selftests/bpf: ringbuf: Use runtime page size

Replace hardcoded 4096 with runtime value in the userspace part of
the test and set bpf table sizes dynamically according to the value.

Do not switch to ASSERT macros, keep CHECK, for consistency with the
rest of the test. Can be a separate cleanup patch.
Signed-off-by: Yauheni Kaliuta <yauheni.kaliuta@redhat.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210408061310.95877-6-yauheni.kaliuta@redhat.com

tools/testing/selftests/bpf/prog_tests/ringbuf.c

@@ -87,11 +87,20 @@ void test_ringbuf(void)
 	pthread_t thread;
 	long bg_ret = -1;
 	int err, cnt;
+	int page_size = getpagesize();
 
-	skel = test_ringbuf__open_and_load();
-	if (CHECK(!skel, "skel_open_load", "skeleton open&load failed\n"))
+	skel = test_ringbuf__open();
+	if (CHECK(!skel, "skel_open", "skeleton open failed\n"))
 		return;
 
+	err = bpf_map__set_max_entries(skel->maps.ringbuf, page_size);
+	if (CHECK(err != 0, "bpf_map__set_max_entries", "bpf_map__set_max_entries failed\n"))
+		goto cleanup;
+
+	err = test_ringbuf__load(skel);
+	if (CHECK(err != 0, "skel_load", "skeleton load failed\n"))
+		goto cleanup;
+
 	/* only trigger BPF program for current process */
 	skel->bss->pid = getpid();
 
@@ -110,9 +119,9 @@ void test_ringbuf(void)
 	CHECK(skel->bss->avail_data != 3 * rec_sz,
 	      "err_avail_size", "exp %ld, got %ld\n",
 	      3L * rec_sz, skel->bss->avail_data);
-	CHECK(skel->bss->ring_size != 4096,
+	CHECK(skel->bss->ring_size != page_size,
 	      "err_ring_size", "exp %ld, got %ld\n",
-	      4096L, skel->bss->ring_size);
+	      (long)page_size, skel->bss->ring_size);
 	CHECK(skel->bss->cons_pos != 0,
 	      "err_cons_pos", "exp %ld, got %ld\n",
 	      0L, skel->bss->cons_pos);

tools/testing/selftests/bpf/progs/test_ringbuf.c

@@ -15,7 +15,6 @@ struct sample {
 
 struct {
 	__uint(type, BPF_MAP_TYPE_RINGBUF);
-	__uint(max_entries, 1 << 12);
 } ringbuf SEC(".maps");
 
 /* inputs */