1 /*
2 * Copyright (c) 1997, 2025, 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 "cds/metaspaceShared.hpp"
26 #include "classfile/classLoaderDataGraph.hpp"
27 #include "classfile/javaClasses.hpp"
28 #include "classfile/systemDictionary.hpp"
29 #include "classfile/vmSymbols.hpp"
30 #include "interpreter/linkResolver.hpp"
31 #include "jvm.h"
32 #include "logging/log.hpp"
33 #include "logging/logStream.hpp"
34 #include "memory/resourceArea.hpp"
35 #include "memory/universe.hpp"
36 #include "oops/instanceKlass.inline.hpp"
37 #include "oops/klass.inline.hpp"
38 #include "oops/klassVtable.hpp"
39 #include "oops/method.hpp"
40 #include "oops/objArrayOop.hpp"
41 #include "oops/oop.inline.hpp"
42 #include "runtime/flags/flagSetting.hpp"
43 #include "runtime/java.hpp"
44 #include "runtime/handles.inline.hpp"
45 #include "runtime/safepointVerifiers.hpp"
46 #include "utilities/copy.hpp"
47
48 inline InstanceKlass* klassVtable::ik() const {
49 return InstanceKlass::cast(_klass);
50 }
51
52 bool klassVtable::is_preinitialized_vtable() {
53 return _klass->is_shared() && !MetaspaceShared::remapped_readwrite() && _klass->verified_at_dump_time();
54 }
55
56
57 // this function computes the vtable size (including the size needed for miranda
58 // methods) and the number of miranda methods in this class.
59 // Note on Miranda methods: Let's say there is a class C that implements
60 // interface I, and none of C's superclasses implements I.
61 // Let's say there is an abstract method m in I that neither C
62 // nor any of its super classes implement (i.e there is no method of any access,
63 // with the same name and signature as m), then m is a Miranda method which is
64 // entered as a public abstract method in C's vtable. From then on it should
65 // treated as any other public method in C for method over-ride purposes.
66 void klassVtable::compute_vtable_size_and_num_mirandas(
67 int* vtable_length_ret, int* num_new_mirandas,
68 GrowableArray<Method*>* all_mirandas, const Klass* super,
69 Array<Method*>* methods, AccessFlags class_flags, u2 major_version,
70 Handle classloader, Symbol* classname, Array<InstanceKlass*>* local_interfaces) {
71 NoSafepointVerifier nsv;
72
73 // set up default result values
74 int vtable_length = 0;
75
76 // start off with super's vtable length
77 vtable_length = super == nullptr ? 0 : super->vtable_length();
78
79 // go thru each method in the methods table to see if it needs a new entry
80 int len = methods->length();
81 for (int i = 0; i < len; i++) {
82 Method* method = methods->at(i);
83
84 if (needs_new_vtable_entry(method, super, classloader, classname, class_flags, major_version)) {
85 assert(!method->is_private(), "private methods should not need a vtable entry");
86 vtable_length += vtableEntry::size(); // we need a new entry
87 }
88 }
89
90 GrowableArray<Method*> new_mirandas(20);
91 // compute the number of mirandas methods that must be added to the end
92 get_mirandas(&new_mirandas, all_mirandas, super, methods, nullptr, local_interfaces,
93 class_flags.is_interface());
94 *num_new_mirandas = new_mirandas.length();
95
96 // Interfaces do not need interface methods in their vtables
97 // This includes miranda methods and during later processing, default methods
98 if (!class_flags.is_interface()) {
99 vtable_length += *num_new_mirandas * vtableEntry::size();
100 }
101
102 if (Universe::is_bootstrapping() && vtable_length == 0) {
103 // array classes don't have their superclass set correctly during
104 // bootstrapping
105 vtable_length = Universe::base_vtable_size();
106 }
107
108 if (super == nullptr && vtable_length != Universe::base_vtable_size()) {
109 if (Universe::is_bootstrapping()) {
110 // Someone is attempting to override java.lang.Object incorrectly on the
111 // bootclasspath. The JVM cannot recover from this error including throwing
112 // an exception
113 vm_exit_during_initialization("Incompatible definition of java.lang.Object");
114 } else {
115 // Someone is attempting to redefine java.lang.Object incorrectly. The
116 // only way this should happen is from
117 // SystemDictionary::resolve_from_stream(), which will detect this later
118 // and throw a security exception. So don't assert here to let
119 // the exception occur.
120 vtable_length = Universe::base_vtable_size();
121 }
122 }
123 assert(vtable_length % vtableEntry::size() == 0, "bad vtable length");
124 assert(vtable_length >= Universe::base_vtable_size(), "vtable too small");
125
126 *vtable_length_ret = vtable_length;
127 }
128
129 // Copy super class's vtable to the first part (prefix) of this class's vtable,
130 // and return the number of entries copied. Expects that 'super' is the Java
131 // super class (arrays can have "array" super classes that must be skipped).
132 int klassVtable::initialize_from_super(Klass* super) {
133 if (super == nullptr) {
134 return 0;
135 } else if (is_preinitialized_vtable()) {
136 // A shared class' vtable is preinitialized at dump time. No need to copy
137 // methods from super class for shared class, as that was already done
138 // during archiving time. However, if Jvmti has redefined a class,
139 // copy super class's vtable in case the super class has changed.
140 return super->vtable().length();
141 } else {
142 // copy methods from superKlass
143 klassVtable superVtable = super->vtable();
144 assert(superVtable.length() <= _length, "vtable too short");
145 #ifdef ASSERT
146 superVtable.verify(tty, true);
147 #endif
148 superVtable.copy_vtable_to(table());
149 if (log_develop_is_enabled(Trace, vtables)) {
150 ResourceMark rm;
151 log_develop_trace(vtables)("copy vtable from %s to %s size %d",
152 super->internal_name(), klass()->internal_name(),
153 _length);
154 }
155 return superVtable.length();
156 }
157 }
158
159 //
160 // Revised lookup semantics introduced 1.3 (Kestrel beta)
161 void klassVtable::initialize_vtable(GrowableArray<InstanceKlass*>* supers) {
162
163 // Note: Arrays can have intermediate array supers. Use java_super to skip them.
164 InstanceKlass* super = _klass->java_super();
165
166 bool is_shared = _klass->is_shared();
167 Thread* current = Thread::current();
168
169 if (!_klass->is_array_klass()) {
170 ResourceMark rm(current);
171 log_develop_debug(vtables)("Initializing: %s", _klass->name()->as_C_string());
172 }
173
174 #ifdef ASSERT
175 oop* end_of_obj = (oop*)_klass + _klass->size();
176 oop* end_of_vtable = (oop*)&table()[_length];
177 assert(end_of_vtable <= end_of_obj, "vtable extends beyond end");
178 #endif
179
180 if (Universe::is_bootstrapping()) {
181 assert(!is_shared, "sanity");
182 // just clear everything
183 for (int i = 0; i < _length; i++) table()[i].clear();
184 return;
185 }
186
187 int super_vtable_len = initialize_from_super(super);
188 if (_klass->is_array_klass()) {
189 assert(super_vtable_len == _length, "arrays shouldn't introduce new methods");
190 } else {
191 assert(_klass->is_instance_klass(), "must be InstanceKlass");
192
193 Array<Method*>* methods = ik()->methods();
194 int len = methods->length();
195 int initialized = super_vtable_len;
196
197 // Check each of this class's methods against super;
198 // if override, replace in copy of super vtable, otherwise append to end
199 for (int i = 0; i < len; i++) {
200 // update_inherited_vtable can stop for gc - ensure using handles
201 methodHandle mh(current, methods->at(i));
202
203 bool needs_new_entry = update_inherited_vtable(current, mh, super_vtable_len, -1, supers);
204
205 if (needs_new_entry) {
206 put_method_at(mh(), initialized);
207 mh->set_vtable_index(initialized); // set primary vtable index
208 initialized++;
209 }
210 }
211
212 // update vtable with default_methods
213 Array<Method*>* default_methods = ik()->default_methods();
214 if (default_methods != nullptr) {
215 len = default_methods->length();
216 if (len > 0) {
217 Array<int>* def_vtable_indices = ik()->default_vtable_indices();
218 assert(def_vtable_indices != nullptr, "should be created");
219 assert(def_vtable_indices->length() == len, "reinit vtable len?");
220 for (int i = 0; i < len; i++) {
221 bool needs_new_entry;
222 {
223 // Reduce the scope of this handle so that it is fetched again.
224 // The methodHandle keeps it from being deleted by RedefineClasses while
225 // we're using it.
226 methodHandle mh(current, default_methods->at(i));
227 assert(!mh->is_private(), "private interface method in the default method list");
228 needs_new_entry = update_inherited_vtable(current, mh, super_vtable_len, i, supers);
229 }
230
231 // needs new entry
232 if (needs_new_entry) {
233 // Refetch this default method in case of redefinition that might
234 // happen during constraint checking in the update_inherited_vtable call above.
235 Method* method = default_methods->at(i);
236 put_method_at(method, initialized);
237 if (is_preinitialized_vtable()) {
238 // At runtime initialize_vtable is rerun for a shared class
239 // (loaded by the non-boot loader) as part of link_class_impl().
240 // The dumptime vtable index should be the same as the runtime index.
241 assert(def_vtable_indices->at(i) == initialized,
242 "dump time vtable index is different from runtime index");
243 } else {
244 def_vtable_indices->at_put(i, initialized); //set vtable index
245 }
246 initialized++;
247 }
248 }
249 }
250 }
251
252 // add miranda methods; it will also return the updated initialized
253 // Interfaces do not need interface methods in their vtables
254 // This includes miranda methods and during later processing, default methods
255 if (!ik()->is_interface()) {
256 initialized = fill_in_mirandas(current, initialized);
257 }
258
259 // In class hierarchies where the accessibility is not increasing (i.e., going from private ->
260 // package_private -> public/protected), the vtable might actually be smaller than our initial
261 // calculation, for classfile versions for which we do not do transitive override
262 // calculations.
263 if (ik()->major_version() >= VTABLE_TRANSITIVE_OVERRIDE_VERSION) {
264 assert(initialized == _length, "vtable initialization failed");
265 } else {
266 assert(initialized <= _length, "vtable initialization failed");
267 for(;initialized < _length; initialized++) {
268 table()[initialized].clear();
269 }
270 }
271 NOT_PRODUCT(verify(tty, true));
272 }
273 }
274
275 // Returns true iff super_method can be overridden by a method in targetclassname
276 // See JLS 8.4.8.1
277 // Assumes name-signature match
278 // Note that the InstanceKlass of the method in the targetclassname has not always been created yet
279 static bool can_be_overridden(Method* super_method, Handle targetclassloader, Symbol* targetclassname) {
280 // Private methods can not be overridden
281 assert(!super_method->is_private(), "shouldn't call with a private method");
282
283 // If super method is accessible, then override
284 if ((super_method->is_protected()) ||
285 (super_method->is_public())) {
286 return true;
287 }
288 // Package-private methods are not inherited outside of package
289 assert(super_method->is_package_private(), "must be package private");
290 return(super_method->method_holder()->is_same_class_package(targetclassloader(), targetclassname));
291 }
292
293
294 // Called for cases where a method does not override its superclass' vtable entry
295 // For bytecodes not produced by javac together it is possible that a method does not override
296 // the superclass's method, but might indirectly override a super-super class's vtable entry
297 // If none found, return a null superk, else return the superk of the method this does override
298 // For public and protected methods: if they override a superclass, they will
299 // also be overridden themselves appropriately.
300 // Private methods do not override, and are not overridden and are not in the vtable.
301 // Package Private methods are trickier:
302 // e.g. P1.A, pub m
303 // P2.B extends A, package private m
304 // P1.C extends B, public m
305 // P1.C.m needs to override P1.A.m and can not override P2.B.m
306 // Therefore: all package private methods need their own vtable entries for
307 // them to be the root of an inheritance overriding decision
308 // Package private methods may also override other vtable entries
309 InstanceKlass* klassVtable::find_transitive_override(InstanceKlass* initialsuper,
310 const methodHandle& target_method,
311 int vtable_index,
312 Handle target_loader,
313 Symbol* target_classname) {
314
315 InstanceKlass* superk = initialsuper;
316 while (superk != nullptr && superk->super() != nullptr) {
317 klassVtable ssVtable = (superk->super())->vtable();
318 if (vtable_index < ssVtable.length()) {
319 Method* super_method = ssVtable.method_at(vtable_index);
320 #ifndef PRODUCT
321 Symbol* name= target_method()->name();
322 Symbol* signature = target_method()->signature();
323 assert(super_method->name() == name && super_method->signature() == signature, "vtable entry name/sig mismatch");
324 #endif
325
326 if (can_be_overridden(super_method, target_loader, target_classname)) {
327 if (log_develop_is_enabled(Trace, vtables)) {
328 ResourceMark rm;
329 LogTarget(Trace, vtables) lt;
330 LogStream ls(lt);
331 char* sig = target_method()->name_and_sig_as_C_string();
332 ls.print("transitive overriding superclass %s with %s index %d, original flags: ",
333 super_method->method_holder()->internal_name(),
334 sig, vtable_index);
335 super_method->print_linkage_flags(&ls);
336 ls.print("overriders flags: ");
337 target_method->print_linkage_flags(&ls);
338 ls.cr();
339 }
340
341 break; // return found superk
342 }
343 } else {
344 // super class has no vtable entry here, stop transitive search
345 superk = (InstanceKlass*)nullptr;
346 break;
347 }
348 // if no override found yet, continue to search up
349 superk = superk->super() == nullptr ? nullptr : InstanceKlass::cast(superk->super());
350 }
351
352 return superk;
353 }
354
355 static void log_vtables(int i, bool overrides, const methodHandle& target_method,
356 Klass* target_klass, Method* super_method) {
357 #ifndef PRODUCT
358 if (log_develop_is_enabled(Trace, vtables)) {
359 ResourceMark rm;
360 LogTarget(Trace, vtables) lt;
361 LogStream ls(lt);
362 char* sig = target_method()->name_and_sig_as_C_string();
363 if (overrides) {
364 ls.print("overriding with %s index %d, original flags: ",
365 sig, i);
366 } else {
367 ls.print("NOT overriding with %s index %d, original flags: ",
368 sig, i);
369 }
370 super_method->print_linkage_flags(&ls);
371 ls.print("overriders flags: ");
372 target_method->print_linkage_flags(&ls);
373 ls.cr();
374 }
375 #endif
376 }
377
378 // Update child's copy of super vtable for overrides
379 // OR return true if a new vtable entry is required.
380 // Only called for InstanceKlass's, i.e. not for arrays
381 // If that changed, could not use _klass as handle for klass
382 bool klassVtable::update_inherited_vtable(Thread* current,
383 const methodHandle& target_method,
384 int super_vtable_len, int default_index,
385 GrowableArray<InstanceKlass*>* supers) {
386 bool allocate_new = true;
387
388 InstanceKlass* klass = ik();
389
390 Array<int>* def_vtable_indices = nullptr;
391 bool is_default = false;
392
393 // default methods are non-private concrete methods in superinterfaces which are added
394 // to the vtable with their real method_holder.
395 // Since vtable and itable indices share the same storage, don't touch
396 // the default method's real vtable/itable index.
397 // default_vtable_indices stores the vtable value relative to this inheritor
398 if (default_index >= 0 ) {
399 is_default = true;
400 def_vtable_indices = klass->default_vtable_indices();
401 assert(!target_method->is_private(), "private interface method flagged as default");
402 assert(def_vtable_indices != nullptr, "def vtable alloc?");
403 assert(default_index <= def_vtable_indices->length(), "def vtable len?");
404 } else {
405 assert(klass == target_method->method_holder(), "caller resp.");
406 // Initialize the method's vtable index to "nonvirtual".
407 // If we allocate a vtable entry, we will update it to a non-negative number.
408 target_method->set_vtable_index(Method::nonvirtual_vtable_index);
409 }
410
411 // Private, static and <init> methods are never in
412 if (target_method->is_private() || target_method->is_static() ||
413 (target_method->name()->fast_compare(vmSymbols::object_initializer_name()) == 0)) {
414 return false;
415 }
416
417 if (target_method->is_final_method(klass->access_flags())) {
418 // a final method never needs a new entry; final methods can be statically
419 // resolved and they have to be present in the vtable only if they override
420 // a super's method, in which case they re-use its entry
421 allocate_new = false;
422 } else if (klass->is_interface()) {
423 allocate_new = false; // see note below in needs_new_vtable_entry
424 // An interface never allocates new vtable slots, only inherits old ones.
425 // This method will either be assigned its own itable index later,
426 // or be assigned an inherited vtable index in the loop below.
427 // default methods inherited by classes store their vtable indices
428 // in the inheritor's default_vtable_indices.
429 // default methods inherited by interfaces may already have a
430 // valid itable index, if so, don't change it.
431 // Overpass methods in an interface will be assigned an itable index later
432 // by an inheriting class.
433 if ((!is_default || !target_method->has_itable_index())) {
434 target_method->set_vtable_index(Method::pending_itable_index);
435 }
436 }
437
438 // we need a new entry if there is no superclass
439 Klass* super = klass->super();
440 if (super == nullptr) {
441 return allocate_new;
442 }
443
444 // search through the vtable and update overridden entries
445 // Since check_signature_loaders acquires SystemDictionary_lock
446 // which can block for gc, once we are in this loop, use handles
447 // For classfiles built with >= jdk7, we now look for transitive overrides
448
449 Symbol* name = target_method->name();
450 Symbol* signature = target_method->signature();
451
452 Klass* target_klass = target_method->method_holder();
453 assert(target_klass != nullptr, "impossible");
454 if (target_klass == nullptr) {
455 target_klass = _klass;
456 }
457
458 HandleMark hm(current);
459 Handle target_loader(current, target_klass->class_loader());
460
461 Symbol* target_classname = target_klass->name();
462 for(int i = 0; i < super_vtable_len; i++) {
463 Method* super_method;
464 if (is_preinitialized_vtable()) {
465 // If this is a shared class, the vtable is already in the final state (fully
466 // initialized). Need to look at the super's vtable.
467 klassVtable superVtable = super->vtable();
468 super_method = superVtable.method_at(i);
469 } else {
470 super_method = method_at(i);
471 }
472 // Check if method name matches. Ignore match if klass is an interface and the
473 // matching method is a non-public java.lang.Object method. (See JVMS 5.4.3.4)
474 // This is safe because the method at this slot should never get invoked.
475 // (TBD: put in a method to throw NoSuchMethodError if this slot is ever used.)
476 if (super_method->name() == name && super_method->signature() == signature &&
477 (!klass->is_interface() ||
478 !SystemDictionary::is_nonpublic_Object_method(super_method))) {
479
480 // get super_klass for method_holder for the found method
481 InstanceKlass* super_klass = super_method->method_holder();
482
483 // Whether the method is being overridden
484 bool overrides = false;
485
486 // private methods are also never overridden
487 if (!super_method->is_private() &&
488 (is_default ||
489 can_be_overridden(super_method, target_loader, target_classname) ||
490 (klass->major_version() >= VTABLE_TRANSITIVE_OVERRIDE_VERSION &&
491 (super_klass = find_transitive_override(super_klass,
492 target_method, i, target_loader,
493 target_classname)) != nullptr))) {
494
495 // Package private methods always need a new entry to root their own
496 // overriding. They may also override other methods.
497 if (!target_method->is_package_private()) {
498 allocate_new = false;
499 }
500
501 // Set the vtable index before the constraint check safepoint, which potentially
502 // redefines this method if this method is a default method belonging to a
503 // super class or interface.
504 put_method_at(target_method(), i);
505 // Save super for constraint checking.
506 if (supers != nullptr) {
507 supers->at_put(i, super_klass);
508 }
509
510 overrides = true;
511 if (!is_default) {
512 target_method->set_vtable_index(i);
513 } else {
514 if (def_vtable_indices != nullptr) {
515 if (is_preinitialized_vtable()) {
516 // At runtime initialize_vtable is rerun as part of link_class_impl()
517 // for a shared class loaded by the non-boot loader.
518 // The dumptime vtable index should be the same as the runtime index.
519 assert(def_vtable_indices->at(default_index) == i,
520 "dump time vtable index is different from runtime index");
521 } else {
522 def_vtable_indices->at_put(default_index, i);
523 }
524 }
525 assert(super_method->is_default_method() || super_method->is_overpass()
526 || super_method->is_abstract(), "default override error");
527 }
528 } else {
529 overrides = false;
530 }
531 log_vtables(i, overrides, target_method, target_klass, super_method);
532 }
533 }
534 return allocate_new;
535 }
536
537 void klassVtable::put_method_at(Method* m, int index) {
538 assert(!m->is_private(), "private methods should not be in vtable");
539 JVMTI_ONLY(assert(!m->is_old() || ik()->is_being_redefined(), "old methods should not be in vtable"));
540 if (is_preinitialized_vtable()) {
541 // At runtime initialize_vtable is rerun as part of link_class_impl()
542 // for shared class loaded by the non-boot loader to obtain the loader
543 // constraints based on the runtime classloaders' context. The dumptime
544 // method at the vtable index should be the same as the runtime method.
545 assert(table()[index].method() == m,
546 "archived method is different from the runtime method");
547 } else {
548 if (log_develop_is_enabled(Trace, vtables)) {
549 ResourceMark rm;
550 LogTarget(Trace, vtables) lt;
551 LogStream ls(lt);
552 const char* sig = (m != nullptr) ? m->name_and_sig_as_C_string() : "<null>";
553 ls.print("adding %s at index %d, flags: ", sig, index);
554 if (m != nullptr) {
555 m->print_linkage_flags(&ls);
556 }
557 ls.cr();
558 }
559 table()[index].set(m);
560 }
561 }
562
563 void klassVtable::check_constraints(GrowableArray<InstanceKlass*>* supers, TRAPS) {
564 assert(supers->length() == length(), "lengths are different");
565 // For each method in the vtable, check constraints against any super class
566 // if overridden.
567 for (int i = 0; i < length(); i++) {
568 methodHandle target_method(THREAD, unchecked_method_at(i));
569 InstanceKlass* super_klass = supers->at(i);
570 if (target_method() != nullptr && super_klass != nullptr) {
571 // Do not check loader constraints for overpass methods because overpass
572 // methods are created by the jvm to throw exceptions.
573 if (!target_method->is_overpass()) {
574 HandleMark hm(THREAD);
575 // Override vtable entry if passes loader constraint check
576 // if loader constraint checking requested
577 // No need to visit his super, since he and his super
578 // have already made any needed loader constraints.
579 // Since loader constraints are transitive, it is enough
580 // to link to the first super, and we get all the others.
581 Handle super_loader(THREAD, super_klass->class_loader());
582 InstanceKlass* target_klass = target_method->method_holder();
583 Handle target_loader(THREAD, target_klass->class_loader());
584
585 if (target_loader() != super_loader()) {
586 ResourceMark rm(THREAD);
587 Symbol* failed_type_symbol =
588 SystemDictionary::check_signature_loaders(target_method->signature(),
589 _klass,
590 target_loader, super_loader,
591 true);
592 if (failed_type_symbol != nullptr) {
593 stringStream ss;
594 ss.print("loader constraint violation for class %s: when selecting "
595 "overriding method '", _klass->external_name());
596 target_method->print_external_name(&ss),
597 ss.print("' the class loader %s of the "
598 "selected method's type %s, and the class loader %s for its super "
599 "type %s have different Class objects for the type %s used in the signature (%s; %s)",
600 target_klass->class_loader_data()->loader_name_and_id(),
601 target_klass->external_name(),
602 super_klass->class_loader_data()->loader_name_and_id(),
603 super_klass->external_name(),
604 failed_type_symbol->as_klass_external_name(),
605 target_klass->class_in_module_of_loader(false, true),
606 super_klass->class_in_module_of_loader(false, true));
607 THROW_MSG(vmSymbols::java_lang_LinkageError(), ss.as_string());
608 }
609 }
610 }
611 }
612 }
613 }
614
615 void klassVtable::initialize_vtable_and_check_constraints(TRAPS) {
616 // Save a superclass from each vtable entry to do constraint checking
617 ResourceMark rm(THREAD);
618 GrowableArray<InstanceKlass*>* supers = new GrowableArray<InstanceKlass*>(_length, _length, nullptr);
619 initialize_vtable(supers);
620 check_constraints(supers, CHECK);
621 }
622
623
624 // Find out if a method "m" with superclass "super", loader "classloader" and
625 // name "classname" needs a new vtable entry. Let P be a class package defined
626 // by "classloader" and "classname".
627 // NOTE: The logic used here is very similar to the one used for computing
628 // the vtables indices for a method. We cannot directly use that function because,
629 // we allocate the InstanceKlass at load time, and that requires that the
630 // superclass has been loaded.
631 // However, the vtable entries are filled in at link time, and therefore
632 // the superclass' vtable may not yet have been filled in.
633 bool klassVtable::needs_new_vtable_entry(Method* target_method,
634 const Klass* super,
635 Handle classloader,
636 Symbol* classname,
637 AccessFlags class_flags,
638 u2 major_version) {
639 if (class_flags.is_interface()) {
640 // Interfaces do not use vtables, except for java.lang.Object methods,
641 // so there is no point to assigning
642 // a vtable index to any of their local methods. If we refrain from doing this,
643 // we can use Method::_vtable_index to hold the itable index
644 return false;
645 }
646
647 if (target_method->is_final_method(class_flags) ||
648 // a final method never needs a new entry; final methods can be statically
649 // resolved and they have to be present in the vtable only if they override
650 // a super's method, in which case they re-use its entry
651 (target_method->is_private()) ||
652 // private methods don't need to be in vtable
653 (target_method->is_static()) ||
654 // static methods don't need to be in vtable
655 (target_method->name()->fast_compare(vmSymbols::object_initializer_name()) == 0)
656 // <init> is never called dynamically-bound
657 ) {
658 return false;
659 }
660
661 // Concrete interface methods do not need new entries, they override
662 // abstract method entries using default inheritance rules
663 if (target_method->method_holder() != nullptr &&
664 target_method->method_holder()->is_interface() &&
665 !target_method->is_abstract()) {
666 assert(target_method->is_default_method(),
667 "unexpected interface method type");
668 return false;
669 }
670
671 // we need a new entry if there is no superclass
672 if (super == nullptr) {
673 return true;
674 }
675
676 // Package private methods always need a new entry to root their own
677 // overriding. This allows transitive overriding to work.
678 if (target_method->is_package_private()) {
679 return true;
680 }
681
682 // search through the super class hierarchy to see if we need
683 // a new entry
684 Symbol* name = target_method->name();
685 Symbol* signature = target_method->signature();
686 const Klass* k = super;
687 Method* super_method = nullptr;
688 InstanceKlass *holder = nullptr;
689 Method* recheck_method = nullptr;
690 bool found_pkg_prvt_method = false;
691 while (k != nullptr) {
692 // lookup through the hierarchy for a method with matching name and sign.
693 super_method = InstanceKlass::cast(k)->lookup_method(name, signature);
694 if (super_method == nullptr) {
695 break; // we still have to search for a matching miranda method
696 }
697 // get the class holding the matching method
698 InstanceKlass* superk = super_method->method_holder();
699 // we want only instance method matches
700 // ignore private methods found via lookup_method since they do not participate in overriding,
701 // and since we do override around them: e.g. a.m pub/b.m private/c.m pub,
702 // ignore private, c.m pub does override a.m pub
703 // For classes that were not javac'd together, we also do transitive overriding around
704 // methods that have less accessibility
705 if (!super_method->is_static() &&
706 !super_method->is_private()) {
707 if (can_be_overridden(super_method, classloader, classname)) {
708 return false;
709 // else keep looking for transitive overrides
710 }
711 // If we get here then one of the super classes has a package private method
712 // that will not get overridden because it is in a different package. But,
713 // that package private method does "override" any matching methods in super
714 // interfaces, so there will be no miranda vtable entry created. So, set flag
715 // to TRUE for use below, in case there are no methods in super classes that
716 // this target method overrides.
717 assert(super_method->is_package_private(), "super_method must be package private");
718 assert(!superk->is_same_class_package(classloader(), classname),
719 "Must be different packages");
720 found_pkg_prvt_method = true;
721 }
722
723 // Start with lookup result and continue to search up, for versions supporting transitive override
724 if (major_version >= VTABLE_TRANSITIVE_OVERRIDE_VERSION) {
725 k = superk->super(); // haven't found an override match yet; continue to look
726 } else {
727 break;
728 }
729 }
730
731 // If found_pkg_prvt_method is set, then the ONLY matching method in the
732 // superclasses is package private in another package. That matching method will
733 // prevent a miranda vtable entry from being created. Because the target method can not
734 // override the package private method in another package, then it needs to be the root
735 // for its own vtable entry.
736 if (found_pkg_prvt_method) {
737 return true;
738 }
739
740 // if the target method is public or protected it may have a matching
741 // miranda method in the super, whose entry it should re-use.
742 // Actually, to handle cases that javac would not generate, we need
743 // this check for all access permissions.
744 const InstanceKlass *sk = InstanceKlass::cast(super);
745 if (sk->has_miranda_methods()) {
746 if (sk->lookup_method_in_all_interfaces(name, signature, Klass::DefaultsLookupMode::find) != nullptr) {
747 return false; // found a matching miranda; we do not need a new entry
748 }
749 }
750 return true; // found no match; we need a new entry
751 }
752
753 // Support for miranda methods
754
755 // get the vtable index of a miranda method with matching "name" and "signature"
756 int klassVtable::index_of_miranda(Symbol* name, Symbol* signature) {
757 // search from the bottom, might be faster
758 for (int i = (length() - 1); i >= 0; i--) {
759 Method* m = table()[i].method();
760 if (is_miranda_entry_at(i) &&
761 m->name() == name && m->signature() == signature) {
762 return i;
763 }
764 }
765 return Method::invalid_vtable_index;
766 }
767
768 // check if an entry at an index is miranda
769 // requires that method m at entry be declared ("held") by an interface.
770 bool klassVtable::is_miranda_entry_at(int i) {
771 Method* m = method_at(i);
772 InstanceKlass* holder = m->method_holder();
773
774 // miranda methods are public abstract instance interface methods in a class's vtable
775 if (holder->is_interface()) {
776 assert(m->is_public(), "should be public");
777 assert(ik()->implements_interface(holder) , "this class should implement the interface");
778 if (is_miranda(m, ik()->methods(), ik()->default_methods(), ik()->super(), klass()->is_interface())) {
779 return true;
780 }
781 }
782 return false;
783 }
784
785 // Check if a method is a miranda method, given a class's methods array,
786 // its default_method table and its super class.
787 // "Miranda" means an abstract non-private method that would not be
788 // overridden for the local class.
789 // A "miranda" method should only include non-private interface
790 // instance methods, i.e. not private methods, not static methods,
791 // not default methods (concrete interface methods), not overpass methods.
792 // If a given class already has a local (including overpass) method, a
793 // default method, or any of its superclasses has the same which would have
794 // overridden an abstract method, then this is not a miranda method.
795 //
796 // Miranda methods are checked multiple times.
797 // Pass 1: during class load/class file parsing: before vtable size calculation:
798 // include superinterface abstract and default methods (non-private instance).
799 // We include potential default methods to give them space in the vtable.
800 // During the first run, the current instanceKlass has not yet been
801 // created, the superclasses and superinterfaces do have instanceKlasses
802 // but may not have vtables, the default_methods list is empty, no overpasses.
803 // Default method generation uses the all_mirandas array as the starter set for
804 // maximally-specific default method calculation. So, for both classes and
805 // interfaces, it is necessary that the first pass will find all non-private
806 // interface instance methods, whether or not they are concrete.
807 //
808 // Pass 2: recalculated during vtable initialization: only include abstract methods.
809 // The goal of pass 2 is to walk through the superinterfaces to see if any of
810 // the superinterface methods (which were all abstract pre-default methods)
811 // need to be added to the vtable.
812 // With the addition of default methods, we have three new challenges:
813 // overpasses, static interface methods and private interface methods.
814 // Static and private interface methods do not get added to the vtable and
815 // are not seen by the method resolution process, so we skip those.
816 // Overpass methods are already in the vtable, so vtable lookup will
817 // find them and we don't need to add a miranda method to the end of
818 // the vtable. So we look for overpass methods and if they are found we
819 // return false. Note that we inherit our superclasses vtable, so
820 // the superclass' search also needs to use find_overpass so that if
821 // one is found we return false.
822 // False means - we don't need a miranda method added to the vtable.
823 //
824 // During the second run, default_methods is set up, so concrete methods from
825 // superinterfaces with matching names/signatures to default_methods are already
826 // in the default_methods list and do not need to be appended to the vtable
827 // as mirandas. Abstract methods may already have been handled via
828 // overpasses - either local or superclass overpasses, which may be
829 // in the vtable already.
830 //
831 // Pass 3: They are also checked by link resolution and selection,
832 // for invocation on a method (not interface method) reference that
833 // resolves to a method with an interface as its method_holder.
834 // Used as part of walking from the bottom of the vtable to find
835 // the vtable index for the miranda method.
836 //
837 // Part of the Miranda Rights in the US mean that if you do not have
838 // an attorney one will be appointed for you.
839 bool klassVtable::is_miranda(Method* m, Array<Method*>* class_methods,
840 Array<Method*>* default_methods, const Klass* super,
841 bool is_interface) {
842 if (m->is_static() || m->is_private() || m->is_overpass()) {
843 return false;
844 }
845 Symbol* name = m->name();
846 Symbol* signature = m->signature();
847
848 // First look in local methods to see if already covered
849 if (InstanceKlass::find_local_method(class_methods, name, signature,
850 Klass::OverpassLookupMode::find,
851 Klass::StaticLookupMode::skip,
852 Klass::PrivateLookupMode::skip) != nullptr)
853 {
854 return false;
855 }
856
857 // Check local default methods
858 if ((default_methods != nullptr) &&
859 (InstanceKlass::find_method(default_methods, name, signature) != nullptr))
860 {
861 return false;
862 }
863
864 // Iterate on all superclasses, which should be InstanceKlasses.
865 // Note that we explicitly look for overpasses at each level.
866 // Overpasses may or may not exist for supers for pass 1,
867 // they should have been created for pass 2 and later.
868
869 for (const Klass* cursuper = super; cursuper != nullptr; cursuper = cursuper->super())
870 {
871 Method* found_mth = InstanceKlass::cast(cursuper)->find_local_method(name, signature,
872 Klass::OverpassLookupMode::find,
873 Klass::StaticLookupMode::skip,
874 Klass::PrivateLookupMode::skip);
875 // Ignore non-public methods in java.lang.Object if klass is an interface.
876 if (found_mth != nullptr && (!is_interface ||
877 !SystemDictionary::is_nonpublic_Object_method(found_mth))) {
878 return false;
879 }
880 }
881
882 return true;
883 }
884
885 // Scans current_interface_methods for miranda methods that do not
886 // already appear in new_mirandas, or default methods, and are also not defined-and-non-private
887 // in super (superclass). These mirandas are added to all_mirandas if it is
888 // not null; in addition, those that are not duplicates of miranda methods
889 // inherited by super from its interfaces are added to new_mirandas.
890 // Thus, new_mirandas will be the set of mirandas that this class introduces,
891 // all_mirandas will be the set of all mirandas applicable to this class
892 // including all defined in superclasses.
893 void klassVtable::add_new_mirandas_to_lists(
894 GrowableArray<Method*>* new_mirandas, GrowableArray<Method*>* all_mirandas,
895 Array<Method*>* current_interface_methods, Array<Method*>* class_methods,
896 Array<Method*>* default_methods, const Klass* super, bool is_interface) {
897
898 // iterate thru the current interface's method to see if it a miranda
899 int num_methods = current_interface_methods->length();
900 for (int i = 0; i < num_methods; i++) {
901 Method* im = current_interface_methods->at(i);
902 bool is_duplicate = false;
903 int num_of_current_mirandas = new_mirandas->length();
904 // check for duplicate mirandas in different interfaces we implement
905 for (int j = 0; j < num_of_current_mirandas; j++) {
906 Method* miranda = new_mirandas->at(j);
907 if ((im->name() == miranda->name()) &&
908 (im->signature() == miranda->signature())) {
909 is_duplicate = true;
910 break;
911 }
912 }
913
914 if (!is_duplicate) { // we don't want duplicate miranda entries in the vtable
915 if (is_miranda(im, class_methods, default_methods, super, is_interface)) { // is it a miranda at all?
916 const InstanceKlass *sk = InstanceKlass::cast(super);
917 // check if it is a duplicate of a super's miranda
918 if (sk->lookup_method_in_all_interfaces(im->name(), im->signature(), Klass::DefaultsLookupMode::find) == nullptr) {
919 new_mirandas->append(im);
920 }
921 if (all_mirandas != nullptr) {
922 all_mirandas->append(im);
923 }
924 }
925 }
926 }
927 }
928
929 void klassVtable::get_mirandas(GrowableArray<Method*>* new_mirandas,
930 GrowableArray<Method*>* all_mirandas,
931 const Klass* super,
932 Array<Method*>* class_methods,
933 Array<Method*>* default_methods,
934 Array<InstanceKlass*>* local_interfaces,
935 bool is_interface) {
936 assert((new_mirandas->length() == 0) , "current mirandas must be 0");
937
938 // iterate thru the local interfaces looking for a miranda
939 int num_local_ifs = local_interfaces->length();
940 for (int i = 0; i < num_local_ifs; i++) {
941 InstanceKlass *ik = local_interfaces->at(i);
942 add_new_mirandas_to_lists(new_mirandas, all_mirandas,
943 ik->methods(), class_methods,
944 default_methods, super, is_interface);
945 // iterate thru each local's super interfaces
946 Array<InstanceKlass*>* super_ifs = ik->transitive_interfaces();
947 int num_super_ifs = super_ifs->length();
948 for (int j = 0; j < num_super_ifs; j++) {
949 InstanceKlass *sik = super_ifs->at(j);
950 add_new_mirandas_to_lists(new_mirandas, all_mirandas,
951 sik->methods(), class_methods,
952 default_methods, super, is_interface);
953 }
954 }
955 }
956
957 // Discover miranda methods ("miranda" = "interface abstract, no binding"),
958 // and append them into the vtable starting at index initialized,
959 // return the new value of initialized.
960 // Miranda methods use vtable entries, but do not get assigned a vtable_index
961 // The vtable_index is discovered by searching from the end of the vtable
962 int klassVtable::fill_in_mirandas(Thread* current, int initialized) {
963 ResourceMark rm(current);
964 GrowableArray<Method*> mirandas(20);
965 get_mirandas(&mirandas, nullptr, ik()->super(), ik()->methods(),
966 ik()->default_methods(), ik()->local_interfaces(),
967 klass()->is_interface());
968 for (int i = 0; i < mirandas.length(); i++) {
969 if (log_develop_is_enabled(Trace, vtables)) {
970 Method* meth = mirandas.at(i);
971 LogTarget(Trace, vtables) lt;
972 LogStream ls(lt);
973 if (meth != nullptr) {
974 char* sig = meth->name_and_sig_as_C_string();
975 ls.print("fill in mirandas with %s index %d, flags: ",
976 sig, initialized);
977 meth->print_linkage_flags(&ls);
978 ls.cr();
979 }
980 }
981 put_method_at(mirandas.at(i), initialized);
982 ++initialized;
983 }
984 return initialized;
985 }
986
987 // Copy this class's vtable to the vtable beginning at start.
988 // Used to copy superclass vtable to prefix of subclass's vtable.
989 void klassVtable::copy_vtable_to(vtableEntry* start) {
990 Copy::disjoint_words((HeapWord*)table(), (HeapWord*)start, _length * vtableEntry::size());
991 }
992
993 #if INCLUDE_JVMTI
994 bool klassVtable::adjust_default_method(int vtable_index, Method* old_method, Method* new_method) {
995 // If old_method is default, find this vtable index in default_vtable_indices
996 // and replace that method in the _default_methods list
997 bool updated = false;
998
999 Array<Method*>* default_methods = ik()->default_methods();
1000 if (default_methods != nullptr) {
1001 int len = default_methods->length();
1002 for (int idx = 0; idx < len; idx++) {
1003 if (vtable_index == ik()->default_vtable_indices()->at(idx)) {
1004 if (default_methods->at(idx) == old_method) {
1005 default_methods->at_put(idx, new_method);
1006 updated = true;
1007 }
1008 break;
1009 }
1010 }
1011 }
1012 return updated;
1013 }
1014
1015 // search the vtable for uses of either obsolete or EMCP methods
1016 void klassVtable::adjust_method_entries(bool * trace_name_printed) {
1017 int prn_enabled = 0;
1018 ResourceMark rm;
1019
1020 for (int index = 0; index < length(); index++) {
1021 Method* old_method = unchecked_method_at(index);
1022 if (old_method == nullptr || !old_method->is_old()) {
1023 continue; // skip uninteresting entries
1024 }
1025 assert(!old_method->is_deleted(), "vtable methods may not be deleted");
1026
1027 Method* new_method = old_method->get_new_method();
1028 put_method_at(new_method, index);
1029
1030 // For default methods, need to update the _default_methods array
1031 // which can only have one method entry for a given signature
1032 bool updated_default = false;
1033 if (old_method->is_default_method()) {
1034 updated_default = adjust_default_method(index, old_method, new_method);
1035 }
1036
1037 if (!(*trace_name_printed)) {
1038 log_info(redefine, class, update)
1039 ("adjust: klassname=%s for methods from name=%s",
1040 _klass->external_name(), old_method->method_holder()->external_name());
1041 *trace_name_printed = true;
1042 }
1043 log_trace(redefine, class, update, vtables)
1044 ("vtable method update: class: %s method: %s, updated default = %s",
1045 _klass->external_name(), new_method->external_name(), updated_default ? "true" : "false");
1046 }
1047 }
1048
1049 // a vtable should never contain old or obsolete methods
1050 bool klassVtable::check_no_old_or_obsolete_entries() {
1051 ResourceMark rm;
1052
1053 for (int i = 0; i < length(); i++) {
1054 Method* m = unchecked_method_at(i);
1055 if (m != nullptr &&
1056 (NOT_PRODUCT(!m->is_valid() ||) m->is_old() || m->is_obsolete())) {
1057 log_trace(redefine, class, update, vtables)
1058 ("vtable check found old method entry: class: %s old: %d obsolete: %d, method: %s",
1059 _klass->external_name(), m->is_old(), m->is_obsolete(), m->external_name());
1060 return false;
1061 }
1062 }
1063 return true;
1064 }
1065
1066 void klassVtable::dump_vtable() {
1067 tty->print_cr("vtable dump --");
1068 for (int i = 0; i < length(); i++) {
1069 Method* m = unchecked_method_at(i);
1070 if (m != nullptr) {
1071 tty->print(" (%5d) ", i);
1072 m->access_flags().print_on(tty);
1073 if (m->is_default_method()) {
1074 tty->print("default ");
1075 }
1076 if (m->is_overpass()) {
1077 tty->print("overpass");
1078 }
1079 tty->print(" -- ");
1080 m->print_name(tty);
1081 tty->cr();
1082 }
1083 }
1084 }
1085 #endif // INCLUDE_JVMTI
1086
1087 //-----------------------------------------------------------------------------------------
1088 // Itable code
1089
1090 // Initialize a itableMethodEntry
1091 void itableMethodEntry::initialize(InstanceKlass* klass, Method* m) {
1092 if (m == nullptr) return;
1093
1094 #ifdef ASSERT
1095 if (MetaspaceShared::is_in_shared_metaspace((void*)&_method) &&
1096 !MetaspaceShared::remapped_readwrite() &&
1097 m->method_holder()->verified_at_dump_time() &&
1098 klass->verified_at_dump_time()) {
1099 // At runtime initialize_itable is rerun as part of link_class_impl()
1100 // for a shared class loaded by the non-boot loader.
1101 // The dumptime itable method entry should be the same as the runtime entry.
1102 // For a shared old class which was not linked during dump time, we can't compare the dumptime
1103 // itable method entry with the runtime entry.
1104 assert(_method == m, "sanity");
1105 }
1106 #endif
1107 _method = m;
1108 }
1109
1110 klassItable::klassItable(InstanceKlass* klass) {
1111 _klass = klass;
1112
1113 if (klass->itable_length() > 0) {
1114 itableOffsetEntry* offset_entry = (itableOffsetEntry*)klass->start_of_itable();
1115 if (offset_entry != nullptr && offset_entry->interface_klass() != nullptr) { // Check that itable is initialized
1116 // First offset entry points to the first method_entry
1117 intptr_t* method_entry = (intptr_t *)(((address)klass) + offset_entry->offset());
1118 intptr_t* end = klass->end_of_itable();
1119
1120 _table_offset = int((intptr_t*)offset_entry - (intptr_t*)klass);
1121 _size_offset_table = int((method_entry - ((intptr_t*)offset_entry)) / itableOffsetEntry::size());
1122 _size_method_table = int((end - method_entry) / itableMethodEntry::size());
1123 assert(_table_offset >= 0 && _size_offset_table >= 0 && _size_method_table >= 0, "wrong computation");
1124 return;
1125 }
1126 }
1127
1128 // The length of the itable was either zero, or it has not yet been initialized.
1129 _table_offset = 0;
1130 _size_offset_table = 0;
1131 _size_method_table = 0;
1132 }
1133
1134 static int initialize_count = 0;
1135
1136 // Initialization
1137 void klassItable::initialize_itable(GrowableArray<Method*>* supers) {
1138 if (_klass->is_interface()) {
1139 // This needs to go after vtable indices are assigned but
1140 // before implementors need to know the number of itable indices.
1141 assign_itable_indices_for_interface(InstanceKlass::cast(_klass));
1142 }
1143
1144 // Cannot be setup doing bootstrapping, interfaces don't have
1145 // itables, and klass with only ones entry have empty itables
1146 if (Universe::is_bootstrapping() ||
1147 _klass->is_interface() ||
1148 _klass->itable_length() == itableOffsetEntry::size()) return;
1149
1150 // There's always an extra itable entry so we can null-terminate it.
1151 guarantee(size_offset_table() >= 1, "too small");
1152 int num_interfaces = size_offset_table() - 1;
1153 if (num_interfaces > 0) {
1154 if (log_develop_is_enabled(Debug, itables)) {
1155 ResourceMark rm;
1156 log_develop_debug(itables)("%3d: Initializing itables for %s", ++initialize_count,
1157 _klass->name()->as_C_string());
1158 }
1159
1160 // Iterate through all interfaces
1161 for(int i = 0; i < num_interfaces; i++) {
1162 itableOffsetEntry* ioe = offset_entry(i);
1163 InstanceKlass* interf = ioe->interface_klass();
1164 assert(interf != nullptr && ioe->offset() != 0, "bad offset entry in itable");
1165 initialize_itable_for_interface(ioe->offset(), interf, supers,
1166 (ioe->offset() - offset_entry(0)->offset())/wordSize);
1167 }
1168 }
1169 // Check that the last entry is empty
1170 itableOffsetEntry* ioe = offset_entry(size_offset_table() - 1);
1171 guarantee(ioe->interface_klass() == nullptr && ioe->offset() == 0, "terminator entry missing");
1172 }
1173
1174 void klassItable::check_constraints(GrowableArray<Method*>* supers, TRAPS) {
1175
1176 assert(_size_method_table == supers->length(), "wrong size");
1177 itableMethodEntry* ime = method_entry(0);
1178 for (int i = 0; i < _size_method_table; i++) {
1179 Method* target = ime->method();
1180 Method* interface_method = supers->at(i); // method overridden
1181
1182 if (target != nullptr && interface_method != nullptr) {
1183 InstanceKlass* method_holder = target->method_holder();
1184 InstanceKlass* interf = interface_method->method_holder();
1185 HandleMark hm(THREAD);
1186 Handle method_holder_loader(THREAD, method_holder->class_loader());
1187 Handle interface_loader(THREAD, interf->class_loader());
1188
1189 if (method_holder_loader() != interface_loader()) {
1190 ResourceMark rm(THREAD);
1191 Symbol* failed_type_symbol =
1192 SystemDictionary::check_signature_loaders(target->signature(),
1193 _klass,
1194 method_holder_loader,
1195 interface_loader,
1196 true);
1197 if (failed_type_symbol != nullptr) {
1198 stringStream ss;
1199 ss.print("loader constraint violation in interface itable"
1200 " initialization for class %s: when selecting method '",
1201 _klass->external_name());
1202 interface_method->print_external_name(&ss),
1203 ss.print("' the class loader %s for super interface %s, and the class"
1204 " loader %s of the selected method's %s, %s have"
1205 " different Class objects for the type %s used in the signature (%s; %s)",
1206 interf->class_loader_data()->loader_name_and_id(),
1207 interf->external_name(),
1208 method_holder->class_loader_data()->loader_name_and_id(),
1209 method_holder->external_kind(),
1210 method_holder->external_name(),
1211 failed_type_symbol->as_klass_external_name(),
1212 interf->class_in_module_of_loader(false, true),
1213 method_holder->class_in_module_of_loader(false, true));
1214 THROW_MSG(vmSymbols::java_lang_LinkageError(), ss.as_string());
1215 }
1216 }
1217 }
1218 ime++;
1219 }
1220 }
1221
1222 void klassItable::initialize_itable_and_check_constraints(TRAPS) {
1223 // Save a super interface from each itable entry to do constraint checking
1224 ResourceMark rm(THREAD);
1225 GrowableArray<Method*>* supers =
1226 new GrowableArray<Method*>(_size_method_table, _size_method_table, nullptr);
1227 initialize_itable(supers);
1228 check_constraints(supers, CHECK);
1229 }
1230
1231 inline bool interface_method_needs_itable_index(Method* m) {
1232 if (m->is_static()) return false; // e.g., Stream.empty
1233 if (m->is_private()) return false; // uses direct call
1234 if (m->is_object_constructor()) return false; // <init>(...)V
1235 if (m->is_class_initializer()) return false; // <clinit>()V
1236 // If an interface redeclares a method from java.lang.Object,
1237 // it should already have a vtable index, don't touch it.
1238 // e.g., CharSequence.toString (from initialize_vtable)
1239 // if (m->has_vtable_index()) return false; // NO!
1240 return true;
1241 }
1242
1243 int klassItable::assign_itable_indices_for_interface(InstanceKlass* klass) {
1244 // an interface does not have an itable, but its methods need to be numbered
1245 if (log_develop_is_enabled(Trace, itables)) {
1246 ResourceMark rm;
1247 log_develop_debug(itables)("%3d: Initializing itable indices for interface %s",
1248 ++initialize_count, klass->name()->as_C_string());
1249 }
1250
1251 Array<Method*>* methods = klass->methods();
1252 int nof_methods = methods->length();
1253 int ime_num = 0;
1254 for (int i = 0; i < nof_methods; i++) {
1255 Method* m = methods->at(i);
1256 if (interface_method_needs_itable_index(m)) {
1257 assert(!m->is_final_method(), "no final interface methods");
1258 // If m is already assigned a vtable index, do not disturb it.
1259 if (log_develop_is_enabled(Trace, itables)) {
1260 ResourceMark rm;
1261 LogTarget(Trace, itables) lt;
1262 LogStream ls(lt);
1263 assert(m != nullptr, "methods can never be null");
1264 const char* sig = m->name_and_sig_as_C_string();
1265 if (m->has_vtable_index()) {
1266 ls.print("vtable index %d for method: %s, flags: ", m->vtable_index(), sig);
1267 } else {
1268 ls.print("itable index %d for method: %s, flags: ", ime_num, sig);
1269 }
1270 m->print_linkage_flags(&ls);
1271 ls.cr();
1272 }
1273 if (!m->has_vtable_index()) {
1274 // A shared method could have an initialized itable_index that
1275 // is < 0.
1276 assert(m->vtable_index() == Method::pending_itable_index ||
1277 m->is_shared(),
1278 "set by initialize_vtable");
1279 m->set_itable_index(ime_num);
1280 // Progress to next itable entry
1281 ime_num++;
1282 }
1283 }
1284 }
1285 assert(ime_num == method_count_for_interface(klass), "proper sizing");
1286 return ime_num;
1287 }
1288
1289 int klassItable::method_count_for_interface(InstanceKlass* interf) {
1290 assert(interf->is_interface(), "must be");
1291 Array<Method*>* methods = interf->methods();
1292 int nof_methods = methods->length();
1293 int length = 0;
1294 while (nof_methods > 0) {
1295 Method* m = methods->at(nof_methods-1);
1296 if (m->has_itable_index()) {
1297 length = m->itable_index() + 1;
1298 break;
1299 }
1300 nof_methods -= 1;
1301 }
1302 #ifdef ASSERT
1303 int nof_methods_copy = nof_methods;
1304 while (nof_methods_copy > 0) {
1305 Method* mm = methods->at(--nof_methods_copy);
1306 assert(!mm->has_itable_index() || mm->itable_index() < length, "");
1307 }
1308 #endif //ASSERT
1309 // return the rightmost itable index, plus one; or 0 if no methods have
1310 // itable indices
1311 return length;
1312 }
1313
1314
1315 void klassItable::initialize_itable_for_interface(int method_table_offset, InstanceKlass* interf,
1316 GrowableArray<Method*>* supers,
1317 int start_offset) {
1318 assert(interf->is_interface(), "must be");
1319 Array<Method*>* methods = interf->methods();
1320 int nof_methods = methods->length();
1321
1322 int ime_count = method_count_for_interface(interf);
1323 for (int i = 0; i < nof_methods; i++) {
1324 Method* m = methods->at(i);
1325 Method* target = nullptr;
1326 if (m->has_itable_index()) {
1327 // This search must match the runtime resolution, i.e. selection search for invokeinterface
1328 // to correctly enforce loader constraints for interface method inheritance.
1329 // Private methods are skipped as a private class method can never be the implementation
1330 // of an interface method.
1331 // Invokespecial does not perform selection based on the receiver, so it does not use
1332 // the cached itable.
1333 target = LinkResolver::lookup_instance_method_in_klasses(_klass, m->name(), m->signature(),
1334 Klass::PrivateLookupMode::skip);
1335 }
1336 if (target == nullptr || !target->is_public() || target->is_abstract() || target->is_overpass()) {
1337 assert(target == nullptr || !target->is_overpass() || target->is_public(),
1338 "Non-public overpass method!");
1339 // Entry does not resolve. Leave it empty for AbstractMethodError or other error.
1340 if (!(target == nullptr) && !target->is_public()) {
1341 // Stuff an IllegalAccessError throwing method in there instead.
1342 itableOffsetEntry::method_entry(_klass, method_table_offset)[m->itable_index()].
1343 initialize(_klass, Universe::throw_illegal_access_error());
1344 }
1345 } else {
1346
1347 int ime_num = m->itable_index();
1348 assert(ime_num < ime_count, "oob");
1349
1350 // Save super interface method to perform constraint checks.
1351 // The method is in the error message, that's why.
1352 if (supers != nullptr) {
1353 supers->at_put(start_offset + ime_num, m);
1354 }
1355
1356 itableOffsetEntry::method_entry(_klass, method_table_offset)[ime_num].initialize(_klass, target);
1357 if (log_develop_is_enabled(Trace, itables)) {
1358 ResourceMark rm;
1359 if (target != nullptr) {
1360 LogTarget(Trace, itables) lt;
1361 LogStream ls(lt);
1362 char* sig = target->name_and_sig_as_C_string();
1363 ls.print("interface: %s, ime_num: %d, target: %s, method_holder: %s ",
1364 interf->internal_name(), ime_num, sig,
1365 target->method_holder()->internal_name());
1366 ls.print("target_method flags: ");
1367 target->print_linkage_flags(&ls);
1368 ls.cr();
1369 }
1370 }
1371 }
1372 }
1373 }
1374
1375 #if INCLUDE_JVMTI
1376 // search the itable for uses of either obsolete or EMCP methods
1377 void klassItable::adjust_method_entries(bool * trace_name_printed) {
1378 ResourceMark rm;
1379 itableMethodEntry* ime = method_entry(0);
1380
1381 for (int i = 0; i < _size_method_table; i++, ime++) {
1382 Method* old_method = ime->method();
1383 if (old_method == nullptr || !old_method->is_old()) {
1384 continue; // skip uninteresting entries
1385 }
1386 assert(!old_method->is_deleted(), "itable methods may not be deleted");
1387 Method* new_method = old_method->get_new_method();
1388 ime->initialize(_klass, new_method);
1389
1390 if (!(*trace_name_printed)) {
1391 log_info(redefine, class, update)("adjust: name=%s", old_method->method_holder()->external_name());
1392 *trace_name_printed = true;
1393 }
1394 log_trace(redefine, class, update, itables)
1395 ("itable method update: class: %s method: %s", _klass->external_name(), new_method->external_name());
1396 }
1397 }
1398
1399 // an itable should never contain old or obsolete methods
1400 bool klassItable::check_no_old_or_obsolete_entries() {
1401 ResourceMark rm;
1402 itableMethodEntry* ime = method_entry(0);
1403
1404 for (int i = 0; i < _size_method_table; i++) {
1405 Method* m = ime->method();
1406 if (m != nullptr &&
1407 (NOT_PRODUCT(!m->is_valid() ||) m->is_old() || m->is_obsolete())) {
1408 log_trace(redefine, class, update, itables)
1409 ("itable check found old method entry: class: %s old: %d obsolete: %d, method: %s",
1410 _klass->external_name(), m->is_old(), m->is_obsolete(), m->external_name());
1411 return false;
1412 }
1413 ime++;
1414 }
1415 return true;
1416 }
1417
1418 void klassItable::dump_itable() {
1419 itableMethodEntry* ime = method_entry(0);
1420 tty->print_cr("itable dump --");
1421 for (int i = 0; i < _size_method_table; i++) {
1422 Method* m = ime->method();
1423 if (m != nullptr) {
1424 tty->print(" (%5d) ", i);
1425 m->access_flags().print_on(tty);
1426 if (m->is_default_method()) {
1427 tty->print("default ");
1428 }
1429 tty->print(" -- ");
1430 m->print_name(tty);
1431 tty->cr();
1432 }
1433 ime++;
1434 }
1435 }
1436 #endif // INCLUDE_JVMTI
1437
1438 // Setup
1439 class InterfaceVisiterClosure : public StackObj {
1440 public:
1441 virtual void doit(InstanceKlass* intf, int method_count) = 0;
1442 };
1443
1444 int count_interface_methods_needing_itable_index(Array<Method*>* methods) {
1445 int method_count = 0;
1446 if (methods->length() > 0) {
1447 for (int i = methods->length(); --i >= 0; ) {
1448 if (interface_method_needs_itable_index(methods->at(i))) {
1449 method_count++;
1450 }
1451 }
1452 }
1453 return method_count;
1454 }
1455
1456 // Visit all interfaces with at least one itable method
1457 static void visit_all_interfaces(Array<InstanceKlass*>* transitive_intf, InterfaceVisiterClosure *blk) {
1458 // Handle array argument
1459 for(int i = 0; i < transitive_intf->length(); i++) {
1460 InstanceKlass* intf = transitive_intf->at(i);
1461 assert(intf->is_interface(), "sanity check");
1462
1463 // Find no. of itable methods
1464 int method_count = 0;
1465 // method_count = klassItable::method_count_for_interface(intf);
1466 Array<Method*>* methods = intf->methods();
1467 if (methods->length() > 0) {
1468 for (int i = methods->length(); --i >= 0; ) {
1469 if (interface_method_needs_itable_index(methods->at(i))) {
1470 method_count++;
1471 }
1472 }
1473 }
1474
1475 // Visit all interfaces which either have any methods or can participate in receiver type check.
1476 // We do not bother to count methods in transitive interfaces, although that would allow us to skip
1477 // this step in the rare case of a zero-method interface extending another zero-method interface.
1478 if (method_count > 0 || intf->transitive_interfaces()->length() > 0) {
1479 blk->doit(intf, method_count);
1480 }
1481 }
1482 }
1483
1484 class CountInterfacesClosure : public InterfaceVisiterClosure {
1485 private:
1486 int _nof_methods;
1487 int _nof_interfaces;
1488 public:
1489 CountInterfacesClosure() { _nof_methods = 0; _nof_interfaces = 0; }
1490
1491 int nof_methods() const { return _nof_methods; }
1492 int nof_interfaces() const { return _nof_interfaces; }
1493
1494 void doit(InstanceKlass* intf, int method_count) { _nof_methods += method_count; _nof_interfaces++; }
1495 };
1496
1497 class SetupItableClosure : public InterfaceVisiterClosure {
1498 private:
1499 itableOffsetEntry* _offset_entry;
1500 itableMethodEntry* _method_entry;
1501 address _klass_begin;
1502 public:
1503 SetupItableClosure(address klass_begin, itableOffsetEntry* offset_entry, itableMethodEntry* method_entry) {
1504 _klass_begin = klass_begin;
1505 _offset_entry = offset_entry;
1506 _method_entry = method_entry;
1507 }
1508
1509 itableMethodEntry* method_entry() const { return _method_entry; }
1510
1511 void doit(InstanceKlass* intf, int method_count) {
1512 int offset = int(((address)_method_entry) - _klass_begin);
1513 _offset_entry->initialize(intf, offset);
1514 _offset_entry++;
1515 _method_entry += method_count;
1516 }
1517 };
1518
1519 int klassItable::compute_itable_size(Array<InstanceKlass*>* transitive_interfaces) {
1520 // Count no of interfaces and total number of interface methods
1521 CountInterfacesClosure cic;
1522 visit_all_interfaces(transitive_interfaces, &cic);
1523
1524 // There's always an extra itable entry so we can null-terminate it.
1525 int itable_size = calc_itable_size(cic.nof_interfaces() + 1, cic.nof_methods());
1526
1527 return itable_size;
1528 }
1529
1530
1531 // Fill out offset table and interface klasses into the itable space
1532 void klassItable::setup_itable_offset_table(InstanceKlass* klass) {
1533 if (klass->itable_length() == 0) return;
1534 assert(!klass->is_interface(), "Should have zero length itable");
1535
1536 // Count no of interfaces and total number of interface methods
1537 CountInterfacesClosure cic;
1538 visit_all_interfaces(klass->transitive_interfaces(), &cic);
1539 int nof_methods = cic.nof_methods();
1540 int nof_interfaces = cic.nof_interfaces();
1541
1542 // Add one extra entry so we can null-terminate the table
1543 nof_interfaces++;
1544
1545 assert(compute_itable_size(klass->transitive_interfaces()) ==
1546 calc_itable_size(nof_interfaces, nof_methods),
1547 "mismatch calculation of itable size");
1548
1549 // Fill-out offset table
1550 itableOffsetEntry* ioe = (itableOffsetEntry*)klass->start_of_itable();
1551 itableMethodEntry* ime = (itableMethodEntry*)(ioe + nof_interfaces);
1552 intptr_t* end = klass->end_of_itable();
1553 assert((oop*)(ime + nof_methods) <= (oop*)klass->start_of_nonstatic_oop_maps(), "wrong offset calculation (1)");
1554 assert((oop*)(end) == (oop*)(ime + nof_methods), "wrong offset calculation (2)");
1555
1556 // Visit all interfaces and initialize itable offset table
1557 SetupItableClosure sic((address)klass, ioe, ime);
1558 visit_all_interfaces(klass->transitive_interfaces(), &sic);
1559
1560 #ifdef ASSERT
1561 ime = sic.method_entry();
1562 oop* v = (oop*) klass->end_of_itable();
1563 assert( (oop*)(ime) == v, "wrong offset calculation (2)");
1564 #endif
1565 }
1566
1567 void klassVtable::verify(outputStream* st, bool forced) {
1568 // make sure table is initialized
1569 if (!Universe::is_fully_initialized()) return;
1570 #ifndef PRODUCT
1571 // avoid redundant verifies
1572 if (!forced && _verify_count == Universe::verify_count()) return;
1573 _verify_count = Universe::verify_count();
1574 #endif
1575 oop* end_of_obj = (oop*)_klass + _klass->size();
1576 oop* end_of_vtable = (oop *)&table()[_length];
1577 if (end_of_vtable > end_of_obj) {
1578 ResourceMark rm;
1579 fatal("klass %s: klass object too short (vtable extends beyond end)",
1580 _klass->internal_name());
1581 }
1582
1583 for (int i = 0; i < _length; i++) table()[i].verify(this, st);
1584 // verify consistency with superKlass vtable
1585 Klass* super = _klass->super();
1586 if (super != nullptr) {
1587 InstanceKlass* sk = InstanceKlass::cast(super);
1588 klassVtable vt = sk->vtable();
1589 for (int i = 0; i < vt.length(); i++) {
1590 verify_against(st, &vt, i);
1591 }
1592 }
1593 }
1594
1595 void klassVtable::verify_against(outputStream* st, klassVtable* vt, int index) {
1596 vtableEntry* vte = &vt->table()[index];
1597 if (vte->method()->name() != table()[index].method()->name() ||
1598 vte->method()->signature() != table()[index].method()->signature()) {
1599 fatal("mismatched name/signature of vtable entries");
1600 }
1601 }
1602
1603 #ifndef PRODUCT
1604 void klassVtable::print() {
1605 ResourceMark rm;
1606 tty->print("klassVtable for klass %s (length %d):\n", _klass->internal_name(), length());
1607 for (int i = 0; i < length(); i++) {
1608 table()[i].print();
1609 tty->cr();
1610 }
1611 }
1612 #endif
1613
1614 void vtableEntry::verify(klassVtable* vt, outputStream* st) {
1615 Klass* vtklass = vt->klass();
1616 if (vtklass->is_instance_klass() &&
1617 (InstanceKlass::cast(vtklass)->major_version() >= klassVtable::VTABLE_TRANSITIVE_OVERRIDE_VERSION)) {
1618 assert(method() != nullptr, "must have set method");
1619 }
1620 if (method() != nullptr) {
1621 method()->verify();
1622 // we sub_type, because it could be a miranda method
1623 if (!vtklass->is_subtype_of(method()->method_holder())) {
1624 #ifndef PRODUCT
1625 print();
1626 #endif
1627 fatal("vtableEntry " PTR_FORMAT ": method is from subclass", p2i(this));
1628 }
1629 }
1630 }
1631
1632 #ifndef PRODUCT
1633
1634 void vtableEntry::print() {
1635 ResourceMark rm;
1636 tty->print("vtableEntry %s: ", method()->name()->as_C_string());
1637 if (Verbose) {
1638 tty->print("m " PTR_FORMAT " ", p2i(method()));
1639 }
1640 }
1641 #endif // PRODUCT