// Copyright 2019 the V8 project authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. #include "src/objects/backing-store.h" #include <cstring> #include "src/execution/isolate.h" #include "src/handles/global-handles.h" #include "src/logging/counters.h" #include "src/wasm/wasm-constants.h" #include "src/wasm/wasm-engine.h" #include "src/wasm/wasm-limits.h" #include "src/wasm/wasm-objects-inl.h" #define TRACE_BS(...) \ do { \ if (FLAG_trace_backing_store) PrintF(__VA_ARGS__); \ } while (false) namespace v8 { namespace internal { namespace { #if V8_TARGET_ARCH_64_BIT constexpr bool kUseGuardRegions = true; #else constexpr bool kUseGuardRegions = false; #endif #if V8_TARGET_ARCH_MIPS64 // MIPS64 has a user space of 2^40 bytes on most processors, // address space limits needs to be smaller. constexpr size_t kAddressSpaceLimit = 0x8000000000L; // 512 GiB #elif V8_TARGET_ARCH_64_BIT constexpr size_t kAddressSpaceLimit = 0x10100000000L; // 1 TiB + 4 GiB #else constexpr size_t kAddressSpaceLimit = 0xC0000000; // 3 GiB #endif constexpr uint64_t kOneGiB = 1024 * 1024 * 1024; constexpr uint64_t kNegativeGuardSize = 2 * kOneGiB; #if V8_TARGET_ARCH_64_BIT constexpr uint64_t kFullGuardSize = 10 * kOneGiB; #endif std::atomic<uint64_t> reserved_address_space_{0}; // Allocation results are reported to UMA // // See wasm_memory_allocation_result in counters.h enum class AllocationStatus { kSuccess, // Succeeded on the first try kSuccessAfterRetry, // Succeeded after garbage collection kAddressSpaceLimitReachedFailure, // Failed because Wasm is at its address // space limit kOtherFailure // Failed for an unknown reason }; #if V8_TARGET_ARCH_64_BIT base::AddressRegion GetGuardedRegion(void* buffer_start, size_t byte_length) { // Guard regions always look like this: // |xxx(2GiB)xxx|.......(4GiB)..xxxxx|xxxxxx(4GiB)xxxxxx| // ^ buffer_start // ^ byte_length // ^ negative guard region ^ positive guard region Address start = reinterpret_cast<Address>(buffer_start); DCHECK_EQ(8, sizeof(size_t)); // only use on 64-bit DCHECK_EQ(0, start % AllocatePageSize()); return base::AddressRegion(start - (2 * kOneGiB), static_cast<size_t>(kFullGuardSize)); } #endif base::AddressRegion GetRegion(bool has_guard_regions, void* buffer_start, size_t byte_length, size_t byte_capacity) { #if V8_TARGET_ARCH_64_BIT if (has_guard_regions) return GetGuardedRegion(buffer_start, byte_length); #else DCHECK(!has_guard_regions); #endif return base::AddressRegion(reinterpret_cast<Address>(buffer_start), byte_capacity); } size_t GetReservationSize(bool has_guard_regions, size_t byte_capacity) { #if V8_TARGET_ARCH_64_BIT if (has_guard_regions) return kFullGuardSize; #else DCHECK(!has_guard_regions); #endif return byte_capacity; } void RecordStatus(Isolate* isolate, AllocationStatus status) { isolate->counters()->wasm_memory_allocation_result()->AddSample( static_cast<int>(status)); } inline void DebugCheckZero(void* start, size_t byte_length) { #if DEBUG // Double check memory is zero-initialized. Despite being DEBUG-only, // this function is somewhat optimized for the benefit of test suite // execution times (some tests allocate several gigabytes). const byte* bytes = reinterpret_cast<const byte*>(start); const size_t kBaseCase = 32; for (size_t i = 0; i < kBaseCase && i < byte_length; i++) { DCHECK_EQ(0, bytes[i]); } // Having checked the first kBaseCase bytes to be zero, we can now use // {memcmp} to compare the range against itself shifted by that amount, // thereby inductively checking the remaining bytes. if (byte_length > kBaseCase) { DCHECK_EQ(0, memcmp(bytes, bytes + kBaseCase, byte_length - kBaseCase)); } #endif } } // namespace bool BackingStore::ReserveAddressSpace(uint64_t num_bytes) { uint64_t reservation_limit = kAddressSpaceLimit; uint64_t old_count = reserved_address_space_.load(std::memory_order_relaxed); while (true) { if (old_count > reservation_limit) return false; if (reservation_limit - old_count < num_bytes) return false; if (reserved_address_space_.compare_exchange_weak( old_count, old_count + num_bytes, std::memory_order_acq_rel)) { return true; } } } void BackingStore::ReleaseReservation(uint64_t num_bytes) { uint64_t old_reserved = reserved_address_space_.fetch_sub(num_bytes); USE(old_reserved); DCHECK_LE(num_bytes, old_reserved); } // The backing store for a Wasm shared memory remembers all the isolates // with which it has been shared. struct SharedWasmMemoryData { std::vector<Isolate*> isolates_; }; void BackingStore::Clear() { buffer_start_ = nullptr; byte_length_ = 0; has_guard_regions_ = false; if (holds_shared_ptr_to_allocator_) { type_specific_data_.v8_api_array_buffer_allocator_shared .std::shared_ptr<v8::ArrayBuffer::Allocator>::~shared_ptr(); holds_shared_ptr_to_allocator_ = false; } type_specific_data_.v8_api_array_buffer_allocator = nullptr; } BackingStore::~BackingStore() { GlobalBackingStoreRegistry::Unregister(this); if (buffer_start_ == nullptr) return; // nothing to deallocate if (is_wasm_memory_) { DCHECK(free_on_destruct_); DCHECK(!custom_deleter_); TRACE_BS("BSw:free bs=%p mem=%p (length=%zu, capacity=%zu)\n", this, buffer_start_, byte_length(), byte_capacity_); if (is_shared_) { // Deallocate the list of attached memory objects. SharedWasmMemoryData* shared_data = get_shared_wasm_memory_data(); delete shared_data; type_specific_data_.shared_wasm_memory_data = nullptr; } // Wasm memories are always allocated through the page allocator. auto region = GetRegion(has_guard_regions_, buffer_start_, byte_length_, byte_capacity_); bool pages_were_freed = region.size() == 0 /* no need to free any pages */ || FreePages(GetPlatformPageAllocator(), reinterpret_cast<void*>(region.begin()), region.size()); CHECK(pages_were_freed); BackingStore::ReleaseReservation( GetReservationSize(has_guard_regions_, byte_capacity_)); Clear(); return; } if (custom_deleter_) { DCHECK(free_on_destruct_); TRACE_BS("BS:custome deleter bs=%p mem=%p (length=%zu, capacity=%zu)\n", this, buffer_start_, byte_length(), byte_capacity_); type_specific_data_.deleter.callback(buffer_start_, byte_length_, type_specific_data_.deleter.data); Clear(); return; } if (free_on_destruct_) { // JSArrayBuffer backing store. Deallocate through the embedder's allocator. auto allocator = get_v8_api_array_buffer_allocator(); TRACE_BS("BS:free bs=%p mem=%p (length=%zu, capacity=%zu)\n", this, buffer_start_, byte_length(), byte_capacity_); allocator->Free(buffer_start_, byte_length_); } Clear(); } // Allocate a backing store using the array buffer allocator from the embedder. std::unique_ptr<BackingStore> BackingStore::Allocate( Isolate* isolate, size_t byte_length, SharedFlag shared, InitializedFlag initialized) { void* buffer_start = nullptr; auto allocator = isolate->array_buffer_allocator(); CHECK_NOT_NULL(allocator); if (byte_length != 0) { auto counters = isolate->counters(); int mb_length = static_cast<int>(byte_length / MB); if (mb_length > 0) { counters->array_buffer_big_allocations()->AddSample(mb_length); } if (shared == SharedFlag::kShared) { counters->shared_array_allocations()->AddSample(mb_length); } auto allocate_buffer = [allocator, initialized](size_t byte_length) { if (initialized == InitializedFlag::kUninitialized) { return allocator->AllocateUninitialized(byte_length); } void* buffer_start = allocator->Allocate(byte_length); if (buffer_start) { // TODO(wasm): node does not implement the zero-initialization API. // Reenable this debug check when node does implement it properly. constexpr bool kDebugCheckZeroDisabledDueToNodeNotImplementingZeroInitAPI = true; if ((!(kDebugCheckZeroDisabledDueToNodeNotImplementingZeroInitAPI)) && !FLAG_mock_arraybuffer_allocator) { DebugCheckZero(buffer_start, byte_length); } } return buffer_start; }; buffer_start = isolate->heap()->AllocateExternalBackingStore( allocate_buffer, byte_length); if (buffer_start == nullptr) { // Allocation failed. counters->array_buffer_new_size_failures()->AddSample(mb_length); return {}; } } auto result = new BackingStore(buffer_start, // start byte_length, // length byte_length, // capacity shared, // shared false, // is_wasm_memory true, // free_on_destruct false, // has_guard_regions false, // custom_deleter false); // empty_deleter TRACE_BS("BS:alloc bs=%p mem=%p (length=%zu)\n", result, result->buffer_start(), byte_length); result->SetAllocatorFromIsolate(isolate); return std::unique_ptr<BackingStore>(result); } void BackingStore::SetAllocatorFromIsolate(Isolate* isolate) { if (auto allocator_shared = isolate->array_buffer_allocator_shared()) { holds_shared_ptr_to_allocator_ = true; new (&type_specific_data_.v8_api_array_buffer_allocator_shared) std::shared_ptr<v8::ArrayBuffer::Allocator>( std::move(allocator_shared)); } else { type_specific_data_.v8_api_array_buffer_allocator = isolate->array_buffer_allocator(); } } // Allocate a backing store for a Wasm memory. Always use the page allocator // and add guard regions. std::unique_ptr<BackingStore> BackingStore::TryAllocateWasmMemory( Isolate* isolate, size_t initial_pages, size_t maximum_pages, SharedFlag shared) { // Cannot reserve 0 pages on some OSes. if (maximum_pages == 0) maximum_pages = 1; TRACE_BS("BSw:try %zu pages, %zu max\n", initial_pages, maximum_pages); bool guards = kUseGuardRegions; // For accounting purposes, whether a GC was necessary. bool did_retry = false; // A helper to try running a function up to 3 times, executing a GC // if the first and second attempts failed. auto gc_retry = [&](const std::function<bool()>& fn) { for (int i = 0; i < 3; i++) { if (fn()) return true; // Collect garbage and retry. did_retry = true; // TODO(wasm): try Heap::EagerlyFreeExternalMemory() first? isolate->heap()->MemoryPressureNotification( MemoryPressureLevel::kCritical, true); } return false; }; // Compute size of reserved memory. size_t engine_max_pages = wasm::max_maximum_mem_pages(); maximum_pages = std::min(engine_max_pages, maximum_pages); CHECK_LE(maximum_pages, std::numeric_limits<size_t>::max() / wasm::kWasmPageSize); size_t byte_capacity = maximum_pages * wasm::kWasmPageSize; size_t reservation_size = GetReservationSize(guards, byte_capacity); //-------------------------------------------------------------------------- // 1. Enforce maximum address space reservation per engine. //-------------------------------------------------------------------------- auto reserve_memory_space = [&] { return BackingStore::ReserveAddressSpace(reservation_size); }; if (!gc_retry(reserve_memory_space)) { // Crash on out-of-memory if the correctness fuzzer is running. if (FLAG_correctness_fuzzer_suppressions) { FATAL("could not allocate wasm memory backing store"); } RecordStatus(isolate, AllocationStatus::kAddressSpaceLimitReachedFailure); TRACE_BS("BSw:try failed to reserve address space\n"); return {}; } //-------------------------------------------------------------------------- // 2. Allocate pages (inaccessible by default). //-------------------------------------------------------------------------- void* allocation_base = nullptr; auto allocate_pages = [&] { allocation_base = AllocatePages(GetPlatformPageAllocator(), nullptr, reservation_size, wasm::kWasmPageSize, PageAllocator::kNoAccess); return allocation_base != nullptr; }; if (!gc_retry(allocate_pages)) { // Page allocator could not reserve enough pages. BackingStore::ReleaseReservation(reservation_size); RecordStatus(isolate, AllocationStatus::kOtherFailure); TRACE_BS("BSw:try failed to allocate pages\n"); return {}; } // Get a pointer to the start of the buffer, skipping negative guard region // if necessary. byte* buffer_start = reinterpret_cast<byte*>(allocation_base) + (guards ? kNegativeGuardSize : 0); //-------------------------------------------------------------------------- // 3. Commit the initial pages (allow read/write). //-------------------------------------------------------------------------- size_t byte_length = initial_pages * wasm::kWasmPageSize; auto commit_memory = [&] { return byte_length == 0 || SetPermissions(GetPlatformPageAllocator(), buffer_start, byte_length, PageAllocator::kReadWrite); }; if (!gc_retry(commit_memory)) { // SetPermissions put us over the process memory limit. V8::FatalProcessOutOfMemory(nullptr, "BackingStore::AllocateWasmMemory()"); TRACE_BS("BSw:try failed to set permissions\n"); } DebugCheckZero(buffer_start, byte_length); // touch the bytes. RecordStatus(isolate, did_retry ? AllocationStatus::kSuccessAfterRetry : AllocationStatus::kSuccess); auto result = new BackingStore(buffer_start, // start byte_length, // length byte_capacity, // capacity shared, // shared true, // is_wasm_memory true, // free_on_destruct guards, // has_guard_regions false, // custom_deleter false); // empty_deleter TRACE_BS("BSw:alloc bs=%p mem=%p (length=%zu, capacity=%zu)\n", result, result->buffer_start(), byte_length, byte_capacity); // Shared Wasm memories need an anchor for the memory object list. if (shared == SharedFlag::kShared) { result->type_specific_data_.shared_wasm_memory_data = new SharedWasmMemoryData(); } return std::unique_ptr<BackingStore>(result); } // Allocate a backing store for a Wasm memory. Always use the page allocator // and add guard regions. std::unique_ptr<BackingStore> BackingStore::AllocateWasmMemory( Isolate* isolate, size_t initial_pages, size_t maximum_pages, SharedFlag shared) { // Wasm pages must be a multiple of the allocation page size. DCHECK_EQ(0, wasm::kWasmPageSize % AllocatePageSize()); // Enforce engine limitation on the maximum number of pages. if (initial_pages > wasm::kV8MaxWasmMemoryPages) return nullptr; // Trying to allocate 4 GiB on a 32-bit platform is guaranteed to fail. // We don't lower the official max_maximum_mem_pages() limit because that // would be observable upon instantiation; this way the effective limit // on 32-bit platforms is defined by the allocator. constexpr size_t kPlatformMax = std::numeric_limits<size_t>::max() / wasm::kWasmPageSize; if (initial_pages > kPlatformMax) return nullptr; auto backing_store = TryAllocateWasmMemory(isolate, initial_pages, maximum_pages, shared); if (!backing_store && maximum_pages > initial_pages) { // If reserving {maximum_pages} failed, try with maximum = initial. backing_store = TryAllocateWasmMemory(isolate, initial_pages, initial_pages, shared); } return backing_store; } std::unique_ptr<BackingStore> BackingStore::CopyWasmMemory(Isolate* isolate, size_t new_pages) { // Note that we could allocate uninitialized to save initialization cost here, // but since Wasm memories are allocated by the page allocator, the zeroing // cost is already built-in. // TODO(titzer): should we use a suitable maximum here? auto new_backing_store = BackingStore::AllocateWasmMemory( isolate, new_pages, new_pages, is_shared() ? SharedFlag::kShared : SharedFlag::kNotShared); if (!new_backing_store || new_backing_store->has_guard_regions() != has_guard_regions_) { return {}; } if (byte_length_ > 0) { // If the allocation was successful, then the new buffer must be at least // as big as the old one. DCHECK_GE(new_pages * wasm::kWasmPageSize, byte_length_); memcpy(new_backing_store->buffer_start(), buffer_start_, byte_length_); } return new_backing_store; } // Try to grow the size of a wasm memory in place, without realloc + copy. bool BackingStore::GrowWasmMemoryInPlace(Isolate* isolate, size_t delta_pages, size_t max_pages) { DCHECK(is_wasm_memory_); max_pages = std::min(max_pages, byte_capacity_ / wasm::kWasmPageSize); if (delta_pages == 0) return true; // degenerate grow. if (delta_pages > max_pages) return false; // would never work. // Do a compare-exchange loop, because we also need to adjust page // permissions. Note that multiple racing grows both try to set page // permissions for the entire range (to be RW), so the operating system // should deal with that raciness. We know we succeeded when we can // compare/swap the old length with the new length. size_t old_length = byte_length_.load(std::memory_order_relaxed); size_t new_length = 0; while (true) { size_t current_pages = old_length / wasm::kWasmPageSize; // Check if we have exceed the supplied maximum. if (current_pages > (max_pages - delta_pages)) return false; new_length = (current_pages + delta_pages) * wasm::kWasmPageSize; // Try to adjust the permissions on the memory. if (!i::SetPermissions(GetPlatformPageAllocator(), buffer_start_, new_length, PageAllocator::kReadWrite)) { return false; } if (byte_length_.compare_exchange_weak(old_length, new_length, std::memory_order_acq_rel)) { // Successfully updated both the length and permissions. break; } } if (!is_shared_ && free_on_destruct_) { // Only do per-isolate accounting for non-shared backing stores. reinterpret_cast<v8::Isolate*>(isolate) ->AdjustAmountOfExternalAllocatedMemory(new_length - old_length); } return true; } void BackingStore::AttachSharedWasmMemoryObject( Isolate* isolate, Handle<WasmMemoryObject> memory_object) { DCHECK(is_wasm_memory_); DCHECK(is_shared_); // We need to take the global registry lock for this operation. GlobalBackingStoreRegistry::AddSharedWasmMemoryObject(isolate, this, memory_object); } void BackingStore::BroadcastSharedWasmMemoryGrow( Isolate* isolate, std::shared_ptr<BackingStore> backing_store, size_t new_pages) { GlobalBackingStoreRegistry::BroadcastSharedWasmMemoryGrow( isolate, backing_store, new_pages); } void BackingStore::RemoveSharedWasmMemoryObjects(Isolate* isolate) { GlobalBackingStoreRegistry::Purge(isolate); } void BackingStore::UpdateSharedWasmMemoryObjects(Isolate* isolate) { GlobalBackingStoreRegistry::UpdateSharedWasmMemoryObjects(isolate); } std::unique_ptr<BackingStore> BackingStore::WrapAllocation( Isolate* isolate, void* allocation_base, size_t allocation_length, SharedFlag shared, bool free_on_destruct) { auto result = new BackingStore(allocation_base, // start allocation_length, // length allocation_length, // capacity shared, // shared false, // is_wasm_memory free_on_destruct, // free_on_destruct false, // has_guard_regions false, // custom_deleter false); // empty_deleter result->SetAllocatorFromIsolate(isolate); TRACE_BS("BS:wrap bs=%p mem=%p (length=%zu)\n", result, result->buffer_start(), result->byte_length()); return std::unique_ptr<BackingStore>(result); } std::unique_ptr<BackingStore> BackingStore::WrapAllocation( void* allocation_base, size_t allocation_length, v8::BackingStore::DeleterCallback deleter, void* deleter_data, SharedFlag shared) { bool is_empty_deleter = (deleter == v8::BackingStore::EmptyDeleter); auto result = new BackingStore(allocation_base, // start allocation_length, // length allocation_length, // capacity shared, // shared false, // is_wasm_memory true, // free_on_destruct false, // has_guard_regions true, // custom_deleter is_empty_deleter); // empty_deleter result->type_specific_data_.deleter = {deleter, deleter_data}; TRACE_BS("BS:wrap bs=%p mem=%p (length=%zu)\n", result, result->buffer_start(), result->byte_length()); return std::unique_ptr<BackingStore>(result); } std::unique_ptr<BackingStore> BackingStore::EmptyBackingStore( SharedFlag shared) { auto result = new BackingStore(nullptr, // start 0, // length 0, // capacity shared, // shared false, // is_wasm_memory true, // free_on_destruct false, // has_guard_regions false, // custom_deleter false); // empty_deleter return std::unique_ptr<BackingStore>(result); } bool BackingStore::Reallocate(Isolate* isolate, size_t new_byte_length) { CHECK(!is_wasm_memory_ && !custom_deleter_ && !globally_registered_ && free_on_destruct_); auto allocator = get_v8_api_array_buffer_allocator(); CHECK_EQ(isolate->array_buffer_allocator(), allocator); CHECK_EQ(byte_length_, byte_capacity_); void* new_start = allocator->Reallocate(buffer_start_, byte_length_, new_byte_length); if (!new_start) return false; buffer_start_ = new_start; byte_capacity_ = new_byte_length; byte_length_ = new_byte_length; return true; } v8::ArrayBuffer::Allocator* BackingStore::get_v8_api_array_buffer_allocator() { CHECK(!is_wasm_memory_); auto array_buffer_allocator = holds_shared_ptr_to_allocator_ ? type_specific_data_.v8_api_array_buffer_allocator_shared.get() : type_specific_data_.v8_api_array_buffer_allocator; CHECK_NOT_NULL(array_buffer_allocator); return array_buffer_allocator; } SharedWasmMemoryData* BackingStore::get_shared_wasm_memory_data() { CHECK(is_wasm_memory_ && is_shared_); auto shared_wasm_memory_data = type_specific_data_.shared_wasm_memory_data; CHECK(shared_wasm_memory_data); return shared_wasm_memory_data; } namespace { // Implementation details of GlobalBackingStoreRegistry. struct GlobalBackingStoreRegistryImpl { GlobalBackingStoreRegistryImpl() {} base::Mutex mutex_; std::unordered_map<const void*, std::weak_ptr<BackingStore>> map_; }; base::LazyInstance<GlobalBackingStoreRegistryImpl>::type global_registry_impl_ = LAZY_INSTANCE_INITIALIZER; inline GlobalBackingStoreRegistryImpl* impl() { return global_registry_impl_.Pointer(); } } // namespace void GlobalBackingStoreRegistry::Register( std::shared_ptr<BackingStore> backing_store) { if (!backing_store || !backing_store->buffer_start()) return; if (!backing_store->free_on_destruct()) { // If the backing store buffer is managed by the embedder, // then we don't have to guarantee that there is single unique // BackingStore per buffer_start() because the destructor of // of the BackingStore will be a no-op in that case. // All WASM memory has to be registered. CHECK(!backing_store->is_wasm_memory()); return; } base::MutexGuard scope_lock(&impl()->mutex_); if (backing_store->globally_registered_) return; TRACE_BS("BS:reg bs=%p mem=%p (length=%zu, capacity=%zu)\n", backing_store.get(), backing_store->buffer_start(), backing_store->byte_length(), backing_store->byte_capacity()); std::weak_ptr<BackingStore> weak = backing_store; auto result = impl()->map_.insert({backing_store->buffer_start(), weak}); CHECK(result.second); backing_store->globally_registered_ = true; } void GlobalBackingStoreRegistry::Unregister(BackingStore* backing_store) { if (!backing_store->globally_registered_) return; DCHECK_NOT_NULL(backing_store->buffer_start()); base::MutexGuard scope_lock(&impl()->mutex_); const auto& result = impl()->map_.find(backing_store->buffer_start()); if (result != impl()->map_.end()) { DCHECK(!result->second.lock()); impl()->map_.erase(result); } backing_store->globally_registered_ = false; } std::shared_ptr<BackingStore> GlobalBackingStoreRegistry::Lookup( void* buffer_start, size_t length) { base::MutexGuard scope_lock(&impl()->mutex_); TRACE_BS("BS:lookup mem=%p (%zu bytes)\n", buffer_start, length); const auto& result = impl()->map_.find(buffer_start); if (result == impl()->map_.end()) { return std::shared_ptr<BackingStore>(); } auto backing_store = result->second.lock(); CHECK_EQ(buffer_start, backing_store->buffer_start()); if (backing_store->is_wasm_memory()) { // Grow calls to shared WebAssembly threads can be triggered from different // workers, length equality cannot be guaranteed here. CHECK_LE(length, backing_store->byte_length()); } else { CHECK_EQ(length, backing_store->byte_length()); } return backing_store; } void GlobalBackingStoreRegistry::Purge(Isolate* isolate) { // We need to keep a reference to all backing stores that are inspected // in the purging loop below. Otherwise, we might get a deadlock // if the temporary backing store reference created in the loop is // the last reference. In that case the destructor of the backing store // may try to take the &impl()->mutex_ in order to unregister itself. std::vector<std::shared_ptr<BackingStore>> prevent_destruction_under_lock; base::MutexGuard scope_lock(&impl()->mutex_); // Purge all entries in the map that refer to the given isolate. for (auto& entry : impl()->map_) { auto backing_store = entry.second.lock(); prevent_destruction_under_lock.emplace_back(backing_store); if (!backing_store) continue; // skip entries where weak ptr is null if (!backing_store->is_wasm_memory()) continue; // skip non-wasm memory if (!backing_store->is_shared()) continue; // skip non-shared memory SharedWasmMemoryData* shared_data = backing_store->get_shared_wasm_memory_data(); // Remove this isolate from the isolates list. auto& isolates = shared_data->isolates_; for (size_t i = 0; i < isolates.size(); i++) { if (isolates[i] == isolate) isolates[i] = nullptr; } } } void GlobalBackingStoreRegistry::AddSharedWasmMemoryObject( Isolate* isolate, BackingStore* backing_store, Handle<WasmMemoryObject> memory_object) { // Add to the weak array list of shared memory objects in the isolate. isolate->AddSharedWasmMemory(memory_object); // Add the isolate to the list of isolates sharing this backing store. base::MutexGuard scope_lock(&impl()->mutex_); SharedWasmMemoryData* shared_data = backing_store->get_shared_wasm_memory_data(); auto& isolates = shared_data->isolates_; int free_entry = -1; for (size_t i = 0; i < isolates.size(); i++) { if (isolates[i] == isolate) return; if (isolates[i] == nullptr) free_entry = static_cast<int>(i); } if (free_entry >= 0) isolates[free_entry] = isolate; else isolates.push_back(isolate); } void GlobalBackingStoreRegistry::BroadcastSharedWasmMemoryGrow( Isolate* isolate, std::shared_ptr<BackingStore> backing_store, size_t new_pages) { { // The global lock protects the list of isolates per backing store. base::MutexGuard scope_lock(&impl()->mutex_); SharedWasmMemoryData* shared_data = backing_store->get_shared_wasm_memory_data(); for (Isolate* other : shared_data->isolates_) { if (other && other != isolate) { other->stack_guard()->RequestGrowSharedMemory(); } } } // Update memory objects in this isolate. UpdateSharedWasmMemoryObjects(isolate); } void GlobalBackingStoreRegistry::UpdateSharedWasmMemoryObjects( Isolate* isolate) { HandleScope scope(isolate); Handle<WeakArrayList> shared_wasm_memories = isolate->factory()->shared_wasm_memories(); for (int i = 0; i < shared_wasm_memories->length(); i++) { HeapObject obj; if (!shared_wasm_memories->Get(i).GetHeapObject(&obj)) continue; Handle<WasmMemoryObject> memory_object(WasmMemoryObject::cast(obj), isolate); Handle<JSArrayBuffer> old_buffer(memory_object->array_buffer(), isolate); std::shared_ptr<BackingStore> backing_store = old_buffer->GetBackingStore(); Handle<JSArrayBuffer> new_buffer = isolate->factory()->NewJSSharedArrayBuffer(std::move(backing_store)); memory_object->update_instances(isolate, new_buffer); } } } // namespace internal } // namespace v8 #undef TRACE_BS