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Two Addresses, One Page: Finding the Firmware Bug Behind NetBSD Corruption on the Milk-V Mars

 · 16 min read

NetBSD booted on my Milk-V Mars, joined the network, and then overwrote its own kernel with pkgsrc file data under sustained write load. The evidence first pointed at a double allocation inside UVM. That diagnosis was wrong. A custom PGAUDIT kernel, a Mars-shaped QEMU target, 256 permanent canary pages, and a controlled cache-flush experiment in DDB eventually showed two physical addresses exactly 4 GiB apart reaching the same DDR backing. The unsafe 8 GiB map came from a blank EEPROM and U-Boot SPL's private memory default. This is the sequel to my original bring-up article: the wrong theories, the two device trees hiding in one boot chain, the one-line firmware correction, and the 600-second hardware A/B that contained the corruption.
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Hardware Reviews

FriendlyElec NanoPC-T6N Review: The Fastest Board on My Bench, and the Benchmark That Outgrew Itself

 · 28 min read

Hands-on review of the FriendlyElec NanoPC-T6N, a Rockchip RK3588 SBC with 16 GB RAM, dual 2.5GbE, and a 6 TOPS NPU running Debian 13 on FriendlyELEC's BSP. It posts the fastest ARM compile time on my bench (52.55s), pushes 2.19 GB/s of AES-128-GCM, and never throttles - peaking at 56.4C under sustained eight-core load. Also the story of why my standard benchmark stopped being comparable to its own history, and what the microSD it shipped booting from is costing it.
Operating Systems

Four Partitions and a Borrowed Bootloader: NetBSD on the Milk-V Mars

 · 17 min read

NetBSD now runs on my Milk-V Mars: 28 GB root filesystem, gigabit Ethernet at 0.0% packet loss, SSH like any other machine on the shelf. It is the only documented NetBSD Mars I'm aware of, and getting there took a weekend of archaeology: a vendor bootloader whose advertised boot logic is dead code, a QEMU time machine built from Debian's snapshot archive, an SD card doubling as a flight recorder, a serial console that demolished every blind theory in ten minutes, a kernel panic caught with full backtrace, and a filesystem-corruption incident I caused myself by "fixing" a safety mechanism I hadn't understood. The final fix for the whole device-tree saga is one line in a U-Boot defconfig. The whole build is scripted and reproducible; a flashable image is next.
Hardware Reviews

Banana Pi BPI-R4 Pro Review: A 10-Gigabit Router Board I Put to Work as a Bastion

 · 21 min read

Hands-on review of the Banana Pi BPI-R4 Pro, a MediaTek MT7988A (Filogic 880) router board with quad Cortex-A73, dual 10GbE, and 8GB RAM running OpenWRT. Benchmarked for what a router actually does - CoreMark 9533/37952, ~1 GB/s hardware AES, GbE line-rate networking, 50C under load - and deployed as a real SSH bastion and nginx reverse proxy. A different animal from a compute SBC, reviewed as one.
Infrastructure

Nothing Was Using the Cores: Three Idle Arm64 Boards, One HA k3s Cluster, and a BSD Build Farm

 · 18 min read

I had three small Arm64 boards on a shelf, each doing one modest thing and idling the rest of the time — an Orange Pi 5 Max running an occasional local LLM, two Raspberry Pi–class machines mostly serving a web page. Between them they had sixteen cores, forty gigabytes of RAM, and four terabytes of NVMe, and almost none of it was doing anything at any given moment. This is the story of resisting the urge to buy two more boards into a memory shortage, and instead turning that idle majority into a real three-node HA k3s cluster with embedded etcd, then teaching it to do the job the boxes had quietly been built for all along — compiling native FreeBSD, OpenBSD, and NetBSD Arm64 binaries — and the small pile of gotchas that stood between "three SBCs" and "a build farm," from a big.LITTLE crash loop to golden images that turned out to be live disks. And then everything else the reclaimed capacity paid for.
Operating Systems

The Driver Nobody Wrote: OpenBSD's ena(4) Works Now — and Can't Go Upstream

 · 17 min read

Five weeks ago I ended a post about writing OpenBSD's missing ena(4) driver with a confession disguised as a list — every way the thing didn't work yet. This is the post where I cross them all off. The driver does a full disk install now, comes up multiuser with the AWS network card as its only interface, lets me SSH in over it, pushes 3.16 Gbit across multiple queues with receive-side scaling, and runs unchanged on OpenBSD-current. It is, by every technical measure I set for myself, done. And that is exactly when it walked into the one wall effort can't move: code an AI wrote has no human author, so it cannot go into OpenBSD's tree — not for lack of quality, but for lack of a person. This is the story of finishing it, the one bug I never cracked, and what it means to write working systems code that, in the eyes of the thing it was written for, nobody wrote.
Operating Systems

The Doorbell That Killed the Device: Writing OpenBSD's Missing ena(4) Driver

 · 18 min read

A weeks ago I wrote about getting native OpenBSD/arm64 builds on Graviton by refusing to let OpenBSD touch AWS's network card at all — running it as a QEMU guest behind a virtio shim, because OpenBSD has no driver for Amazon's ENA adapter. This is the other half of that itch: actually writing the driver. It's the story of getting ena(4) to attach, watching the device kill itself a few microseconds after every bring-up, chasing five increasingly exotic theories for why, and finding that the real cause was the most boring thing imaginable — I initialized a queue in the wrong order. Plus the part nobody writes down: what "working" actually means, and exactly how far from "done" that still is.

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Retro Computing AI & Inference Hardware Projects Philosophy Economics Systems Programming

Reading Series

8+ posts Jevons Paradox & AI Economics What happens when cognitive output gets cheaper. Demand expansion, the biological ceiling, and the AI vampire. 3 parts Heidegger & Technology Enframing, standing reserve, and what happens when AI treats specifications as raw material for code generation. 8+ posts Z80 RetroShield Running a real Z80 on modern hardware. CP/M, Forth, Zork, custom PCBs, and a dual-processor design. 3 parts Sampo CPU & Compilers A custom RISC CPU from ISA design through FPGA implementation to an LLVM backend. 6 posts Tesla P40 Home Lab Four eBay GPUs, 96GB of VRAM, and every workload we can throw at them. LLMs, TTS, video generation. 3 parts The Lattice Language A programming language where mutability is a phase transition. Novel type system, bytecode VM, 100 opcodes.
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Written by Alex Jokela Software engineer by trade, tinkerer by nature, single-board computer hoarder by choice. More about me →