arch/x86/mm/kasan_init_64.c

   1 #include <linux/bootmem.h>
   2 #include <linux/kasan.h>
   3 #include <linux/kdebug.h>
   4 #include <linux/mm.h>
   5 #include <linux/sched.h>
   6 #include <linux/vmalloc.h>
   7
   8 #include <asm/tlbflush.h>
   9 #include <asm/sections.h>
  10
  11 extern pgd_t early_level4_pgt[PTRS_PER_PGD];
  12 extern struct range pfn_mapped[E820_X_MAX];
  13
  14 static pud_t kasan_zero_pud[PTRS_PER_PUD] __page_aligned_bss;
  15 static pmd_t kasan_zero_pmd[PTRS_PER_PMD] __page_aligned_bss;
  16 static pte_t kasan_zero_pte[PTRS_PER_PTE] __page_aligned_bss;
  17
  18 /*
  19  * This page used as early shadow. We don't use empty_zero_page
  20  * at early stages, stack instrumentation could write some garbage
  21  * to this page.
  22  * Latter we reuse it as zero shadow for large ranges of memory
  23  * that allowed to access, but not instrumented by kasan
  24  * (vmalloc/vmemmap ...).
  25  */
  26 static unsigned char kasan_zero_page[PAGE_SIZE] __page_aligned_bss;
  27
  28 static int __init map_range(struct range *range)
  29 {
  30         unsigned long start;
  31         unsigned long end;
  32
  33         start = (unsigned long)kasan_mem_to_shadow(pfn_to_kaddr(range->start));
  34         end = (unsigned long)kasan_mem_to_shadow(pfn_to_kaddr(range->end));
  35
  36         /*
  37          * end + 1 here is intentional. We check several shadow bytes in advance
  38          * to slightly speed up fastpath. In some rare cases we could cross
  39          * boundary of mapped shadow, so we just map some more here.
  40          */
  41         return vmemmap_populate(start, end + 1, NUMA_NO_NODE);
  42 }
  43
  44 static void __init clear_pgds(unsigned long start,
  45                         unsigned long end)
  46 {
  47         for (; start < end; start += PGDIR_SIZE)
  48                 pgd_clear(pgd_offset_k(start));
  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 static int __init zero_pte_populate(pmd_t *pmd, unsigned long addr,
  65                                 unsigned long end)
  66 {
  67         pte_t *pte = pte_offset_kernel(pmd, addr);
  68
  69         while (addr + PAGE_SIZE <= end) {
  70                 WARN_ON(!pte_none(*pte));
  71                 set_pte(pte, __pte(__pa_nodebug(kasan_zero_page)
  72                                         | __PAGE_KERNEL_RO));
  73                 addr += PAGE_SIZE;
  74                 pte = pte_offset_kernel(pmd, addr);
  75         }
  76         return 0;
  77 }
  78
  79 static int __init zero_pmd_populate(pud_t *pud, unsigned long addr,
  80                                 unsigned long end)
  81 {
  82         int ret = 0;
  83         pmd_t *pmd = pmd_offset(pud, addr);
  84
  85         while (IS_ALIGNED(addr, PMD_SIZE) && addr + PMD_SIZE <= end) {
  86                 WARN_ON(!pmd_none(*pmd));
  87                 set_pmd(pmd, __pmd(__pa_nodebug(kasan_zero_pte)
  88                                         | __PAGE_KERNEL_RO));
  89                 addr += PMD_SIZE;
  90                 pmd = pmd_offset(pud, addr);
  91         }
  92         if (addr < end) {
  93                 if (pmd_none(*pmd)) {
  94                         void *p = vmemmap_alloc_block(PAGE_SIZE, NUMA_NO_NODE);
  95                         if (!p)
  96                                 return -ENOMEM;
  97                         set_pmd(pmd, __pmd(__pa_nodebug(p) | _KERNPG_TABLE));
  98                 }
  99                 ret = zero_pte_populate(pmd, addr, end);
 100         }
 101         return ret;
 102 }
 103
 104
 105 static int __init zero_pud_populate(pgd_t *pgd, unsigned long addr,
 106                                 unsigned long end)
 107 {
 108         int ret = 0;
 109         pud_t *pud = pud_offset(pgd, addr);
 110
 111         while (IS_ALIGNED(addr, PUD_SIZE) && addr + PUD_SIZE <= end) {
 112                 WARN_ON(!pud_none(*pud));
 113                 set_pud(pud, __pud(__pa_nodebug(kasan_zero_pmd)
 114                                         | __PAGE_KERNEL_RO));
 115                 addr += PUD_SIZE;
 116                 pud = pud_offset(pgd, addr);
 117         }
 118
 119         if (addr < end) {
 120                 if (pud_none(*pud)) {
 121                         void *p = vmemmap_alloc_block(PAGE_SIZE, NUMA_NO_NODE);
 122                         if (!p)
 123                                 return -ENOMEM;
 124                         set_pud(pud, __pud(__pa_nodebug(p) | _KERNPG_TABLE));
 125                 }
 126                 ret = zero_pmd_populate(pud, addr, end);
 127         }
 128         return ret;
 129 }
 130
 131 static int __init zero_pgd_populate(unsigned long addr, unsigned long end)
 132 {
 133         int ret = 0;
 134         pgd_t *pgd = pgd_offset_k(addr);
 135
 136         while (IS_ALIGNED(addr, PGDIR_SIZE) && addr + PGDIR_SIZE <= end) {
 137                 WARN_ON(!pgd_none(*pgd));
 138                 set_pgd(pgd, __pgd(__pa_nodebug(kasan_zero_pud)
 139                                         | __PAGE_KERNEL_RO));
 140                 addr += PGDIR_SIZE;
 141                 pgd = pgd_offset_k(addr);
 142         }
 143
 144         if (addr < end) {
 145                 if (pgd_none(*pgd)) {
 146                         void *p = vmemmap_alloc_block(PAGE_SIZE, NUMA_NO_NODE);
 147                         if (!p)
 148                                 return -ENOMEM;
 149                         set_pgd(pgd, __pgd(__pa_nodebug(p) | _KERNPG_TABLE));
 150                 }
 151                 ret = zero_pud_populate(pgd, addr, end);
 152         }
 153         return ret;
 154 }
 155
 156
 157 static void __init populate_zero_shadow(const void *start, const void *end)
 158 {
 159         if (zero_pgd_populate((unsigned long)start, (unsigned long)end))
 160                 panic("kasan: unable to map zero shadow!");
 161 }
 162
 163
 164 #ifdef CONFIG_KASAN_INLINE
 165 static int kasan_die_handler(struct notifier_block *self,
 166                              unsigned long val,
 167                              void *data)
 168 {
 169         if (val == DIE_GPF) {
 170                 pr_emerg("CONFIG_KASAN_INLINE enabled");
 171                 pr_emerg("GPF could be caused by NULL-ptr deref or user memory access");
 172         }
 173         return NOTIFY_OK;
 174 }
 175
 176 static struct notifier_block kasan_die_notifier = {
 177         .notifier_call = kasan_die_handler,
 178 };
 179 #endif
 180
 181 void __init kasan_early_init(void)
 182 {
 183         int i;
 184         pteval_t pte_val = __pa_nodebug(kasan_zero_page) | __PAGE_KERNEL;
 185         pmdval_t pmd_val = __pa_nodebug(kasan_zero_pte) | _KERNPG_TABLE;
 186         pudval_t pud_val = __pa_nodebug(kasan_zero_pmd) | _KERNPG_TABLE;
 187
 188         for (i = 0; i < PTRS_PER_PTE; i++)
 189                 kasan_zero_pte[i] = __pte(pte_val);
 190
 191         for (i = 0; i < PTRS_PER_PMD; i++)
 192                 kasan_zero_pmd[i] = __pmd(pmd_val);
 193
 194         for (i = 0; i < PTRS_PER_PUD; i++)
 195                 kasan_zero_pud[i] = __pud(pud_val);
 196
 197         kasan_map_early_shadow(early_level4_pgt);
 198         kasan_map_early_shadow(init_level4_pgt);
 199 }
 200
 201 void __init kasan_init(void)
 202 {
 203         int i;
 204
 205 #ifdef CONFIG_KASAN_INLINE
 206         register_die_notifier(&kasan_die_notifier);
 207 #endif
 208
 209         memcpy(early_level4_pgt, init_level4_pgt, sizeof(early_level4_pgt));
 210         load_cr3(early_level4_pgt);
 211         __flush_tlb_all();
 212
 213         clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
 214
 215         populate_zero_shadow((void *)KASAN_SHADOW_START,
 216                         kasan_mem_to_shadow((void *)PAGE_OFFSET));
 217
 218         for (i = 0; i < E820_X_MAX; i++) {
 219                 if (pfn_mapped[i].end == 0)
 220                         break;
 221
 222                 if (map_range(&pfn_mapped[i]))
 223                         panic("kasan: unable to allocate shadow!");
 224         }
 225         populate_zero_shadow(kasan_mem_to_shadow((void *)PAGE_OFFSET + MAXMEM),
 226                         kasan_mem_to_shadow((void *)__START_KERNEL_map));
 227
 228         vmemmap_populate((unsigned long)kasan_mem_to_shadow(_stext),
 229                         (unsigned long)kasan_mem_to_shadow(_end),
 230                         NUMA_NO_NODE);
 231
 232         populate_zero_shadow(kasan_mem_to_shadow((void *)MODULES_END),
 233                         (void *)KASAN_SHADOW_END);
 234
 235         memset(kasan_zero_page, 0, PAGE_SIZE);
 236
 237         load_cr3(init_level4_pgt);
 238         __flush_tlb_all();
 239         init_task.kasan_depth = 0;
 240 }