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