Managing and Developing Dynamically Loadable Kernel Modules

Developing Dynamically Loadable Kernel Modules

Chapter 12 529

A module having BOOT2 as its conﬁgured loading phase will be loaded

just after the statically linked device drivers have been initialized. Any

modules either referenced by an auto-loading stub linked into the static

kernel, or depended-upon by other modules loaded during the boot

process, are loaded when they are referenced at boot time. They must,

however, be conﬁgured with the applicable loading phase in their

supported loading phase speciﬁcation.

Module Component Files

A DLKM module must be modularly packaged (see “Managing

Dynamically Loadable Kernel Modules” on page 493). A DLKM module

is installed on disk as a set of ﬁles, which includes the module’s object ﬁle

and other conﬁguration ﬁles needed to install the module into the

system. The ﬁles are located in a single directory having an arbitrary

name. The kminstall(1M) command must then be used to copy the

module’s installation component ﬁles into the locations at which the

kernel conﬁguration tools expect to ﬁnd them.

The component ﬁles for a DLKM module are:

❏ mod.o – the object ﬁle for the module

❏ master – the master conﬁguration ﬁle for the module

❏ system – the system conﬁguration ﬁle for the module

❏ space.h (optional) – a conﬁguration ﬁle that allocates and initializes

some module variables (tunable parameters)

❏ Modstub.o (optional) – an object ﬁle used by the DLKM stubs

mechanism

mod.o File Deﬁnition

The C program source code for a DLKM module, which is compiled and

possibly linked to become mod.o, is similar to the source code for a static

module except that it contains the following additional information:

❏ The source code for a DLKM module includes two additional header

ﬁles, <mod_conf.h> and <sys/moddefs.h>.