xreadatoff
if (xreadatoff(fd, &ehdr, 0, sizeof ehdr, fn) != sizeof ehdr)
if (xreadatoff(fd, shdrp, xewtoh(ehdr.e_shoff), shdrsize, fn) !=
if ((size_t)xreadatoff(fd, shstrtabp, xewtoh(shstrtabshdr->sh_offset),
if ((size_t)xreadatoff(fd, layoutp[i].bufp, off, size, fn) !=