/*

 * Copyright (c) 2012, 2018, 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.

 *

 */

// A ClassLoaderData identifies the full set of class types that a class

// loader's name resolution strategy produces for a given configuration of the

// class loader.

// Class types in the ClassLoaderData may be defined by from class file binaries

// provided by the class loader, or from other class loader it interacts with

// according to its name resolution strategy.

//

// Class loaders that implement a deterministic name resolution strategy

// (including with respect to their delegation behavior), such as the boot, the

// platform, and the system loaders of the JDK's built-in class loader

// hierarchy, always produce the same linkset for a given configuration.

//

// ClassLoaderData carries information related to a linkset (e.g.,

// metaspace holding its klass definitions).

// The System Dictionary and related data structures (e.g., placeholder table,

// loader constraints table) as well as the runtime representation of classes

// only reference ClassLoaderData.

//

// Instances of java.lang.ClassLoader holds a pointer to a ClassLoaderData that

// that represent the loader's "linking domain" in the JVM.

//

// The bootstrap loader (represented by NULL) also has a ClassLoaderData,

// the singleton class the_null_class_loader_data().

#include "precompiled.hpp"

#include "classfile/classLoaderData.hpp"

#include "classfile/classLoaderData.inline.hpp"

#include "classfile/dictionary.hpp"

#include "classfile/javaClasses.hpp"

#include "classfile/metadataOnStackMark.hpp"

#include "classfile/moduleEntry.hpp"

#include "classfile/packageEntry.hpp"

#include "classfile/systemDictionary.hpp"

#include "code/codeCache.hpp"

#include "gc/shared/gcLocker.hpp"

#include "logging/log.hpp"

#include "logging/logStream.hpp"

#include "memory/allocation.inline.hpp"

#include "memory/metadataFactory.hpp"

#include "memory/metaspaceShared.hpp"

#include "memory/oopFactory.hpp"

#include "memory/resourceArea.hpp"

#include "oops/access.inline.hpp"

#include "oops/objArrayOop.inline.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/atomic.hpp"

#include "runtime/handles.inline.hpp"

#include "runtime/javaCalls.hpp"

#include "runtime/jniHandles.hpp"

#include "runtime/mutex.hpp"

#include "runtime/orderAccess.hpp"

#include "runtime/safepoint.hpp"

#include "runtime/synchronizer.hpp"

#include "utilities/growableArray.hpp"

#include "utilities/macros.hpp"

#include "utilities/ostream.hpp"

#if INCLUDE_TRACE

#include "trace/tracing.hpp"

#endif

volatile size_t ClassLoaderDataGraph::_num_array_classes = 0;

volatile size_t ClassLoaderDataGraph::_num_instance_classes = 0;

ClassLoaderData * ClassLoaderData::_the_null_class_loader_data = NULL;

void ClassLoaderData::init_null_class_loader_data() {

  assert(_the_null_class_loader_data == NULL, "cannot initialize twice");

  assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice");

  _the_null_class_loader_data = new ClassLoaderData(Handle(), false);

  ClassLoaderDataGraph::_head = _the_null_class_loader_data;

  assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be");

  LogTarget(Debug, class, loader, data) lt;

  if (lt.is_enabled()) {

    ResourceMark rm;

    LogStream ls(lt);

    ls.print("create ");

    _the_null_class_loader_data->print_value_on(&ls);

    ls.cr();

  }

}

ClassLoaderData::ClassLoaderData(Handle h_class_loader, bool is_anonymous) :

  _class_loader(h_class_loader()),

  _is_anonymous(is_anonymous),

  // An anonymous class loader data doesn't have anything to keep

  // it from being unloaded during parsing of the anonymous class.

  // The null-class-loader should always be kept alive.

  _keep_alive((is_anonymous || h_class_loader.is_null()) ? 1 : 0),

  _metaspace(NULL), _unloading(false), _klasses(NULL),

  _modules(NULL), _packages(NULL),

  _claimed(0), _modified_oops(true), _accumulated_modified_oops(false),

  _jmethod_ids(NULL), _handles(), _deallocate_list(NULL),

  _next(NULL),

  _metaspace_lock(new Mutex(Monitor::leaf+1, "Metaspace allocation lock", true,

                            Monitor::_safepoint_check_never)) {

  // A ClassLoaderData created solely for an anonymous class should never have a

  // ModuleEntryTable or PackageEntryTable created for it. The defining package

  // and module for an anonymous class will be found in its host class.

  if (!is_anonymous) {

    _packages = new PackageEntryTable(PackageEntryTable::_packagetable_entry_size);

    if (h_class_loader.is_null()) {

      // Create unnamed module for boot loader

      _unnamed_module = ModuleEntry::create_boot_unnamed_module(this);

    } else {

      // Create unnamed module for all other loaders

      _unnamed_module = ModuleEntry::create_unnamed_module(this);

    }

    _dictionary = create_dictionary();

  } else {

    _packages = NULL;

    _unnamed_module = NULL;

    _dictionary = NULL;

  }

  NOT_PRODUCT(_dependency_count = 0); // number of class loader dependencies

  TRACE_INIT_ID(this);

}

ClassLoaderData::ChunkedHandleList::~ChunkedHandleList() {

  Chunk* c = _head;

  while (c != NULL) {

    Chunk* next = c->_next;

    delete c;

    c = next;

  }

}

oop* ClassLoaderData::ChunkedHandleList::add(oop o) {

  if (_head == NULL || _head->_size == Chunk::CAPACITY) {

    Chunk* next = new Chunk(_head);

    OrderAccess::release_store(&_head, next);

  }

  oop* handle = &_head->_data[_head->_size];

  *handle = o;

  OrderAccess::release_store(&_head->_size, _head->_size + 1);

  return handle;

}

int ClassLoaderData::ChunkedHandleList::count() const {

  int count = 0;

  Chunk* chunk = _head;

  while (chunk != NULL) {

    count += chunk->_size;

    chunk = chunk->_next;

  }

  return count;

}

inline void ClassLoaderData::ChunkedHandleList::oops_do_chunk(OopClosure* f, Chunk* c, const juint size) {

  for (juint i = 0; i < size; i++) {

    if (c->_data[i] != NULL) {

      f->do_oop(&c->_data[i]);

    }

  }

}

void ClassLoaderData::ChunkedHandleList::oops_do(OopClosure* f) {

  Chunk* head = OrderAccess::load_acquire(&_head);

  if (head != NULL) {

    // Must be careful when reading size of head

    oops_do_chunk(f, head, OrderAccess::load_acquire(&head->_size));

    for (Chunk* c = head->_next; c != NULL; c = c->_next) {

      oops_do_chunk(f, c, c->_size);

    }

  }

}

class VerifyContainsOopClosure : public OopClosure {

  oop  _target;

  bool _found;

 public:

  VerifyContainsOopClosure(oop target) : _target(target), _found(false) {}

  void do_oop(oop* p) {

    if (p != NULL && *p == _target) {

      _found = true;

    }

  }

  void do_oop(narrowOop* p) {

    // The ChunkedHandleList should not contain any narrowOop

    ShouldNotReachHere();

  }

  bool found() const {

    return _found;

  }

};

bool ClassLoaderData::ChunkedHandleList::contains(oop p) {

  VerifyContainsOopClosure cl(p);

  oops_do(&cl);

  return cl.found();

}

bool ClassLoaderData::claim() {

  if (_claimed == 1) {

    return false;

  }

  return (int) Atomic::cmpxchg(1, &_claimed, 0) == 0;

}

// Anonymous classes have their own ClassLoaderData that is marked to keep alive

// while the class is being parsed, and if the class appears on the module fixup list.

// Due to the uniqueness that no other class shares the anonymous class' name or

// ClassLoaderData, no other non-GC thread has knowledge of the anonymous class while

// it is being defined, therefore _keep_alive is not volatile or atomic.

void ClassLoaderData::inc_keep_alive() {

  if (is_anonymous()) {

    assert(_keep_alive >= 0, "Invalid keep alive increment count");

    _keep_alive++;

  }

}

void ClassLoaderData::dec_keep_alive() {

  if (is_anonymous()) {

    assert(_keep_alive > 0, "Invalid keep alive decrement count");

    _keep_alive--;

  }

}

void ClassLoaderData::oops_do(OopClosure* f, bool must_claim, bool clear_mod_oops) {

  if (must_claim && !claim()) {

    return;

  }

  // Only clear modified_oops after the ClassLoaderData is claimed.

  if (clear_mod_oops) {

    clear_modified_oops();

  }

  f->do_oop(&_class_loader);

  _handles.oops_do(f);

}

void ClassLoaderData::classes_do(KlassClosure* klass_closure) {

  // Lock-free access requires load_acquire

  for (Klass* k = OrderAccess::load_acquire(&_klasses); k != NULL; k = k->next_link()) {

    klass_closure->do_klass(k);

    assert(k != k->next_link(), "no loops!");

  }

}

void ClassLoaderData::classes_do(void f(Klass * const)) {

  // Lock-free access requires load_acquire

  for (Klass* k = OrderAccess::load_acquire(&_klasses); k != NULL; k = k->next_link()) {

    f(k);

    assert(k != k->next_link(), "no loops!");

  }

}

void ClassLoaderData::methods_do(void f(Method*)) {

  // Lock-free access requires load_acquire

  for (Klass* k = OrderAccess::load_acquire(&_klasses); k != NULL; k = k->next_link()) {

    if (k->is_instance_klass() && InstanceKlass::cast(k)->is_loaded()) {

      InstanceKlass::cast(k)->methods_do(f);

    }

  }

}

void ClassLoaderData::loaded_classes_do(KlassClosure* klass_closure) {

  // Lock-free access requires load_acquire

  for (Klass* k = OrderAccess::load_acquire(&_klasses); k != NULL; k = k->next_link()) {

    // Do not filter ArrayKlass oops here...

    if (k->is_array_klass() || (k->is_instance_klass() && InstanceKlass::cast(k)->is_loaded())) {

      klass_closure->do_klass(k);

    }

  }

}

void ClassLoaderData::classes_do(void f(InstanceKlass*)) {

  // Lock-free access requires load_acquire

  for (Klass* k = OrderAccess::load_acquire(&_klasses); k != NULL; k = k->next_link()) {

    if (k->is_instance_klass()) {

      f(InstanceKlass::cast(k));

    }

    assert(k != k->next_link(), "no loops!");

  }

}

void ClassLoaderData::modules_do(void f(ModuleEntry*)) {

  assert_locked_or_safepoint(Module_lock);

  if (_unnamed_module != NULL) {

    f(_unnamed_module);

  }

  if (_modules != NULL) {

    for (int i = 0; i < _modules->table_size(); i++) {

      for (ModuleEntry* entry = _modules->bucket(i);

           entry != NULL;

           entry = entry->next()) {

        f(entry);

      }

    }

  }

}

void ClassLoaderData::packages_do(void f(PackageEntry*)) {

  assert_locked_or_safepoint(Module_lock);

  if (_packages != NULL) {

    for (int i = 0; i < _packages->table_size(); i++) {

      for (PackageEntry* entry = _packages->bucket(i);

           entry != NULL;

           entry = entry->next()) {

        f(entry);

      }

    }

  }

}

void ClassLoaderData::record_dependency(const Klass* k) {

  assert(k != NULL, "invariant");

  ClassLoaderData * const from_cld = this;

  ClassLoaderData * const to_cld = k->class_loader_data();

  // Do not need to record dependency if the dependency is to a class whose

  // class loader data is never freed.  (i.e. the dependency's class loader

  // is one of the three builtin class loaders and the dependency is not

  // anonymous.)

  if (to_cld->is_permanent_class_loader_data()) {

    return;

  }

  oop to;

  if (to_cld->is_anonymous()) {

    // Just return if an anonymous class is attempting to record a dependency

    // to itself.  (Note that every anonymous class has its own unique class

    // loader data.)

    if (to_cld == from_cld) {

      return;

    }

    // Anonymous class dependencies are through the mirror.

    to = k->java_mirror();

  } else {

    to = to_cld->class_loader();

    oop from = from_cld->class_loader();

    // Just return if this dependency is to a class with the same or a parent

    // class_loader.

    if (from == to || java_lang_ClassLoader::isAncestor(from, to)) {

      return; // this class loader is in the parent list, no need to add it.

    }

  }

  // It's a dependency we won't find through GC, add it.

  if (!_handles.contains(to)) {

    NOT_PRODUCT(Atomic::inc(&_dependency_count));

    LogTarget(Trace, class, loader, data) lt;

    if (lt.is_enabled()) {

      ResourceMark rm;

      LogStream ls(lt);

      ls.print("adding dependency from ");

      print_value_on(&ls);

      ls.print(" to ");

      to_cld->print_value_on(&ls);

      ls.cr();

    }

    Handle dependency(Thread::current(), to);

    add_handle(dependency);

    // Added a potentially young gen oop to the ClassLoaderData

    record_modified_oops();

  }

}

void ClassLoaderDataGraph::clear_claimed_marks() {

  for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {

    cld->clear_claimed();

  }

}

void ClassLoaderData::add_class(Klass* k, bool publicize /* true */) {

  {

    MutexLockerEx ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);

    Klass* old_value = _klasses;

    k->set_next_link(old_value);

    // Link the new item into the list, making sure the linked class is stable

    // since the list can be walked without a lock

    OrderAccess::release_store(&_klasses, k);

    if (k->is_array_klass()) {

      ClassLoaderDataGraph::inc_array_classes(1);

    } else {

      ClassLoaderDataGraph::inc_instance_classes(1);

    }

  }

  if (publicize) {

    LogTarget(Trace, class, loader, data) lt;

    if (lt.is_enabled()) {

      ResourceMark rm;

      LogStream ls(lt);

      ls.print("Adding k: " PTR_FORMAT " %s to ", p2i(k), k->external_name());

      print_value_on(&ls);

      ls.cr();

    }

  }

}

// Class iterator used by the compiler.  It gets some number of classes at

// a safepoint to decay invocation counters on the methods.

class ClassLoaderDataGraphKlassIteratorStatic {

  ClassLoaderData* _current_loader_data;

  Klass*           _current_class_entry;

 public:

  ClassLoaderDataGraphKlassIteratorStatic() : _current_loader_data(NULL), _current_class_entry(NULL) {}

  InstanceKlass* try_get_next_class() {

    assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");

    size_t max_classes = ClassLoaderDataGraph::num_instance_classes();

    assert(max_classes > 0, "should not be called with no instance classes");

    for (size_t i = 0; i < max_classes; ) {

      if (_current_class_entry != NULL) {

        Klass* k = _current_class_entry;

        _current_class_entry = _current_class_entry->next_link();

        if (k->is_instance_klass()) {

          InstanceKlass* ik = InstanceKlass::cast(k);

          i++;  // count all instance classes found

          // Not yet loaded classes are counted in max_classes

          // but only return loaded classes.

          if (ik->is_loaded()) {

            return ik;

          }

        }

      } else {

        // Go to next CLD

        if (_current_loader_data != NULL) {

          _current_loader_data = _current_loader_data->next();

        }

        // Start at the beginning

        if (_current_loader_data == NULL) {

          _current_loader_data = ClassLoaderDataGraph::_head;

        }

        _current_class_entry = _current_loader_data->klasses();

      }

    }

    // Should never be reached unless all instance classes have failed or are not fully loaded.

    // Caller handles NULL.

    return NULL;

  }

  // If the current class for the static iterator is a class being unloaded or

  // deallocated, adjust the current class.

  void adjust_saved_class(ClassLoaderData* cld) {

    if (_current_loader_data == cld) {

      _current_loader_data = cld->next();

      if (_current_loader_data != NULL) {

        _current_class_entry = _current_loader_data->klasses();

      }  // else try_get_next_class will start at the head

    }

  }

  void adjust_saved_class(Klass* klass) {

    if (_current_class_entry == klass) {

      _current_class_entry = klass->next_link();

    }

  }

};

static ClassLoaderDataGraphKlassIteratorStatic static_klass_iterator;