread* current) {
1804   TempNewSymbol klass_name = SymbolTable::new_symbol(ARCHIVED_BOOT_LAYER_CLASS);
1805   InstanceKlass* k = SystemDictionary::find_instance_klass(current, klass_name, Handle(), Handle());
1806   if (k == nullptr) {
1807     return false;
1808   } else {
1809     TempNewSymbol field_name = SymbolTable::new_symbol(ARCHIVED_BOOT_LAYER_FIELD);
1810     TempNewSymbol field_signature = SymbolTable::new_symbol("Ljdk/internal/module/ArchivedBootLayer;");
1811     fieldDescriptor fd;
1812     if (k->find_field(field_name, field_signature, true, &fd) != nullptr) {
1813       oop m = k->java_mirror();
1814       oop f = m->obj_field(fd.offset());
1815       if (CompressedOops::is_null(f)) {
1816         return false;
1817       }
1818     } else {
1819       return false;
1820     }
1821   }
1822   return true;
1823 }
1824 
1825 #endif // INCLUDE_CDS_JAVA_HEAP