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         pgd_t *pgd;
  37
  38         for (; start < end; start += PGDIR_SIZE) {
  39                 pgd = pgd_offset_k(start);
  40                 /*
  41                  * With folded p4d, pgd_clear() is nop, use p4d_clear()
  42                  * instead.
  43                  */
  44                 if (CONFIG_PGTABLE_LEVELS < 5)
  45                         p4d_clear(p4d_offset(pgd, start));
  46                 else
  47                         pgd_clear(pgd);
  48         }
  49 }
  50
  51 static void __init kasan_map_early_shadow(pgd_t *pgd)
  52 {
  53         int i;
  54         unsigned long start = KASAN_SHADOW_START;
  55         unsigned long end = KASAN_SHADOW_END;
  56
  57         for (i = pgd_index(start); start < end; i++) {
  58                 pgd[i] = __pgd(__pa_nodebug(kasan_zero_pud)
  59                                 | _KERNPG_TABLE);
  60                 start += PGDIR_SIZE;
  61         }
  62 }
  63
  64 #ifdef CONFIG_KASAN_INLINE
  65 static int kasan_die_handler(struct notifier_block *self,
  66                              unsigned long val,
  67                              void *data)
  68 {
  69         if (val == DIE_GPF) {
  70                 pr_emerg("CONFIG_KASAN_INLINE enabled\n");
  71                 pr_emerg("GPF could be caused by NULL-ptr deref or user memory access\n");
  72         }
  73         return NOTIFY_OK;
  74 }
  75
  76 static struct notifier_block kasan_die_notifier = {
  77         .notifier_call = kasan_die_handler,
  78 };
  79 #endif
  80
  81 void __init kasan_early_init(void)
  82 {
  83         int i;
  84         pteval_t pte_val = __pa_nodebug(kasan_zero_page) | __PAGE_KERNEL;
  85         pmdval_t pmd_val = __pa_nodebug(kasan_zero_pte) | _KERNPG_TABLE;
  86         pudval_t pud_val = __pa_nodebug(kasan_zero_pmd) | _KERNPG_TABLE;
  87
  88         for (i = 0; i < PTRS_PER_PTE; i++)
  89                 kasan_zero_pte[i] = __pte(pte_val);
  90
  91         for (i = 0; i < PTRS_PER_PMD; i++)
  92                 kasan_zero_pmd[i] = __pmd(pmd_val);
  93
  94         for (i = 0; i < PTRS_PER_PUD; i++)
  95                 kasan_zero_pud[i] = __pud(pud_val);
  96
  97         kasan_map_early_shadow(early_level4_pgt);
  98         kasan_map_early_shadow(init_level4_pgt);
  99 }
 100
 101 void __init kasan_init(void)
 102 {
 103         int i;
 104
 105 #ifdef CONFIG_KASAN_INLINE
 106         register_die_notifier(&kasan_die_notifier);
 107 #endif
 108
 109         memcpy(early_level4_pgt, init_level4_pgt, sizeof(early_level4_pgt));
 110         load_cr3(early_level4_pgt);
 111         __flush_tlb_all();
 112
 113         clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
 114
 115         kasan_populate_zero_shadow((void *)KASAN_SHADOW_START,
 116                         kasan_mem_to_shadow((void *)PAGE_OFFSET));
 117
 118         for (i = 0; i < E820_X_MAX; i++) {
 119                 if (pfn_mapped[i].end == 0)
 120                         break;
 121
 122                 if (map_range(&pfn_mapped[i]))
 123                         panic("kasan: unable to allocate shadow!");
 124         }
 125         kasan_populate_zero_shadow(
 126                 kasan_mem_to_shadow((void *)PAGE_OFFSET + MAXMEM),
 127                 kasan_mem_to_shadow((void *)__START_KERNEL_map));
 128
 129         vmemmap_populate((unsigned long)kasan_mem_to_shadow(_stext),
 130                         (unsigned long)kasan_mem_to_shadow(_end),
 131                         NUMA_NO_NODE);
 132
 133         kasan_populate_zero_shadow(kasan_mem_to_shadow((void *)MODULES_END),
 134                         (void *)KASAN_SHADOW_END);
 135
 136         load_cr3(init_level4_pgt);
 137         __flush_tlb_all();
 138
 139         /*
 140          * kasan_zero_page has been used as early shadow memory, thus it may
 141          * contain some garbage. Now we can clear and write protect it, since
 142          * after the TLB flush no one should write to it.
 143          */
 144         memset(kasan_zero_page, 0, PAGE_SIZE);
 145         for (i = 0; i < PTRS_PER_PTE; i++) {
 146                 pte_t pte = __pte(__pa(kasan_zero_page) | __PAGE_KERNEL_RO);
 147                 set_pte(&kasan_zero_pte[i], pte);
 148         }
 149         /* Flush TLBs again to be sure that write protection applied. */
 150         __flush_tlb_all();
 151
 152         init_task.kasan_depth = 0;
 153         pr_info("KernelAddressSanitizer initialized\n");
 154 }