K 10
svn:author
V 3
kib
K 8
svn:date
V 27
2019-07-31T20:23:10.532477Z
K 7
svn:log
V 567
Make randomized stack gap between strings and pointers to argv/envs.

This effectively makes the stack base on the csu _start entry
randomized.

The gap is enabled if ASLR is for the ABI is enabled, and then
kern.elf{64,32}.aslr.stack_gap specify the max percentage of the
initial stack size that can be wasted for gap.  Setting it to zero
disables the gap, and max is capped at 50%.

Only amd64 for now.

Reviewed by:	cem, markj
Discussed with:	emaste
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
Differential revision:	https://reviews.freebsd.org/D21081

END