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_top_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         pgd_t *pgd;
  38
  39         for (; start < end; start += PGDIR_SIZE) {
  40                 pgd = pgd_offset_k(start);
  41                 /*
  42                  * With folded p4d, pgd_clear() is nop, use p4d_clear()
  43                  * instead.
  44                  */
  45                 if (CONFIG_PGTABLE_LEVELS < 5)
  46                         p4d_clear(p4d_offset(pgd, start));
  47                 else
  48                         pgd_clear(pgd);
  49         }
  50 }
  51
  52 static void __init kasan_map_early_shadow(pgd_t *pgd)
  53 {
  54         int i;
  55         unsigned long start = KASAN_SHADOW_START;
  56         unsigned long end = KASAN_SHADOW_END;
  57
  58         for (i = pgd_index(start); start < end; i++) {
  59                 switch (CONFIG_PGTABLE_LEVELS) {
  60                 case 4:
  61                         pgd[i] = __pgd(__pa_nodebug(kasan_zero_pud) |
  62                                         _KERNPG_TABLE);
  63                         break;
  64                 case 5:
  65                         pgd[i] = __pgd(__pa_nodebug(kasan_zero_p4d) |
  66                                         _KERNPG_TABLE);
  67                         break;
  68                 default:
  69                         BUILD_BUG();
  70                 }
  71                 start += PGDIR_SIZE;
  72         }
  73 }
  74
  75 #ifdef CONFIG_KASAN_INLINE
  76 static int kasan_die_handler(struct notifier_block *self,
  77                              unsigned long val,
  78                              void *data)
  79 {
  80         if (val == DIE_GPF) {
  81                 pr_emerg("CONFIG_KASAN_INLINE enabled\n");
  82                 pr_emerg("GPF could be caused by NULL-ptr deref or user memory access\n");
  83         }
  84         return NOTIFY_OK;
  85 }
  86
  87 static struct notifier_block kasan_die_notifier = {
  88         .notifier_call = kasan_die_handler,
  89 };
  90 #endif
  91
  92 void __init kasan_early_init(void)
  93 {
  94         int i;
  95         pteval_t pte_val = __pa_nodebug(kasan_zero_page) | __PAGE_KERNEL;
  96         pmdval_t pmd_val = __pa_nodebug(kasan_zero_pte) | _KERNPG_TABLE;
  97         pudval_t pud_val = __pa_nodebug(kasan_zero_pmd) | _KERNPG_TABLE;
  98         p4dval_t p4d_val = __pa_nodebug(kasan_zero_pud) | _KERNPG_TABLE;
  99
 100         for (i = 0; i < PTRS_PER_PTE; i++)
 101                 kasan_zero_pte[i] = __pte(pte_val);
 102
 103         for (i = 0; i < PTRS_PER_PMD; i++)
 104                 kasan_zero_pmd[i] = __pmd(pmd_val);
 105
 106         for (i = 0; i < PTRS_PER_PUD; i++)
 107                 kasan_zero_pud[i] = __pud(pud_val);
 108
 109         for (i = 0; CONFIG_PGTABLE_LEVELS >= 5 && i < PTRS_PER_P4D; i++)
 110                 kasan_zero_p4d[i] = __p4d(p4d_val);
 111
 112         kasan_map_early_shadow(early_top_pgt);
 113         kasan_map_early_shadow(init_top_pgt);
 114 }
 115
 116 void __init kasan_init(void)
 117 {
 118         int i;
 119
 120 #ifdef CONFIG_KASAN_INLINE
 121         register_die_notifier(&kasan_die_notifier);
 122 #endif
 123
 124         memcpy(early_top_pgt, init_top_pgt, sizeof(early_top_pgt));
 125         load_cr3(early_top_pgt);
 126         __flush_tlb_all();
 127
 128         clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
 129
 130         kasan_populate_zero_shadow((void *)KASAN_SHADOW_START,
 131                         kasan_mem_to_shadow((void *)PAGE_OFFSET));
 132
 133         for (i = 0; i < E820_MAX_ENTRIES; i++) {
 134                 if (pfn_mapped[i].end == 0)
 135                         break;
 136
 137                 if (map_range(&pfn_mapped[i]))
 138                         panic("kasan: unable to allocate shadow!");
 139         }
 140         kasan_populate_zero_shadow(
 141                 kasan_mem_to_shadow((void *)PAGE_OFFSET + MAXMEM),
 142                 kasan_mem_to_shadow((void *)__START_KERNEL_map));
 143
 144         vmemmap_populate((unsigned long)kasan_mem_to_shadow(_stext),
 145                         (unsigned long)kasan_mem_to_shadow(_end),
 146                         NUMA_NO_NODE);
 147
 148         kasan_populate_zero_shadow(kasan_mem_to_shadow((void *)MODULES_END),
 149                         (void *)KASAN_SHADOW_END);
 150
 151         load_cr3(init_top_pgt);
 152         __flush_tlb_all();
 153
 154         /*
 155          * kasan_zero_page has been used as early shadow memory, thus it may
 156          * contain some garbage. Now we can clear and write protect it, since
 157          * after the TLB flush no one should write to it.
 158          */
 159         memset(kasan_zero_page, 0, PAGE_SIZE);
 160         for (i = 0; i < PTRS_PER_PTE; i++) {
 161                 pte_t pte = __pte(__pa(kasan_zero_page) | __PAGE_KERNEL_RO);
 162                 set_pte(&kasan_zero_pte[i], pte);
 163         }
 164         /* Flush TLBs again to be sure that write protection applied. */
 165         __flush_tlb_all();
 166
 167         init_task.kasan_depth = 0;
 168         pr_info("KernelAddressSanitizer initialized\n");
 169 }