arch/x86/mm/kasan_init_64.c

   1 #define DISABLE_BRANCH_PROFILING
   2 #define pr_fmt(fmt) "kasan: " fmt
   3 #include <linux/bootmem.h>
   4 #include <linux/kasan.h>
   5 #include <linux/kdebug.h>
   6 #include <linux/mm.h>
   7 #include <linux/sched.h>
   8 #include <linux/sched/task.h>
   9 #include <linux/vmalloc.h>
  10
  11 #include <asm/e820/types.h>
  12 #include <asm/tlbflush.h>
  13 #include <asm/sections.h>
  14
  15 extern pgd_t early_level4_pgt[PTRS_PER_PGD];
  16 extern struct range pfn_mapped[E820_MAX_ENTRIES];
  17
  18 static int __init map_range(struct range *range)
  19 {
  20         unsigned long start;
  21         unsigned long end;
  22
  23         start = (unsigned long)kasan_mem_to_shadow(pfn_to_kaddr(range->start));
  24         end = (unsigned long)kasan_mem_to_shadow(pfn_to_kaddr(range->end));
  25
  26         /*
  27          * end + 1 here is intentional. We check several shadow bytes in advance
  28          * to slightly speed up fastpath. In some rare cases we could cross
  29          * boundary of mapped shadow, so we just map some more here.
  30          */
  31         return vmemmap_populate(start, end + 1, NUMA_NO_NODE);
  32 }
  33
  34 static void __init clear_pgds(unsigned long start,
  35                         unsigned long end)
  36 {
  37         for (; start < end; start += PGDIR_SIZE)
  38                 pgd_clear(pgd_offset_k(start));
  39 }
  40
  41 static void __init kasan_map_early_shadow(pgd_t *pgd)
  42 {
  43         int i;
  44         unsigned long start = KASAN_SHADOW_START;
  45         unsigned long end = KASAN_SHADOW_END;
  46
  47         for (i = pgd_index(start); start < end; i++) {
  48                 pgd[i] = __pgd(__pa_nodebug(kasan_zero_pud)
  49                                 | _KERNPG_TABLE);
  50                 start += PGDIR_SIZE;
  51         }
  52 }
  53
  54 #ifdef CONFIG_KASAN_INLINE
  55 static int kasan_die_handler(struct notifier_block *self,
  56                              unsigned long val,
  57                              void *data)
  58 {
  59         if (val == DIE_GPF) {
  60                 pr_emerg("CONFIG_KASAN_INLINE enabled\n");
  61                 pr_emerg("GPF could be caused by NULL-ptr deref or user memory access\n");
  62         }
  63         return NOTIFY_OK;
  64 }
  65
  66 static struct notifier_block kasan_die_notifier = {
  67         .notifier_call = kasan_die_handler,
  68 };
  69 #endif
  70
  71 void __init kasan_early_init(void)
  72 {
  73         int i;
  74         pteval_t pte_val = __pa_nodebug(kasan_zero_page) | __PAGE_KERNEL;
  75         pmdval_t pmd_val = __pa_nodebug(kasan_zero_pte) | _KERNPG_TABLE;
  76         pudval_t pud_val = __pa_nodebug(kasan_zero_pmd) | _KERNPG_TABLE;
  77
  78         for (i = 0; i < PTRS_PER_PTE; i++)
  79                 kasan_zero_pte[i] = __pte(pte_val);
  80
  81         for (i = 0; i < PTRS_PER_PMD; i++)
  82                 kasan_zero_pmd[i] = __pmd(pmd_val);
  83
  84         for (i = 0; i < PTRS_PER_PUD; i++)
  85                 kasan_zero_pud[i] = __pud(pud_val);
  86
  87         kasan_map_early_shadow(early_level4_pgt);
  88         kasan_map_early_shadow(init_level4_pgt);
  89 }
  90
  91 void __init kasan_init(void)
  92 {
  93         int i;
  94
  95 #ifdef CONFIG_KASAN_INLINE
  96         register_die_notifier(&kasan_die_notifier);
  97 #endif
  98
  99         memcpy(early_level4_pgt, init_level4_pgt, sizeof(early_level4_pgt));
 100         load_cr3(early_level4_pgt);
 101         __flush_tlb_all();
 102
 103         clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
 104
 105         kasan_populate_zero_shadow((void *)KASAN_SHADOW_START,
 106                         kasan_mem_to_shadow((void *)PAGE_OFFSET));
 107
 108         for (i = 0; i < E820_MAX_ENTRIES; i++) {
 109                 if (pfn_mapped[i].end == 0)
 110                         break;
 111
 112                 if (map_range(&pfn_mapped[i]))
 113                         panic("kasan: unable to allocate shadow!");
 114         }
 115         kasan_populate_zero_shadow(
 116                 kasan_mem_to_shadow((void *)PAGE_OFFSET + MAXMEM),
 117                 kasan_mem_to_shadow((void *)__START_KERNEL_map));
 118
 119         vmemmap_populate((unsigned long)kasan_mem_to_shadow(_stext),
 120                         (unsigned long)kasan_mem_to_shadow(_end),
 121                         NUMA_NO_NODE);
 122
 123         kasan_populate_zero_shadow(kasan_mem_to_shadow((void *)MODULES_END),
 124                         (void *)KASAN_SHADOW_END);
 125
 126         load_cr3(init_level4_pgt);
 127         __flush_tlb_all();
 128
 129         /*
 130          * kasan_zero_page has been used as early shadow memory, thus it may
 131          * contain some garbage. Now we can clear and write protect it, since
 132          * after the TLB flush no one should write to it.
 133          */
 134         memset(kasan_zero_page, 0, PAGE_SIZE);
 135         for (i = 0; i < PTRS_PER_PTE; i++) {
 136                 pte_t pte = __pte(__pa(kasan_zero_page) | __PAGE_KERNEL_RO);
 137                 set_pte(&kasan_zero_pte[i], pte);
 138         }
 139         /* Flush TLBs again to be sure that write protection applied. */
 140         __flush_tlb_all();
 141
 142         init_task.kasan_depth = 0;
 143         pr_info("KernelAddressSanitizer initialized\n");
 144 }