selftests/bpf: Test access to ringbuf position with map pointer

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>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/bpf/20260331070434.10037-1-dongml2@chinatelecom.cn

diff --git a/tools/testing/selftests/bpf/progs/map_ptr_kern.c b/tools/testing/selftests/bpf/progs/map_ptr_kern.c
index efaf622c28ddec5561b2a37c4b5233204ad3dbf8..373c8d17ea557d48cf386b51d756e5293e3f2954 100644 (file)
--- 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;
 }