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c2988a7dd5
Instead, smuggle it in as a `void*` private data and let Javascript aware code cast out that pointer to a VM&. In order to make this split, rename JS::Cell to JS::CellImpl. Once we have a LibGC, this will become GC::Cell. CellImpl then has no specific knowledge of the VM& and Realm&. That knowledge is instead put into JS::Cell, which inherits from CellImpl. JS::Cell is responsible for JavaScript's realm initialization, as well as converting of the void* private data to what it knows should be the VM&.
64 lines
2.3 KiB
C++
64 lines
2.3 KiB
C++
/*
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* Copyright (c) 2020-2024, Andreas Kling <andreas@ladybird.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/Assertions.h>
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#include <AK/NonnullOwnPtr.h>
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#include <AK/Platform.h>
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#include <LibJS/Heap/Heap.h>
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#include <LibJS/Heap/HeapBlock.h>
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#include <stdio.h>
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#include <sys/mman.h>
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#ifdef HAS_ADDRESS_SANITIZER
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# include <sanitizer/asan_interface.h>
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#endif
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namespace JS {
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size_t HeapBlockBase::block_size = PAGE_SIZE;
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NonnullOwnPtr<HeapBlock> HeapBlock::create_with_cell_size(Heap& heap, CellAllocator& cell_allocator, size_t cell_size, [[maybe_unused]] char const* class_name)
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{
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char const* name = nullptr;
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auto* block = static_cast<HeapBlock*>(cell_allocator.block_allocator().allocate_block(name));
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new (block) HeapBlock(heap, cell_allocator, cell_size);
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return NonnullOwnPtr<HeapBlock>(NonnullOwnPtr<HeapBlock>::Adopt, *block);
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}
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HeapBlock::HeapBlock(Heap& heap, CellAllocator& cell_allocator, size_t cell_size)
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: HeapBlockBase(heap)
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, m_cell_allocator(cell_allocator)
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, m_cell_size(cell_size)
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{
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VERIFY(cell_size >= sizeof(FreelistEntry));
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ASAN_POISON_MEMORY_REGION(m_storage, block_size - sizeof(HeapBlock));
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}
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void HeapBlock::deallocate(CellImpl* cell)
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{
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VERIFY(is_valid_cell_pointer(cell));
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VERIFY(!m_freelist || is_valid_cell_pointer(m_freelist));
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VERIFY(cell->state() == CellImpl::State::Live);
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VERIFY(!cell->is_marked());
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cell->~CellImpl();
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auto* freelist_entry = new (cell) FreelistEntry();
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freelist_entry->set_state(CellImpl::State::Dead);
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freelist_entry->next = m_freelist;
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m_freelist = freelist_entry;
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#ifdef HAS_ADDRESS_SANITIZER
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auto dword_after_freelist = round_up_to_power_of_two(reinterpret_cast<uintptr_t>(freelist_entry) + sizeof(FreelistEntry), 8);
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VERIFY((dword_after_freelist - reinterpret_cast<uintptr_t>(freelist_entry)) <= m_cell_size);
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VERIFY(m_cell_size >= sizeof(FreelistEntry));
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// We can't poision the cell tracking data, nor the FreeListEntry's vtable or next pointer
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// This means there's sizeof(FreelistEntry) data at the front of each cell that is always read/write
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// On x86_64, this ends up being 24 bytes due to the size of the FreeListEntry's vtable, while on x86, it's only 12 bytes.
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ASAN_POISON_MEMORY_REGION(reinterpret_cast<void*>(dword_after_freelist), m_cell_size - sizeof(FreelistEntry));
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#endif
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}
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}
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