linux-kernel - Re: [PATCH -tip 2/8] [BUGFIX] perf-tools: Load map before using map->map

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Message-ID: <20140123144324.GB17572@ghostprotocols.net>
Date:	Thu, 23 Jan 2014 11:43:24 -0300
From:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	David Ahern <dsahern@...il.com>, linux-kernel@...r.kernel.org,
	"Steven Rostedt (Red Hat)" <rostedt@...dmis.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	"David A. Long" <dave.long@...aro.org>,
	yrl.pp-manager.tt@...achi.com, Namhyung Kim <namhyung@...nel.org>
Subject: Re: [PATCH -tip 2/8] [BUGFIX] perf-tools: Load map before using
 map->map_ip

Em Thu, Jan 23, 2014 at 02:29:50AM +0000, Masami Hiramatsu escreveu:
> In map_groups__find_symbol() map->map_ip is used without
> ensuring the map is loaded. Then the address passed
> to map->map_ip isn't mapped at the first time.
> 
> E.g. below code always fails to get a symbol at the first call;
> 
> 	addr = /* Somewhere in the kernel text */
> 	symbol_conf.try_vmlinux_path = true;
> 	symbol__init();
> 	host_machine = machine__new_host();
> 	sym = machine__find_kernel_function(host_machine,
> 					 addr, NULL, NULL);
> 	/* Note that machine__find_kernel_function calls
> 	   map_groups__find_symbol */
> 
> This ensures it by calling map__load before using it in
> map_groups__find_symbol().

Good catch! map__find_symbol() will load it if necessary, but that is
after map->map_ip() is called.

Applying.

- Arnaldo
 
> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> ---
>  tools/perf/util/map.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
> index 9b9bd71..6a805e7 100644
> --- a/tools/perf/util/map.c
> +++ b/tools/perf/util/map.c
> @@ -386,7 +386,8 @@ struct symbol *map_groups__find_symbol(struct map_groups *mg,
>  {
>  	struct map *map = map_groups__find(mg, type, addr);
>  
> -	if (map != NULL) {
> +	/* Ensure map is loaded before using map->map_ip */
> +	if (map != NULL && map__load(map, filter) >= 0) {
>  		if (mapp != NULL)
>  			*mapp = map;
>  		return map__find_symbol(map, map->map_ip(map, addr), filter);
> 
--
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