Messages in this thread | | | Date | Mon, 28 Aug 2006 07:54:36 -0700 | From | "H. J. Lu" <> | Subject | Re: [PATCH RFC 3/6] Use %gs as the PDA base-segment in the kernel. |
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On Mon, Aug 28, 2006 at 10:51:00AM +0100, Jan Beulich wrote: > >>> Andi Kleen <ak@suse.de> 27.08.06 20:19 >>> > >On Sunday 27 August 2006 19:20, Jeremy Fitzhardinge wrote: > >> Andi Kleen wrote: > >> >> +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. > > This was an intentional change (by H.J. if I recall right) as using movl > with segment registers gives the incorrect impression that one gets a > 32-bit memory access (especially for stores this is important, since > there's really nothing stored to the upper 16 bits). One should always > use suffix-less 'mov' for segment register accesses.
mov will generate the optimal opcode with old and new assemblers.
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