PMD_SECT_AF
#define pmd_young(pmd) (pmd_isset((pmd), PMD_SECT_AF))
PMD_BIT_FUNC(mkold, &= ~PMD_SECT_AF);
PMD_BIT_FUNC(mkyoung, |= PMD_SECT_AF);
prot |= PMD_TYPE_SECT | PMD_SECT_AP_WRITE | PMD_SECT_AF;
mem_types[i].prot_sect |= PMD_SECT_AF;
#define PROT_SECT_DEFAULT (PMD_TYPE_SECT | PMD_MAYBE_NG | PMD_MAYBE_SHARED | PMD_SECT_AF)