linux-kernel - Re: [PATCH] x86, efi: Fix unaligned access and endian issues

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Message-Id: <20120223093140.3f8ad47252f9f331d355ea57@canb.auug.org.au>
Date:	Thu, 23 Feb 2012 09:31:40 +1100
From:	Stephen Rothwell <sfr@...b.auug.org.au>
To:	Matt Fleming <matt@...sole-pimps.org>
Cc:	x86@...nel.org, linux-kernel@...r.kernel.org,
	Matt Fleming <matt.fleming@...el.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] x86, efi: Fix unaligned access and endian issues

Hi Matt,

On Wed, 22 Feb 2012 14:00:08 +0000 Matt Fleming <matt@...sole-pimps.org> wrote:
>
> From: Matt Fleming <matt.fleming@...el.com>
> 
> We need to read from and write to 'buf' a byte at a time otherwise
> it's possible we'll perform an unaligned access, which can lead to a
> segfault when cross-building an x86 kernel on risc architectures.
> 
> Also, we may need to convert the endianness of the data we read
> from/write to buf, so let's add some helper functions to do that.
> 
> Stephen Rothwell noticed this bug when he hit a segfault while
> cross-building an x86_64 allmodconfig kernel on PowerPC.
> 
> Cc: H. Peter Anvin <hpa@...or.com>
> Reported-by: Stephen Rothwell <sfr@...b.auug.org.au>
> Signed-off-by: Matt Fleming <matt.fleming@...el.com>

Tested-by: Stephen Rothwell <sfr@...b.auug.org.au> (cross build only)

The bzImage from a ARCH=x86_64 defconfig+CONFIG_EFI_STUB cross build is
in http://ozlabs.org/~sfr/bzImage if you want to attempt to boot it.

One little thing is that those two new functions may we warned about as
unused if CONFIG_EFI_STUB is not set (I have not done that build yet).

-- 
Cheers,
Stephen Rothwell                    sfr@...b.auug.org.au

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