Andreas K. Huettel posted on Fri, 15 Mar 2024 19:12:54 +0100 as excerpted:

Note 3: amd64 now has CET turned on by default. https://docs.kernel.org/next/x86/shstk.html If you have already used the unannounced 23.0 profiles, you should wipe your package cache and emerge
-ev world now.

There's not much about CET in any of the links. While the kernel.org link describes what it does (in a line, "yese": yet another security
enhancement) a bit, it doesn't say how to actually find whether your
hardware supports it, and the gentoo wiki and bug links say even less --
in particular, unless I missed it, the changes and update instructions
links don't appear to mention CET or shadow-stacks AT ALL.

What I ended up doing here after some DDG googling, was emerging cpuid,
then doing:

$$ cpuid -1 | grep -i 'cet\|shadow'
CET_SS: CET shadow stack = false
CET_IBT: CET indirect branch tracking = false
CET_U user state = false
CET_S supervisor state = false
supervisor shadow stack = false

With all of those false it would seem CET can't work here in any case so there's no point rebuilding again, which is what I already suspected but
wanted to /know/. (I've been on a 23.0 merged-usr profile[1] for some
time now as I already had much of what it does already enabled before the
new profiles were announced here, so it /would/ be "rebuilding again" to
get that, but as it seems it won't do anything useful anyway...)

Clearer instructions for finding that out (and preferably what actually
has to be true, I still don't know that for sure) so others don't have to google it, could be useful.

---
[1] Already on a merged-usr profile: Of course including developing an auto-applied-on-update patch to do s:[[ ! -h "${EROOT%/}/bin" ]]:false: to
the profile bashrc after that test was added, because I am indeed usr-
merged (on systemd) here but that test fails because the operating symlink
is /usr -> . instead, aka reverse-usrmerge. Tho making the canonical
path /realbin and doing /bin -> /realbin would appear to satisfy the test
too, and would allow me to avoid patching the profile bashrc, but at least here, having /bin be the system's real bin location is part of the _point_
of a reverse-usrmerge.

--
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"Every nonfree program has a lord, a master --
and if you use the program, he is your master." Richard Stallman

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