SchOS/docs/building.md
Nexoniarz 4ac7e19397 Prepare for the move to Fedora
tools/posix/setup-fedora.sh installs the toolchain and reports what it
cannot: PowerShell has no Fedora package, and bootcheck is the test
suite, so the script says how to get pwsh rather than failing quietly.
It also checks /dev/kvm, since a Ryzen box can run the tests at native
speed.

docs/moving-to-linux.md is the actual procedure: copy the repo, restore
the memory, install, build. The memory travels inside the repo and
`memory-sync.sh import` puts it under the key this machine derives from
its own path -- /home/nexoniarz/Documents/SchOS becomes
-home-nexoniarz-Documents-SchOS, where D:\DEV\SchOS was D--DEV-SchOS.

OVMF discovery no longer assumes QEMU's Windows layout. Fedora ships
edk2-ovmf to /usr/share/edk2/ovmf/, Debian and Arch differ again, so the
Makefile searches a list and names the packages when it finds nothing.
Tested through the shell rather than $(wildcard): on Windows make is a
native binary using Win32 file calls, while `command -v` returns an MSYS
path like /c/Users/..., which $(wildcard) cannot see -- it returned
nothing on a machine that had the firmware.

Two things only that machine can test: `make ports` builds musl, toybox
and mksh from source, which Windows cannot do at all; and the SchFS
round-trip needs symlinks and hard links, so it has never actually run.
2026-08-09 17:25:07 +02:00

5.1 KiB

Building SchOS

Supported hosts: Linux, macOS, FreeBSD/OpenBSD/NetBSD, and Windows (under Git Bash or MSYS2). The build is developed from both Windows and Linux, so a change that only works on one of them is a bug.

make          # kernel + bootloader + root filesystem -> schos.img
make qemu     # build and boot it

Prerequisites

Need Why Windows Linux macOS BSD
clang, ld.lld, llvm-objcopy, llvm-objdump cross-compiles the kernel, the 16/32-bit boot code, and musl userland LLVM installer clang lld llvm brew install llvm pkg install llvm
make — Git Bash make Xcode CLT gmake
perl generates the interrupt vector table Git Bash usually present present pkg install perl5
python3 boot logo, crash-screen QR python.org (python) python3 brew install python pkg install python3
qemu-system-x86_64 running and testing scoop install qemu qemu-system-x86 brew install qemu pkg install qemu
curl, tar fetching ports Git Bash present present present
xorriso or mkisofs make iso only scoop install cdrtools xorriso brew install xorriso pkg install xorriso

A host C compiler (cc) is also needed, for the tools that build the disk images. On Windows that must be mingw-w64's gcc, not clang: clang defaults to an MSVC target there, and tools/mkfs.c needs <unistd.h> and <dirent.h>, which the Windows SDK does not have.

Why clang rather than a cross-gcc

clang is a cross-compiler by construction, so one ordinary LLVM install targets everything this tree needs — bare-metal ELF, code linked below one megabyte, and Linux/musl userland — from any host. A cross binutils+gcc would be a day of setup per platform that then rots, and on macOS it means brewing x86_64-elf-gcc before anything builds at all.

The Makefile selects clang+lld whenever both are on PATH. To force the GNU toolchain instead:

make USE_GNU=1                    # needs a cross toolchain that emits x86_64 ELF
make USE_GNU=1 TOOLPREFIX=x86_64-elf-

Testing

tools/windows/bootcheck.ps1            # boots, drives the shell, asserts on output
tools/windows/bootcheck.ps1 -Tty -Ps   # plus terminal behaviour and process listing
make schfs-check                       # SchFS unit, object and image suites

bootcheck is PowerShell, and PowerShell 7 (pwsh) runs on Linux, macOS and the BSDs as well as Windows — brew install powershell, or your distribution's powershell package. It finds QEMU on PATH.

Booting to a prompt proves nothing on its own: a filesystem can mount and still fail the first real command, which has happened here. bootcheck types commands at the serial console and greps the transcript for the answers they should produce.

Ports

musl, toybox and mksh are built from source into sysroot/. This does not work on a Windows host — make prints ports: skipped and uses whatever is already staged in sysroot/. Building them needs a Linux host (or any other Unix); do it once and the staged result serves the Windows builds.

Where the tools live

tools/ is grouped by what runs the file, so it is obvious at a glance which tools a given host can use:

tools/
  windows/   .ps1   PowerShell (pwsh runs these on Linux and macOS too)
  posix/     .sh    shell
  python/    .py
  *.c               host programs -- compiled by the build, run everywhere
  *.pl              perl, likewise

The .c and .pl files stay at the top level because they are not host-specific: the build compiles or invokes them on every platform.

A script that needs the repo root derives it from its own location, so anything moved between these directories has to have that adjusted — the PowerShell tools use Split-Path (Split-Path $PSScriptRoot -Parent) -Parent, two levels up.

Known host differences, already handled

Listed because they are the shape of the next such bug, not because anything is outstanding:

  • <sys/sysmacros.h> is glibc/musl only. macOS and the BSDs take major() and minor() from <sys/types.h>.
  • sha256sum exists on Linux and Git Bash; macOS has shasum -a 256, FreeBSD/NetBSD sha256, OpenBSD cksum -a sha256. tools/posix/sha256check.sh finds whichever is present.
  • nproc is coreutils, so absent on macOS and BSD, where it is sysctl -n hw.ncpu.
  • In the PowerShell tools, path literals must use forward slashes: Join-Path $root 'build\x' produces a filename containing a backslash on a Unix host.

Fedora, in one command

tools/posix/setup-fedora.sh --check   # what is missing
tools/posix/setup-fedora.sh           # install it

Moving an existing checkout to a Linux machine: see moving-to-linux.md.

Working on two machines

Claude Code's project memory is kept in the repo and moved with:

tools/posix/memory-sync.sh status
tools/posix/memory-sync.sh export   # after a session that learned something; then commit
tools/posix/memory-sync.sh import   # after cloning or pulling elsewhere