Merge branch 'post-11' into post-12

The `#[alloc_error_handler]` attribute was removed

.cargo/config

@@ -1,5 +0,0 @@
-[build]
-target = "x86_64-blog_os.json"
-
-[target.'cfg(target_os = "none")']
-runner = "bootimage runner"

.cargo/config.toml

@@ -0,0 +1,9 @@
+[unstable]
+build-std = ["core", "compiler_builtins", "alloc"]
+build-std-features = ["compiler-builtins-mem"]
+
+[build]
+target = "x86_64-blog_os.json"
+
+[target.'cfg(target_os = "none")']
+runner = "bootimage runner"

.github/workflows/build-code.yml

@@ -1,96 +0,0 @@
-name: Build Code
-
-on:
-  push:
-    branches:
-      - '*'
-      - '!staging.tmp'
-    tags:
-      - '*'
-  schedule:
-    - cron: '40 3 * * *'   # every day at 3:40
-  pull_request:
-
-jobs:
-  test:
-    name: "Test"
-
-    strategy:
-      matrix:
-        platform: [
-          ubuntu-latest,
-          macos-latest,
-          windows-latest
-        ]
-
-    runs-on: ${{ matrix.platform }}
-    timeout-minutes: 15
-
-    steps:
-    - name: "Checkout Repository"
-      uses: actions/checkout@v1
-
-    - name: Install Rustup
-      run: |
-        curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain nightly
-        echo ::add-path::$HOME/.cargo/bin
-      if: runner.os == 'macOS'
-
-    - name: "Print Rust Version"
-      run: |
-        rustc -Vv
-        cargo -Vv
-
-    - name: "Install Rustup Components"
-      run: rustup component add rust-src llvm-tools-preview
-    - name: "Install cargo-xbuild"
-      run: cargo install cargo-xbuild --debug
-    - name: "Install bootimage"
-      run: cargo install bootimage --debug
-
-    - name: "Run cargo xbuild"
-      run: cargo xbuild
-    - name: "Create Bootimage"
-      run: cargo bootimage
-
-     # install QEMU
-    - name: Install QEMU (Linux)
-      run: sudo apt update && sudo apt install qemu-system-x86
-      if: runner.os == 'Linux'
-    - name: Install QEMU (macOS)
-      run: brew install qemu
-      if: runner.os == 'macOS'
-      env:
-        HOMEBREW_NO_AUTO_UPDATE: 1
-        HOMEBREW_NO_BOTTLE_SOURCE_FALLBACK: 1
-        HOMEBREW_NO_INSTALL_CLEANUP: 1
-    - name: Install Scoop (Windows)
-      run: |
-        Invoke-Expression (New-Object System.Net.WebClient).DownloadString('https://get.scoop.sh')
-        echo ::add-path::$HOME\scoop\shims
-      if: runner.os == 'Windows'
-      shell: pwsh
-    - name: Install QEMU (Windows)
-      run: scoop install qemu
-      if: runner.os == 'Windows'
-      shell: pwsh
-    - name: "Print QEMU Version"
-      run: qemu-system-x86_64 --version
-
-    - name: "Run cargo xtest"
-      run: cargo xtest
-
-  check_formatting:
-    name: "Check Formatting"
-    runs-on: ubuntu-latest
-    timeout-minutes: 2
-    steps:
-    - uses: actions/checkout@v1
-    - name: "Use the latest Rust nightly with rustfmt"
-      uses: actions-rs/toolchain@v1
-      with:
-          toolchain: nightly
-          profile: minimal
-          components: rustfmt
-          override: true
-    - run: cargo fmt -- --check

.github/workflows/code.yml

@@ -0,0 +1,130 @@
+name: Code
+
+on:
+  push:
+    branches:
+      - '*'
+      - '!staging.tmp'
+    tags:
+      - '*'
+  schedule:
+    - cron: '40 3 * * *'   # every day at 3:40
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  check:
+    name: Check
+    strategy:
+      fail-fast: false
+      matrix:
+        platform: [
+          ubuntu-latest,
+          macos-latest,
+          windows-latest
+        ]
+    runs-on: ${{ matrix.platform }}
+    steps:
+      - name: Checkout Repository
+        uses: actions/checkout@v2
+      - name: Install Rust Toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: nightly
+      - name: Install `rust-src` Rustup Component
+        run: rustup component add rust-src
+      - name: Run `cargo check`
+        uses: actions-rs/cargo@v1
+        with:
+          command: check
+
+  test:
+    name: Test
+    strategy:
+      fail-fast: false
+      matrix:
+        platform: [
+          ubuntu-latest,
+          macos-latest,
+          windows-latest
+        ]
+    runs-on: ${{ matrix.platform }}
+    steps:
+      - name: Install Rust Toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: nightly
+      - name: Install bootimage
+        run: cargo install bootimage --debug
+      - name: Checkout Repository
+        uses: actions/checkout@v2
+      - name: Install Rustup Components
+        run: rustup component add rust-src llvm-tools-preview
+      - name: Run `cargo bootimage`
+        uses: actions-rs/cargo@v1
+        with:
+          command: bootimage
+
+      # install QEMU
+      - name: Install QEMU (Linux)
+        run: sudo apt update && sudo apt install qemu-system-x86
+        if: runner.os == 'Linux'
+      - name: Install QEMU (macOS)
+        run: brew install qemu
+        if: runner.os == 'macOS'
+        env:
+          HOMEBREW_NO_AUTO_UPDATE: 1
+          HOMEBREW_NO_BOTTLE_SOURCE_FALLBACK: 1
+          HOMEBREW_NO_INSTALL_CLEANUP: 1
+      - name: Install QEMU (Windows)
+        run: |
+          choco install qemu --version 2021.5.5
+          echo "$Env:Programfiles\qemu" | Out-File -FilePath $env:GITHUB_PATH -Encoding utf8 -Append
+        if: runner.os == 'Windows'
+        shell: pwsh
+      - name: "Print QEMU Version"
+        run: qemu-system-x86_64 --version
+
+      - name: Run `cargo test`
+        uses: actions-rs/cargo@v1
+        with:
+          command: test
+
+  check_formatting:
+    name: Check Formatting
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout Repository
+        uses: actions/checkout@v2
+      - name: Install Rust Toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: nightly
+          components: rustfmt
+          override: true
+      - name: Run `cargo fmt`
+        uses: actions-rs/cargo@v1
+        with:
+          command: fmt
+          args: --all -- --check
+
+  clippy:
+    name: Clippy
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout Repository
+        uses: actions/checkout@v2
+      - name: Install Rust Toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: nightly
+          components: clippy, rust-src
+          override: true
+      - name: Run `cargo clippy`
+        uses: actions-rs/cargo@v1
+        with:
+          command: clippy

Cargo.lock

@@ -1,16 +1,18 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
+version = 3
+
 [[package]]
 name = "autocfg"
-version = "1.0.0"
+version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f8aac770f1885fd7e387acedd76065302551364496e46b3dd00860b2f8359b9d"
+checksum = "cdb031dd78e28731d87d56cc8ffef4a8f36ca26c38fe2de700543e627f8a464a"
 
 [[package]]
 name = "bit_field"
-version = "0.9.0"
+version = "0.10.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ed8765909f9009617974ab6b7d332625b320b33c326b1e9321382ef1999b5d56"
+checksum = "dcb6dd1c2376d2e096796e234a70e17e94cc2d5d54ff8ce42b28cef1d0d359a4"
 
 [[package]]
 name = "bitflags"
@@ -29,18 +31,18 @@ dependencies = [
  "lazy_static",
  "linked_list_allocator",
  "pc-keyboard",
- "pic8259_simple",
+ "pic8259",
  "spin",
  "uart_16550",
- "volatile",
+ "volatile 0.2.7",
  "x86_64",
 ]
 
 [[package]]
 name = "bootloader"
-version = "0.8.8"
+version = "0.9.23"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c3ed4f735c4e455ba86a3d2939b1c0729414153642106c9d035693355630a42c"
+checksum = "b6e02311b16c9819e7c72866d379cdd3026c3b7b25c1edf161f548f8e887e7ff"
 
 [[package]]
 name = "cfg-if"
@@ -50,9 +52,9 @@ checksum = "4785bdd1c96b2a846b2bd7cc02e86b6b3dbf14e7e53446c4f54c92a361040822"
 
 [[package]]
 name = "conquer-once"
-version = "0.2.0"
+version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6f7644600a548ecad74e4a918392af1798f7dd045be610be3203b9e129b4f98f"
+checksum = "96eb12fb69466716fbae9009d389e6a30830ae8975e170eff2d2cff579f9efa3"
 dependencies = [
  "conquer-util",
 ]
@@ -63,20 +65,15 @@ version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "654fb2472cc369d311c547103a1fa81d467bef370ae7a0680f65939895b1182a"
 
-[[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"
+version = "0.2.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c695eeca1e7173472a32221542ae469b3e9aac3a4fc81f7696bcad82029493db"
+checksum = "774ba60a54c213d409d5353bda12d49cd68d14e45036a285234c8d6f91f92570"
 dependencies = [
  "cfg-if",
  "crossbeam-utils",
+ "maybe-uninit",
 ]
 
 [[package]]
@@ -91,24 +88,26 @@ dependencies = [
 
 [[package]]
 name = "futures-core"
-version = "0.3.4"
+version = "0.3.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f25592f769825e89b92358db00d26f965761e094951ac44d3663ef25b7ac464a"
+checksum = "0402f765d8a89a26043b889b26ce3c4679d268fa6bb22cd7c6aad98340e179d1"
 
 [[package]]
 name = "futures-task"
-version = "0.3.4"
+version = "0.3.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7b0a34e53cf6cdcd0178aa573aed466b646eb3db769570841fda0c7ede375a27"
+checksum = "8a16bef9fc1a4dddb5bee51c989e3fbba26569cbb0e31f5b303c184e3dd33dae"
 
 [[package]]
 name = "futures-util"
-version = "0.3.4"
+version = "0.3.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "22766cf25d64306bedf0384da004d05c9974ab104fcc4528f1236181c18004c5"
+checksum = "feb5c238d27e2bf94ffdfd27b2c29e3df4a68c4193bb6427384259e2bf191967"
 dependencies = [
+ "autocfg",
  "futures-core",
  "futures-task",
+ "pin-project-lite",
  "pin-utils",
 ]
 
@@ -123,42 +122,54 @@ dependencies = [
 
 [[package]]
 name = "linked_list_allocator"
-version = "0.8.0"
+version = "0.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "18c618c431dfe4419afbe22852f6aceffbc17bd82ba0a18b982def291000824c"
+checksum = "d0b725207570aa16096962d0b20c79f8a543df2280bd3c903022b9b0b4d7ea68"
 dependencies = [
  "spinning_top",
 ]
 
 [[package]]
 name = "lock_api"
-version = "0.3.3"
+version = "0.4.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "79b2de95ecb4691949fea4716ca53cdbcfccb2c612e19644a8bad05edcf9f47b"
+checksum = "0382880606dff6d15c9476c416d18690b72742aa7b605bb6dd6ec9030fbf07eb"
 dependencies = [
  "scopeguard",
 ]
 
 [[package]]
-name = "pc-keyboard"
+name = "maybe-uninit"
-version = "0.5.0"
+version = "2.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c48392db76c4e9a69e0b3be356c5f97ebb7b14413c5e4fd0af4755dbf86e2fce"
+checksum = "60302e4db3a61da70c0cb7991976248362f30319e88850c487b9b95bbf059e00"
 
 [[package]]
-name = "pic8259_simple"
+name = "pc-keyboard"
-version = "0.1.1"
+version = "0.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dc64b2fd10828da8521b6cdabe0679385d7d2a3a6d4c336b819d1fa31ba35c72"
+checksum = "5c6f2d937e3b8d63449b01401e2bae4041bc9dd1129c2e3e0d239407cf6635ac"
+
+[[package]]
+name = "pic8259"
+version = "0.10.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "08cc920d83ee33c0f9b73aa441e75468bf2d10c959a3eb6260cf720b05ac91a1"
 dependencies = [
- "cpuio",
+ "x86_64",
 ]
 
 [[package]]
-name = "pin-utils"
+name = "pin-project-lite"
-version = "0.1.0-alpha.4"
+version = "0.2.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5894c618ce612a3fa23881b152b608bafb8c56cfc22f434a3ba3120b40f7b587"
+checksum = "dc0e1f259c92177c30a4c9d177246edd0a3568b25756a977d0632cf8fa37e905"
+
+[[package]]
+name = "pin-utils"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8b870d8c151b6f2fb93e84a13146138f05d02ed11c7e7c54f8826aaaf7c9f184"
 
 [[package]]
 name = "scopeguard"
@@ -174,18 +185,18 @@ checksum = "6e63cff320ae2c57904679ba7cb63280a3dc4613885beafb148ee7bf9aa9042d"
 
 [[package]]
 name = "spinning_top"
-version = "0.1.0"
+version = "0.2.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "32d801a3a53bcf5071f85fef8d5cab9e5f638fc5580a37e6eb7aba4b37438d24"
+checksum = "75adad84ee84b521fb2cca2d4fd0f1dab1d8d026bda3c5bea4ca63b5f9f9293c"
 dependencies = [
  "lock_api",
 ]
 
 [[package]]
 name = "uart_16550"
-version = "0.2.4"
+version = "0.2.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d44b0f30cb82b0fbc15b78ade1064226529ad52028bc8cb8accb98ff6f3d7131"
+checksum = "503a6c0e6d82daa87985e662d120c0176b09587c92a68db22781b28ae95405dd"
 dependencies = [
  "bitflags",
  "x86_64",
@@ -193,16 +204,23 @@ dependencies = [
 
 [[package]]
 name = "volatile"
-version = "0.2.6"
+version = "0.2.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6af0edf5b4faacc31fc51159244d78d65ec580f021afcef7bd53c04aeabc7f29"
+checksum = "f6b06ad3ed06fef1713569d547cdbdb439eafed76341820fb0e0344f29a41945"
+
+[[package]]
+name = "volatile"
+version = "0.4.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e4c2dbd44eb8b53973357e6e207e370f0c1059990df850aca1eca8947cf464f0"
 
 [[package]]
 name = "x86_64"
-version = "0.9.6"
+version = "0.14.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4206b60c9f99766329b66962aa8ddc01df6c7edd02edc046b7a69d5df9fcdbcf"
+checksum = "fb611915c917c6296d11e23f71ff1ecfe49c5766daba92cd3df52df6b58285b6"
 dependencies = [
  "bit_field",
  "bitflags",
+ "volatile 0.4.4",
 ]

Cargo.toml

@@ -13,14 +13,14 @@ name = "stack_overflow"
 harness = false
 
 [dependencies]
-bootloader = { version = "0.8.0", features = ["map_physical_memory"]}
+bootloader = { version = "0.9.8", features = ["map_physical_memory"]}
 volatile = "0.2.6"
 spin = "0.5.2"
-x86_64 = "0.9.6"
+x86_64 = "0.14.2"
 uart_16550 = "0.2.0"
-pic8259_simple = "0.1.1"
+pic8259 = "0.10.1"
 pc-keyboard = "0.5.0"
-linked_list_allocator = "0.8.0"
+linked_list_allocator = "0.9.0"
 
 [dependencies.lazy_static]
 version = "1.0"
@@ -31,15 +31,15 @@ version = "0.2.1"
 default-features = false
 features = ["alloc"]
 
-[dependencies.futures-util]
-version = "0.3.4"
-default-features = false
-features = ["alloc", "async-await"]
-
 [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 = [
     "-device", "isa-debug-exit,iobase=0xf4,iosize=0x04", "-serial", "stdio",

README.md

@@ -1,28 +1,32 @@
-# Blog OS (Heap Allocation)
+# Blog OS (Async/Await)
 
-[![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)
+[![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)
 
-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.
+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.
 
-[post]: https://os.phil-opp.com/heap-allocation/
+[post]: https://os.phil-opp.com/async-await/
 
 **Check out the [master branch](https://github.com/phil-opp/blog_os) for more information.**
 
 ## Building
 
-You need a nightly Rust compiler. First you need to install the `cargo-xbuild` and `bootimage` tools:
+This project requires a nightly version of Rust because it uses some unstable features. At least nightly _2020-07-15_ is required for building. You might need to run `rustup update nightly --force` to update to the latest nightly even if some components such as `rustfmt` are missing it.
+
+You can build the project by running:
 
 ```
-cargo install cargo-xbuild bootimage
+cargo build
 ```
 
-Then you can build the project by running:
+To create a bootable disk image from the compiled kernel, you need to install the [`bootimage`] tool:
+
+[`bootimage`]: https://github.com/rust-osdev/bootimage
 
 ```
-cargo xbuild
+cargo install bootimage
 ```
 
-To create a bootable disk image, run:
+After installing, you can create the bootable disk image by running:
 
 ```
 cargo bootimage
@@ -39,10 +43,10 @@ You can run the disk image in [QEMU] through:
 [QEMU]: https://www.qemu.org/
 
 ```
-cargo xrun
+cargo run
 ```
 
-Of course [QEMU] needs to be installed for this.
+[QEMU] and the [`bootimage`] tool need to be installed for this.
 
 You can also write the image to an USB stick for booting it on a real machine. On Linux, the command for this is:
 

src/allocator.rs

@@ -35,7 +35,7 @@ pub fn init_heap(
             .allocate_frame()
             .ok_or(MapToError::FrameAllocationFailed)?;
         let flags = PageTableFlags::PRESENT | PageTableFlags::WRITABLE;
-        mapper.map_to(page, frame, flags, frame_allocator)?.flush();
+        unsafe { mapper.map_to(page, frame, flags, frame_allocator)?.flush() };
     }
 
     unsafe {

src/allocator/fixed_size_block.rs

@@ -31,8 +31,9 @@ pub struct FixedSizeBlockAllocator {
 impl FixedSizeBlockAllocator {
     /// Creates an empty FixedSizeBlockAllocator.
     pub const fn new() -> Self {
+        const EMPTY: Option<&'static mut ListNode> = None;
         FixedSizeBlockAllocator {
-            list_heads: [None; BLOCK_SIZES.len()],
+            list_heads: [EMPTY; BLOCK_SIZES.len()],
             fallback_allocator: linked_list_allocator::Heap::empty(),
         }
     }

src/allocator/linked_list.rs

@@ -45,7 +45,7 @@ impl LinkedListAllocator {
     /// 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_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

src/driver/keyboard.rs

@@ -1,75 +0,0 @@
-use crate::{print, println, task::interrupt_wake};
-use conquer_once::spin::OnceCell;
-use core::future::Future;
-use core::{
-    pin::Pin,
-    task::{Context, Poll},
-};
-use crossbeam_queue::ArrayQueue;
-use futures_util::task::AtomicWaker;
-use pc_keyboard::{layouts, DecodedKey, HandleControl, Keyboard, ScancodeSet1};
-
-static WAKER: AtomicWaker = AtomicWaker::new();
-static SCANCODE_QUEUE: OnceCell<ArrayQueue<u8>> = OnceCell::uninit();
-
-pub fn init() {
-    SCANCODE_QUEUE
-        .try_init_once(|| ArrayQueue::new(10))
-        .expect("failed to init scancode queue");
-}
-
-/// Called by the keyboard interrupt handler
-///
-/// Must not block (including spinlocks).
-pub(crate) fn keyboard_scancode(scancode: u8) {
-    let scancode_queue = SCANCODE_QUEUE
-        .try_get()
-        .expect("scancode queue not initialized");
-    if let Err(_) = scancode_queue.push(scancode) {
-        println!("WARNING: dropping keyboard input");
-    }
-    if let Some(waker) = WAKER.take() {
-        interrupt_wake(waker);
-    }
-}
-
-fn next_scancode() -> impl Future<Output = u8> {
-    NextScancode
-}
-
-struct NextScancode;
-
-impl Future for NextScancode {
-    type Output = u8;
-
-    fn poll(self: Pin<&mut Self>, cx: &mut Context) -> Poll<u8> {
-        let scancodes = SCANCODE_QUEUE
-            .try_get()
-            .expect("scancode queue not initialized");
-        // fast path
-        if let Ok(scancode) = scancodes.pop() {
-            return Poll::Ready(scancode);
-        }
-
-        WAKER.register(&cx.waker());
-        match scancodes.pop() {
-            Ok(scancode) => Poll::Ready(scancode),
-            Err(crossbeam_queue::PopError) => Poll::Pending,
-        }
-    }
-}
-
-pub async fn keyboard_task() {
-    let mut keyboard = Keyboard::new(layouts::Us104Key, ScancodeSet1, HandleControl::Ignore);
-
-    loop {
-        if let Ok(Some(key_event)) = keyboard.add_byte(next_scancode().await) {
-            if let Some(key) = keyboard.process_keyevent(key_event) {
-                match key {
-                    DecodedKey::Unicode(character) => print!("{}", character),
-                    DecodedKey::RawKey(key) => print!("{:?}", key),
-                }
-            }
-        }
-    }
-}

src/driver/mod.rs

@@ -1,6 +0,0 @@
-pub mod keyboard;
-pub mod timer;
-
-pub fn init() {
-    keyboard::init();
-}

src/driver/timer.rs

@@ -1,55 +0,0 @@
-use crate::{print, task::interrupt_wake};
-use core::future::Future;
-use core::{
-    pin::Pin,
-    sync::atomic::{AtomicU64, Ordering},
-    task::{Context, Poll},
-};
-use futures_util::task::AtomicWaker;
-
-static TICKS: AtomicU64 = AtomicU64::new(0);
-static WAKER: AtomicWaker = AtomicWaker::new();
-
-/// Called by the timer interrupt handler
-///
-/// Must not block (including spinlocks).
-pub(crate) fn tick() {
-    TICKS.fetch_add(1, Ordering::Release);
-    if let Some(waker) = WAKER.take() {
-        interrupt_wake(waker);
-    }
-}
-
-fn next_tick() -> impl Future<Output = u64> {
-    static NEXT_TICK: AtomicU64 = AtomicU64::new(1);
-
-    NextTick {
-        ticks: NEXT_TICK.fetch_add(1, Ordering::Release),
-    }
-}
-
-struct NextTick {
-    ticks: u64,
-}
-
-impl Future for NextTick {
-    type Output = u64;
-
-    fn poll(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<u64> {
-        WAKER.register(&cx.waker());
-        let current_ticks = TICKS.load(Ordering::Acquire);
-        if self.ticks < current_ticks {
-            self.ticks += 1;
-            Poll::Ready(self.ticks)
-        } else {
-            Poll::Pending
-        }
-    }
-}
-
-pub async fn timer_task() {
-    loop {
-        next_tick().await;
-        print!(".");
-    }
-}

src/gdt.rs

@@ -9,7 +9,7 @@ lazy_static! {
     static ref TSS: TaskStateSegment = {
         let mut tss = TaskStateSegment::new();
         tss.interrupt_stack_table[DOUBLE_FAULT_IST_INDEX as usize] = {
-            const STACK_SIZE: usize = 4096;
+            const STACK_SIZE: usize = 4096 * 5;
             static mut STACK: [u8; STACK_SIZE] = [0; STACK_SIZE];
 
             let stack_start = VirtAddr::from_ptr(unsafe { &STACK });
@@ -41,12 +41,12 @@ struct Selectors {
 }
 
 pub fn init() {
-    use x86_64::instructions::segmentation::set_cs;
+    use x86_64::instructions::segmentation::{Segment, CS};
     use x86_64::instructions::tables::load_tss;
 
     GDT.0.load();
     unsafe {
-        set_cs(GDT.1.code_selector);
+        CS::set_reg(GDT.1.code_selector);
         load_tss(GDT.1.tss_selector);
     }
 }

src/interrupts.rs

@@ -1,6 +1,6 @@
-use crate::{gdt, hlt_loop, println};
+use crate::{gdt, hlt_loop, print, println};
 use lazy_static::lazy_static;
-use pic8259_simple::ChainedPics;
+use pic8259::ChainedPics;
 use spin;
 use x86_64::structures::idt::{InterruptDescriptorTable, InterruptStackFrame, PageFaultErrorCode};
 
@@ -47,12 +47,12 @@ pub fn init_idt() {
     IDT.load();
 }
 
-extern "x86-interrupt" fn breakpoint_handler(stack_frame: &mut InterruptStackFrame) {
+extern "x86-interrupt" fn breakpoint_handler(stack_frame: InterruptStackFrame) {
     println!("EXCEPTION: BREAKPOINT\n{:#?}", stack_frame);
 }
 
 extern "x86-interrupt" fn page_fault_handler(
-    stack_frame: &mut InterruptStackFrame,
+    stack_frame: InterruptStackFrame,
     error_code: PageFaultErrorCode,
 ) {
     use x86_64::registers::control::Cr2;
@@ -65,27 +65,26 @@ extern "x86-interrupt" fn page_fault_handler(
 }
 
 extern "x86-interrupt" fn double_fault_handler(
-    stack_frame: &mut InterruptStackFrame,
+    stack_frame: InterruptStackFrame,
     _error_code: u64,
 ) -> ! {
     panic!("EXCEPTION: DOUBLE FAULT\n{:#?}", stack_frame);
 }
 
-extern "x86-interrupt" fn timer_interrupt_handler(_stack_frame: &mut InterruptStackFrame) {
+extern "x86-interrupt" fn timer_interrupt_handler(_stack_frame: InterruptStackFrame) {
-    crate::driver::timer::tick();
+    print!(".");
-
     unsafe {
         PICS.lock()
             .notify_end_of_interrupt(InterruptIndex::Timer.as_u8());
     }
 }
 
-extern "x86-interrupt" fn keyboard_interrupt_handler(_stack_frame: &mut InterruptStackFrame) {
+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);
-    crate::driver::keyboard::keyboard_scancode(scancode);
 
     unsafe {
         PICS.lock()
@@ -93,13 +92,8 @@ extern "x86-interrupt" fn keyboard_interrupt_handler(_stack_frame: &mut Interrup
     }
 }
 
-#[cfg(test)]
-use crate::{serial_print, serial_println};
-
 #[test_case]
 fn test_breakpoint_exception() {
-    serial_print!("test_breakpoint_exception...");
     // invoke a breakpoint exception
     x86_64::instructions::interrupts::int3();
-    serial_println!("[ok]");
 }

src/lib.rs

@@ -2,22 +2,14 @@
 #![cfg_attr(test, no_main)]
 #![feature(custom_test_frameworks)]
 #![feature(abi_x86_interrupt)]
-#![feature(alloc_error_handler)]
+#![feature(const_mut_refs)]
-#![feature(const_fn)]
-#![feature(alloc_layout_extra)]
-#![feature(wake_trait)]
-#![feature(const_in_array_repeat_expressions)]
-#![feature(type_alias_impl_trait)]
-#![feature(asm)]
 #![test_runner(crate::test_runner)]
 #![reexport_test_harness_main = "test_main"]
 
 extern crate alloc;
-
 use core::panic::PanicInfo;
 
 pub mod allocator;
-pub mod driver;
 pub mod gdt;
 pub mod interrupts;
 pub mod memory;
@@ -29,17 +21,27 @@ pub fn init() {
     gdt::init();
     interrupts::init_idt();
     unsafe { interrupts::PICS.lock().initialize() };
+    x86_64::instructions::interrupts::enable();
+}
+pub trait Testable {
+    fn run(&self) -> ();
 }
 
-pub fn init_heap_structures() {
+impl<T> Testable for T
-    task::init();
+where
-    driver::init();
+    T: Fn(),
+{
+    fn run(&self) {
+        serial_print!("{}...\t", core::any::type_name::<T>());
+        self();
+        serial_println!("[ok]");
+    }
 }
 
-pub fn test_runner(tests: &[&dyn Fn()]) {
+pub fn test_runner(tests: &[&dyn Testable]) {
     serial_println!("Running {} tests", tests.len());
     for test in tests {
-        test();
+        test.run();
     }
     exit_qemu(QemuExitCode::Success);
 }
@@ -92,8 +94,3 @@ fn test_kernel_main(_boot_info: &'static BootInfo) -> ! {
 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

@@ -6,8 +6,8 @@
 
 extern crate alloc;
 
-use alloc::{boxed::Box, rc::Rc, vec, vec::Vec};
 use blog_os::println;
+use blog_os::task::{executor::Executor, keyboard, Task};
 use bootloader::{entry_point, BootInfo};
 use core::panic::PanicInfo;
 
@@ -26,49 +26,13 @@ fn kernel_main(boot_info: &'static BootInfo) -> ! {
     let mut frame_allocator = unsafe { BootInfoFrameAllocator::init(&boot_info.memory_map) };
 
     allocator::init_heap(&mut mapper, &mut frame_allocator).expect("heap initialization failed");
-    blog_os::init_heap_structures();
 
-    // allocate a number on the heap
+    #[cfg(test)]
-    let heap_value = Box::new(41);
+    test_main();
-    println!("heap_value at {:p}", heap_value);
-
-    // create a dynamically sized vector
-    let mut vec = Vec::new();
-    for i in 0..500 {
-        vec.push(i);
-    }
-    println!("vec at {:p}", vec.as_slice());
-
-    // create a reference counted vector -> will be freed when count reaches 0
-    let reference_counted = Rc::new(vec![1, 2, 3]);
-    let cloned_reference = reference_counted.clone();
-    println!(
-        "current reference count is {}",
-        Rc::strong_count(&cloned_reference)
-    );
-    core::mem::drop(reference_counted);
-    println!(
-        "reference count is {} now",
-        Rc::strong_count(&cloned_reference)
-    );
-
-    use blog_os::task::executor::Executor;
 
     let mut executor = Executor::new();
-    executor.spawn(bar());
+    executor.spawn(Task::new(example_task()));
-
+    executor.spawn(Task::new(keyboard::print_keypresses()));
-    executor.spawn(async {
-        #[cfg(test)]
-        test_main();
-    });
-
-    executor.spawn(async {
-        println!("It did not crash!");
-    });
-
-    executor.spawn(blog_os::driver::timer::timer_task());
-    executor.spawn(blog_os::driver::keyboard::keyboard_task());
-
     executor.run();
 }
 
@@ -86,14 +50,16 @@ fn panic(info: &PanicInfo) -> ! {
     blog_os::test_panic_handler(info)
 }
 
-async fn test() -> u32 {
+async fn async_number() -> u32 {
     42
 }
 
-async fn foo() -> u32 {
+async fn example_task() {
-    test().await * 2
+    let number = async_number().await;
+    println!("async number: {}", number);
 }
 
-async fn bar() {
+#[test_case]
-    println!("foo result: {}", foo().await);
+fn trivial_assertion() {
+    assert_eq!(1, 1);
 }

src/memory.rs

@@ -1,9 +1,6 @@
 use bootloader::bootinfo::{MemoryMap, MemoryRegionType};
 use x86_64::{
-    structures::paging::{
+    structures::paging::{FrameAllocator, OffsetPageTable, PageTable, PhysFrame, Size4KiB},
-        FrameAllocator, Mapper, OffsetPageTable, Page, PageTable, PhysFrame, Size4KiB,
-        UnusedPhysFrame,
-    },
     PhysAddr, VirtAddr,
 };
 
@@ -36,28 +33,11 @@ unsafe fn active_level_4_table(physical_memory_offset: VirtAddr) -> &'static mut
     &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> {
+    fn allocate_frame(&mut self) -> Option<PhysFrame> {
         None
     }
 }
@@ -82,7 +62,7 @@ impl BootInfoFrameAllocator {
     }
 
     /// Returns an iterator over the usable frames specified in the memory map.
-    fn usable_frames(&self) -> impl Iterator<Item = UnusedPhysFrame> {
+    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);
@@ -91,14 +71,12 @@ impl BootInfoFrameAllocator {
         // 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)));
+        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> {
+    fn allocate_frame(&mut self) -> Option<PhysFrame> {
         let frame = self.usable_frames().nth(self.next);
         self.next += 1;
         frame

src/task/executor.rs

@@ -1,127 +1,102 @@
-use super::interrupt_wakeups::interrupt_wakeups;
+use super::{Task, TaskId};
-use crate::println;
+use alloc::{collections::BTreeMap, sync::Arc, task::Wake};
-use alloc::{
+use core::task::{Context, Poll, Waker};
-    boxed::Box,
+use crossbeam_queue::ArrayQueue;
-    collections::{BTreeMap, VecDeque},
-    sync::Arc,
-    task::Wake,
-};
-use core::{
-    future::Future,
-    pin::Pin,
-    task::{Context, Poll},
-};
-use crossbeam_queue::SegQueue;
-
-pub type Task = Pin<Box<dyn Future<Output = ()>>>;
-type TaskId = usize;
 
 pub struct Executor {
-    task_queue: VecDeque<Task>,
+    tasks: BTreeMap<TaskId, Task>,
-    wake_queue: Arc<SegQueue<TaskId>>,
+    task_queue: Arc<ArrayQueue<TaskId>>,
-    pending_tasks: BTreeMap<TaskId, Task>,
+    waker_cache: BTreeMap<TaskId, Waker>,
 }
 
 impl Executor {
     pub fn new() -> Self {
         Executor {
-            task_queue: VecDeque::new(),
+            tasks: BTreeMap::new(),
-            wake_queue: Arc::new(SegQueue::new()),
+            task_queue: Arc::new(ArrayQueue::new(100)),
-            pending_tasks: BTreeMap::new(),
+            waker_cache: BTreeMap::new(),
         }
     }
 
-    pub fn spawn(&mut self, task: impl Future<Output = ()> + 'static) {
+    pub fn spawn(&mut self, task: Task) {
-        self.task_queue.push_back(Box::pin(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.apply_interrupt_wakeups();
+            self.sleep_if_idle();
-            self.wake_waiting_tasks();
-            self.hlt_if_idle();
         }
     }
 
     fn run_ready_tasks(&mut self) {
-        while let Some(mut task) = self.task_queue.pop_front() {
+        // destructure `self` to avoid borrow checker errors
-            let waker = self.create_waker(&task).into();
+        let Self {
-            let mut context = Context::from_waker(&waker);
+            tasks,
-            match task.as_mut().poll(&mut context) {
+            task_queue,
-                Poll::Ready(()) => {} // task done
+            waker_cache,
-                Poll::Pending => {
+        } = self;
-                    // add task to pending_tasks and wait for wakeup
+
-                    let task_id = Self::task_id(&task);
+        while let Ok(task_id) = task_queue.pop() {
-                    if self.pending_tasks.insert(task_id, task).is_some() {
+            let task = match tasks.get_mut(&task_id) {
-                        panic!("Task with same ID already in pending_tasks");
+                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 => {}
             }
         }
     }
 
-    /// Invoke wakers for tasks woken by interrupts
+    fn sleep_if_idle(&self) {
-    ///
+        use x86_64::instructions::interrupts::{self, enable_and_hlt};
-    /// The interrupt handlers can't invoke the waker directly since wakers
-    /// might execute arbitrary code, e.g. allocate, which should not be done
-    /// in interrupt handlers to avoid deadlocks.
-    fn apply_interrupt_wakeups(&mut self) {
-        while let Ok(waker) = interrupt_wakeups().pop() {
-            waker.wake();
-        }
-    }
 
-    fn wake_waiting_tasks(&mut self) {
+        interrupts::disable();
-        while let Ok(task_id) = self.wake_queue.pop() {
-            if let Some(task) = self.pending_tasks.remove(&task_id) {
-                self.task_queue.push_back(task);
-            } else {
-                println!("WARNING: woken task not found in pending_tasks");
-            }
-        }
-    }
-
-    /// Executes the `hlt` instruction if there are no ready tasks
-    fn hlt_if_idle(&self) {
         if self.task_queue.is_empty() {
-            // disable interrupts to avoid races
+            enable_and_hlt();
-            x86_64::instructions::interrupts::disable();
+        } else {
-            // check if relevant interrupts occured since the last check
+            interrupts::enable();
-            if interrupt_wakeups().is_empty() {
-                // no interrupts occured -> hlt to wait for next interrupt
-                x86_64::instructions::interrupts::enable_interrupts_and_hlt();
-            } else {
-                // there were some new wakeups -> continue execution
-                x86_64::instructions::interrupts::enable();
-            }
         }
     }
-
-    fn task_id(task: &Task) -> TaskId {
-        let future_ref: &dyn Future<Output = ()> = &**task;
-        future_ref as *const _ as *const () as usize
-    }
-
-    fn create_waker(&self, task: &Task) -> Arc<Waker> {
-        Arc::new(Waker {
-            wake_queue: self.wake_queue.clone(),
-            task_id: Self::task_id(task),
-        })
-    }
 }
 
-pub struct Waker {
+struct TaskWaker {
-    wake_queue: Arc<SegQueue<TaskId>>,
     task_id: TaskId,
+    task_queue: Arc<ArrayQueue<TaskId>>,
 }
 
-impl Wake for Waker {
+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_by_ref();
+        self.wake_task();
     }
 
     fn wake_by_ref(self: &Arc<Self>) {
-        self.wake_queue.push(self.task_id);
+        self.wake_task();
     }
 }

src/task/interrupt_wakeups.rs

@@ -1,25 +0,0 @@
-use crate::println;
-use conquer_once::spin::OnceCell;
-use core::task::Waker;
-use crossbeam_queue::ArrayQueue;
-
-static INTERRUPT_WAKEUPS: OnceCell<ArrayQueue<Waker>> = OnceCell::uninit();
-
-pub fn init() {
-    INTERRUPT_WAKEUPS
-        .try_init_once(|| ArrayQueue::new(10))
-        .expect("failed to init interrupt wakeup queue");
-}
-
-/// Queues a waker for waking in an interrupt-safe way
-pub(crate) fn interrupt_wake(waker: Waker) {
-    if let Err(_) = interrupt_wakeups().push(waker) {
-        println!("WARNING: dropping interrupt wakeup");
-    }
-}
-
-pub(super) fn interrupt_wakeups() -> &'static ArrayQueue<Waker> {
-    INTERRUPT_WAKEUPS
-        .try_get()
-        .expect("interrupt wakeup queue not initialized")
-}

src/task/keyboard.rs

@@ -0,0 +1,83 @@
+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::{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) => {
+                WAKER.take();
+                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

@@ -1,8 +1,39 @@
-pub(crate) use interrupt_wakeups::interrupt_wake;
+use alloc::boxed::Box;
+use core::{
+    future::Future,
+    pin::Pin,
+    sync::atomic::{AtomicU64, Ordering},
+    task::{Context, Poll},
+};
 
 pub mod executor;
-mod interrupt_wakeups;
+pub mod keyboard;
+pub mod simple_executor;
 
-pub fn init() {
+pub struct Task {
-    interrupt_wakeups::init();
+    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

@@ -0,0 +1,44 @@
+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

@@ -3,9 +3,6 @@ use lazy_static::lazy_static;
 use spin::Mutex;
 use volatile::Volatile;
 
-#[cfg(test)]
-use crate::{serial_print, serial_println};
-
 lazy_static! {
     /// A global `Writer` instance that can be used for printing to the VGA text buffer.
     ///
@@ -180,18 +177,14 @@ pub fn _print(args: fmt::Arguments) {
 
 #[test_case]
 fn test_println_simple() {
-    serial_print!("test_println... ");
     println!("test_println_simple output");
-    serial_println!("[ok]");
 }
 
 #[test_case]
 fn test_println_many() {
-    serial_print!("test_println_many... ");
     for _ in 0..200 {
         println!("test_println_many output");
     }
-    serial_println!("[ok]");
 }
 
 #[test_case]
@@ -199,8 +192,6 @@ 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";
     interrupts::without_interrupts(|| {
         let mut writer = WRITER.lock();
@@ -210,6 +201,4 @@ fn test_println_output() {
             assert_eq!(char::from(screen_char.ascii_character), c);
         }
     });
-
-    serial_println!("[ok]");
 }

tests/basic_boot.rs

@@ -4,7 +4,7 @@
 #![test_runner(blog_os::test_runner)]
 #![reexport_test_harness_main = "test_main"]
 
-use blog_os::{println, serial_print, serial_println};
+use blog_os::println;
 use core::panic::PanicInfo;
 
 #[no_mangle] // don't mangle the name of this function
@@ -21,7 +21,5 @@ fn panic(info: &PanicInfo) -> ! {
 
 #[test_case]
 fn test_println() {
-    serial_print!("test_println... ");
     println!("test_println output");
-    serial_println!("[ok]");
 }

tests/heap_allocation.rs

@@ -7,7 +7,7 @@
 extern crate alloc;
 
 use alloc::{boxed::Box, vec::Vec};
-use blog_os::{allocator::HEAP_SIZE, serial_print, serial_println};
+use blog_os::allocator::HEAP_SIZE;
 use bootloader::{entry_point, BootInfo};
 use core::panic::PanicInfo;
 
@@ -30,44 +30,38 @@ fn main(boot_info: &'static BootInfo) -> ! {
 
 #[test_case]
 fn simple_allocation() {
-    serial_print!("simple_allocation... ");
+    let heap_value_1 = Box::new(41);
-    let heap_value = Box::new(41);
+    let heap_value_2 = Box::new(13);
-    assert_eq!(*heap_value, 41);
+    assert_eq!(*heap_value_1, 41);
-    serial_println!("[ok]");
+    assert_eq!(*heap_value_2, 13);
 }
 
 #[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]

tests/should_panic.rs

@@ -13,7 +13,7 @@ pub extern "C" fn _start() -> ! {
 }
 
 fn should_fail() {
-    serial_print!("should_fail... ");
+    serial_print!("should_panic::should_fail...\t");
     assert_eq!(0, 1);
 }
 

tests/stack_overflow.rs

@@ -9,7 +9,7 @@ use x86_64::structures::idt::{InterruptDescriptorTable, InterruptStackFrame};
 
 #[no_mangle]
 pub extern "C" fn _start() -> ! {
-    serial_print!("stack_overflow... ");
+    serial_print!("stack_overflow::stack_overflow...\t");
 
     blog_os::gdt::init();
     init_test_idt();
@@ -23,6 +23,7 @@ pub extern "C" fn _start() -> ! {
 #[allow(unconditional_recursion)]
 fn stack_overflow() {
     stack_overflow(); // for each recursion, the return address is pushed
+    volatile::Volatile::new(0).read(); // prevent tail recursion optimizations
 }
 
 lazy_static! {
@@ -43,7 +44,7 @@ pub fn init_test_idt() {
 }
 
 extern "x86-interrupt" fn test_double_fault_handler(
-    _stack_frame: &mut InterruptStackFrame,
+    _stack_frame: InterruptStackFrame,
     _error_code: u64,
 ) -> ! {
     serial_println!("[ok]");