Make monotonic counter optional (was: Relax monotonic counter nonvolatility)

ARM-software / ebbr

Embedded Base Boot Requirements Specification

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Make monotonic counter optional (was: Relax monotonic counter nonvolatility) #104

Closed vstehle closed 1 year ago

vstehle commented 1 year ago

Allow the high 32-bit part of the platform's monotonic counter to be volatile.

This is consistent with current U-Boot's implementation.

vstehle commented 1 year ago

Changing direction a bit as per the solution suggested by @apalos during the call of Mar 13 and make the monotonic counter optional:

Either it is not implemented at all and the software knows it (thanks to the status code).
Or it is implemented and its non-volatility can be relied upon (for capsule, crypto, etc.).

Returning EFI_DEVICE_ERROR in GetNextMonotonicCount() does not prevent an OS to boot (this has been rapidly verified on U-Boot with Debian, Ubuntu, openSUSE and Fedora).

apalos commented 1 year ago

Acked-by: Ilias Apalodimas ilias.apalodimas@linaro.org