Re: [PATCH v2 04/22] iommu: Add iommu_copy_struct_to_user helper

[Pranjal Shrivastava <praan@google.com>]

On Fri, Apr 25, 2025 at 10:57:59PM -0700, Nicolin Chen wrote:
> Similar to the iommu_copy_struct_from_user helper receiving data from the
> user space, add an iommu_copy_struct_to_user helper to report output data
> back to the user space data pointer.
> 
> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
> ---
>  include/linux/iommu.h | 40 ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 40 insertions(+)
> 
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index ba7add27e9a0..634ff647888d 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -562,6 +562,46 @@ iommu_copy_struct_from_full_user_array(void *kdst, size_t kdst_entry_size,
>  	return 0;
>  }
>  
> +/**
> + * __iommu_copy_struct_to_user - Report iommu driver specific user space data
> + * @dst_data: Pointer to a struct iommu_user_data for user space data location
> + * @src_data: Pointer to an iommu driver specific user data that is defined in
> + *            include/uapi/linux/iommufd.h
> + * @data_type: The data type of the @dst_data. Must match with @src_data.type
								   ^
Nit: Must match with @dst_data type.

> + * @data_len: Length of current user data structure, i.e. sizeof(struct _src)
> + * @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_to_user(const struct iommu_user_data *dst_data,
> +			    void *src_data, unsigned int data_type,
> +			    size_t data_len, size_t min_len)
> +{
> +	if (WARN_ON(!dst_data || !src_data))
> +		return -EINVAL;
> +	if (dst_data->type != data_type)
> +		return -EINVAL;
> +	if (dst_data->len < min_len || data_len < dst_data->len)
> +		return -EINVAL;
> +	return copy_struct_to_user(dst_data->uptr, dst_data->len, src_data,
> +				   data_len, NULL);
> +}
> +
> +/**
> + * iommu_copy_struct_to_user - Report iommu driver specific user space data
> + * @user_data: Pointer to a struct iommu_user_data for user space data location
> + * @ksrc: Pointer to an iommu driver specific user data that is defined in
> + *        include/uapi/linux/iommufd.h
> + * @data_type: The data type of the @ksrc. Must match with @user_data->type
> + * @min_last: The last member of the data structure @ksrc points in the initial
> + *            version.
> + * Return 0 for success, otherwise -error.
> + */
> +#define iommu_copy_struct_to_user(user_data, ksrc, data_type, min_last)        \
> +	__iommu_copy_struct_to_user(user_data, ksrc, data_type, sizeof(*ksrc), \
> +				    offsetofend(typeof(*ksrc), min_last))
> +
>  /**
>   * struct iommu_ops - iommu ops and capabilities
>   * @capable: check capability

With the above nit.
Reviewed-by: Pranjal Shrivastava <praan@google.com>

> -- 
> 2.43.0
>