linux-kernel - Re: [PATCH] x86/efi: Map EFI memmap entries in-order at runtime

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Date:	Wed, 16 Sep 2015 12:08:20 +0200
From:	Borislav Petkov <bp@...e.de>
To:	Matt Fleming <matt@...eblueprint.co.uk>
Cc:	joeyli <jlee@...e.com>, linux-efi@...r.kernel.org,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	Matt Fleming <matt.fleming@...el.com>,
	LeifLindholm@...ux-rxt1.site, leif.lindholm@...aro.org,
	Peter Jones <pjones@...hat.com>,
	James Bottomley <JBottomley@...n.com>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	"H. Peter Anvin" <hpa@...or.com>, Dave Young <dyoung@...hat.com>,
	stable@...r.kernel.org, Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: Re: [PATCH] x86/efi: Map EFI memmap entries in-order at runtime

On Wed, Sep 09, 2015 at 12:21:23PM +0100, Matt Fleming wrote:
> On Wed, 09 Sep, at 08:33:07AM, joeyli wrote:
> > 
> > Yes, the machine on my hand has EFI_PROPERTIES_TABLE enabled, and it doesn't
> > boot without your patch.
> 
> Awesome. Could you test the following patch instead?
> 
> ---
> 
> From 24d324b781a3b688dcc265995949a9cf4e8af687 Mon Sep 17 00:00:00 2001
> From: Matt Fleming <matt.fleming@...el.com>
> Date: Thu, 3 Sep 2015 15:56:25 +0100
> Subject: [PATCH v2] x86/efi: Map EFI memmap entries in-order at runtime
> 
> Beginning with UEFI v2.5 EFI_PROPERTIES_TABLE was introduced that
> signals that the firmware PE/COFF loader supports splitting code and
> data sections of PE/COFF images into separate EFI memory map entries.
> This allows the kernel to map those regions with strict memory
> protections, e.g. EFI_MEMORY_RO for code, EFI_MEMORY_XP for data, etc.
> 
> Unfortunately, an unwritten requirement of this new feature is that
> the regions need to be mapped with the same offsets relative to each
> other as observed in the EFI memory map. If this is not done crashes

Let me get this straight: this looks like the next EFI screwup which
practically requires specific mapping placement in VA space just
because it uses relative addresses? And since you say "unwritten" this
practically a requirement is not even in the spec?

Can we state explicitly in the spec NOT to rely on mapping VA placement?
I mean, this "unwritten" requirement is seriously screwed on soo many
levels...

What else are we to expect? Spelled out virtual addresses which are
going to be the EFI-allowed ones only??!

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
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