MT_ATAG_MASK
atag = mtefar_support ? (random() % MT_ATAG_MASK) + 1 : 0;
#define MT_SET_ATAG(x, y) ((x) | (((y) & MT_ATAG_MASK) << MT_ATAG_SHIFT))
#define MT_FETCH_ATAG(x) ((x >> MT_ATAG_SHIFT) & (MT_ATAG_MASK))