linux-kernel - Re: [patch 07/15] clocksource: Provide unbind interface in sysfs

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, 29 Apr 2013 18:11:03 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Magnus Damm <magnus.damm@...il.com>
Subject: Re: [patch 07/15] clocksource: Provide unbind interface in sysfs

On 04/25/2013 01:31 PM, Thomas Gleixner wrote:
> With the module refcount held for the current clocksource there is no
> way to unload the module.
>
> Provide a sysfs interface which allows to unbind the clocksource. One
> could argue that the clocksource override could be (ab)used to do so,
> but the clocksource override cannot be used from the kernel itself,
> while an unbind function can be used to programmatically check whether
> a clocksource can be shutdown or not.
>
> The unbind functionality uses the new skip current feature of
> clocksource_select and verifies that a fallback clocksource has been
> installed. If the clocksource which should be unbound is the current
> clocksource and no fallback can be found, unbind returns -EBUSY.
>
> This does not support the unbinding of a clocksource which is used as
> the watchdog clocksource. No point in fostering crappy hardware.

So.. if the clocksource you want to unbind is the highest rated 
continuous clocksource that doesn't need a watchdog (basically what's 
likely to be in-use and required to be unbinded), its likely to be 
selected as the watchdog already.

ie: on a system that has only HPET/ACPI_PM, you can't unbind HPET, since 
its a watchdog.

Or are you really wanting to prohibit this functionality for all 
CONFIG_CLOCKSOURCE_WATCHDOG hardware, which would be easier to do via 
build time ifdefs?

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/