[for-next][PATCH 13/16] samples/ftrace: Prevent division by zero when nr_function_calls is zero

[Steven Rostedt]

From: Samuel Moelius <sam.moelius@xxxxxxxxxxxxxxx>

The ftrace-ops sample exposes nr_function_calls as a module parameter
and uses it as the divisor when printing the measured time per call.
Loading the module with nr_function_calls=0 skips the benchmark loop and
then divides the elapsed time by zero, crashing the kernel during sample
module initialization.

Keep accepting the parameter value, but report -1LL as the per-call
duration when the call count is zero instead of dividing by it.

Link: https://patch.msgid.link/20260629152616.107080.e19bfbed249c.ftrace-ops-zero-function-calls-div0@xxxxxxxxxxxxxxx
Assisted-by: Codex:gpt-5.5-cyber-preview
Signed-off-by: Samuel Moelius <sam.moelius@xxxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 samples/ftrace/ftrace-ops.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/samples/ftrace/ftrace-ops.c b/samples/ftrace/ftrace-ops.c
index 152ffc1a30b6..8cae38d8b879 100644
--- a/samples/ftrace/ftrace-ops.c
+++ b/samples/ftrace/ftrace-ops.c
@@ -223,7 +223,7 @@ static int __init ftrace_ops_sample_init(void)
 
 	pr_info("Attempted %u calls to %ps in %lluns (%lluns / call)\n",
 		nr_function_calls, tracee_relevant,
-		period, div_u64(period, nr_function_calls));
+		period, nr_function_calls ? div_u64(period, nr_function_calls) : -1LL);
 
 	if (persist)
 		return 0;
-- 
2.53.0