WebKit/Source/JavaScriptCore/assembler/ProbeStack.h at main · WebKit/WebKit · GitHub

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* 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 <JavaScriptCore/CPU.h>

#include <wtf/HashMap.h>

#include <wtf/Platform.h>

#include <wtf/StdLibExtras.h>

#include <wtf/TZoneMalloc.h>

#include <wtf/Threading.h>

#if ENABLE(ASSEMBLER)

WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN

namespace JSC {

namespace Probe {

class Page {

WTF_MAKE_TZONE_ALLOCATED(Page);

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>(static_cast<uint8_t*>(logicalBaseAddress) + offset);

}

template<typename T>

void set(void* logicalAddress, T value)

{

if constexpr (sizeof(T) <= s_chunkSize)

m_dirtyBits |= dirtyBitFor(logicalAddress);

else {

size_t numberOfChunks = roundUpToMultipleOf<sizeof(T)>(s_chunkSize) / s_chunkSize;

uint8_t* dirtyAddress = static_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>(static_cast<uint8_t*>(logicalBaseAddress) + offset, value);

}

bool hasWritesToFlush() const { return !!m_dirtyBits; }

void flushWritesIfNeeded()

{

if (m_dirtyBits)

flushWrites();

}

void* NODELETE 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 static_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 = isAddress64Bit() ? 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");

alignas(uintptr_t) std::byte m_buffer[s_pageSize];

};

class Stack {

WTF_MAKE_TZONE_ALLOCATED(Stack);

public:

Stack()

: m_stackBounds(Thread::currentSingleton().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>(static_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>(static_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 (Page::baseAddressFor(address) == m_lastAccessedPageBaseAddress) [[likely]]

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;

UncheckedKeyHashMap<void*, std::unique_ptr<Page>> m_pages;

#if ASSERT_ENABLED

bool m_isValid { true };

#endif

};

} // namespace Probe

} // namespace JSC

WTF_ALLOW_UNSAFE_BUFFER_USAGE_END

#endif // ENABLE(ASSEMBLER)

WebKit/Source/JavaScriptCore/assembler/ProbeStack.h at main · WebKit/WebKit · GitHub

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