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

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Date:	Fri, 29 Aug 2008 08:20:30 +0200
From:	"Rafał Miłecki" <zajec5@...il.com>
To:	"Jeremy Fitzhardinge" <jeremy@...p.org>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	"Alan Jenkins" <alan-jenkins@...fmail.co.uk>,
	"Hugh Dickens" <hugh@...itas.com>,
	"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

2008/8/28 Jeremy Fitzhardinge <jeremy@...p.org>:
> Some BIOSes have been observed to corrupt memory in the low 64k.  This
> patch does two things:
>  - Reserves all memory which does not have to be in that area, to
>   prevent it from being used as general memory by the kernel.  Things
>   like the SMP trampoline are still in the memory, however.
>  - Clears the reserved memory so we can observe changes to it.
>  - Adds a function check_for_bios_corruption() which checks and reports on
>   memory becoming unexpectedly non-zero.  Currently it's called in the
>   x86 fault handler, and the powermanagement debug output.
>
> RFC: What other places should we check for corruption in?
>
> [ Alan, Rafał: could you check you see:
>   1: corruption messages
>   2: no crashes
>  Thanks -J
> ]

I was trying my best to crash system with this patch applied and failed :)

Works great.

Just wonder if I should expect any printk from
check_for_bios_corruption? I do not see any:

zajec@...y:~> dmesg | grep -i corr
scanning 2 areas for BIOS corruption

-- 
Rafał Miłecki