Re: [PATCH v6 2/2] perf parse: Copy string to perf_evsel_config_term

[Leo Yan]

On Fri, Jan 17, 2020 at 10:34:09AM -0300, Arnaldo Carvalho de Melo wrote:
> Em Fri, Jan 17, 2020 at 01:52:51PM +0800, Leo Yan escreveu:
> > perf with CoreSight fails to record trace data with command:
> > 
> >   perf record -e cs_etm/@tmc_etr0/u --per-thread ls
> >   failed to set sink "" on event cs_etm/@tmc_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, term->val.str);
> >       __t->val.str = term->val.str;
> >         `> __t->val.str 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.str;
> >       `> sink string has been freed.
> > 
> > To fix this issue, in the function get_config_terms(), this patch
> > changes to use strdup() for allocation a new duplicate string rather
> > than directly assignment string pointer.
> > 
> > This patch addes a new field 'free_str' in the data structure
> > perf_evsel_config_term; 'free_str' is set to true when the union is used
> > as a string pointer; thus it can tell perf_evsel__free_config_terms() to
> > free the string.
> > 
> > Fixes: 1dc925568f01 ("perf parse: Add a deep delete for parse event terms")
> > Suggested-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> > Signed-off-by: Leo Yan <leo.yan@xxxxxxxxxx>
> > Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> > ---
> >  tools/perf/util/evsel.c        | 2 ++
> >  tools/perf/util/evsel_config.h | 1 +
> >  tools/perf/util/parse-events.c | 7 ++++++-
> >  3 files changed, 9 insertions(+), 1 deletion(-)
> > 
> > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> > index 549abd43816f..6fe9e28180e5 100644
> > --- a/tools/perf/util/evsel.c
> > +++ b/tools/perf/util/evsel.c
> > @@ -1265,6 +1265,8 @@ static void perf_evsel__free_config_terms(struct evsel *evsel)
> >  
> >  	list_for_each_entry_safe(term, h, &evsel->config_terms, list) {
> >  		list_del_init(&term->list);
> > +		if (term->free_str)
> > +			free(term->val.str);
> 
> I'm replacing this with zfree, so that we can catch possible bugs where
> term gets used after freed, just like you do below, in ADD_CONFIG_TERM_STR()

Thanks a lot, Arnaldo.

> >  		free(term);
> >  	}
> >  }
> > diff --git a/tools/perf/util/evsel_config.h b/tools/perf/util/evsel_config.h
> > index b4a65201e4f7..e026ab67b008 100644
> > --- a/tools/perf/util/evsel_config.h
> > +++ b/tools/perf/util/evsel_config.h
> > @@ -32,6 +32,7 @@ enum evsel_term_type {
> >  struct perf_evsel_config_term {
> >  	struct list_head      list;
> >  	enum evsel_term_type  type;
> > +	bool		      free_str;
> >  	union {
> >  		u64	      period;
> >  		u64	      freq;
> > diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> > index f59f3c8da473..c01ba6f8fdad 100644
> > --- a/tools/perf/util/parse-events.c
> > +++ b/tools/perf/util/parse-events.c
> > @@ -1240,7 +1240,12 @@ do {								\
> >  #define ADD_CONFIG_TERM_STR(__type, __val)			\
> >  do {								\
> >  	ADD_CONFIG_TERM(__type);				\
> > -	__t->val.str = __val;					\
> > +	__t->val.str = strdup(__val);				\
> > +	if (!__t->val.str) {					\
> > +		zfree(&__t);					\
> > +		return -ENOMEM;					\
> > +	}							\
> > +	__t->free_str = true;					\
> >  } while (0)
> >  
> >  	struct parse_events_term *term;
> > -- 
> > 2.17.1
>