about the alien thread

Wei Jin coder.soap at gmail.com
Sat Jan 11 21:57:07 CET 2014


I'm tring to understand how the alien thread works. I'm not confident in
what I have got.

Please correct me:

When an alien thread invokes an IPC call, it raises an exception, which
would be caught by the
excenption handler as configured.

The exception handler could get the status of the alien thread by reading
exception regs in UTCB
( l4_utcb_exc<http://os.inf.tu-dresden.de/L4Re/doc/group__l4__utcb__exc__api.html#ga3d957c3c28e526804e2c1a2e183df88f>
() ).

The exception handler could also set this IPC call allowed or not.

If this IPC call is allowed, the alien thread acts like a non-alien thread
the performs the IPC call.
// This is what I doubt since the alien example does not provide a valid
IPC call.

If this IPC call is not allowed, the alien thread executes from where it
raise the exception.
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