perf probe: Fix error reported when offset without function

This patch fixes a bug that, when offset is provided but function is
lost, parse_perf_probe_point() will give a "" string as function name,
so the checking code at the end of parse_perf_probe_point() become
useless.  For example:

  # perf probe +0x1234
  Failed to find symbol  in kernel
    Error: Failed to add events.

After this patch:

  # perf probe +0x1234
  Semantic error :Offset requires an entry function.
    Error: Command Parse Error.

Signed-off-by: Wang Nan <[email protected]>
Acked-by: Masami Hiramatsu <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Zefan Li <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

1 files changed, 7 insertions, 3 deletions

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 926bcecc4a44..eaacb58b9b36 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -1194,9 +1194,13 @@ static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev)
 		*ptr++ = '\0';
 	}
 
-	tmp = strdup(arg);
-	if (tmp == NULL)
-		return -ENOMEM;
+	if (arg[0] == '\0')
+		tmp = NULL;
+	else {
+		tmp = strdup(arg);
+		if (tmp == NULL)
+			return -ENOMEM;
+	}
 
 	if (file_spec)
 		pp->file = tmp;