netdev - [PATCH v1 1/4] perf trace: Exit when build eBPF program failure

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Date:   Thu,  6 Jun 2019 15:56:14 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Mike Leach <mike.leach@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Cc:     Leo Yan <leo.yan@...aro.org>
Subject: [PATCH v1 1/4] perf trace: Exit when build eBPF program failure

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.

Signed-off-by: Leo Yan <leo.yan@...aro.org>
---
 tools/perf/builtin-trace.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 54b2d0fd0d02..4b5d004aab74 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -3664,6 +3664,14 @@ static int trace__config(const char *var, const char *value, void *arg)
 					       "event selector. use 'perf list' to list available events",
 					       parse_events_option);
 		err = parse_events_option(&o, value, 0);
+
+		/*
+		 * When parse option successfully parse_events_option() will
+		 * return 0, otherwise means the paring failure.  And it
+		 * returns 1 for eBPF program building failure; so adjust the
+		 * err value to -1 for the failure.
+		 */
+		err = err ? -1 : 0;
 	} else if (!strcmp(var, "trace.show_timestamp")) {
 		trace->show_tstamp = perf_config_bool(var, value);
 	} else if (!strcmp(var, "trace.show_duration")) {
-- 
2.17.1