linux-kernel - Re: [PATCH] perf parse: Copy string to perf_evsel_config

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Date:   Mon, 6 Jan 2020 16:12:41 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Leo Yan <leo.yan@...aro.org>
Cc:     Arnaldo Carvalho de Melo <acme@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Andi Kleen <ak@...ux.intel.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf parse: Copy string to perf_evsel_config_term

On Thu, Jan 02, 2020 at 11:13:26PM +0800, Leo Yan wrote:
> perf with CoreSight fails to record trace data with command:
> 
>   perf record -e cs_etm/@..._etr0/u --per-thread ls
>   failed to set sink "" on event cs_etm/@..._etr0/u with 21 (Is a
>   directory)/perf/
> 
> This failure is root caused with the commit 1dc925568f01 ("perf
> parse: Add a deep delete for parse event terms").
> 
> The log shows, cs_etm fails to parse the sink attribution; cs_etm event
> relies on the event configuration to pass sink name, but the event
> specific configuration data cannot be passed properly with flow:
> 
>   get_config_terms()
>     ADD_CONFIG_TERM(DRV_CFG, drv_cfg, term->val.str);
>       __t->val.drv_cfg = term->val.str;
>         `> __t->val.drv_cfg is assigned to term->val.str;
> 
>   parse_events_terms__purge()
>     parse_events_term__delete()
>       zfree(&term->val.str);
>         `> term->val.str is freed and assigned to NULL pointer;
> 
>   cs_etm_set_sink_attr()
>     sink = __t->val.drv_cfg;
>       `> sink string has been freed.
> 
> To fix this issue, in the function get_config_terms(), this patch
> changes from directly assignment pointer value for the strings to
> use strdup() for allocation a new duplicate string for the cases:
> 
>   perf_evsel_config_term::val.callgraph
>   perf_evsel_config_term::val.branch
>   perf_evsel_config_term::val.drv_cfg.
> 
> Fixes: 1dc925568f01 ("perf parse: Add a deep delete for parse event terms")
> Signed-off-by: Leo Yan <leo.yan@...aro.org>
> ---
>  tools/perf/util/parse-events.c | 49 ++++++++++++++++++++--------------
>  1 file changed, 29 insertions(+), 20 deletions(-)
> 
> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> index ed7c008b9c8b..5972acdd40d6 100644
> --- a/tools/perf/util/parse-events.c
> +++ b/tools/perf/util/parse-events.c
> @@ -1220,7 +1220,6 @@ static int get_config_terms(struct list_head *head_config,
>  			    struct list_head *head_terms __maybe_unused)
>  {
>  #define ADD_CONFIG_TERM(__type, __name, __val)			\
> -do {								\
>  	struct perf_evsel_config_term *__t;			\
>  								\
>  	__t = zalloc(sizeof(*__t));				\
> @@ -1229,9 +1228,19 @@ do {								\
>  								\
>  	INIT_LIST_HEAD(&__t->list);				\
>  	__t->type       = PERF_EVSEL__CONFIG_TERM_ ## __type;	\
> -	__t->val.__name = __val;				\
>  	__t->weak	= term->weak;				\
> -	list_add_tail(&__t->list, head_terms);			\
> +	list_add_tail(&__t->list, head_terms)
> +
> +#define ADD_CONFIG_TERM_VAL(__type, __name, __val)		\
> +do {								\
> +	ADD_CONFIG_TERM(__type, __name, __val);			\
> +	__t->val.__name = __val;				\
> +} while (0)
> +
> +#define ADD_CONFIG_TERM_STR(__type, __name, __val)		\
> +do {								\
> +	ADD_CONFIG_TERM(__type, __name, __val);			\
> +	__t->val.__name = strdup(__val);			\

ok, I understand now.. we move the pointer to the perf_evsel_config_term,
but release it after in parse_events_terms__purge

the change seems ok, but please check on the strdup return value
and cleanup and return -ENOMEM if it fails in here

thanks,
jirka