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

Alan Jenkins
2008-08-29T12:09:33Z

Rafał Miłecki wrote:
> 2008/8/29 Hugh Dickins <hugh@veritas.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