1 .\" Copyright (c) 1993 Christopher G. Demetriou
2 .\" All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
7 .\" 1. Redistributions of source code must retain the above copyright
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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
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15 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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26 .\" $FreeBSD: src/share/man/man4/kld.4,v 1.5.2.6 2001/08/17 13:08:38 ru Exp $
33 .Nd dynamic kernel linker facility
35 The LKM (Loadable Kernel Modules) facility has been deprecated in
37 and above in favor of the
40 This interface, like its
41 predecessor, allows the system administrator to dynamically add and remove
42 functionality from a running system.
43 This ability also helps software
44 developers to develop new parts of the kernel without constantly rebooting
45 to test their changes.
47 Various types of modules can be loaded into the system.
48 There are several defined module types, listed below, which can
49 be added to the system in a predefined way.
51 is a generic type, for which the module itself handles loading and
56 system makes extensive use of loadable kernel modules, and provides loadable
57 versions of most filesystems, the
59 client and server, and all the screen-savers.
61 modules are placed by default in the
67 interface is used through the
76 program can load either
78 or ELF formatted loadable modules.
81 program unloads any given loaded module, if no other module is dependent
82 upon the given module.
85 program is used to check the status of the modules currently loaded into the
88 .Bl -tag -width ".In sys/module.h" -compact
90 directory containing module binaries shipped with the system
92 file containing definitions required to compile a
95 .It Pa /usr/share/examples/kld
96 example source code implementing a sample kld module
113 and was designed as a replacement for the
115 facility, which was similar in functionality to the loadable kernel modules
122 facility was originally implemented by
123 .An Doug Rabson Aq Mt dfr@FreeBSD.org .
125 If a module B, is dependent on another module A, but is not compiled with
126 module A as a dependency, then
128 fails to load module B, even if module A is already present in the system.
130 If multiple modules are dependent on module A, and are compiled with module
131 A as a dependency, then
133 loads an instance of module A when any of the modules are loaded.
135 If a custom entry point is used for a module, and the module is compiled as
140 fails to execute the entry point.
143 returns the cryptic message
144 .Sq Li "Exec format error"
145 for any error encountered while loading a module.
147 When system internal interfaces change, old modules often cannot
148 detect this, and such modules when loaded will often cause crashes or