tracing: Fix smatch warning for null glob in event_hist_trigger_parse()

The recent rename of event_hist_trigger_parse() caused smatch
re-evaluation of trace_events_hist.c and as a result an old warning
was found:

    kernel/trace/trace_events_hist.c:6174 event_hist_trigger_parse()
    error: we previously assumed 'glob' could be null (see line 6166)

glob should never be null (and apparently smatch can also figure that
out and skip the warning when using the cross-function DB (but which
can't be used with a 0day build as it takes too much time to
generate)).

Nonetheless for clarity, remove the test but add a WARN_ON() in case
the code ever changes.

Link: https://lkml.kernel.org/r/96925e5c1f116654ada7ea0613d930b1266b5e1c.1643319703.git.zanussi@kernel.org
Fixes: f404da6e1d46c ("tracing: Add 'last error' error facility for hist triggers")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index cd96106..e086014 100644 (file)
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -6164,7 +6164,9 @@ static int event_hist_trigger_parse(struct event_command *cmd_ops,
 
        lockdep_assert_held(&event_mutex);
 
-       if (glob && strlen(glob)) {
+       WARN_ON(!glob);
+
+       if (strlen(glob)) {
                hist_err_clear();
                last_cmd_set(file, param);
        }