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