/*

 * Copyright (c) 2003, 2018, 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/dictionary.hpp"

#include "classfile/classLoaderData.inline.hpp"

#include "classfile/loaderConstraints.hpp"

#include "logging/log.hpp"

#include "memory/resourceArea.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/handles.inline.hpp"

#include "runtime/safepoint.hpp"

#include "utilities/hashtable.inline.hpp"

void LoaderConstraintEntry::set_loader(int i, oop p) {

  set_loader_data(i, ClassLoaderData::class_loader_data(p));

}

LoaderConstraintTable::LoaderConstraintTable(int table_size)

  : Hashtable<InstanceKlass*, mtClass>(table_size, sizeof(LoaderConstraintEntry)) {};

LoaderConstraintEntry* LoaderConstraintTable::new_entry(

                                 unsigned int hash, Symbol* name,

                                 InstanceKlass* klass, int num_loaders,

                                 int max_loaders) {

  LoaderConstraintEntry* entry;

  entry = (LoaderConstraintEntry*)Hashtable<InstanceKlass*, mtClass>::new_entry(hash, klass);

  entry->set_name(name);

  entry->set_num_loaders(num_loaders);

  entry->set_max_loaders(max_loaders);

  return entry;

}

void LoaderConstraintTable::free_entry(LoaderConstraintEntry *entry) {

  // decrement name refcount before freeing

  entry->name()->decrement_refcount();

  Hashtable<InstanceKlass*, mtClass>::free_entry(entry);

}

// The loaderConstraintTable must always be accessed with the

// SystemDictionary lock held. This is true even for readers as

// entries in the table could be being dynamically resized.

LoaderConstraintEntry** LoaderConstraintTable::find_loader_constraint(

                                    Symbol* name, Handle loader) {

  unsigned int hash = compute_hash(name);

  int index = hash_to_index(hash);

  LoaderConstraintEntry** pp = bucket_addr(index);

  ClassLoaderData* loader_data = ClassLoaderData::class_loader_data(loader());

  while (*pp) {

    LoaderConstraintEntry* p = *pp;

    if (p->hash() == hash) {

      if (p->name() == name) {

        for (int i = p->num_loaders() - 1; i >= 0; i--) {

          if (p->loader_data(i) == loader_data) {

            return pp;

          }

        }

      }

    }

    pp = p->next_addr();

  }

  return pp;

}

void LoaderConstraintTable::purge_loader_constraints() {

  assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");

  LogTarget(Info, class, loader, constraints) lt;

  // Remove unloaded entries from constraint table

  for (int index = 0; index < table_size(); index++) {

    LoaderConstraintEntry** p = bucket_addr(index);

    while(*p) {

      LoaderConstraintEntry* probe = *p;

      InstanceKlass* klass = probe->klass();

      // Remove klass that is no longer alive

      if (klass != NULL &&

          !klass->is_loader_alive()) {

        probe->set_klass(NULL);

        if (lt.is_enabled()) {

          ResourceMark rm;

          lt.print("purging class object from constraint for name %s,"

                     " loader list:",

                     probe->name()->as_C_string());

          for (int i = 0; i < probe->num_loaders(); i++) {

            lt.print("    [%d]: %s", i,

                          probe->loader_data(i)->loader_name());

          }

        }

      }

      // Remove entries no longer alive from loader array

      int n = 0;

      while (n < probe->num_loaders()) {

        if (probe->loader_data(n)->is_unloading()) {

          if (lt.is_enabled()) {

            ResourceMark rm;

            lt.print("purging loader %s from constraint for name %s",

                     probe->loader_data(n)->loader_name(),

                     probe->name()->as_C_string()

                     );

          }

          // Compact array

          int num = probe->num_loaders() - 1;

          probe->set_num_loaders(num);

          probe->set_loader_data(n, probe->loader_data(num));

          probe->set_loader_data(num, NULL);

          if (lt.is_enabled()) {

            ResourceMark rm;

            lt.print("new loader list:");

            for (int i = 0; i < probe->num_loaders(); i++) {

              lt.print("    [%d]: %s", i,

                            probe->loader_data(i)->loader_name());

            }

          }

          continue;  // current element replaced, so restart without

                     // incrementing n

          }

        n++;

      }

      // Check whether entry should be purged

      if (probe->num_loaders() < 2) {

            if (lt.is_enabled()) {

              ResourceMark rm;

              lt.print("purging complete constraint for name %s",

                         probe->name()->as_C_string());

            }

        // Purge entry

        *p = probe->next();

        FREE_C_HEAP_ARRAY(oop, probe->loaders());

        free_entry(probe);

      } else {

#ifdef ASSERT

        if (probe->klass() != NULL) {

          assert(probe->klass()->is_loader_alive(), "klass should be live");

        }

#endif

        // Go to next entry

        p = probe->next_addr();

      }

    }

  }

}

void log_ldr_constraint_msg(Symbol* class_name, const char* reason,

                        Handle class_loader1, Handle class_loader2) {

  LogTarget(Info, class, loader, constraints) lt;

  if (lt.is_enabled()) {

    ResourceMark rm;

    lt.print("Failed to add constraint for name: %s, loader[0]: %s,"

                " loader[1]: %s, Reason: %s",

                  class_name->as_C_string(),

                  SystemDictionary::loader_name(class_loader1()),

                  SystemDictionary::loader_name(class_loader2()),

                  reason);

  }

}

bool LoaderConstraintTable::add_entry(Symbol* class_name,

                                      InstanceKlass* klass1, Handle class_loader1,

                                      InstanceKlass* klass2, Handle class_loader2) {

  LogTarget(Info, class, loader, constraints) lt;

  if (klass1 != NULL && klass2 != NULL) {

    if (klass1 == klass2) {

      // Same type already loaded in both places.  There is no need for any constraint.

      return true;

    } else {

      log_ldr_constraint_msg(class_name,

                             "The class objects presented by loader[0] and loader[1] "

                             "are different",

                             class_loader1, class_loader2);

      return false;

    }

  }

  InstanceKlass* klass = klass1 != NULL ? klass1 : klass2;

  LoaderConstraintEntry** pp1 = find_loader_constraint(class_name, class_loader1);

  if (*pp1 != NULL && (*pp1)->klass() != NULL) {

    if (klass != NULL) {

      if (klass != (*pp1)->klass()) {

        log_ldr_constraint_msg(class_name,

                               "The class object presented by loader[0] does not match "

                               "the stored class object in the constraint",

                               class_loader1, class_loader2);

        return false;

      }

    } else {

      klass = (*pp1)->klass();

    }

  }

  LoaderConstraintEntry** pp2 = find_loader_constraint(class_name, class_loader2);

  if (*pp2 != NULL && (*pp2)->klass() != NULL) {

    if (klass != NULL) {

      if (klass != (*pp2)->klass()) {

        log_ldr_constraint_msg(class_name,

                               "The class object presented by loader[1] does not match "

                               "the stored class object in the constraint",

                               class_loader1, class_loader2);

        return false;

      }

    } else {

      klass = (*pp2)->klass();

    }

  }

  if (*pp1 == NULL && *pp2 == NULL) {

    unsigned int hash = compute_hash(class_name);

    int index = hash_to_index(hash);

    LoaderConstraintEntry* p;

    p = new_entry(hash, class_name, klass, 2, 2);

    p->set_loaders(NEW_C_HEAP_ARRAY(ClassLoaderData*, 2, mtClass));

    p->set_loader(0, class_loader1());

    p->set_loader(1, class_loader2());

    p->set_klass(klass);

    p->set_next(bucket(index));

    set_entry(index, p);

    if (lt.is_enabled()) {

      ResourceMark rm;

      lt.print("adding new constraint for name: %s, loader[0]: %s,"

                    " loader[1]: %s",

                    class_name->as_C_string(),

                    SystemDictionary::loader_name(class_loader1()),

                    SystemDictionary::loader_name(class_loader2())

                    );

    }

  } else if (*pp1 == *pp2) {

    /* constraint already imposed */

    if ((*pp1)->klass() == NULL) {

      (*pp1)->set_klass(klass);

      if (lt.is_enabled()) {

        ResourceMark rm;

        lt.print("setting class object in existing constraint for"

                      " name: %s and loader %s",

                      class_name->as_C_string(),

                      SystemDictionary::loader_name(class_loader1())

                      );

      }

    } else {

      assert((*pp1)->klass() == klass, "loader constraints corrupted");

    }

  } else if (*pp1 == NULL) {

    extend_loader_constraint(*pp2, class_loader1, klass);

  } else if (*pp2 == NULL) {

    extend_loader_constraint(*pp1, class_loader2, klass);

  } else {

    merge_loader_constraints(pp1, pp2, klass);

  }

  return true;

}

// return true if the constraint was updated, false if the constraint is

// violated

bool LoaderConstraintTable::check_or_update(InstanceKlass* k,

                                            Handle loader,

                                            Symbol* name) {

  LogTarget(Info, class, loader, constraints) lt;

  LoaderConstraintEntry* p = *(find_loader_constraint(name, loader));

  if (p && p->klass() != NULL && p->klass() != k) {

    if (lt.is_enabled()) {

      ResourceMark rm;

      lt.print("constraint check failed for name %s, loader %s: "

                 "the presented class object differs from that stored",

                 name->as_C_string(),

                 SystemDictionary::loader_name(loader()));

    }

    return false;

  } else {

    if (p && p->klass() == NULL) {

      p->set_klass(k);

      if (lt.is_enabled()) {

        ResourceMark rm;

        lt.print("updating constraint for name %s, loader %s, "

                   "by setting class object",

                   name->as_C_string(),

                   SystemDictionary::loader_name(loader()));

      }

    }

    return true;

  }

}

InstanceKlass* LoaderConstraintTable::find_constrained_klass(Symbol* name,

                                                       Handle loader) {

  LoaderConstraintEntry *p = *(find_loader_constraint(name, loader));

  if (p != NULL && p->klass() != NULL) {

    assert(p->klass()->is_instance_klass(), "sanity");

    if (!p->klass()->is_loaded()) {

      // Only return fully loaded classes.  Classes found through the

      // constraints might still be in the process of loading.

      return NULL;

    }

    return p->klass();

  }

  // No constraints, or else no klass loaded yet.

  return NULL;

}

void LoaderConstraintTable::ensure_loader_constraint_capacity(

                                                     LoaderConstraintEntry *p,

                                                    int nfree) {

    if (p->max_loaders() - p->num_loaders() < nfree) {

        int n = nfree + p->num_loaders();

        ClassLoaderData** new_loaders = NEW_C_HEAP_ARRAY(ClassLoaderData*, n, mtClass);

        memcpy(new_loaders, p->loaders(), sizeof(ClassLoaderData*) * p->num_loaders());

        p->set_max_loaders(n);

        FREE_C_HEAP_ARRAY(ClassLoaderData*, p->loaders());

        p->set_loaders(new_loaders);

    }

}

void LoaderConstraintTable::extend_loader_constraint(LoaderConstraintEntry* p,

                                                     Handle loader,

                                                     InstanceKlass* klass) {

  ensure_loader_constraint_capacity(p, 1);

  int num = p->num_loaders();

  p->set_loader(num, loader());

  p->set_num_loaders(num + 1);

  LogTarget(Info, class, loader, constraints) lt;

  if (lt.is_enabled()) {

    ResourceMark rm;

    lt.print("extending constraint for name %s by adding loader[%d]: %s %s",

               p->name()->as_C_string(),

               num,

               SystemDictionary::loader_name(loader()),

               (p->klass() == NULL ? " and setting class object" : "")

               );

  }

  if (p->klass() == NULL) {

    p->set_klass(klass);

  } else {

    assert(klass == NULL || p->klass() == klass, "constraints corrupted");

  }

}

void LoaderConstraintTable::merge_loader_constraints(

                                                   LoaderConstraintEntry** pp1,

                                                   LoaderConstraintEntry** pp2,

                                                   InstanceKlass* klass) {

  // make sure *pp1 has higher capacity

  if ((*pp1)->max_loaders() < (*pp2)->max_loaders()) {

    LoaderConstraintEntry** tmp = pp2;

    pp2 = pp1;

    pp1 = tmp;

  }

  LoaderConstraintEntry* p1 = *pp1;

  LoaderConstraintEntry* p2 = *pp2;

  ensure_loader_constraint_capacity(p1, p2->num_loaders());

  for (int i = 0; i < p2->num_loaders(); i++) {

    int num = p1->num_loaders();

    p1->set_loader_data(num, p2->loader_data(i));

    p1->set_num_loaders(num + 1);

  }

  LogTarget(Info, class, loader, constraints) lt;

  if (lt.is_enabled()) {

    ResourceMark rm;

    lt.print("merged constraints for name %s, new loader list:",

                  p1->name()->as_C_string()

                  );

    for (int i = 0; i < p1->num_loaders(); i++) {

      lt.print("    [%d]: %s", i,

                    p1->loader_data(i)->loader_name());

    }

    if (p1->klass() == NULL) {

      lt.print("... and setting class object");

    }

  }

  // p1->klass() will hold NULL if klass, p2->klass(), and old

  // p1->klass() are all NULL.  In addition, all three must have

  // matching non-NULL values, otherwise either the constraints would

  // have been violated, or the constraints had been corrupted (and an

  // assertion would fail).

  if (p2->klass() != NULL) {

    assert(p2->klass() == klass, "constraints corrupted");

  }

  if (p1->klass() == NULL) {

    p1->set_klass(klass);

  } else {

    assert(p1->klass() == klass, "constraints corrupted");

  }

  *pp2 = p2->next();

  FREE_C_HEAP_ARRAY(oop, p2->loaders());

  free_entry(p2);

  return;

}

void LoaderConstraintTable::verify(PlaceholderTable* placeholders) {

  Thread *thread = Thread::current();

  for (int cindex = 0; cindex < table_size(); cindex++) {

    for (LoaderConstraintEntry* probe = bucket(cindex);

                                probe != NULL;

                                probe = probe->next()) {

      if (probe->klass() != NULL) {

        InstanceKlass* ik = probe->klass();

        guarantee(ik->name() == probe->name(), "name should match");

        Symbol* name = ik->name();

        ClassLoaderData* loader_data = ik->class_loader_data();

        Dictionary* dictionary = loader_data->dictionary();

        unsigned int d_hash = dictionary->compute_hash(name);

        int d_index = dictionary->hash_to_index(d_hash);

        InstanceKlass* k = dictionary->find_class(d_index, d_hash, name);

        if (k != NULL) {

          // We found the class in the dictionary, so we should

          // make sure that the Klass* matches what we already have.

          guarantee(k == probe->klass(), "klass should be in dictionary");

        } else {

          // If we don't find the class in the dictionary, it

          // has to be in the placeholders table.

          unsigned int p_hash = placeholders->compute_hash(name);

          int p_index = placeholders->hash_to_index(p_hash);

          PlaceholderEntry* entry = placeholders->get_entry(p_index, p_hash,

                                                            name, loader_data);

          // The InstanceKlass might not be on the entry, so the only

          // thing we can check here is whether we were successful in

          // finding the class in the placeholders table.

          guarantee(entry != NULL, "klass should be in the placeholders");

        }

      }

      for (int n = 0; n< probe->num_loaders(); n++) {

        assert(ClassLoaderDataGraph::contains_loader_data(probe->loader_data(n)), "The loader is missing");

      }

    }

  }

}

// Called with the system dictionary lock held

void LoaderConstraintTable::print_on(outputStream* st) const {

  ResourceMark rm;

  assert_locked_or_safepoint(SystemDictionary_lock);

  st->print_cr("Java loader constraints (table_size=%d, constraints=%d)",

               table_size(), number_of_entries());

  for (int cindex = 0; cindex < table_size(); cindex++) {

    for (LoaderConstraintEntry* probe = bucket(cindex);

                                probe != NULL;

                                probe = probe->next()) {

      st->print("%4d: ", cindex);

      probe->name()->print_on(st);

      st->print(" , loaders:");

      for (int n = 0; n < probe->num_loaders(); n++) {

        probe->loader_data(n)->print_value_on(st);

        st->print(", ");

      }

      st->cr();

    }

  }

}