1 /*
   2  * Copyright (c) 2018, 2021, 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/archiveUtils.hpp"
  28 #include "cds/filemap.hpp"
  29 #include "cds/heapShared.inline.hpp"
  30 #include "cds/metaspaceShared.hpp"
  31 #include "classfile/classLoaderData.hpp"
  32 #include "classfile/classLoaderDataShared.hpp"
  33 #include "classfile/javaClasses.inline.hpp"
  34 #include "classfile/moduleEntry.hpp"
  35 #include "classfile/stringTable.hpp"
  36 #include "classfile/symbolTable.hpp"
  37 #include "classfile/systemDictionary.hpp"
  38 #include "classfile/systemDictionaryShared.hpp"
  39 #include "classfile/vmClasses.hpp"
  40 #include "classfile/vmSymbols.hpp"
  41 #include "gc/shared/gcLocker.hpp"
  42 #include "gc/shared/gcVMOperations.hpp"
  43 #include "logging/log.hpp"
  44 #include "logging/logMessage.hpp"
  45 #include "logging/logStream.hpp"
  46 #include "memory/iterator.inline.hpp"
  47 #include "memory/metadataFactory.hpp"
  48 #include "memory/metaspaceClosure.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.hpp"
  54 #include "oops/oop.inline.hpp"
  55 #include "prims/jvmtiExport.hpp"
  56 #include "runtime/fieldDescriptor.inline.hpp"
  57 #include "runtime/globals_extension.hpp"
  58 #include "runtime/init.hpp"
  59 #include "runtime/java.hpp"
  60 #include "runtime/javaCalls.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 bool HeapShared::_closed_archive_heap_region_mapped = false;
  71 bool HeapShared::_open_archive_heap_region_mapped = false;
  72 bool HeapShared::_archive_heap_region_fixed = false;
  73 address   HeapShared::_narrow_oop_base;
  74 int       HeapShared::_narrow_oop_shift;
  75 DumpedInternedStrings *HeapShared::_dumped_interned_strings = NULL;
  76 
  77 //
  78 // If you add new entries to the following tables, you should know what you're doing!
  79 //
  80 
  81 // Entry fields for shareable subgraphs archived in the closed archive heap
  82 // region. Warning: Objects in the subgraphs should not have reference fields
  83 // assigned at runtime.
  84 static ArchivableStaticFieldInfo closed_archive_subgraph_entry_fields[] = {
  85   {"java/lang/Integer$IntegerCache",              "archivedCache"},
  86   {"java/lang/Long$LongCache",                    "archivedCache"},
  87   {"java/lang/Byte$ByteCache",                    "archivedCache"},
  88   {"java/lang/Short$ShortCache",                  "archivedCache"},
  89   {"java/lang/Character$CharacterCache",          "archivedCache"},
  90   {"java/util/jar/Attributes$Name",               "KNOWN_NAMES"},
  91   {"sun/util/locale/BaseLocale",                  "constantBaseLocales"},
  92 };
  93 // Entry fields for subgraphs archived in the open archive heap region.
  94 static ArchivableStaticFieldInfo open_archive_subgraph_entry_fields[] = {
  95   {"jdk/internal/module/ArchivedModuleGraph",     "archivedModuleGraph"},
  96   {"java/util/ImmutableCollections",              "archivedObjects"},
  97   {"java/lang/ModuleLayer",                       "EMPTY_LAYER"},
  98   {"java/lang/module/Configuration",              "EMPTY_CONFIGURATION"},
  99   {"jdk/internal/math/FDBigInteger",              "archivedCaches"},
 100 };
 101 
 102 // Entry fields for subgraphs archived in the open archive heap region (full module graph).
 103 static ArchivableStaticFieldInfo fmg_open_archive_subgraph_entry_fields[] = {
 104   {"jdk/internal/loader/ArchivedClassLoaders",    "archivedClassLoaders"},
 105   {"jdk/internal/module/ArchivedBootLayer",       "archivedBootLayer"},
 106   {"java/lang/Module$ArchivedData",               "archivedData"},
 107 };
 108 
 109 const static int num_closed_archive_subgraph_entry_fields =
 110   sizeof(closed_archive_subgraph_entry_fields) / sizeof(ArchivableStaticFieldInfo);
 111 const static int num_open_archive_subgraph_entry_fields =
 112   sizeof(open_archive_subgraph_entry_fields) / sizeof(ArchivableStaticFieldInfo);
 113 const static int num_fmg_open_archive_subgraph_entry_fields =
 114   sizeof(fmg_open_archive_subgraph_entry_fields) / sizeof(ArchivableStaticFieldInfo);
 115 
 116 GrowableArrayCHeap<oop, mtClassShared>* HeapShared::_pending_roots = NULL;
 117 narrowOop HeapShared::_roots_narrow;
 118 OopHandle HeapShared::_roots;
 119 
 120 ////////////////////////////////////////////////////////////////
 121 //
 122 // Java heap object archiving support
 123 //
 124 ////////////////////////////////////////////////////////////////
 125 void HeapShared::fixup_mapped_heap_regions() {
 126   FileMapInfo *mapinfo = FileMapInfo::current_info();
 127   mapinfo->fixup_mapped_heap_regions();
 128   set_archive_heap_region_fixed();
 129   if (is_mapped()) {
 130     _roots = OopHandle(Universe::vm_global(), decode_from_archive(_roots_narrow));
 131     if (!MetaspaceShared::use_full_module_graph()) {
 132       // Need to remove all the archived java.lang.Module objects from HeapShared::roots().
 133       ClassLoaderDataShared::clear_archived_oops();
 134     }
 135   }
 136   SystemDictionaryShared::update_archived_mirror_native_pointers();
 137 }
 138 
 139 unsigned HeapShared::oop_hash(oop const& p) {
 140   assert(!p->mark().has_bias_pattern(),
 141          "this object should never have been locked");  // so identity_hash won't safepoin
 142   unsigned hash = (unsigned)p->identity_hash();
 143   return hash;
 144 }
 145 
 146 static void reset_states(oop obj, TRAPS) {
 147   Handle h_obj(THREAD, obj);
 148   InstanceKlass* klass = InstanceKlass::cast(obj->klass());
 149   TempNewSymbol method_name = SymbolTable::new_symbol("resetArchivedStates");
 150   Symbol* method_sig = vmSymbols::void_method_signature();
 151 
 152   while (klass != NULL) {
 153     Method* method = klass->find_method(method_name, method_sig);
 154     if (method != NULL) {
 155       assert(method->is_private(), "must be");
 156       if (log_is_enabled(Debug, cds)) {
 157         ResourceMark rm(THREAD);
 158         log_debug(cds)("  calling %s", method->name_and_sig_as_C_string());
 159       }
 160       JavaValue result(T_VOID);
 161       JavaCalls::call_special(&result, h_obj, klass,
 162                               method_name, method_sig, CHECK);
 163     }
 164     klass = klass->java_super();
 165   }
 166 }
 167 
 168 void HeapShared::reset_archived_object_states(TRAPS) {
 169   assert(DumpSharedSpaces, "dump-time only");
 170   log_debug(cds)("Resetting platform loader");
 171   reset_states(SystemDictionary::java_platform_loader(), CHECK);
 172   log_debug(cds)("Resetting system loader");
 173   reset_states(SystemDictionary::java_system_loader(), CHECK);
 174 }
 175 
 176 HeapShared::ArchivedObjectCache* HeapShared::_archived_object_cache = NULL;
 177 oop HeapShared::find_archived_heap_object(oop obj) {
 178   assert(DumpSharedSpaces, "dump-time only");
 179   ArchivedObjectCache* cache = archived_object_cache();
 180   oop* p = cache->get(obj);
 181   if (p != NULL) {
 182     return *p;
 183   } else {
 184     return NULL;
 185   }
 186 }
 187 
 188 int HeapShared::append_root(oop obj) {
 189   assert(DumpSharedSpaces, "dump-time only");
 190 
 191   // No GC should happen since we aren't scanning _pending_roots.
 192   assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
 193 
 194   if (_pending_roots == NULL) {
 195     _pending_roots = new GrowableArrayCHeap<oop, mtClassShared>(500);
 196   }
 197 
 198   return _pending_roots->append(obj);
 199 }
 200 
 201 objArrayOop HeapShared::roots() {
 202   if (DumpSharedSpaces) {
 203     assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
 204     if (!is_heap_object_archiving_allowed()) {
 205       return NULL;
 206     }
 207   } else {
 208     assert(UseSharedSpaces, "must be");
 209   }
 210 
 211   objArrayOop roots = (objArrayOop)_roots.resolve();
 212   assert(roots != NULL, "should have been initialized");
 213   return roots;
 214 }
 215 
 216 void HeapShared::set_roots(narrowOop roots) {
 217   assert(UseSharedSpaces, "runtime only");
 218   assert(open_archive_heap_region_mapped(), "must be");
 219   _roots_narrow = roots;
 220 }
 221 
 222 // Returns an objArray that contains all the roots of the archived objects
 223 oop HeapShared::get_root(int index, bool clear) {
 224   assert(index >= 0, "sanity");
 225   if (DumpSharedSpaces) {
 226     assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
 227     assert(_pending_roots != NULL, "sanity");
 228     return _pending_roots->at(index);
 229   } else {
 230     assert(UseSharedSpaces, "must be");
 231     assert(!_roots.is_empty(), "must have loaded shared heap");
 232     oop result = roots()->obj_at(index);
 233     if (clear) {
 234       clear_root(index);
 235     }
 236     return result;
 237   }
 238 }
 239 
 240 void HeapShared::clear_root(int index) {
 241   assert(index >= 0, "sanity");
 242   assert(UseSharedSpaces, "must be");
 243   if (open_archive_heap_region_mapped()) {
 244     if (log_is_enabled(Debug, cds, heap)) {
 245       oop old = roots()->obj_at(index);
 246       log_debug(cds, heap)("Clearing root %d: was " PTR_FORMAT, index, p2i(old));
 247     }
 248     roots()->obj_at_put(index, NULL);
 249   }
 250 }
 251 
 252 oop HeapShared::archive_heap_object(oop obj) {
 253   assert(DumpSharedSpaces, "dump-time only");
 254 
 255   oop ao = find_archived_heap_object(obj);
 256   if (ao != NULL) {
 257     // already archived
 258     return ao;
 259   }
 260 
 261   int len = obj->size();
 262   if (G1CollectedHeap::heap()->is_archive_alloc_too_large(len)) {
 263     log_debug(cds, heap)("Cannot archive, object (" PTR_FORMAT ") is too large: " SIZE_FORMAT,
 264                          p2i(obj), (size_t)obj->size());
 265     return NULL;
 266   }
 267 
 268   oop archived_oop = cast_to_oop(G1CollectedHeap::heap()->archive_mem_allocate(len));
 269   if (archived_oop != NULL) {
 270     Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(obj), cast_from_oop<HeapWord*>(archived_oop), len);
 271     // Reinitialize markword to remove age/marking/locking/etc.
 272     //
 273     // We need to retain the identity_hash, because it may have been used by some hashtables
 274     // in the shared heap. This also has the side effect of pre-initializing the
 275     // identity_hash for all shared objects, so they are less likely to be written
 276     // into during run time, increasing the potential of memory sharing.
 277     int hash_original = obj->identity_hash();
 278     archived_oop->set_mark(markWord::prototype().copy_set_hash(hash_original));
 279     assert(archived_oop->mark().is_unlocked(), "sanity");
 280 
 281     DEBUG_ONLY(int hash_archived = archived_oop->identity_hash());
 282     assert(hash_original == hash_archived, "Different hash codes: original %x, archived %x", hash_original, hash_archived);
 283 
 284     ArchivedObjectCache* cache = archived_object_cache();
 285     cache->put(obj, archived_oop);
 286     if (log_is_enabled(Debug, cds, heap)) {
 287       ResourceMark rm;
 288       log_debug(cds, heap)("Archived heap object " PTR_FORMAT " ==> " PTR_FORMAT " : %s",
 289                            p2i(obj), p2i(archived_oop), obj->klass()->external_name());
 290     }
 291   } else {
 292     log_error(cds, heap)(
 293       "Cannot allocate space for object " PTR_FORMAT " in archived heap region",
 294       p2i(obj));
 295     vm_direct_exit(-1,
 296       err_msg("Out of memory. Please run with a larger Java heap, current MaxHeapSize = "
 297               SIZE_FORMAT "M", MaxHeapSize/M));
 298   }
 299   return archived_oop;
 300 }
 301 
 302 void HeapShared::archive_klass_objects() {
 303   GrowableArray<Klass*>* klasses = ArchiveBuilder::current()->klasses();
 304   assert(klasses != NULL, "sanity");
 305   for (int i = 0; i < klasses->length(); i++) {
 306     Klass* k = ArchiveBuilder::get_relocated_klass(klasses->at(i));
 307 
 308     // archive mirror object
 309     java_lang_Class::archive_mirror(k);
 310 
 311     // archive the resolved_referenes array
 312     if (k->is_instance_klass()) {
 313       InstanceKlass* ik = InstanceKlass::cast(k);
 314       ik->constants()->archive_resolved_references();
 315     }
 316   }
 317 }
 318 
 319 void HeapShared::run_full_gc_in_vm_thread() {
 320   if (is_heap_object_archiving_allowed()) {
 321     // Avoid fragmentation while archiving heap objects.
 322     // We do this inside a safepoint, so that no further allocation can happen after GC
 323     // has finished.
 324     if (GCLocker::is_active()) {
 325       // Just checking for safety ...
 326       // This should not happen during -Xshare:dump. If you see this, probably the Java core lib
 327       // has been modified such that JNI code is executed in some clean up threads after
 328       // we have finished class loading.
 329       log_warning(cds)("GC locker is held, unable to start extra compacting GC. This may produce suboptimal results.");
 330     } else {
 331       log_info(cds)("Run GC ...");
 332       Universe::heap()->collect_as_vm_thread(GCCause::_archive_time_gc);
 333       log_info(cds)("Run GC done");
 334     }
 335   }
 336 }
 337 
 338 void HeapShared::archive_java_heap_objects(GrowableArray<MemRegion>* closed,
 339                                            GrowableArray<MemRegion>* open) {
 340 
 341   G1HeapVerifier::verify_ready_for_archiving();
 342 
 343   {
 344     NoSafepointVerifier nsv;
 345 
 346     // Cache for recording where the archived objects are copied to
 347     create_archived_object_cache();
 348 
 349     log_info(cds)("Heap range = [" PTR_FORMAT " - "  PTR_FORMAT "]",
 350                   p2i(CompressedOops::begin()), p2i(CompressedOops::end()));
 351     log_info(cds)("Dumping objects to closed archive heap region ...");
 352     copy_closed_archive_heap_objects(closed);
 353 
 354     log_info(cds)("Dumping objects to open archive heap region ...");
 355     copy_open_archive_heap_objects(open);
 356 
 357     destroy_archived_object_cache();
 358   }
 359 
 360   G1HeapVerifier::verify_archive_regions();
 361 }
 362 
 363 void HeapShared::copy_closed_archive_heap_objects(
 364                                     GrowableArray<MemRegion> * closed_archive) {
 365   assert(is_heap_object_archiving_allowed(), "Cannot archive java heap objects");
 366 
 367   G1CollectedHeap::heap()->begin_archive_alloc_range();
 368 
 369   // Archive interned string objects
 370   StringTable::write_to_archive(_dumped_interned_strings);
 371 
 372   archive_object_subgraphs(closed_archive_subgraph_entry_fields,
 373                            num_closed_archive_subgraph_entry_fields,
 374                            true /* is_closed_archive */,
 375                            false /* is_full_module_graph */);
 376 
 377   G1CollectedHeap::heap()->end_archive_alloc_range(closed_archive,
 378                                                    os::vm_allocation_granularity());
 379 }
 380 
 381 void HeapShared::copy_open_archive_heap_objects(
 382                                     GrowableArray<MemRegion> * open_archive) {
 383   assert(is_heap_object_archiving_allowed(), "Cannot archive java heap objects");
 384 
 385   G1CollectedHeap::heap()->begin_archive_alloc_range(true /* open */);
 386 
 387   java_lang_Class::archive_basic_type_mirrors();
 388 
 389   archive_klass_objects();
 390 
 391   archive_object_subgraphs(open_archive_subgraph_entry_fields,
 392                            num_open_archive_subgraph_entry_fields,
 393                            false /* is_closed_archive */,
 394                            false /* is_full_module_graph */);
 395   if (MetaspaceShared::use_full_module_graph()) {
 396     archive_object_subgraphs(fmg_open_archive_subgraph_entry_fields,
 397                              num_fmg_open_archive_subgraph_entry_fields,
 398                              false /* is_closed_archive */,
 399                              true /* is_full_module_graph */);
 400     ClassLoaderDataShared::init_archived_oops();
 401   }
 402 
 403   copy_roots();
 404 
 405   G1CollectedHeap::heap()->end_archive_alloc_range(open_archive,
 406                                                    os::vm_allocation_granularity());
 407 }
 408 
 409 // Copy _pending_archive_roots into an objArray
 410 void HeapShared::copy_roots() {
 411   int length = _pending_roots != NULL ? _pending_roots->length() : 0;
 412   int size = objArrayOopDesc::object_size(length);
 413   Klass* k = Universe::objectArrayKlassObj(); // already relocated to point to archived klass
 414   HeapWord* mem = G1CollectedHeap::heap()->archive_mem_allocate(size);
 415 
 416   memset(mem, 0, size * BytesPerWord);
 417   {
 418     // This is copied from MemAllocator::finish
 419     if (UseBiasedLocking) {
 420       oopDesc::set_mark(mem, k->prototype_header());
 421     } else {
 422       oopDesc::set_mark(mem, markWord::prototype());
 423     }
 424     oopDesc::release_set_klass(mem, k);
 425   }
 426   {
 427     // This is copied from ObjArrayAllocator::initialize
 428     arrayOopDesc::set_length(mem, length);
 429   }
 430 
 431   _roots = OopHandle(Universe::vm_global(), cast_to_oop(mem));
 432   for (int i = 0; i < length; i++) {
 433     roots()->obj_at_put(i, _pending_roots->at(i));
 434   }
 435   log_info(cds)("archived obj roots[%d] = %d words, klass = %p, obj = %p", length, size, k, mem);
 436 }
 437 
 438 void HeapShared::init_narrow_oop_decoding(address base, int shift) {
 439   _narrow_oop_base = base;
 440   _narrow_oop_shift = shift;
 441 }
 442 
 443 //
 444 // Subgraph archiving support
 445 //
 446 HeapShared::DumpTimeKlassSubGraphInfoTable* HeapShared::_dump_time_subgraph_info_table = NULL;
 447 HeapShared::RunTimeKlassSubGraphInfoTable   HeapShared::_run_time_subgraph_info_table;
 448 
 449 // Get the subgraph_info for Klass k. A new subgraph_info is created if
 450 // there is no existing one for k. The subgraph_info records the relocated
 451 // Klass* of the original k.
 452 KlassSubGraphInfo* HeapShared::init_subgraph_info(Klass* k, bool is_full_module_graph) {
 453   assert(DumpSharedSpaces, "dump time only");
 454   bool created;
 455   Klass* relocated_k = ArchiveBuilder::get_relocated_klass(k);
 456   KlassSubGraphInfo* info =
 457     _dump_time_subgraph_info_table->put_if_absent(relocated_k, KlassSubGraphInfo(relocated_k, is_full_module_graph),
 458                                                   &created);
 459   assert(created, "must not initialize twice");
 460   return info;
 461 }
 462 
 463 KlassSubGraphInfo* HeapShared::get_subgraph_info(Klass* k) {
 464   assert(DumpSharedSpaces, "dump time only");
 465   Klass* relocated_k = ArchiveBuilder::get_relocated_klass(k);
 466   KlassSubGraphInfo* info = _dump_time_subgraph_info_table->get(relocated_k);
 467   assert(info != NULL, "must have been initialized");
 468   return info;
 469 }
 470 
 471 // Add an entry field to the current KlassSubGraphInfo.
 472 void KlassSubGraphInfo::add_subgraph_entry_field(
 473       int static_field_offset, oop v, bool is_closed_archive) {
 474   assert(DumpSharedSpaces, "dump time only");
 475   if (_subgraph_entry_fields == NULL) {
 476     _subgraph_entry_fields =
 477       new(ResourceObj::C_HEAP, mtClass) GrowableArray<int>(10, mtClass);
 478   }
 479   _subgraph_entry_fields->append(static_field_offset);
 480   _subgraph_entry_fields->append(HeapShared::append_root(v));
 481 }
 482 
 483 // Add the Klass* for an object in the current KlassSubGraphInfo's subgraphs.
 484 // Only objects of boot classes can be included in sub-graph.
 485 void KlassSubGraphInfo::add_subgraph_object_klass(Klass* orig_k) {
 486   assert(DumpSharedSpaces, "dump time only");
 487   Klass* relocated_k = ArchiveBuilder::get_relocated_klass(orig_k);
 488 
 489   if (_subgraph_object_klasses == NULL) {
 490     _subgraph_object_klasses =
 491       new(ResourceObj::C_HEAP, mtClass) GrowableArray<Klass*>(50, mtClass);
 492   }
 493 
 494   assert(ArchiveBuilder::current()->is_in_buffer_space(relocated_k), "must be a shared class");
 495 
 496   if (_k == relocated_k) {
 497     // Don't add the Klass containing the sub-graph to it's own klass
 498     // initialization list.
 499     return;
 500   }
 501 
 502   if (relocated_k->is_instance_klass()) {
 503     assert(InstanceKlass::cast(relocated_k)->is_shared_boot_class(),
 504           "must be boot class");
 505     // vmClasses::xxx_klass() are not updated, need to check
 506     // the original Klass*
 507     if (orig_k == vmClasses::String_klass() ||
 508         orig_k == vmClasses::Object_klass()) {
 509       // Initialized early during VM initialization. No need to be added
 510       // to the sub-graph object class list.
 511       return;
 512     }
 513   } else if (relocated_k->is_objArray_klass()) {
 514     Klass* abk = ObjArrayKlass::cast(relocated_k)->bottom_klass();
 515     if (abk->is_instance_klass()) {
 516       assert(InstanceKlass::cast(abk)->is_shared_boot_class(),
 517             "must be boot class");
 518     }
 519     if (relocated_k == Universe::objectArrayKlassObj()) {
 520       // Initialized early during Universe::genesis. No need to be added
 521       // to the list.
 522       return;
 523     }
 524   } else {
 525     assert(relocated_k->is_typeArray_klass(), "must be");
 526     // Primitive type arrays are created early during Universe::genesis.
 527     return;
 528   }
 529 
 530   if (log_is_enabled(Debug, cds, heap)) {
 531     if (!_subgraph_object_klasses->contains(relocated_k)) {
 532       ResourceMark rm;
 533       log_debug(cds, heap)("Adding klass %s", orig_k->external_name());
 534     }
 535   }
 536 
 537   _subgraph_object_klasses->append_if_missing(relocated_k);
 538   _has_non_early_klasses |= is_non_early_klass(orig_k);
 539 }
 540 
 541 bool KlassSubGraphInfo::is_non_early_klass(Klass* k) {
 542   if (k->is_objArray_klass()) {
 543     k = ObjArrayKlass::cast(k)->bottom_klass();
 544   }
 545   if (k->is_instance_klass()) {
 546     if (!SystemDictionaryShared::is_early_klass(InstanceKlass::cast(k))) {
 547       ResourceMark rm;
 548       log_info(cds, heap)("non-early: %s", k->external_name());
 549       return true;
 550     } else {
 551       return false;
 552     }
 553   } else {
 554     return false;
 555   }
 556 }
 557 
 558 // Initialize an archived subgraph_info_record from the given KlassSubGraphInfo.
 559 void ArchivedKlassSubGraphInfoRecord::init(KlassSubGraphInfo* info) {
 560   _k = info->klass();
 561   _entry_field_records = NULL;
 562   _subgraph_object_klasses = NULL;
 563   _is_full_module_graph = info->is_full_module_graph();
 564 
 565   if (_is_full_module_graph) {
 566     // Consider all classes referenced by the full module graph as early -- we will be
 567     // allocating objects of these classes during JVMTI early phase, so they cannot
 568     // be processed by (non-early) JVMTI ClassFileLoadHook
 569     _has_non_early_klasses = false;
 570   } else {
 571     _has_non_early_klasses = info->has_non_early_klasses();
 572   }
 573 
 574   if (_has_non_early_klasses) {
 575     ResourceMark rm;
 576     log_info(cds, heap)(
 577           "Subgraph of klass %s has non-early klasses and cannot be used when JVMTI ClassFileLoadHook is enabled",
 578           _k->external_name());
 579   }
 580 
 581   // populate the entry fields
 582   GrowableArray<int>* entry_fields = info->subgraph_entry_fields();
 583   if (entry_fields != NULL) {
 584     int num_entry_fields = entry_fields->length();
 585     assert(num_entry_fields % 2 == 0, "sanity");
 586     _entry_field_records =
 587       ArchiveBuilder::new_ro_array<int>(num_entry_fields);
 588     for (int i = 0 ; i < num_entry_fields; i++) {
 589       _entry_field_records->at_put(i, entry_fields->at(i));
 590     }
 591   }
 592 
 593   // the Klasses of the objects in the sub-graphs
 594   GrowableArray<Klass*>* subgraph_object_klasses = info->subgraph_object_klasses();
 595   if (subgraph_object_klasses != NULL) {
 596     int num_subgraphs_klasses = subgraph_object_klasses->length();
 597     _subgraph_object_klasses =
 598       ArchiveBuilder::new_ro_array<Klass*>(num_subgraphs_klasses);
 599     for (int i = 0; i < num_subgraphs_klasses; i++) {
 600       Klass* subgraph_k = subgraph_object_klasses->at(i);
 601       if (log_is_enabled(Info, cds, heap)) {
 602         ResourceMark rm;
 603         log_info(cds, heap)(
 604           "Archived object klass %s (%2d) => %s",
 605           _k->external_name(), i, subgraph_k->external_name());
 606       }
 607       _subgraph_object_klasses->at_put(i, subgraph_k);
 608       ArchivePtrMarker::mark_pointer(_subgraph_object_klasses->adr_at(i));
 609     }
 610   }
 611 
 612   ArchivePtrMarker::mark_pointer(&_k);
 613   ArchivePtrMarker::mark_pointer(&_entry_field_records);
 614   ArchivePtrMarker::mark_pointer(&_subgraph_object_klasses);
 615 }
 616 
 617 struct CopyKlassSubGraphInfoToArchive : StackObj {
 618   CompactHashtableWriter* _writer;
 619   CopyKlassSubGraphInfoToArchive(CompactHashtableWriter* writer) : _writer(writer) {}
 620 
 621   bool do_entry(Klass* klass, KlassSubGraphInfo& info) {
 622     if (info.subgraph_object_klasses() != NULL || info.subgraph_entry_fields() != NULL) {
 623       ArchivedKlassSubGraphInfoRecord* record =
 624         (ArchivedKlassSubGraphInfoRecord*)ArchiveBuilder::ro_region_alloc(sizeof(ArchivedKlassSubGraphInfoRecord));
 625       record->init(&info);
 626 
 627       unsigned int hash = SystemDictionaryShared::hash_for_shared_dictionary((address)klass);
 628       u4 delta = ArchiveBuilder::current()->any_to_offset_u4(record);
 629       _writer->add(hash, delta);
 630     }
 631     return true; // keep on iterating
 632   }
 633 };
 634 
 635 // Build the records of archived subgraph infos, which include:
 636 // - Entry points to all subgraphs from the containing class mirror. The entry
 637 //   points are static fields in the mirror. For each entry point, the field
 638 //   offset, value and is_closed_archive flag are recorded in the sub-graph
 639 //   info. The value is stored back to the corresponding field at runtime.
 640 // - A list of klasses that need to be loaded/initialized before archived
 641 //   java object sub-graph can be accessed at runtime.
 642 void HeapShared::write_subgraph_info_table() {
 643   // Allocate the contents of the hashtable(s) inside the RO region of the CDS archive.
 644   DumpTimeKlassSubGraphInfoTable* d_table = _dump_time_subgraph_info_table;
 645   CompactHashtableStats stats;
 646 
 647   _run_time_subgraph_info_table.reset();
 648 
 649   CompactHashtableWriter writer(d_table->_count, &stats);
 650   CopyKlassSubGraphInfoToArchive copy(&writer);
 651   d_table->iterate(&copy);
 652 
 653   writer.dump(&_run_time_subgraph_info_table, "subgraphs");
 654 }
 655 
 656 void HeapShared::serialize_subgraph_info_table_header(SerializeClosure* soc) {
 657   _run_time_subgraph_info_table.serialize_header(soc);
 658 }
 659 
 660 static void verify_the_heap(Klass* k, const char* which) {
 661   if (VerifyArchivedFields) {
 662     ResourceMark rm;
 663     log_info(cds, heap)("Verify heap %s initializing static field(s) in %s",
 664                         which, k->external_name());
 665 
 666     VM_Verify verify_op;
 667     VMThread::execute(&verify_op);
 668 
 669     if (!FLAG_IS_DEFAULT(VerifyArchivedFields)) {
 670       // If VerifyArchivedFields has a non-default value (e.g., specified on the command-line), do
 671       // more expensive checks.
 672       if (is_init_completed()) {
 673         FlagSetting fs1(VerifyBeforeGC, true);
 674         FlagSetting fs2(VerifyDuringGC, true);
 675         FlagSetting fs3(VerifyAfterGC,  true);
 676         Universe::heap()->collect(GCCause::_java_lang_system_gc);
 677       }
 678     }
 679   }
 680 }
 681 
 682 // Before GC can execute, we must ensure that all oops reachable from HeapShared::roots()
 683 // have a valid klass. I.e., oopDesc::klass() must have already been resolved.
 684 //
 685 // Note: if a ArchivedKlassSubGraphInfoRecord contains non-early classes, and JVMTI
 686 // ClassFileLoadHook is enabled, it's possible for this class to be dynamically replaced. In
 687 // this case, we will not load the ArchivedKlassSubGraphInfoRecord and will clear its roots.
 688 void HeapShared::resolve_classes(JavaThread* THREAD) {
 689   if (!is_mapped()) {
 690     return; // nothing to do
 691   }
 692   resolve_classes_for_subgraphs(closed_archive_subgraph_entry_fields,
 693                                 num_closed_archive_subgraph_entry_fields,
 694                                 THREAD);
 695   resolve_classes_for_subgraphs(open_archive_subgraph_entry_fields,
 696                                 num_open_archive_subgraph_entry_fields,
 697                                 THREAD);
 698   resolve_classes_for_subgraphs(fmg_open_archive_subgraph_entry_fields,
 699                                 num_fmg_open_archive_subgraph_entry_fields,
 700                                 THREAD);
 701 }
 702 
 703 void HeapShared::resolve_classes_for_subgraphs(ArchivableStaticFieldInfo fields[],
 704                                                int num, JavaThread* THREAD) {
 705   for (int i = 0; i < num; i++) {
 706     ArchivableStaticFieldInfo* info = &fields[i];
 707     TempNewSymbol klass_name = SymbolTable::new_symbol(info->klass_name);
 708     InstanceKlass* k = SystemDictionaryShared::find_builtin_class(klass_name);
 709     assert(k != NULL && k->is_shared_boot_class(), "sanity");
 710     resolve_classes_for_subgraph_of(k, THREAD);
 711   }
 712 }
 713 
 714 void HeapShared::resolve_classes_for_subgraph_of(Klass* k, JavaThread* THREAD) {
 715   ExceptionMark em(THREAD);
 716   const ArchivedKlassSubGraphInfoRecord* record =
 717    resolve_or_init_classes_for_subgraph_of(k, /*do_init=*/false, THREAD);
 718   if (HAS_PENDING_EXCEPTION) {
 719    CLEAR_PENDING_EXCEPTION;
 720   }
 721   if (record == NULL) {
 722    clear_archived_roots_of(k);
 723   }
 724 }
 725 
 726 void HeapShared::initialize_from_archived_subgraph(Klass* k, JavaThread* THREAD) {
 727   if (!is_mapped()) {
 728     return; // nothing to do
 729   }
 730 
 731   ExceptionMark em(THREAD);
 732   const ArchivedKlassSubGraphInfoRecord* record =
 733     resolve_or_init_classes_for_subgraph_of(k, /*do_init=*/true, THREAD);
 734 
 735   if (HAS_PENDING_EXCEPTION) {
 736     CLEAR_PENDING_EXCEPTION;
 737     // None of the field value will be set if there was an exception when initializing the classes.
 738     // The java code will not see any of the archived objects in the
 739     // subgraphs referenced from k in this case.
 740     return;
 741   }
 742 
 743   if (record != NULL) {
 744     init_archived_fields_for(k, record);
 745   }
 746 }
 747 
 748 const ArchivedKlassSubGraphInfoRecord*
 749 HeapShared::resolve_or_init_classes_for_subgraph_of(Klass* k, bool do_init, TRAPS) {
 750   assert(!DumpSharedSpaces, "Should not be called with DumpSharedSpaces");
 751 
 752   if (!k->is_shared()) {
 753     return NULL;
 754   }
 755   unsigned int hash = SystemDictionaryShared::hash_for_shared_dictionary_quick(k);
 756   const ArchivedKlassSubGraphInfoRecord* record = _run_time_subgraph_info_table.lookup(k, hash, 0);
 757 
 758   // Initialize from archived data. Currently this is done only
 759   // during VM initialization time. No lock is needed.
 760   if (record != NULL) {
 761     if (record->is_full_module_graph() && !MetaspaceShared::use_full_module_graph()) {
 762       if (log_is_enabled(Info, cds, heap)) {
 763         ResourceMark rm(THREAD);
 764         log_info(cds, heap)("subgraph %s cannot be used because full module graph is disabled",
 765                             k->external_name());
 766       }
 767       return NULL;
 768     }
 769 
 770     if (record->has_non_early_klasses() && JvmtiExport::should_post_class_file_load_hook()) {
 771       if (log_is_enabled(Info, cds, heap)) {
 772         ResourceMark rm(THREAD);
 773         log_info(cds, heap)("subgraph %s cannot be used because JVMTI ClassFileLoadHook is enabled",
 774                             k->external_name());
 775       }
 776       return NULL;
 777     }
 778 
 779     resolve_or_init(k, do_init, CHECK_NULL);
 780 
 781     // Load/link/initialize the klasses of the objects in the subgraph.
 782     // NULL class loader is used.
 783     Array<Klass*>* klasses = record->subgraph_object_klasses();
 784     if (klasses != NULL) {
 785       for (int i = 0; i < klasses->length(); i++) {
 786         Klass* klass = klasses->at(i);
 787         if (!klass->is_shared()) {
 788           return NULL;
 789         }
 790         resolve_or_init(klass, do_init, CHECK_NULL);
 791       }
 792     }
 793   }
 794 
 795   return record;
 796 }
 797 
 798 void HeapShared::resolve_or_init(Klass* k, bool do_init, TRAPS) {
 799   if (!do_init) {
 800     if (k->class_loader_data() == NULL) {
 801       Klass* resolved_k = SystemDictionary::resolve_or_null(k->name(), CHECK);
 802       assert(resolved_k == k, "classes used by archived heap must not be replaced by JVMTI ClassFileLoadHook");
 803     }
 804   } else {
 805     assert(k->class_loader_data() != NULL, "must have been resolved by HeapShared::resolve_classes");
 806     if (k->is_instance_klass()) {
 807       InstanceKlass* ik = InstanceKlass::cast(k);
 808       ik->initialize(CHECK);
 809     } else if (k->is_objArray_klass()) {
 810       ObjArrayKlass* oak = ObjArrayKlass::cast(k);
 811       oak->initialize(CHECK);
 812     }
 813   }
 814 }
 815 
 816 void HeapShared::init_archived_fields_for(Klass* k, const ArchivedKlassSubGraphInfoRecord* record) {
 817   verify_the_heap(k, "before");
 818 
 819   // Load the subgraph entry fields from the record and store them back to
 820   // the corresponding fields within the mirror.
 821   oop m = k->java_mirror();
 822   Array<int>* entry_field_records = record->entry_field_records();
 823   if (entry_field_records != NULL) {
 824     int efr_len = entry_field_records->length();
 825     assert(efr_len % 2 == 0, "sanity");
 826     for (int i = 0; i < efr_len; i += 2) {
 827       int field_offset = entry_field_records->at(i);
 828       int root_index = entry_field_records->at(i+1);
 829       oop v = get_root(root_index, /*clear=*/true);
 830       m->obj_field_put(field_offset, v);
 831       log_debug(cds, heap)("  " PTR_FORMAT " init field @ %2d = " PTR_FORMAT, p2i(k), field_offset, p2i(v));
 832     }
 833 
 834     // Done. Java code can see the archived sub-graphs referenced from k's
 835     // mirror after this point.
 836     if (log_is_enabled(Info, cds, heap)) {
 837       ResourceMark rm;
 838       log_info(cds, heap)("initialize_from_archived_subgraph %s " PTR_FORMAT "%s",
 839                           k->external_name(), p2i(k), JvmtiExport::is_early_phase() ? " (early)" : "");
 840     }
 841   }
 842 
 843   verify_the_heap(k, "after ");
 844 }
 845 
 846 void HeapShared::clear_archived_roots_of(Klass* k) {
 847   unsigned int hash = SystemDictionaryShared::hash_for_shared_dictionary_quick(k);
 848   const ArchivedKlassSubGraphInfoRecord* record = _run_time_subgraph_info_table.lookup(k, hash, 0);
 849   if (record != NULL) {
 850     Array<int>* entry_field_records = record->entry_field_records();
 851     if (entry_field_records != NULL) {
 852       int efr_len = entry_field_records->length();
 853       assert(efr_len % 2 == 0, "sanity");
 854       for (int i = 0; i < efr_len; i += 2) {
 855         int root_index = entry_field_records->at(i+1);
 856         clear_root(root_index);
 857       }
 858     }
 859   }
 860 }
 861 
 862 class WalkOopAndArchiveClosure: public BasicOopIterateClosure {
 863   int _level;
 864   bool _is_closed_archive;
 865   bool _record_klasses_only;
 866   KlassSubGraphInfo* _subgraph_info;
 867   oop _orig_referencing_obj;
 868   oop _archived_referencing_obj;
 869  public:
 870   WalkOopAndArchiveClosure(int level,
 871                            bool is_closed_archive,
 872                            bool record_klasses_only,
 873                            KlassSubGraphInfo* subgraph_info,
 874                            oop orig, oop archived) :
 875     _level(level), _is_closed_archive(is_closed_archive),
 876     _record_klasses_only(record_klasses_only),
 877     _subgraph_info(subgraph_info),
 878     _orig_referencing_obj(orig), _archived_referencing_obj(archived) {}
 879   void do_oop(narrowOop *p) { WalkOopAndArchiveClosure::do_oop_work(p); }
 880   void do_oop(      oop *p) { WalkOopAndArchiveClosure::do_oop_work(p); }
 881 
 882  protected:
 883   template <class T> void do_oop_work(T *p) {
 884     oop obj = RawAccess<>::oop_load(p);
 885     if (!CompressedOops::is_null(obj)) {
 886       assert(!HeapShared::is_archived_object(obj),
 887              "original objects must not point to archived objects");
 888 
 889       size_t field_delta = pointer_delta(p, _orig_referencing_obj, sizeof(char));
 890       T* new_p = (T*)(cast_from_oop<address>(_archived_referencing_obj) + field_delta);
 891 
 892       if (!_record_klasses_only && log_is_enabled(Debug, cds, heap)) {
 893         ResourceMark rm;
 894         log_debug(cds, heap)("(%d) %s[" SIZE_FORMAT "] ==> " PTR_FORMAT " size %d %s", _level,
 895                              _orig_referencing_obj->klass()->external_name(), field_delta,
 896                              p2i(obj), obj->size() * HeapWordSize, obj->klass()->external_name());
 897         LogTarget(Trace, cds, heap) log;
 898         LogStream out(log);
 899         obj->print_on(&out);
 900       }
 901 
 902       oop archived = HeapShared::archive_reachable_objects_from(
 903           _level + 1, _subgraph_info, obj, _is_closed_archive);
 904       assert(archived != NULL, "VM should have exited with unarchivable objects for _level > 1");
 905       assert(HeapShared::is_archived_object(archived), "must be");
 906 
 907       if (!_record_klasses_only) {
 908         // Update the reference in the archived copy of the referencing object.
 909         log_debug(cds, heap)("(%d) updating oop @[" PTR_FORMAT "] " PTR_FORMAT " ==> " PTR_FORMAT,
 910                              _level, p2i(new_p), p2i(obj), p2i(archived));
 911         RawAccess<IS_NOT_NULL>::oop_store(new_p, archived);
 912       }
 913     }
 914   }
 915 };
 916 
 917 void HeapShared::check_closed_archive_heap_region_object(InstanceKlass* k) {
 918   // Check fields in the object
 919   for (JavaFieldStream fs(k); !fs.done(); fs.next()) {
 920     if (!fs.access_flags().is_static()) {
 921       BasicType ft = fs.field_descriptor().field_type();
 922       if (!fs.access_flags().is_final() && is_reference_type(ft)) {
 923         ResourceMark rm;
 924         log_warning(cds, heap)(
 925           "Please check reference field in %s instance in closed archive heap region: %s %s",
 926           k->external_name(), (fs.name())->as_C_string(),
 927           (fs.signature())->as_C_string());
 928       }
 929     }
 930   }
 931 }
 932 
 933 void HeapShared::check_module_oop(oop orig_module_obj) {
 934   assert(DumpSharedSpaces, "must be");
 935   assert(java_lang_Module::is_instance(orig_module_obj), "must be");
 936   ModuleEntry* orig_module_ent = java_lang_Module::module_entry_raw(orig_module_obj);
 937   if (orig_module_ent == NULL) {
 938     // These special Module objects are created in Java code. They are not
 939     // defined via Modules::define_module(), so they don't have a ModuleEntry:
 940     //     java.lang.Module::ALL_UNNAMED_MODULE
 941     //     java.lang.Module::EVERYONE_MODULE
 942     //     jdk.internal.loader.ClassLoaders$BootClassLoader::unnamedModule
 943     assert(java_lang_Module::name(orig_module_obj) == NULL, "must be unnamed");
 944     log_info(cds, heap)("Module oop with No ModuleEntry* @[" PTR_FORMAT "]", p2i(orig_module_obj));
 945   } else {
 946     ClassLoaderData* loader_data = orig_module_ent->loader_data();
 947     assert(loader_data->is_builtin_class_loader_data(), "must be");
 948   }
 949 }
 950 
 951 
 952 // (1) If orig_obj has not been archived yet, archive it.
 953 // (2) If orig_obj has not been seen yet (since start_recording_subgraph() was called),
 954 //     trace all  objects that are reachable from it, and make sure these objects are archived.
 955 // (3) Record the klasses of all orig_obj and all reachable objects.
 956 oop HeapShared::archive_reachable_objects_from(int level,
 957                                                KlassSubGraphInfo* subgraph_info,
 958                                                oop orig_obj,
 959                                                bool is_closed_archive) {
 960   assert(orig_obj != NULL, "must be");
 961   assert(!is_archived_object(orig_obj), "sanity");
 962 
 963   if (!JavaClasses::is_supported_for_archiving(orig_obj)) {
 964     // This object has injected fields that cannot be supported easily, so we disallow them for now.
 965     // If you get an error here, you probably made a change in the JDK library that has added
 966     // these objects that are referenced (directly or indirectly) by static fields.
 967     ResourceMark rm;
 968     log_error(cds, heap)("Cannot archive object of class %s", orig_obj->klass()->external_name());
 969     vm_direct_exit(1);
 970   }
 971 
 972   // java.lang.Class instances cannot be included in an archived object sub-graph. We only support
 973   // them as Klass::_archived_mirror because they need to be specially restored at run time.
 974   //
 975   // If you get an error here, you probably made a change in the JDK library that has added a Class
 976   // object that is referenced (directly or indirectly) by static fields.
 977   if (java_lang_Class::is_instance(orig_obj)) {
 978     log_error(cds, heap)("(%d) Unknown java.lang.Class object is in the archived sub-graph", level);
 979     vm_direct_exit(1);
 980   }
 981 
 982   oop archived_obj = find_archived_heap_object(orig_obj);
 983   if (java_lang_String::is_instance(orig_obj) && archived_obj != NULL) {
 984     // To save time, don't walk strings that are already archived. They just contain
 985     // pointers to a type array, whose klass doesn't need to be recorded.
 986     return archived_obj;
 987   }
 988 
 989   if (has_been_seen_during_subgraph_recording(orig_obj)) {
 990     // orig_obj has already been archived and traced. Nothing more to do.
 991     return archived_obj;
 992   } else {
 993     set_has_been_seen_during_subgraph_recording(orig_obj);
 994   }
 995 
 996   bool record_klasses_only = (archived_obj != NULL);
 997   if (archived_obj == NULL) {
 998     ++_num_new_archived_objs;
 999     archived_obj = archive_heap_object(orig_obj);
1000     if (archived_obj == NULL) {
1001       // Skip archiving the sub-graph referenced from the current entry field.
1002       ResourceMark rm;
1003       log_error(cds, heap)(
1004         "Cannot archive the sub-graph referenced from %s object ("
1005         PTR_FORMAT ") size %d, skipped.",
1006         orig_obj->klass()->external_name(), p2i(orig_obj), orig_obj->size() * HeapWordSize);
1007       if (level == 1) {
1008         // Don't archive a subgraph root that's too big. For archives static fields, that's OK
1009         // as the Java code will take care of initializing this field dynamically.
1010         return NULL;
1011       } else {
1012         // We don't know how to handle an object that has been archived, but some of its reachable
1013         // objects cannot be archived. Bail out for now. We might need to fix this in the future if
1014         // we have a real use case.
1015         vm_direct_exit(1);
1016       }
1017     }
1018 
1019     if (java_lang_Module::is_instance(orig_obj)) {
1020       check_module_oop(orig_obj);
1021       java_lang_Module::set_module_entry(archived_obj, NULL);
1022       java_lang_Module::set_loader(archived_obj, NULL);
1023     } else if (java_lang_ClassLoader::is_instance(orig_obj)) {
1024       // class_data will be restored explicitly at run time.
1025       guarantee(orig_obj == SystemDictionary::java_platform_loader() ||
1026                 orig_obj == SystemDictionary::java_system_loader() ||
1027                 java_lang_ClassLoader::loader_data_raw(orig_obj) == NULL, "must be");
1028       java_lang_ClassLoader::release_set_loader_data(archived_obj, NULL);
1029     }
1030   }
1031 
1032   assert(archived_obj != NULL, "must be");
1033   Klass *orig_k = orig_obj->klass();
1034   subgraph_info->add_subgraph_object_klass(orig_k);
1035 
1036   WalkOopAndArchiveClosure walker(level, is_closed_archive, record_klasses_only,
1037                                   subgraph_info, orig_obj, archived_obj);
1038   orig_obj->oop_iterate(&walker);
1039   if (is_closed_archive && orig_k->is_instance_klass()) {
1040     check_closed_archive_heap_region_object(InstanceKlass::cast(orig_k));
1041   }
1042   return archived_obj;
1043 }
1044 
1045 //
1046 // Start from the given static field in a java mirror and archive the
1047 // complete sub-graph of java heap objects that are reached directly
1048 // or indirectly from the starting object by following references.
1049 // Sub-graph archiving restrictions (current):
1050 //
1051 // - All classes of objects in the archived sub-graph (including the
1052 //   entry class) must be boot class only.
1053 // - No java.lang.Class instance (java mirror) can be included inside
1054 //   an archived sub-graph. Mirror can only be the sub-graph entry object.
1055 //
1056 // The Java heap object sub-graph archiving process (see
1057 // WalkOopAndArchiveClosure):
1058 //
1059 // 1) Java object sub-graph archiving starts from a given static field
1060 // within a Class instance (java mirror). If the static field is a
1061 // refererence field and points to a non-null java object, proceed to
1062 // the next step.
1063 //
1064 // 2) Archives the referenced java object. If an archived copy of the
1065 // current object already exists, updates the pointer in the archived
1066 // copy of the referencing object to point to the current archived object.
1067 // Otherwise, proceed to the next step.
1068 //
1069 // 3) Follows all references within the current java object and recursively
1070 // archive the sub-graph of objects starting from each reference.
1071 //
1072 // 4) Updates the pointer in the archived copy of referencing object to
1073 // point to the current archived object.
1074 //
1075 // 5) The Klass of the current java object is added to the list of Klasses
1076 // for loading and initialzing before any object in the archived graph can
1077 // be accessed at runtime.
1078 //
1079 void HeapShared::archive_reachable_objects_from_static_field(InstanceKlass *k,
1080                                                              const char* klass_name,
1081                                                              int field_offset,
1082                                                              const char* field_name,
1083                                                              bool is_closed_archive) {
1084   assert(DumpSharedSpaces, "dump time only");
1085   assert(k->is_shared_boot_class(), "must be boot class");
1086 
1087   oop m = k->java_mirror();
1088 
1089   KlassSubGraphInfo* subgraph_info = get_subgraph_info(k);
1090   oop f = m->obj_field(field_offset);
1091 
1092   log_debug(cds, heap)("Start archiving from: %s::%s (" PTR_FORMAT ")", klass_name, field_name, p2i(f));
1093 
1094   if (!CompressedOops::is_null(f)) {
1095     if (log_is_enabled(Trace, cds, heap)) {
1096       LogTarget(Trace, cds, heap) log;
1097       LogStream out(log);
1098       f->print_on(&out);
1099     }
1100 
1101     oop af = archive_reachable_objects_from(1, subgraph_info, f, is_closed_archive);
1102 
1103     if (af == NULL) {
1104       log_error(cds, heap)("Archiving failed %s::%s (some reachable objects cannot be archived)",
1105                            klass_name, field_name);
1106     } else {
1107       // Note: the field value is not preserved in the archived mirror.
1108       // Record the field as a new subGraph entry point. The recorded
1109       // information is restored from the archive at runtime.
1110       subgraph_info->add_subgraph_entry_field(field_offset, af, is_closed_archive);
1111       log_info(cds, heap)("Archived field %s::%s => " PTR_FORMAT, klass_name, field_name, p2i(af));
1112     }
1113   } else {
1114     // The field contains null, we still need to record the entry point,
1115     // so it can be restored at runtime.
1116     subgraph_info->add_subgraph_entry_field(field_offset, NULL, false);
1117   }
1118 }
1119 
1120 #ifndef PRODUCT
1121 class VerifySharedOopClosure: public BasicOopIterateClosure {
1122  private:
1123   bool _is_archived;
1124 
1125  public:
1126   VerifySharedOopClosure(bool is_archived) : _is_archived(is_archived) {}
1127 
1128   void do_oop(narrowOop *p) { VerifySharedOopClosure::do_oop_work(p); }
1129   void do_oop(      oop *p) { VerifySharedOopClosure::do_oop_work(p); }
1130 
1131  protected:
1132   template <class T> void do_oop_work(T *p) {
1133     oop obj = RawAccess<>::oop_load(p);
1134     if (!CompressedOops::is_null(obj)) {
1135       HeapShared::verify_reachable_objects_from(obj, _is_archived);
1136     }
1137   }
1138 };
1139 
1140 void HeapShared::verify_subgraph_from_static_field(InstanceKlass* k, int field_offset) {
1141   assert(DumpSharedSpaces, "dump time only");
1142   assert(k->is_shared_boot_class(), "must be boot class");
1143 
1144   oop m = k->java_mirror();
1145   oop f = m->obj_field(field_offset);
1146   if (!CompressedOops::is_null(f)) {
1147     verify_subgraph_from(f);
1148   }
1149 }
1150 
1151 void HeapShared::verify_subgraph_from(oop orig_obj) {
1152   oop archived_obj = find_archived_heap_object(orig_obj);
1153   if (archived_obj == NULL) {
1154     // It's OK for the root of a subgraph to be not archived. See comments in
1155     // archive_reachable_objects_from().
1156     return;
1157   }
1158 
1159   // Verify that all objects reachable from orig_obj are archived.
1160   init_seen_objects_table();
1161   verify_reachable_objects_from(orig_obj, false);
1162   delete_seen_objects_table();
1163 
1164   // Note: we could also verify that all objects reachable from the archived
1165   // copy of orig_obj can only point to archived objects, with:
1166   //      init_seen_objects_table();
1167   //      verify_reachable_objects_from(archived_obj, true);
1168   //      init_seen_objects_table();
1169   // but that's already done in G1HeapVerifier::verify_archive_regions so we
1170   // won't do it here.
1171 }
1172 
1173 void HeapShared::verify_reachable_objects_from(oop obj, bool is_archived) {
1174   _num_total_verifications ++;
1175   if (!has_been_seen_during_subgraph_recording(obj)) {
1176     set_has_been_seen_during_subgraph_recording(obj);
1177 
1178     if (is_archived) {
1179       assert(is_archived_object(obj), "must be");
1180       assert(find_archived_heap_object(obj) == NULL, "must be");
1181     } else {
1182       assert(!is_archived_object(obj), "must be");
1183       assert(find_archived_heap_object(obj) != NULL, "must be");
1184     }
1185 
1186     VerifySharedOopClosure walker(is_archived);
1187     obj->oop_iterate(&walker);
1188   }
1189 }
1190 #endif
1191 
1192 HeapShared::SeenObjectsTable* HeapShared::_seen_objects_table = NULL;
1193 int HeapShared::_num_new_walked_objs;
1194 int HeapShared::_num_new_archived_objs;
1195 int HeapShared::_num_old_recorded_klasses;
1196 
1197 int HeapShared::_num_total_subgraph_recordings = 0;
1198 int HeapShared::_num_total_walked_objs = 0;
1199 int HeapShared::_num_total_archived_objs = 0;
1200 int HeapShared::_num_total_recorded_klasses = 0;
1201 int HeapShared::_num_total_verifications = 0;
1202 
1203 bool HeapShared::has_been_seen_during_subgraph_recording(oop obj) {
1204   return _seen_objects_table->get(obj) != NULL;
1205 }
1206 
1207 void HeapShared::set_has_been_seen_during_subgraph_recording(oop obj) {
1208   assert(!has_been_seen_during_subgraph_recording(obj), "sanity");
1209   _seen_objects_table->put(obj, true);
1210   ++ _num_new_walked_objs;
1211 }
1212 
1213 void HeapShared::start_recording_subgraph(InstanceKlass *k, const char* class_name, bool is_full_module_graph) {
1214   log_info(cds, heap)("Start recording subgraph(s) for archived fields in %s", class_name);
1215   init_subgraph_info(k, is_full_module_graph);
1216   init_seen_objects_table();
1217   _num_new_walked_objs = 0;
1218   _num_new_archived_objs = 0;
1219   _num_old_recorded_klasses = get_subgraph_info(k)->num_subgraph_object_klasses();
1220 }
1221 
1222 void HeapShared::done_recording_subgraph(InstanceKlass *k, const char* class_name) {
1223   int num_new_recorded_klasses = get_subgraph_info(k)->num_subgraph_object_klasses() -
1224     _num_old_recorded_klasses;
1225   log_info(cds, heap)("Done recording subgraph(s) for archived fields in %s: "
1226                       "walked %d objs, archived %d new objs, recorded %d classes",
1227                       class_name, _num_new_walked_objs, _num_new_archived_objs,
1228                       num_new_recorded_klasses);
1229 
1230   delete_seen_objects_table();
1231 
1232   _num_total_subgraph_recordings ++;
1233   _num_total_walked_objs      += _num_new_walked_objs;
1234   _num_total_archived_objs    += _num_new_archived_objs;
1235   _num_total_recorded_klasses +=  num_new_recorded_klasses;
1236 }
1237 
1238 class ArchivableStaticFieldFinder: public FieldClosure {
1239   InstanceKlass* _ik;
1240   Symbol* _field_name;
1241   bool _found;
1242   int _offset;
1243 public:
1244   ArchivableStaticFieldFinder(InstanceKlass* ik, Symbol* field_name) :
1245     _ik(ik), _field_name(field_name), _found(false), _offset(-1) {}
1246 
1247   virtual void do_field(fieldDescriptor* fd) {
1248     if (fd->name() == _field_name) {
1249       assert(!_found, "fields cannot be overloaded");
1250       assert(is_reference_type(fd->field_type()), "can archive only fields that are references");
1251       _found = true;
1252       _offset = fd->offset();
1253     }
1254   }
1255   bool found()     { return _found;  }
1256   int offset()     { return _offset; }
1257 };
1258 
1259 void HeapShared::init_subgraph_entry_fields(ArchivableStaticFieldInfo fields[],
1260                                             int num, TRAPS) {
1261   for (int i = 0; i < num; i++) {
1262     ArchivableStaticFieldInfo* info = &fields[i];
1263     TempNewSymbol klass_name =  SymbolTable::new_symbol(info->klass_name);
1264     TempNewSymbol field_name =  SymbolTable::new_symbol(info->field_name);
1265 
1266     Klass* k = SystemDictionary::resolve_or_fail(klass_name, true, CHECK);
1267     InstanceKlass* ik = InstanceKlass::cast(k);
1268     assert(InstanceKlass::cast(ik)->is_shared_boot_class(),
1269            "Only support boot classes");
1270     ik->initialize(CHECK);
1271 
1272     ArchivableStaticFieldFinder finder(ik, field_name);
1273     ik->do_local_static_fields(&finder);
1274     assert(finder.found(), "field must exist");
1275 
1276     info->klass = ik;
1277     info->offset = finder.offset();
1278   }
1279 }
1280 
1281 void HeapShared::init_subgraph_entry_fields(TRAPS) {
1282   assert(is_heap_object_archiving_allowed(), "Sanity check");
1283   _dump_time_subgraph_info_table = new (ResourceObj::C_HEAP, mtClass)DumpTimeKlassSubGraphInfoTable();
1284   init_subgraph_entry_fields(closed_archive_subgraph_entry_fields,
1285                              num_closed_archive_subgraph_entry_fields,
1286                              CHECK);
1287   init_subgraph_entry_fields(open_archive_subgraph_entry_fields,
1288                              num_open_archive_subgraph_entry_fields,
1289                              CHECK);
1290   if (MetaspaceShared::use_full_module_graph()) {
1291     init_subgraph_entry_fields(fmg_open_archive_subgraph_entry_fields,
1292                                num_fmg_open_archive_subgraph_entry_fields,
1293                                CHECK);
1294   }
1295 }
1296 
1297 void HeapShared::init_for_dumping(TRAPS) {
1298   if (is_heap_object_archiving_allowed()) {
1299     _dumped_interned_strings = new (ResourceObj::C_HEAP, mtClass)DumpedInternedStrings();
1300     init_subgraph_entry_fields(CHECK);
1301   }
1302 }
1303 
1304 void HeapShared::archive_object_subgraphs(ArchivableStaticFieldInfo fields[],
1305                                           int num, bool is_closed_archive,
1306                                           bool is_full_module_graph) {
1307   _num_total_subgraph_recordings = 0;
1308   _num_total_walked_objs = 0;
1309   _num_total_archived_objs = 0;
1310   _num_total_recorded_klasses = 0;
1311   _num_total_verifications = 0;
1312 
1313   // For each class X that has one or more archived fields:
1314   // [1] Dump the subgraph of each archived field
1315   // [2] Create a list of all the class of the objects that can be reached
1316   //     by any of these static fields.
1317   //     At runtime, these classes are initialized before X's archived fields
1318   //     are restored by HeapShared::initialize_from_archived_subgraph().
1319   int i;
1320   for (i = 0; i < num; ) {
1321     ArchivableStaticFieldInfo* info = &fields[i];
1322     const char* klass_name = info->klass_name;
1323     start_recording_subgraph(info->klass, klass_name, is_full_module_graph);
1324 
1325     // If you have specified consecutive fields of the same klass in
1326     // fields[], these will be archived in the same
1327     // {start_recording_subgraph ... done_recording_subgraph} pass to
1328     // save time.
1329     for (; i < num; i++) {
1330       ArchivableStaticFieldInfo* f = &fields[i];
1331       if (f->klass_name != klass_name) {
1332         break;
1333       }
1334 
1335       archive_reachable_objects_from_static_field(f->klass, f->klass_name,
1336                                                   f->offset, f->field_name,
1337                                                   is_closed_archive);
1338     }
1339     done_recording_subgraph(info->klass, klass_name);
1340   }
1341 
1342   log_info(cds, heap)("Archived subgraph records in %s archive heap region = %d",
1343                       is_closed_archive ? "closed" : "open",
1344                       _num_total_subgraph_recordings);
1345   log_info(cds, heap)("  Walked %d objects", _num_total_walked_objs);
1346   log_info(cds, heap)("  Archived %d objects", _num_total_archived_objs);
1347   log_info(cds, heap)("  Recorded %d klasses", _num_total_recorded_klasses);
1348 
1349 #ifndef PRODUCT
1350   for (int i = 0; i < num; i++) {
1351     ArchivableStaticFieldInfo* f = &fields[i];
1352     verify_subgraph_from_static_field(f->klass, f->offset);
1353   }
1354   log_info(cds, heap)("  Verified %d references", _num_total_verifications);
1355 #endif
1356 }
1357 
1358 // Not all the strings in the global StringTable are dumped into the archive, because
1359 // some of those strings may be only referenced by classes that are excluded from
1360 // the archive. We need to explicitly mark the strings that are:
1361 //   [1] used by classes that WILL be archived;
1362 //   [2] included in the SharedArchiveConfigFile.
1363 void HeapShared::add_to_dumped_interned_strings(oop string) {
1364   assert_at_safepoint(); // DumpedInternedStrings uses raw oops
1365   bool created;
1366   _dumped_interned_strings->put_if_absent(string, true, &created);
1367 }
1368 
1369 // At dump-time, find the location of all the non-null oop pointers in an archived heap
1370 // region. This way we can quickly relocate all the pointers without using
1371 // BasicOopIterateClosure at runtime.
1372 class FindEmbeddedNonNullPointers: public BasicOopIterateClosure {
1373   narrowOop* _start;
1374   BitMap *_oopmap;
1375   int _num_total_oops;
1376   int _num_null_oops;
1377  public:
1378   FindEmbeddedNonNullPointers(narrowOop* start, BitMap* oopmap)
1379     : _start(start), _oopmap(oopmap), _num_total_oops(0),  _num_null_oops(0) {}
1380 
1381   virtual void do_oop(narrowOop* p) {
1382     _num_total_oops ++;
1383     narrowOop v = *p;
1384     if (!CompressedOops::is_null(v)) {
1385       size_t idx = p - _start;
1386       _oopmap->set_bit(idx);
1387     } else {
1388       _num_null_oops ++;
1389     }
1390   }
1391   virtual void do_oop(oop *p) {
1392     ShouldNotReachHere();
1393   }
1394   int num_total_oops() const { return _num_total_oops; }
1395   int num_null_oops()  const { return _num_null_oops; }
1396 };
1397 
1398 ResourceBitMap HeapShared::calculate_oopmap(MemRegion region) {
1399   assert(UseCompressedOops, "must be");
1400   size_t num_bits = region.byte_size() / sizeof(narrowOop);
1401   ResourceBitMap oopmap(num_bits);
1402 
1403   HeapWord* p   = region.start();
1404   HeapWord* end = region.end();
1405   FindEmbeddedNonNullPointers finder((narrowOop*)p, &oopmap);
1406   ArchiveBuilder* builder = DumpSharedSpaces ? ArchiveBuilder::current() : NULL;
1407 
1408   int num_objs = 0;
1409   while (p < end) {
1410     oop o = cast_to_oop(p);
1411     o->oop_iterate(&finder);
1412     p += o->size();
1413     if (DumpSharedSpaces) {
1414       builder->relocate_klass_ptr(o);
1415     }
1416     ++ num_objs;
1417   }
1418 
1419   log_info(cds, heap)("calculate_oopmap: objects = %6d, embedded oops = %7d, nulls = %7d",
1420                       num_objs, finder.num_total_oops(), finder.num_null_oops());
1421   return oopmap;
1422 }
1423 
1424 // Patch all the embedded oop pointers inside an archived heap region,
1425 // to be consistent with the runtime oop encoding.
1426 class PatchEmbeddedPointers: public BitMapClosure {
1427   narrowOop* _start;
1428 
1429  public:
1430   PatchEmbeddedPointers(narrowOop* start) : _start(start) {}
1431 
1432   bool do_bit(size_t offset) {
1433     narrowOop* p = _start + offset;
1434     narrowOop v = *p;
1435     assert(!CompressedOops::is_null(v), "null oops should have been filtered out at dump time");
1436     oop o = HeapShared::decode_from_archive(v);
1437     RawAccess<IS_NOT_NULL>::oop_store(p, o);
1438     return true;
1439   }
1440 };
1441 
1442 void HeapShared::patch_archived_heap_embedded_pointers(MemRegion region, address oopmap,
1443                                                        size_t oopmap_size_in_bits) {
1444   BitMapView bm((BitMap::bm_word_t*)oopmap, oopmap_size_in_bits);
1445 
1446 #ifndef PRODUCT
1447   ResourceMark rm;
1448   ResourceBitMap checkBm = calculate_oopmap(region);
1449   assert(bm.is_same(checkBm), "sanity");
1450 #endif
1451 
1452   PatchEmbeddedPointers patcher((narrowOop*)region.start());
1453   bm.iterate(&patcher);
1454 }
1455 
1456 #endif // INCLUDE_CDS_JAVA_HEAP