Merge branch 'add libbpf getters for individual ringbuffers'

Martin Kelly says:

====================
This patch series adds a new ring__ API to libbpf exposing getters for
accessing the individual ringbuffers inside a struct ring_buffer. This is
useful for polling individually, getting available data, or similar use
cases. The API looks like this, and was roughly proposed by Andrii Nakryiko
in another thread:

Getting a ring struct:
struct ring *ring_buffer__ring(struct ring_buffer *rb, unsigned int idx);

Using the ring struct:
unsigned long ring__consumer_pos(const struct ring *r);
unsigned long ring__producer_pos(const struct ring *r);
size_t ring__avail_data_size(const struct ring *r);
size_t ring__size(const struct ring *r);
int ring__map_fd(const struct ring *r);
int ring__consume(struct ring *r);

Changes in v2:
- Addressed all feedback from Andrii Nakryiko
====================

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

2 files changed, 41 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/ringbuf.c b/tools/testing/selftests/bpf/prog_tests/ringbuf.c
index ac104dc652e3..48c5695b7abf 100644
--- a/tools/testing/selftests/bpf/prog_tests/ringbuf.c
+++ b/tools/testing/selftests/bpf/prog_tests/ringbuf.c
@@ -91,6 +91,9 @@ static void ringbuf_subtest(void)
 	int err, cnt, rb_fd;
 	int page_size = getpagesize();
 	void *mmap_ptr, *tmp_ptr;
+	struct ring *ring;
+	int map_fd;
+	unsigned long avail_data, ring_size, cons_pos, prod_pos;
 
 	skel = test_ringbuf_lskel__open();
 	if (CHECK(!skel, "skel_open", "skeleton open failed\n"))
@@ -162,6 +165,13 @@ static void ringbuf_subtest(void)
 
 	trigger_samples();
 
+	ring = ring_buffer__ring(ringbuf, 0);
+	if (!ASSERT_OK_PTR(ring, "ring_buffer__ring_idx_0"))
+		goto cleanup;
+
+	map_fd = ring__map_fd(ring);
+	ASSERT_EQ(map_fd, skel->maps.ringbuf.map_fd, "ring_map_fd");
+
 	/* 2 submitted + 1 discarded records */
 	CHECK(skel->bss->avail_data != 3 * rec_sz,
 	      "err_avail_size", "exp %ld, got %ld\n",
@@ -176,6 +186,18 @@ static void ringbuf_subtest(void)
 	      "err_prod_pos", "exp %ld, got %ld\n",
 	      3L * rec_sz, skel->bss->prod_pos);
 
+	/* verify getting this data directly via the ring object yields the same
+	 * results
+	 */
+	avail_data = ring__avail_data_size(ring);
+	ASSERT_EQ(avail_data, 3 * rec_sz, "ring_avail_size");
+	ring_size = ring__size(ring);
+	ASSERT_EQ(ring_size, page_size, "ring_ring_size");
+	cons_pos = ring__consumer_pos(ring);
+	ASSERT_EQ(cons_pos, 0, "ring_cons_pos");
+	prod_pos = ring__producer_pos(ring);
+	ASSERT_EQ(prod_pos, 3 * rec_sz, "ring_prod_pos");
+
 	/* poll for samples */
 	err = ring_buffer__poll(ringbuf, -1);
 
@@ -282,6 +304,10 @@ static void ringbuf_subtest(void)
 	err = ring_buffer__consume(ringbuf);
 	CHECK(err < 0, "rb_consume", "failed: %d\b", err);
 
+	/* also consume using ring__consume to make sure it works the same */
+	err = ring__consume(ring);
+	ASSERT_GE(err, 0, "ring_consume");
+
 	/* 3 rounds, 2 samples each */
 	cnt = atomic_xchg(&sample_cnt, 0);
 	CHECK(cnt != 6, "cnt", "exp %d samples, got %d\n", 6, cnt);
diff --git a/tools/testing/selftests/bpf/prog_tests/ringbuf_multi.c b/tools/testing/selftests/bpf/prog_tests/ringbuf_multi.c
index 1455911d9fcb..58522195081b 100644
--- a/tools/testing/selftests/bpf/prog_tests/ringbuf_multi.c
+++ b/tools/testing/selftests/bpf/prog_tests/ringbuf_multi.c
@@ -42,6 +42,8 @@ void test_ringbuf_multi(void)
 {
 	struct test_ringbuf_multi *skel;
 	struct ring_buffer *ringbuf = NULL;
+	struct ring *ring_old;
+	struct ring *ring;
 	int err;
 	int page_size = getpagesize();
 	int proto_fd = -1;
@@ -84,11 +86,24 @@ void test_ringbuf_multi(void)
 	if (CHECK(!ringbuf, "ringbuf_create", "failed to create ringbuf\n"))
 		goto cleanup;
 
+	/* verify ring_buffer__ring returns expected results */
+	ring = ring_buffer__ring(ringbuf, 0);
+	if (!ASSERT_OK_PTR(ring, "ring_buffer__ring_idx_0"))
+		goto cleanup;
+	ring_old = ring;
+	ring = ring_buffer__ring(ringbuf, 1);
+	ASSERT_ERR_PTR(ring, "ring_buffer__ring_idx_1");
+
 	err = ring_buffer__add(ringbuf, bpf_map__fd(skel->maps.ringbuf2),
 			      process_sample, (void *)(long)2);
 	if (CHECK(err, "ringbuf_add", "failed to add another ring\n"))
 		goto cleanup;
 
+	/* verify adding a new ring didn't invalidate our older pointer */
+	ring = ring_buffer__ring(ringbuf, 0);
+	if (!ASSERT_EQ(ring, ring_old, "ring_buffer__ring_again"))
+		goto cleanup;
+
 	err = test_ringbuf_multi__attach(skel);
 	if (CHECK(err, "skel_attach", "skeleton attachment failed: %d\n", err))
 		goto cleanup;