On 24.05.18 11:16, Daniel Thompson wrote: > On Wed, May 23, 2018 at 04:08:52PM +0200, Alexander Graf wrote: >>>>> +MBR partitioning >>>>> +^^^^^^^^^^^^^^^^ >>>>> + >>>>> +Protective partitions should have a partition type of 0xF8 unless some >>>>> +immutable feature of the platform makes this impossible. >>>> I'd like to be rid of the caveat here too, but there is a lot more >>>> legacy to support with MBR. >>> The known behaviour wiki mentions that RPi dictates 0x0C. >> >> On the RPI we simply use the ESP as firmware partition, so we don't have any >> need for a protective partition there. > > Hmmnnnn... this moves towards one of Grants' comments on the need to > follow up my work with some rules about managing the ESP. Specifically > what tells the OS that formatting the ESP will delete vital firmware > (normally it only destroys other OS and firmware *extensions*).
Firmware extensions may well be a driver necessary to actually boot the system. I'd be very surprised if any installer thought it was a good idea to remove the ESP. And if they do, it must be considered bad behavior. >> So maybe we could just allow the ESP to have type 0xC instead of 0xEF if >> dictated by firmware? That should cover all cases except for Altera then >> which has its bootloader in a 0xAF or so partition. > > I think I'm OK with this. > > Do we *have* to specify the alternative partition type is 0x0C or can we > rely on searching for the EFI/ directory of FAT partitions when no other > ESP presents itself? I admit I'm struggling a little to see how the > pieces fit together but there are definitely clues that firmware might > choose to searching for the EFI directory (albeit for GPT rather than > MBR): > > "UEFI implementations may allow the use of conforming FAT partitions > which do not use the ESP GUID. Partition creators may prevent UEFI > firmware from examining and using a specific partition by setting bit > 1 of the Partition Attributes" I think what our ESP search order should be is: * ESP GUID / ESP MBR partition ID * All partitions marked with bootable flag That should cover all cases IMHO. Alex _______________________________________________ boot-architecture mailing list [email protected] https://lists.linaro.org/mailman/listinfo/boot-architecture
