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

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Date:	Fri, 29 Aug 2008 11:24:44 +0100 (BST)
From:	Hugh Dickins <hugh@...itas.com>
To:	Rafał Miłecki <zajec5@...il.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

> 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;
 		}
 	}