xp_errx
xp_errx(1, __LINE__, "rump doesn't support munmap");
xp_errx(1, __LINE__, "unknown prot %x\n", prot);
xp_errx(1, __LINE__, "requnit < 0 not implemented.");
void xp_errx(int, int, const char *, ...) __printflike(3, 4) __dead;