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Capsule Update releases

Dasharo releases that support Capsule Updates need to include a number of additional options in their coreboot configuration file. The options correspond to the required payload data described in Capsule Updates Details - Required Payload Data

Configuration

The coreboot configuration file can be found in the coreboot repository in the configs/ directory under the name of config.<coreboot_mainboard_vendor>_<coreboot_mainboard_model>.

The options that need to be set are:

  • CONFIG_DRIVERS_EFI_MAIN_FW_GUID
  • CONFIG_DRIVERS_EFI_MAIN_FW_VERSION
  • CONFIG_DRIVERS_EFI_MAIN_FW_LSV

CONFIG_DRIVERS_EFI_MAIN_FW_GUID

The value is a unique identifier of a firmware variant. The exact value is not important as long as it is the same in all compatible versions of a firmware variant and different from incompatible ones. When creating a new release compatible with the previous one, the value should not change. When creating a new release, for example when adding support to a new platform, the value has to be set. To get a new UUID for this config options on Linux, use the uuidgen command.

Examples:

  • An example UUID generated using uuidgen - CONFIG_DRIVERS_EFI_MAIN_FW_GUID="27ec159a-bfeb-4ddd-a0b1-bc9c664e4216"

CONFIG_DRIVERS_EFI_MAIN_FW_VERSION

The value represents the version of the current firmware as a 32bit number. This option is used to allow for reliable ordering and comparing different versions of the firmware that might exist and could be used to perform a Capsule Update. The CONFIG_LOCALVERSION option is a string representation of the version which does not allow reliable comparisons. The value consists of 8 hexadecimal digits which are grouped into four groups of two numbers. Each group represents a single component of a Dasharo version according to the Versioning CONFIG_DRIVERS_EFI_MAIN_FW_VERSION has to be updated on new releases to always match the CONFIG_LOCALVERSION.

The value looks like 0xMMmmpprr, where:

  • MM - the MAJOR version
  • mm - the MINOR version
  • pp - the PATCH version
  • rr - optional Release Candidate number

For release versions the Release Candidate number is generally set to 80 (128 decimal) to make sure the version number is higher than any release candidate but still leave some headroom for increasing just in case.

Examples:

  • Release Candidate v1.5.2-rc3 - CONFIG_DRIVERS_EFI_MAIN_FW_VERSION="0x01050203"
  • Release v0.9.1 - CONFIG_DRIVERS_EFI_MAIN_FW_VERSION="0x000901FF"

CONFIG_DRIVERS_EFI_MAIN_FW_LSV

The value represents the lowest firmware version, that will be accepted as a valid one. A Capsule Update to a version lower than CONFIG_DRIVERS_EFI_MAIN_FW_LSV will not be allowed. May be used to forbid downgrading to versions with severe security vulnerabilities. The value takes the same format as CONFIG_DRIVERS_EFI_MAIN_FW_VERSION

Examples:

  • Forbid changing the version to anything below release v0.1.0 - CONFIG_DRIVERS_EFI_MAIN_FW_LSV="0x000100FF"