Merginng branch with main

src/allocator.rs

@@ -1,3 +1,6 @@
+pub mod fixed_size_block;
+pub mod linked_list;
+pub mod bump;
 use x86_64::{
     structures::paging::{
         mapper::MapToError, FrameAllocator, Mapper, Page, PageTableFlags, Size4KiB,
@@ -6,13 +9,36 @@ use x86_64::{
 };
 use alloc::alloc::{GlobalAlloc, Layout};
 use core::ptr::null_mut;
-use linked_list_allocator::LockedHeap;
+use fixed_size_block::FixedSizeBlockAllocator;
+
 
 pub const HEAP_START: usize = 0x_4444_4444_0000;
 pub const HEAP_SIZE: usize = 100 * 1024; // 100 KiB
 
 #[global_allocator]
-static ALLOCATOR: LockedHeap = LockedHeap::empty();
+static ALLOCATOR: Locked<FixedSizeBlockAllocator> = Locked::new(
+    FixedSizeBlockAllocator::new());
+/// A wrapper around spin::Mutex to permit trait implementations.
+pub struct Locked<A> {
+    inner: spin::Mutex<A>,
+}
+
+impl<A> Locked<A> {
+    pub const fn new(inner: A) -> Self {
+        Locked {
+            inner: spin::Mutex::new(inner),
+        }
+    }
+
+    pub fn lock(&self) -> spin::MutexGuard<A> {
+        self.inner.lock()
+    }
+}
+
+fn align_up(addr: usize, align: usize) -> usize {
+    (addr + align - 1) & !(align - 1)
+}
+
 pub struct Dummy;
 
 unsafe impl GlobalAlloc for Dummy {

src/allocator/bump.rs

@@ -0,0 +1,56 @@
+use super::{align_up,Locked};
+use alloc::alloc::{GlobalAlloc, Layout};
+use core::ptr;
+
+pub struct BumpAllocator {
+    heap_start: usize,
+    heap_end: usize,
+    next: usize,
+    allocations: usize,
+}
+
+impl BumpAllocator {
+    /// Creates a new empty bump allocator.
+    pub const fn new() -> Self {
+        BumpAllocator {
+            heap_start: 0,
+            heap_end: 0,
+            next: 0,
+            allocations: 0,
+        }
+    }
+    pub unsafe fn init(&mut self, heap_start: usize, heap_size: usize) {
+        self.heap_start = heap_start;
+        self.heap_end = heap_start + heap_size;
+        self.next = heap_start;
+    }
+}
+
+unsafe impl GlobalAlloc for Locked<BumpAllocator> {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        let mut bump = self.lock(); // get a mutable reference
+
+        let alloc_start = align_up(bump.next, layout.align());
+        let alloc_end = match alloc_start.checked_add(layout.size()) {
+            Some(end) => end,
+            None => return ptr::null_mut(),
+        };
+
+        if alloc_end > bump.heap_end {
+            ptr::null_mut() // out of memory
+        } else {
+            bump.next = alloc_end;
+            bump.allocations += 1;
+            alloc_start as *mut u8
+        }
+    }
+
+    unsafe fn dealloc(&self, _ptr: *mut u8, _layout: Layout) {
+        let mut bump = self.lock(); // get a mutable reference
+
+        bump.allocations -= 1;
+        if bump.allocations == 0 {
+            bump.next = bump.heap_start;
+        }
+    }
+}

src/allocator/fixed_size_block.rs

@@ -0,0 +1,90 @@
+use super::Locked;
+use alloc::alloc::GlobalAlloc;
+use alloc::alloc::Layout;
+use core::{mem, ptr, ptr::NonNull};
+struct ListNode {
+    next: Option<&'static mut ListNode>,
+}
+
+const BLOCK_SIZES: &[usize] = &[8, 16, 32, 64, 128, 256, 512, 1024, 2048];
+
+pub struct FixedSizeBlockAllocator {
+    list_heads: [Option<&'static mut ListNode>; BLOCK_SIZES.len()],
+    fallback_allocator: linked_list_allocator::Heap,
+}
+
+unsafe impl GlobalAlloc for Locked<FixedSizeBlockAllocator> {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        let mut allocator = self.lock();
+        match FixedSizeBlockAllocator::list_index(&layout) {
+            Some(index) => {
+                match allocator.list_heads[index].take() {
+                    Some(node) => {
+                       allocator.list_heads[index] = node.next.take();
+                       node as *mut ListNode as *mut u8
+                    }
+                    None => {
+                    // no block exists in list => allocate new block
+                    let block_size = BLOCK_SIZES[index];
+                    // only works if all block sizes are a power of 2
+                    let block_align = block_size;
+                    let layout = Layout::from_size_align(block_size, block_align)
+                        .unwrap();
+                    allocator.fallback_alloc(layout)
+                }
+            }
+        }
+        None => allocator.fallback_alloc(layout),
+        }
+    }
+
+    unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
+        let mut allocator = self.lock();
+    match FixedSizeBlockAllocator::list_index(&layout) {
+        Some(index) => {
+            let new_node = ListNode {
+                next: allocator.list_heads[index].take(),
+            };
+            // verify that block has size and alignment required for storing node
+            assert!(mem::size_of::<ListNode>() <= BLOCK_SIZES[index]);
+            assert!(mem::align_of::<ListNode>() <= BLOCK_SIZES[index]);
+            let new_node_ptr = ptr as *mut ListNode;
+            new_node_ptr.write(new_node);
+            allocator.list_heads[index] = Some(&mut *new_node_ptr);
+        }
+        None => {
+            let ptr = NonNull::new(ptr).unwrap();
+            allocator.fallback_allocator.deallocate(ptr, layout);
+        }
+    }
+    }
+}
+
+impl FixedSizeBlockAllocator {
+    /// Creates an empty FixedSizeBlockAllocator.
+    pub const fn new() -> Self {
+        const EMPTY: Option<&'static mut ListNode> = None;
+        FixedSizeBlockAllocator {
+            list_heads: [EMPTY; BLOCK_SIZES.len()],
+            fallback_allocator: linked_list_allocator::Heap::empty(),
+        }
+    }
+
+    pub unsafe fn init(&mut self, heap_start: usize, heap_size: usize) {
+        self.fallback_allocator.init(heap_start, heap_size);
+    }
+
+    /// Allocates using the fallback allocator.
+    fn fallback_alloc(&mut self, layout: Layout) -> *mut u8 {
+        match self.fallback_allocator.allocate_first_fit(layout) {
+            Ok(ptr) => ptr.as_ptr(),
+            Err(_) => ptr::null_mut(),
+        }
+    }
+
+    /// Returns an index into the `BLOCK_SIZES` array.
+    fn list_index(layout: &Layout) -> Option<usize> {
+        let required_block_size = layout.size().max(layout.align());
+        BLOCK_SIZES.iter().position(|&s| s >= required_block_size)
+    }
+}

src/allocator/linked_list.rs

@@ -0,0 +1,132 @@
+use super::align_up;
+use core::mem;
+use super::Locked;
+use alloc::alloc::{GlobalAlloc, Layout};
+use core::ptr;
+
+pub struct LinkedListAllocator {
+    head: ListNode,
+}
+
+unsafe impl GlobalAlloc for Locked<LinkedListAllocator> {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        // perform layout adjustments
+        let (size, align) = LinkedListAllocator::size_align(layout);
+        let mut allocator = self.lock();
+
+        if let Some((region, alloc_start)) = allocator.find_region(size, align) {
+            let alloc_end = alloc_start.checked_add(size).expect("overflow");
+            let excess_size = region.end_addr() - alloc_end;
+            if excess_size > 0 {
+                allocator.add_free_region(alloc_end, excess_size);
+            }
+            alloc_start as *mut u8
+        } else {
+            ptr::null_mut()
+        }
+    }
+
+    unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
+        // perform layout adjustments
+        let (size, _) = LinkedListAllocator::size_align(layout);
+
+        self.lock().add_free_region(ptr as usize, size)
+    }
+}
+
+
+impl LinkedListAllocator {
+    /// Creates an empty LinkedListAllocator.
+    pub const fn new() -> Self {
+        Self {
+            head: ListNode::new(0),
+        }
+    }
+    pub unsafe fn init(&mut self, heap_start: usize, heap_size: usize) {
+        self.add_free_region(heap_start, heap_size);
+    }
+    unsafe fn add_free_region(&mut self, addr: usize, size: usize) {
+        assert_eq!(align_up(addr, mem::align_of::<ListNode>()), addr);
+        assert!(size >= mem::size_of::<ListNode>());
+
+        // create a new list node and append it at the start of the list
+        let mut node = ListNode::new(size);
+        node.next = self.head.next.take();
+        let node_ptr = addr as *mut ListNode;
+        node_ptr.write(node);
+        self.head.next = Some(&mut *node_ptr)
+    }
+
+    fn find_region(&mut self, size: usize, align: usize)
+        -> Option<(&'static mut ListNode, usize)>
+    {
+        // reference to current list node, updated for each iteration
+        let mut current = &mut self.head;
+        // look for a large enough memory region in linked list
+        while let Some(ref mut region) = current.next {
+            if let Ok(alloc_start) = Self::alloc_from_region(&region, size, align) {
+                // region suitable for allocation -> remove node from list
+                let next = region.next.take();
+                let ret = Some((current.next.take().unwrap(), alloc_start));
+                current.next = next;
+                return ret;
+            } else {
+                // region not suitable -> continue with next region
+                current = current.next.as_mut().unwrap();
+            }
+        }
+
+        // no suitable region found
+        None
+    }
+
+    fn alloc_from_region(region: &ListNode, size: usize, align: usize)
+        -> Result<usize, ()>
+    {
+        let alloc_start = align_up(region.start_addr(), align);
+        let alloc_end = alloc_start.checked_add(size).ok_or(())?;
+
+        if alloc_end > region.end_addr() {
+            // region too small
+            return Err(());
+        }
+
+        let excess_size = region.end_addr() - alloc_end;
+        if excess_size > 0 && excess_size < mem::size_of::<ListNode>() {
+            // rest of region too small to hold a ListNode (required because the
+            // allocation splits the region in a used and a free part)
+            return Err(());
+        }
+
+        // region suitable for allocation
+        Ok(alloc_start)
+    }
+
+    fn size_align(layout: Layout) -> (usize, usize) {
+        let layout = layout
+            .align_to(mem::align_of::<ListNode>())
+            .expect("adjusting alignment failed")
+            .pad_to_align();
+        let size = layout.size().max(mem::size_of::<ListNode>());
+        (size, layout.align())
+    }
+}
+struct ListNode {
+    size: usize,
+    next: Option<&'static mut ListNode>,
+}
+
+impl ListNode {
+    const fn new(size: usize) -> Self {
+        ListNode { size, next: None }
+    }
+
+    fn start_addr(&self) -> usize {
+        self as *const Self as usize
+    }
+
+    fn end_addr(&self) -> usize {
+        self.start_addr() + self.size
+    }
+}
+

src/lib.rs

@@ -5,6 +5,7 @@
 #![reexport_test_harness_main = "test_main"]
 #![feature(abi_x86_interrupt)]
 #![feature(alloc_error_handler)]
+#![feature(const_mut_refs)]
 
 #[cfg(test)]
 use bootloader::{entry_point, BootInfo};
@@ -18,7 +19,7 @@ pub mod gdt;
 pub mod memory;
 pub mod allocator;
 
-use core::{alloc::Layout, panic::PanicInfo};
+use core::panic::PanicInfo;
 
 pub trait Testable {
     fn run(&self) -> ();

tests/heap_allocation.rs

@@ -61,3 +61,13 @@ fn many_boxes() {
         assert_eq!(*x, i);
     }
 }
+
+#[test_case]
+fn many_boxes_long_lived() {
+    let long_lived = Box::new(1); // new
+    for i in 0..HEAP_SIZE {
+        let x = Box::new(i);
+        assert_eq!(*x, i);
+    }
+    assert_eq!(*long_lived, 1); // new
+}