Given the note file in devproc and the awake system call we can implement the alarm service as a filesystem in user space.
alarmfs [-dD] [-S servicename]
$home/lib/profile may mount an alarmfs to /dev
The attach specifier must provide a root pid: the server will only send alarms to process identified by that pid or its descendants and attach will fail if the current user cannot write its note file.
Alarmfs will serve a single folder alarms/ that
is owned by the user owning the process provided on attach
has permission 700
has qid.path containing the root pid
provides the list of pending alarms as readonly files. Each file is named after the pid it will notify.