sysctlfn
sysctlfn func, u_quad_t qv, void *newp, size_t newlen,
sysctlfn fn;
fn = (sysctlfn)sysctl_lookup; /* XXX may write to rnode */
fn = (sysctlfn)sysctl_create; /* we own the rnode */
fn = (sysctlfn)sysctl_destroy; /* we own the rnode */
fn = (sysctlfn)sysctl_mmap; /* we own the rnode */
typedef int (*sysctlfn)(SYSCTLFN_PROTO);
sysctlfn, u_quad_t, void *, size_t, ...);
__sysc_pad(sysctlfn) _sysctl_func; /* access helper function */