linux-kernel - Re: [linux-pm] intermittent suspend problem again

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Date:	Wed, 02 Dec 2009 02:58:41 +0100
From:	Ferenc Wagner <wferi@...f.hu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	linux-pm@...ts.linux-foundation.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [linux-pm] intermittent suspend problem again

"Rafael J. Wysocki" <rjw@...k.pl> writes:

> On Tuesday 01 December 2009, Ferenc Wagner wrote:
>
>> "Rafael J. Wysocki" <rjw@...k.pl> writes:
>> 
>>> On Tuesday 01 December 2009, Ferenc Wagner wrote:
>>>
>>>> "Rafael J. Wysocki" <rjw@...k.pl> writes:
>>>>
>>>>> In addition to that, you can run multiple hibernation/resume cycles in
>>>>> a tight loop using the RTC wakealarm.
>>>> 
>>>> I'll do so, as soon as I find a way to automatically supply the dm-crypt
>>>> passphrase... or even better, learn to hibernate to ramdisk from the
>>>> initramfs. :)
>>>
>>> Well, you don't need to use swap encryption for _testing_. :-)
>> 
>> I use partition encryption, everything except for /boot is encrypted.
>
> If /boot is big enough, you could use a swap file in /boot for the testing.

Ramdisk worked good.  Maybe too good, because I left the machine doing
s2disks while I was having dinner, and it achieved some 120 suspends
without a freeze.  Only the e100 and the mii modules were loaded.

After some script munging I got the machine automatically boot with an
alternate passphrase, so in vivo testing is possible now.  I mean,
tomorrow.

Btw. s2disk has a strange effect of simulating enters during suspend.
It looks like this in a terminal:

$ sudo s2disk



















$ 
$ 
$ 
$ 
$ 
$ 
$ 
$ 
$ 
$ 
$ 
$ 
$ 
$ 
$ 
$ 
$ 
$ 
$ 
$ <cursor is here>

Can you also see this?

>> Apropos: does s2disk perform encryption with a temporary key even if I
>> don't supply and RSA key, to protect mlocked application data from being
>> present in the swap after restore?
>
> It can do that, but you need to provide a key during suspend and resume.
>
> Otherwise it doesn't use a random key, because it would have to store it in
> the clear in the image header.

So you don't feel like the "What is this 'Encrypt suspend image' for?"
Q&A in Documentation/swsusp.txt describes a real threat, do you?  If
an "application" has direct access to swap, then it's game over anyway.
-- 
Thanks,
Feri.
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