From: Michael Ellerman <mpe@ellerman•id.au>
To: Alan Modra <amodra@gmail•com>
Cc: linuxppc-dev@ozlabs•org, anton@samba•org
Subject: Re: [RFC PATCH] powerpc: Fix dubious r0 usage
Date: Sat, 18 Feb 2017 19:06:03 +1100 [thread overview]
Message-ID: <87d1efj53o.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <20170217132125.GV3731@bubble.grove.modra.org>
Alan Modra <amodra@gmail•com> writes:
> On Fri, Feb 17, 2017 at 11:08:53PM +1100, Michael Ellerman wrote:
>> Bleeding edge binutils no longer accepts r0 in places where the CPU
>> interprets the value as a literal 0.
>
> Wow! That was quite some cleanup. I think I'd better turn the error
> into a warning..
That would be my preference :)
If it remains a hard error we'll need to backport this patch to multiple
stable versions so that people can build those older kernels with new
binutils. Which we can do, but it's a bit of a pain.
>> --- a/arch/powerpc/purgatory/trampoline.S
>> +++ b/arch/powerpc/purgatory/trampoline.S
>> @@ -67,7 +67,7 @@ master:
>> mr %r16,%r3 /* save dt address in reg16 */
>> li %r4,20
>> LWZX_BE %r6,%r3,%r4 /* fetch __be32 version number at byte 20 */
>> - cmpwi %r0,%r6,2 /* v2 or later? */
>> + cmpwi 0,%r6,2 /* v2 or later? */
>> blt 1f
>> li %r4,28
>> STWX_BE %r17,%r3,%r4 /* Store my cpu as __be32 at byte 28 */
>
> With this one, it would probably be better to omit the zero (BF
> field).
Yeah good point, thanks for reviewing.
cheers
prev parent reply other threads:[~2017-02-18 8:06 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-17 12:08 [RFC PATCH] powerpc: Fix dubious r0 usage Michael Ellerman
2017-02-17 13:21 ` Alan Modra
2017-02-17 20:03 ` Segher Boessenkool
2017-02-18 8:06 ` Michael Ellerman [this message]
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