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