AsterOS

A from-source bring-up of a minimal Darwin 19 (Catalina, xnu-6153.141.1) x86_64 system: real XNU kernel + BSD/Mach, a custom UEFI bootloader (Apple's own boot.efi isn't open source), a real userland — dyld, libSystem, libobjc, launchd, real pthreads, CoreFoundation/Foundation/libdispatch/Security/libxpc, prelinked kext loading, networking, and an X11 desktop (Xfbdev + twm + xterm + xclock) — booting to an interactive shell and GUI in QEMU.

See docs/architecture.md for the full set of design decisions and why they were made. See patches/ for every source patch applied to the upstream Apple/X.org sources, each with a rationale. See logs/ for build/boot logs. See TODO.md for the full phase-by-phase build log and current status — it's long, but it's the authoritative record of what's actually done versus in progress.

Layout

• src/ — pinned checkouts of every vendored upstream project this system is built from: XNU and other apple-oss-distributions components, the X.org stack (xorg-server, libX11, twm, xterm, xclock, and their dependencies), BusyBox, LLVM, and a handful of smaller pieces. See THIRD_PARTY_LICENSES.md for what's licensed how.
• userland/ — this project's own userland: the libc, launchd/launchctl, build scripts for every vendored/native component, and small original tools (xsetbg, startx.sh, etc).
• boot/ — the custom EFI bootloader source and disk-image assembly scripts (mkesp.sh).
• build/ — all build output. build/SDKs/MacOSX10.15.sdk is a local, header-patched copy of the host's SDK (no real Catalina SDK exists on this host); build/tools/bin holds host build tools including an xcrun shim and the ctf tools.
• patches/ — one markdown file per patch, numbered, each self-contained.
• docs/ — architecture notes.
• logs/ — build and boot logs.

Building and running

make run

Builds the kernel, bootloader, userland, and root filesystem, assembles the ESP disk image, and boots it in QEMU. See the Makefile for individual targets (kernel, image, clean, etc) if you want to build a specific piece. build-kernel.sh is the older, lower-level entry point for just the kernel bring-up phase (ctf tools, exporthdrs, then the kernel proper into build/kernel/kernel.development) — see patches/0001-0020.md for what it took to get a stock XNU tree building against a modern host toolchain.

Once booted, startx brings up the X11 desktop (twm window manager, three xterms, xclock).

License

This project's own original code — the bootloader, kernel patches that aren't themselves modifications of vendored upstream source, userland tools, build scripts, and documentation — is licensed under the European Union Public Licence v1.2 (EUPL-1.2), a strong-copyleft license: see LICENSE.

Everything under src/ is a real, pinned checkout of someone else's project and keeps its own original license (APSL-2.0 for XNU and other Apple components, GPL-2.0 for BusyBox, MIT/X11 for the X.org stack, and a few others) — see THIRD_PARTY_LICENSES.md for the full breakdown.