freebsd/share/man/man9/SYSINIT.9

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.Dd December 1, 2010
.Dt SYSINIT 9
.Os
.Sh NAME
.Nm SYSINIT ,
.Nm SYSUNINIT
.Nd a framework for dynamic kernel initialization
.Sh SYNOPSIS
.In sys/param.h
.In sys/kernel.h
.Fn SYSINIT "uniquifier" "enum sysinit_sub_id subsystem" "enum sysinit_elem_order order" "sysinit_cfunc_t func" "const void *ident"
.Fn SYSUNINIT "uniquifier" "enum sysinit_sub_id subsystem" "enum sysinit_elem_order order" "sysinit_cfunc_t func" "const void *ident"
.Sh DESCRIPTION
.Nm
is a mechanism for scheduling the execution of initialization and teardown
routines.
This is similar to init and fini routines with the addition of explicit
ordering metadata.
It allows runtime ordering of subsystem initialization in the kernel as well
as kernel modules (KLDs).
.Pp
The
.Fn SYSINIT
macro creates a
.Vt struct sysinit
and stores it in a startup linker set.
The
.Vt struct sysinit
type as well as the subsystem identifier constants
.Pq Dv SI_SUB_*
and initialization ordering constants
.Pq Dv SI_ORDER_*
are defined in
.In sys/kernel.h :
.Bd -literal
struct sysinit {
	enum sysinit_sub_id subsystem;	/* subsystem identifier*/
	enum sysinit_elem_order	order;	/* init order within subsystem*/
	sysinit_cfunc_t func;		/* function             */
	const void	*udata;		/* multiplexer/argument */
};
.Ed
.Pp
The
.Fn SYSINIT
macro takes a
.Fa uniquifier
argument to identify the particular function dispatch data,
the
.Fa subsystem
type of startup interface, the subsystem element
.Fa order
of initialization within the subsystem, the
.Fa func
function to call,
and the data specified in
.Fa ident
argument to pass the function.
.Pp
The
.Fn SYSUNINIT
macro behaves similarly to the
.Fn SYSINIT
macro except that it adds the data to a shutdown linker set.
.Pp
The startup linker set for the kernel is scanned during boot to build a
sorted list of initialization routines.
The initialization routines are then executed in the sorted order.
The
.Fa subsystem
is used as the primary key and is sorted in ascending order.
The
.Fa order
is used as the secondary key and is sorted in ascending order.
The relative order of two routines that have the same
.Fa subsystem
and
.Fa order
is undefined.
.Pp
The startup linker sets for modules that are loaded together with the kernel
by the boot loader are scanned during the
.Dv SI_SUB_KLD
subsystem initialization.
These modules' initialization routines are sorted and merged into the kernel's
list of startup routines and are executed during boot along with the kernel's
initialization routines.
Note that this has the effect that any initialization routines in a kernel
module that are scheduled earlier than
.Dv SI_SUB_KLD
are not executed until after
.Dv SI_SUB_KLD
during boot.
.Pp
The startup linker set for a kernel module loaded at runtime via
.Xr kldload 2
is scanned, sorted, and executed when the module is loaded.
.Pp
The shutdown linker set for a kernel module is scanned, sorted, and executed
when a kernel module is unloaded.
The teardown routines are sorted in the reverse order of the initialization
routines.
The teardown routines of the kernel and any loaded modules are
.Sy not
executed during shutdown.
.Sh EXAMPLES
This example shows the SYSINIT which displays the copyright notice during boot:
.Bd -literal -offset indent
static void
print_caddr_t(void *data)
{
	printf("%s", (char *)data);
}
SYSINIT(announce, SI_SUB_COPYRIGHT, SI_ORDER_FIRST, print_caddr_t,
    copyright);
.Ed
.Sh SEE ALSO
.Xr kld 4 ,
.Xr DECLARE_MODULE 9 ,
.Xr DEV_MODULE 9 ,
.Xr DRIVER_MODULE 9 ,
.Xr MTX_SYSINIT 9 ,
.Xr SYSCALL_MODULE 9
.Sh HISTORY
The
.Nm
framework first appeared in
.Fx 2.2 .
.Sh AUTHORS
.An -nosplit
The
.Nm
framework was written by
.An Terrence Lambert Aq terry@FreeBSD.org .
.Pp
This manual page was written by
.An Hiten Pandya Aq hmp@FreeBSD.org .