linux-kernel - Re: [PATCH RFC] Watchdog: sbsa

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:	Thu, 5 May 2016 09:43:00 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Timur Tabi <timur@...eaurora.org>
Cc:	Pratyush Anand <panand@...hat.com>, fu.wei@...aro.org,
	Suravee.Suthikulpanit@....com, wim@...ana.be,
	linux-arm-kernel@...ts.infradead.org,
	linux-watchdog@...r.kernel.org,
	open list <linux-kernel@...r.kernel.org>,
	Dave Young <dyoung@...hat.com>
Subject: Re: [PATCH RFC] Watchdog: sbsa_gwdt: Enhance timeout range

On Wed, May 04, 2016 at 11:17:29AM -0500, Timur Tabi wrote:
> Pratyush Anand wrote:
> >Its unique to SBSA because you have very little timeout here. kexec-tools
> >upstream does not have any mechanism to handle watchdog timeout. Lets say even
> >if we implement a framework there, the best it can do is to ping the watchdog
> >again.
> 
> Ok, so it's more accurate to say that kexec has a minimum watchdog timeout
> requirement.  What happens if the system admin sets the timeout to 5 seconds
> arbitrarily?  The system will reset during kexec, no matter which hardware
> is used.
> 
> This still sounds like a band-aid to me.  We're just assuming that we need a
> timeout of at least 20 seconds to support kexec.  Frankly, this still sounds
> like a problem the kexec developers needs to acknowledge and deal with.
> 
> Still I'm okay with a patch that extends the timeout by programming WCV, but
> it has to be commented as a hack specifically to support kexec because the
> timeout might be too short.  Then Wim can decide whether he supports such
> changes.
> 
I don't even understand how kexec-tools is involved in the first place.
kexec-tools sounds like user space, which should execute _after_ the kernel
and its modules are loaded (assuming modules are loaded from initramfs).
If kexec-tools can somehow ping the watchdog (presumably by writing into
the HW directly), I don't understand why it doesn't simply load the watchdog
driver instead and let the watchdog core handle the heartbeats.

I am really missing something here. How can kexec-tools do anything before
the kernel is loaded ?

Guenter