1 /*
   2  * Copyright (c) 1997, 2015, 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 #ifndef SHARE_VM_MEMORY_ITERATOR_HPP
  26 #define SHARE_VM_MEMORY_ITERATOR_HPP
  27 
  28 #include "memory/allocation.hpp"
  29 #include "memory/memRegion.hpp"
  30 #include "utilities/top.hpp"
  31 
  32 class CodeBlob;
  33 class nmethod;
  34 class ReferenceProcessor;
  35 class DataLayout;
  36 class KlassClosure;
  37 class ClassLoaderData;
  38 
  39 // The following classes are C++ `closures` for iterating over objects, roots and spaces
  40 
  41 class Closure : public StackObj { };
  42 
  43 // OopClosure is used for iterating through references to Java objects.
  44 class OopClosure : public Closure {
  45  public:
  46   virtual void do_oop(oop* o) = 0;
  47   virtual void do_oop(narrowOop* o) = 0;
  48 };
  49 
  50 // ExtendedOopClosure adds extra code to be run during oop iterations.
  51 // This is needed by the GC and is extracted to a separate type to not
  52 // pollute the OopClosure interface.
  53 class ExtendedOopClosure : public OopClosure {
  54  private:
  55   ReferenceProcessor* _ref_processor;
  56 
  57  protected:
  58   ExtendedOopClosure(ReferenceProcessor* rp) : _ref_processor(rp) { }
  59   ExtendedOopClosure() : _ref_processor(NULL) { }
  60   ~ExtendedOopClosure() { }
  61 
  62   void set_ref_processor_internal(ReferenceProcessor* rp) { _ref_processor = rp; }
  63 
  64  public:
  65   ReferenceProcessor* ref_processor() const { return _ref_processor; }
  66 
  67   // If the do_metadata functions return "true",
  68   // we invoke the following when running oop_iterate():
  69   //
  70   // 1) do_klass on the header klass pointer.
  71   // 2) do_klass on the klass pointer in the mirrors.
  72   // 3) do_cld   on the class loader data in class loaders.
  73   //
  74   // The virtual (without suffix) and the non-virtual (with _nv suffix) need
  75   // to be updated together, or else the devirtualization will break.
  76   //
  77   // Providing default implementations of the _nv functions unfortunately
  78   // removes the compile-time safeness, but reduces the clutter for the
  79   // ExtendedOopClosures that don't need to walk the metadata.
  80   // Currently, only CMS and G1 need these.
  81 
  82   bool do_metadata_nv()      { return false; }
  83   virtual bool do_metadata() { return do_metadata_nv(); }
  84 
  85   void do_klass_nv(Klass* k)      { ShouldNotReachHere(); }
  86   virtual void do_klass(Klass* k) { do_klass_nv(k); }
  87 
  88   void do_cld_nv(ClassLoaderData* cld)      { ShouldNotReachHere(); }
  89   virtual void do_cld(ClassLoaderData* cld) { do_cld_nv(cld); }
  90 
  91   // True iff this closure may be safely applied more than once to an oop
  92   // location without an intervening "major reset" (like the end of a GC).
  93   virtual bool idempotent() { return false; }
  94   virtual bool apply_to_weak_ref_discovered_field() { return false; }
  95 
  96 #ifdef ASSERT
  97   // Default verification of each visited oop field.
  98   template <typename T> void verify(T* p);
  99 
 100   // Can be used by subclasses to turn off the default verification of oop fields.
 101   virtual bool should_verify_oops() { return true; }
 102 #endif
 103 };
 104 
 105 // Wrapper closure only used to implement oop_iterate_no_header().
 106 class NoHeaderExtendedOopClosure : public ExtendedOopClosure {
 107   OopClosure* _wrapped_closure;
 108  public:
 109   NoHeaderExtendedOopClosure(OopClosure* cl) : _wrapped_closure(cl) {}
 110   // Warning: this calls the virtual version do_oop in the the wrapped closure.
 111   void do_oop_nv(oop* p)       { _wrapped_closure->do_oop(p); }
 112   void do_oop_nv(narrowOop* p) { _wrapped_closure->do_oop(p); }
 113 
 114   void do_oop(oop* p)          { assert(false, "Only the _nv versions should be used");
 115                                  _wrapped_closure->do_oop(p); }
 116   void do_oop(narrowOop* p)    { assert(false, "Only the _nv versions should be used");
 117                                  _wrapped_closure->do_oop(p);}
 118 };
 119 
 120 class KlassClosure : public Closure {
 121  public:
 122   virtual void do_klass(Klass* k) = 0;
 123 };
 124 
 125 class CLDClosure : public Closure {
 126  public:
 127   virtual void do_cld(ClassLoaderData* cld) = 0;
 128 };
 129 
 130 class KlassToOopClosure : public KlassClosure {
 131   friend class MetadataAwareOopClosure;
 132   friend class MetadataAwareOopsInGenClosure;
 133 
 134   OopClosure* _oop_closure;
 135 
 136   // Used when _oop_closure couldn't be set in an initialization list.
 137   void initialize(OopClosure* oop_closure) {
 138     assert(_oop_closure == NULL, "Should only be called once");
 139     _oop_closure = oop_closure;
 140   }
 141 
 142  public:
 143   KlassToOopClosure(OopClosure* oop_closure = NULL) : _oop_closure(oop_closure) {}
 144 
 145   virtual void do_klass(Klass* k);
 146 };
 147 
 148 class CLDToOopClosure : public CLDClosure {
 149   OopClosure*       _oop_closure;
 150   KlassToOopClosure _klass_closure;
 151   bool              _must_claim_cld;
 152 
 153  public:
 154   CLDToOopClosure(OopClosure* oop_closure, bool must_claim_cld = true) :
 155       _oop_closure(oop_closure),
 156       _klass_closure(oop_closure),
 157       _must_claim_cld(must_claim_cld) {}
 158 
 159   void do_cld(ClassLoaderData* cld);
 160 };
 161 
 162 class CLDToKlassAndOopClosure : public CLDClosure {
 163   friend class G1CollectedHeap;
 164  protected:
 165   OopClosure*   _oop_closure;
 166   KlassClosure* _klass_closure;
 167   bool          _must_claim_cld;
 168  public:
 169   CLDToKlassAndOopClosure(KlassClosure* klass_closure,
 170                           OopClosure* oop_closure,
 171                           bool must_claim_cld) :
 172                               _oop_closure(oop_closure),
 173                               _klass_closure(klass_closure),
 174                               _must_claim_cld(must_claim_cld) {}
 175   void do_cld(ClassLoaderData* cld);
 176 };
 177 
 178 // The base class for all concurrent marking closures,
 179 // that participates in class unloading.
 180 // It's used to proxy through the metadata to the oops defined in them.
 181 class MetadataAwareOopClosure: public ExtendedOopClosure {
 182   KlassToOopClosure _klass_closure;
 183 
 184  public:
 185   MetadataAwareOopClosure() : ExtendedOopClosure() {
 186     _klass_closure.initialize(this);
 187   }
 188   MetadataAwareOopClosure(ReferenceProcessor* rp) : ExtendedOopClosure(rp) {
 189     _klass_closure.initialize(this);
 190   }
 191 
 192   bool do_metadata_nv()      { return true; }
 193   virtual bool do_metadata() { return do_metadata_nv(); }
 194 
 195   void do_klass_nv(Klass* k);
 196   virtual void do_klass(Klass* k) { do_klass_nv(k); }
 197 
 198   void do_cld_nv(ClassLoaderData* cld);
 199   virtual void do_cld(ClassLoaderData* cld) { do_cld_nv(cld); }
 200 };
 201 
 202 // ObjectClosure is used for iterating through an object space
 203 
 204 class ObjectClosure : public Closure {
 205  public:
 206   // Called for each object.
 207   virtual void do_object(oop obj) = 0;
 208 };
 209 
 210 
 211 class BoolObjectClosure : public Closure {
 212  public:
 213   virtual bool do_object_b(oop obj) = 0;
 214 };
 215 
 216 // Applies an oop closure to all ref fields in objects iterated over in an
 217 // object iteration.
 218 class ObjectToOopClosure: public ObjectClosure {
 219   ExtendedOopClosure* _cl;
 220 public:
 221   void do_object(oop obj);
 222   ObjectToOopClosure(ExtendedOopClosure* cl) : _cl(cl) {}
 223 };
 224 
 225 // A version of ObjectClosure that is expected to be robust
 226 // in the face of possibly uninitialized objects.
 227 class ObjectClosureCareful : public ObjectClosure {
 228  public:
 229   virtual size_t do_object_careful_m(oop p, MemRegion mr) = 0;
 230   virtual size_t do_object_careful(oop p) = 0;
 231 };
 232 
 233 // The following are used in CompactibleFreeListSpace and
 234 // ConcurrentMarkSweepGeneration.
 235 
 236 // Blk closure (abstract class)
 237 class BlkClosure : public StackObj {
 238  public:
 239   virtual size_t do_blk(HeapWord* addr) = 0;
 240 };
 241 
 242 // A version of BlkClosure that is expected to be robust
 243 // in the face of possibly uninitialized objects.
 244 class BlkClosureCareful : public BlkClosure {
 245  public:
 246   size_t do_blk(HeapWord* addr) {
 247     guarantee(false, "call do_blk_careful instead");
 248     return 0;
 249   }
 250   virtual size_t do_blk_careful(HeapWord* addr) = 0;
 251 };
 252 
 253 // SpaceClosure is used for iterating over spaces
 254 
 255 class Space;
 256 class CompactibleSpace;
 257 
 258 class SpaceClosure : public StackObj {
 259  public:
 260   // Called for each space
 261   virtual void do_space(Space* s) = 0;
 262 };
 263 
 264 class CompactibleSpaceClosure : public StackObj {
 265  public:
 266   // Called for each compactible space
 267   virtual void do_space(CompactibleSpace* s) = 0;
 268 };
 269 
 270 
 271 // CodeBlobClosure is used for iterating through code blobs
 272 // in the code cache or on thread stacks
 273 
 274 class CodeBlobClosure : public Closure {
 275  public:
 276   // Called for each code blob.
 277   virtual void do_code_blob(CodeBlob* cb) = 0;
 278 };
 279 
 280 // Applies an oop closure to all ref fields in code blobs
 281 // iterated over in an object iteration.
 282 class CodeBlobToOopClosure : public CodeBlobClosure {
 283   OopClosure* _cl;
 284   bool _fix_relocations;
 285  protected:
 286   void do_nmethod(nmethod* nm);
 287  public:
 288   // If fix_relocations(), then cl must copy objects to their new location immediately to avoid
 289   // patching nmethods with the old locations.
 290   CodeBlobToOopClosure(OopClosure* cl, bool fix_relocations) : _cl(cl), _fix_relocations(fix_relocations) {}
 291   virtual void do_code_blob(CodeBlob* cb);
 292 
 293   bool fix_relocations() const { return _fix_relocations; }
 294   const static bool FixRelocations = true;
 295 };
 296 
 297 class MarkingCodeBlobClosure : public CodeBlobToOopClosure {
 298  public:
 299   MarkingCodeBlobClosure(OopClosure* cl, bool fix_relocations) : CodeBlobToOopClosure(cl, fix_relocations) {}
 300   // Called for each code blob, but at most once per unique blob.
 301 
 302   virtual void do_code_blob(CodeBlob* cb);
 303 };
 304 
 305 // MonitorClosure is used for iterating over monitors in the monitors cache
 306 
 307 class ObjectMonitor;
 308 
 309 class MonitorClosure : public StackObj {
 310  public:
 311   // called for each monitor in cache
 312   virtual void do_monitor(ObjectMonitor* m) = 0;
 313 };
 314 
 315 // A closure that is applied without any arguments.
 316 class VoidClosure : public StackObj {
 317  public:
 318   // I would have liked to declare this a pure virtual, but that breaks
 319   // in mysterious ways, for unknown reasons.
 320   virtual void do_void();
 321 };
 322 
 323 
 324 // YieldClosure is intended for use by iteration loops
 325 // to incrementalize their work, allowing interleaving
 326 // of an interruptable task so as to allow other
 327 // threads to run (which may not otherwise be able to access
 328 // exclusive resources, for instance). Additionally, the
 329 // closure also allows for aborting an ongoing iteration
 330 // by means of checking the return value from the polling
 331 // call.
 332 class YieldClosure : public StackObj {
 333   public:
 334    virtual bool should_return() = 0;
 335 };
 336 
 337 // Abstract closure for serializing data (read or write).
 338 
 339 class SerializeClosure : public Closure {
 340 public:
 341   // Return bool indicating whether closure implements read or write.
 342   virtual bool reading() const = 0;
 343 
 344   // Read/write the void pointer pointed to by p.
 345   virtual void do_ptr(void** p) = 0;
 346 
 347   // Read/write the region specified.
 348   virtual void do_region(u_char* start, size_t size) = 0;
 349 
 350   // Check/write the tag.  If reading, then compare the tag against
 351   // the passed in value and fail is they don't match.  This allows
 352   // for verification that sections of the serialized data are of the
 353   // correct length.
 354   virtual void do_tag(int tag) = 0;
 355 };
 356 
 357 class SymbolClosure : public StackObj {
 358  public:
 359   virtual void do_symbol(Symbol**) = 0;
 360 
 361   // Clear LSB in symbol address; it can be set by CPSlot.
 362   static Symbol* load_symbol(Symbol** p) {
 363     return (Symbol*)(intptr_t(*p) & ~1);
 364   }
 365 
 366   // Store symbol, adjusting new pointer if the original pointer was adjusted
 367   // (symbol references in constant pool slots have their LSB set to 1).
 368   static void store_symbol(Symbol** p, Symbol* sym) {
 369     *p = (Symbol*)(intptr_t(sym) | (intptr_t(*p) & 1));
 370   }
 371 };
 372 
 373 // The two class template specializations are used to dispatch calls
 374 // to the ExtendedOopClosure functions. If use_non_virtual_call is true,
 375 // the non-virtual versions are called (E.g. do_oop_nv), otherwise the
 376 // virtual versions are called (E.g. do_oop).
 377 
 378 template <bool use_non_virtual_call>
 379 class Devirtualizer {};
 380 
 381 // Dispatches to the non-virtual functions.
 382 template <> class Devirtualizer<true> {
 383  public:
 384   template <class OopClosureType, typename T> static void do_oop(OopClosureType* closure, T* p);
 385   template <class OopClosureType>             static void do_klass(OopClosureType* closure, Klass* k);
 386   template <class OopClosureType>             static void do_cld(OopClosureType* closure, ClassLoaderData* cld);
 387   template <class OopClosureType>             static bool do_metadata(OopClosureType* closure);
 388 };
 389 
 390 // Dispatches to the virtual functions.
 391 template <> class Devirtualizer<false> {
 392  public:
 393   template <class OopClosureType, typename T> static void do_oop(OopClosureType* closure, T* p);
 394   template <class OopClosureType>             static void do_klass(OopClosureType* closure, Klass* k);
 395   template <class OopClosureType>             static void do_cld(OopClosureType* closure, ClassLoaderData* cld);
 396   template <class OopClosureType>             static bool do_metadata(OopClosureType* closure);
 397 };
 398 
 399 #endif // SHARE_VM_MEMORY_ITERATOR_HPP