selftests/hid: Add a test for BPF_F_INSERT_HEAD

Insert 3 programs to check that we are doing the correct thing:
'2', '1', '3' are inserted, but '1' is supposed to be executed first.

Signed-off-by: Benjamin Tissoires <[e-mail]>
Signed-off-by: Jiri Kosina <[e-mail]>

tools/testing/selftests/hid/hid_bpf.c

···
 	int prog_fd;
 	unsigned int hid;
 	int retval;
+	int insert_head;
 };
 
 struct hid_hw_request_syscall_args {
···
 
 struct test_program {
 	const char *name;
+	int insert_head;
 };
 #define LOAD_PROGRAMS(progs) \
 	load_programs(progs, ARRAY_SIZE(progs), _metadata, self, variant)
···
 
 		args.prog_fd = bpf_program__fd(prog);
 		args.hid = self->hid_id;
+		args.insert_head = programs[i].insert_head;
 		err = bpf_prog_test_run_opts(attach_fd, &tattr);
 		ASSERT_OK(args.retval) TH_LOG("attach_hid(%s): %d", programs[i].name, args.retval);
 	}
···
 	ASSERT_EQ(args.retval, 2);
 
 	ASSERT_EQ(args.data[1], 2);
+}
+
+/*
+ * Attach hid_insert{0,1,2} to the given uhid device,
+ * retrieve and open the matching hidraw node,
+ * inject one event in the uhid device,
+ * check that the programs have been inserted in the correct order.
+ */
+TEST_F(hid_bpf, test_hid_attach_flags)
+{
+	const struct test_program progs[] = {
+		{
+			.name = "hid_test_insert2",
+			.insert_head = 0,
+		},
+		{
+			.name = "hid_test_insert1",
+			.insert_head = 1,
+		},
+		{
+			.name = "hid_test_insert3",
+			.insert_head = 0,
+		},
+	};
+	__u8 buf[10] = {0};
+	int err;
+
+	LOAD_PROGRAMS(progs);
+
+	/* inject one event */
+	buf[0] = 1;
+	uhid_send_event(_metadata, self->uhid_fd, buf, 6);
+
+	/* read the data from hidraw */
+	memset(buf, 0, sizeof(buf));
+	err = read(self->hidraw_fd, buf, sizeof(buf));
+	ASSERT_EQ(err, 6) TH_LOG("read_hidraw");
+	ASSERT_EQ(buf[1], 1);
+	ASSERT_EQ(buf[2], 2);
+	ASSERT_EQ(buf[3], 3);
 }
 
 /*

tools/testing/selftests/hid/progs/hid.c

···
 	int prog_fd;
 	unsigned int hid;
 	int retval;
+	int insert_head;
 };
 
 __u64 callback_check = 52;
···
 {
 	ctx->retval = hid_bpf_attach_prog(ctx->hid,
 					  ctx->prog_fd,
-					  0);
+					  ctx->insert_head ? HID_BPF_FLAG_INSERT_HEAD :
+							     HID_BPF_FLAG_NONE);
 	return 0;
 }
 
···
 	data[4] = 0x42;
 
 	return sizeof(rdesc) + 73;
+}
+
+SEC("?fmod_ret/hid_bpf_device_event")
+int BPF_PROG(hid_test_insert1, struct hid_bpf_ctx *hid_ctx)
+{
+	__u8 *data = hid_bpf_get_data(hid_ctx, 0 /* offset */, 4 /* size */);
+
+	if (!data)
+		return 0; /* EPERM check */
+
+	/* we need to be run first */
+	if (data[2] || data[3])
+		return -1;
+
+	data[1] = 1;
+
+	return 0;
+}
+
+SEC("?fmod_ret/hid_bpf_device_event")
+int BPF_PROG(hid_test_insert2, struct hid_bpf_ctx *hid_ctx)
+{
+	__u8 *data = hid_bpf_get_data(hid_ctx, 0 /* offset */, 4 /* size */);
+
+	if (!data)
+		return 0; /* EPERM check */
+
+	/* after insert0 and before insert2 */
+	if (!data[1] || data[3])
+		return -1;
+
+	data[2] = 2;
+
+	return 0;
+}
+
+SEC("?fmod_ret/hid_bpf_device_event")
+int BPF_PROG(hid_test_insert3, struct hid_bpf_ctx *hid_ctx)
+{
+	__u8 *data = hid_bpf_get_data(hid_ctx, 0 /* offset */, 4 /* size */);
+
+	if (!data)
+		return 0; /* EPERM check */
+
+	/* at the end */
+	if (!data[1] || !data[2])
+		return -1;
+
+	data[3] = 3;
+
+	return 0;
 }