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         return vmemmap_populate(start, end, NUMA_NO_NODE);
  27 }
  28
  29 static void __init clear_pgds(unsigned long start,
  30                         unsigned long end)
  31 {
  32         pgd_t *pgd;
  33
  34         for (; start < end; start += PGDIR_SIZE) {
  35                 pgd = pgd_offset_k(start);
  36                 /*
  37                  * With folded p4d, pgd_clear() is nop, use p4d_clear()
  38                  * instead.
  39                  */
  40                 if (CONFIG_PGTABLE_LEVELS < 5)
  41                         p4d_clear(p4d_offset(pgd, start));
  42                 else
  43                         pgd_clear(pgd);
  44         }
  45 }
  46
  47 static void __init kasan_map_early_shadow(pgd_t *pgd)
  48 {
  49         int i;
  50         unsigned long start = KASAN_SHADOW_START;
  51         unsigned long end = KASAN_SHADOW_END;
  52
  53         for (i = pgd_index(start); start < end; i++) {
  54                 switch (CONFIG_PGTABLE_LEVELS) {
  55                 case 4:
  56                         pgd[i] = __pgd(__pa_nodebug(kasan_zero_pud) |
  57                                         _KERNPG_TABLE);
  58                         break;
  59                 case 5:
  60                         pgd[i] = __pgd(__pa_nodebug(kasan_zero_p4d) |
  61                                         _KERNPG_TABLE);
  62                         break;
  63                 default:
  64                         BUILD_BUG();
  65                 }
  66                 start += PGDIR_SIZE;
  67         }
  68 }
  69
  70 #ifdef CONFIG_KASAN_INLINE
  71 static int kasan_die_handler(struct notifier_block *self,
  72                              unsigned long val,
  73                              void *data)
  74 {
  75         if (val == DIE_GPF) {
  76                 pr_emerg("CONFIG_KASAN_INLINE enabled\n");
  77                 pr_emerg("GPF could be caused by NULL-ptr deref or user memory access\n");
  78         }
  79         return NOTIFY_OK;
  80 }
  81
  82 static struct notifier_block kasan_die_notifier = {
  83         .notifier_call = kasan_die_handler,
  84 };
  85 #endif
  86
  87 void __init kasan_early_init(void)
  88 {
  89         int i;
  90         pteval_t pte_val = __pa_nodebug(kasan_zero_page) | __PAGE_KERNEL;
  91         pmdval_t pmd_val = __pa_nodebug(kasan_zero_pte) | _KERNPG_TABLE;
  92         pudval_t pud_val = __pa_nodebug(kasan_zero_pmd) | _KERNPG_TABLE;
  93         p4dval_t p4d_val = __pa_nodebug(kasan_zero_pud) | _KERNPG_TABLE;
  94
  95         for (i = 0; i < PTRS_PER_PTE; i++)
  96                 kasan_zero_pte[i] = __pte(pte_val);
  97
  98         for (i = 0; i < PTRS_PER_PMD; i++)
  99                 kasan_zero_pmd[i] = __pmd(pmd_val);
 100
 101         for (i = 0; i < PTRS_PER_PUD; i++)
 102                 kasan_zero_pud[i] = __pud(pud_val);
 103
 104         for (i = 0; CONFIG_PGTABLE_LEVELS >= 5 && i < PTRS_PER_P4D; i++)
 105                 kasan_zero_p4d[i] = __p4d(p4d_val);
 106
 107         kasan_map_early_shadow(early_top_pgt);
 108         kasan_map_early_shadow(init_top_pgt);
 109 }
 110
 111 void __init kasan_init(void)
 112 {
 113         int i;
 114
 115 #ifdef CONFIG_KASAN_INLINE
 116         register_die_notifier(&kasan_die_notifier);
 117 #endif
 118
 119         memcpy(early_top_pgt, init_top_pgt, sizeof(early_top_pgt));
 120         load_cr3(early_top_pgt);
 121         __flush_tlb_all();
 122
 123         clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
 124
 125         kasan_populate_zero_shadow((void *)KASAN_SHADOW_START,
 126                         kasan_mem_to_shadow((void *)PAGE_OFFSET));
 127
 128         for (i = 0; i < E820_MAX_ENTRIES; i++) {
 129                 if (pfn_mapped[i].end == 0)
 130                         break;
 131
 132                 if (map_range(&pfn_mapped[i]))
 133                         panic("kasan: unable to allocate shadow!");
 134         }
 135         kasan_populate_zero_shadow(
 136                 kasan_mem_to_shadow((void *)PAGE_OFFSET + MAXMEM),
 137                 kasan_mem_to_shadow((void *)__START_KERNEL_map));
 138
 139         vmemmap_populate((unsigned long)kasan_mem_to_shadow(_stext),
 140                         (unsigned long)kasan_mem_to_shadow(_end),
 141                         NUMA_NO_NODE);
 142
 143         kasan_populate_zero_shadow(kasan_mem_to_shadow((void *)MODULES_END),
 144                         (void *)KASAN_SHADOW_END);
 145
 146         load_cr3(init_top_pgt);
 147         __flush_tlb_all();
 148
 149         /*
 150          * kasan_zero_page has been used as early shadow memory, thus it may
 151          * contain some garbage. Now we can clear and write protect it, since
 152          * after the TLB flush no one should write to it.
 153          */
 154         memset(kasan_zero_page, 0, PAGE_SIZE);
 155         for (i = 0; i < PTRS_PER_PTE; i++) {
 156                 pte_t pte = __pte(__pa(kasan_zero_page) | __PAGE_KERNEL_RO);
 157                 set_pte(&kasan_zero_pte[i], pte);
 158         }
 159         /* Flush TLBs again to be sure that write protection applied. */
 160         __flush_tlb_all();
 161
 162         init_task.kasan_depth = 0;
 163         pr_info("KernelAddressSanitizer initialized\n");
 164 }