kern/172894: Out-of-tree kernel module compilation with GNU xargs in $PATH

[Richard Yao]

>Number:         172894
>Category:       kern
>Synopsis:       Out-of-tree kernel module compilation with GNU xargs in $PATH
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Oct 20 03:10:01 UTC 2012
>Closed-Date:
>Last-Modified:
>Originator:     Richard Yao
>Release:        FreeBSD 9.1-BETA1
>Organization:
Gentoo BSD Team
>Environment:
FreeBSD freebsd 9.1-BETA1 FreeBSD 9.1-BETA1 #0: Fri Jul 20 21:39:23 EDT 2012     root at freebsd:/usr/obj/usr/src/sys/GENERIC  amd64
>Description:
I was working on a port of a Linux kernel module to FreeBSD. I decided to
rebase on FreeBSD 9.1-BETA1. I installed Gentoo Prefix so that I would
be able to work on this port in a more familiar development environment.

Unfortunately, there was an issue where /usr/src/sys/conf/kmod.mk invokes
xargs with -J, which Gentoo Prefix's GNU xargs does not support. I have
written a patch for kmod.mk that will attempt shell substitution in
place of xargs when the current command that relies on xargs fails.

This report was originally submitted to hackers at FreeBSD.org three months ago. Eitan Adler requested that I file a problem report.
>How-To-Repeat:
1. Install Gentoo Prefix
2. Start Prefix Shell  (to put GNU xargs in $PATH)
3. Try building an out-of-tree kernel module.
>Fix:
--- /usr/src/sys/conf/kmod.mk.orig	2012-08-02 23:49:09.749192513 -0400
+++ /usr/src/sys/conf/kmod.mk	2012-08-04 08:57:25.719110508 -0400
@@ -217,7 +217,8 @@ ${FULLPROG}: ${OBJS}
 	grep -v '^#' < ${EXPORT_SYMS} > export_syms
 .endif
 	awk -f ${SYSDIR}/conf/kmod_syms.awk ${.TARGET} \
-	    export_syms | xargs -J% ${OBJCOPY} % ${.TARGET}
+	    export_syms | xargs -J% ${OBJCOPY} % ${.TARGET} || \
+	    ${OBJCOPY} $(awk -f ${SYSDIR}/conf/kmod_syms.awk ${.TARGET} export_syms) ${.TARGET}
 .endif
 .endif
 .if !defined(DEBUG_FLAGS) && ${__KLD_SHARED} == no

>Release-Note:
>Audit-Trail:
>Unformatted: