/*

 * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

#include "precompiled.hpp"

#include "classfile/classLoaderData.inline.hpp"

#include "classfile/classLoaderDataGraph.inline.hpp"

#include "classfile/dictionary.hpp"

#include "classfile/javaClasses.hpp"

#include "classfile/moduleEntry.hpp"

#include "classfile/systemDictionary.hpp"

#include "classfile/vmSymbols.hpp"

#include "gc/shared/collectedHeap.inline.hpp"

#include "logging/log.hpp"

#include "memory/heapInspection.hpp"

#include "memory/heapShared.hpp"

#include "memory/metadataFactory.hpp"

#include "memory/metaspaceClosure.hpp"

#include "memory/metaspaceShared.hpp"

#include "memory/oopFactory.hpp"

#include "memory/resourceArea.hpp"

#include "memory/universe.hpp"

#include "oops/compressedOops.inline.hpp"

#include "oops/instanceKlass.hpp"

#include "oops/klass.inline.hpp"

#include "oops/oop.inline.hpp"

#include "oops/oopHandle.inline.hpp"

#include "runtime/atomic.hpp"

#include "runtime/handles.inline.hpp"

#include "utilities/macros.hpp"

#include "utilities/stack.inline.hpp"

void Klass::set_java_mirror(Handle m) {

  assert(!m.is_null(), "New mirror should never be null.");

  assert(_java_mirror.resolve() == NULL, "should only be used to initialize mirror");

  _java_mirror = class_loader_data()->add_handle(m);

}

oop Klass::java_mirror_no_keepalive() const {

  return _java_mirror.peek();

}

bool Klass::is_cloneable() const {

  return _access_flags.is_cloneable_fast() ||

         is_subtype_of(SystemDictionary::Cloneable_klass());

}

void Klass::set_is_cloneable() {

  if (name() == vmSymbols::java_lang_invoke_MemberName()) {

    assert(is_final(), "no subclasses allowed");

    // MemberName cloning should not be intrinsified and always happen in JVM_Clone.

  } else if (is_instance_klass() && InstanceKlass::cast(this)->reference_type() != REF_NONE) {

    // Reference cloning should not be intrinsified and always happen in JVM_Clone.

  } else {

    _access_flags.set_is_cloneable_fast();

  }

}

void Klass::set_name(Symbol* n) {

  _name = n;

  if (_name != NULL) _name->increment_refcount();

}

bool Klass::is_subclass_of(const Klass* k) const {

  // Run up the super chain and check

  if (this == k) return true;

  Klass* t = const_cast<Klass*>(this)->super();

  while (t != NULL) {

    if (t == k) return true;

    t = t->super();

  }

  return false;

}

bool Klass::search_secondary_supers(Klass* k) const {

  // Put some extra logic here out-of-line, before the search proper.

  // This cuts down the size of the inline method.

  // This is necessary, since I am never in my own secondary_super list.

  if (this == k)

    return true;

  // Scan the array-of-objects for a match

  int cnt = secondary_supers()->length();

  for (int i = 0; i < cnt; i++) {

    if (secondary_supers()->at(i) == k) {

      ((Klass*)this)->set_secondary_super_cache(k);

      return true;

    }

  }

  return false;

}

// Return self, except for abstract classes with exactly 1

// implementor.  Then return the 1 concrete implementation.

Klass *Klass::up_cast_abstract() {

  Klass *r = this;

  while( r->is_abstract() ) {   // Receiver is abstract?

    Klass *s = r->subklass();   // Check for exactly 1 subklass

    if (s == NULL || s->next_sibling() != NULL) // Oops; wrong count; give up

      return this;              // Return 'this' as a no-progress flag

    r = s;                    // Loop till find concrete class

  }

  return r;                   // Return the 1 concrete class

}

// Find LCA in class hierarchy

Klass *Klass::LCA( Klass *k2 ) {

  Klass *k1 = this;

  while( 1 ) {

    if( k1->is_subtype_of(k2) ) return k2;

    if( k2->is_subtype_of(k1) ) return k1;

    k1 = k1->super();

    k2 = k2->super();

  }

}

void Klass::check_valid_for_instantiation(bool throwError, TRAPS) {

  ResourceMark rm(THREAD);

  THROW_MSG(throwError ? vmSymbols::java_lang_InstantiationError()

            : vmSymbols::java_lang_InstantiationException(), external_name());

}

void Klass::copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS) {

  ResourceMark rm(THREAD);

  assert(s != NULL, "Throw NPE!");

  THROW_MSG(vmSymbols::java_lang_ArrayStoreException(),

            err_msg("arraycopy: source type %s is not an array", s->klass()->external_name()));

}

void Klass::initialize(TRAPS) {

  ShouldNotReachHere();

}

Klass* Klass::find_field(Symbol* name, Symbol* sig, fieldDescriptor* fd) const {

#ifdef ASSERT

  tty->print_cr("Error: find_field called on a klass oop."

                " Likely error: reflection method does not correctly"

                " wrap return value in a mirror object.");

#endif

  ShouldNotReachHere();

  return NULL;

}

Method* Klass::uncached_lookup_method(const Symbol* name, const Symbol* signature,

                                      OverpassLookupMode overpass_mode,

                                      PrivateLookupMode private_mode) const {

#ifdef ASSERT

  tty->print_cr("Error: uncached_lookup_method called on a klass oop."

                " Likely error: reflection method does not correctly"

                " wrap return value in a mirror object.");

#endif

  ShouldNotReachHere();

  return NULL;

}

void* Klass::operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw() {

  return Metaspace::allocate(loader_data, word_size, MetaspaceObj::ClassType, THREAD);

}

// "Normal" instantiation is preceeded by a MetaspaceObj allocation

// which zeros out memory - calloc equivalent.

// The constructor is also used from CppVtableCloner,

// which doesn't zero out the memory before calling the constructor.

// Need to set the _java_mirror field explicitly to not hit an assert that the field

// should be NULL before setting it.

Klass::Klass(KlassID id) : _id(id),

                           _java_mirror(NULL),

                           _prototype_header(markWord::prototype()),

                           _shared_class_path_index(-1) {

  CDS_ONLY(_shared_class_flags = 0;)

  CDS_JAVA_HEAP_ONLY(_archived_mirror = 0;)

  _primary_supers[0] = this;

  set_super_check_offset(in_bytes(primary_supers_offset()));

}

jint Klass::array_layout_helper(BasicType etype) {

  assert(etype >= T_BOOLEAN && etype <= T_OBJECT, "valid etype");

  // Note that T_ARRAY is not allowed here.

  int  hsize = arrayOopDesc::base_offset_in_bytes(etype);

  int  esize = type2aelembytes(etype);

  bool isobj = (etype == T_OBJECT);

  int  tag   =  isobj ? _lh_array_tag_obj_value : _lh_array_tag_type_value;

  int lh = array_layout_helper(tag, hsize, etype, exact_log2(esize));

  assert(lh < (int)_lh_neutral_value, "must look like an array layout");

  assert(layout_helper_is_array(lh), "correct kind");

  assert(layout_helper_is_objArray(lh) == isobj, "correct kind");

  assert(layout_helper_is_typeArray(lh) == !isobj, "correct kind");

  assert(layout_helper_header_size(lh) == hsize, "correct decode");

  assert(layout_helper_element_type(lh) == etype, "correct decode");

  assert(1 << layout_helper_log2_element_size(lh) == esize, "correct decode");

  return lh;

}

bool Klass::can_be_primary_super_slow() const {

  if (super() == NULL)

    return true;

  else if (super()->super_depth() >= primary_super_limit()-1)

    return false;

  else

    return true;

}

void Klass::initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS) {

  if (k == NULL) {

    set_super(NULL);

    _primary_supers[0] = this;

    assert(super_depth() == 0, "Object must already be initialized properly");

  } else if (k != super() || k == SystemDictionary::Object_klass()) {

    assert(super() == NULL || super() == SystemDictionary::Object_klass(),

           "initialize this only once to a non-trivial value");

    set_super(k);

    Klass* sup = k;

    int sup_depth = sup->super_depth();

    juint my_depth  = MIN2(sup_depth + 1, (int)primary_super_limit());

    if (!can_be_primary_super_slow())

      my_depth = primary_super_limit();

    for (juint i = 0; i < my_depth; i++) {

      _primary_supers[i] = sup->_primary_supers[i];

    }

    Klass* *super_check_cell;

    if (my_depth < primary_super_limit()) {

      _primary_supers[my_depth] = this;

      super_check_cell = &_primary_supers[my_depth];

    } else {

      // Overflow of the primary_supers array forces me to be secondary.

      super_check_cell = &_secondary_super_cache;

    }

    set_super_check_offset((address)super_check_cell - (address) this);

#ifdef ASSERT

    {

      juint j = super_depth();

      assert(j == my_depth, "computed accessor gets right answer");

      Klass* t = this;

      while (!t->can_be_primary_super()) {

        t = t->super();

        j = t->super_depth();

      }

      for (juint j1 = j+1; j1 < primary_super_limit(); j1++) {

        assert(primary_super_of_depth(j1) == NULL, "super list padding");

      }

      while (t != NULL) {

        assert(primary_super_of_depth(j) == t, "super list initialization");

        t = t->super();

        --j;

      }

      assert(j == (juint)-1, "correct depth count");

    }

#endif

  }

  if (secondary_supers() == NULL) {

    // Now compute the list of secondary supertypes.

    // Secondaries can occasionally be on the super chain,

    // if the inline "_primary_supers" array overflows.

    int extras = 0;

    Klass* p;

    for (p = super(); !(p == NULL || p->can_be_primary_super()); p = p->super()) {

      ++extras;

    }

    ResourceMark rm(THREAD);  // need to reclaim GrowableArrays allocated below

    // Compute the "real" non-extra secondaries.

    GrowableArray<Klass*>* secondaries = compute_secondary_supers(extras, transitive_interfaces);

    if (secondaries == NULL) {

      // secondary_supers set by compute_secondary_supers

      return;

    }

    GrowableArray<Klass*>* primaries = new GrowableArray<Klass*>(extras);

    for (p = super(); !(p == NULL || p->can_be_primary_super()); p = p->super()) {

      int i;                    // Scan for overflow primaries being duplicates of 2nd'arys

      // This happens frequently for very deeply nested arrays: the

      // primary superclass chain overflows into the secondary.  The

      // secondary list contains the element_klass's secondaries with

      // an extra array dimension added.  If the element_klass's

      // secondary list already contains some primary overflows, they

      // (with the extra level of array-ness) will collide with the

      // normal primary superclass overflows.

      for( i = 0; i < secondaries->length(); i++ ) {

        if( secondaries->at(i) == p )

          break;

      }

      if( i < secondaries->length() )

        continue;               // It's a dup, don't put it in

      primaries->push(p);

    }

    // Combine the two arrays into a metadata object to pack the array.

    // The primaries are added in the reverse order, then the secondaries.

    int new_length = primaries->length() + secondaries->length();

    Array<Klass*>* s2 = MetadataFactory::new_array<Klass*>(

                                       class_loader_data(), new_length, CHECK);

    int fill_p = primaries->length();

    for (int j = 0; j < fill_p; j++) {

      s2->at_put(j, primaries->pop());  // add primaries in reverse order.

    }

    for( int j = 0; j < secondaries->length(); j++ ) {

      s2->at_put(j+fill_p, secondaries->at(j));  // add secondaries on the end.

    }

  #ifdef ASSERT

      // We must not copy any NULL placeholders left over from bootstrap.

    for (int j = 0; j < s2->length(); j++) {

      assert(s2->at(j) != NULL, "correct bootstrapping order");

    }

  #endif

    set_secondary_supers(s2);

  }

}

GrowableArray<Klass*>* Klass::compute_secondary_supers(int num_extra_slots,

                                                       Array<InstanceKlass*>* transitive_interfaces) {

  assert(num_extra_slots == 0, "override for complex klasses");

  assert(transitive_interfaces == NULL, "sanity");

  set_secondary_supers(Universe::the_empty_klass_array());

  return NULL;

}

// superklass links

InstanceKlass* Klass::superklass() const {

  assert(super() == NULL || super()->is_instance_klass(), "must be instance klass");

  return _super == NULL ? NULL : InstanceKlass::cast(_super);

}

// subklass links.  Used by the compiler (and vtable initialization)

// May be cleaned concurrently, so must use the Compile_lock.

// The log parameter is for clean_weak_klass_links to report unlinked classes.

Klass* Klass::subklass(bool log) const {

  // Need load_acquire on the _subklass, because it races with inserts that

  // publishes freshly initialized data.

  for (Klass* chain = Atomic::load_acquire(&_subklass);

       chain != NULL;

       // Do not need load_acquire on _next_sibling, because inserts never

       // create _next_sibling edges to dead data.

       chain = Atomic::load(&chain->_next_sibling))

  {

    if (chain->is_loader_alive()) {

      return chain;

    } else if (log) {

      if (log_is_enabled(Trace, class, unload)) {

        ResourceMark rm;

        log_trace(class, unload)("unlinking class (subclass): %s", chain->external_name());

      }

    }

  }

  return NULL;

}

Klass* Klass::next_sibling(bool log) const {

  // Do not need load_acquire on _next_sibling, because inserts never

  // create _next_sibling edges to dead data.

  for (Klass* chain = Atomic::load(&_next_sibling);

       chain != NULL;

       chain = Atomic::load(&chain->_next_sibling)) {

    // Only return alive klass, there may be stale klass

    // in this chain if cleaned concurrently.

    if (chain->is_loader_alive()) {

      return chain;

    } else if (log) {

      if (log_is_enabled(Trace, class, unload)) {

        ResourceMark rm;

        log_trace(class, unload)("unlinking class (sibling): %s", chain->external_name());

      }

    }

  }

  return NULL;

}

void Klass::set_subklass(Klass* s) {

  assert(s != this, "sanity check");

  Atomic::release_store(&_subklass, s);

}

void Klass::set_next_sibling(Klass* s) {

  assert(s != this, "sanity check");

  // Does not need release semantics. If used by cleanup, it will link to

  // already safely published data, and if used by inserts, will be published

  // safely using cmpxchg.

  Atomic::store(&_next_sibling, s);

}

void Klass::append_to_sibling_list() {

  assert_locked_or_safepoint(Compile_lock);

  debug_only(verify();)

  // add ourselves to superklass' subklass list

  InstanceKlass* super = superklass();

  if (super == NULL) return;        // special case: class Object

  assert((!super->is_interface()    // interfaces cannot be supers

          && (super->superklass() == NULL || !is_interface())),

         "an interface can only be a subklass of Object");

  // Make sure there is no stale subklass head

  super->clean_subklass();

  for (;;) {

    Klass* prev_first_subklass = Atomic::load_acquire(&_super->_subklass);

    if (prev_first_subklass != NULL) {

      // set our sibling to be the superklass' previous first subklass

      assert(prev_first_subklass->is_loader_alive(), "May not attach not alive klasses");

      set_next_sibling(prev_first_subklass);

    }

    // Note that the prev_first_subklass is always alive, meaning no sibling_next links

    // are ever created to not alive klasses. This is an important invariant of the lock-free

    // cleaning protocol, that allows us to safely unlink dead klasses from the sibling list.

    if (Atomic::cmpxchg(&super->_subklass, prev_first_subklass, this) == prev_first_subklass) {

      return;

    }

  }

  debug_only(verify();)

}

void Klass::clean_subklass() {

  for (;;) {

    // Need load_acquire, due to contending with concurrent inserts

    Klass* subklass = Atomic::load_acquire(&_subklass);

    if (subklass == NULL || subklass->is_loader_alive()) {

      return;

    }

    // Try to fix _subklass until it points at something not dead.

    Atomic::cmpxchg(&_subklass, subklass, subklass->next_sibling());

  }

}

void Klass::clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses) {

  if (!ClassUnloading || !unloading_occurred) {

    return;

  }

  Klass* root = SystemDictionary::Object_klass();

  Stack<Klass*, mtGC> stack;

  stack.push(root);

  while (!stack.is_empty()) {

    Klass* current = stack.pop();

    assert(current->is_loader_alive(), "just checking, this should be live");

    // Find and set the first alive subklass

    Klass* sub = current->subklass(true);

    current->clean_subklass();

    if (sub != NULL) {

      stack.push(sub);

    }

    // Find and set the first alive sibling

    Klass* sibling = current->next_sibling(true);

    current->set_next_sibling(sibling);

    if (sibling != NULL) {

      stack.push(sibling);

    }

    // Clean the implementors list and method data.

    if (clean_alive_klasses && current->is_instance_klass()) {

      InstanceKlass* ik = InstanceKlass::cast(current);

      ik->clean_weak_instanceklass_links();

      // JVMTI RedefineClasses creates previous versions that are not in

      // the class hierarchy, so process them here.

      while ((ik = ik->previous_versions()) != NULL) {

        ik->clean_weak_instanceklass_links();

      }

    }

  }

}