linux-kernel - [for-linus][PATCH 07/10] tracing: Fix smatch warning for null glob in event_hist_trigger

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Date:   Fri, 28 Jan 2022 11:18:09 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kernel test robot <lkp@...el.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Tom Zanussi <zanussi@...nel.org>
Subject: [for-linus][PATCH 07/10] tracing: Fix smatch warning for null glob in
 event_hist_trigger_parse()

From: Tom Zanussi <zanussi@...nel.org>

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@...el.com>
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Tom Zanussi <zanussi@...nel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 kernel/trace/trace_events_hist.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index cd9610688ddc..e0860146dd39 100644
--- 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);
 	}
-- 
2.33.0