tools lib fs debugfs: Introduce debugfs__strerror_open_tp

There will be other cases where not just a tracepoint event is being
opened below the debugfs mountpoint, but it is rather common, so provide
one helper for that.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-q6e6zct49ql6nbcw8kkg0lbj@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/lib/api/fs/debugfs.c

@@ -125,3 +125,12 @@ int debugfs__strerror_open(int err, char *buf, size_t size, const char *filename
 
 	return 0;
 }
+
+int debugfs__strerror_open_tp(int err, char *buf, size_t size, const char *sys, const char *name)
+{
+	char path[PATH_MAX];
+
+	snprintf(path, PATH_MAX, "tracing/events/%s/%s", sys, name ?: "*");
+
+	return debugfs__strerror_open(err, buf, size, path);
+}

tools/lib/api/fs/debugfs.h

@@ -27,5 +27,6 @@ char *debugfs_mount(const char *mountpoint);
 extern char debugfs_mountpoint[];
 
 int debugfs__strerror_open(int err, char *buf, size_t size, const char *filename);
+int debugfs__strerror_open_tp(int err, char *buf, size_t size, const char *sys, const char *name);
 
 #endif /* __API_DEBUGFS_H__ */

tools/perf/builtin-trace.c

@@ -2071,9 +2071,9 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
 		goto out_error_mem;
 
 	if (trace->sched &&
-		perf_evlist__add_newtp(evlist, "sched", "sched_stat_runtime",
-				trace__sched_stat_runtime))
-		goto out_error_tp;
+	    perf_evlist__add_newtp(evlist, "sched", "sched_stat_runtime",
+				   trace__sched_stat_runtime))
+		goto out_error_sched_stat_runtime;
 
 	err = perf_evlist__create_maps(evlist, &trace->opts.target);
 	if (err < 0) {
@@ -2203,9 +2203,12 @@ out:
 {
 	char errbuf[BUFSIZ];
 
-out_error_tp:
+out_error_sched_stat_runtime:
+	debugfs__strerror_open_tp(errno, errbuf, sizeof(errbuf), "sched", "sched_stat_runtime");
+	goto out_error;
+
 out_error_raw_syscalls:
-	debugfs__strerror_open(errno, errbuf, sizeof(errbuf), "tracing/events/raw_syscalls");
+	debugfs__strerror_open_tp(errno, errbuf, sizeof(errbuf), "raw_syscalls", "sys_(enter|exit)");
 	goto out_error;
 
 out_error_mmap: