d73985633b
Shift is the logo, Guru is the icon, SchCotie is the mascot, and the difference
between them is not stylistic. An icon works once, at one size, in one state. A
mascot has to be able to *do* things -- confused, pleased, asleep, seen from
behind -- which is why it costs more and is drawn last. Written down because
this is exactly the kind of decision that gets re-derived badly.
Assets/ becomes docs/branding/, which also fixes two things:
* Filenames had spaces in them, so every reference needed quoting. They are
lowercase and hyphenated now.
* Assets/ held hand-written SVG and generated PNG in one directory, which is
the one rule docs/guides/layout.md states.
The guide records what was previously only in people's heads:
* The constraint everything answers to -- include/logo.h is a 128x128
single-channel coverage mask, so a mark has to survive as a solid shape in
one colour and be recognisable at 24 px. Colour is the last decision, never
the first.
* Guru's purple is load-bearing. PSOGM_BG #4B1D9A is deliberately not the
accent #7C5CFF, and theme.h's rule is that the full-bleed purple belongs
entirely to failure. If Guru appears in accent violet on a sticker, the deep
purple stops meaning "the machine stopped" -- and it is the only colour in
the system that means anything.
* Why shift-mask.svg is a separate file from shift.svg. mklogo.py reads ink as
(255 - luminance) * alpha, so tones survive as coverage and the relationship
inverts: darkest here is brightest on screen. Copying the violet fills would
light the object from below.
* Why a raster is committed beside its SVG. inkscape is not a build
prerequisite, so requiring a vector rasteriser would break the build on most
hosts for a file that changes about once a year.
* That the BSD daemon is copyrighted and SchCotie must be drawn from the
concept rather than from Beastie. A daemon is a Greek daimon and a Unix
background process; neither is ownable. The pitchfork, the sneakers and that
face are.
Format rule: SVG, or PNG at high resolution with no lossy compression, nothing
else. SVG is the source of truth for every mark and a raster is generated from
it, never edited.
include/logo.h regenerates byte-identical from the new path -- only the source
comment differs. The two old wordmark SVGs were deleted outside this session and
are left deleted; their PNGs are kept as superseded-*.png for reference.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VQ7Qx8E1q1M1bbCq8QLHS2
166 lines
6.9 KiB
Markdown
166 lines
6.9 KiB
Markdown
<div align="center">
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<img src="docs/branding/superseded-full-logo.png" alt="SchOS" width="360">
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**A 64-bit operating system, written from the metal up.**
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SMP · copy-on-write filesystem · TCP/IP · PCI, USB and virtio drivers · TrueType text · Linux syscall ABI
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</div>
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---
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SchOS began as [xv6](https://github.com/mit-pdos/xv6-public) and is now mostly
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something else. The scheduler, the memory manager and the trap path have been
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rewritten for x86-64 and for more than one processor; the filesystem has been
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replaced outright; the syscall table speaks Linux numbering so that real
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software — musl, toybox, mksh — runs unmodified.
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It is a hobby system built by one person, and it is honest about that: what
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works below has been *run*, not inferred, and the gaps are listed as plainly as
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the features.
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## The pieces
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| Layer | Name | What it is |
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|---|---|---|
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| System | **SchOS** | The distribution — kernel, userland, tooling |
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| Kernel | **SchIFT** | Multi-core x86-64 kernel with a modular VFS |
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| Filesystem | **SchFS** | Transactional, copy-on-write, the root filesystem |
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| API | **SchAPI** | System programming interface — the stable surface |
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| Compositor | **SchCom** | Display compositor *(planned)* |
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| Window manager | **SchWM** | *(planned)* |
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| Desktop | **SchDE** | *(planned)* |
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`uname -s` reports `SchIFT`, the way every Unix reports its kernel rather than
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its distribution.
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## What works
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**Kernel** — Long mode, 4-level paging, preemptive multitasking. **SMP**: one,
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two and four processors all boot, with CPU enumeration from the ACPI MADT rather
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than the 1994 MP table. Memory sized from the E820 map, so it runs in tens of
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megabytes rather than demanding hundreds.
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**Filesystem** — **SchFS** is the root: a copy-on-write B-tree with a
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uberblock ring, so a crash leaves either the old tree or the new one and there
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is nothing to repair. Free space is derived from the tree rather than stored
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beside it, which removes a whole class of disagreement. `/proc/schfs` shows the
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generation counter advancing as writes commit.
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**Processes** — fork, exec, wait, pipes, signals, sessions and process groups,
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`mmap` (anonymous and file-backed), POSIX shared memory, Unix domain sockets,
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`poll`.
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**Devices** — PCI enumeration with a bus-agnostic device model at
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`/proc/devices`. Drivers for **e1000** networking, **virtio-gpu** and stdvga
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displays, **xHCI** USB with HID, hub and mass-storage class drivers, IDE, PS/2,
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serial. `/dev/fb0` speaks the Linux fbdev interface.
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**Networking** — ARP, IPv4, ICMP, UDP, TCP and DHCP, on lwIP behind a
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driver-agnostic interface class. Verified end to end from the host, both
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directions, rather than by inspection.
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**Userland** — musl, toybox and mksh, built from source. `ls`, `cat`, `ps`,
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`top`, `wc`, `cp`, `mount` and the rest behave the way you expect, because they
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are the real programs.
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**Text** — a TrueType rasteriser (`glyf` outlines, composite glyphs, cmap
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format 4) replacing the 8×16 cell grid. JetBrains Mono for the terminal, Roboto
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for the desktop layer to come.
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**When it dies** — PSOGM, the Purple Screen of Guru Meditation: stop code,
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fault address, call chain, and a QR code containing a text copy of the whole
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report.
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## Quick start
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```sh
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make # kernel + UEFI loader + root filesystem
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make qemu # build it and boot it
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make iso # a bootable ISO for VMware or real hardware
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```
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Builds on **Linux, macOS, FreeBSD/OpenBSD/NetBSD and Windows** (Git Bash). The
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toolchain is clang + lld everywhere — it is a cross-compiler by construction, so
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one LLVM install targets the bare-metal kernel, the 16-bit boot code and musl
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userland from any host. See **[docs/guides/building.md](docs/guides/building.md)** for
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prerequisites per platform, and
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**[docs/history/moving-to-linux.md](docs/history/moving-to-linux.md)** for moving a checkout
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between machines.
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## Testing
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Booting to a prompt proves nothing: a filesystem can mount and still fail the
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first real command, and that has happened here. So the test harness drives the
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serial console and asserts on what comes back.
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```sh
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tools/windows/bootcheck.ps1 # boot, run real commands, check the answers
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tools/windows/bootcheck.ps1 -Tty -Ps # terminal behaviour, process enumeration
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make schfs-check # SchFS B-tree, object and image suites
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```
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`bootcheck` is PowerShell because `pwsh` runs on every supported host.
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## Layout
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```
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kernel/ arch/ core/ dev/ drivers/ fs/ net/ proc/ sys/
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fs/schfs/ the filesystem -- same source the host tools compile
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include/ kernel and userland headers
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boot/ uefi/ (PE loader) common/ (shared loader UI)
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lib/ cmd/ first-party userland runtime and programs
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ports/ third-party software built from source
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tools/ windows/ (.ps1) posix/ (.sh) python/ (.py) and .c/.pl
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docs/ architecture/ (what it is) plan/ (what's next)
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guides/ (how to work on it) history/ (why it's like this)
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```
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**[docs/README.md](docs/README.md)** is the index. If you are reading the tree
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for the first time, [docs/architecture/README.md](docs/architecture/README.md)
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is the system layer by layer.
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One rule worth knowing: **the kernel and the host tools compile the same SchFS
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source**. `mkschfs` cannot disagree with the kernel about the on-disk format,
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because there is only one implementation — found and fixed on the host, where a
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test takes a second instead of a boot.
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Another: **syscalls are declared in exactly one place**,
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`kernel/sys/table.inc`. Everything else is generated from it.
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## Not there yet
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- **No desktop.** Schcom composites and routes input; the plan is now to put it
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on Wayland and delete the homegrown protocol. See
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[docs/plan/wayland.md](docs/plan/wayland.md).
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- **No descriptor passing.** No `sendmsg`/`recvmsg`, so no `SCM_RIGHTS` — which
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is what the GUI work stops at. [docs/plan/foundations.md](docs/plan/foundations.md).
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- **No dynamic linking.** `exec` handles static `ET_EXEC` only.
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- **No page cache**, so writable `MAP_SHARED` of a file is refused rather than
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faked.
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- **A USB disk cannot be booted from** — the root device is compiled in rather
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than selectable.
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- SchFS has no Linux driver yet; the plan is on-disk format version first, then
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FUSE, then a kernel module.
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- CFF/OpenType outlines and TrueType hinting are deliberately out of scope.
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## Licensing
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**Apache-2.0**, copyright Nexoniarz. See [LICENSE](LICENSE).
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The kernel derives from xv6, which is MIT — see [LICENSE.MIT](LICENSE.MIT).
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Third-party code redistributed in a built image (musl, toybox, mksh, the fonts)
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keeps its own licence; [NOTICE](NOTICE) carries the attributions.
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Drivers may be adapted from BSD sources, which are compatible. Linux drivers are
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not: GPL-2.0-only and Apache-2.0 cannot be combined and redistributed. Reading
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Linux to understand hardware is fine; translating a driver is not. Best of all
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is the public specification — xHCI, virtio, AHCI, e1000 — which carries no
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licence on what you write from it.
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---
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<div align="center">
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<sub>Built with stubbornness and a serial console.</sub>
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</div>
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