perf top: Fix potential NULL pointer dereference detected by the smatch tool

Based on the following report from Smatch, fix the potential NULL
pointer dereference check.

  tools/perf/builtin-top.c:109
  perf_top__parse_source() warn: variable dereferenced before check 'he'
  (see line 103)

  tools/perf/builtin-top.c:233
  perf_top__show_details() warn: variable dereferenced before check 'he'
  (see line 228)

  tools/perf/builtin-top.c
  101 static int perf_top__parse_source(struct perf_top *top, struct hist_entry *he)
  102 {
  103         struct perf_evsel *evsel = hists_to_evsel(he->hists);
                                                        ^^^^
  104         struct symbol *sym;
  105         struct annotation *notes;
  106         struct map *map;
  107         int err = -1;
  108
  109         if (!he || !he->ms.sym)
  110                 return -1;

This patch moves the values assignment after validating pointer 'he'.
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: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: Alexios Zavras <alexios.zavras@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Changbin Du <changbin.du@intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Eric Saint-Etienne <eric.saint.etienne@oracle.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Song Liu <songliubraving@fb.com>
Cc: Suzuki Poulouse <suzuki.poulose@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/20190702103420.27540-4-leo.yan@linaro.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-top.c

@@ -101,7 +101,7 @@ static void perf_top__resize(struct perf_top *top)
 
 static int perf_top__parse_source(struct perf_top *top, struct hist_entry *he)
 {
-	struct perf_evsel *evsel = hists_to_evsel(he->hists);
+	struct perf_evsel *evsel;
 	struct symbol *sym;
 	struct annotation *notes;
 	struct map *map;
@@ -110,6 +110,8 @@ static int perf_top__parse_source(struct perf_top *top, struct hist_entry *he)
 	if (!he || !he->ms.sym)
 		return -1;
 
+	evsel = hists_to_evsel(he->hists);
+
 	sym = he->ms.sym;
 	map = he->ms.map;
 
@@ -226,7 +228,7 @@ static void perf_top__record_precise_ip(struct perf_top *top,
 static void perf_top__show_details(struct perf_top *top)
 {
 	struct hist_entry *he = top->sym_filter_entry;
-	struct perf_evsel *evsel = hists_to_evsel(he->hists);
+	struct perf_evsel *evsel;
 	struct annotation *notes;
 	struct symbol *symbol;
 	int more;
@@ -234,6 +236,8 @@ static void perf_top__show_details(struct perf_top *top)
 	if (!he)
 		return;
 
+	evsel = hists_to_evsel(he->hists);
+
 	symbol = he->ms.sym;
 	notes = symbol__annotation(symbol);