[PATCH 1/5 v4] efi_loader: Add device path related functions for initrd via Boot####

[Heinrich Schuchardt]

On 3/17/21 8:54 PM, Ilias Apalodimas wrote:
> On the following patches we allow for an initrd path to be stored in
> Boot#### variables.  Specifically we encode in the FIlePathList[] of
> the EFI_LOAD_OPTIONS for each Boot#### variable.
>
> The FilePathList[] array looks like this:
> kernel - 0xff - VenMedia(initrd GUID) - initrd1 - 0x01 initrd2 - 0xff
> So let's add the relevant functions to concatenate and retrieve a device
> path based on a Vendor GUID.
>
> Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
> ---
>   include/efi_loader.h             |   4 ++
>   lib/efi_loader/efi_device_path.c | 106 +++++++++++++++++++++++++++++--
>   2 files changed, 105 insertions(+), 5 deletions(-)
>
> diff --git a/include/efi_loader.h b/include/efi_loader.h
> index 68daa1a4a9dc..5d534e69bb59 100644
> --- a/include/efi_loader.h
> +++ b/include/efi_loader.h
> @@ -744,6 +744,10 @@ struct efi_load_option {
>   	const u8 *optional_data;
>   };
>
> +struct efi_device_path *efi_dp_from_lo(struct efi_load_option *lo,
> +				       efi_uintn_t *size, efi_guid_t guid);
> +struct efi_device_path *efi_dp_concat(const struct efi_device_path *dp1,
> +				      const struct efi_device_path *dp2);
>   efi_status_t efi_deserialize_load_option(struct efi_load_option *lo, u8 *data,
>   					 efi_uintn_t *size);
>   unsigned long efi_serialize_load_option(struct efi_load_option *lo, u8 **data);
> diff --git a/lib/efi_loader/efi_device_path.c b/lib/efi_loader/efi_device_path.c
> index c9315dd45857..1491251e224b 100644
> --- a/lib/efi_loader/efi_device_path.c
> +++ b/lib/efi_loader/efi_device_path.c
> @@ -282,11 +282,30 @@ struct efi_device_path *efi_dp_dup(const struct efi_device_path *dp)
>   	return ndp;
>   }
>
> -struct efi_device_path *efi_dp_append(const struct efi_device_path *dp1,
> -				      const struct efi_device_path *dp2)
> +/** efi_dp_append_or_concatenate() - Append or concatenate two device paths.

Wrong line. You can't put his on the line with /**.

> + *				     Concatenated device path will be separated
> + *				     by a sub-type 0xff end node
> + *
> + * @dp1:	First device path
> + * @dp2:	Second device path
> + * @concat:	If true the two device paths will be concatenated and separated
> + *		by an end of entrire device path sub-type 0xff end node.
> + *		If true the second device path will be appended to the first and
> + *		terminated by an end node
> + *
> + * Return:	concatenated device path or NULL. Caller must free the returned
> + *              value

Multiple line comments for Return: have to start on a new line or
formatting by Sphinx will fail.

> + */
> +static struct
> +efi_device_path *efi_dp_append_or_concatenate(const struct efi_device_path *dp1,
> +					      const struct efi_device_path *dp2,
> +					      bool concat)
>   {
>   	struct efi_device_path *ret;
> +	size_t end_size = sizeof(END);
>
> +	if (concat)
> +		end_size = 2 * sizeof(END);
>   	if (!dp1 && !dp2) {
>   		/* return an end node */
>   		ret = efi_dp_dup(&END);
> @@ -298,18 +317,56 @@ struct efi_device_path *efi_dp_append(const struct efi_device_path *dp1,
>   		/* both dp1 and dp2 are non-null */
>   		unsigned sz1 = efi_dp_size(dp1);
>   		unsigned sz2 = efi_dp_size(dp2);
> -		void *p = dp_alloc(sz1 + sz2 + sizeof(END));
> +		void *p = dp_alloc(sz1 + sz2 + end_size);
>   		if (!p)
>   			return NULL;
> +		ret = p;
>   		memcpy(p, dp1, sz1);
> +		p += sz1;
> +
> +		if (concat) {
> +			memcpy(p, &END, sizeof(END));
> +			p += sizeof(END);
> +		}
> +
>   		/* the end node of the second device path has to be retained */
> -		memcpy(p + sz1, dp2, sz2 + sizeof(END));
> -		ret = p;
> +		memcpy(p, dp2, sz2);
> +		p += sz2;
> +		memcpy(p, &END, sizeof(END));
>   	}
>
>   	return ret;
>   }
>
> +/** efi_dp_append() - Append a device to an existing device path.
> + *
> + * @dp1:	First device path
> + * @dp2:	Second device path
> + *
> + * Return:	concatenated device path or NULL. Caller must free the returned
> + *              value
> + */
> +struct efi_device_path *efi_dp_append(const struct efi_device_path *dp1,
> +				      const struct efi_device_path *dp2)
> +{
> +	return efi_dp_append_or_concatenate(dp1, dp2, false);
> +}
> +
> +/** efi_dp_concat() - Concatenate 2 device paths. The final device path will
> + *                    contain two device paths separated by and end node (0xff).
> + *
> + * @dp1:	First device path
> + * @dp2:	Second device path
> + *
> + * Return:	concatenated device path or NULL. Caller must free the returned
> + *              value
> + */
> +struct efi_device_path *efi_dp_concat(const struct efi_device_path *dp1,
> +				      const struct efi_device_path *dp2)
> +{
> +	return efi_dp_append_or_concatenate(dp1, dp2, true);
> +}
> +
>   struct efi_device_path *efi_dp_append_node(const struct efi_device_path *dp,
>   					   const struct efi_device_path *node)
>   {
> @@ -1160,3 +1217,42 @@ ssize_t efi_dp_check_length(const struct efi_device_path *dp,
>   		dp = (const struct efi_device_path *)((const u8 *)dp + len);
>   	}
>   }
> +
> +/**
> + * efi_dp_from_lo() - Get the instance of a VenMedia node in a
> + *                    multi-instance device path that matches
> + *                    a specific GUID. This kind of device paths
> + *                    is found in Boot#### options describing an
> + *                    initrd location
> + *
> + * @load_option: EFI_LOAD_OPTION containing a valid device path

@lo:

I will correct the function comments when merging.

Reviewed-by: Heinrich Schuchardt <xypron.glpk at gmx.de>

> + * @size:	 size of the discovered device path
> + * @guid:	 guid to search for
> + *
> + * Return:	 device path including the VenMedia node or NULL.
> + *               Caller must free the returned value
> + */
> +struct
> +efi_device_path *efi_dp_from_lo(struct efi_load_option *lo,
> +				efi_uintn_t *size, efi_guid_t guid)
> +{
> +	struct efi_device_path *fp = lo->file_path;
> +	struct efi_device_path_vendor *vendor;
> +	int lo_len = lo->file_path_length;
> +
> +	for (; lo_len >=  sizeof(struct efi_device_path);
> +	     lo_len -= fp->length, fp = (void *)fp + fp->length) {
> +		if (lo_len < 0 || efi_dp_check_length(fp, lo_len) < 0)
> +			break;
> +		if (fp->type != DEVICE_PATH_TYPE_MEDIA_DEVICE ||
> +		    fp->sub_type != DEVICE_PATH_SUB_TYPE_VENDOR_PATH)
> +			continue;
> +
> +		vendor = (struct efi_device_path_vendor *)fp;
> +		if (!guidcmp(&vendor->guid, &guid))
> +			return efi_dp_dup(fp);
> +	}
> +	log_debug("VenMedia(%pUl) not found in %ls\n", &guid, lo->label);
> +
> +	return NULL;
> +}
>