jdk/src/hotspot/share/classfile/classLoaderDataShared.cpp

 /*
 * Copyright (c) 2020, 2026, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#include "cds/aotLogging.hpp"
#include "cds/cdsConfig.hpp"
#include "cds/heapShared.inline.hpp"
#include "cds/serializeClosure.hpp"
#include "classfile/classLoaderData.inline.hpp"
#include "classfile/classLoaderDataShared.hpp"
#include "classfile/moduleEntry.hpp"
#include "classfile/modules.hpp"
#include "classfile/packageEntry.hpp"
#include "classfile/systemDictionary.hpp"
#include "logging/log.hpp"
#include "memory/metaspaceClosure.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/safepoint.hpp"

#if INCLUDE_CDS_JAVA_HEAP

bool ClassLoaderDataShared::_full_module_graph_loaded = false;

class ArchivedClassLoaderData {
  Array<PackageEntry*>* _packages;
  Array<ModuleEntry*>* _modules;
  ModuleEntry* _unnamed_module;

  void assert_valid(ClassLoaderData* loader_data) {
    // loader_data may be null if the boot layer has loaded no modules for the platform or
    // system loaders (e.g., if you create a custom JDK image with only java.base).
    if (loader_data != nullptr) {
      assert(!loader_data->has_class_mirror_holder(),
             "loaders for non-strong hidden classes not supported");
    }
  }
public:
  ArchivedClassLoaderData() : _packages(nullptr), _modules(nullptr), _unnamed_module(nullptr) {}

  void iterate_roots(MetaspaceClosure* closure);
  void build_tables(ClassLoaderData* loader_data, TRAPS);
  void remove_unshareable_info();
  ModuleEntry* unnamed_module() {
    return _unnamed_module;
  }

  void serialize(SerializeClosure* f) {
    f->do_ptr(&_packages);
    f->do_ptr(&_modules);
    f->do_ptr(&_unnamed_module);
  }

  void restore(ClassLoaderData* loader_data, bool do_entries, bool do_oops);
  void clear_archived_oops();
};

static ArchivedClassLoaderData _archived_boot_loader_data;
static ArchivedClassLoaderData _archived_platform_loader_data;
static ArchivedClassLoaderData _archived_system_loader_data;
static ModuleEntry* _archived_javabase_moduleEntry = nullptr;
static int _platform_loader_root_index = -1;
static int _system_loader_root_index = -1;

void ArchivedClassLoaderData::iterate_roots(MetaspaceClosure* it) {
  assert(CDSConfig::is_dumping_full_module_graph(), "must be");
  it->push(&_packages);
  it->push(&_modules);
  it->push(&_unnamed_module);
}

void ArchivedClassLoaderData::build_tables(ClassLoaderData* loader_data, TRAPS) {
  assert(CDSConfig::is_dumping_full_module_graph(), "must be");
  assert_valid(loader_data);
  if (loader_data != nullptr) {
    // We can't create hashtables at dump time because the hashcode depends on the
    // address of the Symbols, which may be relocated at runtime due to ASLR.
    // So we store the packages/modules in Arrays. At runtime, we create
    // the hashtables using these arrays.
    _packages = loader_data->packages()->build_aot_table(loader_data, CHECK);
    _modules  = loader_data->modules()->build_aot_table(loader_data, CHECK);
    _unnamed_module = loader_data->unnamed_module();
  }
}

void ArchivedClassLoaderData::remove_unshareable_info() {
  if (_packages != nullptr) {
    _packages = ArchiveBuilder::current()->get_buffered_addr(_packages);
    for (int i = 0; i < _packages->length(); i++) {
      _packages->at(i)->remove_unshareable_info();
    }
  }
  if (_modules != nullptr) {
    _modules = ArchiveBuilder::current()->get_buffered_addr(_modules);
    for (int i = 0; i < _modules->length(); i++) {
      _modules->at(i)->remove_unshareable_info();
    }
  }
  if (_unnamed_module != nullptr) {
    _unnamed_module = ArchiveBuilder::current()->get_buffered_addr(_unnamed_module);
    _unnamed_module->remove_unshareable_info();
  }
}

void ArchivedClassLoaderData::restore(ClassLoaderData* loader_data, bool do_entries, bool do_oops) {
  assert(CDSConfig::is_using_archive(), "must be");
  assert_valid(loader_data);
  if (_modules != nullptr) { // Could be null if we have archived no modules for platform/system loaders
    ModuleEntryTable* modules = loader_data->modules();
    PackageEntryTable* packages = loader_data->packages();

    MutexLocker m1(Module_lock);
    if (do_entries) {
      modules->load_archived_entries(loader_data, _modules);
      packages->load_archived_entries(_packages);
    }
    if (do_oops) {
      modules->restore_archived_oops(loader_data, _modules);
      if (_unnamed_module != nullptr) {
        oop module_oop = _unnamed_module->module_oop();
        assert(module_oop != nullptr, "must be already set");
        assert(_unnamed_module == java_lang_Module::module_entry(module_oop), "must be already set");
        assert(loader_data->class_loader() == java_lang_Module::loader(module_oop), "must be set in dump time");
      }
    }
  }
}

void ArchivedClassLoaderData::clear_archived_oops() {
  assert(CDSConfig::is_using_archive(), "must be");
  if (_modules != nullptr) {
    for (int i = 0; i < _modules->length(); i++) {
      _modules->at(i)->clear_archived_oops();
    }
    if (_unnamed_module != nullptr) {
      _unnamed_module->clear_archived_oops();
    }
  }
}

// ------------------------------

void ClassLoaderDataShared::load_archived_platform_and_system_class_loaders() {
  // The streaming object loader prefers loading the class loader related objects before
  //  the CLD constructor which has a NoSafepointVerifier.
  if (!HeapShared::is_loading_streaming_mode()) {
    return;
  }

  // Ensure these class loaders are eagerly materialized before their CLDs are created.
  HeapShared::get_root(_platform_loader_root_index, false /* clear */);
  HeapShared::get_root(_system_loader_root_index, false /* clear */);

  if (Universe::is_module_initialized() || !CDSConfig::is_using_full_module_graph()) {
    return;
  }

  // When using the full module graph, we need to load unnamed modules too.
  ModuleEntry* platform_loader_module_entry = _archived_platform_loader_data.unnamed_module();
  if (platform_loader_module_entry != nullptr) {
    platform_loader_module_entry->preload_archived_oops();
  }

  ModuleEntry* system_loader_module_entry = _archived_system_loader_data.unnamed_module();
  if (system_loader_module_entry != nullptr) {
    system_loader_module_entry->preload_archived_oops();
  }
}

static ClassLoaderData* null_class_loader_data() {
  ClassLoaderData* loader_data = ClassLoaderData::the_null_class_loader_data();
  assert(loader_data != nullptr, "must be");
  return loader_data;
}

static ClassLoaderData* java_platform_loader_data_or_null() {
  return ClassLoaderData::class_loader_data_or_null(SystemDictionary::java_platform_loader());
}

static ClassLoaderData* java_system_loader_data_or_null() {
  return ClassLoaderData::class_loader_data_or_null(SystemDictionary::java_system_loader());
}

// ModuleEntryTables (even if empty) are required for iterate_symbols() to scan the
// platform/system loaders inside the CDS safepoint, but the tables can be created only
// when outside of safepoints. Let's do that now.
void ClassLoaderDataShared::ensure_module_entry_tables_exist() {
  assert(!SafepointSynchronize::is_at_safepoint(), "sanity");
  ensure_module_entry_table_exists(SystemDictionary::java_platform_loader());
  ensure_module_entry_table_exists(SystemDictionary::java_system_loader());
}

void ClassLoaderDataShared::ensure_module_entry_table_exists(oop class_loader) {
  Handle h_loader(JavaThread::current(), class_loader);
  ModuleEntryTable* met = Modules::get_module_entry_table(h_loader);
  assert(met != nullptr, "sanity");
}

void ClassLoaderDataShared::build_tables(TRAPS) {
  assert(CDSConfig::is_dumping_full_module_graph(), "must be");
  _archived_boot_loader_data.build_tables(null_class_loader_data(), CHECK);
  _archived_platform_loader_data.build_tables(java_platform_loader_data_or_null(), CHECK);
  _archived_system_loader_data.build_tables(java_system_loader_data_or_null(), CHECK);
}

void ClassLoaderDataShared::iterate_roots(MetaspaceClosure* it) {
  assert(CDSConfig::is_dumping_full_module_graph(), "must be");
  _archived_boot_loader_data.iterate_roots(it);
  _archived_platform_loader_data.iterate_roots(it);
  _archived_system_loader_data.iterate_roots(it);
}

void ClassLoaderDataShared::remove_unshareable_info() {
  assert(CDSConfig::is_dumping_full_module_graph(), "must be");
  _archived_boot_loader_data.remove_unshareable_info();
  _archived_platform_loader_data.remove_unshareable_info();
  _archived_system_loader_data.remove_unshareable_info();

  _archived_javabase_moduleEntry = ArchiveBuilder::current()->get_buffered_addr(ModuleEntryTable::javabase_moduleEntry());

  _platform_loader_root_index = HeapShared::append_root(SystemDictionary::java_platform_loader());
  _system_loader_root_index = HeapShared::append_root(SystemDictionary::java_system_loader());
}

void ClassLoaderDataShared::serialize(SerializeClosure* f) {
  _archived_boot_loader_data.serialize(f);
  _archived_platform_loader_data.serialize(f);
  _archived_system_loader_data.serialize(f);
  f->do_ptr(&_archived_javabase_moduleEntry);
  f->do_int(&_platform_loader_root_index);
  f->do_int(&_system_loader_root_index);
}

ModuleEntry* ClassLoaderDataShared::archived_boot_unnamed_module() {
  if (CDSConfig::is_using_full_module_graph()) {
    return _archived_boot_loader_data.unnamed_module();
  } else {
    return nullptr;
  }
}

ModuleEntry* ClassLoaderDataShared::archived_unnamed_module(ClassLoaderData* loader_data) {
  ModuleEntry* archived_module = nullptr;

  if (!Universe::is_module_initialized() && CDSConfig::is_using_full_module_graph()) {
    precond(_platform_loader_root_index >= 0);
    precond(_system_loader_root_index >= 0);

    if (loader_data->class_loader() == HeapShared::get_root(_platform_loader_root_index)) {
      archived_module = _archived_platform_loader_data.unnamed_module();
    } else if (loader_data->class_loader() == HeapShared::get_root(_system_loader_root_index)) {
      archived_module = _archived_system_loader_data.unnamed_module();
    }
  }

  return archived_module;
}

void ClassLoaderDataShared::clear_archived_oops() {
  assert(!CDSConfig::is_using_full_module_graph(), "must be");
  _archived_boot_loader_data.clear_archived_oops();
  _archived_platform_loader_data.clear_archived_oops();
  _archived_system_loader_data.clear_archived_oops();
  if (_platform_loader_root_index >= 0) {
    HeapShared::clear_root(_platform_loader_root_index);
    HeapShared::clear_root(_system_loader_root_index);
  }
}

// Must be done before ClassLoader::create_javabase()
void ClassLoaderDataShared::restore_archived_entries_for_null_class_loader_data() {
  precond(CDSConfig::is_using_full_module_graph());
  _archived_boot_loader_data.restore(null_class_loader_data(), true, false);
  ModuleEntryTable::set_javabase_moduleEntry(_archived_javabase_moduleEntry);
  aot_log_info(aot)("use_full_module_graph = true; java.base = " INTPTR_FORMAT,
                    p2i(_archived_javabase_moduleEntry));
}

oop ClassLoaderDataShared::restore_archived_oops_for_null_class_loader_data() {
  assert(CDSConfig::is_using_full_module_graph(), "must be");
  _archived_boot_loader_data.restore(null_class_loader_data(), false, true);
  return _archived_javabase_moduleEntry->module_oop();
}

void ClassLoaderDataShared::restore_java_platform_loader_from_archive(ClassLoaderData* loader_data) {
  assert(CDSConfig::is_using_full_module_graph(), "must be");
  _archived_platform_loader_data.restore(loader_data, true, true);
}

void ClassLoaderDataShared::restore_java_system_loader_from_archive(ClassLoaderData* loader_data) {
  assert(CDSConfig::is_using_full_module_graph(), "must be");
  _archived_system_loader_data.restore(loader_data, true, true);
  _full_module_graph_loaded = true;
}

// This is called before AOTLinkedClassBulkLoader starts preloading classes. It makes sure that
// when we preload any class, its module is already valid.
void ClassLoaderDataShared::restore_archived_modules_for_preloading_classes(JavaThread* current) {
  precond(CDSConfig::is_using_aot_linked_classes());

  precond(_platform_loader_root_index >= 0);
  precond(_system_loader_root_index >= 0);

  Handle h_platform_loader(current, HeapShared::get_root(_platform_loader_root_index));
  Handle h_system_loader(current, HeapShared::get_root(_system_loader_root_index));
  Modules::init_archived_modules(current, h_platform_loader, h_system_loader);
}

#endif // INCLUDE_CDS_JAVA_HEAP