linux-kernel - Re: [PATCH 0/2][concept RFC] x86: BIOS-save kernel log to disk upon panic

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Message-ID: <20110203143644.GA4085@ucw.cz>
Date:	Thu, 3 Feb 2011 15:36:45 +0100
From:	Pavel Machek <pavel@....cz>
To:	Tejun Heo <tj@...nel.org>
Cc:	Ingo Molnar <mingo@...e.hu>,
	"Ahmed S. Darwish" <darwish.07@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, X86-ML <x86@...nel.org>,
	Tony Luck <tony.luck@...el.com>, Dave Jones <davej@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Randy Dunlap <rdunlap@...otime.net>,
	Willy Tarreau <wtarreau@...a.kernel.org>,
	Willy Tarreau <w@....eu>, Dirk Hohndel <hohndel@...radead.org>,
	Dirk.Hohndel@...el.com, IDE-ML <linux-ide@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Fr?d?ric Weisbecker <fweisbec@...il.com>,
	Borislav Petkov <bp@...en8.de>,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: [PATCH 0/2][concept RFC] x86: BIOS-save kernel log to disk
 upon panic

Hi!

> > I think the biggest areas of practical concern would be:
> > 
> >  - Can this mechanism ever, under any circumstance corrupt any real
> >    data, destroy the MBR or do other nasties. Can you think of any
> >    additional fail-safe measures where you could _further robustify
> >    the BIOS calls_ to make sure it can never go to the wrong
> >    sector(s)? I really do not want to think of trusting a BIOS to
> >    _write to my disk_.
> 
> It's quite unlikely but I wouldn't say it's completely impossible.
> It's common for ATA controllers to have dual modes of operation - the
> old IDE compatible interface by emulation which is used by BIOS and
> older operating systems and newer interface (ahci) to be used by
> modern OS.  Some need to be explicitly switched and some just need to
> be accessed carefully.  If the controller is accessed by bIOS after
> switched to ahci or commands are in progress via ahci, anything can
> happen.

Could we read the log area, first, verify it contains signature, write
it back?
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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