arch/x86/mm/ident_map.c

   1 /*
   2  * Helper routines for building identity mapping page tables. This is
   3  * included by both the compressed kernel and the regular kernel.
   4  */
   5
   6 static void ident_pmd_init(unsigned long pmd_flag, pmd_t *pmd_page,
   7                            unsigned long addr, unsigned long end)
   8 {
   9         addr &= PMD_MASK;
  10         for (; addr < end; addr += PMD_SIZE) {
  11                 pmd_t *pmd = pmd_page + pmd_index(addr);
  12
  13                 if (!pmd_present(*pmd))
  14                         set_pmd(pmd, __pmd(addr | pmd_flag));
  15         }
  16 }
  17
  18 static int ident_pud_init(struct x86_mapping_info *info, pud_t *pud_page,
  19                           unsigned long addr, unsigned long end)
  20 {
  21         unsigned long next;
  22
  23         for (; addr < end; addr = next) {
  24                 pud_t *pud = pud_page + pud_index(addr);
  25                 pmd_t *pmd;
  26
  27                 next = (addr & PUD_MASK) + PUD_SIZE;
  28                 if (next > end)
  29                         next = end;
  30
  31                 if (pud_present(*pud)) {
  32                         pmd = pmd_offset(pud, 0);
  33                         ident_pmd_init(info->pmd_flag, pmd, addr, next);
  34                         continue;
  35                 }
  36                 pmd = (pmd_t *)info->alloc_pgt_page(info->context);
  37                 if (!pmd)
  38                         return -ENOMEM;
  39                 ident_pmd_init(info->pmd_flag, pmd, addr, next);
  40                 set_pud(pud, __pud(__pa(pmd) | _KERNPG_TABLE));
  41         }
  42
  43         return 0;
  44 }
  45
  46 int kernel_ident_mapping_init(struct x86_mapping_info *info, pgd_t *pgd_page,
  47                               unsigned long addr, unsigned long end)
  48 {
  49         unsigned long next;
  50         int result;
  51         int off = info->kernel_mapping ? pgd_index(__PAGE_OFFSET) : 0;
  52
  53         for (; addr < end; addr = next) {
  54                 pgd_t *pgd = pgd_page + pgd_index(addr) + off;
  55                 pud_t *pud;
  56
  57                 next = (addr & PGDIR_MASK) + PGDIR_SIZE;
  58                 if (next > end)
  59                         next = end;
  60
  61                 if (pgd_present(*pgd)) {
  62                         pud = pud_offset(pgd, 0);
  63                         result = ident_pud_init(info, pud, addr, next);
  64                         if (result)
  65                                 return result;
  66                         continue;
  67                 }
  68
  69                 pud = (pud_t *)info->alloc_pgt_page(info->context);
  70                 if (!pud)
  71                         return -ENOMEM;
  72                 result = ident_pud_init(info, pud, addr, next);
  73                 if (result)
  74                         return result;
  75                 set_pgd(pgd, __pgd(__pa(pud) | _KERNPG_TABLE));
  76         }
  77
  78         return 0;
  79 }