[PATCH v2 1/2] tracing/kprobes: add a helper method to return number of probe hits

From: Marcin Nowakowski
Date: Fri Dec 09 2016 - 09:19:48 EST


The number of probe hits is stored in a percpu variable and therefore
can't be read directly. Add a helper method trace_kprobe_nhit() that
performs the required calculation.

It will be used in a follow-up commit that changes kprobe selftests to
verify the number of probe hits.

Signed-off-by: Marcin Nowakowski <marcin.nowakowski@xxxxxxxxxx>
---
kernel/trace/trace_kprobe.c | 19 +++++++++++++------
1 file changed, 13 insertions(+), 6 deletions(-)

v2: improved commit message as suggested by Steven Rostedt

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index eb6c9f1..a2af1bc 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -73,6 +73,17 @@ static nokprobe_inline bool trace_kprobe_is_on_module(struct trace_kprobe *tk)
return !!strchr(trace_kprobe_symbol(tk), ':');
}

+static nokprobe_inline unsigned long trace_kprobe_nhit(struct trace_kprobe *tk)
+{
+ unsigned long nhit = 0;
+ int cpu;
+
+ for_each_possible_cpu(cpu)
+ nhit += *per_cpu_ptr(tk->nhit, cpu);
+
+ return nhit;
+}
+
static int register_kprobe_event(struct trace_kprobe *tk);
static int unregister_kprobe_event(struct trace_kprobe *tk);

@@ -882,14 +893,10 @@ static const struct file_operations kprobe_events_ops = {
static int probes_profile_seq_show(struct seq_file *m, void *v)
{
struct trace_kprobe *tk = v;
- unsigned long nhit = 0;
- int cpu;
-
- for_each_possible_cpu(cpu)
- nhit += *per_cpu_ptr(tk->nhit, cpu);

seq_printf(m, " %-44s %15lu %15lu\n",
- trace_event_name(&tk->tp.call), nhit,
+ trace_event_name(&tk->tp.call),
+ trace_kprobe_nhit(tk),
tk->rp.kp.nmissed);

return 0;
--
2.7.4