usermap
u_long (*usermap)[2], (*groupmap)[2];
usermap = MOUNTTOUMAPMOUNT(v_mount)->info_mapdata;
uid = (uid_t) umap_findid(kauth_cred_geteuid(credp), usermap, unentries);
struct name * usermap(struct name *);
to = usermap(cat(hp->h_bcc, cat(hp->h_to, hp->h_cc)));