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: head/share/man/man4/kld.4 60750 2000-05-21 03:16:35Z hoek $
27.\"
28.Dd November 08, 1998
29.Dt KLD 4
30.\".Os FreeBSD 3.0
31.Sh NAME
32.Nm kld
33.Nd dynamic kernel linker facility
34.Sh DESCRIPTION
35The LKM (Loadable Kernel Modules) facility has been deprecated in FreeBSD
363.0 and above in favor of the
37.Nm
38interface.
39This interface, like its
40predecessor, allows the system administrator to dynamically add and remove
41functionality from a running system. This ability also helps software
42developers to develop new parts of the kernel without constantly rebooting
43to test their changes.
44.Pp
45Various types of modules can be loaded into the system.
46There are several defined module types, listed below, which can
47be added to the system in a predefined way. In addition, there
48is a generic type, for which the module itself handles loading and
49unloading.
50.Pp
51The
52.Tn FreeBSD
53system makes extensive use of loadable kernel modules, and provides loadable
54versions of most filesystems, the
55.Tn NFS
56client and server, all the screen-savers, and the
57.Tn iBCS2
58and
59.Tn Linux
60emulators.
61.Nm
62modules are placed by default in the
63.Pa /modules
64directory.
65.Pp
66The
67.Nm
68interface is used through the
69.Xr kldload 8 ,
70.Xr kldunload 8
71and
72.Xr kldstat 8
73programs.
74.Pp
75The
76.Xr kldload 8
77program can load either
78.Xr a.out 5
79or ELF formatted loadable modules.
80The
81.Xr kldunload 8
82program unloads any given loaded module, if no other module is dependent
83upon the given module.
84The
85.Xr kldstat 8
86program is used to check the status of the modules currently loaded into the
87system.
88.Sh "MODULE TYPES"
89.Bl -ohang
90.It Em "Device Driver modules"
91New block and character device
92drivers may be loaded into the system with
93.Nm KLD .
94The major problem with loading
95a device driver is that the driver's
96device nodes must exist for the
97devices to be accessed. They are usually
98created by using
99.Xr MAKEDEV 8
100or
101.Xr mknod 8
102(if the device is not supported by the
103.Xr MAKEDEV 8
104script) or, by writing a
105shell script to run
106.Xr kldload 8
107which should run the appropriate program to create the devices when the
108driver has been successfully loaded.
109.El
110.Sh FILES
111.Bl -tag -width /usr/include/sys/module.h -compact
112.It Pa /modules
113directory containing module binaries shipped with the system
114.It Pa /usr/include/sys/module.h
115file containing definitions required to compile a
116.Nm
117module
118.It Pa /usr/share/examples/kld
119example source code implementing a sample kld module
120.Sh SEE ALSO
121.Xr kldfind 2 ,
122.Xr kldfirstmod 2 ,
123.Xr kldload 2 ,
124.Xr kldnext 2 ,
125.Xr kldstat 2 ,
126.Xr kldunload 2 ,
127.Xr kldload 8 ,
128.Xr kldstat 8 ,
129.Xr kldunload 8
130.Sh BUGS
131If a module B, is dependent on another module A, but is not compiled with
132module A as a dependency, then
133.Xr kldload 8
134fails to load module B, even if module A is already present in the system.
135.Pp
136If multiple modules are dependent on module A, and are compiled with module
137A as a dependency, then
138.Xr kldload 8
139loads an instance of module A when any of the modules are loaded.
140.Pp
141If a custom entry point is used for a module, and the module is compiled as
142an
143.Sq ELF
144binary, then
145.Xr kldload 8
146fails to execute the entry point.
147.Pp
148.Xr kldload 8
149returns the cryptic message
150.Sq ENOEXEC Po Exec format error Pc
151for any error encountered while loading a module.
152.Pp
153When system internal interfaces change, old modules often cannot
154detect this, and such modules when loaded will often cause crashes or
155mysterious failures.
156.Sh AUTHORS
157The
158.Nm
159facility was originally implemented by
160.An Doug Rabson Aq dfr@FreeBSD.org .
161.Sh HISTORY
162The
163.Nm
164facility appeared in
165.Fx 3.0
166and was designed as a replacement for the
167.Xr lkm 4
168facility, which was similar in functionality to the loadable kernel modules
169facility provided by
170.Tn SunOS
1714.1.3.
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: head/share/man/man4/kld.4 60750 2000-05-21 03:16:35Z hoek $
27.\"
28.Dd November 08, 1998
29.Dt KLD 4
30.\".Os FreeBSD 3.0
31.Sh NAME
32.Nm kld
33.Nd dynamic kernel linker facility
34.Sh DESCRIPTION
35The LKM (Loadable Kernel Modules) facility has been deprecated in FreeBSD
363.0 and above in favor of the
37.Nm
38interface.
39This interface, like its
40predecessor, allows the system administrator to dynamically add and remove
41functionality from a running system. This ability also helps software
42developers to develop new parts of the kernel without constantly rebooting
43to test their changes.
44.Pp
45Various types of modules can be loaded into the system.
46There are several defined module types, listed below, which can
47be added to the system in a predefined way. In addition, there
48is a generic type, for which the module itself handles loading and
49unloading.
50.Pp
51The
52.Tn FreeBSD
53system makes extensive use of loadable kernel modules, and provides loadable
54versions of most filesystems, the
55.Tn NFS
56client and server, all the screen-savers, and the
57.Tn iBCS2
58and
59.Tn Linux
60emulators.
61.Nm
62modules are placed by default in the
63.Pa /modules
64directory.
65.Pp
66The
67.Nm
68interface is used through the
69.Xr kldload 8 ,
70.Xr kldunload 8
71and
72.Xr kldstat 8
73programs.
74.Pp
75The
76.Xr kldload 8
77program can load either
78.Xr a.out 5
79or ELF formatted loadable modules.
80The
81.Xr kldunload 8
82program unloads any given loaded module, if no other module is dependent
83upon the given module.
84The
85.Xr kldstat 8
86program is used to check the status of the modules currently loaded into the
87system.
88.Sh "MODULE TYPES"
89.Bl -ohang
90.It Em "Device Driver modules"
91New block and character device
92drivers may be loaded into the system with
93.Nm KLD .
94The major problem with loading
95a device driver is that the driver's
96device nodes must exist for the
97devices to be accessed. They are usually
98created by using
99.Xr MAKEDEV 8
100or
101.Xr mknod 8
102(if the device is not supported by the
103.Xr MAKEDEV 8
104script) or, by writing a
105shell script to run
106.Xr kldload 8
107which should run the appropriate program to create the devices when the
108driver has been successfully loaded.
109.El
110.Sh FILES
111.Bl -tag -width /usr/include/sys/module.h -compact
112.It Pa /modules
113directory containing module binaries shipped with the system
114.It Pa /usr/include/sys/module.h
115file containing definitions required to compile a
116.Nm
117module
118.It Pa /usr/share/examples/kld
119example source code implementing a sample kld module
120.Sh SEE ALSO
121.Xr kldfind 2 ,
122.Xr kldfirstmod 2 ,
123.Xr kldload 2 ,
124.Xr kldnext 2 ,
125.Xr kldstat 2 ,
126.Xr kldunload 2 ,
127.Xr kldload 8 ,
128.Xr kldstat 8 ,
129.Xr kldunload 8
130.Sh BUGS
131If a module B, is dependent on another module A, but is not compiled with
132module A as a dependency, then
133.Xr kldload 8
134fails to load module B, even if module A is already present in the system.
135.Pp
136If multiple modules are dependent on module A, and are compiled with module
137A as a dependency, then
138.Xr kldload 8
139loads an instance of module A when any of the modules are loaded.
140.Pp
141If a custom entry point is used for a module, and the module is compiled as
142an
143.Sq ELF
144binary, then
145.Xr kldload 8
146fails to execute the entry point.
147.Pp
148.Xr kldload 8
149returns the cryptic message
150.Sq ENOEXEC Po Exec format error Pc
151for any error encountered while loading a module.
152.Pp
153When system internal interfaces change, old modules often cannot
154detect this, and such modules when loaded will often cause crashes or
155mysterious failures.
156.Sh AUTHORS
157The
158.Nm
159facility was originally implemented by
160.An Doug Rabson Aq dfr@FreeBSD.org .
161.Sh HISTORY
162The
163.Nm
164facility appeared in
165.Fx 3.0
166and was designed as a replacement for the
167.Xr lkm 4
168facility, which was similar in functionality to the loadable kernel modules
169facility provided by
170.Tn SunOS
1714.1.3.