Merge branch 'post-11' into post-12

Merge branch 'post-10' into post-11
Merge branch 'post-09' into post-10
2025-12-16 22:37:49 +00:00 · 2025-08-26 16:41:45 +02:00 · 2025-08-26 16:41:45 +02:00 · 2025-08-26 16:41:45 +02:00 · 2025-08-26 16:41:45 +02:00 · 2025-08-26 16:41:45 +02:00
30 changed files with 728 additions and 842 deletions
--- a/.cargo/config
+++ b/.cargo/config
@@ -1,5 +0,0 @@
-[build]
-target = "x86_64-blog_os.json"
-
-[target.'cfg(target_os = "none")']
-runner = "bootimage runner"
--- a/.cargo/config.toml
+++ b/.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"
--- a/.github/workflows/build-code.yml
+++ b/.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
--- a/.github/workflows/code.yml
+++ b/.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
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1,124 +1,175 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
+version = 4
+
 [[package]]
-name = "array-init"
-version = "0.0.4"
+name = "autocfg"
+version = "1.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "23589ecb866b460d3a0f1278834750268c607e8e28a1b982c907219f3178cd72"
-dependencies = [
- "nodrop",
-]
+checksum = "c08606f8c3cbf4ce6ec8e28fb0014a2c086708fe954eaa885384a6165172e7e8"

 [[package]]
 name = "bit_field"
-version = "0.9.0"
+version = "0.10.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ed8765909f9009617974ab6b7d332625b320b33c326b1e9321382ef1999b5d56"
+checksum = "dc827186963e592360843fb5ba4b973e145841266c1357f7180c43526f2e5b61"

 [[package]]
 name = "bitflags"
-version = "1.2.1"
+version = "1.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cf1de2fe8c75bc145a2f577add951f8134889b4795d47466a54a5c846d691693"
+checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
+
+[[package]]
+name = "bitflags"
+version = "2.9.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6a65b545ab31d687cff52899d4890855fec459eb6afe0da6417b8a18da87aa29"

 [[package]]
 name = "blog_os"
 version = "0.1.0"
 dependencies = [
 "bootloader",
+ "conquer-once",
+ "crossbeam-queue",
+ "futures-util",
 "lazy_static",
 "linked_list_allocator",
 "pc-keyboard",
- "pic8259_simple",
- "spin",
+ "pic8259",
+ "spin 0.5.2",
 "uart_16550",
- "volatile",
- "x86_64 0.8.1",
+ "volatile 0.2.7",
+ "x86_64",
 ]

 [[package]]
 name = "bootloader"
-version = "0.8.3"
+version = "0.9.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d596849a47f28abdea62d7a6a25c4f6e69c3d9b09b0a2877db6e9cda004ca993"
+checksum = "1ea119c3ed05625c179e09d17d0914570a3753ca09c890a73d98f6b72aea00d2"

 [[package]]
-name = "cast"
-version = "0.2.3"
+name = "conquer-once"
+version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4b9434b9a5aa1450faa3f9cb14ea0e8c53bb5d2b3c1bfd1ab4fc03e9f33fbfb0"
+checksum = "96eb12fb69466716fbae9009d389e6a30830ae8975e170eff2d2cff579f9efa3"
 dependencies = [
- "rustc_version",
+ "conquer-util",
 ]

 [[package]]
-name = "cpuio"
+name = "conquer-util"
 version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "22b8e308ccfc5acf3b82f79c0eac444cf6114cb2ac67a230ca6c177210068daa"
+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"
-version = "1.4.0"
+version = "1.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
+checksum = "bbd2bcb4c963f2ddae06a2efc7e9f3591312473c50c6685e1f298068316e66fe"
 dependencies = [
- "spin",
+ "spin 0.9.8",
 ]

 [[package]]
 name = "linked_list_allocator"
-version = "0.6.4"
+version = "0.9.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "47314ec1d29aa869ee7cb5a5be57be9b1055c56567d59c3fb6689926743e0bea"
+checksum = "549ce1740e46b291953c4340adcd74c59bcf4308f4cac050fd33ba91b7168f4a"
 dependencies = [
- "spin",
+ "spinning_top",
 ]

 [[package]]
-name = "nodrop"
-version = "0.1.14"
+name = "lock_api"
+version = "0.4.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "72ef4a56884ca558e5ddb05a1d1e7e1bfd9a68d9ed024c21704cc98872dae1bb"
+checksum = "96936507f153605bddfcda068dd804796c84324ed2510809e5b2a624c81da765"
+dependencies = [
+ "autocfg",
+ "scopeguard",
+]

 [[package]]
 name = "pc-keyboard"
-version = "0.3.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fff50ab09ba31bcebc0669f4e64c0952fae1acdca9e6e0587e68e4e8443808ac"
-
-[[package]]
-name = "pic8259_simple"
-version = "0.1.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dc64b2fd10828da8521b6cdabe0679385d7d2a3a6d4c336b819d1fa31ba35c72"
-dependencies = [
- "cpuio",
-]
-
-[[package]]
-name = "rustc_version"
-version = "0.2.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "138e3e0acb6c9fb258b19b67cb8abd63c00679d2851805ea151465464fe9030a"
-dependencies = [
- "semver",
-]
-
-[[package]]
-name = "semver"
-version = "0.9.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1d7eb9ef2c18661902cc47e535f9bc51b78acd254da71d375c2f6720d9a40403"
-dependencies = [
- "semver-parser",
-]
-
-[[package]]
-name = "semver-parser"
 version = "0.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "388a1df253eca08550bef6c72392cfe7c30914bf41df5269b68cbd6ff8f570a3"
+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"
@@ -127,48 +178,51 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6e63cff320ae2c57904679ba7cb63280a3dc4613885beafb148ee7bf9aa9042d"

 [[package]]
-name = "uart_16550"
-version = "0.2.1"
+name = "spin"
+version = "0.9.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "803ea8cb602dbb32c1a657a866d2dd79fe7dbeab0fb2ac667cb4dcc7de12a58b"
+checksum = "6980e8d7511241f8acf4aebddbb1ff938df5eebe98691418c4468d0b72a96a67"
+
+[[package]]
+name = "spinning_top"
+version = "0.2.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5b9eb1a2f4c41445a3a0ff9abc5221c5fcd28e1f13cd7c0397706f9ac938ddb0"
 dependencies = [
- "bitflags",
- "x86_64 0.7.7",
+ "lock_api",
 ]

 [[package]]
-name = "ux"
-version = "0.1.3"
+name = "uart_16550"
+version = "0.2.19"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "88dfeb711b61ce620c0cb6fd9f8e3e678622f0c971da2a63c4b3e25e88ed012f"
+checksum = "614ff2a87880d4bd4374722268598a970bbad05ced8bf630439417347254ab2e"
+dependencies = [
+ "bitflags 1.3.2",
+ "rustversion",
+ "x86_64",
+]

 [[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 = "0.4.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "442887c63f2c839b346c192d047a7c87e73d0689c9157b00b53dcc27dd5ea793"

 [[package]]
 name = "x86_64"
-version = "0.7.7"
+version = "0.14.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1f27d9168654aee1b0c1b73746caeb4aa33248f8b8c8f6e100e697fcc2a794b2"
+checksum = "c101112411baafbb4bf8d33e4c4a80ab5b02d74d2612331c61e8192fc9710491"
 dependencies = [
- "array-init",
 "bit_field",
- "bitflags",
- "cast",
- "ux",
-]
-
-[[package]]
-name = "x86_64"
-version = "0.8.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f21672dcbed52bc09eea030d189600c0189c66c97bc5b31779eb780e064a201f"
-dependencies = [
- "array-init",
- "bit_field",
- "bitflags",
- "cast",
+ "bitflags 2.9.2",
+ "rustversion",
+ "volatile 0.4.6",
 ]
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -2,7 +2,7 @@
 name = "blog_os"
 version = "0.1.0"
 authors = ["Philipp Oppermann <dev@phil-opp.com>"]
-edition = "2018"
+edition = "2024"

 [[test]]
 name = "should_panic"
@@ -13,26 +13,45 @@ name = "stack_overflow"
 harness = false

 [dependencies]
-bootloader = { version = "0.8.0", features = ["map_physical_memory"]}
+bootloader = { version = "0.9", features = ["map_physical_memory"] }
 volatile = "0.2.6"
 spin = "0.5.2"
-x86_64 = "0.8.1"
+x86_64 = "0.14.2"
 uart_16550 = "0.2.0"
-pic8259_simple = "0.1.1"
-pc-keyboard = "0.3.1"
-linked_list_allocator = "0.6.4"
+pic8259 = "0.10.1"
+pc-keyboard = "0.7.0"
+linked_list_allocator = "0.9.0"

 [dependencies.lazy_static]
 version = "1.0"
 features = ["spin_no_std"]

+[[bin]]
+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 = [
-    "-device", "isa-debug-exit,iobase=0xf4,iosize=0x04", "-serial", "stdio",
-    "-display", "none"
+    "-device",
+    "isa-debug-exit,iobase=0xf4,iosize=0x04",
+    "-serial",
+    "stdio",
+    "-display",
+    "none",
 ]
-test-success-exit-code = 33         # (0x10 << 1) | 1
-
-[profile.release]
-lto = true
+test-success-exit-code = 33 # (0x10 << 1) | 1
--- a/README.md
+++ b/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:

--- a/src/allocator/mod.rs
+++ b/src/allocator/mod.rs
@@ -2,10 +2,10 @@ 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,
+    structures::paging::{
+        FrameAllocator, Mapper, Page, PageTableFlags, Size4KiB, mapper::MapToError,
+    },
 };

 pub mod bump;
@@ -21,7 +21,7 @@ static ALLOCATOR: Locked<FixedSizeBlockAllocator> = Locked::new(FixedSizeBlockAl
 pub fn init_heap(
    mapper: &mut impl Mapper<Size4KiB>,
    frame_allocator: &mut impl FrameAllocator<Size4KiB>,
-) -> Result<(), MapToError> {
+) -> Result<(), MapToError<Size4KiB>> {
    let page_range = {
        let heap_start = VirtAddr::new(HEAP_START as u64);
        let heap_end = heap_start + HEAP_SIZE - 1u64;
@@ -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 {
@@ -74,11 +74,9 @@ impl<A> Locked<A> {
    }
 }

+/// 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 {
-    let remainder = addr % align;
-    if remainder == 0 {
-        addr // addr already aligned
-    } else {
-        addr - remainder + align
-    }
+    (addr + align - 1) & !(align - 1)
 }
--- a/src/allocator/bump.rs
+++ b/src/allocator/bump.rs
@@ -1,4 +1,4 @@
-use super::{align_up, Locked};
+use super::{Locked, align_up};
 use alloc::alloc::{GlobalAlloc, Layout};
 use core::ptr;

@@ -26,7 +26,7 @@ impl BumpAllocator {
    /// 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 + heap_size;
+        self.heap_end = heap_start.saturating_add(heap_size);
        self.next = heap_start;
    }
 }
@@ -36,7 +36,10 @@ unsafe impl GlobalAlloc for Locked<BumpAllocator> {
        let mut bump = self.lock(); // get a mutable reference

        let alloc_start = align_up(bump.next, layout.align());
-        let alloc_end = alloc_start + layout.size();
+        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
--- a/src/allocator/fixed_size_block.rs
+++ b/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(),
        }
    }
@@ -43,7 +44,9 @@ impl FixedSizeBlockAllocator {
    /// 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);
+        unsafe {
+            self.fallback_allocator.init(heap_start, heap_size);
+        }
    }

    /// Allocates using the fallback allocator.
@@ -90,12 +93,16 @@ unsafe impl GlobalAlloc for Locked<FixedSizeBlockAllocator> {
                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);
+                unsafe {
+                    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);
+                unsafe {
+                    allocator.fallback_allocator.deallocate(ptr, layout);
+                }
            }
        }
    }
--- a/src/allocator/linked_list.rs
+++ b/src/allocator/linked_list.rs
@@ -1,4 +1,4 @@
-use super::{align_up, Locked};
+use super::{Locked, align_up};
 use alloc::alloc::{GlobalAlloc, Layout};
 use core::{mem, ptr};

@@ -39,21 +39,25 @@ impl LinkedListAllocator {
    /// 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);
+        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!(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
        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)
+        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
@@ -86,7 +90,7 @@ impl LinkedListAllocator {
    /// 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 + size;
+        let alloc_end = alloc_start.checked_add(size).ok_or(())?;

        if alloc_end > region.end_addr() {
            // region too small
@@ -122,13 +126,15 @@ 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.inner.lock();
+        let mut allocator = self.lock();

        if let Some((region, alloc_start)) = allocator.find_region(size, align) {
-            let alloc_end = alloc_start + size;
+            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);
+                unsafe {
+                    allocator.add_free_region(alloc_end, excess_size);
+                }
            }
            alloc_start as *mut u8
        } else {
@@ -140,6 +146,6 @@ unsafe impl GlobalAlloc for Locked<LinkedListAllocator> {
        // perform layout adjustments
        let (size, _) = LinkedListAllocator::size_align(layout);

-        self.inner.lock().add_free_region(ptr as usize, size)
+        unsafe { self.lock().add_free_region(ptr as usize, size) }
    }
 }
--- a/src/gdt.rs
+++ b/src/gdt.rs
@@ -1,7 +1,7 @@
 use lazy_static::lazy_static;
+use x86_64::VirtAddr;
 use x86_64::structures::gdt::{Descriptor, GlobalDescriptorTable, SegmentSelector};
 use x86_64::structures::tss::TaskStateSegment;
-use x86_64::VirtAddr;

 pub const DOUBLE_FAULT_IST_INDEX: u16 = 0;

@@ -9,10 +9,10 @@ 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 });
+            let stack_start = VirtAddr::from_ptr(&raw const STACK);
            let stack_end = stack_start + STACK_SIZE;
            stack_end
        };
@@ -41,12 +41,12 @@ struct Selectors {
 }

 pub fn init() {
-    use x86_64::instructions::segmentation::set_cs;
+    use x86_64::instructions::segmentation::{CS, Segment};
    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);
    }
 }
--- a/src/interrupts.rs
+++ b/src/interrupts.rs
@@ -1,6 +1,6 @@
 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;
@@ -65,43 +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) {
    print!(".");
    unsafe {
        PICS.lock()
            .notify_end_of_interrupt(InterruptIndex::Timer.as_u8());
    }
-    crate::multitasking::invoke_scheduler();
 }

-extern "x86-interrupt" fn keyboard_interrupt_handler(_stack_frame: &mut InterruptStackFrame) {
-    use pc_keyboard::{layouts, DecodedKey, Keyboard, ScancodeSet1};
-    use spin::Mutex;
+extern "x86-interrupt" fn keyboard_interrupt_handler(_stack_frame: InterruptStackFrame) {
    use x86_64::instructions::port::Port;

-    lazy_static! {
-        static ref KEYBOARD: Mutex<Keyboard<layouts::Us104Key, ScancodeSet1>> =
-            Mutex::new(Keyboard::new(layouts::Us104Key, ScancodeSet1));
-    }
-
-    let mut keyboard = KEYBOARD.lock();
    let mut port = Port::new(0x60);
-
    let scancode: u8 = unsafe { port.read() };
-    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),
-            }
-        }
-    }
+    crate::task::keyboard::add_scancode(scancode);

    unsafe {
        PICS.lock()
@@ -109,13 +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]");
 }
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -2,29 +2,18 @@
 #![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)]
-#![feature(global_asm)]
-#![feature(asm)]
-#![feature(raw)]
-#![feature(never_type)]
-#![feature(naked_functions)]
-#![feature(option_expect_none)]
 #![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 multitasking;
 pub mod serial;
+pub mod task;
 pub mod vga_buffer;

 pub fn init() {
@@ -33,11 +22,25 @@ pub fn init() {
    unsafe { interrupts::PICS.lock().initialize() };
    x86_64::instructions::interrupts::enable();
 }
+pub trait Testable {
+    fn run(&self) -> ();
+}

-pub fn test_runner(tests: &[&dyn Fn()]) {
+impl<T> Testable for T
+where
+    T: Fn(),
+{
+    fn run(&self) {
+        serial_print!("{}...\t", core::any::type_name::<T>());
+        self();
+        serial_println!("[ok]");
+    }
+}
+
+pub fn test_runner(tests: &[&dyn Testable]) {
    serial_println!("Running {} tests", tests.len());
    for test in tests {
-        test();
+        test.run();
    }
    exit_qemu(QemuExitCode::Success);
 }
@@ -72,7 +75,7 @@ pub fn hlt_loop() -> ! {
 }

 #[cfg(test)]
-use bootloader::{entry_point, BootInfo};
+use bootloader::{BootInfo, entry_point};

 #[cfg(test)]
 entry_point!(test_kernel_main);
@@ -90,8 +93,3 @@ 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)
-}
--- a/src/main.rs
+++ b/src/main.rs
@@ -6,10 +6,9 @@

 extern crate alloc;

-use alloc::{boxed::Box, rc::Rc, vec, vec::Vec};
-use blog_os::multitasking::{self, thread::Thread, with_scheduler};
-use blog_os::{print, println};
-use bootloader::{entry_point, BootInfo};
+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);
@@ -28,72 +27,19 @@ fn kernel_main(boot_info: &'static BootInfo) -> ! {

    allocator::init_heap(&mut mapper, &mut frame_allocator).expect("heap initialization failed");

-    // allocate a number on the heap
-    let heap_value = Box::new(41);
-    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)
-    );
-
    #[cfg(test)]
    test_main();

-    let idle_thread = Thread::create(idle_thread, 2, &mut mapper, &mut frame_allocator).unwrap();
-    with_scheduler(|s| s.set_idle_thread(idle_thread));
-
-    for _ in 0..10 {
-        let thread = Thread::create(thread_entry, 2, &mut mapper, &mut frame_allocator).unwrap();
-        with_scheduler(|s| s.add_new_thread(thread));
-    }
-    let thread =
-        Thread::create_from_closure(|| thread_entry(), 2, &mut mapper, &mut frame_allocator)
-            .unwrap();
-    with_scheduler(|s| s.add_new_thread(thread));
-
-    println!("It did not crash!");
-    thread_entry();
-}
-
-fn idle_thread() -> ! {
-    loop {
-        x86_64::instructions::hlt();
-        multitasking::yield_now();
-    }
-}
-
-fn thread_entry() -> ! {
-    let thread_id = with_scheduler(|s| s.current_thread_id()).as_u64();
-    for _ in 0..=thread_id {
-        print!("{}", thread_id);
-        x86_64::instructions::hlt();
-    }
-    multitasking::exit_thread();
+    let mut executor = Executor::new();
+    executor.spawn(Task::new(example_task()));
+    executor.spawn(Task::new(keyboard::print_keypresses()));
+    executor.run();
 }

 /// This function is called on panic.
 #[cfg(not(test))]
 #[panic_handler]
 fn panic(info: &PanicInfo) -> ! {
-    unsafe {
-        blog_os::vga_buffer::WRITER.force_unlock();
-    }
    println!("{}", info);
    blog_os::hlt_loop();
 }
@@ -103,3 +49,17 @@ fn panic(info: &PanicInfo) -> ! {
 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);
+}
--- a/src/memory.rs
+++ b/src/memory.rs
@@ -1,10 +1,7 @@
 use bootloader::bootinfo::{MemoryMap, MemoryRegionType};
 use x86_64::{
-    structures::paging::{
-        mapper, FrameAllocator, Mapper, OffsetPageTable, Page, PageTable, PhysFrame, Size4KiB,
-        UnusedPhysFrame,
-    },
    PhysAddr, VirtAddr,
+    structures::paging::{FrameAllocator, OffsetPageTable, PageTable, PhysFrame, Size4KiB},
 };

 /// Initialize a new OffsetPageTable.
@@ -14,8 +11,10 @@ use x86_64::{
 /// `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)
+    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.
@@ -33,79 +32,14 @@ unsafe fn active_level_4_table(physical_memory_offset: VirtAddr) -> &'static mut
    let virt = physical_memory_offset + phys.as_u64();
    let page_table_ptr: *mut PageTable = virt.as_mut_ptr();

-    &mut *page_table_ptr // unsafe
-}
-
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub struct StackBounds {
-    start: VirtAddr,
-    end: VirtAddr,
-}
-
-impl StackBounds {
-    pub fn start(&self) -> VirtAddr {
-        self.start
-    }
-
-    pub fn end(&self) -> VirtAddr {
-        self.end
-    }
-}
-
-pub fn alloc_stack(
-    size_in_pages: u64,
-    mapper: &mut impl Mapper<Size4KiB>,
-    frame_allocator: &mut impl FrameAllocator<Size4KiB>,
-) -> Result<StackBounds, mapper::MapToError> {
-    use core::sync::atomic::{AtomicU64, Ordering};
-    use x86_64::structures::paging::PageTableFlags as Flags;
-
-    static STACK_ALLOC_NEXT: AtomicU64 = AtomicU64::new(0x_5555_5555_0000);
-
-    let guard_page_start = STACK_ALLOC_NEXT.fetch_add(
-        (size_in_pages + 1) * Page::<Size4KiB>::SIZE,
-        Ordering::SeqCst,
-    );
-    let guard_page = Page::from_start_address(VirtAddr::new(guard_page_start))
-        .expect("`STACK_ALLOC_NEXT` not page aligned");
-
-    let stack_start = guard_page + 1;
-    let stack_end = stack_start + size_in_pages;
-    let flags = Flags::PRESENT | Flags::WRITABLE;
-    for page in Page::range(stack_start, stack_end) {
-        let frame = frame_allocator
-            .allocate_frame()
-            .ok_or(mapper::MapToError::FrameAllocationFailed)?;
-        mapper.map_to(page, frame, flags, frame_allocator)?.flush();
-    }
-    Ok(StackBounds {
-        start: stack_start.start_address(),
-        end: stack_end.start_address(),
-    })
-}
-
-/// 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();
+    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<UnusedPhysFrame> {
+    fn allocate_frame(&mut self) -> Option<PhysFrame> {
        None
    }
 }
@@ -130,7 +64,7 @@ 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);
@@ -139,14 +73,12 @@ 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)));
-        // we know that the frames are really unused
-        frames.map(|f| unsafe { UnusedPhysFrame::new(f) })
+        frame_addresses.map(|addr| PhysFrame::containing_address(PhysAddr::new(addr)))
    }
 }

 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
--- a/src/multitasking/context_switch.rs
+++ b/src/multitasking/context_switch.rs
@@ -1,105 +0,0 @@
-use super::{with_scheduler, SwitchReason};
-use crate::multitasking::thread::ThreadId;
-use alloc::boxed::Box;
-use core::mem;
-use core::raw::TraitObject;
-use x86_64::VirtAddr;
-
-pub struct Stack {
-    pointer: VirtAddr,
-}
-
-impl Stack {
-    pub unsafe fn new(stack_pointer: VirtAddr) -> Self {
-        Stack {
-            pointer: stack_pointer,
-        }
-    }
-
-    pub fn get_stack_pointer(self) -> VirtAddr {
-        self.pointer
-    }
-
-    pub fn set_up_for_closure(&mut self, closure: Box<dyn FnOnce() -> !>) {
-        let trait_object: TraitObject = unsafe { mem::transmute(closure) };
-        unsafe { self.push(trait_object.data) };
-        unsafe { self.push(trait_object.vtable) };
-
-        self.set_up_for_entry_point(call_closure_entry);
-    }
-
-    pub fn set_up_for_entry_point(&mut self, entry_point: fn() -> !) {
-        unsafe { self.push(entry_point) };
-        let rflags: u64 = 0x200;
-        unsafe { self.push(rflags) };
-    }
-
-    unsafe fn push<T>(&mut self, value: T) {
-        self.pointer -= core::mem::size_of::<T>();
-        let ptr: *mut T = self.pointer.as_mut_ptr();
-        ptr.write(value);
-    }
-}
-
-pub unsafe fn context_switch_to(
-    new_stack_pointer: VirtAddr,
-    prev_thread_id: ThreadId,
-    switch_reason: SwitchReason,
-) {
-    asm!(
-        "call asm_context_switch"
-        :
-        : "{rdi}"(new_stack_pointer), "{rsi}"(prev_thread_id), "{rdx}"(switch_reason as u64)
-        : "rax", "rbx", "rcx", "rdx", "rsi", "rdi", "rbp", "r8", "r9", "r10",
-        "r11", "r12", "r13", "r14", "r15", "rflags", "memory"
-        : "intel", "volatile"
-    );
-}
-
-global_asm!(
-    "
-    .intel_syntax noprefix
-
-    // asm_context_switch(stack_pointer: u64, thread_id: u64)
-    asm_context_switch:
-        pushfq
-
-        mov rax, rsp
-        mov rsp, rdi
-
-        mov rdi, rax
-        call add_paused_thread
-
-        popfq
-        ret
-"
-);
-
-#[no_mangle]
-pub extern "C" fn add_paused_thread(
-    paused_stack_pointer: VirtAddr,
-    paused_thread_id: ThreadId,
-    switch_reason: SwitchReason,
-) {
-    with_scheduler(|s| s.add_paused_thread(paused_stack_pointer, paused_thread_id, switch_reason));
-}
-
-#[naked]
-fn call_closure_entry() -> ! {
-    unsafe {
-        asm!("
-        pop rsi
-        pop rdi
-        call call_closure
-    " ::: "mem" : "intel", "volatile")
-    };
-    unreachable!();
-}
-
-// no_mangle required because of https://github.com/rust-lang/rust/issues/68136
-#[no_mangle]
-extern "C" fn call_closure(data: *mut (), vtable: *mut ()) -> ! {
-    let trait_object = TraitObject { data, vtable };
-    let f: Box<dyn FnOnce() -> !> = unsafe { mem::transmute(trait_object) };
-    f()
-}
--- a/src/multitasking/mod.rs
+++ b/src/multitasking/mod.rs
@@ -1,57 +0,0 @@
-use scheduler::Scheduler;
-
-pub mod context_switch;
-pub mod scheduler;
-pub mod thread;
-
-static SCHEDULER: spin::Mutex<Option<Scheduler>> = spin::Mutex::new(None);
-
-#[repr(u64)]
-pub enum SwitchReason {
-    Paused,
-    Yield,
-    Blocked,
-    Exit,
-}
-
-pub fn invoke_scheduler() {
-    let next = SCHEDULER
-        .try_lock()
-        .and_then(|mut scheduler| scheduler.as_mut().and_then(|s| s.schedule()));
-    if let Some((next_stack_pointer, prev_thread_id)) = next {
-        unsafe {
-            context_switch::context_switch_to(
-                next_stack_pointer,
-                prev_thread_id,
-                SwitchReason::Paused,
-            )
-        };
-    }
-}
-
-pub fn exit_thread() -> ! {
-    synchronous_context_switch(SwitchReason::Exit).expect("can't exit last thread");
-    unreachable!("finished thread continued");
-}
-
-pub fn yield_now() {
-    let _ = synchronous_context_switch(SwitchReason::Yield);
-}
-
-fn synchronous_context_switch(reason: SwitchReason) -> Result<(), ()> {
-    let next = with_scheduler(|s| s.schedule());
-    match next {
-        Some((next_stack_pointer, prev_thread_id)) => unsafe {
-            context_switch::context_switch_to(next_stack_pointer, prev_thread_id, reason);
-            Ok(())
-        },
-        None => Err(()),
-    }
-}
-
-pub fn with_scheduler<F, T>(f: F) -> T
-where
-    F: FnOnce(&mut Scheduler) -> T,
-{
-    f(SCHEDULER.lock().get_or_insert_with(Scheduler::new))
-}
--- a/src/multitasking/scheduler.rs
+++ b/src/multitasking/scheduler.rs
@@ -1,122 +0,0 @@
-use super::SwitchReason;
-use crate::multitasking::thread::{Thread, ThreadId};
-use alloc::collections::{BTreeMap, BTreeSet, VecDeque};
-use core::mem;
-use x86_64::VirtAddr;
-
-pub struct Scheduler {
-    threads: BTreeMap<ThreadId, Thread>,
-    idle_thread_id: Option<ThreadId>,
-    current_thread_id: ThreadId,
-    paused_threads: VecDeque<ThreadId>,
-    blocked_threads: BTreeSet<ThreadId>,
-    wakeups: BTreeSet<ThreadId>,
-}
-
-impl Scheduler {
-    pub fn new() -> Self {
-        let root_thread = Thread::create_root_thread();
-        let root_id = root_thread.id();
-        let mut threads = BTreeMap::new();
-        threads
-            .insert(root_id, root_thread)
-            .expect_none("map is not empty after creation");
-        Scheduler {
-            threads,
-            current_thread_id: root_id,
-            paused_threads: VecDeque::new(),
-            blocked_threads: BTreeSet::new(),
-            wakeups: BTreeSet::new(),
-            idle_thread_id: None,
-        }
-    }
-
-    fn next_thread(&mut self) -> Option<ThreadId> {
-        self.paused_threads.pop_front()
-    }
-
-    pub fn schedule(&mut self) -> Option<(VirtAddr, ThreadId)> {
-        let mut next_thread_id = self.next_thread();
-        if next_thread_id.is_none() && Some(self.current_thread_id) != self.idle_thread_id {
-            next_thread_id = self.idle_thread_id
-        }
-        if let Some(next_id) = next_thread_id {
-            let next_thread = self
-                .threads
-                .get_mut(&next_id)
-                .expect("next thread does not exist");
-            let next_stack_pointer = next_thread
-                .stack_pointer()
-                .take()
-                .expect("paused thread has no stack pointer");
-            let prev_thread_id = mem::replace(&mut self.current_thread_id, next_thread.id());
-            Some((next_stack_pointer, prev_thread_id))
-        } else {
-            None
-        }
-    }
-
-    pub(super) fn add_paused_thread(
-        &mut self,
-        paused_stack_pointer: VirtAddr,
-        paused_thread_id: ThreadId,
-        switch_reason: SwitchReason,
-    ) {
-        let paused_thread = self
-            .threads
-            .get_mut(&paused_thread_id)
-            .expect("paused thread does not exist");
-        paused_thread
-            .stack_pointer()
-            .replace(paused_stack_pointer)
-            .expect_none("running thread should have stack pointer set to None");
-        if Some(paused_thread_id) == self.idle_thread_id {
-            return; // do nothing
-        }
-        match switch_reason {
-            SwitchReason::Paused | SwitchReason::Yield => {
-                self.paused_threads.push_back(paused_thread_id)
-            }
-            SwitchReason::Blocked => {
-                self.blocked_threads.insert(paused_thread_id);
-                self.check_for_wakeup(paused_thread_id);
-            }
-            SwitchReason::Exit => {
-                let thread = self
-                    .threads
-                    .remove(&paused_thread_id)
-                    .expect("thread not found");
-                // TODO: free stack memory again
-            }
-        }
-    }
-
-    pub fn add_new_thread(&mut self, thread: Thread) {
-        let thread_id = thread.id();
-        self.threads
-            .insert(thread_id, thread)
-            .expect_none("thread already exists");
-        self.paused_threads.push_back(thread_id);
-    }
-
-    pub fn set_idle_thread(&mut self, thread: Thread) {
-        let thread_id = thread.id();
-        self.threads
-            .insert(thread_id, thread)
-            .expect_none("thread already exists");
-        self.idle_thread_id
-            .replace(thread_id)
-            .expect_none("idle thread should be set only once");
-    }
-
-    pub fn current_thread_id(&self) -> ThreadId {
-        self.current_thread_id
-    }
-
-    fn check_for_wakeup(&mut self, thread_id: ThreadId) {
-        if self.wakeups.remove(&thread_id) {
-            assert!(self.blocked_threads.remove(&thread_id));
-            self.paused_threads.push_back(thread_id);
-        }
-    }
-}
--- a/src/multitasking/thread.rs
+++ b/src/multitasking/thread.rs
@@ -1,82 +0,0 @@
-use crate::memory::{alloc_stack, StackBounds};
-use crate::multitasking::context_switch::Stack;
-use alloc::boxed::Box;
-use x86_64::{
-    structures::paging::{mapper, FrameAllocator, Mapper, Size4KiB},
-    VirtAddr,
-};
-
-#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
-pub struct ThreadId(u64);
-
-impl ThreadId {
-    pub fn as_u64(&self) -> u64 {
-        self.0
-    }
-
-    fn new() -> Self {
-        use core::sync::atomic::{AtomicU64, Ordering};
-        static NEXT_THREAD_ID: AtomicU64 = AtomicU64::new(1);
-        ThreadId(NEXT_THREAD_ID.fetch_add(1, Ordering::SeqCst))
-    }
-}
-
-#[derive(Debug)]
-pub struct Thread {
-    id: ThreadId,
-    stack_pointer: Option<VirtAddr>,
-    stack_bounds: Option<StackBounds>,
-}
-
-impl Thread {
-    pub fn create(
-        entry_point: fn() -> !,
-        stack_size: u64,
-        mapper: &mut impl Mapper<Size4KiB>,
-        frame_allocator: &mut impl FrameAllocator<Size4KiB>,
-    ) -> Result<Self, mapper::MapToError> {
-        let stack_bounds = alloc_stack(stack_size, mapper, frame_allocator)?;
-        let mut stack = unsafe { Stack::new(stack_bounds.end()) };
-        stack.set_up_for_entry_point(entry_point);
-        Ok(Self::new(stack.get_stack_pointer(), stack_bounds))
-    }
-
-    pub fn create_from_closure<F>(
-        closure: F,
-        stack_size: u64,
-        mapper: &mut impl Mapper<Size4KiB>,
-        frame_allocator: &mut impl FrameAllocator<Size4KiB>,
-    ) -> Result<Self, mapper::MapToError>
-    where
-        F: FnOnce() -> ! + 'static + Send + Sync,
-    {
-        let stack_bounds = alloc_stack(stack_size, mapper, frame_allocator)?;
-        let mut stack = unsafe { Stack::new(stack_bounds.end()) };
-        stack.set_up_for_closure(Box::new(closure));
-        Ok(Self::new(stack.get_stack_pointer(), stack_bounds))
-    }
-
-    fn new(stack_pointer: VirtAddr, stack_bounds: StackBounds) -> Self {
-        Thread {
-            id: ThreadId::new(),
-            stack_pointer: Some(stack_pointer),
-            stack_bounds: Some(stack_bounds),
-        }
-    }
-
-    pub(super) fn create_root_thread() -> Self {
-        Thread {
-            id: ThreadId(0),
-            stack_pointer: None,
-            stack_bounds: None,
-        }
-    }
-
-    pub fn id(&self) -> ThreadId {
-        self.id
-    }
-
-    pub(super) fn stack_pointer(&mut self) -> &mut Option<VirtAddr> {
-        &mut self.stack_pointer
-    }
-}
--- a/src/task/executor.rs
+++ b/src/task/executor.rs
@@ -0,0 +1,102 @@
+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();
+    }
+}
--- a/src/task/keyboard.rs
+++ b/src/task/keyboard.rs
@@ -0,0 +1,87 @@
+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),
+                }
+            }
+        }
+    }
+}
--- a/src/task/mod.rs
+++ b/src/task/mod.rs
@@ -0,0 +1,39 @@
+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))
+    }
+}
--- a/src/task/simple_executor.rs
+++ b/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()) }
+}
--- a/src/vga_buffer.rs
+++ b/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]");
 }
--- a/tests/basic_boot.rs
+++ b/tests/basic_boot.rs
@@ -4,10 +4,10 @@
 #![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
+#[unsafe(no_mangle)] // don't mangle the name of this function
 pub extern "C" fn _start() -> ! {
    test_main();

@@ -21,7 +21,5 @@ fn panic(info: &PanicInfo) -> ! {

 #[test_case]
 fn test_println() {
-    serial_print!("test_println... ");
    println!("test_println output");
-    serial_println!("[ok]");
 }
--- a/tests/heap_allocation.rs
+++ b/tests/heap_allocation.rs
@@ -7,8 +7,8 @@
 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 blog_os::allocator::HEAP_SIZE;
+use bootloader::{BootInfo, entry_point};
 use core::panic::PanicInfo;

 entry_point!(main);
@@ -30,44 +30,38 @@ fn main(boot_info: &'static BootInfo) -> ! {

 #[test_case]
 fn simple_allocation() {
-    serial_print!("simple_allocation... ");
-    let heap_value = Box::new(41);
-    assert_eq!(*heap_value, 41);
-    serial_println!("[ok]");
+    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() {
-    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]
--- a/tests/should_panic.rs
+++ b/tests/should_panic.rs
@@ -1,10 +1,10 @@
 #![no_std]
 #![no_main]

-use blog_os::{exit_qemu, serial_print, serial_println, QemuExitCode};
+use blog_os::{QemuExitCode, exit_qemu, serial_print, serial_println};
 use core::panic::PanicInfo;

-#[no_mangle]
+#[unsafe(no_mangle)]
 pub extern "C" fn _start() -> ! {
    should_fail();
    serial_println!("[test did not panic]");
@@ -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);
 }

--- a/tests/stack_overflow.rs
+++ b/tests/stack_overflow.rs
@@ -2,14 +2,14 @@
 #![no_main]
 #![feature(abi_x86_interrupt)]

-use blog_os::{exit_qemu, serial_print, serial_println, QemuExitCode};
+use blog_os::{QemuExitCode, exit_qemu, serial_print, serial_println};
 use core::panic::PanicInfo;
 use lazy_static::lazy_static;
 use x86_64::structures::idt::{InterruptDescriptorTable, InterruptStackFrame};

-#[no_mangle]
+#[unsafe(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]");
--- a/x86_64-blog_os.json
+++ b/x86_64-blog_os.json
@@ -1,15 +1,16 @@
 {
    "llvm-target": "x86_64-unknown-none",
-    "data-layout": "e-m:e-i64:64-f80:128-n8:16:32:64-S128",
+    "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-c-int-width": "32",
+    "target-c-int-width": 32,
    "os": "none",
    "executables": true,
    "linker-flavor": "ld.lld",
    "linker": "rust-lld",
    "panic-strategy": "abort",
    "disable-redzone": true,
-    "features": "-mmx,-sse,+soft-float"
+    "features": "-mmx,-sse,+soft-float",
+    "rustc-abi": "x86-softfloat"
  }