linux-kernel - Re: [PATCH RFC 3/6] Use %gs as the PDA base-segment in the kernel.

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Message-ID: <Pine.LNX.4.61.0608272202200.21315@yvahk01.tjqt.qr>
Date:	Sun, 27 Aug 2006 22:03:38 +0200 (MEST)
From:	Jan Engelhardt <jengelh@...ux01.gwdg.de>
To:	Andi Kleen <ak@...e.de>
cc:	Jeremy Fitzhardinge <jeremy@...p.org>,
	linux-kernel@...r.kernel.org,
	Chuck Ebbert <76306.1226@...puserve.com>,
	Zachary Amsden <zach@...are.com>,
	Jan Beulich <jbeulich@...ell.com>,
	Andrew Morton <akpm@...l.org>
Subject: Re: [PATCH RFC 3/6] Use %gs as the PDA base-segment in the kernel.

>> >> +1:	movw GS(%esp), %gs
>> >
>> > movl is recommended in 32bit mode
>> 
>> arch/i386/kernel/entry.S: Assembler messages:
>> arch/i386/kernel/entry.S:334: Error: suffix or operands invalid for `mov'
>
>Looks like a gas bug to me.

So the suffixing (MOVW vs MOVL) does not depend on the source operand?
%gs is only 16 bit wide so MOVW seems reasonable. If the destination 
operand was a 32 bit location, something like MOVZX would be needed, would 
not it?

Jan Engelhardt
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