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 Atomic<uint32_t> Object::hash_code_seed(987654321U + std::time(nullptr));
43 
44 class CopyReferenceFieldsWithReadBarrierVisitor {
45  public:
CopyReferenceFieldsWithReadBarrierVisitor(Object * dest_obj)46   explicit CopyReferenceFieldsWithReadBarrierVisitor(Object* dest_obj)
47       : dest_obj_(dest_obj) {}
48 
operator ()(Object * obj,MemberOffset offset,bool) const49   void operator()(Object* obj, MemberOffset offset, bool /* is_static */) const
50       ALWAYS_INLINE SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
51     // GetFieldObject() contains a RB.
52     Object* ref = obj->GetFieldObject<Object>(offset);
53     // No WB here as a large object space does not have a card table
54     // coverage. Instead, cards will be marked separately.
55     dest_obj_->SetFieldObjectWithoutWriteBarrier<false, false>(offset, ref);
56   }
57 
operator ()(mirror::Class * klass,mirror::Reference * ref) const58   void operator()(mirror::Class* klass, mirror::Reference* ref) const
59       ALWAYS_INLINE SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
60     // Copy java.lang.ref.Reference.referent which isn't visited in
61     // Object::VisitReferences().
62     DCHECK(klass->IsTypeOfReferenceClass());
63     this->operator()(ref, mirror::Reference::ReferentOffset(), false);
64   }
65 
66  private:
67   Object* const dest_obj_;
68 };
69 
CopyObject(Thread * self,mirror::Object * dest,mirror::Object * src,size_t num_bytes)70 Object* Object::CopyObject(Thread* self, mirror::Object* dest, mirror::Object* src,
71                            size_t num_bytes) {
72   // Copy instance data.  We assume memcpy copies by words.
73   // TODO: expose and use move32.
74   byte* src_bytes = reinterpret_cast<byte*>(src);
75   byte* dst_bytes = reinterpret_cast<byte*>(dest);
76   size_t offset = sizeof(Object);
77   memcpy(dst_bytes + offset, src_bytes + offset, num_bytes - offset);
78   if (kUseBakerOrBrooksReadBarrier) {
79     // We need a RB here. After the memcpy that covers the whole
80     // object above, copy references fields one by one again with a
81     // RB. TODO: Optimize this later?
82     CopyReferenceFieldsWithReadBarrierVisitor visitor(dest);
83     src->VisitReferences<true>(visitor, visitor);
84   }
85   gc::Heap* heap = Runtime::Current()->GetHeap();
86   // Perform write barriers on copied object references.
87   Class* c = src->GetClass();
88   if (c->IsArrayClass()) {
89     if (!c->GetComponentType()->IsPrimitive()) {
90       ObjectArray<Object>* array = dest->AsObjectArray<Object>();
91       heap->WriteBarrierArray(dest, 0, array->GetLength());
92     }
93   } else {
94     heap->WriteBarrierEveryFieldOf(dest);
95   }
96   if (c->IsFinalizable()) {
97     heap->AddFinalizerReference(self, &dest);
98   }
99   return dest;
100 }
101 
102 // An allocation pre-fence visitor that copies the object.
103 class CopyObjectVisitor {
104  public:
CopyObjectVisitor(Thread * self,Handle<Object> * orig,size_t num_bytes)105   explicit CopyObjectVisitor(Thread* self, Handle<Object>* orig, size_t num_bytes)
106       : self_(self), orig_(orig), num_bytes_(num_bytes) {
107   }
108 
operator ()(Object * obj,size_t usable_size) const109   void operator()(Object* obj, size_t usable_size) const
110       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
111     UNUSED(usable_size);
112     Object::CopyObject(self_, obj, orig_->Get(), num_bytes_);
113   }
114 
115  private:
116   Thread* const self_;
117   Handle<Object>* const orig_;
118   const size_t num_bytes_;
119   DISALLOW_COPY_AND_ASSIGN(CopyObjectVisitor);
120 };
121 
Clone(Thread * self)122 Object* Object::Clone(Thread* self) {
123   CHECK(!IsClass()) << "Can't clone classes.";
124   // Object::SizeOf gets the right size even if we're an array. Using c->AllocObject() here would
125   // be wrong.
126   gc::Heap* heap = Runtime::Current()->GetHeap();
127   size_t num_bytes = SizeOf();
128   StackHandleScope<1> hs(self);
129   Handle<Object> this_object(hs.NewHandle(this));
130   Object* copy;
131   CopyObjectVisitor visitor(self, &this_object, num_bytes);
132   if (heap->IsMovableObject(this)) {
133     copy = heap->AllocObject<true>(self, GetClass(), num_bytes, visitor);
134   } else {
135     copy = heap->AllocNonMovableObject<true>(self, GetClass(), num_bytes, visitor);
136   }
137   return copy;
138 }
139 
GenerateIdentityHashCode()140 uint32_t Object::GenerateIdentityHashCode() {
141   uint32_t expected_value, new_value;
142   do {
143     expected_value = hash_code_seed.LoadRelaxed();
144     new_value = expected_value * 1103515245 + 12345;
145   } while (!hash_code_seed.CompareExchangeWeakRelaxed(expected_value, new_value) ||
146       (expected_value & LockWord::kHashMask) == 0);
147   return expected_value & LockWord::kHashMask;
148 }
149 
SetHashCodeSeed(uint32_t new_seed)150 void Object::SetHashCodeSeed(uint32_t new_seed) {
151   hash_code_seed.StoreRelaxed(new_seed);
152 }
153 
IdentityHashCode() const154 int32_t Object::IdentityHashCode() const {
155   mirror::Object* current_this = const_cast<mirror::Object*>(this);
156   while (true) {
157     LockWord lw = current_this->GetLockWord(false);
158     switch (lw.GetState()) {
159       case LockWord::kUnlocked: {
160         // Try to compare and swap in a new hash, if we succeed we will return the hash on the next
161         // loop iteration.
162         LockWord hash_word(LockWord::FromHashCode(GenerateIdentityHashCode()));
163         DCHECK_EQ(hash_word.GetState(), LockWord::kHashCode);
164         if (const_cast<Object*>(this)->CasLockWordWeakRelaxed(lw, hash_word)) {
165           return hash_word.GetHashCode();
166         }
167         break;
168       }
169       case LockWord::kThinLocked: {
170         // Inflate the thin lock to a monitor and stick the hash code inside of the monitor. May
171         // fail spuriously.
172         Thread* self = Thread::Current();
173         StackHandleScope<1> hs(self);
174         Handle<mirror::Object> h_this(hs.NewHandle(current_this));
175         Monitor::InflateThinLocked(self, h_this, lw, GenerateIdentityHashCode());
176         // A GC may have occurred when we switched to kBlocked.
177         current_this = h_this.Get();
178         break;
179       }
180       case LockWord::kFatLocked: {
181         // Already inflated, return the has stored in the monitor.
182         Monitor* monitor = lw.FatLockMonitor();
183         DCHECK(monitor != nullptr);
184         return monitor->GetHashCode();
185       }
186       case LockWord::kHashCode: {
187         return lw.GetHashCode();
188       }
189       default: {
190         LOG(FATAL) << "Invalid state during hashcode " << lw.GetState();
191         break;
192       }
193     }
194   }
195   LOG(FATAL) << "Unreachable";
196   return 0;
197 }
198 
CheckFieldAssignmentImpl(MemberOffset field_offset,Object * new_value)199 void Object::CheckFieldAssignmentImpl(MemberOffset field_offset, Object* new_value) {
200   Class* c = GetClass();
201   Runtime* runtime = Runtime::Current();
202   if (runtime->GetClassLinker() == nullptr || !runtime->IsStarted() ||
203       !runtime->GetHeap()->IsObjectValidationEnabled() || !c->IsResolved()) {
204     return;
205   }
206   for (Class* cur = c; cur != NULL; cur = cur->GetSuperClass()) {
207     ObjectArray<ArtField>* fields = cur->GetIFields();
208     if (fields != NULL) {
209       size_t num_ifields = fields->GetLength();
210       for (size_t i = 0; i < num_ifields; ++i) {
211         ArtField* field = fields->Get(i);
212         if (field->GetOffset().Int32Value() == field_offset.Int32Value()) {
213           CHECK_NE(field->GetTypeAsPrimitiveType(), Primitive::kPrimNot);
214           StackHandleScope<1> hs(Thread::Current());
215           FieldHelper fh(hs.NewHandle(field));
216           CHECK(fh.GetType()->IsAssignableFrom(new_value->GetClass()));
217           return;
218         }
219       }
220     }
221   }
222   if (c->IsArrayClass()) {
223     // Bounds and assign-ability done in the array setter.
224     return;
225   }
226   if (IsClass()) {
227     ObjectArray<ArtField>* fields = AsClass()->GetSFields();
228     if (fields != NULL) {
229       size_t num_sfields = fields->GetLength();
230       for (size_t i = 0; i < num_sfields; ++i) {
231         ArtField* field = fields->Get(i);
232         if (field->GetOffset().Int32Value() == field_offset.Int32Value()) {
233           CHECK_NE(field->GetTypeAsPrimitiveType(), Primitive::kPrimNot);
234           StackHandleScope<1> hs(Thread::Current());
235           FieldHelper fh(hs.NewHandle(field));
236           CHECK(fh.GetType()->IsAssignableFrom(new_value->GetClass()));
237           return;
238         }
239       }
240     }
241   }
242   LOG(FATAL) << "Failed to find field for assignment to " << reinterpret_cast<void*>(this)
243       << " of type " << PrettyDescriptor(c) << " at offset " << field_offset;
244 }
245 
246 }  // namespace mirror
247 }  // namespace art
248