linux-kernel - Re: [PATCH] ARM: zImage: ensure header in LE format for BE8 kernels

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Message-ID: <7hk38cvcrm.fsf@paris.lan>
Date:	Thu, 19 Jun 2014 13:57:01 -0700
From:	Kevin Hilman <khilman@...aro.org>
To:	Nicolas Pitre <nicolas.pitre@...aro.org>
Cc:	Stephen Boyd <sboyd@...eaurora.org>,
	Taras Kondratiuk <taras.kondratiuk@...aro.org>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Russell King <linux@....linux.org.uk>,
	Jason Cooper <jason@...edaemon.net>,
	Victor Kamensky <victor.kamensky@...aro.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Ben Dooks <ben.dooks@...ethink.co.uk>,
	Olof Johansson <olof@...om.net>,
	Linaro Networking <linaro-networking@...aro.org>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] ARM: zImage: ensure header in LE format for BE8 kernels

Nicolas Pitre <nicolas.pitre@...aro.org> writes:

> On Thu, 19 Jun 2014, Kevin Hilman wrote:
>
>> I think this should probably be officialized since we've taken away the
>> ability for magic-number checking tools (like 'file') to distinguish
>> between big- and little-endian zImages.
>> 
>> For now, I've updated my tools to check for 'setend be' in ARM and
>> Thumb2 mode, but if this does get officialized, I'll gladly move over to
>> it.
>
> Would you ACK this patch?
>
> ----- >8
> ARM: zImage: identify kernel endianness
>
> With patch #8067/1 applied, it is no longer possible to determine the

minor nit: I'd rather see a commit id (commit subject) instead of the
reference in RMK's patch tracker, but other than that...

> endianness of a compiled kernel image.  This normally shouldn't matter
> to the boot environment, except for those cases where the selection of
> a ramdisk or root filesystem with a matching endianness has to be
> automated.
>
> Let's add a flag to the zImage header indicating the actual endianness.
> Four bytes from offset 0x30 can be interpreted as follows:
>
> 	04 03 02 01	big endian kernel
>
> 	01 02 03 04	little endian kernel
>
> Anything else should be interpreted as "unknown", in which case it is
> most likely that patch #8067/1 was not applied either and the zImage
> magic number at offset 0x24 could be used instead to determine
> endianness. No zImage before this patch ever produced 0x01020304 nor
> 0x04030201 at offset 0x30 so there is no confusion possible.
>
> Signed-off-by: Nicolas Pitre <nico@...aro.org>

Acked-by: Kevin Hilman <khilman@...aro.org>
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