andrew acaab8fb10 Use the saved program state register to detect when an exception frame is
from userpsace. Previously we could have triggered a panic by trying to
jump to a kernel address from userland as the trap handling code thought we
received an ast in kernel mode.

Obtained from:	ABT Systems Ltd
Sponsored by:	The FreeBSD Foundation
2016-03-22 08:36:25 +00:00
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