Re: [PATCH v1 00/12] x86, alternatives: Instruction padding and more robust JMPs

From: Ingo Molnar
Date: Wed Feb 18 2015 - 16:20:25 EST

* Borislav Petkov <bp@xxxxxxxxx> wrote:

> From: Borislav Petkov <bp@xxxxxxx>
> [ Changelog is in version-increasing number so that one can follow the
> evolution of the patch set in a more natural way (i.e., latest version
> comes at the end. ]
> v0:
> this is something which hpa and I talked about recently:
> the ability for the alternatives code to add padding to
> the original instruction in case the replacement is
> longer and also to be able to simply write "jmp" and not
> care about which JMP exactly the compiler generates and
> whether the relative offsets are correct.
> So this is a stab at it, it seems to boot in kvm here but
> it needs more staring to make sure we're actually
> generating the proper code at all times.

Ok, this looks really cool.

Do you have any stats about how many such (affected) patch
sites we have in say the 64-bit defconfig kernel?

I.e. what's the scope of this optimization?


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