text: #ifndef _SUN3_PGTABLE_H
  #define _SUN3_PGTABLE_H
  
  #include <asm/sun3mmu.h>
  
  #ifndef __ASSEMBLY__
  #include <asm/virtconvert.h>
  #include <linux/linkage.h>
  
  /*
   * This file contains all the things which change drastically for the sun3
   * pagetable stuff, to avoid making too much of a mess of the generic m68k
   * `pgtable.h'; this should only be included from the generic file. --m
   */
  
  /* For virtual address to physical address conversion */
  #define VTOP(addr)	__pa(addr)
  #define PTOV(addr)	__va(addr)
  
  
  #endif	/* !__ASSEMBLY__ */
  
  /* These need to be defined for compatibility although the sun3 doesn't use them */
  #define _PAGE_NOCACHE030 0x040
  #define _CACHEMASK040   (~0x060)
  #define _PAGE_NOCACHE_S 0x040
  
  /* Page protection values within PTE. */
  #define SUN3_PAGE_VALID     (0x80000000)
  #define SUN3_PAGE_WRITEABLE (0x40000000)
  #define SUN3_PAGE_SYSTEM    (0x20000000)
  #define SUN3_PAGE_NOCACHE   (0x10000000)
  #define SUN3_PAGE_ACCESSED  (0x02000000)
  #define SUN3_PAGE_MODIFIED  (0x01000000)
  
  
  /* Externally used page protection values. */
  #define _PAGE_PRESENT	(SUN3_PAGE_VALID)
  #define _PAGE_ACCESSED	(SUN3_PAGE_ACCESSED)
  
  #define PTE_FILE_MAX_BITS 28
  
  /* Compound page protection values. */
  //todo: work out which ones *should* have SUN3_PAGE_NOCACHE and fix...
  // is it just PAGE_KERNEL and PAGE_SHARED?
  #define PAGE_NONE	__pgprot(SUN3_PAGE_VALID \
  				 | SUN3_PAGE_ACCESSED \
  				 | SUN3_PAGE_NOCACHE)
  #define PAGE_SHARED	__pgprot(SUN3_PAGE_VALID \
  				 | SUN3_PAGE_WRITEABLE \
  				 | SUN3_PAGE_ACCESSED \
  				 | SUN3_PAGE_NOCACHE)
  #define PAGE_COPY	__pgprot(SUN3_PAGE_VALID \
  				 | SUN3_PAGE_ACCESSED \
  				 | SUN3_PAGE_NOCACHE)
  #define PAGE_READONLY	__pgprot(SUN3_PAGE_VALID \
  				 | SUN3_PAGE_ACCESSED \
  				 | SUN3_PAGE_NOCACHE)
  #define PAGE_KERNEL	__pgprot(SUN3_PAGE_VALID \
  				 | SUN3_PAGE_WRITEABLE \
  				 | SUN3_PAGE_SYSTEM \
  				 | SUN3_PAGE_NOCACHE \
  				 | SUN3_PAGE_ACCESSED \
  				 | SUN3_PAGE_MODIFIED)
  #define PAGE_INIT	__pgprot(SUN3_PAGE_VALID \
  				 | SUN3_PAGE_WRITEABLE \
  				 | SUN3_PAGE_SYSTEM \
  				 | SUN3_PAGE_NOCACHE)
  
  /*
   * Page protections for initialising protection_map. The sun3 has only two
   * protection settings, valid (implying read and execute) and writeable. These
   * are as close as we can get...
   */
  #define __P000	PAGE_NONE
  #define __P001	PAGE_READONLY
  #define __P010	PAGE_COPY
  #define __P011	PAGE_COPY
  #define __P100	PAGE_READONLY
  #define __P101	PAGE_READONLY
  #define __P110	PAGE_COPY
  #define __P111	PAGE_COPY
  
  #define __S000	PAGE_NONE
  #define __S001	PAGE_READONLY
  #define __S010	PAGE_SHARED
  #define __S011	PAGE_SHARED
  #define __S100	PAGE_READONLY
  #define __S101	PAGE_READONLY
  #define __S110	PAGE_SHARED
  #define __S111	PAGE_SHARED
  
  /* Use these fake page-protections on PMDs. */
  #define SUN3_PMD_VALID	(0x00000001)
  #define SUN3_PMD_MASK	(0x0000003F)
  #define SUN3_PMD_MAGIC	(0x0000002B)
  
  #ifndef __ASSEMBLY__
  
  /*
   * Conversion functions: convert a page and protection to a page entry,
   * and a page entry and page directory to the page they refer to.
   */
  #define mk_pte(page, pgprot) pfn_pte(page_to_pfn(page), (pgprot))
  
  static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
  {
  	pte_val(pte) = (pte_val(pte) & SUN3_PAGE_CHG_MASK) | pgprot_val(newprot);
  	return pte;
  }
  
  #define pmd_set(pmdp,ptep) do {} while (0)
  
  static inline void pgd_set(pgd_t *pgdp, pmd_t *pmdp)
  {
  	pgd_val(*pgdp) = virt_to_phys(pmdp);
  }
  
  #define __pte_page(pte) \
  ((unsigned long) __va ((pte_val (pte) & SUN3_PAGE_PGNUM_MASK) << PAGE_SHIFT))
  #define __pmd_page(pmd) \
  ((unsigned long) __va (pmd_val (pmd) & PAGE_MASK))
  
  static inline int pte_none (pte_t pte) { return !pte_val (pte); }
  static inline int pte_present (pte_t pte) { return pte_val (pte) & SUN3_PAGE_VALID; }
  static inline void pte_clear (struct mm_struct *mm, unsigned long addr, pte_t *ptep)
  {
  	pte_val (*ptep) = 0;
  }
  
  #define pte_pfn(pte)            (pte_val(pte) & SUN3_PAGE_PGNUM_MASK)
  #define pfn_pte(pfn, pgprot) \
  ({ pte_t __pte; pte_val(__pte) = pfn | pgprot_val(pgprot); __pte; })
  
  #define pte_page(pte)		virt_to_page(__pte_page(pte))
  #define pmd_page(pmd)		virt_to_page(__pmd_page(pmd))
  
  
  static inline int pmd_none2 (pmd_t *pmd) { return !pmd_val (*pmd); }
  #define pmd_none(pmd) pmd_none2(&(pmd))
  //static inline int pmd_bad (pmd_t pmd) { return (pmd_val (pmd) & SUN3_PMD_MASK) != SUN3_PMD_MAGIC; }
  static inline int pmd_bad2 (pmd_t *pmd) { return 0; }
  #define pmd_bad(pmd) pmd_bad2(&(pmd))
  static inline int pmd_present2 (pmd_t *pmd) { return pmd_val (*pmd) & SUN3_PMD_VALID; }
  /* #define pmd_present(pmd) pmd_present2(&(pmd)) */
  #define pmd_present(pmd) (!pmd_none2(&(pmd)))
  static inline void pmd_clear (pmd_t *pmdp) { pmd_val (*pmdp) = 0; }
  
  static inline int pgd_none (pgd_t pgd) { return 0; }
  static inline int pgd_bad (pgd_t pgd) { return 0; }
  static inline int pgd_present (pgd_t pgd) { return 1; }
  static inline void pgd_clear (pgd_t *pgdp) {}
  
  
  #define pte_ERROR(e) \
  	printk("%s:%d: bad pte %08lx.\n", __FILE__, __LINE__, pte_val(e))
  #define pmd_ERROR(e) \
  	printk("%s:%d: bad pmd %08lx.\n", __FILE__, __LINE__, pmd_val(e))
  #define pgd_ERROR(e) \
  	printk("%s:%d: bad pgd %08lx.\n", __FILE__, __LINE__, pgd_val(e))
  
  
  /*
   * The following only work if pte_present() is true.
   * Undefined behaviour if not...
   * [we have the full set here even if they don't change from m68k]
   */
  static inline int pte_write(pte_t pte)		{ return pte_val(pte) & SUN3_PAGE_WRITEABLE; }
  static inline int pte_dirty(pte_t pte)		{ return pte_val(pte) & SUN3_PAGE_MODIFIED; }
  static inline int pte_young(pte_t pte)		{ return pte_val(pte) & SUN3_PAGE_ACCESSED; }
  static inline int pte_file(pte_t pte)		{ return pte_val(pte) & SUN3_PAGE_ACCESSED; }
  
  static inline pte_t pte_wrprotect(pte_t pte)	{ pte_val(pte) &= ~SUN3_PAGE_WRITEABLE; return pte; }
  static inline pte_t pte_mkclean(pte_t pte)	{ pte_val(pte) &= ~SUN3_PAGE_MODIFIED; return pte; }
  static inline pte_t pte_mkold(pte_t pte)	{ pte_val(pte) &= ~SUN3_PAGE_ACCESSED; return pte; }
  static inline pte_t pte_mkwrite(pte_t pte)	{ pte_val(pte) |= SUN3_PAGE_WRITEABLE; return pte; }
  static inline pte_t pte_mkdirty(pte_t pte)	{ pte_val(pte) |= SUN3_PAGE_MODIFIED; return pte; }
  static inline pte_t pte_mkyoung(pte_t pte)	{ pte_val(pte) |= SUN3_PAGE_ACCESSED; return pte; }
  static inline pte_t pte_mknocache(pte_t pte)	{ pte_val(pte) |= SUN3_PAGE_NOCACHE; return pte; }
  // use this version when caches work...
  //static inline pte_t pte_mkcache(pte_t pte)	{ pte_val(pte) &= SUN3_PAGE_NOCACHE; return pte; }
  // until then, use:
  static inline pte_t pte_mkcache(pte_t pte)	{ return pte; }
  
  extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
  extern pgd_t kernel_pg_dir[PTRS_PER_PGD];
  
  /* Find an entry in a pagetable directory. */
  #define pgd_index(address)     ((address) >> PGDIR_SHIFT)
  
  #define pgd_offset(mm, address) \
  ((mm)->pgd + pgd_index(address))
  
  /* Find an entry in a kernel pagetable directory. */
  #define pgd_offset_k(address) pgd_offset(&init_mm, address)
  
  /* Find an entry in the second-level pagetable. */
  static inline pmd_t *pmd_offset (pgd_t *pgd, unsigned long address)
  {
  	return (pmd_t *) pgd;
  }
  
  static inline unsigned long pte_to_pgoff(pte_t pte)
  {
  	return pte.pte & SUN3_PAGE_PGNUM_MASK;
  }
  
  static inline pte_t pgoff_to_pte(unsigned off)
  {
  	pte_t pte = { off + SUN3_PAGE_ACCESSED };
  	return pte;
  }
  
  
  /* Find an entry in the third-level pagetable. */
  #define pte_index(address) ((address >> PAGE_SHIFT) & (PTRS_PER_PTE-1))
  #define pte_offset_kernel(pmd, address) ((pte_t *) __pmd_page(*pmd) + pte_index(address))
  /* FIXME: should we bother with kmap() here? */
  #define pte_offset_map(pmd, address) ((pte_t *)kmap(pmd_page(*pmd)) + pte_index(address))
  #define pte_offset_map_nested(pmd, address) pte_offset_map(pmd, address)
  #define pte_unmap(pte) kunmap(pte)
  #define pte_unmap_nested(pte) kunmap(pte)
  
  /* Macros to (de)construct the fake PTEs representing swap pages. */
  #define __swp_type(x)		((x).val & 0x7F)
  #define __swp_offset(x)		(((x).val) >> 7)
  #define __swp_entry(type,offset) ((swp_entry_t) { ((type) | ((offset) << 7)) })
  #define __pte_to_swp_entry(pte)	((swp_entry_t) { pte_val(pte) })
  #define __swp_entry_to_pte(x)	((pte_t) { (x).val })
  
  #endif	/* !__ASSEMBLY__ */
  #endif	/* !_SUN3_PGTABLE_H */
  