optee: use export_uuid() to copy client UUID

Prior to this patch optee_open_session() was making assumptions about
the internal format of uuid_t by casting a memory location in a
parameter struct to uuid_t *. Fix this using export_uuid() to get a well
defined binary representation and also add an octets field in struct
optee_msg_param in order to avoid casting.

Fixes: c5b4312b ("tee: optee: Add support for session login client UUID generation")
Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>

drivers/tee/optee/call.c

@@ -220,6 +220,7 @@ int optee_open_session(struct tee_context *ctx,
 	struct optee_msg_arg *msg_arg;
 	phys_addr_t msg_parg;
 	struct optee_session *sess = NULL;
+	uuid_t client_uuid;
 
 	/* +2 for the meta parameters added below */
 	shm = get_msg_arg(ctx, arg->num_params + 2, &msg_arg, &msg_parg);
@@ -240,10 +241,11 @@ int optee_open_session(struct tee_context *ctx,
 	memcpy(&msg_arg->params[0].u.value, arg->uuid, sizeof(arg->uuid));
 	msg_arg->params[1].u.value.c = arg->clnt_login;
 
-	rc = tee_session_calc_client_uuid((uuid_t *)&msg_arg->params[1].u.value,
-					  arg->clnt_login, arg->clnt_uuid);
+	rc = tee_session_calc_client_uuid(&client_uuid, arg->clnt_login,
+					  arg->clnt_uuid);
 	if (rc)
 		goto out;
+	export_uuid(msg_arg->params[1].u.octets, &client_uuid);
 
 	rc = optee_to_msg_param(msg_arg->params + 2, arg->num_params, param);
 	if (rc)

drivers/tee/optee/optee_msg.h

@@ -9,7 +9,7 @@
 #include <linux/types.h>
 
 /*
- * This file defines the OP-TEE message protocol used to communicate
+ * This file defines the OP-TEE message protocol (ABI) used to communicate
  * with an instance of OP-TEE running in secure world.
  *
  * This file is divided into two sections.
@@ -144,9 +144,10 @@ struct optee_msg_param_value {
  * @tmem:	parameter by temporary memory reference
  * @rmem:	parameter by registered memory reference
  * @value:	parameter by opaque value
+ * @octets:	parameter by octet string
  *
  * @attr & OPTEE_MSG_ATTR_TYPE_MASK indicates if tmem, rmem or value is used in
- * the union. OPTEE_MSG_ATTR_TYPE_VALUE_* indicates value,
+ * the union. OPTEE_MSG_ATTR_TYPE_VALUE_* indicates value or octets,
  * OPTEE_MSG_ATTR_TYPE_TMEM_* indicates @tmem and
  * OPTEE_MSG_ATTR_TYPE_RMEM_* indicates @rmem,
  * OPTEE_MSG_ATTR_TYPE_NONE indicates that none of the members are used.
@@ -157,6 +158,7 @@ struct optee_msg_param {
 		struct optee_msg_param_tmem tmem;
 		struct optee_msg_param_rmem rmem;
 		struct optee_msg_param_value value;
+		u8 octets[24];
 	} u;
 };