text: /*
   * 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);
  }
  
  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() {
    verify_table<ModuleEntry>("Module Entry Table");
  }
  
  void ModuleEntry::verify() {
    guarantee(loader_data() != NULL, "A module entry must be associated with a loader.");
  }
  