Added a global allocator and heap support

.cargo/config.toml

@@ -1,5 +1,5 @@
 [unstable]
-build-std = ["core"]
+build-std = ["core", "compiler_builtins", "alloc"]
 build-std-features = ["compiler-builtins-mem"]
 
 [build]

Cargo.toml

@@ -4,6 +4,7 @@ name = "lateral"
 version = "0.1.0"
 
 [dependencies]
+linked_list_allocator = "0.9.0"
 pc-keyboard = "0.5.0"
 pic8259 = "0.10.1"
 spin = "0.9.1"

src/alloc/block.rs

@@ -0,0 +1,96 @@
+use core::alloc::GlobalAlloc;
+use core::alloc::Layout;
+use core::mem;
+use core::ptr;
+use core::ptr::NonNull;
+
+use super::lock::Locked;
+
+const BLOCK_SIZES: &[usize] = &[8, 16, 32, 64, 128, 256, 512, 1024, 2048];
+
+struct ListNode {
+    next: Option<&'static mut ListNode>,
+}
+
+pub struct FixedSizeBlockAllocator {
+    list_heads: [Option<&'static mut ListNode>; BLOCK_SIZES.len()],
+    fallback_allocator: linked_list_allocator::Heap,
+}
+
+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(),
+        }
+    }
+
+    /// Initialize the allocator with the given heap bounds.
+    ///
+    /// This function is unsafe because the caller must guarantee that the given
+    /// heap bounds are valid and that the heap is unused. This method must be
+    /// called only once.
+    pub unsafe fn init(&mut self, heap_start: usize, heap_size: usize) {
+        self.fallback_allocator.init(heap_start, heap_size);
+    }
+
+    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(),
+        }
+    }
+}
+
+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)
+}
+
+unsafe impl GlobalAlloc for Locked<FixedSizeBlockAllocator> {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        let mut allocator = self.lock();
+        match 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 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);
+            }
+        }
+    }
+}

src/alloc/global.rs

@@ -0,0 +1,23 @@
+extern crate alloc as rust_alloc;
+
+use core::ptr::null_mut;
+use rust_alloc::alloc::{GlobalAlloc, Layout};
+
+use super::block::FixedSizeBlockAllocator;
+use super::lock::Locked;
+
+#[global_allocator]
+pub(super) static ALLOCATOR: Locked<FixedSizeBlockAllocator> =
+    Locked::new(FixedSizeBlockAllocator::new());
+
+pub struct Dummy;
+
+unsafe impl GlobalAlloc for Dummy {
+    unsafe fn alloc(&self, _layout: Layout) -> *mut u8 {
+        null_mut()
+    }
+
+    unsafe fn dealloc(&self, _ptr: *mut u8, _layout: Layout) {
+        panic!("dealloc should be never called")
+    }
+}

src/alloc/heap.rs

@@ -0,0 +1,38 @@
+use crate::alloc::global::ALLOCATOR;
+
+const KIB: usize = 0x400;
+pub const HEAP_START: usize = 0x_4444_4444_0000;
+pub const HEAP_SIZE: usize = 100 * KIB;
+
+use x86_64::{
+    structures::paging::{
+        mapper::MapToError, FrameAllocator, Mapper, Page, PageTableFlags, Size4KiB,
+    },
+    VirtAddr,
+};
+pub fn init_heap(
+    mapper: &mut impl Mapper<Size4KiB>,
+    frame_allocator: &mut impl FrameAllocator<Size4KiB>,
+) -> Result<(), MapToError<Size4KiB>> {
+    let page_range = {
+        let heap_start = VirtAddr::new(HEAP_START as u64);
+        let heap_end = heap_start + HEAP_SIZE - 1u64;
+        let heap_start_page = Page::containing_address(heap_start);
+        let heap_end_page = Page::containing_address(heap_end);
+        Page::range_inclusive(heap_start_page, heap_end_page)
+    };
+
+    for page in page_range {
+        let frame = frame_allocator
+            .allocate_frame()
+            .ok_or(MapToError::FrameAllocationFailed)?;
+        let flags = PageTableFlags::PRESENT | PageTableFlags::WRITABLE;
+        unsafe { mapper.map_to(page, frame, flags, frame_allocator)?.flush() };
+    }
+
+    unsafe {
+        ALLOCATOR.lock().init(HEAP_START, HEAP_SIZE);
+    }
+
+    Ok(())
+}

src/alloc/lock.rs

@@ -0,0 +1,15 @@
+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()
+    }
+}

src/alloc/mod.rs

@@ -0,0 +1,4 @@
+pub mod block;
+pub mod global;
+pub mod heap;
+pub mod lock;

src/lib.rs

@@ -5,7 +5,12 @@
 #![feature(custom_test_frameworks)]
 #![test_runner(crate::test::runner)]
 #![reexport_test_harness_main = "test_harness"]
+#![feature(alloc_error_handler)]
+#![feature(const_mut_refs)]
 
+extern crate alloc as rust_alloc;
+
+pub mod alloc;
 pub mod cpu;
 pub mod io;
 pub mod mem;
@@ -40,3 +45,8 @@ pub fn init() {
     unsafe { cpu::interrupt::PICS.lock().initialize() };
     x86_64::instructions::interrupts::enable();
 }
+
+#[alloc_error_handler]
+fn alloc_error_handler(layout: rust_alloc::alloc::Layout) -> ! {
+    panic!("allocation error: {:?}", layout)
+}

src/main.rs

@@ -11,9 +11,11 @@ bootloader::entry_point!(tests::main);
 
 #[cfg(not(test))]
 mod kernel {
+    extern crate alloc as rust_alloc;
     use lateral::mem::frame::BootInfoFrameAllocator;
     use lateral::mem::paging;
     use lateral::println;
+    use rust_alloc::boxed::Box;
     use x86_64::structures::paging::Page;
     use x86_64::VirtAddr;
 
@@ -32,6 +34,12 @@ mod kernel {
         let page_ptr: *mut u64 = page.start_address().as_mut_ptr();
         unsafe { page_ptr.offset(400).write_volatile(0x_f021_f077_f065_f04e) };
 
+        lateral::alloc::heap::init_heap(&mut mapper, &mut frame_allocator)
+            .expect("heap initialization failed");
+
+        let x = Box::new(100);
+        println!("{}", x);
+
         println!("Hello World!");
         lateral::halt_loop();
     }