I found out there's such thing as dm-verity and that it's used in various embed devices like phones. While I think it's quite fair that embeds can have some ROM memory that can't be modified and it can be used to help verification of kernel eg. - can this mechanism be used on typical PC (server precisely) which frequently updates kernel and performs rw on basically whole storage? How would it work then? I mean lets say that something messed with fs without booting OS - is there anything that would protect anyone from being able to just recalculate all hashes, replace keys, alter kernel image to make everything look "legit"?