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/*
* Copyright (C) 2017-2021 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. AND ITS CONTRIBUTORS ``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 ITS 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 <wtf/Gigacage.h>
#include <wtf/MathExtras.h>
#include <wtf/PtrTag.h>
#include <wtf/RawPtrTraits.h>
#include <climits>
#if OS(DARWIN)
#include <mach/vm_param.h>
#endif
namespace WTF {
constexpr bool tagCagedPtr = true;
template<Gigacage::Kind passedKind, typename T, bool shouldTag = false, typename PtrTraits = RawPtrTraits<T>>
class CagedPtr {
public:
static constexpr Gigacage::Kind kind = passedKind;
static constexpr unsigned numberOfPointerBits = sizeof(T*) * CHAR_BIT;
static constexpr unsigned maxNumberOfAllowedPACBits = numberOfPointerBits - OS_CONSTANT(EFFECTIVE_ADDRESS_WIDTH);
static constexpr uintptr_t nonPACBitsMask = (1ull << (numberOfPointerBits - maxNumberOfAllowedPACBits)) - 1;
CagedPtr() : CagedPtr(nullptr) { }
CagedPtr(std::nullptr_t)
: m_ptr(shouldTag ? tagArrayPtr<T>(nullptr, 0) : nullptr)
{ }
CagedPtr(T* ptr, size_t size)
: m_ptr(shouldTag ? tagArrayPtr(ptr, size) : ptr)
{ }
T* get(size_t size) const
{
ASSERT(m_ptr);
T* ptr = PtrTraits::unwrap(m_ptr);
T* cagedPtr = Gigacage::caged(kind, ptr);
T* untaggedPtr = shouldTag ? untagArrayPtr(mergePointers(ptr, cagedPtr), size) : cagedPtr;
return untaggedPtr;
}
T* getMayBeNull(size_t size) const
{
T* ptr = PtrTraits::unwrap(m_ptr);
if (!removeArrayPtrTag(ptr))
return nullptr;
T* cagedPtr = Gigacage::caged(kind, ptr);
T* untaggedPtr = shouldTag ? untagArrayPtr(mergePointers(ptr, cagedPtr), size) : cagedPtr;
return untaggedPtr;
}
T* getUnsafe() const
{
T* ptr = PtrTraits::unwrap(m_ptr);
ptr = shouldTag ? removeArrayPtrTag(ptr) : ptr;
return Gigacage::cagedMayBeNull(kind, ptr);
}
// We need the template here so that the type of U is deduced at usage time rather than class time. U should always be T.
template<typename U = T>
typename std::enable_if<!std::is_same<void, U>::value, T>::type&
/* T& */ at(size_t index, size_t size) const { return get(size)[index]; }
void recage(size_t oldSize, size_t newSize)
{
auto ptr = get(oldSize);
ASSERT(ptr == getUnsafe());
*this = CagedPtr(ptr, newSize);
}
CagedPtr(CagedPtr& other)
: m_ptr(other.m_ptr)
{
}
CagedPtr& operator=(const CagedPtr& ptr)
{
m_ptr = ptr.m_ptr;
return *this;
}
CagedPtr(CagedPtr&& other)
: m_ptr(PtrTraits::exchange(other.m_ptr, nullptr))
{
}
CagedPtr& operator=(CagedPtr&& ptr)
{
m_ptr = PtrTraits::exchange(ptr.m_ptr, nullptr);
return *this;
}
bool operator==(const CagedPtr& other) const
{
bool result = m_ptr == other.m_ptr;
ASSERT(result == (getUnsafe() == other.getUnsafe()));
return result;
}
bool operator!=(const CagedPtr& other) const
{
return !(*this == other);
}
explicit operator bool() const
{
return getUnsafe() != nullptr;
}
T* rawBits() const
{
return bitwise_cast<T*>(m_ptr);
}
protected:
static inline T* mergePointers(T* sourcePtr, T* cagedPtr)
{
#if CPU(ARM64E)
return reinterpret_cast<T*>((reinterpret_cast<uintptr_t>(sourcePtr) & ~nonPACBitsMask) | (reinterpret_cast<uintptr_t>(cagedPtr) & nonPACBitsMask));
#else
UNUSED_PARAM(sourcePtr);
return cagedPtr;
#endif
}
typename PtrTraits::StorageType m_ptr;
};
} // namespace WTF
using WTF::CagedPtr;
using WTF::tagCagedPtr;
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