1 /*
2 * Copyright (c) 2003, 2017, 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.inline.hpp"
27 #include "classfile/loaderConstraints.hpp"
28 #include "memory/resourceArea.hpp"
29 #include "oops/oop.inline.hpp"
30 #include "runtime/handles.inline.hpp"
31 #include "runtime/safepoint.hpp"
32 #include "utilities/hashtable.inline.hpp"
33
34 void LoaderConstraintEntry::set_loader(int i, oop p) {
35 set_loader_data(i, ClassLoaderData::class_loader_data(p));
36 }
37
38 LoaderConstraintTable::LoaderConstraintTable(int nof_buckets)
39 : Hashtable<InstanceKlass*, mtClass>(nof_buckets, sizeof(LoaderConstraintEntry)) {};
40
41
42 LoaderConstraintEntry* LoaderConstraintTable::new_entry(
43 unsigned int hash, Symbol* name,
44 InstanceKlass* klass, int num_loaders,
45 int max_loaders) {
46 LoaderConstraintEntry* entry;
47 entry = (LoaderConstraintEntry*)Hashtable<InstanceKlass*, mtClass>::new_entry(hash, klass);
48 entry->set_name(name);
49 entry->set_num_loaders(num_loaders);
50 entry->set_max_loaders(max_loaders);
51 return entry;
52 }
53
54 void LoaderConstraintTable::free_entry(LoaderConstraintEntry *entry) {
55 // decrement name refcount before freeing
56 entry->name()->decrement_refcount();
57 Hashtable<InstanceKlass*, mtClass>::free_entry(entry);
58 }
59
60 // The loaderConstraintTable must always be accessed with the
61 // SystemDictionary lock held. This is true even for readers as
62 // entries in the table could be being dynamically resized.
63
64 LoaderConstraintEntry** LoaderConstraintTable::find_loader_constraint(
65 Symbol* name, Handle loader) {
66
67 unsigned int hash = compute_hash(name);
68 int index = hash_to_index(hash);
69 LoaderConstraintEntry** pp = bucket_addr(index);
70 ClassLoaderData* loader_data = ClassLoaderData::class_loader_data(loader());
71
72 while (*pp) {
73 LoaderConstraintEntry* p = *pp;
74 if (p->hash() == hash) {
75 if (p->name() == name) {
76 for (int i = p->num_loaders() - 1; i >= 0; i--) {
77 if (p->loader_data(i) == loader_data) {
78 return pp;
79 }
80 }
81 }
82 }
83 pp = p->next_addr();
84 }
85 return pp;
86 }
87
88
89 void LoaderConstraintTable::purge_loader_constraints() {
90 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
91 // Remove unloaded entries from constraint table
92 for (int index = 0; index < table_size(); index++) {
93 LoaderConstraintEntry** p = bucket_addr(index);
94 while(*p) {
95 LoaderConstraintEntry* probe = *p;
96 InstanceKlass* klass = probe->klass();
97 // Remove klass that is no longer alive
98 if (klass != NULL &&
99 klass->class_loader_data()->is_unloading()) {
100 probe->set_klass(NULL);
101 if (log_is_enabled(Info, class, loader, constraints)) {
102 ResourceMark rm;
103 outputStream* out = Log(class, loader, constraints)::info_stream();
104 out->print_cr("purging class object from constraint for name %s,"
105 " loader list:",
106 probe->name()->as_C_string());
107 for (int i = 0; i < probe->num_loaders(); i++) {
108 out->print_cr(" [%d]: %s", i,
109 probe->loader_data(i)->loader_name());
110 }
111 }
112 }
113 // Remove entries no longer alive from loader array
114 int n = 0;
115 while (n < probe->num_loaders()) {
116 if (probe->loader_data(n)->is_unloading()) {
117 if (log_is_enabled(Info, class, loader, constraints)) {
118 ResourceMark rm;
119 outputStream* out = Log(class, loader, constraints)::info_stream();
120 out->print_cr("purging loader %s from constraint for name %s",
121 probe->loader_data(n)->loader_name(),
122 probe->name()->as_C_string()
123 );
124 }
125
126 // Compact array
127 int num = probe->num_loaders() - 1;
128 probe->set_num_loaders(num);
129 probe->set_loader_data(n, probe->loader_data(num));
130 probe->set_loader_data(num, NULL);
131
132 if (log_is_enabled(Info, class, loader, constraints)) {
133 ResourceMark rm;
134 outputStream* out = Log(class, loader, constraints)::info_stream();
135 out->print_cr("new loader list:");
136 for (int i = 0; i < probe->num_loaders(); i++) {
137 out->print_cr(" [%d]: %s", i,
138 probe->loader_data(i)->loader_name());
139 }
140 }
141
142 continue; // current element replaced, so restart without
143 // incrementing n
144 }
145 n++;
146 }
147 // Check whether entry should be purged
148 if (probe->num_loaders() < 2) {
149 if (log_is_enabled(Info, class, loader, constraints)) {
150 ResourceMark rm;
151 outputStream* out = Log(class, loader, constraints)::info_stream();
152 out->print_cr("purging complete constraint for name %s",
153 probe->name()->as_C_string());
154 }
155
156 // Purge entry
157 *p = probe->next();
158 FREE_C_HEAP_ARRAY(oop, probe->loaders());
159 free_entry(probe);
160 } else {
161 #ifdef ASSERT
162 if (probe->klass() != NULL) {
163 ClassLoaderData* loader_data =
164 probe->klass()->class_loader_data();
165 assert(!loader_data->is_unloading(), "klass should be live");
166 }
167 #endif
168 // Go to next entry
169 p = probe->next_addr();
170 }
171 }
172 }
173 }
174
175 bool LoaderConstraintTable::add_entry(Symbol* class_name,
176 InstanceKlass* klass1, Handle class_loader1,
177 InstanceKlass* klass2, Handle class_loader2) {
178 int failure_code = 0; // encode different reasons for failing
179
180 if (klass1 != NULL && klass2 != NULL && klass1 != klass2) {
181 failure_code = 1;
182 } else {
183 InstanceKlass* klass = klass1 != NULL ? klass1 : klass2;
184
185 LoaderConstraintEntry** pp1 = find_loader_constraint(class_name,
186 class_loader1);
187 if (*pp1 != NULL && (*pp1)->klass() != NULL) {
188 if (klass != NULL) {
189 if (klass != (*pp1)->klass()) {
190 failure_code = 2;
191 }
192 } else {
193 klass = (*pp1)->klass();
194 }
195 }
196
197 LoaderConstraintEntry** pp2 = find_loader_constraint(class_name,
198 class_loader2);
199 if (*pp2 != NULL && (*pp2)->klass() != NULL) {
200 if (klass != NULL) {
201 if (klass != (*pp2)->klass()) {
202 failure_code = 3;
203 }
204 } else {
205 klass = (*pp2)->klass();
206 }
207 }
208
209 if (failure_code == 0) {
210 if (*pp1 == NULL && *pp2 == NULL) {
211 unsigned int hash = compute_hash(class_name);
212 int index = hash_to_index(hash);
213 LoaderConstraintEntry* p;
214 p = new_entry(hash, class_name, klass, 2, 2);
215 p->set_loaders(NEW_C_HEAP_ARRAY(ClassLoaderData*, 2, mtClass));
216 p->set_loader(0, class_loader1());
217 p->set_loader(1, class_loader2());
218 p->set_klass(klass);
219 p->set_next(bucket(index));
220 set_entry(index, p);
221 if (log_is_enabled(Info, class, loader, constraints)) {
222 ResourceMark rm;
223 outputStream* out = Log(class, loader, constraints)::info_stream();
224 out->print_cr("adding new constraint for name: %s, loader[0]: %s,"
225 " loader[1]: %s",
226 class_name->as_C_string(),
227 SystemDictionary::loader_name(class_loader1()),
228 SystemDictionary::loader_name(class_loader2())
229 );
230 }
231 } else if (*pp1 == *pp2) {
232 /* constraint already imposed */
233 if ((*pp1)->klass() == NULL) {
234 (*pp1)->set_klass(klass);
235 if (log_is_enabled(Info, class, loader, constraints)) {
236 ResourceMark rm;
237 outputStream* out = Log(class, loader, constraints)::info_stream();
238 out->print_cr("setting class object in existing constraint for"
239 " name: %s and loader %s",
240 class_name->as_C_string(),
241 SystemDictionary::loader_name(class_loader1())
242 );
243 }
244 } else {
245 assert((*pp1)->klass() == klass, "loader constraints corrupted");
246 }
247 } else if (*pp1 == NULL) {
248 extend_loader_constraint(*pp2, class_loader1, klass);
249 } else if (*pp2 == NULL) {
250 extend_loader_constraint(*pp1, class_loader2, klass);
251 } else {
252 merge_loader_constraints(pp1, pp2, klass);
253 }
254 }
255 }
256
257 if (failure_code != 0 && log_is_enabled(Info, class, loader, constraints)) {
258 ResourceMark rm;
259 outputStream* out = Log(class, loader, constraints)::info_stream();
260 const char* reason = "";
261 switch(failure_code) {
262 case 1: reason = "the class objects presented by loader[0] and loader[1]"
263 " are different"; break;
264 case 2: reason = "the class object presented by loader[0] does not match"
265 " the stored class object in the constraint"; break;
266 case 3: reason = "the class object presented by loader[1] does not match"
267 " the stored class object in the constraint"; break;
268 default: reason = "unknown reason code";
269 }
270 out->print_cr("failed to add constraint for name: %s, loader[0]: %s,"
271 " loader[1]: %s, Reason: %s",
272 class_name->as_C_string(),
273 SystemDictionary::loader_name(class_loader1()),
274 SystemDictionary::loader_name(class_loader2()),
275 reason
276 );
277 }
278
279 return failure_code == 0;
280 }
281
282
283 // return true if the constraint was updated, false if the constraint is
284 // violated
285 bool LoaderConstraintTable::check_or_update(InstanceKlass* k,
286 Handle loader,
287 Symbol* name) {
288 LoaderConstraintEntry* p = *(find_loader_constraint(name, loader));
289 if (p && p->klass() != NULL && p->klass() != k) {
290 if (log_is_enabled(Info, class, loader, constraints)) {
291 ResourceMark rm;
292 outputStream* out = Log(class, loader, constraints)::info_stream();
293 out->print_cr("constraint check failed for name %s, loader %s: "
294 "the presented class object differs from that stored",
295 name->as_C_string(),
296 SystemDictionary::loader_name(loader()));
297 }
298 return false;
299 } else {
300 if (p && p->klass() == NULL) {
301 p->set_klass(k);
302 if (log_is_enabled(Info, class, loader, constraints)) {
303 ResourceMark rm;
304 outputStream* out = Log(class, loader, constraints)::info_stream();
305 out->print_cr("updating constraint for name %s, loader %s, "
306 "by setting class object",
307 name->as_C_string(),
308 SystemDictionary::loader_name(loader()));
309 }
310 }
311 return true;
312 }
313 }
314
315 InstanceKlass* LoaderConstraintTable::find_constrained_klass(Symbol* name,
316 Handle loader) {
317 LoaderConstraintEntry *p = *(find_loader_constraint(name, loader));
318 if (p != NULL && p->klass() != NULL) {
319 assert(p->klass()->is_instance_klass(), "sanity");
320 if (p->klass()->is_loaded()) {
321 // Only return fully loaded classes. Classes found through the
322 // constraints might still be in the process of loading.
323 return NULL;
324 }
325 return p->klass();
326 }
327
328 // No constraints, or else no klass loaded yet.
329 return NULL;
330 }
331
332 void LoaderConstraintTable::ensure_loader_constraint_capacity(
333 LoaderConstraintEntry *p,
334 int nfree) {
335 if (p->max_loaders() - p->num_loaders() < nfree) {
336 int n = nfree + p->num_loaders();
337 ClassLoaderData** new_loaders = NEW_C_HEAP_ARRAY(ClassLoaderData*, n, mtClass);
338 memcpy(new_loaders, p->loaders(), sizeof(ClassLoaderData*) * p->num_loaders());
339 p->set_max_loaders(n);
340 FREE_C_HEAP_ARRAY(ClassLoaderData*, p->loaders());
341 p->set_loaders(new_loaders);
342 }
343 }
344
345
346 void LoaderConstraintTable::extend_loader_constraint(LoaderConstraintEntry* p,
347 Handle loader,
348 InstanceKlass* klass) {
349 ensure_loader_constraint_capacity(p, 1);
350 int num = p->num_loaders();
351 p->set_loader(num, loader());
352 p->set_num_loaders(num + 1);
353 if (log_is_enabled(Info, class, loader, constraints)) {
354 ResourceMark rm;
355 outputStream* out = Log(class, loader, constraints)::info_stream();
356 out->print_cr("extending constraint for name %s by adding loader[%d]: %s %s",
357 p->name()->as_C_string(),
358 num,
359 SystemDictionary::loader_name(loader()),
360 (p->klass() == NULL ? " and setting class object" : "")
361 );
362 }
363 if (p->klass() == NULL) {
364 p->set_klass(klass);
365 } else {
366 assert(klass == NULL || p->klass() == klass, "constraints corrupted");
367 }
368 }
369
370
371 void LoaderConstraintTable::merge_loader_constraints(
372 LoaderConstraintEntry** pp1,
373 LoaderConstraintEntry** pp2,
374 InstanceKlass* klass) {
375 // make sure *pp1 has higher capacity
376 if ((*pp1)->max_loaders() < (*pp2)->max_loaders()) {
377 LoaderConstraintEntry** tmp = pp2;
378 pp2 = pp1;
379 pp1 = tmp;
380 }
381
382 LoaderConstraintEntry* p1 = *pp1;
383 LoaderConstraintEntry* p2 = *pp2;
384
385 ensure_loader_constraint_capacity(p1, p2->num_loaders());
386
387 for (int i = 0; i < p2->num_loaders(); i++) {
388 int num = p1->num_loaders();
389 p1->set_loader_data(num, p2->loader_data(i));
390 p1->set_num_loaders(num + 1);
391 }
392
393 if (log_is_enabled(Info, class, loader, constraints)) {
394 ResourceMark rm;
395 outputStream* out = Log(class, loader, constraints)::info_stream();
396 out->print_cr("merged constraints for name %s, new loader list:",
397 p1->name()->as_C_string()
398 );
399
400 for (int i = 0; i < p1->num_loaders(); i++) {
401 out->print_cr(" [%d]: %s", i,
402 p1->loader_data(i)->loader_name());
403 }
404 if (p1->klass() == NULL) {
405 out->print_cr("... and setting class object");
406 }
407 }
408
409 // p1->klass() will hold NULL if klass, p2->klass(), and old
410 // p1->klass() are all NULL. In addition, all three must have
411 // matching non-NULL values, otherwise either the constraints would
412 // have been violated, or the constraints had been corrupted (and an
413 // assertion would fail).
414 if (p2->klass() != NULL) {
415 assert(p2->klass() == klass, "constraints corrupted");
416 }
417 if (p1->klass() == NULL) {
418 p1->set_klass(klass);
419 } else {
420 assert(p1->klass() == klass, "constraints corrupted");
421 }
422
423 *pp2 = p2->next();
424 FREE_C_HEAP_ARRAY(oop, p2->loaders());
425 free_entry(p2);
426 return;
427 }
428
429
430 void LoaderConstraintTable::verify(Dictionary* dictionary,
431 PlaceholderTable* placeholders) {
432 Thread *thread = Thread::current();
433 for (int cindex = 0; cindex < _loader_constraint_size; cindex++) {
434 for (LoaderConstraintEntry* probe = bucket(cindex);
435 probe != NULL;
436 probe = probe->next()) {
437 if (probe->klass() != NULL) {
438 InstanceKlass* ik = probe->klass();
439 guarantee(ik->name() == probe->name(), "name should match");
440 Symbol* name = ik->name();
441 ClassLoaderData* loader_data = ik->class_loader_data();
442 unsigned int d_hash = dictionary->compute_hash(name, loader_data);
443 int d_index = dictionary->hash_to_index(d_hash);
444 InstanceKlass* k = dictionary->find_class(d_index, d_hash, name, loader_data);
445 if (k != NULL) {
446 // We found the class in the system dictionary, so we should
447 // make sure that the Klass* matches what we already have.
448 guarantee(k == probe->klass(), "klass should be in dictionary");
449 } else {
450 // If we don't find the class in the system dictionary, it
451 // has to be in the placeholders table.
452 unsigned int p_hash = placeholders->compute_hash(name, loader_data);
453 int p_index = placeholders->hash_to_index(p_hash);
454 PlaceholderEntry* entry = placeholders->get_entry(p_index, p_hash,
455 name, loader_data);
456
457 // The InstanceKlass might not be on the entry, so the only
458 // thing we can check here is whether we were successful in
459 // finding the class in the placeholders table.
460 guarantee(entry != NULL, "klass should be in the placeholders");
461 }
462 }
463 for (int n = 0; n< probe->num_loaders(); n++) {
464 assert(ClassLoaderDataGraph::contains_loader_data(probe->loader_data(n)), "The loader is missing");
465 }
466 }
467 }
468 }
469
470 #ifndef PRODUCT
471
472 // Called with the system dictionary lock held
473 void LoaderConstraintTable::print() {
474 ResourceMark rm;
475 assert_locked_or_safepoint(SystemDictionary_lock);
476 tty->print_cr("Java loader constraints (entries=%d)", _loader_constraint_size);
477 for (int cindex = 0; cindex < _loader_constraint_size; cindex++) {
478 for (LoaderConstraintEntry* probe = bucket(cindex);
479 probe != NULL;
480 probe = probe->next()) {
481 tty->print("%4d: ", cindex);
482 probe->name()->print();
483 tty->print(" , loaders:");
484 for (int n = 0; n < probe->num_loaders(); n++) {
485 probe->loader_data(n)->print_value();
486 tty->print(", ");
487 }
488 tty->cr();
489 }
490 }
491 }
492 #endif