linux-kernel - Re: [PATCH] fix perf Annotation of Thumb code

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Date:	Fri, 21 Jan 2011 15:13:03 -0200
From:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
To:	"Dr. David Alan Gilbert" <david.gilbert@...aro.org>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	mingo@...e.hu, dave.martin@...aro.org
Subject: Re: [PATCH] fix perf Annotation of Thumb code

Em Fri, Jan 21, 2011 at 04:40:19PM +0000, Dr. David Alan Gilbert escreveu:
> Hi,
>   In ARM's Thumb mode the bottom bit of the symbol address is set to mark
> the function as Thumb; the instructions are in reality 2 or 4 byte on 2
> byte alignments, and when the +1 address is used in annotate it causes
> objdump to disassemble invalid instructions.  
> 
>   The patch removes that bottom bit during symbol loading.
>   This patch is against current linus's git, (2b1caf.....).
>   Many thinks to Dave Martin for comments on an initial version of the patch.

Thanks, adding it to perf/urgent.

- Arnaldo
   
>  
> Dave
> 
> (For reference this corresponds to this bug
> https://bugs.launchpad.net/linux-linaro/+bug/677547 )
> 
>         Signed-off-by: Dr. David Alan Gilbert <david.gilbert@...aro.org>  
> ---
> 
> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> index 15ccfba..36e76c1 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -1161,6 +1161,13 @@ static int dso__load_sym(struct dso *self, struct map *map, const char *name,
>  
>  		section_name = elf_sec__name(&shdr, secstrs);
>  
> +		/* On ARM, symbols for thumb functions have 1 added to
> +		 * the symbol address as a flag - remove it */
> +		if ((ehdr.e_machine == EM_ARM) &&
> +			(map->type == MAP__FUNCTION) &&
> +			(sym.st_value & 1))
> +			sym.st_value-=1;
> +
>  		if (self->kernel != DSO_TYPE_USER || kmodule) {
>  			char dso_name[PATH_MAX];
>  
--
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