Editing preinit on rom (not overlay) without reflashing


I have an hardware that is failing. For debug purpose I would like to modify the preinit file on the rom (not the overlay since it is not taken into acount at boot) without re-flashing.

Is it possible?

Thank's in advance!


Note also that typically the rom part is compressed, so editing any file there is not even possible with low-level storage handling tools.

Thanks a lot!