1 /*
   2  * Copyright (c) 1997, 2016, 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 "oops/oopsHierarchy.hpp"
  31 
  32 class CodeBlob;
  33 class nmethod;
  34 class ReferenceProcessor;
  35 class DataLayout;
  36 class KlassClosure;
  37 class ClassLoaderData;
  38 class Symbol;
  39 
  40 // The following classes are C++ `closures` for iterating over objects, roots and spaces
  41 
  42 class Closure : public StackObj { };
  43 
  44 // OopClosure is used for iterating through references to Java objects.
  45 class OopClosure : public Closure {
  46  public:
  47   virtual void do_oop(oop* o) = 0;
  48   virtual void do_oop(narrowOop* o) = 0;
  49 };
  50 
  51 // ExtendedOopClosure adds extra code to be run during oop iterations.
  52 // This is needed by the GC and is extracted to a separate type to not
  53 // pollute the OopClosure interface.
  54 class ExtendedOopClosure : public OopClosure {
  55  private:
  56   ReferenceProcessor* _ref_processor;
  57 
  58  protected:
  59   ExtendedOopClosure(ReferenceProcessor* rp) : _ref_processor(rp) { }
  60   ExtendedOopClosure() : _ref_processor(NULL) { }
  61   ~ExtendedOopClosure() { }
  62 
  63   void set_ref_processor_internal(ReferenceProcessor* rp) { _ref_processor = rp; }
  64 
  65  public:
  66   ReferenceProcessor* ref_processor() const { return _ref_processor; }
  67 
  68   // If the do_metadata functions return "true",
  69   // we invoke the following when running oop_iterate():
  70   //
  71   // 1) do_klass on the header klass pointer.
  72   // 2) do_klass on the klass pointer in the mirrors.
  73   // 3) do_cld   on the class loader data in class loaders.
  74   //
  75   // The virtual (without suffix) and the non-virtual (with _nv suffix) need
  76   // to be updated together, or else the devirtualization will break.
  77   //
  78   // Providing default implementations of the _nv functions unfortunately
  79   // removes the compile-time safeness, but reduces the clutter for the
  80   // ExtendedOopClosures that don't need to walk the metadata.
  81   // Currently, only CMS and G1 need these.
  82 
  83   bool do_metadata_nv()      { return false; }
  84   virtual bool do_metadata() { return do_metadata_nv(); }
  85 
  86   void do_klass_nv(Klass* k)      { ShouldNotReachHere(); }
  87   virtual void do_klass(Klass* k) { do_klass_nv(k); }
  88 
  89   void do_cld_nv(ClassLoaderData* cld)      { ShouldNotReachHere(); }
  90   virtual void do_cld(ClassLoaderData* cld) { do_cld_nv(cld); }
  91 
  92   // True iff this closure may be safely applied more than once to an oop
  93   // location without an intervening "major reset" (like the end of a GC).
  94   virtual bool idempotent() { return false; }
  95   virtual bool apply_to_weak_ref_discovered_field() { return false; }
  96 
  97 #ifdef ASSERT
  98   // Default verification of each visited oop field.
  99   template <typename T> void verify(T* p);
 100 
 101   // Can be used by subclasses to turn off the default verification of oop fields.
 102   virtual bool should_verify_oops() { return true; }
 103 #endif
 104 };
 105 
 106 // Wrapper closure only used to implement oop_iterate_no_header().
 107 class NoHeaderExtendedOopClosure : public ExtendedOopClosure {
 108   OopClosure* _wrapped_closure;
 109  public:
 110   NoHeaderExtendedOopClosure(OopClosure* cl) : _wrapped_closure(cl) {}
 111   // Warning: this calls the virtual version do_oop in the the wrapped closure.
 112   void do_oop_nv(oop* p)       { _wrapped_closure->do_oop(p); }
 113   void do_oop_nv(narrowOop* p) { _wrapped_closure->do_oop(p); }
 114 
 115   void do_oop(oop* p)          { assert(false, "Only the _nv versions should be used");
 116                                  _wrapped_closure->do_oop(p); }
 117   void do_oop(narrowOop* p)    { assert(false, "Only the _nv versions should be used");
 118                                  _wrapped_closure->do_oop(p);}
 119 };
 120 
 121 class KlassClosure : public Closure {
 122  public:
 123   virtual void do_klass(Klass* k) = 0;
 124 };
 125 
 126 class CLDClosure : public Closure {
 127  public:
 128   virtual void do_cld(ClassLoaderData* cld) = 0;
 129 };
 130 
 131 class KlassToOopClosure : public KlassClosure {
 132   friend class MetadataAwareOopClosure;
 133   friend class MetadataAwareOopsInGenClosure;
 134 
 135   OopClosure* _oop_closure;
 136 
 137   // Used when _oop_closure couldn't be set in an initialization list.
 138   void initialize(OopClosure* oop_closure) {
 139     assert(_oop_closure == NULL, "Should only be called once");
 140     _oop_closure = oop_closure;
 141   }
 142 
 143  public:
 144   KlassToOopClosure(OopClosure* oop_closure = NULL) : _oop_closure(oop_closure) {}
 145 
 146   virtual void do_klass(Klass* k);
 147 };
 148 
 149 class CLDToOopClosure : public CLDClosure {
 150   OopClosure*       _oop_closure;
 151   KlassToOopClosure _klass_closure;
 152   bool              _must_claim_cld;
 153 
 154  public:
 155   CLDToOopClosure(OopClosure* oop_closure, bool must_claim_cld = true) :
 156       _oop_closure(oop_closure),
 157       _klass_closure(oop_closure),
 158       _must_claim_cld(must_claim_cld) {}
 159 
 160   void do_cld(ClassLoaderData* cld);
 161 };
 162 
 163 class CLDToKlassAndOopClosure : public CLDClosure {
 164   friend class G1CollectedHeap;
 165  protected:
 166   OopClosure*   _oop_closure;
 167   KlassClosure* _klass_closure;
 168   bool          _must_claim_cld;
 169  public:
 170   CLDToKlassAndOopClosure(KlassClosure* klass_closure,
 171                           OopClosure* oop_closure,
 172                           bool must_claim_cld) :
 173                               _oop_closure(oop_closure),
 174                               _klass_closure(klass_closure),
 175                               _must_claim_cld(must_claim_cld) {}
 176   void do_cld(ClassLoaderData* cld);
 177 };
 178 
 179 // The base class for all concurrent marking closures,
 180 // that participates in class unloading.
 181 // It's used to proxy through the metadata to the oops defined in them.
 182 class MetadataAwareOopClosure: public ExtendedOopClosure {
 183   KlassToOopClosure _klass_closure;
 184 
 185  public:
 186   MetadataAwareOopClosure() : ExtendedOopClosure() {
 187     _klass_closure.initialize(this);
 188   }
 189   MetadataAwareOopClosure(ReferenceProcessor* rp) : ExtendedOopClosure(rp) {
 190     _klass_closure.initialize(this);
 191   }
 192 
 193   bool do_metadata_nv()      { return true; }
 194   virtual bool do_metadata() { return do_metadata_nv(); }
 195 
 196   void do_klass_nv(Klass* k);
 197   virtual void do_klass(Klass* k) { do_klass_nv(k); }
 198 
 199   void do_cld_nv(ClassLoaderData* cld);
 200   virtual void do_cld(ClassLoaderData* cld) { do_cld_nv(cld); }
 201 };
 202 
 203 // ObjectClosure is used for iterating through an object space
 204 
 205 class ObjectClosure : public Closure {
 206  public:
 207   // Called for each object.
 208   virtual void do_object(oop obj) = 0;
 209 };
 210 
 211 
 212 class BoolObjectClosure : public Closure {
 213  public:
 214   virtual bool do_object_b(oop obj) = 0;
 215 };
 216 
 217 class AlwaysTrueClosure: public BoolObjectClosure {
 218  public:
 219   bool do_object_b(oop p) { return true; }
 220 };
 221 
 222 class AlwaysFalseClosure : public BoolObjectClosure {
 223  public:
 224   bool do_object_b(oop p) { return false; }
 225 };
 226 
 227 // Applies an oop closure to all ref fields in objects iterated over in an
 228 // object iteration.
 229 class ObjectToOopClosure: public ObjectClosure {
 230   ExtendedOopClosure* _cl;
 231 public:
 232   void do_object(oop obj);
 233   ObjectToOopClosure(ExtendedOopClosure* cl) : _cl(cl) {}
 234 };
 235 
 236 // A version of ObjectClosure that is expected to be robust
 237 // in the face of possibly uninitialized objects.
 238 class ObjectClosureCareful : public ObjectClosure {
 239  public:
 240   virtual size_t do_object_careful_m(oop p, MemRegion mr) = 0;
 241   virtual size_t do_object_careful(oop p) = 0;
 242 };
 243 
 244 // The following are used in CompactibleFreeListSpace and
 245 // ConcurrentMarkSweepGeneration.
 246 
 247 // Blk closure (abstract class)
 248 class BlkClosure : public StackObj {
 249  public:
 250   virtual size_t do_blk(HeapWord* addr) = 0;
 251 };
 252 
 253 // A version of BlkClosure that is expected to be robust
 254 // in the face of possibly uninitialized objects.
 255 class BlkClosureCareful : public BlkClosure {
 256  public:
 257   size_t do_blk(HeapWord* addr) {
 258     guarantee(false, "call do_blk_careful instead");
 259     return 0;
 260   }
 261   virtual size_t do_blk_careful(HeapWord* addr) = 0;
 262 };
 263 
 264 // SpaceClosure is used for iterating over spaces
 265 
 266 class Space;
 267 class CompactibleSpace;
 268 
 269 class SpaceClosure : public StackObj {
 270  public:
 271   // Called for each space
 272   virtual void do_space(Space* s) = 0;
 273 };
 274 
 275 class CompactibleSpaceClosure : public StackObj {
 276  public:
 277   // Called for each compactible space
 278   virtual void do_space(CompactibleSpace* s) = 0;
 279 };
 280 
 281 
 282 // CodeBlobClosure is used for iterating through code blobs
 283 // in the code cache or on thread stacks
 284 
 285 class CodeBlobClosure : public Closure {
 286  public:
 287   // Called for each code blob.
 288   virtual void do_code_blob(CodeBlob* cb) = 0;
 289 };
 290 
 291 // Applies an oop closure to all ref fields in code blobs
 292 // iterated over in an object iteration.
 293 class CodeBlobToOopClosure : public CodeBlobClosure {
 294   OopClosure* _cl;
 295   bool _fix_relocations;
 296  protected:
 297   void do_nmethod(nmethod* nm);
 298  public:
 299   // If fix_relocations(), then cl must copy objects to their new location immediately to avoid
 300   // patching nmethods with the old locations.
 301   CodeBlobToOopClosure(OopClosure* cl, bool fix_relocations) : _cl(cl), _fix_relocations(fix_relocations) {}
 302   virtual void do_code_blob(CodeBlob* cb);
 303 
 304   bool fix_relocations() const { return _fix_relocations; }
 305   const static bool FixRelocations = true;
 306 };
 307 
 308 class MarkingCodeBlobClosure : public CodeBlobToOopClosure {
 309  public:
 310   MarkingCodeBlobClosure(OopClosure* cl, bool fix_relocations) : CodeBlobToOopClosure(cl, fix_relocations) {}
 311   // Called for each code blob, but at most once per unique blob.
 312 
 313   virtual void do_code_blob(CodeBlob* cb);
 314 };
 315 
 316 // MonitorClosure is used for iterating over monitors in the monitors cache
 317 
 318 class ObjectMonitor;
 319 
 320 class MonitorClosure : public StackObj {
 321  public:
 322   // called for each monitor in cache
 323   virtual void do_monitor(ObjectMonitor* m) = 0;
 324 };
 325 
 326 // A closure that is applied without any arguments.
 327 class VoidClosure : public StackObj {
 328  public:
 329   // I would have liked to declare this a pure virtual, but that breaks
 330   // in mysterious ways, for unknown reasons.
 331   virtual void do_void();
 332 };
 333 
 334 
 335 // YieldClosure is intended for use by iteration loops
 336 // to incrementalize their work, allowing interleaving
 337 // of an interruptable task so as to allow other
 338 // threads to run (which may not otherwise be able to access
 339 // exclusive resources, for instance). Additionally, the
 340 // closure also allows for aborting an ongoing iteration
 341 // by means of checking the return value from the polling
 342 // call.
 343 class YieldClosure : public StackObj {
 344   public:
 345    virtual bool should_return() = 0;
 346 };
 347 
 348 // Abstract closure for serializing data (read or write).
 349 
 350 class SerializeClosure : public Closure {
 351 public:
 352   // Return bool indicating whether closure implements read or write.
 353   virtual bool reading() const = 0;
 354 
 355   // Read/write the void pointer pointed to by p.
 356   virtual void do_ptr(void** p) = 0;
 357 
 358   // Read/write the 32-bit unsigned integer pointed to by p.
 359   virtual void do_u4(u4* p) = 0;
 360 
 361   // Read/write the region specified.
 362   virtual void do_region(u_char* start, size_t size) = 0;
 363 
 364   // Check/write the tag.  If reading, then compare the tag against
 365   // the passed in value and fail is they don't match.  This allows
 366   // for verification that sections of the serialized data are of the
 367   // correct length.
 368   virtual void do_tag(int tag) = 0;
 369 
 370   bool writing() {
 371     return !reading();
 372   }
 373 };
 374 
 375 class SymbolClosure : public StackObj {
 376  public:
 377   virtual void do_symbol(Symbol**) = 0;
 378 
 379   // Clear LSB in symbol address; it can be set by CPSlot.
 380   static Symbol* load_symbol(Symbol** p) {
 381     return (Symbol*)(intptr_t(*p) & ~1);
 382   }
 383 
 384   // Store symbol, adjusting new pointer if the original pointer was adjusted
 385   // (symbol references in constant pool slots have their LSB set to 1).
 386   static void store_symbol(Symbol** p, Symbol* sym) {
 387     *p = (Symbol*)(intptr_t(sym) | (intptr_t(*p) & 1));
 388   }
 389 };
 390 
 391 // The two class template specializations are used to dispatch calls
 392 // to the ExtendedOopClosure functions. If use_non_virtual_call is true,
 393 // the non-virtual versions are called (E.g. do_oop_nv), otherwise the
 394 // virtual versions are called (E.g. do_oop).
 395 
 396 template <bool use_non_virtual_call>
 397 class Devirtualizer {};
 398 
 399 // Dispatches to the non-virtual functions.
 400 template <> class Devirtualizer<true> {
 401  public:
 402   template <class OopClosureType, typename T> static void do_oop(OopClosureType* closure, T* p);
 403   template <class OopClosureType>             static void do_klass(OopClosureType* closure, Klass* k);
 404   template <class OopClosureType>             static void do_cld(OopClosureType* closure, ClassLoaderData* cld);
 405   template <class OopClosureType>             static bool do_metadata(OopClosureType* closure);
 406 };
 407 
 408 // Dispatches to the virtual functions.
 409 template <> class Devirtualizer<false> {
 410  public:
 411   template <class OopClosureType, typename T> static void do_oop(OopClosureType* closure, T* p);
 412   template <class OopClosureType>             static void do_klass(OopClosureType* closure, Klass* k);
 413   template <class OopClosureType>             static void do_cld(OopClosureType* closure, ClassLoaderData* cld);
 414   template <class OopClosureType>             static bool do_metadata(OopClosureType* closure);
 415 };
 416 
 417 #endif // SHARE_VM_MEMORY_ITERATOR_HPP