gdt_statist_t
gdt_statist_t gdt_stat;
bzero(&gdt_stat, sizeof(gdt_statist_t));
#define GDT_IOCTL_STATIST _IOR('J', 9, gdt_statist_t) /* get statistics */
gdt_statist_t *p;
p = (gdt_statist_t *)ap->a_data;
bcopy(&gdt_stat, p, sizeof(gdt_statist_t));
extern gdt_statist_t gdt_stat;