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comparison: src/share/vm/classfile/loaderConstraints.cpp

src/share/vm/classfile/loaderConstraints.cpp

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1 /*
2 * Copyright (c) 2003, 2012, 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<Klass*, mtClass>(nof_buckets, sizeof(LoaderConstraintEntry)) {};
40
41
42 LoaderConstraintEntry* LoaderConstraintTable::new_entry(
43 unsigned int hash, Symbol* name,
44 Klass* klass, int num_loaders,
45 int max_loaders) {
46 LoaderConstraintEntry* entry;
47 entry = (LoaderConstraintEntry*)Hashtable<Klass*, 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<Klass*, mtClass>::free_entry(entry);
58 }
59
60 // Enhanced Class Redefinition support
61 void LoaderConstraintTable::classes_do(KlassClosure* f) {
62 for (int index = 0; index < table_size(); index++) {
63 for (LoaderConstraintEntry* probe = bucket(index);
64 probe != NULL;
65 probe = probe->next()) {
66 if (probe->klass() != NULL) {
67 f->do_klass(probe->klass());
68 }
69 }
70 }
71 }
72
73 // The loaderConstraintTable must always be accessed with the
74 // SystemDictionary lock held. This is true even for readers as
75 // entries in the table could be being dynamically resized.
76
77 LoaderConstraintEntry** LoaderConstraintTable::find_loader_constraint(
78 Symbol* name, Handle loader) {
79
80 unsigned int hash = compute_hash(name);
81 int index = hash_to_index(hash);
82 LoaderConstraintEntry** pp = bucket_addr(index);
83 ClassLoaderData* loader_data = ClassLoaderData::class_loader_data(loader());
84
85 while (*pp) {
86 LoaderConstraintEntry* p = *pp;
87 if (p->hash() == hash) {
88 if (p->name() == name) {
89 for (int i = p->num_loaders() - 1; i >= 0; i--) {
90 if (p->loader_data(i) == loader_data) {
91 return pp;
92 }
93 }
94 }
95 }
96 pp = p->next_addr();
97 }
98 return pp;
99 }
100
101
102 void LoaderConstraintTable::purge_loader_constraints() {
103 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
104 // Remove unloaded entries from constraint table
105 for (int index = 0; index < table_size(); index++) {
106 LoaderConstraintEntry** p = bucket_addr(index);
107 while(*p) {
108 LoaderConstraintEntry* probe = *p;
109 Klass* klass = probe->klass();
110 // Remove klass that is no longer alive
111 if (klass != NULL &&
112 klass->class_loader_data()->is_unloading()) {
113 probe->set_klass(NULL);
114 if (TraceLoaderConstraints) {
115 ResourceMark rm;
116 tty->print_cr("[Purging class object from constraint for name %s,"
117 " loader list:",
118 probe->name()->as_C_string());
119 for (int i = 0; i < probe->num_loaders(); i++) {
120 tty->print_cr("[ [%d]: %s", i,
121 probe->loader_data(i)->loader_name());
122 }
123 }
124 }
125 // Remove entries no longer alive from loader array
126 int n = 0;
127 while (n < probe->num_loaders()) {
128 if (probe->loader_data(n)->is_unloading()) {
129 if (TraceLoaderConstraints) {
130 ResourceMark rm;
131 tty->print_cr("[Purging loader %s from constraint for name %s",
132 probe->loader_data(n)->loader_name(),
133 probe->name()->as_C_string()
134 );
135 }
136
137 // Compact array
138 int num = probe->num_loaders() - 1;
139 probe->set_num_loaders(num);
140 probe->set_loader_data(n, probe->loader_data(num));
141 probe->set_loader_data(num, NULL);
142
143 if (TraceLoaderConstraints) {
144 ResourceMark rm;
145 tty->print_cr("[New loader list:");
146 for (int i = 0; i < probe->num_loaders(); i++) {
147 tty->print_cr("[ [%d]: %s", i,
148 probe->loader_data(i)->loader_name());
149 }
150 }
151
152 continue; // current element replaced, so restart without
153 // incrementing n
154 }
155 n++;
156 }
157 // Check whether entry should be purged
158 if (probe->num_loaders() < 2) {
159 if (TraceLoaderConstraints) {
160 ResourceMark rm;
161 tty->print("[Purging complete constraint for name %s\n",
162 probe->name()->as_C_string());
163 }
164
165 // Purge entry
166 *p = probe->next();
167 FREE_C_HEAP_ARRAY(oop, probe->loaders(), mtClass);
168 free_entry(probe);
169 } else {
170 #ifdef ASSERT
171 if (probe->klass() != NULL) {
172 ClassLoaderData* loader_data =
173 probe->klass()->class_loader_data();
174 assert(!loader_data->is_unloading(), "klass should be live");
175 }
176 #endif
177 // Go to next entry
178 p = probe->next_addr();
179 }
180 }
181 }
182 }
183
184 bool LoaderConstraintTable::add_entry(Symbol* class_name,
185 Klass* klass1, Handle class_loader1,
186 Klass* klass2, Handle class_loader2) {
187 int failure_code = 0; // encode different reasons for failing
188
189 if (klass1 != NULL && klass2 != NULL && klass1 != klass2) {
190 failure_code = 1;
191 } else {
192 Klass* klass = klass1 != NULL ? klass1 : klass2;
193
194 LoaderConstraintEntry** pp1 = find_loader_constraint(class_name,
195 class_loader1);
196 if (*pp1 != NULL && (*pp1)->klass() != NULL) {
197 if (klass != NULL) {
198 if (klass != (*pp1)->klass()) {
199 failure_code = 2;
200 }
201 } else {
202 klass = (*pp1)->klass();
203 }
204 }
205
206 LoaderConstraintEntry** pp2 = find_loader_constraint(class_name,
207 class_loader2);
208 if (*pp2 != NULL && (*pp2)->klass() != NULL) {
209 if (klass != NULL) {
210 if (klass != (*pp2)->klass()) {
211 failure_code = 3;
212 }
213 } else {
214 klass = (*pp2)->klass();
215 }
216 }
217
218 if (failure_code == 0) {
219 if (*pp1 == NULL && *pp2 == NULL) {
220 unsigned int hash = compute_hash(class_name);
221 int index = hash_to_index(hash);
222 LoaderConstraintEntry* p;
223 p = new_entry(hash, class_name, klass, 2, 2);
224 p->set_loaders(NEW_C_HEAP_ARRAY(ClassLoaderData*, 2, mtClass));
225 p->set_loader(0, class_loader1());
226 p->set_loader(1, class_loader2());
227 p->set_klass(klass);
228 p->set_next(bucket(index));
229 set_entry(index, p);
230 if (TraceLoaderConstraints) {
231 ResourceMark rm;
232 tty->print("[Adding new constraint for name: %s, loader[0]: %s,"
233 " loader[1]: %s ]\n",
234 class_name->as_C_string(),
235 SystemDictionary::loader_name(class_loader1()),
236 SystemDictionary::loader_name(class_loader2())
237 );
238 }
239 } else if (*pp1 == *pp2) {
240 /* constraint already imposed */
241 if ((*pp1)->klass() == NULL) {
242 (*pp1)->set_klass(klass);
243 if (TraceLoaderConstraints) {
244 ResourceMark rm;
245 tty->print("[Setting class object in existing constraint for"
246 " name: %s and loader %s ]\n",
247 class_name->as_C_string(),
248 SystemDictionary::loader_name(class_loader1())
249 );
250 }
251 } else {
252 assert((*pp1)->klass() == klass, "loader constraints corrupted");
253 }
254 } else if (*pp1 == NULL) {
255 extend_loader_constraint(*pp2, class_loader1, klass);
256 } else if (*pp2 == NULL) {
257 extend_loader_constraint(*pp1, class_loader2, klass);
258 } else {
259 merge_loader_constraints(pp1, pp2, klass);
260 }
261 }
262 }
263
264 if (failure_code != 0 && TraceLoaderConstraints) {
265 ResourceMark rm;
266 const char* reason = "";
267 switch(failure_code) {
268 case 1: reason = "the class objects presented by loader[0] and loader[1]"
269 " are different"; break;
270 case 2: reason = "the class object presented by loader[0] does not match"
271 " the stored class object in the constraint"; break;
272 case 3: reason = "the class object presented by loader[1] does not match"
273 " the stored class object in the constraint"; break;
274 default: reason = "unknown reason code";
275 }
276 tty->print("[Failed to add constraint for name: %s, loader[0]: %s,"
277 " loader[1]: %s, Reason: %s ]\n",
278 class_name->as_C_string(),
279 SystemDictionary::loader_name(class_loader1()),
280 SystemDictionary::loader_name(class_loader2()),
281 reason
282 );
283 }
284
285 return failure_code == 0;
286 }
287
288
289 // return true if the constraint was updated, false if the constraint is
290 // violated
291 bool LoaderConstraintTable::check_or_update(instanceKlassHandle k,
292 Handle loader,
293 Symbol* name) {
294 LoaderConstraintEntry* p = *(find_loader_constraint(name, loader));
295 if (p && p->klass() != NULL && p->klass() != k()) {
296 if (TraceLoaderConstraints) {
297 ResourceMark rm;
298 tty->print("[Constraint check failed for name %s, loader %s: "
299 "the presented class object differs from that stored ]\n",
300 name->as_C_string(),
301 SystemDictionary::loader_name(loader()));
302 }
303 return false;
304 } else {
305 if (p && p->klass() == NULL) {
306 p->set_klass(k());
307 if (TraceLoaderConstraints) {
308 ResourceMark rm;
309 tty->print("[Updating constraint for name %s, loader %s, "
310 "by setting class object ]\n",
311 name->as_C_string(),
312 SystemDictionary::loader_name(loader()));
313 }
314 }
315 return true;
316 }
317 }
318
319 Klass* LoaderConstraintTable::find_constrained_klass(Symbol* name,
320 Handle loader) {
321 LoaderConstraintEntry *p = *(find_loader_constraint(name, loader));
322 if (p != NULL && p->klass() != NULL) {
323 if (p->klass()->oop_is_instance() && !InstanceKlass::cast(p->klass())->is_loaded()) {
324 // Only return fully loaded classes. Classes found through the
325 // constraints might still be in the process of loading.
326 return NULL;
327 }
328 return p->klass();
329 }
330
331 // No constraints, or else no klass loaded yet.
332 return NULL;
333 }
334
335 void LoaderConstraintTable::ensure_loader_constraint_capacity(
336 LoaderConstraintEntry *p,
337 int nfree) {
338 if (p->max_loaders() - p->num_loaders() < nfree) {
339 int n = nfree + p->num_loaders();
340 ClassLoaderData** new_loaders = NEW_C_HEAP_ARRAY(ClassLoaderData*, n, mtClass);
341 memcpy(new_loaders, p->loaders(), sizeof(ClassLoaderData*) * p->num_loaders());
342 p->set_max_loaders(n);
343 FREE_C_HEAP_ARRAY(ClassLoaderData*, p->loaders(), mtClass);
344 p->set_loaders(new_loaders);
345 }
346 }
347
348
349 void LoaderConstraintTable::extend_loader_constraint(LoaderConstraintEntry* p,
350 Handle loader,
351 Klass* klass) {
352 ensure_loader_constraint_capacity(p, 1);
353 int num = p->num_loaders();
354 p->set_loader(num, loader());
355 p->set_num_loaders(num + 1);
356 if (TraceLoaderConstraints) {
357 ResourceMark rm;
358 tty->print("[Extending constraint for name %s by adding loader[%d]: %s %s",
359 p->name()->as_C_string(),
360 num,
361 SystemDictionary::loader_name(loader()),
362 (p->klass() == NULL ? " and setting class object ]\n" : " ]\n")
363 );
364 }
365 if (p->klass() == NULL) {
366 p->set_klass(klass);
367 } else {
368 assert(klass == NULL || p->klass() == klass, "constraints corrupted");
369 }
370 }
371
372
373 void LoaderConstraintTable::merge_loader_constraints(
374 LoaderConstraintEntry** pp1,
375 LoaderConstraintEntry** pp2,
376 Klass* klass) {
377 // make sure *pp1 has higher capacity
378 if ((*pp1)->max_loaders() < (*pp2)->max_loaders()) {
379 LoaderConstraintEntry** tmp = pp2;
380 pp2 = pp1;
381 pp1 = tmp;
382 }
383
384 LoaderConstraintEntry* p1 = *pp1;
385 LoaderConstraintEntry* p2 = *pp2;
386
387 ensure_loader_constraint_capacity(p1, p2->num_loaders());
388
389 for (int i = 0; i < p2->num_loaders(); i++) {
390 int num = p1->num_loaders();
391 p1->set_loader_data(num, p2->loader_data(i));
392 p1->set_num_loaders(num + 1);
393 }
394
395 if (TraceLoaderConstraints) {
396 ResourceMark rm;
397 tty->print_cr("[Merged constraints for name %s, new loader list:",
398 p1->name()->as_C_string()
399 );
400
401 for (int i = 0; i < p1->num_loaders(); i++) {
402 tty->print_cr("[ [%d]: %s", i,
403 p1->loader_data(i)->loader_name());
404 }
405 if (p1->klass() == NULL) {
406 tty->print_cr("[... and setting class object]");
407 }
408 }
409
410 // p1->klass() will hold NULL if klass, p2->klass(), and old
411 // p1->klass() are all NULL. In addition, all three must have
412 // matching non-NULL values, otherwise either the constraints would
413 // have been violated, or the constraints had been corrupted (and an
414 // assertion would fail).
415 if (p2->klass() != NULL) {
416 assert(p2->klass() == klass, "constraints corrupted");
417 }
418 if (p1->klass() == NULL) {
419 p1->set_klass(klass);
420 } else {
421 assert(p1->klass() == klass, "constraints corrupted");
422 }
423
424 *pp2 = p2->next();
425 FREE_C_HEAP_ARRAY(oop, p2->loaders(), mtClass);
426 free_entry(p2);
427 return;
428 }
429
430
431 void LoaderConstraintTable::verify(Dictionary* dictionary,
432 PlaceholderTable* placeholders) {
433 Thread *thread = Thread::current();
434 for (int cindex = 0; cindex < _loader_constraint_size; cindex++) {
435 for (LoaderConstraintEntry* probe = bucket(cindex);
436 probe != NULL;
437 probe = probe->next()) {
438 if (probe->klass() != NULL) {
439 InstanceKlass* ik = InstanceKlass::cast(probe->klass());
440 guarantee(ik->name() == probe->name(), "name should match");
441 Symbol* name = ik->name();
442 ClassLoaderData* loader_data = ik->class_loader_data();
443 unsigned int d_hash = dictionary->compute_hash(name, loader_data);
444 int d_index = dictionary->hash_to_index(d_hash);
445 Klass* k = dictionary->find_class(d_index, d_hash, name, loader_data);
446 if (k != NULL) {
447 // We found the class in the system dictionary, so we should
448 // make sure that the Klass* matches what we already have.
449 guarantee(k == probe->klass(), "klass should be in dictionary");
450 } else {
451 // If we don't find the class in the system dictionary, it
452 // has to be in the placeholders table.
453 unsigned int p_hash = placeholders->compute_hash(name, loader_data);
454 int p_index = placeholders->hash_to_index(p_hash);
455 PlaceholderEntry* entry = placeholders->get_entry(p_index, p_hash,
456 name, loader_data);
457
458 // The InstanceKlass might not be on the entry, so the only
459 // thing we can check here is whether we were successful in
460 // finding the class in the placeholders table.
461 guarantee(entry != NULL, "klass should be in the placeholders");
462 }
463 }
464 for (int n = 0; n< probe->num_loaders(); n++) {
465 assert(ClassLoaderDataGraph::contains_loader_data(probe->loader_data(n)), "The loader is missing");
466 }
467 }
468 }
469 }
470
471 #ifndef PRODUCT
472
473 // Called with the system dictionary lock held
474 void LoaderConstraintTable::print() {
475 ResourceMark rm;
476
477 assert_locked_or_safepoint(SystemDictionary_lock);
478 tty->print_cr("Java loader constraints (entries=%d)", _loader_constraint_size);
479 for (int cindex = 0; cindex < _loader_constraint_size; cindex++) {
480 for (LoaderConstraintEntry* probe = bucket(cindex);
481 probe != NULL;
482 probe = probe->next()) {
483 tty->print("%4d: ", cindex);
484 probe->name()->print();
485 tty->print(" , loaders:");
486 for (int n = 0; n < probe->num_loaders(); n++) {
487 probe->loader_data(n)->print_value();
488 tty->print(", ");
489 }
490 tty->cr();
491 }
492 }
493 }
494 #endif

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