coreboot-kgpe-d16/Documentation/drivers/cbfs_smbios.md

CBFS SMBIOS hooks

The document describes the coreboot options how to make CBFS files populate platform-unique SMBIOS data.

SMBIOS System UUID

The DMTF SMBIOS specification defines a field in the type 1 System Information Structure called System UUID. It is a 16 bytes value compliant with RFC4122 and assumed to be unique per platform. Certain mainboard ports have SMBIOS hooks to generate the UUID from external data, e.g. Lenovo Thinkpads (see DRIVER_LENOVO_SERIALS). This driver aims to provide an option to populate the UUID from CBFS for boards that can't generate the UUID from any source.

Usage

In the coreboot configuration menu (make menuconfig) go to Generic Drivers and select an option System UUID in CBFS. The Kconfig system will enable DRIVERS_GENERIC_CBFS_UUID and the relevant code parts will be compiled into coreboot image.

After the coreboot build for your board completes, use the cbfstool to include the file containing the UUID:

./build/cbfstool build/coreboot.rom add -n system_uuid -t raw -f /path/to/uuid_file.txt

Where uuid_file.txt is the unterminated string representation of the SMBIOS type 1 UUID, e.g. 4c4c4544-0051-3410-8051-b5c04f375931. If you use vboot with 1 or 2 RW partitions you will have to specify the RW regions where the file is going to be added too. By default the RW CBFS partitions are truncated, so the files would probably not fit, one needs to expand them first.

./build/cbfstool build/coreboot.rom expand -r FW_MAIN_A
./build/cbfstool build/coreboot.rom add -n system_uuid -t raw \
	-f /path/to/uuid_file.txt -r FW_MAIN_A
./build/cbfstool build/coreboot.rom truncate -r FW_MAIN_A

./build/cbfstool build/coreboot.rom expand -r FW_MAIN_B
./build/cbfstool build/coreboot.rom add -n system_uuid -t raw \
	-f /path/to/uuid_file.txt -r FW_MAIN_B
./build/cbfstool build/coreboot.rom truncate -r FW_MAIN_B

By default cbfstool adds files to COREBOOT region only, so when vboot is enabled and the platform is booting from RW partition, the file would not be picked up by the driver.

One may retrieve the UUID from running system (if it exists) using the following command:

echo -n `sudo dmidecode -s system-uuid` > uuid_file.txt

The above command ensures the file does not end with whitespaces like LF and/or CR. The above command will not add any whitespaces. But the driver will handle situations where up to 2 additional bytes like CR and LF will be included in the file. Any more than that will make the driver fail to populate UUID in SMBIOS.