sysinit(9) [freebsd man page]

SYSINIT(9)						   BSD Kernel Developer's Manual						SYSINIT(9)

NAME

     SYSINIT, SYSUNINIT -- a framework for dynamic kernel initialization

SYNOPSIS

     #include <sys/param.h>
     #include <sys/kernel.h>

     SYSINIT(uniquifier, enum sysinit_sub_id subsystem, enum sysinit_elem_order order, sysinit_cfunc_t func, const void *ident);

     SYSUNINIT(uniquifier, enum sysinit_sub_id subsystem, enum sysinit_elem_order order, sysinit_cfunc_t func, const void *ident);

DESCRIPTION

     SYSINIT 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).

     The SYSINIT() macro creates a struct sysinit and stores it in a startup linker set.  The struct sysinit type as well as the subsystem identi-
     fier constants (SI_SUB_*) and initialization ordering constants (SI_ORDER_*) are defined in <sys/kernel.h>:

     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 */
     };

     The SYSINIT() macro takes a uniquifier argument to identify the particular function dispatch data, the subsystem type of startup interface,
     the subsystem element order of initialization within the subsystem, the func function to call, and the data specified in ident argument to
     pass the function.

     The SYSUNINIT() macro behaves similarly to the SYSINIT() macro except that it adds the data to a shutdown linker set.

     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 subsystem is used as the primary key and is sorted in ascending order.  The order is used as the
     secondary key and is sorted in ascending order.  The relative order of two routines that have the same subsystem and order is undefined.

     The startup linker sets for modules that are loaded together with the kernel by the boot loader are scanned during the 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 mod-
     ule that are scheduled earlier than SI_SUB_KLD are not executed until after SI_SUB_KLD during boot.

     The startup linker set for a kernel module loaded at runtime via kldload(2) is scanned, sorted, and executed when the module is loaded.

     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 not executed dur-
     ing shutdown.

EXAMPLES

     This example shows the SYSINIT which displays the copyright notice during boot:

	   static void
	   print_caddr_t(void *data)
	   {
		   printf("%s", (char *)data);
	   }
	   SYSINIT(announce, SI_SUB_COPYRIGHT, SI_ORDER_FIRST, print_caddr_t,
	       copyright);

SEE ALSO

     kld(4), DECLARE_MODULE(9), DEV_MODULE(9), DRIVER_MODULE(9), MTX_SYSINIT(9), SYSCALL_MODULE(9)

HISTORY

     The SYSINIT framework first appeared in FreeBSD 2.2.

AUTHORS

     The SYSINIT framework was written by Terrence Lambert <terry@FreeBSD.org>.

     This manual page was written by Hiten Pandya <hmp@FreeBSD.org>.

BSD
								 December 1, 2010							       BSD