1.\" Copyright (c) 1993 Christopher G. Demetriou 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. The name of the author may not be used to endorse or promote products 13.\" derived from this software without specific prior written permission 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25.\" 26.\" $FreeBSD: src/share/man/man4/kld.4,v 1.5.2.6 2001/08/17 13:08:38 ru Exp $ 27.\" $DragonFly: src/share/man/man4/kld.4,v 1.3 2004/03/11 12:28:55 hmp Exp $ 28.\" 29.Dd November 8, 1998 30.Dt KLD 4 31.Os 32.Sh NAME 33.Nm kld 34.Nd dynamic kernel linker facility 35.Sh DESCRIPTION 36The LKM (Loadable Kernel Modules) facility has been deprecated in 37.Fx 3.0 38and above in favor of the 39.Nm 40interface. 41This interface, like its 42predecessor, allows the system administrator to dynamically add and remove 43functionality from a running system. This ability also helps software 44developers to develop new parts of the kernel without constantly rebooting 45to test their changes. 46.Pp 47Various types of modules can be loaded into the system. 48There are several defined module types, listed below, which can 49be added to the system in a predefined way. In addition, there 50is a generic type, for which the module itself handles loading and 51unloading. 52.Pp 53The 54.Dx 55system makes extensive use of loadable kernel modules, and provides loadable 56versions of most filesystems, the 57.Tn NFS 58client and server, all the screen-savers, and the 59.Tn iBCS2 60and 61.Tn Linux 62emulators. 63.Nm 64modules are placed by default in the 65.Pa /modules 66directory. 67.Pp 68The 69.Nm 70interface is used through the 71.Xr kldload 8 , 72.Xr kldunload 8 73and 74.Xr kldstat 8 75programs. 76.Pp 77The 78.Xr kldload 8 79program can load either 80.Xr a.out 5 81or ELF formatted loadable modules. 82The 83.Xr kldunload 8 84program unloads any given loaded module, if no other module is dependent 85upon the given module. 86The 87.Xr kldstat 8 88program is used to check the status of the modules currently loaded into the 89system. 90.Sh "MODULE TYPES" 91.Bl -ohang 92.It Em "Device Driver modules" 93New block and character device 94drivers may be loaded into the system with 95.Nm . 96The major problem with loading 97a device driver is that the driver's 98device nodes must exist for the 99devices to be accessed. They are usually 100created by using 101.Xr MAKEDEV 8 102or 103.Xr mknod 8 104(if the device is not supported by the 105.Xr MAKEDEV 8 106script) or, by writing a 107shell script to run 108.Xr kldload 8 109which should run the appropriate program to create the devices when the 110driver has been successfully loaded. 111.El 112.Sh FILES 113.Bl -tag -width /usr/include/sys/module.h -compact 114.It Pa /modules 115directory containing module binaries shipped with the system 116.It Pa /usr/include/sys/module.h 117file containing definitions required to compile a 118.Nm 119module 120.It Pa /usr/share/examples/kld 121example source code implementing a sample kld module 122.El 123.Sh SEE ALSO 124.Xr kldfind 2 , 125.Xr kldfirstmod 2 , 126.Xr kldload 2 , 127.Xr kldnext 2 , 128.Xr kldstat 2 , 129.Xr kldunload 2 , 130.Xr kldload 8 , 131.Xr kldstat 8 , 132.Xr kldunload 8 133.Sh BUGS 134If a module B, is dependent on another module A, but is not compiled with 135module A as a dependency, then 136.Xr kldload 8 137fails to load module B, even if module A is already present in the system. 138.Pp 139If multiple modules are dependent on module A, and are compiled with module 140A as a dependency, then 141.Xr kldload 8 142loads an instance of module A when any of the modules are loaded. 143.Pp 144If a custom entry point is used for a module, and the module is compiled as 145an 146.Sq ELF 147binary, then 148.Xr kldload 8 149fails to execute the entry point. 150.Pp 151.Xr kldload 8 152returns the cryptic message 153.Sq Li "ENOEXEC (Exec format error)" 154for any error encountered while loading a module. 155.Pp 156When system internal interfaces change, old modules often cannot 157detect this, and such modules when loaded will often cause crashes or 158mysterious failures. 159.Sh AUTHORS 160The 161.Nm 162facility was originally implemented by 163.An Doug Rabson Aq dfr@FreeBSD.org . 164.Sh HISTORY 165The 166.Nm 167facility appeared in 168.Fx 3.0 169and was designed as a replacement for the 170.Xr lkm 4 171facility, which was similar in functionality to the loadable kernel modules 172facility provided by 173.Tn SunOS 1744.1.3. 175