Refactor: Move interrupt wakers/operations into separate modules

Let executor enable interrupts
Use new enable_interrupts_and_hlt function of x86_64
2025-12-16 14:27:49 +00:00 · 2020-03-09 08:25:24 +01:00 · 2020-03-08 14:51:51 +01:00 · 2020-03-08 14:50:58 +01:00 · 2020-03-08 14:48:33 +01:00 · 2020-03-08 14:39:38 +01:00
27 changed files with 1276 additions and 293 deletions
--- a/.cargo/config.toml
+++ b/.cargo/config.toml
@@ -1,7 +1,3 @@
-[unstable]
-build-std = ["core", "compiler_builtins"]
-build-std-features = ["compiler-builtins-mem"]
-
 [build]
 target = "x86_64-blog_os.json"

--- a/.github/workflows/build-code.yml
+++ b/.github/workflows/build-code.yml
@@ -0,0 +1,96 @@
+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
@@ -1,130 +0,0 @@
-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
@@ -1,74 +1,170 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
-version = 4
+[[package]]
+name = "autocfg"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f8aac770f1885fd7e387acedd76065302551364496e46b3dd00860b2f8359b9d"

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

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

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

 [[package]]
 name = "bootloader"
-version = "0.9.32"
+version = "0.8.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1ea119c3ed05625c179e09d17d0914570a3753ca09c890a73d98f6b72aea00d2"
+checksum = "c3ed4f735c4e455ba86a3d2939b1c0729414153642106c9d035693355630a42c"
+
+[[package]]
+name = "cfg-if"
+version = "0.1.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4785bdd1c96b2a846b2bd7cc02e86b6b3dbf14e7e53446c4f54c92a361040822"
+
+[[package]]
+name = "conquer-once"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6f7644600a548ecad74e4a918392af1798f7dd045be610be3203b9e129b4f98f"
+dependencies = [
+ "conquer-util",
+]
+
+[[package]]
+name = "conquer-util"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "654fb2472cc369d311c547103a1fa81d467bef370ae7a0680f65939895b1182a"
+
+[[package]]
+name = "cpuio"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "22b8e308ccfc5acf3b82f79c0eac444cf6114cb2ac67a230ca6c177210068daa"
+
+[[package]]
+name = "crossbeam-queue"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c695eeca1e7173472a32221542ae469b3e9aac3a4fc81f7696bcad82029493db"
+dependencies = [
+ "cfg-if",
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-utils"
+version = "0.7.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c3c7c73a2d1e9fc0886a08b93e98eb643461230d5f1925e4036204d5f2e261a8"
+dependencies = [
+ "autocfg",
+ "cfg-if",
+]
+
+[[package]]
+name = "futures-core"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f25592f769825e89b92358db00d26f965761e094951ac44d3663ef25b7ac464a"
+
+[[package]]
+name = "futures-task"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7b0a34e53cf6cdcd0178aa573aed466b646eb3db769570841fda0c7ede375a27"
+
+[[package]]
+name = "futures-util"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "22766cf25d64306bedf0384da004d05c9974ab104fcc4528f1236181c18004c5"
+dependencies = [
+ "futures-core",
+ "futures-task",
+ "pin-utils",
+]

 [[package]]
 name = "lazy_static"
-version = "1.5.0"
+version = "1.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bbd2bcb4c963f2ddae06a2efc7e9f3591312473c50c6685e1f298068316e66fe"
+checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
 dependencies = [
- "spin 0.9.8",
+ "spin",
+]
+
+[[package]]
+name = "linked_list_allocator"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "18c618c431dfe4419afbe22852f6aceffbc17bd82ba0a18b982def291000824c"
+dependencies = [
+ "spinning_top",
+]
+
+[[package]]
+name = "lock_api"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "79b2de95ecb4691949fea4716ca53cdbcfccb2c612e19644a8bad05edcf9f47b"
+dependencies = [
+ "scopeguard",
 ]

 [[package]]
 name = "pc-keyboard"
-version = "0.7.0"
+version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ed089a1fbffe3337a1a345501c981f1eb1e47e69de5a40e852433e12953c3174"
+checksum = "c48392db76c4e9a69e0b3be356c5f97ebb7b14413c5e4fd0af4755dbf86e2fce"

 [[package]]
-name = "pic8259"
-version = "0.10.4"
+name = "pic8259_simple"
+version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cb844b5b01db1e0b17938685738f113bfc903846f18932b378bc0eabfa40e194"
+checksum = "dc64b2fd10828da8521b6cdabe0679385d7d2a3a6d4c336b819d1fa31ba35c72"
 dependencies = [
- "x86_64",
+ "cpuio",
 ]

 [[package]]
-name = "rustversion"
-version = "1.0.22"
+name = "pin-utils"
+version = "0.1.0-alpha.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b39cdef0fa800fc44525c84ccb54a029961a8215f9619753635a9c0d2538d46d"
+checksum = "5894c618ce612a3fa23881b152b608bafb8c56cfc22f434a3ba3120b40f7b587"
+
+[[package]]
+name = "scopeguard"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"

 [[package]]
 name = "spin"
@@ -77,42 +173,36 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6e63cff320ae2c57904679ba7cb63280a3dc4613885beafb148ee7bf9aa9042d"

 [[package]]
-name = "spin"
-version = "0.9.8"
+name = "spinning_top"
+version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6980e8d7511241f8acf4aebddbb1ff938df5eebe98691418c4468d0b72a96a67"
+checksum = "32d801a3a53bcf5071f85fef8d5cab9e5f638fc5580a37e6eb7aba4b37438d24"
+dependencies = [
+ "lock_api",
+]

 [[package]]
 name = "uart_16550"
-version = "0.2.19"
+version = "0.2.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "614ff2a87880d4bd4374722268598a970bbad05ced8bf630439417347254ab2e"
+checksum = "d44b0f30cb82b0fbc15b78ade1064226529ad52028bc8cb8accb98ff6f3d7131"
 dependencies = [
- "bitflags 1.3.2",
- "rustversion",
+ "bitflags",
 "x86_64",
 ]

 [[package]]
 name = "volatile"
-version = "0.2.7"
+version = "0.2.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f6b06ad3ed06fef1713569d547cdbdb439eafed76341820fb0e0344f29a41945"
-
-[[package]]
-name = "volatile"
-version = "0.4.6"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "442887c63f2c839b346c192d047a7c87e73d0689c9157b00b53dcc27dd5ea793"
+checksum = "6af0edf5b4faacc31fc51159244d78d65ec580f021afcef7bd53c04aeabc7f29"

 [[package]]
 name = "x86_64"
-version = "0.14.13"
+version = "0.9.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c101112411baafbb4bf8d33e4c4a80ab5b02d74d2612331c61e8192fc9710491"
+checksum = "4206b60c9f99766329b66962aa8ddc01df6c7edd02edc046b7a69d5df9fcdbcf"
 dependencies = [
 "bit_field",
- "bitflags 2.9.2",
- "rustversion",
- "volatile 0.4.6",
+ "bitflags",
 ]
--- 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 = "2024"
+edition = "2018"

 [[test]]
 name = "should_panic"
@@ -13,31 +13,36 @@ name = "stack_overflow"
 harness = false

 [dependencies]
-bootloader = "0.9"
+bootloader = { version = "0.8.0", features = ["map_physical_memory"]}
 volatile = "0.2.6"
 spin = "0.5.2"
-x86_64 = "0.14.2"
+x86_64 = "0.9.6"
 uart_16550 = "0.2.0"
-pic8259 = "0.10.1"
-pc-keyboard = "0.7.0"
+pic8259_simple = "0.1.1"
+pc-keyboard = "0.5.0"
+linked_list_allocator = "0.8.0"

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

-[[bin]]
-name = "blog_os"
-test = true
-bench = false
+[dependencies.crossbeam-queue]
+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

 [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
--- a/README.md
+++ b/README.md
@@ -1,32 +1,28 @@
-# Blog OS (Introduction to Paging)
+# Blog OS (Heap Allocation)

-[![Build Status](https://github.com/phil-opp/blog_os/workflows/Code/badge.svg?branch=post-08)](https://github.com/phil-opp/blog_os/actions?query=workflow%3A%22Code%22+branch%3Apost-08)
+[![Build Status](https://github.com/phil-opp/blog_os/workflows/Build%20Code/badge.svg?branch=post-10)](https://github.com/phil-opp/blog_os/actions?query=workflow%3A%22Build+Code%22+branch%3Apost-10)

-This repository contains the source code for the [Introduction to Paging][post] post of the [Writing an OS in Rust](https://os.phil-opp.com) series.
+This repository contains the source code for the [Heap Allocation][post] post of the [Writing an OS in Rust](https://os.phil-opp.com) series.

-[post]: https://os.phil-opp.com/paging-introduction/
+[post]: https://os.phil-opp.com/heap-allocation/

 **Check out the [master branch](https://github.com/phil-opp/blog_os) for more information.**

 ## Building

-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:
+You need a nightly Rust compiler. First you need to install the `cargo-xbuild` and `bootimage` tools:

 ```
-cargo build
+cargo install cargo-xbuild bootimage
 ```

-To create a bootable disk image from the compiled kernel, you need to install the [`bootimage`] tool:
-
-[`bootimage`]: https://github.com/rust-osdev/bootimage
+Then you can build the project by running:

 ```
-cargo install bootimage
+cargo xbuild
 ```

-After installing, you can create the bootable disk image by running:
+To create a bootable disk image, run:

 ```
 cargo bootimage
@@ -43,10 +39,10 @@ You can run the disk image in [QEMU] through:
 [QEMU]: https://www.qemu.org/

 ```
-cargo run
+cargo xrun
 ```

-[QEMU] and the [`bootimage`] tool need to be installed for this.
+Of course [QEMU] needs 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.rs
+++ b/src/allocator.rs
@@ -0,0 +1,82 @@
+use alloc::alloc::{GlobalAlloc, Layout};
+use core::ptr::null_mut;
+use fixed_size_block::FixedSizeBlockAllocator;
+use x86_64::{
+    structures::paging::{
+        mapper::MapToError, FrameAllocator, Mapper, Page, PageTableFlags, Size4KiB,
+    },
+    VirtAddr,
+};
+
+pub mod bump;
+pub mod fixed_size_block;
+pub mod linked_list;
+
+pub const HEAP_START: usize = 0x_4444_4444_0000;
+pub const HEAP_SIZE: usize = 100 * 1024; // 100 KiB
+
+#[global_allocator]
+static ALLOCATOR: Locked<FixedSizeBlockAllocator> = Locked::new(FixedSizeBlockAllocator::new());
+
+pub fn init_heap(
+    mapper: &mut impl Mapper<Size4KiB>,
+    frame_allocator: &mut impl FrameAllocator<Size4KiB>,
+) -> Result<(), MapToError<Size4KiB>> {
+    let page_range = {
+        let heap_start = VirtAddr::new(HEAP_START as u64);
+        let heap_end = heap_start + HEAP_SIZE - 1u64;
+        let heap_start_page = Page::containing_address(heap_start);
+        let heap_end_page = Page::containing_address(heap_end);
+        Page::range_inclusive(heap_start_page, heap_end_page)
+    };
+
+    for page in page_range {
+        let frame = frame_allocator
+            .allocate_frame()
+            .ok_or(MapToError::FrameAllocationFailed)?;
+        let flags = PageTableFlags::PRESENT | PageTableFlags::WRITABLE;
+        mapper.map_to(page, frame, flags, frame_allocator)?.flush();
+    }
+
+    unsafe {
+        ALLOCATOR.lock().init(HEAP_START, HEAP_SIZE);
+    }
+
+    Ok(())
+}
+
+pub struct Dummy;
+
+unsafe impl GlobalAlloc for Dummy {
+    unsafe fn alloc(&self, _layout: Layout) -> *mut u8 {
+        null_mut()
+    }
+
+    unsafe fn dealloc(&self, _ptr: *mut u8, _layout: Layout) {
+        panic!("dealloc should be never called")
+    }
+}
+
+/// A wrapper around spin::Mutex to permit trait implementations.
+pub struct Locked<A> {
+    inner: spin::Mutex<A>,
+}
+
+impl<A> Locked<A> {
+    pub const fn new(inner: A) -> Self {
+        Locked {
+            inner: spin::Mutex::new(inner),
+        }
+    }
+
+    pub fn lock(&self) -> spin::MutexGuard<A> {
+        self.inner.lock()
+    }
+}
+
+/// Align the given address `addr` upwards to alignment `align`.
+///
+/// Requires that `align` is a power of two.
+fn align_up(addr: usize, align: usize) -> usize {
+    (addr + align - 1) & !(align - 1)
+}
--- a/src/allocator/bump.rs
+++ b/src/allocator/bump.rs
@@ -0,0 +1,61 @@
+use super::{align_up, Locked};
+use alloc::alloc::{GlobalAlloc, Layout};
+use core::ptr;
+
+pub struct BumpAllocator {
+    heap_start: usize,
+    heap_end: usize,
+    next: usize,
+    allocations: usize,
+}
+
+impl BumpAllocator {
+    /// Creates a new empty bump allocator.
+    pub const fn new() -> Self {
+        BumpAllocator {
+            heap_start: 0,
+            heap_end: 0,
+            next: 0,
+            allocations: 0,
+        }
+    }
+
+    /// Initializes the bump allocator with the given heap bounds.
+    ///
+    /// This method is unsafe because the caller must ensure that the given
+    /// memory range is unused. Also, this method must be called only once.
+    pub unsafe fn init(&mut self, heap_start: usize, heap_size: usize) {
+        self.heap_start = heap_start;
+        self.heap_end = heap_start.saturating_add(heap_size);
+        self.next = heap_start;
+    }
+}
+
+unsafe impl GlobalAlloc for Locked<BumpAllocator> {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        let mut bump = self.lock(); // get a mutable reference
+
+        let alloc_start = align_up(bump.next, layout.align());
+        let alloc_end = match alloc_start.checked_add(layout.size()) {
+            Some(end) => end,
+            None => return ptr::null_mut(),
+        };
+
+        if alloc_end > bump.heap_end {
+            ptr::null_mut() // out of memory
+        } else {
+            bump.next = alloc_end;
+            bump.allocations += 1;
+            alloc_start as *mut u8
+        }
+    }
+
+    unsafe fn dealloc(&self, _ptr: *mut u8, _layout: Layout) {
+        let mut bump = self.lock(); // get a mutable reference
+
+        bump.allocations -= 1;
+        if bump.allocations == 0 {
+            bump.next = bump.heap_start;
+        }
+    }
+}
--- a/src/allocator/fixed_size_block.rs
+++ b/src/allocator/fixed_size_block.rs
@@ -0,0 +1,102 @@
+use super::Locked;
+use alloc::alloc::{GlobalAlloc, Layout};
+use core::{
+    mem,
+    ptr::{self, NonNull},
+};
+
+/// The block sizes to use.
+///
+/// The sizes must each be power of 2 because they are also used as
+/// the block alignment (alignments must be always powers of 2).
+const BLOCK_SIZES: &[usize] = &[8, 16, 32, 64, 128, 256, 512, 1024, 2048];
+
+/// Choose an appropriate block size for the given layout.
+///
+/// Returns an index into the `BLOCK_SIZES` array.
+fn list_index(layout: &Layout) -> Option<usize> {
+    let required_block_size = layout.size().max(layout.align());
+    BLOCK_SIZES.iter().position(|&s| s >= required_block_size)
+}
+
+struct ListNode {
+    next: Option<&'static mut ListNode>,
+}
+
+pub struct FixedSizeBlockAllocator {
+    list_heads: [Option<&'static mut ListNode>; BLOCK_SIZES.len()],
+    fallback_allocator: linked_list_allocator::Heap,
+}
+
+impl FixedSizeBlockAllocator {
+    /// Creates an empty FixedSizeBlockAllocator.
+    pub const fn new() -> Self {
+        FixedSizeBlockAllocator {
+            list_heads: [None; BLOCK_SIZES.len()],
+            fallback_allocator: linked_list_allocator::Heap::empty(),
+        }
+    }
+
+    /// Initialize the allocator with the given heap bounds.
+    ///
+    /// This function is unsafe because the caller must guarantee that the given
+    /// heap bounds are valid and that the heap is unused. This method must be
+    /// called only once.
+    pub unsafe fn init(&mut self, heap_start: usize, heap_size: usize) {
+        self.fallback_allocator.init(heap_start, heap_size);
+    }
+
+    /// Allocates using the fallback allocator.
+    fn fallback_alloc(&mut self, layout: Layout) -> *mut u8 {
+        match self.fallback_allocator.allocate_first_fit(layout) {
+            Ok(ptr) => ptr.as_ptr(),
+            Err(_) => ptr::null_mut(),
+        }
+    }
+}
+
+unsafe impl GlobalAlloc for Locked<FixedSizeBlockAllocator> {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        let mut allocator = self.lock();
+        match list_index(&layout) {
+            Some(index) => {
+                match allocator.list_heads[index].take() {
+                    Some(node) => {
+                        allocator.list_heads[index] = node.next.take();
+                        node as *mut ListNode as *mut u8
+                    }
+                    None => {
+                        // no block exists in list => allocate new block
+                        let block_size = BLOCK_SIZES[index];
+                        // only works if all block sizes are a power of 2
+                        let block_align = block_size;
+                        let layout = Layout::from_size_align(block_size, block_align).unwrap();
+                        allocator.fallback_alloc(layout)
+                    }
+                }
+            }
+            None => allocator.fallback_alloc(layout),
+        }
+    }
+
+    unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
+        let mut allocator = self.lock();
+        match list_index(&layout) {
+            Some(index) => {
+                let new_node = ListNode {
+                    next: allocator.list_heads[index].take(),
+                };
+                // verify that block has size and alignment required for storing node
+                assert!(mem::size_of::<ListNode>() <= BLOCK_SIZES[index]);
+                assert!(mem::align_of::<ListNode>() <= BLOCK_SIZES[index]);
+                let new_node_ptr = ptr as *mut ListNode;
+                new_node_ptr.write(new_node);
+                allocator.list_heads[index] = Some(&mut *new_node_ptr);
+            }
+            None => {
+                let ptr = NonNull::new(ptr).unwrap();
+                allocator.fallback_allocator.deallocate(ptr, layout);
+            }
+        }
+    }
+}
--- a/src/allocator/linked_list.rs
+++ b/src/allocator/linked_list.rs
@@ -0,0 +1,145 @@
+use super::{align_up, Locked};
+use alloc::alloc::{GlobalAlloc, Layout};
+use core::{mem, ptr};
+
+struct ListNode {
+    size: usize,
+    next: Option<&'static mut ListNode>,
+}
+
+impl ListNode {
+    const fn new(size: usize) -> Self {
+        ListNode { size, next: None }
+    }
+
+    fn start_addr(&self) -> usize {
+        self as *const Self as usize
+    }
+
+    fn end_addr(&self) -> usize {
+        self.start_addr() + self.size
+    }
+}
+
+pub struct LinkedListAllocator {
+    head: ListNode,
+}
+
+impl LinkedListAllocator {
+    /// Creates an empty LinkedListAllocator.
+    pub const fn new() -> Self {
+        Self {
+            head: ListNode::new(0),
+        }
+    }
+
+    /// Initialize the allocator with the given heap bounds.
+    ///
+    /// This function is unsafe because the caller must guarantee that the given
+    /// heap bounds are valid and that the heap is unused. This method must be
+    /// called only once.
+    pub unsafe fn init(&mut self, heap_start: usize, heap_size: usize) {
+        self.add_free_region(heap_start, heap_size);
+    }
+
+    /// Adds the given memory region to the front of the list.
+    unsafe fn add_free_region(&mut self, addr: usize, size: usize) {
+        // ensure that the freed region is capable of holding ListNode
+        assert!(align_up(addr, mem::align_of::<ListNode>()) == addr);
+        assert!(size >= mem::size_of::<ListNode>());
+
+        // create a new list node and append it at the start of the list
+        let mut node = ListNode::new(size);
+        node.next = self.head.next.take();
+        let node_ptr = addr as *mut ListNode;
+        node_ptr.write(node);
+        self.head.next = Some(&mut *node_ptr)
+    }
+
+    /// Looks for a free region with the given size and alignment and removes
+    /// it from the list.
+    ///
+    /// Returns a tuple of the list node and the start address of the allocation.
+    fn find_region(&mut self, size: usize, align: usize) -> Option<(&'static mut ListNode, usize)> {
+        // reference to current list node, updated for each iteration
+        let mut current = &mut self.head;
+        // look for a large enough memory region in linked list
+        while let Some(ref mut region) = current.next {
+            if let Ok(alloc_start) = Self::alloc_from_region(&region, size, align) {
+                // region suitable for allocation -> remove node from list
+                let next = region.next.take();
+                let ret = Some((current.next.take().unwrap(), alloc_start));
+                current.next = next;
+                return ret;
+            } else {
+                // region not suitable -> continue with next region
+                current = current.next.as_mut().unwrap();
+            }
+        }
+
+        // no suitable region found
+        None
+    }
+
+    /// Try to use the given region for an allocation with given size and alignment.
+    ///
+    /// Returns the allocation start address on success.
+    fn alloc_from_region(region: &ListNode, size: usize, align: usize) -> Result<usize, ()> {
+        let alloc_start = align_up(region.start_addr(), align);
+        let alloc_end = alloc_start.checked_add(size).ok_or(())?;
+
+        if alloc_end > region.end_addr() {
+            // region too small
+            return Err(());
+        }
+
+        let excess_size = region.end_addr() - alloc_end;
+        if excess_size > 0 && excess_size < mem::size_of::<ListNode>() {
+            // rest of region too small to hold a ListNode (required because the
+            // allocation splits the region in a used and a free part)
+            return Err(());
+        }
+
+        // region suitable for allocation
+        Ok(alloc_start)
+    }
+
+    /// Adjust the given layout so that the resulting allocated memory
+    /// region is also capable of storing a `ListNode`.
+    ///
+    /// Returns the adjusted size and alignment as a (size, align) tuple.
+    fn size_align(layout: Layout) -> (usize, usize) {
+        let layout = layout
+            .align_to(mem::align_of::<ListNode>())
+            .expect("adjusting alignment failed")
+            .pad_to_align();
+        let size = layout.size().max(mem::size_of::<ListNode>());
+        (size, layout.align())
+    }
+}
+
+unsafe impl GlobalAlloc for Locked<LinkedListAllocator> {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        // perform layout adjustments
+        let (size, align) = LinkedListAllocator::size_align(layout);
+        let mut allocator = self.lock();
+
+        if let Some((region, alloc_start)) = allocator.find_region(size, align) {
+            let alloc_end = alloc_start.checked_add(size).expect("overflow");
+            let excess_size = region.end_addr() - alloc_end;
+            if excess_size > 0 {
+                allocator.add_free_region(alloc_end, excess_size);
+            }
+            alloc_start as *mut u8
+        } else {
+            ptr::null_mut()
+        }
+    }
+
+    unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
+        // perform layout adjustments
+        let (size, _) = LinkedListAllocator::size_align(layout);
+
+        self.lock().add_free_region(ptr as usize, size)
+    }
+}
--- a/src/driver/keyboard.rs
+++ b/src/driver/keyboard.rs
@@ -0,0 +1,75 @@
+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),
+                }
+            }
+        }
+    }
+}
--- a/src/driver/mod.rs
+++ b/src/driver/mod.rs
@@ -0,0 +1,6 @@
+pub mod keyboard;
+pub mod timer;
+
+pub fn init() {
+    keyboard::init();
+}
--- a/src/driver/timer.rs
+++ b/src/driver/timer.rs
@@ -0,0 +1,55 @@
+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!(".");
+    }
+}
--- 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 * 5;
+            const STACK_SIZE: usize = 4096;
            static mut STACK: [u8; STACK_SIZE] = [0; STACK_SIZE];

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

 pub fn init() {
-    use x86_64::instructions::segmentation::{CS, Segment};
+    use x86_64::instructions::segmentation::set_cs;
    use x86_64::instructions::tables::load_tss;

    GDT.0.load();
    unsafe {
-        CS::set_reg(GDT.1.code_selector);
+        set_cs(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 crate::{gdt, hlt_loop, println};
 use lazy_static::lazy_static;
-use pic8259::ChainedPics;
+use pic8259_simple::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: InterruptStackFrame) {
+extern "x86-interrupt" fn breakpoint_handler(stack_frame: &mut InterruptStackFrame) {
    println!("EXCEPTION: BREAKPOINT\n{:#?}", stack_frame);
 }

 extern "x86-interrupt" fn page_fault_handler(
-    stack_frame: InterruptStackFrame,
+    stack_frame: &mut InterruptStackFrame,
    error_code: PageFaultErrorCode,
 ) {
    use x86_64::registers::control::Cr2;
@@ -65,46 +65,27 @@ extern "x86-interrupt" fn page_fault_handler(
 }

 extern "x86-interrupt" fn double_fault_handler(
-    stack_frame: InterruptStackFrame,
+    stack_frame: &mut InterruptStackFrame,
    _error_code: u64,
 ) -> ! {
    panic!("EXCEPTION: DOUBLE FAULT\n{:#?}", stack_frame);
 }

-extern "x86-interrupt" fn timer_interrupt_handler(_stack_frame: InterruptStackFrame) {
-    print!(".");
+extern "x86-interrupt" fn timer_interrupt_handler(_stack_frame: &mut InterruptStackFrame) {
+    crate::driver::timer::tick();
+
    unsafe {
        PICS.lock()
            .notify_end_of_interrupt(InterruptIndex::Timer.as_u8());
    }
 }

-extern "x86-interrupt" fn keyboard_interrupt_handler(_stack_frame: InterruptStackFrame) {
-    use pc_keyboard::{DecodedKey, HandleControl, Keyboard, ScancodeSet1, layouts};
-    use spin::Mutex;
+extern "x86-interrupt" fn keyboard_interrupt_handler(_stack_frame: &mut InterruptStackFrame) {
    use x86_64::instructions::port::Port;
-
-    lazy_static! {
-        static ref KEYBOARD: Mutex<Keyboard<layouts::Us104Key, ScancodeSet1>> =
-            Mutex::new(Keyboard::new(
-                ScancodeSet1::new(),
-                layouts::Us104Key,
-                HandleControl::Ignore
-            ));
-    }
-
-    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::driver::keyboard::keyboard_scancode(scancode);

    unsafe {
        PICS.lock()
@@ -112,8 +93,13 @@ extern "x86-interrupt" fn keyboard_interrupt_handler(_stack_frame: InterruptStac
    }
 }

+#[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
@@ -2,41 +2,44 @@
 #![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(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;
 pub mod serial;
+pub mod task;
 pub mod vga_buffer;

 pub fn init() {
    gdt::init();
    interrupts::init_idt();
    unsafe { interrupts::PICS.lock().initialize() };
-    x86_64::instructions::interrupts::enable();
-}
-pub trait Testable {
-    fn run(&self) -> ();
 }

-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 init_heap_structures() {
+    task::init();
+    driver::init();
 }

-pub fn test_runner(tests: &[&dyn Testable]) {
+pub fn test_runner(tests: &[&dyn Fn()]) {
    serial_println!("Running {} tests", tests.len());
    for test in tests {
-        test.run();
+        test();
    }
    exit_qemu(QemuExitCode::Success);
 }
@@ -70,10 +73,15 @@ pub fn hlt_loop() -> ! {
    }
 }

+#[cfg(test)]
+use bootloader::{entry_point, BootInfo};
+
+#[cfg(test)]
+entry_point!(test_kernel_main);
+
 /// Entry point for `cargo xtest`
 #[cfg(test)]
-#[unsafe(no_mangle)]
-pub extern "C" fn _start() -> ! {
+fn test_kernel_main(_boot_info: &'static BootInfo) -> ! {
    init();
    test_main();
    hlt_loop();
@@ -84,3 +92,8 @@ pub extern "C" fn _start() -> ! {
 fn panic(info: &PanicInfo) -> ! {
    test_panic_handler(info)
 }
+
+#[alloc_error_handler]
+fn alloc_error_handler(layout: alloc::alloc::Layout) -> ! {
+    panic!("allocation error: {:?}", layout)
+}
--- a/src/main.rs
+++ b/src/main.rs
@@ -4,27 +4,72 @@
 #![test_runner(blog_os::test_runner)]
 #![reexport_test_harness_main = "test_main"]

+extern crate alloc;
+
+use alloc::{boxed::Box, rc::Rc, vec, vec::Vec};
 use blog_os::println;
+use bootloader::{entry_point, BootInfo};
 use core::panic::PanicInfo;

-#[unsafe(no_mangle)]
-pub extern "C" fn _start() -> ! {
-    use x86_64::registers::control::Cr3;
-    println!("Hello World{}", "!");
+entry_point!(kernel_main);

+fn kernel_main(boot_info: &'static BootInfo) -> ! {
+    use blog_os::allocator;
+    use blog_os::memory::{self, BootInfoFrameAllocator};
+    use x86_64::VirtAddr;
+
+    println!("Hello World{}", "!");
    blog_os::init();

-    let (level_4_page_table, _) = Cr3::read();
+    let phys_mem_offset = VirtAddr::new(boot_info.physical_memory_offset);
+    let mut mapper = unsafe { memory::init(phys_mem_offset) };
+    let mut frame_allocator = unsafe { BootInfoFrameAllocator::init(&boot_info.memory_map) };
+
+    allocator::init_heap(&mut mapper, &mut frame_allocator).expect("heap initialization failed");
+    blog_os::init_heap_structures();
+
+    // 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!(
-        "Level 4 page table at: {:?}",
-        level_4_page_table.start_address()
+        "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(async {
        #[cfg(test)]
        test_main();
+    });

+    executor.spawn(async {
        println!("It did not crash!");
-    blog_os::hlt_loop();
+    });
+
+    executor.spawn(blog_os::driver::timer::timer_task());
+    executor.spawn(blog_os::driver::keyboard::keyboard_task());
+
+    executor.run();
 }

 /// This function is called on panic.
@@ -41,7 +86,14 @@ fn panic(info: &PanicInfo) -> ! {
    blog_os::test_panic_handler(info)
 }

-#[test_case]
-fn trivial_assertion() {
-    assert_eq!(1, 1);
+async fn test() -> u32 {
+    42
+}
+
+async fn foo() -> u32 {
+    test().await * 2
+}
+
+async fn bar() {
+    println!("foo result: {}", foo().await);
 }
--- a/src/memory.rs
+++ b/src/memory.rs
@@ -0,0 +1,106 @@
+use bootloader::bootinfo::{MemoryMap, MemoryRegionType};
+use x86_64::{
+    structures::paging::{
+        FrameAllocator, Mapper, OffsetPageTable, Page, PageTable, PhysFrame, Size4KiB,
+        UnusedPhysFrame,
+    },
+    PhysAddr, VirtAddr,
+};
+
+/// Initialize a new OffsetPageTable.
+///
+/// This function is unsafe because the caller must guarantee that the
+/// complete physical memory is mapped to virtual memory at the passed
+/// `physical_memory_offset`. Also, this function must be only called once
+/// to avoid aliasing `&mut` references (which is undefined behavior).
+pub unsafe fn init(physical_memory_offset: VirtAddr) -> OffsetPageTable<'static> {
+    let level_4_table = active_level_4_table(physical_memory_offset);
+    OffsetPageTable::new(level_4_table, physical_memory_offset)
+}
+
+/// Returns a mutable reference to the active level 4 table.
+///
+/// This function is unsafe because the caller must guarantee that the
+/// complete physical memory is mapped to virtual memory at the passed
+/// `physical_memory_offset`. Also, this function must be only called once
+/// to avoid aliasing `&mut` references (which is undefined behavior).
+unsafe fn active_level_4_table(physical_memory_offset: VirtAddr) -> &'static mut PageTable {
+    use x86_64::registers::control::Cr3;
+
+    let (level_4_table_frame, _) = Cr3::read();
+
+    let phys = level_4_table_frame.start_address();
+    let virt = physical_memory_offset + phys.as_u64();
+    let page_table_ptr: *mut PageTable = virt.as_mut_ptr();
+
+    &mut *page_table_ptr // unsafe
+}
+
+/// Creates an example mapping for the given page to frame `0xb8000`.
+pub fn create_example_mapping(
+    page: Page,
+    mapper: &mut OffsetPageTable,
+    frame_allocator: &mut impl FrameAllocator<Size4KiB>,
+) {
+    use x86_64::structures::paging::PageTableFlags as Flags;
+
+    let frame = PhysFrame::containing_address(PhysAddr::new(0xb8000));
+    // FIXME: ONLY FOR TEMPORARY TESTING
+    let unused_frame = unsafe { UnusedPhysFrame::new(frame) };
+    let flags = Flags::PRESENT | Flags::WRITABLE;
+
+    let map_to_result = mapper.map_to(page, unused_frame, flags, frame_allocator);
+    map_to_result.expect("map_to failed").flush();
+}
+
+/// A FrameAllocator that always returns `None`.
+pub struct EmptyFrameAllocator;
+
+unsafe impl FrameAllocator<Size4KiB> for EmptyFrameAllocator {
+    fn allocate_frame(&mut self) -> Option<UnusedPhysFrame> {
+        None
+    }
+}
+
+/// A FrameAllocator that returns usable frames from the bootloader's memory map.
+pub struct BootInfoFrameAllocator {
+    memory_map: &'static MemoryMap,
+    next: usize,
+}
+
+impl BootInfoFrameAllocator {
+    /// Create a FrameAllocator from the passed memory map.
+    ///
+    /// This function is unsafe because the caller must guarantee that the passed
+    /// memory map is valid. The main requirement is that all frames that are marked
+    /// as `USABLE` in it are really unused.
+    pub unsafe fn init(memory_map: &'static MemoryMap) -> Self {
+        BootInfoFrameAllocator {
+            memory_map,
+            next: 0,
+        }
+    }
+
+    /// Returns an iterator over the usable frames specified in the memory map.
+    fn usable_frames(&self) -> impl Iterator<Item = UnusedPhysFrame> {
+        // get usable regions from memory map
+        let regions = self.memory_map.iter();
+        let usable_regions = regions.filter(|r| r.region_type == MemoryRegionType::Usable);
+        // map each region to its address range
+        let addr_ranges = usable_regions.map(|r| r.range.start_addr()..r.range.end_addr());
+        // transform to an iterator of frame start addresses
+        let frame_addresses = addr_ranges.flat_map(|r| r.step_by(4096));
+        // create `PhysFrame` types from the start addresses
+        let frames = frame_addresses.map(|addr| PhysFrame::containing_address(PhysAddr::new(addr)));
+        // we know that the frames are really unused
+        frames.map(|f| unsafe { UnusedPhysFrame::new(f) })
+    }
+}
+
+unsafe impl FrameAllocator<Size4KiB> for BootInfoFrameAllocator {
+    fn allocate_frame(&mut self) -> Option<UnusedPhysFrame> {
+        let frame = self.usable_frames().nth(self.next);
+        self.next += 1;
+        frame
+    }
+}
--- a/src/task/executor.rs
+++ b/src/task/executor.rs
@@ -0,0 +1,127 @@
+use super::interrupt_wakeups::interrupt_wakeups;
+use crate::println;
+use alloc::{
+    boxed::Box,
+    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>,
+    wake_queue: Arc<SegQueue<TaskId>>,
+    pending_tasks: BTreeMap<TaskId, Task>,
+}
+
+impl Executor {
+    pub fn new() -> Self {
+        Executor {
+            task_queue: VecDeque::new(),
+            wake_queue: Arc::new(SegQueue::new()),
+            pending_tasks: BTreeMap::new(),
+        }
+    }
+
+    pub fn spawn(&mut self, task: impl Future<Output = ()> + 'static) {
+        self.task_queue.push_back(Box::pin(task))
+    }
+
+    pub fn run(&mut self) -> ! {
+        loop {
+            self.run_ready_tasks();
+            self.apply_interrupt_wakeups();
+            self.wake_waiting_tasks();
+            self.hlt_if_idle();
+        }
+    }
+
+    fn run_ready_tasks(&mut self) {
+        while let Some(mut task) = self.task_queue.pop_front() {
+            let waker = self.create_waker(&task).into();
+            let mut context = Context::from_waker(&waker);
+            match task.as_mut().poll(&mut context) {
+                Poll::Ready(()) => {} // task done
+                Poll::Pending => {
+                    // add task to pending_tasks and wait for wakeup
+                    let task_id = Self::task_id(&task);
+                    if self.pending_tasks.insert(task_id, task).is_some() {
+                        panic!("Task with same ID already in pending_tasks");
+                    }
+                }
+            }
+        }
+    }
+
+    /// Invoke wakers for tasks woken by interrupts
+    ///
+    /// 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) {
+        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
+            x86_64::instructions::interrupts::disable();
+            // check if relevant interrupts occured since the last check
+            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 {
+    wake_queue: Arc<SegQueue<TaskId>>,
+    task_id: TaskId,
+}
+
+impl Wake for Waker {
+    fn wake(self: Arc<Self>) {
+        self.wake_by_ref();
+    }
+
+    fn wake_by_ref(self: &Arc<Self>) {
+        self.wake_queue.push(self.task_id);
+    }
+}
--- a/src/task/interrupt_wakeups.rs
+++ b/src/task/interrupt_wakeups.rs
@@ -0,0 +1,25 @@
+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")
+}
--- a/src/task/mod.rs
+++ b/src/task/mod.rs
@@ -0,0 +1,8 @@
+pub(crate) use interrupt_wakeups::interrupt_wake;
+
+pub mod executor;
+mod interrupt_wakeups;
+
+pub fn init() {
+    interrupt_wakeups::init();
+}
--- a/src/vga_buffer.rs
+++ b/src/vga_buffer.rs
@@ -3,6 +3,9 @@ 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.
    ///
@@ -177,14 +180,18 @@ 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]
@@ -192,6 +199,8 @@ 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();
@@ -201,4 +210,6 @@ 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;
+use blog_os::{println, serial_print, serial_println};
 use core::panic::PanicInfo;

-#[unsafe(no_mangle)] // don't mangle the name of this function
+#[no_mangle] // don't mangle the name of this function
 pub extern "C" fn _start() -> ! {
    test_main();

@@ -21,5 +21,7 @@ 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
@@ -0,0 +1,76 @@
+#![no_std]
+#![no_main]
+#![feature(custom_test_frameworks)]
+#![test_runner(blog_os::test_runner)]
+#![reexport_test_harness_main = "test_main"]
+
+extern crate alloc;
+
+use alloc::{boxed::Box, vec::Vec};
+use blog_os::{allocator::HEAP_SIZE, serial_print, serial_println};
+use bootloader::{entry_point, BootInfo};
+use core::panic::PanicInfo;
+
+entry_point!(main);
+
+fn main(boot_info: &'static BootInfo) -> ! {
+    use blog_os::allocator;
+    use blog_os::memory::{self, BootInfoFrameAllocator};
+    use x86_64::VirtAddr;
+
+    blog_os::init();
+    let phys_mem_offset = VirtAddr::new(boot_info.physical_memory_offset);
+    let mut mapper = unsafe { memory::init(phys_mem_offset) };
+    let mut frame_allocator = unsafe { BootInfoFrameAllocator::init(&boot_info.memory_map) };
+    allocator::init_heap(&mut mapper, &mut frame_allocator).expect("heap initialization failed");
+
+    test_main();
+    loop {}
+}
+
+#[test_case]
+fn simple_allocation() {
+    serial_print!("simple_allocation... ");
+    let heap_value = Box::new(41);
+    assert_eq!(*heap_value, 41);
+    serial_println!("[ok]");
+}
+
+#[test_case]
+fn large_vec() {
+    serial_print!("large_vec... ");
+    let n = 1000;
+    let mut vec = Vec::new();
+    for i in 0..n {
+        vec.push(i);
+    }
+    assert_eq!(vec.iter().sum::<u64>(), (n - 1) * n / 2);
+    serial_println!("[ok]");
+}
+
+#[test_case]
+fn many_boxes() {
+    serial_print!("many_boxes... ");
+    for i in 0..HEAP_SIZE {
+        let x = Box::new(i);
+        assert_eq!(*x, i);
+    }
+    serial_println!("[ok]");
+}
+
+#[test_case]
+fn many_boxes_long_lived() {
+    serial_print!("many_boxes_long_lived... ");
+    let long_lived = Box::new(1); // new
+    for i in 0..HEAP_SIZE {
+        let x = Box::new(i);
+        assert_eq!(*x, i);
+    }
+    assert_eq!(*long_lived, 1); // new
+    serial_println!("[ok]");
+}
+
+#[panic_handler]
+fn panic(info: &PanicInfo) -> ! {
+    blog_os::test_panic_handler(info)
+}
--- a/tests/should_panic.rs
+++ b/tests/should_panic.rs
@@ -1,10 +1,10 @@
 #![no_std]
 #![no_main]

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

-#[unsafe(no_mangle)]
+#[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_panic::should_fail...\t");
+    serial_print!("should_fail... ");
    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::{QemuExitCode, exit_qemu, serial_print, serial_println};
+use blog_os::{exit_qemu, serial_print, serial_println, QemuExitCode};
 use core::panic::PanicInfo;
 use lazy_static::lazy_static;
 use x86_64::structures::idt::{InterruptDescriptorTable, InterruptStackFrame};

-#[unsafe(no_mangle)]
+#[no_mangle]
 pub extern "C" fn _start() -> ! {
-    serial_print!("stack_overflow::stack_overflow...\t");
+    serial_print!("stack_overflow... ");

    blog_os::gdt::init();
    init_test_idt();
@@ -23,7 +23,6 @@ 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! {
@@ -44,7 +43,7 @@ pub fn init_test_idt() {
 }

 extern "x86-interrupt" fn test_double_fault_handler(
-    _stack_frame: InterruptStackFrame,
+    _stack_frame: &mut InterruptStackFrame,
    _error_code: u64,
 ) -> ! {
    serial_println!("[ok]");
--- a/x86_64-blog_os.json
+++ b/x86_64-blog_os.json
@@ -1,16 +1,15 @@
 {
    "llvm-target": "x86_64-unknown-none",
-    "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",
+    "data-layout": "e-m:e-i64:64-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",
-    "rustc-abi": "x86-softfloat"
+    "features": "-mmx,-sse,+soft-float"
  }