.\" $NetBSD: lkm.4,v 1.4 1994/11/30 16:22:22 jtc Exp $ .\" .\" Copyright (c) 1993 Christopher G. Demetriou .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. The name of the author may not be used to endorse or promote products .\" derived from this software without specific prior written permission .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd September 4, 1993 .Dt LKM 4 .Os OpenBSD .Sh NAME .Nm LKM .Nd Loadable Kernel Modules interface .Sh SYNOPSIS .Cd "options LKM" .Sh DESCRIPTION Loadable kernel modules allow the system administrator to dynamically add and remove functionality from a running system. This ability also helps software developers to develop new parts of the kernel without constantly rebooting to test their changes. .Pp Various types of modules can be loaded into the sytem. There are several defined module types, listed below, which can be added to the system in a predefined way. In addition, there is a generic type, for which the module itself handles loading and unloading. .Pp The .Nm interface is used by performing .Xr ioctl 2 calls on the .Pa /dev/lkm device. Normally all operations involving Loadable Kernel Modules are handled by the .Xr modload 8 , .Xr modunload 8 , and .Xr modstat 8 programs. Users should never have to interact with .Pa /dev/lkm directly. .Sh "MODULE TYPES" .Bl -tag -width indent .It System Call modules System calls may be replaced by loading new ones via the .Nm interface. All system calls may be replaced, but special care should be taken with the .Xr ioctl 2 system call, as it is used to load and unload modules. .Pp When a system call module is unloaded, the system call which was replaced by the loadable module is returned to its rightful place in the system call table. .It Virtual File System modules Virtual file systems may be added via the .Nm interface. At this time, only file systems which are already known to the system can be added, because of the way the .Xr mount 2 system call is implemented. .It Device Driver modules New block and character device drivers may be loaded into the system with .Nm LKM . The major problem with loading a device driver is that the driver's device nodes must be exist for the devices to be accessed. They are usually created by instructing .Xr modload 8 to run an appropriate program when the driver has been successfully loaded. .It Execution Interpreters Execution interpreters allow the loading and execution of binaries which are normally not usable by the operating system. .It Miscellaneous modules Miscellaneous modules are modules for which there are not currently well-defined or well-used interfaces for extension. The user is expected to write their own loader to manipulate whatever kernel data structures necessary to enable and disable the new module when it is loaded and unloaded. .El .Sh FILES .Bl -tag -width /usr/include/sys/lkm.h -compact .It Pa /dev/lkm .Nm interface device .It Pa /usr/include/sys/lkm.h file containing defitions of module types .It Pa /usr/share/lkm example source code implementing several of the modules types .Sh SEE ALSO .Xr modload 8 , .Xr modunload 8 , .Xr modstat 8 .Sh HISTORY The .Nm facility was designed to be similar in functionality to the loadable kernel modules facility provided by .Tn "SunOS 4.1.3" . .Sh AUTHOR .Bl -tag Terrence R. Lambert, terry@cs.weber.edu .El .Sh BUGS Loading a bogus module is likely to kill your machine. .Pp Loadable streams modules should and will be implemented when a streams implementation is written.