[RFC PATCH] powerpc: Fix dubious r0 usage
mpe at ellerman.id.au
Sat Feb 18 19:06:03 AEDT 2017
Alan Modra <amodra at 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
Yeah good point, thanks for reviewing.
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