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