74 lines
3.5 KiB
C++
74 lines
3.5 KiB
C++
/*
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* Copyright (C) 2019 Apple Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include "IsoPage.h"
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#include "StdLibExtras.h"
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#include "VMAllocate.h"
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namespace bmalloc {
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// IsoSharedPage never becomes empty state again after we allocate some cells from IsoSharedPage. This makes IsoSharedPage management super simple.
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// This is because empty IsoSharedPage is still split into various different objects that should keep some part of virtual memory region dedicated.
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// We cannot set up bump allocation for such a page. Not freeing IsoSharedPages are OK since IsoSharedPage is only used for the lower tier of IsoHeap.
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template<typename Config, typename Type>
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void IsoSharedPage::free(const LockHolder&, api::IsoHeap<Type>& handle, void* ptr)
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{
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auto& heapImpl = handle.impl();
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uint8_t index = *indexSlotFor<Config>(ptr) & IsoHeapImplBase::maxAllocationFromSharedMask;
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// IsoDeallocator::deallocate is called from delete operator. This is dispatched by vtable if virtual destructor exists.
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// If vptr is replaced to the other vptr, we may accidentally chain this pointer to the incorrect HeapImplBase, which totally breaks the IsoHeap's goal.
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// To harden that, we validate that this pointer is actually allocated for a specific HeapImplBase here by checking whether this pointer is listed in HeapImplBase's shared cells.
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RELEASE_BASSERT(heapImpl.m_sharedCells[index].get() == ptr);
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heapImpl.m_availableShared |= (1U << index);
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}
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inline VariadicBumpAllocator IsoSharedPage::startAllocating(const LockHolder&)
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{
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static constexpr bool verbose = false;
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if (verbose) {
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fprintf(stderr, "%p: starting shared allocation.\n", this);
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fprintf(stderr, "%p: preparing to shared bump.\n", this);
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}
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char* payloadEnd = reinterpret_cast<char*>(this) + IsoSharedPage::pageSize;
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unsigned remaining = static_cast<unsigned>(roundDownToMultipleOf<alignmentForIsoSharedAllocation>(static_cast<uintptr_t>(IsoSharedPage::pageSize - sizeof(IsoSharedPage))));
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return VariadicBumpAllocator(payloadEnd, remaining);
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}
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inline void IsoSharedPage::stopAllocating(const LockHolder&)
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{
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static constexpr bool verbose = false;
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if (verbose)
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fprintf(stderr, "%p: stopping shared allocation.\n", this);
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}
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} // namespace bmalloc
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