1 /*
2 * Copyright (c) 1997, 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 #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 ReferenceDiscoverer;
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 class DoNothingClosure : public OopClosure {
52 public:
53 virtual void do_oop(oop* p) {}
54 virtual void do_oop(narrowOop* p) {}
55 };
56 extern DoNothingClosure do_nothing_cl;
57
58 // OopIterateClosure adds extra code to be run during oop iterations.
59 // This is needed by the GC and is extracted to a separate type to not
60 // pollute the OopClosure interface.
61 class OopIterateClosure : public OopClosure {
62 private:
63 ReferenceDiscoverer* _ref_discoverer;
64
65 protected:
66 OopIterateClosure(ReferenceDiscoverer* rd) : _ref_discoverer(rd) { }
67 OopIterateClosure() : _ref_discoverer(NULL) { }
68 ~OopIterateClosure() { }
69
70 void set_ref_discoverer_internal(ReferenceDiscoverer* rd) { _ref_discoverer = rd; }
71
72 public:
73 ReferenceDiscoverer* ref_discoverer() const { return _ref_discoverer; }
74
75 // Iteration of InstanceRefKlasses differ depending on the closure,
76 // the below enum describes the different alternatives.
77 enum ReferenceIterationMode {
78 DO_DISCOVERY, // Apply closure and discover references
79 DO_DISCOVERED_AND_DISCOVERY, // Apply closure to discovered field and do discovery
80 DO_FIELDS // Apply closure to all fields
81 };
82
83 // The default iteration mode is to do discovery.
84 virtual ReferenceIterationMode reference_iteration_mode() { return DO_DISCOVERY; }
85
86 // If the do_metadata functions return "true",
87 // we invoke the following when running oop_iterate():
88 //
89 // 1) do_klass on the header klass pointer.
90 // 2) do_klass on the klass pointer in the mirrors.
91 // 3) do_cld on the class loader data in class loaders.
92
93 virtual bool do_metadata() = 0;
94 virtual void do_klass(Klass* k) = 0;
95 virtual void do_cld(ClassLoaderData* cld) = 0;
96
97 // True iff this closure may be safely applied more than once to an oop
98 // location without an intervening "major reset" (like the end of a GC).
99 virtual bool idempotent() { return false; }
100
101 #ifdef ASSERT
102 // Default verification of each visited oop field.
103 template <typename T> void verify(T* p);
104
105 // Can be used by subclasses to turn off the default verification of oop fields.
106 virtual bool should_verify_oops() { return true; }
107 #endif
108 };
109
110 // An OopIterateClosure that can be used when there's no need to visit the Metadata.
111 class BasicOopIterateClosure : public OopIterateClosure {
112 public:
113 BasicOopIterateClosure(ReferenceDiscoverer* rd = NULL) : OopIterateClosure(rd) {}
114
115 virtual bool do_metadata() { return false; }
116 virtual void do_klass(Klass* k) { ShouldNotReachHere(); }
117 virtual void do_cld(ClassLoaderData* cld) { ShouldNotReachHere(); }
118 };
119
120 // Wrapper closure only used to implement oop_iterate_no_header().
121 class NoHeaderExtendedOopClosure : public BasicOopIterateClosure {
122 OopClosure* _wrapped_closure;
123 public:
124 NoHeaderExtendedOopClosure(OopClosure* cl) : _wrapped_closure(cl) {}
125 // Warning: this calls the virtual version do_oop in the the wrapped closure.
126 virtual void do_oop(oop* p) { _wrapped_closure->do_oop(p); }
127 virtual void do_oop(narrowOop* p) { _wrapped_closure->do_oop(p); }
128 };
129
130 class KlassClosure : public Closure {
131 public:
132 virtual void do_klass(Klass* k) = 0;
133 };
134
135 class CLDClosure : public Closure {
136 public:
137 virtual void do_cld(ClassLoaderData* cld) = 0;
138 };
139
140
141 class CLDToOopClosure : public CLDClosure {
142 OopClosure* _oop_closure;
143 bool _must_claim_cld;
144
145 public:
146 CLDToOopClosure(OopClosure* oop_closure, bool must_claim_cld = true) :
147 _oop_closure(oop_closure),
148 _must_claim_cld(must_claim_cld) {}
149
150 void do_cld(ClassLoaderData* cld);
151 };
152
153 // The base class for all concurrent marking closures,
154 // that participates in class unloading.
155 // It's used to proxy through the metadata to the oops defined in them.
156 class MetadataVisitingOopIterateClosure: public OopIterateClosure {
157 public:
158 MetadataVisitingOopIterateClosure(ReferenceDiscoverer* rd = NULL) : OopIterateClosure(rd) { }
159
160 virtual bool do_metadata() { return true; }
161 virtual void do_klass(Klass* k);
162 virtual void do_cld(ClassLoaderData* cld);
163 };
164
165 // ObjectClosure is used for iterating through an object space
166
167 class ObjectClosure : public Closure {
168 public:
169 // Called for each object.
170 virtual void do_object(oop obj) = 0;
171 };
172
173
174 class BoolObjectClosure : public Closure {
175 public:
176 virtual bool do_object_b(oop obj) = 0;
177 };
178
179 class AlwaysTrueClosure: public BoolObjectClosure {
180 public:
181 bool do_object_b(oop p) { return true; }
182 };
183
184 class AlwaysFalseClosure : public BoolObjectClosure {
185 public:
186 bool do_object_b(oop p) { return false; }
187 };
188
189 // Applies an oop closure to all ref fields in objects iterated over in an
190 // object iteration.
191 class ObjectToOopClosure: public ObjectClosure {
192 OopIterateClosure* _cl;
193 public:
194 void do_object(oop obj);
195 ObjectToOopClosure(OopIterateClosure* cl) : _cl(cl) {}
196 };
197
198 // A version of ObjectClosure that is expected to be robust
199 // in the face of possibly uninitialized objects.
200 class ObjectClosureCareful : public ObjectClosure {
201 public:
202 virtual size_t do_object_careful_m(oop p, MemRegion mr) = 0;
203 virtual size_t do_object_careful(oop p) = 0;
204 };
205
206 // The following are used in CompactibleFreeListSpace and
207 // ConcurrentMarkSweepGeneration.
208
209 // Blk closure (abstract class)
210 class BlkClosure : public StackObj {
211 public:
212 virtual size_t do_blk(HeapWord* addr) = 0;
213 };
214
215 // A version of BlkClosure that is expected to be robust
216 // in the face of possibly uninitialized objects.
217 class BlkClosureCareful : public BlkClosure {
218 public:
219 size_t do_blk(HeapWord* addr) {
220 guarantee(false, "call do_blk_careful instead");
221 return 0;
222 }
223 virtual size_t do_blk_careful(HeapWord* addr) = 0;
224 };
225
226 // SpaceClosure is used for iterating over spaces
227
228 class Space;
229 class CompactibleSpace;
230
231 class SpaceClosure : public StackObj {
232 public:
233 // Called for each space
234 virtual void do_space(Space* s) = 0;
235 };
236
237 class CompactibleSpaceClosure : public StackObj {
238 public:
239 // Called for each compactible space
240 virtual void do_space(CompactibleSpace* s) = 0;
241 };
242
243
244 // CodeBlobClosure is used for iterating through code blobs
245 // in the code cache or on thread stacks
246
247 class CodeBlobClosure : public Closure {
248 public:
249 // Called for each code blob.
250 virtual void do_code_blob(CodeBlob* cb) = 0;
251 };
252
253 // Applies an oop closure to all ref fields in code blobs
254 // iterated over in an object iteration.
255 class CodeBlobToOopClosure : public CodeBlobClosure {
256 OopClosure* _cl;
257 bool _fix_relocations;
258 protected:
259 void do_nmethod(nmethod* nm);
260 public:
261 // If fix_relocations(), then cl must copy objects to their new location immediately to avoid
262 // patching nmethods with the old locations.
263 CodeBlobToOopClosure(OopClosure* cl, bool fix_relocations) : _cl(cl), _fix_relocations(fix_relocations) {}
264 virtual void do_code_blob(CodeBlob* cb);
265
266 bool fix_relocations() const { return _fix_relocations; }
267 const static bool FixRelocations = true;
268 };
269
270 class MarkingCodeBlobClosure : public CodeBlobToOopClosure {
271 public:
272 MarkingCodeBlobClosure(OopClosure* cl, bool fix_relocations) : CodeBlobToOopClosure(cl, fix_relocations) {}
273 // Called for each code blob, but at most once per unique blob.
274
275 virtual void do_code_blob(CodeBlob* cb);
276 };
277
278 // MonitorClosure is used for iterating over monitors in the monitors cache
279
280 class ObjectMonitor;
281
282 class MonitorClosure : public StackObj {
283 public:
284 // called for each monitor in cache
285 virtual void do_monitor(ObjectMonitor* m) = 0;
286 };
287
288 // A closure that is applied without any arguments.
289 class VoidClosure : public StackObj {
290 public:
291 // I would have liked to declare this a pure virtual, but that breaks
292 // in mysterious ways, for unknown reasons.
293 virtual void do_void();
294 };
295
296
297 // YieldClosure is intended for use by iteration loops
298 // to incrementalize their work, allowing interleaving
299 // of an interruptable task so as to allow other
300 // threads to run (which may not otherwise be able to access
301 // exclusive resources, for instance). Additionally, the
302 // closure also allows for aborting an ongoing iteration
303 // by means of checking the return value from the polling
304 // call.
305 class YieldClosure : public StackObj {
306 public:
307 virtual bool should_return() = 0;
308
309 // Yield on a fine-grain level. The check in case of not yielding should be very fast.
310 virtual bool should_return_fine_grain() { return false; }
311 };
312
313 // Abstract closure for serializing data (read or write).
314
315 class SerializeClosure : public Closure {
316 public:
317 // Return bool indicating whether closure implements read or write.
318 virtual bool reading() const = 0;
319
320 // Read/write the void pointer pointed to by p.
321 virtual void do_ptr(void** p) = 0;
322
323 // Read/write the 32-bit unsigned integer pointed to by p.
324 virtual void do_u4(u4* p) = 0;
325
326 // Read/write the region specified.
327 virtual void do_region(u_char* start, size_t size) = 0;
328
329 // Check/write the tag. If reading, then compare the tag against
330 // the passed in value and fail is they don't match. This allows
331 // for verification that sections of the serialized data are of the
332 // correct length.
333 virtual void do_tag(int tag) = 0;
334
335 // Read/write the oop
336 virtual void do_oop(oop* o) = 0;
337
338 bool writing() {
339 return !reading();
340 }
341 };
342
343 class SymbolClosure : public StackObj {
344 public:
345 virtual void do_symbol(Symbol**) = 0;
346
347 // Clear LSB in symbol address; it can be set by CPSlot.
348 static Symbol* load_symbol(Symbol** p) {
349 return (Symbol*)(intptr_t(*p) & ~1);
350 }
351
352 // Store symbol, adjusting new pointer if the original pointer was adjusted
353 // (symbol references in constant pool slots have their LSB set to 1).
354 static void store_symbol(Symbol** p, Symbol* sym) {
355 *p = (Symbol*)(intptr_t(sym) | (intptr_t(*p) & 1));
356 }
357 };
358
359 // Dispatches to the non-virtual functions if OopClosureType has
360 // a concrete implementation, otherwise a virtual call is taken.
361 class Devirtualizer {
362 public:
363 template <typename OopClosureType, typename T> static void do_oop_no_verify(OopClosureType* closure, T* p);
364 template <typename OopClosureType, typename T> static void do_oop(OopClosureType* closure, T* p);
365 template <typename OopClosureType> static void do_klass(OopClosureType* closure, Klass* k);
366 template <typename OopClosureType> static void do_cld(OopClosureType* closure, ClassLoaderData* cld);
367 template <typename OopClosureType> static bool do_metadata(OopClosureType* closure);
368 };
369
370 class OopClosureDispatch {
371 public:
372 template <typename OopClosureType> static void oop_oop_iterate(OopClosureType* cl, oop obj, Klass* klass);
373 template <typename OopClosureType> static void oop_oop_iterate(OopClosureType* cl, oop obj, Klass* klass, MemRegion mr);
374 template <typename OopClosureType> static void oop_oop_iterate_backwards(OopClosureType* cl, oop obj, Klass* klass);
375 };
376
377 #endif // SHARE_VM_MEMORY_ITERATOR_HPP