arch/x86/mm/ident_map.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Helper routines for building identity mapping page tables. This is
   4  * included by both the compressed kernel and the regular kernel.
   5  */
   6
   7 static void ident_pmd_init(struct x86_mapping_info *info, pmd_t *pmd_page,
   8                            unsigned long addr, unsigned long end)
   9 {
  10         addr &= PMD_MASK;
  11         for (; addr < end; addr += PMD_SIZE) {
  12                 pmd_t *pmd = pmd_page + pmd_index(addr);
  13
  14                 if (pmd_present(*pmd))
  15                         continue;
  16
  17                 set_pmd(pmd, __pmd((addr - info->offset) | info->page_flag));
  18         }
  19 }
  20
  21 static int ident_pud_init(struct x86_mapping_info *info, pud_t *pud_page,
  22                           unsigned long addr, unsigned long end)
  23 {
  24         unsigned long next;
  25
  26         for (; addr < end; addr = next) {
  27                 pud_t *pud = pud_page + pud_index(addr);
  28                 pmd_t *pmd;
  29
  30                 next = (addr & PUD_MASK) + PUD_SIZE;
  31                 if (next > end)
  32                         next = end;
  33
  34                 if (info->direct_gbpages) {
  35                         pud_t pudval;
  36
  37                         if (pud_present(*pud))
  38                                 continue;
  39
  40                         addr &= PUD_MASK;
  41                         pudval = __pud((addr - info->offset) | info->page_flag);
  42                         set_pud(pud, pudval);
  43                         continue;
  44                 }
  45
  46                 if (pud_present(*pud)) {
  47                         pmd = pmd_offset(pud, 0);
  48                         ident_pmd_init(info, pmd, addr, next);
  49                         continue;
  50                 }
  51                 pmd = (pmd_t *)info->alloc_pgt_page(info->context);
  52                 if (!pmd)
  53                         return -ENOMEM;
  54                 ident_pmd_init(info, pmd, addr, next);
  55                 set_pud(pud, __pud(__pa(pmd) | info->kernpg_flag));
  56         }
  57
  58         return 0;
  59 }
  60
  61 static int ident_p4d_init(struct x86_mapping_info *info, p4d_t *p4d_page,
  62                           unsigned long addr, unsigned long end)
  63 {
  64         unsigned long next;
  65
  66         for (; addr < end; addr = next) {
  67                 p4d_t *p4d = p4d_page + p4d_index(addr);
  68                 pud_t *pud;
  69
  70                 next = (addr & P4D_MASK) + P4D_SIZE;
  71                 if (next > end)
  72                         next = end;
  73
  74                 if (p4d_present(*p4d)) {
  75                         pud = pud_offset(p4d, 0);
  76                         ident_pud_init(info, pud, addr, next);
  77                         continue;
  78                 }
  79                 pud = (pud_t *)info->alloc_pgt_page(info->context);
  80                 if (!pud)
  81                         return -ENOMEM;
  82                 ident_pud_init(info, pud, addr, next);
  83                 set_p4d(p4d, __p4d(__pa(pud) | info->kernpg_flag));
  84         }
  85
  86         return 0;
  87 }
  88
  89 int kernel_ident_mapping_init(struct x86_mapping_info *info, pgd_t *pgd_page,
  90                               unsigned long pstart, unsigned long pend)
  91 {
  92         unsigned long addr = pstart + info->offset;
  93         unsigned long end = pend + info->offset;
  94         unsigned long next;
  95         int result;
  96
  97         /* Set the default pagetable flags if not supplied */
  98         if (!info->kernpg_flag)
  99                 info->kernpg_flag = _KERNPG_TABLE;
 100
 101         /* Filter out unsupported __PAGE_KERNEL_* bits: */
 102         info->kernpg_flag &= __default_kernel_pte_mask;
 103
 104         for (; addr < end; addr = next) {
 105                 pgd_t *pgd = pgd_page + pgd_index(addr);
 106                 p4d_t *p4d;
 107
 108                 next = (addr & PGDIR_MASK) + PGDIR_SIZE;
 109                 if (next > end)
 110                         next = end;
 111
 112                 if (pgd_present(*pgd)) {
 113                         p4d = p4d_offset(pgd, 0);
 114                         result = ident_p4d_init(info, p4d, addr, next);
 115                         if (result)
 116                                 return result;
 117                         continue;
 118                 }
 119
 120                 p4d = (p4d_t *)info->alloc_pgt_page(info->context);
 121                 if (!p4d)
 122                         return -ENOMEM;
 123                 result = ident_p4d_init(info, p4d, addr, next);
 124                 if (result)
 125                         return result;
 126                 if (IS_ENABLED(CONFIG_X86_5LEVEL)) {
 127                         set_pgd(pgd, __pgd(__pa(p4d) | info->kernpg_flag));
 128                 } else {
 129                         /*
 130                          * With p4d folded, pgd is equal to p4d.
 131                          * The pgd entry has to point to the pud page table in this case.
 132                          */
 133                         pud_t *pud = pud_offset(p4d, 0);
 134                         set_pgd(pgd, __pgd(__pa(pud) | info->kernpg_flag));
 135                 }
 136         }
 137
 138         return 0;
 139 }