1 /*
2 * Copyright (C) 2011 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include <ctime>
18
19 #include "object.h"
20
21 #include "art_field.h"
22 #include "art_field-inl.h"
23 #include "array-inl.h"
24 #include "class.h"
25 #include "class-inl.h"
26 #include "class_linker-inl.h"
27 #include "field_helper.h"
28 #include "gc/accounting/card_table-inl.h"
29 #include "gc/heap.h"
30 #include "iftable-inl.h"
31 #include "monitor.h"
32 #include "object-inl.h"
33 #include "object_array-inl.h"
34 #include "runtime.h"
35 #include "handle_scope-inl.h"
36 #include "throwable.h"
37 #include "well_known_classes.h"
38
39 namespace art {
40 namespace mirror {
41
42 class CopyReferenceFieldsWithReadBarrierVisitor {
43 public:
CopyReferenceFieldsWithReadBarrierVisitor(Object * dest_obj)44 explicit CopyReferenceFieldsWithReadBarrierVisitor(Object* dest_obj)
45 : dest_obj_(dest_obj) {}
46
operator ()(Object * obj,MemberOffset offset,bool) const47 void operator()(Object* obj, MemberOffset offset, bool /* is_static */) const
48 ALWAYS_INLINE SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
49 // GetFieldObject() contains a RB.
50 Object* ref = obj->GetFieldObject<Object>(offset);
51 // No WB here as a large object space does not have a card table
52 // coverage. Instead, cards will be marked separately.
53 dest_obj_->SetFieldObjectWithoutWriteBarrier<false, false>(offset, ref);
54 }
55
operator ()(mirror::Class * klass,mirror::Reference * ref) const56 void operator()(mirror::Class* klass, mirror::Reference* ref) const
57 ALWAYS_INLINE SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
58 // Copy java.lang.ref.Reference.referent which isn't visited in
59 // Object::VisitReferences().
60 DCHECK(klass->IsTypeOfReferenceClass());
61 this->operator()(ref, mirror::Reference::ReferentOffset(), false);
62 }
63
64 private:
65 Object* const dest_obj_;
66 };
67
CopyObject(Thread * self,mirror::Object * dest,mirror::Object * src,size_t num_bytes)68 Object* Object::CopyObject(Thread* self, mirror::Object* dest, mirror::Object* src,
69 size_t num_bytes) {
70 // Copy instance data. We assume memcpy copies by words.
71 // TODO: expose and use move32.
72 byte* src_bytes = reinterpret_cast<byte*>(src);
73 byte* dst_bytes = reinterpret_cast<byte*>(dest);
74 size_t offset = sizeof(Object);
75 memcpy(dst_bytes + offset, src_bytes + offset, num_bytes - offset);
76 if (kUseBakerOrBrooksReadBarrier) {
77 // We need a RB here. After the memcpy that covers the whole
78 // object above, copy references fields one by one again with a
79 // RB. TODO: Optimize this later?
80 CopyReferenceFieldsWithReadBarrierVisitor visitor(dest);
81 src->VisitReferences<true>(visitor, visitor);
82 }
83 gc::Heap* heap = Runtime::Current()->GetHeap();
84 // Perform write barriers on copied object references.
85 Class* c = src->GetClass();
86 if (c->IsArrayClass()) {
87 if (!c->GetComponentType()->IsPrimitive()) {
88 ObjectArray<Object>* array = dest->AsObjectArray<Object>();
89 heap->WriteBarrierArray(dest, 0, array->GetLength());
90 }
91 } else {
92 heap->WriteBarrierEveryFieldOf(dest);
93 }
94 if (c->IsFinalizable()) {
95 heap->AddFinalizerReference(self, &dest);
96 }
97 return dest;
98 }
99
100 // An allocation pre-fence visitor that copies the object.
101 class CopyObjectVisitor {
102 public:
CopyObjectVisitor(Thread * self,Handle<Object> * orig,size_t num_bytes)103 explicit CopyObjectVisitor(Thread* self, Handle<Object>* orig, size_t num_bytes)
104 : self_(self), orig_(orig), num_bytes_(num_bytes) {
105 }
106
operator ()(Object * obj,size_t usable_size) const107 void operator()(Object* obj, size_t usable_size) const
108 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
109 UNUSED(usable_size);
110 Object::CopyObject(self_, obj, orig_->Get(), num_bytes_);
111 }
112
113 private:
114 Thread* const self_;
115 Handle<Object>* const orig_;
116 const size_t num_bytes_;
117 DISALLOW_COPY_AND_ASSIGN(CopyObjectVisitor);
118 };
119
Clone(Thread * self)120 Object* Object::Clone(Thread* self) {
121 CHECK(!IsClass()) << "Can't clone classes.";
122 // Object::SizeOf gets the right size even if we're an array. Using c->AllocObject() here would
123 // be wrong.
124 gc::Heap* heap = Runtime::Current()->GetHeap();
125 size_t num_bytes = SizeOf();
126 StackHandleScope<1> hs(self);
127 Handle<Object> this_object(hs.NewHandle(this));
128 Object* copy;
129 CopyObjectVisitor visitor(self, &this_object, num_bytes);
130 if (heap->IsMovableObject(this)) {
131 copy = heap->AllocObject<true>(self, GetClass(), num_bytes, visitor);
132 } else {
133 copy = heap->AllocNonMovableObject<true>(self, GetClass(), num_bytes, visitor);
134 }
135 return copy;
136 }
137
GenerateIdentityHashCode()138 int32_t Object::GenerateIdentityHashCode() {
139 static AtomicInteger seed(987654321 + std::time(nullptr));
140 int32_t expected_value, new_value;
141 do {
142 expected_value = static_cast<uint32_t>(seed.LoadRelaxed());
143 new_value = expected_value * 1103515245 + 12345;
144 } while ((expected_value & LockWord::kHashMask) == 0 ||
145 !seed.CompareExchangeWeakRelaxed(expected_value, new_value));
146 return expected_value & LockWord::kHashMask;
147 }
148
IdentityHashCode() const149 int32_t Object::IdentityHashCode() const {
150 mirror::Object* current_this = const_cast<mirror::Object*>(this);
151 while (true) {
152 LockWord lw = current_this->GetLockWord(false);
153 switch (lw.GetState()) {
154 case LockWord::kUnlocked: {
155 // Try to compare and swap in a new hash, if we succeed we will return the hash on the next
156 // loop iteration.
157 LockWord hash_word(LockWord::FromHashCode(GenerateIdentityHashCode()));
158 DCHECK_EQ(hash_word.GetState(), LockWord::kHashCode);
159 if (const_cast<Object*>(this)->CasLockWordWeakRelaxed(lw, hash_word)) {
160 return hash_word.GetHashCode();
161 }
162 break;
163 }
164 case LockWord::kThinLocked: {
165 // Inflate the thin lock to a monitor and stick the hash code inside of the monitor. May
166 // fail spuriously.
167 Thread* self = Thread::Current();
168 StackHandleScope<1> hs(self);
169 Handle<mirror::Object> h_this(hs.NewHandle(current_this));
170 Monitor::InflateThinLocked(self, h_this, lw, GenerateIdentityHashCode());
171 // A GC may have occurred when we switched to kBlocked.
172 current_this = h_this.Get();
173 break;
174 }
175 case LockWord::kFatLocked: {
176 // Already inflated, return the has stored in the monitor.
177 Monitor* monitor = lw.FatLockMonitor();
178 DCHECK(monitor != nullptr);
179 return monitor->GetHashCode();
180 }
181 case LockWord::kHashCode: {
182 return lw.GetHashCode();
183 }
184 default: {
185 LOG(FATAL) << "Invalid state during hashcode " << lw.GetState();
186 break;
187 }
188 }
189 }
190 LOG(FATAL) << "Unreachable";
191 return 0;
192 }
193
CheckFieldAssignmentImpl(MemberOffset field_offset,Object * new_value)194 void Object::CheckFieldAssignmentImpl(MemberOffset field_offset, Object* new_value) {
195 Class* c = GetClass();
196 Runtime* runtime = Runtime::Current();
197 if (runtime->GetClassLinker() == nullptr || !runtime->IsStarted() ||
198 !runtime->GetHeap()->IsObjectValidationEnabled() || !c->IsResolved()) {
199 return;
200 }
201 for (Class* cur = c; cur != NULL; cur = cur->GetSuperClass()) {
202 ObjectArray<ArtField>* fields = cur->GetIFields();
203 if (fields != NULL) {
204 size_t num_ref_ifields = cur->NumReferenceInstanceFields();
205 for (size_t i = 0; i < num_ref_ifields; ++i) {
206 ArtField* field = fields->Get(i);
207 if (field->GetOffset().Int32Value() == field_offset.Int32Value()) {
208 StackHandleScope<1> hs(Thread::Current());
209 FieldHelper fh(hs.NewHandle(field));
210 CHECK(fh.GetType()->IsAssignableFrom(new_value->GetClass()));
211 return;
212 }
213 }
214 }
215 }
216 if (c->IsArrayClass()) {
217 // Bounds and assign-ability done in the array setter.
218 return;
219 }
220 if (IsClass()) {
221 ObjectArray<ArtField>* fields = AsClass()->GetSFields();
222 if (fields != NULL) {
223 size_t num_ref_sfields = AsClass()->NumReferenceStaticFields();
224 for (size_t i = 0; i < num_ref_sfields; ++i) {
225 ArtField* field = fields->Get(i);
226 if (field->GetOffset().Int32Value() == field_offset.Int32Value()) {
227 StackHandleScope<1> hs(Thread::Current());
228 FieldHelper fh(hs.NewHandle(field));
229 CHECK(fh.GetType()->IsAssignableFrom(new_value->GetClass()));
230 return;
231 }
232 }
233 }
234 }
235 LOG(FATAL) << "Failed to find field for assignment to " << reinterpret_cast<void*>(this)
236 << " of type " << PrettyDescriptor(c) << " at offset " << field_offset;
237 }
238
239 } // namespace mirror
240 } // namespace art
241