1 /*
2 * Copyright (c) 1997, 2018, 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 "jvm.h"
27 #include "classfile/javaClasses.hpp"
28 #include "classfile/systemDictionary.hpp"
29 #include "classfile/vmSymbols.hpp"
30 #include "interpreter/linkResolver.hpp"
31 #include "logging/log.hpp"
32 #include "logging/logStream.hpp"
33 #include "memory/metaspaceShared.hpp"
34 #include "memory/resourceArea.hpp"
35 #include "memory/universe.hpp"
36 #include "oops/instanceKlass.hpp"
37 #include "oops/klassVtable.hpp"
38 #include "oops/method.hpp"
39 #include "oops/objArrayOop.hpp"
40 #include "oops/oop.inline.hpp"
41 #include "runtime/arguments.hpp"
42 #include "runtime/flags/flagSetting.hpp"
43 #include "runtime/handles.inline.hpp"
44 #include "runtime/safepointVerifiers.hpp"
45 #include "utilities/copy.hpp"
46
ik() const47 inline InstanceKlass* klassVtable::ik() const {
48 return InstanceKlass::cast(_klass);
49 }
50
is_preinitialized_vtable()51 bool klassVtable::is_preinitialized_vtable() {
52 return _klass->is_shared() && !MetaspaceShared::remapped_readwrite();
53 }
54
55
56 // this function computes the vtable size (including the size needed for miranda
57 // methods) and the number of miranda methods in this class.
58 // Note on Miranda methods: Let's say there is a class C that implements
59 // interface I, and none of C's superclasses implements I.
60 // Let's say there is an abstract method m in I that neither C
61 // nor any of its super classes implement (i.e there is no method of any access,
62 // with the same name and signature as m), then m is a Miranda method which is
63 // entered as a public abstract method in C's vtable. From then on it should
64 // treated as any other public method in C for method over-ride purposes.
compute_vtable_size_and_num_mirandas(int * vtable_length_ret,int * num_new_mirandas,GrowableArray<Method * > * all_mirandas,const Klass * super,Array<Method * > * methods,AccessFlags class_flags,u2 major_version,Handle classloader,Symbol * classname,Array<Klass * > * local_interfaces,TRAPS)65 void klassVtable::compute_vtable_size_and_num_mirandas(
66 int* vtable_length_ret, int* num_new_mirandas,
67 GrowableArray<Method*>* all_mirandas, const Klass* super,
68 Array<Method*>* methods, AccessFlags class_flags, u2 major_version,
69 Handle classloader, Symbol* classname, Array<Klass*>* local_interfaces,
70 TRAPS) {
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 == NULL ? 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 assert(methods->at(i)->is_method(), "must be a Method*");
83 methodHandle mh(THREAD, methods->at(i));
84
85 if (needs_new_vtable_entry(mh, super, classloader, classname, class_flags, major_version, THREAD)) {
86 assert(!methods->at(i)->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, NULL, 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 == NULL && 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
index_of(Method * m,int len) const130 int klassVtable::index_of(Method* m, int len) const {
131 assert(m->has_vtable_index(), "do not ask this of non-vtable methods");
132 return m->vtable_index();
133 }
134
135 // Copy super class's vtable to the first part (prefix) of this class's vtable,
136 // and return the number of entries copied. Expects that 'super' is the Java
137 // super class (arrays can have "array" super classes that must be skipped).
initialize_from_super(Klass * super)138 int klassVtable::initialize_from_super(Klass* super) {
139 if (super == NULL) {
140 return 0;
141 } else if (is_preinitialized_vtable()) {
142 // A shared class' vtable is preinitialized at dump time. No need to copy
143 // methods from super class for shared class, as that was already done
144 // during archiving time. However, if Jvmti has redefined a class,
145 // copy super class's vtable in case the super class has changed.
146 return super->vtable().length();
147 } else {
148 // copy methods from superKlass
149 klassVtable superVtable = super->vtable();
150 assert(superVtable.length() <= _length, "vtable too short");
151 #ifdef ASSERT
152 superVtable.verify(tty, true);
153 #endif
154 superVtable.copy_vtable_to(table());
155 if (log_develop_is_enabled(Trace, vtables)) {
156 ResourceMark rm;
157 log_develop_trace(vtables)("copy vtable from %s to %s size %d",
158 super->internal_name(), klass()->internal_name(),
159 _length);
160 }
161 return superVtable.length();
162 }
163 }
164
165 //
166 // Revised lookup semantics introduced 1.3 (Kestrel beta)
initialize_vtable(bool checkconstraints,TRAPS)167 void klassVtable::initialize_vtable(bool checkconstraints, TRAPS) {
168
169 // Note: Arrays can have intermediate array supers. Use java_super to skip them.
170 Klass* super = _klass->java_super();
171 int nofNewEntries = 0;
172
173 bool is_shared = _klass->is_shared();
174
175 if (!_klass->is_array_klass()) {
176 ResourceMark rm(THREAD);
177 log_develop_debug(vtables)("Initializing: %s", _klass->name()->as_C_string());
178 }
179
180 #ifdef ASSERT
181 oop* end_of_obj = (oop*)_klass + _klass->size();
182 oop* end_of_vtable = (oop*)&table()[_length];
183 assert(end_of_vtable <= end_of_obj, "vtable extends beyond end");
184 #endif
185
186 if (Universe::is_bootstrapping()) {
187 assert(!is_shared, "sanity");
188 // just clear everything
189 for (int i = 0; i < _length; i++) table()[i].clear();
190 return;
191 }
192
193 int super_vtable_len = initialize_from_super(super);
194 if (_klass->is_array_klass()) {
195 assert(super_vtable_len == _length, "arrays shouldn't introduce new methods");
196 } else {
197 assert(_klass->is_instance_klass(), "must be InstanceKlass");
198
199 Array<Method*>* methods = ik()->methods();
200 int len = methods->length();
201 int initialized = super_vtable_len;
202
203 // Check each of this class's methods against super;
204 // if override, replace in copy of super vtable, otherwise append to end
205 for (int i = 0; i < len; i++) {
206 // update_inherited_vtable can stop for gc - ensure using handles
207 HandleMark hm(THREAD);
208 assert(methods->at(i)->is_method(), "must be a Method*");
209 methodHandle mh(THREAD, methods->at(i));
210
211 bool needs_new_entry = update_inherited_vtable(ik(), mh, super_vtable_len, -1, checkconstraints, CHECK);
212
213 if (needs_new_entry) {
214 put_method_at(mh(), initialized);
215 mh()->set_vtable_index(initialized); // set primary vtable index
216 initialized++;
217 }
218 }
219
220 // update vtable with default_methods
221 Array<Method*>* default_methods = ik()->default_methods();
222 if (default_methods != NULL) {
223 len = default_methods->length();
224 if (len > 0) {
225 Array<int>* def_vtable_indices = NULL;
226 if ((def_vtable_indices = ik()->default_vtable_indices()) == NULL) {
227 assert(!is_shared, "shared class def_vtable_indices does not exist");
228 def_vtable_indices = ik()->create_new_default_vtable_indices(len, CHECK);
229 } else {
230 assert(def_vtable_indices->length() == len, "reinit vtable len?");
231 }
232 for (int i = 0; i < len; i++) {
233 HandleMark hm(THREAD);
234 assert(default_methods->at(i)->is_method(), "must be a Method*");
235 methodHandle mh(THREAD, default_methods->at(i));
236 assert(!mh->is_private(), "private interface method in the default method list");
237 bool needs_new_entry = update_inherited_vtable(ik(), mh, super_vtable_len, i, checkconstraints, CHECK);
238
239 // needs new entry
240 if (needs_new_entry) {
241 put_method_at(mh(), initialized);
242 if (is_preinitialized_vtable()) {
243 // At runtime initialize_vtable is rerun for a shared class
244 // (loaded by the non-boot loader) as part of link_class_impl().
245 // The dumptime vtable index should be the same as the runtime index.
246 assert(def_vtable_indices->at(i) == initialized,
247 "dump time vtable index is different from runtime index");
248 } else {
249 def_vtable_indices->at_put(i, initialized); //set vtable index
250 }
251 initialized++;
252 }
253 }
254 }
255 }
256
257 // add miranda methods; it will also return the updated initialized
258 // Interfaces do not need interface methods in their vtables
259 // This includes miranda methods and during later processing, default methods
260 if (!ik()->is_interface()) {
261 initialized = fill_in_mirandas(initialized);
262 }
263
264 // In class hierarchies where the accessibility is not increasing (i.e., going from private ->
265 // package_private -> public/protected), the vtable might actually be smaller than our initial
266 // calculation, for classfile versions for which we do not do transitive override
267 // calculations.
268 if (ik()->major_version() >= VTABLE_TRANSITIVE_OVERRIDE_VERSION) {
269 assert(initialized == _length, "vtable initialization failed");
270 } else {
271 assert(initialized <= _length, "vtable initialization failed");
272 for(;initialized < _length; initialized++) {
273 table()[initialized].clear();
274 }
275 }
276 NOT_PRODUCT(verify(tty, true));
277 }
278 }
279
280 // Called for cases where a method does not override its superclass' vtable entry
281 // For bytecodes not produced by javac together it is possible that a method does not override
282 // the superclass's method, but might indirectly override a super-super class's vtable entry
283 // If none found, return a null superk, else return the superk of the method this does override
284 // For public and protected methods: if they override a superclass, they will
285 // also be overridden themselves appropriately.
286 // Private methods do not override, and are not overridden and are not in the vtable.
287 // Package Private methods are trickier:
288 // e.g. P1.A, pub m
289 // P2.B extends A, package private m
290 // P1.C extends B, public m
291 // P1.C.m needs to override P1.A.m and can not override P2.B.m
292 // Therefore: all package private methods need their own vtable entries for
293 // them to be the root of an inheritance overriding decision
294 // Package private methods may also override other vtable entries
find_transitive_override(InstanceKlass * initialsuper,const methodHandle & target_method,int vtable_index,Handle target_loader,Symbol * target_classname,Thread * THREAD)295 InstanceKlass* klassVtable::find_transitive_override(InstanceKlass* initialsuper, const methodHandle& target_method,
296 int vtable_index, Handle target_loader, Symbol* target_classname, Thread * THREAD) {
297 InstanceKlass* superk = initialsuper;
298 while (superk != NULL && superk->super() != NULL) {
299 klassVtable ssVtable = (superk->super())->vtable();
300 if (vtable_index < ssVtable.length()) {
301 Method* super_method = ssVtable.method_at(vtable_index);
302 // get the class holding the matching method
303 // make sure you use that class for is_override
304 InstanceKlass* supermethodholder = super_method->method_holder();
305 #ifndef PRODUCT
306 Symbol* name= target_method()->name();
307 Symbol* signature = target_method()->signature();
308 assert(super_method->name() == name && super_method->signature() == signature, "vtable entry name/sig mismatch");
309 #endif
310
311 if (supermethodholder->is_override(super_method, target_loader, target_classname, THREAD)) {
312 if (log_develop_is_enabled(Trace, vtables)) {
313 ResourceMark rm(THREAD);
314 LogTarget(Trace, vtables) lt;
315 LogStream ls(lt);
316 char* sig = target_method()->name_and_sig_as_C_string();
317 ls.print("transitive overriding superclass %s with %s index %d, original flags: ",
318 supermethodholder->internal_name(),
319 sig, vtable_index);
320 super_method->print_linkage_flags(&ls);
321 ls.print("overriders flags: ");
322 target_method->print_linkage_flags(&ls);
323 ls.cr();
324 }
325
326 break; // return found superk
327 }
328 } else {
329 // super class has no vtable entry here, stop transitive search
330 superk = (InstanceKlass*)NULL;
331 break;
332 }
333 // if no override found yet, continue to search up
334 superk = superk->super() == NULL ? NULL : InstanceKlass::cast(superk->super());
335 }
336
337 return superk;
338 }
339
log_vtables(int i,bool overrides,const methodHandle & target_method,Klass * target_klass,Method * super_method,Thread * thread)340 static void log_vtables(int i, bool overrides, const methodHandle& target_method,
341 Klass* target_klass, Method* super_method,
342 Thread* thread) {
343 #ifndef PRODUCT
344 if (log_develop_is_enabled(Trace, vtables)) {
345 ResourceMark rm(thread);
346 LogTarget(Trace, vtables) lt;
347 LogStream ls(lt);
348 char* sig = target_method()->name_and_sig_as_C_string();
349 if (overrides) {
350 ls.print("overriding with %s index %d, original flags: ",
351 sig, i);
352 } else {
353 ls.print("NOT overriding with %s index %d, original flags: ",
354 sig, i);
355 }
356 super_method->print_linkage_flags(&ls);
357 ls.print("overriders flags: ");
358 target_method->print_linkage_flags(&ls);
359 ls.cr();
360 }
361 #endif
362 }
363
364 // Update child's copy of super vtable for overrides
365 // OR return true if a new vtable entry is required.
366 // Only called for InstanceKlass's, i.e. not for arrays
367 // If that changed, could not use _klass as handle for klass
update_inherited_vtable(InstanceKlass * klass,const methodHandle & target_method,int super_vtable_len,int default_index,bool checkconstraints,TRAPS)368 bool klassVtable::update_inherited_vtable(InstanceKlass* klass, const methodHandle& target_method,
369 int super_vtable_len, int default_index,
370 bool checkconstraints, TRAPS) {
371 ResourceMark rm;
372 bool allocate_new = true;
373 assert(klass->is_instance_klass(), "must be InstanceKlass");
374
375 Array<int>* def_vtable_indices = NULL;
376 bool is_default = false;
377
378 // default methods are non-private concrete methods in superinterfaces which are added
379 // to the vtable with their real method_holder.
380 // Since vtable and itable indices share the same storage, don't touch
381 // the default method's real vtable/itable index.
382 // default_vtable_indices stores the vtable value relative to this inheritor
383 if (default_index >= 0 ) {
384 is_default = true;
385 def_vtable_indices = klass->default_vtable_indices();
386 assert(!target_method()->is_private(), "private interface method flagged as default");
387 assert(def_vtable_indices != NULL, "def vtable alloc?");
388 assert(default_index <= def_vtable_indices->length(), "def vtable len?");
389 } else {
390 assert(klass == target_method()->method_holder(), "caller resp.");
391 // Initialize the method's vtable index to "nonvirtual".
392 // If we allocate a vtable entry, we will update it to a non-negative number.
393 target_method()->set_vtable_index(Method::nonvirtual_vtable_index);
394 }
395
396 // Private, static and <init> methods are never in
397 if (target_method()->is_private() || target_method()->is_static() ||
398 (target_method()->name()->fast_compare(vmSymbols::object_initializer_name()) == 0)) {
399 return false;
400 }
401
402 if (target_method->is_final_method(klass->access_flags())) {
403 // a final method never needs a new entry; final methods can be statically
404 // resolved and they have to be present in the vtable only if they override
405 // a super's method, in which case they re-use its entry
406 allocate_new = false;
407 } else if (klass->is_interface()) {
408 allocate_new = false; // see note below in needs_new_vtable_entry
409 // An interface never allocates new vtable slots, only inherits old ones.
410 // This method will either be assigned its own itable index later,
411 // or be assigned an inherited vtable index in the loop below.
412 // default methods inherited by classes store their vtable indices
413 // in the inheritor's default_vtable_indices.
414 // default methods inherited by interfaces may already have a
415 // valid itable index, if so, don't change it.
416 // Overpass methods in an interface will be assigned an itable index later
417 // by an inheriting class.
418 if ((!is_default || !target_method()->has_itable_index())) {
419 target_method()->set_vtable_index(Method::pending_itable_index);
420 }
421 }
422
423 // we need a new entry if there is no superclass
424 Klass* super = klass->super();
425 if (super == NULL) {
426 return allocate_new;
427 }
428
429 // search through the vtable and update overridden entries
430 // Since check_signature_loaders acquires SystemDictionary_lock
431 // which can block for gc, once we are in this loop, use handles
432 // For classfiles built with >= jdk7, we now look for transitive overrides
433
434 Symbol* name = target_method()->name();
435 Symbol* signature = target_method()->signature();
436
437 Klass* target_klass = target_method()->method_holder();
438 if (target_klass == NULL) {
439 target_klass = _klass;
440 }
441
442 Handle target_loader(THREAD, target_klass->class_loader());
443
444 Symbol* target_classname = target_klass->name();
445 for(int i = 0; i < super_vtable_len; i++) {
446 Method* super_method;
447 if (is_preinitialized_vtable()) {
448 // If this is a shared class, the vtable is already in the final state (fully
449 // initialized). Need to look at the super's vtable.
450 klassVtable superVtable = super->vtable();
451 super_method = superVtable.method_at(i);
452 } else {
453 super_method = method_at(i);
454 }
455 // Check if method name matches. Ignore match if klass is an interface and the
456 // matching method is a non-public java.lang.Object method. (See JVMS 5.4.3.4)
457 // This is safe because the method at this slot should never get invoked.
458 // (TBD: put in a method to throw NoSuchMethodError if this slot is ever used.)
459 if (super_method->name() == name && super_method->signature() == signature &&
460 (!_klass->is_interface() ||
461 !SystemDictionary::is_nonpublic_Object_method(super_method))) {
462
463 // get super_klass for method_holder for the found method
464 InstanceKlass* super_klass = super_method->method_holder();
465
466 // Whether the method is being overridden
467 bool overrides = false;
468
469 // private methods are also never overridden
470 if (!super_method->is_private() &&
471 (is_default
472 || ((super_klass->is_override(super_method, target_loader, target_classname, THREAD))
473 || ((klass->major_version() >= VTABLE_TRANSITIVE_OVERRIDE_VERSION)
474 && ((super_klass = find_transitive_override(super_klass,
475 target_method, i, target_loader,
476 target_classname, THREAD))
477 != (InstanceKlass*)NULL)))))
478 {
479 // Package private methods always need a new entry to root their own
480 // overriding. They may also override other methods.
481 if (!target_method()->is_package_private()) {
482 allocate_new = false;
483 }
484
485 // Do not check loader constraints for overpass methods because overpass
486 // methods are created by the jvm to throw exceptions.
487 if (checkconstraints && !target_method()->is_overpass()) {
488 // Override vtable entry if passes loader constraint check
489 // if loader constraint checking requested
490 // No need to visit his super, since he and his super
491 // have already made any needed loader constraints.
492 // Since loader constraints are transitive, it is enough
493 // to link to the first super, and we get all the others.
494 Handle super_loader(THREAD, super_klass->class_loader());
495
496 if (target_loader() != super_loader()) {
497 ResourceMark rm(THREAD);
498 Symbol* failed_type_symbol =
499 SystemDictionary::check_signature_loaders(signature, target_loader,
500 super_loader, true,
501 CHECK_(false));
502 if (failed_type_symbol != NULL) {
503 stringStream ss;
504 ss.print("loader constraint violation for class %s: when selecting "
505 "overriding method '", klass->external_name());
506 target_method()->print_external_name(&ss),
507 ss.print("' the class loader %s of the "
508 "selected method's type %s, and the class loader %s for its super "
509 "type %s have different Class objects for the type %s used in the signature (%s; %s)",
510 target_klass->class_loader_data()->loader_name_and_id(),
511 target_klass->external_name(),
512 super_klass->class_loader_data()->loader_name_and_id(),
513 super_klass->external_name(),
514 failed_type_symbol->as_klass_external_name(),
515 target_klass->class_in_module_of_loader(false, true),
516 super_klass->class_in_module_of_loader(false, true));
517 THROW_MSG_(vmSymbols::java_lang_LinkageError(), ss.as_string(), false);
518 }
519 }
520 }
521
522 put_method_at(target_method(), i);
523 overrides = true;
524 if (!is_default) {
525 target_method()->set_vtable_index(i);
526 } else {
527 if (def_vtable_indices != NULL) {
528 if (is_preinitialized_vtable()) {
529 // At runtime initialize_vtable is rerun as part of link_class_impl()
530 // for a shared class loaded by the non-boot loader.
531 // The dumptime vtable index should be the same as the runtime index.
532 assert(def_vtable_indices->at(default_index) == i,
533 "dump time vtable index is different from runtime index");
534 } else {
535 def_vtable_indices->at_put(default_index, i);
536 }
537 }
538 assert(super_method->is_default_method() || super_method->is_overpass()
539 || super_method->is_abstract(), "default override error");
540 }
541 } else {
542 overrides = false;
543 }
544 log_vtables(i, overrides, target_method, target_klass, super_method, THREAD);
545 }
546 }
547 return allocate_new;
548 }
549
put_method_at(Method * m,int index)550 void klassVtable::put_method_at(Method* m, int index) {
551 assert(!m->is_private(), "private methods should not be in vtable");
552 if (is_preinitialized_vtable()) {
553 // At runtime initialize_vtable is rerun as part of link_class_impl()
554 // for shared class loaded by the non-boot loader to obtain the loader
555 // constraints based on the runtime classloaders' context. The dumptime
556 // method at the vtable index should be the same as the runtime method.
557 assert(table()[index].method() == m,
558 "archived method is different from the runtime method");
559 } else {
560 if (log_develop_is_enabled(Trace, vtables)) {
561 ResourceMark rm;
562 LogTarget(Trace, vtables) lt;
563 LogStream ls(lt);
564 const char* sig = (m != NULL) ? m->name_and_sig_as_C_string() : "<NULL>";
565 ls.print("adding %s at index %d, flags: ", sig, index);
566 if (m != NULL) {
567 m->print_linkage_flags(&ls);
568 }
569 ls.cr();
570 }
571 table()[index].set(m);
572 }
573 }
574
575 // Find out if a method "m" with superclass "super", loader "classloader" and
576 // name "classname" needs a new vtable entry. Let P be a class package defined
577 // by "classloader" and "classname".
578 // NOTE: The logic used here is very similar to the one used for computing
579 // the vtables indices for a method. We cannot directly use that function because,
580 // we allocate the InstanceKlass at load time, and that requires that the
581 // superclass has been loaded.
582 // However, the vtable entries are filled in at link time, and therefore
583 // the superclass' vtable may not yet have been filled in.
needs_new_vtable_entry(const methodHandle & target_method,const Klass * super,Handle classloader,Symbol * classname,AccessFlags class_flags,u2 major_version,TRAPS)584 bool klassVtable::needs_new_vtable_entry(const methodHandle& target_method,
585 const Klass* super,
586 Handle classloader,
587 Symbol* classname,
588 AccessFlags class_flags,
589 u2 major_version,
590 TRAPS) {
591 if (class_flags.is_interface()) {
592 // Interfaces do not use vtables, except for java.lang.Object methods,
593 // so there is no point to assigning
594 // a vtable index to any of their local methods. If we refrain from doing this,
595 // we can use Method::_vtable_index to hold the itable index
596 return false;
597 }
598
599 if (target_method->is_final_method(class_flags) ||
600 // a final method never needs a new entry; final methods can be statically
601 // resolved and they have to be present in the vtable only if they override
602 // a super's method, in which case they re-use its entry
603 (target_method()->is_private()) ||
604 // private methods don't need to be in vtable
605 (target_method()->is_static()) ||
606 // static methods don't need to be in vtable
607 (target_method()->name()->fast_compare(vmSymbols::object_initializer_name()) == 0)
608 // <init> is never called dynamically-bound
609 ) {
610 return false;
611 }
612
613 // Concrete interface methods do not need new entries, they override
614 // abstract method entries using default inheritance rules
615 if (target_method()->method_holder() != NULL &&
616 target_method()->method_holder()->is_interface() &&
617 !target_method()->is_abstract()) {
618 assert(target_method()->is_default_method(),
619 "unexpected interface method type");
620 return false;
621 }
622
623 // we need a new entry if there is no superclass
624 if (super == NULL) {
625 return true;
626 }
627
628 // Package private methods always need a new entry to root their own
629 // overriding. This allows transitive overriding to work.
630 if (target_method()->is_package_private()) {
631 return true;
632 }
633
634 // search through the super class hierarchy to see if we need
635 // a new entry
636 ResourceMark rm(THREAD);
637 Symbol* name = target_method()->name();
638 Symbol* signature = target_method()->signature();
639 const Klass* k = super;
640 Method* super_method = NULL;
641 InstanceKlass *holder = NULL;
642 Method* recheck_method = NULL;
643 bool found_pkg_prvt_method = false;
644 while (k != NULL) {
645 // lookup through the hierarchy for a method with matching name and sign.
646 super_method = InstanceKlass::cast(k)->lookup_method(name, signature);
647 if (super_method == NULL) {
648 break; // we still have to search for a matching miranda method
649 }
650 // get the class holding the matching method
651 // make sure you use that class for is_override
652 InstanceKlass* superk = super_method->method_holder();
653 // we want only instance method matches
654 // ignore private methods found via lookup_method since they do not participate in overriding,
655 // and since we do override around them: e.g. a.m pub/b.m private/c.m pub,
656 // ignore private, c.m pub does override a.m pub
657 // For classes that were not javac'd together, we also do transitive overriding around
658 // methods that have less accessibility
659 if ((!super_method->is_static()) &&
660 (!super_method->is_private())) {
661 if (superk->is_override(super_method, classloader, classname, THREAD)) {
662 return false;
663 // else keep looking for transitive overrides
664 }
665 // If we get here then one of the super classes has a package private method
666 // that will not get overridden because it is in a different package. But,
667 // that package private method does "override" any matching methods in super
668 // interfaces, so there will be no miranda vtable entry created. So, set flag
669 // to TRUE for use below, in case there are no methods in super classes that
670 // this target method overrides.
671 assert(super_method->is_package_private(), "super_method must be package private");
672 assert(!superk->is_same_class_package(classloader(), classname),
673 "Must be different packages");
674 found_pkg_prvt_method = true;
675 }
676
677 // Start with lookup result and continue to search up, for versions supporting transitive override
678 if (major_version >= VTABLE_TRANSITIVE_OVERRIDE_VERSION) {
679 k = superk->super(); // haven't found an override match yet; continue to look
680 } else {
681 break;
682 }
683 }
684
685 // If found_pkg_prvt_method is set, then the ONLY matching method in the
686 // superclasses is package private in another package. That matching method will
687 // prevent a miranda vtable entry from being created. Because the target method can not
688 // override the package private method in another package, then it needs to be the root
689 // for its own vtable entry.
690 if (found_pkg_prvt_method) {
691 return true;
692 }
693
694 // if the target method is public or protected it may have a matching
695 // miranda method in the super, whose entry it should re-use.
696 // Actually, to handle cases that javac would not generate, we need
697 // this check for all access permissions.
698 const InstanceKlass *sk = InstanceKlass::cast(super);
699 if (sk->has_miranda_methods()) {
700 if (sk->lookup_method_in_all_interfaces(name, signature, Klass::find_defaults) != NULL) {
701 return false; // found a matching miranda; we do not need a new entry
702 }
703 }
704 return true; // found no match; we need a new entry
705 }
706
707 // Support for miranda methods
708
709 // get the vtable index of a miranda method with matching "name" and "signature"
index_of_miranda(Symbol * name,Symbol * signature)710 int klassVtable::index_of_miranda(Symbol* name, Symbol* signature) {
711 // search from the bottom, might be faster
712 for (int i = (length() - 1); i >= 0; i--) {
713 Method* m = table()[i].method();
714 if (is_miranda_entry_at(i) &&
715 m->name() == name && m->signature() == signature) {
716 return i;
717 }
718 }
719 return Method::invalid_vtable_index;
720 }
721
722 // check if an entry at an index is miranda
723 // requires that method m at entry be declared ("held") by an interface.
is_miranda_entry_at(int i)724 bool klassVtable::is_miranda_entry_at(int i) {
725 Method* m = method_at(i);
726 Klass* method_holder = m->method_holder();
727 InstanceKlass *mhk = InstanceKlass::cast(method_holder);
728
729 // miranda methods are public abstract instance interface methods in a class's vtable
730 if (mhk->is_interface()) {
731 assert(m->is_public(), "should be public");
732 assert(ik()->implements_interface(method_holder) , "this class should implement the interface");
733 if (is_miranda(m, ik()->methods(), ik()->default_methods(), ik()->super(), klass()->is_interface())) {
734 return true;
735 }
736 }
737 return false;
738 }
739
740 // Check if a method is a miranda method, given a class's methods array,
741 // its default_method table and its super class.
742 // "Miranda" means an abstract non-private method that would not be
743 // overridden for the local class.
744 // A "miranda" method should only include non-private interface
745 // instance methods, i.e. not private methods, not static methods,
746 // not default methods (concrete interface methods), not overpass methods.
747 // If a given class already has a local (including overpass) method, a
748 // default method, or any of its superclasses has the same which would have
749 // overridden an abstract method, then this is not a miranda method.
750 //
751 // Miranda methods are checked multiple times.
752 // Pass 1: during class load/class file parsing: before vtable size calculation:
753 // include superinterface abstract and default methods (non-private instance).
754 // We include potential default methods to give them space in the vtable.
755 // During the first run, the current instanceKlass has not yet been
756 // created, the superclasses and superinterfaces do have instanceKlasses
757 // but may not have vtables, the default_methods list is empty, no overpasses.
758 // Default method generation uses the all_mirandas array as the starter set for
759 // maximally-specific default method calculation. So, for both classes and
760 // interfaces, it is necessary that the first pass will find all non-private
761 // interface instance methods, whether or not they are concrete.
762 //
763 // Pass 2: recalculated during vtable initialization: only include abstract methods.
764 // The goal of pass 2 is to walk through the superinterfaces to see if any of
765 // the superinterface methods (which were all abstract pre-default methods)
766 // need to be added to the vtable.
767 // With the addition of default methods, we have three new challenges:
768 // overpasses, static interface methods and private interface methods.
769 // Static and private interface methods do not get added to the vtable and
770 // are not seen by the method resolution process, so we skip those.
771 // Overpass methods are already in the vtable, so vtable lookup will
772 // find them and we don't need to add a miranda method to the end of
773 // the vtable. So we look for overpass methods and if they are found we
774 // return false. Note that we inherit our superclasses vtable, so
775 // the superclass' search also needs to use find_overpass so that if
776 // one is found we return false.
777 // False means - we don't need a miranda method added to the vtable.
778 //
779 // During the second run, default_methods is set up, so concrete methods from
780 // superinterfaces with matching names/signatures to default_methods are already
781 // in the default_methods list and do not need to be appended to the vtable
782 // as mirandas. Abstract methods may already have been handled via
783 // overpasses - either local or superclass overpasses, which may be
784 // in the vtable already.
785 //
786 // Pass 3: They are also checked by link resolution and selection,
787 // for invocation on a method (not interface method) reference that
788 // resolves to a method with an interface as its method_holder.
789 // Used as part of walking from the bottom of the vtable to find
790 // the vtable index for the miranda method.
791 //
792 // Part of the Miranda Rights in the US mean that if you do not have
793 // an attorney one will be appointed for you.
is_miranda(Method * m,Array<Method * > * class_methods,Array<Method * > * default_methods,const Klass * super,bool is_interface)794 bool klassVtable::is_miranda(Method* m, Array<Method*>* class_methods,
795 Array<Method*>* default_methods, const Klass* super,
796 bool is_interface) {
797 if (m->is_static() || m->is_private() || m->is_overpass()) {
798 return false;
799 }
800 Symbol* name = m->name();
801 Symbol* signature = m->signature();
802
803 // First look in local methods to see if already covered
804 if (InstanceKlass::find_local_method(class_methods, name, signature,
805 Klass::find_overpass, Klass::skip_static, Klass::skip_private) != NULL)
806 {
807 return false;
808 }
809
810 // Check local default methods
811 if ((default_methods != NULL) &&
812 (InstanceKlass::find_method(default_methods, name, signature) != NULL))
813 {
814 return false;
815 }
816
817 // Iterate on all superclasses, which should be InstanceKlasses.
818 // Note that we explicitly look for overpasses at each level.
819 // Overpasses may or may not exist for supers for pass 1,
820 // they should have been created for pass 2 and later.
821
822 for (const Klass* cursuper = super; cursuper != NULL; cursuper = cursuper->super())
823 {
824 Method* found_mth = InstanceKlass::cast(cursuper)->find_local_method(name, signature,
825 Klass::find_overpass, Klass::skip_static, Klass::skip_private);
826 // Ignore non-public methods in java.lang.Object if klass is an interface.
827 if (found_mth != NULL && (!is_interface ||
828 !SystemDictionary::is_nonpublic_Object_method(found_mth))) {
829 return false;
830 }
831 }
832
833 return true;
834 }
835
836 // Scans current_interface_methods for miranda methods that do not
837 // already appear in new_mirandas, or default methods, and are also not defined-and-non-private
838 // in super (superclass). These mirandas are added to all_mirandas if it is
839 // not null; in addition, those that are not duplicates of miranda methods
840 // inherited by super from its interfaces are added to new_mirandas.
841 // Thus, new_mirandas will be the set of mirandas that this class introduces,
842 // all_mirandas will be the set of all mirandas applicable to this class
843 // including all defined in superclasses.
add_new_mirandas_to_lists(GrowableArray<Method * > * new_mirandas,GrowableArray<Method * > * all_mirandas,Array<Method * > * current_interface_methods,Array<Method * > * class_methods,Array<Method * > * default_methods,const Klass * super,bool is_interface)844 void klassVtable::add_new_mirandas_to_lists(
845 GrowableArray<Method*>* new_mirandas, GrowableArray<Method*>* all_mirandas,
846 Array<Method*>* current_interface_methods, Array<Method*>* class_methods,
847 Array<Method*>* default_methods, const Klass* super, bool is_interface) {
848
849 // iterate thru the current interface's method to see if it a miranda
850 int num_methods = current_interface_methods->length();
851 for (int i = 0; i < num_methods; i++) {
852 Method* im = current_interface_methods->at(i);
853 bool is_duplicate = false;
854 int num_of_current_mirandas = new_mirandas->length();
855 // check for duplicate mirandas in different interfaces we implement
856 for (int j = 0; j < num_of_current_mirandas; j++) {
857 Method* miranda = new_mirandas->at(j);
858 if ((im->name() == miranda->name()) &&
859 (im->signature() == miranda->signature())) {
860 is_duplicate = true;
861 break;
862 }
863 }
864
865 if (!is_duplicate) { // we don't want duplicate miranda entries in the vtable
866 if (is_miranda(im, class_methods, default_methods, super, is_interface)) { // is it a miranda at all?
867 const InstanceKlass *sk = InstanceKlass::cast(super);
868 // check if it is a duplicate of a super's miranda
869 if (sk->lookup_method_in_all_interfaces(im->name(), im->signature(), Klass::find_defaults) == NULL) {
870 new_mirandas->append(im);
871 }
872 if (all_mirandas != NULL) {
873 all_mirandas->append(im);
874 }
875 }
876 }
877 }
878 }
879
get_mirandas(GrowableArray<Method * > * new_mirandas,GrowableArray<Method * > * all_mirandas,const Klass * super,Array<Method * > * class_methods,Array<Method * > * default_methods,Array<Klass * > * local_interfaces,bool is_interface)880 void klassVtable::get_mirandas(GrowableArray<Method*>* new_mirandas,
881 GrowableArray<Method*>* all_mirandas,
882 const Klass* super,
883 Array<Method*>* class_methods,
884 Array<Method*>* default_methods,
885 Array<Klass*>* local_interfaces,
886 bool is_interface) {
887 assert((new_mirandas->length() == 0) , "current mirandas must be 0");
888
889 // iterate thru the local interfaces looking for a miranda
890 int num_local_ifs = local_interfaces->length();
891 for (int i = 0; i < num_local_ifs; i++) {
892 InstanceKlass *ik = InstanceKlass::cast(local_interfaces->at(i));
893 add_new_mirandas_to_lists(new_mirandas, all_mirandas,
894 ik->methods(), class_methods,
895 default_methods, super, is_interface);
896 // iterate thru each local's super interfaces
897 Array<Klass*>* super_ifs = ik->transitive_interfaces();
898 int num_super_ifs = super_ifs->length();
899 for (int j = 0; j < num_super_ifs; j++) {
900 InstanceKlass *sik = InstanceKlass::cast(super_ifs->at(j));
901 add_new_mirandas_to_lists(new_mirandas, all_mirandas,
902 sik->methods(), class_methods,
903 default_methods, super, is_interface);
904 }
905 }
906 }
907
908 // Discover miranda methods ("miranda" = "interface abstract, no binding"),
909 // and append them into the vtable starting at index initialized,
910 // return the new value of initialized.
911 // Miranda methods use vtable entries, but do not get assigned a vtable_index
912 // The vtable_index is discovered by searching from the end of the vtable
fill_in_mirandas(int initialized)913 int klassVtable::fill_in_mirandas(int initialized) {
914 GrowableArray<Method*> mirandas(20);
915 get_mirandas(&mirandas, NULL, ik()->super(), ik()->methods(),
916 ik()->default_methods(), ik()->local_interfaces(),
917 klass()->is_interface());
918 for (int i = 0; i < mirandas.length(); i++) {
919 if (log_develop_is_enabled(Trace, vtables)) {
920 Method* meth = mirandas.at(i);
921 ResourceMark rm(Thread::current());
922 LogTarget(Trace, vtables) lt;
923 LogStream ls(lt);
924 if (meth != NULL) {
925 char* sig = meth->name_and_sig_as_C_string();
926 ls.print("fill in mirandas with %s index %d, flags: ",
927 sig, initialized);
928 meth->print_linkage_flags(&ls);
929 ls.cr();
930 }
931 }
932 put_method_at(mirandas.at(i), initialized);
933 ++initialized;
934 }
935 return initialized;
936 }
937
938 // Copy this class's vtable to the vtable beginning at start.
939 // Used to copy superclass vtable to prefix of subclass's vtable.
copy_vtable_to(vtableEntry * start)940 void klassVtable::copy_vtable_to(vtableEntry* start) {
941 Copy::disjoint_words((HeapWord*)table(), (HeapWord*)start, _length * vtableEntry::size());
942 }
943
944 #if INCLUDE_JVMTI
adjust_default_method(int vtable_index,Method * old_method,Method * new_method)945 bool klassVtable::adjust_default_method(int vtable_index, Method* old_method, Method* new_method) {
946 // If old_method is default, find this vtable index in default_vtable_indices
947 // and replace that method in the _default_methods list
948 bool updated = false;
949
950 Array<Method*>* default_methods = ik()->default_methods();
951 if (default_methods != NULL) {
952 int len = default_methods->length();
953 for (int idx = 0; idx < len; idx++) {
954 if (vtable_index == ik()->default_vtable_indices()->at(idx)) {
955 if (default_methods->at(idx) == old_method) {
956 default_methods->at_put(idx, new_method);
957 updated = true;
958 }
959 break;
960 }
961 }
962 }
963 return updated;
964 }
965
966 // search the vtable for uses of either obsolete or EMCP methods
adjust_method_entries(InstanceKlass * holder,bool * trace_name_printed)967 void klassVtable::adjust_method_entries(InstanceKlass* holder, bool * trace_name_printed) {
968 int prn_enabled = 0;
969 for (int index = 0; index < length(); index++) {
970 Method* old_method = unchecked_method_at(index);
971 if (old_method == NULL || old_method->method_holder() != holder || !old_method->is_old()) {
972 continue; // skip uninteresting entries
973 }
974 assert(!old_method->is_deleted(), "vtable methods may not be deleted");
975
976 Method* new_method = holder->method_with_idnum(old_method->orig_method_idnum());
977
978 assert(new_method != NULL, "method_with_idnum() should not be NULL");
979 assert(old_method != new_method, "sanity check");
980
981 put_method_at(new_method, index);
982 // For default methods, need to update the _default_methods array
983 // which can only have one method entry for a given signature
984 bool updated_default = false;
985 if (old_method->is_default_method()) {
986 updated_default = adjust_default_method(index, old_method, new_method);
987 }
988
989 if (log_is_enabled(Info, redefine, class, update)) {
990 ResourceMark rm;
991 if (!(*trace_name_printed)) {
992 log_info(redefine, class, update)
993 ("adjust: klassname=%s for methods from name=%s",
994 _klass->external_name(), old_method->method_holder()->external_name());
995 *trace_name_printed = true;
996 }
997 log_debug(redefine, class, update, vtables)
998 ("vtable method update: %s(%s), updated default = %s",
999 new_method->name()->as_C_string(), new_method->signature()->as_C_string(), updated_default ? "true" : "false");
1000 }
1001 }
1002 }
1003
1004 // a vtable should never contain old or obsolete methods
check_no_old_or_obsolete_entries()1005 bool klassVtable::check_no_old_or_obsolete_entries() {
1006 for (int i = 0; i < length(); i++) {
1007 Method* m = unchecked_method_at(i);
1008 if (m != NULL &&
1009 (NOT_PRODUCT(!m->is_valid() ||) m->is_old() || m->is_obsolete())) {
1010 return false;
1011 }
1012 }
1013 return true;
1014 }
1015
dump_vtable()1016 void klassVtable::dump_vtable() {
1017 tty->print_cr("vtable dump --");
1018 for (int i = 0; i < length(); i++) {
1019 Method* m = unchecked_method_at(i);
1020 if (m != NULL) {
1021 tty->print(" (%5d) ", i);
1022 m->access_flags().print_on(tty);
1023 if (m->is_default_method()) {
1024 tty->print("default ");
1025 }
1026 if (m->is_overpass()) {
1027 tty->print("overpass");
1028 }
1029 tty->print(" -- ");
1030 m->print_name(tty);
1031 tty->cr();
1032 }
1033 }
1034 }
1035 #endif // INCLUDE_JVMTI
1036
1037 // CDS/RedefineClasses support - clear vtables so they can be reinitialized
clear_vtable()1038 void klassVtable::clear_vtable() {
1039 for (int i = 0; i < _length; i++) table()[i].clear();
1040 }
1041
is_initialized()1042 bool klassVtable::is_initialized() {
1043 return _length == 0 || table()[0].method() != NULL;
1044 }
1045
1046 //-----------------------------------------------------------------------------------------
1047 // Itable code
1048
1049 // Initialize a itableMethodEntry
initialize(Method * m)1050 void itableMethodEntry::initialize(Method* m) {
1051 if (m == NULL) return;
1052
1053 #ifdef ASSERT
1054 if (MetaspaceShared::is_in_shared_metaspace((void*)&_method) &&
1055 !MetaspaceShared::remapped_readwrite()) {
1056 // At runtime initialize_itable is rerun as part of link_class_impl()
1057 // for a shared class loaded by the non-boot loader.
1058 // The dumptime itable method entry should be the same as the runtime entry.
1059 assert(_method == m, "sanity");
1060 }
1061 #endif
1062 _method = m;
1063 }
1064
klassItable(InstanceKlass * klass)1065 klassItable::klassItable(InstanceKlass* klass) {
1066 _klass = klass;
1067
1068 if (klass->itable_length() > 0) {
1069 itableOffsetEntry* offset_entry = (itableOffsetEntry*)klass->start_of_itable();
1070 if (offset_entry != NULL && offset_entry->interface_klass() != NULL) { // Check that itable is initialized
1071 // First offset entry points to the first method_entry
1072 intptr_t* method_entry = (intptr_t *)(((address)klass) + offset_entry->offset());
1073 intptr_t* end = klass->end_of_itable();
1074
1075 _table_offset = (intptr_t*)offset_entry - (intptr_t*)klass;
1076 _size_offset_table = (method_entry - ((intptr_t*)offset_entry)) / itableOffsetEntry::size();
1077 _size_method_table = (end - method_entry) / itableMethodEntry::size();
1078 assert(_table_offset >= 0 && _size_offset_table >= 0 && _size_method_table >= 0, "wrong computation");
1079 return;
1080 }
1081 }
1082
1083 // The length of the itable was either zero, or it has not yet been initialized.
1084 _table_offset = 0;
1085 _size_offset_table = 0;
1086 _size_method_table = 0;
1087 }
1088
1089 static int initialize_count = 0;
1090
1091 // Initialization
initialize_itable(bool checkconstraints,TRAPS)1092 void klassItable::initialize_itable(bool checkconstraints, TRAPS) {
1093 if (_klass->is_interface()) {
1094 // This needs to go after vtable indices are assigned but
1095 // before implementors need to know the number of itable indices.
1096 assign_itable_indices_for_interface(_klass);
1097 }
1098
1099 // Cannot be setup doing bootstrapping, interfaces don't have
1100 // itables, and klass with only ones entry have empty itables
1101 if (Universe::is_bootstrapping() ||
1102 _klass->is_interface() ||
1103 _klass->itable_length() == itableOffsetEntry::size()) return;
1104
1105 // There's alway an extra itable entry so we can null-terminate it.
1106 guarantee(size_offset_table() >= 1, "too small");
1107 int num_interfaces = size_offset_table() - 1;
1108 if (num_interfaces > 0) {
1109 log_develop_debug(itables)("%3d: Initializing itables for %s", ++initialize_count,
1110 _klass->name()->as_C_string());
1111
1112
1113 // Iterate through all interfaces
1114 int i;
1115 for(i = 0; i < num_interfaces; i++) {
1116 itableOffsetEntry* ioe = offset_entry(i);
1117 HandleMark hm(THREAD);
1118 Klass* interf = ioe->interface_klass();
1119 assert(interf != NULL && ioe->offset() != 0, "bad offset entry in itable");
1120 initialize_itable_for_interface(ioe->offset(), interf, checkconstraints, CHECK);
1121 }
1122
1123 }
1124 // Check that the last entry is empty
1125 itableOffsetEntry* ioe = offset_entry(size_offset_table() - 1);
1126 guarantee(ioe->interface_klass() == NULL && ioe->offset() == 0, "terminator entry missing");
1127 }
1128
1129
interface_method_needs_itable_index(Method * m)1130 inline bool interface_method_needs_itable_index(Method* m) {
1131 if (m->is_static()) return false; // e.g., Stream.empty
1132 if (m->is_initializer()) return false; // <init> or <clinit>
1133 if (m->is_private()) return false; // uses direct call
1134 // If an interface redeclares a method from java.lang.Object,
1135 // it should already have a vtable index, don't touch it.
1136 // e.g., CharSequence.toString (from initialize_vtable)
1137 // if (m->has_vtable_index()) return false; // NO!
1138 return true;
1139 }
1140
assign_itable_indices_for_interface(Klass * klass)1141 int klassItable::assign_itable_indices_for_interface(Klass* klass) {
1142 // an interface does not have an itable, but its methods need to be numbered
1143 log_develop_debug(itables)("%3d: Initializing itable indices for interface %s",
1144 ++initialize_count, klass->name()->as_C_string());
1145 Array<Method*>* methods = InstanceKlass::cast(klass)->methods();
1146 int nof_methods = methods->length();
1147 int ime_num = 0;
1148 for (int i = 0; i < nof_methods; i++) {
1149 Method* m = methods->at(i);
1150 if (interface_method_needs_itable_index(m)) {
1151 assert(!m->is_final_method(), "no final interface methods");
1152 // If m is already assigned a vtable index, do not disturb it.
1153 if (log_develop_is_enabled(Trace, itables)) {
1154 ResourceMark rm;
1155 LogTarget(Trace, itables) lt;
1156 LogStream ls(lt);
1157 assert(m != NULL, "methods can never be null");
1158 const char* sig = m->name_and_sig_as_C_string();
1159 if (m->has_vtable_index()) {
1160 ls.print("vtable index %d for method: %s, flags: ", m->vtable_index(), sig);
1161 } else {
1162 ls.print("itable index %d for method: %s, flags: ", ime_num, sig);
1163 }
1164 m->print_linkage_flags(&ls);
1165 ls.cr();
1166 }
1167 if (!m->has_vtable_index()) {
1168 // A shared method could have an initialized itable_index that
1169 // is < 0.
1170 assert(m->vtable_index() == Method::pending_itable_index ||
1171 m->is_shared(),
1172 "set by initialize_vtable");
1173 m->set_itable_index(ime_num);
1174 // Progress to next itable entry
1175 ime_num++;
1176 }
1177 }
1178 }
1179 assert(ime_num == method_count_for_interface(klass), "proper sizing");
1180 return ime_num;
1181 }
1182
method_count_for_interface(Klass * interf)1183 int klassItable::method_count_for_interface(Klass* interf) {
1184 assert(interf->is_instance_klass(), "must be");
1185 assert(interf->is_interface(), "must be");
1186 Array<Method*>* methods = InstanceKlass::cast(interf)->methods();
1187 int nof_methods = methods->length();
1188 int length = 0;
1189 while (nof_methods > 0) {
1190 Method* m = methods->at(nof_methods-1);
1191 if (m->has_itable_index()) {
1192 length = m->itable_index() + 1;
1193 break;
1194 }
1195 nof_methods -= 1;
1196 }
1197 #ifdef ASSERT
1198 int nof_methods_copy = nof_methods;
1199 while (nof_methods_copy > 0) {
1200 Method* mm = methods->at(--nof_methods_copy);
1201 assert(!mm->has_itable_index() || mm->itable_index() < length, "");
1202 }
1203 #endif //ASSERT
1204 // return the rightmost itable index, plus one; or 0 if no methods have
1205 // itable indices
1206 return length;
1207 }
1208
1209
initialize_itable_for_interface(int method_table_offset,Klass * interf,bool checkconstraints,TRAPS)1210 void klassItable::initialize_itable_for_interface(int method_table_offset, Klass* interf, bool checkconstraints, TRAPS) {
1211 Array<Method*>* methods = InstanceKlass::cast(interf)->methods();
1212 int nof_methods = methods->length();
1213 HandleMark hm;
1214 Handle interface_loader (THREAD, InstanceKlass::cast(interf)->class_loader());
1215
1216 int ime_count = method_count_for_interface(interf);
1217 for (int i = 0; i < nof_methods; i++) {
1218 Method* m = methods->at(i);
1219 methodHandle target;
1220 if (m->has_itable_index()) {
1221 // This search must match the runtime resolution, i.e. selection search for invokeinterface
1222 // to correctly enforce loader constraints for interface method inheritance.
1223 // Private methods are skipped as a private class method can never be the implementation
1224 // of an interface method.
1225 // Invokespecial does not perform selection based on the receiver, so it does not use
1226 // the cached itable.
1227 target = LinkResolver::lookup_instance_method_in_klasses(_klass, m->name(), m->signature(),
1228 Klass::skip_private, CHECK);
1229 }
1230 if (target == NULL || !target->is_public() || target->is_abstract() || target->is_overpass()) {
1231 assert(target == NULL || !target->is_overpass() || target->is_public(),
1232 "Non-public overpass method!");
1233 // Entry does not resolve. Leave it empty for AbstractMethodError or other error.
1234 if (!(target == NULL) && !target->is_public()) {
1235 // Stuff an IllegalAccessError throwing method in there instead.
1236 itableOffsetEntry::method_entry(_klass, method_table_offset)[m->itable_index()].
1237 initialize(Universe::throw_illegal_access_error());
1238 }
1239 } else {
1240 // Entry did resolve, check loader constraints before initializing
1241 // if checkconstraints requested
1242 if (checkconstraints) {
1243 Handle method_holder_loader (THREAD, target->method_holder()->class_loader());
1244 if (method_holder_loader() != interface_loader()) {
1245 ResourceMark rm(THREAD);
1246 Symbol* failed_type_symbol =
1247 SystemDictionary::check_signature_loaders(m->signature(),
1248 method_holder_loader,
1249 interface_loader,
1250 true, CHECK);
1251 if (failed_type_symbol != NULL) {
1252 stringStream ss;
1253 ss.print("loader constraint violation in interface itable"
1254 " initialization for class %s: when selecting method '",
1255 _klass->external_name());
1256 m->print_external_name(&ss),
1257 ss.print("' the class loader %s for super interface %s, and the class"
1258 " loader %s of the selected method's %s, %s have"
1259 " different Class objects for the type %s used in the signature (%s; %s)",
1260 interf->class_loader_data()->loader_name_and_id(),
1261 interf->external_name(),
1262 target()->method_holder()->class_loader_data()->loader_name_and_id(),
1263 target()->method_holder()->external_kind(),
1264 target()->method_holder()->external_name(),
1265 failed_type_symbol->as_klass_external_name(),
1266 interf->class_in_module_of_loader(false, true),
1267 target()->method_holder()->class_in_module_of_loader(false, true));
1268 THROW_MSG(vmSymbols::java_lang_LinkageError(), ss.as_string());
1269 }
1270 }
1271 }
1272
1273 // ime may have moved during GC so recalculate address
1274 int ime_num = m->itable_index();
1275 assert(ime_num < ime_count, "oob");
1276 itableOffsetEntry::method_entry(_klass, method_table_offset)[ime_num].initialize(target());
1277 if (log_develop_is_enabled(Trace, itables)) {
1278 ResourceMark rm(THREAD);
1279 if (target() != NULL) {
1280 LogTarget(Trace, itables) lt;
1281 LogStream ls(lt);
1282 char* sig = target()->name_and_sig_as_C_string();
1283 ls.print("interface: %s, ime_num: %d, target: %s, method_holder: %s ",
1284 interf->internal_name(), ime_num, sig,
1285 target()->method_holder()->internal_name());
1286 ls.print("target_method flags: ");
1287 target()->print_linkage_flags(&ls);
1288 ls.cr();
1289 }
1290 }
1291 }
1292 }
1293 }
1294
1295 #if INCLUDE_JVMTI
1296 // search the itable for uses of either obsolete or EMCP methods
adjust_method_entries(InstanceKlass * holder,bool * trace_name_printed)1297 void klassItable::adjust_method_entries(InstanceKlass* holder, bool * trace_name_printed) {
1298
1299 itableMethodEntry* ime = method_entry(0);
1300 for (int i = 0; i < _size_method_table; i++, ime++) {
1301 Method* old_method = ime->method();
1302 if (old_method == NULL || old_method->method_holder() != holder || !old_method->is_old()) {
1303 continue; // skip uninteresting entries
1304 }
1305 assert(!old_method->is_deleted(), "itable methods may not be deleted");
1306
1307 Method* new_method = holder->method_with_idnum(old_method->orig_method_idnum());
1308
1309 assert(new_method != NULL, "method_with_idnum() should not be NULL");
1310 assert(old_method != new_method, "sanity check");
1311
1312 ime->initialize(new_method);
1313
1314 if (log_is_enabled(Info, redefine, class, update)) {
1315 ResourceMark rm;
1316 if (!(*trace_name_printed)) {
1317 log_info(redefine, class, update)("adjust: name=%s", old_method->method_holder()->external_name());
1318 *trace_name_printed = true;
1319 }
1320 log_trace(redefine, class, update, itables)
1321 ("itable method update: %s(%s)", new_method->name()->as_C_string(), new_method->signature()->as_C_string());
1322 }
1323 }
1324 }
1325
1326 // an itable should never contain old or obsolete methods
check_no_old_or_obsolete_entries()1327 bool klassItable::check_no_old_or_obsolete_entries() {
1328 itableMethodEntry* ime = method_entry(0);
1329 for (int i = 0; i < _size_method_table; i++) {
1330 Method* m = ime->method();
1331 if (m != NULL &&
1332 (NOT_PRODUCT(!m->is_valid() ||) m->is_old() || m->is_obsolete())) {
1333 return false;
1334 }
1335 ime++;
1336 }
1337 return true;
1338 }
1339
dump_itable()1340 void klassItable::dump_itable() {
1341 itableMethodEntry* ime = method_entry(0);
1342 tty->print_cr("itable dump --");
1343 for (int i = 0; i < _size_method_table; i++) {
1344 Method* m = ime->method();
1345 if (m != NULL) {
1346 tty->print(" (%5d) ", i);
1347 m->access_flags().print_on(tty);
1348 if (m->is_default_method()) {
1349 tty->print("default ");
1350 }
1351 tty->print(" -- ");
1352 m->print_name(tty);
1353 tty->cr();
1354 }
1355 ime++;
1356 }
1357 }
1358 #endif // INCLUDE_JVMTI
1359
1360 // Setup
1361 class InterfaceVisiterClosure : public StackObj {
1362 public:
1363 virtual void doit(Klass* intf, int method_count) = 0;
1364 };
1365
1366 // Visit all interfaces with at least one itable method
visit_all_interfaces(Array<Klass * > * transitive_intf,InterfaceVisiterClosure * blk)1367 void visit_all_interfaces(Array<Klass*>* transitive_intf, InterfaceVisiterClosure *blk) {
1368 // Handle array argument
1369 for(int i = 0; i < transitive_intf->length(); i++) {
1370 Klass* intf = transitive_intf->at(i);
1371 assert(intf->is_interface(), "sanity check");
1372
1373 // Find no. of itable methods
1374 int method_count = 0;
1375 // method_count = klassItable::method_count_for_interface(intf);
1376 Array<Method*>* methods = InstanceKlass::cast(intf)->methods();
1377 if (methods->length() > 0) {
1378 for (int i = methods->length(); --i >= 0; ) {
1379 if (interface_method_needs_itable_index(methods->at(i))) {
1380 method_count++;
1381 }
1382 }
1383 }
1384
1385 // Visit all interfaces which either have any methods or can participate in receiver type check.
1386 // We do not bother to count methods in transitive interfaces, although that would allow us to skip
1387 // this step in the rare case of a zero-method interface extending another zero-method interface.
1388 if (method_count > 0 || InstanceKlass::cast(intf)->transitive_interfaces()->length() > 0) {
1389 blk->doit(intf, method_count);
1390 }
1391 }
1392 }
1393
1394 class CountInterfacesClosure : public InterfaceVisiterClosure {
1395 private:
1396 int _nof_methods;
1397 int _nof_interfaces;
1398 public:
CountInterfacesClosure()1399 CountInterfacesClosure() { _nof_methods = 0; _nof_interfaces = 0; }
1400
nof_methods() const1401 int nof_methods() const { return _nof_methods; }
nof_interfaces() const1402 int nof_interfaces() const { return _nof_interfaces; }
1403
doit(Klass * intf,int method_count)1404 void doit(Klass* intf, int method_count) { _nof_methods += method_count; _nof_interfaces++; }
1405 };
1406
1407 class SetupItableClosure : public InterfaceVisiterClosure {
1408 private:
1409 itableOffsetEntry* _offset_entry;
1410 itableMethodEntry* _method_entry;
1411 address _klass_begin;
1412 public:
SetupItableClosure(address klass_begin,itableOffsetEntry * offset_entry,itableMethodEntry * method_entry)1413 SetupItableClosure(address klass_begin, itableOffsetEntry* offset_entry, itableMethodEntry* method_entry) {
1414 _klass_begin = klass_begin;
1415 _offset_entry = offset_entry;
1416 _method_entry = method_entry;
1417 }
1418
method_entry() const1419 itableMethodEntry* method_entry() const { return _method_entry; }
1420
doit(Klass * intf,int method_count)1421 void doit(Klass* intf, int method_count) {
1422 int offset = ((address)_method_entry) - _klass_begin;
1423 _offset_entry->initialize(intf, offset);
1424 _offset_entry++;
1425 _method_entry += method_count;
1426 }
1427 };
1428
compute_itable_size(Array<Klass * > * transitive_interfaces)1429 int klassItable::compute_itable_size(Array<Klass*>* transitive_interfaces) {
1430 // Count no of interfaces and total number of interface methods
1431 CountInterfacesClosure cic;
1432 visit_all_interfaces(transitive_interfaces, &cic);
1433
1434 // There's alway an extra itable entry so we can null-terminate it.
1435 int itable_size = calc_itable_size(cic.nof_interfaces() + 1, cic.nof_methods());
1436
1437 // Statistics
1438 update_stats(itable_size * wordSize);
1439
1440 return itable_size;
1441 }
1442
1443
1444 // Fill out offset table and interface klasses into the itable space
setup_itable_offset_table(InstanceKlass * klass)1445 void klassItable::setup_itable_offset_table(InstanceKlass* klass) {
1446 if (klass->itable_length() == 0) return;
1447 assert(!klass->is_interface(), "Should have zero length itable");
1448
1449 // Count no of interfaces and total number of interface methods
1450 CountInterfacesClosure cic;
1451 visit_all_interfaces(klass->transitive_interfaces(), &cic);
1452 int nof_methods = cic.nof_methods();
1453 int nof_interfaces = cic.nof_interfaces();
1454
1455 // Add one extra entry so we can null-terminate the table
1456 nof_interfaces++;
1457
1458 assert(compute_itable_size(klass->transitive_interfaces()) ==
1459 calc_itable_size(nof_interfaces, nof_methods),
1460 "mismatch calculation of itable size");
1461
1462 // Fill-out offset table
1463 itableOffsetEntry* ioe = (itableOffsetEntry*)klass->start_of_itable();
1464 itableMethodEntry* ime = (itableMethodEntry*)(ioe + nof_interfaces);
1465 intptr_t* end = klass->end_of_itable();
1466 assert((oop*)(ime + nof_methods) <= (oop*)klass->start_of_nonstatic_oop_maps(), "wrong offset calculation (1)");
1467 assert((oop*)(end) == (oop*)(ime + nof_methods), "wrong offset calculation (2)");
1468
1469 // Visit all interfaces and initialize itable offset table
1470 SetupItableClosure sic((address)klass, ioe, ime);
1471 visit_all_interfaces(klass->transitive_interfaces(), &sic);
1472
1473 #ifdef ASSERT
1474 ime = sic.method_entry();
1475 oop* v = (oop*) klass->end_of_itable();
1476 assert( (oop*)(ime) == v, "wrong offset calculation (2)");
1477 #endif
1478 }
1479
1480
1481 // inverse to itable_index
method_for_itable_index(Klass * intf,int itable_index)1482 Method* klassItable::method_for_itable_index(Klass* intf, int itable_index) {
1483 assert(InstanceKlass::cast(intf)->is_interface(), "sanity check");
1484 assert(intf->verify_itable_index(itable_index), "");
1485 Array<Method*>* methods = InstanceKlass::cast(intf)->methods();
1486
1487 if (itable_index < 0 || itable_index >= method_count_for_interface(intf))
1488 return NULL; // help caller defend against bad indices
1489
1490 int index = itable_index;
1491 Method* m = methods->at(index);
1492 int index2 = -1;
1493 while (!m->has_itable_index() ||
1494 (index2 = m->itable_index()) != itable_index) {
1495 assert(index2 < itable_index, "monotonic");
1496 if (++index == methods->length())
1497 return NULL;
1498 m = methods->at(index);
1499 }
1500 assert(m->itable_index() == itable_index, "correct inverse");
1501
1502 return m;
1503 }
1504
verify(outputStream * st,bool forced)1505 void klassVtable::verify(outputStream* st, bool forced) {
1506 // make sure table is initialized
1507 if (!Universe::is_fully_initialized()) return;
1508 #ifndef PRODUCT
1509 // avoid redundant verifies
1510 if (!forced && _verify_count == Universe::verify_count()) return;
1511 _verify_count = Universe::verify_count();
1512 #endif
1513 oop* end_of_obj = (oop*)_klass + _klass->size();
1514 oop* end_of_vtable = (oop *)&table()[_length];
1515 if (end_of_vtable > end_of_obj) {
1516 fatal("klass %s: klass object too short (vtable extends beyond end)",
1517 _klass->internal_name());
1518 }
1519
1520 for (int i = 0; i < _length; i++) table()[i].verify(this, st);
1521 // verify consistency with superKlass vtable
1522 Klass* super = _klass->super();
1523 if (super != NULL) {
1524 InstanceKlass* sk = InstanceKlass::cast(super);
1525 klassVtable vt = sk->vtable();
1526 for (int i = 0; i < vt.length(); i++) {
1527 verify_against(st, &vt, i);
1528 }
1529 }
1530 }
1531
verify_against(outputStream * st,klassVtable * vt,int index)1532 void klassVtable::verify_against(outputStream* st, klassVtable* vt, int index) {
1533 vtableEntry* vte = &vt->table()[index];
1534 if (vte->method()->name() != table()[index].method()->name() ||
1535 vte->method()->signature() != table()[index].method()->signature()) {
1536 fatal("mismatched name/signature of vtable entries");
1537 }
1538 }
1539
1540 #ifndef PRODUCT
print()1541 void klassVtable::print() {
1542 ResourceMark rm;
1543 tty->print("klassVtable for klass %s (length %d):\n", _klass->internal_name(), length());
1544 for (int i = 0; i < length(); i++) {
1545 table()[i].print();
1546 tty->cr();
1547 }
1548 }
1549 #endif
1550
verify(klassVtable * vt,outputStream * st)1551 void vtableEntry::verify(klassVtable* vt, outputStream* st) {
1552 NOT_PRODUCT(FlagSetting fs(IgnoreLockingAssertions, true));
1553 Klass* vtklass = vt->klass();
1554 if (vtklass->is_instance_klass() &&
1555 (InstanceKlass::cast(vtklass)->major_version() >= klassVtable::VTABLE_TRANSITIVE_OVERRIDE_VERSION)) {
1556 assert(method() != NULL, "must have set method");
1557 }
1558 if (method() != NULL) {
1559 method()->verify();
1560 // we sub_type, because it could be a miranda method
1561 if (!vtklass->is_subtype_of(method()->method_holder())) {
1562 #ifndef PRODUCT
1563 print();
1564 #endif
1565 fatal("vtableEntry " PTR_FORMAT ": method is from subclass", p2i(this));
1566 }
1567 }
1568 }
1569
1570 #ifndef PRODUCT
1571
print()1572 void vtableEntry::print() {
1573 ResourceMark rm;
1574 tty->print("vtableEntry %s: ", method()->name()->as_C_string());
1575 if (Verbose) {
1576 tty->print("m " PTR_FORMAT " ", p2i(method()));
1577 }
1578 }
1579
1580 class VtableStats : AllStatic {
1581 public:
1582 static int no_klasses; // # classes with vtables
1583 static int no_array_klasses; // # array classes
1584 static int no_instance_klasses; // # instanceKlasses
1585 static int sum_of_vtable_len; // total # of vtable entries
1586 static int sum_of_array_vtable_len; // total # of vtable entries in array klasses only
1587 static int fixed; // total fixed overhead in bytes
1588 static int filler; // overhead caused by filler bytes
1589 static int entries; // total bytes consumed by vtable entries
1590 static int array_entries; // total bytes consumed by array vtable entries
1591
do_class(Klass * k)1592 static void do_class(Klass* k) {
1593 Klass* kl = k;
1594 klassVtable vt = kl->vtable();
1595 no_klasses++;
1596 if (kl->is_instance_klass()) {
1597 no_instance_klasses++;
1598 kl->array_klasses_do(do_class);
1599 }
1600 if (kl->is_array_klass()) {
1601 no_array_klasses++;
1602 sum_of_array_vtable_len += vt.length();
1603 }
1604 sum_of_vtable_len += vt.length();
1605 }
1606
compute()1607 static void compute() {
1608 ClassLoaderDataGraph::classes_do(do_class);
1609 fixed = no_klasses * oopSize; // vtable length
1610 // filler size is a conservative approximation
1611 filler = oopSize * (no_klasses - no_instance_klasses) * (sizeof(InstanceKlass) - sizeof(ArrayKlass) - 1);
1612 entries = sizeof(vtableEntry) * sum_of_vtable_len;
1613 array_entries = sizeof(vtableEntry) * sum_of_array_vtable_len;
1614 }
1615 };
1616
1617 int VtableStats::no_klasses = 0;
1618 int VtableStats::no_array_klasses = 0;
1619 int VtableStats::no_instance_klasses = 0;
1620 int VtableStats::sum_of_vtable_len = 0;
1621 int VtableStats::sum_of_array_vtable_len = 0;
1622 int VtableStats::fixed = 0;
1623 int VtableStats::filler = 0;
1624 int VtableStats::entries = 0;
1625 int VtableStats::array_entries = 0;
1626
print_statistics()1627 void klassVtable::print_statistics() {
1628 ResourceMark rm;
1629 HandleMark hm;
1630 VtableStats::compute();
1631 tty->print_cr("vtable statistics:");
1632 tty->print_cr("%6d classes (%d instance, %d array)", VtableStats::no_klasses, VtableStats::no_instance_klasses, VtableStats::no_array_klasses);
1633 int total = VtableStats::fixed + VtableStats::filler + VtableStats::entries;
1634 tty->print_cr("%6d bytes fixed overhead (refs + vtable object header)", VtableStats::fixed);
1635 tty->print_cr("%6d bytes filler overhead", VtableStats::filler);
1636 tty->print_cr("%6d bytes for vtable entries (%d for arrays)", VtableStats::entries, VtableStats::array_entries);
1637 tty->print_cr("%6d bytes total", total);
1638 }
1639
1640 int klassItable::_total_classes; // Total no. of classes with itables
1641 long klassItable::_total_size; // Total no. of bytes used for itables
1642
print_statistics()1643 void klassItable::print_statistics() {
1644 tty->print_cr("itable statistics:");
1645 tty->print_cr("%6d classes with itables", _total_classes);
1646 tty->print_cr("%6lu K uses for itables (average by class: %ld bytes)", _total_size / K, _total_size / _total_classes);
1647 }
1648
1649 #endif // PRODUCT
1650