/*

 * Copyright (c) 2016, 2017, 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 "classfile/classLoaderData.hpp"

#include "classfile/javaClasses.hpp"

#include "classfile/moduleEntry.hpp"

#include "logging/log.hpp"

#include "memory/resourceArea.hpp"

#include "oops/symbol.hpp"

#include "prims/jni.h"

#include "runtime/handles.inline.hpp"

#include "runtime/safepoint.hpp"

#include "trace/traceMacros.hpp"

#include "utilities/events.hpp"

#include "utilities/growableArray.hpp"

#include "utilities/hashtable.inline.hpp"

#include "utilities/ostream.hpp"

ModuleEntry* ModuleEntryTable::_javabase_module = NULL;

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();

  }

}

bool ModuleEntry::is_non_jdk_module() {

  ResourceMark rm;

  if (location() != NULL) {

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

    if (strncmp(loc, "jrt:/java.", 10) != 0 && strncmp(loc, "jrt:/jdk.", 9) != 0) {

      return true;

    }

  }

  return false;

}

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

Handle ModuleEntry::shared_protection_domain() {

  return Handle(JNIHandles::resolve(_pd));

}

// 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.

  // If someone beats us setting the _pd cache, the created handle is destroyed.

  jobject obj = loader_data->add_handle(pd_h);

  if (Atomic::cmpxchg_ptr(obj, &_pd, NULL) != NULL) {

    loader_data->remove_handle_unsafe(obj);

  }

}

// 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()) {

    return false;

  } else {

    return _reads->contains(m);

  }

}

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

void ModuleEntry::add_read(ModuleEntry* m) {

  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_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, modules)) {

      ResourceMark rm;

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

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

    }

  }

}

bool ModuleEntry::has_reads() 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()) {

    // 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, modules)) {

      ResourceMark rm;

      log_trace(modules)("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* const f) {

  assert_locked_or_safepoint(Module_lock);

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

  if (has_reads()) {

    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;

}

ModuleEntryTable::ModuleEntryTable(int table_size)

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

{

}

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;

      log_debug(modules)("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();

}

void ModuleEntryTable::create_unnamed_module(ClassLoaderData* loader_data) {

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

  // Each ModuleEntryTable has exactly one unnamed module

  if (loader_data->is_the_null_class_loader_data()) {

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

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

    _unnamed_module = new_entry(0, Handle(NULL), NULL, NULL, NULL, loader_data);

  } else {

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

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

    _unnamed_module = new_entry(0, Handle(module), NULL, NULL, NULL, loader_data);

    // object.

  }

  // Add to bucket 0, no name to hash on

  add_entry(0, _unnamed_module);

}

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

                                         Symbol* version, Symbol* location,

                                         ClassLoaderData* loader_data) {

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

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

  // Initialize everything BasicHashtable would

  entry->set_next(NULL);

  entry->set_hash(hash);

  entry->set_literal(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);

  if (ClassLoader::is_in_patch_mod_entries(name)) {

    entry->set_is_patched();

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

      ResourceMark rm;

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

    }

  }

  TRACE_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,

                                                           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, 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) {

  if (name == NULL) {

    // Return this table's unnamed module

    return unnamed_module();

  }

  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);

  }

  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

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

}

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 "

  }

  // 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(KlassHandle(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);

}

void ModuleEntryTable::print(outputStream* st) {

  st->print_cr("Module Entry Table (table_size=%d, entries=%d)",

               table_size(), number_of_entries());

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

    for (ModuleEntry* probe = bucket(i);

                              probe != NULL;

                              probe = probe->next()) {

      probe->print(st);

    }

  }

}

void ModuleEntry::print(outputStream* st) {

  ResourceMark rm;

  st->print_cr("entry " PTR_FORMAT " name %s module " PTR_FORMAT " loader %s version %s location %s strict %s next " PTR_FORMAT,

               p2i(this),

               name() == NULL ? UNNAMED_MODULE : name()->as_C_string(),

               p2i(module()),

               loader_data()->loader_name(),

               version() != NULL ? version()->as_C_string() : "NULL",

               location() != NULL ? location()->as_C_string() : "NULL",

               BOOL_TO_STR(!can_read_all_unnamed()), p2i(next()));

}

void ModuleEntryTable::verify() {

  int element_count = 0;

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

    for (ModuleEntry* probe = bucket(i);

                              probe != NULL;

                              probe = probe->next()) {

      probe->verify();

      element_count++;

    }

  }

  guarantee(number_of_entries() == element_count,

            "Verify of Module Entry Table failed");

  DEBUG_ONLY(verify_lookup_length((double)number_of_entries() / table_size(), "Module Entry Table"));

}

void ModuleEntry::verify() {

  guarantee(loader_data() != NULL, "A module entry must be associated with a loader.");

}