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 "dex_file-inl.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-refvisitor-inl.h"
34 #include "object_array-inl.h"
35 #include "runtime.h"
36 #include "handle_scope-inl.h"
37 #include "throwable.h"
38 #include "well_known_classes.h"
39 
40 namespace art {
41 namespace mirror {
42 
43 Atomic<uint32_t> Object::hash_code_seed(987654321U + std::time(nullptr));
44 
45 class CopyReferenceFieldsWithReadBarrierVisitor {
46  public:
CopyReferenceFieldsWithReadBarrierVisitor(ObjPtr<Object> dest_obj)47   explicit CopyReferenceFieldsWithReadBarrierVisitor(ObjPtr<Object> dest_obj)
48       : dest_obj_(dest_obj) {}
49 
operator ()(ObjPtr<Object> obj,MemberOffset offset,bool) const50   void operator()(ObjPtr<Object> obj, MemberOffset offset, bool /* is_static */) const
51       ALWAYS_INLINE REQUIRES_SHARED(Locks::mutator_lock_) {
52     // GetFieldObject() contains a RB.
53     ObjPtr<Object> ref = obj->GetFieldObject<Object>(offset);
54     // No WB here as a large object space does not have a card table
55     // coverage. Instead, cards will be marked separately.
56     dest_obj_->SetFieldObjectWithoutWriteBarrier<false, false>(offset, ref);
57   }
58 
operator ()(ObjPtr<mirror::Class> klass,mirror::Reference * ref) const59   void operator()(ObjPtr<mirror::Class> klass, mirror::Reference* ref) const
60       ALWAYS_INLINE REQUIRES_SHARED(Locks::mutator_lock_) {
61     // Copy java.lang.ref.Reference.referent which isn't visited in
62     // Object::VisitReferences().
63     DCHECK(klass->IsTypeOfReferenceClass());
64     this->operator()(ref, mirror::Reference::ReferentOffset(), false);
65   }
66 
67   // Unused since we don't copy class native roots.
VisitRootIfNonNull(mirror::CompressedReference<mirror::Object> * root ATTRIBUTE_UNUSED) const68   void VisitRootIfNonNull(mirror::CompressedReference<mirror::Object>* root ATTRIBUTE_UNUSED)
69       const {}
VisitRoot(mirror::CompressedReference<mirror::Object> * root ATTRIBUTE_UNUSED) const70   void VisitRoot(mirror::CompressedReference<mirror::Object>* root ATTRIBUTE_UNUSED) const {}
71 
72  private:
73   ObjPtr<Object> const dest_obj_;
74 };
75 
CopyObject(ObjPtr<mirror::Object> dest,ObjPtr<mirror::Object> src,size_t num_bytes)76 Object* Object::CopyObject(ObjPtr<mirror::Object> dest,
77                            ObjPtr<mirror::Object> src,
78                            size_t num_bytes) {
79   // Copy instance data.  Don't assume memcpy copies by words (b/32012820).
80   {
81     const size_t offset = sizeof(Object);
82     uint8_t* src_bytes = reinterpret_cast<uint8_t*>(src.Ptr()) + offset;
83     uint8_t* dst_bytes = reinterpret_cast<uint8_t*>(dest.Ptr()) + offset;
84     num_bytes -= offset;
85     DCHECK_ALIGNED(src_bytes, sizeof(uintptr_t));
86     DCHECK_ALIGNED(dst_bytes, sizeof(uintptr_t));
87     // Use word sized copies to begin.
88     while (num_bytes >= sizeof(uintptr_t)) {
89       reinterpret_cast<Atomic<uintptr_t>*>(dst_bytes)->StoreRelaxed(
90           reinterpret_cast<Atomic<uintptr_t>*>(src_bytes)->LoadRelaxed());
91       src_bytes += sizeof(uintptr_t);
92       dst_bytes += sizeof(uintptr_t);
93       num_bytes -= sizeof(uintptr_t);
94     }
95     // Copy possible 32 bit word.
96     if (sizeof(uintptr_t) != sizeof(uint32_t) && num_bytes >= sizeof(uint32_t)) {
97       reinterpret_cast<Atomic<uint32_t>*>(dst_bytes)->StoreRelaxed(
98           reinterpret_cast<Atomic<uint32_t>*>(src_bytes)->LoadRelaxed());
99       src_bytes += sizeof(uint32_t);
100       dst_bytes += sizeof(uint32_t);
101       num_bytes -= sizeof(uint32_t);
102     }
103     // Copy remaining bytes, avoid going past the end of num_bytes since there may be a redzone
104     // there.
105     while (num_bytes > 0) {
106       reinterpret_cast<Atomic<uint8_t>*>(dst_bytes)->StoreRelaxed(
107           reinterpret_cast<Atomic<uint8_t>*>(src_bytes)->LoadRelaxed());
108       src_bytes += sizeof(uint8_t);
109       dst_bytes += sizeof(uint8_t);
110       num_bytes -= sizeof(uint8_t);
111     }
112   }
113 
114   if (kUseReadBarrier) {
115     // We need a RB here. After copying the whole object above, copy references fields one by one
116     // again with a RB to make sure there are no from space refs. TODO: Optimize this later?
117     CopyReferenceFieldsWithReadBarrierVisitor visitor(dest);
118     src->VisitReferences(visitor, visitor);
119   }
120   gc::Heap* heap = Runtime::Current()->GetHeap();
121   // Perform write barriers on copied object references.
122   ObjPtr<Class> c = src->GetClass();
123   if (c->IsArrayClass()) {
124     if (!c->GetComponentType()->IsPrimitive()) {
125       ObjectArray<Object>* array = dest->AsObjectArray<Object>();
126       heap->WriteBarrierArray(dest, 0, array->GetLength());
127     }
128   } else {
129     heap->WriteBarrierEveryFieldOf(dest);
130   }
131   return dest.Ptr();
132 }
133 
134 // An allocation pre-fence visitor that copies the object.
135 class CopyObjectVisitor {
136  public:
CopyObjectVisitor(Handle<Object> * orig,size_t num_bytes)137   CopyObjectVisitor(Handle<Object>* orig, size_t num_bytes)
138       : orig_(orig), num_bytes_(num_bytes) {}
139 
operator ()(ObjPtr<Object> obj,size_t usable_size ATTRIBUTE_UNUSED) const140   void operator()(ObjPtr<Object> obj, size_t usable_size ATTRIBUTE_UNUSED) const
141       REQUIRES_SHARED(Locks::mutator_lock_) {
142     Object::CopyObject(obj, orig_->Get(), num_bytes_);
143   }
144 
145  private:
146   Handle<Object>* const orig_;
147   const size_t num_bytes_;
148   DISALLOW_COPY_AND_ASSIGN(CopyObjectVisitor);
149 };
150 
Clone(Thread * self)151 Object* Object::Clone(Thread* self) {
152   CHECK(!IsClass()) << "Can't clone classes.";
153   // Object::SizeOf gets the right size even if we're an array. Using c->AllocObject() here would
154   // be wrong.
155   gc::Heap* heap = Runtime::Current()->GetHeap();
156   size_t num_bytes = SizeOf();
157   StackHandleScope<1> hs(self);
158   Handle<Object> this_object(hs.NewHandle(this));
159   ObjPtr<Object> copy;
160   CopyObjectVisitor visitor(&this_object, num_bytes);
161   if (heap->IsMovableObject(this)) {
162     copy = heap->AllocObject<true>(self, GetClass(), num_bytes, visitor);
163   } else {
164     copy = heap->AllocNonMovableObject<true>(self, GetClass(), num_bytes, visitor);
165   }
166   if (this_object->GetClass()->IsFinalizable()) {
167     heap->AddFinalizerReference(self, &copy);
168   }
169   return copy.Ptr();
170 }
171 
GenerateIdentityHashCode()172 uint32_t Object::GenerateIdentityHashCode() {
173   uint32_t expected_value, new_value;
174   do {
175     expected_value = hash_code_seed.LoadRelaxed();
176     new_value = expected_value * 1103515245 + 12345;
177   } while (!hash_code_seed.CompareExchangeWeakRelaxed(expected_value, new_value) ||
178       (expected_value & LockWord::kHashMask) == 0);
179   return expected_value & LockWord::kHashMask;
180 }
181 
SetHashCodeSeed(uint32_t new_seed)182 void Object::SetHashCodeSeed(uint32_t new_seed) {
183   hash_code_seed.StoreRelaxed(new_seed);
184 }
185 
IdentityHashCode()186 int32_t Object::IdentityHashCode() {
187   ObjPtr<Object> current_this = this;  // The this pointer may get invalidated by thread suspension.
188   while (true) {
189     LockWord lw = current_this->GetLockWord(false);
190     switch (lw.GetState()) {
191       case LockWord::kUnlocked: {
192         // Try to compare and swap in a new hash, if we succeed we will return the hash on the next
193         // loop iteration.
194         LockWord hash_word = LockWord::FromHashCode(GenerateIdentityHashCode(), lw.GCState());
195         DCHECK_EQ(hash_word.GetState(), LockWord::kHashCode);
196         if (current_this->CasLockWordWeakRelaxed(lw, hash_word)) {
197           return hash_word.GetHashCode();
198         }
199         break;
200       }
201       case LockWord::kThinLocked: {
202         // Inflate the thin lock to a monitor and stick the hash code inside of the monitor. May
203         // fail spuriously.
204         Thread* self = Thread::Current();
205         StackHandleScope<1> hs(self);
206         Handle<mirror::Object> h_this(hs.NewHandle(current_this));
207         Monitor::InflateThinLocked(self, h_this, lw, GenerateIdentityHashCode());
208         // A GC may have occurred when we switched to kBlocked.
209         current_this = h_this.Get();
210         break;
211       }
212       case LockWord::kFatLocked: {
213         // Already inflated, return the hash stored in the monitor.
214         Monitor* monitor = lw.FatLockMonitor();
215         DCHECK(monitor != nullptr);
216         return monitor->GetHashCode();
217       }
218       case LockWord::kHashCode: {
219         return lw.GetHashCode();
220       }
221       default: {
222         LOG(FATAL) << "Invalid state during hashcode " << lw.GetState();
223         break;
224       }
225     }
226   }
227   UNREACHABLE();
228 }
229 
CheckFieldAssignmentImpl(MemberOffset field_offset,ObjPtr<Object> new_value)230 void Object::CheckFieldAssignmentImpl(MemberOffset field_offset, ObjPtr<Object> new_value) {
231   ObjPtr<Class> c = GetClass();
232   Runtime* runtime = Runtime::Current();
233   if (runtime->GetClassLinker() == nullptr || !runtime->IsStarted() ||
234       !runtime->GetHeap()->IsObjectValidationEnabled() || !c->IsResolved()) {
235     return;
236   }
237   for (ObjPtr<Class> cur = c; cur != nullptr; cur = cur->GetSuperClass()) {
238     for (ArtField& field : cur->GetIFields()) {
239       if (field.GetOffset().Int32Value() == field_offset.Int32Value()) {
240         CHECK_NE(field.GetTypeAsPrimitiveType(), Primitive::kPrimNot);
241         // TODO: resolve the field type for moving GC.
242         ObjPtr<mirror::Class> field_type = field.GetType<!kMovingCollector>();
243         if (field_type != nullptr) {
244           CHECK(field_type->IsAssignableFrom(new_value->GetClass()));
245         }
246         return;
247       }
248     }
249   }
250   if (c->IsArrayClass()) {
251     // Bounds and assign-ability done in the array setter.
252     return;
253   }
254   if (IsClass()) {
255     for (ArtField& field : AsClass()->GetSFields()) {
256       if (field.GetOffset().Int32Value() == field_offset.Int32Value()) {
257         CHECK_NE(field.GetTypeAsPrimitiveType(), Primitive::kPrimNot);
258         // TODO: resolve the field type for moving GC.
259         ObjPtr<mirror::Class> field_type = field.GetType<!kMovingCollector>();
260         if (field_type != nullptr) {
261           CHECK(field_type->IsAssignableFrom(new_value->GetClass()));
262         }
263         return;
264       }
265     }
266   }
267   LOG(FATAL) << "Failed to find field for assignment to " << reinterpret_cast<void*>(this)
268       << " of type " << c->PrettyDescriptor() << " at offset " << field_offset;
269   UNREACHABLE();
270 }
271 
FindFieldByOffset(MemberOffset offset)272 ArtField* Object::FindFieldByOffset(MemberOffset offset) {
273   return IsClass() ? ArtField::FindStaticFieldWithOffset(AsClass(), offset.Uint32Value())
274       : ArtField::FindInstanceFieldWithOffset(GetClass(), offset.Uint32Value());
275 }
276 
PrettyTypeOf(ObjPtr<mirror::Object> obj)277 std::string Object::PrettyTypeOf(ObjPtr<mirror::Object> obj) {
278   if (obj == nullptr) {
279     return "null";
280   }
281   return obj->PrettyTypeOf();
282 }
283 
PrettyTypeOf()284 std::string Object::PrettyTypeOf() {
285   // From-space version is the same as the to-space version since the dex file never changes.
286   // Avoiding the read barrier here is important to prevent recursive AssertToSpaceInvariant
287   // issues.
288   ObjPtr<mirror::Class> klass = GetClass<kDefaultVerifyFlags, kWithoutReadBarrier>();
289   if (klass == nullptr) {
290     return "(raw)";
291   }
292   std::string temp;
293   std::string result(PrettyDescriptor(klass->GetDescriptor(&temp)));
294   if (klass->IsClassClass()) {
295     result += "<" + PrettyDescriptor(AsClass()->GetDescriptor(&temp)) + ">";
296   }
297   return result;
298 }
299 
300 }  // namespace mirror
301 }  // namespace art
302