From owner-freebsd-hackers@FreeBSD.ORG  Wed Apr 20 05:07:36 2005
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Date: Tue, 19 Apr 2005 22:07:31 -0700
To: freebsd-hackers@freebsd.org
Cc: 
From: "James Thomason" <james@divide.org>
Subject: Re: linux call_usermodehelper equivalent in freebsd?
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>Is there an equivalent in FreeBSD to the Linux kernel function
>'call_usermodehelper' which wraps execve to do as its name 
>suggests, call a user mode helper program?

Andrew, 

It depends on what your user mode helper program is intended to do, 
but the traditional approach is to create a user mode program that 
blocks on a custom system call waiting for an event.  See the 
following 2001 freebsd-hackers thread from Terry Lambert, titled 
"Invoking a userland function from kernel" for further details and 
design considerations:

http://docs.freebsd.org/cgi/mid.cgi?3B646AAB.688669C5

Regards, 
James