Loadable Kernel Modules interface
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.
Various types of modules can be loaded into the system. 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.
interface is used by performing
calls on the
device. Normally all operations
involving Loadable Kernel Modules are handled by the
programs. Users should never have to interact with
directly. The loading and
unloading of modules is also dependent on the system
- System Call modules
- System calls may be replaced by loading new ones via the
LKM interface. All system calls may be
replaced, but special care should be taken with the
call, as it is used to load and unload modules.
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
- Virtual File System modules
- Virtual file systems may be added via the
- Device Driver modules
- New block and character device drivers may be loaded into the system with
LKM. The major problem with loading a
device driver is that the driver's device nodes must exist for the devices
to be accessed. They are usually created by instructing
run an appropriate program when the driver has been successfully
- Execution Interpreters
- Execution interpreters allow the loading and execution of binaries which
are normally not usable by the operating system.
- 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
LKM interface device.
- File containing definitions of module types.
- Example source code implementing several of the modules types.
facility was designed to be similar
in functionality to the loadable kernel modules facility provided by SunOS
Terrence R. Lambert
Loading a bogus module is likely to kill your machine.