blob: cc62b71e5b63514b42e1c8adb2b9b14e98a174b5 [file] [log] [blame]
// 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 <memory>
#include <utility>
#include <vector>
#include "src/base/macros.h"
#include "src/base/optional.h"
#include "src/objects/heap-object.h"
#include "src/objects/objects.h"
#include "src/roots/roots.h"
namespace v8 {
class SharedMemoryStatistics;
namespace internal {
class BasicMemoryChunk;
class Isolate;
class Page;
class ReadOnlyArtifacts;
class ReadOnlyDeserializer;
class ReadOnlyPage;
class ReadOnlySpace;
class SharedReadOnlySpace;
// This class transparently manages read-only space, roots and cache creation
// and destruction.
class ReadOnlyHeap {
static constexpr size_t kEntriesCount =
virtual ~ReadOnlyHeap() = default;
// If necessary creates read-only heap and initializes its artifacts (if the
// deserializer is provided). Then attaches the read-only heap to the isolate.
// If the deserializer is not provided, then the read-only heap will be only
// finish initializing when initial heap object creation in the Isolate is
// completed, which is signalled by calling OnCreateHeapObjectsComplete. When
// V8_SHARED_RO_HEAP is enabled, a lock will be held until that method is
// called.
// TODO(v8:7464): Ideally we'd create this without needing a heap.
static void SetUp(Isolate* isolate, ReadOnlyDeserializer* des);
// Indicates that the isolate has been set up and all read-only space objects
// have been created and will not be written to. This should only be called if
// a deserializer was not previously provided to Setup. When V8_SHARED_RO_HEAP
// is enabled, this releases the ReadOnlyHeap creation lock.
void OnCreateHeapObjectsComplete(Isolate* isolate);
// Indicates that the current isolate no longer requires the read-only heap
// and it may be safely disposed of.
virtual void OnHeapTearDown(Heap* heap);
// If the read-only heap is shared, then populate |statistics| with its stats,
// otherwise the read-only heap stats are set to 0.
static void PopulateReadOnlySpaceStatistics(
SharedMemoryStatistics* statistics);
// Returns whether the address is within the read-only space.
V8_EXPORT_PRIVATE static bool Contains(Address address);
// Returns whether the object resides in the read-only space.
V8_EXPORT_PRIVATE static bool Contains(HeapObject object);
// Gets read-only roots from an appropriate root list: shared read-only root
// list if the shared read-only heap has been initialized or the isolate
// specific roots table.
V8_EXPORT_PRIVATE inline static ReadOnlyRoots GetReadOnlyRoots(
HeapObject object);
// Extends the read-only object cache with new zero smi and returns a
// reference to it.
Object* ExtendReadOnlyObjectCache();
// Returns a read-only cache entry at a particular index.
Object cached_read_only_object(size_t i) const;
bool read_only_object_cache_is_initialized() const;
ReadOnlySpace* read_only_space() const { return read_only_space_; }
// Returns whether the ReadOnlySpace will actually be shared taking into
// account whether shared memory is available with pointer compression.
static bool IsReadOnlySpaceShared() {
(!COMPRESS_POINTERS_BOOL || IsSharedMemoryAvailable());
virtual void InitializeIsolateRoots(Isolate* isolate) {}
virtual void InitializeFromIsolateRoots(Isolate* isolate) {}
virtual bool IsOwnedByIsolate() { return true; }
friend class ReadOnlyArtifacts;
friend class PointerCompressedReadOnlyArtifacts;
// Creates a new read-only heap and attaches it to the provided isolate. Only
// used the first time when creating a ReadOnlyHeap for sharing.
static ReadOnlyHeap* CreateInitalHeapForBootstrapping(
Isolate* isolate, std::shared_ptr<ReadOnlyArtifacts> artifacts);
// Runs the read-only deserializer and calls InitFromIsolate to complete
// read-only heap initialization.
void DeseralizeIntoIsolate(Isolate* isolate, ReadOnlyDeserializer* des);
// Initializes read-only heap from an already set-up isolate, copying
// read-only roots from the isolate. This then seals the space off from
// further writes, marks it as read-only and detaches it from the heap
// (unless sharing is disabled).
void InitFromIsolate(Isolate* isolate);
bool init_complete_ = false;
ReadOnlySpace* read_only_space_ = nullptr;
std::vector<Object> read_only_object_cache_;
// Returns whether shared memory can be allocated and then remapped to
// additional addresses.
static bool IsSharedMemoryAvailable();
explicit ReadOnlyHeap(ReadOnlySpace* ro_space) : read_only_space_(ro_space) {}
ReadOnlyHeap(ReadOnlyHeap* ro_heap, ReadOnlySpace* ro_space);
// This is used without pointer compression when there is just a single
// ReadOnlyHeap object shared between all Isolates.
class SoleReadOnlyHeap : public ReadOnlyHeap {
void InitializeIsolateRoots(Isolate* isolate) override;
void InitializeFromIsolateRoots(Isolate* isolate) override;
void OnHeapTearDown(Heap* heap) override;
bool IsOwnedByIsolate() override { return false; }
friend class ReadOnlyHeap;
explicit SoleReadOnlyHeap(ReadOnlySpace* ro_space) : ReadOnlyHeap(ro_space) {}
Address read_only_roots_[kEntriesCount];
V8_EXPORT_PRIVATE static SoleReadOnlyHeap* shared_ro_heap_;
// This class enables iterating over all read-only heap objects.
class V8_EXPORT_PRIVATE ReadOnlyHeapObjectIterator {
explicit ReadOnlyHeapObjectIterator(ReadOnlyHeap* ro_heap);
explicit ReadOnlyHeapObjectIterator(ReadOnlySpace* ro_space);
HeapObject Next();
ReadOnlySpace* const ro_space_;
std::vector<ReadOnlyPage*>::const_iterator current_page_;
Address current_addr_;
} // namespace internal
} // namespace v8