perf stat: Fix error check for bpf_program__attach

It seems the bpf_program__attach() returns a negative error code instead
of a NULL pointer in case of error.

Fixes: 7fac83aaf2ee ("perf stat: Introduce 'bperf' to share hardware PMCs with BPF")
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Link: http://lore.kernel.org/lkml/20210527220052.1657578-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/bpf_counter.c b/tools/perf/util/bpf_counter.c
index ddb52f748c8e8613cc293a366d4475d3b2f73bd1..974f10e356f063340e28f02c6895d1e02b78a0ab 100644 (file)
--- a/tools/perf/util/bpf_counter.c
+++ b/tools/perf/util/bpf_counter.c
@@ -451,10 +451,10 @@ static int bperf_reload_leader_program(struct evsel *evsel, int attr_map_fd,
                goto out;
        }
 
-       err = -1;
        link = bpf_program__attach(skel->progs.on_switch);
-       if (!link) {
+       if (IS_ERR(link)) {
                pr_err("Failed to attach leader program\n");
+               err = PTR_ERR(link);
                goto out;
        }