/* SPDX-License-Identifier: GPL-2.0 */

  #ifndef _LINUX_PGTABLE_H
  #define _LINUX_PGTABLE_H

  #include <linux/pfn.h>

  #include <asm/pgtable.h>

  #ifndef __ASSEMBLY__

  #ifdef CONFIG_MMU

  #include <linux/mm_types.h>

  #include <linux/bug.h>

  #include <linux/errno.h>

  #include <asm-generic/pgtable_uffd.h>

  #if 5 - defined(__PAGETABLE_P4D_FOLDED) - defined(__PAGETABLE_PUD_FOLDED) - \
  	defined(__PAGETABLE_PMD_FOLDED) != CONFIG_PGTABLE_LEVELS
  #error CONFIG_PGTABLE_LEVELS is not consistent with __PAGETABLE_{P4D,PUD,PMD}_FOLDED

  #endif

  /*
   * On almost all architectures and configurations, 0 can be used as the
   * upper ceiling to free_pgtables(): on many architectures it has the same
   * effect as using TASK_SIZE.  However, there is one configuration which
   * must impose a more careful limit, to avoid freeing kernel pgtables.
   */
  #ifndef USER_PGTABLES_CEILING
  #define USER_PGTABLES_CEILING	0UL
  #endif

  /*

   * A page table page can be thought of an array like this: pXd_t[PTRS_PER_PxD]
   *
   * The pXx_index() functions return the index of the entry in the page
   * table page which would control the given virtual address
   *
   * As these functions may be used by the same code for different levels of
   * the page table folding, they are always available, regardless of
   * CONFIG_PGTABLE_LEVELS value. For the folded levels they simply return 0
   * because in such cases PTRS_PER_PxD equals 1.
   */
  
  static inline unsigned long pte_index(unsigned long address)
  {
  	return (address >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
  }
  
  #ifndef pmd_index
  static inline unsigned long pmd_index(unsigned long address)
  {
  	return (address >> PMD_SHIFT) & (PTRS_PER_PMD - 1);
  }
  #define pmd_index pmd_index
  #endif
  
  #ifndef pud_index
  static inline unsigned long pud_index(unsigned long address)
  {
  	return (address >> PUD_SHIFT) & (PTRS_PER_PUD - 1);
  }
  #define pud_index pud_index
  #endif
  
  #ifndef pgd_index
  /* Must be a compile-time constant, so implement it as a macro */
  #define pgd_index(a)  (((a) >> PGDIR_SHIFT) & (PTRS_PER_PGD - 1))
  #endif
  
  #ifndef pte_offset_kernel
  static inline pte_t *pte_offset_kernel(pmd_t *pmd, unsigned long address)
  {
  	return (pte_t *)pmd_page_vaddr(*pmd) + pte_index(address);
  }
  #define pte_offset_kernel pte_offset_kernel
  #endif
  
  #if defined(CONFIG_HIGHPTE)
  #define pte_offset_map(dir, address)				\
  	((pte_t *)kmap_atomic(pmd_page(*(dir))) +		\
  	 pte_index((address)))
  #define pte_unmap(pte) kunmap_atomic((pte))
  #else
  #define pte_offset_map(dir, address)	pte_offset_kernel((dir), (address))
  #define pte_unmap(pte) ((void)(pte))	/* NOP */
  #endif
  
  /* Find an entry in the second-level page table.. */
  #ifndef pmd_offset
  static inline pmd_t *pmd_offset(pud_t *pud, unsigned long address)
  {
  	return (pmd_t *)pud_page_vaddr(*pud) + pmd_index(address);
  }
  #define pmd_offset pmd_offset
  #endif
  
  #ifndef pud_offset
  static inline pud_t *pud_offset(p4d_t *p4d, unsigned long address)
  {
  	return (pud_t *)p4d_page_vaddr(*p4d) + pud_index(address);
  }
  #define pud_offset pud_offset
  #endif
  
  static inline pgd_t *pgd_offset_pgd(pgd_t *pgd, unsigned long address)
  {
  	return (pgd + pgd_index(address));
  };
  
  /*
   * a shortcut to get a pgd_t in a given mm
   */
  #ifndef pgd_offset
  #define pgd_offset(mm, address)		pgd_offset_pgd((mm)->pgd, (address))
  #endif
  
  /*
   * a shortcut which implies the use of the kernel's pgd, instead
   * of a process's
   */

  #ifndef pgd_offset_k

  #define pgd_offset_k(address)		pgd_offset(&init_mm, (address))

  #endif

  
  /*

   * In many cases it is known that a virtual address is mapped at PMD or PTE
   * level, so instead of traversing all the page table levels, we can get a
   * pointer to the PMD entry in user or kernel page table or translate a virtual
   * address to the pointer in the PTE in the kernel page tables with simple
   * helpers.
   */
  static inline pmd_t *pmd_off(struct mm_struct *mm, unsigned long va)
  {
  	return pmd_offset(pud_offset(p4d_offset(pgd_offset(mm, va), va), va), va);
  }
  
  static inline pmd_t *pmd_off_k(unsigned long va)
  {
  	return pmd_offset(pud_offset(p4d_offset(pgd_offset_k(va), va), va), va);
  }
  
  static inline pte_t *virt_to_kpte(unsigned long vaddr)
  {
  	pmd_t *pmd = pmd_off_k(vaddr);
  
  	return pmd_none(*pmd) ? NULL : pte_offset_kernel(pmd, vaddr);
  }

  #ifndef __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS

  extern int ptep_set_access_flags(struct vm_area_struct *vma,
  				 unsigned long address, pte_t *ptep,
  				 pte_t entry, int dirty);
  #endif
  
  #ifndef __HAVE_ARCH_PMDP_SET_ACCESS_FLAGS

  #ifdef CONFIG_TRANSPARENT_HUGEPAGE

  extern int pmdp_set_access_flags(struct vm_area_struct *vma,
  				 unsigned long address, pmd_t *pmdp,
  				 pmd_t entry, int dirty);

  extern int pudp_set_access_flags(struct vm_area_struct *vma,
  				 unsigned long address, pud_t *pudp,
  				 pud_t entry, int dirty);

  #else
  static inline int pmdp_set_access_flags(struct vm_area_struct *vma,
  					unsigned long address, pmd_t *pmdp,
  					pmd_t entry, int dirty)
  {
  	BUILD_BUG();
  	return 0;
  }

  static inline int pudp_set_access_flags(struct vm_area_struct *vma,
  					unsigned long address, pud_t *pudp,
  					pud_t entry, int dirty)
  {
  	BUILD_BUG();
  	return 0;
  }

  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */

  #endif
  
  #ifndef __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG

  static inline int ptep_test_and_clear_young(struct vm_area_struct *vma,
  					    unsigned long address,
  					    pte_t *ptep)
  {
  	pte_t pte = *ptep;
  	int r = 1;
  	if (!pte_young(pte))
  		r = 0;
  	else
  		set_pte_at(vma->vm_mm, address, ptep, pte_mkold(pte));
  	return r;
  }
  #endif
  
  #ifndef __HAVE_ARCH_PMDP_TEST_AND_CLEAR_YOUNG
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
  					    unsigned long address,
  					    pmd_t *pmdp)
  {
  	pmd_t pmd = *pmdp;
  	int r = 1;
  	if (!pmd_young(pmd))
  		r = 0;
  	else
  		set_pmd_at(vma->vm_mm, address, pmdp, pmd_mkold(pmd));
  	return r;
  }

  #else

  static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
  					    unsigned long address,
  					    pmd_t *pmdp)
  {

  	BUILD_BUG();

  	return 0;
  }
  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */

  #endif
  
  #ifndef __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH

  int ptep_clear_flush_young(struct vm_area_struct *vma,
  			   unsigned long address, pte_t *ptep);
  #endif
  
  #ifndef __HAVE_ARCH_PMDP_CLEAR_YOUNG_FLUSH

  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  extern int pmdp_clear_flush_young(struct vm_area_struct *vma,
  				  unsigned long address, pmd_t *pmdp);
  #else
  /*
   * Despite relevant to THP only, this API is called from generic rmap code
   * under PageTransHuge(), hence needs a dummy implementation for !THP
   */
  static inline int pmdp_clear_flush_young(struct vm_area_struct *vma,
  					 unsigned long address, pmd_t *pmdp)
  {
  	BUILD_BUG();
  	return 0;
  }
  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */

  #endif

  #ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR

  static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
  				       unsigned long address,
  				       pte_t *ptep)
  {
  	pte_t pte = *ptep;
  	pte_clear(mm, address, ptep);
  	return pte;
  }
  #endif

  #ifndef __HAVE_ARCH_PTEP_GET
  static inline pte_t ptep_get(pte_t *ptep)
  {
  	return READ_ONCE(*ptep);
  }
  #endif

  #ifdef CONFIG_TRANSPARENT_HUGEPAGE

  #ifndef __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR

  static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
  					    unsigned long address,
  					    pmd_t *pmdp)

  {
  	pmd_t pmd = *pmdp;

  	pmd_clear(pmdp);

  	return pmd;

  }

  #endif /* __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR */
  #ifndef __HAVE_ARCH_PUDP_HUGE_GET_AND_CLEAR
  static inline pud_t pudp_huge_get_and_clear(struct mm_struct *mm,
  					    unsigned long address,
  					    pud_t *pudp)
  {
  	pud_t pud = *pudp;
  
  	pud_clear(pudp);
  	return pud;
  }
  #endif /* __HAVE_ARCH_PUDP_HUGE_GET_AND_CLEAR */

  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */

  #ifdef CONFIG_TRANSPARENT_HUGEPAGE

  #ifndef __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR_FULL

  static inline pmd_t pmdp_huge_get_and_clear_full(struct vm_area_struct *vma,

  					    unsigned long address, pmd_t *pmdp,
  					    int full)
  {

  	return pmdp_huge_get_and_clear(vma->vm_mm, address, pmdp);

  }

  #endif

  #ifndef __HAVE_ARCH_PUDP_HUGE_GET_AND_CLEAR_FULL
  static inline pud_t pudp_huge_get_and_clear_full(struct mm_struct *mm,
  					    unsigned long address, pud_t *pudp,
  					    int full)
  {
  	return pudp_huge_get_and_clear(mm, address, pudp);
  }
  #endif
  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */

  #ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR_FULL

  static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm,
  					    unsigned long address, pte_t *ptep,
  					    int full)
  {
  	pte_t pte;
  	pte = ptep_get_and_clear(mm, address, ptep);
  	return pte;
  }

  #endif

  
  /*
   * If two threads concurrently fault at the same page, the thread that
   * won the race updates the PTE and its local TLB/Cache. The other thread
   * gives up, simply does nothing, and continues; on architectures where
   * software can update TLB,  local TLB can be updated here to avoid next page
   * fault. This function updates TLB only, do nothing with cache or others.
   * It is the difference with function update_mmu_cache.
   */
  #ifndef __HAVE_ARCH_UPDATE_MMU_TLB
  static inline void update_mmu_tlb(struct vm_area_struct *vma,
  				unsigned long address, pte_t *ptep)
  {
  }
  #define __HAVE_ARCH_UPDATE_MMU_TLB
  #endif

  /*
   * Some architectures may be able to avoid expensive synchronization
   * primitives when modifications are made to PTE's which are already
   * not present, or in the process of an address space destruction.
   */
  #ifndef __HAVE_ARCH_PTE_CLEAR_NOT_PRESENT_FULL

  static inline void pte_clear_not_present_full(struct mm_struct *mm,
  					      unsigned long address,
  					      pte_t *ptep,
  					      int full)
  {
  	pte_clear(mm, address, ptep);
  }

  #endif

  #ifndef __HAVE_ARCH_PTEP_CLEAR_FLUSH

  extern pte_t ptep_clear_flush(struct vm_area_struct *vma,
  			      unsigned long address,
  			      pte_t *ptep);
  #endif

  #ifndef __HAVE_ARCH_PMDP_HUGE_CLEAR_FLUSH
  extern pmd_t pmdp_huge_clear_flush(struct vm_area_struct *vma,

  			      unsigned long address,
  			      pmd_t *pmdp);

  extern pud_t pudp_huge_clear_flush(struct vm_area_struct *vma,
  			      unsigned long address,
  			      pud_t *pudp);

  #endif
  
  #ifndef __HAVE_ARCH_PTEP_SET_WRPROTECT

  struct mm_struct;

  static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long address, pte_t *ptep)
  {
  	pte_t old_pte = *ptep;
  	set_pte_at(mm, address, ptep, pte_wrprotect(old_pte));
  }
  #endif

  /*
   * On some architectures hardware does not set page access bit when accessing
   * memory page, it is responsibilty of software setting this bit. It brings
   * out extra page fault penalty to track page access bit. For optimization page
   * access bit can be set during all page fault flow on these arches.
   * To be differentiate with macro pte_mkyoung, this macro is used on platforms
   * where software maintains page access bit.
   */
  #ifndef pte_sw_mkyoung
  static inline pte_t pte_sw_mkyoung(pte_t pte)
  {
  	return pte;
  }
  #define pte_sw_mkyoung	pte_sw_mkyoung
  #endif

  #ifndef pte_savedwrite
  #define pte_savedwrite pte_write
  #endif
  
  #ifndef pte_mk_savedwrite
  #define pte_mk_savedwrite pte_mkwrite
  #endif

  #ifndef pte_clear_savedwrite
  #define pte_clear_savedwrite pte_wrprotect
  #endif

  #ifndef pmd_savedwrite
  #define pmd_savedwrite pmd_write
  #endif
  
  #ifndef pmd_mk_savedwrite
  #define pmd_mk_savedwrite pmd_mkwrite
  #endif

  #ifndef pmd_clear_savedwrite
  #define pmd_clear_savedwrite pmd_wrprotect
  #endif

  #ifndef __HAVE_ARCH_PMDP_SET_WRPROTECT
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  static inline void pmdp_set_wrprotect(struct mm_struct *mm,
  				      unsigned long address, pmd_t *pmdp)
  {
  	pmd_t old_pmd = *pmdp;
  	set_pmd_at(mm, address, pmdp, pmd_wrprotect(old_pmd));
  }

  #else

  static inline void pmdp_set_wrprotect(struct mm_struct *mm,
  				      unsigned long address, pmd_t *pmdp)
  {

  	BUILD_BUG();

  }
  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
  #endif

  #ifndef __HAVE_ARCH_PUDP_SET_WRPROTECT
  #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
  static inline void pudp_set_wrprotect(struct mm_struct *mm,
  				      unsigned long address, pud_t *pudp)
  {
  	pud_t old_pud = *pudp;
  
  	set_pud_at(mm, address, pudp, pud_wrprotect(old_pud));
  }
  #else
  static inline void pudp_set_wrprotect(struct mm_struct *mm,
  				      unsigned long address, pud_t *pudp)
  {
  	BUILD_BUG();
  }
  #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
  #endif

  #ifndef pmdp_collapse_flush
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE

  extern pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
  				 unsigned long address, pmd_t *pmdp);

  #else
  static inline pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
  					unsigned long address,
  					pmd_t *pmdp)
  {
  	BUILD_BUG();
  	return *pmdp;
  }
  #define pmdp_collapse_flush pmdp_collapse_flush
  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
  #endif

  #ifndef __HAVE_ARCH_PGTABLE_DEPOSIT

  extern void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
  				       pgtable_t pgtable);

  #endif
  
  #ifndef __HAVE_ARCH_PGTABLE_WITHDRAW

  extern pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp);

  #endif

  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  /*
   * This is an implementation of pmdp_establish() that is only suitable for an
   * architecture that doesn't have hardware dirty/accessed bits. In this case we
   * can't race with CPU which sets these bits and non-atomic aproach is fine.
   */
  static inline pmd_t generic_pmdp_establish(struct vm_area_struct *vma,
  		unsigned long address, pmd_t *pmdp, pmd_t pmd)
  {
  	pmd_t old_pmd = *pmdp;
  	set_pmd_at(vma->vm_mm, address, pmdp, pmd);
  	return old_pmd;
  }
  #endif

  #ifndef __HAVE_ARCH_PMDP_INVALIDATE

  extern pmd_t pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,

  			    pmd_t *pmdp);
  #endif

  #ifndef __HAVE_ARCH_PTE_SAME

  static inline int pte_same(pte_t pte_a, pte_t pte_b)
  {
  	return pte_val(pte_a) == pte_val(pte_b);
  }
  #endif

  #ifndef __HAVE_ARCH_PTE_UNUSED
  /*
   * Some architectures provide facilities to virtualization guests
   * so that they can flag allocated pages as unused. This allows the
   * host to transparently reclaim unused pages. This function returns
   * whether the pte's page is unused.
   */
  static inline int pte_unused(pte_t pte)
  {
  	return 0;
  }
  #endif

  #ifndef pte_access_permitted
  #define pte_access_permitted(pte, write) \
  	(pte_present(pte) && (!(write) || pte_write(pte)))
  #endif
  
  #ifndef pmd_access_permitted
  #define pmd_access_permitted(pmd, write) \
  	(pmd_present(pmd) && (!(write) || pmd_write(pmd)))
  #endif
  
  #ifndef pud_access_permitted
  #define pud_access_permitted(pud, write) \
  	(pud_present(pud) && (!(write) || pud_write(pud)))
  #endif
  
  #ifndef p4d_access_permitted
  #define p4d_access_permitted(p4d, write) \
  	(p4d_present(p4d) && (!(write) || p4d_write(p4d)))
  #endif
  
  #ifndef pgd_access_permitted
  #define pgd_access_permitted(pgd, write) \
  	(pgd_present(pgd) && (!(write) || pgd_write(pgd)))
  #endif

  #ifndef __HAVE_ARCH_PMD_SAME

  static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b)
  {
  	return pmd_val(pmd_a) == pmd_val(pmd_b);
  }

  
  static inline int pud_same(pud_t pud_a, pud_t pud_b)
  {
  	return pud_val(pud_a) == pud_val(pud_b);
  }

  #endif

  #ifndef __HAVE_ARCH_P4D_SAME
  static inline int p4d_same(p4d_t p4d_a, p4d_t p4d_b)
  {
  	return p4d_val(p4d_a) == p4d_val(p4d_b);
  }
  #endif
  
  #ifndef __HAVE_ARCH_PGD_SAME
  static inline int pgd_same(pgd_t pgd_a, pgd_t pgd_b)
  {
  	return pgd_val(pgd_a) == pgd_val(pgd_b);
  }
  #endif

  /*
   * Use set_p*_safe(), and elide TLB flushing, when confident that *no*
   * TLB flush will be required as a result of the "set". For example, use
   * in scenarios where it is known ahead of time that the routine is
   * setting non-present entries, or re-setting an existing entry to the
   * same value. Otherwise, use the typical "set" helpers and flush the
   * TLB.
   */
  #define set_pte_safe(ptep, pte) \
  ({ \
  	WARN_ON_ONCE(pte_present(*ptep) && !pte_same(*ptep, pte)); \
  	set_pte(ptep, pte); \
  })
  
  #define set_pmd_safe(pmdp, pmd) \
  ({ \
  	WARN_ON_ONCE(pmd_present(*pmdp) && !pmd_same(*pmdp, pmd)); \
  	set_pmd(pmdp, pmd); \
  })
  
  #define set_pud_safe(pudp, pud) \
  ({ \
  	WARN_ON_ONCE(pud_present(*pudp) && !pud_same(*pudp, pud)); \
  	set_pud(pudp, pud); \
  })
  
  #define set_p4d_safe(p4dp, p4d) \
  ({ \
  	WARN_ON_ONCE(p4d_present(*p4dp) && !p4d_same(*p4dp, p4d)); \
  	set_p4d(p4dp, p4d); \
  })
  
  #define set_pgd_safe(pgdp, pgd) \
  ({ \
  	WARN_ON_ONCE(pgd_present(*pgdp) && !pgd_same(*pgdp, pgd)); \
  	set_pgd(pgdp, pgd); \
  })

  #ifndef __HAVE_ARCH_DO_SWAP_PAGE
  /*
   * Some architectures support metadata associated with a page. When a
   * page is being swapped out, this metadata must be saved so it can be
   * restored when the page is swapped back in. SPARC M7 and newer
   * processors support an ADI (Application Data Integrity) tag for the
   * page as metadata for the page. arch_do_swap_page() can restore this
   * metadata when a page is swapped back in.
   */
  static inline void arch_do_swap_page(struct mm_struct *mm,
  				     struct vm_area_struct *vma,
  				     unsigned long addr,
  				     pte_t pte, pte_t oldpte)
  {
  
  }
  #endif
  
  #ifndef __HAVE_ARCH_UNMAP_ONE
  /*
   * Some architectures support metadata associated with a page. When a
   * page is being swapped out, this metadata must be saved so it can be
   * restored when the page is swapped back in. SPARC M7 and newer
   * processors support an ADI (Application Data Integrity) tag for the
   * page as metadata for the page. arch_unmap_one() can save this
   * metadata on a swap-out of a page.
   */
  static inline int arch_unmap_one(struct mm_struct *mm,
  				  struct vm_area_struct *vma,
  				  unsigned long addr,
  				  pte_t orig_pte)
  {
  	return 0;
  }
  #endif

  /*
   * Allow architectures to preserve additional metadata associated with
   * swapped-out pages. The corresponding __HAVE_ARCH_SWAP_* macros and function
   * prototypes must be defined in the arch-specific asm/pgtable.h file.
   */
  #ifndef __HAVE_ARCH_PREPARE_TO_SWAP
  static inline int arch_prepare_to_swap(struct page *page)
  {
  	return 0;
  }
  #endif
  
  #ifndef __HAVE_ARCH_SWAP_INVALIDATE
  static inline void arch_swap_invalidate_page(int type, pgoff_t offset)
  {
  }
  
  static inline void arch_swap_invalidate_area(int type)
  {
  }
  #endif
  
  #ifndef __HAVE_ARCH_SWAP_RESTORE
  static inline void arch_swap_restore(swp_entry_t entry, struct page *page)
  {
  }
  #endif

  #ifndef __HAVE_ARCH_PGD_OFFSET_GATE
  #define pgd_offset_gate(mm, addr)	pgd_offset(mm, addr)
  #endif

  #ifndef __HAVE_ARCH_MOVE_PTE

  #define move_pte(pte, prot, old_addr, new_addr)	(pte)

  #endif

  #ifndef pte_accessible

  # define pte_accessible(mm, pte)	((void)(pte), 1)

  #endif

  #ifndef flush_tlb_fix_spurious_fault
  #define flush_tlb_fix_spurious_fault(vma, address) flush_tlb_page(vma, address)
  #endif

  /*

   * When walking page tables, get the address of the next boundary,
   * or the end address of the range if that comes earlier.  Although no
   * vma end wraps to 0, rounded up __boundary may wrap to 0 throughout.

   */

  #define pgd_addr_end(addr, end)						\
  ({	unsigned long __boundary = ((addr) + PGDIR_SIZE) & PGDIR_MASK;	\
  	(__boundary - 1 < (end) - 1)? __boundary: (end);		\
  })

  #ifndef p4d_addr_end
  #define p4d_addr_end(addr, end)						\
  ({	unsigned long __boundary = ((addr) + P4D_SIZE) & P4D_MASK;	\
  	(__boundary - 1 < (end) - 1)? __boundary: (end);		\
  })
  #endif

  #ifndef pud_addr_end
  #define pud_addr_end(addr, end)						\
  ({	unsigned long __boundary = ((addr) + PUD_SIZE) & PUD_MASK;	\
  	(__boundary - 1 < (end) - 1)? __boundary: (end);		\
  })
  #endif
  
  #ifndef pmd_addr_end
  #define pmd_addr_end(addr, end)						\
  ({	unsigned long __boundary = ((addr) + PMD_SIZE) & PMD_MASK;	\
  	(__boundary - 1 < (end) - 1)? __boundary: (end);		\
  })
  #endif

  /*
   * When walking page tables, we usually want to skip any p?d_none entries;
   * and any p?d_bad entries - reporting the error before resetting to none.
   * Do the tests inline, but report and clear the bad entry in mm/memory.c.
   */
  void pgd_clear_bad(pgd_t *);

  
  #ifndef __PAGETABLE_P4D_FOLDED

  void p4d_clear_bad(p4d_t *);

  #else
  #define p4d_clear_bad(p4d)        do { } while (0)
  #endif
  
  #ifndef __PAGETABLE_PUD_FOLDED

  void pud_clear_bad(pud_t *);

  #else
  #define pud_clear_bad(p4d)        do { } while (0)
  #endif

  void pmd_clear_bad(pmd_t *);
  
  static inline int pgd_none_or_clear_bad(pgd_t *pgd)
  {
  	if (pgd_none(*pgd))
  		return 1;
  	if (unlikely(pgd_bad(*pgd))) {
  		pgd_clear_bad(pgd);
  		return 1;
  	}
  	return 0;
  }

  static inline int p4d_none_or_clear_bad(p4d_t *p4d)
  {
  	if (p4d_none(*p4d))
  		return 1;
  	if (unlikely(p4d_bad(*p4d))) {
  		p4d_clear_bad(p4d);
  		return 1;
  	}
  	return 0;
  }

  static inline int pud_none_or_clear_bad(pud_t *pud)
  {
  	if (pud_none(*pud))
  		return 1;
  	if (unlikely(pud_bad(*pud))) {
  		pud_clear_bad(pud);
  		return 1;
  	}
  	return 0;
  }
  
  static inline int pmd_none_or_clear_bad(pmd_t *pmd)
  {
  	if (pmd_none(*pmd))
  		return 1;
  	if (unlikely(pmd_bad(*pmd))) {
  		pmd_clear_bad(pmd);
  		return 1;
  	}
  	return 0;
  }

  static inline pte_t __ptep_modify_prot_start(struct vm_area_struct *vma,

  					     unsigned long addr,
  					     pte_t *ptep)
  {
  	/*
  	 * Get the current pte state, but zero it out to make it
  	 * non-present, preventing the hardware from asynchronously
  	 * updating it.
  	 */

  	return ptep_get_and_clear(vma->vm_mm, addr, ptep);

  }

  static inline void __ptep_modify_prot_commit(struct vm_area_struct *vma,

  					     unsigned long addr,
  					     pte_t *ptep, pte_t pte)
  {
  	/*
  	 * The pte is non-present, so there's no hardware state to
  	 * preserve.
  	 */

  	set_pte_at(vma->vm_mm, addr, ptep, pte);

  }
  
  #ifndef __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION
  /*
   * Start a pte protection read-modify-write transaction, which
   * protects against asynchronous hardware modifications to the pte.
   * The intention is not to prevent the hardware from making pte
   * updates, but to prevent any updates it may make from being lost.
   *
   * This does not protect against other software modifications of the
   * pte; the appropriate pte lock must be held over the transation.
   *
   * Note that this interface is intended to be batchable, meaning that
   * ptep_modify_prot_commit may not actually update the pte, but merely
   * queue the update to be done at some later time.  The update must be
   * actually committed before the pte lock is released, however.
   */

  static inline pte_t ptep_modify_prot_start(struct vm_area_struct *vma,

  					   unsigned long addr,
  					   pte_t *ptep)
  {

  	return __ptep_modify_prot_start(vma, addr, ptep);

  }
  
  /*
   * Commit an update to a pte, leaving any hardware-controlled bits in
   * the PTE unmodified.
   */

  static inline void ptep_modify_prot_commit(struct vm_area_struct *vma,

  					   unsigned long addr,

  					   pte_t *ptep, pte_t old_pte, pte_t pte)

  {

  	__ptep_modify_prot_commit(vma, addr, ptep, pte);

  }
  #endif /* __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION */

  #endif /* CONFIG_MMU */

  /*

   * No-op macros that just return the current protection value. Defined here

   * because these macros can be used even if CONFIG_MMU is not defined.

   */

  
  #ifndef pgprot_nx
  #define pgprot_nx(prot)	(prot)
  #endif
  
  #ifndef pgprot_noncached
  #define pgprot_noncached(prot)	(prot)
  #endif
  
  #ifndef pgprot_writecombine
  #define pgprot_writecombine pgprot_noncached
  #endif
  
  #ifndef pgprot_writethrough
  #define pgprot_writethrough pgprot_noncached
  #endif
  
  #ifndef pgprot_device
  #define pgprot_device pgprot_noncached
  #endif
  
  #ifdef CONFIG_MMU
  #ifndef pgprot_modify
  #define pgprot_modify pgprot_modify
  static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
  {
  	if (pgprot_val(oldprot) == pgprot_val(pgprot_noncached(oldprot)))
  		newprot = pgprot_noncached(newprot);
  	if (pgprot_val(oldprot) == pgprot_val(pgprot_writecombine(oldprot)))
  		newprot = pgprot_writecombine(newprot);
  	if (pgprot_val(oldprot) == pgprot_val(pgprot_device(oldprot)))
  		newprot = pgprot_device(newprot);
  	return newprot;
  }
  #endif
  #endif /* CONFIG_MMU */

  #ifndef pgprot_encrypted
  #define pgprot_encrypted(prot)	(prot)
  #endif
  
  #ifndef pgprot_decrypted
  #define pgprot_decrypted(prot)	(prot)
  #endif
  
  /*

   * A facility to provide lazy MMU batching.  This allows PTE updates and
   * page invalidations to be delayed until a call to leave lazy MMU mode
   * is issued.  Some architectures may benefit from doing this, and it is
   * beneficial for both shadow and direct mode hypervisors, which may batch
   * the PTE updates which happen during this window.  Note that using this
   * interface requires that read hazards be removed from the code.  A read
   * hazard could result in the direct mode hypervisor case, since the actual
   * write to the page tables may not yet have taken place, so reads though
   * a raw PTE pointer after it has been modified are not guaranteed to be
   * up to date.  This mode can only be entered and left under the protection of
   * the page table locks for all page tables which may be modified.  In the UP
   * case, this is required so that preemption is disabled, and in the SMP case,
   * it must synchronize the delayed page table writes properly on other CPUs.
   */
  #ifndef __HAVE_ARCH_ENTER_LAZY_MMU_MODE
  #define arch_enter_lazy_mmu_mode()	do {} while (0)
  #define arch_leave_lazy_mmu_mode()	do {} while (0)
  #define arch_flush_lazy_mmu_mode()	do {} while (0)
  #endif
  
  /*

   * A facility to provide batching of the reload of page tables and
   * other process state with the actual context switch code for
   * paravirtualized guests.  By convention, only one of the batched
   * update (lazy) modes (CPU, MMU) should be active at any given time,
   * entry should never be nested, and entry and exits should always be
   * paired.  This is for sanity of maintaining and reasoning about the
   * kernel code.  In this case, the exit (end of the context switch) is
   * in architecture-specific code, and so doesn't need a generic
   * definition.

   */

  #ifndef __HAVE_ARCH_START_CONTEXT_SWITCH

  #define arch_start_context_switch(prev)	do {} while (0)

  #endif

  #ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY
  #ifndef CONFIG_ARCH_ENABLE_THP_MIGRATION
  static inline pmd_t pmd_swp_mksoft_dirty(pmd_t pmd)
  {
  	return pmd;
  }
  
  static inline int pmd_swp_soft_dirty(pmd_t pmd)
  {
  	return 0;
  }
  
  static inline pmd_t pmd_swp_clear_soft_dirty(pmd_t pmd)
  {
  	return pmd;
  }
  #endif
  #else /* !CONFIG_HAVE_ARCH_SOFT_DIRTY */

  static inline int pte_soft_dirty(pte_t pte)
  {
  	return 0;
  }
  
  static inline int pmd_soft_dirty(pmd_t pmd)
  {
  	return 0;
  }
  
  static inline pte_t pte_mksoft_dirty(pte_t pte)
  {
  	return pte;
  }
  
  static inline pmd_t pmd_mksoft_dirty(pmd_t pmd)
  {
  	return pmd;
  }

  static inline pte_t pte_clear_soft_dirty(pte_t pte)
  {
  	return pte;
  }
  
  static inline pmd_t pmd_clear_soft_dirty(pmd_t pmd)
  {
  	return pmd;
  }

  static inline pte_t pte_swp_mksoft_dirty(pte_t pte)
  {
  	return pte;
  }
  
  static inline int pte_swp_soft_dirty(pte_t pte)
  {
  	return 0;
  }
  
  static inline pte_t pte_swp_clear_soft_dirty(pte_t pte)
  {
  	return pte;
  }

  
  static inline pmd_t pmd_swp_mksoft_dirty(pmd_t pmd)
  {
  	return pmd;
  }
  
  static inline int pmd_swp_soft_dirty(pmd_t pmd)
  {
  	return 0;
  }
  
  static inline pmd_t pmd_swp_clear_soft_dirty(pmd_t pmd)
  {
  	return pmd;
  }

  #endif

  #ifndef __HAVE_PFNMAP_TRACKING
  /*

   * Interfaces that can be used by architecture code to keep track of
   * memory type of pfn mappings specified by the remap_pfn_range,

   * vmf_insert_pfn.

   */
  
  /*
   * track_pfn_remap is called when a _new_ pfn mapping is being established
   * by remap_pfn_range() for physical range indicated by pfn and size.

   */

  static inline int track_pfn_remap(struct vm_area_struct *vma, pgprot_t *prot,

  				  unsigned long pfn, unsigned long addr,
  				  unsigned long size)

  {
  	return 0;
  }
  
  /*

   * track_pfn_insert is called when a _new_ single pfn is established

   * by vmf_insert_pfn().

   */

  static inline void track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot,
  				    pfn_t pfn)

  {

  }
  
  /*
   * track_pfn_copy is called when vma that is covering the pfnmap gets

   * copied through copy_page_range().
   */

  static inline int track_pfn_copy(struct vm_area_struct *vma)

  {
  	return 0;
  }
  
  /*

   * untrack_pfn is called while unmapping a pfnmap for a region.

   * untrack can be called for a specific region indicated by pfn and size or

   * can be for the entire vma (in which case pfn, size are zero).

   */

  static inline void untrack_pfn(struct vm_area_struct *vma,
  			       unsigned long pfn, unsigned long size)

  {
  }

  
  /*
   * untrack_pfn_moved is called while mremapping a pfnmap for a new region.
   */
  static inline void untrack_pfn_moved(struct vm_area_struct *vma)
  {
  }

  #else

  extern int track_pfn_remap(struct vm_area_struct *vma, pgprot_t *prot,

  			   unsigned long pfn, unsigned long addr,
  			   unsigned long size);

  extern void track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot,
  			     pfn_t pfn);

  extern int track_pfn_copy(struct vm_area_struct *vma);
  extern void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn,
  			unsigned long size);

  extern void untrack_pfn_moved(struct vm_area_struct *vma);

  #endif

  #ifdef __HAVE_COLOR_ZERO_PAGE
  static inline int is_zero_pfn(unsigned long pfn)
  {
  	extern unsigned long zero_pfn;
  	unsigned long offset_from_zero_pfn = pfn - zero_pfn;
  	return offset_from_zero_pfn <= (zero_page_mask >> PAGE_SHIFT);
  }

  #define my_zero_pfn(addr)	page_to_pfn(ZERO_PAGE(addr))

  #else
  static inline int is_zero_pfn(unsigned long pfn)
  {
  	extern unsigned long zero_pfn;
  	return pfn == zero_pfn;
  }
  
  static inline unsigned long my_zero_pfn(unsigned long addr)
  {
  	extern unsigned long zero_pfn;
  	return zero_pfn;
  }
  #endif

  #ifdef CONFIG_MMU

  #ifndef CONFIG_TRANSPARENT_HUGEPAGE
  static inline int pmd_trans_huge(pmd_t pmd)
  {
  	return 0;
  }

  #ifndef pmd_write

  static inline int pmd_write(pmd_t pmd)
  {
  	BUG();
  	return 0;
  }

  #endif /* pmd_write */

  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */

  #ifndef pud_write
  static inline int pud_write(pud_t pud)
  {
  	BUG();
  	return 0;
  }
  #endif /* pud_write */

  #if !defined(CONFIG_ARCH_HAS_PTE_DEVMAP) || !defined(CONFIG_TRANSPARENT_HUGEPAGE)
  static inline int pmd_devmap(pmd_t pmd)
  {
  	return 0;
  }
  static inline int pud_devmap(pud_t pud)
  {
  	return 0;
  }
  static inline int pgd_devmap(pgd_t pgd)
  {
  	return 0;
  }
  #endif

  #if !defined(CONFIG_TRANSPARENT_HUGEPAGE) || \
  	(defined(CONFIG_TRANSPARENT_HUGEPAGE) && \
  	 !defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD))
  static inline int pud_trans_huge(pud_t pud)
  {
  	return 0;
  }
  #endif

  /* See pmd_none_or_trans_huge_or_clear_bad for discussion. */
  static inline int pud_none_or_trans_huge_or_dev_or_clear_bad(pud_t *pud)
  {
  	pud_t pudval = READ_ONCE(*pud);
  
  	if (pud_none(pudval) || pud_trans_huge(pudval) || pud_devmap(pudval))
  		return 1;
  	if (unlikely(pud_bad(pudval))) {
  		pud_clear_bad(pud);
  		return 1;
  	}
  	return 0;
  }
  
  /* See pmd_trans_unstable for discussion. */
  static inline int pud_trans_unstable(pud_t *pud)
  {
  #if defined(CONFIG_TRANSPARENT_HUGEPAGE) &&			\
  	defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD)
  	return pud_none_or_trans_huge_or_dev_or_clear_bad(pud);
  #else
  	return 0;
  #endif
  }

  #ifndef pmd_read_atomic
  static inline pmd_t pmd_read_atomic(pmd_t *pmdp)
  {
  	/*
  	 * Depend on compiler for an atomic pmd read. NOTE: this is
  	 * only going to work, if the pmdval_t isn't larger than
  	 * an unsigned long.
  	 */
  	return *pmdp;
  }
  #endif

  #ifndef arch_needs_pgtable_deposit
  #define arch_needs_pgtable_deposit() (false)
  #endif

  /*
   * This function is meant to be used by sites walking pagetables with

   * the mmap_lock held in read mode to protect against MADV_DONTNEED and

   * transhuge page faults. MADV_DONTNEED can convert a transhuge pmd
   * into a null pmd and the transhuge page fault can convert a null pmd
   * into an hugepmd or into a regular pmd (if the hugepage allocation

   * fails). While holding the mmap_lock in read mode the pmd becomes

   * stable and stops changing under us only if it's not null and not a
   * transhuge pmd. When those races occurs and this function makes a
   * difference vs the standard pmd_none_or_clear_bad, the result is
   * undefined so behaving like if the pmd was none is safe (because it
   * can return none anyway). The compiler level barrier() is critically
   * important to compute the two checks atomically on the same pmdval.

   *
   * For 32bit kernels with a 64bit large pmd_t this automatically takes
   * care of reading the pmd atomically to avoid SMP race conditions

   * against pmd_populate() when the mmap_lock is hold for reading by the

   * caller (a special atomic read not done by "gcc" as in the generic
   * version above, is also needed when THP is disabled because the page
   * fault can populate the pmd from under us).

   */
  static inline int pmd_none_or_trans_huge_or_clear_bad(pmd_t *pmd)
  {

  	pmd_t pmdval = pmd_read_atomic(pmd);

  	/*
  	 * The barrier will stabilize the pmdval in a register or on
  	 * the stack so that it will stop changing under the code.

  	 *
  	 * When CONFIG_TRANSPARENT_HUGEPAGE=y on x86 32bit PAE,
  	 * pmd_read_atomic is allowed to return a not atomic pmdval
  	 * (for example pointing to an hugepage that has never been
  	 * mapped in the pmd). The below checks will only care about
  	 * the low part of the pmd with 32bit PAE x86 anyway, with the
  	 * exception of pmd_none(). So the important thing is that if
  	 * the low part of the pmd is found null, the high part will
  	 * be also null or the pmd_none() check below would be
  	 * confused.

  	 */
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  	barrier();
  #endif

  	/*
  	 * !pmd_present() checks for pmd migration entries
  	 *
  	 * The complete check uses is_pmd_migration_entry() in linux/swapops.h
  	 * But using that requires moving current function and pmd_trans_unstable()
  	 * to linux/swapops.h to resovle dependency, which is too much code move.
  	 *
  	 * !pmd_present() is equivalent to is_pmd_migration_entry() currently,
  	 * because !pmd_present() pages can only be under migration not swapped
  	 * out.
  	 *
  	 * pmd_none() is preseved for future condition checks on pmd migration
  	 * entries and not confusing with this function name, although it is
  	 * redundant with !pmd_present().
  	 */
  	if (pmd_none(pmdval) || pmd_trans_huge(pmdval) ||
  		(IS_ENABLED(CONFIG_ARCH_ENABLE_THP_MIGRATION) && !pmd_present(pmdval)))

  		return 1;
  	if (unlikely(pmd_bad(pmdval))) {

  		pmd_clear_bad(pmd);

  		return 1;
  	}
  	return 0;
  }
  
  /*
   * This is a noop if Transparent Hugepage Support is not built into
   * the kernel. Otherwise it is equivalent to
   * pmd_none_or_trans_huge_or_clear_bad(), and shall only be called in
   * places that already verified the pmd is not none and they want to
   * walk ptes while holding the mmap sem in read mode (write mode don't
   * need this). If THP is not enabled, the pmd can't go away under the
   * code even if MADV_DONTNEED runs, but if THP is enabled we need to
   * run a pmd_trans_unstable before walking the ptes after

   * split_huge_pmd returns (because it may have run when the pmd become
   * null, but then a page fault can map in a THP and not a regular page).

   */
  static inline int pmd_trans_unstable(pmd_t *pmd)
  {
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  	return pmd_none_or_trans_huge_or_clear_bad(pmd);
  #else
  	return 0;

  #endif

  }

  #ifndef CONFIG_NUMA_BALANCING
  /*
   * Technically a PTE can be PROTNONE even when not doing NUMA balancing but
   * the only case the kernel cares is for NUMA balancing and is only ever set
   * when the VMA is accessible. For PROT_NONE VMAs, the PTEs are not marked

   * _PAGE_PROTNONE so by default, implement the helper as "always no". It

   * is the responsibility of the caller to distinguish between PROT_NONE
   * protections and NUMA hinting fault protections.
   */
  static inline int pte_protnone(pte_t pte)
  {
  	return 0;
  }
  
  static inline int pmd_protnone(pmd_t pmd)
  {
  	return 0;
  }
  #endif /* CONFIG_NUMA_BALANCING */

  #endif /* CONFIG_MMU */

  #ifdef CONFIG_HAVE_ARCH_HUGE_VMAP

  
  #ifndef __PAGETABLE_P4D_FOLDED
  int p4d_set_huge(p4d_t *p4d, phys_addr_t addr, pgprot_t prot);
  int p4d_clear_huge(p4d_t *p4d);
  #else
  static inline int p4d_set_huge(p4d_t *p4d, phys_addr_t addr, pgprot_t prot)
  {
  	return 0;
  }
  static inline int p4d_clear_huge(p4d_t *p4d)
  {
  	return 0;
  }
  #endif /* !__PAGETABLE_P4D_FOLDED */

  int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot);
  int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot);

  int pud_clear_huge(pud_t *pud);
  int pmd_clear_huge(pmd_t *pmd);

  int p4d_free_pud_page(p4d_t *p4d, unsigned long addr);

  int pud_free_pmd_page(pud_t *pud, unsigned long addr);
  int pmd_free_pte_page(pmd_t *pmd, unsigned long addr);

  #else	/* !CONFIG_HAVE_ARCH_HUGE_VMAP */

  static inline int p4d_set_huge(p4d_t *p4d, phys_addr_t addr, pgprot_t prot)
  {
  	return 0;
  }

  static inline int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot)
  {
  	return 0;
  }
  static inline int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot)
  {
  	return 0;
  }

  static inline int p4d_clear_huge(p4d_t *p4d)
  {
  	return 0;
  }

  static inline int pud_clear_huge(pud_t *pud)
  {
  	return 0;
  }
  static inline int pmd_clear_huge(pmd_t *pmd)
  {
  	return 0;
  }

  static inline int p4d_free_pud_page(p4d_t *p4d, unsigned long addr)
  {
  	return 0;
  }

  static inline int pud_free_pmd_page(pud_t *pud, unsigned long addr)

  {
  	return 0;
  }

  static inline int pmd_free_pte_page(pmd_t *pmd, unsigned long addr)

  {
  	return 0;
  }

  #endif	/* CONFIG_HAVE_ARCH_HUGE_VMAP */

  #ifndef __HAVE_ARCH_FLUSH_PMD_TLB_RANGE
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  /*
   * ARCHes with special requirements for evicting THP backing TLB entries can
   * implement this. Otherwise also, it can help optimize normal TLB flush in

   * THP regime. Stock flush_tlb_range() typically has optimization to nuke the
   * entire TLB if flush span is greater than a threshold, which will
   * likely be true for a single huge page. Thus a single THP flush will
   * invalidate the entire TLB which is not desirable.

   * e.g. see arch/arc: flush_pmd_tlb_range
   */
  #define flush_pmd_tlb_range(vma, addr, end)	flush_tlb_range(vma, addr, end)

  #define flush_pud_tlb_range(vma, addr, end)	flush_tlb_range(vma, addr, end)

  #else
  #define flush_pmd_tlb_range(vma, addr, end)	BUILD_BUG()

  #define flush_pud_tlb_range(vma, addr, end)	BUILD_BUG()

  #endif
  #endif

  struct file;
  int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
  			unsigned long size, pgprot_t *vma_prot);

  
  #ifndef CONFIG_X86_ESPFIX64
  static inline void init_espfix_bsp(void) { }
  #endif

  extern void __init pgtable_cache_init(void);

  #ifndef __HAVE_ARCH_PFN_MODIFY_ALLOWED
  static inline bool pfn_modify_allowed(unsigned long pfn, pgprot_t prot)
  {
  	return true;
  }
  
  static inline bool arch_has_pfn_modify_check(void)
  {
  	return false;
  }
  #endif /* !_HAVE_ARCH_PFN_MODIFY_ALLOWED */

  /*
   * Architecture PAGE_KERNEL_* fallbacks
   *
   * Some architectures don't define certain PAGE_KERNEL_* flags. This is either
   * because they really don't support them, or the port needs to be updated to
   * reflect the required functionality. Below are a set of relatively safe
   * fallbacks, as best effort, which we can count on in lieu of the architectures
   * not defining them on their own yet.
   */
  
  #ifndef PAGE_KERNEL_RO
  # define PAGE_KERNEL_RO PAGE_KERNEL
  #endif

  #ifndef PAGE_KERNEL_EXEC
  # define PAGE_KERNEL_EXEC PAGE_KERNEL
  #endif

  /*
   * Page Table Modification bits for pgtbl_mod_mask.
   *
   * These are used by the p?d_alloc_track*() set of functions an in the generic
   * vmalloc/ioremap code to track at which page-table levels entries have been
   * modified. Based on that the code can better decide when vmalloc and ioremap
   * mapping changes need to be synchronized to other page-tables in the system.
   */
  #define		__PGTBL_PGD_MODIFIED	0
  #define		__PGTBL_P4D_MODIFIED	1
  #define		__PGTBL_PUD_MODIFIED	2
  #define		__PGTBL_PMD_MODIFIED	3
  #define		__PGTBL_PTE_MODIFIED	4
  
  #define		PGTBL_PGD_MODIFIED	BIT(__PGTBL_PGD_MODIFIED)
  #define		PGTBL_P4D_MODIFIED	BIT(__PGTBL_P4D_MODIFIED)
  #define		PGTBL_PUD_MODIFIED	BIT(__PGTBL_PUD_MODIFIED)
  #define		PGTBL_PMD_MODIFIED	BIT(__PGTBL_PMD_MODIFIED)
  #define		PGTBL_PTE_MODIFIED	BIT(__PGTBL_PTE_MODIFIED)
  
  /* Page-Table Modification Mask */
  typedef unsigned int pgtbl_mod_mask;

  #endif /* !__ASSEMBLY__ */

  #if !defined(MAX_POSSIBLE_PHYSMEM_BITS) && !defined(CONFIG_64BIT)
  #ifdef CONFIG_PHYS_ADDR_T_64BIT
  /*
   * ZSMALLOC needs to know the highest PFN on 32-bit architectures
   * with physical address space extension, but falls back to
   * BITS_PER_LONG otherwise.
   */
  #error Missing MAX_POSSIBLE_PHYSMEM_BITS definition
  #else
  #define MAX_POSSIBLE_PHYSMEM_BITS 32
  #endif
  #endif

  #ifndef has_transparent_hugepage
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  #define has_transparent_hugepage() 1
  #else
  #define has_transparent_hugepage() 0
  #endif
  #endif

  /*
   * On some architectures it depends on the mm if the p4d/pud or pmd
   * layer of the page table hierarchy is folded or not.
   */
  #ifndef mm_p4d_folded
  #define mm_p4d_folded(mm)	__is_defined(__PAGETABLE_P4D_FOLDED)
  #endif
  
  #ifndef mm_pud_folded
  #define mm_pud_folded(mm)	__is_defined(__PAGETABLE_PUD_FOLDED)
  #endif
  
  #ifndef mm_pmd_folded
  #define mm_pmd_folded(mm)	__is_defined(__PAGETABLE_PMD_FOLDED)
  #endif

  #ifndef p4d_offset_lockless
  #define p4d_offset_lockless(pgdp, pgd, address) p4d_offset(&(pgd), address)
  #endif
  #ifndef pud_offset_lockless
  #define pud_offset_lockless(p4dp, p4d, address) pud_offset(&(p4d), address)
  #endif
  #ifndef pmd_offset_lockless
  #define pmd_offset_lockless(pudp, pud, address) pmd_offset(&(pud), address)
  #endif

  /*
   * p?d_leaf() - true if this entry is a final mapping to a physical address.
   * This differs from p?d_huge() by the fact that they are always available (if
   * the architecture supports large pages at the appropriate level) even
   * if CONFIG_HUGETLB_PAGE is not defined.
   * Only meaningful when called on a valid entry.
   */
  #ifndef pgd_leaf
  #define pgd_leaf(x)	0
  #endif
  #ifndef p4d_leaf
  #define p4d_leaf(x)	0
  #endif
  #ifndef pud_leaf
  #define pud_leaf(x)	0
  #endif
  #ifndef pmd_leaf
  #define pmd_leaf(x)	0
  #endif

  #endif /* _LINUX_PGTABLE_H */