/*

 * Copyright (c) 2016, 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.

 *

 */

#include "precompiled.hpp"

#include "jni.h"

#include "classfile/classLoaderData.inline.hpp"

#include "classfile/javaClasses.inline.hpp"

#include "classfile/moduleEntry.hpp"

#include "logging/log.hpp"

#include "memory/resourceArea.hpp"

#include "oops/oopHandle.inline.hpp"

#include "oops/symbol.hpp"

#include "runtime/handles.inline.hpp"

#include "runtime/safepoint.hpp"

#include "utilities/events.hpp"

#include "utilities/growableArray.hpp"

#include "utilities/hashtable.inline.hpp"

#include "utilities/ostream.hpp"

ModuleEntry* ModuleEntryTable::_javabase_module = NULL;

oop ModuleEntry::module() const { return _module.resolve(); }

void ModuleEntry::set_location(Symbol* location) {

  if (_location != NULL) {

    // _location symbol's refcounts are managed by ModuleEntry,

    // must decrement the old one before updating.

    _location->decrement_refcount();

  }

  _location = location;

  if (location != NULL) {

    location->increment_refcount();

  }

}

// Return true if the module's version should be displayed in error messages,

// logging, etc.

// Return false if the module's version is null, if it is unnamed, or if the

// module is not an upgradeable module.

// Detect if the module is not upgradeable by checking:

//     1. Module location is "jrt:/java." and its loader is boot or platform

//     2. Module location is "jrt:/jdk.", its loader is one of the builtin loaders

//        and its version is the same as module java.base's version

// The above check is imprecise but should work in almost all cases.

bool ModuleEntry::should_show_version() {

  if (version() == NULL || !is_named()) return false;

  if (location() != NULL) {

    ResourceMark rm;

    const char* loc = location()->as_C_string();

    ClassLoaderData* cld = loader_data();

    if ((cld->is_the_null_class_loader_data() || cld->is_platform_class_loader_data()) &&

        (strncmp(loc, "jrt:/java.", 10) == 0)) {

      return false;

    }

    if ((ModuleEntryTable::javabase_moduleEntry()->version()->fast_compare(version()) == 0) &&

        cld->is_permanent_class_loader_data() && (strncmp(loc, "jrt:/jdk.", 9) == 0)) {

      return false;

    }

  }

  return true;

}

void ModuleEntry::set_version(Symbol* version) {

  if (_version != NULL) {

    // _version symbol's refcounts are managed by ModuleEntry,

    // must decrement the old one before updating.

    _version->decrement_refcount();

  }

  _version = version;

  if (version != NULL) {

    version->increment_refcount();

  }

}

// Returns the shared ProtectionDomain

oop ModuleEntry::shared_protection_domain() {

  return _pd.resolve();

}

// Set the shared ProtectionDomain atomically

void ModuleEntry::set_shared_protection_domain(ClassLoaderData *loader_data,

                                               Handle pd_h) {

  // Create a handle for the shared ProtectionDomain and save it atomically.

  // init_handle_locked checks if someone beats us setting the _pd cache.

  loader_data->init_handle_locked(_pd, pd_h);

}

// Returns true if this module can read module m

bool ModuleEntry::can_read(ModuleEntry* m) const {

  assert(m != NULL, "No module to lookup in this module's reads list");

  // Unnamed modules read everyone and all modules

  // read java.base.  If either of these conditions

  // hold, readability has been established.

  if (!this->is_named() ||

      (m == ModuleEntryTable::javabase_moduleEntry())) {

    return true;

  }

  MutexLocker m1(Module_lock);

  // This is a guard against possible race between agent threads that redefine

  // or retransform classes in this module. Only one of them is adding the

  // default read edges to the unnamed modules of the boot and app class loaders

  // with an upcall to jdk.internal.module.Modules.transformedByAgent.

  // At the same time, another thread can instrument the module classes by

  // injecting dependencies that require the default read edges for resolution.

  if (this->has_default_read_edges() && !m->is_named()) {

    ClassLoaderData* cld = m->loader_data();

    if (cld->is_the_null_class_loader_data() || cld->is_system_class_loader_data()) {

      return true; // default read edge

    }

  }

  if (!has_reads_list()) {

    return false;

  } else {

    return _reads->contains(m);

  }

}

// Add a new module to this module's reads list

void ModuleEntry::add_read(ModuleEntry* m) {

  // Unnamed module is special cased and can read all modules

  if (!is_named()) {

    return;

  }

  MutexLocker m1(Module_lock);

  if (m == NULL) {

    set_can_read_all_unnamed();

  } else {

    if (_reads == NULL) {

      // Lazily create a module's reads list

      _reads = new (ResourceObj::C_HEAP, mtModule)GrowableArray<ModuleEntry*>(MODULE_READS_SIZE, true);

    }

    // Determine, based on this newly established read edge to module m,

    // if this module's read list should be walked at a GC safepoint.

    set_read_walk_required(m->loader_data());

    // Establish readability to module m

    _reads->append_if_missing(m);

  }

}

// If the module's loader, that a read edge is being established to, is

// not the same loader as this module's and is not one of the 3 builtin

// class loaders, then this module's reads list must be walked at GC

// safepoint. Modules have the same life cycle as their defining class

// loaders and should be removed if dead.

void ModuleEntry::set_read_walk_required(ClassLoaderData* m_loader_data) {

  assert(is_named(), "Cannot call set_read_walk_required on unnamed module");

  assert_locked_or_safepoint(Module_lock);

  if (!_must_walk_reads &&

      loader_data() != m_loader_data &&

      !m_loader_data->is_builtin_class_loader_data()) {

    _must_walk_reads = true;

    if (log_is_enabled(Trace, module)) {

      ResourceMark rm;

      log_trace(module)("ModuleEntry::set_read_walk_required(): module %s reads list must be walked",

                        (name() != NULL) ? name()->as_C_string() : UNNAMED_MODULE);

    }

  }

}

// Set whether the module is open, i.e. all its packages are unqualifiedly exported

void ModuleEntry::set_is_open(bool is_open) {

  assert_lock_strong(Module_lock);

  _is_open = is_open;

}

// Returns true if the module has a non-empty reads list. As such, the unnamed

// module will return false.

bool ModuleEntry::has_reads_list() const {

  assert_locked_or_safepoint(Module_lock);

  return ((_reads != NULL) && !_reads->is_empty());

}

// Purge dead module entries out of reads list.

void ModuleEntry::purge_reads() {

  assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");

  if (_must_walk_reads && has_reads_list()) {

    // This module's _must_walk_reads flag will be reset based

    // on the remaining live modules on the reads list.

    _must_walk_reads = false;

    if (log_is_enabled(Trace, module)) {

      ResourceMark rm;

      log_trace(module)("ModuleEntry::purge_reads(): module %s reads list being walked",

                        (name() != NULL) ? name()->as_C_string() : UNNAMED_MODULE);

    }

    // Go backwards because this removes entries that are dead.

    int len = _reads->length();

    for (int idx = len - 1; idx >= 0; idx--) {

      ModuleEntry* module_idx = _reads->at(idx);

      ClassLoaderData* cld_idx = module_idx->loader_data();

      if (cld_idx->is_unloading()) {

        _reads->delete_at(idx);

      } else {

        // Update the need to walk this module's reads based on live modules

        set_read_walk_required(cld_idx);

      }

    }

  }

}

void ModuleEntry::module_reads_do(ModuleClosure* f) {

  assert_locked_or_safepoint(Module_lock);

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

  if (has_reads_list()) {

    int reads_len = _reads->length();

    for (int i = 0; i < reads_len; ++i) {

      f->do_module(_reads->at(i));

    }

  }

}

void ModuleEntry::delete_reads() {

  assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");

  delete _reads;

  _reads = NULL;

}

ModuleEntry* ModuleEntry::create_unnamed_module(ClassLoaderData* cld) {

  // The java.lang.Module for this loader's

  // corresponding unnamed module can be found in the java.lang.ClassLoader object.

  oop module = java_lang_ClassLoader::unnamedModule(cld->class_loader());

  // Ensure that the unnamed module was correctly set when the class loader was constructed.

  // Guarantee will cause a recognizable crash if the user code has circumvented calling the ClassLoader constructor.

  ResourceMark rm;

  guarantee(java_lang_Module::is_instance(module),

            "The unnamed module for ClassLoader %s, is null or not an instance of java.lang.Module. The class loader has not been initialized correctly.",

            cld->loader_name());

  ModuleEntry* unnamed_module = new_unnamed_module_entry(Handle(Thread::current(), module), cld);

  // Store pointer to the ModuleEntry in the unnamed module's java.lang.Module object.

  java_lang_Module::set_module_entry(module, unnamed_module);

  return unnamed_module;

}

ModuleEntry* ModuleEntry::create_boot_unnamed_module(ClassLoaderData* cld) {

  // For the boot loader, the java.lang.Module for the unnamed module

  // is not known until a call to JVM_SetBootLoaderUnnamedModule is made. At

  // this point initially create the ModuleEntry for the unnamed module.

  ModuleEntry* unnamed_module = new_unnamed_module_entry(Handle(), cld);

  assert(unnamed_module != NULL, "boot loader unnamed module should not be null");

  return unnamed_module;

}

// When creating an unnamed module, this is called without holding the Module_lock.

// This is okay because the unnamed module gets created before the ClassLoaderData

// is available to other threads.

ModuleEntry* ModuleEntry::new_unnamed_module_entry(Handle module_handle, ClassLoaderData* cld) {

  ModuleEntry* entry = (ModuleEntry*) NEW_C_HEAP_ARRAY(char, sizeof(ModuleEntry), mtModule);

  // Initialize everything BasicHashtable would

  entry->set_next(NULL);

  entry->set_hash(0);

  entry->set_literal(NULL);

  // Initialize fields specific to a ModuleEntry

  entry->init();

  // Unnamed modules can read all other unnamed modules.

  entry->set_can_read_all_unnamed();

  if (!module_handle.is_null()) {

    entry->set_module(cld->add_handle(module_handle));

  }

  entry->set_loader_data(cld);

  entry->_is_open = true;

  JFR_ONLY(INIT_ID(entry);)

  return entry;

}

void ModuleEntry::delete_unnamed_module() {

  // Do not need unlink_entry() since the unnamed module is not in the hashtable

  FREE_C_HEAP_ARRAY(char, this);

}

ModuleEntryTable::ModuleEntryTable(int table_size)

  : Hashtable<Symbol*, mtModule>(table_size, sizeof(ModuleEntry))

{

}

ModuleEntryTable::~ModuleEntryTable() {

  assert_locked_or_safepoint(Module_lock);

  // Walk through all buckets and all entries in each bucket,

  // freeing each entry.

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

    for (ModuleEntry* m = bucket(i); m != NULL;) {

      ModuleEntry* to_remove = m;

      // read next before freeing.

      m = m->next();

      ResourceMark rm;

      if (to_remove->name() != NULL) {

        log_info(module, unload)("unloading module %s", to_remove->name()->as_C_string());

      }

      log_debug(module)("ModuleEntryTable: deleting module: %s", to_remove->name() != NULL ?

                        to_remove->name()->as_C_string() : UNNAMED_MODULE);

      // Clean out the C heap allocated reads list first before freeing the entry

      to_remove->delete_reads();

      if (to_remove->name() != NULL) {

        to_remove->name()->decrement_refcount();

      }

      if (to_remove->version() != NULL) {

        to_remove->version()->decrement_refcount();

      }

      if (to_remove->location() != NULL) {

        to_remove->location()->decrement_refcount();

      }

      // Unlink from the Hashtable prior to freeing

      unlink_entry(to_remove);

      FREE_C_HEAP_ARRAY(char, to_remove);

    }

  }

  assert(number_of_entries() == 0, "should have removed all entries");

  assert(new_entry_free_list() == NULL, "entry present on ModuleEntryTable's free list");

  free_buckets();

}

ModuleEntry* ModuleEntryTable::new_entry(unsigned int hash, Handle module_handle,

                                         bool is_open, Symbol* name,

                                         Symbol* version, Symbol* location,

                                         ClassLoaderData* loader_data) {

  assert(Module_lock->owned_by_self(), "should have the Module_lock");

  ModuleEntry* entry = (ModuleEntry*)Hashtable<Symbol*, mtModule>::allocate_new_entry(hash, name);

  // Initialize fields specific to a ModuleEntry

  entry->init();

  if (name != NULL) {

    name->increment_refcount();

  } else {

    // Unnamed modules can read all other unnamed modules.

    entry->set_can_read_all_unnamed();

  }

  if (!module_handle.is_null()) {

    entry->set_module(loader_data->add_handle(module_handle));

  }

  entry->set_loader_data(loader_data);

  entry->set_version(version);

  entry->set_location(location);

  entry->set_is_open(is_open);

  if (ClassLoader::is_in_patch_mod_entries(name)) {

    entry->set_is_patched();

    if (log_is_enabled(Trace, module, patch)) {

      ResourceMark rm;

      log_trace(module, patch)("Marked module %s as patched from --patch-module", name->as_C_string());

    }

  }

  JFR_ONLY(INIT_ID(entry);)

  return entry;

}

void ModuleEntryTable::add_entry(int index, ModuleEntry* new_entry) {

  assert(Module_lock->owned_by_self(), "should have the Module_lock");

  Hashtable<Symbol*, mtModule>::add_entry(index, (HashtableEntry<Symbol*, mtModule>*)new_entry);

}

ModuleEntry* ModuleEntryTable::locked_create_entry_or_null(Handle module_handle,

                                                           bool is_open,

                                                           Symbol* module_name,

                                                           Symbol* module_version,

                                                           Symbol* module_location,

                                                           ClassLoaderData* loader_data) {

  assert(module_name != NULL, "ModuleEntryTable locked_create_entry_or_null should never be called for unnamed module.");

  assert(Module_lock->owned_by_self(), "should have the Module_lock");

  // Check if module already exists.

  if (lookup_only(module_name) != NULL) {

    return NULL;

  } else {

    ModuleEntry* entry = new_entry(compute_hash(module_name), module_handle, is_open, module_name,

                                   module_version, module_location, loader_data);

    add_entry(index_for(module_name), entry);

    return entry;

  }

}

// lookup_only by Symbol* to find a ModuleEntry.

ModuleEntry* ModuleEntryTable::lookup_only(Symbol* name) {

  assert(name != NULL, "name cannot be NULL");

  int index = index_for(name);

  for (ModuleEntry* m = bucket(index); m != NULL; m = m->next()) {

    if (m->name()->fast_compare(name) == 0) {

      return m;

    }

  }

  return NULL;

}

// Remove dead modules from all other alive modules' reads list.

// This should only occur at class unloading.

void ModuleEntryTable::purge_all_module_reads() {

  assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");

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

    for (ModuleEntry* entry = bucket(i);

                      entry != NULL;

                      entry = entry->next()) {

      entry->purge_reads();

    }

  }

}

void ModuleEntryTable::finalize_javabase(Handle module_handle, Symbol* version, Symbol* location) {

  assert(Module_lock->owned_by_self(), "should have the Module_lock");

  ClassLoaderData* boot_loader_data = ClassLoaderData::the_null_class_loader_data();

  ModuleEntryTable* module_table = boot_loader_data->modules();

  assert(module_table != NULL, "boot loader's ModuleEntryTable not defined");

  if (module_handle.is_null()) {

    fatal("Unable to finalize module definition for " JAVA_BASE_NAME);

  }

  // Set java.lang.Module, version and location for java.base

  ModuleEntry* jb_module = javabase_moduleEntry();

  assert(jb_module != NULL, JAVA_BASE_NAME " ModuleEntry not defined");

  jb_module->set_version(version);

  jb_module->set_location(location);

  // Once java.base's ModuleEntry _module field is set with the known

  // java.lang.Module, java.base is considered "defined" to the VM.

  jb_module->set_module(boot_loader_data->add_handle(module_handle));

  // Store pointer to the ModuleEntry for java.base in the java.lang.Module object.

  java_lang_Module::set_module_entry(module_handle(), jb_module);

}

// Within java.lang.Class instances there is a java.lang.Module field that must

// be set with the defining module.  During startup, prior to java.base's definition,

// classes needing their module field set are added to the fixup_module_list.

// Their module field is set once java.base's java.lang.Module is known to the VM.

void ModuleEntryTable::patch_javabase_entries(Handle module_handle) {

  if (module_handle.is_null()) {

    fatal("Unable to patch the module field of classes loaded prior to "

          JAVA_BASE_NAME "'s definition, invalid java.lang.Module");

  }

  // Do the fixups for the basic primitive types

  java_lang_Class::set_module(Universe::int_mirror(), module_handle());

  java_lang_Class::set_module(Universe::float_mirror(), module_handle());

  java_lang_Class::set_module(Universe::double_mirror(), module_handle());

  java_lang_Class::set_module(Universe::byte_mirror(), module_handle());

  java_lang_Class::set_module(Universe::bool_mirror(), module_handle());

  java_lang_Class::set_module(Universe::char_mirror(), module_handle());

  java_lang_Class::set_module(Universe::long_mirror(), module_handle());

  java_lang_Class::set_module(Universe::short_mirror(), module_handle());

  java_lang_Class::set_module(Universe::void_mirror(), module_handle());

  // Do the fixups for classes that have already been created.

  GrowableArray <Klass*>* list = java_lang_Class::fixup_module_field_list();

  int list_length = list->length();

  for (int i = 0; i < list_length; i++) {

    Klass* k = list->at(i);

    assert(k->is_klass(), "List should only hold classes");

    java_lang_Class::fixup_module_field(k, module_handle);

    k->class_loader_data()->dec_keep_alive();

  }

  delete java_lang_Class::fixup_module_field_list();

  java_lang_Class::set_fixup_module_field_list(NULL);

}