linux-kernel - Re: [PATCH v3 1/3] Documentation: arm: add UEFI support documentation

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Message-ID: <20131204224447.GA19265@srcf.ucam.org>
Date:	Wed, 4 Dec 2013 22:44:47 +0000
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	Matt Sealey <neko@...uhatsu.net>
Cc:	Leif Lindholm <leif.lindholm@...aro.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>, linux-efi@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Russell King <linux@....linux.org.uk>, matt.fleming@...el.com,
	Grant Likely <grant.likely@...aro.org>,
	Roy Franz <roy.franz@...aro.org>,
	Mark Salter <msalter@...hat.com>,
	Patch Tracking <patches@...aro.org>,
	linaro-uefi@...ts.linaro.org, Mark Rutland <mark.rutland@....com>,
	Rob Landley <rob@...dley.net>, linux-doc@...r.kernel.org
Subject: Re: [PATCH v3 1/3] Documentation: arm: add UEFI support
 documentation

On Wed, Dec 04, 2013 at 03:06:47PM -0600, Matt Sealey wrote:

> there's no guarantee that the kernel hasn't been decompressed over 
> some important UEFI feature or some memory hasn't been trashed. You 
> can't make that guarantee because by entering the plain zImage, you 
> forfeited that information.

The stub is responsible for ensuring that the compressed kernel is 
loaded at a suitable address. Take a look at efi_relocate_kernel().

> Most of the guessing is ideally not required to be a guess at all, the
> restrictions are purely to deal with the lack of trust for the
> bootloader environment. Why can't we trust UEFI? Or at least hold it
> to a higher standard. If someone ships a broken UEFI, they screw a
> feature or have a horrible bug and ship it, laud the fact Linux
> doesn't boot on it and the fact that it's their fault - over their
> head. It actually works these days, Linux actually has "market share,"
> companies really go out of their way to rescue their "image" and
> resolve the situation when someone blogs about a serious UEFI bug on
> their $1300 laptops, or even $300 tablets.

Yeah, that hasn't actually worked out too well for us.

-- 
Matthew Garrett | mjg59@...f.ucam.org
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