BITS_PER_PTE
#define PTRS_PER_PTE (1UL << BITS_PER_PTE)
#define PMD_SHIFT (PLD_SHIFT + BITS_PER_PTE)
#define PGDIR_SHIFT (PLD_SHIFT + BITS_PER_PTE + BITS_PER_PMD)
#if (KERNEL_INITIAL_ORDER) >= (PLD_SHIFT + BITS_PER_PTE)
# define PT_INITIAL (1 << (KERNEL_INITIAL_ORDER - PLD_SHIFT - BITS_PER_PTE))
DEFINE(ASM_BITS_PER_PTE, BITS_PER_PTE);
BUILD_BUG_ON(PAGE_SHIFT + BITS_PER_PTE + BITS_PER_PMD + BITS_PER_PGD