drvread
static int drvread(void *, unsigned, unsigned);
if (drvread(sec, DOSBBSECTOR, 1))
if (drvread(sec, dsk.start, (sizeof(struct disklabel64) + 511) / 512))
if (drvread(sec, dsk.start + LABELSECTOR32, 1))
return drvread(buf, dsk.start + lba, nblk);