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ArrayBufferObject.cpp
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ArrayBufferObject.cpp
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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "vm/ArrayBufferObject-inl.h"
#include "vm/ArrayBufferObject.h"
#include "mozilla/Alignment.h"
#include "mozilla/Assertions.h"
#include "mozilla/Attributes.h"
#include "mozilla/CheckedInt.h"
#include "mozilla/FloatingPoint.h"
#include "mozilla/Likely.h"
#include "mozilla/Maybe.h"
#include "mozilla/PodOperations.h"
#include "mozilla/TaggedAnonymousMemory.h"
#include <algorithm>
#include <string.h>
#ifndef XP_WIN
# include <sys/mman.h>
#endif
#ifdef MOZ_VALGRIND
# include <valgrind/memcheck.h>
#endif
#include "jsapi.h"
#include "jsfriendapi.h"
#include "jsnum.h"
#include "jstypes.h"
#include "builtin/Array.h"
#include "builtin/DataViewObject.h"
#include "gc/Barrier.h"
#include "gc/Memory.h"
#include "js/ArrayBuffer.h"
#include "js/Conversions.h"
#include "js/MemoryMetrics.h"
#include "js/PropertySpec.h"
#include "js/SharedArrayBuffer.h"
#include "js/Wrapper.h"
#include "util/Windows.h"
#include "vm/GlobalObject.h"
#include "vm/Interpreter.h"
#include "vm/JSContext.h"
#include "vm/JSObject.h"
#include "vm/SharedArrayObject.h"
#include "vm/WrapperObject.h"
#include "wasm/WasmSignalHandlers.h"
#include "wasm/WasmTypes.h"
#include "gc/FreeOp-inl.h"
#include "gc/Marking-inl.h"
#include "gc/Nursery-inl.h"
#include "vm/JSAtom-inl.h"
#include "vm/NativeObject-inl.h"
#include "vm/Shape-inl.h"
using JS::ToInt32;
using mozilla::Atomic;
using mozilla::CheckedInt;
using mozilla::Maybe;
using mozilla::Nothing;
using mozilla::Some;
using mozilla::Unused;
using namespace js;
// If there are too many wasm memory buffers (typically 6GB each) live we run up
// against system resource exhaustion (address space or number of memory map
// descriptors), see bug 1068684, bug 1073934, bug 1517412, bug 1502733 for
// details. The limiting case seems to be Android on ARM64, where the
// per-process address space is limited to 4TB (39 bits) by the organization of
// the page tables. An earlier problem was Windows Vista Home 64-bit, where the
// per-process address space is limited to 8TB (40 bits).
//
// Thus we track the number of live objects, and set a limit of the number of
// live buffer objects per process. We trigger GC work when we approach the
// limit and we throw an OOM error if the per-process limit is exceeded. The
// limit (MaximumLiveMappedBuffers) is specific to architecture, OS, and OS
// configuration.
//
// Since the MaximumLiveMappedBuffers limit is not generally accounted for by
// any existing GC-trigger heuristics, we need an extra heuristic for triggering
// GCs when the caller is allocating memories rapidly without other garbage.
// Thus, once the live buffer count crosses the threshold
// StartTriggeringAtLiveBufferCount, we start triggering GCs every
// AllocatedBuffersPerTrigger allocations. Once we reach
// StartSyncFullGCAtLiveBufferCount live buffers, we perform expensive
// non-incremental full GCs as a last-ditch effort to avoid unnecessary failure.
// Once we reach MaximumLiveMappedBuffers, we perform further full GCs before
// giving up.
#if defined(JS_CODEGEN_ARM64) && defined(ANDROID)
// With 6GB mappings, the hard limit is 84 buffers. 75 cuts it close.
static const int32_t MaximumLiveMappedBuffers = 75;
#elif defined(MOZ_TSAN) || defined(MOZ_ASAN)
// ASAN and TSAN use a ton of vmem for bookkeeping leaving a lot less for the
// program so use a lower limit.
static const int32_t MaximumLiveMappedBuffers = 500;
#else
static const int32_t MaximumLiveMappedBuffers = 1000;
#endif
// StartTriggeringAtLiveBufferCount + AllocatedBuffersPerTrigger must be well
// below StartSyncFullGCAtLiveBufferCount in order to provide enough time for
// incremental GC to do its job.
#if defined(JS_CODEGEN_ARM64) && defined(ANDROID)
static const int32_t StartTriggeringAtLiveBufferCount = 15;
static const int32_t StartSyncFullGCAtLiveBufferCount =
MaximumLiveMappedBuffers - 15;
static const int32_t AllocatedBuffersPerTrigger = 15;
#else
static const int32_t StartTriggeringAtLiveBufferCount = 100;
static const int32_t StartSyncFullGCAtLiveBufferCount =
MaximumLiveMappedBuffers - 100;
static const int32_t AllocatedBuffersPerTrigger = 100;
#endif
static Atomic<int32_t, mozilla::ReleaseAcquire> liveBufferCount(0);
static Atomic<int32_t, mozilla::ReleaseAcquire> allocatedSinceLastTrigger(0);
int32_t js::LiveMappedBufferCount() { return liveBufferCount; }
void* js::MapBufferMemory(size_t mappedSize, size_t initialCommittedSize) {
MOZ_ASSERT(mappedSize % gc::SystemPageSize() == 0);
MOZ_ASSERT(initialCommittedSize % gc::SystemPageSize() == 0);
MOZ_ASSERT(initialCommittedSize <= mappedSize);
// Test >= to guard against the case where multiple extant runtimes
// race to allocate.
if (++liveBufferCount >= MaximumLiveMappedBuffers) {
if (OnLargeAllocationFailure) {
OnLargeAllocationFailure();
}
if (liveBufferCount >= MaximumLiveMappedBuffers) {
liveBufferCount--;
return nullptr;
}
}
#ifdef XP_WIN
void* data = VirtualAlloc(nullptr, mappedSize, MEM_RESERVE, PAGE_NOACCESS);
if (!data) {
liveBufferCount--;
return nullptr;
}
if (!VirtualAlloc(data, initialCommittedSize, MEM_COMMIT, PAGE_READWRITE)) {
VirtualFree(data, 0, MEM_RELEASE);
liveBufferCount--;
return nullptr;
}
#else // XP_WIN
void* data =
MozTaggedAnonymousMmap(nullptr, mappedSize, PROT_NONE,
MAP_PRIVATE | MAP_ANON, -1, 0, "wasm-reserved");
if (data == MAP_FAILED) {
liveBufferCount--;
return nullptr;
}
// Note we will waste a page on zero-sized memories here
if (mprotect(data, initialCommittedSize, PROT_READ | PROT_WRITE)) {
munmap(data, mappedSize);
liveBufferCount--;
return nullptr;
}
#endif // !XP_WIN
#if defined(MOZ_VALGRIND) && \
defined(VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE)
VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE(
(unsigned char*)data + initialCommittedSize,
mappedSize - initialCommittedSize);
#endif
return data;
}
bool js::CommitBufferMemory(void* dataEnd, uint32_t delta) {
MOZ_ASSERT(delta);
MOZ_ASSERT(delta % gc::SystemPageSize() == 0);
#ifdef XP_WIN
if (!VirtualAlloc(dataEnd, delta, MEM_COMMIT, PAGE_READWRITE)) {
return false;
}
#else // XP_WIN
if (mprotect(dataEnd, delta, PROT_READ | PROT_WRITE)) {
return false;
}
#endif // !XP_WIN
#if defined(MOZ_VALGRIND) && \
defined(VALGRIND_DISABLE_ADDR_ERROR_REPORTING_IN_RANGE)
VALGRIND_ENABLE_ADDR_ERROR_REPORTING_IN_RANGE((unsigned char*)dataEnd, delta);
#endif
return true;
}
bool js::ExtendBufferMapping(void* dataPointer, size_t mappedSize,
size_t newMappedSize) {
MOZ_ASSERT(mappedSize % gc::SystemPageSize() == 0);
MOZ_ASSERT(newMappedSize % gc::SystemPageSize() == 0);
MOZ_ASSERT(newMappedSize >= mappedSize);
#ifdef XP_WIN
void* mappedEnd = (char*)dataPointer + mappedSize;
uint32_t delta = newMappedSize - mappedSize;
if (!VirtualAlloc(mappedEnd, delta, MEM_RESERVE, PAGE_NOACCESS)) {
return false;
}
return true;
#elif defined(XP_LINUX)
// Note this will not move memory (no MREMAP_MAYMOVE specified)
if (MAP_FAILED == mremap(dataPointer, mappedSize, newMappedSize, 0)) {
return false;
}
return true;
#else
// No mechanism for remapping on MacOS and other Unices. Luckily
// shouldn't need it here as most of these are 64-bit.
return false;
#endif
}
void js::UnmapBufferMemory(void* base, size_t mappedSize) {
MOZ_ASSERT(mappedSize % gc::SystemPageSize() == 0);
#ifdef XP_WIN
VirtualFree(base, 0, MEM_RELEASE);
#else // XP_WIN
munmap(base, mappedSize);
#endif // !XP_WIN
#if defined(MOZ_VALGRIND) && \
defined(VALGRIND_ENABLE_ADDR_ERROR_REPORTING_IN_RANGE)
VALGRIND_ENABLE_ADDR_ERROR_REPORTING_IN_RANGE((unsigned char*)base,
mappedSize);
#endif
// Decrement the buffer counter at the end -- otherwise, a race condition
// could enable the creation of unlimited buffers.
liveBufferCount--;
}
/*
* ArrayBufferObject
*
* This class holds the underlying raw buffer that the TypedArrayObject classes
* access. It can be created explicitly and passed to a TypedArrayObject, or
* can be created implicitly by constructing a TypedArrayObject with a size.
*/
/*
* ArrayBufferObject (base)
*/
static const JSClassOps ArrayBufferObjectClassOps = {
nullptr, // addProperty
nullptr, // delProperty
nullptr, // enumerate
nullptr, // newEnumerate
nullptr, // resolve
nullptr, // mayResolve
ArrayBufferObject::finalize, // finalize
nullptr, // call
nullptr, // hasInstance
nullptr, // construct
nullptr, // trace
};
static const JSFunctionSpec arraybuffer_functions[] = {
JS_FN("isView", ArrayBufferObject::fun_isView, 1, 0), JS_FS_END};
static const JSPropertySpec arraybuffer_properties[] = {
JS_SELF_HOSTED_SYM_GET(species, "$ArrayBufferSpecies", 0), JS_PS_END};
static const JSFunctionSpec arraybuffer_proto_functions[] = {
JS_SELF_HOSTED_FN("slice", "ArrayBufferSlice", 2, 0), JS_FS_END};
static const JSPropertySpec arraybuffer_proto_properties[] = {
JS_PSG("byteLength", ArrayBufferObject::byteLengthGetter, 0),
JS_STRING_SYM_PS(toStringTag, "ArrayBuffer", JSPROP_READONLY), JS_PS_END};
static const ClassSpec ArrayBufferObjectClassSpec = {
GenericCreateConstructor<ArrayBufferObject::class_constructor, 1,
gc::AllocKind::FUNCTION>,
GenericCreatePrototype<ArrayBufferObject>,
arraybuffer_functions,
arraybuffer_properties,
arraybuffer_proto_functions,
arraybuffer_proto_properties};
static const ClassExtension ArrayBufferObjectClassExtension = {
ArrayBufferObject::objectMoved, // objectMovedOp
};
const JSClass ArrayBufferObject::class_ = {
"ArrayBuffer",
JSCLASS_DELAY_METADATA_BUILDER |
JSCLASS_HAS_RESERVED_SLOTS(RESERVED_SLOTS) |
JSCLASS_HAS_CACHED_PROTO(JSProto_ArrayBuffer) |
JSCLASS_BACKGROUND_FINALIZE,
&ArrayBufferObjectClassOps, &ArrayBufferObjectClassSpec,
&ArrayBufferObjectClassExtension};
const JSClass ArrayBufferObject::protoClass_ = {
"ArrayBufferPrototype", JSCLASS_HAS_CACHED_PROTO(JSProto_ArrayBuffer),
JS_NULL_CLASS_OPS, &ArrayBufferObjectClassSpec};
bool js::IsArrayBuffer(HandleValue v) {
return v.isObject() && v.toObject().is<ArrayBufferObject>();
}
bool js::IsArrayBuffer(JSObject* obj) { return obj->is<ArrayBufferObject>(); }
ArrayBufferObject& js::AsArrayBuffer(JSObject* obj) {
MOZ_ASSERT(IsArrayBuffer(obj));
return obj->as<ArrayBufferObject>();
}
bool js::IsArrayBufferMaybeShared(HandleValue v) {
return v.isObject() && v.toObject().is<ArrayBufferObjectMaybeShared>();
}
bool js::IsArrayBufferMaybeShared(JSObject* obj) {
return obj->is<ArrayBufferObjectMaybeShared>();
}
ArrayBufferObjectMaybeShared& js::AsArrayBufferMaybeShared(JSObject* obj) {
MOZ_ASSERT(IsArrayBufferMaybeShared(obj));
return obj->as<ArrayBufferObjectMaybeShared>();
}
MOZ_ALWAYS_INLINE bool ArrayBufferObject::byteLengthGetterImpl(
JSContext* cx, const CallArgs& args) {
MOZ_ASSERT(IsArrayBuffer(args.thisv()));
args.rval().setInt32(
args.thisv().toObject().as<ArrayBufferObject>().byteLength());
return true;
}
bool ArrayBufferObject::byteLengthGetter(JSContext* cx, unsigned argc,
Value* vp) {
CallArgs args = CallArgsFromVp(argc, vp);
return CallNonGenericMethod<IsArrayBuffer, byteLengthGetterImpl>(cx, args);
}
/*
* ArrayBuffer.isView(obj); ES6 (Dec 2013 draft) 24.1.3.1
*/
bool ArrayBufferObject::fun_isView(JSContext* cx, unsigned argc, Value* vp) {
CallArgs args = CallArgsFromVp(argc, vp);
args.rval().setBoolean(args.get(0).isObject() &&
JS_IsArrayBufferViewObject(&args.get(0).toObject()));
return true;
}
// ES2017 draft 24.1.2.1
bool ArrayBufferObject::class_constructor(JSContext* cx, unsigned argc,
Value* vp) {
CallArgs args = CallArgsFromVp(argc, vp);
// Step 1.
if (!ThrowIfNotConstructing(cx, args, "ArrayBuffer")) {
return false;
}
// Step 2.
uint64_t byteLength;
if (!ToIndex(cx, args.get(0), &byteLength)) {
return false;
}
// Step 3 (Inlined 24.1.1.1 AllocateArrayBuffer).
// 24.1.1.1, step 1 (Inlined 9.1.14 OrdinaryCreateFromConstructor).
RootedObject proto(cx);
if (!GetPrototypeFromBuiltinConstructor(cx, args, JSProto_ArrayBuffer,
&proto)) {
return false;
}
// 24.1.1.1, step 3 (Inlined 6.2.6.1 CreateByteDataBlock, step 2).
// Refuse to allocate too large buffers, currently limited to ~2 GiB.
if (byteLength > INT32_MAX) {
JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
JSMSG_BAD_ARRAY_LENGTH);
return false;
}
// 24.1.1.1, steps 1 and 4-6.
JSObject* bufobj = createZeroed(cx, uint32_t(byteLength), proto);
if (!bufobj) {
return false;
}
args.rval().setObject(*bufobj);
return true;
}
static uint8_t* AllocateArrayBufferContents(JSContext* cx, uint32_t nbytes) {
auto* p =
cx->pod_arena_callocCanGC<uint8_t>(js::ArrayBufferContentsArena, nbytes);
if (!p) {
ReportOutOfMemory(cx);
}
return p;
}
static uint8_t* NewCopiedBufferContents(JSContext* cx,
Handle<ArrayBufferObject*> buffer) {
uint8_t* dataCopy = AllocateArrayBufferContents(cx, buffer->byteLength());
if (dataCopy) {
if (auto count = buffer->byteLength()) {
memcpy(dataCopy, buffer->dataPointer(), count);
}
}
return dataCopy;
}
/* static */
void ArrayBufferObject::detach(JSContext* cx,
Handle<ArrayBufferObject*> buffer) {
cx->check(buffer);
MOZ_ASSERT(!buffer->isPreparedForAsmJS());
MOZ_ASSERT(!buffer->hasTypedObjectViews());
auto NoteViewBufferWasDetached = [&cx](ArrayBufferViewObject* view) {
MOZ_ASSERT(!view->isSharedMemory());
view->notifyBufferDetached();
// Notify compiled jit code that the base pointer has moved.
MarkObjectStateChange(cx, view);
};
// Update all views of the buffer to account for the buffer having been
// detached, and clear the buffer's data and list of views.
//
// Typed object buffers are not exposed and cannot be detached.
auto& innerViews = ObjectRealm::get(buffer).innerViews.get();
if (InnerViewTable::ViewVector* views =
innerViews.maybeViewsUnbarriered(buffer)) {
for (size_t i = 0; i < views->length(); i++) {
JSObject* view = (*views)[i];
NoteViewBufferWasDetached(&view->as<ArrayBufferViewObject>());
}
innerViews.removeViews(buffer);
}
if (JSObject* view = buffer->firstView()) {
NoteViewBufferWasDetached(&view->as<ArrayBufferViewObject>());
buffer->setFirstView(nullptr);
}
if (buffer->dataPointer()) {
buffer->releaseData(cx->runtime()->defaultFreeOp());
buffer->setDataPointer(BufferContents::createNoData());
}
buffer->setByteLength(0);
buffer->setIsDetached();
}
/*
* [SMDOC] WASM Linear Memory structure
*
* Wasm Raw Buf Linear Memory Structure
*
* The linear heap in Wasm is an mmaped array buffer. Several
* constants manage its lifetime:
*
* - length - the wasm-visible current length of the buffer. Accesses in the
* range [0, length] succeed. May only increase.
*
* - boundsCheckLimit - the size against which we perform bounds checks. It is
* always a constant offset smaller than mappedSize. Currently that constant
* offset is 64k (wasm::GuardSize).
*
* - maxSize - the optional declared limit on how much length can grow.
*
* - mappedSize - the actual mmaped size. Access in the range
* [0, mappedSize] will either succeed, or be handled by the wasm signal
* handlers.
*
* The below diagram shows the layout of the wasm heap. The wasm-visible
* portion of the heap starts at 0. There is one extra page prior to the
* start of the wasm heap which contains the WasmArrayRawBuffer struct at
* its end (i.e. right before the start of the WASM heap).
*
* WasmArrayRawBuffer
* \ ArrayBufferObject::dataPointer()
* \ /
* \ |
* ______|_|____________________________________________________________
* |______|_|______________|___________________|____________|____________|
* 0 length maxSize boundsCheckLimit mappedSize
*
* \_______________________/
* COMMITED
* \____________________________________________/
* SLOP
* \_____________________________________________________________________/
* MAPPED
*
* Invariants:
* - length only increases
* - 0 <= length <= maxSize (if present) <= boundsCheckLimit <= mappedSize
* - on ARM boundsCheckLimit must be a valid ARM immediate.
* - if maxSize is not specified, boundsCheckLimit/mappedSize may grow. They
* are otherwise constant.
*
* NOTE: For asm.js on non-x64 we guarantee that
*
* length == maxSize == boundsCheckLimit == mappedSize
*
* That is, signal handlers will not be invoked, since they cannot emulate
* asm.js accesses on non-x64 architectures.
*
* The region between length and mappedSize is the SLOP - an area where we use
* signal handlers to catch things that slip by bounds checks. Logically it has
* two parts:
*
* - from length to boundsCheckLimit - this part of the SLOP serves to catch
* accesses to memory we have reserved but not yet grown into. This allows us
* to grow memory up to max (when present) without having to patch/update the
* bounds checks.
*
* - from boundsCheckLimit to mappedSize - this part of the SLOP allows us to
* bounds check against base pointers and fold some constant offsets inside
* loads. This enables better Bounds Check Elimination.
*
*/
MOZ_MUST_USE bool WasmArrayRawBuffer::growToSizeInPlace(uint32_t oldSize,
uint32_t newSize) {
MOZ_ASSERT(newSize >= oldSize);
MOZ_ASSERT_IF(maxSize(), newSize <= maxSize().value());
MOZ_ASSERT(newSize <= mappedSize());
uint32_t delta = newSize - oldSize;
MOZ_ASSERT(delta % wasm::PageSize == 0);
uint8_t* dataEnd = dataPointer() + oldSize;
MOZ_ASSERT(uintptr_t(dataEnd) % gc::SystemPageSize() == 0);
if (delta && !CommitBufferMemory(dataEnd, delta)) {
return false;
}
length_ = newSize;
return true;
}
bool WasmArrayRawBuffer::extendMappedSize(uint32_t maxSize) {
size_t newMappedSize = wasm::ComputeMappedSize(maxSize);
MOZ_ASSERT(mappedSize_ <= newMappedSize);
if (mappedSize_ == newMappedSize) {
return true;
}
if (!ExtendBufferMapping(dataPointer(), mappedSize_, newMappedSize)) {
return false;
}
mappedSize_ = newMappedSize;
return true;
}
void WasmArrayRawBuffer::tryGrowMaxSizeInPlace(uint32_t deltaMaxSize) {
CheckedInt<uint32_t> newMaxSize = maxSize_.value();
newMaxSize += deltaMaxSize;
MOZ_ASSERT(newMaxSize.isValid());
MOZ_ASSERT(newMaxSize.value() % wasm::PageSize == 0);
if (!extendMappedSize(newMaxSize.value())) {
return;
}
maxSize_ = Some(newMaxSize.value());
}
/* static */
WasmArrayRawBuffer* WasmArrayRawBuffer::Allocate(uint32_t numBytes,
const Maybe<uint32_t>& maxSize,
const Maybe<size_t>& mapped) {
MOZ_RELEASE_ASSERT(numBytes <= ArrayBufferObject::MaxBufferByteLength);
size_t mappedSize = mapped.isSome()
? *mapped
: wasm::ComputeMappedSize(maxSize.valueOr(numBytes));
MOZ_RELEASE_ASSERT(mappedSize <= SIZE_MAX - gc::SystemPageSize());
MOZ_RELEASE_ASSERT(numBytes <= maxSize.valueOr(UINT32_MAX));
MOZ_ASSERT(numBytes % gc::SystemPageSize() == 0);
MOZ_ASSERT(mappedSize % gc::SystemPageSize() == 0);
uint64_t mappedSizeWithHeader = mappedSize + gc::SystemPageSize();
uint64_t numBytesWithHeader = numBytes + gc::SystemPageSize();
void* data =
MapBufferMemory((size_t)mappedSizeWithHeader, (size_t)numBytesWithHeader);
if (!data) {
return nullptr;
}
uint8_t* base = reinterpret_cast<uint8_t*>(data) + gc::SystemPageSize();
uint8_t* header = base - sizeof(WasmArrayRawBuffer);
auto rawBuf =
new (header) WasmArrayRawBuffer(base, maxSize, mappedSize, numBytes);
return rawBuf;
}
/* static */
void WasmArrayRawBuffer::Release(void* mem) {
WasmArrayRawBuffer* header =
(WasmArrayRawBuffer*)((uint8_t*)mem - sizeof(WasmArrayRawBuffer));
MOZ_RELEASE_ASSERT(header->mappedSize() <= SIZE_MAX - gc::SystemPageSize());
size_t mappedSizeWithHeader = header->mappedSize() + gc::SystemPageSize();
UnmapBufferMemory(header->basePointer(), mappedSizeWithHeader);
}
WasmArrayRawBuffer* ArrayBufferObject::BufferContents::wasmBuffer() const {
MOZ_RELEASE_ASSERT(kind_ == WASM);
return (WasmArrayRawBuffer*)(data_ - sizeof(WasmArrayRawBuffer));
}
template <typename ObjT, typename RawbufT>
static bool CreateSpecificWasmBuffer(
JSContext* cx, uint32_t initialSize, const Maybe<uint32_t>& maxSize,
MutableHandleArrayBufferObjectMaybeShared maybeSharedObject) {
bool useHugeMemory = wasm::IsHugeMemoryEnabled();
Maybe<uint32_t> clampedMaxSize = maxSize;
if (clampedMaxSize) {
#ifdef JS_64BIT
// On 64-bit platforms when we aren't using huge memory, clamp
// clampedMaxSize to a smaller value that satisfies the 32-bit invariants
// clampedMaxSize + wasm::PageSize < UINT32_MAX and clampedMaxSize %
// wasm::PageSize == 0
if (!useHugeMemory &&
clampedMaxSize.value() >= (UINT32_MAX - wasm::PageSize)) {
uint32_t clamp = (wasm::MaxMemoryMaximumPages - 2) * wasm::PageSize;
MOZ_ASSERT(clamp < UINT32_MAX);
MOZ_ASSERT(initialSize <= clamp);
clampedMaxSize = Some(clamp);
}
#else
static_assert(sizeof(uintptr_t) == 4, "assuming not 64 bit implies 32 bit");
// On 32-bit platforms, prevent applications specifying a large max
// (like UINT32_MAX) from unintentially OOMing the browser: they just
// want "a lot of memory". Maintain the invariant that
// initialSize <= clampedMaxSize.
static const uint32_t OneGiB = 1 << 30;
uint32_t clamp = std::max(OneGiB, initialSize);
clampedMaxSize = Some(std::min(clamp, *clampedMaxSize));
#endif
}
Maybe<size_t> mappedSize;
#ifdef WASM_SUPPORTS_HUGE_MEMORY
if (useHugeMemory) {
mappedSize = Some(wasm::HugeMappedSize);
}
#endif
RawbufT* buffer = RawbufT::Allocate(initialSize, clampedMaxSize, mappedSize);
if (!buffer) {
if (useHugeMemory) {
JS_ReportErrorFlagsAndNumberASCII(cx, JSREPORT_WARNING, GetErrorMessage,
nullptr, JSMSG_WASM_HUGE_MEMORY_FAILED);
if (cx->isExceptionPending()) {
cx->clearPendingException();
}
ReportOutOfMemory(cx);
return false;
}
// If we fail, and have a clampedMaxSize, try to reserve the biggest chunk
// in the range [initialSize, clampedMaxSize) using log backoff.
if (!clampedMaxSize) {
wasm::Log(cx, "new Memory({initial=%u bytes}) failed", initialSize);
ReportOutOfMemory(cx);
return false;
}
uint32_t cur = clampedMaxSize.value() / 2;
for (; cur > initialSize; cur /= 2) {
uint32_t clampedMaxSize = RoundUp(cur, wasm::PageSize);
buffer = RawbufT::Allocate(initialSize, Some(clampedMaxSize), mappedSize);
if (buffer) {
break;
}
}
if (!buffer) {
wasm::Log(cx, "new Memory({initial=%u bytes}) failed", initialSize);
ReportOutOfMemory(cx);
return false;
}
// Try to grow our chunk as much as possible.
for (size_t d = cur / 2; d >= wasm::PageSize; d /= 2) {
buffer->tryGrowMaxSizeInPlace(RoundUp(d, wasm::PageSize));
}
}
// ObjT::createFromNewRawBuffer assumes ownership of |buffer| even in case
// of failure.
RootedArrayBufferObjectMaybeShared object(
cx, ObjT::createFromNewRawBuffer(cx, buffer, initialSize));
if (!object) {
return false;
}
maybeSharedObject.set(object);
// See MaximumLiveMappedBuffers comment above.
if (liveBufferCount > StartSyncFullGCAtLiveBufferCount) {
JS::PrepareForFullGC(cx);
JS::NonIncrementalGC(cx, GC_NORMAL, JS::GCReason::TOO_MUCH_WASM_MEMORY);
allocatedSinceLastTrigger = 0;
} else if (liveBufferCount > StartTriggeringAtLiveBufferCount) {
allocatedSinceLastTrigger++;
if (allocatedSinceLastTrigger > AllocatedBuffersPerTrigger) {
Unused << cx->runtime()->gc.triggerGC(JS::GCReason::TOO_MUCH_WASM_MEMORY);
allocatedSinceLastTrigger = 0;
}
} else {
allocatedSinceLastTrigger = 0;
}
if (clampedMaxSize) {
if (useHugeMemory) {
wasm::Log(cx,
"new Memory({initial:%u bytes, maximum:%u bytes}) succeeded",
unsigned(initialSize), unsigned(*clampedMaxSize));
} else {
wasm::Log(cx,
"new Memory({initial:%u bytes, maximum:%u bytes}) succeeded "
"with internal maximum of %u",
unsigned(initialSize), unsigned(*clampedMaxSize),
unsigned(object->wasmMaxSize().value()));
}
} else {
wasm::Log(cx, "new Memory({initial:%u bytes}) succeeded",
unsigned(initialSize));
}
return true;
}
bool js::CreateWasmBuffer(JSContext* cx, const wasm::Limits& memory,
MutableHandleArrayBufferObjectMaybeShared buffer) {
MOZ_ASSERT(memory.initial % wasm::PageSize == 0);
MOZ_RELEASE_ASSERT(cx->wasmHaveSignalHandlers);
MOZ_RELEASE_ASSERT((memory.initial / wasm::PageSize) <=
wasm::MaxMemoryInitialPages);
if (memory.shared == wasm::Shareable::True) {
if (!cx->realm()->creationOptions().getSharedMemoryAndAtomicsEnabled()) {
JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
JSMSG_WASM_NO_SHMEM_LINK);
return false;
}
return CreateSpecificWasmBuffer<SharedArrayBufferObject,
SharedArrayRawBuffer>(
cx, memory.initial, memory.maximum, buffer);
}
return CreateSpecificWasmBuffer<ArrayBufferObject, WasmArrayRawBuffer>(
cx, memory.initial, memory.maximum, buffer);
}
bool ArrayBufferObject::prepareForAsmJS() {
MOZ_ASSERT(byteLength() % wasm::PageSize == 0,
"prior size checking should have guaranteed page-size multiple");
MOZ_ASSERT(byteLength() > 0,
"prior size checking should have excluded empty buffers");
switch (bufferKind()) {
case MALLOCED:
case MAPPED:
case EXTERNAL:
// It's okay if this uselessly sets the flag a second time.
setIsPreparedForAsmJS();
return true;
case INLINE_DATA:
static_assert(wasm::PageSize > MaxInlineBytes,
"inline data must be too small to be a page size multiple");
MOZ_ASSERT_UNREACHABLE(
"inline-data buffers should be implicitly excluded by size checks");
return false;
case NO_DATA:
MOZ_ASSERT_UNREACHABLE(
"size checking should have excluded detached or empty buffers");
return false;
// asm.js code and associated buffers are potentially long-lived. Yet a
// buffer of user-owned data *must* be detached by the user before the
// user-owned data is disposed. No caller wants to use a user-owned
// ArrayBuffer with asm.js, so just don't support this and avoid a mess of
// complexity.
case USER_OWNED:
// wasm buffers can be detached at any time.
case WASM:
MOZ_ASSERT(!isPreparedForAsmJS());
return false;
case BAD1:
MOZ_ASSERT_UNREACHABLE("invalid bufferKind() encountered");
return false;
}
MOZ_ASSERT_UNREACHABLE("non-exhaustive kind-handling switch?");
return false;
}
ArrayBufferObject::BufferContents ArrayBufferObject::createMappedContents(
int fd, size_t offset, size_t length) {
void* data =
gc::AllocateMappedContent(fd, offset, length, ARRAY_BUFFER_ALIGNMENT);
return BufferContents::createMapped(data);
}
uint8_t* ArrayBufferObject::inlineDataPointer() const {
return static_cast<uint8_t*>(fixedData(JSCLASS_RESERVED_SLOTS(&class_)));
}
uint8_t* ArrayBufferObject::dataPointer() const {
return static_cast<uint8_t*>(getFixedSlot(DATA_SLOT).toPrivate());
}
SharedMem<uint8_t*> ArrayBufferObject::dataPointerShared() const {
return SharedMem<uint8_t*>::unshared(getFixedSlot(DATA_SLOT).toPrivate());
}
ArrayBufferObject::FreeInfo* ArrayBufferObject::freeInfo() const {
MOZ_ASSERT(isExternal());
return reinterpret_cast<FreeInfo*>(inlineDataPointer());
}
void ArrayBufferObject::releaseData(JSFreeOp* fop) {
switch (bufferKind()) {
case INLINE_DATA:
// Inline data doesn't require releasing.
break;
case MALLOCED:
fop->free_(this, dataPointer(), byteLength(),
MemoryUse::ArrayBufferContents);
break;
case NO_DATA:
// There's nothing to release if there's no data.
MOZ_ASSERT(dataPointer() == nullptr);
break;
case USER_OWNED:
// User-owned data is released by, well, the user.
break;
case MAPPED:
gc::DeallocateMappedContent(dataPointer(), byteLength());
fop->removeCellMemory(this, associatedBytes(),
MemoryUse::ArrayBufferContents);
break;
case WASM:
WasmArrayRawBuffer::Release(dataPointer());
fop->removeCellMemory(this, byteLength(), MemoryUse::ArrayBufferContents);
break;
case EXTERNAL:
if (freeInfo()->freeFunc) {
// The analyzer can't know for sure whether the embedder-supplied
// free function will GC. We give the analyzer a hint here.
// (Doing a GC in the free function is considered a programmer
// error.)
JS::AutoSuppressGCAnalysis nogc;
freeInfo()->freeFunc(dataPointer(), freeInfo()->freeUserData);
}
break;
case BAD1:
MOZ_CRASH("invalid BufferKind encountered");
break;
}
}
void ArrayBufferObject::setDataPointer(BufferContents contents) {
setFixedSlot(DATA_SLOT, PrivateValue(contents.data()));
setFlags((flags() & ~KIND_MASK) | contents.kind());
if (isExternal()) {
auto info = freeInfo();
info->freeFunc = contents.freeFunc();
info->freeUserData = contents.freeUserData();
}
}
uint32_t ArrayBufferObject::byteLength() const {
return getFixedSlot(BYTE_LENGTH_SLOT).toInt32();
}
inline size_t ArrayBufferObject::associatedBytes() const {
if (bufferKind() == MALLOCED) {
return byteLength();
} else if (bufferKind() == MAPPED) {
return RoundUp(byteLength(), js::gc::SystemPageSize());
} else {
MOZ_CRASH("Unexpected buffer kind");
}
}
void ArrayBufferObject::setByteLength(uint32_t length) {
MOZ_ASSERT(length <= INT32_MAX);
setFixedSlot(BYTE_LENGTH_SLOT, Int32Value(length));
}
size_t ArrayBufferObject::wasmMappedSize() const {
if (isWasm()) {
return contents().wasmBuffer()->mappedSize();
}
return byteLength();
}
size_t js::WasmArrayBufferMappedSize(const ArrayBufferObjectMaybeShared* buf) {
if (buf->is<ArrayBufferObject>()) {
return buf->as<ArrayBufferObject>().wasmMappedSize();
}
return buf->as<SharedArrayBufferObject>().wasmMappedSize();
}
Maybe<uint32_t> ArrayBufferObject::wasmMaxSize() const {
if (isWasm()) {
return contents().wasmBuffer()->maxSize();
} else {
return Some<uint32_t>(byteLength());
}
}
Maybe<uint32_t> js::WasmArrayBufferMaxSize(
const ArrayBufferObjectMaybeShared* buf) {
if (buf->is<ArrayBufferObject>()) {
return buf->as<ArrayBufferObject>().wasmMaxSize();
}
return buf->as<SharedArrayBufferObject>().wasmMaxSize();
}
static void CheckStealPreconditions(Handle<ArrayBufferObject*> buffer,
JSContext* cx) {
cx->check(buffer);
MOZ_ASSERT(!buffer->isDetached(), "can't steal from a detached buffer");
MOZ_ASSERT(!buffer->isPreparedForAsmJS(),
"asm.js-prepared buffers don't have detachable/stealable data");
MOZ_ASSERT(!buffer->hasTypedObjectViews(),
"buffers for typed objects don't have detachable/stealable data");
}
/* static */
bool ArrayBufferObject::wasmGrowToSizeInPlace(
uint32_t newSize, HandleArrayBufferObject oldBuf,
MutableHandleArrayBufferObject newBuf, JSContext* cx) {
CheckStealPreconditions(oldBuf, cx);
MOZ_ASSERT(oldBuf->isWasm());
// On failure, do not throw and ensure that the original buffer is
// unmodified and valid. After WasmArrayRawBuffer::growToSizeInPlace(), the
// wasm-visible length of the buffer has been increased so it must be the
// last fallible operation.
if (newSize > ArrayBufferObject::MaxBufferByteLength) {
return false;
}
newBuf.set(ArrayBufferObject::createEmpty(cx));
if (!newBuf) {
cx->clearPendingException();
return false;
}
MOZ_ASSERT(newBuf->isNoData());
if (!oldBuf->contents().wasmBuffer()->growToSizeInPlace(oldBuf->byteLength(),
newSize)) {
return false;
}
// Extract the grown contents from |oldBuf|.