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 "array-inl.h"
22 #include "art_field-inl.h"
23 #include "art_field.h"
24 #include "class-inl.h"
25 #include "class.h"
26 #include "class_linker-inl.h"
27 #include "dex/descriptors_names.h"
28 #include "dex/dex_file-inl.h"
29 #include "gc/accounting/card_table-inl.h"
30 #include "gc/heap-inl.h"
31 #include "handle_scope-inl.h"
32 #include "iftable-inl.h"
33 #include "monitor.h"
34 #include "object-inl.h"
35 #include "object-refvisitor-inl.h"
36 #include "object_array-inl.h"
37 #include "runtime.h"
38 #include "throwable.h"
39 #include "well_known_classes.h"
40
41 namespace art {
42 namespace mirror {
43
44 Atomic<uint32_t> Object::hash_code_seed(987654321U + std::time(nullptr));
45
46 class CopyReferenceFieldsWithReadBarrierVisitor {
47 public:
CopyReferenceFieldsWithReadBarrierVisitor(ObjPtr<Object> dest_obj)48 explicit CopyReferenceFieldsWithReadBarrierVisitor(ObjPtr<Object> dest_obj)
49 : dest_obj_(dest_obj) {}
50
operator ()(ObjPtr<Object> obj,MemberOffset offset,bool) const51 void operator()(ObjPtr<Object> obj, MemberOffset offset, bool /* is_static */) const
52 ALWAYS_INLINE REQUIRES_SHARED(Locks::mutator_lock_) {
53 // GetFieldObject() contains a RB.
54 ObjPtr<Object> ref = obj->GetFieldObject<Object>(offset);
55 // No WB here as a large object space does not have a card table
56 // coverage. Instead, cards will be marked separately.
57 dest_obj_->SetFieldObjectWithoutWriteBarrier<false, false>(offset, ref);
58 }
59
operator ()(ObjPtr<mirror::Class> klass,ObjPtr<mirror::Reference> ref) const60 void operator()(ObjPtr<mirror::Class> klass, ObjPtr<mirror::Reference> ref) const
61 ALWAYS_INLINE REQUIRES_SHARED(Locks::mutator_lock_) {
62 // Copy java.lang.ref.Reference.referent which isn't visited in
63 // Object::VisitReferences().
64 DCHECK(klass->IsTypeOfReferenceClass());
65 this->operator()(ref, mirror::Reference::ReferentOffset(), false);
66 }
67
68 // Unused since we don't copy class native roots.
VisitRootIfNonNull(mirror::CompressedReference<mirror::Object> * root ATTRIBUTE_UNUSED) const69 void VisitRootIfNonNull(mirror::CompressedReference<mirror::Object>* root ATTRIBUTE_UNUSED)
70 const {}
VisitRoot(mirror::CompressedReference<mirror::Object> * root ATTRIBUTE_UNUSED) const71 void VisitRoot(mirror::CompressedReference<mirror::Object>* root ATTRIBUTE_UNUSED) const {}
72
73 private:
74 const ObjPtr<Object> dest_obj_;
75 };
76
CopyObject(ObjPtr<mirror::Object> dest,ObjPtr<mirror::Object> src,size_t num_bytes)77 ObjPtr<Object> Object::CopyObject(ObjPtr<mirror::Object> dest,
78 ObjPtr<mirror::Object> src,
79 size_t num_bytes) {
80 // Copy instance data. Don't assume memcpy copies by words (b/32012820).
81 {
82 const size_t offset = sizeof(Object);
83 uint8_t* src_bytes = reinterpret_cast<uint8_t*>(src.Ptr()) + offset;
84 uint8_t* dst_bytes = reinterpret_cast<uint8_t*>(dest.Ptr()) + offset;
85 num_bytes -= offset;
86 DCHECK_ALIGNED(src_bytes, sizeof(uintptr_t));
87 DCHECK_ALIGNED(dst_bytes, sizeof(uintptr_t));
88 // Use word sized copies to begin.
89 while (num_bytes >= sizeof(uintptr_t)) {
90 reinterpret_cast<Atomic<uintptr_t>*>(dst_bytes)->store(
91 reinterpret_cast<Atomic<uintptr_t>*>(src_bytes)->load(std::memory_order_relaxed),
92 std::memory_order_relaxed);
93 src_bytes += sizeof(uintptr_t);
94 dst_bytes += sizeof(uintptr_t);
95 num_bytes -= sizeof(uintptr_t);
96 }
97 // Copy possible 32 bit word.
98 if (sizeof(uintptr_t) != sizeof(uint32_t) && num_bytes >= sizeof(uint32_t)) {
99 reinterpret_cast<Atomic<uint32_t>*>(dst_bytes)->store(
100 reinterpret_cast<Atomic<uint32_t>*>(src_bytes)->load(std::memory_order_relaxed),
101 std::memory_order_relaxed);
102 src_bytes += sizeof(uint32_t);
103 dst_bytes += sizeof(uint32_t);
104 num_bytes -= sizeof(uint32_t);
105 }
106 // Copy remaining bytes, avoid going past the end of num_bytes since there may be a redzone
107 // there.
108 while (num_bytes > 0) {
109 reinterpret_cast<Atomic<uint8_t>*>(dst_bytes)->store(
110 reinterpret_cast<Atomic<uint8_t>*>(src_bytes)->load(std::memory_order_relaxed),
111 std::memory_order_relaxed);
112 src_bytes += sizeof(uint8_t);
113 dst_bytes += sizeof(uint8_t);
114 num_bytes -= sizeof(uint8_t);
115 }
116 }
117
118 if (kUseReadBarrier) {
119 // We need a RB here. After copying the whole object above, copy references fields one by one
120 // again with a RB to make sure there are no from space refs. TODO: Optimize this later?
121 CopyReferenceFieldsWithReadBarrierVisitor visitor(dest);
122 src->VisitReferences(visitor, visitor);
123 }
124 // Perform write barriers on copied object references.
125 ObjPtr<Class> c = src->GetClass();
126 if (c->IsArrayClass()) {
127 if (!c->GetComponentType()->IsPrimitive()) {
128 ObjPtr<ObjectArray<Object>> array = dest->AsObjectArray<Object>();
129 WriteBarrier::ForArrayWrite(dest, 0, array->GetLength());
130 }
131 } else {
132 WriteBarrier::ForEveryFieldWrite(dest);
133 }
134 return dest;
135 }
136
137 // An allocation pre-fence visitor that copies the object.
138 class CopyObjectVisitor {
139 public:
CopyObjectVisitor(Handle<Object> * orig,size_t num_bytes)140 CopyObjectVisitor(Handle<Object>* orig, size_t num_bytes)
141 : orig_(orig), num_bytes_(num_bytes) {}
142
operator ()(ObjPtr<Object> obj,size_t usable_size ATTRIBUTE_UNUSED) const143 void operator()(ObjPtr<Object> obj, size_t usable_size ATTRIBUTE_UNUSED) const
144 REQUIRES_SHARED(Locks::mutator_lock_) {
145 Object::CopyObject(obj, orig_->Get(), num_bytes_);
146 }
147
148 private:
149 Handle<Object>* const orig_;
150 const size_t num_bytes_;
151 DISALLOW_COPY_AND_ASSIGN(CopyObjectVisitor);
152 };
153
Clone(Thread * self)154 ObjPtr<Object> Object::Clone(Thread* self) {
155 CHECK(!IsClass()) << "Can't clone classes.";
156 // Object::SizeOf gets the right size even if we're an array. Using c->AllocObject() here would
157 // be wrong.
158 gc::Heap* heap = Runtime::Current()->GetHeap();
159 size_t num_bytes = SizeOf();
160 StackHandleScope<1> hs(self);
161 Handle<Object> this_object(hs.NewHandle(this));
162 ObjPtr<Object> copy;
163 CopyObjectVisitor visitor(&this_object, num_bytes);
164 if (heap->IsMovableObject(this)) {
165 copy = heap->AllocObject<true>(self, GetClass(), num_bytes, visitor);
166 } else {
167 copy = heap->AllocNonMovableObject<true>(self, GetClass(), num_bytes, visitor);
168 }
169 if (this_object->GetClass()->IsFinalizable()) {
170 heap->AddFinalizerReference(self, ©);
171 }
172 return copy;
173 }
174
GenerateIdentityHashCode()175 uint32_t Object::GenerateIdentityHashCode() {
176 uint32_t expected_value, new_value;
177 do {
178 expected_value = hash_code_seed.load(std::memory_order_relaxed);
179 new_value = expected_value * 1103515245 + 12345;
180 } while (!hash_code_seed.CompareAndSetWeakRelaxed(expected_value, new_value) ||
181 (expected_value & LockWord::kHashMask) == 0);
182 return expected_value & LockWord::kHashMask;
183 }
184
SetHashCodeSeed(uint32_t new_seed)185 void Object::SetHashCodeSeed(uint32_t new_seed) {
186 hash_code_seed.store(new_seed, std::memory_order_relaxed);
187 }
188
IdentityHashCode()189 int32_t Object::IdentityHashCode() {
190 ObjPtr<Object> current_this = this; // The this pointer may get invalidated by thread suspension.
191 while (true) {
192 LockWord lw = current_this->GetLockWord(false);
193 switch (lw.GetState()) {
194 case LockWord::kUnlocked: {
195 // Try to compare and swap in a new hash, if we succeed we will return the hash on the next
196 // loop iteration.
197 LockWord hash_word = LockWord::FromHashCode(GenerateIdentityHashCode(), lw.GCState());
198 DCHECK_EQ(hash_word.GetState(), LockWord::kHashCode);
199 // Use a strong CAS to prevent spurious failures since these can make the boot image
200 // non-deterministic.
201 if (current_this->CasLockWord(lw, hash_word, CASMode::kStrong, std::memory_order_relaxed)) {
202 return hash_word.GetHashCode();
203 }
204 break;
205 }
206 case LockWord::kThinLocked: {
207 // Inflate the thin lock to a monitor and stick the hash code inside of the monitor. May
208 // fail spuriously.
209 Thread* self = Thread::Current();
210 StackHandleScope<1> hs(self);
211 Handle<mirror::Object> h_this(hs.NewHandle(current_this));
212 Monitor::InflateThinLocked(self, h_this, lw, GenerateIdentityHashCode());
213 // A GC may have occurred when we switched to kBlocked.
214 current_this = h_this.Get();
215 break;
216 }
217 case LockWord::kFatLocked: {
218 // Already inflated, return the hash stored in the monitor.
219 Monitor* monitor = lw.FatLockMonitor();
220 DCHECK(monitor != nullptr);
221 return monitor->GetHashCode();
222 }
223 case LockWord::kHashCode: {
224 return lw.GetHashCode();
225 }
226 default: {
227 LOG(FATAL) << "Invalid state during hashcode " << lw.GetState();
228 UNREACHABLE();
229 }
230 }
231 }
232 }
233
CheckFieldAssignmentImpl(MemberOffset field_offset,ObjPtr<Object> new_value)234 void Object::CheckFieldAssignmentImpl(MemberOffset field_offset, ObjPtr<Object> new_value) {
235 ObjPtr<Class> c = GetClass();
236 Runtime* runtime = Runtime::Current();
237 if (runtime->GetClassLinker() == nullptr || !runtime->IsStarted() ||
238 !runtime->GetHeap()->IsObjectValidationEnabled() || !c->IsResolved()) {
239 return;
240 }
241 for (ObjPtr<Class> cur = c; cur != nullptr; cur = cur->GetSuperClass()) {
242 for (ArtField& field : cur->GetIFields()) {
243 if (field.GetOffset().Int32Value() == field_offset.Int32Value()) {
244 CHECK_NE(field.GetTypeAsPrimitiveType(), Primitive::kPrimNot);
245 // TODO: resolve the field type for moving GC.
246 ObjPtr<mirror::Class> field_type =
247 kMovingCollector ? field.LookupResolvedType() : field.ResolveType();
248 if (field_type != nullptr) {
249 CHECK(field_type->IsAssignableFrom(new_value->GetClass()));
250 }
251 return;
252 }
253 }
254 }
255 if (c->IsArrayClass()) {
256 // Bounds and assign-ability done in the array setter.
257 return;
258 }
259 if (IsClass()) {
260 for (ArtField& field : AsClass()->GetSFields()) {
261 if (field.GetOffset().Int32Value() == field_offset.Int32Value()) {
262 CHECK_NE(field.GetTypeAsPrimitiveType(), Primitive::kPrimNot);
263 // TODO: resolve the field type for moving GC.
264 ObjPtr<mirror::Class> field_type =
265 kMovingCollector ? field.LookupResolvedType() : field.ResolveType();
266 if (field_type != nullptr) {
267 CHECK(field_type->IsAssignableFrom(new_value->GetClass()));
268 }
269 return;
270 }
271 }
272 }
273 LOG(FATAL) << "Failed to find field for assignment to " << reinterpret_cast<void*>(this)
274 << " of type " << c->PrettyDescriptor() << " at offset " << field_offset;
275 UNREACHABLE();
276 }
277
FindFieldByOffset(MemberOffset offset)278 ArtField* Object::FindFieldByOffset(MemberOffset offset) {
279 return IsClass() ? ArtField::FindStaticFieldWithOffset(AsClass(), offset.Uint32Value())
280 : ArtField::FindInstanceFieldWithOffset(GetClass(), offset.Uint32Value());
281 }
282
PrettyTypeOf(ObjPtr<mirror::Object> obj)283 std::string Object::PrettyTypeOf(ObjPtr<mirror::Object> obj) {
284 return (obj == nullptr) ? "null" : obj->PrettyTypeOf();
285 }
286
PrettyTypeOf()287 std::string Object::PrettyTypeOf() {
288 // From-space version is the same as the to-space version since the dex file never changes.
289 // Avoiding the read barrier here is important to prevent recursive AssertToSpaceInvariant
290 // issues.
291 ObjPtr<mirror::Class> klass = GetClass<kDefaultVerifyFlags, kWithoutReadBarrier>();
292 if (klass == nullptr) {
293 return "(raw)";
294 }
295 std::string temp;
296 std::string result(PrettyDescriptor(klass->GetDescriptor(&temp)));
297 if (klass->IsClassClass()) {
298 result += "<" + PrettyDescriptor(AsClass()->GetDescriptor(&temp)) + ">";
299 }
300 return result;
301 }
302
303 } // namespace mirror
304 } // namespace art
305