A project to write a kernel in Swift that can run on x86_64 hardware. The main aim is to get a simple kernel booting up with a CLI with full concurrency/thread support on multiple CPUs.

The code has been rewritten to work on Embedded Swift, originally it used a version of Swift with a modified runtime and standard library. Some small additions to Embedded Swift needed to be made, currently a separate toolchain is required. See swift-kstdlib for more details. Hopefully the changes will be upstreamed into the main Swift project at some point.

29/09/2025

• XHCI host controller, sufficient to support keyboard and mouse but does not currently support hubs.
• Intel GPU driver to use the 2D blitter engine for text mode. Only supports for specific GPU currently.

21/07/2025

• Rewritten ACPI interpreter, required due to heavy use of existentials which are not supported in Embedded Swift. This also fixed a lot of ACPI bugs.
• Improved EFI Framebuffer driver to speed up the text console. This reduces boot time significantly.
• UHCI host controller driver and basic hub enumeration now works although hot-plug does not.
• Support for USB keyboards and mice using Boot protocol. This allows the keyboard on some hardware to work.

The next major tasks are:

• XHCI USB host controller to use USB devices on newer hardware.
• GPU driver for Intel GPUs to speed up the text console on high resolution screens.

• Boots up under QEMU, Bochs and VMWare. Also boots on Macbook 3,1 (13inch Late 2007)
• Installs interrupts and exception/fault handlers
• Sets up paging
• Scans ACPI/SMBIOS tables
• Parses ACPI tables including AML byte code in DSDT, SSDT tables
• Initialises the APIC and IO/APIC (or PIC)
• Traverses the ACPI device tree adding known devices according to topology.
• Scans PCI bus (MMIO or PIO) to show vendor/device IDs
• Initialises the PIT and PS/2 keyboard controller
• Sets up an APIC and PIT timers and shows a test message with interrupt counts.
• Runs a simple task reading keyboard scan codes from a circular buffer and translates them to ASCII codes to show on the screen. The Macbook doesn't have an i8042 PS/2 keyboard controller so the keyboard will not work.

Currently working on enabling ACPI to process ACPI events and setting up more devices including the Real-time Clock and PCI interrupts.

A custom Swift toolchain is currently required to build the kernel as it contains a modified version of the Embedded Swift runtime for x86-64. For more details see swift-kstdlib

The project has a Package.swift but this is only used for building and running the tests, the kernel itself is built using Makefiles and make.

Use Docker to build a container that downloads the Swift compiler with the modified stdlib using the Dockerfile in Docker/Dockerfile.

# Build the docker container
$ docker build --tag=swift-kstdlib Docker
# Build the kernel and disk images
$ docker run --rm -v `pwd`:`pwd` -w `pwd` -t swift-kstdlib make

Download the toolchain and untar it in the home directory, the toolchain will be installed under Library/Developer/Toolchains/. Some extra tools need to be installed as well.

brew install nasm x86_64-elf-binutils qemu xorriso mtools
make

To run under qemu with a copy of the console output being sent to a virtual serial port use:

./run_qemu.sh

or to use with UEFI/OVMF BIOS ./run_qemu.sh --efi

Copyright (c) 2015 - 2025 Simon Evans

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.