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efi_loader: Add device path related functions for initrd via Boot####

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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@linaro.org>
Reformat function descriptions.
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
This commit is contained in:
Ilias Apalodimas 2021-03-17 21:54:58 +02:00 committed by Heinrich Schuchardt
parent 7dbd7dd399
commit 76e8acce12
2 changed files with 110 additions and 6 deletions
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4
include/efi_loader.h
View file

@ -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);

112
lib/efi_loader/efi_device_path.c
View file

@ -282,11 +282,31 @@ 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.
* 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
*/
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 +318,58 @@ 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;
memcpy(p, dp1, sz1);
/* the end node of the second device path has to be retained */
memcpy(p + sz1, dp2, sz2 + sizeof(END));
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, 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)
{
@ -1183,3 +1243,43 @@ 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
*
* @lo: EFI_LOAD_OPTION containing a valid device path
* @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;
}