RUMP_VOP_OPEN
rv = RUMP_VOP_OPEN(vp, mode, cred);
rv = RUMP_VOP_OPEN(devvp, pr_open->pm_fmt, rootcred);
rv = RUMP_VOP_OPEN(devvp, pr_open->pm_fmt, rootcred);
int RUMP_VOP_OPEN(struct vnode *, int, struct kauth_cred *);