mirror of
https://github.com/RGBCube/serenity
synced 2025-05-14 05:05:00 +00:00
b6d4eea7ac
Instead of returning HeapBlock memory to the kernel (or a non-type specific shared cache), we now keep a BlockAllocator per CellAllocator and implement "deallocation" by basically informing the kernel that we don't need the physical memory right now. This is done with MADV_FREE or MADV_DONTNEED if available, but for other platforms (including SerenityOS) we munmap and then re-mmap the memory to achieve the same effect. It's definitely clunky, so I've added a FIXME about implementing the madvise options on SerenityOS too. The important outcome of this change is that GC types that use a type-specific allocator become immune to use-after-free type confusion attacks, since their virtual addresses will only ever be re-used for the same exact type again and again. Fixes #22274
52 lines
1.3 KiB
C++
52 lines
1.3 KiB
C++
/*
|
|
* Copyright (c) 2020-2023, Andreas Kling <kling@serenityos.org>
|
|
*
|
|
* SPDX-License-Identifier: BSD-2-Clause
|
|
*/
|
|
|
|
#include <AK/Badge.h>
|
|
#include <LibJS/Heap/BlockAllocator.h>
|
|
#include <LibJS/Heap/CellAllocator.h>
|
|
#include <LibJS/Heap/Heap.h>
|
|
#include <LibJS/Heap/HeapBlock.h>
|
|
|
|
namespace JS {
|
|
|
|
CellAllocator::CellAllocator(size_t cell_size)
|
|
: m_cell_size(cell_size)
|
|
{
|
|
}
|
|
|
|
Cell* CellAllocator::allocate_cell(Heap& heap)
|
|
{
|
|
if (!m_list_node.is_in_list())
|
|
heap.register_cell_allocator({}, *this);
|
|
|
|
if (m_usable_blocks.is_empty()) {
|
|
auto block = HeapBlock::create_with_cell_size(heap, *this, m_cell_size);
|
|
m_usable_blocks.append(*block.leak_ptr());
|
|
}
|
|
|
|
auto& block = *m_usable_blocks.last();
|
|
auto* cell = block.allocate();
|
|
VERIFY(cell);
|
|
if (block.is_full())
|
|
m_full_blocks.append(*m_usable_blocks.last());
|
|
return cell;
|
|
}
|
|
|
|
void CellAllocator::block_did_become_empty(Badge<Heap>, HeapBlock& block)
|
|
{
|
|
block.m_list_node.remove();
|
|
// NOTE: HeapBlocks are managed by the BlockAllocator, so we don't want to `delete` the block here.
|
|
block.~HeapBlock();
|
|
m_block_allocator.deallocate_block(&block);
|
|
}
|
|
|
|
void CellAllocator::block_did_become_usable(Badge<Heap>, HeapBlock& block)
|
|
{
|
|
VERIFY(!block.is_full());
|
|
m_usable_blocks.append(block);
|
|
}
|
|
|
|
}
|