Could/should firmware be placed on a GPT disk outside the useable LBAs

ARM-software / ebbr

Embedded Base Boot Requirements Specification

Creative Commons Attribution Share Alike 4.0 International

114 stars 37 forks source link

Could/should firmware be placed on a GPT disk outside the useable LBAs #21

Closed daniel-thompson closed 5 years ago

daniel-thompson commented 6 years ago

On systems where the boot ROM is hardcoded to fetch firmware from a block address >=2 and <34 (yes, they exist) it appears possible and standards compliant to place (for example):

Protective MBR at LBA0
GPT header in LBA1
Firmware at LBA16
GPT partition table in LBA(8192 - 32)
First usable LBA: LBA8192

Current EBBR text is unclear about whether the above is permitted or not. Currently we require GPT except where it is impossible and we require firmware to reside within protective partitions except where impossible. It's not clear which of these rules should take precedent!

wmamills commented 6 years ago

I think such firmware is protected by the MBR and seems protected by the GPT. The fact that it is not in a "partition" is not relevant.

However, partition editing tools may break this. This should be tested with several partition tools.

glikely commented 5 years ago

I think it would be worthwhile to revisit the shared block device scheme, but I don't think we've got any actions against EBBR at the moment. I'm going to close this issue until we've got a concrete way forward.

I've been discussing a possible better approach with Steve McIntyre that should make it easier to support the distros, but we need to get it written up into something that can be posted to the boot-architecture mailing list.