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 #include "precompiled.hpp"
26 #include "classfile/classLoaderData.hpp"
27 #include "classfile/javaClasses.hpp"
28 #include "classfile/moduleEntry.hpp"
29 #include "logging/log.hpp"
30 #include "memory/resourceArea.hpp"
31 #include "oops/symbol.hpp"
32 #include "prims/jni.h"
33 #include "runtime/handles.inline.hpp"
34 #include "runtime/safepoint.hpp"
35 #include "trace/traceMacros.hpp"
36 #include "utilities/events.hpp"
37 #include "utilities/growableArray.hpp"
38 #include "utilities/hashtable.inline.hpp"
39 #include "utilities/ostream.hpp"
40
41 ModuleEntry* ModuleEntryTable::_javabase_module = NULL;
42
43 void ModuleEntry::set_location(Symbol* location) {
44 if (_location != NULL) {
45 // _location symbol's refcounts are managed by ModuleEntry,
46 // must decrement the old one before updating.
47 _location->decrement_refcount();
48 }
49
50 _location = location;
51
52 if (location != NULL) {
53 location->increment_refcount();
54 }
55 }
56
57 void ModuleEntry::set_version(Symbol* version) {
58 if (_version != NULL) {
59 // _version symbol's refcounts are managed by ModuleEntry,
60 // must decrement the old one before updating.
61 _version->decrement_refcount();
62 }
63
64 _version = version;
65
66 if (version != NULL) {
67 version->increment_refcount();
68 }
69 }
70
71 // Returns the shared ProtectionDomain
72 Handle ModuleEntry::shared_protection_domain() {
73 return Handle(JNIHandles::resolve(_pd));
74 }
75
76 // Set the shared ProtectionDomain atomically
77 void ModuleEntry::set_shared_protection_domain(ClassLoaderData *loader_data,
78 Handle pd_h) {
79 // Create a JNI handle for the shared ProtectionDomain and save it atomically.
80 // If someone beats us setting the _pd cache, the created JNI handle is destroyed.
81 jobject obj = loader_data->add_handle(pd_h);
82 if (Atomic::cmpxchg_ptr(obj, &_pd, NULL) != NULL) {
83 loader_data->remove_handle(obj);
84 }
85 }
86
87 // Returns true if this module can read module m
88 bool ModuleEntry::can_read(ModuleEntry* m) const {
89 assert(m != NULL, "No module to lookup in this module's reads list");
90
91 // Unnamed modules read everyone and all modules
92 // read java.base. If either of these conditions
93 // hold, readability has been established.
94 if (!this->is_named() ||
95 (m == ModuleEntryTable::javabase_moduleEntry())) {
96 return true;
97 }
98
99 MutexLocker m1(Module_lock);
100 if (!has_reads()) {
101 return false;
102 } else {
103 return _reads->contains(m);
104 }
105 }
106
107 // Add a new module to this module's reads list
108 void ModuleEntry::add_read(ModuleEntry* m) {
109 MutexLocker m1(Module_lock);
110 if (m == NULL) {
111 set_can_read_all_unnamed();
112 } else {
113 if (_reads == NULL) {
114 // Lazily create a module's reads list
115 _reads = new (ResourceObj::C_HEAP, mtModule)GrowableArray<ModuleEntry*>(MODULE_READS_SIZE, true);
116 }
117
118 // Determine, based on this newly established read edge to module m,
119 // if this module's read list should be walked at a GC safepoint.
120 set_read_walk_required(m->loader_data());
121
122 // Establish readability to module m
123 _reads->append_if_missing(m);
124 }
125 }
126
127 // If the module's loader, that a read edge is being established to, is
128 // not the same loader as this module's and is not one of the 3 builtin
129 // class loaders, then this module's reads list must be walked at GC
130 // safepoint. Modules have the same life cycle as their defining class
131 // loaders and should be removed if dead.
132 void ModuleEntry::set_read_walk_required(ClassLoaderData* m_loader_data) {
133 assert_locked_or_safepoint(Module_lock);
134 if (!_must_walk_reads &&
135 loader_data() != m_loader_data &&
136 !m_loader_data->is_builtin_class_loader_data()) {
137 _must_walk_reads = true;
138 if (log_is_enabled(Trace, modules)) {
139 ResourceMark rm;
140 log_trace(modules)("ModuleEntry::set_read_walk_required(): module %s reads list must be walked",
141 (name() != NULL) ? name()->as_C_string() : UNNAMED_MODULE);
142 }
143 }
144 }
145
146 bool ModuleEntry::has_reads() const {
147 assert_locked_or_safepoint(Module_lock);
148 return ((_reads != NULL) && !_reads->is_empty());
149 }
150
151 // Purge dead module entries out of reads list.
152 void ModuleEntry::purge_reads() {
153 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
154
155 if (_must_walk_reads && has_reads()) {
156 // This module's _must_walk_reads flag will be reset based
157 // on the remaining live modules on the reads list.
158 _must_walk_reads = false;
159
160 if (log_is_enabled(Trace, modules)) {
161 ResourceMark rm;
162 log_trace(modules)("ModuleEntry::purge_reads(): module %s reads list being walked",
163 (name() != NULL) ? name()->as_C_string() : UNNAMED_MODULE);
164 }
165
166 // Go backwards because this removes entries that are dead.
167 int len = _reads->length();
168 for (int idx = len - 1; idx >= 0; idx--) {
169 ModuleEntry* module_idx = _reads->at(idx);
170 ClassLoaderData* cld_idx = module_idx->loader_data();
171 if (cld_idx->is_unloading()) {
172 _reads->delete_at(idx);
173 } else {
174 // Update the need to walk this module's reads based on live modules
175 set_read_walk_required(cld_idx);
176 }
177 }
178 }
179 }
180
181 void ModuleEntry::module_reads_do(ModuleClosure* const f) {
182 assert_locked_or_safepoint(Module_lock);
183 assert(f != NULL, "invariant");
184
185 if (has_reads()) {
186 int reads_len = _reads->length();
187 for (int i = 0; i < reads_len; ++i) {
188 f->do_module(_reads->at(i));
189 }
190 }
191 }
192
193 void ModuleEntry::delete_reads() {
194 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
195 delete _reads;
196 _reads = NULL;
197 }
198
199 ModuleEntryTable::ModuleEntryTable(int table_size)
200 : Hashtable<Symbol*, mtModule>(table_size, sizeof(ModuleEntry)), _unnamed_module(NULL)
201 {
202 }
203
204 ModuleEntryTable::~ModuleEntryTable() {
205 assert_locked_or_safepoint(Module_lock);
206
207 // Walk through all buckets and all entries in each bucket,
208 // freeing each entry.
209 for (int i = 0; i < table_size(); ++i) {
210 for (ModuleEntry* m = bucket(i); m != NULL;) {
211 ModuleEntry* to_remove = m;
212 // read next before freeing.
213 m = m->next();
214
215 ResourceMark rm;
216 log_debug(modules)("ModuleEntryTable: deleting module: %s", to_remove->name() != NULL ?
217 to_remove->name()->as_C_string() : UNNAMED_MODULE);
218
219 // Clean out the C heap allocated reads list first before freeing the entry
220 to_remove->delete_reads();
221 if (to_remove->name() != NULL) {
222 to_remove->name()->decrement_refcount();
223 }
224 if (to_remove->version() != NULL) {
225 to_remove->version()->decrement_refcount();
226 }
227 if (to_remove->location() != NULL) {
228 to_remove->location()->decrement_refcount();
229 }
230
231 // Unlink from the Hashtable prior to freeing
232 unlink_entry(to_remove);
233 FREE_C_HEAP_ARRAY(char, to_remove);
234 }
235 }
236 assert(number_of_entries() == 0, "should have removed all entries");
237 assert(new_entry_free_list() == NULL, "entry present on ModuleEntryTable's free list");
238 free_buckets();
239 }
240
241 void ModuleEntryTable::create_unnamed_module(ClassLoaderData* loader_data) {
242 assert(Module_lock->owned_by_self(), "should have the Module_lock");
243
244 // Each ModuleEntryTable has exactly one unnamed module
245 if (loader_data->is_the_null_class_loader_data()) {
246 // For the boot loader, the java.lang.reflect.Module for the unnamed module
247 // is not known until a call to JVM_SetBootLoaderUnnamedModule is made. At
248 // this point initially create the ModuleEntry for the unnamed module.
249 _unnamed_module = new_entry(0, Handle(NULL), NULL, NULL, NULL, loader_data);
250 } else {
251 // For all other class loaders the java.lang.reflect.Module for their
252 // corresponding unnamed module can be found in the java.lang.ClassLoader object.
253 oop module = java_lang_ClassLoader::unnamedModule(loader_data->class_loader());
254 _unnamed_module = new_entry(0, Handle(module), NULL, NULL, NULL, loader_data);
255
256 // Store pointer to the ModuleEntry in the unnamed module's java.lang.reflect.Module
257 // object.
258 java_lang_reflect_Module::set_module_entry(module, _unnamed_module);
259 }
260
261 // Add to bucket 0, no name to hash on
262 add_entry(0, _unnamed_module);
263 }
264
265 ModuleEntry* ModuleEntryTable::new_entry(unsigned int hash, Handle module_handle, Symbol* name,
266 Symbol* version, Symbol* location,
267 ClassLoaderData* loader_data) {
268 assert(Module_lock->owned_by_self(), "should have the Module_lock");
269 ModuleEntry* entry = (ModuleEntry*) NEW_C_HEAP_ARRAY(char, entry_size(), mtModule);
270
271 // Initialize everything BasicHashtable would
272 entry->set_next(NULL);
273 entry->set_hash(hash);
274 entry->set_literal(name);
275
276 // Initialize fields specific to a ModuleEntry
277 entry->init();
278 if (name != NULL) {
279 name->increment_refcount();
280 } else {
281 // Unnamed modules can read all other unnamed modules.
282 entry->set_can_read_all_unnamed();
283 }
284
285 if (!module_handle.is_null()) {
286 entry->set_module(loader_data->add_handle(module_handle));
287 }
288
289 entry->set_loader_data(loader_data);
290 entry->set_version(version);
291 entry->set_location(location);
292
293 TRACE_INIT_MODULE_ID(entry);
294
295 return entry;
296 }
297
298 void ModuleEntryTable::add_entry(int index, ModuleEntry* new_entry) {
299 assert(Module_lock->owned_by_self(), "should have the Module_lock");
300 Hashtable<Symbol*, mtModule>::add_entry(index, (HashtableEntry<Symbol*, mtModule>*)new_entry);
301 }
302
303 ModuleEntry* ModuleEntryTable::locked_create_entry_or_null(Handle module_handle,
304 Symbol* module_name,
305 Symbol* module_version,
306 Symbol* module_location,
307 ClassLoaderData* loader_data) {
308 assert(module_name != NULL, "ModuleEntryTable locked_create_entry_or_null should never be called for unnamed module.");
309 assert(Module_lock->owned_by_self(), "should have the Module_lock");
310 // Check if module already exists.
311 if (lookup_only(module_name) != NULL) {
312 return NULL;
313 } else {
314 ModuleEntry* entry = new_entry(compute_hash(module_name), module_handle, module_name,
315 module_version, module_location, loader_data);
316 add_entry(index_for(module_name), entry);
317 return entry;
318 }
319 }
320
321 // lookup_only by Symbol* to find a ModuleEntry.
322 ModuleEntry* ModuleEntryTable::lookup_only(Symbol* name) {
323 if (name == NULL) {
324 // Return this table's unnamed module
325 return unnamed_module();
326 }
327 int index = index_for(name);
328 for (ModuleEntry* m = bucket(index); m != NULL; m = m->next()) {
329 if (m->name()->fast_compare(name) == 0) {
330 return m;
331 }
332 }
333 return NULL;
334 }
335
336 // Remove dead modules from all other alive modules' reads list.
337 // This should only occur at class unloading.
338 void ModuleEntryTable::purge_all_module_reads() {
339 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
340 for (int i = 0; i < table_size(); i++) {
341 for (ModuleEntry* entry = bucket(i);
342 entry != NULL;
343 entry = entry->next()) {
344 entry->purge_reads();
345 }
346 }
347 }
348
349 void ModuleEntryTable::finalize_javabase(Handle module_handle, Symbol* version, Symbol* location) {
350 assert(Module_lock->owned_by_self(), "should have the Module_lock");
351 ClassLoaderData* boot_loader_data = ClassLoaderData::the_null_class_loader_data();
352 ModuleEntryTable* module_table = boot_loader_data->modules();
353
354 assert(module_table != NULL, "boot loader's ModuleEntryTable not defined");
355
356 if (module_handle.is_null()) {
357 fatal("Unable to finalize module definition for java.base");
358 }
359
360 // Set java.lang.reflect.Module, version and location for java.base
361 ModuleEntry* jb_module = javabase_moduleEntry();
362 assert(jb_module != NULL, "java.base ModuleEntry not defined");
363 jb_module->set_version(version);
364 jb_module->set_location(location);
365 // Once java.base's ModuleEntry _module field is set with the known
366 // java.lang.reflect.Module, java.base is considered "defined" to the VM.
367 jb_module->set_module(boot_loader_data->add_handle(module_handle));
368
369 // Store pointer to the ModuleEntry for java.base in the java.lang.reflect.Module object.
370 java_lang_reflect_Module::set_module_entry(module_handle(), jb_module);
371 }
372
373 // Within java.lang.Class instances there is a java.lang.reflect.Module field
374 // that must be set with the defining module. During startup, prior to java.base's
375 // definition, classes needing their module field set are added to the fixup_module_list.
376 // Their module field is set once java.base's java.lang.reflect.Module is known to the VM.
377 void ModuleEntryTable::patch_javabase_entries(Handle module_handle) {
378 if (module_handle.is_null()) {
379 fatal("Unable to patch the module field of classes loaded prior to java.base's definition, invalid java.lang.reflect.Module");
380 }
381
382 // Do the fixups for the basic primitive types
383 java_lang_Class::set_module(Universe::int_mirror(), module_handle());
384 java_lang_Class::set_module(Universe::float_mirror(), module_handle());
385 java_lang_Class::set_module(Universe::double_mirror(), module_handle());
386 java_lang_Class::set_module(Universe::byte_mirror(), module_handle());
387 java_lang_Class::set_module(Universe::bool_mirror(), module_handle());
388 java_lang_Class::set_module(Universe::char_mirror(), module_handle());
389 java_lang_Class::set_module(Universe::long_mirror(), module_handle());
390 java_lang_Class::set_module(Universe::short_mirror(), module_handle());
391 java_lang_Class::set_module(Universe::void_mirror(), module_handle());
392
393 // Do the fixups for classes that have already been created.
394 GrowableArray <Klass*>* list = java_lang_Class::fixup_module_field_list();
395 int list_length = list->length();
396 for (int i = 0; i < list_length; i++) {
397 Klass* k = list->at(i);
398 assert(k->is_klass(), "List should only hold classes");
399 java_lang_Class::fixup_module_field(KlassHandle(k), module_handle);
400 k->class_loader_data()->dec_keep_alive();
401 }
402
403 delete java_lang_Class::fixup_module_field_list();
404 java_lang_Class::set_fixup_module_field_list(NULL);
405 }
406
407 void ModuleEntryTable::print(outputStream* st) {
408 st->print_cr("Module Entry Table (table_size=%d, entries=%d)",
409 table_size(), number_of_entries());
410 for (int i = 0; i < table_size(); i++) {
411 for (ModuleEntry* probe = bucket(i);
412 probe != NULL;
413 probe = probe->next()) {
414 probe->print(st);
415 }
416 }
417 }
418
419 void ModuleEntry::print(outputStream* st) {
420 ResourceMark rm;
421 st->print_cr("entry " PTR_FORMAT " name %s module " PTR_FORMAT " loader %s version %s location %s strict %s next " PTR_FORMAT,
422 p2i(this),
423 name() == NULL ? UNNAMED_MODULE : name()->as_C_string(),
424 p2i(module()),
425 loader_data()->loader_name(),
426 version() != NULL ? version()->as_C_string() : "NULL",
427 location() != NULL ? location()->as_C_string() : "NULL",
428 BOOL_TO_STR(!can_read_all_unnamed()), p2i(next()));
429 }
430
431 void ModuleEntryTable::verify() {
432 int element_count = 0;
433 for (int i = 0; i < table_size(); i++) {
434 for (ModuleEntry* probe = bucket(i);
435 probe != NULL;
436 probe = probe->next()) {
437 probe->verify();
438 element_count++;
439 }
440 }
441 guarantee(number_of_entries() == element_count,
442 "Verify of Module Entry Table failed");
443 DEBUG_ONLY(verify_lookup_length((double)number_of_entries() / table_size(), "Module Entry Table"));
444 }
445
446 void ModuleEntry::verify() {
447 guarantee(loader_data() != NULL, "A module entry must be associated with a loader.");
448 }