1 /*
   2  * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_CLASSFILE_MODULEENTRY_HPP
  26 #define SHARE_VM_CLASSFILE_MODULEENTRY_HPP
  27 
  28 #include "classfile/classLoaderData.hpp"
  29 #include "classfile/vmSymbols.hpp"
  30 #include "oops/symbol.hpp"
  31 #include "prims/jni.h"
  32 #include "runtime/mutexLocker.hpp"
  33 #include "trace/traceMacros.hpp"
  34 #include "utilities/growableArray.hpp"
  35 #include "utilities/hashtable.hpp"
  36 #include "utilities/ostream.hpp"
  37 
  38 #define UNNAMED_MODULE "Unnamed Module"
  39 
  40 class ModuleClosure;
  41 
  42 // A ModuleEntry describes a module that has been defined by a call to JVM_DefineModule.
  43 // It contains:
  44 //   - Symbol* containing the module's name.
  45 //   - pointer to the java.lang.reflect.Module for this module.
  46 //   - pointer to the java.security.ProtectionDomain shared by classes defined to this module.
  47 //   - ClassLoaderData*, class loader of this module.
  48 //   - a growable array containg other module entries that this module can read.
  49 //   - a flag indicating if this module can read all unnamed modules.
  50 //
  51 // The Mutex Module_lock is shared between ModuleEntry and PackageEntry, to lock either
  52 // data structure.
  53 class ModuleEntry : public HashtableEntry<Symbol*, mtModule> {
  54 private:
  55   jobject _module;                     // java.lang.reflect.Module
  56   jobject _pd;                         // java.security.ProtectionDomain, cached
  57                                        // for shared classes from this module
  58   ClassLoaderData* _loader_data;
  59   GrowableArray<ModuleEntry*>* _reads; // list of modules that are readable by this module
  60   Symbol* _version;                    // module version number
  61   Symbol* _location;                   // module location
  62   bool _can_read_all_unnamed;
  63   bool _has_default_read_edges;        // JVMTI redefine/retransform support
  64   bool _must_walk_reads;               // walk module's reads list at GC safepoints to purge out dead modules
  65   TRACE_DEFINE_TRACE_ID_FIELD;
  66   enum {MODULE_READS_SIZE = 101};      // Initial size of list of modules that the module can read.
  67 
  68 public:
  69   void init() {
  70     _module = NULL;
  71     _loader_data = NULL;
  72     _pd = NULL;
  73     _reads = NULL;
  74     _version = NULL;
  75     _location = NULL;
  76     _can_read_all_unnamed = false;
  77     _has_default_read_edges = false;
  78     _must_walk_reads = false;
  79   }
  80 
  81   Symbol*          name() const                        { return literal(); }
  82   void             set_name(Symbol* n)                 { set_literal(n); }
  83 
  84   jobject          module() const                      { return _module; }
  85   void             set_module(jobject j)               { _module = j; }
  86 
  87   // The shared ProtectionDomain reference is set once the VM loads a shared class
  88   // originated from the current Module. The referenced ProtectionDomain object is
  89   // created by the ClassLoader when loading a class (shared or non-shared) from the
  90   // Module for the first time. This ProtectionDomain object is used for all
  91   // classes from the Module loaded by the same ClassLoader.
  92   Handle           shared_protection_domain();
  93   void             set_shared_protection_domain(ClassLoaderData *loader_data, Handle pd);
  94 
  95   ClassLoaderData* loader_data() const                 { return _loader_data; }
  96   void             set_loader_data(ClassLoaderData* l) { _loader_data = l; }
  97 
  98   Symbol*          version() const                     { return _version; }
  99   void             set_version(Symbol* version);
 100 
 101   Symbol*          location() const                    { return _location; }
 102   void             set_location(Symbol* location);

 103 
 104   bool             can_read(ModuleEntry* m) const;
 105   bool             has_reads() const;
 106   void             add_read(ModuleEntry* m);
 107   void             set_read_walk_required(ClassLoaderData* m_loader_data);
 108 
 109   bool             is_named() const                    { return (name() != NULL); }
 110 
 111   bool can_read_all_unnamed() const {
 112     assert(is_named() || _can_read_all_unnamed == true,
 113            "unnamed modules can always read all unnamed modules");
 114     return _can_read_all_unnamed;
 115   }
 116 
 117   // Modules can only go from strict to loose.
 118   void set_can_read_all_unnamed() { _can_read_all_unnamed = true; }
 119 
 120   bool has_default_read_edges() const {
 121     return _has_default_read_edges;
 122   }
 123 
 124   // Sets true and returns the previous value.
 125   bool set_has_default_read_edges() {
 126     MutexLocker ml(Module_lock);
 127     bool prev = _has_default_read_edges;
 128     _has_default_read_edges = true;
 129     return prev;
 130   }
 131 
 132   ModuleEntry* next() const {
 133     return (ModuleEntry*)HashtableEntry<Symbol*, mtModule>::next();
 134   }
 135   ModuleEntry** next_addr() {
 136     return (ModuleEntry**)HashtableEntry<Symbol*, mtModule>::next_addr();
 137   }
 138 
 139   // iteration support for readability
 140   void module_reads_do(ModuleClosure* const f);
 141 
 142   TRACE_DEFINE_TRACE_ID_METHODS;
 143 
 144   // Purge dead weak references out of reads list when any given class loader is unloaded.
 145   void purge_reads();
 146   void delete_reads();
 147 
 148   void print(outputStream* st = tty);
 149   void verify();
 150 };
 151 
 152 // Iterator interface
 153 class ModuleClosure: public StackObj {
 154  public:
 155   virtual void do_module(ModuleEntry* const module) = 0;
 156 };
 157 
 158 
 159 // The ModuleEntryTable is a Hashtable containing a list of all modules defined
 160 // by a particular class loader.  Each module is represented as a ModuleEntry node.
 161 //
 162 // Each ModuleEntryTable contains a _javabase_module field which allows for the
 163 // creation of java.base's ModuleEntry very early in bootstrapping before the
 164 // corresponding JVM_DefineModule call for java.base occurs during module system
 165 // initialization.  Setting up java.base's ModuleEntry early enables classes,
 166 // loaded prior to the module system being initialized to be created with their
 167 // PackageEntry node's correctly pointing at java.base's ModuleEntry.  No class
 168 // outside of java.base is allowed to be loaded pre-module system initialization.
 169 //
 170 // The ModuleEntryTable's lookup is lock free.
 171 //
 172 class ModuleEntryTable : public Hashtable<Symbol*, mtModule> {
 173   friend class VMStructs;
 174 public:
 175   enum Constants {
 176     _moduletable_entry_size  = 109 // number of entries in module entry table
 177   };
 178 
 179 private:
 180   static ModuleEntry* _javabase_module;
 181   ModuleEntry* _unnamed_module;
 182 
 183   ModuleEntry* new_entry(unsigned int hash, Handle module_handle, Symbol* name, Symbol* version,
 184                          Symbol* location, ClassLoaderData* loader_data);
 185   void add_entry(int index, ModuleEntry* new_entry);
 186 
 187   int entry_size() const { return BasicHashtable<mtModule>::entry_size(); }
 188 
 189   ModuleEntry** bucket_addr(int i) {
 190     return (ModuleEntry**)Hashtable<Symbol*, mtModule>::bucket_addr(i);
 191   }
 192 
 193   static unsigned int compute_hash(Symbol* name) { return ((name == NULL) ? 0 : (unsigned int)(name->identity_hash())); }
 194   int index_for(Symbol* name) const              { return hash_to_index(compute_hash(name)); }
 195 
 196 public:
 197   ModuleEntryTable(int table_size);
 198   ~ModuleEntryTable();
 199 
 200   ModuleEntry* bucket(int i) {
 201     return (ModuleEntry*)Hashtable<Symbol*, mtModule>::bucket(i);
 202   }
 203 
 204   // Create module in loader's module entry table, if already exists then
 205   // return null.  Assume Module_lock has been locked by caller.
 206   ModuleEntry* locked_create_entry_or_null(Handle module_handle,
 207                                            Symbol* module_name,
 208                                            Symbol* module_version,
 209                                            Symbol* module_location,
 210                                            ClassLoaderData* loader_data);
 211 
 212   // Only lookup module within loader's module entry table.  The table read is lock-free.
 213   ModuleEntry* lookup_only(Symbol* name);
 214 
 215   // purge dead weak references out of reads list
 216   void purge_all_module_reads();
 217 
 218   // Special handling for unnamed module, one per class loader's ModuleEntryTable
 219   void create_unnamed_module(ClassLoaderData* loader_data);
 220   ModuleEntry* unnamed_module()                                { return _unnamed_module; }
 221 
 222   // Special handling for java.base
 223   static ModuleEntry* javabase_moduleEntry()                   { return _javabase_module; }
 224   static void set_javabase_moduleEntry(ModuleEntry* java_base) { _javabase_module = java_base; }
 225   static bool javabase_defined()                               { return ((_javabase_module != NULL) &&
 226                                                                          (_javabase_module->module() != NULL)); }
 227   static void finalize_javabase(Handle module_handle, Symbol* version, Symbol* location);
 228   static void patch_javabase_entries(Handle module_handle);
 229 
 230   void print(outputStream* st = tty);
 231   void verify();
 232 };
 233 
 234 #endif // SHARE_VM_CLASSFILE_MODULEENTRY_HPP
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