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| Filename | Latest commit message | Latest commit date |
|---|---|---|
64e4835524
The first piece of the two loaders that is genuinely common code rather than a contract they both honour. It can be, because the difference between the firmwares is entirely in how a framebuffer is *obtained* -- VBE in real mode, or GOP -- and not in what you do with one afterwards. boot/common/ui.c takes a base, a size and a stride and draws; it knows nothing about disks, memory maps or mode setting, which is what lets it compile into a 16/32/64-bit BIOS loader and a PE/COFF UEFI application without either leaking into it. The look is deliberately quiet: dark ground, the mark centred, one thin bar beneath it, nothing on screen that is not load-bearing. The whole group is laid out from the centre outwards rather than from the top down, so it sits identically at 800x600 and at 1600x1200 instead of drifting up the screen as the mode grows. UEFI had no graphical splash at all -- it printed text to a console the QEMU window is usually not even showing. It draws the same screen as the BIOS path now, with the bar tracking bytes of kernel actually written rather than a segment count, which says nothing about how long each takes. Two ordering bugs found by looking at the pixels rather than the code: setup_framebuffer ran *after* the kernel was read, so every progress tick went to a framebuffer that did not exist yet and the splash then painted over the result; and that also put the resolution prompt after the slowest step instead of at the start. The display is set up first now. Verified from the host with screendump: background is exactly SCH_BG, the bar is 4px tall and width/4 wide at y=495 on a 1280x800 screen, which is where centring the group puts it. UEFI still boots to cpu0; BIOS bootcheck 27/27. Not yet shared: the BIOS loader still draws with its own copy of this code. Deleting that copy in favour of this one is the next step and the point of the exercise -- until then this is one loader using shared code and one duplicating it. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> |
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| etc | ||
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| LICENSE | ||
| LICENSE.MIT | ||
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| 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, and docs/moving-to-linux.md for moving a checkout between machines.
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/ bios/ (MBR, stage 2, VBE splash) uefi/ (PE loader)
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.