On 07.08.2019 06:23, Persmule wrote:
I found the typical fmap for a coreboot build using vboot (e.g. those
for chromeos) is quite complex, at least with two RW sections
containing CBFS, but I only want to use vboot to perform TPM
measurement (like what head does with a patched coreboot), so
the simple scheme with a single CBFS containing all stages and
payloads is prefered.
Here is an example:
My question is: if vboot is only used to perform TPM measurement, at
least which sections must be added to the fmap, in addition to default
ones (RW_MRC_CACHE and CBFS), allowing vboot to work?
Vboot is responsible for
firmware verification (checks firmware
signature blocks). The TPM measurements are only an extension to Vboot
logic adopted in coreboot. In order to have verified boot, at least one
RW partition must exists. for Measured boot, only single CBFS is fine.
to support verified and measured boot, one RW partition is sufficient.
The example linked above has the minimal fmap layout for verified and
measured boot for Lenovo x220. SMMSTORE is optional as well as RW_VPD
and RO_VPD (depends on use case). SI_GBE region is mandatory for vPRO
platforms to support Gigabit Ethernet, SI_ME and SI_DESC are Intel ME
and Flash descriptor regions, also mandatory.
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