Deterimine which of BR-BCT copies was used for boot

Robotics & Edge Computing Jetson & Embedded Systems Jetson AGX Orin
1

I’m trying to implement resilient update for Orin, which will fallback to previous version in case if the update files are invalid(for example due to misconfiguration of build server).

I have examined how A/B update is implemented in UEFI code. Every partition is duplicated including GPT table of bootloader, so in that part everything is working out of the box.

Only problem is BR-BCTs. There are 4 copies, which is more than enough. But I can’t determine which one of 4 copies was used during boot.

Let’s imagine a situation where update has random data instead of valid BCT, rest of partitions are valid.
Current Boot-Chain Slot is A(0), we update slot B(1).
I update all partitions and then update BCT copies 1 and 0.
After that I set BootChain in BootChainRegister to 1 to boot slot B.
After reboot I can compare the current Boot-Chain Slot and br-bct boot-chain in logs:
new BCT is invalid, rest of partitions are valid:

I> Current Boot-Chain Slot: 1
I> BR-BCT Boot-Chain is 0, and status is 0. Set UPDATE_BRBCT bit to 0

New BCT valid, rest of parititions are invalid

I> Current Boot-Chain Slot: 0
I> BR-BCT Boot-Chain is 1, and status is 1. Set UPDATE_BRBCT bit to 1

All new partitions are invalid

I> Current Boot-Chain Slot: 0
I> BR-BCT Boot-Chain is 0, and status is 0. Set UPDATE_BRBCT bit to 0

Update ok

I> Current Boot-Chain Slot: 1
I> BR-BCT Boot-Chain is 1, and status is 0. Set UPDATE_BRBCT bit to 0

I want to get value of BR-BCT Boot-Chain(which I can clearly see in logs) in UEFI to determine if new BCT(from copy 0) is used for boot, or copies 0,1 are invalid and copy 2 or 3 was used.
I have found the U32NonGpioSelectBootChain value in uefi, which looks like exactly what I need, but for some reason it’s always zero.

Is there some way to get the BR-BCT Boot-Chain from UEFI?

5

Sorry for the late response.
Is this still an issue to support? Any result can be shared?

6

it’s BootChainFwStatus UEFI variable, which is created by UEFI when UEFI updates the bootloader partition.

8

This topic was automatically closed 14 days after the last reply. New replies are no longer allowed.