RDMA/core: Add UVERBS_ATTR_RAW_FD

This uses the same passing protocol as UVERBS_ATTR_FD (eg len = 0 data_s64
= fd), except that the FD is not required to be a uverbs object and the
core code does not covert the FD to an object handle automatically.

Access to the int fd is provided by uverbs_get_raw_fd().

Link: https://lore.kernel.org/r/2-v1-bd147097458e+ede-umem_dmabuf_jgg@nvidia.com
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/core/uverbs_ioctl.c

@@ -337,6 +337,14 @@ static int uverbs_process_attr(struct bundle_priv *pbundle,
 
 		break;
 
+	case UVERBS_ATTR_TYPE_RAW_FD:
+		if (uattr->attr_data.reserved || uattr->len != 0 ||
+		    uattr->data_s64 < INT_MIN || uattr->data_s64 > INT_MAX)
+			return -EINVAL;
+		/* _uverbs_get_const_signed() is the accessor */
+		e->ptr_attr.data = uattr->data_s64;
+		break;
+
 	case UVERBS_ATTR_TYPE_IDRS_ARRAY:
 		return uverbs_process_idrs_array(pbundle, attr_uapi,
 						 &e->objs_arr_attr, uattr,

include/rdma/uverbs_ioctl.h

@@ -24,6 +24,7 @@ enum uverbs_attr_type {
 	UVERBS_ATTR_TYPE_PTR_OUT,
 	UVERBS_ATTR_TYPE_IDR,
 	UVERBS_ATTR_TYPE_FD,
+	UVERBS_ATTR_TYPE_RAW_FD,
 	UVERBS_ATTR_TYPE_ENUM_IN,
 	UVERBS_ATTR_TYPE_IDRS_ARRAY,
 };
@@ -521,6 +522,11 @@ struct uapi_definition {
 			  .u.obj.access = _access,                             \
 			  __VA_ARGS__ } })
 
+#define UVERBS_ATTR_RAW_FD(_attr_id, ...)                                      \
+	(&(const struct uverbs_attr_def){                                      \
+		.id = (_attr_id),                                              \
+		.attr = { .type = UVERBS_ATTR_TYPE_RAW_FD, __VA_ARGS__ } })
+
 #define UVERBS_ATTR_PTR_IN(_attr_id, _type, ...)                               \
 	(&(const struct uverbs_attr_def){                                      \
 		.id = _attr_id,                                                \
@@ -999,4 +1005,11 @@ _uverbs_get_const_unsigned(u64 *to,
 		 uverbs_get_const_default_unsigned(_to, _attrs_bundle, _idx,   \
 						    _default))
 
+static inline int
+uverbs_get_raw_fd(int *to, const struct uverbs_attr_bundle *attrs_bundle,
+		  size_t idx)
+{
+	return uverbs_get_const_signed(to, attrs_bundle, idx);
+}
+
 #endif