[PATCH bpf-next 05/14] libbpf: add ring__producer_pos, ring__consumer_pos

[Martin Kelly <martin.kelly@xxxxxxxxxxxxxxx>]

Add APIs to get the producer and consumer position for a given
ringbuffer.

Signed-off-by: Martin Kelly <martin.kelly@xxxxxxxxxxxxxxx>
---
 tools/lib/bpf/libbpf.h   | 16 ++++++++++++++++
 tools/lib/bpf/libbpf.map |  2 ++
 tools/lib/bpf/ringbuf.c  | 14 ++++++++++++++
 3 files changed, 32 insertions(+)

diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 2d6c39e20863..935162dbb3bf 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -1263,6 +1263,22 @@ LIBBPF_API int ring_buffer__epoll_fd(const struct ring_buffer *rb);
 LIBBPF_API struct ring *ring_buffer__ring(struct ring_buffer *rb,
 					  unsigned int idx);
 
+/**
+ * @brief **ring__consumer_pos()** returns the current consumer position.
+ *
+ * @param r A ring object.
+ * @return The current consumer position.
+ */
+LIBBPF_API unsigned long ring__consumer_pos(const struct ring *r);
+
+/**
+ * @brief **ring__producer_pos()** returns the current producer position.
+ *
+ * @param r A ring object.
+ * @return The current producer position.
+ */
+LIBBPF_API unsigned long ring__producer_pos(const struct ring *r);
+
 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 7a7370c2bc25..1c532fe7a445 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -401,4 +401,6 @@ LIBBPF_1.3.0 {
 		bpf_program__attach_tcx;
 		bpf_program__attach_uprobe_multi;
 		ring_buffer__ring;
+		ring__consumer_pos;
+		ring__producer_pos;
 } LIBBPF_1.2.0;
diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c
index 2857df0f2d03..54c596db57a4 100644
--- a/tools/lib/bpf/ringbuf.c
+++ b/tools/lib/bpf/ringbuf.c
@@ -336,6 +336,20 @@ struct ring *ring_buffer__ring(struct ring_buffer *rb, unsigned int idx)
 	return rb->rings[idx];
 }
 
+unsigned long ring__consumer_pos(const struct ring *r)
+{
+	/* Synchronizes with smp_store_release() in ringbuf_process_ring(). */
+	return smp_load_acquire(r->consumer_pos);
+}
+
+unsigned long ring__producer_pos(const struct ring *r)
+{
+	/* Synchronizes with smp_store_release() in __bpf_ringbuf_reserve() in
+	 * the kernel.
+	 */
+	return smp_load_acquire(r->producer_pos);
+}
+
 static void user_ringbuf_unmap_ring(struct user_ring_buffer *rb)
 {
 	if (rb->consumer_pos) {
-- 
2.34.1