1 /*
   2  * Copyright (c) 2016, 2018, 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 "jni.h"
  29 #include "classfile/classLoaderData.hpp"
  30 #include "classfile/vmSymbols.hpp"
  31 #include "oops/oopHandle.hpp"
  32 #include "oops/symbol.hpp"
  33 #include "runtime/jniHandles.hpp"
  34 #include "runtime/mutexLocker.hpp"
  35 #include "utilities/growableArray.hpp"
  36 #include "utilities/hashtable.hpp"
  37 #include "utilities/macros.hpp"
  38 #include "utilities/ostream.hpp"
  39 #if INCLUDE_JFR
  40 #include "jfr/support/jfrTraceIdExtension.hpp"
  41 #endif
  42 
  43 #define UNNAMED_MODULE "Unnamed Module"
  44 #define JAVAPKG "java"
  45 #define JAVAPKG_LEN 4
  46 #define JAVA_BASE_NAME "java.base"
  47 
  48 class ModuleClosure;
  49 
  50 // A ModuleEntry describes a module that has been defined by a call to JVM_DefineModule.
  51 // It contains:
  52 //   - Symbol* containing the module's name.
  53 //   - pointer to the java.lang.Module for this module.
  54 //   - pointer to the java.security.ProtectionDomain shared by classes defined to this module.
  55 //   - ClassLoaderData*, class loader of this module.
  56 //   - a growable array containg other module entries that this module can read.
  57 //   - a flag indicating if this module can read all unnamed modules.
  58 //
  59 // The Mutex Module_lock is shared between ModuleEntry and PackageEntry, to lock either
  60 // data structure.
  61 class ModuleEntry : public HashtableEntry<Symbol*, mtModule> {
  62 private:
  63   OopHandle _module;                   // java.lang.Module
  64   OopHandle _pd;                       // java.security.ProtectionDomain, cached
  65                                        // for shared classes from this module
  66   ClassLoaderData* _loader_data;
  67   GrowableArray<ModuleEntry*>* _reads; // list of modules that are readable by this module
  68   Symbol* _version;                    // module version number
  69   Symbol* _location;                   // module location
  70   bool _can_read_all_unnamed;
  71   bool _has_default_read_edges;        // JVMTI redefine/retransform support
  72   bool _must_walk_reads;               // walk module's reads list at GC safepoints to purge out dead modules
  73   bool _is_open;                       // whether the packages in the module are all unqualifiedly exported
  74   bool _is_patched;                    // whether the module is patched via --patch-module
  75   JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
  76   enum {MODULE_READS_SIZE = 101};      // Initial size of list of modules that the module can read.
  77 
  78 public:
  79   void init() {
  80     _module = NULL;
  81     _loader_data = NULL;
  82     _pd = NULL;
  83     _reads = NULL;
  84     _version = NULL;
  85     _location = NULL;
  86     _can_read_all_unnamed = false;
  87     _has_default_read_edges = false;
  88     _must_walk_reads = false;
  89     _is_patched = false;
  90     _is_open = false;
  91   }
  92 
  93   Symbol*          name() const                        { return literal(); }
  94   void             set_name(Symbol* n)                 { set_literal(n); }
  95 
  96   oop              module() const;
  97   OopHandle        module_handle() const               { return _module; }
  98   void             set_module(OopHandle j)             { _module = j; }
  99 
 100   // The shared ProtectionDomain reference is set once the VM loads a shared class
 101   // originated from the current Module. The referenced ProtectionDomain object is
 102   // created by the ClassLoader when loading a class (shared or non-shared) from the
 103   // Module for the first time. This ProtectionDomain object is used for all
 104   // classes from the Module loaded by the same ClassLoader.
 105   oop              shared_protection_domain();
 106   void             set_shared_protection_domain(ClassLoaderData *loader_data, Handle pd);
 107 
 108   ClassLoaderData* loader_data() const                 { return _loader_data; }
 109 
 110   void set_loader_data(ClassLoaderData* cld) {
 111     assert(!cld->is_anonymous(), "Unexpected anonymous class loader data");
 112     _loader_data = cld;
 113   }
 114 
 115   Symbol*          version() const                     { return _version; }
 116   void             set_version(Symbol* version);
 117 
 118   Symbol*          location() const                    { return _location; }
 119   void             set_location(Symbol* location);
 120   bool             should_show_version();
 121 
 122   bool             can_read(ModuleEntry* m) const;
 123   bool             has_reads_list() const;
 124   void             add_read(ModuleEntry* m);
 125   void             set_read_walk_required(ClassLoaderData* m_loader_data);
 126 
 127   bool             is_open() const                     { return _is_open; }
 128   void             set_is_open(bool is_open);
 129 
 130   bool             is_named() const                    { return (name() != NULL); }
 131 
 132   bool can_read_all_unnamed() const {
 133     assert(is_named() || _can_read_all_unnamed == true,
 134            "unnamed modules can always read all unnamed modules");
 135     return _can_read_all_unnamed;
 136   }
 137 
 138   // Modules can only go from strict to loose.
 139   void set_can_read_all_unnamed() { _can_read_all_unnamed = true; }
 140 
 141   bool has_default_read_edges() const {
 142     return _has_default_read_edges;
 143   }
 144 
 145   // Sets true and returns the previous value.
 146   bool set_has_default_read_edges() {
 147     MutexLocker ml(Module_lock);
 148     bool prev = _has_default_read_edges;
 149     _has_default_read_edges = true;
 150     return prev;
 151   }
 152 
 153   void set_is_patched() {
 154       _is_patched = true;
 155   }
 156   bool is_patched() {
 157       return _is_patched;
 158   }
 159 
 160   ModuleEntry* next() const {
 161     return (ModuleEntry*)HashtableEntry<Symbol*, mtModule>::next();
 162   }
 163   ModuleEntry** next_addr() {
 164     return (ModuleEntry**)HashtableEntry<Symbol*, mtModule>::next_addr();
 165   }
 166 
 167   // iteration support for readability
 168   void module_reads_do(ModuleClosure* const f);
 169 
 170   // Purge dead weak references out of reads list when any given class loader is unloaded.
 171   void purge_reads();
 172   void delete_reads();
 173 
 174   // Special handling for unnamed module, one per class loader
 175   static ModuleEntry* create_unnamed_module(ClassLoaderData* cld);
 176   static ModuleEntry* create_boot_unnamed_module(ClassLoaderData* cld);
 177   static ModuleEntry* new_unnamed_module_entry(Handle module_handle, ClassLoaderData* cld);
 178   void delete_unnamed_module();
 179 
 180   void print(outputStream* st = tty);
 181   void verify();
 182 
 183   JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
 184 };
 185 
 186 // Iterator interface
 187 class ModuleClosure: public StackObj {
 188  public:
 189   virtual void do_module(ModuleEntry* module) = 0;
 190 };
 191 
 192 
 193 // The ModuleEntryTable is a Hashtable containing a list of all modules defined
 194 // by a particular class loader.  Each module is represented as a ModuleEntry node.
 195 //
 196 // Each ModuleEntryTable contains a _javabase_module field which allows for the
 197 // creation of java.base's ModuleEntry very early in bootstrapping before the
 198 // corresponding JVM_DefineModule call for java.base occurs during module system
 199 // initialization.  Setting up java.base's ModuleEntry early enables classes,
 200 // loaded prior to the module system being initialized to be created with their
 201 // PackageEntry node's correctly pointing at java.base's ModuleEntry.  No class
 202 // outside of java.base is allowed to be loaded pre-module system initialization.
 203 //
 204 // The ModuleEntryTable's lookup is lock free.
 205 //
 206 class ModuleEntryTable : public Hashtable<Symbol*, mtModule> {
 207   friend class VMStructs;
 208 public:
 209   enum Constants {
 210     _moduletable_entry_size  = 109 // number of entries in module entry table
 211   };
 212 
 213 private:
 214   static ModuleEntry* _javabase_module;
 215 
 216   ModuleEntry* new_entry(unsigned int hash, Handle module_handle, bool is_open,
 217                          Symbol* name, Symbol* version, Symbol* location, ClassLoaderData* loader_data);
 218   void add_entry(int index, ModuleEntry* new_entry);
 219 
 220   int entry_size() const { return BasicHashtable<mtModule>::entry_size(); }
 221 
 222   ModuleEntry** bucket_addr(int i) {
 223     return (ModuleEntry**)Hashtable<Symbol*, mtModule>::bucket_addr(i);
 224   }
 225 
 226   static unsigned int compute_hash(Symbol* name) { return ((name == NULL) ? 0 : (unsigned int)(name->identity_hash())); }
 227   int index_for(Symbol* name) const              { return hash_to_index(compute_hash(name)); }
 228 
 229 public:
 230   ModuleEntryTable(int table_size);
 231   ~ModuleEntryTable();
 232 
 233   ModuleEntry* bucket(int i) {
 234     return (ModuleEntry*)Hashtable<Symbol*, mtModule>::bucket(i);
 235   }
 236 
 237   // Create module in loader's module entry table, if already exists then
 238   // return null.  Assume Module_lock has been locked by caller.
 239   ModuleEntry* locked_create_entry_or_null(Handle module_handle,
 240                                            bool is_open,
 241                                            Symbol* module_name,
 242                                            Symbol* module_version,
 243                                            Symbol* module_location,
 244                                            ClassLoaderData* loader_data);
 245 
 246   // Only lookup module within loader's module entry table.  The table read is lock-free.
 247   ModuleEntry* lookup_only(Symbol* name);
 248 
 249   // purge dead weak references out of reads list
 250   void purge_all_module_reads();
 251 
 252   // Special handling for java.base
 253   static ModuleEntry* javabase_moduleEntry()                   { return _javabase_module; }
 254   static void set_javabase_moduleEntry(ModuleEntry* java_base) { _javabase_module = java_base; }
 255 
 256   static bool javabase_defined() { return ((_javabase_module != NULL) &&
 257                                            (_javabase_module->module() != NULL)); }
 258   static void finalize_javabase(Handle module_handle, Symbol* version, Symbol* location);
 259   static void patch_javabase_entries(Handle module_handle);
 260 
 261   void print(outputStream* st = tty);
 262   void verify();
 263 };
 264 
 265 #endif // SHARE_VM_CLASSFILE_MODULEENTRY_HPP