I think it may be necessary to put some parts of the NuttX kernel into RAM so that it can keep executing while the bus is stuck. I don't know off the top of my head whether we currently have a built-in way to do that.
Yes, they are called ramfuncs and are automatically copied to RAM at boot time. This does not appear to be implemented for STM32F4, but search for referernces to CONFIG_ARCH_RAMFUNCS or ramfuncs in arch/ and include/
$ find arch -name *_start.* | xargs grep -i CONFIG_ARCH_RAMFUNCS $ grep -r ramfuncs boards
