linux-kernel - Re: [PATCH 6/7] Add EFI stub for ARM

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Date:	Mon, 5 Aug 2013 17:33:19 +0200
From:	Leif Lindholm <leif.lindholm@...aro.org>
To:	Dave Martin <Dave.Martin@....com>
Cc:	Roy Franz <roy.franz@...aro.org>, linux-kernel@...r.kernel.org,
	linux-efi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	matt.fleming@...el.com, linux@....linux.org.uk
Subject: Re: [PATCH 6/7] Add EFI stub for ARM

On Mon, Aug 05, 2013 at 03:11:49PM +0100, Dave Martin wrote:
> > diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
> > index 75189f1..4c70b9e 100644
> > --- a/arch/arm/boot/compressed/head.S
> > +++ b/arch/arm/boot/compressed/head.S
> > @@ -122,19 +122,106 @@
> >  		.arm				@ Always enter in ARM state
> >  start:
> >  		.type	start,#function
> > -		.rept	7
> > +#ifdef CONFIG_EFI_STUB
> > +		@ Magic MSDOS signature for PE/COFF + ADD opcode
> > +		.word	0x62805a4d
> 
> What about BE32?
 
The ARM bindings for UEFI specify that the processor must be in
little-endian mode.

> In that case, the instruction is a coprocessor load, that loads from a
> random address to a coprocessor that almost certainly doesn't exist.
> This will probably fault.
> 
> Since BE32 is only for older platforms (<v6) and this is not easily
> solvable, it might be sensible to make the EFI stub support depend on
> !CPU_ENDIAN_BE32.
 
Well, it would make more sense to make EFI_STUB depend on EFI and
EFI depend on !CPU_ENDIAN_BE32. Which is something I can add to
my next set of general ARM UEFI patches. Thanks.

/
    Leif
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