From: Steven Rostedt <rostedt@kernel.org>
To: linux-kernel@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Andrew Morton <akpm@linux-foundation.org>,
Samuel Moelius <sam.moelius@trailofbits.com>
Subject: [for-next][PATCH 13/16] samples/ftrace: Prevent division by zero when nr_function_calls is zero
Date: Tue, 28 Jul 2026 20:05:36 -0400 [thread overview]
Message-ID: <20260729000557.215624909@kernel.org> (raw)
In-Reply-To: 20260729000523.093060274@kernel.org
From: Samuel Moelius <sam.moelius@trailofbits.com>
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@trailofbits.com
Assisted-by: Codex:gpt-5.5-cyber-preview
Signed-off-by: Samuel Moelius <sam.moelius@trailofbits.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
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
next prev parent reply other threads:[~2026-07-29 0:05 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-29 0:05 [for-next][PATCH 00/16] tracing: Updates for v7.3 Steven Rostedt
2026-07-29 0:05 ` [for-next][PATCH 01/16] bpf: Make btf_get_module_btf() and btf_relocate_id() non-static Steven Rostedt
2026-07-29 0:05 ` [for-next][PATCH 02/16] tracing: Expose tracepoint BTF ids via tracefs Steven Rostedt
2026-07-29 0:05 ` [for-next][PATCH 03/16] selftests/bpf: Add test for tracepoint btf_ids tracefs file Steven Rostedt
2026-07-29 0:05 ` [for-next][PATCH 04/16] tracing: Point constant hist field type to string literal Steven Rostedt
2026-07-29 0:05 ` [for-next][PATCH 05/16] kernel/trace/trace_printk: Use kstrdup() instead of kmalloc() and strcpy() Steven Rostedt
2026-07-29 0:05 ` [for-next][PATCH 06/16] tracing: Use __free() for expr_str() buffer Steven Rostedt
2026-07-29 0:05 ` [for-next][PATCH 07/16] tracing: Return ERR_PTR() from expr_str() Steven Rostedt
2026-07-29 0:05 ` [for-next][PATCH 08/16] tracing: Bound histogram expression strings with seq_buf Steven Rostedt
2026-07-29 0:05 ` [for-next][PATCH 09/16] tracing/user_events: Use seq_putc() in two functions Steven Rostedt
2026-07-29 0:05 ` [for-next][PATCH 10/16] tracing/user_events: Replace a seq_printf() call by seq_puts() in user_seq_show() Steven Rostedt
2026-07-29 0:05 ` [for-next][PATCH 11/16] fgraph: Use trace_seq_putc() in print_graph_return() Steven Rostedt
2026-07-29 0:05 ` [for-next][PATCH 12/16] tracing: Reject invalid preemptirq_delay_test CPU affinity Steven Rostedt
2026-07-29 0:05 ` Steven Rostedt [this message]
2026-07-29 0:05 ` [for-next][PATCH 14/16] tracing: Warn when an event dereferences a pointer in TP_printk() Steven Rostedt
2026-07-29 0:05 ` [for-next][PATCH 15/16] tracing: Use strscpy() instead of strcpy() in trace_sched_switch Steven Rostedt
2026-07-29 0:05 ` [for-next][PATCH 16/16] tracing: Use seq_buf for string concatenation Steven Rostedt
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