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                 walk->action = ACTION_CONTINUE;
  46         }
  47
  48         return 0;
  49 }
  50
  51 static int ptdump_p4d_entry(p4d_t *p4d, unsigned long addr,
  52                             unsigned long next, struct mm_walk *walk)
  53 {
  54         struct ptdump_state *st = walk->private;
  55         p4d_t val = READ_ONCE(*p4d);
  56
  57 #if CONFIG_PGTABLE_LEVELS > 3 && \
  58                 (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS))
  59         if (p4d_page(val) == virt_to_page(lm_alias(kasan_early_shadow_pud)))
  60                 return note_kasan_page_table(walk, addr);
  61 #endif
  62
  63         if (st->effective_prot)
  64                 st->effective_prot(st, 1, p4d_val(val));
  65
  66         if (p4d_leaf(val)) {
  67                 st->note_page(st, addr, 1, p4d_val(val));
  68                 walk->action = ACTION_CONTINUE;
  69         }
  70
  71         return 0;
  72 }
  73
  74 static int ptdump_pud_entry(pud_t *pud, unsigned long addr,
  75                             unsigned long next, struct mm_walk *walk)
  76 {
  77         struct ptdump_state *st = walk->private;
  78         pud_t val = READ_ONCE(*pud);
  79
  80 #if CONFIG_PGTABLE_LEVELS > 2 && \
  81                 (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS))
  82         if (pud_page(val) == virt_to_page(lm_alias(kasan_early_shadow_pmd)))
  83                 return note_kasan_page_table(walk, addr);
  84 #endif
  85
  86         if (st->effective_prot)
  87                 st->effective_prot(st, 2, pud_val(val));
  88
  89         if (pud_leaf(val)) {
  90                 st->note_page(st, addr, 2, pud_val(val));
  91                 walk->action = ACTION_CONTINUE;
  92         }
  93
  94         return 0;
  95 }
  96
  97 static int ptdump_pmd_entry(pmd_t *pmd, unsigned long addr,
  98                             unsigned long next, struct mm_walk *walk)
  99 {
 100         struct ptdump_state *st = walk->private;
 101         pmd_t val = READ_ONCE(*pmd);
 102
 103 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
 104         if (pmd_page(val) == virt_to_page(lm_alias(kasan_early_shadow_pte)))
 105                 return note_kasan_page_table(walk, addr);
 106 #endif
 107
 108         if (st->effective_prot)
 109                 st->effective_prot(st, 3, pmd_val(val));
 110         if (pmd_leaf(val)) {
 111                 st->note_page(st, addr, 3, pmd_val(val));
 112                 walk->action = ACTION_CONTINUE;
 113         }
 114
 115         return 0;
 116 }
 117
 118 static int ptdump_pte_entry(pte_t *pte, unsigned long addr,
 119                             unsigned long next, struct mm_walk *walk)
 120 {
 121         struct ptdump_state *st = walk->private;
 122         pte_t val = ptep_get(pte);
 123
 124         if (st->effective_prot)
 125                 st->effective_prot(st, 4, pte_val(val));
 126
 127         st->note_page(st, addr, 4, pte_val(val));
 128
 129         return 0;
 130 }
 131
 132 static int ptdump_hole(unsigned long addr, unsigned long next,
 133                        int depth, struct mm_walk *walk)
 134 {
 135         struct ptdump_state *st = walk->private;
 136
 137         st->note_page(st, addr, depth, 0);
 138
 139         return 0;
 140 }
 141
 142 static const struct mm_walk_ops ptdump_ops = {
 143         .pgd_entry      = ptdump_pgd_entry,
 144         .p4d_entry      = ptdump_p4d_entry,
 145         .pud_entry      = ptdump_pud_entry,
 146         .pmd_entry      = ptdump_pmd_entry,
 147         .pte_entry      = ptdump_pte_entry,
 148         .pte_hole       = ptdump_hole,
 149 };
 150
 151 void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm, pgd_t *pgd)
 152 {
 153         const struct ptdump_range *range = st->range;
 154
 155         mmap_write_lock(mm);
 156         while (range->start != range->end) {
 157                 walk_page_range_novma(mm, range->start, range->end,
 158                                       &ptdump_ops, pgd, st);
 159                 range++;
 160         }
 161         mmap_write_unlock(mm);
 162
 163         /* Flush out the last page */
 164         st->note_page(st, 0, -1, 0);
 165 }