1 /*
  2  * Copyright (c) 1997, 2022, 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/globals.hpp"
 52 #include "runtime/handles.inline.hpp"
 53 #include "utilities/align.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 oop Klass::java_mirror_no_keepalive() const {
 65   return _java_mirror.peek();
 66 }
 67 
 68 void Klass::replace_java_mirror(oop mirror) {
 69   _java_mirror.replace(mirror);
 70 }
 71 
 72 bool Klass::is_cloneable() const {
 73   return _access_flags.is_cloneable_fast() ||
 74          is_subtype_of(vmClasses::Cloneable_klass());
 75 }
 76 
 77 void Klass::set_is_cloneable() {
 78   if (name() == vmSymbols::java_lang_invoke_MemberName()) {
 79     assert(is_final(), "no subclasses allowed");
 80     // MemberName cloning should not be intrinsified and always happen in JVM_Clone.
 81   } else if (is_instance_klass() && InstanceKlass::cast(this)->reference_type() != REF_NONE) {
 82     // Reference cloning should not be intrinsified and always happen in JVM_Clone.
 83   } else {
 84     _access_flags.set_is_cloneable_fast();
 85   }
 86 }
 87 
 88 void Klass::set_name(Symbol* n) {
 89   _name = n;
 90   if (_name != NULL) _name->increment_refcount();
 91 
 92   if (Arguments::is_dumping_archive() && is_instance_klass()) {
 93     SystemDictionaryShared::init_dumptime_info(InstanceKlass::cast(this));
 94   }
 95 }
 96 
 97 bool Klass::is_subclass_of(const Klass* k) const {
 98   // Run up the super chain and check
 99   if (this == k) return true;
100 
101   Klass* t = const_cast<Klass*>(this)->super();
102 
103   while (t != NULL) {
104     if (t == k) return true;
105     t = t->super();
106   }
107   return false;
108 }
109 
110 void Klass::release_C_heap_structures(bool release_constant_pool) {
111   if (_name != NULL) _name->decrement_refcount();
112 }
113 
114 bool Klass::search_secondary_supers(Klass* k) const {
115   // Put some extra logic here out-of-line, before the search proper.
116   // This cuts down the size of the inline method.
117 
118   // This is necessary, since I am never in my own secondary_super list.
119   if (this == k)
120     return true;
121   // Scan the array-of-objects for a match
122   int cnt = secondary_supers()->length();
123   for (int i = 0; i < cnt; i++) {
124     if (secondary_supers()->at(i) == k) {
125       ((Klass*)this)->set_secondary_super_cache(k);
126       return true;
127     }
128   }
129   return false;
130 }
131 
132 // Return self, except for abstract classes with exactly 1
133 // implementor.  Then return the 1 concrete implementation.
134 Klass *Klass::up_cast_abstract() {
135   Klass *r = this;
136   while( r->is_abstract() ) {   // Receiver is abstract?
137     Klass *s = r->subklass();   // Check for exactly 1 subklass
138     if (s == NULL || s->next_sibling() != NULL) // Oops; wrong count; give up
139       return this;              // Return 'this' as a no-progress flag
140     r = s;                    // Loop till find concrete class
141   }
142   return r;                   // Return the 1 concrete class
143 }
144 
145 // Find LCA in class hierarchy
146 Klass *Klass::LCA( Klass *k2 ) {
147   Klass *k1 = this;
148   while( 1 ) {
149     if( k1->is_subtype_of(k2) ) return k2;
150     if( k2->is_subtype_of(k1) ) return k1;
151     k1 = k1->super();
152     k2 = k2->super();
153   }
154 }
155 
156 
157 void Klass::check_valid_for_instantiation(bool throwError, TRAPS) {
158   ResourceMark rm(THREAD);
159   THROW_MSG(throwError ? vmSymbols::java_lang_InstantiationError()
160             : vmSymbols::java_lang_InstantiationException(), external_name());
161 }
162 
163 
164 void Klass::copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS) {
165   ResourceMark rm(THREAD);
166   assert(s != NULL, "Throw NPE!");
167   THROW_MSG(vmSymbols::java_lang_ArrayStoreException(),
168             err_msg("arraycopy: source type %s is not an array", s->klass()->external_name()));
169 }
170 
171 
172 void Klass::initialize(TRAPS) {
173   ShouldNotReachHere();
174 }
175 
176 Klass* Klass::find_field(Symbol* name, Symbol* sig, fieldDescriptor* fd) const {
177 #ifdef ASSERT
178   tty->print_cr("Error: find_field called on a klass oop."
179                 " Likely error: reflection method does not correctly"
180                 " wrap return value in a mirror object.");
181 #endif
182   ShouldNotReachHere();
183   return NULL;
184 }
185 
186 Method* Klass::uncached_lookup_method(const Symbol* name, const Symbol* signature,
187                                       OverpassLookupMode overpass_mode,
188                                       PrivateLookupMode private_mode) const {
189 #ifdef ASSERT
190   tty->print_cr("Error: uncached_lookup_method called on a klass oop."
191                 " Likely error: reflection method does not correctly"
192                 " wrap return value in a mirror object.");
193 #endif
194   ShouldNotReachHere();
195   return NULL;
196 }
197 
198 void* Klass::operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw() {
199   MetaWord* p = Metaspace::allocate(loader_data, word_size, MetaspaceObj::ClassType, THREAD);
200   assert(is_aligned(p, KlassAlignmentInBytes), "metaspace returned badly aligned memory.");
201   return p;
202 }
203 
204 // "Normal" instantiation is preceded by a MetaspaceObj allocation
205 // which zeros out memory - calloc equivalent.
206 // The constructor is also used from CppVtableCloner,
207 // which doesn't zero out the memory before calling the constructor.
208 Klass::Klass(KlassKind kind) : _kind(kind),
209                            _prototype_header(markWord::prototype() LP64_ONLY(.set_klass(this))),
210                            _shared_class_path_index(-1) {
211   CDS_ONLY(_shared_class_flags = 0;)
212   CDS_JAVA_HEAP_ONLY(_archived_mirror_index = -1;)
213   _primary_supers[0] = this;
214   set_super_check_offset(in_bytes(primary_supers_offset()));
215 }
216 
217 jint Klass::array_layout_helper(BasicType etype) {
218   assert(etype >= T_BOOLEAN && etype <= T_OBJECT, "valid etype");
219   // Note that T_ARRAY is not allowed here.
220   int  hsize = arrayOopDesc::base_offset_in_bytes(etype);
221   int  esize = type2aelembytes(etype);
222   bool isobj = (etype == T_OBJECT);
223   int  tag   =  isobj ? _lh_array_tag_obj_value : _lh_array_tag_type_value;
224   int lh = array_layout_helper(tag, hsize, etype, exact_log2(esize));
225 
226   assert(lh < (int)_lh_neutral_value, "must look like an array layout");
227   assert(layout_helper_is_array(lh), "correct kind");
228   assert(layout_helper_is_objArray(lh) == isobj, "correct kind");
229   assert(layout_helper_is_typeArray(lh) == !isobj, "correct kind");
230   assert(layout_helper_header_size(lh) == hsize, "correct decode");
231   assert(layout_helper_element_type(lh) == etype, "correct decode");
232   assert(1 << layout_helper_log2_element_size(lh) == esize, "correct decode");
233 
234   return lh;
235 }
236 
237 bool Klass::can_be_primary_super_slow() const {
238   if (super() == NULL)
239     return true;
240   else if (super()->super_depth() >= primary_super_limit()-1)
241     return false;
242   else
243     return true;
244 }
245 
246 void Klass::initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS) {
247   if (k == NULL) {
248     set_super(NULL);
249     _primary_supers[0] = this;
250     assert(super_depth() == 0, "Object must already be initialized properly");
251   } else if (k != super() || k == vmClasses::Object_klass()) {
252     assert(super() == NULL || super() == vmClasses::Object_klass(),
253            "initialize this only once to a non-trivial value");
254     set_super(k);
255     Klass* sup = k;
256     int sup_depth = sup->super_depth();
257     juint my_depth  = MIN2(sup_depth + 1, (int)primary_super_limit());
258     if (!can_be_primary_super_slow())
259       my_depth = primary_super_limit();
260     for (juint i = 0; i < my_depth; i++) {
261       _primary_supers[i] = sup->_primary_supers[i];
262     }
263     Klass* *super_check_cell;
264     if (my_depth < primary_super_limit()) {
265       _primary_supers[my_depth] = this;
266       super_check_cell = &_primary_supers[my_depth];
267     } else {
268       // Overflow of the primary_supers array forces me to be secondary.
269       super_check_cell = &_secondary_super_cache;
270     }
271     set_super_check_offset((address)super_check_cell - (address) this);
272 
273 #ifdef ASSERT
274     {
275       juint j = super_depth();
276       assert(j == my_depth, "computed accessor gets right answer");
277       Klass* t = this;
278       while (!t->can_be_primary_super()) {
279         t = t->super();
280         j = t->super_depth();
281       }
282       for (juint j1 = j+1; j1 < primary_super_limit(); j1++) {
283         assert(primary_super_of_depth(j1) == NULL, "super list padding");
284       }
285       while (t != NULL) {
286         assert(primary_super_of_depth(j) == t, "super list initialization");
287         t = t->super();
288         --j;
289       }
290       assert(j == (juint)-1, "correct depth count");
291     }
292 #endif
293   }
294 
295   if (secondary_supers() == NULL) {
296 
297     // Now compute the list of secondary supertypes.
298     // Secondaries can occasionally be on the super chain,
299     // if the inline "_primary_supers" array overflows.
300     int extras = 0;
301     Klass* p;
302     for (p = super(); !(p == NULL || p->can_be_primary_super()); p = p->super()) {
303       ++extras;
304     }
305 
306     ResourceMark rm(THREAD);  // need to reclaim GrowableArrays allocated below
307 
308     // Compute the "real" non-extra secondaries.
309     GrowableArray<Klass*>* secondaries = compute_secondary_supers(extras, transitive_interfaces);
310     if (secondaries == NULL) {
311       // secondary_supers set by compute_secondary_supers
312       return;
313     }
314 
315     GrowableArray<Klass*>* primaries = new GrowableArray<Klass*>(extras);
316 
317     for (p = super(); !(p == NULL || p->can_be_primary_super()); p = p->super()) {
318       int i;                    // Scan for overflow primaries being duplicates of 2nd'arys
319 
320       // This happens frequently for very deeply nested arrays: the
321       // primary superclass chain overflows into the secondary.  The
322       // secondary list contains the element_klass's secondaries with
323       // an extra array dimension added.  If the element_klass's
324       // secondary list already contains some primary overflows, they
325       // (with the extra level of array-ness) will collide with the
326       // normal primary superclass overflows.
327       for( i = 0; i < secondaries->length(); i++ ) {
328         if( secondaries->at(i) == p )
329           break;
330       }
331       if( i < secondaries->length() )
332         continue;               // It's a dup, don't put it in
333       primaries->push(p);
334     }
335     // Combine the two arrays into a metadata object to pack the array.
336     // The primaries are added in the reverse order, then the secondaries.
337     int new_length = primaries->length() + secondaries->length();
338     Array<Klass*>* s2 = MetadataFactory::new_array<Klass*>(
339                                        class_loader_data(), new_length, CHECK);
340     int fill_p = primaries->length();
341     for (int j = 0; j < fill_p; j++) {
342       s2->at_put(j, primaries->pop());  // add primaries in reverse order.
343     }
344     for( int j = 0; j < secondaries->length(); j++ ) {
345       s2->at_put(j+fill_p, secondaries->at(j));  // add secondaries on the end.
346     }
347 
348   #ifdef ASSERT
349       // We must not copy any NULL placeholders left over from bootstrap.
350     for (int j = 0; j < s2->length(); j++) {
351       assert(s2->at(j) != NULL, "correct bootstrapping order");
352     }
353   #endif
354 
355     set_secondary_supers(s2);
356   }
357 }
358 
359 GrowableArray<Klass*>* Klass::compute_secondary_supers(int num_extra_slots,
360                                                        Array<InstanceKlass*>* transitive_interfaces) {
361   assert(num_extra_slots == 0, "override for complex klasses");
362   assert(transitive_interfaces == NULL, "sanity");
363   set_secondary_supers(Universe::the_empty_klass_array());
364   return NULL;
365 }
366 
367 
368 // superklass links
369 InstanceKlass* Klass::superklass() const {
370   assert(super() == NULL || super()->is_instance_klass(), "must be instance klass");
371   return _super == NULL ? NULL : InstanceKlass::cast(_super);
372 }
373 
374 // subklass links.  Used by the compiler (and vtable initialization)
375 // May be cleaned concurrently, so must use the Compile_lock.
376 // The log parameter is for clean_weak_klass_links to report unlinked classes.
377 Klass* Klass::subklass(bool log) const {
378   // Need load_acquire on the _subklass, because it races with inserts that
379   // publishes freshly initialized data.
380   for (Klass* chain = Atomic::load_acquire(&_subklass);
381        chain != NULL;
382        // Do not need load_acquire on _next_sibling, because inserts never
383        // create _next_sibling edges to dead data.
384        chain = Atomic::load(&chain->_next_sibling))
385   {
386     if (chain->is_loader_alive()) {
387       return chain;
388     } else if (log) {
389       if (log_is_enabled(Trace, class, unload)) {
390         ResourceMark rm;
391         log_trace(class, unload)("unlinking class (subclass): %s", chain->external_name());
392       }
393     }
394   }
395   return NULL;
396 }
397 
398 Klass* Klass::next_sibling(bool log) const {
399   // Do not need load_acquire on _next_sibling, because inserts never
400   // create _next_sibling edges to dead data.
401   for (Klass* chain = Atomic::load(&_next_sibling);
402        chain != NULL;
403        chain = Atomic::load(&chain->_next_sibling)) {
404     // Only return alive klass, there may be stale klass
405     // in this chain if cleaned concurrently.
406     if (chain->is_loader_alive()) {
407       return chain;
408     } else if (log) {
409       if (log_is_enabled(Trace, class, unload)) {
410         ResourceMark rm;
411         log_trace(class, unload)("unlinking class (sibling): %s", chain->external_name());
412       }
413     }
414   }
415   return NULL;
416 }
417 
418 void Klass::set_subklass(Klass* s) {
419   assert(s != this, "sanity check");
420   Atomic::release_store(&_subklass, s);
421 }
422 
423 void Klass::set_next_sibling(Klass* s) {
424   assert(s != this, "sanity check");
425   // Does not need release semantics. If used by cleanup, it will link to
426   // already safely published data, and if used by inserts, will be published
427   // safely using cmpxchg.
428   Atomic::store(&_next_sibling, s);
429 }
430 
431 void Klass::append_to_sibling_list() {
432   if (Universe::is_fully_initialized()) {
433     assert_locked_or_safepoint(Compile_lock);
434   }
435   debug_only(verify();)
436   // add ourselves to superklass' subklass list
437   InstanceKlass* super = superklass();
438   if (super == NULL) return;        // special case: class Object
439   assert((!super->is_interface()    // interfaces cannot be supers
440           && (super->superklass() == NULL || !is_interface())),
441          "an interface can only be a subklass of Object");
442 
443   // Make sure there is no stale subklass head
444   super->clean_subklass();
445 
446   for (;;) {
447     Klass* prev_first_subklass = Atomic::load_acquire(&_super->_subklass);
448     if (prev_first_subklass != NULL) {
449       // set our sibling to be the superklass' previous first subklass
450       assert(prev_first_subklass->is_loader_alive(), "May not attach not alive klasses");
451       set_next_sibling(prev_first_subklass);
452     }
453     // Note that the prev_first_subklass is always alive, meaning no sibling_next links
454     // are ever created to not alive klasses. This is an important invariant of the lock-free
455     // cleaning protocol, that allows us to safely unlink dead klasses from the sibling list.
456     if (Atomic::cmpxchg(&super->_subklass, prev_first_subklass, this) == prev_first_subklass) {
457       return;
458     }
459   }
460   debug_only(verify();)
461 }
462 
463 void Klass::clean_subklass() {
464   for (;;) {
465     // Need load_acquire, due to contending with concurrent inserts
466     Klass* subklass = Atomic::load_acquire(&_subklass);
467     if (subklass == NULL || subklass->is_loader_alive()) {
468       return;
469     }
470     // Try to fix _subklass until it points at something not dead.
471     Atomic::cmpxchg(&_subklass, subklass, subklass->next_sibling());
472   }
473 }
474 
475 void Klass::clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses) {
476   if (!ClassUnloading || !unloading_occurred) {
477     return;
478   }
479 
480   Klass* root = vmClasses::Object_klass();
481   Stack<Klass*, mtGC> stack;
482 
483   stack.push(root);
484   while (!stack.is_empty()) {
485     Klass* current = stack.pop();
486 
487     assert(current->is_loader_alive(), "just checking, this should be live");
488 
489     // Find and set the first alive subklass
490     Klass* sub = current->subklass(true);
491     current->clean_subklass();
492     if (sub != NULL) {
493       stack.push(sub);
494     }
495 
496     // Find and set the first alive sibling
497     Klass* sibling = current->next_sibling(true);
498     current->set_next_sibling(sibling);
499     if (sibling != NULL) {
500       stack.push(sibling);
501     }
502 
503     // Clean the implementors list and method data.
504     if (clean_alive_klasses && current->is_instance_klass()) {
505       InstanceKlass* ik = InstanceKlass::cast(current);
506       ik->clean_weak_instanceklass_links();
507 
508       // JVMTI RedefineClasses creates previous versions that are not in
509       // the class hierarchy, so process them here.
510       while ((ik = ik->previous_versions()) != NULL) {
511         ik->clean_weak_instanceklass_links();
512       }
513     }
514   }
515 }
516 
517 void Klass::metaspace_pointers_do(MetaspaceClosure* it) {
518   if (log_is_enabled(Trace, cds)) {
519     ResourceMark rm;
520     log_trace(cds)("Iter(Klass): %p (%s)", this, external_name());
521   }
522 
523   it->push(&_name);
524   it->push(&_secondary_super_cache);
525   it->push(&_secondary_supers);
526   for (int i = 0; i < _primary_super_limit; i++) {
527     it->push(&_primary_supers[i]);
528   }
529   it->push(&_super);
530   if (!Arguments::is_dumping_archive()) {
531     // If dumping archive, these may point to excluded classes. There's no need
532     // to follow these pointers anyway, as they will be set to NULL in
533     // remove_unshareable_info().
534     it->push((Klass**)&_subklass);
535     it->push((Klass**)&_next_sibling);
536     it->push(&_next_link);
537   }
538 
539   vtableEntry* vt = start_of_vtable();
540   for (int i=0; i<vtable_length(); i++) {
541     it->push(vt[i].method_addr());
542   }
543 }
544 
545 void Klass::remove_unshareable_info() {
546   assert (Arguments::is_dumping_archive(),
547           "only called during CDS dump time");
548   JFR_ONLY(REMOVE_ID(this);)
549   if (log_is_enabled(Trace, cds, unshareable)) {
550     ResourceMark rm;
551     log_trace(cds, unshareable)("remove: %s", external_name());
552   }
553 
554   set_subklass(NULL);
555   set_next_sibling(NULL);
556   set_next_link(NULL);
557 
558   // Null out class_loader_data because we don't share that yet.
559   set_class_loader_data(NULL);
560   set_is_shared();
561 }
562 
563 void Klass::remove_java_mirror() {
564   Arguments::assert_is_dumping_archive();
565   if (log_is_enabled(Trace, cds, unshareable)) {
566     ResourceMark rm;
567     log_trace(cds, unshareable)("remove java_mirror: %s", external_name());
568   }
569   // Just null out the mirror.  The class_loader_data() no longer exists.
570   clear_java_mirror_handle();
571 }
572 
573 void Klass::restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS) {
574   assert(is_klass(), "ensure C++ vtable is restored");
575   assert(is_shared(), "must be set");
576   JFR_ONLY(RESTORE_ID(this);)
577   if (log_is_enabled(Trace, cds, unshareable)) {
578     ResourceMark rm(THREAD);
579     log_trace(cds, unshareable)("restore: %s", external_name());
580   }
581 
582   // If an exception happened during CDS restore, some of these fields may already be
583   // set.  We leave the class on the CLD list, even if incomplete so that we don't
584   // modify the CLD list outside a safepoint.
585   if (class_loader_data() == NULL) {
586     set_class_loader_data(loader_data);
587 
588     // Add to class loader list first before creating the mirror
589     // (same order as class file parsing)
590     loader_data->add_class(this);
591   }
592 
593   Handle loader(THREAD, loader_data->class_loader());
594   ModuleEntry* module_entry = NULL;
595   Klass* k = this;
596   if (k->is_objArray_klass()) {
597     k = ObjArrayKlass::cast(k)->bottom_klass();
598   }
599   // Obtain klass' module.
600   if (k->is_instance_klass()) {
601     InstanceKlass* ik = (InstanceKlass*) k;
602     module_entry = ik->module();
603   } else {
604     module_entry = ModuleEntryTable::javabase_moduleEntry();
605   }
606   // Obtain java.lang.Module, if available
607   Handle module_handle(THREAD, ((module_entry != NULL) ? module_entry->module() : (oop)NULL));
608 
609   if (this->has_archived_mirror_index()) {
610     ResourceMark rm(THREAD);
611     log_debug(cds, mirror)("%s has raw archived mirror", external_name());
612     if (HeapShared::are_archived_mirrors_available()) {
613       bool present = java_lang_Class::restore_archived_mirror(this, loader, module_handle,
614                                                               protection_domain,
615                                                               CHECK);
616       if (present) {
617         return;
618       }
619     }
620 
621     // No archived mirror data
622     log_debug(cds, mirror)("No archived mirror data for %s", external_name());
623     clear_java_mirror_handle();
624     this->clear_archived_mirror_index();
625   }
626 
627   // Only recreate it if not present.  A previous attempt to restore may have
628   // gotten an OOM later but keep the mirror if it was created.
629   if (java_mirror() == NULL) {
630     ResourceMark rm(THREAD);
631     log_trace(cds, mirror)("Recreate mirror for %s", external_name());
632     java_lang_Class::create_mirror(this, loader, module_handle, protection_domain, Handle(), CHECK);
633   }
634 }
635 
636 #if INCLUDE_CDS_JAVA_HEAP
637 oop Klass::archived_java_mirror() {
638   assert(has_archived_mirror_index(), "must have archived mirror");
639   return HeapShared::get_root(_archived_mirror_index);
640 }
641 
642 void Klass::clear_archived_mirror_index() {
643   if (_archived_mirror_index >= 0) {
644     HeapShared::clear_root(_archived_mirror_index);
645   }
646   _archived_mirror_index = -1;
647 }
648 
649 // No GC barrier
650 void Klass::set_archived_java_mirror(oop m) {
651   assert(DumpSharedSpaces, "called only during runtime");
652   _archived_mirror_index = HeapShared::append_root(m);
653 }
654 #endif // INCLUDE_CDS_JAVA_HEAP
655 
656 void Klass::check_array_allocation_length(int length, int max_length, TRAPS) {
657   if (length > max_length) {
658     if (!THREAD->in_retryable_allocation()) {
659       report_java_out_of_memory("Requested array size exceeds VM limit");
660       JvmtiExport::post_array_size_exhausted();
661       THROW_OOP(Universe::out_of_memory_error_array_size());
662     } else {
663       THROW_OOP(Universe::out_of_memory_error_retry());
664     }
665   } else if (length < 0) {
666     THROW_MSG(vmSymbols::java_lang_NegativeArraySizeException(), err_msg("%d", length));
667   }
668 }
669 
670 // Replace the last '+' char with '/'.
671 static char* convert_hidden_name_to_java(Symbol* name) {
672   size_t name_len = name->utf8_length();
673   char* result = NEW_RESOURCE_ARRAY(char, name_len + 1);
674   name->as_klass_external_name(result, (int)name_len + 1);
675   for (int index = (int)name_len; index > 0; index--) {
676     if (result[index] == '+') {
677       result[index] = JVM_SIGNATURE_SLASH;
678       break;
679     }
680   }
681   return result;
682 }
683 
684 // In product mode, this function doesn't have virtual function calls so
685 // there might be some performance advantage to handling InstanceKlass here.
686 const char* Klass::external_name() const {
687   if (is_instance_klass()) {
688     const InstanceKlass* ik = static_cast<const InstanceKlass*>(this);
689     if (ik->is_hidden()) {
690       char* result = convert_hidden_name_to_java(name());
691       return result;
692     }
693   } else if (is_objArray_klass() && ObjArrayKlass::cast(this)->bottom_klass()->is_hidden()) {
694     char* result = convert_hidden_name_to_java(name());
695     return result;
696   }
697   if (name() == NULL)  return "<unknown>";
698   return name()->as_klass_external_name();
699 }
700 
701 const char* Klass::signature_name() const {
702   if (name() == NULL)  return "<unknown>";
703   if (is_objArray_klass() && ObjArrayKlass::cast(this)->bottom_klass()->is_hidden()) {
704     size_t name_len = name()->utf8_length();
705     char* result = NEW_RESOURCE_ARRAY(char, name_len + 1);
706     name()->as_C_string(result, (int)name_len + 1);
707     for (int index = (int)name_len; index > 0; index--) {
708       if (result[index] == '+') {
709         result[index] = JVM_SIGNATURE_DOT;
710         break;
711       }
712     }
713     return result;
714   }
715   return name()->as_C_string();
716 }
717 
718 const char* Klass::external_kind() const {
719   if (is_interface()) return "interface";
720   if (is_abstract()) return "abstract class";
721   return "class";
722 }
723 
724 // Unless overridden, jvmti_class_status has no flags set.
725 jint Klass::jvmti_class_status() const {
726   return 0;
727 }
728 
729 
730 // Printing
731 
732 void Klass::print_on(outputStream* st) const {
733   ResourceMark rm;
734   // print title
735   st->print("%s", internal_name());
736   print_address_on(st);
737   st->cr();
738 }
739 
740 #define BULLET  " - "
741 
742 // Caller needs ResourceMark
743 void Klass::oop_print_on(oop obj, outputStream* st) {
744   // print title
745   st->print_cr("%s ", internal_name());
746   obj->print_address_on(st);
747 
748   if (WizardMode) {
749      // print header
750      obj->mark().print_on(st);
751      st->cr();
752      st->print(BULLET"prototype_header: " INTPTR_FORMAT, _prototype_header.value());
753      st->cr();
754   }
755 
756   // print class
757   st->print(BULLET"klass: ");
758   obj->klass()->print_value_on(st);
759   st->cr();
760 }
761 
762 void Klass::oop_print_value_on(oop obj, outputStream* st) {
763   // print title
764   ResourceMark rm;              // Cannot print in debug mode without this
765   st->print("%s", internal_name());
766   obj->print_address_on(st);
767 }
768 
769 // Verification
770 
771 void Klass::verify_on(outputStream* st) {
772 
773   // This can be expensive, but it is worth checking that this klass is actually
774   // in the CLD graph but not in production.
775   assert(Metaspace::contains((address)this), "Should be");
776 
777   if (UseCompressedClassPointers) {
778     assert(is_aligned(this, KlassAlignmentInBytes), "misaligned Klass structure");
779   }
780 
781   guarantee(this->is_klass(),"should be klass");
782 
783   if (super() != NULL) {
784     guarantee(super()->is_klass(), "should be klass");
785   }
786   if (secondary_super_cache() != NULL) {
787     Klass* ko = secondary_super_cache();
788     guarantee(ko->is_klass(), "should be klass");
789   }
790   for ( uint i = 0; i < primary_super_limit(); i++ ) {
791     Klass* ko = _primary_supers[i];
792     if (ko != NULL) {
793       guarantee(ko->is_klass(), "should be klass");
794     }
795   }
796 
797   if (java_mirror_no_keepalive() != NULL) {
798     guarantee(oopDesc::is_oop(java_mirror_no_keepalive()), "should be instance");
799   }
800 }
801 
802 void Klass::oop_verify_on(oop obj, outputStream* st) {
803   guarantee(oopDesc::is_oop(obj),  "should be oop");
804   guarantee(obj->klass()->is_klass(), "klass field is not a klass");
805 }
806 
807 bool Klass::is_valid(Klass* k) {
808   if (!is_aligned(k, sizeof(MetaWord))) return false;
809   if ((size_t)k < os::min_page_size()) return false;
810 
811   if (!os::is_readable_range(k, k + 1)) return false;
812   if (!Metaspace::contains(k)) return false;
813 
814   if (!Symbol::is_valid(k->name())) return false;
815   return ClassLoaderDataGraph::is_valid(k->class_loader_data());
816 }
817 
818 Method* Klass::method_at_vtable(int index)  {
819 #ifndef PRODUCT
820   assert(index >= 0, "valid vtable index");
821   if (DebugVtables) {
822     verify_vtable_index(index);
823   }
824 #endif
825   return start_of_vtable()[index].method();
826 }
827 
828 
829 #ifndef PRODUCT
830 
831 bool Klass::verify_vtable_index(int i) {
832   int limit = vtable_length()/vtableEntry::size();
833   assert(i >= 0 && i < limit, "index %d out of bounds %d", i, limit);
834   return true;
835 }
836 
837 #endif // PRODUCT
838 
839 // Caller needs ResourceMark
840 // joint_in_module_of_loader provides an optimization if 2 classes are in
841 // the same module to succinctly print out relevant information about their
842 // module name and class loader's name_and_id for error messages.
843 // Format:
844 //   <fully-qualified-external-class-name1> and <fully-qualified-external-class-name2>
845 //                      are in module <module-name>[@<version>]
846 //                      of loader <loader-name_and_id>[, parent loader <parent-loader-name_and_id>]
847 const char* Klass::joint_in_module_of_loader(const Klass* class2, bool include_parent_loader) const {
848   assert(module() == class2->module(), "classes do not have the same module");
849   const char* class1_name = external_name();
850   size_t len = strlen(class1_name) + 1;
851 
852   const char* class2_description = class2->class_in_module_of_loader(true, include_parent_loader);
853   len += strlen(class2_description);
854 
855   len += strlen(" and ");
856 
857   char* joint_description = NEW_RESOURCE_ARRAY_RETURN_NULL(char, len);
858 
859   // Just return the FQN if error when allocating string
860   if (joint_description == NULL) {
861     return class1_name;
862   }
863 
864   jio_snprintf(joint_description, len, "%s and %s",
865                class1_name,
866                class2_description);
867 
868   return joint_description;
869 }
870 
871 // Caller needs ResourceMark
872 // class_in_module_of_loader provides a standard way to include
873 // relevant information about a class, such as its module name as
874 // well as its class loader's name_and_id, in error messages and logging.
875 // Format:
876 //   <fully-qualified-external-class-name> is in module <module-name>[@<version>]
877 //                                         of loader <loader-name_and_id>[, parent loader <parent-loader-name_and_id>]
878 const char* Klass::class_in_module_of_loader(bool use_are, bool include_parent_loader) const {
879   // 1. fully qualified external name of class
880   const char* klass_name = external_name();
881   size_t len = strlen(klass_name) + 1;
882 
883   // 2. module name + @version
884   const char* module_name = "";
885   const char* version = "";
886   bool has_version = false;
887   bool module_is_named = false;
888   const char* module_name_phrase = "";
889   const Klass* bottom_klass = is_objArray_klass() ?
890                                 ObjArrayKlass::cast(this)->bottom_klass() : this;
891   if (bottom_klass->is_instance_klass()) {
892     ModuleEntry* module = InstanceKlass::cast(bottom_klass)->module();
893     if (module->is_named()) {
894       module_is_named = true;
895       module_name_phrase = "module ";
896       module_name = module->name()->as_C_string();
897       len += strlen(module_name);
898       // Use version if exists and is not a jdk module
899       if (module->should_show_version()) {
900         has_version = true;
901         version = module->version()->as_C_string();
902         // Include stlen(version) + 1 for the "@"
903         len += strlen(version) + 1;
904       }
905     } else {
906       module_name = UNNAMED_MODULE;
907       len += UNNAMED_MODULE_LEN;
908     }
909   } else {
910     // klass is an array of primitives, module is java.base
911     module_is_named = true;
912     module_name_phrase = "module ";
913     module_name = JAVA_BASE_NAME;
914     len += JAVA_BASE_NAME_LEN;
915   }
916 
917   // 3. class loader's name_and_id
918   ClassLoaderData* cld = class_loader_data();
919   assert(cld != NULL, "class_loader_data should not be null");
920   const char* loader_name_and_id = cld->loader_name_and_id();
921   len += strlen(loader_name_and_id);
922 
923   // 4. include parent loader information
924   const char* parent_loader_phrase = "";
925   const char* parent_loader_name_and_id = "";
926   if (include_parent_loader &&
927       !cld->is_builtin_class_loader_data()) {
928     oop parent_loader = java_lang_ClassLoader::parent(class_loader());
929     ClassLoaderData *parent_cld = ClassLoaderData::class_loader_data_or_null(parent_loader);
930     // The parent loader's ClassLoaderData could be null if it is
931     // a delegating class loader that has never defined a class.
932     // In this case the loader's name must be obtained via the parent loader's oop.
933     if (parent_cld == NULL) {
934       oop cl_name_and_id = java_lang_ClassLoader::nameAndId(parent_loader);
935       if (cl_name_and_id != NULL) {
936         parent_loader_name_and_id = java_lang_String::as_utf8_string(cl_name_and_id);
937       }
938     } else {
939       parent_loader_name_and_id = parent_cld->loader_name_and_id();
940     }
941     parent_loader_phrase = ", parent loader ";
942     len += strlen(parent_loader_phrase) + strlen(parent_loader_name_and_id);
943   }
944 
945   // Start to construct final full class description string
946   len += ((use_are) ? strlen(" are in ") : strlen(" is in "));
947   len += strlen(module_name_phrase) + strlen(" of loader ");
948 
949   char* class_description = NEW_RESOURCE_ARRAY_RETURN_NULL(char, len);
950 
951   // Just return the FQN if error when allocating string
952   if (class_description == NULL) {
953     return klass_name;
954   }
955 
956   jio_snprintf(class_description, len, "%s %s in %s%s%s%s of loader %s%s%s",
957                klass_name,
958                (use_are) ? "are" : "is",
959                module_name_phrase,
960                module_name,
961                (has_version) ? "@" : "",
962                (has_version) ? version : "",
963                loader_name_and_id,
964                parent_loader_phrase,
965                parent_loader_name_and_id);
966 
967   return class_description;
968 }