[PATCH bpf-next 03/14] libbpf: add ring_buffer__ring

[Martin Kelly <martin.kelly@xxxxxxxxxxxxxxx>]

Add a new function ring_buffer__ring, which exposes struct ring * to the
user, representing a single ringbuffer.

Signed-off-by: Martin Kelly <martin.kelly@xxxxxxxxxxxxxxx>
---
 tools/lib/bpf/libbpf.h   | 14 ++++++++++++++
 tools/lib/bpf/libbpf.map |  1 +
 tools/lib/bpf/ringbuf.c  |  8 ++++++++
 3 files changed, 23 insertions(+)

diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 0e52621cba43..2d6c39e20863 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -1229,6 +1229,7 @@ LIBBPF_API int bpf_tc_query(const struct bpf_tc_hook *hook,
 
 /* Ring buffer APIs */
 struct ring_buffer;
+struct ring;
 struct user_ring_buffer;
 
 typedef int (*ring_buffer_sample_fn)(void *ctx, void *data, size_t size);
@@ -1249,6 +1250,19 @@ LIBBPF_API int ring_buffer__poll(struct ring_buffer *rb, int timeout_ms);
 LIBBPF_API int ring_buffer__consume(struct ring_buffer *rb);
 LIBBPF_API int ring_buffer__epoll_fd(const struct ring_buffer *rb);
 
+/**
+ * @brief **ring_buffer__ring()** returns the ring object inside a given
+ * ringbuffer.
+ *
+ * @param rb A ringbuffer object.
+ * @param idx An index into the rings contained within the ringbuffer object.
+ * The index is 0-based and corresponds to the order in which ring_buffer__add
+ * was called.
+ * @return A ring object on success; NULL and errno set if the index is invalid.
+ */
+LIBBPF_API struct ring *ring_buffer__ring(struct ring_buffer *rb,
+					  unsigned int idx);
+
 struct user_ring_buffer_opts {
 	size_t sz; /* size of this struct, for forward/backward compatibility */
 };
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 57712321490f..7a7370c2bc25 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -400,4 +400,5 @@ LIBBPF_1.3.0 {
 		bpf_program__attach_netfilter;
 		bpf_program__attach_tcx;
 		bpf_program__attach_uprobe_multi;
+		ring_buffer__ring;
 } LIBBPF_1.2.0;
diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c
index c2c79e10cfea..2857df0f2d03 100644
--- a/tools/lib/bpf/ringbuf.c
+++ b/tools/lib/bpf/ringbuf.c
@@ -328,6 +328,14 @@ int ring_buffer__epoll_fd(const struct ring_buffer *rb)
 	return rb->epoll_fd;
 }
 
+struct ring *ring_buffer__ring(struct ring_buffer *rb, unsigned int idx)
+{
+	if (idx >= rb->ring_cnt)
+		return errno = ERANGE, NULL;
+
+	return rb->rings[idx];
+}
+
 static void user_ringbuf_unmap_ring(struct user_ring_buffer *rb)
 {
 	if (rb->consumer_pos) {
-- 
2.34.1