Source/JavaScriptCore/wasm/WasmInstance.cpp - external/github.com/WebKit/webkit - Git at Google

 /*
  * Copyright (C) 2017-2019 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "config.h"
 #include "WasmInstance.h"

 #if ENABLE(WEBASSEMBLY)

 #include "JSCJSValueInlines.h"
 #include "JSWebAssemblyHelpers.h"
 #include "JSWebAssemblyInstance.h"
 #include "Register.h"
 #include "WasmModuleInformation.h"
 #include "WasmSignatureInlines.h"
 #include <wtf/CheckedArithmetic.h>

 namespace JSC { namespace Wasm {

 namespace {
 size_t globalMemoryByteSize(Module& module)
 {
     return Checked<size_t>(module.moduleInformation().globals.size()) * sizeof(Register);
 }
 }

 Instance::Instance(Context* context, Ref<Module>&& module, EntryFrame** pointerToTopEntryFrame, void** pointerToActualStackLimit, StoreTopCallFrameCallback&& storeTopCallFrame)
     : m_context(context)
     , m_module(WTFMove(module))
     , m_globals(MallocPtr<Global::Value, VMMalloc>::malloc(globalMemoryByteSize(m_module.get())))
     , m_globalsToMark(m_module.get().moduleInformation().globals.size())
     , m_globalsToBinding(m_module.get().moduleInformation().globals.size())
     , m_pointerToTopEntryFrame(pointerToTopEntryFrame)
     , m_pointerToActualStackLimit(pointerToActualStackLimit)
     , m_storeTopCallFrame(WTFMove(storeTopCallFrame))
     , m_numImportFunctions(m_module->moduleInformation().importFunctionCount())
     , m_passiveElements(m_module->moduleInformation().elementCount())
     , m_passiveDataSegments(m_module->moduleInformation().dataSegmentsCount())
 {
     for (unsigned i = 0; i < m_numImportFunctions; ++i)
         new (importFunctionInfo(i)) ImportFunctionInfo();
     memset(static_cast<void*>(m_globals.get()), 0, globalMemoryByteSize(m_module.get()));
     for (unsigned i = 0; i < m_module->moduleInformation().globals.size(); ++i) {
         const Wasm::GlobalInformation& global = m_module.get().moduleInformation().globals[i];
         if (global.bindingMode == Wasm::GlobalInformation::BindingMode::Portable) {
             // This is kept alive by JSWebAssemblyInstance -> JSWebAssemblyGlobal -> binding.
             m_globalsToBinding.set(i);
         } else if (isRefType(global.type)) {
             // This is kept alive by JSWebAssemblyInstance -> binding.
             m_globalsToMark.set(i);
         }
     }
     memset(bitwise_cast<char*>(this) + offsetOfTablePtr(m_numImportFunctions, 0), 0, m_module->moduleInformation().tableCount() * sizeof(Table*));
     for (unsigned elementIndex = 0; elementIndex < m_module->moduleInformation().elementCount(); ++elementIndex) {
         const auto& element = m_module->moduleInformation().elements[elementIndex];
         if (element.isPassive())
             m_passiveElements.quickSet(elementIndex);
     }

     for (unsigned dataSegmentIndex = 0; dataSegmentIndex < m_module->moduleInformation().dataSegmentsCount(); ++dataSegmentIndex) {
         const auto& dataSegment = m_module->moduleInformation().data[dataSegmentIndex];
         if (dataSegment->isPassive())
             m_passiveDataSegments.quickSet(dataSegmentIndex);
     }
 }

 Ref<Instance> Instance::create(Context* context, Ref<Module>&& module, EntryFrame** pointerToTopEntryFrame, void** pointerToActualStackLimit, StoreTopCallFrameCallback&& storeTopCallFrame)
 {
     return adoptRef(*new (NotNull, fastMalloc(allocationSize(module->moduleInformation().importFunctionCount(), module->moduleInformation().tableCount()))) Instance(context, WTFMove(module), pointerToTopEntryFrame, pointerToActualStackLimit, WTFMove(storeTopCallFrame)));
 }

 Instance::~Instance() { }

 size_t Instance::extraMemoryAllocated() const
 {
     return globalMemoryByteSize(m_module.get()) + allocationSize(m_numImportFunctions, m_module->moduleInformation().tableCount());
 }

 void Instance::setGlobal(unsigned i, JSValue value)
 {
     Global::Value* slot = m_globals.get() + i;
     if (m_globalsToBinding.get(i)) {
         Wasm::Global* global = getGlobalBinding(i);
         if (!global)
             return;
         global->valuePointer()->m_externref.set(owner<JSWebAssemblyInstance>()->vm(), global->owner<JSWebAssemblyGlobal>(), value);
         return;
     }
     ASSERT(m_owner);
     slot->m_externref.set(owner<JSWebAssemblyInstance>()->vm(), owner<JSWebAssemblyInstance>(), value);
 }

 JSValue Instance::getFunctionWrapper(unsigned i) const
 {
     JSValue value = m_functionWrappers.get(i).get();
     if (value.isEmpty())
         return jsNull();
     return value;
 }

 void Instance::setFunctionWrapper(unsigned i, JSValue value)
 {
     ASSERT(m_owner);
     ASSERT(value.isCallable(owner<JSWebAssemblyInstance>()->vm()));
     ASSERT(!m_functionWrappers.contains(i));
     Locker locker { owner<JSWebAssemblyInstance>()->cellLock() };
     m_functionWrappers.set(i, WriteBarrier<Unknown>(owner<JSWebAssemblyInstance>()->vm(), owner<JSWebAssemblyInstance>(), value));
     ASSERT(getFunctionWrapper(i) == value);
 }

 Table* Instance::table(unsigned i)
 {
     RELEASE_ASSERT(i < m_module->moduleInformation().tableCount());
     return *bitwise_cast<Table**>(bitwise_cast<char*>(this) + offsetOfTablePtr(m_numImportFunctions, i));
 }

 void Instance::tableCopy(uint32_t dstOffset, uint32_t srcOffset, uint32_t length, uint32_t dstTableIndex, uint32_t srcTableIndex)
 {
     RELEASE_ASSERT(srcTableIndex < m_module->moduleInformation().tableCount());
     RELEASE_ASSERT(dstTableIndex < m_module->moduleInformation().tableCount());

     Table* dstTable = table(dstTableIndex);
     Table* srcTable = table(srcTableIndex);
     RELEASE_ASSERT(dstTable->type() == srcTable->type());

     auto forEachTableElement = [&](auto fn) {
         if (dstTableIndex == srcTableIndex && dstOffset > srcOffset) {
             for (uint32_t index = length; index--;)
                 fn(dstTable, srcTable, dstOffset + index, srcOffset + index);
         } else if (dstTableIndex == srcTableIndex && dstOffset == srcOffset)
             return;
         else {
             for (uint32_t index = 0; index < length; ++index)
                 fn(dstTable, srcTable, dstOffset + index, srcOffset + index);
         }
     };

     if (dstTable->isExternrefTable()) {
         forEachTableElement([](Table* dstTable, Table* srcTable, uint32_t dstIndex, uint32_t srcIndex) {
             dstTable->copy(srcTable, dstIndex, srcIndex);
         });
         return;
     }

     forEachTableElement([](Table* dstTable, Table* srcTable, uint32_t dstIndex, uint32_t srcIndex) {
         dstTable->asFuncrefTable()->copyFunction(srcTable->asFuncrefTable(), dstIndex, srcIndex);
     });
 }

 void Instance::elemDrop(uint32_t elementIndex)
 {
     m_passiveElements.quickClear(elementIndex);
 }

 bool Instance::memoryInit(uint32_t dstAddress, uint32_t srcAddress, uint32_t length, uint32_t dataSegmentIndex)
 {
     RELEASE_ASSERT(dataSegmentIndex < module().moduleInformation().dataSegmentsCount());

     if (sumOverflows<uint32_t>(srcAddress, length))
         return false;

     const Segment::Ptr& segment = module().moduleInformation().data[dataSegmentIndex];
     const uint32_t segmentSizeInBytes = m_passiveDataSegments.quickGet(dataSegmentIndex) ? segment->sizeInBytes : 0U;
     if (srcAddress + length > segmentSizeInBytes)
         return false;

     const uint8_t* segmentData = !length ? nullptr : &segment->byte(srcAddress);

     ASSERT(memory());
     return memory()->init(dstAddress, segmentData, length);
 }

 void Instance::dataDrop(uint32_t dataSegmentIndex)
 {
     m_passiveDataSegments.quickClear(dataSegmentIndex);
 }

 const Element* Instance::elementAt(unsigned index) const
 {
     RELEASE_ASSERT(index < m_module->moduleInformation().elementCount());

     if (m_passiveElements.quickGet(index))
         return &m_module->moduleInformation().elements[index];
     return nullptr;
 }

 void Instance::initElementSegment(uint32_t tableIndex, const Element& segment, uint32_t dstOffset, uint32_t srcOffset, uint32_t length)
 {
     RELEASE_ASSERT(length <= segment.length());

     JSWebAssemblyInstance* jsInstance = owner<JSWebAssemblyInstance>();
     JSWebAssemblyTable* jsTable = jsInstance->table(tableIndex);
     JSGlobalObject* globalObject = jsInstance->globalObject();
     VM& vm = globalObject->vm();

     for (uint32_t index = 0; index < length; ++index) {
         const auto srcIndex = srcOffset + index;
         const auto dstIndex = dstOffset + index;

         if (Element::isNullFuncIndex(segment.functionIndices[srcIndex])) {
             jsTable->clear(dstIndex);
             continue;
         }

         // FIXME: This essentially means we're exporting an import.
         // We need a story here. We need to create a WebAssemblyFunction
         // for the import.
         // https://bugs.webkit.org/show_bug.cgi?id=165510
         uint32_t functionIndex = segment.functionIndices[srcIndex];
         SignatureIndex signatureIndex = m_module->signatureIndexFromFunctionIndexSpace(functionIndex);
         if (isImportFunction(functionIndex)) {
             JSObject* functionImport = importFunction<WriteBarrier<JSObject>>(functionIndex)->get();
             if (isWebAssemblyHostFunction(vm, functionImport)) {
                 WebAssemblyFunction* wasmFunction = jsDynamicCast<WebAssemblyFunction*>(vm, functionImport);
                 // If we ever import a WebAssemblyWrapperFunction, we set the import as the unwrapped value.
                 // Because a WebAssemblyWrapperFunction can never wrap another WebAssemblyWrapperFunction,
                 // the only type this could be is WebAssemblyFunction.
                 RELEASE_ASSERT(wasmFunction);
                 jsTable->set(dstIndex, wasmFunction);
                 continue;
             }
             auto* wrapperFunction = WebAssemblyWrapperFunction::create(
                 vm,
                 globalObject,
                 globalObject->webAssemblyWrapperFunctionStructure(),
                 functionImport,
                 functionIndex,
                 jsInstance,
                 signatureIndex);
             jsTable->set(dstIndex, wrapperFunction);
             continue;
         }

         Callee& embedderEntrypointCallee = codeBlock()->embedderEntrypointCalleeFromFunctionIndexSpace(functionIndex);
         WasmToWasmImportableFunction::LoadLocation entrypointLoadLocation = codeBlock()->entrypointLoadLocationFromFunctionIndexSpace(functionIndex);
         const Signature& signature = SignatureInformation::get(signatureIndex);
         // FIXME: Say we export local function "foo" at function index 0.
         // What if we also set it to the table an Element w/ index 0.
         // Does (new Instance(...)).exports.foo === table.get(0)?
         // https://bugs.webkit.org/show_bug.cgi?id=165825
         WebAssemblyFunction* function = WebAssemblyFunction::create(
             vm,
             globalObject,
             globalObject->webAssemblyFunctionStructure(),
             signature.argumentCount(),
             String(),
             jsInstance,
             embedderEntrypointCallee,
             entrypointLoadLocation,
             signatureIndex);
         jsTable->set(dstIndex, function);
     }
 }

 void Instance::tableInit(uint32_t dstOffset, uint32_t srcOffset, uint32_t length, uint32_t elementIndex, uint32_t tableIndex)
 {
     RELEASE_ASSERT(elementIndex < m_module->moduleInformation().elementCount());
     RELEASE_ASSERT(tableIndex < m_module->moduleInformation().tableCount());

     const Element* elementSegment = elementAt(elementIndex);
     RELEASE_ASSERT(elementSegment);
     RELEASE_ASSERT(elementSegment->isPassive());
     initElementSegment(tableIndex, *elementSegment, dstOffset, srcOffset, length);
 }

 void Instance::setTable(unsigned i, Ref<Table>&& table)
 {
     RELEASE_ASSERT(i < m_module->moduleInformation().tableCount());
     ASSERT(!this->table(i));
     *bitwise_cast<Table**>(bitwise_cast<char*>(this) + offsetOfTablePtr(m_numImportFunctions, i)) = &table.leakRef();
 }

 void Instance::linkGlobal(unsigned i, Ref<Global>&& global)
 {
     m_globals.get()[i].m_pointer = global->valuePointer();
     m_linkedGlobals.set(i, WTFMove(global));
 }

 } } // namespace JSC::Wasm

 #endif // ENABLE(WEBASSEMBLY)
	/*
	* Copyright (C) 2017-2019 Apple Inc. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	*
	* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
	* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
	* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
	* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
	* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
	* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
	* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
	* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "config.h"
	#include "WasmInstance.h"

	#if ENABLE(WEBASSEMBLY)

	#include "JSCJSValueInlines.h"
	#include "JSWebAssemblyHelpers.h"
	#include "JSWebAssemblyInstance.h"
	#include "Register.h"
	#include "WasmModuleInformation.h"
	#include "WasmSignatureInlines.h"
	#include <wtf/CheckedArithmetic.h>

	namespace JSC { namespace Wasm {

	namespace {
	size_t globalMemoryByteSize(Module& module)
	{
	return Checked<size_t>(module.moduleInformation().globals.size()) * sizeof(Register);
	}
	}

	Instance::Instance(Context* context, Ref<Module>&& module, EntryFrame pointerToTopEntryFrame, void pointerToActualStackLimit, StoreTopCallFrameCallback&& storeTopCallFrame)
	: m_context(context)
	, m_module(WTFMove(module))
	, m_globals(MallocPtr<Global::Value, VMMalloc>::malloc(globalMemoryByteSize(m_module.get())))
	, m_globalsToMark(m_module.get().moduleInformation().globals.size())
	, m_globalsToBinding(m_module.get().moduleInformation().globals.size())
	, m_pointerToTopEntryFrame(pointerToTopEntryFrame)
	, m_pointerToActualStackLimit(pointerToActualStackLimit)
	, m_storeTopCallFrame(WTFMove(storeTopCallFrame))
	, m_numImportFunctions(m_module->moduleInformation().importFunctionCount())
	, m_passiveElements(m_module->moduleInformation().elementCount())
	, m_passiveDataSegments(m_module->moduleInformation().dataSegmentsCount())
	{
	for (unsigned i = 0; i < m_numImportFunctions; ++i)
	new (importFunctionInfo(i)) ImportFunctionInfo();
	memset(static_cast<void*>(m_globals.get()), 0, globalMemoryByteSize(m_module.get()));
	for (unsigned i = 0; i < m_module->moduleInformation().globals.size(); ++i) {
	const Wasm::GlobalInformation& global = m_module.get().moduleInformation().globals[i];
	if (global.bindingMode == Wasm::GlobalInformation::BindingMode::Portable) {
	// This is kept alive by JSWebAssemblyInstance -> JSWebAssemblyGlobal -> binding.
	m_globalsToBinding.set(i);
	} else if (isRefType(global.type)) {
	// This is kept alive by JSWebAssemblyInstance -> binding.
	m_globalsToMark.set(i);
	}
	}
	memset(bitwise_cast<char>(this) + offsetOfTablePtr(m_numImportFunctions, 0), 0, m_module->moduleInformation().tableCount() sizeof(Table*));
	for (unsigned elementIndex = 0; elementIndex < m_module->moduleInformation().elementCount(); ++elementIndex) {
	const auto& element = m_module->moduleInformation().elements[elementIndex];
	if (element.isPassive())
	m_passiveElements.quickSet(elementIndex);
	}

	for (unsigned dataSegmentIndex = 0; dataSegmentIndex < m_module->moduleInformation().dataSegmentsCount(); ++dataSegmentIndex) {
	const auto& dataSegment = m_module->moduleInformation().data[dataSegmentIndex];
	if (dataSegment->isPassive())
	m_passiveDataSegments.quickSet(dataSegmentIndex);
	}
	}

	Ref<Instance> Instance::create(Context* context, Ref<Module>&& module, EntryFrame pointerToTopEntryFrame, void pointerToActualStackLimit, StoreTopCallFrameCallback&& storeTopCallFrame)
	{
	return adoptRef(*new (NotNull, fastMalloc(allocationSize(module->moduleInformation().importFunctionCount(), module->moduleInformation().tableCount()))) Instance(context, WTFMove(module), pointerToTopEntryFrame, pointerToActualStackLimit, WTFMove(storeTopCallFrame)));
	}

	Instance::~Instance() { }

	size_t Instance::extraMemoryAllocated() const
	{
	return globalMemoryByteSize(m_module.get()) + allocationSize(m_numImportFunctions, m_module->moduleInformation().tableCount());
	}

	void Instance::setGlobal(unsigned i, JSValue value)
	{
	Global::Value* slot = m_globals.get() + i;
	if (m_globalsToBinding.get(i)) {
	Wasm::Global* global = getGlobalBinding(i);
	if (!global)
	return;
	global->valuePointer()->m_externref.set(owner<JSWebAssemblyInstance>()->vm(), global->owner<JSWebAssemblyGlobal>(), value);
	return;
	}
	ASSERT(m_owner);
	slot->m_externref.set(owner<JSWebAssemblyInstance>()->vm(), owner<JSWebAssemblyInstance>(), value);
	}

	JSValue Instance::getFunctionWrapper(unsigned i) const
	{
	JSValue value = m_functionWrappers.get(i).get();
	if (value.isEmpty())
	return jsNull();
	return value;
	}

	void Instance::setFunctionWrapper(unsigned i, JSValue value)
	{
	ASSERT(m_owner);
	ASSERT(value.isCallable(owner<JSWebAssemblyInstance>()->vm()));
	ASSERT(!m_functionWrappers.contains(i));
	Locker locker { owner<JSWebAssemblyInstance>()->cellLock() };
	m_functionWrappers.set(i, WriteBarrier<Unknown>(owner<JSWebAssemblyInstance>()->vm(), owner<JSWebAssemblyInstance>(), value));
	ASSERT(getFunctionWrapper(i) == value);
	}

	Table* Instance::table(unsigned i)
	{
	RELEASE_ASSERT(i < m_module->moduleInformation().tableCount());
	return bitwise_cast<Table>(bitwise_cast<char>(this) + offsetOfTablePtr(m_numImportFunctions, i));
	}

	void Instance::tableCopy(uint32_t dstOffset, uint32_t srcOffset, uint32_t length, uint32_t dstTableIndex, uint32_t srcTableIndex)
	{
	RELEASE_ASSERT(srcTableIndex < m_module->moduleInformation().tableCount());
	RELEASE_ASSERT(dstTableIndex < m_module->moduleInformation().tableCount());

	Table* dstTable = table(dstTableIndex);
	Table* srcTable = table(srcTableIndex);
	RELEASE_ASSERT(dstTable->type() == srcTable->type());

	auto forEachTableElement = [&](auto fn) {
	if (dstTableIndex == srcTableIndex && dstOffset > srcOffset) {
	for (uint32_t index = length; index--;)
	fn(dstTable, srcTable, dstOffset + index, srcOffset + index);
	} else if (dstTableIndex == srcTableIndex && dstOffset == srcOffset)
	return;
	else {
	for (uint32_t index = 0; index < length; ++index)
	fn(dstTable, srcTable, dstOffset + index, srcOffset + index);
	}
	};

	if (dstTable->isExternrefTable()) {
	forEachTableElement([](Table* dstTable, Table* srcTable, uint32_t dstIndex, uint32_t srcIndex) {
	dstTable->copy(srcTable, dstIndex, srcIndex);
	});
	return;
	}

	forEachTableElement([](Table* dstTable, Table* srcTable, uint32_t dstIndex, uint32_t srcIndex) {
	dstTable->asFuncrefTable()->copyFunction(srcTable->asFuncrefTable(), dstIndex, srcIndex);
	});
	}

	void Instance::elemDrop(uint32_t elementIndex)
	{
	m_passiveElements.quickClear(elementIndex);
	}

	bool Instance::memoryInit(uint32_t dstAddress, uint32_t srcAddress, uint32_t length, uint32_t dataSegmentIndex)
	{
	RELEASE_ASSERT(dataSegmentIndex < module().moduleInformation().dataSegmentsCount());

	if (sumOverflows<uint32_t>(srcAddress, length))
	return false;

	const Segment::Ptr& segment = module().moduleInformation().data[dataSegmentIndex];
	const uint32_t segmentSizeInBytes = m_passiveDataSegments.quickGet(dataSegmentIndex) ? segment->sizeInBytes : 0U;
	if (srcAddress + length > segmentSizeInBytes)
	return false;

	const uint8_t* segmentData = !length ? nullptr : &segment->byte(srcAddress);

	ASSERT(memory());
	return memory()->init(dstAddress, segmentData, length);
	}

	void Instance::dataDrop(uint32_t dataSegmentIndex)
	{
	m_passiveDataSegments.quickClear(dataSegmentIndex);
	}

	const Element* Instance::elementAt(unsigned index) const
	{
	RELEASE_ASSERT(index < m_module->moduleInformation().elementCount());

	if (m_passiveElements.quickGet(index))
	return &m_module->moduleInformation().elements[index];
	return nullptr;
	}

	void Instance::initElementSegment(uint32_t tableIndex, const Element& segment, uint32_t dstOffset, uint32_t srcOffset, uint32_t length)
	{
	RELEASE_ASSERT(length <= segment.length());

	JSWebAssemblyInstance* jsInstance = owner<JSWebAssemblyInstance>();
	JSWebAssemblyTable* jsTable = jsInstance->table(tableIndex);
	JSGlobalObject* globalObject = jsInstance->globalObject();
	VM& vm = globalObject->vm();

	for (uint32_t index = 0; index < length; ++index) {
	const auto srcIndex = srcOffset + index;
	const auto dstIndex = dstOffset + index;

	if (Element::isNullFuncIndex(segment.functionIndices[srcIndex])) {
	jsTable->clear(dstIndex);
	continue;
	}

	// FIXME: This essentially means we're exporting an import.
	// We need a story here. We need to create a WebAssemblyFunction
	// for the import.
	// https://bugs.webkit.org/show_bug.cgi?id=165510
	uint32_t functionIndex = segment.functionIndices[srcIndex];
	SignatureIndex signatureIndex = m_module->signatureIndexFromFunctionIndexSpace(functionIndex);
	if (isImportFunction(functionIndex)) {
	JSObject* functionImport = importFunction<WriteBarrier<JSObject>>(functionIndex)->get();
	if (isWebAssemblyHostFunction(vm, functionImport)) {
	WebAssemblyFunction* wasmFunction = jsDynamicCast<WebAssemblyFunction*>(vm, functionImport);
	// If we ever import a WebAssemblyWrapperFunction, we set the import as the unwrapped value.
	// Because a WebAssemblyWrapperFunction can never wrap another WebAssemblyWrapperFunction,
	// the only type this could be is WebAssemblyFunction.
	RELEASE_ASSERT(wasmFunction);
	jsTable->set(dstIndex, wasmFunction);
	continue;
	}
	auto* wrapperFunction = WebAssemblyWrapperFunction::create(
	vm,
	globalObject,
	globalObject->webAssemblyWrapperFunctionStructure(),
	functionImport,
	functionIndex,
	jsInstance,
	signatureIndex);
	jsTable->set(dstIndex, wrapperFunction);
	continue;
	}

	Callee& embedderEntrypointCallee = codeBlock()->embedderEntrypointCalleeFromFunctionIndexSpace(functionIndex);
	WasmToWasmImportableFunction::LoadLocation entrypointLoadLocation = codeBlock()->entrypointLoadLocationFromFunctionIndexSpace(functionIndex);
	const Signature& signature = SignatureInformation::get(signatureIndex);
	// FIXME: Say we export local function "foo" at function index 0.
	// What if we also set it to the table an Element w/ index 0.
	// Does (new Instance(...)).exports.foo === table.get(0)?
	// https://bugs.webkit.org/show_bug.cgi?id=165825
	WebAssemblyFunction* function = WebAssemblyFunction::create(
	vm,
	globalObject,
	globalObject->webAssemblyFunctionStructure(),
	signature.argumentCount(),
	String(),
	jsInstance,
	embedderEntrypointCallee,
	entrypointLoadLocation,
	signatureIndex);
	jsTable->set(dstIndex, function);
	}
	}

	void Instance::tableInit(uint32_t dstOffset, uint32_t srcOffset, uint32_t length, uint32_t elementIndex, uint32_t tableIndex)
	{
	RELEASE_ASSERT(elementIndex < m_module->moduleInformation().elementCount());
	RELEASE_ASSERT(tableIndex < m_module->moduleInformation().tableCount());

	const Element* elementSegment = elementAt(elementIndex);
	RELEASE_ASSERT(elementSegment);
	RELEASE_ASSERT(elementSegment->isPassive());
	initElementSegment(tableIndex, *elementSegment, dstOffset, srcOffset, length);
	}

	void Instance::setTable(unsigned i, Ref<Table>&& table)
	{
	RELEASE_ASSERT(i < m_module->moduleInformation().tableCount());
	ASSERT(!this->table(i));
	bitwise_cast<Table>(bitwise_cast<char>(this) + offsetOfTablePtr(m_numImportFunctions, i)) = &table.leakRef();
	}

	void Instance::linkGlobal(unsigned i, Ref<Global>&& global)
	{
	m_globals.get()[i].m_pointer = global->valuePointer();
	m_linkedGlobals.set(i, WTFMove(global));
	}

	} } // namespace JSC::Wasm

	#endif // ENABLE(WEBASSEMBLY)