linux-kernel - Re: [PATCH RFC] x86: check for and defend against BIOS memory corruption

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Date:	Fri, 29 Aug 2008 13:09:18 +0100
From:	Alan Jenkins <alan-jenkins@...fmail.co.uk>
To:	Rafał Miłecki <zajec5@...il.com>
CC:	Hugh Dickins <hugh@...itas.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Yinghai Lu <yhlu.kernel@...il.com>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC] x86: check for and defend against BIOS memory corruption

Rafał Miłecki wrote:
> 2008/8/29 Hugh Dickins <hugh@...itas.com>:
>   
>>> On Fri, 29 Aug 2008, Rafał Miłecki wrote:
>>>
>>> Out of current discussion I tried using s2ram on patched kernel (I did
>>> not try s2ram earlier, my problem was (un)plugging HDMI - some ACPI
>>> code probably).
>>>
>>> Corruption output is quite huge, I attached it to bug report:
>>> http://bugzilla.kernel.org/show_bug.cgi?id=11237
>>> http://bugzilla.kernel.org/attachment.cgi?id=17526
>>>       
>> Not quite the output we were expecting!  I've not got around to trying
>> it yet, so beware, but I think Jeremy's patch needs the following on top.
>> Or you may prefer to wait until one of us reports that it is now working
>> as intended.
>>
>> --- a/arch/x86/kernel/setup.c   2008-08-29 11:17:16.000000000 +0100
>> +++ b/arch/x86/kernel/setup.c   2008-08-29 11:19:24.000000000 +0100
>> @@ -636,11 +636,12 @@ void check_for_bios_corruption(void)
>>                unsigned long *addr = __va(scan_areas[i].addr);
>>                unsigned long size = scan_areas[i].size;
>>
>> -               for(; size; addr++, size--) {
>> +               for(; size; addr++, size -= sizeof(unsigned long)) {
>>                        if (!*addr)
>>                                continue;
>>                        printk(KERN_ERR "Corrupted low memory at %p (%lx phys) = %08lx\n",
>>                               addr, __pa(addr), *addr);
>> +                       *addr = 0;
>>                        corruption = 1;
>>                }
>>        }
>>     
>
> I tried your patch anyway (after applying Jeremy's patch of course)
> and it doesn't seem to work. The only output is:
> scanning 2 areas for BIOS corruption
> after using s2ram. I do not get any
> Corrupted low memory at*
>   
It seemed to work for me.  Did you remember to plug HDMI to trigger the
corruption before you used s2ram?

[   71.663828] Back to C!
[   71.663828] Corrupted low memory at ffff8800000083e8 (83e8 phys) =
803c85370cfc0000
[   71.663828] Corrupted low memory at ffff8800000083f0 (83f0 phys) =
00003000
[   71.663828] Pid: 7335, comm: pm-suspend Not tainted
2.6.27-rc4-00216-ge1c9c9d-dirty #152
[   71.663828]
[   71.663828] Call Trace:
[   71.663828]  [<ffffffff8020fdd5>] check_for_bios_corruption+0xb5/0xd0
[   71.663828]  [<ffffffff803a3e1a>] pm_dev_dbg+0x2a/0xa0
[   71.663828]  [<ffffffff803a49c2>] dpm_power_up+0x32/0xf0

Alan
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