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https://github.com/RGBCube/serenity
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6aba64b60f
Mark the entirety of a heap block's storage poisoned at construction. Unpoison all of a Cell's memory before allocating it, and re-poison as much as possible on deallocation. Unfortunately, the entirety of the FreelistEntry must be kept unpoisoned in order for reallocation to work correctly. Decreasing the size of FreelistEntry or adding a larger redzone to Cells would make the instrumentation even better.
62 lines
2.1 KiB
C++
62 lines
2.1 KiB
C++
/*
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* Copyright (c) 2020, Andreas Kling <kling@serenityos.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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NonnullOwnPtr<HeapBlock> HeapBlock::create_with_cell_size(Heap& heap, size_t cell_size)
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{
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char name[64];
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snprintf(name, sizeof(name), "LibJS: HeapBlock(%zu)", cell_size);
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auto* block = static_cast<HeapBlock*>(heap.block_allocator().allocate_block(name));
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new (block) HeapBlock(heap, 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, size_t cell_size)
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: m_heap(heap)
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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);
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}
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void HeapBlock::deallocate(Cell* 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() == Cell::State::Live);
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VERIFY(!cell->is_marked());
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cell->~Cell();
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auto* freelist_entry = new (cell) FreelistEntry();
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freelist_entry->set_state(Cell::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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