linux-kernel - Re: [PATCH/RFC 3/9] perf symbols: Discard symbols in kallsyms for loaded modules

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Date:   Fri, 23 Jun 2017 10:51:05 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Jiri Olsa <jolsa@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>, kernel-team@....com,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Andi Kleen <andi@...stfloor.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Wang Nan <wangnan0@...wei.com>
Subject: Re: [PATCH/RFC 3/9] perf symbols: Discard symbols in kallsyms for
 loaded modules

Em Fri, Jun 23, 2017 at 02:48:21PM +0900, Namhyung Kim escreveu:
> If a module is already loaded, it should have symbols and no need to
> load new symbols from kallsyms.  Actually kallsyms can have different
> addresses if the module was reloaded.

Well, if it is loaded, then it should match what is in kallsyms, no?
 
> Current code just discards the first symbols only, but it should do the
> same for all symbols in the module.  Note that the kernel doesn't set
> the dso->loaded bit so simply checking it would do the job IMHO.

The kernel sets dso->loaded? Can you rephrase this part? And if this
procedure doesn't set dso->loaded how can simply checking it do the job?

Can you clarify the above sentence? Please elaborate the scenario more
fully.

- Arnaldo
 
> Cc: Adrian Hunter <adrian.hunter@...el.com>
> Cc: Wang Nan <wangnan0@...wei.com>
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> ---
>  tools/perf/util/symbol.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> index e7a98dbd2aed..74078ba595b3 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -787,11 +787,12 @@ static int dso__split_kallsyms(struct dso *dso, struct map *map, u64 delta)
>  					curr_map = map;
>  					goto discard_symbol;
>  				}
> -
> -				if (curr_map->dso->loaded &&
> -				    !machine__is_default_guest(machine))
> -					goto discard_symbol;
>  			}
> +
> +			if (curr_map->dso->loaded &&
> +			    !machine__is_default_guest(machine))
> +				goto discard_symbol;
> +
>  			/*
>  			 * So that we look just like we get from .ko files,
>  			 * i.e. not prelinked, relative to map->start.
> -- 
> 2.13.1