linux-kernel - Re: [PATCH 3/4] EFI: Add support for variables longer than 1024 bytes

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Date:	Wed, 14 Dec 2011 14:44:34 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Matthew Garrett <mjg59@...f.ucam.org>
CC:	Mike Waychison <mikew@...gle.com>, linux-kernel@...r.kernel.org,
	x86@...nel.org
Subject: Re: [PATCH 3/4] EFI: Add support for variables longer than 1024 bytes

On 12/14/2011 02:39 PM, Matthew Garrett wrote:
> 
>> We need to be careful here.  The store_raw ABI is broken, in the sense
>> that the ABI from compat mode differs from that in 32bit mode (there
>> is a long in the efi_variable structure which changes the offsets).  I
>> don't know how to fix it properly and still maintain proper ABI
>> compatibility.
> 
> True.
> 
>> What are your thoughts on _not_ wrapping efi_variable with
>> extended_efi_variable, and instead just using a
>> "internal_efi_variable" structure that we copy stuff into/outof.  I
>> think that would make the memory management for dealing with the
>> different sizes a lot easier to follow.
> 
> Hm. I think that'd only work if we expose a new interface. Writes would 
> be easy enough to handle, but reads still need to work for old apps.
> 

Would making the old ABI readonly and add a new write interface resolve
the problem with compat mode?

	-hpa
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