iommu: Add iommu_copy_struct_from_user helper

Wrap up the data type/pointer/len sanity and a copy_struct_from_user call
for iommu drivers to copy driver specific data via struct iommu_user_data.
And expect it to be used in the domain_alloc_user op for example.

Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Nicolin Chen <[email protected]>
Co-developed-by: Yi Liu <[email protected]>
Signed-off-by: Yi Liu <[email protected]>
Reviewed-by: Kevin Tian <[email protected]>
Reviewed-by: Jason Gunthorpe <[email protected]>
Signed-off-by: Jason Gunthorpe <[email protected]>

Author: nicolinc

include/linux/iommu.h

@@ -280,6 +280,46 @@ struct iommu_user_data {
 	size_t len;
 };
 
+/**
+ * __iommu_copy_struct_from_user - Copy iommu driver specific user space data
+ * @dst_data: Pointer to an iommu driver specific user data that is defined in
+ *            include/uapi/linux/iommufd.h
+ * @src_data: Pointer to a struct iommu_user_data for user space data info
+ * @data_type: The data type of the @dst_data. Must match with @src_data.type
+ * @data_len: Length of current user data structure, i.e. sizeof(struct _dst)
+ * @min_len: Initial length of user data structure for backward compatibility.
+ *           This should be offsetofend using the last member in the user data
+ *           struct that was initially added to include/uapi/linux/iommufd.h
+ */
+static inline int __iommu_copy_struct_from_user(
+	void *dst_data, const struct iommu_user_data *src_data,
+	unsigned int data_type, size_t data_len, size_t min_len)
+{
+	if (src_data->type != data_type)
+		return -EINVAL;
+	if (WARN_ON(!dst_data || !src_data))
+		return -EINVAL;
+	if (src_data->len < min_len || data_len < src_data->len)
+		return -EINVAL;
+	return copy_struct_from_user(dst_data, data_len, src_data->uptr,
+				     src_data->len);
+}
+
+/**
+ * iommu_copy_struct_from_user - Copy iommu driver specific user space data
+ * @kdst: Pointer to an iommu driver specific user data that is defined in
+ *        include/uapi/linux/iommufd.h
+ * @user_data: Pointer to a struct iommu_user_data for user space data info
+ * @data_type: The data type of the @kdst. Must match with @user_data->type
+ * @min_last: The last memember of the data structure @kdst points in the
+ *            initial version.
+ * Return 0 for success, otherwise -error.
+ */
+#define iommu_copy_struct_from_user(kdst, user_data, data_type, min_last) \
+	__iommu_copy_struct_from_user(kdst, user_data, data_type,         \
+				      sizeof(*kdst),                      \
+				      offsetofend(typeof(*kdst), min_last))
+
 /**
  * struct iommu_ops - iommu ops and capabilities
  * @capable: check capability