1 /*
  2  * Copyright (c) 1997, 2021, 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_io.h"
 27 #include "cds/heapShared.hpp"
 28 #include "classfile/classLoaderData.inline.hpp"
 29 #include "classfile/classLoaderDataGraph.inline.hpp"
 30 #include "classfile/javaClasses.hpp"
 31 #include "classfile/moduleEntry.hpp"
 32 #include "classfile/systemDictionary.hpp"
 33 #include "classfile/systemDictionaryShared.hpp"
 34 #include "classfile/vmClasses.hpp"
 35 #include "classfile/vmSymbols.hpp"
 36 #include "gc/shared/collectedHeap.inline.hpp"
 37 #include "logging/log.hpp"
 38 #include "memory/metadataFactory.hpp"
 39 #include "memory/metaspaceClosure.hpp"
 40 #include "memory/oopFactory.hpp"
 41 #include "memory/resourceArea.hpp"
 42 #include "memory/universe.hpp"
 43 #include "oops/compressedOops.inline.hpp"
 44 #include "oops/instanceKlass.hpp"
 45 #include "oops/klass.inline.hpp"
 46 #include "oops/oop.inline.hpp"
 47 #include "oops/oopHandle.inline.hpp"
 48 #include "prims/jvmtiExport.hpp"
 49 #include "runtime/arguments.hpp"
 50 #include "runtime/atomic.hpp"
 51 #include "runtime/handles.inline.hpp"
 52 #include "utilities/macros.hpp"
 53 #include "utilities/powerOfTwo.hpp"
 54 #include "utilities/stack.inline.hpp"
 55 
 56 void Klass::set_java_mirror(Handle m) {
 57   assert(!m.is_null(), "New mirror should never be null.");
 58   assert(_java_mirror.is_empty(), "should only be used to initialize mirror");
 59   _java_mirror = class_loader_data()->add_handle(m);
 60 }
 61 
 62 oop Klass::java_mirror_no_keepalive() const {
 63   return _java_mirror.peek();
 64 }
 65 
 66 void Klass::replace_java_mirror(oop mirror) {
 67   _java_mirror.replace(mirror);
 68 }
 69 
 70 bool Klass::is_cloneable() const {
 71   return _access_flags.is_cloneable_fast() ||
 72          is_subtype_of(vmClasses::Cloneable_klass());
 73 }
 74 
 75 void Klass::set_is_cloneable() {
 76   if (name() == vmSymbols::java_lang_invoke_MemberName()) {
 77     assert(is_final(), "no subclasses allowed");
 78     // MemberName cloning should not be intrinsified and always happen in JVM_Clone.
 79   } else if (is_instance_klass() && InstanceKlass::cast(this)->reference_type() != REF_NONE) {
 80     // Reference cloning should not be intrinsified and always happen in JVM_Clone.
 81   } else {
 82     _access_flags.set_is_cloneable_fast();
 83   }
 84 }
 85 
 86 void Klass::set_name(Symbol* n) {
 87   _name = n;
 88   if (_name != NULL) _name->increment_refcount();
 89 
 90   if (Arguments::is_dumping_archive() && is_instance_klass()) {
 91     SystemDictionaryShared::init_dumptime_info(InstanceKlass::cast(this));
 92   }
 93 }
 94 
 95 bool Klass::is_subclass_of(const Klass* k) const {
 96   // Run up the super chain and check
 97   if (this == k) return true;
 98 
 99   Klass* t = const_cast<Klass*>(this)->super();
100 
101   while (t != NULL) {
102     if (t == k) return true;
103     t = t->super();
104   }
105   return false;
106 }
107 
108 void Klass::release_C_heap_structures(bool release_constant_pool) {
109   if (_name != NULL) _name->decrement_refcount();
110 }
111 
112 bool Klass::search_secondary_supers(Klass* k) const {
113   // Put some extra logic here out-of-line, before the search proper.
114   // This cuts down the size of the inline method.
115 
116   // This is necessary, since I am never in my own secondary_super list.
117   if (this == k)
118     return true;
119   // Scan the array-of-objects for a match
120   int cnt = secondary_supers()->length();
121   for (int i = 0; i < cnt; i++) {
122     if (secondary_supers()->at(i) == k) {
123       ((Klass*)this)->set_secondary_super_cache(k);
124       return true;
125     }
126   }
127   return false;
128 }
129 
130 // Return self, except for abstract classes with exactly 1
131 // implementor.  Then return the 1 concrete implementation.
132 Klass *Klass::up_cast_abstract() {
133   Klass *r = this;
134   while( r->is_abstract() ) {   // Receiver is abstract?
135     Klass *s = r->subklass();   // Check for exactly 1 subklass
136     if (s == NULL || s->next_sibling() != NULL) // Oops; wrong count; give up
137       return this;              // Return 'this' as a no-progress flag
138     r = s;                    // Loop till find concrete class
139   }
140   return r;                   // Return the 1 concrete class
141 }
142 
143 // Find LCA in class hierarchy
144 Klass *Klass::LCA( Klass *k2 ) {
145   Klass *k1 = this;
146   while( 1 ) {
147     if( k1->is_subtype_of(k2) ) return k2;
148     if( k2->is_subtype_of(k1) ) return k1;
149     k1 = k1->super();
150     k2 = k2->super();
151   }
152 }
153 
154 
155 void Klass::check_valid_for_instantiation(bool throwError, TRAPS) {
156   ResourceMark rm(THREAD);
157   THROW_MSG(throwError ? vmSymbols::java_lang_InstantiationError()
158             : vmSymbols::java_lang_InstantiationException(), external_name());
159 }
160 
161 
162 void Klass::copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS) {
163   ResourceMark rm(THREAD);
164   assert(s != NULL, "Throw NPE!");
165   THROW_MSG(vmSymbols::java_lang_ArrayStoreException(),
166             err_msg("arraycopy: source type %s is not an array", s->klass()->external_name()));
167 }
168 
169 
170 void Klass::initialize(TRAPS) {
171   ShouldNotReachHere();
172 }
173 
174 Klass* Klass::find_field(Symbol* name, Symbol* sig, fieldDescriptor* fd) const {
175 #ifdef ASSERT
176   tty->print_cr("Error: find_field called on a klass oop."
177                 " Likely error: reflection method does not correctly"
178                 " wrap return value in a mirror object.");
179 #endif
180   ShouldNotReachHere();
181   return NULL;
182 }
183 
184 Method* Klass::uncached_lookup_method(const Symbol* name, const Symbol* signature,
185                                       OverpassLookupMode overpass_mode,
186                                       PrivateLookupMode private_mode) const {
187 #ifdef ASSERT
188   tty->print_cr("Error: uncached_lookup_method called on a klass oop."
189                 " Likely error: reflection method does not correctly"
190                 " wrap return value in a mirror object.");
191 #endif
192   ShouldNotReachHere();
193   return NULL;
194 }
195 
196 void* Klass::operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw() {
197   return Metaspace::allocate(loader_data, word_size, MetaspaceObj::ClassType, THREAD);
198 }
199 
200 // "Normal" instantiation is preceeded by a MetaspaceObj allocation
201 // which zeros out memory - calloc equivalent.
202 // The constructor is also used from CppVtableCloner,
203 // which doesn't zero out the memory before calling the constructor.
204 Klass::Klass(KlassID id) : _id(id),
205                            _prototype_header(markWord::prototype() LP64_ONLY(.set_klass(this))),
206                            _shared_class_path_index(-1) {
207   CDS_ONLY(_shared_class_flags = 0;)
208   CDS_JAVA_HEAP_ONLY(_archived_mirror_index = -1;)
209   _primary_supers[0] = this;
210   set_super_check_offset(in_bytes(primary_supers_offset()));
211 }
212 
213 jint Klass::array_layout_helper(BasicType etype) {
214   assert(etype >= T_BOOLEAN && etype <= T_OBJECT, "valid etype");
215   // Note that T_ARRAY is not allowed here.
216   int  hsize = arrayOopDesc::base_offset_in_bytes(etype);
217   int  esize = type2aelembytes(etype);
218   bool isobj = (etype == T_OBJECT);
219   int  tag   =  isobj ? _lh_array_tag_obj_value : _lh_array_tag_type_value;
220   int lh = array_layout_helper(tag, hsize, etype, exact_log2(esize));
221 
222   assert(lh < (int)_lh_neutral_value, "must look like an array layout");
223   assert(layout_helper_is_array(lh), "correct kind");
224   assert(layout_helper_is_objArray(lh) == isobj, "correct kind");
225   assert(layout_helper_is_typeArray(lh) == !isobj, "correct kind");
226   assert(layout_helper_header_size(lh) == hsize, "correct decode");
227   assert(layout_helper_element_type(lh) == etype, "correct decode");
228   assert(1 << layout_helper_log2_element_size(lh) == esize, "correct decode");
229 
230   return lh;
231 }
232 
233 bool Klass::can_be_primary_super_slow() const {
234   if (super() == NULL)
235     return true;
236   else if (super()->super_depth() >= primary_super_limit()-1)
237     return false;
238   else
239     return true;
240 }
241 
242 void Klass::initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS) {
243   if (k == NULL) {
244     set_super(NULL);
245     _primary_supers[0] = this;
246     assert(super_depth() == 0, "Object must already be initialized properly");
247   } else if (k != super() || k == vmClasses::Object_klass()) {
248     assert(super() == NULL || super() == vmClasses::Object_klass(),
249            "initialize this only once to a non-trivial value");
250     set_super(k);
251     Klass* sup = k;
252     int sup_depth = sup->super_depth();
253     juint my_depth  = MIN2(sup_depth + 1, (int)primary_super_limit());
254     if (!can_be_primary_super_slow())
255       my_depth = primary_super_limit();
256     for (juint i = 0; i < my_depth; i++) {
257       _primary_supers[i] = sup->_primary_supers[i];
258     }
259     Klass* *super_check_cell;
260     if (my_depth < primary_super_limit()) {
261       _primary_supers[my_depth] = this;
262       super_check_cell = &_primary_supers[my_depth];
263     } else {
264       // Overflow of the primary_supers array forces me to be secondary.
265       super_check_cell = &_secondary_super_cache;
266     }
267     set_super_check_offset((address)super_check_cell - (address) this);
268 
269 #ifdef ASSERT
270     {
271       juint j = super_depth();
272       assert(j == my_depth, "computed accessor gets right answer");
273       Klass* t = this;
274       while (!t->can_be_primary_super()) {
275         t = t->super();
276         j = t->super_depth();
277       }
278       for (juint j1 = j+1; j1 < primary_super_limit(); j1++) {
279         assert(primary_super_of_depth(j1) == NULL, "super list padding");
280       }
281       while (t != NULL) {
282         assert(primary_super_of_depth(j) == t, "super list initialization");
283         t = t->super();
284         --j;
285       }
286       assert(j == (juint)-1, "correct depth count");
287     }
288 #endif
289   }
290 
291   if (secondary_supers() == NULL) {
292 
293     // Now compute the list of secondary supertypes.
294     // Secondaries can occasionally be on the super chain,
295     // if the inline "_primary_supers" array overflows.
296     int extras = 0;
297     Klass* p;
298     for (p = super(); !(p == NULL || p->can_be_primary_super()); p = p->super()) {
299       ++extras;
300     }
301 
302     ResourceMark rm(THREAD);  // need to reclaim GrowableArrays allocated below
303 
304     // Compute the "real" non-extra secondaries.
305     GrowableArray<Klass*>* secondaries = compute_secondary_supers(extras, transitive_interfaces);
306     if (secondaries == NULL) {
307       // secondary_supers set by compute_secondary_supers
308       return;
309     }
310 
311     GrowableArray<Klass*>* primaries = new GrowableArray<Klass*>(extras);
312 
313     for (p = super(); !(p == NULL || p->can_be_primary_super()); p = p->super()) {
314       int i;                    // Scan for overflow primaries being duplicates of 2nd'arys
315 
316       // This happens frequently for very deeply nested arrays: the
317       // primary superclass chain overflows into the secondary.  The
318       // secondary list contains the element_klass's secondaries with
319       // an extra array dimension added.  If the element_klass's
320       // secondary list already contains some primary overflows, they
321       // (with the extra level of array-ness) will collide with the
322       // normal primary superclass overflows.
323       for( i = 0; i < secondaries->length(); i++ ) {
324         if( secondaries->at(i) == p )
325           break;
326       }
327       if( i < secondaries->length() )
328         continue;               // It's a dup, don't put it in
329       primaries->push(p);
330     }
331     // Combine the two arrays into a metadata object to pack the array.
332     // The primaries are added in the reverse order, then the secondaries.
333     int new_length = primaries->length() + secondaries->length();
334     Array<Klass*>* s2 = MetadataFactory::new_array<Klass*>(
335                                        class_loader_data(), new_length, CHECK);
336     int fill_p = primaries->length();
337     for (int j = 0; j < fill_p; j++) {
338       s2->at_put(j, primaries->pop());  // add primaries in reverse order.
339     }
340     for( int j = 0; j < secondaries->length(); j++ ) {
341       s2->at_put(j+fill_p, secondaries->at(j));  // add secondaries on the end.
342     }
343 
344   #ifdef ASSERT
345       // We must not copy any NULL placeholders left over from bootstrap.
346     for (int j = 0; j < s2->length(); j++) {
347       assert(s2->at(j) != NULL, "correct bootstrapping order");
348     }
349   #endif
350 
351     set_secondary_supers(s2);
352   }
353 }
354 
355 GrowableArray<Klass*>* Klass::compute_secondary_supers(int num_extra_slots,
356                                                        Array<InstanceKlass*>* transitive_interfaces) {
357   assert(num_extra_slots == 0, "override for complex klasses");
358   assert(transitive_interfaces == NULL, "sanity");
359   set_secondary_supers(Universe::the_empty_klass_array());
360   return NULL;
361 }
362 
363 
364 // superklass links
365 InstanceKlass* Klass::superklass() const {
366   assert(super() == NULL || super()->is_instance_klass(), "must be instance klass");
367   return _super == NULL ? NULL : InstanceKlass::cast(_super);
368 }
369 
370 // subklass links.  Used by the compiler (and vtable initialization)
371 // May be cleaned concurrently, so must use the Compile_lock.
372 // The log parameter is for clean_weak_klass_links to report unlinked classes.
373 Klass* Klass::subklass(bool log) const {
374   // Need load_acquire on the _subklass, because it races with inserts that
375   // publishes freshly initialized data.
376   for (Klass* chain = Atomic::load_acquire(&_subklass);
377        chain != NULL;
378        // Do not need load_acquire on _next_sibling, because inserts never
379        // create _next_sibling edges to dead data.
380        chain = Atomic::load(&chain->_next_sibling))
381   {
382     if (chain->is_loader_alive()) {
383       return chain;
384     } else if (log) {
385       if (log_is_enabled(Trace, class, unload)) {
386         ResourceMark rm;
387         log_trace(class, unload)("unlinking class (subclass): %s", chain->external_name());
388       }
389     }
390   }
391   return NULL;
392 }
393 
394 Klass* Klass::next_sibling(bool log) const {
395   // Do not need load_acquire on _next_sibling, because inserts never
396   // create _next_sibling edges to dead data.
397   for (Klass* chain = Atomic::load(&_next_sibling);
398        chain != NULL;
399        chain = Atomic::load(&chain->_next_sibling)) {
400     // Only return alive klass, there may be stale klass
401     // in this chain if cleaned concurrently.
402     if (chain->is_loader_alive()) {
403       return chain;
404     } else if (log) {
405       if (log_is_enabled(Trace, class, unload)) {
406         ResourceMark rm;
407         log_trace(class, unload)("unlinking class (sibling): %s", chain->external_name());
408       }
409     }
410   }
411   return NULL;
412 }
413 
414 void Klass::set_subklass(Klass* s) {
415   assert(s != this, "sanity check");
416   Atomic::release_store(&_subklass, s);
417 }
418 
419 void Klass::set_next_sibling(Klass* s) {
420   assert(s != this, "sanity check");
421   // Does not need release semantics. If used by cleanup, it will link to
422   // already safely published data, and if used by inserts, will be published
423   // safely using cmpxchg.
424   Atomic::store(&_next_sibling, s);
425 }
426 
427 void Klass::append_to_sibling_list() {
428   if (Universe::is_fully_initialized()) {
429     assert_locked_or_safepoint(Compile_lock);
430   }
431   debug_only(verify();)
432   // add ourselves to superklass' subklass list
433   InstanceKlass* super = superklass();
434   if (super == NULL) return;        // special case: class Object
435   assert((!super->is_interface()    // interfaces cannot be supers
436           && (super->superklass() == NULL || !is_interface())),
437          "an interface can only be a subklass of Object");
438 
439   // Make sure there is no stale subklass head
440   super->clean_subklass();
441 
442   for (;;) {
443     Klass* prev_first_subklass = Atomic::load_acquire(&_super->_subklass);
444     if (prev_first_subklass != NULL) {
445       // set our sibling to be the superklass' previous first subklass
446       assert(prev_first_subklass->is_loader_alive(), "May not attach not alive klasses");
447       set_next_sibling(prev_first_subklass);
448     }
449     // Note that the prev_first_subklass is always alive, meaning no sibling_next links
450     // are ever created to not alive klasses. This is an important invariant of the lock-free
451     // cleaning protocol, that allows us to safely unlink dead klasses from the sibling list.
452     if (Atomic::cmpxchg(&super->_subklass, prev_first_subklass, this) == prev_first_subklass) {
453       return;
454     }
455   }
456   debug_only(verify();)
457 }
458 
459 void Klass::clean_subklass() {
460   for (;;) {
461     // Need load_acquire, due to contending with concurrent inserts
462     Klass* subklass = Atomic::load_acquire(&_subklass);
463     if (subklass == NULL || subklass->is_loader_alive()) {
464       return;
465     }
466     // Try to fix _subklass until it points at something not dead.
467     Atomic::cmpxchg(&_subklass, subklass, subklass->next_sibling());
468   }
469 }
470 
471 void Klass::clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses) {
472   if (!ClassUnloading || !unloading_occurred) {
473     return;
474   }
475 
476   Klass* root = vmClasses::Object_klass();
477   Stack<Klass*, mtGC> stack;
478 
479   stack.push(root);
480   while (!stack.is_empty()) {
481     Klass* current = stack.pop();
482 
483     assert(current->is_loader_alive(), "just checking, this should be live");
484 
485     // Find and set the first alive subklass
486     Klass* sub = current->subklass(true);
487     current->clean_subklass();
488     if (sub != NULL) {
489       stack.push(sub);
490     }
491 
492     // Find and set the first alive sibling
493     Klass* sibling = current->next_sibling(true);
494     current->set_next_sibling(sibling);
495     if (sibling != NULL) {
496       stack.push(sibling);
497     }
498 
499     // Clean the implementors list and method data.
500     if (clean_alive_klasses && current->is_instance_klass()) {
501       InstanceKlass* ik = InstanceKlass::cast(current);
502       ik->clean_weak_instanceklass_links();
503 
504       // JVMTI RedefineClasses creates previous versions that are not in
505       // the class hierarchy, so process them here.
506       while ((ik = ik->previous_versions()) != NULL) {
507         ik->clean_weak_instanceklass_links();
508       }
509     }
510   }
511 }
512 
513 void Klass::metaspace_pointers_do(MetaspaceClosure* it) {
514   if (log_is_enabled(Trace, cds)) {
515     ResourceMark rm;
516     log_trace(cds)("Iter(Klass): %p (%s)", this, external_name());
517   }
518 
519   it->push(&_name);
520   it->push(&_secondary_super_cache);
521   it->push(&_secondary_supers);
522   for (int i = 0; i < _primary_super_limit; i++) {
523     it->push(&_primary_supers[i]);
524   }
525   it->push(&_super);
526   if (!Arguments::is_dumping_archive()) {
527     // If dumping archive, these may point to excluded classes. There's no need
528     // to follow these pointers anyway, as they will be set to NULL in
529     // remove_unshareable_info().
530     it->push((Klass**)&_subklass);
531     it->push((Klass**)&_next_sibling);
532     it->push(&_next_link);
533   }
534 
535   vtableEntry* vt = start_of_vtable();
536   for (int i=0; i<vtable_length(); i++) {
537     it->push(vt[i].method_addr());
538   }
539 }
540 
541 void Klass::remove_unshareable_info() {
542   assert (Arguments::is_dumping_archive(),
543           "only called during CDS dump time");
544   JFR_ONLY(REMOVE_ID(this);)
545   if (log_is_enabled(Trace, cds, unshareable)) {
546     ResourceMark rm;
547     log_trace(cds, unshareable)("remove: %s", external_name());
548   }
549 
550   set_subklass(NULL);
551   set_next_sibling(NULL);
552   set_next_link(NULL);
553 
554   // Null out class_loader_data because we don't share that yet.
555   set_class_loader_data(NULL);
556   set_is_shared();
557 }
558 
559 void Klass::remove_java_mirror() {
560   Arguments::assert_is_dumping_archive();
561   if (log_is_enabled(Trace, cds, unshareable)) {
562     ResourceMark rm;
563     log_trace(cds, unshareable)("remove java_mirror: %s", external_name());
564   }
565   // Just null out the mirror.  The class_loader_data() no longer exists.
566   clear_java_mirror_handle();
567 }
568 
569 void Klass::restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS) {
570   assert(is_klass(), "ensure C++ vtable is restored");
571   assert(is_shared(), "must be set");
572   JFR_ONLY(RESTORE_ID(this);)
573   if (log_is_enabled(Trace, cds, unshareable)) {
574     ResourceMark rm(THREAD);
575     log_trace(cds, unshareable)("restore: %s", external_name());
576   }
577 
578   // If an exception happened during CDS restore, some of these fields may already be
579   // set.  We leave the class on the CLD list, even if incomplete so that we don't
580   // modify the CLD list outside a safepoint.
581   if (class_loader_data() == NULL) {
582     set_class_loader_data(loader_data);
583 
584     // Add to class loader list first before creating the mirror
585     // (same order as class file parsing)
586     loader_data->add_class(this);
587   }
588 
589   Handle loader(THREAD, loader_data->class_loader());
590   ModuleEntry* module_entry = NULL;
591   Klass* k = this;
592   if (k->is_objArray_klass()) {
593     k = ObjArrayKlass::cast(k)->bottom_klass();
594   }
595   // Obtain klass' module.
596   if (k->is_instance_klass()) {
597     InstanceKlass* ik = (InstanceKlass*) k;
598     module_entry = ik->module();
599   } else {
600     module_entry = ModuleEntryTable::javabase_moduleEntry();
601   }
602   // Obtain java.lang.Module, if available
603   Handle module_handle(THREAD, ((module_entry != NULL) ? module_entry->module() : (oop)NULL));
604 
605   if (this->has_archived_mirror_index()) {
606     ResourceMark rm(THREAD);
607     log_debug(cds, mirror)("%s has raw archived mirror", external_name());
608     if (HeapShared::are_archived_mirrors_available()) {
609       bool present = java_lang_Class::restore_archived_mirror(this, loader, module_handle,
610                                                               protection_domain,
611                                                               CHECK);
612       if (present) {
613         return;
614       }
615     }
616 
617     // No archived mirror data
618     log_debug(cds, mirror)("No archived mirror data for %s", external_name());
619     clear_java_mirror_handle();
620     this->clear_archived_mirror_index();
621   }
622 
623   // Only recreate it if not present.  A previous attempt to restore may have
624   // gotten an OOM later but keep the mirror if it was created.
625   if (java_mirror() == NULL) {
626     ResourceMark rm(THREAD);
627     log_trace(cds, mirror)("Recreate mirror for %s", external_name());
628     java_lang_Class::create_mirror(this, loader, module_handle, protection_domain, Handle(), CHECK);
629   }
630 }
631 
632 #if INCLUDE_CDS_JAVA_HEAP
633 oop Klass::archived_java_mirror() {
634   assert(has_archived_mirror_index(), "must have archived mirror");
635   return HeapShared::get_root(_archived_mirror_index);
636 }
637 
638 void Klass::clear_archived_mirror_index() {
639   if (_archived_mirror_index >= 0) {
640     HeapShared::clear_root(_archived_mirror_index);
641   }
642   _archived_mirror_index = -1;
643 }
644 
645 // No GC barrier
646 void Klass::set_archived_java_mirror(oop m) {
647   assert(DumpSharedSpaces, "called only during runtime");
648   _archived_mirror_index = HeapShared::append_root(m);
649 }
650 #endif // INCLUDE_CDS_JAVA_HEAP
651 
652 void Klass::check_array_allocation_length(int length, int max_length, TRAPS) {
653   if (length > max_length) {
654     if (!THREAD->in_retryable_allocation()) {
655       report_java_out_of_memory("Requested array size exceeds VM limit");
656       JvmtiExport::post_array_size_exhausted();
657       THROW_OOP(Universe::out_of_memory_error_array_size());
658     } else {
659       THROW_OOP(Universe::out_of_memory_error_retry());
660     }
661   } else if (length < 0) {
662     THROW_MSG(vmSymbols::java_lang_NegativeArraySizeException(), err_msg("%d", length));
663   }
664 }
665 
666 // Replace the last '+' char with '/'.
667 static char* convert_hidden_name_to_java(Symbol* name) {
668   size_t name_len = name->utf8_length();
669   char* result = NEW_RESOURCE_ARRAY(char, name_len + 1);
670   name->as_klass_external_name(result, (int)name_len + 1);
671   for (int index = (int)name_len; index > 0; index--) {
672     if (result[index] == '+') {
673       result[index] = JVM_SIGNATURE_SLASH;
674       break;
675     }
676   }
677   return result;
678 }
679 
680 // In product mode, this function doesn't have virtual function calls so
681 // there might be some performance advantage to handling InstanceKlass here.
682 const char* Klass::external_name() const {
683   if (is_instance_klass()) {
684     const InstanceKlass* ik = static_cast<const InstanceKlass*>(this);
685     if (ik->is_hidden()) {
686       char* result = convert_hidden_name_to_java(name());
687       return result;
688     }
689   } else if (is_objArray_klass() && ObjArrayKlass::cast(this)->bottom_klass()->is_hidden()) {
690     char* result = convert_hidden_name_to_java(name());
691     return result;
692   }
693   if (name() == NULL)  return "<unknown>";
694   return name()->as_klass_external_name();
695 }
696 
697 const char* Klass::signature_name() const {
698   if (name() == NULL)  return "<unknown>";
699   if (is_objArray_klass() && ObjArrayKlass::cast(this)->bottom_klass()->is_hidden()) {
700     size_t name_len = name()->utf8_length();
701     char* result = NEW_RESOURCE_ARRAY(char, name_len + 1);
702     name()->as_C_string(result, (int)name_len + 1);
703     for (int index = (int)name_len; index > 0; index--) {
704       if (result[index] == '+') {
705         result[index] = JVM_SIGNATURE_DOT;
706         break;
707       }
708     }
709     return result;
710   }
711   return name()->as_C_string();
712 }
713 
714 const char* Klass::external_kind() const {
715   if (is_interface()) return "interface";
716   if (is_abstract()) return "abstract class";
717   return "class";
718 }
719 
720 // Unless overridden, jvmti_class_status has no flags set.
721 jint Klass::jvmti_class_status() const {
722   return 0;
723 }
724 
725 
726 // Printing
727 
728 void Klass::print_on(outputStream* st) const {
729   ResourceMark rm;
730   // print title
731   st->print("%s", internal_name());
732   print_address_on(st);
733   st->cr();
734 }
735 
736 #define BULLET  " - "
737 
738 // Caller needs ResourceMark
739 void Klass::oop_print_on(oop obj, outputStream* st) {
740   // print title
741   st->print_cr("%s ", internal_name());
742   obj->print_address_on(st);
743 
744   if (WizardMode) {
745      // print header
746      obj->mark().print_on(st);
747      st->cr();
748      st->print(BULLET"prototype_header: " INTPTR_FORMAT, _prototype_header.value());
749      st->cr();
750   }
751 
752   // print class
753   st->print(BULLET"klass: ");
754   obj->klass()->print_value_on(st);
755   st->cr();
756 }
757 
758 void Klass::oop_print_value_on(oop obj, outputStream* st) {
759   // print title
760   ResourceMark rm;              // Cannot print in debug mode without this
761   st->print("%s", internal_name());
762   obj->print_address_on(st);
763 }
764 
765 // Verification
766 
767 void Klass::verify_on(outputStream* st) {
768 
769   // This can be expensive, but it is worth checking that this klass is actually
770   // in the CLD graph but not in production.
771   assert(Metaspace::contains((address)this), "Should be");
772 
773   guarantee(this->is_klass(),"should be klass");
774 
775   if (super() != NULL) {
776     guarantee(super()->is_klass(), "should be klass");
777   }
778   if (secondary_super_cache() != NULL) {
779     Klass* ko = secondary_super_cache();
780     guarantee(ko->is_klass(), "should be klass");
781   }
782   for ( uint i = 0; i < primary_super_limit(); i++ ) {
783     Klass* ko = _primary_supers[i];
784     if (ko != NULL) {
785       guarantee(ko->is_klass(), "should be klass");
786     }
787   }
788 
789   if (java_mirror_no_keepalive() != NULL) {
790     guarantee(oopDesc::is_oop(java_mirror_no_keepalive()), "should be instance");
791   }
792 }
793 
794 void Klass::oop_verify_on(oop obj, outputStream* st) {
795   guarantee(oopDesc::is_oop(obj),  "should be oop");
796   guarantee(obj->klass()->is_klass(), "klass field is not a klass");
797 }
798 
799 bool Klass::is_valid(Klass* k) {
800   if (!is_aligned(k, sizeof(MetaWord))) return false;
801   if ((size_t)k < os::min_page_size()) return false;
802 
803   if (!os::is_readable_range(k, k + 1)) return false;
804   if (!Metaspace::contains(k)) return false;
805 
806   if (!Symbol::is_valid(k->name())) return false;
807   return ClassLoaderDataGraph::is_valid(k->class_loader_data());
808 }
809 
810 Method* Klass::method_at_vtable(int index)  {
811 #ifndef PRODUCT
812   assert(index >= 0, "valid vtable index");
813   if (DebugVtables) {
814     verify_vtable_index(index);
815   }
816 #endif
817   return start_of_vtable()[index].method();
818 }
819 
820 
821 #ifndef PRODUCT
822 
823 bool Klass::verify_vtable_index(int i) {
824   int limit = vtable_length()/vtableEntry::size();
825   assert(i >= 0 && i < limit, "index %d out of bounds %d", i, limit);
826   return true;
827 }
828 
829 #endif // PRODUCT
830 
831 // Caller needs ResourceMark
832 // joint_in_module_of_loader provides an optimization if 2 classes are in
833 // the same module to succinctly print out relevant information about their
834 // module name and class loader's name_and_id for error messages.
835 // Format:
836 //   <fully-qualified-external-class-name1> and <fully-qualified-external-class-name2>
837 //                      are in module <module-name>[@<version>]
838 //                      of loader <loader-name_and_id>[, parent loader <parent-loader-name_and_id>]
839 const char* Klass::joint_in_module_of_loader(const Klass* class2, bool include_parent_loader) const {
840   assert(module() == class2->module(), "classes do not have the same module");
841   const char* class1_name = external_name();
842   size_t len = strlen(class1_name) + 1;
843 
844   const char* class2_description = class2->class_in_module_of_loader(true, include_parent_loader);
845   len += strlen(class2_description);
846 
847   len += strlen(" and ");
848 
849   char* joint_description = NEW_RESOURCE_ARRAY_RETURN_NULL(char, len);
850 
851   // Just return the FQN if error when allocating string
852   if (joint_description == NULL) {
853     return class1_name;
854   }
855 
856   jio_snprintf(joint_description, len, "%s and %s",
857                class1_name,
858                class2_description);
859 
860   return joint_description;
861 }
862 
863 // Caller needs ResourceMark
864 // class_in_module_of_loader provides a standard way to include
865 // relevant information about a class, such as its module name as
866 // well as its class loader's name_and_id, in error messages and logging.
867 // Format:
868 //   <fully-qualified-external-class-name> is in module <module-name>[@<version>]
869 //                                         of loader <loader-name_and_id>[, parent loader <parent-loader-name_and_id>]
870 const char* Klass::class_in_module_of_loader(bool use_are, bool include_parent_loader) const {
871   // 1. fully qualified external name of class
872   const char* klass_name = external_name();
873   size_t len = strlen(klass_name) + 1;
874 
875   // 2. module name + @version
876   const char* module_name = "";
877   const char* version = "";
878   bool has_version = false;
879   bool module_is_named = false;
880   const char* module_name_phrase = "";
881   const Klass* bottom_klass = is_objArray_klass() ?
882                                 ObjArrayKlass::cast(this)->bottom_klass() : this;
883   if (bottom_klass->is_instance_klass()) {
884     ModuleEntry* module = InstanceKlass::cast(bottom_klass)->module();
885     if (module->is_named()) {
886       module_is_named = true;
887       module_name_phrase = "module ";
888       module_name = module->name()->as_C_string();
889       len += strlen(module_name);
890       // Use version if exists and is not a jdk module
891       if (module->should_show_version()) {
892         has_version = true;
893         version = module->version()->as_C_string();
894         // Include stlen(version) + 1 for the "@"
895         len += strlen(version) + 1;
896       }
897     } else {
898       module_name = UNNAMED_MODULE;
899       len += UNNAMED_MODULE_LEN;
900     }
901   } else {
902     // klass is an array of primitives, module is java.base
903     module_is_named = true;
904     module_name_phrase = "module ";
905     module_name = JAVA_BASE_NAME;
906     len += JAVA_BASE_NAME_LEN;
907   }
908 
909   // 3. class loader's name_and_id
910   ClassLoaderData* cld = class_loader_data();
911   assert(cld != NULL, "class_loader_data should not be null");
912   const char* loader_name_and_id = cld->loader_name_and_id();
913   len += strlen(loader_name_and_id);
914 
915   // 4. include parent loader information
916   const char* parent_loader_phrase = "";
917   const char* parent_loader_name_and_id = "";
918   if (include_parent_loader &&
919       !cld->is_builtin_class_loader_data()) {
920     oop parent_loader = java_lang_ClassLoader::parent(class_loader());
921     ClassLoaderData *parent_cld = ClassLoaderData::class_loader_data_or_null(parent_loader);
922     // The parent loader's ClassLoaderData could be null if it is
923     // a delegating class loader that has never defined a class.
924     // In this case the loader's name must be obtained via the parent loader's oop.
925     if (parent_cld == NULL) {
926       oop cl_name_and_id = java_lang_ClassLoader::nameAndId(parent_loader);
927       if (cl_name_and_id != NULL) {
928         parent_loader_name_and_id = java_lang_String::as_utf8_string(cl_name_and_id);
929       }
930     } else {
931       parent_loader_name_and_id = parent_cld->loader_name_and_id();
932     }
933     parent_loader_phrase = ", parent loader ";
934     len += strlen(parent_loader_phrase) + strlen(parent_loader_name_and_id);
935   }
936 
937   // Start to construct final full class description string
938   len += ((use_are) ? strlen(" are in ") : strlen(" is in "));
939   len += strlen(module_name_phrase) + strlen(" of loader ");
940 
941   char* class_description = NEW_RESOURCE_ARRAY_RETURN_NULL(char, len);
942 
943   // Just return the FQN if error when allocating string
944   if (class_description == NULL) {
945     return klass_name;
946   }
947 
948   jio_snprintf(class_description, len, "%s %s in %s%s%s%s of loader %s%s%s",
949                klass_name,
950                (use_are) ? "are" : "is",
951                module_name_phrase,
952                module_name,
953                (has_version) ? "@" : "",
954                (has_version) ? version : "",
955                loader_name_and_id,
956                parent_loader_phrase,
957                parent_loader_name_and_id);
958 
959   return class_description;
960 }