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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. ``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 <algorithm>
#include <wtf/StackPointer.h>
#include <wtf/ThreadingPrimitives.h>
WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN
namespace WTF {
class StackBounds {
WTF_MAKE_FAST_ALLOCATED;
public:
// This 64k number was picked because a sampling of stack usage differences
// between consecutive entries into one of the Interpreter::execute...()
// functions was seen to be as high as 27k. Hence, 64k is chosen as a
// conservative availability value that is not too large but comfortably
// exceeds 27k with some buffer for error.
#if !ASAN_ENABLED
static constexpr size_t DefaultReservedZone = 64 * 1024;
#else
// ASAN inflates stack frames a lot. A factor of 3 was empirically found to
// be the ratio of inflation of stack usage between 2 consecutive stack
// recursion checkpoints. So, we'll also multiply the reserved zone size
// accordingly to accommodate this.
static constexpr size_t DefaultReservedZone = 64 * 1024 * 3;
#endif
static constexpr StackBounds emptyBounds() { return StackBounds(); }
#if HAVE(STACK_BOUNDS_FOR_NEW_THREAD)
// This function is only effective for newly created threads. In some platform, it returns a bogus value for the main thread.
static StackBounds newThreadStackBounds(PlatformThreadHandle);
#endif
static StackBounds currentThreadStackBounds()
{
auto result = currentThreadStackBoundsInternal();
result.checkConsistency();
return result;
}
void* origin() const
{
ASSERT(m_origin);
return m_origin;
}
void* end() const
{
ASSERT(m_bound);
return m_bound;
}
size_t size() const
{
return static_cast<char*>(m_origin) - static_cast<char*>(m_bound);
}
bool isEmpty() const { return !m_origin; }
bool contains(void* p) const
{
if (isEmpty())
return false;
return (m_origin >= p) && (p > m_bound);
}
void* recursionLimit(size_t minReservedZone = DefaultReservedZone) const
{
checkConsistency();
return static_cast<char*>(m_bound) + minReservedZone;
}
void* recursionLimit(char* startOfUserStack, size_t maxUserStack, size_t reservedZoneSize) const
{
checkConsistency();
if (maxUserStack < reservedZoneSize)
reservedZoneSize = maxUserStack;
size_t maxUserStackWithReservedZone = maxUserStack - reservedZoneSize;
char* endOfStackWithReservedZone = reinterpret_cast<char*>(m_bound) + reservedZoneSize;
if (startOfUserStack < endOfStackWithReservedZone)
return endOfStackWithReservedZone;
size_t availableUserStack = startOfUserStack - endOfStackWithReservedZone;
if (maxUserStackWithReservedZone > availableUserStack)
maxUserStackWithReservedZone = availableUserStack;
return startOfUserStack - maxUserStackWithReservedZone;
}
StackBounds withSoftOrigin(void* origin) const
{
ASSERT(contains(origin));
return StackBounds(origin, m_bound);
}
private:
StackBounds(void* origin, void* end)
: m_origin(origin)
, m_bound(end)
{
ASSERT(isGrowingDownwards());
}
constexpr StackBounds()
: m_origin(nullptr)
, m_bound(nullptr)
{
}
inline bool isGrowingDownwards() const
{
ASSERT(m_origin && m_bound);
return m_bound <= m_origin;
}
WTF_EXPORT_PRIVATE static StackBounds currentThreadStackBoundsInternal();
void checkConsistency() const
{
#if ASSERT_ENABLED
void* currentPosition = currentStackPointer();
ASSERT(m_origin != m_bound);
ASSERT(currentPosition < m_origin && currentPosition > m_bound);
#endif
}
void* m_origin;
void* m_bound;
friend class StackStats;
};
} // namespace WTF
using WTF::StackBounds;
WTF_ALLOW_UNSAFE_BUFFER_USAGE_END
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