linux-kernel - Re: [PATCH] RTC: Add an alarm disable quirk

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 19 Jul 2013 17:13:21 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	John Stultz <john.stultz@...aro.org>
Cc:	LKML <linux-kernel@...r.kernel.org>, Jiri Kosina <jkosina@...e.cz>,
	Borislav Petkov <bp@...e.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Rabin Vincent <rabin.vincent@...ricsson.com>
Subject: Re: [PATCH] RTC: Add an alarm disable quirk

On Fri, Jul 19, 2013 at 04:26:28PM +0200, Borislav Petkov wrote:
> On Fri, Jul 19, 2013 at 12:53:49AM +0200, Borislav Petkov wrote:
> > > I assumed it was some sort of BIOS issue where any modification of the
> > > RTC_AIE bit caused the alarm irq line to be left high(or something
> > > like that) that triggered the immediate power-on on shutdown. But I've
> > > not been able to dig down on this.
> > 
> > Ha, this actually fits like an ass on a bucket (don't ask - German
> > proverb :-)).
> > 
> > If what you're saying is actually the case, then this explains why not
> > writing to 0xb doesn't cause the alarm irq to fire.
> > 
> > Btw, in the trace above we do the disabling twice. Once from
> > rtc_timer_remove() and then again from rtc_timer_do_work().
> > 
> > So, if we disable it once and we touch RTC_AIE again causing the second
> > time to rearm the alarm irq, this would explain the issue. Which reminds
> > me:
> > 
> > Maybe we should read out the alarm interrupt first and disable it only
> > if it is enabled - that would save us the modification of RTC_AIE. Cool,
> > I'll try that tomorrow.
> 
> Well, the below seems to do the trick. But since I don't trust the BIOS
> in any way, I'll run it a couple more days here. Btw, I think we should
> commit this regardless, as it saves us unneeded writes:

Nope, this doesn't help - box just rebooted. :(

So I'm back to the DMI quirk patch...

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
--
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/