linux-kernel - Re: [PATCH] Add a text

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Message-ID: <5298F66A.2010600@zytor.com>
Date:	Fri, 29 Nov 2013 12:17:46 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Oleg Nesterov <oleg@...hat.com>, Andi Kleen <andi@...stfloor.org>
CC:	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	x86@...nel.org, Andi Kleen <ak@...ux.intel.com>,
	Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH] Add a text_poke syscall v2

On 11/29/2013 12:05 PM, Oleg Nesterov wrote:
> 
> Can't we invalidate pte (so that any user will stuck in page fault),
> update the page(s), restore the pte and drop the locks?
> 

That would require a global TLB shootdown (and wouldn't help
shared-memory code segments, if we care about that at all.)  It also
means much bigger code ranges would be affected.

The performance requirements are part of what makes the INT3 solution
attractive, but anything is going to inherently be slow.

> This way sys_text_poke() won't be x86-specific, and it will be per-mm.

That is definitely an appeal.

	-hpa


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