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| Filename | Latest commit message | Latest commit date |
|---|---|---|
c84d06c5b1
Gate 0's last item, "delete the cell grid" -- done as far as it should be, and the rest of it retired, which is the part worth explaining. include/text.h made the case against the grid in four charges: it cannot do variable-width glyphs, cannot position text off a multiple of eight, cannot anti-alias, and cannot hold a codepoint above 255. Every one of those was about the *drawing layer*, and every one is now false -- glyphs carry metrics, PSOGM positions text at arbitrary pixels, the TrueType path blends 8-bit coverage, and vtcell.ch is a uint32. What is left is a grid in vt.c, and deleting that would not modernise the console; it would stop it being a terminal. VT100 escapes address columns, TIOCGWINSZ reports rows and columns, and every program that draws a box assumes both. So the item is checked with its remainder rewritten to say what was actually wrong, rather than ticked as if the original wording had been carried out. **What was actually wrong was the duplicate.** gfx.c walked font_data and blitted glyphs its own way; text.c did the same job into a struct surface, for no caller but a sysrq self-test. Two implementations of bearings, coverage and clipping, which had to agree about a cell size only one of them was told had changed -- and they did not agree, which is why every line of PSOGM once drew the next character's bitmap underneath itself. There is one now, and the mechanism is the pleasing part: the console hands text_draw_glyph() **the cell as a surface of its own** -- same pixels, same stride, origin moved and bounds set to that cell. Clipping a tall ascender to its line is then the same bounds check that clips to the edge of a screen, and there is no second notion of clipping in the tree. `surface_sub()` is six lines and replaced fourteen of hand-written comparisons. The bitmap is reached through font_builtin() like any other provider, so the early console and the real one are one path with different metrics, and the `if (!cfont)` branch that walked the array is gone. gfx.c no longer includes font.h; text.c does, being the only file left that reads it -- which also retires the note in text.c explaining why it could not. struct surface gained a bpp, because gfx_draw_pixel handles 16, 24 and 32 and whatever replaces it has to as well. Zero means 32: a UEFI GOP has no other format and the loader publishes 32 unconditionally, so callers that do not care say nothing. One behaviour change, and it is the documented one: a codepoint the font cannot draw is now a substituted glyph rather than a blank cell. text.h argues for that directly -- "a missing glyph that draws nothing makes text silently shorter and the fault impossible to see". Verified by screendump: the console renders correctly, PSOGM renders correctly, and `echo t > /proc/sysrq` still draws its specimen through the surface path with the back buffer at 32bpp. Both supported configurations: one boot each, no traps, no panics, socktest and memfdtest green. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> |
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A 64-bit operating system, written from the metal up.
SMP · copy-on-write filesystem · TCP/IP · 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.
Networking — ARP, IPv4, ICMP, UDP, TCP and DHCP, on lwIP behind a
driver-agnostic interface class. Verified end to end from the host, both
directions, rather than by inspection. Names resolve, so wget http://host/
works; httpd serves a directory back the other way.
Userland — musl, toybox, mksh and zsh, built from source. 268 applets:
ls, cat, ps, top, wc, cp, mount, awk, bc, diff and the rest
behave the way you expect, because they are the real programs. edit is
kilo — arrow keys, Ctrl-S, Ctrl-Q, nothing
to learn.
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 + UEFI loader + root filesystem
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/guides/building.md for prerequisites per platform, and docs/history/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/ uefi/ (PE loader) common/ (shared loader UI)
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/ (what it is) plan/ (what's next)
guides/ (how to work on it) history/ (why it's like this)
docs/README.md is the index. If you are reading the tree for the first time, docs/architecture/README.md is the system layer by layer.
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 desktop. Schcom composites and routes input; the plan is now to put it on Wayland and delete the homegrown protocol. See docs/plan/wayland.md.
- No descriptor passing. No
sendmsg/recvmsg, so noSCM_RIGHTS— which is what the GUI work stops at. docs/plan/foundations.md. - No dynamic linking.
exechandles staticET_EXEConly. - No page cache, so writable
MAP_SHAREDof a file is refused rather than faked. - A USB disk cannot be booted from — the root device is compiled in rather than selectable.
- 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, zsh, kilo, the fonts) keeps its own licence; NOTICE carries the attributions. All of it is permissive — there is no GPL in an image this builds, which is why the userland is toybox and not BusyBox and the editor is kilo and not nano. See docs/licensing.md.
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.