perf tools: Optimize parse_subsystem_tracepoint_event()

Uses of strcat are almost always signs that someone is too lazy
to think about the code a bit more carefully.  One always has to
know about the lengths of the strings involved to avoid buffer
overflows.

This is one case where the size of the object code for me is
reduced by 38 bytes.  The code should also be faster, especially
if flags is non-NULL.

Signed-off-by: Ulrich Drepper <drepper@redhat.com>
Cc: a.p.zijlstra@chello.nl
Cc: fweisbec@gmail.com
Cc: jaswinderrajput@gmail.com
Cc: paulus@samba.org
LKML-Reference: <200912061825.nB6IPUa1023306@hs20-bc2-1.build.redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 448a13b520150e16ce777d25a103dbcac5093254..e5bc0fb016b2c130b873ba5808f4ed3d33896400 100644 (file)
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -467,7 +467,6 @@ parse_subsystem_tracepoint_event(char *sys_name, char *flags)
        while ((evt_ent = readdir(evt_dir))) {
                char event_opt[MAX_EVOPT_LEN + 1];
                int len;
-               unsigned int rem = MAX_EVOPT_LEN;
 
                if (!strcmp(evt_ent->d_name, ".")
                    || !strcmp(evt_ent->d_name, "..")
@@ -475,20 +474,12 @@ parse_subsystem_tracepoint_event(char *sys_name, char *flags)
                    || !strcmp(evt_ent->d_name, "filter"))
                        continue;
 
-               len = snprintf(event_opt, MAX_EVOPT_LEN, "%s:%s", sys_name,
-                              evt_ent->d_name);
+               len = snprintf(event_opt, MAX_EVOPT_LEN, "%s:%s%s%s", sys_name,
+                              evt_ent->d_name, flags ? ":" : "",
+                              flags ?: "");
                if (len < 0)
                        return EVT_FAILED;
 
-               rem -= len;
-               if (flags) {
-                       if (rem < strlen(flags) + 1)
-                               return EVT_FAILED;
-
-                       strcat(event_opt, ":");
-                       strcat(event_opt, flags);
-               }
-
                if (parse_events(NULL, event_opt, 0))
                        return EVT_FAILED;
        }