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 /*

  * 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/systemDictionary.hpp"

 #include "memory/universe.inline.hpp"

 #include "prims/jvmtiGetLoadedClasses.hpp"

 #include "runtime/thread.hpp"

 #if INCLUDE_ALL_GCS

 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp"

 #endif

 // The closure for GetLoadedClasses

 class LoadedClassesClosure : public KlassClosure {

 private:

   Stack<jclass, mtInternal> _classStack;

   JvmtiEnv* _env;

 // Tell the GC to keep this klass alive

 static void ensure_klass_alive(oop o) {

   // A klass that was previously considered dead can be looked up in the

   // CLD/SD, and its _java_mirror or _class_loader can be stored in a root

   // or a reachable object making it alive again. The SATB part of G1 needs

   // to get notified about this potential resurrection, otherwise the marking

   // might not find the object.

 #if INCLUDE_ALL_GCS

   if (UseG1GC && o != NULL) {

     G1SATBCardTableModRefBS::enqueue(o);

   }

 #endif

 }

 public:

   LoadedClassesClosure(JvmtiEnv* env) {

     _env = env;

   }

   void do_klass(Klass* k) {

     // Collect all jclasses

     _classStack.push((jclass) _env->jni_reference(k->java_mirror()));

     ensure_klass_alive(k->java_mirror());

   }

   int extract(jclass* result_list) {

     // The size of the Stack will be 0 after extract, so get it here

     int count = (int)_classStack.size();

     int i = count;

     // Pop all jclasses, fill backwards

     while (!_classStack.is_empty()) {

       result_list[--i] = _classStack.pop();

     }

     // Return the number of elements written

     return count;

   }

   // Return current size of the Stack

   int get_count() {

     return (int)_classStack.size();

   }

 };

 // The closure for GetClassLoaderClasses

 class JvmtiGetLoadedClassesClosure : public StackObj {

   // Since the SystemDictionary::classes_do callback

   // doesn't pass a closureData pointer,

   // we use a thread-local slot to hold a pointer to

   // a stack allocated instance of this structure.

  private:

   jobject _initiatingLoader;

   int     _count;

   Handle* _list;

   int     _index;

  private:

   // Getting and setting the thread local pointer

   static JvmtiGetLoadedClassesClosure* get_this() {

     JvmtiGetLoadedClassesClosure* result = NULL;

     JavaThread* thread = JavaThread::current();

     result = thread->get_jvmti_get_loaded_classes_closure();

     return result;

   }

   static void set_this(JvmtiGetLoadedClassesClosure* that) {

     JavaThread* thread = JavaThread::current();

     thread->set_jvmti_get_loaded_classes_closure(that);

   }

  public:

   // Constructor/Destructor

   JvmtiGetLoadedClassesClosure() {

     JvmtiGetLoadedClassesClosure* that = get_this();

     assert(that == NULL, "JvmtiGetLoadedClassesClosure in use");

     _initiatingLoader = NULL;

     _count = 0;

     _list = NULL;

     _index = 0;

     set_this(this);

   }

   JvmtiGetLoadedClassesClosure(jobject initiatingLoader) {

     JvmtiGetLoadedClassesClosure* that = get_this();

     assert(that == NULL, "JvmtiGetLoadedClassesClosure in use");

     _initiatingLoader = initiatingLoader;

     _count = 0;

     _list = NULL;

     _index = 0;

     set_this(this);

   }

   ~JvmtiGetLoadedClassesClosure() {

     JvmtiGetLoadedClassesClosure* that = get_this();

     assert(that != NULL, "JvmtiGetLoadedClassesClosure not found");

     set_this(NULL);

     _initiatingLoader = NULL;

     _count = 0;

     if (_list != NULL) {

       FreeHeap(_list);

       _list = NULL;

     }

     _index = 0;

   }

   // Accessors.

   jobject get_initiatingLoader() {

     return _initiatingLoader;

   }

   int get_count() {

     return _count;

   }

   void set_count(int value) {

     _count = value;

   }

   Handle* get_list() {

     return _list;

   }

   void set_list(Handle* value) {

     _list = value;

   }

   int get_index() {

     return _index;

   }

   void set_index(int value) {

     _index = value;

   }

   Handle get_element(int index) {

     if ((_list != NULL) && (index < _count)) {

       return _list[index];

     } else {

       assert(false, "empty get_element");

       return Handle();

     }

   }

   void set_element(int index, Handle value) {

     if ((_list != NULL) && (index < _count)) {

       _list[index] = value;

     } else {

       assert(false, "bad set_element");

     }

   }

   // Other predicates

   bool available() {

     return (_list != NULL);

   }

 #ifdef ASSERT

   // For debugging.

   void check(int limit) {

     for (int i = 0; i < limit; i += 1) {

       assert(Universe::heap()->is_in(get_element(i)()), "check fails");

     }

   }

 #endif

   // Public methods that get called within the scope of the closure

   void allocate() {

     _list = NEW_C_HEAP_ARRAY(Handle, _count, mtInternal);

     assert(_list != NULL, "Out of memory");

     if (_list == NULL) {

       _count = 0;

     }

   }

   void extract(JvmtiEnv *env, jclass* result) {

     for (int index = 0; index < _count; index += 1) {

       result[index] = (jclass) env->jni_reference(get_element(index));

     }

   }

   static void increment_with_loader(Klass* k, ClassLoaderData* loader_data) {

     JvmtiGetLoadedClassesClosure* that = JvmtiGetLoadedClassesClosure::get_this();

     oop class_loader = loader_data->class_loader();

     if (class_loader == JNIHandles::resolve(that->get_initiatingLoader())) {

       for (Klass* l = k; l != NULL; l = l->array_klass_or_null()) {

         that->set_count(that->get_count() + 1);

       }

     }

   }

   static void prim_array_increment_with_loader(Klass* array, ClassLoaderData* loader_data) {

     JvmtiGetLoadedClassesClosure* that = JvmtiGetLoadedClassesClosure::get_this();

     oop class_loader = loader_data->class_loader();

     if (class_loader == JNIHandles::resolve(that->get_initiatingLoader())) {

       that->set_count(that->get_count() + 1);

     }

   }

   static void add_with_loader(Klass* k, ClassLoaderData* loader_data) {

     JvmtiGetLoadedClassesClosure* that = JvmtiGetLoadedClassesClosure::get_this();

     if (that->available()) {

       oop class_loader = loader_data->class_loader();

       if (class_loader == JNIHandles::resolve(that->get_initiatingLoader())) {

         for (Klass* l = k; l != NULL; l = l->array_klass_or_null()) {

           oop mirror = l->java_mirror();

           that->set_element(that->get_index(), mirror);

           that->set_index(that->get_index() + 1);

         }

       }

     }

   }

   // increment the count for the given basic type array class (and any

   // multi-dimensional arrays). For example, for [B we check for

   // [[B, [[[B, .. and the count is incremented for each one that exists.

   static void increment_for_basic_type_arrays(Klass* k) {

     JvmtiGetLoadedClassesClosure* that = JvmtiGetLoadedClassesClosure::get_this();

     assert(that != NULL, "no JvmtiGetLoadedClassesClosure");

     for (Klass* l = k; l != NULL; l = l->array_klass_or_null()) {

       that->set_count(that->get_count() + 1);

     }

   }

   // add the basic type array class and its multi-dimensional array classes to the list

   static void add_for_basic_type_arrays(Klass* k) {

     JvmtiGetLoadedClassesClosure* that = JvmtiGetLoadedClassesClosure::get_this();

     assert(that != NULL, "no JvmtiGetLoadedClassesClosure");

     assert(that->available(), "no list");

     for (Klass* l = k; l != NULL; l = l->array_klass_or_null()) {

       oop mirror = l->java_mirror();

       that->set_element(that->get_index(), mirror);

       that->set_index(that->get_index() + 1);

     }

   }

 };

 jvmtiError

 JvmtiGetLoadedClasses::getLoadedClasses(JvmtiEnv *env, jint* classCountPtr, jclass** classesPtr) {

   LoadedClassesClosure closure(env);

   {

     // To get a consistent list of classes we need MultiArray_lock to ensure

     // array classes aren't created.

     MutexLocker ma(MultiArray_lock);

     // Iterate through all classes in ClassLoaderDataGraph

     // and collect them using the LoadedClassesClosure

     ClassLoaderDataGraph::loaded_classes_do(&closure);

   }

   // Return results by extracting the collected contents into a list

   // allocated via JvmtiEnv

   jclass* result_list;

   jvmtiError error = env->Allocate(closure.get_count() * sizeof(jclass),

                                (unsigned char**)&result_list);

   if (error == JVMTI_ERROR_NONE) {

     int count = closure.extract(result_list);

     *classCountPtr = count;

     *classesPtr = result_list;

   }

   return error;

 }

 jvmtiError

 JvmtiGetLoadedClasses::getClassLoaderClasses(JvmtiEnv *env, jobject initiatingLoader,

                                              jint* classCountPtr, jclass** classesPtr) {

   // Since SystemDictionary::classes_do only takes a function pointer

   // and doesn't call back with a closure data pointer,

   // we can only pass static methods.

   JvmtiGetLoadedClassesClosure closure(initiatingLoader);

   {

     // To get a consistent list of classes we need MultiArray_lock to ensure

     // array classes aren't created, and SystemDictionary_lock to ensure that

     // classes aren't added to the system dictionary,

     MutexLocker ma(MultiArray_lock);

     MutexLocker sd(SystemDictionary_lock);

     // First, count the classes in the system dictionary which have this loader recorded

     // as an initiating loader. For basic type arrays this information is not recorded

     // so GetClassLoaderClasses will return all of the basic type arrays. This is okay

     // because the defining loader for basic type arrays is always the boot class loader

     // and these classes are "visible" to all loaders.

     SystemDictionary::classes_do(&JvmtiGetLoadedClassesClosure::increment_with_loader);

     Universe::basic_type_classes_do(&JvmtiGetLoadedClassesClosure::increment_for_basic_type_arrays);

     // Next, fill in the classes

     closure.allocate();

     SystemDictionary::classes_do(&JvmtiGetLoadedClassesClosure::add_with_loader);

     Universe::basic_type_classes_do(&JvmtiGetLoadedClassesClosure::add_for_basic_type_arrays);

     // Drop the SystemDictionary_lock, so the results could be wrong from here,

     // but we still have a snapshot.

   }

   // Post results

   jclass* result_list;

   jvmtiError err = env->Allocate(closure.get_count() * sizeof(jclass),

                                  (unsigned char**)&result_list);

   if (err != JVMTI_ERROR_NONE) {

     return err;

   }

   closure.extract(env, result_list);

   *classCountPtr = closure.get_count();

   *classesPtr = result_list;

   return JVMTI_ERROR_NONE;

 }