Hi, Following implementation (or work towards) of EBBR 1.0 + UEFI Secure boot + UEFI update capsule we learnt a lot.
Here are some topics that may need some clarification on the EBBR specs and It looks timely to start working on EBBR evolution. 0.1 - EBBR goal May be a reassessment on the "for what" the specification is built. Following all the discussions with prominent industry players, I start to think that limiting the constraints to be EBBR compliant may become counter productive. There will be both EBBR non compliant and EBBR compliant systems. This is inevitable. But EBBR exist for a number of use cases in a number of markets. The value of EBBR is consistent behavior across those. Maximising number of EBBR compliant systems without stating use case parameters ( "why" and "for what") may not be the best goal. Out of things to be more explicit are supported secure boot flows (with/without shim+grub or direct). Some vendors require shim+grub while industry players want the exact opposite: nothing but UEFI. This drivers a number of requirements in terms of UEFI protocols needed 0.2 - normative text The normative section shall be stated clearly: is " 1.2. Guiding Principles" normative? IETF and ETSI have different language conventions to express absolutely mandated and various levels of optionality. This spec may be red by Telecom people or Linux people. Their interpretation may be erroneous on words such as "shall" (ETSI "SHALL" = "IETF "MUST"). The language need to be explicit. I - protective offsets EBBR 1.0 states in "4.1. Partitioning of Shared Storage" that "Automatic partitioning tools (e.g. an OS installer) must not create partitions within the first 1MiB of storage, or delete, move, or modify protective partition entries." StandaloneMM is 2.5MB by itself with U-Boot being over 1MB without the variable rework done and update capsules. 4MB seems the minimum. 8MB to get margin and 16MB for A/B scheme. EBBR same paragraph also states: "Automatic partitioning tools (e.g. an OS installer) must not create partitions within the first 1MiB of storage, or delete, move, or modify protective partition entries. Manual partitioning tools should provide warnings when modifying protective partitions or creating partitions within the first 1MiB." is it expected that Linaro upstreams changes in installation tools, partition tools to conform to this (with updated to be agreed minimum)? II - identifying partitions Having two EFI partitions defined with EFI_GUID need a precise behaviour defined: boot with first or boot with second. Shall we have a EFI_GUID_ALT defined for A/B partition schemes? If not, the BootXXX variables should be used as selector? We lean towards BootXXX variables and not defining a new GUID. But this would mean explicit behavior to be stated in case of lack of BootXXX. I think GPT volume mirroring should be used in conjunction with A/B: A/B to recover version failures with current hardware, surrounding software; mirroring to protect against storage failures. Is there any recommendation on mirrored EFI volumes handling ? III - 32 bits are there any 32 bits specific considerations to be added? IV - UEFI_RNG_PROTOCOL Following my view in 0) I think this shall be made mandatory Linaro has upstreamed this in U-Boot and started to implement additional hardware drivers. KASLR is thus functional in 64 bits and will be in 32bits. V - UEFI SecureBoot Following my view in 0) I think this shall be made mandatory UEFI SecureBoot is not mentioned in section 2.6 so we need to clarify what needs to be implemented. In particular, we need to implement EFI_LOAD_FILE2_PROTOCOL for initrd signature checking. VI - UEFI update capsules Following my view in 0) I think this shall be made mandatory Section 2.6 of UEFI spec 2.7 mentions At some point in time we will need to propose UEFI specification update for: - anti-bricking anti rollback expected behavior - abstract capsules for "start transaction", "commit", "rollback" when we will be dealing with system wide transactional updates. There is probably a lot to state here but I am just starting the discussion. VII - UEFI watchdog Following my view in 0) I think this shall be made mandatory In addition to its definition, it should also integrate consistent parameters to define total duration covered as well as number of failed consecutive updates to be triggered as well as how it is delivered (powercycle, NMI, secureIRQ...) Cheers -- François-Frédéric _______________________________________________ boot-architecture mailing list [email protected] https://lists.linaro.org/mailman/listinfo/boot-architecture
