perf parse: Copy string to perf_evsel_config_term

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 1dc92556 ("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: 1dc92556 ("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>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suzuki Poulouse <suzuki.poulose@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lore.kernel.org/lkml/20200117055251.24058-2-leo.yan@linaro.org


[ Use zfree() in perf_evsel__free_config_terms ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

:#	modified:   tools/perf/util/evsel_config.h