3182da3965
Claude Code keeps per-project memory at <home>/.claude/projects/<key>/,
where <key> is the project's absolute path with every separator and the
drive colon turned into a dash. That makes it both rename-fragile and
machine-specific, and this project has hit each of those once:
- D:\DEV\Schunix -> D:\DEV\SchOS changed the key, and 43 memories were
invisible until moved across by hand.
- Development happens from Windows and from Linux, and each looks in a
different place for the same checkout.
Committing .claude/memory/ fixes both -- git carries it across renames
and between hosts -- and `import` puts it wherever the local machine
expects. .claude/settings.local.json stays ignored: those are per-machine
permissions.
The colon maps to a dash rather than being dropped. Deleting it gives
D-DEV-SchOS, which matches nothing and silently finds zero memories; that
was the first attempt. On Git Bash the key comes from `cygpath -w`,
because Claude Code is a Windows program and sees D:\DEV\SchOS, not
/d/DEV/SchOS.
57 lines
2.6 KiB
Markdown
57 lines
2.6 KiB
Markdown
---
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name: schunix-crash-screen
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description: "PSOGM crash screen lives in kernel/core/panic.c; test it with `echo c > /proc/sysrq` and tools/crashshot.ps1"
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metadata:
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node_type: memory
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type: project
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originSessionId: a665e14b-86bd-4b41-a228-51377f3e9225
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modified: 2026-08-03T15:09:42.189Z
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---
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**The crash screen is `kernel/core/panic.c`** (rewritten 2026-08-03; it used to
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live inside `console.c`). **PSOGM — Purple Screen of Guru Meditation.** Solid
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purple, big white `:(` drawn from primitives, Windows-style left-aligned
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headline and field table, then a raw call-chain dump. Nexoniarz picked this
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after a first attempt that dimmed the desktop and floated a dark panel with a
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cartoon emoji over it — **the emoji and the muted palette read as out of
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place**; the name says purple screen, so it is one.
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A "Stop code" field is derived from the panic message (uppercased up to the
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first colon: `"sysrq: crash requested"` → `SYSRQ`), so no call site has to
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supply one.
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**To see it, crash on purpose:**
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```
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echo c > /proc/sysrq # from inside Schunix
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```
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**To photograph it:** `pwsh -File tools/crashshot.ps1` (or `make crashshot`)
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after `make ramroot`. It boots, fills the screen with real output, crashes,
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and pulls a PPM out through QEMU's monitor on TCP 55555. Convert with
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`convert build/crashscreen.ppm build/crashscreen.png` — ImageMagick is in the
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WSL Fedora box as `convert`, not `magick`.
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Why the trigger exists at all: **the crash screen is the one part of the system
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you cannot look at by using the system**, so without a deliberate trigger it is
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only ever seen when something is already wrong, and it quietly rots.
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**Three things that will bite anyone editing it:**
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- There is no libm. `isqrt` in panic.c uses Newton's method iterated *while the
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estimate decreases*; the obvious "stop when it stops changing" version does
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not terminate, because on a non-square it settles into a two-cycle
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(`isqrt(3)` alternates 1, 2, 1, 2...). That shipped once and hung the panic
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handler with the screen half drawn — a hang with no way to find out why.
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- `vga_draw_char` fills the *background* of every glyph with `vga_bg`. Drawing
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panel text without setting `vga_set_bg(PSOGM_PANEL)` first puts every line in
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a cream-coloured box.
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- `cprintf` writes to the framebuffer as well as the serial line, so the serial
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report scrolls straight over the panel. `cons_panic_mode()` sets
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`cons_serial_only`, which is what keeps the two apart — paint order alone
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does not.
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The serial copy is the one that survives, and it is what `tools/bootcheck.ps1`
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reads. It is also all you get when the panic happens before there is a
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framebuffer. See [[schunix-verify-by-driving-shell]].
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