[PATCH bpf-next v3] selftests/bpf: test access to ringbuf position with map pointer

Menglong Dong
2026-03-31T07:04:55Z

Add the testing to access the bpf_ringbuf with the map pointer.
"consumer_pos" and "producer_pos" is accessed in this testing. We reserve
128 bytes in the ringbuf to test the producer_pos, which should be
"128 + BPF_RINGBUF_HDR_SZ".

It will be helpful if we want to evaluate the usage of the ringbuf in bpf
prog with the consumer and producer position.

Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
---
v3:
- use BPF_RINGBUF_HDR_SZ instead of 8 in check_ringbuf()

v2:
- don't set the max_entries for the ringbuf map
- add comment for the producer_pos
---
.../testing/selftests/bpf/progs/map_ptr_kern.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/map_ptr_kern.c b/tools/testing/selftests/bpf/progs/map_ptr_kern.c
index efaf622c28dd..373c8d17ea55 100644
--- a/tools/testing/selftests/bpf/progs/map_ptr_kern.c
+++ b/tools/testing/selftests/bpf/progs/map_ptr_kern.c
@@ -647,8 +647,14 @@ static inline int check_devmap_hash(void)
return 1;
}

+struct bpf_ringbuf {
+ unsigned long consumer_pos;
+ unsigned long producer_pos;
+} __attribute__((preserve_access_index));
+
struct bpf_ringbuf_map {
struct bpf_map map;
+ struct bpf_ringbuf *rb;
} __attribute__((preserve_access_index));

struct {
@@ -659,9 +665,20 @@ static inline int check_ringbuf(void)
{
struct bpf_ringbuf_map *ringbuf = (struct bpf_ringbuf_map *)&m_ringbuf;
struct bpf_map *map = (struct bpf_map *)&m_ringbuf;
+ struct bpf_ringbuf *rb;
+ void *ptr;

VERIFY(check(&ringbuf->map, map, 0, 0, page_size));

+ ptr = bpf_ringbuf_reserve(&m_ringbuf, 128, 0);
+ VERIFY(ptr);
+
+ bpf_ringbuf_discard(ptr, 0);
+ rb = ringbuf->rb;
+ VERIFY(rb);
+ VERIFY(rb->consumer_pos == 0);
+ VERIFY(rb->producer_pos == 128 + BPF_RINGBUF_HDR_SZ);
+
return 1;
}

--
2.53.0