66 lines
2.6 KiB
Markdown
66 lines
2.6 KiB
Markdown
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# CBFS SMBIOS hooks
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The document describes the coreboot options how to make CBFS files populate
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platform-unique SMBIOS data.
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## SMBIOS System UUID
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The [DMTF SMBIOS specification] defines a field in the type 1 System
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Information Structure called System UUID. It is a 16 bytes value compliant with
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[RFC4122] and assumed to be unique per platform. Certain mainboard ports have
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SMBIOS hooks to generate the UUID from external data, e.g. Lenovo Thinkpads
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(see DRIVER_LENOVO_SERIALS). This driver aims to provide an option to populate
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the UUID from CBFS for boards that can't generate the UUID from any source.
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### Usage
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In the coreboot configuration menu (`make menuconfig`) go to `Generic Drivers`
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and select an option `System UUID in CBFS`. The Kconfig system will enable
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`DRIVERS_GENERIC_CBFS_UUID` and the relevant code parts will be compiled into
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coreboot image.
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After the coreboot build for your board completes, use the cbfstool to include
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the file containing the UUID:
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```shell
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./build/cbfstool build/coreboot.rom add -n system_uuid -t raw -f /path/to/uuid_file.txt
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```
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Where `uuid_file.txt` is the unterminated string representation of the SMBIOS
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type 1 UUID, e.g. `4c4c4544-0051-3410-8051-b5c04f375931`. If you use vboot with
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1 or 2 RW partitions you will have to specify the RW regions where the file is
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going to be added too. By default the RW CBFS partitions are truncated, so the
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files would probably not fit, one needs to expand them first.
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```shell
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./build/cbfstool build/coreboot.rom expand -r FW_MAIN_A
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./build/cbfstool build/coreboot.rom add -n system_uuid -t raw \
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-f /path/to/uuid_file.txt -r FW_MAIN_A
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./build/cbfstool build/coreboot.rom truncate -r FW_MAIN_A
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./build/cbfstool build/coreboot.rom expand -r FW_MAIN_B
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./build/cbfstool build/coreboot.rom add -n system_uuid -t raw \
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-f /path/to/uuid_file.txt -r FW_MAIN_B
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./build/cbfstool build/coreboot.rom truncate -r FW_MAIN_B
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```
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By default cbfstool adds files to COREBOOT region only, so when vboot is
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enabled and the platform is booting from RW partition, the file would not be
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picked up by the driver.
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One may retrieve the UUID from running system (if it exists) using the
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following command:
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```shell
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echo -n `sudo dmidecode -s system-uuid` > uuid_file.txt
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```
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The above command ensures the file does not end with whitespaces like LF and/or
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CR. The above command will not add any whitespaces. But the driver will handle
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situations where up to 2 additional bytes like CR and LF will be included in
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the file. Any more than that will make the driver fail to populate UUID in
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SMBIOS.
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[DMTF SMBIOS specification]: https://www.dmtf.org/standards/smbios
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[RFC4122]: https://www.ietf.org/rfc/rfc4122.txt
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