perf record: Add --dry-run option to check cmdline options

With '--dry-run', 'perf record' doesn't do reall recording. Combine with
llvm.dump-obj option, --dry-run can be used to help compile BPF objects
for embedded platform.

Signed-off-by: Wang Nan <[e-mail]>
Cc: Alexei Starovoitov <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: [e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/Documentation/perf-record.txt

···
 
 Implies --timestamp-filename, --no-buildid and --no-buildid-cache.
 
+--dry-run::
+Parse options then exit. --dry-run can be used to detect errors in cmdline
+options.
+
+'perf record --dry-run -e' can act as a BPF script compiler if llvm.dump-obj
+in config file is set to true.
+
 SEE ALSO
 --------
 linkperf:perf-stat[1], linkperf:perf-list[1]

tools/perf/builtin-record.c

···
 const char record_callchain_help[] = CALLCHAIN_RECORD_HELP
 	"\n\t\t\t\tDefault: fp";
 
+static bool dry_run;
+
 /*
  * XXX Will stay a global variable till we fix builtin-script.c to stop messing
  * with it and switch to use the library functions in perf_evlist that came
···
 		    "append timestamp to output filename"),
 	OPT_BOOLEAN(0, "switch-output", &record.switch_output,
 		    "Switch output when receive SIGUSR2"),
+	OPT_BOOLEAN(0, "dry-run", &dry_run,
+		    "Parse options then exit"),
 	OPT_END()
 };
 
···
 					      rec->opts.auxtrace_snapshot_opts);
 	if (err)
 		return err;
+
+	if (dry_run)
+		return 0;
 
 	err = bpf__setup_stdout(rec->evlist);
 	if (err) {