selftests/bpf: test eager BPF ringbuf size adjustment logic

Add test validating that libbpf adjusts (and reflects adjusted) ringbuf
size early, before bpf_object is loaded. Also make sure we can't
successfully resize ringbuf map after bpf_object is loaded.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20220715230952.2219271-2-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/prog_tests/ringbuf_multi.c b/tools/testing/selftests/bpf/prog_tests/ringbuf_multi.c
index eb5f7f5aa81a27b404a8adf3d76a7e4cdbf8a61a..1455911d9fcbe7d769306382229e8ea3fd8902dc 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/ringbuf_multi.c
+++ b/tools/testing/selftests/bpf/prog_tests/ringbuf_multi.c
@@ -50,6 +50,13 @@ void test_ringbuf_multi(void)
        if (CHECK(!skel, "skel_open", "skeleton open failed\n"))
                return;
 
+       /* validate ringbuf size adjustment logic */
+       ASSERT_EQ(bpf_map__max_entries(skel->maps.ringbuf1), page_size, "rb1_size_before");
+       ASSERT_OK(bpf_map__set_max_entries(skel->maps.ringbuf1, page_size + 1), "rb1_resize");
+       ASSERT_EQ(bpf_map__max_entries(skel->maps.ringbuf1), 2 * page_size, "rb1_size_after");
+       ASSERT_OK(bpf_map__set_max_entries(skel->maps.ringbuf1, page_size), "rb1_reset");
+       ASSERT_EQ(bpf_map__max_entries(skel->maps.ringbuf1), page_size, "rb1_size_final");
+
        proto_fd = bpf_map_create(BPF_MAP_TYPE_RINGBUF, NULL, 0, 0, page_size, NULL);
        if (CHECK(proto_fd < 0, "bpf_map_create", "bpf_map_create failed\n"))
                goto cleanup;
@@ -65,6 +72,10 @@ void test_ringbuf_multi(void)
        close(proto_fd);
        proto_fd = -1;
 
+       /* make sure we can't resize ringbuf after object load */
+       if (!ASSERT_ERR(bpf_map__set_max_entries(skel->maps.ringbuf1, 3 * page_size), "rb1_resize_after_load"))
+               goto cleanup;
+
        /* only trigger BPF program for current process */
        skel->bss->pid = getpid();