linux-kernel - Re: [PATCH v15 13/25] x86/reboot: Add ljmp instructions to stacktool whitelist

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Date:	Fri, 15 Jan 2016 12:13:45 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Josh Poimboeuf <jpoimboe@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, live-patching@...r.kernel.org,
	Michal Marek <mmarek@...e.cz>,
	Peter Zijlstra <peterz@...radead.org>,
	Andy Lutomirski <luto@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Pedro Alves <palves@...hat.com>,
	Namhyung Kim <namhyung@...il.com>,
	Bernd Petrovitsch <bernd@...rovitsch.priv.at>,
	Chris J Arges <chris.j.arges@...onical.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Slaby <jslaby@...e.cz>,
	Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: [PATCH v15 13/25] x86/reboot: Add ljmp instructions to stacktool
 whitelist


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

> On Fri, Jan 15, 2016 at 12:00:00PM +0100, Ingo Molnar wrote:
> > All of the cases Josh listed involve some sort of special case where we do 
> > something non-standard. (Where 'standard' == 'regular kernel C function'.)
> 
> My only worry is that next time we have to do something non-standard,
> we'll have to annotate it as well. bpf_jit case-in-point.

but that's generally OK: it's not a problem if something non-standard is visibly 
non-standard on the source code level as well.

> OTOH, I guess the generic, tool-agnostic annotation could be a step in the 
> (more-)right direction as we're saying "we're doing something special here, and 
> we're stating that fact with this here annotation."

Yeah, I think so too!

Thanks,

	Ingo