QSOE Development Blog

Part 1 ended with Skimmer at v0.5 — a sound microkernel with QNX-shape synchronous IPC, and nothing running on top of it. This post is the rest: how Skimmer became QSOE/N, an actual operating system with processes, a C library, drivers, and a conformance suite that passes a full lap. All of it still in QEMU; real hardware is part 3. The umbrella QSOE — "Quick and Secure Operating Environment" — is a QNX-Neutrino-style operating environment for 64-bit RISC-V, built entirely under Apache-2.0. It comes in two variants that share almost everything: QSOE/N (project NQ), the native-kernel variant, running on Skimmer. QSOE/L (project LQ), running the same userspace on the seL4 microkernel. The split is deliberately thin. The kernel differs, the system process (taskman) differs, and a small OS-dependent slice of libc differs. Everything else — the C library body, the drivers, the utilities — is shared between the two systems. That constraint shaped a lot of the decisions below,...

This is the first of three posts tracing QSOE/N from its first commit to its first boot on real hardware. This one is about the kernel alone — Skimmer — before there was any userspace to speak of. The whole point of v0.1 through v0.5 was to answer one question: is the core sound? Everything after it assumes the answer is yes. I built all of it alongside Claude Code (Opus 4.7 for this stretch, 4.8 later). The commits carry the co-author line; I'm not going to repeat it every paragraph, but the race hunts below were genuinely a two-party effort. Where the design comes from Skimmer is a from-scratch microkernel for 64-bit RISC-V, Apache-2.0, written to a QNX shape. The concurrency model is not QNX's, though — it's DragonFly BSD's. The two ideas I took are Light Weight Kernel Threads (LWKT) and message ports: per-CPU run queues with no cross-CPU locks on the hot path, and cross-CPU work expressed as messages routed through per-CPU rings rather than as foreign writes into...

It was the first of April, and work on QRV — my port of QNX to RISC-V — was in full swing. A couple of weeks earlier I had put up an open petition asking QNX Software Systems and BlackBerry to re-license the historical 2007–2009 QNX Neutrino source under Apache 2.0. Around this time a thought settled in: there's a real chance it gets ignored completely. I needed a plan B. I've kept the L4 microkernel in the back of my mind for a long time. I first read about it in the early 2000s, along with its various implementations — the ones with the nutty names (Hazelnut, Pistachio), and the one with the funny name, Fiasco, from the group in Dresden. I met those people in person about ten years ago. I never really stopped thinking about L4 after that; I knew about L4Linux and the rest. And I got particularly interested when I learned about seL4. What seL4's authors did still strikes me as a genuinely novel approach: a real microkernel with a machine-checked proof of functional corr...