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c0806d1b64
lwIP 2.2.0, fetched by ports/lwip and compiled straight into the kernel. Not written from scratch, and the reason is not the packet formats: it is congestion control, retransmission, window management and twenty years of corner cases that only show up against a real peer. Not FreeBSD's netinet either, though the licence would have allowed it -- that stack is not a library, it reaches into mbufs, epoch(9), netisr, VNET and uma(9), so adopting it means porting FreeBSD's kernel infrastructure first. lwIP was written for exactly this situation: a small kernel with a raw Ethernet driver and a port layer of a few hundred lines. It is kernel code, so nothing is installed into the sysroot and there is no second build system: the top-level Makefile compiles the files it wants against our port headers. The file list is explicit rather than a wildcard, because lwIP ships IPv6, 6LoWPAN, PPP, SLIP, DNS-SD and a dozen apps in the same tree, and building what is not configured yields either dead code or a link error naming a port function nobody meant to write. Its sources are unmodified and its warnings are silenced for its files only -- patching them would mean maintaining a fork. The port layer is ours: a lock, a clock, the netif that hands frames to e1000, lwipopts.h, and a shim/ directory of tiny headers so lwIP's <string.h> and friends resolve to the kernel's functions instead of the host's, whose prototypes disagree and would otherwise be found on the default include path. NO_SYS=1, so lwIP has no threads of its own and one kernel thread feeds it. A thread rather than the interrupt handler, because a call into lwIP can reach the driver, the driver can sleep, and an interrupt handler cannot -- so the interrupt still only clears the cause register and the thread polls. kthread_create is new and generally useful: a process with a kernel-only page directory, no files, no cwd, no parent, dispatched from forkret, which can therefore sleep and be preempted like anything else. DHCP obtains an address at boot and the console says which one. AF_INET went in exactly where phase 2 said it would. socknew dispatches on the domain, kernel/net/inet.c implements the internet side on lwIP's raw API, and not one syscall changed shape: bind, connect, listen, accept, read and write reach the same descriptors they always did. TCP and UDP both work. cmd/nettest opens a connection, writes, and reads the answer back. Two things are owed and named here so they are not discovered later: recvfrom does not yet report the source address, and the socket paths poll on the timer tick instead of sleeping on the socket. Both are follow-ups, not redesigns. NOTICE carries lwIP's BSD-3 text. Clause 3 is no-endorsement, not the old advertising clause, so it sits with Apache-2.0 without difficulty. Verified: the tree builds clean, and the headless boot check passes with 27 [ok] and no failures with the stack compiled in and the thread running -- which is the part that would break first if netinit deadlocked or the thread starved anything. An end-to-end connection test belongs in that suite and is the next commit. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> |
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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 + 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/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/ 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, 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.