pgtable.h

讲述linux的初始化过程

/* page table for 0-4MB for everybody */
extern unsigned long pg0[1024];

/* number of bits that fit into a memory pointer */
#define BITS_PER_PTR                    (8*sizeof(unsigned long))

/* to align the pointer to a pointer address */
#define PTR_MASK                        (~(sizeof(void*)-1))

/* sizeof(void*)==1<<SIZEOF_PTR_LOG2 */
/* 64-bit machines, beware!  SRB. */
#define SIZEOF_PTR_LOG2                 2

/* to find an entry in a page-table */
#define PAGE_PTR(address) \
((unsigned long)(address)>>(PAGE_SHIFT-SIZEOF_PTR_LOG2)&PTR_MASK&~PAGE_MASK)



/* 
 * CR 7 (SPST) and cr 13 (HPST) are set to the user pgdir. 
 * Kernel is running in its own, disjunct address space,
 * running in primary address space.
 * Copy to/from user is done via access register mode with
 * access registers set to 0 or 1. For that purpose we need 
 * set up CR 7 with the user pgd.  
 * 
 */

#define SET_PAGE_DIR(tsk,pgdir)                                              \
do {                                                                         \
        unsigned long __pgdir = (__pa(pgdir) & PAGE_MASK ) | _SEGMENT_TABLE; \
        (tsk)->thread.user_seg = __pgdir;                                    \
        if ((tsk) == current) {                                              \
                __asm__ __volatile__("lctl  7,7,%0": :"m" (__pgdir));        \
                __asm__ __volatile__("lctl  13,13,%0": :"m" (__pgdir));      \
        }                                                                    \
} while (0)

/* 
 * CR 7 (SPST) and cr 13 (HPST) are set to the user pgdir. 
 * Kernel is running in its own, disjunct address space,
 * running in primary address space.
 * Copy to/from user is done via access register mode with
 * access registers set to 0 or 1. For that purpose we need 
 * set up CR 7 with the user pgd.  
 * 
 */

#define SET_PAGE_DIR(tsk,pgdir)                                              \
do {                                                                         \
        unsigned long __pgdir = (__pa(pgdir) & PAGE_MASK ) | _SEGMENT_TABLE; \
        (tsk)->thread.user_seg = __pgdir;                                    \
        if ((tsk) == current) {                                              \
                __asm__ __volatile__("lctl  7,7,%0": :"m" (__pgdir));        \
                __asm__ __volatile__("lctl  13,13,%0": :"m" (__pgdir));      \
        }                                                                    \
} while (0)


extern inline int pte_none(pte_t pte)           { return ((pte_val(pte) & (_PAGE_INVALID | _PAGE_RO)) == _PAGE_INVALID); } 
extern inline int pte_present(pte_t pte)        { return pte_val(pte) & _PAGE_PRESENT; }
extern inline void pte_clear(pte_t *ptep)       { pte_val(*ptep) = _PAGE_INVALID; }
#define PTE_INIT(x) pte_clear(x)

extern inline int pmd_none(pmd_t pmd)           { return pmd_val(pmd) & _PAGE_TABLE_INV; }
extern inline int pmd_bad(pmd_t pmd)            { return (pmd_val(pmd) == 0); }
extern inline int pmd_present(pmd_t pmd)        { return pmd_val(pmd) & _SEG_PRESENT; }
extern inline void pmd_clear(pmd_t * pmdp)      {
                                                        pmd_val(pmdp[0]) = _PAGE_TABLE_INV;
                                                        pmd_val(pmdp[1]) = _PAGE_TABLE_INV;
                                                        pmd_val(pmdp[2]) = _PAGE_TABLE_INV;
                                                        pmd_val(pmdp[3]) = _PAGE_TABLE_INV;
                                                }

/*
 * The "pgd_xxx()" functions here are trivial for a folded two-level
 * setup: the pgd is never bad, and a pmd always exists (as it's folded
 * into the pgd entry)
 */
extern inline int pgd_none(pgd_t pgd)           { return 0; }
extern inline int pgd_bad(pgd_t pgd)            { return 0; }
extern inline int pgd_present(pgd_t pgd)        { return 1; }
extern inline void pgd_clear(pgd_t * pgdp)      { }


/*
 * The following only work if pte_present() is true.
 * Undefined behaviour if not..
 */
extern inline int pte_write(pte_t pte)          { return !(pte_val(pte) & _PAGE_RO); }
extern inline int pte_dirty(pte_t pte)          { return pte_val(pte) & _PAGE_DIRTY; }
extern inline int pte_young(pte_t pte)          { return pte_val(pte) & _PAGE_ACCESSED; }

/* who needs that
extern inline int pte_read(pte_t pte)           { return !(pte_val(pte) & _PAGE_INVALID); }
extern inline int pte_exec(pte_t pte)           { return !(pte_val(pte) & _PAGE_INVALID); }
extern inline pte_t pte_rdprotect(pte_t pte)    { pte_val(pte) |= _PAGE_INVALID; return pte; }
extern inline pte_t pte_exprotect(pte_t pte)    { pte_val(pte) |= _PAGE_INVALID; return pte; }
extern inline pte_t pte_mkread(pte_t pte)       { pte_val(pte) &= _PAGE_INVALID; return pte; }
extern inline pte_t pte_mkexec(pte_t pte)       { pte_val(pte) &= _PAGE_INVALID; return pte; }
*/

extern inline pte_t pte_wrprotect(pte_t pte)    { pte_val(pte) |= _PAGE_RO; return pte; }
extern inline pte_t pte_mkwrite(pte_t pte)      { pte_val(pte) &= ~_PAGE_RO ; return pte; }

extern inline pte_t pte_mkclean(pte_t pte)      { pte_val(pte) &= ~_PAGE_DIRTY; return pte; }
extern inline pte_t pte_mkdirty(pte_t pte)      { pte_val(pte) |= _PAGE_DIRTY; return pte; }

extern inline pte_t pte_mkold(pte_t pte)        { pte_val(pte) &= ~_PAGE_ACCESSED; return pte; }
extern inline pte_t pte_mkyoung(pte_t pte)      { pte_val(pte) |= _PAGE_ACCESSED; return pte; }


/*
 * 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) \
({ pte_t __pte; pte_val(__pte) = __pa(((page)-mem_map)<<PAGE_SHIFT) + pgprot_val(pgprot); __pte; })

/* This takes a physical page address that is used by the remapping functions */
#define mk_pte_phys(physpage, pgprot) \
({ pte_t __pte; pte_val(__pte) = physpage + pgprot_val(pgprot); __pte; })

extern inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
{ pte_val(pte) = (pte_val(pte) & PAGE_MASK) | pgprot_val(newprot); return pte; }

#define page_address(page)  ((page)->virtual)
#define pte_page(x) (mem_map+(unsigned long)((pte_val(pte) >> PAGE_SHIFT)))

#define pmd_page(pmd) \
((unsigned long) __va(pmd_val(pmd) & PAGE_MASK))

/* to find an entry in a page-table-directory */
#define pgd_index(address) ((address >> PGDIR_SHIFT) & (PTRS_PER_PGD-1))

#define __pgd_offset(address) pgd_index(address)

#define pgd_offset(mm, address) ((mm)->pgd+pgd_index(address))

/* to find an entry in a kernel page-table-directory */
#define pgd_offset_k(address) pgd_offset(&init_mm, address)

/* Find an entry in the second-level page table.. */
extern inline pmd_t * pmd_offset(pgd_t * dir, unsigned long address)
{
        return (pmd_t *) dir;
}

/* Find an entry in the third-level page table.. */
#define pte_offset(pmd, address) \
((pte_t *) (pmd_page(*pmd) + ((address>>10) & ((PTRS_PER_PTE-1)<<2))))


/* We don't use pmd cache, so these are dummy routines */
extern __inline__ pmd_t *get_pmd_fast(void)
{
        return (pmd_t *)0;
}

extern __inline__ void free_pmd_fast(pmd_t *pmd)
{
}

extern __inline__ void free_pmd_slow(pmd_t *pmd)
{
}

extern void __handle_bad_pmd(pmd_t *pmd);
extern void __handle_bad_pmd_kernel(pmd_t *pmd);

/*
 * The S390 doesn't have any external MMU info: the kernel page
 * tables contain all the necessary information.
 */
extern inline void update_mmu_cache(struct vm_area_struct * vma,
        unsigned long address, pte_t pte)
{
}

/*
 * a page-table entry has only 19 bit for offset and 7 bit for type
 * if bits 0, 20 or 23 are set, a translation specification exceptions occures, and it's
 * hard to find out the failing address
 * therefor, we zero out this bits
 */

#define SWP_TYPE(entry) (((entry).val >> 1) & 0x3f)
#define SWP_OFFSET(entry) (((entry).val >> 12) & 0x7FFFF )
#define SWP_ENTRY(type,offset) ((swp_entry_t) { (((type) << 1) | \
                                                 ((offset) << 12) | \
                                                 _PAGE_INVALID | _PAGE_RO) \
                                                 & 0x7ffff6fe })

#define pte_to_swp_entry(pte)           ((swp_entry_t) { pte_val(pte) })
#define swp_entry_to_pte(x)             ((pte_t) { (x).val })

#include <asm-generic/pgtable.h>

#endif /* !__ASSEMBLY__ */

/* Needs to be defined here and not in linux/mm.h, as it is arch dependent */
#define PageSkip(page)          (0)
#define kern_addr_valid(addr)   (1)

#endif /* _S390_PAGE_H */