1 /*
  2  * Copyright (c) 1997, 2023, Oracle and/or its affiliates. All rights reserved.
  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  4  *
  5  * This code is free software; you can redistribute it and/or modify it
  6  * under the terms of the GNU General Public License version 2 only, as
  7  * published by the Free Software Foundation.
  8  *
  9  * This code is distributed in the hope that it will be useful, but WITHOUT
 10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 12  * version 2 for more details (a copy is included in the LICENSE file that
 13  * accompanied this code).
 14  *
 15  * You should have received a copy of the GNU General Public License version
 16  * 2 along with this work; if not, write to the Free Software Foundation,
 17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 18  *
 19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 20  * or visit www.oracle.com if you need additional information or have any
 21  * questions.
 22  *
 23  */
 24 
 25 #include "precompiled.hpp"
 26 #include "cds/archiveHeapLoader.hpp"
 27 #include "cds/cdsConfig.hpp"
 28 #include "cds/heapShared.hpp"
 29 #include "classfile/classLoaderData.inline.hpp"
 30 #include "classfile/classLoaderDataGraph.inline.hpp"
 31 #include "classfile/javaClasses.inline.hpp"
 32 #include "classfile/moduleEntry.hpp"
 33 #include "classfile/systemDictionary.hpp"
 34 #include "classfile/systemDictionaryShared.hpp"
 35 #include "classfile/vmClasses.hpp"
 36 #include "classfile/vmSymbols.hpp"
 37 #include "gc/shared/collectedHeap.inline.hpp"
 38 #include "jvm_io.h"
 39 #include "logging/log.hpp"
 40 #include "memory/metadataFactory.hpp"
 41 #include "memory/metaspaceClosure.hpp"
 42 #include "memory/oopFactory.hpp"
 43 #include "memory/resourceArea.hpp"
 44 #include "memory/universe.hpp"
 45 #include "oops/compressedOops.inline.hpp"
 46 #include "oops/instanceKlass.hpp"
 47 #include "oops/klass.inline.hpp"
 48 #include "oops/objArrayKlass.hpp"
 49 #include "oops/oop.inline.hpp"
 50 #include "oops/oopHandle.inline.hpp"
 51 #include "prims/jvmtiExport.hpp"
 52 #include "runtime/atomic.hpp"
 53 #include "runtime/handles.inline.hpp"
 54 #include "utilities/macros.hpp"
 55 #include "utilities/powerOfTwo.hpp"
 56 #include "utilities/stack.inline.hpp"
 57 
 58 void Klass::set_java_mirror(Handle m) {
 59   assert(!m.is_null(), "New mirror should never be null.");
 60   assert(_java_mirror.is_empty(), "should only be used to initialize mirror");
 61   _java_mirror = class_loader_data()->add_handle(m);
 62 }
 63 
 64 bool Klass::is_cloneable() const {
 65   return _access_flags.is_cloneable_fast() ||
 66          is_subtype_of(vmClasses::Cloneable_klass());
 67 }
 68 
 69 void Klass::set_is_cloneable() {
 70   if (name() == vmSymbols::java_lang_invoke_MemberName()) {
 71     assert(is_final(), "no subclasses allowed");
 72     // MemberName cloning should not be intrinsified and always happen in JVM_Clone.
 73   } else if (is_instance_klass() && InstanceKlass::cast(this)->reference_type() != REF_NONE) {
 74     // Reference cloning should not be intrinsified and always happen in JVM_Clone.
 75   } else {
 76     _access_flags.set_is_cloneable_fast();
 77   }
 78 }
 79 
 80 void Klass::set_name(Symbol* n) {
 81   _name = n;
 82   if (_name != nullptr) _name->increment_refcount();
 83 
 84   if (CDSConfig::is_dumping_archive() && is_instance_klass()) {
 85     SystemDictionaryShared::init_dumptime_info(InstanceKlass::cast(this));
 86   }
 87 }
 88 
 89 bool Klass::is_subclass_of(const Klass* k) const {
 90   // Run up the super chain and check
 91   if (this == k) return true;
 92 
 93   Klass* t = const_cast<Klass*>(this)->super();
 94 
 95   while (t != nullptr) {
 96     if (t == k) return true;
 97     t = t->super();
 98   }
 99   return false;
100 }
101 
102 void Klass::release_C_heap_structures(bool release_constant_pool) {
103   if (_name != nullptr) _name->decrement_refcount();
104 }
105 
106 bool Klass::search_secondary_supers(Klass* k) const {
107   // Put some extra logic here out-of-line, before the search proper.
108   // This cuts down the size of the inline method.
109 
110   // This is necessary, since I am never in my own secondary_super list.
111   if (this == k)
112     return true;
113   // Scan the array-of-objects for a match
114   int cnt = secondary_supers()->length();
115   for (int i = 0; i < cnt; i++) {
116     if (secondary_supers()->at(i) == k) {
117       ((Klass*)this)->set_secondary_super_cache(k);
118       return true;
119     }
120   }
121   return false;
122 }
123 
124 // Return self, except for abstract classes with exactly 1
125 // implementor.  Then return the 1 concrete implementation.
126 Klass *Klass::up_cast_abstract() {
127   Klass *r = this;
128   while( r->is_abstract() ) {   // Receiver is abstract?
129     Klass *s = r->subklass();   // Check for exactly 1 subklass
130     if (s == nullptr || s->next_sibling() != nullptr) // Oops; wrong count; give up
131       return this;              // Return 'this' as a no-progress flag
132     r = s;                    // Loop till find concrete class
133   }
134   return r;                   // Return the 1 concrete class
135 }
136 
137 // Find LCA in class hierarchy
138 Klass *Klass::LCA( Klass *k2 ) {
139   Klass *k1 = this;
140   while( 1 ) {
141     if( k1->is_subtype_of(k2) ) return k2;
142     if( k2->is_subtype_of(k1) ) return k1;
143     k1 = k1->super();
144     k2 = k2->super();
145   }
146 }
147 
148 
149 void Klass::check_valid_for_instantiation(bool throwError, TRAPS) {
150   ResourceMark rm(THREAD);
151   THROW_MSG(throwError ? vmSymbols::java_lang_InstantiationError()
152             : vmSymbols::java_lang_InstantiationException(), external_name());
153 }
154 
155 
156 void Klass::copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS) {
157   ResourceMark rm(THREAD);
158   assert(s != nullptr, "Throw NPE!");
159   THROW_MSG(vmSymbols::java_lang_ArrayStoreException(),
160             err_msg("arraycopy: source type %s is not an array", s->klass()->external_name()));
161 }
162 
163 
164 void Klass::initialize(TRAPS) {
165   ShouldNotReachHere();
166 }
167 
168 Klass* Klass::find_field(Symbol* name, Symbol* sig, fieldDescriptor* fd) const {
169 #ifdef ASSERT
170   tty->print_cr("Error: find_field called on a klass oop."
171                 " Likely error: reflection method does not correctly"
172                 " wrap return value in a mirror object.");
173 #endif
174   ShouldNotReachHere();
175   return nullptr;
176 }
177 
178 Method* Klass::uncached_lookup_method(const Symbol* name, const Symbol* signature,
179                                       OverpassLookupMode overpass_mode,
180                                       PrivateLookupMode private_mode) const {
181 #ifdef ASSERT
182   tty->print_cr("Error: uncached_lookup_method called on a klass oop."
183                 " Likely error: reflection method does not correctly"
184                 " wrap return value in a mirror object.");
185 #endif
186   ShouldNotReachHere();
187   return nullptr;
188 }
189 
190 void* Klass::operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw() {
191   return Metaspace::allocate(loader_data, word_size, MetaspaceObj::ClassType, THREAD);
192 }
193 
194 Klass::Klass() : _kind(UnknownKlassKind) {
195   assert(CDSConfig::is_dumping_static_archive() || UseSharedSpaces, "only for cds");
196 }
197 
198 // "Normal" instantiation is preceded by a MetaspaceObj allocation
199 // which zeros out memory - calloc equivalent.
200 // The constructor is also used from CppVtableCloner,
201 // which doesn't zero out the memory before calling the constructor.
202 Klass::Klass(KlassKind kind) : _kind(kind),
203                            _shared_class_path_index(-1) {
204   CDS_ONLY(_shared_class_flags = 0;)
205   CDS_JAVA_HEAP_ONLY(_archived_mirror_index = -1;)
206   _primary_supers[0] = this;
207   set_super_check_offset(in_bytes(primary_supers_offset()));
208 }
209 
210 jint Klass::array_layout_helper(BasicType etype) {
211   assert(etype >= T_BOOLEAN && etype <= T_OBJECT, "valid etype");
212   // Note that T_ARRAY is not allowed here.
213   int  hsize = arrayOopDesc::base_offset_in_bytes(etype);
214   int  esize = type2aelembytes(etype);
215   bool isobj = (etype == T_OBJECT);
216   int  tag   =  isobj ? _lh_array_tag_obj_value : _lh_array_tag_type_value;
217   int lh = array_layout_helper(tag, hsize, etype, exact_log2(esize));
218 
219   assert(lh < (int)_lh_neutral_value, "must look like an array layout");
220   assert(layout_helper_is_array(lh), "correct kind");
221   assert(layout_helper_is_objArray(lh) == isobj, "correct kind");
222   assert(layout_helper_is_typeArray(lh) == !isobj, "correct kind");
223   assert(layout_helper_header_size(lh) == hsize, "correct decode");
224   assert(layout_helper_element_type(lh) == etype, "correct decode");
225   assert(1 << layout_helper_log2_element_size(lh) == esize, "correct decode");
226 
227   return lh;
228 }
229 
230 bool Klass::can_be_primary_super_slow() const {
231   if (super() == nullptr)
232     return true;
233   else if (super()->super_depth() >= primary_super_limit()-1)
234     return false;
235   else
236     return true;
237 }
238 
239 void Klass::initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS) {
240   if (k == nullptr) {
241     set_super(nullptr);
242     _primary_supers[0] = this;
243     assert(super_depth() == 0, "Object must already be initialized properly");
244   } else if (k != super() || k == vmClasses::Object_klass()) {
245     assert(super() == nullptr || super() == vmClasses::Object_klass(),
246            "initialize this only once to a non-trivial value");
247     set_super(k);
248     Klass* sup = k;
249     int sup_depth = sup->super_depth();
250     juint my_depth  = MIN2(sup_depth + 1, (int)primary_super_limit());
251     if (!can_be_primary_super_slow())
252       my_depth = primary_super_limit();
253     for (juint i = 0; i < my_depth; i++) {
254       _primary_supers[i] = sup->_primary_supers[i];
255     }
256     Klass* *super_check_cell;
257     if (my_depth < primary_super_limit()) {
258       _primary_supers[my_depth] = this;
259       super_check_cell = &_primary_supers[my_depth];
260     } else {
261       // Overflow of the primary_supers array forces me to be secondary.
262       super_check_cell = &_secondary_super_cache;
263     }
264     set_super_check_offset(u4((address)super_check_cell - (address) this));
265 
266 #ifdef ASSERT
267     {
268       juint j = super_depth();
269       assert(j == my_depth, "computed accessor gets right answer");
270       Klass* t = this;
271       while (!t->can_be_primary_super()) {
272         t = t->super();
273         j = t->super_depth();
274       }
275       for (juint j1 = j+1; j1 < primary_super_limit(); j1++) {
276         assert(primary_super_of_depth(j1) == nullptr, "super list padding");
277       }
278       while (t != nullptr) {
279         assert(primary_super_of_depth(j) == t, "super list initialization");
280         t = t->super();
281         --j;
282       }
283       assert(j == (juint)-1, "correct depth count");
284     }
285 #endif
286   }
287 
288   if (secondary_supers() == nullptr) {
289 
290     // Now compute the list of secondary supertypes.
291     // Secondaries can occasionally be on the super chain,
292     // if the inline "_primary_supers" array overflows.
293     int extras = 0;
294     Klass* p;
295     for (p = super(); !(p == nullptr || p->can_be_primary_super()); p = p->super()) {
296       ++extras;
297     }
298 
299     ResourceMark rm(THREAD);  // need to reclaim GrowableArrays allocated below
300 
301     // Compute the "real" non-extra secondaries.
302     GrowableArray<Klass*>* secondaries = compute_secondary_supers(extras, transitive_interfaces);
303     if (secondaries == nullptr) {
304       // secondary_supers set by compute_secondary_supers
305       return;
306     }
307 
308     GrowableArray<Klass*>* primaries = new GrowableArray<Klass*>(extras);
309 
310     for (p = super(); !(p == nullptr || p->can_be_primary_super()); p = p->super()) {
311       int i;                    // Scan for overflow primaries being duplicates of 2nd'arys
312 
313       // This happens frequently for very deeply nested arrays: the
314       // primary superclass chain overflows into the secondary.  The
315       // secondary list contains the element_klass's secondaries with
316       // an extra array dimension added.  If the element_klass's
317       // secondary list already contains some primary overflows, they
318       // (with the extra level of array-ness) will collide with the
319       // normal primary superclass overflows.
320       for( i = 0; i < secondaries->length(); i++ ) {
321         if( secondaries->at(i) == p )
322           break;
323       }
324       if( i < secondaries->length() )
325         continue;               // It's a dup, don't put it in
326       primaries->push(p);
327     }
328     // Combine the two arrays into a metadata object to pack the array.
329     // The primaries are added in the reverse order, then the secondaries.
330     int new_length = primaries->length() + secondaries->length();
331     Array<Klass*>* s2 = MetadataFactory::new_array<Klass*>(
332                                        class_loader_data(), new_length, CHECK);
333     int fill_p = primaries->length();
334     for (int j = 0; j < fill_p; j++) {
335       s2->at_put(j, primaries->pop());  // add primaries in reverse order.
336     }
337     for( int j = 0; j < secondaries->length(); j++ ) {
338       s2->at_put(j+fill_p, secondaries->at(j));  // add secondaries on the end.
339     }
340 
341   #ifdef ASSERT
342       // We must not copy any null placeholders left over from bootstrap.
343     for (int j = 0; j < s2->length(); j++) {
344       assert(s2->at(j) != nullptr, "correct bootstrapping order");
345     }
346   #endif
347 
348     set_secondary_supers(s2);
349   }
350 }
351 
352 GrowableArray<Klass*>* Klass::compute_secondary_supers(int num_extra_slots,
353                                                        Array<InstanceKlass*>* transitive_interfaces) {
354   assert(num_extra_slots == 0, "override for complex klasses");
355   assert(transitive_interfaces == nullptr, "sanity");
356   set_secondary_supers(Universe::the_empty_klass_array());
357   return nullptr;
358 }
359 
360 
361 // superklass links
362 InstanceKlass* Klass::superklass() const {
363   assert(super() == nullptr || super()->is_instance_klass(), "must be instance klass");
364   return _super == nullptr ? nullptr : InstanceKlass::cast(_super);
365 }
366 
367 // subklass links.  Used by the compiler (and vtable initialization)
368 // May be cleaned concurrently, so must use the Compile_lock.
369 // The log parameter is for clean_weak_klass_links to report unlinked classes.
370 Klass* Klass::subklass(bool log) const {
371   // Need load_acquire on the _subklass, because it races with inserts that
372   // publishes freshly initialized data.
373   for (Klass* chain = Atomic::load_acquire(&_subklass);
374        chain != nullptr;
375        // Do not need load_acquire on _next_sibling, because inserts never
376        // create _next_sibling edges to dead data.
377        chain = Atomic::load(&chain->_next_sibling))
378   {
379     if (chain->is_loader_alive()) {
380       return chain;
381     } else if (log) {
382       if (log_is_enabled(Trace, class, unload)) {
383         ResourceMark rm;
384         log_trace(class, unload)("unlinking class (subclass): %s", chain->external_name());
385       }
386     }
387   }
388   return nullptr;
389 }
390 
391 Klass* Klass::next_sibling(bool log) const {
392   // Do not need load_acquire on _next_sibling, because inserts never
393   // create _next_sibling edges to dead data.
394   for (Klass* chain = Atomic::load(&_next_sibling);
395        chain != nullptr;
396        chain = Atomic::load(&chain->_next_sibling)) {
397     // Only return alive klass, there may be stale klass
398     // in this chain if cleaned concurrently.
399     if (chain->is_loader_alive()) {
400       return chain;
401     } else if (log) {
402       if (log_is_enabled(Trace, class, unload)) {
403         ResourceMark rm;
404         log_trace(class, unload)("unlinking class (sibling): %s", chain->external_name());
405       }
406     }
407   }
408   return nullptr;
409 }
410 
411 void Klass::set_subklass(Klass* s) {
412   assert(s != this, "sanity check");
413   Atomic::release_store(&_subklass, s);
414 }
415 
416 void Klass::set_next_sibling(Klass* s) {
417   assert(s != this, "sanity check");
418   // Does not need release semantics. If used by cleanup, it will link to
419   // already safely published data, and if used by inserts, will be published
420   // safely using cmpxchg.
421   Atomic::store(&_next_sibling, s);
422 }
423 
424 void Klass::append_to_sibling_list() {
425   if (Universe::is_fully_initialized()) {
426     assert_locked_or_safepoint(Compile_lock);
427   }
428   debug_only(verify();)
429   // add ourselves to superklass' subklass list
430   InstanceKlass* super = superklass();
431   if (super == nullptr) return;     // special case: class Object
432   assert((!super->is_interface()    // interfaces cannot be supers
433           && (super->superklass() == nullptr || !is_interface())),
434          "an interface can only be a subklass of Object");
435 
436   // Make sure there is no stale subklass head
437   super->clean_subklass();
438 
439   for (;;) {
440     Klass* prev_first_subklass = Atomic::load_acquire(&_super->_subklass);
441     if (prev_first_subklass != nullptr) {
442       // set our sibling to be the superklass' previous first subklass
443       assert(prev_first_subklass->is_loader_alive(), "May not attach not alive klasses");
444       set_next_sibling(prev_first_subklass);
445     }
446     // Note that the prev_first_subklass is always alive, meaning no sibling_next links
447     // are ever created to not alive klasses. This is an important invariant of the lock-free
448     // cleaning protocol, that allows us to safely unlink dead klasses from the sibling list.
449     if (Atomic::cmpxchg(&super->_subklass, prev_first_subklass, this) == prev_first_subklass) {
450       return;
451     }
452   }
453   debug_only(verify();)
454 }
455 
456 void Klass::clean_subklass() {
457   for (;;) {
458     // Need load_acquire, due to contending with concurrent inserts
459     Klass* subklass = Atomic::load_acquire(&_subklass);
460     if (subklass == nullptr || subklass->is_loader_alive()) {
461       return;
462     }
463     // Try to fix _subklass until it points at something not dead.
464     Atomic::cmpxchg(&_subklass, subklass, subklass->next_sibling());
465   }
466 }
467 
468 void Klass::clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses) {
469   if (!ClassUnloading || !unloading_occurred) {
470     return;
471   }
472 
473   Klass* root = vmClasses::Object_klass();
474   Stack<Klass*, mtGC> stack;
475 
476   stack.push(root);
477   while (!stack.is_empty()) {
478     Klass* current = stack.pop();
479 
480     assert(current->is_loader_alive(), "just checking, this should be live");
481 
482     // Find and set the first alive subklass
483     Klass* sub = current->subklass(true);
484     current->clean_subklass();
485     if (sub != nullptr) {
486       stack.push(sub);
487     }
488 
489     // Find and set the first alive sibling
490     Klass* sibling = current->next_sibling(true);
491     current->set_next_sibling(sibling);
492     if (sibling != nullptr) {
493       stack.push(sibling);
494     }
495 
496     // Clean the implementors list and method data.
497     if (clean_alive_klasses && current->is_instance_klass()) {
498       InstanceKlass* ik = InstanceKlass::cast(current);
499       ik->clean_weak_instanceklass_links();
500 
501       // JVMTI RedefineClasses creates previous versions that are not in
502       // the class hierarchy, so process them here.
503       while ((ik = ik->previous_versions()) != nullptr) {
504         ik->clean_weak_instanceklass_links();
505       }
506     }
507   }
508 }
509 
510 void Klass::metaspace_pointers_do(MetaspaceClosure* it) {
511   if (log_is_enabled(Trace, cds)) {
512     ResourceMark rm;
513     log_trace(cds)("Iter(Klass): %p (%s)", this, external_name());
514   }
515 
516   it->push(&_name);
517   it->push(&_secondary_super_cache);
518   it->push(&_secondary_supers);
519   for (int i = 0; i < _primary_super_limit; i++) {
520     it->push(&_primary_supers[i]);
521   }
522   it->push(&_super);
523   if (!CDSConfig::is_dumping_archive()) {
524     // If dumping archive, these may point to excluded classes. There's no need
525     // to follow these pointers anyway, as they will be set to null in
526     // remove_unshareable_info().
527     it->push((Klass**)&_subklass);
528     it->push((Klass**)&_next_sibling);
529     it->push(&_next_link);
530   }
531 
532   vtableEntry* vt = start_of_vtable();
533   for (int i=0; i<vtable_length(); i++) {
534     it->push(vt[i].method_addr());
535   }
536 }
537 
538 #if INCLUDE_CDS
539 void Klass::remove_unshareable_info() {
540   assert(CDSConfig::is_dumping_archive(),
541           "only called during CDS dump time");
542   JFR_ONLY(REMOVE_ID(this);)
543   if (log_is_enabled(Trace, cds, unshareable)) {
544     ResourceMark rm;
545     log_trace(cds, unshareable)("remove: %s", external_name());
546   }
547 
548   set_subklass(nullptr);
549   set_next_sibling(nullptr);
550   set_next_link(nullptr);
551 
552   // Null out class_loader_data because we don't share that yet.
553   set_class_loader_data(nullptr);
554   set_is_shared();
555 }
556 
557 void Klass::remove_java_mirror() {
558   assert(CDSConfig::is_dumping_archive(), "sanity");
559   if (log_is_enabled(Trace, cds, unshareable)) {
560     ResourceMark rm;
561     log_trace(cds, unshareable)("remove java_mirror: %s", external_name());
562   }
563   // Just null out the mirror.  The class_loader_data() no longer exists.
564   clear_java_mirror_handle();
565 }
566 
567 void Klass::restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS) {
568   assert(is_klass(), "ensure C++ vtable is restored");
569   assert(is_shared(), "must be set");
570   JFR_ONLY(RESTORE_ID(this);)
571   if (log_is_enabled(Trace, cds, unshareable)) {
572     ResourceMark rm(THREAD);
573     oop class_loader = loader_data->class_loader();
574     log_trace(cds, unshareable)("restore: %s with class loader: %s", external_name(),
575       class_loader != nullptr ? class_loader->klass()->external_name() : "boot");
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() == nullptr) {
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 = nullptr;
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 != nullptr) ? module_entry->module() : (oop)nullptr));
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 (ArchiveHeapLoader::is_in_use()) {
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() == nullptr) {
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 #endif // INCLUDE_CDS
632 
633 #if INCLUDE_CDS_JAVA_HEAP
634 oop Klass::archived_java_mirror() {
635   assert(has_archived_mirror_index(), "must have archived mirror");
636   return HeapShared::get_root(_archived_mirror_index);
637 }
638 
639 void Klass::clear_archived_mirror_index() {
640   if (_archived_mirror_index >= 0) {
641     HeapShared::clear_root(_archived_mirror_index);
642   }
643   _archived_mirror_index = -1;
644 }
645 
646 // No GC barrier
647 void Klass::set_archived_java_mirror(int mirror_index) {
648   assert(CDSConfig::is_dumping_heap(), "sanity");
649   _archived_mirror_index = mirror_index;
650 }
651 #endif // INCLUDE_CDS_JAVA_HEAP
652 
653 void Klass::check_array_allocation_length(int length, int max_length, TRAPS) {
654   if (length > max_length) {
655     if (!THREAD->in_retryable_allocation()) {
656       report_java_out_of_memory("Requested array size exceeds VM limit");
657       JvmtiExport::post_array_size_exhausted();
658       THROW_OOP(Universe::out_of_memory_error_array_size());
659     } else {
660       THROW_OOP(Universe::out_of_memory_error_retry());
661     }
662   } else if (length < 0) {
663     THROW_MSG(vmSymbols::java_lang_NegativeArraySizeException(), err_msg("%d", length));
664   }
665 }
666 
667 // Replace the last '+' char with '/'.
668 static char* convert_hidden_name_to_java(Symbol* name) {
669   size_t name_len = name->utf8_length();
670   char* result = NEW_RESOURCE_ARRAY(char, name_len + 1);
671   name->as_klass_external_name(result, (int)name_len + 1);
672   for (int index = (int)name_len; index > 0; index--) {
673     if (result[index] == '+') {
674       result[index] = JVM_SIGNATURE_SLASH;
675       break;
676     }
677   }
678   return result;
679 }
680 
681 // In product mode, this function doesn't have virtual function calls so
682 // there might be some performance advantage to handling InstanceKlass here.
683 const char* Klass::external_name() const {
684   if (is_instance_klass()) {
685     const InstanceKlass* ik = static_cast<const InstanceKlass*>(this);
686     if (ik->is_hidden()) {
687       char* result = convert_hidden_name_to_java(name());
688       return result;
689     }
690   } else if (is_objArray_klass() && ObjArrayKlass::cast(this)->bottom_klass()->is_hidden()) {
691     char* result = convert_hidden_name_to_java(name());
692     return result;
693   }
694   if (name() == nullptr)  return "<unknown>";
695   return name()->as_klass_external_name();
696 }
697 
698 const char* Klass::signature_name() const {
699   if (name() == nullptr)  return "<unknown>";
700   if (is_objArray_klass() && ObjArrayKlass::cast(this)->bottom_klass()->is_hidden()) {
701     size_t name_len = name()->utf8_length();
702     char* result = NEW_RESOURCE_ARRAY(char, name_len + 1);
703     name()->as_C_string(result, (int)name_len + 1);
704     for (int index = (int)name_len; index > 0; index--) {
705       if (result[index] == '+') {
706         result[index] = JVM_SIGNATURE_DOT;
707         break;
708       }
709     }
710     return result;
711   }
712   return name()->as_C_string();
713 }
714 
715 const char* Klass::external_kind() const {
716   if (is_interface()) return "interface";
717   if (is_abstract()) return "abstract class";
718   return "class";
719 }
720 
721 // Unless overridden, jvmti_class_status has no flags set.
722 jint Klass::jvmti_class_status() const {
723   return 0;
724 }
725 
726 
727 // Printing
728 
729 void Klass::print_on(outputStream* st) const {
730   ResourceMark rm;
731   // print title
732   st->print("%s", internal_name());
733   print_address_on(st);
734   st->cr();
735 }
736 
737 #define BULLET  " - "
738 
739 // Caller needs ResourceMark
740 void Klass::oop_print_on(oop obj, outputStream* st) {
741   // print title
742   st->print_cr("%s ", internal_name());
743   obj->print_address_on(st);
744 
745   if (WizardMode) {
746      // print header
747      obj->mark().print_on(st);
748      st->cr();
749   }
750 
751   // print class
752   st->print(BULLET"klass: ");
753   obj->klass()->print_value_on(st);
754   st->cr();
755 }
756 
757 void Klass::oop_print_value_on(oop obj, outputStream* st) {
758   // print title
759   ResourceMark rm;              // Cannot print in debug mode without this
760   st->print("%s", internal_name());
761   obj->print_address_on(st);
762 }
763 
764 // Verification
765 
766 void Klass::verify_on(outputStream* st) {
767 
768   // This can be expensive, but it is worth checking that this klass is actually
769   // in the CLD graph but not in production.
770   assert(Metaspace::contains((address)this), "Should be");
771 
772   guarantee(this->is_klass(),"should be klass");
773 
774   if (super() != nullptr) {
775     guarantee(super()->is_klass(), "should be klass");
776   }
777   if (secondary_super_cache() != nullptr) {
778     Klass* ko = secondary_super_cache();
779     guarantee(ko->is_klass(), "should be klass");
780   }
781   for ( uint i = 0; i < primary_super_limit(); i++ ) {
782     Klass* ko = _primary_supers[i];
783     if (ko != nullptr) {
784       guarantee(ko->is_klass(), "should be klass");
785     }
786   }
787 
788   if (java_mirror_no_keepalive() != nullptr) {
789     guarantee(java_lang_Class::is_instance(java_mirror_no_keepalive()), "should be instance");
790   }
791 }
792 
793 void Klass::oop_verify_on(oop obj, outputStream* st) {
794   guarantee(oopDesc::is_oop(obj),  "should be oop");
795   guarantee(obj->klass()->is_klass(), "klass field is not a klass");
796 }
797 
798 bool Klass::is_valid(Klass* k) {
799   if (!is_aligned(k, sizeof(MetaWord))) return false;
800   if ((size_t)k < os::min_page_size()) return false;
801 
802   if (!os::is_readable_range(k, k + 1)) return false;
803   if (!Metaspace::contains(k)) return false;
804 
805   if (!Symbol::is_valid(k->name())) return false;
806   return ClassLoaderDataGraph::is_valid(k->class_loader_data());
807 }
808 
809 Method* Klass::method_at_vtable(int index)  {
810 #ifndef PRODUCT
811   assert(index >= 0, "valid vtable index");
812   if (DebugVtables) {
813     verify_vtable_index(index);
814   }
815 #endif
816   return start_of_vtable()[index].method();
817 }
818 
819 
820 #ifndef PRODUCT
821 
822 bool Klass::verify_vtable_index(int i) {
823   int limit = vtable_length()/vtableEntry::size();
824   assert(i >= 0 && i < limit, "index %d out of bounds %d", i, limit);
825   return true;
826 }
827 
828 #endif // PRODUCT
829 
830 // Caller needs ResourceMark
831 // joint_in_module_of_loader provides an optimization if 2 classes are in
832 // the same module to succinctly print out relevant information about their
833 // module name and class loader's name_and_id for error messages.
834 // Format:
835 //   <fully-qualified-external-class-name1> and <fully-qualified-external-class-name2>
836 //                      are in module <module-name>[@<version>]
837 //                      of loader <loader-name_and_id>[, parent loader <parent-loader-name_and_id>]
838 const char* Klass::joint_in_module_of_loader(const Klass* class2, bool include_parent_loader) const {
839   assert(module() == class2->module(), "classes do not have the same module");
840   const char* class1_name = external_name();
841   size_t len = strlen(class1_name) + 1;
842 
843   const char* class2_description = class2->class_in_module_of_loader(true, include_parent_loader);
844   len += strlen(class2_description);
845 
846   len += strlen(" and ");
847 
848   char* joint_description = NEW_RESOURCE_ARRAY_RETURN_NULL(char, len);
849 
850   // Just return the FQN if error when allocating string
851   if (joint_description == nullptr) {
852     return class1_name;
853   }
854 
855   jio_snprintf(joint_description, len, "%s and %s",
856                class1_name,
857                class2_description);
858 
859   return joint_description;
860 }
861 
862 // Caller needs ResourceMark
863 // class_in_module_of_loader provides a standard way to include
864 // relevant information about a class, such as its module name as
865 // well as its class loader's name_and_id, in error messages and logging.
866 // Format:
867 //   <fully-qualified-external-class-name> is in module <module-name>[@<version>]
868 //                                         of loader <loader-name_and_id>[, parent loader <parent-loader-name_and_id>]
869 const char* Klass::class_in_module_of_loader(bool use_are, bool include_parent_loader) const {
870   // 1. fully qualified external name of class
871   const char* klass_name = external_name();
872   size_t len = strlen(klass_name) + 1;
873 
874   // 2. module name + @version
875   const char* module_name = "";
876   const char* version = "";
877   bool has_version = false;
878   bool module_is_named = false;
879   const char* module_name_phrase = "";
880   const Klass* bottom_klass = is_objArray_klass() ?
881                                 ObjArrayKlass::cast(this)->bottom_klass() : this;
882   if (bottom_klass->is_instance_klass()) {
883     ModuleEntry* module = InstanceKlass::cast(bottom_klass)->module();
884     if (module->is_named()) {
885       module_is_named = true;
886       module_name_phrase = "module ";
887       module_name = module->name()->as_C_string();
888       len += strlen(module_name);
889       // Use version if exists and is not a jdk module
890       if (module->should_show_version()) {
891         has_version = true;
892         version = module->version()->as_C_string();
893         // Include stlen(version) + 1 for the "@"
894         len += strlen(version) + 1;
895       }
896     } else {
897       module_name = UNNAMED_MODULE;
898       len += UNNAMED_MODULE_LEN;
899     }
900   } else {
901     // klass is an array of primitives, module is java.base
902     module_is_named = true;
903     module_name_phrase = "module ";
904     module_name = JAVA_BASE_NAME;
905     len += JAVA_BASE_NAME_LEN;
906   }
907 
908   // 3. class loader's name_and_id
909   ClassLoaderData* cld = class_loader_data();
910   assert(cld != nullptr, "class_loader_data should not be null");
911   const char* loader_name_and_id = cld->loader_name_and_id();
912   len += strlen(loader_name_and_id);
913 
914   // 4. include parent loader information
915   const char* parent_loader_phrase = "";
916   const char* parent_loader_name_and_id = "";
917   if (include_parent_loader &&
918       !cld->is_builtin_class_loader_data()) {
919     oop parent_loader = java_lang_ClassLoader::parent(class_loader());
920     ClassLoaderData *parent_cld = ClassLoaderData::class_loader_data_or_null(parent_loader);
921     // The parent loader's ClassLoaderData could be null if it is
922     // a delegating class loader that has never defined a class.
923     // In this case the loader's name must be obtained via the parent loader's oop.
924     if (parent_cld == nullptr) {
925       oop cl_name_and_id = java_lang_ClassLoader::nameAndId(parent_loader);
926       if (cl_name_and_id != nullptr) {
927         parent_loader_name_and_id = java_lang_String::as_utf8_string(cl_name_and_id);
928       }
929     } else {
930       parent_loader_name_and_id = parent_cld->loader_name_and_id();
931     }
932     parent_loader_phrase = ", parent loader ";
933     len += strlen(parent_loader_phrase) + strlen(parent_loader_name_and_id);
934   }
935 
936   // Start to construct final full class description string
937   len += ((use_are) ? strlen(" are in ") : strlen(" is in "));
938   len += strlen(module_name_phrase) + strlen(" of loader ");
939 
940   char* class_description = NEW_RESOURCE_ARRAY_RETURN_NULL(char, len);
941 
942   // Just return the FQN if error when allocating string
943   if (class_description == nullptr) {
944     return klass_name;
945   }
946 
947   jio_snprintf(class_description, len, "%s %s in %s%s%s%s of loader %s%s%s",
948                klass_name,
949                (use_are) ? "are" : "is",
950                module_name_phrase,
951                module_name,
952                (has_version) ? "@" : "",
953                (has_version) ? version : "",
954                loader_name_and_id,
955                parent_loader_phrase,
956                parent_loader_name_and_id);
957 
958   return class_description;
959 }