PDRMASK
#define trunc_2mpage(x) ((unsigned long)(x) & ~PDRMASK)
#define round_2mpage(x) ((((unsigned long)(x)) + PDRMASK) & ~PDRMASK)
#define trunc_4mpage(x) ((x) & ~PDRMASK)
#define round_4mpage(x) ((((x)) + PDRMASK) & ~PDRMASK)