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/*
* Copyright (C) 2010-2022 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/FastMalloc.h>
#include <wtf/StdLibExtras.h>
WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN
namespace WTF {
// We attempt to guess a value that is *AT LEAST* as large as the system's actual page size.
// This is impossible to do correctly at build time, but JSC really needs it at build time, so
// we have a RELEASE_ASSERT() inside WTF::pageSize to make sure it is set properly at runtime.
// All of these values are going to be incorrect on systems configured to use larger than normal
// page size, so on such systems it is expected that WebKit will crash until this value is changed
// and recompiled. Sorry.
//
// macOS x86_64 uses 4 KiB, but Apple's aarch64 systems use 16 KiB. Use 16 KiB on all Apple systems
// for consistency.
//
// Most Linux and Windows systems use a page size of 4 KiB.
//
// On Linux, Power systems normally use 64 KiB pages.
//
// aarch64 systems seem to be all over the place. Most Linux distros use 4 KiB, but RHEL uses
// 64 KiB. Linux on Apple Silicon uses 16KiB for best performance, so use that for Linux on
// aarch64 by default. USE(64KB_PAGE_BLOCK) allows overriding this.
//
// Use 64 KiB for any unknown CPUs to be conservative.
#if OS(DARWIN) || PLATFORM(PLAYSTATION) || CPU(MIPS) || CPU(MIPS64) || CPU(LOONGARCH64) || (OS(LINUX) && CPU(ARM64) && !USE(64KB_PAGE_BLOCK))
constexpr size_t CeilingOnPageSize = 16 * KB;
#elif USE(64KB_PAGE_BLOCK) || CPU(PPC) || CPU(PPC64) || CPU(PPC64LE) || CPU(UNKNOWN)
constexpr size_t CeilingOnPageSize = 64 * KB;
#elif OS(WINDOWS) || CPU(X86) || CPU(X86_64) || CPU(ARM) || CPU(ARM64) || CPU(RISCV64)
constexpr size_t CeilingOnPageSize = 4 * KB;
#else
#error Must set CeilingOnPageSize in PageBlock.h when adding a new CPU architecture!
#endif
WTF_EXPORT_PRIVATE size_t pageSize();
inline bool isPageAligned(size_t pageSize, void* address) { return !(reinterpret_cast<intptr_t>(address) & (pageSize - 1)); }
inline bool isPageAligned(size_t pageSize, size_t size) { return !(size & (pageSize - 1)); }
inline bool isPageAligned(void* address) { return isPageAligned(pageSize(), address); }
inline bool isPageAligned(size_t size) { return isPageAligned(pageSize(), size); }
class PageBlock {
WTF_MAKE_FAST_ALLOCATED;
public:
PageBlock() = default;
PageBlock(void*, size_t, bool hasGuardPages);
void* base() const { return m_base; }
void* end() const { return static_cast<uint8_t*>(m_base) + size(); }
size_t size() const { return m_size; }
operator bool() const { return !!m_realBase; }
bool contains(void* containedBase, size_t containedSize)
{
return containedBase >= m_base
&& (static_cast<char*>(containedBase) + containedSize) <= (static_cast<char*>(m_base) + m_size);
}
private:
void* m_realBase { nullptr };
void* m_base { nullptr };
size_t m_size { 0 };
};
inline PageBlock::PageBlock(void* base, size_t size, bool hasGuardPages)
: m_realBase(base)
, m_base(static_cast<char*>(base) + ((base && hasGuardPages) ? pageSize() : 0))
, m_size(size)
{
}
} // namespace WTF
using WTF::CeilingOnPageSize;
using WTF::pageSize;
using WTF::isPageAligned;
using WTF::isPowerOfTwo;
WTF_ALLOW_UNSAFE_BUFFER_USAGE_END
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