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

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Message-ID: <1459305500.25307.11.camel@ellerman.id.au>
Date:	Wed, 30 Mar 2016 13:38:20 +1100
From:	Michael Ellerman <mpe@...erman.id.au>
To:	Anton Blanchard <anton@...ba.org>, eranian@...gle.com,
	sukadev@...ux.vnet.ibm.com, acme@...hat.com, cel@...ibm.com
Cc:	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf jit: genelf makes assumptions about endian

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:

>  #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