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:	Mon, 22 Jul 2013 13:59:01 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	Borislav Petkov <bp@...en8.de>
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 07/19/2013 08:13 AM, Borislav Petkov wrote:
> 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...

So did this work some of the time, but not all? Or was the behavior 
totally unchanged with this?

thanks
-john
--
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/