linux-kernel - [tip:perf/core] perf trace: Exit when failing to build eBPF program

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Date:   Mon, 17 Jun 2019 12:17:25 -0700
From:   tip-bot for Leo Yan <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     acme@...hat.com, mingo@...nel.org, hpa@...or.com,
        tglx@...utronix.de, songliubraving@...com,
        linux-kernel@...r.kernel.org, namhyung@...nel.org,
        mathieu.poirier@...aro.org, leo.yan@...aro.org, yhs@...com,
        daniel@...earbox.net, suzuki.poulose@....com,
        mike.leach@...aro.org, alexander.shishkin@...ux.intel.com,
        adrian.hunter@...el.com, ast@...nel.org, jolsa@...hat.com,
        kafai@...com
Subject: [tip:perf/core] perf trace: Exit when failing to build eBPF program

Commit-ID:  012749caf9419f22636891259b664c6dd383e897
Gitweb:     https://git.kernel.org/tip/012749caf9419f22636891259b664c6dd383e897
Author:     Leo Yan <leo.yan@...aro.org>
AuthorDate: Thu, 6 Jun 2019 10:38:59 -0300
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Mon, 10 Jun 2019 15:49:43 -0300

perf trace: Exit when failing to build eBPF program

On my Juno board with ARM64 CPUs, perf trace command reports the eBPF
program building failure but the command will not exit and continue to
run.  If we define an eBPF event in config file, the event will be
parsed with below flow:

  perf_config()
    `> trace__config()
         `> parse_events_option()
              `> parse_events__scanner()
                   `-> parse_events_parse()
                         `> parse_events_load_bpf()
                              `> llvm__compile_bpf()

Though the low level functions return back error values when detect eBPF
building failure, but parse_events_option() returns 1 for this case and
trace__config() passes 1 to perf_config(); perf_config() doesn't treat
the returned value 1 as failure and it continues to parse other
configurations.  Thus the perf command continues to run even without
enabling eBPF event successfully.

This patch changes error handling in trace__config(), when it detects
failure it will return -1 rather than directly pass error value (1);
finally, perf_config() will directly bail out and perf will exit for
this case.

Committer notes:

Simplified the patch to just check directly the return of
parse_events_option() and it it is non-zero, change err from its initial
zero value to -1.

Signed-off-by: Leo Yan <leo.yan@...aro.org>
Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Daniel Borkmann <daniel@...earbox.net>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Martin KaFai Lau <kafai@...com>
Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
Cc: Mike Leach <mike.leach@...aro.org>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Song Liu <songliubraving@...com>
Cc: Suzuki Poulouse <suzuki.poulose@....com>
Cc: Yonghong Song <yhs@...com>
Fixes: ac96287cae08 ("perf trace: Allow specifying a set of events to add in perfconfig")
Link: https://lkml.kernel.org/n/tip-x4i63f5kscykfok0hqim3zma@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/builtin-trace.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index f7e4e50bddbd..1a2a605cf068 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -3703,7 +3703,12 @@ static int trace__config(const char *var, const char *value, void *arg)
 		struct option o = OPT_CALLBACK('e', "event", &trace->evlist, "event",
 					       "event selector. use 'perf list' to list available events",
 					       parse_events_option);
-		err = parse_events_option(&o, value, 0);
+		/*
+		 * We can't propagate parse_event_option() return, as it is 1
+		 * for failure while perf_config() expects -1.
+		 */
+		if (parse_events_option(&o, value, 0))
+			err = -1;
 	} else if (!strcmp(var, "trace.show_timestamp")) {
 		trace->show_tstamp = perf_config_bool(var, value);
 	} else if (!strcmp(var, "trace.show_duration")) {