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
CopyRawObjectData(uint8_t * dst_bytes,ObjPtr<mirror::Object> src,size_t num_bytes)77 void Object::CopyRawObjectData(uint8_t* dst_bytes,
78 ObjPtr<mirror::Object> src,
79 size_t num_bytes) {
80 // Copy instance data. Don't assume memcpy copies by words (b/32012820).
81 const size_t offset = sizeof(Object);
82 uint8_t* src_bytes = reinterpret_cast<uint8_t*>(src.Ptr()) + offset;
83 dst_bytes += offset;
84 DCHECK_ALIGNED(src_bytes, sizeof(uintptr_t));
85 DCHECK_ALIGNED(dst_bytes, sizeof(uintptr_t));
86 // Use word sized copies to begin.
87 while (num_bytes >= sizeof(uintptr_t)) {
88 reinterpret_cast<Atomic<uintptr_t>*>(dst_bytes)->store(
89 reinterpret_cast<Atomic<uintptr_t>*>(src_bytes)->load(std::memory_order_relaxed),
90 std::memory_order_relaxed);
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)->store(
98 reinterpret_cast<Atomic<uint32_t>*>(src_bytes)->load(std::memory_order_relaxed),
99 std::memory_order_relaxed);
100 src_bytes += sizeof(uint32_t);
101 dst_bytes += sizeof(uint32_t);
102 num_bytes -= sizeof(uint32_t);
103 }
104 // Copy remaining bytes, avoid going past the end of num_bytes since there may be a redzone
105 // there.
106 while (num_bytes > 0) {
107 reinterpret_cast<Atomic<uint8_t>*>(dst_bytes)->store(
108 reinterpret_cast<Atomic<uint8_t>*>(src_bytes)->load(std::memory_order_relaxed),
109 std::memory_order_relaxed);
110 src_bytes += sizeof(uint8_t);
111 dst_bytes += sizeof(uint8_t);
112 num_bytes -= sizeof(uint8_t);
113 }
114 }
115
CopyObject(ObjPtr<mirror::Object> dest,ObjPtr<mirror::Object> src,size_t num_bytes)116 ObjPtr<Object> Object::CopyObject(ObjPtr<mirror::Object> dest,
117 ObjPtr<mirror::Object> src,
118 size_t num_bytes) {
119 // Copy everything but the header.
120 CopyRawObjectData(reinterpret_cast<uint8_t*>(dest.Ptr()), src, num_bytes - sizeof(Object));
121
122 if (gUseReadBarrier) {
123 // We need a RB here. After copying the whole object above, copy references fields one by one
124 // again with a RB to make sure there are no from space refs. TODO: Optimize this later?
125 CopyReferenceFieldsWithReadBarrierVisitor visitor(dest);
126 src->VisitReferences(visitor, visitor);
127 }
128 // Perform write barriers on copied object references.
129 ObjPtr<Class> c = src->GetClass();
130 if (c->IsArrayClass()) {
131 if (!c->GetComponentType()->IsPrimitive()) {
132 ObjPtr<ObjectArray<Object>> array = dest->AsObjectArray<Object>();
133 WriteBarrier::ForArrayWrite(dest, 0, array->GetLength());
134 }
135 } else {
136 WriteBarrier::ForEveryFieldWrite(dest);
137 }
138 return dest;
139 }
140
141 // An allocation pre-fence visitor that copies the object.
142 class CopyObjectVisitor {
143 public:
CopyObjectVisitor(Handle<Object> * orig,size_t num_bytes)144 CopyObjectVisitor(Handle<Object>* orig, size_t num_bytes)
145 : orig_(orig), num_bytes_(num_bytes) {}
146
operator ()(ObjPtr<Object> obj,size_t usable_size ATTRIBUTE_UNUSED) const147 void operator()(ObjPtr<Object> obj, size_t usable_size ATTRIBUTE_UNUSED) const
148 REQUIRES_SHARED(Locks::mutator_lock_) {
149 Object::CopyObject(obj, orig_->Get(), num_bytes_);
150 }
151
152 private:
153 Handle<Object>* const orig_;
154 const size_t num_bytes_;
155 DISALLOW_COPY_AND_ASSIGN(CopyObjectVisitor);
156 };
157
Clone(Handle<Object> h_this,Thread * self)158 ObjPtr<Object> Object::Clone(Handle<Object> h_this, Thread* self) {
159 CHECK(!h_this->IsClass()) << "Can't clone classes.";
160 // Object::SizeOf gets the right size even if we're an array. Using c->AllocObject() here would
161 // be wrong.
162 gc::Heap* heap = Runtime::Current()->GetHeap();
163 size_t num_bytes = h_this->SizeOf();
164 CopyObjectVisitor visitor(&h_this, num_bytes);
165 ObjPtr<Object> copy = heap->IsMovableObject(h_this.Get())
166 ? heap->AllocObject(self, h_this->GetClass(), num_bytes, visitor)
167 : heap->AllocNonMovableObject(self, h_this->GetClass(), num_bytes, visitor);
168 if (h_this->GetClass()->IsFinalizable()) {
169 heap->AddFinalizerReference(self, ©);
170 }
171 return copy;
172 }
173
GenerateIdentityHashCode()174 uint32_t Object::GenerateIdentityHashCode() {
175 uint32_t expected_value, new_value;
176 do {
177 expected_value = hash_code_seed.load(std::memory_order_relaxed);
178 new_value = expected_value * 1103515245 + 12345;
179 } while (!hash_code_seed.CompareAndSetWeakRelaxed(expected_value, new_value) ||
180 (expected_value & LockWord::kHashMask) == 0);
181 return expected_value & LockWord::kHashMask;
182 }
183
SetHashCodeSeed(uint32_t new_seed)184 void Object::SetHashCodeSeed(uint32_t new_seed) {
185 hash_code_seed.store(new_seed, std::memory_order_relaxed);
186 }
187
IdentityHashCode()188 int32_t Object::IdentityHashCode() {
189 ObjPtr<Object> current_this = this; // The this pointer may get invalidated by thread suspension.
190 while (true) {
191 LockWord lw = current_this->GetLockWord(false);
192 switch (lw.GetState()) {
193 case LockWord::kUnlocked: {
194 // Try to compare and swap in a new hash, if we succeed we will return the hash on the next
195 // loop iteration.
196 LockWord hash_word = LockWord::FromHashCode(GenerateIdentityHashCode(), lw.GCState());
197 DCHECK_EQ(hash_word.GetState(), LockWord::kHashCode);
198 // Use a strong CAS to prevent spurious failures since these can make the boot image
199 // non-deterministic.
200 if (current_this->CasLockWord(lw, hash_word, CASMode::kStrong, std::memory_order_relaxed)) {
201 return hash_word.GetHashCode();
202 }
203 break;
204 }
205 case LockWord::kThinLocked: {
206 // Inflate the thin lock to a monitor and stick the hash code inside of the monitor. May
207 // fail spuriously.
208 Thread* self = Thread::Current();
209 StackHandleScope<1> hs(self);
210 Handle<mirror::Object> h_this(hs.NewHandle(current_this));
211 Monitor::InflateThinLocked(self, h_this, lw, GenerateIdentityHashCode());
212 // A GC may have occurred when we switched to kBlocked.
213 current_this = h_this.Get();
214 break;
215 }
216 case LockWord::kFatLocked: {
217 // Already inflated, return the hash stored in the monitor.
218 Monitor* monitor = lw.FatLockMonitor();
219 DCHECK(monitor != nullptr);
220 return monitor->GetHashCode();
221 }
222 case LockWord::kHashCode: {
223 return lw.GetHashCode();
224 }
225 default: {
226 LOG(FATAL) << "Invalid state during hashcode " << lw.GetState();
227 UNREACHABLE();
228 }
229 }
230 }
231 }
232
CheckFieldAssignmentImpl(MemberOffset field_offset,ObjPtr<Object> new_value)233 void Object::CheckFieldAssignmentImpl(MemberOffset field_offset, ObjPtr<Object> new_value) {
234 ObjPtr<Class> c = GetClass();
235 Runtime* runtime = Runtime::Current();
236 if (runtime->GetClassLinker() == nullptr || !runtime->IsStarted() ||
237 !runtime->GetHeap()->IsObjectValidationEnabled() || !c->IsResolved()) {
238 return;
239 }
240 for (ObjPtr<Class> cur = c; cur != nullptr; cur = cur->GetSuperClass()) {
241 for (ArtField& field : cur->GetIFields()) {
242 if (field.GetOffset().Int32Value() == field_offset.Int32Value()) {
243 CHECK_NE(field.GetTypeAsPrimitiveType(), Primitive::kPrimNot);
244 // TODO: resolve the field type for moving GC.
245 ObjPtr<mirror::Class> field_type =
246 kMovingCollector ? field.LookupResolvedType() : field.ResolveType();
247 if (field_type != nullptr) {
248 CHECK(field_type->IsAssignableFrom(new_value->GetClass()));
249 }
250 return;
251 }
252 }
253 }
254 if (c->IsArrayClass()) {
255 // Bounds and assign-ability done in the array setter.
256 return;
257 }
258 if (IsClass()) {
259 for (ArtField& field : AsClass()->GetSFields()) {
260 if (field.GetOffset().Int32Value() == field_offset.Int32Value()) {
261 CHECK_NE(field.GetTypeAsPrimitiveType(), Primitive::kPrimNot);
262 // TODO: resolve the field type for moving GC.
263 ObjPtr<mirror::Class> field_type =
264 kMovingCollector ? field.LookupResolvedType() : field.ResolveType();
265 if (field_type != nullptr) {
266 CHECK(field_type->IsAssignableFrom(new_value->GetClass()));
267 }
268 return;
269 }
270 }
271 }
272 LOG(FATAL) << "Failed to find field for assignment to " << reinterpret_cast<void*>(this)
273 << " of type " << c->PrettyDescriptor() << " at offset " << field_offset;
274 UNREACHABLE();
275 }
276
FindFieldByOffset(MemberOffset offset)277 ArtField* Object::FindFieldByOffset(MemberOffset offset) {
278 return IsClass() ? ArtField::FindStaticFieldWithOffset(AsClass(), offset.Uint32Value())
279 : ArtField::FindInstanceFieldWithOffset(GetClass(), offset.Uint32Value());
280 }
281
PrettyTypeOf(ObjPtr<mirror::Object> obj)282 std::string Object::PrettyTypeOf(ObjPtr<mirror::Object> obj) {
283 return (obj == nullptr) ? "null" : obj->PrettyTypeOf();
284 }
285
PrettyTypeOf()286 std::string Object::PrettyTypeOf() {
287 // From-space version is the same as the to-space version since the dex file never changes.
288 // Avoiding the read barrier here is important to prevent recursive AssertToSpaceInvariant
289 // issues.
290 ObjPtr<mirror::Class> klass = GetClass<kDefaultVerifyFlags, kWithoutReadBarrier>();
291 if (klass == nullptr) {
292 return "(raw)";
293 }
294 std::string temp;
295 std::string result(PrettyDescriptor(klass->GetDescriptor(&temp)));
296 if (klass->IsClassClass()) {
297 result += "<" + PrettyDescriptor(AsClass()->GetDescriptor(&temp)) + ">";
298 }
299 return result;
300 }
301
302 } // namespace mirror
303 } // namespace art
304