[PATCH 2/2] efi_loader: use short-form DP for load options

[Heinrich Schuchardt]

On 3/2/22 10:44, AKASHI Takahiro wrote:
> On Sat, Feb 26, 2022 at 12:56:51PM +0100, Heinrich Schuchardt wrote:
>> The GUID of partitions is sufficient for identification and will stay
>> constant in the lifetime of a boot option. The preceding path of the
>> device-path may change due to changes in the enumeration of devices.
>> Therefore it is preferable to use the short-form of device-paths in load
>> options. Adjust the 'efidebug boot add' command accordingly.
>
> Since a "long" device path is still valid, I think that a user should
> be allowed to use a long device path especially if he or she wants to
> limit an interface for loading any image.
> Please add an option to efidebug to select a short or long path.
>
> Furthermore, I would like to ask you to add a test, as you always
> require me to do so, for loading from a short path.
> Otherwise, the feature will never be exercised in CI loop.
>
> -Takahiro Akashi

Dear Takahiro,

thanks for reviewing. In the next round I will alternative options
-b/-B, -i/-I to choose between long and short device path.

I will create a Python test exposes a initrd via LoadFile2 protocol and
then use initrddump.efi as binary payload and to check the content of
the initrd.

Best regards

Heinrich

>
>
>> Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
>> ---
>>   cmd/efidebug.c                   | 15 +++++++++++----
>>   include/efi_loader.h             |  3 ++-
>>   lib/efi_loader/efi_device_path.c | 21 +++++++++++++--------
>>   3 files changed, 26 insertions(+), 13 deletions(-)
>>
>> diff --git a/cmd/efidebug.c b/cmd/efidebug.c
>> index 401d13cc4c..f62a4345fd 100644
>> --- a/cmd/efidebug.c
>> +++ b/cmd/efidebug.c
>> @@ -747,7 +747,7 @@ struct efi_device_path *create_initrd_dp(const char *dev, const char *part,
>>   					 const char *file)
>>
>>   {
>> -	struct efi_device_path *tmp_dp = NULL, *tmp_fp = NULL;
>> +	struct efi_device_path *tmp_dp = NULL, *tmp_fp = NULL, *short_fp;
>>   	struct efi_device_path *initrd_dp = NULL;
>>   	efi_status_t ret;
>>   	const struct efi_initrd_dp id_dp = {
>> @@ -771,9 +771,12 @@ struct efi_device_path *create_initrd_dp(const char *dev, const char *part,
>>   		printf("Cannot create device path for \"%s %s\"\n", part, file);
>>   		goto out;
>>   	}
>> +	short_fp = efi_dp_shorten(tmp_fp);
>> +	if (!short_fp)
>> +		short_fp = tmp_fp;
>>
>>   	initrd_dp = efi_dp_append((const struct efi_device_path *)&id_dp,
>> -				  tmp_fp);
>> +				  short_fp);
>>
>>   out:
>>   	efi_free_pool(tmp_dp);
>> @@ -807,6 +810,7 @@ static int do_efi_boot_add(struct cmd_tbl *cmdtp, int flag,
>>   	size_t label_len, label_len16;
>>   	u16 *label;
>>   	struct efi_device_path *device_path = NULL, *file_path = NULL;
>> +	struct efi_device_path *fp_free = NULL;
>>   	struct efi_device_path *final_fp = NULL;
>>   	struct efi_device_path *initrd_dp = NULL;
>>   	struct efi_load_option lo;
>> @@ -849,13 +853,16 @@ static int do_efi_boot_add(struct cmd_tbl *cmdtp, int flag,
>>
>>   			/* file path */
>>   			ret = efi_dp_from_name(argv[3], argv[4], argv[5],
>> -					       &device_path, &file_path);
>> +					       &device_path, &fp_free);
>>   			if (ret != EFI_SUCCESS) {
>>   				printf("Cannot create device path for \"%s %s\"\n",
>>   				       argv[3], argv[4]);
>>   				r = CMD_RET_FAILURE;
>>   				goto out;
>>   			}
>> +			file_path = efi_dp_shorten(fp_free);
>> +			if (!file_path)
>> +				file_path = fp_free;
>>   			fp_size += efi_dp_size(file_path) +
>>   				sizeof(struct efi_device_path);
>>   			argc -= 5;
>> @@ -927,7 +934,7 @@ out:
>>   	efi_free_pool(final_fp);
>>   	efi_free_pool(initrd_dp);
>>   	efi_free_pool(device_path);
>> -	efi_free_pool(file_path);
>> +	efi_free_pool(fp_free);
>>   	free(lo.label);
>>
>>   	return r;
>> diff --git a/include/efi_loader.h b/include/efi_loader.h
>> index e390d323a9..c7d6b7c7f3 100644
>> --- a/include/efi_loader.h
>> +++ b/include/efi_loader.h
>> @@ -725,7 +725,8 @@ extern void *efi_bounce_buffer;
>>   #define EFI_LOADER_BOUNCE_BUFFER_SIZE (64 * 1024 * 1024)
>>   #endif
>>
>> -
>> +/* shorten device path */
>> +struct efi_device_path *efi_dp_shorten(struct efi_device_path *dp);
>>   struct efi_device_path *efi_dp_next(const struct efi_device_path *dp);
>>   int efi_dp_match(const struct efi_device_path *a,
>>   		 const struct efi_device_path *b);
>> diff --git a/lib/efi_loader/efi_device_path.c b/lib/efi_loader/efi_device_path.c
>> index dc787b4d3d..ddd5f132ec 100644
>> --- a/lib/efi_loader/efi_device_path.c
>> +++ b/lib/efi_loader/efi_device_path.c
>> @@ -122,20 +122,25 @@ int efi_dp_match(const struct efi_device_path *a,
>>   	}
>>   }
>>
>> -/*
>> +/**
>> + * efi_dp_shorten() - shorten device-path
>> + *
>>    * We can have device paths that start with a USB WWID or a USB Class node,
>>    * and a few other cases which don't encode the full device path with bus
>>    * hierarchy:
>>    *
>> - *   - MESSAGING:USB_WWID
>> - *   - MESSAGING:USB_CLASS
>> - *   - MEDIA:FILE_PATH
>> - *   - MEDIA:HARD_DRIVE
>> - *   - MESSAGING:URI
>> + * * MESSAGING:USB_WWID
>> + * * MESSAGING:USB_CLASS
>> + * * MEDIA:FILE_PATH
>> + * * MEDIA:HARD_DRIVE
>> + * * MESSAGING:URI
>>    *
>>    * See UEFI spec (section 3.1.2, about short-form device-paths)
>> + *
>> + * @dp:		original devie-path
>> + * @Return:	shortened device-path or NULL
>>    */
>> -static struct efi_device_path *shorten_path(struct efi_device_path *dp)
>> +struct efi_device_path *efi_dp_shorten(struct efi_device_path *dp)
>>   {
>>   	while (dp) {
>>   		/*
>> @@ -189,7 +194,7 @@ static struct efi_object *find_obj(struct efi_device_path *dp, bool short_path,
>>   				}
>>   			}
>>
>> -			obj_dp = shorten_path(efi_dp_next(obj_dp));
>> +			obj_dp = efi_dp_shorten(efi_dp_next(obj_dp));
>>   		} while (short_path && obj_dp);
>>   	}
>>
>> --
>> 2.34.1
>>