bpf: Add tests for eBPF file mode

Two related tests are added into bpf selftest to test read only map and
write only map. The tests verified the read only and write only flags
are working on hash maps.
Signed-off-by: Chenbo Feng <fengc@google.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools/testing/selftests/bpf/test_maps.c

@@ -1033,6 +1033,51 @@ static void test_map_parallel(void)
 	assert(bpf_map_get_next_key(fd, &key, &key) == -1 && errno == ENOENT);
 }
 
+static void test_map_rdonly(void)
+{
+	int i, fd, key = 0, value = 0;
+
+	fd = bpf_create_map(BPF_MAP_TYPE_HASH, sizeof(key), sizeof(value),
+			    MAP_SIZE, map_flags | BPF_F_RDONLY);
+	if (fd < 0) {
+		printf("Failed to create map for read only test '%s'!\n",
+		       strerror(errno));
+		exit(1);
+	}
+
+	key = 1;
+	value = 1234;
+	/* Insert key=1 element. */
+	assert(bpf_map_update_elem(fd, &key, &value, BPF_ANY) == -1 &&
+	       errno == EPERM);
+
+	/* Check that key=2 is not found. */
+	assert(bpf_map_lookup_elem(fd, &key, &value) == -1 && errno == ENOENT);
+	assert(bpf_map_get_next_key(fd, &key, &value) == -1 && errno == ENOENT);
+}
+
+static void test_map_wronly(void)
+{
+	int i, fd, key = 0, value = 0;
+
+	fd = bpf_create_map(BPF_MAP_TYPE_HASH, sizeof(key), sizeof(value),
+			    MAP_SIZE, map_flags | BPF_F_WRONLY);
+	if (fd < 0) {
+		printf("Failed to create map for read only test '%s'!\n",
+		       strerror(errno));
+		exit(1);
+	}
+
+	key = 1;
+	value = 1234;
+	/* Insert key=1 element. */
+	assert(bpf_map_update_elem(fd, &key, &value, BPF_ANY) == 0)
+
+	/* Check that key=2 is not found. */
+	assert(bpf_map_lookup_elem(fd, &key, &value) == -1 && errno == EPERM);
+	assert(bpf_map_get_next_key(fd, &key, &value) == -1 && errno == EPERM);
+}
+
 static void run_all_tests(void)
 {
 	test_hashmap(0, NULL);
@@ -1050,6 +1095,9 @@ static void run_all_tests(void)
 	test_map_large();
 	test_map_parallel();
 	test_map_stress();
+
+	test_map_rdonly();
+	test_map_wronly();
 }
 
 int main(void)