lwpctl
struct lwpctl;
int _lwp_ctl(int, struct lwpctl **);
_lwp_ctl(int a, struct lwpctl **b)
struct lwpctl *pt_lwpctl; /* Kernel/user comms area */
struct lwpctl *l_lwpctl; /* p: lwpctl block kernel address */
syscallarg(struct lwpctl **) address;