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/*
* Copyright (C) 2015-2019 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.
*/
#pragma once
#include "GenericArguments.h"
#include "JSLexicalEnvironment.h"
namespace JSC {
// This is an Arguments-class object that we create when you say "arguments" inside a function,
// and one or more of the arguments may be captured in the function's activation. The function
// will copy its formally declared arguments into the activation and then create this object. This
// object will store the overflow arguments, if there are any. This object will use the symbol
// table's ScopedArgumentsTable and the activation, or its overflow storage, to handle all indexed
// lookups.
class ScopedArguments final : public GenericArguments<ScopedArguments> {
private:
ScopedArguments(VM&, Structure*, WriteBarrier<Unknown>* storage);
void finishCreation(VM&, JSFunction* callee, ScopedArgumentsTable*, JSLexicalEnvironment*);
using Base = GenericArguments<ScopedArguments>;
public:
template<typename CellType, SubspaceAccess>
static CompleteSubspace* subspaceFor(VM& vm)
{
static_assert(!CellType::needsDestruction, "");
return &vm.variableSizedCellSpace;
}
// Creates an arguments object but leaves it uninitialized. This is dangerous if we GC right
// after allocation.
static ScopedArguments* createUninitialized(VM&, Structure*, JSFunction* callee, ScopedArgumentsTable*, JSLexicalEnvironment*, unsigned totalLength);
// Creates an arguments object and initializes everything to the empty value. Use this if you
// cannot guarantee that you'll immediately initialize all of the elements.
static ScopedArguments* create(VM&, Structure*, JSFunction* callee, ScopedArgumentsTable*, JSLexicalEnvironment*, unsigned totalLength);
// Creates an arguments object by copying the arguments from the stack.
static ScopedArguments* createByCopying(ExecState*, ScopedArgumentsTable*, JSLexicalEnvironment*);
// Creates an arguments object by copying the arguments from a well-defined stack location.
static ScopedArguments* createByCopyingFrom(VM&, Structure*, Register* argumentsStart, unsigned totalLength, JSFunction* callee, ScopedArgumentsTable*, JSLexicalEnvironment*);
static void visitChildren(JSCell*, SlotVisitor&);
uint32_t internalLength() const
{
return storageHeader().totalLength;
}
uint32_t length(ExecState* exec) const
{
VM& vm = exec->vm();
auto scope = DECLARE_THROW_SCOPE(vm);
if (UNLIKELY(storageHeader().overrodeThings)) {
auto value = get(exec, vm.propertyNames->length);
RETURN_IF_EXCEPTION(scope, 0);
RELEASE_AND_RETURN(scope, value.toUInt32(exec));
}
return internalLength();
}
bool isMappedArgument(uint32_t i) const
{
WriteBarrier<Unknown>* storage = overflowStorage();
if (i >= storageHeader(storage).totalLength)
return false;
unsigned namedLength = m_table->length();
if (i < namedLength)
return !!m_table->get(i);
return !!storage[i - namedLength].get();
}
bool isMappedArgumentInDFG(uint32_t i) const
{
return isMappedArgument(i);
}
JSValue getIndexQuickly(uint32_t i) const
{
ASSERT_WITH_SECURITY_IMPLICATION(isMappedArgument(i));
WriteBarrier<Unknown>* storage = overflowStorage();
unsigned totalLength = storageHeader(storage).totalLength;
unsigned namedLength = m_table->length();
if (i < namedLength)
return preciseIndexMaskPtr(i, totalLength, &m_scope->variableAt(m_table->get(i)))->get();
return preciseIndexMaskPtr(i, totalLength, storage + (i - namedLength))->get();
}
void setIndexQuickly(VM& vm, uint32_t i, JSValue value)
{
ASSERT_WITH_SECURITY_IMPLICATION(isMappedArgument(i));
WriteBarrier<Unknown>* storage = overflowStorage();
unsigned totalLength = storageHeader(storage).totalLength;
unsigned namedLength = m_table->length();
if (i < namedLength)
preciseIndexMaskPtr(i, totalLength, &m_scope->variableAt(m_table->get(i)))->set(vm, m_scope.get(), value);
else
preciseIndexMaskPtr(i, totalLength, storage + (i - namedLength))->set(vm, this, value);
}
JSFunction* callee()
{
return m_callee.get();
}
bool overrodeThings() const { return storageHeader().overrodeThings; }
void overrideThings(VM&);
void overrideThingsIfNecessary(VM&);
void unmapArgument(VM&, uint32_t index);
void initModifiedArgumentsDescriptorIfNecessary(VM& vm)
{
GenericArguments<ScopedArguments>::initModifiedArgumentsDescriptorIfNecessary(vm, m_table->length());
}
void setModifiedArgumentDescriptor(VM& vm, unsigned index)
{
GenericArguments<ScopedArguments>::setModifiedArgumentDescriptor(vm, index, m_table->length());
}
bool isModifiedArgumentDescriptor(unsigned index)
{
return GenericArguments<ScopedArguments>::isModifiedArgumentDescriptor(index, m_table->length());
}
void copyToArguments(ExecState*, VirtualRegister firstElementDest, unsigned offset, unsigned length);
DECLARE_INFO;
static Structure* createStructure(VM&, JSGlobalObject*, JSValue prototype);
static ptrdiff_t offsetOfStorage() { return OBJECT_OFFSETOF(ScopedArguments, m_storage); }
static ptrdiff_t offsetOfOverrodeThingsInStorage() { return OBJECT_OFFSETOF(StorageHeader, overrodeThings) - sizeof(WriteBarrier<Unknown>); }
static ptrdiff_t offsetOfTotalLengthInStorage() { return OBJECT_OFFSETOF(StorageHeader, totalLength) - sizeof(WriteBarrier<Unknown>); }
static ptrdiff_t offsetOfTable() { return OBJECT_OFFSETOF(ScopedArguments, m_table); }
static ptrdiff_t offsetOfScope() { return OBJECT_OFFSETOF(ScopedArguments, m_scope); }
static size_t allocationSize(size_t inlineSize)
{
RELEASE_ASSERT(!inlineSize);
return sizeof(ScopedArguments);
}
static size_t storageSize(Checked<size_t> capacity)
{
return (sizeof(WriteBarrier<Unknown>) * (capacity + static_cast<size_t>(1))).unsafeGet();
}
static size_t storageHeaderSize() { return sizeof(WriteBarrier<Unknown>); }
private:
struct StorageHeader {
unsigned totalLength;
bool overrodeThings; // True if length, callee, and caller are fully materialized in the object.
};
WriteBarrier<Unknown>* overflowStorage() const
{
return m_storage.get();
}
static StorageHeader& storageHeader(WriteBarrier<Unknown>* storage)
{
static_assert(sizeof(StorageHeader) <= sizeof(WriteBarrier<Unknown>), "StorageHeader needs to be no bigger than a JSValue");
return *bitwise_cast<StorageHeader*>(storage - 1);
}
StorageHeader& storageHeader() const
{
return storageHeader(overflowStorage());
}
WriteBarrier<JSFunction> m_callee;
WriteBarrier<ScopedArgumentsTable> m_table;
WriteBarrier<JSLexicalEnvironment> m_scope;
AuxiliaryBarrier<WriteBarrier<Unknown>*> m_storage;
};
} // namespace JSC