linux-kernel - Re: Revert commit 5dcd14ecd4 - breaks EFI boot with SLES11 elilo.efi

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Date:	Wed, 6 Mar 2013 12:36:34 -0500
From:	Josh Boyer <jwboyer@...il.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Yinghai Lu <yinghai@...nel.org>, Robin Holt <holt@....com>,
	hpa@....com, linux-kernel@...r.kernel.org, pjones@...hat.com
Subject: Re: Revert commit 5dcd14ecd4 - breaks EFI boot with SLES11 elilo.efi

On Wed, Mar 6, 2013 at 12:26 PM, H. Peter Anvin <hpa@...or.com> wrote:
> On 03/06/2013 08:53 AM, Josh Boyer wrote:
>>
>> I don't think this is limited to elilo.  I have a UEFI machine booting
>> with grub2 that also fails to boot because of this patch.  I was in the
>> middle of bisecting when I found this thread and if I revert 5dcd14ecd4
>> the machine boots again.  Put that commit back in and it doesn't.  We've
>> had three other reports in Fedora of similar cases.
>>
>> I discussed this with Peter Jones this morning.  He was looking into what
>> grub2 does for boot_params and it seems to be read-modify-write instead
>> of clearing the whole thing.  (CC'd Peter now.)
>>
>> The patch for elilo probably works, but if grub2 is hitting this then I'm
>> curious if most bootloaders will.  I'll finish my bisect just to be extra
>> sure, but something probably needs to be done in a more generic fashion
>> here.
>>
>
> Come to think about it...
>
> The EFI field actually has a magic, unless just about all the rest of
> them, so clearing it is probabilistically redundant; in other words we
> almost certainly should exclude it from the clearing, unconditionally.
>
> Does the "elilo" patch made unconditional work for you?

Something like this?

Index: linux-2.6/arch/x86/include/asm/bootparam_utils.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/bootparam_utils.h
+++ linux-2.6/arch/x86/include/asm/bootparam_utils.h
@@ -20,8 +20,11 @@ static void sanitize_boot_params(struct
 	if (boot_params->sentinel) {
 		/*fields in boot_params are not valid, clear them */
 		memset(&boot_params->olpc_ofw_header, 0,
-		       (char *)&boot_params->alt_mem_k -
+		       (char *)&boot_params->efi_info -
 			(char *)&boot_params->olpc_ofw_header);
 		memset(&boot_params->kbd_status, 0,
 		       (char *)&boot_params->hdr -
 		       (char *)&boot_params->kbd_status);

I can try that in a bit.

josh
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