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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. ``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 "CPU.h"
#include <wtf/HashMap.h>
#include <wtf/StdLibExtras.h>
#include <wtf/Threading.h>
#if ENABLE(ASSEMBLER)
namespace JSC {
namespace Probe {
class Page {
WTF_MAKE_FAST_ALLOCATED;
public:
Page(void* baseAddress);
static void* baseAddressFor(void* p)
{
return reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(p) & ~s_pageMask);
}
static void* chunkAddressFor(void* p)
{
return reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(p) & ~s_chunkMask);
}
void* baseAddress() { return m_baseLogicalAddress; }
template<typename T>
T get(void* logicalAddress)
{
void* from = physicalAddressFor(logicalAddress);
typename std::remove_const<T>::type to { };
std::memcpy(&to, from, sizeof(to)); // Use std::memcpy to avoid strict aliasing issues.
return to;
}
template<typename T>
T get(void* logicalBaseAddress, ptrdiff_t offset)
{
return get<T>(reinterpret_cast<uint8_t*>(logicalBaseAddress) + offset);
}
template<typename T>
void set(void* logicalAddress, T value)
{
if (sizeof(T) <= s_chunkSize)
m_dirtyBits |= dirtyBitFor(logicalAddress);
else {
size_t numberOfChunks = roundUpToMultipleOf<sizeof(T)>(s_chunkSize) / s_chunkSize;
uint8_t* dirtyAddress = reinterpret_cast<uint8_t*>(logicalAddress);
for (size_t i = 0; i < numberOfChunks; ++i, dirtyAddress += s_chunkSize)
m_dirtyBits |= dirtyBitFor(dirtyAddress);
}
void* to = physicalAddressFor(logicalAddress);
std::memcpy(to, &value, sizeof(T)); // Use std::memcpy to avoid strict aliasing issues.
}
template<typename T>
void set(void* logicalBaseAddress, ptrdiff_t offset, T value)
{
set<T>(reinterpret_cast<uint8_t*>(logicalBaseAddress) + offset, value);
}
bool hasWritesToFlush() const { return !!m_dirtyBits; }
void flushWritesIfNeeded()
{
if (m_dirtyBits)
flushWrites();
}
void* lowWatermarkFromVisitingDirtyChunks();
private:
uint64_t dirtyBitFor(void* logicalAddress)
{
uintptr_t offset = reinterpret_cast<uintptr_t>(logicalAddress) & s_pageMask;
return static_cast<uint64_t>(1) << (offset >> s_chunkSizeShift);
}
void* physicalAddressFor(void* logicalAddress)
{
return reinterpret_cast<uint8_t*>(logicalAddress) + m_physicalAddressOffset;
}
void flushWrites();
void* m_baseLogicalAddress { nullptr };
ptrdiff_t m_physicalAddressOffset;
uint64_t m_dirtyBits { 0 };
#if ASAN_ENABLED
// The ASan stack may contain poisoned words that may be manipulated at ASan's discretion.
// We would never touch those words anyway, but let's ensure that the page size is set
// such that the chunk size is guaranteed to be exactly sizeof(uintptr_t) so that we won't
// inadvertently overwrite one of ASan's words on the stack when we copy back the dirty
// chunks.
// FIXME: we should consider using the same page size for both ASan and non-ASan builds.
// https://bugs.webkit.org/show_bug.cgi?id=176961
static constexpr size_t s_pageSize = 64 * sizeof(uintptr_t); // because there are 64 bits in m_dirtyBits.
#else // not ASAN_ENABLED
static constexpr size_t s_pageSize = 1024;
#endif // ASAN_ENABLED
static constexpr uintptr_t s_pageMask = s_pageSize - 1;
static constexpr size_t s_chunksPerPage = sizeof(uint64_t) * 8; // number of bits in m_dirtyBits.
static constexpr size_t s_chunkSize = s_pageSize / s_chunksPerPage;
static constexpr uintptr_t s_chunkMask = s_chunkSize - 1;
#if ASAN_ENABLED
static_assert(s_chunkSize == sizeof(uintptr_t), "bad chunkSizeShift");
static constexpr size_t s_chunkSizeShift = is64Bit() ? 3 : 2;
#else // no ASAN_ENABLED
static constexpr size_t s_chunkSizeShift = 4;
#endif // ASAN_ENABLED
static_assert(s_pageSize > s_chunkSize, "bad pageSize or chunkSize");
static_assert(s_chunkSize == (1 << s_chunkSizeShift), "bad chunkSizeShift");
typedef typename std::aligned_storage<s_pageSize, std::alignment_of<uintptr_t>::value>::type Buffer;
Buffer m_buffer;
};
class Stack {
WTF_MAKE_FAST_ALLOCATED;
public:
Stack()
: m_stackBounds(Thread::current().stack())
{ }
Stack(Stack&& other);
void* lowWatermarkFromVisitingDirtyPages();
void* lowWatermark(void* stackPointer)
{
ASSERT(Page::chunkAddressFor(stackPointer) == lowWatermarkFromVisitingDirtyPages());
return Page::chunkAddressFor(stackPointer);
}
template<typename T>
T get(void* address)
{
Page* page = pageFor(address);
return page->get<T>(address);
}
template<typename T>
T get(void* logicalBaseAddress, ptrdiff_t offset)
{
return get<T>(reinterpret_cast<uint8_t*>(logicalBaseAddress) + offset);
}
template<typename T>
void set(void* address, T value)
{
Page* page = pageFor(address);
page->set<T>(address, value);
}
template<typename T>
void set(void* logicalBaseAddress, ptrdiff_t offset, T value)
{
set<T>(reinterpret_cast<uint8_t*>(logicalBaseAddress) + offset, value);
}
JS_EXPORT_PRIVATE Page* ensurePageFor(void* address);
void* savedStackPointer() const { return m_savedStackPointer; }
void setSavedStackPointer(void* sp) { m_savedStackPointer = sp; }
bool hasWritesToFlush();
void flushWrites();
#if ASSERT_ENABLED
bool isValid() { return m_isValid; }
#endif
private:
Page* pageFor(void* address)
{
if (LIKELY(Page::baseAddressFor(address) == m_lastAccessedPageBaseAddress))
return m_lastAccessedPage;
return ensurePageFor(address);
}
void* m_savedStackPointer { nullptr };
// A cache of the last accessed page details for quick access.
void* m_lastAccessedPageBaseAddress { nullptr };
Page* m_lastAccessedPage { nullptr };
StackBounds m_stackBounds;
HashMap<void*, std::unique_ptr<Page>> m_pages;
#if ASSERT_ENABLED
bool m_isValid { true };
#endif
};
} // namespace Probe
} // namespace JSC
#endif // ENABLE(ASSEMBLER)