Switch back to official nightly

The Wake trait is based on Arc, which leads to deallocation on wakes. Since interrupts should not (de)allocate, this can lead to a deadlock.

Cargo.lock

@@ -1,5 +1,11 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
+[[package]]
+name = "autocfg"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f8aac770f1885fd7e387acedd76065302551364496e46b3dd00860b2f8359b9d"
+
 [[package]]
 name = "bit_field"
 version = "0.9.0"
@@ -17,7 +23,14 @@ name = "blog_os"
 version = "0.1.0"
 dependencies = [
  "bootloader",
+ "conquer-once",
+ "cooked-waker",
+ "crossbeam-queue",
+ "futures-util",
  "lazy_static",
+ "linked_list_allocator",
+ "pc-keyboard",
+ "pic8259_simple",
  "spin",
  "uart_16550",
  "volatile",
@@ -26,9 +39,100 @@ dependencies = [
 
 [[package]]
 name = "bootloader"
-version = "0.8.8"
+version = "0.8.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c3ed4f735c4e455ba86a3d2939b1c0729414153642106c9d035693355630a42c"
+checksum = "152a28c753e229e037e910b4cd4cd16a90c53dd9a67fd751fa304b4b4a03970c"
+
+[[package]]
+name = "cfg-if"
+version = "0.1.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4785bdd1c96b2a846b2bd7cc02e86b6b3dbf14e7e53446c4f54c92a361040822"
+
+[[package]]
+name = "conquer-once"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6f7644600a548ecad74e4a918392af1798f7dd045be610be3203b9e129b4f98f"
+dependencies = [
+ "conquer-util",
+]
+
+[[package]]
+name = "conquer-util"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "654fb2472cc369d311c547103a1fa81d467bef370ae7a0680f65939895b1182a"
+
+[[package]]
+name = "cooked-waker"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b0032e8be0680b63daf14b0fd7fd57f85fd6897951e110b041d32e839a831914"
+dependencies = [
+ "cooked-waker-derive",
+ "stowaway",
+]
+
+[[package]]
+name = "cooked-waker-derive"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "74ded02b04a8ff53ea7328cd71297cde598bee70d165ad92512bdb7e20be9d74"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "cpuio"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "22b8e308ccfc5acf3b82f79c0eac444cf6114cb2ac67a230ca6c177210068daa"
+
+[[package]]
+name = "crossbeam-queue"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c695eeca1e7173472a32221542ae469b3e9aac3a4fc81f7696bcad82029493db"
+dependencies = [
+ "cfg-if",
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-utils"
+version = "0.7.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c3c7c73a2d1e9fc0886a08b93e98eb643461230d5f1925e4036204d5f2e261a8"
+dependencies = [
+ "autocfg",
+ "cfg-if",
+]
+
+[[package]]
+name = "futures-core"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f25592f769825e89b92358db00d26f965761e094951ac44d3663ef25b7ac464a"
+
+[[package]]
+name = "futures-task"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7b0a34e53cf6cdcd0178aa573aed466b646eb3db769570841fda0c7ede375a27"
+
+[[package]]
+name = "futures-util"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "22766cf25d64306bedf0384da004d05c9974ab104fcc4528f1236181c18004c5"
+dependencies = [
+ "futures-core",
+ "futures-task",
+ "pin-utils",
+]
 
 [[package]]
 name = "lazy_static"
@@ -39,12 +143,101 @@ dependencies = [
  "spin",
 ]
 
+[[package]]
+name = "linked_list_allocator"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "18c618c431dfe4419afbe22852f6aceffbc17bd82ba0a18b982def291000824c"
+dependencies = [
+ "spinning_top",
+]
+
+[[package]]
+name = "lock_api"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "79b2de95ecb4691949fea4716ca53cdbcfccb2c612e19644a8bad05edcf9f47b"
+dependencies = [
+ "scopeguard",
+]
+
+[[package]]
+name = "pc-keyboard"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c48392db76c4e9a69e0b3be356c5f97ebb7b14413c5e4fd0af4755dbf86e2fce"
+
+[[package]]
+name = "pic8259_simple"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dc64b2fd10828da8521b6cdabe0679385d7d2a3a6d4c336b819d1fa31ba35c72"
+dependencies = [
+ "cpuio",
+]
+
+[[package]]
+name = "pin-utils"
+version = "0.1.0-alpha.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5894c618ce612a3fa23881b152b608bafb8c56cfc22f434a3ba3120b40f7b587"
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6c09721c6781493a2a492a96b5a5bf19b65917fe6728884e7c44dd0c60ca3435"
+dependencies = [
+ "unicode-xid",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2bdc6c187c65bca4260c9011c9e3132efe4909da44726bad24cf7572ae338d7f"
+dependencies = [
+ "proc-macro2",
+]
+
+[[package]]
+name = "scopeguard"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"
+
 [[package]]
 name = "spin"
 version = "0.5.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6e63cff320ae2c57904679ba7cb63280a3dc4613885beafb148ee7bf9aa9042d"
 
+[[package]]
+name = "spinning_top"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "32d801a3a53bcf5071f85fef8d5cab9e5f638fc5580a37e6eb7aba4b37438d24"
+dependencies = [
+ "lock_api",
+]
+
+[[package]]
+name = "stowaway"
+version = "1.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "32b13d61e782863c0eaeeaf7e8e580dc956a625851fd2fb73e5e92db9601c891"
+
+[[package]]
+name = "syn"
+version = "1.0.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0df0eb663f387145cab623dea85b09c2c5b4b0aef44e945d928e682fce71bb03"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-xid",
+]
+
 [[package]]
 name = "uart_16550"
 version = "0.2.4"
@@ -55,6 +248,12 @@ dependencies = [
  "x86_64",
 ]
 
+[[package]]
+name = "unicode-xid"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "826e7639553986605ec5979c7dd957c7895e93eabed50ab2ffa7f6128a75097c"
+
 [[package]]
 name = "volatile"
 version = "0.2.6"

Cargo.toml

@@ -13,16 +13,33 @@ name = "stack_overflow"
 harness = false
 
 [dependencies]
-bootloader = "0.8.0"
+bootloader = { version = "0.8.8", features = ["map_physical_memory"]}
 volatile = "0.2.6"
 spin = "0.5.2"
 x86_64 = "0.9.6"
 uart_16550 = "0.2.0"
+pic8259_simple = "0.1.1"
+pc-keyboard = "0.5.0"
+linked_list_allocator = "0.8.0"
+cooked-waker = "1.0.2"
 
 [dependencies.lazy_static]
 version = "1.0"
 features = ["spin_no_std"]
 
+[dependencies.crossbeam-queue]
+version = "0.2.1"
+default-features = false
+features = ["alloc"]
+
+[dependencies.conquer-once]
+version = "0.2.0"
+default-features = false
+
+[dependencies.futures-util]
+version = "0.3.4"
+default-features = false
+features = ["alloc"]
 
 [package.metadata.bootimage]
 test-args = [

README.md

@@ -1,10 +1,10 @@
-# Blog OS (Double Faults)
+# Blog OS (Heap Allocation)
 
-[![Build Status](https://github.com/phil-opp/blog_os/workflows/Build%20Code/badge.svg?branch=post-06)](https://github.com/phil-opp/blog_os/actions?query=workflow%3A%22Build+Code%22+branch%3Apost-06)
+[![Build Status](https://github.com/phil-opp/blog_os/workflows/Build%20Code/badge.svg?branch=post-10)](https://github.com/phil-opp/blog_os/actions?query=workflow%3A%22Build+Code%22+branch%3Apost-10)
 
-This repository contains the source code for the [Double Faults][post] post of the [Writing an OS in Rust](https://os.phil-opp.com) series.
+This repository contains the source code for the [Heap Allocation][post] post of the [Writing an OS in Rust](https://os.phil-opp.com) series.
 
-[post]: https://os.phil-opp.com/double-fault-exceptions/
+[post]: https://os.phil-opp.com/heap-allocation/
 
 **Check out the [master branch](https://github.com/phil-opp/blog_os) for more information.**
 

src/allocator.rs

@@ -0,0 +1,82 @@
+use alloc::alloc::{GlobalAlloc, Layout};
+use core::ptr::null_mut;
+use fixed_size_block::FixedSizeBlockAllocator;
+use x86_64::{
+    structures::paging::{
+        mapper::MapToError, FrameAllocator, Mapper, Page, PageTableFlags, Size4KiB,
+    },
+    VirtAddr,
+};
+
+pub mod bump;
+pub mod fixed_size_block;
+pub mod linked_list;
+
+pub const HEAP_START: usize = 0x_4444_4444_0000;
+pub const HEAP_SIZE: usize = 100 * 1024; // 100 KiB
+
+#[global_allocator]
+static ALLOCATOR: Locked<FixedSizeBlockAllocator> = Locked::new(FixedSizeBlockAllocator::new());
+
+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;
+        mapper.map_to(page, frame, flags, frame_allocator)?.flush();
+    }
+
+    unsafe {
+        ALLOCATOR.lock().init(HEAP_START, HEAP_SIZE);
+    }
+
+    Ok(())
+}
+
+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")
+    }
+}
+
+/// 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()
+    }
+}
+
+/// Align the given address `addr` upwards to alignment `align`.
+///
+/// Requires that `align` is a power of two.
+fn align_up(addr: usize, align: usize) -> usize {
+    (addr + align - 1) & !(align - 1)
+}

src/allocator/bump.rs

@@ -0,0 +1,61 @@
+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,
+        }
+    }
+
+    /// Initializes the bump allocator with the given heap bounds.
+    ///
+    /// This method is unsafe because the caller must ensure that the given
+    /// memory range is unused. Also, this method must be called only once.
+    pub unsafe fn init(&mut self, heap_start: usize, heap_size: usize) {
+        self.heap_start = heap_start;
+        self.heap_end = heap_start.saturating_add(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 +1,102 @@
+use super::Locked;
+use alloc::alloc::{GlobalAlloc, Layout};
+use core::{
+    mem,
+    ptr::{self, NonNull},
+};
+
+/// The block sizes to use.
+///
+/// The sizes must each be power of 2 because they are also used as
+/// the block alignment (alignments must be always powers of 2).
+const BLOCK_SIZES: &[usize] = &[8, 16, 32, 64, 128, 256, 512, 1024, 2048];
+
+/// Choose an appropriate block size for the given layout.
+///
+/// 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)
+}
+
+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 {
+        FixedSizeBlockAllocator {
+            list_heads: [None; 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);
+    }
+
+    /// 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(),
+        }
+    }
+}
+
+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/allocator/linked_list.rs

@@ -0,0 +1,145 @@
+use super::{align_up, Locked};
+use alloc::alloc::{GlobalAlloc, Layout};
+use core::{mem, ptr};
+
+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
+    }
+}
+
+pub struct LinkedListAllocator {
+    head: ListNode,
+}
+
+impl LinkedListAllocator {
+    /// Creates an empty LinkedListAllocator.
+    pub const fn new() -> Self {
+        Self {
+            head: ListNode::new(0),
+        }
+    }
+
+    /// 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.add_free_region(heap_start, heap_size);
+    }
+
+    /// Adds the given memory region to the front of the list.
+    unsafe fn add_free_region(&mut self, addr: usize, size: usize) {
+        // ensure that the freed region is capable of holding ListNode
+        assert!(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)
+    }
+
+    /// Looks for a free region with the given size and alignment and removes
+    /// it from the list.
+    ///
+    /// Returns a tuple of the list node and the start address of the allocation.
+    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
+    }
+
+    /// Try to use the given region for an allocation with given size and alignment.
+    ///
+    /// Returns the allocation start address on success.
+    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)
+    }
+
+    /// Adjust the given layout so that the resulting allocated memory
+    /// region is also capable of storing a `ListNode`.
+    ///
+    /// Returns the adjusted size and alignment as a (size, align) tuple.
+    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())
+    }
+}
+
+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)
+    }
+}

src/interrupts.rs

@@ -1,16 +1,44 @@
-use crate::{gdt, println};
+use crate::{gdt, hlt_loop, print, println};
 use lazy_static::lazy_static;
-use x86_64::structures::idt::{InterruptDescriptorTable, InterruptStackFrame};
+use pic8259_simple::ChainedPics;
+use spin;
+use x86_64::structures::idt::{InterruptDescriptorTable, InterruptStackFrame, PageFaultErrorCode};
+
+pub const PIC_1_OFFSET: u8 = 32;
+pub const PIC_2_OFFSET: u8 = PIC_1_OFFSET + 8;
+
+#[derive(Debug, Clone, Copy)]
+#[repr(u8)]
+pub enum InterruptIndex {
+    Timer = PIC_1_OFFSET,
+    Keyboard,
+}
+
+impl InterruptIndex {
+    fn as_u8(self) -> u8 {
+        self as u8
+    }
+
+    fn as_usize(self) -> usize {
+        usize::from(self.as_u8())
+    }
+}
+
+pub static PICS: spin::Mutex<ChainedPics> =
+    spin::Mutex::new(unsafe { ChainedPics::new(PIC_1_OFFSET, PIC_2_OFFSET) });
 
 lazy_static! {
     static ref IDT: InterruptDescriptorTable = {
         let mut idt = InterruptDescriptorTable::new();
         idt.breakpoint.set_handler_fn(breakpoint_handler);
+        idt.page_fault.set_handler_fn(page_fault_handler);
         unsafe {
             idt.double_fault
                 .set_handler_fn(double_fault_handler)
                 .set_stack_index(gdt::DOUBLE_FAULT_IST_INDEX);
         }
+        idt[InterruptIndex::Timer.as_usize()].set_handler_fn(timer_interrupt_handler);
+        idt[InterruptIndex::Keyboard.as_usize()].set_handler_fn(keyboard_interrupt_handler);
         idt
     };
 }
@@ -23,6 +51,19 @@ extern "x86-interrupt" fn breakpoint_handler(stack_frame: &mut InterruptStackFra
     println!("EXCEPTION: BREAKPOINT\n{:#?}", stack_frame);
 }
 
+extern "x86-interrupt" fn page_fault_handler(
+    stack_frame: &mut InterruptStackFrame,
+    error_code: PageFaultErrorCode,
+) {
+    use x86_64::registers::control::Cr2;
+
+    println!("EXCEPTION: PAGE FAULT");
+    println!("Accessed Address: {:?}", Cr2::read());
+    println!("Error Code: {:?}", error_code);
+    println!("{:#?}", stack_frame);
+    hlt_loop();
+}
+
 extern "x86-interrupt" fn double_fault_handler(
     stack_frame: &mut InterruptStackFrame,
     _error_code: u64,
@@ -30,6 +71,27 @@ extern "x86-interrupt" fn double_fault_handler(
     panic!("EXCEPTION: DOUBLE FAULT\n{:#?}", stack_frame);
 }
 
+extern "x86-interrupt" fn timer_interrupt_handler(_stack_frame: &mut InterruptStackFrame) {
+    print!(".");
+    unsafe {
+        PICS.lock()
+            .notify_end_of_interrupt(InterruptIndex::Timer.as_u8());
+    }
+}
+
+extern "x86-interrupt" fn keyboard_interrupt_handler(_stack_frame: &mut InterruptStackFrame) {
+    use x86_64::instructions::port::Port;
+
+    let mut port = Port::new(0x60);
+    let scancode: u8 = unsafe { port.read() };
+    crate::task::keyboard::add_scancode(scancode);
+
+    unsafe {
+        PICS.lock()
+            .notify_end_of_interrupt(InterruptIndex::Keyboard.as_u8());
+    }
+}
+
 #[cfg(test)]
 use crate::{serial_print, serial_println};
 

src/lib.rs

@@ -2,19 +2,30 @@
 #![cfg_attr(test, no_main)]
 #![feature(custom_test_frameworks)]
 #![feature(abi_x86_interrupt)]
+#![feature(alloc_error_handler)]
+#![feature(const_fn)]
+#![feature(alloc_layout_extra)]
+#![feature(const_in_array_repeat_expressions)]
 #![test_runner(crate::test_runner)]
 #![reexport_test_harness_main = "test_main"]
 
+extern crate alloc;
+
 use core::panic::PanicInfo;
 
+pub mod allocator;
 pub mod gdt;
 pub mod interrupts;
+pub mod memory;
 pub mod serial;
+pub mod task;
 pub mod vga_buffer;
 
 pub fn init() {
     gdt::init();
     interrupts::init_idt();
+    unsafe { interrupts::PICS.lock().initialize() };
+    x86_64::instructions::interrupts::enable();
 }
 
 pub fn test_runner(tests: &[&dyn Fn()]) {
@@ -29,7 +40,7 @@ pub fn test_panic_handler(info: &PanicInfo) -> ! {
     serial_println!("[failed]\n");
     serial_println!("Error: {}\n", info);
     exit_qemu(QemuExitCode::Failed);
-    loop {}
+    hlt_loop();
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -48,13 +59,24 @@ pub fn exit_qemu(exit_code: QemuExitCode) {
     }
 }
 
+pub fn hlt_loop() -> ! {
+    loop {
+        x86_64::instructions::hlt();
+    }
+}
+
+#[cfg(test)]
+use bootloader::{entry_point, BootInfo};
+
+#[cfg(test)]
+entry_point!(test_kernel_main);
+
 /// Entry point for `cargo xtest`
 #[cfg(test)]
-#[no_mangle]
+fn test_kernel_main(_boot_info: &'static BootInfo) -> ! {
-pub extern "C" fn _start() -> ! {
     init();
     test_main();
-    loop {}
+    hlt_loop();
 }
 
 #[cfg(test)]
@@ -62,3 +84,8 @@ pub extern "C" fn _start() -> ! {
 fn panic(info: &PanicInfo) -> ! {
     test_panic_handler(info)
 }
+
+#[alloc_error_handler]
+fn alloc_error_handler(layout: alloc::alloc::Layout) -> ! {
+    panic!("allocation error: {:?}", layout)
+}

src/main.rs

@@ -4,27 +4,48 @@
 #![test_runner(blog_os::test_runner)]
 #![reexport_test_harness_main = "test_main"]
 
+extern crate alloc;
+
 use blog_os::println;
+use bootloader::{entry_point, BootInfo};
 use core::panic::PanicInfo;
 
-#[no_mangle]
+entry_point!(kernel_main);
-pub extern "C" fn _start() -> ! {
-    println!("Hello World{}", "!");
 
+fn kernel_main(boot_info: &'static BootInfo) -> ! {
+    use blog_os::allocator;
+    use blog_os::memory::{self, BootInfoFrameAllocator};
+    use blog_os::task::{keyboard, simple_executor::SimpleExecutor, Task};
+    use x86_64::VirtAddr;
+
+    println!("Hello World{}", "!");
     blog_os::init();
 
-    fn stack_overflow() {
+    let phys_mem_offset = VirtAddr::new(boot_info.physical_memory_offset);
-        stack_overflow(); // for each recursion, the return address is pushed
+    let mut mapper = unsafe { memory::init(phys_mem_offset) };
-    }
+    let mut frame_allocator = unsafe { BootInfoFrameAllocator::init(&boot_info.memory_map) };
 
-    // uncomment line below to trigger a stack overflow
+    allocator::init_heap(&mut mapper, &mut frame_allocator).expect("heap initialization failed");
-    // stack_overflow();
+
+    let mut executor = SimpleExecutor::new();
+    executor.spawn(Task::new(example_task()));
+    executor.spawn(Task::new(keyboard::print_keypresses()));
+    executor.run();
 
     #[cfg(test)]
     test_main();
 
     println!("It did not crash!");
-    loop {}
+    blog_os::hlt_loop();
+}
+
+async fn async_number() -> u32 {
+    42
+}
+
+async fn example_task() {
+    let number = async_number().await;
+    println!("async number: {}", number);
 }
 
 /// This function is called on panic.
@@ -32,7 +53,7 @@ pub extern "C" fn _start() -> ! {
 #[panic_handler]
 fn panic(info: &PanicInfo) -> ! {
     println!("{}", info);
-    loop {}
+    blog_os::hlt_loop();
 }
 
 #[cfg(test)]

src/memory.rs

@@ -0,0 +1,106 @@
+use bootloader::bootinfo::{MemoryMap, MemoryRegionType};
+use x86_64::{
+    structures::paging::{
+        FrameAllocator, Mapper, OffsetPageTable, Page, PageTable, PhysFrame, Size4KiB,
+        UnusedPhysFrame,
+    },
+    PhysAddr, VirtAddr,
+};
+
+/// Initialize a new OffsetPageTable.
+///
+/// This function is unsafe because the caller must guarantee that the
+/// complete physical memory is mapped to virtual memory at the passed
+/// `physical_memory_offset`. Also, this function must be only called once
+/// to avoid aliasing `&mut` references (which is undefined behavior).
+pub unsafe fn init(physical_memory_offset: VirtAddr) -> OffsetPageTable<'static> {
+    let level_4_table = active_level_4_table(physical_memory_offset);
+    OffsetPageTable::new(level_4_table, physical_memory_offset)
+}
+
+/// Returns a mutable reference to the active level 4 table.
+///
+/// This function is unsafe because the caller must guarantee that the
+/// complete physical memory is mapped to virtual memory at the passed
+/// `physical_memory_offset`. Also, this function must be only called once
+/// to avoid aliasing `&mut` references (which is undefined behavior).
+unsafe fn active_level_4_table(physical_memory_offset: VirtAddr) -> &'static mut PageTable {
+    use x86_64::registers::control::Cr3;
+
+    let (level_4_table_frame, _) = Cr3::read();
+
+    let phys = level_4_table_frame.start_address();
+    let virt = physical_memory_offset + phys.as_u64();
+    let page_table_ptr: *mut PageTable = virt.as_mut_ptr();
+
+    &mut *page_table_ptr // unsafe
+}
+
+/// Creates an example mapping for the given page to frame `0xb8000`.
+pub fn create_example_mapping(
+    page: Page,
+    mapper: &mut OffsetPageTable,
+    frame_allocator: &mut impl FrameAllocator<Size4KiB>,
+) {
+    use x86_64::structures::paging::PageTableFlags as Flags;
+
+    let frame = PhysFrame::containing_address(PhysAddr::new(0xb8000));
+    // FIXME: ONLY FOR TEMPORARY TESTING
+    let unused_frame = unsafe { UnusedPhysFrame::new(frame) };
+    let flags = Flags::PRESENT | Flags::WRITABLE;
+
+    let map_to_result = mapper.map_to(page, unused_frame, flags, frame_allocator);
+    map_to_result.expect("map_to failed").flush();
+}
+
+/// A FrameAllocator that always returns `None`.
+pub struct EmptyFrameAllocator;
+
+unsafe impl FrameAllocator<Size4KiB> for EmptyFrameAllocator {
+    fn allocate_frame(&mut self) -> Option<UnusedPhysFrame> {
+        None
+    }
+}
+
+/// A FrameAllocator that returns usable frames from the bootloader's memory map.
+pub struct BootInfoFrameAllocator {
+    memory_map: &'static MemoryMap,
+    next: usize,
+}
+
+impl BootInfoFrameAllocator {
+    /// Create a FrameAllocator from the passed memory map.
+    ///
+    /// This function is unsafe because the caller must guarantee that the passed
+    /// memory map is valid. The main requirement is that all frames that are marked
+    /// as `USABLE` in it are really unused.
+    pub unsafe fn init(memory_map: &'static MemoryMap) -> Self {
+        BootInfoFrameAllocator {
+            memory_map,
+            next: 0,
+        }
+    }
+
+    /// Returns an iterator over the usable frames specified in the memory map.
+    fn usable_frames(&self) -> impl Iterator<Item = UnusedPhysFrame> {
+        // get usable regions from memory map
+        let regions = self.memory_map.iter();
+        let usable_regions = regions.filter(|r| r.region_type == MemoryRegionType::Usable);
+        // map each region to its address range
+        let addr_ranges = usable_regions.map(|r| r.range.start_addr()..r.range.end_addr());
+        // transform to an iterator of frame start addresses
+        let frame_addresses = addr_ranges.flat_map(|r| r.step_by(4096));
+        // create `PhysFrame` types from the start addresses
+        let frames = frame_addresses.map(|addr| PhysFrame::containing_address(PhysAddr::new(addr)));
+        // we know that the frames are really unused
+        frames.map(|f| unsafe { UnusedPhysFrame::new(f) })
+    }
+}
+
+unsafe impl FrameAllocator<Size4KiB> for BootInfoFrameAllocator {
+    fn allocate_frame(&mut self) -> Option<UnusedPhysFrame> {
+        let frame = self.usable_frames().nth(self.next);
+        self.next += 1;
+        frame
+    }
+}

src/serial.rs

@@ -13,10 +13,14 @@ lazy_static! {
 #[doc(hidden)]
 pub fn _print(args: ::core::fmt::Arguments) {
     use core::fmt::Write;
-    SERIAL1
+    use x86_64::instructions::interrupts;
-        .lock()
+
-        .write_fmt(args)
+    interrupts::without_interrupts(|| {
-        .expect("Printing to serial failed");
+        SERIAL1
+            .lock()
+            .write_fmt(args)
+            .expect("Printing to serial failed");
+    });
 }
 
 /// Prints to the host through the serial interface.

src/task/keyboard.rs

@@ -0,0 +1,79 @@
+use crate::print;
+use crate::println;
+use conquer_once::spin::OnceCell;
+use core::{
+    pin::Pin,
+    task::{Context, Poll},
+};
+use crossbeam_queue::ArrayQueue;
+use futures_util::stream::StreamExt;
+use futures_util::{stream::Stream, task::AtomicWaker};
+use pc_keyboard::{layouts, DecodedKey, HandleControl, Keyboard, ScancodeSet1};
+
+static SCANCODE_QUEUE: OnceCell<ArrayQueue<u8>> = OnceCell::uninit();
+static WAKER: AtomicWaker = AtomicWaker::new();
+
+/// Called by the keyboard interrupt handler
+///
+/// Must not block or allocate.
+pub(crate) fn add_scancode(scancode: u8) {
+    if let Ok(queue) = SCANCODE_QUEUE.try_get() {
+        if let Err(_) = queue.push(scancode) {
+            println!("WARNING: scancode queue full; dropping keyboard input");
+        } else {
+            WAKER.wake();
+        }
+    } else {
+        println!("WARNING: scancode queue uninitialized");
+    }
+}
+
+pub struct ScancodeStream {
+    _private: (),
+}
+
+impl ScancodeStream {
+    pub fn new() -> Self {
+        SCANCODE_QUEUE
+            .try_init_once(|| ArrayQueue::new(100))
+            .expect("ScancodeStream::new should only be called once");
+        ScancodeStream { _private: () }
+    }
+}
+
+impl Stream for ScancodeStream {
+    type Item = u8;
+
+    fn poll_next(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Option<u8>> {
+        let queue = SCANCODE_QUEUE
+            .try_get()
+            .expect("scancode queue not initialized");
+
+        // fast path
+        if let Ok(scancode) = queue.pop() {
+            return Poll::Ready(Some(scancode));
+        }
+
+        WAKER.register(&cx.waker());
+        match queue.pop() {
+            Ok(scancode) => Poll::Ready(Some(scancode)),
+            Err(crossbeam_queue::PopError) => Poll::Pending,
+        }
+    }
+}
+
+pub async fn print_keypresses() {
+    let mut scancodes = ScancodeStream::new();
+    let mut keyboard = Keyboard::new(layouts::Us104Key, ScancodeSet1, HandleControl::Ignore);
+
+    while let Some(scancode) = scancodes.next().await {
+        if let Ok(Some(key_event)) = keyboard.add_byte(scancode) {
+            if let Some(key) = keyboard.process_keyevent(key_event) {
+                match key {
+                    DecodedKey::Unicode(character) => print!("{}", character),
+                    DecodedKey::RawKey(key) => print!("{:?}", key),
+                }
+            }
+        }
+    }
+}

src/task/mod.rs

@@ -0,0 +1,26 @@
+use alloc::boxed::Box;
+use core::task::{Context, Poll};
+use core::{future::Future, pin::Pin};
+
+pub mod keyboard;
+pub mod simple_executor;
+
+pub struct Task {
+    future: Pin<Box<dyn Future<Output = ()>>>,
+}
+
+impl Task {
+    pub fn new(future: impl Future<Output = ()> + 'static) -> Task {
+        Task {
+            future: Box::pin(future),
+        }
+    }
+
+    fn poll(&mut self, context: &mut Context) -> Poll<()> {
+        self.future.as_mut().poll(context)
+    }
+
+    fn id(&self) -> usize {
+        &*self.future as *const _ as *const () as usize
+    }
+}

src/task/simple_executor.rs

@@ -0,0 +1,86 @@
+use super::Task;
+use alloc::{
+    collections::{BTreeMap, VecDeque},
+    sync::Arc,
+};
+use cooked_waker::IntoWaker;
+use core::task::{Context, Poll};
+use crossbeam_queue::ArrayQueue;
+
+pub struct SimpleExecutor {
+    task_queue: VecDeque<Task>,
+    waiting_tasks: BTreeMap<usize, Task>,
+    wake_queue: Arc<ArrayQueue<usize>>,
+}
+
+impl SimpleExecutor {
+    pub fn new() -> SimpleExecutor {
+        SimpleExecutor {
+            task_queue: VecDeque::new(),
+            waiting_tasks: BTreeMap::new(),
+            wake_queue: Arc::new(ArrayQueue::new(100)),
+        }
+    }
+
+    pub fn spawn(&mut self, task: Task) {
+        self.task_queue.push_back(task)
+    }
+
+    pub fn run(&mut self) {
+        loop {
+            self.handle_wakeups();
+            self.run_ready_tasks();
+        }
+    }
+
+    fn handle_wakeups(&mut self) {
+        while let Ok(task_id) = self.wake_queue.pop() {
+            if let Some(task) = self.waiting_tasks.remove(&task_id) {
+                self.task_queue.push_back(task);
+            }
+        }
+    }
+
+    fn run_ready_tasks(&mut self) {
+        while let Some(mut task) = self.task_queue.pop_front() {
+            let waker = TaskWaker {
+                task_id: task.id(),
+                wake_queue: self.wake_queue.clone(),
+            }
+            .into_waker();
+            let mut context = Context::from_waker(&waker);
+            match task.poll(&mut context) {
+                Poll::Ready(()) => {} // task done
+                Poll::Pending => {
+                    if self.waiting_tasks.insert(task.id(), task).is_some() {
+                        panic!("Same task inserted into waiting_tasks twice");
+                    }
+                }
+            }
+        }
+    }
+}
+
+#[derive(Debug, Clone, IntoWaker)]
+struct TaskWaker {
+    task_id: usize,
+    wake_queue: Arc<ArrayQueue<usize>>,
+}
+
+impl TaskWaker {
+    fn wake_task(&self) {
+        self.wake_queue.push(self.task_id).expect("wake queue full");
+    }
+}
+
+impl cooked_waker::WakeRef for TaskWaker {
+    fn wake_by_ref(&self) {
+        self.wake_task();
+    }
+}
+
+impl cooked_waker::Wake for TaskWaker {
+    fn wake(self) {
+        self.wake_task();
+    }
+}

src/vga_buffer.rs

@@ -166,11 +166,16 @@ macro_rules! println {
     ($($arg:tt)*) => ($crate::print!("{}\n", format_args!($($arg)*)));
 }
 
-/// Prints the given formatted string to the VGA text buffer through the global `WRITER` instance.
+/// Prints the given formatted string to the VGA text buffer
+/// through the global `WRITER` instance.
 #[doc(hidden)]
 pub fn _print(args: fmt::Arguments) {
     use core::fmt::Write;
-    WRITER.lock().write_fmt(args).unwrap();
+    use x86_64::instructions::interrupts;
+
+    interrupts::without_interrupts(|| {
+        WRITER.lock().write_fmt(args).unwrap();
+    });
 }
 
 #[test_case]
@@ -191,14 +196,20 @@ fn test_println_many() {
 
 #[test_case]
 fn test_println_output() {
+    use core::fmt::Write;
+    use x86_64::instructions::interrupts;
+
     serial_print!("test_println_output... ");
 
     let s = "Some test string that fits on a single line";
-    println!("{}", s);
+    interrupts::without_interrupts(|| {
-    for (i, c) in s.chars().enumerate() {
+        let mut writer = WRITER.lock();
-        let screen_char = WRITER.lock().buffer.chars[BUFFER_HEIGHT - 2][i].read();
+        writeln!(writer, "\n{}", s).expect("writeln failed");
-        assert_eq!(char::from(screen_char.ascii_character), c);
+        for (i, c) in s.chars().enumerate() {
-    }
+            let screen_char = writer.buffer.chars[BUFFER_HEIGHT - 2][i].read();
+            assert_eq!(char::from(screen_char.ascii_character), c);
+        }
+    });
 
     serial_println!("[ok]");
 }

tests/heap_allocation.rs

@@ -0,0 +1,76 @@
+#![no_std]
+#![no_main]
+#![feature(custom_test_frameworks)]
+#![test_runner(blog_os::test_runner)]
+#![reexport_test_harness_main = "test_main"]
+
+extern crate alloc;
+
+use alloc::{boxed::Box, vec::Vec};
+use blog_os::{allocator::HEAP_SIZE, serial_print, serial_println};
+use bootloader::{entry_point, BootInfo};
+use core::panic::PanicInfo;
+
+entry_point!(main);
+
+fn main(boot_info: &'static BootInfo) -> ! {
+    use blog_os::allocator;
+    use blog_os::memory::{self, BootInfoFrameAllocator};
+    use x86_64::VirtAddr;
+
+    blog_os::init();
+    let phys_mem_offset = VirtAddr::new(boot_info.physical_memory_offset);
+    let mut mapper = unsafe { memory::init(phys_mem_offset) };
+    let mut frame_allocator = unsafe { BootInfoFrameAllocator::init(&boot_info.memory_map) };
+    allocator::init_heap(&mut mapper, &mut frame_allocator).expect("heap initialization failed");
+
+    test_main();
+    loop {}
+}
+
+#[test_case]
+fn simple_allocation() {
+    serial_print!("simple_allocation... ");
+    let heap_value = Box::new(41);
+    assert_eq!(*heap_value, 41);
+    serial_println!("[ok]");
+}
+
+#[test_case]
+fn large_vec() {
+    serial_print!("large_vec... ");
+    let n = 1000;
+    let mut vec = Vec::new();
+    for i in 0..n {
+        vec.push(i);
+    }
+    assert_eq!(vec.iter().sum::<u64>(), (n - 1) * n / 2);
+    serial_println!("[ok]");
+}
+
+#[test_case]
+fn many_boxes() {
+    serial_print!("many_boxes... ");
+    for i in 0..HEAP_SIZE {
+        let x = Box::new(i);
+        assert_eq!(*x, i);
+    }
+    serial_println!("[ok]");
+}
+
+#[test_case]
+fn many_boxes_long_lived() {
+    serial_print!("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
+    serial_println!("[ok]");
+}
+
+#[panic_handler]
+fn panic(info: &PanicInfo) -> ! {
+    blog_os::test_panic_handler(info)
+}