image · how an image is produced and what the board loads

cross-build

Defines how riscv64 artifacts for this board are produced on an x86_64 host, and what is recorded when a package will not cross-compile.

0 of 2 requirements here are not proven.

grounded

The system is produced by cross-compilation, not emulation

grounding

docs/evidence/cross-build.txt. The full system closure was cross-compiled on an x86_64 host with no riscv64 hardware — 353 derivations built locally, ~970 substituted, producing 1.2 GiB across 474 store paths in 4413s. The resulting kernel booted under QEMU to a shell prompt (docs/evidence/qemu-boot.txt).

Building the system SHALL NOT require a riscv64 machine. The build SHALL declare an x86_64-linux build platform and a riscv64-linux host platform, so that derivations cross-compile by default.

Emulation SHALL remain available as a fallback for derivations that cannot cross-compile, and any derivation built under emulation SHALL be named in the repository rather than silently emulated. The distinction matters because emulated builds are slow enough to change what is worth attempting.

evidence in this repository
scenarios

A closure is built on an x86_64 host

  • WHEN someone with no riscv64 hardware builds the system
  • THEN it completes, and produces riscv64 artifacts

A package will not cross-compile

  • WHEN a derivation fails to cross-compile and is built under emulation instead
  • THEN it is listed in the repository as one that needs emulation, with what it cost
grounded

Cache coverage is partial, and the build says which part

Two things are easily conflated, and the difference decides whether a build takes minutes or hours:

- Native riscv64-linux is community-tier in nixpkgs and is not built by the upstream cache. - Cross-compiled pkgsCross.riscv64 derivations are built on x86_64, so upstream does build many of them and they are substitutable.

Because this project cross-compiles, it benefits from that second case. The project SHALL NOT assume full cache coverage, and documentation of the build SHALL state the measured split between substituted and locally built paths, so that a long compile is recognised as normal rather than as a fault.

grounding

measured on this host building the k230 closure — 636 paths substituted from cache.nixos.org, of which 174 were riscv64 outputs, against 164 built locally. Recorded in docs/evidence/cross-build.txt.

evidence in this repository
scenarios

A first build is attempted

  • WHEN someone builds the system for the first time
  • THEN they have been told which parts substitute and which compile, with a measured figure from a known machine

Someone assumes riscv64 is entirely uncached

  • WHEN the build's cost is estimated
  • THEN the estimate distinguishes cross-compiled outputs, which largely substitute, from anything built natively on riscv64, which does not