- C 90.2%
- Makefile 3.2%
- PowerShell 2.3%
- Shell 1.7%
- Python 1.3%
- Other 1.2%
| Filename | Latest commit message | Latest commit date |
|---|---|---|
686d5cf006
Two bugs reported from actual use, plus a test harness that had stopped testing. init could be killed by Ctrl-C, taking the machine with it. SIGINT goes to the foreground process group, init is pgid 1, and any window where tty_fg_pgrp is 1 -- before a shell claims the terminal, after one exits, or between the two while the key is held -- lands it on init. init has no handler, so killed was set, exit() ran, and exit() panics outright on initproc. Spamming Ctrl-C at a frozen program is exactly the input that finds that window. POSIX and Linux both discard a default-action signal for pid 1; init_ignores() now does the same, SIGKILL included, because init is not killable from userspace on any Unix. Everything was slow because BSIZE was 1024 while a SchFS block is 4096, so every block cost four IDE requests, each with its own interrupt and sleep/wakeup. exec() of the 800 KB toybox binary meant ~800 round trips. The giveaway: `seq 1 200`, which touches no file and prints nothing, cost the same 2.0s as `cat /bin/toybox`, and `ls | wc -l` cost exactly double -- both dominated by loading the same binary twice. BSIZE is 4096 now, one request per SchFS block, and NBUF is 256 blocks (1 MB) rather than 90 KB -- smaller than the binary every command execs, so nothing was ever still resident. ideinit() issues SET MULTIPLE MODE, which is what makes a 4096-byte transfer legal: READ/WRITE MULTIPLE move the drive's multiple count per interrupt and nothing had ever set it, which is the real reason idestart() carried a sector_per_block > 7 panic. seq 1 200 2.02s -> 0.06s ls /bin 2.76s -> 0.68s ls /bin | wc -l 4.68s -> 0.73s And the harness. bootcheck called Find-Qemu from a param() default, which is bound before any function in the body exists -- so it died on its first line and printed an error containing neither "FAIL" nor "Exception", the two things being grepped for. It had not run since it was made host-portable. Worse, an earlier index-based edit had deleted the Expect blocks for -Tty, -Usb, -Sock, -Ps and -Evdev, so five of the seven modes asserted nothing at all. Restored, and the USB run gets its own 16 MB build/usbstick.img: it had been pointed at build/fs.img, which nothing builds since SchFS became root, so QEMU refused to start. 242 checks across seven modes, all passing, and make schfs-check green. |
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| .claude/memory | ||
| Assets | ||
| boot | ||
| cmd | ||
| docs | ||
| include | ||
| kernel | ||
| lib | ||
| ports | ||
| projects | ||
| tools | ||
| .gitattributes | ||
| .gitignore | ||
| LICENSE | ||
| LICENSE.MIT | ||
| Makefile | ||
| NOTICE | ||
| README.md | ||
| run.ps1 | ||
A 64-bit operating system, written from the metal up.
SMP · copy-on-write filesystem · PCI, USB and virtio drivers · TrueType text · Linux syscall ABI
SchOS began as xv6 and is now mostly something else. The scheduler, the memory manager and the trap path have been rewritten for x86-64 and for more than one processor; the filesystem has been replaced outright; the syscall table speaks Linux numbering so that real software — musl, toybox, mksh — runs unmodified.
It is a hobby system built by one person, and it is honest about that: what works below has been run, not inferred, and the gaps are listed as plainly as the features.
The pieces
| Layer | Name | What it is |
|---|---|---|
| System | SchOS | The distribution — kernel, userland, tooling |
| Kernel | SchIFT | Multi-core x86-64 kernel with a modular VFS |
| Filesystem | SchFS | Transactional, copy-on-write, the root filesystem |
| API | SchAPI | System programming interface — the stable surface |
| Compositor | SchCom | Display compositor (planned) |
| Window manager | SchWM | (planned) |
| Desktop | SchDE | (planned) |
uname -s reports SchIFT, the way every Unix reports its kernel rather than
its distribution.
What works
Kernel — Long mode, 4-level paging, preemptive multitasking. SMP: one, two and four processors all boot, with CPU enumeration from the ACPI MADT rather than the 1994 MP table. Memory sized from the E820 map, so it runs in tens of megabytes rather than demanding hundreds.
Filesystem — SchFS is the root: a copy-on-write B-tree with a
uberblock ring, so a crash leaves either the old tree or the new one and there
is nothing to repair. Free space is derived from the tree rather than stored
beside it, which removes a whole class of disagreement. /proc/schfs shows the
generation counter advancing as writes commit.
Processes — fork, exec, wait, pipes, signals, sessions and process groups,
mmap (anonymous and file-backed), POSIX shared memory, Unix domain sockets,
poll.
Devices — PCI enumeration with a bus-agnostic device model at
/proc/devices. Drivers for e1000 networking, virtio-gpu and stdvga
displays, xHCI USB with HID, hub and mass-storage class drivers, IDE, PS/2,
serial. /dev/fb0 speaks the Linux fbdev interface.
Userland — musl, toybox and mksh, built from source. ls, cat, ps,
top, wc, cp, mount and the rest behave the way you expect, because they
are the real programs.
Text — a TrueType rasteriser (glyf outlines, composite glyphs, cmap
format 4) replacing the 8×16 cell grid. JetBrains Mono for the terminal, Roboto
for the desktop layer to come.
When it dies — PSOGM, the Purple Screen of Guru Meditation: stop code, fault address, call chain, and a QR code containing a text copy of the whole report.
Quick start
make # kernel + bootloader + root filesystem -> schos.img
make qemu # build it and boot it
make iso # a bootable ISO for VMware or real hardware
Builds on Linux, macOS, FreeBSD/OpenBSD/NetBSD and Windows (Git Bash). The toolchain is clang + lld everywhere — it is a cross-compiler by construction, so one LLVM install targets the bare-metal kernel, the 16-bit boot code and musl userland from any host. See docs/building.md for prerequisites per platform.
Testing
Booting to a prompt proves nothing: a filesystem can mount and still fail the first real command, and that has happened here. So the test harness drives the serial console and asserts on what comes back.
tools/windows/bootcheck.ps1 # boot, run real commands, check the answers
tools/windows/bootcheck.ps1 -Tty -Ps # terminal behaviour, process enumeration
make schfs-check # SchFS B-tree, object and image suites
bootcheck is PowerShell because pwsh runs on every supported host.
Layout
kernel/ arch/ core/ dev/ drivers/ fs/ net/ proc/ sys/
fs/schfs/ the filesystem -- same source the host tools compile
include/ kernel and userland headers
boot/ bootblock and stage 2 (VBE splash, boot menu)
lib/ cmd/ first-party userland runtime and programs
ports/ third-party software built from source
tools/ windows/ (.ps1) posix/ (.sh) python/ (.py) and .c/.pl
docs/ architecture, roadmap, licensing, building
One rule worth knowing: the kernel and the host tools compile the same SchFS
source. mkschfs cannot disagree with the kernel about the on-disk format,
because there is only one implementation — found and fixed on the host, where a
test takes a second instead of a boot.
Another: syscalls are declared in exactly one place,
kernel/sys/table.inc. Everything else is generated from it.
Not there yet
- No TCP/IP. The decision is made — port lwIP rather than write one — but it is not done. The e1000 driver works; nothing speaks to it yet.
- No compositor, window manager or desktop. That is the next large piece.
- SchFS has no Linux driver yet; the plan is on-disk format version first, then FUSE, then a kernel module.
- CFF/OpenType outlines and TrueType hinting are deliberately out of scope.
Licensing
Apache-2.0, copyright Nexoniarz. See LICENSE.
The kernel derives from xv6, which is MIT — see LICENSE.MIT. Third-party code redistributed in a built image (musl, toybox, mksh, the fonts) keeps its own licence; NOTICE carries the attributions.
Drivers may be adapted from BSD sources, which are compatible. Linux drivers are not: GPL-2.0-only and Apache-2.0 cannot be combined and redistributed. Reading Linux to understand hardware is fine; translating a driver is not. Best of all is the public specification — xHCI, virtio, AHCI, e1000 — which carries no licence on what you write from it.