0.4.0 #

General #

• Update to Microkit 2.3.0, which includes seL4 16.0.0.
• Update to sDDF 0.7.0, libvmm 0.2.0 and MicroPython 1.26.1.
• Example systems now inherit their toolchain setup from sDDF’s tools/make snippets, so they can be built with GCC by setting TOOLCHAIN=gcc. Clang remains the default, and the vmm example still requires it.
• The Nix flake follows the stable nixos-25.05 channel instead of nixos-unstable.
• Add MAINTAINERS.md to document component ownership and maintainers across the repository.

Breaking changes #

• The required sdfgen version is now 0.35.0.
• The minimum Python version is now 3.12.
• Components link against a musl-based libc instead of the minimal libc that sDDF provides.
• The POSIX, socket and file system helper libraries have moved out of the NFS client and the MicroPython component into lib/.

POSIX support #

Running unmodified POSIX code on LionsOS previously required linking against a minimal shim inside the NFS client (originally written just to build libnfs). We have extracted and expanded that shim into a standalone library any component can use, adding broader file and socket support (client and server, blocking and non-blocking), memory allocation, and time. File system protocol status codes are now mapped directly to standard POSIX error numbers.

The libc documentation describes what is and is not supported.

Firewall Example #

• Add a firewall example to LionsOS.
• The firewall supports traffic filtering and routing on platforms with 2 or more interfaces.
• It is configurable at build time via the firewall metaprogram, and at run time using the webserver component.
• The example includes a docker environment for running the firewall on QEMU, as well as an automated testing script that sends traffic across each pair of interfaces.

WebAssembly #

• Add an example system that runs the WebAssembly Micro Runtime on top of the POSIX library, with access to both a file system and the network.
• The wasi-sdk toolchain is provided by the Nix flake.

File systems #

• The file system protocol has more precise error cases, so clients can determine why a command failed.
• The NFS component builds against upstream libnfs rather than a patched fork.
• Various minor fixes to the FAT and NFS components.

MicroPython #

• Rework I²C support to use the new sDDF I²C protocol through the non-blocking libi2c API.
• Use sDDF’s lib_sddf_lwip for networking instead of the component’s own lwIP port.
• Improve the keyboard interrupt implementation.
• Fix RISC-V builds.

Examples #

• Add POSIX and WebAssembly test systems that exercise file and socket functionality, and run them in CI along with the other examples.
• Kitty: use MMIO rather than PCI for the virtIO GPU on QEMU, simplifying passthrough configuration for the framebuffer VM.
• Example metaprograms use sDDF’s shared board definitions instead of carrying their own copies.
• On QEMU, lwIP no longer performs address conflict detection, which noticeably shortens the time an example takes to get a DHCP lease.