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

Arnaldo Carvalho de Melo
2020-01-17T13:34:21Z

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@kernel.org>
> Signed-off-by: Leo Yan <leo.yan@linaro.org>
> Acked-by: Jiri Olsa <jolsa@kernel.org>
> ---
> 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,

> 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