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Quite insane how Android both has the system firmware and the OS combined _and_ doesn't have the possibility of reflashing via bootrom for a lot of devices.

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flawedworld

@flawedworlddev

Aug 16

A warning to AOSP devs on 6th generation Pixels, ensure you flash Android 13 to both slots, because if A13 fails to boot and falls back to A12 bootloader, your phone will be perma-bricked. RIP Pixel 6.

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Pixels disable that for security hardening but in the past they only used firmware downgrade protection for the secure element and didn't bother using it to protect against firmware-based verified boot bypasses. It's a new thing that they're upgrading firmware rollback version.

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and

Android 13 on 6th gen Pixels depends on having upgraded firmware, so there isn't much choice if you want to use or work on an Android 13 based OS. It's possible the Android 13 firmware still supports Android 12 but an Android 12 OS ships Android 12 firmware which can't be used.

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Isn't that fuse blown in HLOS after bootup? As far as I can see - you might be able to avoid blowing it if you're careful.

Daniel Micay

@DanielMicay

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@never_released

Yes, it will only happen once it reaches the lockscreen, disables automatic rollback and then updates the OS vbmeta rollback indexes in the secure element. They added extra code to update the SoC firmware boot chain rollback index there too. OS ones can be reset when unlocked.

9:54 AM · Aug 16, 2022Twitter Web App

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and

Rollback can happen until very late in the boot process on devices using f2fs with the checkpoint disable feature including Pixels. They mount data with checkpointing disabled so they can still roll back after mounting data despite migrating arbitrary stuff to the new OS version.

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The progress bar displayed when you reach the lockscreen / home screen is the final part of the process where it locks in the new version. You can actually manage to open an app before it has finished disabling rollback. If you reboot before that's done it rolls back the update.

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