mm/ptdump.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 #include <linux/pagewalk.h>
   4 #include <linux/ptdump.h>
   5 #include <linux/kasan.h>
   6
   7 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
   8 /*
   9  * This is an optimization for KASAN=y case. Since all kasan page tables
  10  * eventually point to the kasan_early_shadow_page we could call note_page()
  11  * right away without walking through lower level page tables. This saves
  12  * us dozens of seconds (minutes for 5-level config) while checking for
  13  * W+X mapping or reading kernel_page_tables debugfs file.
  14  */
  15 static inline int note_kasan_page_table(struct mm_walk *walk,
  16                                         unsigned long addr)
  17 {
  18         struct ptdump_state *st = walk->private;
  19
  20         st->note_page(st, addr, 4, pte_val(kasan_early_shadow_pte[0]));
  21
  22         walk->action = ACTION_CONTINUE;
  23
  24         return 0;
  25 }
  26 #endif
  27
  28 static int ptdump_pgd_entry(pgd_t *pgd, unsigned long addr,
  29                             unsigned long next, struct mm_walk *walk)
  30 {
  31         struct ptdump_state *st = walk->private;
  32         pgd_t val = READ_ONCE(*pgd);
  33
  34 #if CONFIG_PGTABLE_LEVELS > 4 && \
  35                 (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS))
  36         if (pgd_page(val) == virt_to_page(lm_alias(kasan_early_shadow_p4d)))
  37                 return note_kasan_page_table(walk, addr);
  38 #endif
  39
  40         if (st->effective_prot)
  41                 st->effective_prot(st, 0, pgd_val(val));
  42
  43         if (pgd_leaf(val))
  44                 st->note_page(st, addr, 0, pgd_val(val));
  45
  46         return 0;
  47 }
  48
  49 static int ptdump_p4d_entry(p4d_t *p4d, unsigned long addr,
  50                             unsigned long next, struct mm_walk *walk)
  51 {
  52         struct ptdump_state *st = walk->private;
  53         p4d_t val = READ_ONCE(*p4d);
  54
  55 #if CONFIG_PGTABLE_LEVELS > 3 && \
  56                 (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS))
  57         if (p4d_page(val) == virt_to_page(lm_alias(kasan_early_shadow_pud)))
  58                 return note_kasan_page_table(walk, addr);
  59 #endif
  60
  61         if (st->effective_prot)
  62                 st->effective_prot(st, 1, p4d_val(val));
  63
  64         if (p4d_leaf(val))
  65                 st->note_page(st, addr, 1, p4d_val(val));
  66
  67         return 0;
  68 }
  69
  70 static int ptdump_pud_entry(pud_t *pud, unsigned long addr,
  71                             unsigned long next, struct mm_walk *walk)
  72 {
  73         struct ptdump_state *st = walk->private;
  74         pud_t val = READ_ONCE(*pud);
  75
  76 #if CONFIG_PGTABLE_LEVELS > 2 && \
  77                 (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS))
  78         if (pud_page(val) == virt_to_page(lm_alias(kasan_early_shadow_pmd)))
  79                 return note_kasan_page_table(walk, addr);
  80 #endif
  81
  82         if (st->effective_prot)
  83                 st->effective_prot(st, 2, pud_val(val));
  84
  85         if (pud_leaf(val))
  86                 st->note_page(st, addr, 2, pud_val(val));
  87
  88         return 0;
  89 }
  90
  91 static int ptdump_pmd_entry(pmd_t *pmd, unsigned long addr,
  92                             unsigned long next, struct mm_walk *walk)
  93 {
  94         struct ptdump_state *st = walk->private;
  95         pmd_t val = READ_ONCE(*pmd);
  96
  97 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
  98         if (pmd_page(val) == virt_to_page(lm_alias(kasan_early_shadow_pte)))
  99                 return note_kasan_page_table(walk, addr);
 100 #endif
 101
 102         if (st->effective_prot)
 103                 st->effective_prot(st, 3, pmd_val(val));
 104         if (pmd_leaf(val))
 105                 st->note_page(st, addr, 3, pmd_val(val));
 106
 107         return 0;
 108 }
 109
 110 static int ptdump_pte_entry(pte_t *pte, unsigned long addr,
 111                             unsigned long next, struct mm_walk *walk)
 112 {
 113         struct ptdump_state *st = walk->private;
 114         pte_t val = READ_ONCE(*pte);
 115
 116         if (st->effective_prot)
 117                 st->effective_prot(st, 4, pte_val(val));
 118
 119         st->note_page(st, addr, 4, pte_val(val));
 120
 121         return 0;
 122 }
 123
 124 static int ptdump_hole(unsigned long addr, unsigned long next,
 125                        int depth, struct mm_walk *walk)
 126 {
 127         struct ptdump_state *st = walk->private;
 128
 129         st->note_page(st, addr, depth, 0);
 130
 131         return 0;
 132 }
 133
 134 static const struct mm_walk_ops ptdump_ops = {
 135         .pgd_entry      = ptdump_pgd_entry,
 136         .p4d_entry      = ptdump_p4d_entry,
 137         .pud_entry      = ptdump_pud_entry,
 138         .pmd_entry      = ptdump_pmd_entry,
 139         .pte_entry      = ptdump_pte_entry,
 140         .pte_hole       = ptdump_hole,
 141 };
 142
 143 void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm, pgd_t *pgd)
 144 {
 145         const struct ptdump_range *range = st->range;
 146
 147         mmap_read_lock(mm);
 148         while (range->start != range->end) {
 149                 walk_page_range_novma(mm, range->start, range->end,
 150                                       &ptdump_ops, pgd, st);
 151                 range++;
 152         }
 153         mmap_read_unlock(mm);
 154
 155         /* Flush out the last page */
 156         st->note_page(st, 0, -1, 0);
 157 }