Re: git: 3915ffb1c3e0 - main - loader.efi: Fix when staging moves late

On Sat, 6 Jun 2026, Warner Losh wrote:

> The branch main has been updated by imp:
>
> URL: https://cgit.FreeBSD.org/src/commit/?id=3915ffb1c3e04b26d1506bf35d3f665b2e25a915
>
> commit 3915ffb1c3e04b26d1506bf35d3f665b2e25a915
> Author:     Warner Losh <imp@FreeBSD.org>
> AuthorDate: 2026-06-05 05:18:40 +0000
> Commit:     Warner Losh <imp@FreeBSD.org>
> CommitDate: 2026-06-06 01:24:42 +0000
>
>    loader.efi: Fix when staging moves late
>
>    Prior to this commit, we'd compute the page tables and have the last
>    entries point to the staging area. We'd then add some more metadata to
>    the image and boot. This assumed the staging area didn't need to move
>    for this last bit of data.
>
>    However, if we go over the staging limit, when we copyin new data, we
>    grow the staging area, usually be moving it to a lower address.  This
>    overage usually happens when we're loading modules and so things work
>    out nicely. Sometimes we're close to the limit, and we need to do this
>    growing inside bi_load, after we've computed the page table, making the
>    page table wrong, and the code we jump to random rather than the btext
>    routine we normally start at.
>
>    To fix this, move computation of the table (but not its allocation) to
>    after bi_load, but before we call the trampoline.
>
>    This problem was most observed when loading microcode for many peole,
>    but Gleb reproduced the error with a set of modules that didn't include
>    ucode.

I looked through the PR (not all of it) and I have seen little explanations
of how this bug was observed as a user, as in how far did the boot process get
(possibly with beasty disabled).

The reason I am asking is that I am wondering if the various occasions where
people in the last years have seen "Booting [/boot/kernel/kernel]...", possibly
"Loading splash ok" but never saw the boot marker "---<<BOOT>>---" (or any
things in between) anymore could have been the same bug?


>    PR: 294630
>    Reviewed by: kib (prior version)
>    Sponsored by: Netflix
>    MFC After: insta per re@ request
>    Differential Revision: https://reviews.freebsd.org/D57462

-- 
Bjoern A. Zeeb                                                     r15:7