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

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Date:	Fri, 29 Aug 2008 13:54:46 +0200
From:	"Rafał Miłecki" <zajec5@...il.com>
To:	"Hugh Dickins" <hugh@...itas.com>
Cc:	"Alan Cox" <alan@...rguk.ukuu.org.uk>,
	"Jeremy Fitzhardinge" <jeremy@...p.org>,
	"Yinghai Lu" <yhlu.kernel@...il.com>,
	"Ingo Molnar" <mingo@...e.hu>,
	"Alan Jenkins" <alan-jenkins@...fmail.co.uk>,
	"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

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*

-- 
Rafał Miłecki