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