linux-kernel - Re: [PATCH V2] perf tools: Fix maps__find_symbol_by

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Message-ID: <20180910143444.GK5147@kernel.org>
Date:   Mon, 10 Sep 2018 11:34:44 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Jiri Olsa <jolsa@...hat.com>,
        Björn Töpel <bjorn.topel@...el.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] perf tools: Fix maps__find_symbol_by_name()

Em Fri, Sep 07, 2018 at 11:51:16AM +0300, Adrian Hunter escreveu:
> Commit 1c5aae7710bb ("perf machine: Create maps for x86 PTI entry
> trampolines") revealed a problem with maps__find_symbol_by_name() that

Can we have this with a Fixes: 1c5aae7710bb?

So that that, combined with the CC: stable, tells which stable kernels
should get that fix, I think there are scripts harvesting Fixes: tags to
help stable maintainers :-)

- Arnaldo

> resulted in probes not being found e.g.
> 
> 	$ sudo perf probe xsk_mmap
> 	xsk_mmap is out of .text, skip it.
> 	Probe point 'xsk_mmap' not found.
> 	   Error: Failed to add events.
> 
> maps__find_symbol_by_name() can optionally return the map of the found
> symbol. It can get the map wrong because, in fact, the symbol is found
> on the map's dso, not allowing for the possibility that the dso has more
> than one map. Fix by always checking the map contains the symbol.
> 
> Reported-by: Björn Töpel <bjorn.topel@...el.com>
> Tested-by: Björn Töpel <bjorn.topel@...el.com>
> Cc: stable@...r.kernel.org
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
> ---
> 
> 
> Changes in V2:
> 
> 	Expanded commit message
> 	Corrected email address
> 
> 
>  tools/perf/util/map.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
> index 3f07a587c8e6..354e54550d2b 100644
> --- a/tools/perf/util/map.c
> +++ b/tools/perf/util/map.c
> @@ -574,6 +574,13 @@ struct symbol *map_groups__find_symbol(struct map_groups *mg,
>  	return NULL;
>  }
>  
> +static bool map__contains_symbol(struct map *map, struct symbol *sym)
> +{
> +	u64 ip = map->unmap_ip(map, sym->start);
> +
> +	return ip >= map->start && ip < map->end;
> +}
> +
>  struct symbol *maps__find_symbol_by_name(struct maps *maps, const char *name,
>  					 struct map **mapp)
>  {
> @@ -589,6 +596,10 @@ struct symbol *maps__find_symbol_by_name(struct maps *maps, const char *name,
>  
>  		if (sym == NULL)
>  			continue;
> +		if (!map__contains_symbol(pos, sym)) {
> +			sym = NULL;
> +			continue;
> +		}
>  		if (mapp != NULL)
>  			*mapp = pos;
>  		goto out;
> -- 
> 2.17.1