1 /*
2 * Copyright (c) 1997, 2023, 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 "cds/metaspaceShared.hpp"
27 #include "classfile/classLoaderDataGraph.hpp"
28 #include "classfile/javaClasses.hpp"
29 #include "classfile/systemDictionary.hpp"
30 #include "classfile/vmSymbols.hpp"
31 #include "interpreter/linkResolver.hpp"
32 #include "jvm.h"
33 #include "logging/log.hpp"
34 #include "logging/logStream.hpp"
35 #include "memory/resourceArea.hpp"
36 #include "memory/universe.hpp"
37 #include "oops/instanceKlass.inline.hpp"
38 #include "oops/klass.inline.hpp"
39 #include "oops/klassVtable.hpp"
40 #include "oops/method.hpp"
41 #include "oops/objArrayOop.hpp"
42 #include "oops/oop.inline.hpp"
43 #include "runtime/flags/flagSetting.hpp"
44 #include "runtime/java.hpp"
45 #include "runtime/handles.inline.hpp"
46 #include "runtime/safepointVerifiers.hpp"
47 #include "utilities/copy.hpp"
48
49 inline InstanceKlass* klassVtable::ik() const {
50 return InstanceKlass::cast(_klass);
51 }
52
53 bool klassVtable::is_preinitialized_vtable() {
54 return _klass->is_shared() && !MetaspaceShared::remapped_readwrite() && _klass->verified_at_dump_time();
55 }
56
57
58 // this function computes the vtable size (including the size needed for miranda
59 // methods) and the number of miranda methods in this class.
60 // Note on Miranda methods: Let's say there is a class C that implements
61 // interface I, and none of C's superclasses implements I.
62 // Let's say there is an abstract method m in I that neither C
63 // nor any of its super classes implement (i.e there is no method of any access,
64 // with the same name and signature as m), then m is a Miranda method which is
65 // entered as a public abstract method in C's vtable. From then on it should
66 // treated as any other public method in C for method over-ride purposes.
67 void klassVtable::compute_vtable_size_and_num_mirandas(
68 int* vtable_length_ret, int* num_new_mirandas,
69 GrowableArray<Method*>* all_mirandas, const Klass* super,
70 Array<Method*>* methods, AccessFlags class_flags, u2 major_version,
71 Handle classloader, Symbol* classname, Array<InstanceKlass*>* local_interfaces) {
72 NoSafepointVerifier nsv;
73
74 // set up default result values
75 int vtable_length = 0;
76
77 // start off with super's vtable length
78 vtable_length = super == nullptr ? 0 : super->vtable_length();
79
80 // go thru each method in the methods table to see if it needs a new entry
81 int len = methods->length();
82 for (int i = 0; i < len; i++) {
83 Method* method = methods->at(i);
84
85 if (needs_new_vtable_entry(method, super, classloader, classname, class_flags, major_version)) {
86 assert(!method->is_private(), "private methods should not need a vtable entry");
87 vtable_length += vtableEntry::size(); // we need a new entry
88 }
89 }
90
91 GrowableArray<Method*> new_mirandas(20);
92 // compute the number of mirandas methods that must be added to the end
93 get_mirandas(&new_mirandas, all_mirandas, super, methods, nullptr, local_interfaces,
94 class_flags.is_interface());
95 *num_new_mirandas = new_mirandas.length();
96
97 // Interfaces do not need interface methods in their vtables
98 // This includes miranda methods and during later processing, default methods
99 if (!class_flags.is_interface()) {
100 vtable_length += *num_new_mirandas * vtableEntry::size();
101 }
102
103 if (Universe::is_bootstrapping() && vtable_length == 0) {
104 // array classes don't have their superclass set correctly during
105 // bootstrapping
106 vtable_length = Universe::base_vtable_size();
107 }
108
109 if (super == nullptr && vtable_length != Universe::base_vtable_size()) {
110 if (Universe::is_bootstrapping()) {
111 // Someone is attempting to override java.lang.Object incorrectly on the
112 // bootclasspath. The JVM cannot recover from this error including throwing
113 // an exception
114 vm_exit_during_initialization("Incompatible definition of java.lang.Object");
115 } else {
116 // Someone is attempting to redefine java.lang.Object incorrectly. The
117 // only way this should happen is from
118 // SystemDictionary::resolve_from_stream(), which will detect this later
119 // and throw a security exception. So don't assert here to let
120 // the exception occur.
121 vtable_length = Universe::base_vtable_size();
122 }
123 }
124 assert(vtable_length % vtableEntry::size() == 0, "bad vtable length");
125 assert(vtable_length >= Universe::base_vtable_size(), "vtable too small");
126
127 *vtable_length_ret = vtable_length;
128 }
129
130 // Copy super class's vtable to the first part (prefix) of this class's vtable,
131 // and return the number of entries copied. Expects that 'super' is the Java
132 // super class (arrays can have "array" super classes that must be skipped).
133 int klassVtable::initialize_from_super(Klass* super) {
134 if (super == nullptr) {
135 return 0;
136 } else if (is_preinitialized_vtable()) {
137 // A shared class' vtable is preinitialized at dump time. No need to copy
138 // methods from super class for shared class, as that was already done
139 // during archiving time. However, if Jvmti has redefined a class,
140 // copy super class's vtable in case the super class has changed.
141 return super->vtable().length();
142 } else {
143 // copy methods from superKlass
144 klassVtable superVtable = super->vtable();
145 assert(superVtable.length() <= _length, "vtable too short");
146 #ifdef ASSERT
147 superVtable.verify(tty, true);
148 #endif
149 superVtable.copy_vtable_to(table());
150 if (log_develop_is_enabled(Trace, vtables)) {
151 ResourceMark rm;
152 log_develop_trace(vtables)("copy vtable from %s to %s size %d",
153 super->internal_name(), klass()->internal_name(),
154 _length);
155 }
156 return superVtable.length();
157 }
158 }
159
160 //
161 // Revised lookup semantics introduced 1.3 (Kestrel beta)
162 void klassVtable::initialize_vtable(GrowableArray<InstanceKlass*>* supers) {
163
164 // Note: Arrays can have intermediate array supers. Use java_super to skip them.
165 InstanceKlass* super = _klass->java_super();
166
167 bool is_shared = _klass->is_shared();
168 Thread* current = Thread::current();
169
170 if (!_klass->is_array_klass()) {
171 ResourceMark rm(current);
172 log_develop_debug(vtables)("Initializing: %s", _klass->name()->as_C_string());
173 }
174
175 #ifdef ASSERT
176 oop* end_of_obj = (oop*)_klass + _klass->size();
177 oop* end_of_vtable = (oop*)&table()[_length];
178 assert(end_of_vtable <= end_of_obj, "vtable extends beyond end");
179 #endif
180
181 if (Universe::is_bootstrapping()) {
182 assert(!is_shared, "sanity");
183 // just clear everything
184 for (int i = 0; i < _length; i++) table()[i].clear();
185 return;
186 }
187
188 int super_vtable_len = initialize_from_super(super);
189 if (_klass->is_array_klass()) {
190 assert(super_vtable_len == _length, "arrays shouldn't introduce new methods");
191 } else {
192 assert(_klass->is_instance_klass(), "must be InstanceKlass");
193
194 Array<Method*>* methods = ik()->methods();
195 int len = methods->length();
196 int initialized = super_vtable_len;
197
198 // Check each of this class's methods against super;
199 // if override, replace in copy of super vtable, otherwise append to end
200 for (int i = 0; i < len; i++) {
201 // update_inherited_vtable can stop for gc - ensure using handles
202 methodHandle mh(current, methods->at(i));
203
204 bool needs_new_entry = update_inherited_vtable(current, mh, super_vtable_len, -1, supers);
205
206 if (needs_new_entry) {
207 put_method_at(mh(), initialized);
208 mh->set_vtable_index(initialized); // set primary vtable index
209 initialized++;
210 }
211 }
212
213 // update vtable with default_methods
214 Array<Method*>* default_methods = ik()->default_methods();
215 if (default_methods != nullptr) {
216 len = default_methods->length();
217 if (len > 0) {
218 Array<int>* def_vtable_indices = ik()->default_vtable_indices();
219 assert(def_vtable_indices != nullptr, "should be created");
220 assert(def_vtable_indices->length() == len, "reinit vtable len?");
221 for (int i = 0; i < len; i++) {
222 bool needs_new_entry;
223 {
224 // Reduce the scope of this handle so that it is fetched again.
225 // The methodHandle keeps it from being deleted by RedefineClasses while
226 // we're using it.
227 methodHandle mh(current, default_methods->at(i));
228 assert(!mh->is_private(), "private interface method in the default method list");
229 needs_new_entry = update_inherited_vtable(current, mh, super_vtable_len, i, supers);
230 }
231
232 // needs new entry
233 if (needs_new_entry) {
234 // Refetch this default method in case of redefinition that might
235 // happen during constraint checking in the update_inherited_vtable call above.
236 Method* method = default_methods->at(i);
237 put_method_at(method, initialized);
238 if (is_preinitialized_vtable()) {
239 // At runtime initialize_vtable is rerun for a shared class
240 // (loaded by the non-boot loader) as part of link_class_impl().
241 // The dumptime vtable index should be the same as the runtime index.
242 assert(def_vtable_indices->at(i) == initialized,
243 "dump time vtable index is different from runtime index");
244 } else {
245 def_vtable_indices->at_put(i, initialized); //set vtable index
246 }
247 initialized++;
248 }
249 }
250 }
251 }
252
253 // add miranda methods; it will also return the updated initialized
254 // Interfaces do not need interface methods in their vtables
255 // This includes miranda methods and during later processing, default methods
256 if (!ik()->is_interface()) {
257 initialized = fill_in_mirandas(current, initialized);
258 }
259
260 // In class hierarchies where the accessibility is not increasing (i.e., going from private ->
261 // package_private -> public/protected), the vtable might actually be smaller than our initial
262 // calculation, for classfile versions for which we do not do transitive override
263 // calculations.
264 if (ik()->major_version() >= VTABLE_TRANSITIVE_OVERRIDE_VERSION) {
265 assert(initialized == _length, "vtable initialization failed");
266 } else {
267 assert(initialized <= _length, "vtable initialization failed");
268 for(;initialized < _length; initialized++) {
269 table()[initialized].clear();
270 }
271 }
272 NOT_PRODUCT(verify(tty, true));
273 }
274 }
275
276 // Returns true iff super_method can be overridden by a method in targetclassname
277 // See JLS 8.4.8.1
278 // Assumes name-signature match
279 // Note that the InstanceKlass of the method in the targetclassname has not always been created yet
280 static bool can_be_overridden(Method* super_method, Handle targetclassloader, Symbol* targetclassname) {
281 // Private methods can not be overridden
282 assert(!super_method->is_private(), "shouldn't call with a private method");
283
284 // If super method is accessible, then override
285 if ((super_method->is_protected()) ||
286 (super_method->is_public())) {
287 return true;
288 }
289 // Package-private methods are not inherited outside of package
290 assert(super_method->is_package_private(), "must be package private");
291 return(super_method->method_holder()->is_same_class_package(targetclassloader(), targetclassname));
292 }
293
294
295 // Called for cases where a method does not override its superclass' vtable entry
296 // For bytecodes not produced by javac together it is possible that a method does not override
297 // the superclass's method, but might indirectly override a super-super class's vtable entry
298 // If none found, return a null superk, else return the superk of the method this does override
299 // For public and protected methods: if they override a superclass, they will
300 // also be overridden themselves appropriately.
301 // Private methods do not override, and are not overridden and are not in the vtable.
302 // Package Private methods are trickier:
303 // e.g. P1.A, pub m
304 // P2.B extends A, package private m
305 // P1.C extends B, public m
306 // P1.C.m needs to override P1.A.m and can not override P2.B.m
307 // Therefore: all package private methods need their own vtable entries for
308 // them to be the root of an inheritance overriding decision
309 // Package private methods may also override other vtable entries
310 InstanceKlass* klassVtable::find_transitive_override(InstanceKlass* initialsuper,
311 const methodHandle& target_method,
312 int vtable_index,
313 Handle target_loader,
314 Symbol* target_classname) {
315
316 InstanceKlass* superk = initialsuper;
317 while (superk != nullptr && superk->super() != nullptr) {
318 klassVtable ssVtable = (superk->super())->vtable();
319 if (vtable_index < ssVtable.length()) {
320 Method* super_method = ssVtable.method_at(vtable_index);
321 #ifndef PRODUCT
322 Symbol* name= target_method()->name();
323 Symbol* signature = target_method()->signature();
324 assert(super_method->name() == name && super_method->signature() == signature, "vtable entry name/sig mismatch");
325 #endif
326
327 if (can_be_overridden(super_method, target_loader, target_classname)) {
328 if (log_develop_is_enabled(Trace, vtables)) {
329 ResourceMark rm;
330 LogTarget(Trace, vtables) lt;
331 LogStream ls(lt);
332 char* sig = target_method()->name_and_sig_as_C_string();
333 ls.print("transitive overriding superclass %s with %s index %d, original flags: ",
334 super_method->method_holder()->internal_name(),
335 sig, vtable_index);
336 super_method->print_linkage_flags(&ls);
337 ls.print("overriders flags: ");
338 target_method->print_linkage_flags(&ls);
339 ls.cr();
340 }
341
342 break; // return found superk
343 }
344 } else {
345 // super class has no vtable entry here, stop transitive search
346 superk = (InstanceKlass*)nullptr;
347 break;
348 }
349 // if no override found yet, continue to search up
350 superk = superk->super() == nullptr ? nullptr : InstanceKlass::cast(superk->super());
351 }
352
353 return superk;
354 }
355
356 static void log_vtables(int i, bool overrides, const methodHandle& target_method,
357 Klass* target_klass, Method* super_method) {
358 #ifndef PRODUCT
359 if (log_develop_is_enabled(Trace, vtables)) {
360 ResourceMark rm;
361 LogTarget(Trace, vtables) lt;
362 LogStream ls(lt);
363 char* sig = target_method()->name_and_sig_as_C_string();
364 if (overrides) {
365 ls.print("overriding with %s index %d, original flags: ",
366 sig, i);
367 } else {
368 ls.print("NOT overriding with %s index %d, original flags: ",
369 sig, i);
370 }
371 super_method->print_linkage_flags(&ls);
372 ls.print("overriders flags: ");
373 target_method->print_linkage_flags(&ls);
374 ls.cr();
375 }
376 #endif
377 }
378
379 // Update child's copy of super vtable for overrides
380 // OR return true if a new vtable entry is required.
381 // Only called for InstanceKlass's, i.e. not for arrays
382 // If that changed, could not use _klass as handle for klass
383 bool klassVtable::update_inherited_vtable(Thread* current,
384 const methodHandle& target_method,
385 int super_vtable_len, int default_index,
386 GrowableArray<InstanceKlass*>* supers) {
387 bool allocate_new = true;
388
389 InstanceKlass* klass = ik();
390
391 Array<int>* def_vtable_indices = nullptr;
392 bool is_default = false;
393
394 // default methods are non-private concrete methods in superinterfaces which are added
395 // to the vtable with their real method_holder.
396 // Since vtable and itable indices share the same storage, don't touch
397 // the default method's real vtable/itable index.
398 // default_vtable_indices stores the vtable value relative to this inheritor
399 if (default_index >= 0 ) {
400 is_default = true;
401 def_vtable_indices = klass->default_vtable_indices();
402 assert(!target_method->is_private(), "private interface method flagged as default");
403 assert(def_vtable_indices != nullptr, "def vtable alloc?");
404 assert(default_index <= def_vtable_indices->length(), "def vtable len?");
405 } else {
406 assert(klass == target_method->method_holder(), "caller resp.");
407 // Initialize the method's vtable index to "nonvirtual".
408 // If we allocate a vtable entry, we will update it to a non-negative number.
409 target_method->set_vtable_index(Method::nonvirtual_vtable_index);
410 }
411
412 // Private, static and <init> methods are never in
413 if (target_method->is_private() || target_method->is_static() ||
414 (target_method->name()->fast_compare(vmSymbols::object_initializer_name()) == 0)) {
415 return false;
416 }
417
418 if (target_method->is_final_method(klass->access_flags())) {
419 // a final method never needs a new entry; final methods can be statically
420 // resolved and they have to be present in the vtable only if they override
421 // a super's method, in which case they re-use its entry
422 allocate_new = false;
423 } else if (klass->is_interface()) {
424 allocate_new = false; // see note below in needs_new_vtable_entry
425 // An interface never allocates new vtable slots, only inherits old ones.
426 // This method will either be assigned its own itable index later,
427 // or be assigned an inherited vtable index in the loop below.
428 // default methods inherited by classes store their vtable indices
429 // in the inheritor's default_vtable_indices.
430 // default methods inherited by interfaces may already have a
431 // valid itable index, if so, don't change it.
432 // Overpass methods in an interface will be assigned an itable index later
433 // by an inheriting class.
434 if ((!is_default || !target_method->has_itable_index())) {
435 target_method->set_vtable_index(Method::pending_itable_index);
436 }
437 }
438
439 // we need a new entry if there is no superclass
440 Klass* super = klass->super();
441 if (super == nullptr) {
442 return allocate_new;
443 }
444
445 // search through the vtable and update overridden entries
446 // Since check_signature_loaders acquires SystemDictionary_lock
447 // which can block for gc, once we are in this loop, use handles
448 // For classfiles built with >= jdk7, we now look for transitive overrides
449
450 Symbol* name = target_method->name();
451 Symbol* signature = target_method->signature();
452
453 Klass* target_klass = target_method->method_holder();
454 assert(target_klass != nullptr, "impossible");
455 if (target_klass == nullptr) {
456 target_klass = _klass;
457 }
458
459 HandleMark hm(current);
460 Handle target_loader(current, target_klass->class_loader());
461
462 Symbol* target_classname = target_klass->name();
463 for(int i = 0; i < super_vtable_len; i++) {
464 Method* super_method;
465 if (is_preinitialized_vtable()) {
466 // If this is a shared class, the vtable is already in the final state (fully
467 // initialized). Need to look at the super's vtable.
468 klassVtable superVtable = super->vtable();
469 super_method = superVtable.method_at(i);
470 } else {
471 super_method = method_at(i);
472 }
473 // Check if method name matches. Ignore match if klass is an interface and the
474 // matching method is a non-public java.lang.Object method. (See JVMS 5.4.3.4)
475 // This is safe because the method at this slot should never get invoked.
476 // (TBD: put in a method to throw NoSuchMethodError if this slot is ever used.)
477 if (super_method->name() == name && super_method->signature() == signature &&
478 (!klass->is_interface() ||
479 !SystemDictionary::is_nonpublic_Object_method(super_method))) {
480
481 // get super_klass for method_holder for the found method
482 InstanceKlass* super_klass = super_method->method_holder();
483
484 // Whether the method is being overridden
485 bool overrides = false;
486
487 // private methods are also never overridden
488 if (!super_method->is_private() &&
489 (is_default ||
490 can_be_overridden(super_method, target_loader, target_classname) ||
491 (klass->major_version() >= VTABLE_TRANSITIVE_OVERRIDE_VERSION &&
492 (super_klass = find_transitive_override(super_klass,
493 target_method, i, target_loader,
494 target_classname)) != nullptr))) {
495
496 // Package private methods always need a new entry to root their own
497 // overriding. They may also override other methods.
498 if (!target_method->is_package_private()) {
499 allocate_new = false;
500 }
501
502 // Set the vtable index before the constraint check safepoint, which potentially
503 // redefines this method if this method is a default method belonging to a
504 // super class or interface.
505 put_method_at(target_method(), i);
506 // Save super for constraint checking.
507 if (supers != nullptr) {
508 supers->at_put(i, super_klass);
509 }
510
511 overrides = true;
512 if (!is_default) {
513 target_method->set_vtable_index(i);
514 } else {
515 if (def_vtable_indices != nullptr) {
516 if (is_preinitialized_vtable()) {
517 // At runtime initialize_vtable is rerun as part of link_class_impl()
518 // for a shared class loaded by the non-boot loader.
519 // The dumptime vtable index should be the same as the runtime index.
520 assert(def_vtable_indices->at(default_index) == i,
521 "dump time vtable index is different from runtime index");
522 } else {
523 def_vtable_indices->at_put(default_index, i);
524 }
525 }
526 assert(super_method->is_default_method() || super_method->is_overpass()
527 || super_method->is_abstract(), "default override error");
528 }
529 } else {
530 overrides = false;
531 }
532 log_vtables(i, overrides, target_method, target_klass, super_method);
533 }
534 }
535 return allocate_new;
536 }
537
538 void klassVtable::put_method_at(Method* m, int index) {
539 assert(!m->is_private(), "private methods should not be in vtable");
540 JVMTI_ONLY(assert(!m->is_old() || ik()->is_being_redefined(), "old methods should not be in vtable"));
541 if (is_preinitialized_vtable()) {
542 // At runtime initialize_vtable is rerun as part of link_class_impl()
543 // for shared class loaded by the non-boot loader to obtain the loader
544 // constraints based on the runtime classloaders' context. The dumptime
545 // method at the vtable index should be the same as the runtime method.
546 assert(table()[index].method() == m,
547 "archived method is different from the runtime method");
548 } else {
549 if (log_develop_is_enabled(Trace, vtables)) {
550 ResourceMark rm;
551 LogTarget(Trace, vtables) lt;
552 LogStream ls(lt);
553 const char* sig = (m != nullptr) ? m->name_and_sig_as_C_string() : "<null>";
554 ls.print("adding %s at index %d, flags: ", sig, index);
555 if (m != nullptr) {
556 m->print_linkage_flags(&ls);
557 }
558 ls.cr();
559 }
560 table()[index].set(m);
561 }
562 }
563
564 void klassVtable::check_constraints(GrowableArray<InstanceKlass*>* supers, TRAPS) {
565 assert(supers->length() == length(), "lengths are different");
566 // For each method in the vtable, check constraints against any super class
567 // if overridden.
568 for (int i = 0; i < length(); i++) {
569 methodHandle target_method(THREAD, unchecked_method_at(i));
570 InstanceKlass* super_klass = supers->at(i);
571 if (target_method() != nullptr && super_klass != nullptr) {
572 // Do not check loader constraints for overpass methods because overpass
573 // methods are created by the jvm to throw exceptions.
574 if (!target_method->is_overpass()) {
575 HandleMark hm(THREAD);
576 // Override vtable entry if passes loader constraint check
577 // if loader constraint checking requested
578 // No need to visit his super, since he and his super
579 // have already made any needed loader constraints.
580 // Since loader constraints are transitive, it is enough
581 // to link to the first super, and we get all the others.
582 Handle super_loader(THREAD, super_klass->class_loader());
583 InstanceKlass* target_klass = target_method->method_holder();
584 Handle target_loader(THREAD, target_klass->class_loader());
585
586 if (target_loader() != super_loader()) {
587 ResourceMark rm(THREAD);
588 Symbol* failed_type_symbol =
589 SystemDictionary::check_signature_loaders(target_method->signature(),
590 _klass,
591 target_loader, super_loader,
592 true);
593 if (failed_type_symbol != nullptr) {
594 stringStream ss;
595 ss.print("loader constraint violation for class %s: when selecting "
596 "overriding method '", _klass->external_name());
597 target_method->print_external_name(&ss),
598 ss.print("' the class loader %s of the "
599 "selected method's type %s, and the class loader %s for its super "
600 "type %s have different Class objects for the type %s used in the signature (%s; %s)",
601 target_klass->class_loader_data()->loader_name_and_id(),
602 target_klass->external_name(),
603 super_klass->class_loader_data()->loader_name_and_id(),
604 super_klass->external_name(),
605 failed_type_symbol->as_klass_external_name(),
606 target_klass->class_in_module_of_loader(false, true),
607 super_klass->class_in_module_of_loader(false, true));
608 THROW_MSG(vmSymbols::java_lang_LinkageError(), ss.as_string());
609 }
610 }
611 }
612 }
613 }
614 }
615
616 void klassVtable::initialize_vtable_and_check_constraints(TRAPS) {
617 // Save a superclass from each vtable entry to do constraint checking
618 ResourceMark rm(THREAD);
619 GrowableArray<InstanceKlass*>* supers = new GrowableArray<InstanceKlass*>(_length, _length, nullptr);
620 initialize_vtable(supers);
621 check_constraints(supers, CHECK);
622 }
623
624
625 // Find out if a method "m" with superclass "super", loader "classloader" and
626 // name "classname" needs a new vtable entry. Let P be a class package defined
627 // by "classloader" and "classname".
628 // NOTE: The logic used here is very similar to the one used for computing
629 // the vtables indices for a method. We cannot directly use that function because,
630 // we allocate the InstanceKlass at load time, and that requires that the
631 // superclass has been loaded.
632 // However, the vtable entries are filled in at link time, and therefore
633 // the superclass' vtable may not yet have been filled in.
634 bool klassVtable::needs_new_vtable_entry(Method* target_method,
635 const Klass* super,
636 Handle classloader,
637 Symbol* classname,
638 AccessFlags class_flags,
639 u2 major_version) {
640 if (class_flags.is_interface()) {
641 // Interfaces do not use vtables, except for java.lang.Object methods,
642 // so there is no point to assigning
643 // a vtable index to any of their local methods. If we refrain from doing this,
644 // we can use Method::_vtable_index to hold the itable index
645 return false;
646 }
647
648 if (target_method->is_final_method(class_flags) ||
649 // a final method never needs a new entry; final methods can be statically
650 // resolved and they have to be present in the vtable only if they override
651 // a super's method, in which case they re-use its entry
652 (target_method->is_private()) ||
653 // private methods don't need to be in vtable
654 (target_method->is_static()) ||
655 // static methods don't need to be in vtable
656 (target_method->name()->fast_compare(vmSymbols::object_initializer_name()) == 0)
657 // <init> is never called dynamically-bound
658 ) {
659 return false;
660 }
661
662 // Concrete interface methods do not need new entries, they override
663 // abstract method entries using default inheritance rules
664 if (target_method->method_holder() != nullptr &&
665 target_method->method_holder()->is_interface() &&
666 !target_method->is_abstract()) {
667 assert(target_method->is_default_method(),
668 "unexpected interface method type");
669 return false;
670 }
671
672 // we need a new entry if there is no superclass
673 if (super == nullptr) {
674 return true;
675 }
676
677 // Package private methods always need a new entry to root their own
678 // overriding. This allows transitive overriding to work.
679 if (target_method->is_package_private()) {
680 return true;
681 }
682
683 // search through the super class hierarchy to see if we need
684 // a new entry
685 Symbol* name = target_method->name();
686 Symbol* signature = target_method->signature();
687 const Klass* k = super;
688 Method* super_method = nullptr;
689 InstanceKlass *holder = nullptr;
690 Method* recheck_method = nullptr;
691 bool found_pkg_prvt_method = false;
692 while (k != nullptr) {
693 // lookup through the hierarchy for a method with matching name and sign.
694 super_method = InstanceKlass::cast(k)->lookup_method(name, signature);
695 if (super_method == nullptr) {
696 break; // we still have to search for a matching miranda method
697 }
698 // get the class holding the matching method
699 InstanceKlass* superk = super_method->method_holder();
700 // we want only instance method matches
701 // ignore private methods found via lookup_method since they do not participate in overriding,
702 // and since we do override around them: e.g. a.m pub/b.m private/c.m pub,
703 // ignore private, c.m pub does override a.m pub
704 // For classes that were not javac'd together, we also do transitive overriding around
705 // methods that have less accessibility
706 if (!super_method->is_static() &&
707 !super_method->is_private()) {
708 if (can_be_overridden(super_method, classloader, classname)) {
709 return false;
710 // else keep looking for transitive overrides
711 }
712 // If we get here then one of the super classes has a package private method
713 // that will not get overridden because it is in a different package. But,
714 // that package private method does "override" any matching methods in super
715 // interfaces, so there will be no miranda vtable entry created. So, set flag
716 // to TRUE for use below, in case there are no methods in super classes that
717 // this target method overrides.
718 assert(super_method->is_package_private(), "super_method must be package private");
719 assert(!superk->is_same_class_package(classloader(), classname),
720 "Must be different packages");
721 found_pkg_prvt_method = true;
722 }
723
724 // Start with lookup result and continue to search up, for versions supporting transitive override
725 if (major_version >= VTABLE_TRANSITIVE_OVERRIDE_VERSION) {
726 k = superk->super(); // haven't found an override match yet; continue to look
727 } else {
728 break;
729 }
730 }
731
732 // If found_pkg_prvt_method is set, then the ONLY matching method in the
733 // superclasses is package private in another package. That matching method will
734 // prevent a miranda vtable entry from being created. Because the target method can not
735 // override the package private method in another package, then it needs to be the root
736 // for its own vtable entry.
737 if (found_pkg_prvt_method) {
738 return true;
739 }
740
741 // if the target method is public or protected it may have a matching
742 // miranda method in the super, whose entry it should re-use.
743 // Actually, to handle cases that javac would not generate, we need
744 // this check for all access permissions.
745 const InstanceKlass *sk = InstanceKlass::cast(super);
746 if (sk->has_miranda_methods()) {
747 if (sk->lookup_method_in_all_interfaces(name, signature, Klass::DefaultsLookupMode::find) != nullptr) {
748 return false; // found a matching miranda; we do not need a new entry
749 }
750 }
751 return true; // found no match; we need a new entry
752 }
753
754 // Support for miranda methods
755
756 // get the vtable index of a miranda method with matching "name" and "signature"
757 int klassVtable::index_of_miranda(Symbol* name, Symbol* signature) {
758 // search from the bottom, might be faster
759 for (int i = (length() - 1); i >= 0; i--) {
760 Method* m = table()[i].method();
761 if (is_miranda_entry_at(i) &&
762 m->name() == name && m->signature() == signature) {
763 return i;
764 }
765 }
766 return Method::invalid_vtable_index;
767 }
768
769 // check if an entry at an index is miranda
770 // requires that method m at entry be declared ("held") by an interface.
771 bool klassVtable::is_miranda_entry_at(int i) {
772 Method* m = method_at(i);
773 InstanceKlass* holder = m->method_holder();
774
775 // miranda methods are public abstract instance interface methods in a class's vtable
776 if (holder->is_interface()) {
777 assert(m->is_public(), "should be public");
778 assert(ik()->implements_interface(holder) , "this class should implement the interface");
779 if (is_miranda(m, ik()->methods(), ik()->default_methods(), ik()->super(), klass()->is_interface())) {
780 return true;
781 }
782 }
783 return false;
784 }
785
786 // Check if a method is a miranda method, given a class's methods array,
787 // its default_method table and its super class.
788 // "Miranda" means an abstract non-private method that would not be
789 // overridden for the local class.
790 // A "miranda" method should only include non-private interface
791 // instance methods, i.e. not private methods, not static methods,
792 // not default methods (concrete interface methods), not overpass methods.
793 // If a given class already has a local (including overpass) method, a
794 // default method, or any of its superclasses has the same which would have
795 // overridden an abstract method, then this is not a miranda method.
796 //
797 // Miranda methods are checked multiple times.
798 // Pass 1: during class load/class file parsing: before vtable size calculation:
799 // include superinterface abstract and default methods (non-private instance).
800 // We include potential default methods to give them space in the vtable.
801 // During the first run, the current instanceKlass has not yet been
802 // created, the superclasses and superinterfaces do have instanceKlasses
803 // but may not have vtables, the default_methods list is empty, no overpasses.
804 // Default method generation uses the all_mirandas array as the starter set for
805 // maximally-specific default method calculation. So, for both classes and
806 // interfaces, it is necessary that the first pass will find all non-private
807 // interface instance methods, whether or not they are concrete.
808 //
809 // Pass 2: recalculated during vtable initialization: only include abstract methods.
810 // The goal of pass 2 is to walk through the superinterfaces to see if any of
811 // the superinterface methods (which were all abstract pre-default methods)
812 // need to be added to the vtable.
813 // With the addition of default methods, we have three new challenges:
814 // overpasses, static interface methods and private interface methods.
815 // Static and private interface methods do not get added to the vtable and
816 // are not seen by the method resolution process, so we skip those.
817 // Overpass methods are already in the vtable, so vtable lookup will
818 // find them and we don't need to add a miranda method to the end of
819 // the vtable. So we look for overpass methods and if they are found we
820 // return false. Note that we inherit our superclasses vtable, so
821 // the superclass' search also needs to use find_overpass so that if
822 // one is found we return false.
823 // False means - we don't need a miranda method added to the vtable.
824 //
825 // During the second run, default_methods is set up, so concrete methods from
826 // superinterfaces with matching names/signatures to default_methods are already
827 // in the default_methods list and do not need to be appended to the vtable
828 // as mirandas. Abstract methods may already have been handled via
829 // overpasses - either local or superclass overpasses, which may be
830 // in the vtable already.
831 //
832 // Pass 3: They are also checked by link resolution and selection,
833 // for invocation on a method (not interface method) reference that
834 // resolves to a method with an interface as its method_holder.
835 // Used as part of walking from the bottom of the vtable to find
836 // the vtable index for the miranda method.
837 //
838 // Part of the Miranda Rights in the US mean that if you do not have
839 // an attorney one will be appointed for you.
840 bool klassVtable::is_miranda(Method* m, Array<Method*>* class_methods,
841 Array<Method*>* default_methods, const Klass* super,
842 bool is_interface) {
843 if (m->is_static() || m->is_private() || m->is_overpass()) {
844 return false;
845 }
846 Symbol* name = m->name();
847 Symbol* signature = m->signature();
848
849 // First look in local methods to see if already covered
850 if (InstanceKlass::find_local_method(class_methods, name, signature,
851 Klass::OverpassLookupMode::find,
852 Klass::StaticLookupMode::skip,
853 Klass::PrivateLookupMode::skip) != nullptr)
854 {
855 return false;
856 }
857
858 // Check local default methods
859 if ((default_methods != nullptr) &&
860 (InstanceKlass::find_method(default_methods, name, signature) != nullptr))
861 {
862 return false;
863 }
864
865 // Iterate on all superclasses, which should be InstanceKlasses.
866 // Note that we explicitly look for overpasses at each level.
867 // Overpasses may or may not exist for supers for pass 1,
868 // they should have been created for pass 2 and later.
869
870 for (const Klass* cursuper = super; cursuper != nullptr; cursuper = cursuper->super())
871 {
872 Method* found_mth = InstanceKlass::cast(cursuper)->find_local_method(name, signature,
873 Klass::OverpassLookupMode::find,
874 Klass::StaticLookupMode::skip,
875 Klass::PrivateLookupMode::skip);
876 // Ignore non-public methods in java.lang.Object if klass is an interface.
877 if (found_mth != nullptr && (!is_interface ||
878 !SystemDictionary::is_nonpublic_Object_method(found_mth))) {
879 return false;
880 }
881 }
882
883 return true;
884 }
885
886 // Scans current_interface_methods for miranda methods that do not
887 // already appear in new_mirandas, or default methods, and are also not defined-and-non-private
888 // in super (superclass). These mirandas are added to all_mirandas if it is
889 // not null; in addition, those that are not duplicates of miranda methods
890 // inherited by super from its interfaces are added to new_mirandas.
891 // Thus, new_mirandas will be the set of mirandas that this class introduces,
892 // all_mirandas will be the set of all mirandas applicable to this class
893 // including all defined in superclasses.
894 void klassVtable::add_new_mirandas_to_lists(
895 GrowableArray<Method*>* new_mirandas, GrowableArray<Method*>* all_mirandas,
896 Array<Method*>* current_interface_methods, Array<Method*>* class_methods,
897 Array<Method*>* default_methods, const Klass* super, bool is_interface) {
898
899 // iterate thru the current interface's method to see if it a miranda
900 int num_methods = current_interface_methods->length();
901 for (int i = 0; i < num_methods; i++) {
902 Method* im = current_interface_methods->at(i);
903 bool is_duplicate = false;
904 int num_of_current_mirandas = new_mirandas->length();
905 // check for duplicate mirandas in different interfaces we implement
906 for (int j = 0; j < num_of_current_mirandas; j++) {
907 Method* miranda = new_mirandas->at(j);
908 if ((im->name() == miranda->name()) &&
909 (im->signature() == miranda->signature())) {
910 is_duplicate = true;
911 break;
912 }
913 }
914
915 if (!is_duplicate) { // we don't want duplicate miranda entries in the vtable
916 if (is_miranda(im, class_methods, default_methods, super, is_interface)) { // is it a miranda at all?
917 const InstanceKlass *sk = InstanceKlass::cast(super);
918 // check if it is a duplicate of a super's miranda
919 if (sk->lookup_method_in_all_interfaces(im->name(), im->signature(), Klass::DefaultsLookupMode::find) == nullptr) {
920 new_mirandas->append(im);
921 }
922 if (all_mirandas != nullptr) {
923 all_mirandas->append(im);
924 }
925 }
926 }
927 }
928 }
929
930 void klassVtable::get_mirandas(GrowableArray<Method*>* new_mirandas,
931 GrowableArray<Method*>* all_mirandas,
932 const Klass* super,
933 Array<Method*>* class_methods,
934 Array<Method*>* default_methods,
935 Array<InstanceKlass*>* local_interfaces,
936 bool is_interface) {
937 assert((new_mirandas->length() == 0) , "current mirandas must be 0");
938
939 // iterate thru the local interfaces looking for a miranda
940 int num_local_ifs = local_interfaces->length();
941 for (int i = 0; i < num_local_ifs; i++) {
942 InstanceKlass *ik = local_interfaces->at(i);
943 add_new_mirandas_to_lists(new_mirandas, all_mirandas,
944 ik->methods(), class_methods,
945 default_methods, super, is_interface);
946 // iterate thru each local's super interfaces
947 Array<InstanceKlass*>* super_ifs = ik->transitive_interfaces();
948 int num_super_ifs = super_ifs->length();
949 for (int j = 0; j < num_super_ifs; j++) {
950 InstanceKlass *sik = super_ifs->at(j);
951 add_new_mirandas_to_lists(new_mirandas, all_mirandas,
952 sik->methods(), class_methods,
953 default_methods, super, is_interface);
954 }
955 }
956 }
957
958 // Discover miranda methods ("miranda" = "interface abstract, no binding"),
959 // and append them into the vtable starting at index initialized,
960 // return the new value of initialized.
961 // Miranda methods use vtable entries, but do not get assigned a vtable_index
962 // The vtable_index is discovered by searching from the end of the vtable
963 int klassVtable::fill_in_mirandas(Thread* current, int initialized) {
964 ResourceMark rm(current);
965 GrowableArray<Method*> mirandas(20);
966 get_mirandas(&mirandas, nullptr, ik()->super(), ik()->methods(),
967 ik()->default_methods(), ik()->local_interfaces(),
968 klass()->is_interface());
969 for (int i = 0; i < mirandas.length(); i++) {
970 if (log_develop_is_enabled(Trace, vtables)) {
971 Method* meth = mirandas.at(i);
972 LogTarget(Trace, vtables) lt;
973 LogStream ls(lt);
974 if (meth != nullptr) {
975 char* sig = meth->name_and_sig_as_C_string();
976 ls.print("fill in mirandas with %s index %d, flags: ",
977 sig, initialized);
978 meth->print_linkage_flags(&ls);
979 ls.cr();
980 }
981 }
982 put_method_at(mirandas.at(i), initialized);
983 ++initialized;
984 }
985 return initialized;
986 }
987
988 // Copy this class's vtable to the vtable beginning at start.
989 // Used to copy superclass vtable to prefix of subclass's vtable.
990 void klassVtable::copy_vtable_to(vtableEntry* start) {
991 Copy::disjoint_words((HeapWord*)table(), (HeapWord*)start, _length * vtableEntry::size());
992 }
993
994 #if INCLUDE_JVMTI
995 bool klassVtable::adjust_default_method(int vtable_index, Method* old_method, Method* new_method) {
996 // If old_method is default, find this vtable index in default_vtable_indices
997 // and replace that method in the _default_methods list
998 bool updated = false;
999
1000 Array<Method*>* default_methods = ik()->default_methods();
1001 if (default_methods != nullptr) {
1002 int len = default_methods->length();
1003 for (int idx = 0; idx < len; idx++) {
1004 if (vtable_index == ik()->default_vtable_indices()->at(idx)) {
1005 if (default_methods->at(idx) == old_method) {
1006 default_methods->at_put(idx, new_method);
1007 updated = true;
1008 }
1009 break;
1010 }
1011 }
1012 }
1013 return updated;
1014 }
1015
1016 // search the vtable for uses of either obsolete or EMCP methods
1017 void klassVtable::adjust_method_entries(bool * trace_name_printed) {
1018 int prn_enabled = 0;
1019 ResourceMark rm;
1020
1021 for (int index = 0; index < length(); index++) {
1022 Method* old_method = unchecked_method_at(index);
1023 if (old_method == nullptr || !old_method->is_old()) {
1024 continue; // skip uninteresting entries
1025 }
1026 assert(!old_method->is_deleted(), "vtable methods may not be deleted");
1027
1028 Method* new_method = old_method->get_new_method();
1029 put_method_at(new_method, index);
1030
1031 // For default methods, need to update the _default_methods array
1032 // which can only have one method entry for a given signature
1033 bool updated_default = false;
1034 if (old_method->is_default_method()) {
1035 updated_default = adjust_default_method(index, old_method, new_method);
1036 }
1037
1038 if (!(*trace_name_printed)) {
1039 log_info(redefine, class, update)
1040 ("adjust: klassname=%s for methods from name=%s",
1041 _klass->external_name(), old_method->method_holder()->external_name());
1042 *trace_name_printed = true;
1043 }
1044 log_trace(redefine, class, update, vtables)
1045 ("vtable method update: class: %s method: %s, updated default = %s",
1046 _klass->external_name(), new_method->external_name(), updated_default ? "true" : "false");
1047 }
1048 }
1049
1050 // a vtable should never contain old or obsolete methods
1051 bool klassVtable::check_no_old_or_obsolete_entries() {
1052 ResourceMark rm;
1053
1054 for (int i = 0; i < length(); i++) {
1055 Method* m = unchecked_method_at(i);
1056 if (m != nullptr &&
1057 (NOT_PRODUCT(!m->is_valid() ||) m->is_old() || m->is_obsolete())) {
1058 log_trace(redefine, class, update, vtables)
1059 ("vtable check found old method entry: class: %s old: %d obsolete: %d, method: %s",
1060 _klass->external_name(), m->is_old(), m->is_obsolete(), m->external_name());
1061 return false;
1062 }
1063 }
1064 return true;
1065 }
1066
1067 void klassVtable::dump_vtable() {
1068 tty->print_cr("vtable dump --");
1069 for (int i = 0; i < length(); i++) {
1070 Method* m = unchecked_method_at(i);
1071 if (m != nullptr) {
1072 tty->print(" (%5d) ", i);
1073 m->access_flags().print_on(tty);
1074 if (m->is_default_method()) {
1075 tty->print("default ");
1076 }
1077 if (m->is_overpass()) {
1078 tty->print("overpass");
1079 }
1080 tty->print(" -- ");
1081 m->print_name(tty);
1082 tty->cr();
1083 }
1084 }
1085 }
1086 #endif // INCLUDE_JVMTI
1087
1088 //-----------------------------------------------------------------------------------------
1089 // Itable code
1090
1091 // Initialize a itableMethodEntry
1092 void itableMethodEntry::initialize(InstanceKlass* klass, Method* m) {
1093 if (m == nullptr) return;
1094
1095 #ifdef ASSERT
1096 if (MetaspaceShared::is_in_shared_metaspace((void*)&_method) &&
1097 !MetaspaceShared::remapped_readwrite() &&
1098 m->method_holder()->verified_at_dump_time() &&
1099 klass->verified_at_dump_time()) {
1100 // At runtime initialize_itable is rerun as part of link_class_impl()
1101 // for a shared class loaded by the non-boot loader.
1102 // The dumptime itable method entry should be the same as the runtime entry.
1103 // For a shared old class which was not linked during dump time, we can't compare the dumptime
1104 // itable method entry with the runtime entry.
1105 assert(_method == m, "sanity");
1106 }
1107 #endif
1108 _method = m;
1109 }
1110
1111 klassItable::klassItable(InstanceKlass* klass) {
1112 _klass = klass;
1113
1114 if (klass->itable_length() > 0) {
1115 itableOffsetEntry* offset_entry = (itableOffsetEntry*)klass->start_of_itable();
1116 if (offset_entry != nullptr && offset_entry->interface_klass() != nullptr) { // Check that itable is initialized
1117 // First offset entry points to the first method_entry
1118 intptr_t* method_entry = (intptr_t *)(((address)klass) + offset_entry->offset());
1119 intptr_t* end = klass->end_of_itable();
1120
1121 _table_offset = int((intptr_t*)offset_entry - (intptr_t*)klass);
1122 _size_offset_table = int((method_entry - ((intptr_t*)offset_entry)) / itableOffsetEntry::size());
1123 _size_method_table = int((end - method_entry) / itableMethodEntry::size());
1124 assert(_table_offset >= 0 && _size_offset_table >= 0 && _size_method_table >= 0, "wrong computation");
1125 return;
1126 }
1127 }
1128
1129 // The length of the itable was either zero, or it has not yet been initialized.
1130 _table_offset = 0;
1131 _size_offset_table = 0;
1132 _size_method_table = 0;
1133 }
1134
1135 static int initialize_count = 0;
1136
1137 // Initialization
1138 void klassItable::initialize_itable(GrowableArray<Method*>* supers) {
1139 if (_klass->is_interface()) {
1140 // This needs to go after vtable indices are assigned but
1141 // before implementors need to know the number of itable indices.
1142 assign_itable_indices_for_interface(InstanceKlass::cast(_klass));
1143 }
1144
1145 // Cannot be setup doing bootstrapping, interfaces don't have
1146 // itables, and klass with only ones entry have empty itables
1147 if (Universe::is_bootstrapping() ||
1148 _klass->is_interface() ||
1149 _klass->itable_length() == itableOffsetEntry::size()) return;
1150
1151 // There's always an extra itable entry so we can null-terminate it.
1152 guarantee(size_offset_table() >= 1, "too small");
1153 int num_interfaces = size_offset_table() - 1;
1154 if (num_interfaces > 0) {
1155 if (log_develop_is_enabled(Debug, itables)) {
1156 ResourceMark rm;
1157 log_develop_debug(itables)("%3d: Initializing itables for %s", ++initialize_count,
1158 _klass->name()->as_C_string());
1159 }
1160
1161 // Iterate through all interfaces
1162 for(int i = 0; i < num_interfaces; i++) {
1163 itableOffsetEntry* ioe = offset_entry(i);
1164 InstanceKlass* interf = ioe->interface_klass();
1165 assert(interf != nullptr && ioe->offset() != 0, "bad offset entry in itable");
1166 initialize_itable_for_interface(ioe->offset(), interf, supers,
1167 (ioe->offset() - offset_entry(0)->offset())/wordSize);
1168 }
1169 }
1170 // Check that the last entry is empty
1171 itableOffsetEntry* ioe = offset_entry(size_offset_table() - 1);
1172 guarantee(ioe->interface_klass() == nullptr && ioe->offset() == 0, "terminator entry missing");
1173 }
1174
1175 void klassItable::check_constraints(GrowableArray<Method*>* supers, TRAPS) {
1176
1177 assert(_size_method_table == supers->length(), "wrong size");
1178 itableMethodEntry* ime = method_entry(0);
1179 for (int i = 0; i < _size_method_table; i++) {
1180 Method* target = ime->method();
1181 Method* interface_method = supers->at(i); // method overridden
1182
1183 if (target != nullptr && interface_method != nullptr) {
1184 InstanceKlass* method_holder = target->method_holder();
1185 InstanceKlass* interf = interface_method->method_holder();
1186 HandleMark hm(THREAD);
1187 Handle method_holder_loader(THREAD, method_holder->class_loader());
1188 Handle interface_loader(THREAD, interf->class_loader());
1189
1190 if (method_holder_loader() != interface_loader()) {
1191 ResourceMark rm(THREAD);
1192 Symbol* failed_type_symbol =
1193 SystemDictionary::check_signature_loaders(target->signature(),
1194 _klass,
1195 method_holder_loader,
1196 interface_loader,
1197 true);
1198 if (failed_type_symbol != nullptr) {
1199 stringStream ss;
1200 ss.print("loader constraint violation in interface itable"
1201 " initialization for class %s: when selecting method '",
1202 _klass->external_name());
1203 interface_method->print_external_name(&ss),
1204 ss.print("' the class loader %s for super interface %s, and the class"
1205 " loader %s of the selected method's %s, %s have"
1206 " different Class objects for the type %s used in the signature (%s; %s)",
1207 interf->class_loader_data()->loader_name_and_id(),
1208 interf->external_name(),
1209 method_holder->class_loader_data()->loader_name_and_id(),
1210 method_holder->external_kind(),
1211 method_holder->external_name(),
1212 failed_type_symbol->as_klass_external_name(),
1213 interf->class_in_module_of_loader(false, true),
1214 method_holder->class_in_module_of_loader(false, true));
1215 THROW_MSG(vmSymbols::java_lang_LinkageError(), ss.as_string());
1216 }
1217 }
1218 }
1219 ime++;
1220 }
1221 }
1222
1223 void klassItable::initialize_itable_and_check_constraints(TRAPS) {
1224 // Save a super interface from each itable entry to do constraint checking
1225 ResourceMark rm(THREAD);
1226 GrowableArray<Method*>* supers =
1227 new GrowableArray<Method*>(_size_method_table, _size_method_table, nullptr);
1228 initialize_itable(supers);
1229 check_constraints(supers, CHECK);
1230 }
1231
1232 inline bool interface_method_needs_itable_index(Method* m) {
1233 if (m->is_static()) return false; // e.g., Stream.empty
1234 if (m->is_initializer()) return false; // <init> or <clinit>
1235 if (m->is_private()) return false; // uses direct call
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 // Visit all interfaces with at least one itable method
1445 void visit_all_interfaces(Array<InstanceKlass*>* transitive_intf, InterfaceVisiterClosure *blk) {
1446 // Handle array argument
1447 for(int i = 0; i < transitive_intf->length(); i++) {
1448 InstanceKlass* intf = transitive_intf->at(i);
1449 assert(intf->is_interface(), "sanity check");
1450
1451 // Find no. of itable methods
1452 int method_count = 0;
1453 // method_count = klassItable::method_count_for_interface(intf);
1454 Array<Method*>* methods = intf->methods();
1455 if (methods->length() > 0) {
1456 for (int i = methods->length(); --i >= 0; ) {
1457 if (interface_method_needs_itable_index(methods->at(i))) {
1458 method_count++;
1459 }
1460 }
1461 }
1462
1463 // Visit all interfaces which either have any methods or can participate in receiver type check.
1464 // We do not bother to count methods in transitive interfaces, although that would allow us to skip
1465 // this step in the rare case of a zero-method interface extending another zero-method interface.
1466 if (method_count > 0 || intf->transitive_interfaces()->length() > 0) {
1467 blk->doit(intf, method_count);
1468 }
1469 }
1470 }
1471
1472 class CountInterfacesClosure : public InterfaceVisiterClosure {
1473 private:
1474 int _nof_methods;
1475 int _nof_interfaces;
1476 public:
1477 CountInterfacesClosure() { _nof_methods = 0; _nof_interfaces = 0; }
1478
1479 int nof_methods() const { return _nof_methods; }
1480 int nof_interfaces() const { return _nof_interfaces; }
1481
1482 void doit(InstanceKlass* intf, int method_count) { _nof_methods += method_count; _nof_interfaces++; }
1483 };
1484
1485 class SetupItableClosure : public InterfaceVisiterClosure {
1486 private:
1487 itableOffsetEntry* _offset_entry;
1488 itableMethodEntry* _method_entry;
1489 address _klass_begin;
1490 public:
1491 SetupItableClosure(address klass_begin, itableOffsetEntry* offset_entry, itableMethodEntry* method_entry) {
1492 _klass_begin = klass_begin;
1493 _offset_entry = offset_entry;
1494 _method_entry = method_entry;
1495 }
1496
1497 itableMethodEntry* method_entry() const { return _method_entry; }
1498
1499 void doit(InstanceKlass* intf, int method_count) {
1500 int offset = int(((address)_method_entry) - _klass_begin);
1501 _offset_entry->initialize(intf, offset);
1502 _offset_entry++;
1503 _method_entry += method_count;
1504 }
1505 };
1506
1507 int klassItable::compute_itable_size(Array<InstanceKlass*>* transitive_interfaces) {
1508 // Count no of interfaces and total number of interface methods
1509 CountInterfacesClosure cic;
1510 visit_all_interfaces(transitive_interfaces, &cic);
1511
1512 // There's always an extra itable entry so we can null-terminate it.
1513 int itable_size = calc_itable_size(cic.nof_interfaces() + 1, cic.nof_methods());
1514
1515 return itable_size;
1516 }
1517
1518
1519 // Fill out offset table and interface klasses into the itable space
1520 void klassItable::setup_itable_offset_table(InstanceKlass* klass) {
1521 if (klass->itable_length() == 0) return;
1522 assert(!klass->is_interface(), "Should have zero length itable");
1523
1524 // Count no of interfaces and total number of interface methods
1525 CountInterfacesClosure cic;
1526 visit_all_interfaces(klass->transitive_interfaces(), &cic);
1527 int nof_methods = cic.nof_methods();
1528 int nof_interfaces = cic.nof_interfaces();
1529
1530 // Add one extra entry so we can null-terminate the table
1531 nof_interfaces++;
1532
1533 assert(compute_itable_size(klass->transitive_interfaces()) ==
1534 calc_itable_size(nof_interfaces, nof_methods),
1535 "mismatch calculation of itable size");
1536
1537 // Fill-out offset table
1538 itableOffsetEntry* ioe = (itableOffsetEntry*)klass->start_of_itable();
1539 itableMethodEntry* ime = (itableMethodEntry*)(ioe + nof_interfaces);
1540 intptr_t* end = klass->end_of_itable();
1541 assert((oop*)(ime + nof_methods) <= (oop*)klass->start_of_nonstatic_oop_maps(), "wrong offset calculation (1)");
1542 assert((oop*)(end) == (oop*)(ime + nof_methods), "wrong offset calculation (2)");
1543
1544 // Visit all interfaces and initialize itable offset table
1545 SetupItableClosure sic((address)klass, ioe, ime);
1546 visit_all_interfaces(klass->transitive_interfaces(), &sic);
1547
1548 #ifdef ASSERT
1549 ime = sic.method_entry();
1550 oop* v = (oop*) klass->end_of_itable();
1551 assert( (oop*)(ime) == v, "wrong offset calculation (2)");
1552 #endif
1553 }
1554
1555 void klassVtable::verify(outputStream* st, bool forced) {
1556 // make sure table is initialized
1557 if (!Universe::is_fully_initialized()) return;
1558 #ifndef PRODUCT
1559 // avoid redundant verifies
1560 if (!forced && _verify_count == Universe::verify_count()) return;
1561 _verify_count = Universe::verify_count();
1562 #endif
1563 oop* end_of_obj = (oop*)_klass + _klass->size();
1564 oop* end_of_vtable = (oop *)&table()[_length];
1565 if (end_of_vtable > end_of_obj) {
1566 ResourceMark rm;
1567 fatal("klass %s: klass object too short (vtable extends beyond end)",
1568 _klass->internal_name());
1569 }
1570
1571 for (int i = 0; i < _length; i++) table()[i].verify(this, st);
1572 // verify consistency with superKlass vtable
1573 Klass* super = _klass->super();
1574 if (super != nullptr) {
1575 InstanceKlass* sk = InstanceKlass::cast(super);
1576 klassVtable vt = sk->vtable();
1577 for (int i = 0; i < vt.length(); i++) {
1578 verify_against(st, &vt, i);
1579 }
1580 }
1581 }
1582
1583 void klassVtable::verify_against(outputStream* st, klassVtable* vt, int index) {
1584 vtableEntry* vte = &vt->table()[index];
1585 if (vte->method()->name() != table()[index].method()->name() ||
1586 vte->method()->signature() != table()[index].method()->signature()) {
1587 fatal("mismatched name/signature of vtable entries");
1588 }
1589 }
1590
1591 #ifndef PRODUCT
1592 void klassVtable::print() {
1593 ResourceMark rm;
1594 tty->print("klassVtable for klass %s (length %d):\n", _klass->internal_name(), length());
1595 for (int i = 0; i < length(); i++) {
1596 table()[i].print();
1597 tty->cr();
1598 }
1599 }
1600 #endif
1601
1602 void vtableEntry::verify(klassVtable* vt, outputStream* st) {
1603 Klass* vtklass = vt->klass();
1604 if (vtklass->is_instance_klass() &&
1605 (InstanceKlass::cast(vtklass)->major_version() >= klassVtable::VTABLE_TRANSITIVE_OVERRIDE_VERSION)) {
1606 assert(method() != nullptr, "must have set method");
1607 }
1608 if (method() != nullptr) {
1609 method()->verify();
1610 // we sub_type, because it could be a miranda method
1611 if (!vtklass->is_subtype_of(method()->method_holder())) {
1612 #ifndef PRODUCT
1613 print();
1614 #endif
1615 fatal("vtableEntry " PTR_FORMAT ": method is from subclass", p2i(this));
1616 }
1617 }
1618 }
1619
1620 #ifndef PRODUCT
1621
1622 void vtableEntry::print() {
1623 ResourceMark rm;
1624 tty->print("vtableEntry %s: ", method()->name()->as_C_string());
1625 if (Verbose) {
1626 tty->print("m " PTR_FORMAT " ", p2i(method()));
1627 }
1628 }
1629 #endif // PRODUCT