Messages in this thread | | | Date | Thu, 5 Mar 2015 01:32:49 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH v2 07/15] x86/lib/copy_user_64.S: Convert to ALTERNATIVE_2 |
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* 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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