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

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Date:	Wed, 18 Feb 2015 22:20:13 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Borislav Petkov <bp@...en8.de>
Cc:	X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 00/12] x86, alternatives: Instruction padding and more
 robust JMPs


* Borislav Petkov <bp@...en8.de> wrote:

> From: Borislav Petkov <bp@...e.de>
> 
>   [ 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?

Thanks,

	Ingo
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