Source/JavaScriptCore/runtime/ScopedArguments.cpp

/*
 * Copyright (C) 2015-2021 Apple Inc. All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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#include "config.h"
#include "ScopedArguments.h"

#include "GenericArgumentsInlines.h"

namespace JSC {

STATIC_ASSERT_IS_TRIVIALLY_DESTRUCTIBLE(ScopedArguments);

const ClassInfo ScopedArguments::s_info = { "Arguments", &Base::s_info, nullptr, nullptr, CREATE_METHOD_TABLE(ScopedArguments) };

ScopedArguments::ScopedArguments(VM& vm, Structure* structure, WriteBarrier<Unknown>* storage, unsigned totalLength)
    : GenericArguments(vm, structure)
    , m_totalLength(totalLength)
{
    if (storage)
        m_storage.set(vm, this, storage);
}

void ScopedArguments::finishCreation(VM& vm, JSFunction* callee, ScopedArgumentsTable* table, JSLexicalEnvironment* scope)
{
    Base::finishCreation(vm);
    m_callee.set(vm, this, callee);
    m_table.set(vm, this, table);
    m_scope.set(vm, this, scope);
}

ScopedArguments* ScopedArguments::createUninitialized(VM& vm, Structure* structure, JSFunction* callee, ScopedArgumentsTable* table, JSLexicalEnvironment* scope, unsigned totalLength)
{
    WriteBarrier<Unknown>* storage = nullptr;
    if (totalLength > table->length()) {
        Checked<unsigned> overflowLength = totalLength - table->length();
        storage = static_cast<WriteBarrier<Unknown>*>(vm.jsValueGigacageAuxiliarySpace().allocate(vm, overflowLength * sizeof(WriteBarrier<Unknown>), nullptr, AllocationFailureMode::Assert));
    }

    ScopedArguments* result = new (
        NotNull,
        allocateCell<ScopedArguments>(vm))
        ScopedArguments(vm, structure, storage, totalLength);
    result->finishCreation(vm, callee, table, scope);
    return result;
}

ScopedArguments* ScopedArguments::create(VM& vm, Structure* structure, JSFunction* callee, ScopedArgumentsTable* table, JSLexicalEnvironment* scope, unsigned totalLength)
{
    ScopedArguments* result =
        createUninitialized(vm, structure, callee, table, scope, totalLength);

    unsigned namedLength = table->length();
    for (unsigned i = namedLength; i < totalLength; ++i)
        result->storage()[i - namedLength].clear();
    
    return result;
}

ScopedArguments* ScopedArguments::createByCopying(JSGlobalObject* globalObject, CallFrame* callFrame, ScopedArgumentsTable* table, JSLexicalEnvironment* scope)
{
    return createByCopyingFrom(
        globalObject->vm(), globalObject->scopedArgumentsStructure(),
        callFrame->registers() + CallFrame::argumentOffset(0), callFrame->argumentCount(),
        jsCast<JSFunction*>(callFrame->jsCallee()), table, scope);
}

ScopedArguments* ScopedArguments::createByCopyingFrom(VM& vm, Structure* structure, Register* argumentsStart, unsigned totalLength, JSFunction* callee, ScopedArgumentsTable* table, JSLexicalEnvironment* scope)
{
    ScopedArguments* result =
        createUninitialized(vm, structure, callee, table, scope, totalLength);
    
    unsigned namedLength = table->length();
    for (unsigned i = namedLength; i < totalLength; ++i)
        result->storage()[i - namedLength].set(vm, result, argumentsStart[i].jsValue());
    
    return result;
}

template<typename Visitor>
void ScopedArguments::visitChildrenImpl(JSCell* cell, Visitor& visitor)
{
    ScopedArguments* thisObject = static_cast<ScopedArguments*>(cell);
    ASSERT_GC_OBJECT_INHERITS(thisObject, info());
    Base::visitChildren(thisObject, visitor);

    visitor.append(thisObject->m_callee);
    visitor.append(thisObject->m_table);
    visitor.append(thisObject->m_scope);
    
    if (WriteBarrier<Unknown>* storage = thisObject->m_storage.get()) {
        visitor.markAuxiliary(storage);
        if (thisObject->m_totalLength > thisObject->m_table->length())
            visitor.appendValues(storage, thisObject->m_totalLength - thisObject->m_table->length());
    }
}

DEFINE_VISIT_CHILDREN(ScopedArguments);

Structure* ScopedArguments::createStructure(VM& vm, JSGlobalObject* globalObject, JSValue prototype)
{
    return Structure::create(vm, globalObject, prototype, TypeInfo(ScopedArgumentsType, StructureFlags), info());
}

void ScopedArguments::overrideThings(JSGlobalObject* globalObject)
{
    VM& vm = globalObject->vm();

    RELEASE_ASSERT(!m_overrodeThings);
    
    putDirect(vm, vm.propertyNames->length, jsNumber(m_table->length()), static_cast<unsigned>(PropertyAttribute::DontEnum));
    putDirect(vm, vm.propertyNames->callee, m_callee.get(), static_cast<unsigned>(PropertyAttribute::DontEnum));
    putDirect(vm, vm.propertyNames->iteratorSymbol, globalObject->arrayProtoValuesFunction(), static_cast<unsigned>(PropertyAttribute::DontEnum));
    
    m_overrodeThings = true;
}

void ScopedArguments::overrideThingsIfNecessary(JSGlobalObject* globalObject)
{
    if (!m_overrodeThings)
        overrideThings(globalObject);
}

void ScopedArguments::unmapArgument(JSGlobalObject* globalObject, uint32_t i)
{
    VM& vm = globalObject->vm();
    auto scope = DECLARE_THROW_SCOPE(vm);
    ASSERT_WITH_SECURITY_IMPLICATION(i < m_totalLength);
    unsigned namedLength = m_table->length();
    if (i < namedLength) {
        auto* maybeCloned = m_table->trySet(vm, i, ScopeOffset());
        if (UNLIKELY(!maybeCloned)) {
            throwOutOfMemoryError(globalObject, scope);
            return;
        }
        m_table.set(vm, this, maybeCloned);
    } else
        storage()[i - namedLength].clear();
}

void ScopedArguments::copyToArguments(JSGlobalObject* globalObject, JSValue* firstElementDest, unsigned offset, unsigned length)
{
    GenericArguments::copyToArguments(globalObject, firstElementDest, offset, length);
}

} // namespace JSC