[PATCH] UBUNTU: SAUCE: dove: avoid page table overwrite when resuming from hibernation

[Nigel Cunningham]

Hi Rafael.

On 28/05/10 09:29, Rafael J. Wysocki wrote:
> On Thursday 27 May 2010, Nigel Cunningham wrote:
>> Hi.
>>
>> On 28/05/10 01:35, Tim Gardner wrote:
>>> Test results in the LP report look good. Has this patch been upstreamed?
>>> I cannot remember from the original discussions a few weeks ago.
>>
>> I noticed this thread last night and brought it to Rafael's attention,
>> because I don't remember seeing anything like this before.
>
> I'm not sure what patch is being referred to.  Any details, please?

Sorry - I thought I gave you the url to the bug report in my previous email.

http://bugs.launchpad.net/bugs/509006

To quote from the patch Ubuntu is applying:

Resuming from hibernation is OK if 'resume=/dev/sdaX' is explicitly
specified on the kernel command line, but it fails if scripts in
initramfs are used to trigger the resume. It turned out to be page
table being overwritten when restoring the memory content because
it's using a normal user process's page table in the latter case,
which is not safe and could be overwritten. Fix this by using the
safe swapper_pg_dir during restoring.

It's an arm specific fix (touching arch/arm/mach-dove/swsusp.S and the 
Makefile in the same directory) but I wondered whether this might in any 
way be relevant to vanilla. Perhaps there's something more generic, like 
a failure to set KERNEL_DS in that code path that might be a more 
correct fix and might also be relevant to other architectures. (Not that 
I've seen any failures with x86/x86_64) from an initramfs). Hmm - could 
be. I explicitly set KERNEL_DS in TuxOnIce, but don't see it done 
anywhere (from a quick check) in vanilla.

Regards,

Nigel