129 lines
4.6 KiB
Rust
129 lines
4.6 KiB
Rust
use core::alloc::GlobalAlloc;
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use core::mem;
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use core::ptr::NonNull;
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use x86_64::structures::paging::{FrameAllocator, Mapper, Page, PageTableFlags, Size4KiB};
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use x86_64::structures::paging::mapper::MapToError;
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use x86_64::VirtAddr;
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use crate::memory::PageSize;
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use super::Locked;
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pub const HEAP_START: u64 = 0x_4444_4444_0000;
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pub const HEAP_SIZE: u64 = 100 * 1024; // 100 KiB
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#[global_allocator]
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static ALLOCATOR: Locked<FixedSizeBlockAllocator> = Locked::new(FixedSizeBlockAllocator::new());
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const BLOCK_SIZES: &[usize] = &[8, 16, 32, 64, 128, 256, 512, 1024, 2048];
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pub struct FixedSizeBlockAllocator {
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list_heads: [Option<&'static mut FixedSizeBlockNode>; BLOCK_SIZES.len()],
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#[cfg(feature = "f_ll_alloc")]
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fallback_allocator: linked_list_allocator::Heap,
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}
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pub struct FixedSizeBlockNode {
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next: Option<&'static mut FixedSizeBlockNode>,
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}
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impl FixedSizeBlockAllocator {
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pub const fn new() -> Self {
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const EMPTY: Option<&'static mut FixedSizeBlockNode> = None;
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Self {
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list_heads: [EMPTY; BLOCK_SIZES.len()],
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#[cfg(feature = "f_ll_alloc")]
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fallback_allocator: linked_list_allocator::Heap::empty(),
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}
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}
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pub unsafe fn init(&mut self, heap_start: usize, heap_size: usize) {
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self.fallback_allocator.init(heap_start, heap_size);
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}
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fn fallback_alloc(&mut self, layout: core::alloc::Layout) -> *mut u8 {
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match self.fallback_allocator.allocate_first_fit(layout) {
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Ok(ptr) => ptr.as_ptr(),
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Err(_) => core::ptr::null_mut(),
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}
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}
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}
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unsafe impl GlobalAlloc for Locked<FixedSizeBlockAllocator> {
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unsafe fn alloc(&self, layout: core::alloc::Layout) -> *mut u8 {
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let mut allocator = self.lock();
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match list_index(&layout) {
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Some(index) => {
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match allocator.list_heads[index].take() {
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Some(node) => {
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allocator.list_heads[index] = node.next.take();
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node as *mut FixedSizeBlockNode as *mut u8
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}
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None => {
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// no block exists in list => allocate new block
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let block_size = BLOCK_SIZES[index];
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// only works if all block sizes are a power of 2
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let block_align = block_size;
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let layout = core::alloc::Layout::from_size_align(block_size, block_align)
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.unwrap();
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allocator.fallback_alloc(layout)
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}
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}
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}
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None => allocator.fallback_alloc(layout),
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}
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}
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unsafe fn dealloc(&self, ptr: *mut u8, layout: core::alloc::Layout) {
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let mut allocator = self.lock();
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match list_index(&layout) {
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Some(index) => {
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let new_node = FixedSizeBlockNode {
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next: allocator.list_heads[index].take(),
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};
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// verify that block has size and alignment required for storing node
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assert!(mem::size_of::<FixedSizeBlockNode>() <= BLOCK_SIZES[index]);
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assert!(mem::align_of::<FixedSizeBlockNode>() <= BLOCK_SIZES[index]);
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let new_node_ptr = ptr as *mut FixedSizeBlockNode;
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new_node_ptr.write(new_node);
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allocator.list_heads[index] = Some(&mut *new_node_ptr);
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}
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None => {
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let ptr = NonNull::new(ptr).unwrap();
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allocator.fallback_allocator.deallocate(ptr, layout);
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}
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}
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}
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}
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fn list_index(layout: &core::alloc::Layout) -> Option<usize> {
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let required_block_size = layout.size().max(layout.align());
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BLOCK_SIZES.iter().position(|&s| s >= required_block_size)
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}
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pub fn init_heap(
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mapper: &mut impl Mapper<PageSize>,
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frame_allocator: &mut impl FrameAllocator<PageSize>,
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) -> Result<(), MapToError<PageSize>> {
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let page_range = {
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let heap_start = VirtAddr::new(HEAP_START as u64);
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let heap_end = heap_start + HEAP_SIZE - 1u64;
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let heap_start_page = Page::containing_address(heap_start);
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let heap_end_page = Page::containing_address(heap_end);
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Page::range_inclusive(heap_start_page, heap_end_page)
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};
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for page in page_range {
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let frame = frame_allocator
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.allocate_frame()
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.ok_or(MapToError::FrameAllocationFailed)?;
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let flags = PageTableFlags::PRESENT | PageTableFlags::WRITABLE;
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unsafe {
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mapper.map_to(page, frame, flags, frame_allocator)?.flush()
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};
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}
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unsafe {
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ALLOCATOR.lock().init(HEAP_START as usize, HEAP_SIZE as usize);
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}
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Ok(())
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} |