[PATCH] selftests/powerpc: fix build error in powerpc ptrace selftests.

[Simon Guo]

Hi Michael,
On Tue, Oct 10, 2017 at 09:10:32PM +1100, Michael Ellerman wrote:
> wei.guo.simon at gmail.com writes:
> 
> > From: Simon Guo <wei.guo.simon at gmail.com>
> >
> > GCC 7 will take "r2" in clobber list as an error will it will get following
> > build errors for powerpc ptrace selftests even with -fno-pic option:
> >   ptrace-tm-vsx.c: In function ‘tm_vsx’:
> >   ptrace-tm-vsx.c:42:2: error: PIC register clobbered by ‘r2’ in ‘asm’
> >     asm __volatile__(
> >     ^~~
> >   make[1]: *** [ptrace-tm-vsx] Error 1
> >   ptrace-tm-spd-vsx.c: In function ‘tm_spd_vsx’:
> >   ptrace-tm-spd-vsx.c:55:2: error: PIC register clobbered by ‘r2’ in ‘asm’
> >     asm __volatile__(
> >     ^~~
> >   make[1]: *** [ptrace-tm-spd-vsx] Error 1
> >   ptrace-tm-spr.c: In function ‘tm_spr’:
> >   ptrace-tm-spr.c:46:2: error: PIC register clobbered by ‘r2’ in ‘asm’
> >     asm __volatile__(
> >     ^~~
> >
> > This patch fix the build error by removing "r2" out of clobber list.
> 
> But do any of the blocks clobber r2? If so then it should be in the
> clobber list.

I see none of them clobbers r2, and neither does those assembly
functions which those blocks calls, like "loadvsx".

For the change on tools/testing/selftests/powerpc/ptrace/Makefile, it
can be ignored since I noticed recent commit a3c01050584da3 "selftests/powerpc: 
Force ptrace tests to build -fno-pie". Please let me know if you want
a new v2 to remove that change on ptrace/Makefile.

Thanks,
- Simon