/*

 * Copyright (c) 2020-2024, Andreas Kling <andreas@ladybird.org>

 *

 * SPDX-License-Identifier: BSD-2-Clause

 */

#include <AK/Assertions.h>

#include <AK/NonnullOwnPtr.h>

#include <AK/Platform.h>

#include <LibJS/Heap/Heap.h>

#include <LibJS/Heap/HeapBlock.h>

#include <stdio.h>

#include <sys/mman.h>

#ifdef HAS_ADDRESS_SANITIZER

#    include <sanitizer/asan_interface.h>

#endif

namespace JS {

size_t HeapBlockBase::block_size = PAGE_SIZE;

NonnullOwnPtr<HeapBlock> HeapBlock::create_with_cell_size(Heap& heap, CellAllocator& cell_allocator, size_t cell_size, [[maybe_unused]] char const* class_name)

{

#ifdef AK_OS_SERENITY

    char name[64];

    if (class_name)

        snprintf(name, sizeof(name), "LibJS: HeapBlock(%zu): %s", cell_size, class_name);

    else

        snprintf(name, sizeof(name), "LibJS: HeapBlock(%zu)", cell_size);

#else

    char const* name = nullptr;

#endif

    auto* block = static_cast<HeapBlock*>(cell_allocator.block_allocator().allocate_block(name));

    new (block) HeapBlock(heap, cell_allocator, cell_size);

    return NonnullOwnPtr<HeapBlock>(NonnullOwnPtr<HeapBlock>::Adopt, *block);

}

HeapBlock::HeapBlock(Heap& heap, CellAllocator& cell_allocator, size_t cell_size)

    : HeapBlockBase(heap)

    , m_cell_allocator(cell_allocator)

    , m_cell_size(cell_size)

{

    VERIFY(cell_size >= sizeof(FreelistEntry));

    ASAN_POISON_MEMORY_REGION(m_storage, block_size - sizeof(HeapBlock));

}

void HeapBlock::deallocate(Cell* cell)

{

    VERIFY(is_valid_cell_pointer(cell));

    VERIFY(!m_freelist || is_valid_cell_pointer(m_freelist));

    VERIFY(cell->state() == Cell::State::Live);

    VERIFY(!cell->is_marked());

    cell->~Cell();

    auto* freelist_entry = new (cell) FreelistEntry();

    freelist_entry->set_state(Cell::State::Dead);

    freelist_entry->next = m_freelist;

    m_freelist = freelist_entry;

#ifdef HAS_ADDRESS_SANITIZER

    auto dword_after_freelist = round_up_to_power_of_two(reinterpret_cast<uintptr_t>(freelist_entry) + sizeof(FreelistEntry), 8);

    VERIFY((dword_after_freelist - reinterpret_cast<uintptr_t>(freelist_entry)) <= m_cell_size);

    VERIFY(m_cell_size >= sizeof(FreelistEntry));

    // We can't poision the cell tracking data, nor the FreeListEntry's vtable or next pointer

    // This means there's sizeof(FreelistEntry) data at the front of each cell that is always read/write

    // 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.

    ASAN_POISON_MEMORY_REGION(reinterpret_cast<void*>(dword_after_freelist), m_cell_size - sizeof(FreelistEntry));

#endif

}

}