| File: | out/../deps/v8/src/heap/read-only-heap.cc |
| Warning: | line 100, column 7 Value stored to 'ro_heap' is never read |
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| 1 | // Copyright 2019 the V8 project authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | #include "src/heap/read-only-heap.h" |
| 6 | |
| 7 | #include <cstddef> |
| 8 | #include <cstring> |
| 9 | |
| 10 | #include "src/base/lazy-instance.h" |
| 11 | #include "src/base/platform/mutex.h" |
| 12 | #include "src/common/ptr-compr-inl.h" |
| 13 | #include "src/heap/basic-memory-chunk.h" |
| 14 | #include "src/heap/heap-write-barrier-inl.h" |
| 15 | #include "src/heap/memory-chunk.h" |
| 16 | #include "src/heap/read-only-spaces.h" |
| 17 | #include "src/heap/third-party/heap-api.h" |
| 18 | #include "src/objects/heap-object-inl.h" |
| 19 | #include "src/objects/objects-inl.h" |
| 20 | #include "src/objects/smi.h" |
| 21 | #include "src/snapshot/read-only-deserializer.h" |
| 22 | #include "src/utils/allocation.h" |
| 23 | |
| 24 | namespace v8 { |
| 25 | namespace internal { |
| 26 | |
| 27 | namespace { |
| 28 | // Mutex used to ensure that ReadOnlyArtifacts creation is only done once. |
| 29 | base::LazyMutex read_only_heap_creation_mutex_ = LAZY_MUTEX_INITIALIZER{ { 0 }, { {} } }; |
| 30 | |
| 31 | // Weak pointer holding ReadOnlyArtifacts. ReadOnlyHeap::SetUp creates a |
| 32 | // std::shared_ptr from this when it attempts to reuse it. Since all Isolates |
| 33 | // hold a std::shared_ptr to this, the object is destroyed when no Isolates |
| 34 | // remain. |
| 35 | base::LazyInstance<std::weak_ptr<ReadOnlyArtifacts>>::type |
| 36 | read_only_artifacts_ = LAZY_INSTANCE_INITIALIZER{ { 0 }, { {} } }; |
| 37 | |
| 38 | std::shared_ptr<ReadOnlyArtifacts> InitializeSharedReadOnlyArtifacts() { |
| 39 | std::shared_ptr<ReadOnlyArtifacts> artifacts; |
| 40 | if (COMPRESS_POINTERS_IN_ISOLATE_CAGE_BOOLfalse) { |
| 41 | artifacts = std::make_shared<PointerCompressedReadOnlyArtifacts>(); |
| 42 | } else { |
| 43 | artifacts = std::make_shared<SingleCopyReadOnlyArtifacts>(); |
| 44 | } |
| 45 | *read_only_artifacts_.Pointer() = artifacts; |
| 46 | return artifacts; |
| 47 | } |
| 48 | } // namespace |
| 49 | |
| 50 | bool ReadOnlyHeap::IsSharedMemoryAvailable() { |
| 51 | static bool shared_memory_allocation_supported = |
| 52 | GetPlatformPageAllocator()->CanAllocateSharedPages(); |
| 53 | return shared_memory_allocation_supported; |
| 54 | } |
| 55 | |
| 56 | // This ReadOnlyHeap instance will only be accessed by Isolates that are already |
| 57 | // set up. As such it doesn't need to be guarded by a mutex or shared_ptrs, |
| 58 | // since an already set up Isolate will hold a shared_ptr to |
| 59 | // read_only_artifacts_. |
| 60 | SoleReadOnlyHeap* SoleReadOnlyHeap::shared_ro_heap_ = nullptr; |
| 61 | |
| 62 | // static |
| 63 | void ReadOnlyHeap::SetUp(Isolate* isolate, |
| 64 | SnapshotData* read_only_snapshot_data, |
| 65 | bool can_rehash) { |
| 66 | DCHECK_NOT_NULL(isolate)((void) 0); |
| 67 | |
| 68 | if (IsReadOnlySpaceShared()) { |
| 69 | ReadOnlyHeap* ro_heap; |
| 70 | if (read_only_snapshot_data != nullptr) { |
| 71 | bool read_only_heap_created = false; |
| 72 | base::MutexGuard guard(read_only_heap_creation_mutex_.Pointer()); |
| 73 | std::shared_ptr<ReadOnlyArtifacts> artifacts = |
| 74 | read_only_artifacts_.Get().lock(); |
| 75 | if (!artifacts) { |
| 76 | artifacts = InitializeSharedReadOnlyArtifacts(); |
| 77 | artifacts->InitializeChecksum(read_only_snapshot_data); |
| 78 | ro_heap = CreateInitalHeapForBootstrapping(isolate, artifacts); |
| 79 | ro_heap->DeseralizeIntoIsolate(isolate, read_only_snapshot_data, |
| 80 | can_rehash); |
| 81 | read_only_heap_created = true; |
| 82 | } else { |
| 83 | // With pointer compression, there is one ReadOnlyHeap per Isolate. |
| 84 | // Without PC, there is only one shared between all Isolates. |
| 85 | ro_heap = artifacts->GetReadOnlyHeapForIsolate(isolate); |
| 86 | isolate->SetUpFromReadOnlyArtifacts(artifacts, ro_heap); |
| 87 | } |
| 88 | artifacts->VerifyChecksum(read_only_snapshot_data, |
| 89 | read_only_heap_created); |
| 90 | ro_heap->InitializeIsolateRoots(isolate); |
| 91 | } else { |
| 92 | // This path should only be taken in mksnapshot, should only be run once |
| 93 | // before tearing down the Isolate that holds this ReadOnlyArtifacts and |
| 94 | // is not thread-safe. |
| 95 | std::shared_ptr<ReadOnlyArtifacts> artifacts = |
| 96 | read_only_artifacts_.Get().lock(); |
| 97 | CHECK(!artifacts)do { if ((__builtin_expect(!!(!(!artifacts)), 0))) { V8_Fatal ("Check failed: %s.", "!artifacts"); } } while (false); |
| 98 | artifacts = InitializeSharedReadOnlyArtifacts(); |
| 99 | |
| 100 | ro_heap = CreateInitalHeapForBootstrapping(isolate, artifacts); |
Value stored to 'ro_heap' is never read | |
| 101 | artifacts->VerifyChecksum(read_only_snapshot_data, true); |
| 102 | } |
| 103 | } else { |
| 104 | auto* ro_heap = new ReadOnlyHeap(new ReadOnlySpace(isolate->heap())); |
| 105 | isolate->SetUpFromReadOnlyArtifacts(nullptr, ro_heap); |
| 106 | if (read_only_snapshot_data != nullptr) { |
| 107 | ro_heap->DeseralizeIntoIsolate(isolate, read_only_snapshot_data, |
| 108 | can_rehash); |
| 109 | } |
| 110 | } |
| 111 | } |
| 112 | |
| 113 | void ReadOnlyHeap::DeseralizeIntoIsolate(Isolate* isolate, |
| 114 | SnapshotData* read_only_snapshot_data, |
| 115 | bool can_rehash) { |
| 116 | DCHECK_NOT_NULL(read_only_snapshot_data)((void) 0); |
| 117 | ReadOnlyDeserializer des(isolate, read_only_snapshot_data, can_rehash); |
| 118 | des.DeserializeIntoIsolate(); |
| 119 | InitFromIsolate(isolate); |
| 120 | } |
| 121 | |
| 122 | void ReadOnlyHeap::OnCreateHeapObjectsComplete(Isolate* isolate) { |
| 123 | DCHECK_NOT_NULL(isolate)((void) 0); |
| 124 | InitFromIsolate(isolate); |
| 125 | } |
| 126 | |
| 127 | // Only for compressed spaces |
| 128 | ReadOnlyHeap::ReadOnlyHeap(ReadOnlyHeap* ro_heap, ReadOnlySpace* ro_space) |
| 129 | : read_only_space_(ro_space), |
| 130 | read_only_object_cache_(ro_heap->read_only_object_cache_) { |
| 131 | DCHECK(ReadOnlyHeap::IsReadOnlySpaceShared())((void) 0); |
| 132 | DCHECK(COMPRESS_POINTERS_IN_ISOLATE_CAGE_BOOL)((void) 0); |
| 133 | } |
| 134 | |
| 135 | // static |
| 136 | ReadOnlyHeap* ReadOnlyHeap::CreateInitalHeapForBootstrapping( |
| 137 | Isolate* isolate, std::shared_ptr<ReadOnlyArtifacts> artifacts) { |
| 138 | DCHECK(IsReadOnlySpaceShared())((void) 0); |
| 139 | |
| 140 | std::unique_ptr<ReadOnlyHeap> ro_heap; |
| 141 | auto* ro_space = new ReadOnlySpace(isolate->heap()); |
| 142 | if (COMPRESS_POINTERS_IN_ISOLATE_CAGE_BOOLfalse) { |
| 143 | ro_heap.reset(new ReadOnlyHeap(ro_space)); |
| 144 | } else { |
| 145 | std::unique_ptr<SoleReadOnlyHeap> sole_ro_heap( |
| 146 | new SoleReadOnlyHeap(ro_space)); |
| 147 | // The global shared ReadOnlyHeap is only used without pointer compression. |
| 148 | SoleReadOnlyHeap::shared_ro_heap_ = sole_ro_heap.get(); |
| 149 | ro_heap = std::move(sole_ro_heap); |
| 150 | } |
| 151 | artifacts->set_read_only_heap(std::move(ro_heap)); |
| 152 | isolate->SetUpFromReadOnlyArtifacts(artifacts, artifacts->read_only_heap()); |
| 153 | return artifacts->read_only_heap(); |
| 154 | } |
| 155 | |
| 156 | void SoleReadOnlyHeap::InitializeIsolateRoots(Isolate* isolate) { |
| 157 | void* const isolate_ro_roots = |
| 158 | isolate->roots_table().read_only_roots_begin().location(); |
| 159 | std::memcpy(isolate_ro_roots, read_only_roots_, |
| 160 | kEntriesCount * sizeof(Address)); |
| 161 | } |
| 162 | |
| 163 | void SoleReadOnlyHeap::InitializeFromIsolateRoots(Isolate* isolate) { |
| 164 | void* const isolate_ro_roots = |
| 165 | isolate->roots_table().read_only_roots_begin().location(); |
| 166 | std::memcpy(read_only_roots_, isolate_ro_roots, |
| 167 | kEntriesCount * sizeof(Address)); |
| 168 | } |
| 169 | |
| 170 | void ReadOnlyHeap::InitFromIsolate(Isolate* isolate) { |
| 171 | DCHECK(!init_complete_)((void) 0); |
| 172 | read_only_space_->ShrinkPages(); |
| 173 | if (IsReadOnlySpaceShared()) { |
| 174 | InitializeFromIsolateRoots(isolate); |
| 175 | std::shared_ptr<ReadOnlyArtifacts> artifacts( |
| 176 | *read_only_artifacts_.Pointer()); |
| 177 | |
| 178 | read_only_space()->DetachPagesAndAddToArtifacts(artifacts); |
| 179 | artifacts->ReinstallReadOnlySpace(isolate); |
| 180 | |
| 181 | read_only_space_ = artifacts->shared_read_only_space(); |
| 182 | |
| 183 | #ifdef DEBUG |
| 184 | artifacts->VerifyHeapAndSpaceRelationships(isolate); |
| 185 | #endif |
| 186 | } else { |
| 187 | read_only_space_->Seal(ReadOnlySpace::SealMode::kDoNotDetachFromHeap); |
| 188 | } |
| 189 | init_complete_ = true; |
| 190 | } |
| 191 | |
| 192 | void ReadOnlyHeap::OnHeapTearDown(Heap* heap) { |
| 193 | read_only_space_->TearDown(heap->memory_allocator()); |
| 194 | delete read_only_space_; |
| 195 | } |
| 196 | |
| 197 | void SoleReadOnlyHeap::OnHeapTearDown(Heap* heap) { |
| 198 | // Do nothing as ReadOnlyHeap is shared between all Isolates. |
| 199 | } |
| 200 | |
| 201 | // static |
| 202 | void ReadOnlyHeap::PopulateReadOnlySpaceStatistics( |
| 203 | SharedMemoryStatistics* statistics) { |
| 204 | statistics->read_only_space_size_ = 0; |
| 205 | statistics->read_only_space_used_size_ = 0; |
| 206 | statistics->read_only_space_physical_size_ = 0; |
| 207 | if (IsReadOnlySpaceShared()) { |
| 208 | std::shared_ptr<ReadOnlyArtifacts> artifacts = |
| 209 | read_only_artifacts_.Get().lock(); |
| 210 | if (artifacts) { |
| 211 | auto* ro_space = artifacts->shared_read_only_space(); |
| 212 | statistics->read_only_space_size_ = ro_space->CommittedMemory(); |
| 213 | statistics->read_only_space_used_size_ = ro_space->Size(); |
| 214 | statistics->read_only_space_physical_size_ = |
| 215 | ro_space->CommittedPhysicalMemory(); |
| 216 | } |
| 217 | } |
| 218 | } |
| 219 | |
| 220 | // static |
| 221 | bool ReadOnlyHeap::Contains(Address address) { |
| 222 | if (V8_ENABLE_THIRD_PARTY_HEAP_BOOLfalse) { |
| 223 | return third_party_heap::Heap::InReadOnlySpace(address); |
| 224 | } else { |
| 225 | return BasicMemoryChunk::FromAddress(address)->InReadOnlySpace(); |
| 226 | } |
| 227 | } |
| 228 | |
| 229 | // static |
| 230 | bool ReadOnlyHeap::Contains(HeapObject object) { |
| 231 | if (V8_ENABLE_THIRD_PARTY_HEAP_BOOLfalse) { |
| 232 | return third_party_heap::Heap::InReadOnlySpace(object.address()); |
| 233 | } else { |
| 234 | return BasicMemoryChunk::FromHeapObject(object)->InReadOnlySpace(); |
| 235 | } |
| 236 | } |
| 237 | |
| 238 | Object* ReadOnlyHeap::ExtendReadOnlyObjectCache() { |
| 239 | read_only_object_cache_.push_back(Smi::zero()); |
| 240 | return &read_only_object_cache_.back(); |
| 241 | } |
| 242 | |
| 243 | Object ReadOnlyHeap::cached_read_only_object(size_t i) const { |
| 244 | DCHECK_LE(i, read_only_object_cache_.size())((void) 0); |
| 245 | return read_only_object_cache_[i]; |
| 246 | } |
| 247 | |
| 248 | bool ReadOnlyHeap::read_only_object_cache_is_initialized() const { |
| 249 | return read_only_object_cache_.size() > 0; |
| 250 | } |
| 251 | |
| 252 | size_t ReadOnlyHeap::read_only_object_cache_size() const { |
| 253 | return read_only_object_cache_.size(); |
| 254 | } |
| 255 | |
| 256 | ReadOnlyHeapObjectIterator::ReadOnlyHeapObjectIterator( |
| 257 | const ReadOnlyHeap* ro_heap) |
| 258 | : ReadOnlyHeapObjectIterator(ro_heap->read_only_space()) {} |
| 259 | |
| 260 | ReadOnlyHeapObjectIterator::ReadOnlyHeapObjectIterator( |
| 261 | const ReadOnlySpace* ro_space) |
| 262 | : ro_space_(ro_space), |
| 263 | current_page_(V8_ENABLE_THIRD_PARTY_HEAP_BOOLfalse |
| 264 | ? std::vector<ReadOnlyPage*>::iterator() |
| 265 | : ro_space->pages().begin()), |
| 266 | current_addr_(V8_ENABLE_THIRD_PARTY_HEAP_BOOLfalse |
| 267 | ? Address() |
| 268 | : (*current_page_)->GetAreaStart()) {} |
| 269 | |
| 270 | HeapObject ReadOnlyHeapObjectIterator::Next() { |
| 271 | if (V8_ENABLE_THIRD_PARTY_HEAP_BOOLfalse) { |
| 272 | return HeapObject(); // Unsupported |
| 273 | } |
| 274 | |
| 275 | if (current_page_ == ro_space_->pages().end()) { |
| 276 | return HeapObject(); |
| 277 | } |
| 278 | |
| 279 | ReadOnlyPage* current_page = *current_page_; |
| 280 | for (;;) { |
| 281 | Address end = current_page->address() + current_page->area_size() + |
| 282 | MemoryChunkLayout::ObjectStartOffsetInMemoryChunk(RO_SPACE); |
| 283 | DCHECK_LE(current_addr_, end)((void) 0); |
| 284 | if (current_addr_ == end) { |
| 285 | // Progress to the next page. |
| 286 | ++current_page_; |
| 287 | if (current_page_ == ro_space_->pages().end()) { |
| 288 | return HeapObject(); |
| 289 | } |
| 290 | current_page = *current_page_; |
| 291 | current_addr_ = current_page->GetAreaStart(); |
| 292 | } |
| 293 | |
| 294 | if (current_addr_ == ro_space_->top() && |
| 295 | current_addr_ != ro_space_->limit()) { |
| 296 | current_addr_ = ro_space_->limit(); |
| 297 | continue; |
| 298 | } |
| 299 | HeapObject object = HeapObject::FromAddress(current_addr_); |
| 300 | const int object_size = object.Size(); |
| 301 | current_addr_ += object_size; |
| 302 | |
| 303 | if (object.IsFreeSpaceOrFiller()) { |
| 304 | continue; |
| 305 | } |
| 306 | |
| 307 | DCHECK_OBJECT_SIZE(object_size)((void) 0); |
| 308 | return object; |
| 309 | } |
| 310 | } |
| 311 | |
| 312 | } // namespace internal |
| 313 | } // namespace v8 |