| Filename | Latest commit message | Latest commit date |
|---|---|---|
fe32833ade
Three fixes for real machines that broke at any resolution but 800x600: - kmain() took the loader's framebuffer address as uint32, and vga_fb_init() re-published the scanout from that and the 16-bit VBE block. An aperture above 4 GB moved the console onto the wrong memory right after the vga: line. Both now use the loader's 64-bit display block, mapped with ioremap(). - The loader mirrored onto the console splitter's GOP, which forwards to the primary itself, and onto GOPs that share the primary's aperture. After a mode change that rewrote the screen over itself with another mode's stride. Handles without a device path and overlapping apertures are skipped, and a mode change re-matches the remaining mirrors. - A mode whose reported size, stride or aperture does not add up after SetMode is refused, and the loader returns to the previous one. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4 |
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| .. | ||
| kernel.md | ||
| moving-to-linux.md | ||
| README.md | ||
| schfs.md | ||
History
Why SchOS is the way it is. Bugs whose cause was nowhere near their symptom, and the few write-ups that have nowhere better to live.
| kernel.md | The expensive ones. Boot, SMP, signals, ABI assumptions, /proc, input. |
| schfs.md | How the filesystem was built, and what each phase cost. |
| moving-to-linux.md | The Windows-to-Fedora move. |
What belongs in here
A bug whose cause is not visible from the code that fixed it.
That is the whole test. If reading the fix explains the problem, the fix is the documentation and nothing needs writing down. If the fix looks arbitrary — a constant moved by eight, a field reordered, a check inverted — then the strangeness is load-bearing and the next person to touch it deserves to know why before they change it back.
Every entry here is a thing that looked like a different problem than it was.
What does not belong
- A changelog.
git logis the changelog. - A bug that was found and fixed in an hour. Cost is the filter.
- How something works. That is ../architecture/, written in the present tense for somebody who does not care what it used to be.
- Anything still open. An unfinished investigation goes in ../plan/ or in the code as a comment. This directory is past tense.
How to write one
Symptom first, then diagnosis, then the fix, then the transferable part.
The transferable part is the reason the entry exists. __thread being wrong for
per-CPU data is worth more than the specific null dereference it caused;
"a layout constant that several artifacts must agree on wants a check that stops
the build, not a comment asking people to remember" is worth more than the
bootloader offset that taught it.
Say how it was found, when the technique was the hard part. A hardware
watchpoint through QEMU's gdb stub named an instruction on the first run after
three rounds of cprintf had narrowed it to nothing — that is reusable, and the
bug is not.
Do not clean up the embarrassing part. The near-miss where a change passed
every assertion green without having been applied at all is one of the most
useful entries in this directory, and it only works because it admits that a
grep returning three hits was read as confirmation without counting what they
were.