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