RDMA/uverbs: Check for NULL driver methods for every write call

Add annotations to the uverbs_api structure indicating which driver
methods are called by the implementation. If the required method
is NULL the write API will be not be callable.

This effectively duplicates the cmd_mask system, however it does it by
expressing invariants required by the core code, not by delegating
decision making to the driver. This is another step toward eliminating
cmd_mask.
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>

drivers/infiniband/core/uverbs_uapi.c

@@ -60,8 +60,11 @@ static void *uapi_add_get_elm(struct uverbs_api *uapi, u32 key,
 	return elm;
 }
 
-static int uapi_create_write(struct uverbs_api *uapi, struct ib_device *ibdev,
-			     const struct uapi_definition *def, u32 obj_key)
+static int uapi_create_write(struct uverbs_api *uapi,
+			     struct ib_device *ibdev,
+			     const struct uapi_definition *def,
+			     u32 obj_key,
+			     u32 *cur_method_key)
 {
 	struct uverbs_api_write_method *method_elm;
 	u32 method_key = obj_key;
@@ -93,6 +96,8 @@ static int uapi_create_write(struct uverbs_api *uapi, struct ib_device *ibdev,
 		method_elm->disabled = !(ibdev->uverbs_cmd_mask &
 					 BIT_ULL(def->write.command_num));
 	}
+
+	*cur_method_key = method_key;
 	return 0;
 }
 
@@ -218,7 +223,8 @@ static int uapi_merge_obj_tree(struct uverbs_api *uapi,
 
 static int uapi_disable_elm(struct uverbs_api *uapi,
 			    const struct uapi_definition *def,
-			    u32 obj_key)
+			    u32 obj_key,
+			    u32 method_key)
 {
 	bool exists;
 
@@ -233,6 +239,31 @@ static int uapi_disable_elm(struct uverbs_api *uapi,
 		return 0;
 	}
 
+	if (def->scope == UAPI_SCOPE_METHOD &&
+	    uapi_key_is_ioctl_method(method_key)) {
+		struct uverbs_api_ioctl_method *method_elm;
+
+		method_elm = uapi_add_get_elm(uapi, method_key,
+					      sizeof(*method_elm), &exists);
+		if (IS_ERR(method_elm))
+			return PTR_ERR(method_elm);
+		method_elm->disabled = 1;
+		return 0;
+	}
+
+	if (def->scope == UAPI_SCOPE_METHOD &&
+	    (uapi_key_is_write_method(method_key) ||
+	     uapi_key_is_write_ex_method(method_key))) {
+		struct uverbs_api_write_method *write_elm;
+
+		write_elm = uapi_add_get_elm(uapi, method_key,
+					     sizeof(*write_elm), &exists);
+		if (IS_ERR(write_elm))
+			return PTR_ERR(write_elm);
+		write_elm->disabled = 1;
+		return 0;
+	}
+
 	WARN_ON(true);
 	return -EINVAL;
 }
@@ -243,6 +274,7 @@ static int uapi_merge_def(struct uverbs_api *uapi, struct ib_device *ibdev,
 {
 	const struct uapi_definition *def = def_list;
 	u32 cur_obj_key = UVERBS_API_KEY_ERR;
+	u32 cur_method_key = UVERBS_API_KEY_ERR;
 	bool exists;
 	int rc;
 
@@ -277,7 +309,8 @@ static int uapi_merge_def(struct uverbs_api *uapi, struct ib_device *ibdev,
 
 			if (*ibdev_fn)
 				continue;
-			rc = uapi_disable_elm(uapi, def, cur_obj_key);
+			rc = uapi_disable_elm(
+				uapi, def, cur_obj_key, cur_method_key);
 			if (rc)
 				return rc;
 			continue;
@@ -286,7 +319,8 @@ static int uapi_merge_def(struct uverbs_api *uapi, struct ib_device *ibdev,
 		case UAPI_DEF_IS_SUPPORTED_FUNC:
 			if (def->func_is_supported(ibdev))
 				continue;
-			rc = uapi_disable_elm(uapi, def, cur_obj_key);
+			rc = uapi_disable_elm(
+				uapi, def, cur_obj_key, cur_method_key);
 			if (rc)
 				return rc;
 			continue;
@@ -303,7 +337,8 @@ static int uapi_merge_def(struct uverbs_api *uapi, struct ib_device *ibdev,
 		}
 
 		case UAPI_DEF_WRITE:
-			rc = uapi_create_write(uapi, ibdev, def, cur_obj_key);
+			rc = uapi_create_write(
+				uapi, ibdev, def, cur_obj_key, &cur_method_key);
 			if (rc)
 				return rc;
 			continue;

include/rdma/uverbs_ioctl.h

@@ -350,6 +350,7 @@ enum uapi_definition_kind {
 
 enum uapi_definition_scope {
 	UAPI_SCOPE_OBJECT = 1,
+	UAPI_SCOPE_METHOD = 2,
 };
 
 struct uapi_definition {
@@ -422,6 +423,21 @@ struct uapi_definition {
 				sizeof(void *)),                               \
 	}
 
+/*
+ * Method is only supported if the function pointer named ibdev_fn in struct
+ * ib_device is not NULL.
+ */
+#define UAPI_DEF_METHOD_NEEDS_FN(ibdev_fn)                                     \
+	{                                                                      \
+		.kind = UAPI_DEF_IS_SUPPORTED_DEV_FN,                          \
+		.scope = UAPI_SCOPE_METHOD,                                    \
+		.needs_fn_offset =                                             \
+			offsetof(struct ib_device, ibdev_fn) +                 \
+			BUILD_BUG_ON_ZERO(                                     \
+				sizeof(((struct ib_device *)0)->ibdev_fn) !=   \
+				sizeof(void *)),                               \
+	}
+
 /* Call a function to determine if the entire object is supported or not */
 #define UAPI_DEF_IS_OBJ_SUPPORTED(_func)                                       \
 	{                                                                      \