1 /*
   2  * Copyright (c) 2003, 2018, 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 "classfile/systemDictionary.hpp"
  27 #include "memory/universe.inline.hpp"
  28 #include "prims/jvmtiGetLoadedClasses.hpp"
  29 #include "runtime/thread.hpp"
  30 #if INCLUDE_ALL_GCS
  31 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp"
  32 #endif
  33 
  34 
  35 // The closure for GetLoadedClasses
  36 class LoadedClassesClosure : public KlassClosure {
  37 private:
  38   Stack<jclass, mtInternal> _classStack;
  39   JvmtiEnv* _env;
  40 
  41 // Tell the GC to keep this klass alive
  42 static void ensure_klass_alive(oop o) {
  43   // A klass that was previously considered dead can be looked up in the
  44   // CLD/SD, and its _java_mirror or _class_loader can be stored in a root
  45   // or a reachable object making it alive again. The SATB part of G1 needs
  46   // to get notified about this potential resurrection, otherwise the marking
  47   // might not find the object.
  48 #if INCLUDE_ALL_GCS
  49   if ((o != NULL) && (UseG1GC || (UseShenandoahGC && ShenandoahKeepAliveBarrier))) {
  50     G1SATBCardTableModRefBS::enqueue(o);
  51   }
  52 #endif
  53 }
  54 
  55 public:
  56   LoadedClassesClosure(JvmtiEnv* env) {
  57     _env = env;
  58   }
  59 
  60   void do_klass(Klass* k) {
  61     // Collect all jclasses
  62     _classStack.push((jclass) _env->jni_reference(k->java_mirror()));
  63   }
  64 
  65   int extract(jclass* result_list) {
  66     // The size of the Stack will be 0 after extract, so get it here
  67     int count = (int)_classStack.size();
  68     int i = count;
  69 
  70     // Pop all jclasses, fill backwards
  71     while (!_classStack.is_empty()) {
  72       jclass klass_handle = _classStack.pop();
  73       oop klass_mirror = JNIHandles::resolve(klass_handle);
  74       ensure_klass_alive(klass_mirror);
  75       result_list[--i] = klass_handle;
  76     }
  77 
  78     // Return the number of elements written
  79     return count;
  80   }
  81 
  82   // Return current size of the Stack
  83   int get_count() {
  84     return (int)_classStack.size();
  85   }
  86 };
  87 
  88 // The closure for GetClassLoaderClasses
  89 class JvmtiGetLoadedClassesClosure : public StackObj {
  90   // Since the SystemDictionary::classes_do callback
  91   // doesn't pass a closureData pointer,
  92   // we use a thread-local slot to hold a pointer to
  93   // a stack allocated instance of this structure.
  94  private:
  95   jobject _initiatingLoader;
  96   int     _count;
  97   Handle* _list;
  98   int     _index;
  99 
 100  private:
 101   // Getting and setting the thread local pointer
 102   static JvmtiGetLoadedClassesClosure* get_this() {
 103     JvmtiGetLoadedClassesClosure* result = NULL;
 104     JavaThread* thread = JavaThread::current();
 105     result = thread->get_jvmti_get_loaded_classes_closure();
 106     return result;
 107   }
 108   static void set_this(JvmtiGetLoadedClassesClosure* that) {
 109     JavaThread* thread = JavaThread::current();
 110     thread->set_jvmti_get_loaded_classes_closure(that);
 111   }
 112 
 113  public:
 114   // Constructor/Destructor
 115   JvmtiGetLoadedClassesClosure() {
 116     JvmtiGetLoadedClassesClosure* that = get_this();
 117     assert(that == NULL, "JvmtiGetLoadedClassesClosure in use");
 118     _initiatingLoader = NULL;
 119     _count = 0;
 120     _list = NULL;
 121     _index = 0;
 122     set_this(this);
 123   }
 124 
 125   JvmtiGetLoadedClassesClosure(jobject initiatingLoader) {
 126     JvmtiGetLoadedClassesClosure* that = get_this();
 127     assert(that == NULL, "JvmtiGetLoadedClassesClosure in use");
 128     _initiatingLoader = initiatingLoader;
 129     _count = 0;
 130     _list = NULL;
 131     _index = 0;
 132     set_this(this);
 133   }
 134 
 135   ~JvmtiGetLoadedClassesClosure() {
 136     JvmtiGetLoadedClassesClosure* that = get_this();
 137     assert(that != NULL, "JvmtiGetLoadedClassesClosure not found");
 138     set_this(NULL);
 139     _initiatingLoader = NULL;
 140     _count = 0;
 141     if (_list != NULL) {
 142       FreeHeap(_list);
 143       _list = NULL;
 144     }
 145     _index = 0;
 146   }
 147 
 148   // Accessors.
 149   jobject get_initiatingLoader() {
 150     return _initiatingLoader;
 151   }
 152 
 153   int get_count() {
 154     return _count;
 155   }
 156 
 157   void set_count(int value) {
 158     _count = value;
 159   }
 160 
 161   Handle* get_list() {
 162     return _list;
 163   }
 164 
 165   void set_list(Handle* value) {
 166     _list = value;
 167   }
 168 
 169   int get_index() {
 170     return _index;
 171   }
 172 
 173   void set_index(int value) {
 174     _index = value;
 175   }
 176 
 177   Handle get_element(int index) {
 178     if ((_list != NULL) && (index < _count)) {
 179       return _list[index];
 180     } else {
 181       assert(false, "empty get_element");
 182       return Handle();
 183     }
 184   }
 185 
 186   void set_element(int index, Handle value) {
 187     if ((_list != NULL) && (index < _count)) {
 188       _list[index] = value;
 189     } else {
 190       assert(false, "bad set_element");
 191     }
 192   }
 193 
 194   // Other predicates
 195   bool available() {
 196     return (_list != NULL);
 197   }
 198 
 199 #ifdef ASSERT
 200   // For debugging.
 201   void check(int limit) {
 202     for (int i = 0; i < limit; i += 1) {
 203       assert(Universe::heap()->is_in(get_element(i)()), "check fails");
 204     }
 205   }
 206 #endif
 207 
 208   // Public methods that get called within the scope of the closure
 209   void allocate() {
 210     _list = NEW_C_HEAP_ARRAY(Handle, _count, mtInternal);
 211     assert(_list != NULL, "Out of memory");
 212     if (_list == NULL) {
 213       _count = 0;
 214     }
 215   }
 216 
 217   void extract(JvmtiEnv *env, jclass* result) {
 218     for (int index = 0; index < _count; index += 1) {
 219       result[index] = (jclass) env->jni_reference(get_element(index));
 220     }
 221   }
 222 
 223   static void increment_with_loader(Klass* k, ClassLoaderData* loader_data) {
 224     JvmtiGetLoadedClassesClosure* that = JvmtiGetLoadedClassesClosure::get_this();
 225     oop class_loader = loader_data->class_loader();
 226     if (class_loader == JNIHandles::resolve(that->get_initiatingLoader())) {
 227       for (Klass* l = k; l != NULL; l = l->array_klass_or_null()) {
 228         that->set_count(that->get_count() + 1);
 229       }
 230     }
 231   }
 232 
 233   static void prim_array_increment_with_loader(Klass* array, ClassLoaderData* loader_data) {
 234     JvmtiGetLoadedClassesClosure* that = JvmtiGetLoadedClassesClosure::get_this();
 235     oop class_loader = loader_data->class_loader();
 236     if (class_loader == JNIHandles::resolve(that->get_initiatingLoader())) {
 237       that->set_count(that->get_count() + 1);
 238     }
 239   }
 240 
 241   static void add_with_loader(Klass* k, ClassLoaderData* loader_data) {
 242     JvmtiGetLoadedClassesClosure* that = JvmtiGetLoadedClassesClosure::get_this();
 243     if (that->available()) {
 244       oop class_loader = loader_data->class_loader();
 245       if (class_loader == JNIHandles::resolve(that->get_initiatingLoader())) {
 246         for (Klass* l = k; l != NULL; l = l->array_klass_or_null()) {
 247           oop mirror = l->java_mirror();
 248           that->set_element(that->get_index(), mirror);
 249           that->set_index(that->get_index() + 1);
 250         }
 251       }
 252     }
 253   }
 254 
 255   // increment the count for the given basic type array class (and any
 256   // multi-dimensional arrays). For example, for [B we check for
 257   // [[B, [[[B, .. and the count is incremented for each one that exists.
 258   static void increment_for_basic_type_arrays(Klass* k) {
 259     JvmtiGetLoadedClassesClosure* that = JvmtiGetLoadedClassesClosure::get_this();
 260     assert(that != NULL, "no JvmtiGetLoadedClassesClosure");
 261     for (Klass* l = k; l != NULL; l = l->array_klass_or_null()) {
 262       that->set_count(that->get_count() + 1);
 263     }
 264   }
 265 
 266   // add the basic type array class and its multi-dimensional array classes to the list
 267   static void add_for_basic_type_arrays(Klass* k) {
 268     JvmtiGetLoadedClassesClosure* that = JvmtiGetLoadedClassesClosure::get_this();
 269     assert(that != NULL, "no JvmtiGetLoadedClassesClosure");
 270     assert(that->available(), "no list");
 271     for (Klass* l = k; l != NULL; l = l->array_klass_or_null()) {
 272       oop mirror = l->java_mirror();
 273       that->set_element(that->get_index(), mirror);
 274       that->set_index(that->get_index() + 1);
 275     }
 276   }
 277 };
 278 
 279 
 280 jvmtiError
 281 JvmtiGetLoadedClasses::getLoadedClasses(JvmtiEnv *env, jint* classCountPtr, jclass** classesPtr) {
 282 
 283   LoadedClassesClosure closure(env);
 284   {
 285     // To get a consistent list of classes we need MultiArray_lock to ensure
 286     // array classes aren't created.
 287     MutexLocker ma(MultiArray_lock);
 288 
 289     // Iterate through all classes in ClassLoaderDataGraph
 290     // and collect them using the LoadedClassesClosure
 291     ClassLoaderDataGraph::loaded_classes_do(&closure);
 292   }
 293 
 294   // Return results by extracting the collected contents into a list
 295   // allocated via JvmtiEnv
 296   jclass* result_list;
 297   jvmtiError error = env->Allocate(closure.get_count() * sizeof(jclass),
 298                                (unsigned char**)&result_list);
 299 
 300   if (error == JVMTI_ERROR_NONE) {
 301     int count = closure.extract(result_list);
 302     *classCountPtr = count;
 303     *classesPtr = result_list;
 304   }
 305   return error;
 306 }
 307 
 308 jvmtiError
 309 JvmtiGetLoadedClasses::getClassLoaderClasses(JvmtiEnv *env, jobject initiatingLoader,
 310                                              jint* classCountPtr, jclass** classesPtr) {
 311   // Since SystemDictionary::classes_do only takes a function pointer
 312   // and doesn't call back with a closure data pointer,
 313   // we can only pass static methods.
 314   JvmtiGetLoadedClassesClosure closure(initiatingLoader);
 315   {
 316     // To get a consistent list of classes we need MultiArray_lock to ensure
 317     // array classes aren't created, and SystemDictionary_lock to ensure that
 318     // classes aren't added to the system dictionary,
 319     MutexLocker ma(MultiArray_lock);
 320     MutexLocker sd(SystemDictionary_lock);
 321     // First, count the classes in the system dictionary which have this loader recorded
 322     // as an initiating loader. For basic type arrays this information is not recorded
 323     // so GetClassLoaderClasses will return all of the basic type arrays. This is okay
 324     // because the defining loader for basic type arrays is always the boot class loader
 325     // and these classes are "visible" to all loaders.
 326     SystemDictionary::classes_do(&JvmtiGetLoadedClassesClosure::increment_with_loader);
 327     Universe::basic_type_classes_do(&JvmtiGetLoadedClassesClosure::increment_for_basic_type_arrays);
 328     // Next, fill in the classes
 329     closure.allocate();
 330     SystemDictionary::classes_do(&JvmtiGetLoadedClassesClosure::add_with_loader);
 331     Universe::basic_type_classes_do(&JvmtiGetLoadedClassesClosure::add_for_basic_type_arrays);
 332     // Drop the SystemDictionary_lock, so the results could be wrong from here,
 333     // but we still have a snapshot.
 334   }
 335   // Post results
 336   jclass* result_list;
 337   jvmtiError err = env->Allocate(closure.get_count() * sizeof(jclass),
 338                                  (unsigned char**)&result_list);
 339   if (err != JVMTI_ERROR_NONE) {
 340     return err;
 341   }
 342   closure.extract(env, result_list);
 343   *classCountPtr = closure.get_count();
 344   *classesPtr = result_list;
 345   return JVMTI_ERROR_NONE;
 346 }