K 10
svn:author
V 4
tijl
K 8
svn:date
V 27
2017-11-07T17:07:45.126925Z
K 7
svn:log
V 469
MFC r325232

Set the return address for stack entry points to zero.

Stack unwinders treat zero as a stop condition.  The value on the stack can
be non-zero because thread stacks may be arbitrary memory provided via
pthread_attr_setstack(3) or may be recycled from previous threads.

Reference:
https://lists.freebsd.org/pipermail/freebsd-current/2017-August/066855.html
https://lists.freebsd.org/pipermail/freebsd-current/2017-October/067254.html

Discussed with:	kib

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