123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262263264265266267268269270271272273274275276277278279280281282283284285286287288289290291292293294295296297298299300301302303304305306307308309310311312313314315316317318319320321322323324325326327328329330331332333334335336337338339340341342343344345346347348349350351352353354355356357358359360361362363364365366367368369370371372373374375376377378379380381382383384385386387388389390391392393394395396397398399400401402403404405406407408409410411412413414415416417418419420421422423424425426427428429430431432433434435436437438439440441442443444445446447448449450451452453454455456457458459460461462463464465466467468469470471472473474475476477478479480481482483484485486487488489490491492493494495496497498499500501502503504505506507508509510511512513514515516517518519520521522523524525526527528529530531532533534535536537538539540541542543544545546547548549550551552553554555556557558559560561562563564565566567568569570571572573574575576577578579580581582583584585586587588589590591592593594595596597598599600601602603604605606607608609610611612613614615616617618619620621622623624625626627628629630631632633634635636637638639640641642643644645646647648649650651652653654655656657658659660661662663664665666667668669670671672673674675676677678679680681682683684685686687688689690691692693694695696697698699700701702703704705706707708709710711712713714715716717718719720721722723724725726727728729730731732733734735736737738739740741742743744745746747748749750751752753754755756757758759760761762763764765766767768769770771772773774775776777778779780781782783784785786787788789790791792793794795796797798799800801802803804805806807808809810811812813814815816817818819820821822823824825826827828829830831832833834835836837838839840841842843844845846847848849850851852853854855856857858859860861862863864865866867868869870871872873874875876877878879880881882883884885886887888889890891892893894895896897898899900901902903904905906907908909910911912913914915916917918919920921922923924925926927928929930931932933934935936937938939940941942943944945946947948949950951952953954955956957958959960961962963964965966967968969970971972973974975976977978979980981982983984985986987988989990991992993994995996997998999100010011002100310041005100610071008100910101011101210131014101510161017101810191020102110221023102410251026102710281029103010311032103310341035103610371038103910401041104210431044104510461047104810491050105110521053105410551056105710581059106010611062106310641065106610671068106910701071107210731074107510761077107810791080108110821083108410851086108710881089109010911092 |
- // Copyright 2013 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.
- #ifndef V8_V8_PLATFORM_H_
- #define V8_V8_PLATFORM_H_
- #include <stddef.h>
- #include <stdint.h>
- #include <stdlib.h> // For abort.
- #include <memory>
- #include <string>
- #include "v8config.h" // NOLINT(build/include_directory)
- namespace v8 {
- class Isolate;
- // Valid priorities supported by the task scheduling infrastructure.
- enum class TaskPriority : uint8_t {
- /**
- * Best effort tasks are not critical for performance of the application. The
- * platform implementation should preempt such tasks if higher priority tasks
- * arrive.
- */
- kBestEffort,
- /**
- * User visible tasks are long running background tasks that will
- * improve performance and memory usage of the application upon completion.
- * Example: background compilation and garbage collection.
- */
- kUserVisible,
- /**
- * User blocking tasks are highest priority tasks that block the execution
- * thread (e.g. major garbage collection). They must be finished as soon as
- * possible.
- */
- kUserBlocking,
- };
- /**
- * A Task represents a unit of work.
- */
- class Task {
- public:
- virtual ~Task() = default;
- virtual void Run() = 0;
- };
- /**
- * An IdleTask represents a unit of work to be performed in idle time.
- * The Run method is invoked with an argument that specifies the deadline in
- * seconds returned by MonotonicallyIncreasingTime().
- * The idle task is expected to complete by this deadline.
- */
- class IdleTask {
- public:
- virtual ~IdleTask() = default;
- virtual void Run(double deadline_in_seconds) = 0;
- };
- /**
- * A TaskRunner allows scheduling of tasks. The TaskRunner may still be used to
- * post tasks after the isolate gets destructed, but these tasks may not get
- * executed anymore. All tasks posted to a given TaskRunner will be invoked in
- * sequence. Tasks can be posted from any thread.
- */
- class TaskRunner {
- public:
- /**
- * Schedules a task to be invoked by this TaskRunner. The TaskRunner
- * implementation takes ownership of |task|.
- */
- virtual void PostTask(std::unique_ptr<Task> task) = 0;
- /**
- * Schedules a task to be invoked by this TaskRunner. The TaskRunner
- * implementation takes ownership of |task|. The |task| cannot be nested
- * within other task executions.
- *
- * Tasks which shouldn't be interleaved with JS execution must be posted with
- * |PostNonNestableTask| or |PostNonNestableDelayedTask|. This is because the
- * embedder may process tasks in a callback which is called during JS
- * execution.
- *
- * In particular, tasks which execute JS must be non-nestable, since JS
- * execution is not allowed to nest.
- *
- * Requires that |TaskRunner::NonNestableTasksEnabled()| is true.
- */
- virtual void PostNonNestableTask(std::unique_ptr<Task> task) {}
- /**
- * Schedules a task to be invoked by this TaskRunner. The task is scheduled
- * after the given number of seconds |delay_in_seconds|. The TaskRunner
- * implementation takes ownership of |task|.
- */
- virtual void PostDelayedTask(std::unique_ptr<Task> task,
- double delay_in_seconds) = 0;
- /**
- * Schedules a task to be invoked by this TaskRunner. The task is scheduled
- * after the given number of seconds |delay_in_seconds|. The TaskRunner
- * implementation takes ownership of |task|. The |task| cannot be nested
- * within other task executions.
- *
- * Tasks which shouldn't be interleaved with JS execution must be posted with
- * |PostNonNestableTask| or |PostNonNestableDelayedTask|. This is because the
- * embedder may process tasks in a callback which is called during JS
- * execution.
- *
- * In particular, tasks which execute JS must be non-nestable, since JS
- * execution is not allowed to nest.
- *
- * Requires that |TaskRunner::NonNestableDelayedTasksEnabled()| is true.
- */
- virtual void PostNonNestableDelayedTask(std::unique_ptr<Task> task,
- double delay_in_seconds) {}
- /**
- * Schedules an idle task to be invoked by this TaskRunner. The task is
- * scheduled when the embedder is idle. Requires that
- * |TaskRunner::IdleTasksEnabled()| is true. Idle tasks may be reordered
- * relative to other task types and may be starved for an arbitrarily long
- * time if no idle time is available. The TaskRunner implementation takes
- * ownership of |task|.
- */
- virtual void PostIdleTask(std::unique_ptr<IdleTask> task) = 0;
- /**
- * Returns true if idle tasks are enabled for this TaskRunner.
- */
- virtual bool IdleTasksEnabled() = 0;
- /**
- * Returns true if non-nestable tasks are enabled for this TaskRunner.
- */
- virtual bool NonNestableTasksEnabled() const { return false; }
- /**
- * Returns true if non-nestable delayed tasks are enabled for this TaskRunner.
- */
- virtual bool NonNestableDelayedTasksEnabled() const { return false; }
- TaskRunner() = default;
- virtual ~TaskRunner() = default;
- TaskRunner(const TaskRunner&) = delete;
- TaskRunner& operator=(const TaskRunner&) = delete;
- };
- /**
- * Delegate that's passed to Job's worker task, providing an entry point to
- * communicate with the scheduler.
- */
- class JobDelegate {
- public:
- /**
- * Returns true if this thread should return from the worker task on the
- * current thread ASAP. Workers should periodically invoke ShouldYield (or
- * YieldIfNeeded()) as often as is reasonable.
- */
- virtual bool ShouldYield() = 0;
- /**
- * Notifies the scheduler that max concurrency was increased, and the number
- * of worker should be adjusted accordingly. See Platform::PostJob() for more
- * details.
- */
- virtual void NotifyConcurrencyIncrease() = 0;
- /**
- * Returns a task_id unique among threads currently running this job, such
- * that GetTaskId() < worker count. To achieve this, the same task_id may be
- * reused by a different thread after a worker_task returns.
- */
- virtual uint8_t GetTaskId() = 0;
- /**
- * Returns true if the current task is called from the thread currently
- * running JobHandle::Join().
- */
- virtual bool IsJoiningThread() const = 0;
- };
- /**
- * Handle returned when posting a Job. Provides methods to control execution of
- * the posted Job.
- */
- class JobHandle {
- public:
- virtual ~JobHandle() = default;
- /**
- * Notifies the scheduler that max concurrency was increased, and the number
- * of worker should be adjusted accordingly. See Platform::PostJob() for more
- * details.
- */
- virtual void NotifyConcurrencyIncrease() = 0;
- /**
- * Contributes to the job on this thread. Doesn't return until all tasks have
- * completed and max concurrency becomes 0. When Join() is called and max
- * concurrency reaches 0, it should not increase again. This also promotes
- * this Job's priority to be at least as high as the calling thread's
- * priority.
- */
- virtual void Join() = 0;
- /**
- * Forces all existing workers to yield ASAP. Waits until they have all
- * returned from the Job's callback before returning.
- */
- virtual void Cancel() = 0;
- /*
- * Forces all existing workers to yield ASAP but doesn’t wait for them.
- * Warning, this is dangerous if the Job's callback is bound to or has access
- * to state which may be deleted after this call.
- */
- virtual void CancelAndDetach() = 0;
- /**
- * Returns true if there's any work pending or any worker running.
- */
- virtual bool IsActive() = 0;
- /**
- * Returns true if associated with a Job and other methods may be called.
- * Returns false after Join() or Cancel() was called. This may return true
- * even if no workers are running and IsCompleted() returns true
- */
- virtual bool IsValid() = 0;
- /**
- * Returns true if job priority can be changed.
- */
- virtual bool UpdatePriorityEnabled() const { return false; }
- /**
- * Update this Job's priority.
- */
- virtual void UpdatePriority(TaskPriority new_priority) {}
- };
- /**
- * A JobTask represents work to run in parallel from Platform::PostJob().
- */
- class JobTask {
- public:
- virtual ~JobTask() = default;
- virtual void Run(JobDelegate* delegate) = 0;
- /**
- * Controls the maximum number of threads calling Run() concurrently, given
- * the number of threads currently assigned to this job and executing Run().
- * Run() is only invoked if the number of threads previously running Run() was
- * less than the value returned. Since GetMaxConcurrency() is a leaf function,
- * it must not call back any JobHandle methods.
- */
- virtual size_t GetMaxConcurrency(size_t worker_count) const = 0;
- };
- /**
- * The interface represents complex arguments to trace events.
- */
- class ConvertableToTraceFormat {
- public:
- virtual ~ConvertableToTraceFormat() = default;
- /**
- * Append the class info to the provided |out| string. The appended
- * data must be a valid JSON object. Strings must be properly quoted, and
- * escaped. There is no processing applied to the content after it is
- * appended.
- */
- virtual void AppendAsTraceFormat(std::string* out) const = 0;
- };
- /**
- * V8 Tracing controller.
- *
- * Can be implemented by an embedder to record trace events from V8.
- */
- class TracingController {
- public:
- virtual ~TracingController() = default;
- // In Perfetto mode, trace events are written using Perfetto's Track Event
- // API directly without going through the embedder. However, it is still
- // possible to observe tracing being enabled and disabled.
- #if !defined(V8_USE_PERFETTO)
- /**
- * Called by TRACE_EVENT* macros, don't call this directly.
- * The name parameter is a category group for example:
- * TRACE_EVENT0("v8,parse", "V8.Parse")
- * The pointer returned points to a value with zero or more of the bits
- * defined in CategoryGroupEnabledFlags.
- **/
- virtual const uint8_t* GetCategoryGroupEnabled(const char* name) {
- static uint8_t no = 0;
- return &no;
- }
- /**
- * Adds a trace event to the platform tracing system. These function calls are
- * usually the result of a TRACE_* macro from trace_event_common.h when
- * tracing and the category of the particular trace are enabled. It is not
- * advisable to call these functions on their own; they are really only meant
- * to be used by the trace macros. The returned handle can be used by
- * UpdateTraceEventDuration to update the duration of COMPLETE events.
- */
- virtual uint64_t AddTraceEvent(
- char phase, const uint8_t* category_enabled_flag, const char* name,
- const char* scope, uint64_t id, uint64_t bind_id, int32_t num_args,
- const char** arg_names, const uint8_t* arg_types,
- const uint64_t* arg_values,
- std::unique_ptr<ConvertableToTraceFormat>* arg_convertables,
- unsigned int flags) {
- return 0;
- }
- virtual uint64_t AddTraceEventWithTimestamp(
- char phase, const uint8_t* category_enabled_flag, const char* name,
- const char* scope, uint64_t id, uint64_t bind_id, int32_t num_args,
- const char** arg_names, const uint8_t* arg_types,
- const uint64_t* arg_values,
- std::unique_ptr<ConvertableToTraceFormat>* arg_convertables,
- unsigned int flags, int64_t timestamp) {
- return 0;
- }
- /**
- * Sets the duration field of a COMPLETE trace event. It must be called with
- * the handle returned from AddTraceEvent().
- **/
- virtual void UpdateTraceEventDuration(const uint8_t* category_enabled_flag,
- const char* name, uint64_t handle) {}
- #endif // !defined(V8_USE_PERFETTO)
- class TraceStateObserver {
- public:
- virtual ~TraceStateObserver() = default;
- virtual void OnTraceEnabled() = 0;
- virtual void OnTraceDisabled() = 0;
- };
- /** Adds tracing state change observer. */
- virtual void AddTraceStateObserver(TraceStateObserver*) {}
- /** Removes tracing state change observer. */
- virtual void RemoveTraceStateObserver(TraceStateObserver*) {}
- };
- /**
- * A V8 memory page allocator.
- *
- * Can be implemented by an embedder to manage large host OS allocations.
- */
- class PageAllocator {
- public:
- virtual ~PageAllocator() = default;
- /**
- * Gets the page granularity for AllocatePages and FreePages. Addresses and
- * lengths for those calls should be multiples of AllocatePageSize().
- */
- virtual size_t AllocatePageSize() = 0;
- /**
- * Gets the page granularity for SetPermissions and ReleasePages. Addresses
- * and lengths for those calls should be multiples of CommitPageSize().
- */
- virtual size_t CommitPageSize() = 0;
- /**
- * Sets the random seed so that GetRandomMmapAddr() will generate repeatable
- * sequences of random mmap addresses.
- */
- virtual void SetRandomMmapSeed(int64_t seed) = 0;
- /**
- * Returns a randomized address, suitable for memory allocation under ASLR.
- * The address will be aligned to AllocatePageSize.
- */
- virtual void* GetRandomMmapAddr() = 0;
- /**
- * Memory permissions.
- */
- enum Permission {
- kNoAccess,
- kRead,
- kReadWrite,
- kReadWriteExecute,
- kReadExecute,
- // Set this when reserving memory that will later require kReadWriteExecute
- // permissions. The resulting behavior is platform-specific, currently
- // this is used to set the MAP_JIT flag on Apple Silicon.
- // TODO(jkummerow): Remove this when Wasm has a platform-independent
- // w^x implementation.
- // TODO(saelo): Remove this once all JIT pages are allocated through the
- // VirtualAddressSpace API.
- kNoAccessWillJitLater
- };
- /**
- * Allocates memory in range with the given alignment and permission.
- */
- virtual void* AllocatePages(void* address, size_t length, size_t alignment,
- Permission permissions) = 0;
- /**
- * Frees memory in a range that was allocated by a call to AllocatePages.
- */
- virtual bool FreePages(void* address, size_t length) = 0;
- /**
- * Releases memory in a range that was allocated by a call to AllocatePages.
- */
- virtual bool ReleasePages(void* address, size_t length,
- size_t new_length) = 0;
- /**
- * Sets permissions on pages in an allocated range.
- */
- virtual bool SetPermissions(void* address, size_t length,
- Permission permissions) = 0;
- /**
- * Frees memory in the given [address, address + size) range. address and size
- * should be operating system page-aligned. The next write to this
- * memory area brings the memory transparently back. This should be treated as
- * a hint to the OS that the pages are no longer needed. It does not guarantee
- * that the pages will be discarded immediately or at all.
- */
- virtual bool DiscardSystemPages(void* address, size_t size) { return true; }
- /**
- * Decommits any wired memory pages in the given range, allowing the OS to
- * reclaim them, and marks the region as inacessible (kNoAccess). The address
- * range stays reserved and can be accessed again later by changing its
- * permissions. However, in that case the memory content is guaranteed to be
- * zero-initialized again. The memory must have been previously allocated by a
- * call to AllocatePages. Returns true on success, false otherwise.
- */
- virtual bool DecommitPages(void* address, size_t size) = 0;
- /**
- * INTERNAL ONLY: This interface has not been stabilised and may change
- * without notice from one release to another without being deprecated first.
- */
- class SharedMemoryMapping {
- public:
- // Implementations are expected to free the shared memory mapping in the
- // destructor.
- virtual ~SharedMemoryMapping() = default;
- virtual void* GetMemory() const = 0;
- };
- /**
- * INTERNAL ONLY: This interface has not been stabilised and may change
- * without notice from one release to another without being deprecated first.
- */
- class SharedMemory {
- public:
- // Implementations are expected to free the shared memory in the destructor.
- virtual ~SharedMemory() = default;
- virtual std::unique_ptr<SharedMemoryMapping> RemapTo(
- void* new_address) const = 0;
- virtual void* GetMemory() const = 0;
- virtual size_t GetSize() const = 0;
- };
- /**
- * INTERNAL ONLY: This interface has not been stabilised and may change
- * without notice from one release to another without being deprecated first.
- *
- * Reserve pages at a fixed address returning whether the reservation is
- * possible. The reserved memory is detached from the PageAllocator and so
- * should not be freed by it. It's intended for use with
- * SharedMemory::RemapTo, where ~SharedMemoryMapping would free the memory.
- */
- virtual bool ReserveForSharedMemoryMapping(void* address, size_t size) {
- return false;
- }
- /**
- * INTERNAL ONLY: This interface has not been stabilised and may change
- * without notice from one release to another without being deprecated first.
- *
- * Allocates shared memory pages. Not all PageAllocators need support this and
- * so this method need not be overridden.
- * Allocates a new read-only shared memory region of size |length| and copies
- * the memory at |original_address| into it.
- */
- virtual std::unique_ptr<SharedMemory> AllocateSharedPages(
- size_t length, const void* original_address) {
- return {};
- }
- /**
- * INTERNAL ONLY: This interface has not been stabilised and may change
- * without notice from one release to another without being deprecated first.
- *
- * If not overridden and changed to return true, V8 will not attempt to call
- * AllocateSharedPages or RemapSharedPages. If overridden, AllocateSharedPages
- * and RemapSharedPages must also be overridden.
- */
- virtual bool CanAllocateSharedPages() { return false; }
- };
- // Opaque type representing a handle to a shared memory region.
- using PlatformSharedMemoryHandle = intptr_t;
- static constexpr PlatformSharedMemoryHandle kInvalidSharedMemoryHandle = -1;
- // Conversion routines from the platform-dependent shared memory identifiers
- // into the opaque PlatformSharedMemoryHandle type. These use the underlying
- // types (e.g. unsigned int) instead of the typedef'd ones (e.g. mach_port_t)
- // to avoid pulling in large OS header files into this header file. Instead,
- // the users of these routines are expected to include the respecitve OS
- // headers in addition to this one.
- #if V8_OS_MACOS
- // Convert between a shared memory handle and a mach_port_t referencing a memory
- // entry object.
- inline PlatformSharedMemoryHandle SharedMemoryHandleFromMachMemoryEntry(
- unsigned int port) {
- return static_cast<PlatformSharedMemoryHandle>(port);
- }
- inline unsigned int MachMemoryEntryFromSharedMemoryHandle(
- PlatformSharedMemoryHandle handle) {
- return static_cast<unsigned int>(handle);
- }
- #elif V8_OS_FUCHSIA
- // Convert between a shared memory handle and a zx_handle_t to a VMO.
- inline PlatformSharedMemoryHandle SharedMemoryHandleFromVMO(uint32_t handle) {
- return static_cast<PlatformSharedMemoryHandle>(handle);
- }
- inline uint32_t VMOFromSharedMemoryHandle(PlatformSharedMemoryHandle handle) {
- return static_cast<uint32_t>(handle);
- }
- #elif V8_OS_WIN
- // Convert between a shared memory handle and a Windows HANDLE to a file mapping
- // object.
- inline PlatformSharedMemoryHandle SharedMemoryHandleFromFileMapping(
- void* handle) {
- return reinterpret_cast<PlatformSharedMemoryHandle>(handle);
- }
- inline void* FileMappingFromSharedMemoryHandle(
- PlatformSharedMemoryHandle handle) {
- return reinterpret_cast<void*>(handle);
- }
- #else
- // Convert between a shared memory handle and a file descriptor.
- inline PlatformSharedMemoryHandle SharedMemoryHandleFromFileDescriptor(int fd) {
- return static_cast<PlatformSharedMemoryHandle>(fd);
- }
- inline int FileDescriptorFromSharedMemoryHandle(
- PlatformSharedMemoryHandle handle) {
- return static_cast<int>(handle);
- }
- #endif
- /**
- * Possible permissions for memory pages.
- */
- enum class PagePermissions {
- kNoAccess,
- kRead,
- kReadWrite,
- kReadWriteExecute,
- kReadExecute,
- };
- /**
- * Class to manage a virtual memory address space.
- *
- * This class represents a contiguous region of virtual address space in which
- * sub-spaces and (private or shared) memory pages can be allocated, freed, and
- * modified. This interface is meant to eventually replace the PageAllocator
- * interface, and can be used as an alternative in the meantime.
- *
- * This API is not yet stable and may change without notice!
- */
- class VirtualAddressSpace {
- public:
- using Address = uintptr_t;
- VirtualAddressSpace(size_t page_size, size_t allocation_granularity,
- Address base, size_t size,
- PagePermissions max_page_permissions)
- : page_size_(page_size),
- allocation_granularity_(allocation_granularity),
- base_(base),
- size_(size),
- max_page_permissions_(max_page_permissions) {}
- virtual ~VirtualAddressSpace() = default;
- /**
- * The page size used inside this space. Guaranteed to be a power of two.
- * Used as granularity for all page-related operations except for allocation,
- * which use the allocation_granularity(), see below.
- *
- * \returns the page size in bytes.
- */
- size_t page_size() const { return page_size_; }
- /**
- * The granularity of page allocations and, by extension, of subspace
- * allocations. This is guaranteed to be a power of two and a multiple of the
- * page_size(). In practice, this is equal to the page size on most OSes, but
- * on Windows it is usually 64KB, while the page size is 4KB.
- *
- * \returns the allocation granularity in bytes.
- */
- size_t allocation_granularity() const { return allocation_granularity_; }
- /**
- * The base address of the address space managed by this instance.
- *
- * \returns the base address of this address space.
- */
- Address base() const { return base_; }
- /**
- * The size of the address space managed by this instance.
- *
- * \returns the size of this address space in bytes.
- */
- size_t size() const { return size_; }
- /**
- * The maximum page permissions that pages allocated inside this space can
- * obtain.
- *
- * \returns the maximum page permissions.
- */
- PagePermissions max_page_permissions() const { return max_page_permissions_; }
- /**
- * Sets the random seed so that GetRandomPageAddress() will generate
- * repeatable sequences of random addresses.
- *
- * \param The seed for the PRNG.
- */
- virtual void SetRandomSeed(int64_t seed) = 0;
- /**
- * Returns a random address inside this address space, suitable for page
- * allocations hints.
- *
- * \returns a random address aligned to allocation_granularity().
- */
- virtual Address RandomPageAddress() = 0;
- /**
- * Allocates private memory pages with the given alignment and permissions.
- *
- * \param hint If nonzero, the allocation is attempted to be placed at the
- * given address first. If that fails, the allocation is attempted to be
- * placed elsewhere, possibly nearby, but that is not guaranteed. Specifying
- * zero for the hint always causes this function to choose a random address.
- * The hint, if specified, must be aligned to the specified alignment.
- *
- * \param size The size of the allocation in bytes. Must be a multiple of the
- * allocation_granularity().
- *
- * \param alignment The alignment of the allocation in bytes. Must be a
- * multiple of the allocation_granularity() and should be a power of two.
- *
- * \param permissions The page permissions of the newly allocated pages.
- *
- * \returns the start address of the allocated pages on success, zero on
- * failure.
- */
- static constexpr Address kNoHint = 0;
- virtual V8_WARN_UNUSED_RESULT Address
- AllocatePages(Address hint, size_t size, size_t alignment,
- PagePermissions permissions) = 0;
- /**
- * Frees previously allocated pages.
- *
- * This function will terminate the process on failure as this implies a bug
- * in the client. As such, there is no return value.
- *
- * \param address The start address of the pages to free. This address must
- * have been obtained through a call to AllocatePages.
- *
- * \param size The size in bytes of the region to free. This must match the
- * size passed to AllocatePages when the pages were allocated.
- */
- virtual void FreePages(Address address, size_t size) = 0;
- /**
- * Sets permissions of all allocated pages in the given range.
- *
- * \param address The start address of the range. Must be aligned to
- * page_size().
- *
- * \param size The size in bytes of the range. Must be a multiple
- * of page_size().
- *
- * \param permissions The new permissions for the range.
- *
- * \returns true on success, false otherwise.
- */
- virtual V8_WARN_UNUSED_RESULT bool SetPagePermissions(
- Address address, size_t size, PagePermissions permissions) = 0;
- /**
- * Creates a guard region at the specified address.
- *
- * Guard regions are guaranteed to cause a fault when accessed and generally
- * do not count towards any memory consumption limits. Further, allocating
- * guard regions can usually not fail in subspaces if the region does not
- * overlap with another region, subspace, or page allocation.
- *
- * \param address The start address of the guard region. Must be aligned to
- * the allocation_granularity().
- *
- * \param size The size of the guard region in bytes. Must be a multiple of
- * the allocation_granularity().
- *
- * \returns true on success, false otherwise.
- */
- virtual V8_WARN_UNUSED_RESULT bool AllocateGuardRegion(Address address,
- size_t size) = 0;
- /**
- * Frees an existing guard region.
- *
- * This function will terminate the process on failure as this implies a bug
- * in the client. As such, there is no return value.
- *
- * \param address The start address of the guard region to free. This address
- * must have previously been used as address parameter in a successful
- * invocation of AllocateGuardRegion.
- *
- * \param size The size in bytes of the guard region to free. This must match
- * the size passed to AllocateGuardRegion when the region was created.
- */
- virtual void FreeGuardRegion(Address address, size_t size) = 0;
- /**
- * Allocates shared memory pages with the given permissions.
- *
- * \param hint Placement hint. See AllocatePages.
- *
- * \param size The size of the allocation in bytes. Must be a multiple of the
- * allocation_granularity().
- *
- * \param permissions The page permissions of the newly allocated pages.
- *
- * \param handle A platform-specific handle to a shared memory object. See
- * the SharedMemoryHandleFromX routines above for ways to obtain these.
- *
- * \param offset The offset in the shared memory object at which the mapping
- * should start. Must be a multiple of the allocation_granularity().
- *
- * \returns the start address of the allocated pages on success, zero on
- * failure.
- */
- virtual V8_WARN_UNUSED_RESULT Address
- AllocateSharedPages(Address hint, size_t size, PagePermissions permissions,
- PlatformSharedMemoryHandle handle, uint64_t offset) = 0;
- /**
- * Frees previously allocated shared pages.
- *
- * This function will terminate the process on failure as this implies a bug
- * in the client. As such, there is no return value.
- *
- * \param address The start address of the pages to free. This address must
- * have been obtained through a call to AllocateSharedPages.
- *
- * \param size The size in bytes of the region to free. This must match the
- * size passed to AllocateSharedPages when the pages were allocated.
- */
- virtual void FreeSharedPages(Address address, size_t size) = 0;
- /**
- * Whether this instance can allocate subspaces or not.
- *
- * \returns true if subspaces can be allocated, false if not.
- */
- virtual bool CanAllocateSubspaces() = 0;
- /*
- * Allocate a subspace.
- *
- * The address space of a subspace stays reserved in the parent space for the
- * lifetime of the subspace. As such, it is guaranteed that page allocations
- * on the parent space cannot end up inside a subspace.
- *
- * \param hint Hints where the subspace should be allocated. See
- * AllocatePages() for more details.
- *
- * \param size The size in bytes of the subspace. Must be a multiple of the
- * allocation_granularity().
- *
- * \param alignment The alignment of the subspace in bytes. Must be a multiple
- * of the allocation_granularity() and should be a power of two.
- *
- * \param max_page_permissions The maximum permissions that pages allocated in
- * the subspace can obtain.
- *
- * \returns a new subspace or nullptr on failure.
- */
- virtual std::unique_ptr<VirtualAddressSpace> AllocateSubspace(
- Address hint, size_t size, size_t alignment,
- PagePermissions max_page_permissions) = 0;
- //
- // TODO(v8) maybe refactor the methods below before stabilizing the API. For
- // example by combining them into some form of page operation method that
- // takes a command enum as parameter.
- //
- /**
- * Frees memory in the given [address, address + size) range. address and
- * size should be aligned to the page_size(). The next write to this memory
- * area brings the memory transparently back. This should be treated as a
- * hint to the OS that the pages are no longer needed. It does not guarantee
- * that the pages will be discarded immediately or at all.
- *
- * \returns true on success, false otherwise. Since this method is only a
- * hint, a successful invocation does not imply that pages have been removed.
- */
- virtual V8_WARN_UNUSED_RESULT bool DiscardSystemPages(Address address,
- size_t size) {
- return true;
- }
- /**
- * Decommits any wired memory pages in the given range, allowing the OS to
- * reclaim them, and marks the region as inacessible (kNoAccess). The address
- * range stays reserved and can be accessed again later by changing its
- * permissions. However, in that case the memory content is guaranteed to be
- * zero-initialized again. The memory must have been previously allocated by a
- * call to AllocatePages.
- *
- * \returns true on success, false otherwise.
- */
- virtual V8_WARN_UNUSED_RESULT bool DecommitPages(Address address,
- size_t size) = 0;
- private:
- const size_t page_size_;
- const size_t allocation_granularity_;
- const Address base_;
- const size_t size_;
- const PagePermissions max_page_permissions_;
- };
- /**
- * V8 Allocator used for allocating zone backings.
- */
- class ZoneBackingAllocator {
- public:
- using MallocFn = void* (*)(size_t);
- using FreeFn = void (*)(void*);
- virtual MallocFn GetMallocFn() const { return ::malloc; }
- virtual FreeFn GetFreeFn() const { return ::free; }
- };
- /**
- * Observer used by V8 to notify the embedder about entering/leaving sections
- * with high throughput of malloc/free operations.
- */
- class HighAllocationThroughputObserver {
- public:
- virtual void EnterSection() {}
- virtual void LeaveSection() {}
- };
- /**
- * V8 Platform abstraction layer.
- *
- * The embedder has to provide an implementation of this interface before
- * initializing the rest of V8.
- */
- class Platform {
- public:
- virtual ~Platform() = default;
- /**
- * Allows the embedder to manage memory page allocations.
- */
- virtual PageAllocator* GetPageAllocator() {
- // TODO(bbudge) Make this abstract after all embedders implement this.
- return nullptr;
- }
- /**
- * Allows the embedder to specify a custom allocator used for zones.
- */
- virtual ZoneBackingAllocator* GetZoneBackingAllocator() {
- static ZoneBackingAllocator default_allocator;
- return &default_allocator;
- }
- /**
- * Enables the embedder to respond in cases where V8 can't allocate large
- * blocks of memory. V8 retries the failed allocation once after calling this
- * method. On success, execution continues; otherwise V8 exits with a fatal
- * error.
- * Embedder overrides of this function must NOT call back into V8.
- */
- virtual void OnCriticalMemoryPressure() {
- // TODO(bbudge) Remove this when embedders override the following method.
- // See crbug.com/634547.
- }
- /**
- * Enables the embedder to respond in cases where V8 can't allocate large
- * memory regions. The |length| parameter is the amount of memory needed.
- * Returns true if memory is now available. Returns false if no memory could
- * be made available. V8 will retry allocations until this method returns
- * false.
- *
- * Embedder overrides of this function must NOT call back into V8.
- */
- virtual bool OnCriticalMemoryPressure(size_t length) { return false; }
- /**
- * Gets the number of worker threads used by
- * Call(BlockingTask)OnWorkerThread(). This can be used to estimate the number
- * of tasks a work package should be split into. A return value of 0 means
- * that there are no worker threads available. Note that a value of 0 won't
- * prohibit V8 from posting tasks using |CallOnWorkerThread|.
- */
- virtual int NumberOfWorkerThreads() = 0;
- /**
- * Returns a TaskRunner which can be used to post a task on the foreground.
- * The TaskRunner's NonNestableTasksEnabled() must be true. This function
- * should only be called from a foreground thread.
- */
- virtual std::shared_ptr<v8::TaskRunner> GetForegroundTaskRunner(
- Isolate* isolate) = 0;
- /**
- * Schedules a task to be invoked on a worker thread.
- */
- virtual void CallOnWorkerThread(std::unique_ptr<Task> task) = 0;
- /**
- * Schedules a task that blocks the main thread to be invoked with
- * high-priority on a worker thread.
- */
- virtual void CallBlockingTaskOnWorkerThread(std::unique_ptr<Task> task) {
- // Embedders may optionally override this to process these tasks in a high
- // priority pool.
- CallOnWorkerThread(std::move(task));
- }
- /**
- * Schedules a task to be invoked with low-priority on a worker thread.
- */
- virtual void CallLowPriorityTaskOnWorkerThread(std::unique_ptr<Task> task) {
- // Embedders may optionally override this to process these tasks in a low
- // priority pool.
- CallOnWorkerThread(std::move(task));
- }
- /**
- * Schedules a task to be invoked on a worker thread after |delay_in_seconds|
- * expires.
- */
- virtual void CallDelayedOnWorkerThread(std::unique_ptr<Task> task,
- double delay_in_seconds) = 0;
- /**
- * Returns true if idle tasks are enabled for the given |isolate|.
- */
- virtual bool IdleTasksEnabled(Isolate* isolate) { return false; }
- /**
- * Posts |job_task| to run in parallel. Returns a JobHandle associated with
- * the Job, which can be joined or canceled.
- * This avoids degenerate cases:
- * - Calling CallOnWorkerThread() for each work item, causing significant
- * overhead.
- * - Fixed number of CallOnWorkerThread() calls that split the work and might
- * run for a long time. This is problematic when many components post
- * "num cores" tasks and all expect to use all the cores. In these cases,
- * the scheduler lacks context to be fair to multiple same-priority requests
- * and/or ability to request lower priority work to yield when high priority
- * work comes in.
- * A canonical implementation of |job_task| looks like:
- * class MyJobTask : public JobTask {
- * public:
- * MyJobTask(...) : worker_queue_(...) {}
- * // JobTask:
- * void Run(JobDelegate* delegate) override {
- * while (!delegate->ShouldYield()) {
- * // Smallest unit of work.
- * auto work_item = worker_queue_.TakeWorkItem(); // Thread safe.
- * if (!work_item) return;
- * ProcessWork(work_item);
- * }
- * }
- *
- * size_t GetMaxConcurrency() const override {
- * return worker_queue_.GetSize(); // Thread safe.
- * }
- * };
- * auto handle = PostJob(TaskPriority::kUserVisible,
- * std::make_unique<MyJobTask>(...));
- * handle->Join();
- *
- * PostJob() and methods of the returned JobHandle/JobDelegate, must never be
- * called while holding a lock that could be acquired by JobTask::Run or
- * JobTask::GetMaxConcurrency -- that could result in a deadlock. This is
- * because [1] JobTask::GetMaxConcurrency may be invoked while holding
- * internal lock (A), hence JobTask::GetMaxConcurrency can only use a lock (B)
- * if that lock is *never* held while calling back into JobHandle from any
- * thread (A=>B/B=>A deadlock) and [2] JobTask::Run or
- * JobTask::GetMaxConcurrency may be invoked synchronously from JobHandle
- * (B=>JobHandle::foo=>B deadlock).
- *
- * A sufficient PostJob() implementation that uses the default Job provided in
- * libplatform looks like:
- * std::unique_ptr<JobHandle> PostJob(
- * TaskPriority priority, std::unique_ptr<JobTask> job_task) override {
- * return v8::platform::NewDefaultJobHandle(
- * this, priority, std::move(job_task), NumberOfWorkerThreads());
- * }
- */
- virtual std::unique_ptr<JobHandle> PostJob(
- TaskPriority priority, std::unique_ptr<JobTask> job_task) = 0;
- /**
- * Monotonically increasing time in seconds from an arbitrary fixed point in
- * the past. This function is expected to return at least
- * millisecond-precision values. For this reason,
- * it is recommended that the fixed point be no further in the past than
- * the epoch.
- **/
- virtual double MonotonicallyIncreasingTime() = 0;
- /**
- * Current wall-clock time in milliseconds since epoch.
- * This function is expected to return at least millisecond-precision values.
- */
- virtual double CurrentClockTimeMillis() = 0;
- typedef void (*StackTracePrinter)();
- /**
- * Returns a function pointer that print a stack trace of the current stack
- * on invocation. Disables printing of the stack trace if nullptr.
- */
- virtual StackTracePrinter GetStackTracePrinter() { return nullptr; }
- /**
- * Returns an instance of a v8::TracingController. This must be non-nullptr.
- */
- virtual TracingController* GetTracingController() = 0;
- /**
- * Tells the embedder to generate and upload a crashdump during an unexpected
- * but non-critical scenario.
- */
- virtual void DumpWithoutCrashing() {}
- /**
- * Allows the embedder to observe sections with high throughput allocation
- * operations.
- */
- virtual HighAllocationThroughputObserver*
- GetHighAllocationThroughputObserver() {
- static HighAllocationThroughputObserver default_observer;
- return &default_observer;
- }
- protected:
- /**
- * Default implementation of current wall-clock time in milliseconds
- * since epoch. Useful for implementing |CurrentClockTimeMillis| if
- * nothing special needed.
- */
- V8_EXPORT static double SystemClockTimeMillis();
- };
- } // namespace v8
- #endif // V8_V8_PLATFORM_H_
|