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LKUser Development Notes

lkuser is an overlay repository on top of:

  • LK (lk/ submodule) for kernel and base build system
  • external libc (newlib/ submodule, currently)

The repository adds user-space integration and extension code, especially lib/lkuser, while reusing LK's modular build flow.

What This Repo Does

  • Extends LK with extra functionality in lib/lkuser
  • Builds both kernel-side and user-space artifacts
  • Coordinates cross-repo build steps through top-level make targets

Build Model

The top-level makefile orchestrates sub-makes and generated output trees.

Architecture is controlled by ARCH (default: riscv in the top-level makefile). Agent guidance: do not assume host architecture; always check/propagate ARCH when invoking build or test targets.

Typical flow:

  1. build libc/toolchain pieces (newlib/ and related output dirs)
  2. build LK kernel/app modules (via lk/ and LK make system)
  3. produce combined artifacts in build-* directories

Primary entrypoint is the top-level makefile in this repository.

Key Paths

  • lk/: LK kernel source and build system (git submodule)
  • newlib/: libc source (git submodule)
  • lib/lkuser/: overlay library added by this repo
  • apps/, sys/: user-space and integration code
  • build-* directories: generated outputs (do not treat as source)

Editing Guidance

  • Prefer editing overlay code in this repo first (lib/lkuser, apps, sys).
  • Treat lk/ and newlib/ as upstream submodules unless intentional submodule changes are required.
  • Avoid committing generated files from build-*, install-*, or tool output unless explicitly needed.
  • Preserve compatibility with LK module conventions (rules.mk, MODULE_DEPS, etc.) when adding new code.

Quick Commands

Run from repository root:

make
make clean
make spotless
make test

Use specific top-level targets as defined in makefile for libc/toolchain/kernel variants.

  • make spotless: removes all local build outputs, including the newlib build/install trees.
  • make test: builds LK + user-space artifacts, generates a FAT filesystem image, and starts QEMU.

For make test, QEMU launch is architecture-specific in the top-level makefile:

  • ARCH=arm -> qemu-system-arm
  • ARCH=riscv -> qemu-system-riscv64

If adding a new architecture, update top-level test handling and any architecture-specific toolchain/newlib settings under arch/<arch>/.