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SubjectRe: [PATCH v2 07/15] x86/lib/copy_user_64.S: Convert to ALTERNATIVE_2

* Borislav Petkov <bp@alien8.de> wrote:

> > 2) in the future: we could actually do a (limited) re-link of the
> > kernel during bootup, and patch up the original copy_to_user call
> > sites directly to one of the three variants. Alternatives patching
> > done at the symbol level. Does current tooling allow something
> > like this already?
>
> Well, I have a patchset which uses relocs to patch vmlinux at build
> time. And that was the initial approach to this but you cannot know
> which features a CPU supports until boot time so you have to boot.
>
> BUT(!), you can replace stuff like X86_FEATURE_ALWAYS at build time
> already (this is the static_cpu_has_safe() stuff). I'll look into
> that later and dust off my relocs pile.

We could also do a (limited) relink during early bootup, as part of
the alternatives patching pass in essence: for that we need to stick
the relocation info into a section and put that into the vmlinux.

Thanks,

Ingo


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