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

From Michael Ellerman <mpe@ellerman.id.au>
Newsgroups linux.kernel
Subject Re: [PATCH] perf jit: genelf makes assumptions about endian
Date 2016-03-30 04:40 +0200
Message-ID <ried4-7fJ-9@gated-at.bofh.it> (permalink)
References <rhVWO-2De-21@gated-at.bofh.it>
Organization linux.* mail to news gateway

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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@samba.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@ellerman.id.au>

cheers

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Thread

[PATCH] perf jit: genelf makes assumptions about endian Anton Blanchard <anton@samba.org> - 2016-03-29 09:10 +0200
  Re: [PATCH] perf jit: genelf makes assumptions about endian Michael Ellerman <mpe@ellerman.id.au> - 2016-03-30 04:40 +0200
    Re: [PATCH] perf jit: genelf makes assumptions about endian Arnaldo Carvalho de Melo <acme@redhat.com> - 2016-03-30 23:20 +0200
  [tip:perf/urgent] perf jit: genelf makes assumptions about endian tip-bot for Anton Blanchard <tipbot@zytor.com> - 2016-03-31 08:40 +0200

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