# 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:

```shell
./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.

```shell
./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:

```shell
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.

[DMTF SMBIOS specification]: https://www.dmtf.org/standards/smbios
[RFC4122]: https://www.ietf.org/rfc/rfc4122.txt