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

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Date:	Fri, 29 Aug 2008 07:08:18 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Hugh Dickins <hugh@...itas.com>
CC:	Rafał Miłecki <zajec5@...il.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	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

Hugh Dickins wrote:
> 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)) {
>   

Oops, yes.

>  			if (!*addr)
>  				continue;
>  			printk(KERN_ERR "Corrupted low memory at %p (%lx phys) = %08lx\n",
>  			       addr, __pa(addr), *addr);
> +			*addr = 0;
>   

Good idea.

>  			corruption = 1;
>  		}
>  	}


    J
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