Align the double fault stack through a new wrapper type

2025-12-16 22:37:49 +00:00 · 2020-02-19 10:27:26 +01:00
19 changed files with 241 additions and 620 deletions
--- a/.cargo/config
+++ b/.cargo/config
@@ -0,0 +1,5 @@
+[build]
+target = "x86_64-blog_os.json"
+
+[target.'cfg(target_os = "none")']
+runner = "bootimage runner"
--- a/.cargo/config.toml
+++ b/.cargo/config.toml
@@ -1,9 +0,0 @@
-[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
@@ -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
@@ -1,12 +1,19 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
-version = 3
+[[package]]
+name = "array-init"
+version = "0.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "23589ecb866b460d3a0f1278834750268c607e8e28a1b982c907219f3178cd72"
+dependencies = [
+ "nodrop",
+]

 [[package]]
 name = "bit_field"
-version = "0.10.1"
+version = "0.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dcb6dd1c2376d2e096796e234a70e17e94cc2d5d54ff8ce42b28cef1d0d359a4"
+checksum = "ed8765909f9009617974ab6b7d332625b320b33c326b1e9321382ef1999b5d56"

 [[package]]
 name = "bitflags"
@@ -20,20 +27,26 @@ version = "0.1.0"
 dependencies = [
 "bootloader",
 "lazy_static",
- "linked_list_allocator",
- "pc-keyboard",
- "pic8259",
 "spin",
 "uart_16550",
- "volatile 0.2.7",
- "x86_64",
+ "volatile",
+ "x86_64 0.8.1",
 ]

 [[package]]
 name = "bootloader"
-version = "0.9.21"
+version = "0.8.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a62c8f6168cd106687ee36a2b71a46c4144d73399f72814104d33094b8092fd2"
+checksum = "d596849a47f28abdea62d7a6a25c4f6e69c3d9b09b0a2877db6e9cda004ca993"
+
+[[package]]
+name = "cast"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4b9434b9a5aa1450faa3f9cb14ea0e8c53bb5d2b3c1bfd1ab4fc03e9f33fbfb0"
+dependencies = [
+ "rustc_version",
+]

 [[package]]
 name = "lazy_static"
@@ -45,43 +58,34 @@ dependencies = [
 ]

 [[package]]
-name = "linked_list_allocator"
+name = "nodrop"
+version = "0.1.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "72ef4a56884ca558e5ddb05a1d1e7e1bfd9a68d9ed024c21704cc98872dae1bb"
+
+[[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 = "d0b725207570aa16096962d0b20c79f8a543df2280bd3c903022b9b0b4d7ea68"
+checksum = "1d7eb9ef2c18661902cc47e535f9bc51b78acd254da71d375c2f6720d9a40403"
 dependencies = [
- "spinning_top",
+ "semver-parser",
 ]

 [[package]]
-name = "lock_api"
-version = "0.4.4"
+name = "semver-parser"
+version = "0.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0382880606dff6d15c9476c416d18690b72742aa7b605bb6dd6ec9030fbf07eb"
-dependencies = [
- "scopeguard",
-]
-
-[[package]]
-name = "pc-keyboard"
-version = "0.5.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5c6f2d937e3b8d63449b01401e2bae4041bc9dd1129c2e3e0d239407cf6635ac"
-
-[[package]]
-name = "pic8259"
-version = "0.10.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "08cc920d83ee33c0f9b73aa441e75468bf2d10c959a3eb6260cf720b05ac91a1"
-dependencies = [
- "x86_64",
-]
-
-[[package]]
-name = "scopeguard"
-version = "1.1.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"
+checksum = "388a1df253eca08550bef6c72392cfe7c30914bf41df5269b68cbd6ff8f570a3"

 [[package]]
 name = "spin"
@@ -89,44 +93,49 @@ version = "0.5.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6e63cff320ae2c57904679ba7cb63280a3dc4613885beafb148ee7bf9aa9042d"

-[[package]]
-name = "spinning_top"
-version = "0.2.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "75adad84ee84b521fb2cca2d4fd0f1dab1d8d026bda3c5bea4ca63b5f9f9293c"
-dependencies = [
- "lock_api",
-]
-
 [[package]]
 name = "uart_16550"
-version = "0.2.14"
+version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "503a6c0e6d82daa87985e662d120c0176b09587c92a68db22781b28ae95405dd"
+checksum = "803ea8cb602dbb32c1a657a866d2dd79fe7dbeab0fb2ac667cb4dcc7de12a58b"
 dependencies = [
 "bitflags",
- "x86_64",
+ "x86_64 0.7.7",
 ]

 [[package]]
-name = "volatile"
-version = "0.2.7"
+name = "ux"
+version = "0.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f6b06ad3ed06fef1713569d547cdbdb439eafed76341820fb0e0344f29a41945"
+checksum = "88dfeb711b61ce620c0cb6fd9f8e3e678622f0c971da2a63c4b3e25e88ed012f"

 [[package]]
 name = "volatile"
-version = "0.4.4"
+version = "0.2.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e4c2dbd44eb8b53973357e6e207e370f0c1059990df850aca1eca8947cf464f0"
+checksum = "6af0edf5b4faacc31fc51159244d78d65ec580f021afcef7bd53c04aeabc7f29"

 [[package]]
 name = "x86_64"
-version = "0.14.7"
+version = "0.7.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fb611915c917c6296d11e23f71ff1ecfe49c5766daba92cd3df52df6b58285b6"
+checksum = "1f27d9168654aee1b0c1b73746caeb4aa33248f8b8c8f6e100e697fcc2a794b2"
 dependencies = [
+ "array-init",
 "bit_field",
 "bitflags",
- "volatile 0.4.4",
+ "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",
 ]
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,14 +13,11 @@ name = "stack_overflow"
 harness = false

 [dependencies]
-bootloader = { version = "0.9.8", features = ["map_physical_memory"]}
+bootloader = "0.8.0"
 volatile = "0.2.6"
 spin = "0.5.2"
-x86_64 = "0.14.2"
+x86_64 = "0.8.1"
 uart_16550 = "0.2.0"
-pic8259 = "0.10.1"
-pc-keyboard = "0.5.0"
-linked_list_allocator = "0.9.0"

 [dependencies.lazy_static]
 version = "1.0"
--- a/README.md
+++ b/README.md
@@ -1,32 +1,28 @@
-# Blog OS (Heap Allocation)
+# Blog OS (Double Faults)

-[![Build Status](https://github.com/phil-opp/blog_os/workflows/Code/badge.svg?branch=post-10)](https://github.com/phil-opp/blog_os/actions?query=workflow%3A%22Code%22+branch%3Apost-10)
+[![Build Status](https://github.com/phil-opp/blog_os/workflows/Build%20Code/badge.svg?branch=post-06)](https://github.com/phil-opp/blog_os/actions?query=workflow%3A%22Build+Code%22+branch%3Apost-06)

-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 [Double Faults][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/double-fault-exceptions/

 **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
@@ -1,54 +0,0 @@
-use alloc::alloc::{GlobalAlloc, Layout};
-use core::ptr::null_mut;
-use linked_list_allocator::LockedHeap;
-use x86_64::{
-    structures::paging::{
-        mapper::MapToError, FrameAllocator, Mapper, Page, PageTableFlags, Size4KiB,
-    },
-    VirtAddr,
-};
-
-pub const HEAP_START: usize = 0x_4444_4444_0000;
-pub const HEAP_SIZE: usize = 100 * 1024; // 100 KiB
-
-#[global_allocator]
-static ALLOCATOR: LockedHeap = LockedHeap::empty();
-
-pub fn init_heap(
-    mapper: &mut impl Mapper<Size4KiB>,
-    frame_allocator: &mut impl FrameAllocator<Size4KiB>,
-) -> Result<(), MapToError<Size4KiB>> {
-    let page_range = {
-        let heap_start = VirtAddr::new(HEAP_START as u64);
-        let heap_end = heap_start + HEAP_SIZE - 1u64;
-        let heap_start_page = Page::containing_address(heap_start);
-        let heap_end_page = Page::containing_address(heap_end);
-        Page::range_inclusive(heap_start_page, heap_end_page)
-    };
-
-    for page in page_range {
-        let frame = frame_allocator
-            .allocate_frame()
-            .ok_or(MapToError::FrameAllocationFailed)?;
-        let flags = PageTableFlags::PRESENT | PageTableFlags::WRITABLE;
-        unsafe { mapper.map_to(page, frame, flags, frame_allocator)?.flush() };
-    }
-
-    unsafe {
-        ALLOCATOR.lock().init(HEAP_START, HEAP_SIZE);
-    }
-
-    Ok(())
-}
-
-pub struct Dummy;
-
-unsafe impl GlobalAlloc for Dummy {
-    unsafe fn alloc(&self, _layout: Layout) -> *mut u8 {
-        null_mut()
-    }
-
-    unsafe fn dealloc(&self, _ptr: *mut u8, _layout: Layout) {
-        panic!("dealloc should be never called")
-    }
-}
--- a/src/gdt.rs
+++ b/src/gdt.rs
@@ -9,8 +9,12 @@ 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;
-            static mut STACK: [u8; STACK_SIZE] = [0; STACK_SIZE];
+            const STACK_SIZE: usize = 4096;
+
+            #[repr(align(16))]
+            struct Stack([u8; STACK_SIZE]);
+
+            static mut STACK: Stack = Stack([0; STACK_SIZE]);

            let stack_start = VirtAddr::from_ptr(unsafe { &STACK });
            let stack_end = stack_start + STACK_SIZE;
@@ -41,12 +45,12 @@ struct Selectors {
 }

 pub fn init() {
-    use x86_64::instructions::segmentation::{Segment, CS};
+    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
@@ -1,44 +1,16 @@
-use crate::{gdt, hlt_loop, print, println};
+use crate::{gdt, println};
 use lazy_static::lazy_static;
-use pic8259::ChainedPics;
-use spin;
-use x86_64::structures::idt::{InterruptDescriptorTable, InterruptStackFrame, PageFaultErrorCode};
-
-pub const PIC_1_OFFSET: u8 = 32;
-pub const PIC_2_OFFSET: u8 = PIC_1_OFFSET + 8;
-
-#[derive(Debug, Clone, Copy)]
-#[repr(u8)]
-pub enum InterruptIndex {
-    Timer = PIC_1_OFFSET,
-    Keyboard,
-}
-
-impl InterruptIndex {
-    fn as_u8(self) -> u8 {
-        self as u8
-    }
-
-    fn as_usize(self) -> usize {
-        usize::from(self.as_u8())
-    }
-}
-
-pub static PICS: spin::Mutex<ChainedPics> =
-    spin::Mutex::new(unsafe { ChainedPics::new(PIC_1_OFFSET, PIC_2_OFFSET) });
+use x86_64::structures::idt::{InterruptDescriptorTable, InterruptStackFrame};

 lazy_static! {
    static ref IDT: InterruptDescriptorTable = {
        let mut idt = InterruptDescriptorTable::new();
        idt.breakpoint.set_handler_fn(breakpoint_handler);
-        idt.page_fault.set_handler_fn(page_fault_handler);
        unsafe {
            idt.double_fault
                .set_handler_fn(double_fault_handler)
                .set_stack_index(gdt::DOUBLE_FAULT_IST_INDEX);
        }
-        idt[InterruptIndex::Timer.as_usize()].set_handler_fn(timer_interrupt_handler);
-        idt[InterruptIndex::Keyboard.as_usize()].set_handler_fn(keyboard_interrupt_handler);
        idt
    };
 }
@@ -47,70 +19,24 @@ 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,
-    error_code: PageFaultErrorCode,
-) {
-    use x86_64::registers::control::Cr2;
-
-    println!("EXCEPTION: PAGE FAULT");
-    println!("Accessed Address: {:?}", Cr2::read());
-    println!("Error Code: {:?}", error_code);
-    println!("{:#?}", stack_frame);
-    hlt_loop();
-}
-
 extern "x86-interrupt" fn double_fault_handler(
-    stack_frame: InterruptStackFrame,
+    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!(".");
-    unsafe {
-        PICS.lock()
-            .notify_end_of_interrupt(InterruptIndex::Timer.as_u8());
-    }
-}
-
-extern "x86-interrupt" fn keyboard_interrupt_handler(_stack_frame: InterruptStackFrame) {
-    use pc_keyboard::{layouts, DecodedKey, HandleControl, Keyboard, ScancodeSet1};
-    use spin::Mutex;
-    use x86_64::instructions::port::Port;
-
-    lazy_static! {
-        static ref KEYBOARD: Mutex<Keyboard<layouts::Us104Key, ScancodeSet1>> = Mutex::new(
-            Keyboard::new(layouts::Us104Key, ScancodeSet1, 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),
-            }
-        }
-    }
-
-    unsafe {
-        PICS.lock()
-            .notify_end_of_interrupt(InterruptIndex::Keyboard.as_u8());
-    }
-}
+#[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
@@ -2,45 +2,25 @@
 #![cfg_attr(test, no_main)]
 #![feature(custom_test_frameworks)]
 #![feature(abi_x86_interrupt)]
-#![feature(alloc_error_handler)]
 #![test_runner(crate::test_runner)]
 #![reexport_test_harness_main = "test_main"]

-extern crate alloc;
 use core::panic::PanicInfo;

-pub mod allocator;
 pub mod gdt;
 pub mod interrupts;
-pub mod memory;
 pub mod serial;
 pub mod 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 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);
 }
@@ -49,7 +29,7 @@ pub fn test_panic_handler(info: &PanicInfo) -> ! {
    serial_println!("[failed]\n");
    serial_println!("Error: {}\n", info);
    exit_qemu(QemuExitCode::Failed);
-    hlt_loop();
+    loop {}
 }

 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -68,24 +48,13 @@ pub fn exit_qemu(exit_code: QemuExitCode) {
    }
 }

-pub fn hlt_loop() -> ! {
-    loop {
-        x86_64::instructions::hlt();
-    }
-}
-
-#[cfg(test)]
-use bootloader::{entry_point, BootInfo};
-
-#[cfg(test)]
-entry_point!(test_kernel_main);
-
 /// Entry point for `cargo xtest`
 #[cfg(test)]
-fn test_kernel_main(_boot_info: &'static BootInfo) -> ! {
+#[no_mangle]
+pub extern "C" fn _start() -> ! {
    init();
    test_main();
-    hlt_loop();
+    loop {}
 }

 #[cfg(test)]
@@ -93,8 +62,3 @@ 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
@@ -4,58 +4,27 @@
 #![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;

-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;
-
+#[no_mangle]
+pub extern "C" fn _start() -> ! {
    println!("Hello World{}", "!");
+
    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");
-
-    // 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);
+    fn stack_overflow() {
+        stack_overflow(); // for each recursion, the return address is pushed
    }
-    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)
-    );
+    // uncomment line below to trigger a stack overflow
+    // stack_overflow();

    #[cfg(test)]
    test_main();

    println!("It did not crash!");
-    blog_os::hlt_loop();
+    loop {}
 }

 /// This function is called on panic.
@@ -63,7 +32,7 @@ fn kernel_main(boot_info: &'static BootInfo) -> ! {
 #[panic_handler]
 fn panic(info: &PanicInfo) -> ! {
    println!("{}", info);
-    blog_os::hlt_loop();
+    loop {}
 }

 #[cfg(test)]
@@ -71,8 +40,3 @@ fn panic(info: &PanicInfo) -> ! {
 fn panic(info: &PanicInfo) -> ! {
    blog_os::test_panic_handler(info)
 }
-
-#[test_case]
-fn trivial_assertion() {
-    assert_eq!(1, 1);
-}
--- a/src/memory.rs
+++ b/src/memory.rs
@@ -1,84 +0,0 @@
-use bootloader::bootinfo::{MemoryMap, MemoryRegionType};
-use x86_64::{
-    structures::paging::{FrameAllocator, OffsetPageTable, PageTable, PhysFrame, Size4KiB},
-    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
-}
-
-/// A FrameAllocator that always returns `None`.
-pub struct EmptyFrameAllocator;
-
-unsafe impl FrameAllocator<Size4KiB> for EmptyFrameAllocator {
-    fn allocate_frame(&mut self) -> Option<PhysFrame> {
-        None
-    }
-}
-
-/// A FrameAllocator that returns usable frames from the bootloader's memory map.
-pub struct BootInfoFrameAllocator {
-    memory_map: &'static MemoryMap,
-    next: usize,
-}
-
-impl BootInfoFrameAllocator {
-    /// Create a FrameAllocator from the passed memory map.
-    ///
-    /// This function is unsafe because the caller must guarantee that the passed
-    /// memory map is valid. The main requirement is that all frames that are marked
-    /// as `USABLE` in it are really unused.
-    pub unsafe fn init(memory_map: &'static MemoryMap) -> Self {
-        BootInfoFrameAllocator {
-            memory_map,
-            next: 0,
-        }
-    }
-
-    /// Returns an iterator over the usable frames specified in the memory map.
-    fn usable_frames(&self) -> impl Iterator<Item = PhysFrame> {
-        // get usable regions from memory map
-        let regions = self.memory_map.iter();
-        let usable_regions = regions.filter(|r| r.region_type == MemoryRegionType::Usable);
-        // map each region to its address range
-        let addr_ranges = usable_regions.map(|r| r.range.start_addr()..r.range.end_addr());
-        // transform to an iterator of frame start addresses
-        let frame_addresses = addr_ranges.flat_map(|r| r.step_by(4096));
-        // create `PhysFrame` types from the start addresses
-        frame_addresses.map(|addr| PhysFrame::containing_address(PhysAddr::new(addr)))
-    }
-}
-
-unsafe impl FrameAllocator<Size4KiB> for BootInfoFrameAllocator {
-    fn allocate_frame(&mut self) -> Option<PhysFrame> {
-        let frame = self.usable_frames().nth(self.next);
-        self.next += 1;
-        frame
-    }
-}
--- a/src/serial.rs
+++ b/src/serial.rs
@@ -13,14 +13,10 @@ lazy_static! {
 #[doc(hidden)]
 pub fn _print(args: ::core::fmt::Arguments) {
    use core::fmt::Write;
-    use x86_64::instructions::interrupts;
-
-    interrupts::without_interrupts(|| {
-        SERIAL1
-            .lock()
-            .write_fmt(args)
-            .expect("Printing to serial failed");
-    });
+    SERIAL1
+        .lock()
+        .write_fmt(args)
+        .expect("Printing to serial failed");
 }

 /// Prints to the host through the serial interface.
--- 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.
    ///
@@ -163,42 +166,39 @@ macro_rules! println {
    ($($arg:tt)*) => ($crate::print!("{}\n", format_args!($($arg)*)));
 }

-/// Prints the given formatted string to the VGA text buffer
-/// through the global `WRITER` instance.
+/// Prints the given formatted string to the VGA text buffer through the global `WRITER` instance.
 #[doc(hidden)]
 pub fn _print(args: fmt::Arguments) {
    use core::fmt::Write;
-    use x86_64::instructions::interrupts;
-
-    interrupts::without_interrupts(|| {
-        WRITER.lock().write_fmt(args).unwrap();
-    });
+    WRITER.lock().write_fmt(args).unwrap();
 }

 #[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]
 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();
-        writeln!(writer, "\n{}", s).expect("writeln failed");
-        for (i, c) in s.chars().enumerate() {
-            let screen_char = writer.buffer.chars[BUFFER_HEIGHT - 2][i].read();
-            assert_eq!(char::from(screen_char.ascii_character), c);
-        }
-    });
+    println!("{}", s);
+    for (i, c) in s.chars().enumerate() {
+        let screen_char = WRITER.lock().buffer.chars[BUFFER_HEIGHT - 2][i].read();
+        assert_eq!(char::from(screen_char.ascii_character), c);
+    }
+
+    serial_println!("[ok]");
 }
--- a/tests/basic_boot.rs
+++ b/tests/basic_boot.rs
@@ -4,7 +4,7 @@
 #![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;

 #[no_mangle] // don't mangle the name of this function
@@ -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
@@ -1,60 +0,0 @@
-#![no_std]
-#![no_main]
-#![feature(custom_test_frameworks)]
-#![test_runner(blog_os::test_runner)]
-#![reexport_test_harness_main = "test_main"]
-
-extern crate alloc;
-
-use alloc::{boxed::Box, vec::Vec};
-use blog_os::allocator::HEAP_SIZE;
-use bootloader::{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() {
-    let heap_value_1 = Box::new(41);
-    let heap_value_2 = Box::new(13);
-    assert_eq!(*heap_value_1, 41);
-    assert_eq!(*heap_value_2, 13);
-}
-
-#[test_case]
-fn large_vec() {
-    let n = 1000;
-    let mut vec = Vec::new();
-    for i in 0..n {
-        vec.push(i);
-    }
-    assert_eq!(vec.iter().sum::<u64>(), (n - 1) * n / 2);
-}
-
-#[test_case]
-fn many_boxes() {
-    for i in 0..HEAP_SIZE {
-        let x = Box::new(i);
-        assert_eq!(*x, i);
-    }
-}
-
-#[panic_handler]
-fn panic(info: &PanicInfo) -> ! {
-    blog_os::test_panic_handler(info)
-}
--- a/tests/should_panic.rs
+++ b/tests/should_panic.rs
@@ -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
@@ -9,7 +9,7 @@ use x86_64::structures::idt::{InterruptDescriptorTable, InterruptStackFrame};

 #[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]");