With flat addressing the user pollfd list is given directly to the
drivers that perform the notification. This is fine when the addressing
is flat, as there is no ambiguity on who gets notified and the fds memory
is always mapped.
For kernel mode with MMU this does not work. The notification must be done
via a temporary buffer allocated from kernel memory.
Thus, create a copy of the user fds and pass the copy to the drivers.
Afterwards copy the output events back to the user.
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