K 10
svn:author
V 8
jhibbits
K 8
svn:date
V 27
2017-01-23T04:03:12.121767Z
K 7
svn:log
V 444
Avoid using non-zero argument for __builtin_frame_address().

Building kernel with devel/powerpc64-gcc (6.2.0) yields the following error:
/usr/src/sys/powerpc/powerpc/db_trace.c:299:20: error: calling
'__builtin_frame_address' with a nonzero argument is unsafe
[-Werror=frame-address]

Work around this by dereferencing the frame address manually instead.

PR:		215600
Reported by:	Mark Millard <markmi AT dsl-only DOT net>
MFC after:	2 weeks

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