arch/x86/mm/kasan_init_64.c

   1 #define pr_fmt(fmt) "kasan: " fmt
   2 #include <linux/bootmem.h>
   3 #include <linux/kasan.h>
   4 #include <linux/kdebug.h>
   5 #include <linux/mm.h>
   6 #include <linux/sched.h>
   7 #include <linux/sched/task.h>
   8 #include <linux/vmalloc.h>
   9
  10 #include <asm/tlbflush.h>
  11 #include <asm/sections.h>
  12
  13 extern pgd_t early_level4_pgt[PTRS_PER_PGD];
  14 extern struct range pfn_mapped[E820_X_MAX];
  15
  16 static int __init map_range(struct range *range)
  17 {
  18         unsigned long start;
  19         unsigned long end;
  20
  21         start = (unsigned long)kasan_mem_to_shadow(pfn_to_kaddr(range->start));
  22         end = (unsigned long)kasan_mem_to_shadow(pfn_to_kaddr(range->end));
  23
  24         /*
  25          * end + 1 here is intentional. We check several shadow bytes in advance
  26          * to slightly speed up fastpath. In some rare cases we could cross
  27          * boundary of mapped shadow, so we just map some more here.
  28          */
  29         return vmemmap_populate(start, end + 1, NUMA_NO_NODE);
  30 }
  31
  32 static void __init clear_pgds(unsigned long start,
  33                         unsigned long end)
  34 {
  35         pgd_t *pgd;
  36
  37         for (; start < end; start += PGDIR_SIZE) {
  38                 pgd = pgd_offset_k(start);
  39                 /*
  40                  * With folded p4d, pgd_clear() is nop, use p4d_clear()
  41                  * instead.
  42                  */
  43                 if (CONFIG_PGTABLE_LEVELS < 5)
  44                         p4d_clear(p4d_offset(pgd, start));
  45                 else
  46                         pgd_clear(pgd);
  47         }
  48 }
  49
  50 static void __init kasan_map_early_shadow(pgd_t *pgd)
  51 {
  52         int i;
  53         unsigned long start = KASAN_SHADOW_START;
  54         unsigned long end = KASAN_SHADOW_END;
  55
  56         for (i = pgd_index(start); start < end; i++) {
  57                 pgd[i] = __pgd(__pa_nodebug(kasan_zero_pud)
  58                                 | _KERNPG_TABLE);
  59                 start += PGDIR_SIZE;
  60         }
  61 }
  62
  63 #ifdef CONFIG_KASAN_INLINE
  64 static int kasan_die_handler(struct notifier_block *self,
  65                              unsigned long val,
  66                              void *data)
  67 {
  68         if (val == DIE_GPF) {
  69                 pr_emerg("CONFIG_KASAN_INLINE enabled\n");
  70                 pr_emerg("GPF could be caused by NULL-ptr deref or user memory access\n");
  71         }
  72         return NOTIFY_OK;
  73 }
  74
  75 static struct notifier_block kasan_die_notifier = {
  76         .notifier_call = kasan_die_handler,
  77 };
  78 #endif
  79
  80 void __init kasan_early_init(void)
  81 {
  82         int i;
  83         pteval_t pte_val = __pa_nodebug(kasan_zero_page) | __PAGE_KERNEL;
  84         pmdval_t pmd_val = __pa_nodebug(kasan_zero_pte) | _KERNPG_TABLE;
  85         pudval_t pud_val = __pa_nodebug(kasan_zero_pmd) | _KERNPG_TABLE;
  86
  87         for (i = 0; i < PTRS_PER_PTE; i++)
  88                 kasan_zero_pte[i] = __pte(pte_val);
  89
  90         for (i = 0; i < PTRS_PER_PMD; i++)
  91                 kasan_zero_pmd[i] = __pmd(pmd_val);
  92
  93         for (i = 0; i < PTRS_PER_PUD; i++)
  94                 kasan_zero_pud[i] = __pud(pud_val);
  95
  96         kasan_map_early_shadow(early_level4_pgt);
  97         kasan_map_early_shadow(init_level4_pgt);
  98 }
  99
 100 void __init kasan_init(void)
 101 {
 102         int i;
 103
 104 #ifdef CONFIG_KASAN_INLINE
 105         register_die_notifier(&kasan_die_notifier);
 106 #endif
 107
 108         memcpy(early_level4_pgt, init_level4_pgt, sizeof(early_level4_pgt));
 109         load_cr3(early_level4_pgt);
 110         __flush_tlb_all();
 111
 112         clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
 113
 114         kasan_populate_zero_shadow((void *)KASAN_SHADOW_START,
 115                         kasan_mem_to_shadow((void *)PAGE_OFFSET));
 116
 117         for (i = 0; i < E820_X_MAX; i++) {
 118                 if (pfn_mapped[i].end == 0)
 119                         break;
 120
 121                 if (map_range(&pfn_mapped[i]))
 122                         panic("kasan: unable to allocate shadow!");
 123         }
 124         kasan_populate_zero_shadow(
 125                 kasan_mem_to_shadow((void *)PAGE_OFFSET + MAXMEM),
 126                 kasan_mem_to_shadow((void *)__START_KERNEL_map));
 127
 128         vmemmap_populate((unsigned long)kasan_mem_to_shadow(_stext),
 129                         (unsigned long)kasan_mem_to_shadow(_end),
 130                         NUMA_NO_NODE);
 131
 132         kasan_populate_zero_shadow(kasan_mem_to_shadow((void *)MODULES_END),
 133                         (void *)KASAN_SHADOW_END);
 134
 135         load_cr3(init_level4_pgt);
 136         __flush_tlb_all();
 137
 138         /*
 139          * kasan_zero_page has been used as early shadow memory, thus it may
 140          * contain some garbage. Now we can clear and write protect it, since
 141          * after the TLB flush no one should write to it.
 142          */
 143         memset(kasan_zero_page, 0, PAGE_SIZE);
 144         for (i = 0; i < PTRS_PER_PTE; i++) {
 145                 pte_t pte = __pte(__pa(kasan_zero_page) | __PAGE_KERNEL_RO);
 146                 set_pte(&kasan_zero_pte[i], pte);
 147         }
 148         /* Flush TLBs again to be sure that write protection applied. */
 149         __flush_tlb_all();
 150
 151         init_task.kasan_depth = 0;
 152         pr_info("KernelAddressSanitizer initialized\n");
 153 }