HOOK_ESTABLISH(9)

NAME
hook_establish, hook_disestablish - add or remove a hook from a specified list

SYNOPSIS
#include <sys/types.h>
#include <sys/systm.h>
void *
hook_establish(struct hook_desc_head *head, int tail, void (*fn)(void *), void *arg);
void
hook_disestablish(struct hook_desc_head *head, void *cookie);

DESCRIPTION
The hook_establish() function adds fn to the list of hooks invoked by dohooks(9). If tail is non-zero, the hook is added to the tail of the list denoted by the TAILQ_HEAD pointer head, otherwise to the front. The dohooks(9) function will at its invocation call each hook from the front of this list. When invoked, the hook function fn will be passed arg as its only argument.

The hook_disestablish() function removes the hook described by the opaque pointer cookie from the list of hooks denoted by the TAILQ_HEAD pointer head. If cookie is invalid, the result of hook_disestablish() is undefined.

The startup-, mountroot, and shutdownhooks systems use this API for their implementation.

RETURN VALUES
If successful, hook_establish() returns an opaque pointer describing the newly established hook. Otherwise, it returns NULL.

SEE ALSO
dohooks(9), doshutdownhooks(9), dostartuphooks(9), mountroothook_establish(9), shutdownhook_establish(9), startuphook_establish(9)