[PATCHv2 bpf-next 4/9] bpf: Count missed stats in trace_call_bpf

[Jiri Olsa <jolsa@kernel.org>]

Increase misses stats in case bpf array execution is skipped
because of recursion check in trace_call_bpf.

Adding bpf_prog_inc_misses_counters that increase misses
counts for all bpf programs in bpf_prog_array.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 include/linux/bpf.h      | 16 ++++++++++++++++
 kernel/trace/bpf_trace.c |  3 +++
 2 files changed, 19 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 87eeb3a46a1d..abc18d6f2f2e 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2911,6 +2911,22 @@ static inline int sock_map_bpf_prog_query(const union bpf_attr *attr,
 #endif /* CONFIG_BPF_SYSCALL */
 #endif /* CONFIG_NET && CONFIG_BPF_SYSCALL */
 
+static __always_inline void
+bpf_prog_inc_misses_counters(const struct bpf_prog_array *array)
+{
+	const struct bpf_prog_array_item *item;
+	struct bpf_prog *prog;
+
+	if (unlikely(!array))
+		return;
+
+	item = &array->items[0];
+	while ((prog = READ_ONCE(item->prog))) {
+		bpf_prog_inc_misses_counter(prog);
+		item++;
+	}
+}
+
 #if defined(CONFIG_INET) && defined(CONFIG_BPF_SYSCALL)
 void bpf_sk_reuseport_detach(struct sock *sk);
 int bpf_fd_reuseport_array_lookup_elem(struct bpf_map *map, void *key,
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index a9d8634b503c..44f399b19af1 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -117,6 +117,9 @@ unsigned int trace_call_bpf(struct trace_event_call *call, void *ctx)
 		 * and don't send kprobe event into ring-buffer,
 		 * so return zero here
 		 */
+		rcu_read_lock();
+		bpf_prog_inc_misses_counters(rcu_dereference(call->prog_array));
+		rcu_read_unlock();
 		ret = 0;
 		goto out;
 	}
-- 
2.41.0