Bug 24121

The Linux compatibility stuff never seems to load linprocfs and mount it. It appears linprocfs used to be a port, and was merged into FreeBSD itself. The port had some simple install stuff in its Makefile:

LINUX_DIR=	/compat/linux

CATEGORIES=	emulators
MAINTAINER=	vns@delta.odessa.ua

DISTNAME=       linprocfs
MASTER_SITES=	http://www.enst.fr/~beyssac/freebsd/

WRKSRC=		${WRKDIR}/sys/modules/linprocfs
MAKE_ARGS=	"KMODDIR=${PREFIX}/modules"

STARTUP=	${PREFIX}/etc/rc.d/linprocfs.sh 

pre-install: 
	[ -d ${PREFIX}/modules ] || mkdir -p ${PREFIX}/modules 
	${LN} -s /sbin/mount_std ${PREFIX}/sbin/mount_linprocfs
	${ECHO} "Installing ${PREFIX}/etc/rc.d/linprocfs.sh startup file.";
	${ECHO} "#!/bin/sh" > ${PREFIX}/etc/rc.d/linprocfs.sh; 
	${ECHO} "[ -x ${PREFIX}/sbin/mount_linprocfs ] && kldload ${PREFIX}/modules/linprocfs.ko && ${PREFIX}/sbin/mount_linprocfs linprocfs ${LINUX_DIR}/proc && ${ECHO_MSG} -n ' linprocfs'" >> ${STARTUP}
	${CHMOD} ${BINMODE} ${STARTUP}
	${CHOWN} ${BINOWN}:${BINGRP} ${STARTUP}

This doesn't seem to occur anywhere in FreeBSD 4.2 (the port is not present).

Fix: 

Include like a two line file in the product:
/usr/src/etc/rc.d/linprocfs.sh
	#!/bin/sh
	[ -x /sbin/mount_linprocfs ] && kldload /modules/linprocfs.ko && ${PREFIX}/sbin/mount_linprocfs linprocfs /compat/linux/proc linprocfs'

and/or have sysinstall add a line to /etc/fstab something like
linproc /compat/linux linprocfs rw 0 0

It should be simple, relative to everything else in FreeBSD, which means a bit too hard and I'm not sure exactly what to do.
How-To-Repeat: Just try to use a Linux binary that depends on /proc, like VMware, /usr/ports/emulators/vmware2