Merge branch 'post-05' into post-06

Fix: `target-pointer-width` field now expects an integer

.cargo/config.toml

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

Cargo.lock

@@ -2,12 +2,6 @@
 # It is not intended for manual editing.
 version = 4
 
-[[package]]
-name = "autocfg"
-version = "1.5.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c08606f8c3cbf4ce6ec8e28fb0014a2c086708fe954eaa885384a6165172e7e8"
-
 [[package]]
 name = "bit_field"
 version = "0.10.2"
@@ -31,13 +25,7 @@ name = "blog_os"
 version = "0.1.0"
 dependencies = [
  "bootloader",
- "conquer-once",
- "crossbeam-queue",
- "futures-util",
  "lazy_static",
- "linked_list_allocator",
- "pc-keyboard",
- "pic8259",
  "spin 0.5.2",
  "uart_16550",
  "volatile 0.2.7",
@@ -46,63 +34,9 @@ dependencies = [
 
 [[package]]
 name = "bootloader"
-version = "0.9.32"
+version = "0.9.33"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1ea119c3ed05625c179e09d17d0914570a3753ca09c890a73d98f6b72aea00d2"
+checksum = "7bdfddac270bbdd45903296bc1caf29a7fdce6b326aaf0bbab7f04c5f98b7447"
-
-[[package]]
-name = "conquer-once"
-version = "0.2.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "96eb12fb69466716fbae9009d389e6a30830ae8975e170eff2d2cff579f9efa3"
-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 = "crossbeam-queue"
-version = "0.3.12"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0f58bbc28f91df819d0aa2a2c00cd19754769c2fad90579b3592b1c9ba7a3115"
-dependencies = [
- "crossbeam-utils",
-]
-
-[[package]]
-name = "crossbeam-utils"
-version = "0.8.21"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d0a5c400df2834b80a4c3327b3aad3a4c4cd4de0629063962b03235697506a28"
-
-[[package]]
-name = "futures-core"
-version = "0.3.31"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "05f29059c0c2090612e8d742178b0580d2dc940c837851ad723096f87af6663e"
-
-[[package]]
-name = "futures-task"
-version = "0.3.31"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f90f7dce0722e95104fcb095585910c0977252f286e354b5e3bd38902cd99988"
-
-[[package]]
-name = "futures-util"
-version = "0.3.31"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9fa08315bb612088cc391249efdc3bc77536f16c91f6cf495e6fbe85b20a4a81"
-dependencies = [
- "futures-core",
- "futures-task",
- "pin-project-lite",
- "pin-utils",
-]
 
 [[package]]
 name = "lazy_static"
@@ -113,64 +47,12 @@ dependencies = [
  "spin 0.9.8",
 ]
 
-[[package]]
-name = "linked_list_allocator"
-version = "0.9.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "549ce1740e46b291953c4340adcd74c59bcf4308f4cac050fd33ba91b7168f4a"
-dependencies = [
- "spinning_top",
-]
-
-[[package]]
-name = "lock_api"
-version = "0.4.13"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "96936507f153605bddfcda068dd804796c84324ed2510809e5b2a624c81da765"
-dependencies = [
- "autocfg",
- "scopeguard",
-]
-
-[[package]]
-name = "pc-keyboard"
-version = "0.7.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ed089a1fbffe3337a1a345501c981f1eb1e47e69de5a40e852433e12953c3174"
-
-[[package]]
-name = "pic8259"
-version = "0.10.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cb844b5b01db1e0b17938685738f113bfc903846f18932b378bc0eabfa40e194"
-dependencies = [
- "x86_64",
-]
-
-[[package]]
-name = "pin-project-lite"
-version = "0.2.16"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3b3cff922bd51709b605d9ead9aa71031d81447142d828eb4a6eba76fe619f9b"
-
-[[package]]
-name = "pin-utils"
-version = "0.1.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8b870d8c151b6f2fb93e84a13146138f05d02ed11c7e7c54f8826aaaf7c9f184"
-
 [[package]]
 name = "rustversion"
 version = "1.0.22"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b39cdef0fa800fc44525c84ccb54a029961a8215f9619753635a9c0d2538d46d"
 
-[[package]]
-name = "scopeguard"
-version = "1.2.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "94143f37725109f92c262ed2cf5e59bce7498c01bcc1502d7b9afe439a4e9f49"
-
 [[package]]
 name = "spin"
 version = "0.5.2"
@@ -183,15 +65,6 @@ version = "0.9.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6980e8d7511241f8acf4aebddbb1ff938df5eebe98691418c4468d0b72a96a67"
 
-[[package]]
-name = "spinning_top"
-version = "0.2.5"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5b9eb1a2f4c41445a3a0ff9abc5221c5fcd28e1f13cd7c0397706f9ac938ddb0"
-dependencies = [
- "lock_api",
-]
-
 [[package]]
 name = "uart_16550"
 version = "0.2.19"

Cargo.toml

@@ -13,14 +13,11 @@ name = "stack_overflow"
 harness = false
 
 [dependencies]
-bootloader = { version = "0.9", features = ["map_physical_memory"] }
+bootloader = "0.9"
 volatile = "0.2.6"
 spin = "0.5.2"
 x86_64 = "0.14.2"
 uart_16550 = "0.2.0"
-pic8259 = "0.10.1"
-pc-keyboard = "0.7.0"
-linked_list_allocator = "0.9.0"
 
 [dependencies.lazy_static]
 version = "1.0"
@@ -31,19 +28,6 @@ name = "blog_os"
 test = true
 bench = false
 
-[dependencies.crossbeam-queue]
-version = "0.3.11"
-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 (Async/Await)
+# Blog OS (Double Faults)
 
-[![Build Status](https://github.com/phil-opp/blog_os/workflows/Code/badge.svg?branch=post-12)](https://github.com/phil-opp/blog_os/actions?query=workflow%3A%22Code%22+branch%3Apost-12)
+[![Build Status](https://github.com/phil-opp/blog_os/workflows/Code/badge.svg?branch=post-06)](https://github.com/phil-opp/blog_os/actions?query=workflow%3A%22Code%22+branch%3Apost-06)
 
-This repository contains the source code for the [Async/Await][post] post of the [Writing an OS in Rust](https://os.phil-opp.com) series.
+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.
 
-[post]: https://os.phil-opp.com/async-await/
+[post]: https://os.phil-opp.com/double-fault-exceptions/
 
 **Check out the [master branch](https://github.com/phil-opp/blog_os) for more information.**
 

src/allocator.rs

@@ -1,82 +0,0 @@
-use alloc::alloc::{GlobalAlloc, Layout};
-use core::ptr::null_mut;
-use fixed_size_block::FixedSizeBlockAllocator;
-use x86_64::{
-    VirtAddr,
-    structures::paging::{
-        FrameAllocator, Mapper, Page, PageTableFlags, Size4KiB, mapper::MapToError,
-    },
-};
-
-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;
-        unsafe { 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

@@ -1,61 +0,0 @@
-use super::{Locked, align_up};
-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

@@ -1,109 +0,0 @@
-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 {
-        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) {
-        unsafe {
-            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;
-                unsafe {
-                    new_node_ptr.write(new_node);
-                    allocator.list_heads[index] = Some(&mut *new_node_ptr);
-                }
-            }
-            None => {
-                let ptr = NonNull::new(ptr).unwrap();
-                unsafe {
-                    allocator.fallback_allocator.deallocate(ptr, layout);
-                }
-            }
-        }
-    }
-}

src/allocator/linked_list.rs

@@ -1,151 +0,0 @@
-use super::{Locked, align_up};
-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) {
-        unsafe {
-            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_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;
-        unsafe {
-            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 {
-                unsafe {
-                    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);
-
-        unsafe { self.lock().add_free_region(ptr as usize, size) }
-    }
-}

src/interrupts.rs

@@ -1,44 +1,16 @@
-use crate::{gdt, hlt_loop, print, println};
+use crate::{gdt, println};
 use lazy_static::lazy_static;
-use pic8259::ChainedPics;
+use x86_64::structures::idt::{InterruptDescriptorTable, InterruptStackFrame};
-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
     };
 }
@@ -51,19 +23,6 @@ extern "x86-interrupt" fn breakpoint_handler(stack_frame: InterruptStackFrame) {
     println!("EXCEPTION: BREAKPOINT\n{:#?}", stack_frame);
 }
 
-extern "x86-interrupt" fn page_fault_handler(
-    stack_frame: 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: InterruptStackFrame,
     _error_code: u64,
@@ -71,27 +30,6 @@ extern "x86-interrupt" fn double_fault_handler(
     panic!("EXCEPTION: DOUBLE FAULT\n{:#?}", stack_frame);
 }
 
-extern "x86-interrupt" fn timer_interrupt_handler(_stack_frame: InterruptStackFrame) {
-    print!(".");
-    unsafe {
-        PICS.lock()
-            .notify_end_of_interrupt(InterruptIndex::Timer.as_u8());
-    }
-}
-
-extern "x86-interrupt" fn keyboard_interrupt_handler(_stack_frame: 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());
-    }
-}
-
 #[test_case]
 fn test_breakpoint_exception() {
     // invoke a breakpoint exception

src/lib.rs

@@ -5,22 +5,16 @@
 #![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 trait Testable {
     fn run(&self) -> ();
@@ -49,7 +43,7 @@ pub fn test_panic_handler(info: &PanicInfo) -> ! {
     serial_println!("[failed]\n");
     serial_println!("Error: {}\n", info);
     exit_qemu(QemuExitCode::Failed);
-    hlt_loop();
+    loop {}
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -68,24 +62,13 @@ pub fn exit_qemu(exit_code: QemuExitCode) {
     }
 }
 
-pub fn hlt_loop() -> ! {
-    loop {
-        x86_64::instructions::hlt();
-    }
-}
-
-#[cfg(test)]
-use bootloader::{BootInfo, entry_point};
-
-#[cfg(test)]
-entry_point!(test_kernel_main);
-
 /// Entry point for `cargo xtest`
 #[cfg(test)]
-fn test_kernel_main(_boot_info: &'static BootInfo) -> ! {
+#[unsafe(no_mangle)]
+pub extern "C" fn _start() -> ! {
     init();
     test_main();
-    hlt_loop();
+    loop {}
 }
 
 #[cfg(test)]

src/main.rs

@@ -4,36 +4,27 @@
 #![test_runner(blog_os::test_runner)]
 #![reexport_test_harness_main = "test_main"]
 
-extern crate alloc;
-
 use blog_os::println;
-use blog_os::task::{Task, executor::Executor, keyboard};
-use bootloader::{BootInfo, entry_point};
 use core::panic::PanicInfo;
 
-entry_point!(kernel_main);
+#[unsafe(no_mangle)]
-
+pub extern "C" fn _start() -> ! {
-fn kernel_main(boot_info: &'static BootInfo) -> ! {
-    use blog_os::allocator;
-    use blog_os::memory::{self, BootInfoFrameAllocator};
-    use x86_64::VirtAddr;
-
     println!("Hello World{}", "!");
+
     blog_os::init();
 
-    let phys_mem_offset = VirtAddr::new(boot_info.physical_memory_offset);
+    fn stack_overflow() {
-    let mut mapper = unsafe { memory::init(phys_mem_offset) };
+        stack_overflow(); // for each recursion, the return address is pushed
-    let mut frame_allocator = unsafe { BootInfoFrameAllocator::init(&boot_info.memory_map) };
+    }
 
-    allocator::init_heap(&mut mapper, &mut frame_allocator).expect("heap initialization failed");
+    // uncomment line below to trigger a stack overflow
+    // stack_overflow();
 
     #[cfg(test)]
     test_main();
 
-    let mut executor = Executor::new();
+    println!("It did not crash!");
-    executor.spawn(Task::new(example_task()));
+    loop {}
-    executor.spawn(Task::new(keyboard::print_keypresses()));
-    executor.run();
 }
 
 /// This function is called on panic.
@@ -41,7 +32,7 @@ fn kernel_main(boot_info: &'static BootInfo) -> ! {
 #[panic_handler]
 fn panic(info: &PanicInfo) -> ! {
     println!("{}", info);
-    blog_os::hlt_loop();
+    loop {}
 }
 
 #[cfg(test)]
@@ -50,15 +41,6 @@ fn panic(info: &PanicInfo) -> ! {
     blog_os::test_panic_handler(info)
 }
 
-async fn async_number() -> u32 {
-    42
-}
-
-async fn example_task() {
-    let number = async_number().await;
-    println!("async number: {}", number);
-}
-
 #[test_case]
 fn trivial_assertion() {
     assert_eq!(1, 1);

src/memory.rs

@@ -1,86 +0,0 @@
-use bootloader::bootinfo::{MemoryMap, MemoryRegionType};
-use x86_64::{
-    PhysAddr, VirtAddr,
-    structures::paging::{FrameAllocator, OffsetPageTable, PageTable, PhysFrame, Size4KiB},
-};
-
-/// 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> {
-    unsafe {
-        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();
-
-    unsafe { &mut *page_table_ptr }
-}
-
-/// A FrameAllocator that always returns `None`.
-pub struct EmptyFrameAllocator;
-
-unsafe impl FrameAllocator<Size4KiB> for EmptyFrameAllocator {
-    fn allocate_frame(&mut self) -> Option<PhysFrame> {
-        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 = PhysFrame> {
-        // 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
-        frame_addresses.map(|addr| PhysFrame::containing_address(PhysAddr::new(addr)))
-    }
-}
-
-unsafe impl FrameAllocator<Size4KiB> for BootInfoFrameAllocator {
-    fn allocate_frame(&mut self) -> Option<PhysFrame> {
-        let frame = self.usable_frames().nth(self.next);
-        self.next += 1;
-        frame
-    }
-}

src/serial.rs

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

src/task/executor.rs

@@ -1,102 +0,0 @@
-use super::{Task, TaskId};
-use alloc::{collections::BTreeMap, sync::Arc, task::Wake};
-use core::task::{Context, Poll, Waker};
-use crossbeam_queue::ArrayQueue;
-
-pub struct Executor {
-    tasks: BTreeMap<TaskId, Task>,
-    task_queue: Arc<ArrayQueue<TaskId>>,
-    waker_cache: BTreeMap<TaskId, Waker>,
-}
-
-impl Executor {
-    pub fn new() -> Self {
-        Executor {
-            tasks: BTreeMap::new(),
-            task_queue: Arc::new(ArrayQueue::new(100)),
-            waker_cache: BTreeMap::new(),
-        }
-    }
-
-    pub fn spawn(&mut self, task: Task) {
-        let task_id = task.id;
-        if self.tasks.insert(task.id, task).is_some() {
-            panic!("task with same ID already in tasks");
-        }
-        self.task_queue.push(task_id).expect("queue full");
-    }
-
-    pub fn run(&mut self) -> ! {
-        loop {
-            self.run_ready_tasks();
-            self.sleep_if_idle();
-        }
-    }
-
-    fn run_ready_tasks(&mut self) {
-        // destructure `self` to avoid borrow checker errors
-        let Self {
-            tasks,
-            task_queue,
-            waker_cache,
-        } = self;
-
-        while let Some(task_id) = task_queue.pop() {
-            let task = match tasks.get_mut(&task_id) {
-                Some(task) => task,
-                None => continue, // task no longer exists
-            };
-            let waker = waker_cache
-                .entry(task_id)
-                .or_insert_with(|| TaskWaker::new(task_id, task_queue.clone()));
-            let mut context = Context::from_waker(waker);
-            match task.poll(&mut context) {
-                Poll::Ready(()) => {
-                    // task done -> remove it and its cached waker
-                    tasks.remove(&task_id);
-                    waker_cache.remove(&task_id);
-                }
-                Poll::Pending => {}
-            }
-        }
-    }
-
-    fn sleep_if_idle(&self) {
-        use x86_64::instructions::interrupts::{self, enable_and_hlt};
-
-        interrupts::disable();
-        if self.task_queue.is_empty() {
-            enable_and_hlt();
-        } else {
-            interrupts::enable();
-        }
-    }
-}
-
-struct TaskWaker {
-    task_id: TaskId,
-    task_queue: Arc<ArrayQueue<TaskId>>,
-}
-
-impl TaskWaker {
-    fn new(task_id: TaskId, task_queue: Arc<ArrayQueue<TaskId>>) -> Waker {
-        Waker::from(Arc::new(TaskWaker {
-            task_id,
-            task_queue,
-        }))
-    }
-
-    fn wake_task(&self) {
-        self.task_queue.push(self.task_id).expect("task_queue full");
-    }
-}
-
-impl Wake for TaskWaker {
-    fn wake(self: Arc<Self>) {
-        self.wake_task();
-    }
-
-    fn wake_by_ref(self: &Arc<Self>) {
-        self.wake_task();
-    }
-}

src/task/keyboard.rs

@@ -1,87 +0,0 @@
-use crate::{print, println};
-use conquer_once::spin::OnceCell;
-use core::{
-    pin::Pin,
-    task::{Context, Poll},
-};
-use crossbeam_queue::ArrayQueue;
-use futures_util::{
-    stream::{Stream, StreamExt},
-    task::AtomicWaker,
-};
-use pc_keyboard::{DecodedKey, HandleControl, Keyboard, ScancodeSet1, layouts};
-
-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 Some(scancode) = queue.pop() {
-            return Poll::Ready(Some(scancode));
-        }
-
-        WAKER.register(&cx.waker());
-        match queue.pop() {
-            Some(scancode) => {
-                WAKER.take();
-                Poll::Ready(Some(scancode))
-            }
-            None => Poll::Pending,
-        }
-    }
-}
-
-pub async fn print_keypresses() {
-    let mut scancodes = ScancodeStream::new();
-    let mut keyboard = Keyboard::new(
-        ScancodeSet1::new(),
-        layouts::Us104Key,
-        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

@@ -1,39 +0,0 @@
-use alloc::boxed::Box;
-use core::{
-    future::Future,
-    pin::Pin,
-    sync::atomic::{AtomicU64, Ordering},
-    task::{Context, Poll},
-};
-
-pub mod executor;
-pub mod keyboard;
-pub mod simple_executor;
-
-pub struct Task {
-    id: TaskId,
-    future: Pin<Box<dyn Future<Output = ()>>>,
-}
-
-impl Task {
-    pub fn new(future: impl Future<Output = ()> + 'static) -> Task {
-        Task {
-            id: TaskId::new(),
-            future: Box::pin(future),
-        }
-    }
-
-    fn poll(&mut self, context: &mut Context) -> Poll<()> {
-        self.future.as_mut().poll(context)
-    }
-}
-
-#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
-struct TaskId(u64);
-
-impl TaskId {
-    fn new() -> Self {
-        static NEXT_ID: AtomicU64 = AtomicU64::new(0);
-        TaskId(NEXT_ID.fetch_add(1, Ordering::Relaxed))
-    }
-}

src/task/simple_executor.rs

@@ -1,44 +0,0 @@
-use super::Task;
-use alloc::collections::VecDeque;
-use core::task::{Context, Poll, RawWaker, RawWakerVTable, Waker};
-
-pub struct SimpleExecutor {
-    task_queue: VecDeque<Task>,
-}
-
-impl SimpleExecutor {
-    pub fn new() -> SimpleExecutor {
-        SimpleExecutor {
-            task_queue: VecDeque::new(),
-        }
-    }
-
-    pub fn spawn(&mut self, task: Task) {
-        self.task_queue.push_back(task)
-    }
-
-    pub fn run(&mut self) {
-        while let Some(mut task) = self.task_queue.pop_front() {
-            let waker = dummy_waker();
-            let mut context = Context::from_waker(&waker);
-            match task.poll(&mut context) {
-                Poll::Ready(()) => {} // task done
-                Poll::Pending => self.task_queue.push_back(task),
-            }
-        }
-    }
-}
-
-fn dummy_raw_waker() -> RawWaker {
-    fn no_op(_: *const ()) {}
-    fn clone(_: *const ()) -> RawWaker {
-        dummy_raw_waker()
-    }
-
-    let vtable = &RawWakerVTable::new(clone, no_op, no_op, no_op);
-    RawWaker::new(0 as *const (), vtable)
-}
-
-fn dummy_waker() -> Waker {
-    unsafe { Waker::from_raw(dummy_raw_waker()) }
-}

src/vga_buffer.rs

@@ -163,16 +163,11 @@ macro_rules! println {
     ($($arg:tt)*) => ($crate::print!("{}\n", format_args!($($arg)*)));
 }
 
-/// Prints the given formatted string to the VGA text buffer
+/// Prints the given formatted string to the VGA text buffer through the global `WRITER` instance.
-/// through the global `WRITER` instance.
 #[doc(hidden)]
 pub fn _print(args: fmt::Arguments) {
     use core::fmt::Write;
-    use x86_64::instructions::interrupts;
+    WRITER.lock().write_fmt(args).unwrap();
-
-    interrupts::without_interrupts(|| {
-        WRITER.lock().write_fmt(args).unwrap();
-    });
 }
 
 #[test_case]
@@ -189,16 +184,10 @@ fn test_println_many() {
 
 #[test_case]
 fn test_println_output() {
-    use core::fmt::Write;
-    use x86_64::instructions::interrupts;
-
     let s = "Some test string that fits on a single line";
-    interrupts::without_interrupts(|| {
+    println!("{}", s);
-        let mut writer = WRITER.lock();
+    for (i, c) in s.chars().enumerate() {
-        writeln!(writer, "\n{}", s).expect("writeln failed");
+        let screen_char = WRITER.lock().buffer.chars[BUFFER_HEIGHT - 2][i].read();
-        for (i, c) in s.chars().enumerate() {
+        assert_eq!(char::from(screen_char.ascii_character), c);
-            let screen_char = writer.buffer.chars[BUFFER_HEIGHT - 2][i].read();
+    }
-            assert_eq!(char::from(screen_char.ascii_character), c);
-        }
-    });
 }

tests/heap_allocation.rs

@@ -1,70 +0,0 @@
-#![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;
-use bootloader::{BootInfo, entry_point};
-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() {
-    let heap_value_1 = Box::new(41);
-    let heap_value_2 = Box::new(13);
-    assert_eq!(*heap_value_1, 41);
-    assert_eq!(*heap_value_2, 13);
-}
-
-#[test_case]
-fn 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);
-}
-
-#[test_case]
-fn many_boxes() {
-    for i in 0..HEAP_SIZE {
-        let x = Box::new(i);
-        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
-}
-
-#[panic_handler]
-fn panic(info: &PanicInfo) -> ! {
-    blog_os::test_panic_handler(info)
-}

x86_64-blog_os.json

@@ -3,7 +3,7 @@
     "data-layout": "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128",
     "arch": "x86_64",
     "target-endian": "little",
-    "target-pointer-width": "64",
+    "target-pointer-width": 64,
     "target-c-int-width": 32,
     "os": "none",
     "executables": true,