selftests/bpf: test for BPF_F_LOCK

Add C based test that runs 4 bpf programs in parallel
that update the same hash and array maps.
And another 2 threads that read from these two maps
via lookup(key, value, BPF_F_LOCK) api
to make sure the user space sees consistent value in both
hash and array elements while user space races with kernel bpf progs.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 74 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c
index d2e71d697340..a08d026ac396 100644
--- a/tools/testing/selftests/bpf/test_progs.c
+++ b/tools/testing/selftests/bpf/test_progs.c
@@ -2025,6 +2025,79 @@ close_prog_noerr:
 	bpf_object__close(obj);
 }
 
+static void *parallel_map_access(void *arg)
+{
+	int err, map_fd = *(u32 *) arg;
+	int vars[17], i, j, rnd, key = 0;
+
+	for (i = 0; i < 10000; i++) {
+		err = bpf_map_lookup_elem_flags(map_fd, &key, vars, BPF_F_LOCK);
+		if (err) {
+			printf("lookup failed\n");
+			error_cnt++;
+			goto out;
+		}
+		if (vars[0] != 0) {
+			printf("lookup #%d var[0]=%d\n", i, vars[0]);
+			error_cnt++;
+			goto out;
+		}
+		rnd = vars[1];
+		for (j = 2; j < 17; j++) {
+			if (vars[j] == rnd)
+				continue;
+			printf("lookup #%d var[1]=%d var[%d]=%d\n",
+			       i, rnd, j, vars[j]);
+			error_cnt++;
+			goto out;
+		}
+	}
+out:
+	pthread_exit(arg);
+}
+
+static void test_map_lock(void)
+{
+	const char *file = "./test_map_lock.o";
+	int prog_fd, map_fd[2], vars[17] = {};
+	pthread_t thread_id[6];
+	struct bpf_object *obj;
+	int err = 0, key = 0, i;
+	void *ret;
+
+	err = bpf_prog_load(file, BPF_PROG_TYPE_CGROUP_SKB, &obj, &prog_fd);
+	if (err) {
+		printf("test_map_lock:bpf_prog_load errno %d\n", errno);
+		goto close_prog;
+	}
+	map_fd[0] = bpf_find_map(__func__, obj, "hash_map");
+	if (map_fd[0] < 0)
+		goto close_prog;
+	map_fd[1] = bpf_find_map(__func__, obj, "array_map");
+	if (map_fd[1] < 0)
+		goto close_prog;
+
+	bpf_map_update_elem(map_fd[0], &key, vars, BPF_F_LOCK);
+
+	for (i = 0; i < 4; i++)
+		assert(pthread_create(&thread_id[i], NULL,
+				      &test_spin_lock, &prog_fd) == 0);
+	for (i = 4; i < 6; i++)
+		assert(pthread_create(&thread_id[i], NULL,
+				      &parallel_map_access, &map_fd[i - 4]) == 0);
+	for (i = 0; i < 4; i++)
+		assert(pthread_join(thread_id[i], &ret) == 0 &&
+		       ret == (void *)&prog_fd);
+	for (i = 4; i < 6; i++)
+		assert(pthread_join(thread_id[i], &ret) == 0 &&
+		       ret == (void *)&map_fd[i - 4]);
+	goto close_prog_noerr;
+close_prog:
+	error_cnt++;
+close_prog_noerr:
+	bpf_object__close(obj);
+}
+
 int main(void)
 {
 	srand(time(NULL));
@@ -2054,6 +2127,7 @@ int main(void)
 	test_queue_stack_map(STACK);
 	test_flow_dissector();
 	test_spinlock();
+	test_map_lock();
 
 	printf("Summary: %d PASSED, %d FAILED\n", pass_cnt, error_cnt);
 	return error_cnt ? EXIT_FAILURE : EXIT_SUCCESS;