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 static markWord make_prototype(Klass* kls) {
201   markWord prototype = markWord::prototype();
202 #ifdef _LP64
203   if (UseCompactObjectHeaders) {
204     prototype = prototype.set_klass(kls);
205   }
206 #endif
207   return prototype;
208 }
209 
210 // "Normal" instantiation is preceeded by a MetaspaceObj allocation
211 // which zeros out memory - calloc equivalent.
212 // The constructor is also used from CppVtableCloner,
213 // which doesn't zero out the memory before calling the constructor.
214 Klass::Klass(KlassID id) : _id(id),
215                            _prototype_header(make_prototype(this)),
216                            _shared_class_path_index(-1) {
217   CDS_ONLY(_shared_class_flags = 0;)
218   CDS_JAVA_HEAP_ONLY(_archived_mirror_index = -1;)
219   _primary_supers[0] = this;
220   set_super_check_offset(in_bytes(primary_supers_offset()));
221 }
222 
223 jint Klass::array_layout_helper(BasicType etype) {
224   assert(etype >= T_BOOLEAN && etype <= T_OBJECT, "valid etype");
225   // Note that T_ARRAY is not allowed here.
226   int  hsize = arrayOopDesc::base_offset_in_bytes(etype);
227   int  esize = type2aelembytes(etype);
228   bool isobj = (etype == T_OBJECT);
229   int  tag   =  isobj ? _lh_array_tag_obj_value : _lh_array_tag_type_value;
230   int lh = array_layout_helper(tag, hsize, etype, exact_log2(esize));
231 
232   assert(lh < (int)_lh_neutral_value, "must look like an array layout");
233   assert(layout_helper_is_array(lh), "correct kind");
234   assert(layout_helper_is_objArray(lh) == isobj, "correct kind");
235   assert(layout_helper_is_typeArray(lh) == !isobj, "correct kind");
236   assert(layout_helper_header_size(lh) == hsize, "correct decode");
237   assert(layout_helper_element_type(lh) == etype, "correct decode");
238   assert(1 << layout_helper_log2_element_size(lh) == esize, "correct decode");
239 
240   return lh;
241 }
242 
243 bool Klass::can_be_primary_super_slow() const {
244   if (super() == NULL)
245     return true;
246   else if (super()->super_depth() >= primary_super_limit()-1)
247     return false;
248   else
249     return true;
250 }
251 
252 void Klass::initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS) {
253   if (k == NULL) {
254     set_super(NULL);
255     _primary_supers[0] = this;
256     assert(super_depth() == 0, "Object must already be initialized properly");
257   } else if (k != super() || k == vmClasses::Object_klass()) {
258     assert(super() == NULL || super() == vmClasses::Object_klass(),
259            "initialize this only once to a non-trivial value");
260     set_super(k);
261     Klass* sup = k;
262     int sup_depth = sup->super_depth();
263     juint my_depth  = MIN2(sup_depth + 1, (int)primary_super_limit());
264     if (!can_be_primary_super_slow())
265       my_depth = primary_super_limit();
266     for (juint i = 0; i < my_depth; i++) {
267       _primary_supers[i] = sup->_primary_supers[i];
268     }
269     Klass* *super_check_cell;
270     if (my_depth < primary_super_limit()) {
271       _primary_supers[my_depth] = this;
272       super_check_cell = &_primary_supers[my_depth];
273     } else {
274       // Overflow of the primary_supers array forces me to be secondary.
275       super_check_cell = &_secondary_super_cache;
276     }
277     set_super_check_offset((address)super_check_cell - (address) this);
278 
279 #ifdef ASSERT
280     {
281       juint j = super_depth();
282       assert(j == my_depth, "computed accessor gets right answer");
283       Klass* t = this;
284       while (!t->can_be_primary_super()) {
285         t = t->super();
286         j = t->super_depth();
287       }
288       for (juint j1 = j+1; j1 < primary_super_limit(); j1++) {
289         assert(primary_super_of_depth(j1) == NULL, "super list padding");
290       }
291       while (t != NULL) {
292         assert(primary_super_of_depth(j) == t, "super list initialization");
293         t = t->super();
294         --j;
295       }
296       assert(j == (juint)-1, "correct depth count");
297     }
298 #endif
299   }
300 
301   if (secondary_supers() == NULL) {
302 
303     // Now compute the list of secondary supertypes.
304     // Secondaries can occasionally be on the super chain,
305     // if the inline "_primary_supers" array overflows.
306     int extras = 0;
307     Klass* p;
308     for (p = super(); !(p == NULL || p->can_be_primary_super()); p = p->super()) {
309       ++extras;
310     }
311 
312     ResourceMark rm(THREAD);  // need to reclaim GrowableArrays allocated below
313 
314     // Compute the "real" non-extra secondaries.
315     GrowableArray<Klass*>* secondaries = compute_secondary_supers(extras, transitive_interfaces);
316     if (secondaries == NULL) {
317       // secondary_supers set by compute_secondary_supers
318       return;
319     }
320 
321     GrowableArray<Klass*>* primaries = new GrowableArray<Klass*>(extras);
322 
323     for (p = super(); !(p == NULL || p->can_be_primary_super()); p = p->super()) {
324       int i;                    // Scan for overflow primaries being duplicates of 2nd'arys
325 
326       // This happens frequently for very deeply nested arrays: the
327       // primary superclass chain overflows into the secondary.  The
328       // secondary list contains the element_klass's secondaries with
329       // an extra array dimension added.  If the element_klass's
330       // secondary list already contains some primary overflows, they
331       // (with the extra level of array-ness) will collide with the
332       // normal primary superclass overflows.
333       for( i = 0; i < secondaries->length(); i++ ) {
334         if( secondaries->at(i) == p )
335           break;
336       }
337       if( i < secondaries->length() )
338         continue;               // It's a dup, don't put it in
339       primaries->push(p);
340     }
341     // Combine the two arrays into a metadata object to pack the array.
342     // The primaries are added in the reverse order, then the secondaries.
343     int new_length = primaries->length() + secondaries->length();
344     Array<Klass*>* s2 = MetadataFactory::new_array<Klass*>(
345                                        class_loader_data(), new_length, CHECK);
346     int fill_p = primaries->length();
347     for (int j = 0; j < fill_p; j++) {
348       s2->at_put(j, primaries->pop());  // add primaries in reverse order.
349     }
350     for( int j = 0; j < secondaries->length(); j++ ) {
351       s2->at_put(j+fill_p, secondaries->at(j));  // add secondaries on the end.
352     }
353 
354   #ifdef ASSERT
355       // We must not copy any NULL placeholders left over from bootstrap.
356     for (int j = 0; j < s2->length(); j++) {
357       assert(s2->at(j) != NULL, "correct bootstrapping order");
358     }
359   #endif
360 
361     set_secondary_supers(s2);
362   }
363 }
364 
365 GrowableArray<Klass*>* Klass::compute_secondary_supers(int num_extra_slots,
366                                                        Array<InstanceKlass*>* transitive_interfaces) {
367   assert(num_extra_slots == 0, "override for complex klasses");
368   assert(transitive_interfaces == NULL, "sanity");
369   set_secondary_supers(Universe::the_empty_klass_array());
370   return NULL;
371 }
372 
373 
374 // superklass links
375 InstanceKlass* Klass::superklass() const {
376   assert(super() == NULL || super()->is_instance_klass(), "must be instance klass");
377   return _super == NULL ? NULL : InstanceKlass::cast(_super);
378 }
379 
380 // subklass links.  Used by the compiler (and vtable initialization)
381 // May be cleaned concurrently, so must use the Compile_lock.
382 // The log parameter is for clean_weak_klass_links to report unlinked classes.
383 Klass* Klass::subklass(bool log) const {
384   // Need load_acquire on the _subklass, because it races with inserts that
385   // publishes freshly initialized data.
386   for (Klass* chain = Atomic::load_acquire(&_subklass);
387        chain != NULL;
388        // Do not need load_acquire on _next_sibling, because inserts never
389        // create _next_sibling edges to dead data.
390        chain = Atomic::load(&chain->_next_sibling))
391   {
392     if (chain->is_loader_alive()) {
393       return chain;
394     } else if (log) {
395       if (log_is_enabled(Trace, class, unload)) {
396         ResourceMark rm;
397         log_trace(class, unload)("unlinking class (subclass): %s", chain->external_name());
398       }
399     }
400   }
401   return NULL;
402 }
403 
404 Klass* Klass::next_sibling(bool log) const {
405   // Do not need load_acquire on _next_sibling, because inserts never
406   // create _next_sibling edges to dead data.
407   for (Klass* chain = Atomic::load(&_next_sibling);
408        chain != NULL;
409        chain = Atomic::load(&chain->_next_sibling)) {
410     // Only return alive klass, there may be stale klass
411     // in this chain if cleaned concurrently.
412     if (chain->is_loader_alive()) {
413       return chain;
414     } else if (log) {
415       if (log_is_enabled(Trace, class, unload)) {
416         ResourceMark rm;
417         log_trace(class, unload)("unlinking class (sibling): %s", chain->external_name());
418       }
419     }
420   }
421   return NULL;
422 }
423 
424 void Klass::set_subklass(Klass* s) {
425   assert(s != this, "sanity check");
426   Atomic::release_store(&_subklass, s);
427 }
428 
429 void Klass::set_next_sibling(Klass* s) {
430   assert(s != this, "sanity check");
431   // Does not need release semantics. If used by cleanup, it will link to
432   // already safely published data, and if used by inserts, will be published
433   // safely using cmpxchg.
434   Atomic::store(&_next_sibling, s);
435 }
436 
437 void Klass::append_to_sibling_list() {
438   if (Universe::is_fully_initialized()) {
439     assert_locked_or_safepoint(Compile_lock);
440   }
441   debug_only(verify();)
442   // add ourselves to superklass' subklass list
443   InstanceKlass* super = superklass();
444   if (super == NULL) return;        // special case: class Object
445   assert((!super->is_interface()    // interfaces cannot be supers
446           && (super->superklass() == NULL || !is_interface())),
447          "an interface can only be a subklass of Object");
448 
449   // Make sure there is no stale subklass head
450   super->clean_subklass();
451 
452   for (;;) {
453     Klass* prev_first_subklass = Atomic::load_acquire(&_super->_subklass);
454     if (prev_first_subklass != NULL) {
455       // set our sibling to be the superklass' previous first subklass
456       assert(prev_first_subklass->is_loader_alive(), "May not attach not alive klasses");
457       set_next_sibling(prev_first_subklass);
458     }
459     // Note that the prev_first_subklass is always alive, meaning no sibling_next links
460     // are ever created to not alive klasses. This is an important invariant of the lock-free
461     // cleaning protocol, that allows us to safely unlink dead klasses from the sibling list.
462     if (Atomic::cmpxchg(&super->_subklass, prev_first_subklass, this) == prev_first_subklass) {
463       return;
464     }
465   }
466   debug_only(verify();)
467 }
468 
469 void Klass::clean_subklass() {
470   for (;;) {
471     // Need load_acquire, due to contending with concurrent inserts
472     Klass* subklass = Atomic::load_acquire(&_subklass);
473     if (subklass == NULL || subklass->is_loader_alive()) {
474       return;
475     }
476     // Try to fix _subklass until it points at something not dead.
477     Atomic::cmpxchg(&_subklass, subklass, subklass->next_sibling());
478   }
479 }
480 
481 void Klass::clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses) {
482   if (!ClassUnloading || !unloading_occurred) {
483     return;
484   }
485 
486   Klass* root = vmClasses::Object_klass();
487   Stack<Klass*, mtGC> stack;
488 
489   stack.push(root);
490   while (!stack.is_empty()) {
491     Klass* current = stack.pop();
492 
493     assert(current->is_loader_alive(), "just checking, this should be live");
494 
495     // Find and set the first alive subklass
496     Klass* sub = current->subklass(true);
497     current->clean_subklass();
498     if (sub != NULL) {
499       stack.push(sub);
500     }
501 
502     // Find and set the first alive sibling
503     Klass* sibling = current->next_sibling(true);
504     current->set_next_sibling(sibling);
505     if (sibling != NULL) {
506       stack.push(sibling);
507     }
508 
509     // Clean the implementors list and method data.
510     if (clean_alive_klasses && current->is_instance_klass()) {
511       InstanceKlass* ik = InstanceKlass::cast(current);
512       ik->clean_weak_instanceklass_links();
513 
514       // JVMTI RedefineClasses creates previous versions that are not in
515       // the class hierarchy, so process them here.
516       while ((ik = ik->previous_versions()) != NULL) {
517         ik->clean_weak_instanceklass_links();
518       }
519     }
520   }
521 }
522 
523 void Klass::metaspace_pointers_do(MetaspaceClosure* it) {
524   if (log_is_enabled(Trace, cds)) {
525     ResourceMark rm;
526     log_trace(cds)("Iter(Klass): %p (%s)", this, external_name());
527   }
528 
529   it->push(&_name);
530   it->push(&_secondary_super_cache);
531   it->push(&_secondary_supers);
532   for (int i = 0; i < _primary_super_limit; i++) {
533     it->push(&_primary_supers[i]);
534   }
535   it->push(&_super);
536   it->push((Klass**)&_subklass);
537   it->push((Klass**)&_next_sibling);
538   it->push(&_next_link);
539 
540   vtableEntry* vt = start_of_vtable();
541   for (int i=0; i<vtable_length(); i++) {
542     it->push(vt[i].method_addr());
543   }
544 }
545 
546 void Klass::remove_unshareable_info() {
547   assert (Arguments::is_dumping_archive(),
548           "only called during CDS dump time");
549   JFR_ONLY(REMOVE_ID(this);)
550   if (log_is_enabled(Trace, cds, unshareable)) {
551     ResourceMark rm;
552     log_trace(cds, unshareable)("remove: %s", external_name());
553   }
554 
555   set_subklass(NULL);
556   set_next_sibling(NULL);
557   set_next_link(NULL);
558 
559   // Null out class_loader_data because we don't share that yet.
560   set_class_loader_data(NULL);
561   set_is_shared();
562 }
563 
564 void Klass::remove_java_mirror() {
565   Arguments::assert_is_dumping_archive();
566   if (log_is_enabled(Trace, cds, unshareable)) {
567     ResourceMark rm;
568     log_trace(cds, unshareable)("remove java_mirror: %s", external_name());
569   }
570   // Just null out the mirror.  The class_loader_data() no longer exists.
571   clear_java_mirror_handle();
572 }
573 
574 void Klass::restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS) {
575   assert(is_klass(), "ensure C++ vtable is restored");
576   assert(is_shared(), "must be set");
577   JFR_ONLY(RESTORE_ID(this);)
578   if (log_is_enabled(Trace, cds, unshareable)) {
579     ResourceMark rm(THREAD);
580     log_trace(cds, unshareable)("restore: %s", external_name());
581   }
582 
583   // If an exception happened during CDS restore, some of these fields may already be
584   // set.  We leave the class on the CLD list, even if incomplete so that we don't
585   // modify the CLD list outside a safepoint.
586   if (class_loader_data() == NULL) {
587     set_class_loader_data(loader_data);
588 
589     // Add to class loader list first before creating the mirror
590     // (same order as class file parsing)
591     loader_data->add_class(this);
592   }
593 
594   Handle loader(THREAD, loader_data->class_loader());
595   ModuleEntry* module_entry = NULL;
596   Klass* k = this;
597   if (k->is_objArray_klass()) {
598     k = ObjArrayKlass::cast(k)->bottom_klass();
599   }
600   // Obtain klass' module.
601   if (k->is_instance_klass()) {
602     InstanceKlass* ik = (InstanceKlass*) k;
603     module_entry = ik->module();
604   } else {
605     module_entry = ModuleEntryTable::javabase_moduleEntry();
606   }
607   // Obtain java.lang.Module, if available
608   Handle module_handle(THREAD, ((module_entry != NULL) ? module_entry->module() : (oop)NULL));
609 
610   if (this->has_archived_mirror_index()) {
611     ResourceMark rm(THREAD);
612     log_debug(cds, mirror)("%s has raw archived mirror", external_name());
613     if (HeapShared::open_archive_heap_region_mapped()) {
614       bool present = java_lang_Class::restore_archived_mirror(this, loader, module_handle,
615                                                               protection_domain,
616                                                               CHECK);
617       if (present) {
618         return;
619       }
620     }
621 
622     // No archived mirror data
623     log_debug(cds, mirror)("No archived mirror data for %s", external_name());
624     clear_java_mirror_handle();
625     this->clear_archived_mirror_index();
626   }
627 
628   // Only recreate it if not present.  A previous attempt to restore may have
629   // gotten an OOM later but keep the mirror if it was created.
630   if (java_mirror() == NULL) {
631     ResourceMark rm(THREAD);
632     log_trace(cds, mirror)("Recreate mirror for %s", external_name());
633     java_lang_Class::create_mirror(this, loader, module_handle, protection_domain, Handle(), CHECK);
634   }
635 }
636 
637 #if INCLUDE_CDS_JAVA_HEAP
638 oop Klass::archived_java_mirror() {
639   assert(has_archived_mirror_index(), "must have archived mirror");
640   return HeapShared::get_root(_archived_mirror_index);
641 }
642 
643 void Klass::clear_archived_mirror_index() {
644   if (_archived_mirror_index >= 0) {
645     HeapShared::clear_root(_archived_mirror_index);
646   }
647   _archived_mirror_index = -1;
648 }
649 
650 // No GC barrier
651 void Klass::set_archived_java_mirror(oop m) {
652   assert(DumpSharedSpaces, "called only during runtime");
653   _archived_mirror_index = HeapShared::append_root(m);
654 }
655 #endif // INCLUDE_CDS_JAVA_HEAP
656 
657 void Klass::check_array_allocation_length(int length, int max_length, TRAPS) {
658   if (length > max_length) {
659     if (!THREAD->in_retryable_allocation()) {
660       report_java_out_of_memory("Requested array size exceeds VM limit");
661       JvmtiExport::post_array_size_exhausted();
662       THROW_OOP(Universe::out_of_memory_error_array_size());
663     } else {
664       THROW_OOP(Universe::out_of_memory_error_retry());
665     }
666   } else if (length < 0) {
667     THROW_MSG(vmSymbols::java_lang_NegativeArraySizeException(), err_msg("%d", length));
668   }
669 }
670 
671 // Replace the last '+' char with '/'.
672 static char* convert_hidden_name_to_java(Symbol* name) {
673   size_t name_len = name->utf8_length();
674   char* result = NEW_RESOURCE_ARRAY(char, name_len + 1);
675   name->as_klass_external_name(result, (int)name_len + 1);
676   for (int index = (int)name_len; index > 0; index--) {
677     if (result[index] == '+') {
678       result[index] = JVM_SIGNATURE_SLASH;
679       break;
680     }
681   }
682   return result;
683 }
684 
685 // In product mode, this function doesn't have virtual function calls so
686 // there might be some performance advantage to handling InstanceKlass here.
687 const char* Klass::external_name() const {
688   if (is_instance_klass()) {
689     const InstanceKlass* ik = static_cast<const InstanceKlass*>(this);
690     if (ik->is_hidden()) {
691       char* result = convert_hidden_name_to_java(name());
692       return result;
693     }
694   } else if (is_objArray_klass() && ObjArrayKlass::cast(this)->bottom_klass()->is_hidden()) {
695     char* result = convert_hidden_name_to_java(name());
696     return result;
697   }
698   if (name() == NULL)  return "<unknown>";
699   return name()->as_klass_external_name();
700 }
701 
702 const char* Klass::signature_name() const {
703   if (name() == NULL)  return "<unknown>";
704   if (is_objArray_klass() && ObjArrayKlass::cast(this)->bottom_klass()->is_hidden()) {
705     size_t name_len = name()->utf8_length();
706     char* result = NEW_RESOURCE_ARRAY(char, name_len + 1);
707     name()->as_C_string(result, (int)name_len + 1);
708     for (int index = (int)name_len; index > 0; index--) {
709       if (result[index] == '+') {
710         result[index] = JVM_SIGNATURE_DOT;
711         break;
712       }
713     }
714     return result;
715   }
716   return name()->as_C_string();
717 }
718 
719 const char* Klass::external_kind() const {
720   if (is_interface()) return "interface";
721   if (is_abstract()) return "abstract class";
722   return "class";
723 }
724 
725 int Klass::atomic_incr_biased_lock_revocation_count() {
726   return (int) Atomic::add(&_biased_lock_revocation_count, 1);
727 }
728 
729 // Unless overridden, jvmti_class_status has no flags set.
730 jint Klass::jvmti_class_status() const {
731   return 0;
732 }
733 
734 
735 // Printing
736 
737 void Klass::print_on(outputStream* st) const {
738   ResourceMark rm;
739   // print title
740   st->print("%s", internal_name());
741   print_address_on(st);
742   st->cr();
743 }
744 
745 #define BULLET  " - "
746 
747 // Caller needs ResourceMark
748 void Klass::oop_print_on(oop obj, outputStream* st) {
749   // print title
750   st->print_cr("%s ", internal_name());
751   obj->print_address_on(st);
752 
753   if (WizardMode) {
754      // print header
755      obj->mark().print_on(st);
756      st->cr();
757      st->print(BULLET"prototype_header: " INTPTR_FORMAT, _prototype_header.value());
758      st->cr();
759   }
760 
761   // print class
762   st->print(BULLET"klass: ");
763   obj->klass()->print_value_on(st);
764   st->cr();
765 }
766 
767 void Klass::oop_print_value_on(oop obj, outputStream* st) {
768   // print title
769   ResourceMark rm;              // Cannot print in debug mode without this
770   st->print("%s", internal_name());
771   obj->print_address_on(st);
772 }
773 
774 // Verification
775 
776 void Klass::verify_on(outputStream* st) {
777 
778   // This can be expensive, but it is worth checking that this klass is actually
779   // in the CLD graph but not in production.
780   assert(Metaspace::contains((address)this), "Should be");
781 
782   guarantee(this->is_klass(),"should be klass");
783 
784   if (super() != NULL) {
785     guarantee(super()->is_klass(), "should be klass");
786   }
787   if (secondary_super_cache() != NULL) {
788     Klass* ko = secondary_super_cache();
789     guarantee(ko->is_klass(), "should be klass");
790   }
791   for ( uint i = 0; i < primary_super_limit(); i++ ) {
792     Klass* ko = _primary_supers[i];
793     if (ko != NULL) {
794       guarantee(ko->is_klass(), "should be klass");
795     }
796   }
797 
798   if (java_mirror_no_keepalive() != NULL) {
799     guarantee(oopDesc::is_oop(java_mirror_no_keepalive()), "should be instance");
800   }
801 }
802 
803 void Klass::oop_verify_on(oop obj, outputStream* st) {
804   guarantee(oopDesc::is_oop(obj),  "should be oop");
805   guarantee(obj->klass()->is_klass(), "klass field is not a klass");
806 }
807 
808 bool Klass::is_valid(Klass* k) {
809   if (!is_aligned(k, sizeof(MetaWord))) return false;
810   if ((size_t)k < os::min_page_size()) return false;
811 
812   if (!os::is_readable_range(k, k + 1)) return false;
813   if (!Metaspace::contains(k)) return false;
814 
815   if (!Symbol::is_valid(k->name())) return false;
816   return ClassLoaderDataGraph::is_valid(k->class_loader_data());
817 }
818 
819 Method* Klass::method_at_vtable(int index)  {
820 #ifndef PRODUCT
821   assert(index >= 0, "valid vtable index");
822   if (DebugVtables) {
823     verify_vtable_index(index);
824   }
825 #endif
826   return start_of_vtable()[index].method();
827 }
828 
829 
830 #ifndef PRODUCT
831 
832 bool Klass::verify_vtable_index(int i) {
833   int limit = vtable_length()/vtableEntry::size();
834   assert(i >= 0 && i < limit, "index %d out of bounds %d", i, limit);
835   return true;
836 }
837 
838 #endif // PRODUCT
839 
840 // Caller needs ResourceMark
841 // joint_in_module_of_loader provides an optimization if 2 classes are in
842 // the same module to succinctly print out relevant information about their
843 // module name and class loader's name_and_id for error messages.
844 // Format:
845 //   <fully-qualified-external-class-name1> and <fully-qualified-external-class-name2>
846 //                      are in module <module-name>[@<version>]
847 //                      of loader <loader-name_and_id>[, parent loader <parent-loader-name_and_id>]
848 const char* Klass::joint_in_module_of_loader(const Klass* class2, bool include_parent_loader) const {
849   assert(module() == class2->module(), "classes do not have the same module");
850   const char* class1_name = external_name();
851   size_t len = strlen(class1_name) + 1;
852 
853   const char* class2_description = class2->class_in_module_of_loader(true, include_parent_loader);
854   len += strlen(class2_description);
855 
856   len += strlen(" and ");
857 
858   char* joint_description = NEW_RESOURCE_ARRAY_RETURN_NULL(char, len);
859 
860   // Just return the FQN if error when allocating string
861   if (joint_description == NULL) {
862     return class1_name;
863   }
864 
865   jio_snprintf(joint_description, len, "%s and %s",
866                class1_name,
867                class2_description);
868 
869   return joint_description;
870 }
871 
872 // Caller needs ResourceMark
873 // class_in_module_of_loader provides a standard way to include
874 // relevant information about a class, such as its module name as
875 // well as its class loader's name_and_id, in error messages and logging.
876 // Format:
877 //   <fully-qualified-external-class-name> is in module <module-name>[@<version>]
878 //                                         of loader <loader-name_and_id>[, parent loader <parent-loader-name_and_id>]
879 const char* Klass::class_in_module_of_loader(bool use_are, bool include_parent_loader) const {
880   // 1. fully qualified external name of class
881   const char* klass_name = external_name();
882   size_t len = strlen(klass_name) + 1;
883 
884   // 2. module name + @version
885   const char* module_name = "";
886   const char* version = "";
887   bool has_version = false;
888   bool module_is_named = false;
889   const char* module_name_phrase = "";
890   const Klass* bottom_klass = is_objArray_klass() ?
891                                 ObjArrayKlass::cast(this)->bottom_klass() : this;
892   if (bottom_klass->is_instance_klass()) {
893     ModuleEntry* module = InstanceKlass::cast(bottom_klass)->module();
894     if (module->is_named()) {
895       module_is_named = true;
896       module_name_phrase = "module ";
897       module_name = module->name()->as_C_string();
898       len += strlen(module_name);
899       // Use version if exists and is not a jdk module
900       if (module->should_show_version()) {
901         has_version = true;
902         version = module->version()->as_C_string();
903         // Include stlen(version) + 1 for the "@"
904         len += strlen(version) + 1;
905       }
906     } else {
907       module_name = UNNAMED_MODULE;
908       len += UNNAMED_MODULE_LEN;
909     }
910   } else {
911     // klass is an array of primitives, module is java.base
912     module_is_named = true;
913     module_name_phrase = "module ";
914     module_name = JAVA_BASE_NAME;
915     len += JAVA_BASE_NAME_LEN;
916   }
917 
918   // 3. class loader's name_and_id
919   ClassLoaderData* cld = class_loader_data();
920   assert(cld != NULL, "class_loader_data should not be null");
921   const char* loader_name_and_id = cld->loader_name_and_id();
922   len += strlen(loader_name_and_id);
923 
924   // 4. include parent loader information
925   const char* parent_loader_phrase = "";
926   const char* parent_loader_name_and_id = "";
927   if (include_parent_loader &&
928       !cld->is_builtin_class_loader_data()) {
929     oop parent_loader = java_lang_ClassLoader::parent(class_loader());
930     ClassLoaderData *parent_cld = ClassLoaderData::class_loader_data_or_null(parent_loader);
931     // The parent loader's ClassLoaderData could be null if it is
932     // a delegating class loader that has never defined a class.
933     // In this case the loader's name must be obtained via the parent loader's oop.
934     if (parent_cld == NULL) {
935       oop cl_name_and_id = java_lang_ClassLoader::nameAndId(parent_loader);
936       if (cl_name_and_id != NULL) {
937         parent_loader_name_and_id = java_lang_String::as_utf8_string(cl_name_and_id);
938       }
939     } else {
940       parent_loader_name_and_id = parent_cld->loader_name_and_id();
941     }
942     parent_loader_phrase = ", parent loader ";
943     len += strlen(parent_loader_phrase) + strlen(parent_loader_name_and_id);
944   }
945 
946   // Start to construct final full class description string
947   len += ((use_are) ? strlen(" are in ") : strlen(" is in "));
948   len += strlen(module_name_phrase) + strlen(" of loader ");
949 
950   char* class_description = NEW_RESOURCE_ARRAY_RETURN_NULL(char, len);
951 
952   // Just return the FQN if error when allocating string
953   if (class_description == NULL) {
954     return klass_name;
955   }
956 
957   jio_snprintf(class_description, len, "%s %s in %s%s%s%s of loader %s%s%s",
958                klass_name,
959                (use_are) ? "are" : "is",
960                module_name_phrase,
961                module_name,
962                (has_version) ? "@" : "",
963                (has_version) ? version : "",
964                loader_name_and_id,
965                parent_loader_phrase,
966                parent_loader_name_and_id);
967 
968   return class_description;
969 }