mount: linproc: Operation not supported by device

Trying to install Linux compatibility on current fails.  Using the 
following procedure fails with:

Step 1: Enable Linux compatibility and linprocfs

Add linux_enable="YES" to /etc/rc.conf. Add compat.linux.osrelease=2.6.16 
to /etc/sysctl.conf. Add OVERRIDE_LINUX_BASE_PORT=f8 to /etc/make.conf. 
Add this line to /etc/fstab:

linproc /usr/compat/linux/proc linprocfs rw 0 0
Then run these commands:

mkdir -p /usr/compat/linux/proc
mount /usr/compat/linux/proc
/etc/rc.d/abi start
/etc/rc.d/sysctl start

# cat /etc/sysctl.conf
# $FreeBSD: head/etc/sysctl.conf 112200 2003-03-13 18:43:50Z mux $
#
#  This file is read when going to multi-user and its contents piped thru
#  ``sysctl'' to adjust kernel values.  ``man 5 sysctl.conf'' for details.
#

# Uncomment this to prevent users from seeing information about processes 
that
# are being run under another UID.
#security.bsd.see_other_uids=0
compat.linux.osrelease=2.6.16

# cat /etc/make.conf |grep LIN
OVERRIDE_LINUX_BASE_PORT=f10

# cat /etc/fstab
# Device	Mountpoint	FStype	Options	Dump	Pass#
/dev/ada0p2	/		ufs	rw	1	1
/dev/ada0p3	none		swap	sw	0	0

linproc /usr/compat/linux/proc linprocfs rw 0 0

proc           /proc       procfs  rw  0   0

# mount /usr/compat/linux/proc
mount: linproc: Operation not supported by device
And this is from /var/log/messages after:
Dec  6 16:33:11 FBSD10 kernel: link_elf_obj: symbol __mtx_assert undefined
Dec  6 16:33:11 FBSD10 kernel: linker_load_file: Unsupported file type

All ports built with clang.
Any help is appreciated, tia.