linux-kernel - Re: [PATCH] perf jit: genelf makes assumptions about endian

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Message-ID: <20160330211522.GC2793@redhat.com>
Date:	Wed, 30 Mar 2016 18:15:22 -0300
From:	Arnaldo Carvalho de Melo <acme@...hat.com>
To:	Michael Ellerman <mpe@...erman.id.au>
Cc:	Anton Blanchard <anton@...ba.org>, eranian@...gle.com,
	sukadev@...ux.vnet.ibm.com, cel@...ibm.com,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf jit: genelf makes assumptions about endian

Em Wed, Mar 30, 2016 at 01:38:20PM +1100, Michael Ellerman escreveu:
> On Tue, 2016-03-29 at 17:59 +1100, Anton Blanchard wrote:
> 
> > Commit 9b07e27f88b9 ("perf inject: Add jitdump mmap injection support")
> > incorrectly assumed that PowerPC is big endian only.
> > 
> > Simplify things by consolidating the define of GEN_ELF_ENDIAN and checking
> > for __BYTE_ORDER == __BIG_ENDIAN.
> > 
> > The PowerPC checks were also incorrect, they do not match what gcc
> > emits. We should first look for __powerpc64__, then __powerpc__.
> > 
> > Fixes: 9b07e27f88b9 ("perf inject: Add jitdump mmap injection support")
> > Signed-off-by: Anton Blanchard <anton@...ba.org>
> 
> The diff's a little hard to read because you're pulling the endian logic out,
> if I remove that I get something like:

Yeah, I'm taking this patch, but would be better next time to break it
down in two, one doing the reorg, the other doing the actual fix...

Thanks,

- Arnaldo
 
> >  #elif defined(__i386__)
> >  #define GEN_ELF_ARCH	EM_386
> >  #define GEN_ELF_CLASS	ELFCLASS32
> > -#elif defined(__ppcle__)
> > -#define GEN_ELF_ARCH	EM_PPC
> > -#define GEN_ELF_CLASS	ELFCLASS64
> > -#elif defined(__powerpc__)
> > -#define GEN_ELF_ARCH	EM_PPC64
> > -#define GEN_ELF_CLASS	ELFCLASS64
> > -#elif defined(__powerpcle__)
> > +#elif defined(__powerpc64__)
> >  #define GEN_ELF_ARCH	EM_PPC64
> >  #define GEN_ELF_CLASS	ELFCLASS64
> > +#elif defined(__powerpc__)
> > +#define GEN_ELF_ARCH	EM_PPC
> > +#define GEN_ELF_CLASS	ELFCLASS32
> >  #else
> >  #error "unsupported architecture"
> >  #endif
> 
> Which looks correct to me.
> 
> And the consolidation of the endian logic is "obviously correct", so:
> 
> Acked-by: Michael Ellerman <mpe@...erman.id.au>
> 
> cheers