| Filename | Latest commit message | Latest commit date |
|---|---|---|
bcd4d4e2bd
Two reports, and the first one was not an F8 bug at all.
**Choosing "Boot SchOS (verbose)" appeared to do nothing.** The menu worked,
the flag crossed, and the kernel really did boot verbose -- and then the
machine *reset* partway through and the second boot was quiet. So what anybody
ended up looking at was an ordinary boot, which reads as "verbose is broken".
PROBE before startothers, ncpu=2 <- verbose boot
SchOS UEFI loader <- the firmware, again
PROBE before startothers, ncpu=2 <- quiet boot
PROBE after startothers
mpmain() opened with
kinfo("cpu%d: starting\n", cpunum());
enable_sse();
idtinit();
and the order is the bug. enable_sse() clears CR0.EM; until it runs, *any* SSE
instruction on that CPU faults, and the kernel is not built with -mno-sse, so
the compiler emits them freely for struct copies and inline memset. idtinit()
loads that CPU's IDT; until it runs there is nowhere for a fault to go. So the
#UD is not a panic -- it is a double fault with no handler, then a triple
fault, then the firmware comes back up. A triple fault prints nothing, which is
why there was no last line to go on.
**Why only on a verbose boot**, which is what disguised it as an F8 problem:
kinfo() is log-only when the boot is quiet, so the work is a few bytes into a
ring and no XMM is involved. A verbose boot renders that same line through the
TrueType rasteriser, and that is where the SSE lands.
Setup first, announcement second. The general rule, stated where the next
person will meet it: a processor announces that it is up after it is able to
run, not before.
Verbose now boots once and puts the whole log on the screen -- `verbose boot:`
lines, `cpu1: starting`, the mount, `schinit: ready`, the jobs starting -- which
is what F8 was for and what a machine with no serial port needs.
**And vgpud drew a test card.** Three colour bands, four gradients, a
checkerboard, and the driver's own pid in binary along the bottom edge. That
was scaffolding for hybrid.md's H2 and H3: a screenshot had to answer "did a
*userspace process* put this here", and "did the driver come back" needed a
restarted instance to look different from one that never stopped. Both
milestones closed a while ago and the test card stayed, so a second display
showed something garish with nothing to explain it.
It draws the Shift mark on SCH_BG now, from the same include/logo.h the loader
splash and the kernel console use. That answers the same question a black
screen cannot -- something is driving this device -- as the system rather than
as a test rig.
Also: vgpud's "no control socket" line is vputs, not puts. It is progress, not
news, and it was printing on the console of every quiet boot.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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| .. | ||
| architecture | ||
| branding | ||
| guides | ||
| history | ||
| plan | ||
| Website | ||
| licensing.md | ||
| README.md | ||
SchOS documentation
Four kinds of document, kept in four directories, because they answer four different questions and go stale at four different rates.
| architecture/ | What SchOS is | Present tense. Describes what is built and working. |
| plan/ | What SchOS will be | Future tense. Everything here is unbuilt. |
| guides/ | How to work on it | Imperative. Build it, test it, add to it. |
| history/ | Why it is the way it is | Past tense. Bugs whose cause is not visible from the fix. |
Plus two that belong to no category and apply to everything: licensing.md — read it before copying anyone else's code in — and branding/, which holds the marks and the rules for using them.
The rule that keeps this from rotting
When something is finished, it moves from
plan/toarchitecture/and is rewritten as a description of the thing rather than a record of building it.
A completed item is not a ticked checkbox. A ticked checkbox says the work happened; it does not say what the work produced, and six months later the checkbox is the only thing left and it explains nothing.
So finishing a piece of work has three steps, and the third is not optional:
- The code works and is tested.
- The plan entry is deleted.
- A description exists in
architecture/written for somebody who was not there — what it does, what shape it has, what it costs, and what it still does not do.
This is not bookkeeping. The tree has already proved it necessary: the network stack was finished, verified end to end, and for a month afterwards the only description of it anywhere was a checkbox in a roadmap, four levels of indentation deep, written in the past tense of somebody arguing for the work rather than explaining the result.
The "what it does not do" section is the one that pays. Every description in
architecture/ ends with one. A document that only lists a subsystem's
strengths is marketing, and the reader who most needs the document is the one
about to trip over a limitation nobody wrote down.
Start here
New to the tree → architecture/README.md, the system layer by layer, then guides/layout.md for where the files are.
Trying to build it → guides/building.md.
Wondering what happens next → plan/1.0.md, which is the finish line and the register of everything half-built. Then plan/README.md for the order.
About to start something new → the register, first. Nothing new starts while it has rows in it, and a row leaves only by being finished or deleted.
Something is broken and it feels familiar → history/. There is a good chance it is in there.
architecture/ — what SchOS is
| README | The system, layer by layer. Read first. |
| boot.md | Firmware to the first userspace process. |
| kernel.md | SchIFT: memory, processes, scheduling, traps, signals, SMP. |
| syscalls.md | The call table, and the Linux personality that lets real software run. |
| filesystem.md | The VFS, the buffer cache, procfs, mounts. |
| schfs.md | SchFS: the copy-on-write root filesystem. |
| devices.md | The device model, driver binding, the class vtables. |
| usb.md | xHCI, the USB core, and the class drivers. |
| graphics.md | Framebuffer, text rendering, console, and the crash screen. |
| terminals.md | The six virtual terminals, and how one is switched to. |
| networking.md | Drivers, lwIP, sockets — Unix and INET. |
| init.md | schinit, PID 1 as a role, and the job manifests. |
plan/ — what SchOS will be
| README | The three current decisions and the order they happen in. |
| 1.0.md | The finish line, and the freeze. What 1.0 contains, what is deferred, and the register of every half-built thing in the tree. |
| foundations.md | The kernel work everything else is blocked on. |
| wayland.md | The GUI stack, and what gets deleted to make room. |
| hybrid.md | Moving drivers out of the kernel. |
| schapi.md | The long-term API layering, and the compatibility promise. |
| roadmap.md | Everything else still open. |
guides/ — how to work on it
| building.md | Prerequisites and the build, per host. |
| testing.md | The harnesses, and what each one actually proves. |
| layout.md | Repository map, and how to add a program or a port. |
| adding-a-driver.md | Writing one, binding it, publishing its class vtable. |
branding/ — the marks
| README | Shift, the one mark: what it is for, the colour rule, why an icon and a mascot were removed, and why a raster is committed next to its SVG. |
history/ — why it is the way it is
| README | What belongs in here and what does not. |
| kernel.md | Bugs whose cause was nowhere near their symptom. |
| schfs.md | The filesystem's own, from the same period as its design. |
| moving-to-linux.md | The Windows-to-Fedora move, kept for the parts that recur. |
Writing one of these
Four conventions, all of them observable in the existing files:
State the cost. Every design choice gave something up. A document that does not say what is a document that will be argued with later by somebody who only sees the downside.
Prefer the measured number to the remembered one. "500 of 3565 files carry the advertising clause" is worth more than "some do", and it was worth the minute it took to count.
Write down the bug that shaped it. Half the non-obvious code in this tree is non-obvious because something failed once. If a design is strange, the strangeness is load-bearing and the reader deserves to know why before changing it.
No dates in headings. A date in a heading turns a description into a
changelog, and the description is the thing with a long life. Dates belong in
history/, where they mean something.