arch/x86/mm/kasan_init_64.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #define DISABLE_BRANCH_PROFILING
   3 #define pr_fmt(fmt) "kasan: " fmt
   4 #include <linux/bootmem.h>
   5 #include <linux/kasan.h>
   6 #include <linux/kdebug.h>
   7 #include <linux/mm.h>
   8 #include <linux/sched.h>
   9 #include <linux/sched/task.h>
  10 #include <linux/vmalloc.h>
  11
  12 #include <asm/e820/types.h>
  13 #include <asm/tlbflush.h>
  14 #include <asm/sections.h>
  15 #include <asm/pgtable.h>
  16
  17 extern struct range pfn_mapped[E820_MAX_ENTRIES];
  18
  19 static p4d_t tmp_p4d_table[PTRS_PER_P4D] __initdata __aligned(PAGE_SIZE);
  20
  21 static int __init map_range(struct range *range)
  22 {
  23         unsigned long start;
  24         unsigned long end;
  25
  26         start = (unsigned long)kasan_mem_to_shadow(pfn_to_kaddr(range->start));
  27         end = (unsigned long)kasan_mem_to_shadow(pfn_to_kaddr(range->end));
  28
  29         return vmemmap_populate(start, end, NUMA_NO_NODE);
  30 }
  31
  32 static void __init clear_pgds(unsigned long start,
  33                         unsigned long end)
  34 {
  35         pgd_t *pgd;
  36         /* See comment in kasan_init() */
  37         unsigned long pgd_end = end & PGDIR_MASK;
  38
  39         for (; start < pgd_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         pgd = pgd_offset_k(start);
  52         for (; start < end; start += P4D_SIZE)
  53                 p4d_clear(p4d_offset(pgd, start));
  54 }
  55
  56 static inline p4d_t *early_p4d_offset(pgd_t *pgd, unsigned long addr)
  57 {
  58         unsigned long p4d;
  59
  60         if (!IS_ENABLED(CONFIG_X86_5LEVEL))
  61                 return (p4d_t *)pgd;
  62
  63         p4d = __pa_nodebug(pgd_val(*pgd)) & PTE_PFN_MASK;
  64         p4d += __START_KERNEL_map - phys_base;
  65         return (p4d_t *)p4d + p4d_index(addr);
  66 }
  67
  68 static void __init kasan_early_p4d_populate(pgd_t *pgd,
  69                 unsigned long addr,
  70                 unsigned long end)
  71 {
  72         pgd_t pgd_entry;
  73         p4d_t *p4d, p4d_entry;
  74         unsigned long next;
  75
  76         if (pgd_none(*pgd)) {
  77                 pgd_entry = __pgd(_KERNPG_TABLE | __pa_nodebug(kasan_zero_p4d));
  78                 set_pgd(pgd, pgd_entry);
  79         }
  80
  81         p4d = early_p4d_offset(pgd, addr);
  82         do {
  83                 next = p4d_addr_end(addr, end);
  84
  85                 if (!p4d_none(*p4d))
  86                         continue;
  87
  88                 p4d_entry = __p4d(_KERNPG_TABLE | __pa_nodebug(kasan_zero_pud));
  89                 set_p4d(p4d, p4d_entry);
  90         } while (p4d++, addr = next, addr != end && p4d_none(*p4d));
  91 }
  92
  93 static void __init kasan_map_early_shadow(pgd_t *pgd)
  94 {
  95         /* See comment in kasan_init() */
  96         unsigned long addr = KASAN_SHADOW_START & PGDIR_MASK;
  97         unsigned long end = KASAN_SHADOW_END;
  98         unsigned long next;
  99
 100         pgd += pgd_index(addr);
 101         do {
 102                 next = pgd_addr_end(addr, end);
 103                 kasan_early_p4d_populate(pgd, addr, next);
 104         } while (pgd++, addr = next, addr != end);
 105 }
 106
 107 #ifdef CONFIG_KASAN_INLINE
 108 static int kasan_die_handler(struct notifier_block *self,
 109                              unsigned long val,
 110                              void *data)
 111 {
 112         if (val == DIE_GPF) {
 113                 pr_emerg("CONFIG_KASAN_INLINE enabled\n");
 114                 pr_emerg("GPF could be caused by NULL-ptr deref or user memory access\n");
 115         }
 116         return NOTIFY_OK;
 117 }
 118
 119 static struct notifier_block kasan_die_notifier = {
 120         .notifier_call = kasan_die_handler,
 121 };
 122 #endif
 123
 124 void __init kasan_early_init(void)
 125 {
 126         int i;
 127         pteval_t pte_val = __pa_nodebug(kasan_zero_page) | __PAGE_KERNEL | _PAGE_ENC;
 128         pmdval_t pmd_val = __pa_nodebug(kasan_zero_pte) | _KERNPG_TABLE;
 129         pudval_t pud_val = __pa_nodebug(kasan_zero_pmd) | _KERNPG_TABLE;
 130         p4dval_t p4d_val = __pa_nodebug(kasan_zero_pud) | _KERNPG_TABLE;
 131
 132         for (i = 0; i < PTRS_PER_PTE; i++)
 133                 kasan_zero_pte[i] = __pte(pte_val);
 134
 135         for (i = 0; i < PTRS_PER_PMD; i++)
 136                 kasan_zero_pmd[i] = __pmd(pmd_val);
 137
 138         for (i = 0; i < PTRS_PER_PUD; i++)
 139                 kasan_zero_pud[i] = __pud(pud_val);
 140
 141         for (i = 0; IS_ENABLED(CONFIG_X86_5LEVEL) && i < PTRS_PER_P4D; i++)
 142                 kasan_zero_p4d[i] = __p4d(p4d_val);
 143
 144         kasan_map_early_shadow(early_top_pgt);
 145         kasan_map_early_shadow(init_top_pgt);
 146 }
 147
 148 void __init kasan_init(void)
 149 {
 150         int i;
 151
 152 #ifdef CONFIG_KASAN_INLINE
 153         register_die_notifier(&kasan_die_notifier);
 154 #endif
 155
 156         memcpy(early_top_pgt, init_top_pgt, sizeof(early_top_pgt));
 157
 158         /*
 159          * We use the same shadow offset for 4- and 5-level paging to
 160          * facilitate boot-time switching between paging modes.
 161          * As result in 5-level paging mode KASAN_SHADOW_START and
 162          * KASAN_SHADOW_END are not aligned to PGD boundary.
 163          *
 164          * KASAN_SHADOW_START doesn't share PGD with anything else.
 165          * We claim whole PGD entry to make things easier.
 166          *
 167          * KASAN_SHADOW_END lands in the last PGD entry and it collides with
 168          * bunch of things like kernel code, modules, EFI mapping, etc.
 169          * We need to take extra steps to not overwrite them.
 170          */
 171         if (IS_ENABLED(CONFIG_X86_5LEVEL)) {
 172                 void *ptr;
 173
 174                 ptr = (void *)pgd_page_vaddr(*pgd_offset_k(KASAN_SHADOW_END));
 175                 memcpy(tmp_p4d_table, (void *)ptr, sizeof(tmp_p4d_table));
 176                 set_pgd(&early_top_pgt[pgd_index(KASAN_SHADOW_END)],
 177                                 __pgd(__pa(tmp_p4d_table) | _KERNPG_TABLE));
 178         }
 179
 180         load_cr3(early_top_pgt);
 181         __flush_tlb_all();
 182
 183         clear_pgds(KASAN_SHADOW_START & PGDIR_MASK, KASAN_SHADOW_END);
 184
 185         kasan_populate_zero_shadow((void *)(KASAN_SHADOW_START & PGDIR_MASK),
 186                         kasan_mem_to_shadow((void *)PAGE_OFFSET));
 187
 188         for (i = 0; i < E820_MAX_ENTRIES; i++) {
 189                 if (pfn_mapped[i].end == 0)
 190                         break;
 191
 192                 if (map_range(&pfn_mapped[i]))
 193                         panic("kasan: unable to allocate shadow!");
 194         }
 195         kasan_populate_zero_shadow(
 196                 kasan_mem_to_shadow((void *)PAGE_OFFSET + MAXMEM),
 197                 kasan_mem_to_shadow((void *)__START_KERNEL_map));
 198
 199         vmemmap_populate((unsigned long)kasan_mem_to_shadow(_stext),
 200                         (unsigned long)kasan_mem_to_shadow(_end),
 201                         NUMA_NO_NODE);
 202
 203         kasan_populate_zero_shadow(kasan_mem_to_shadow((void *)MODULES_END),
 204                         (void *)KASAN_SHADOW_END);
 205
 206         load_cr3(init_top_pgt);
 207         __flush_tlb_all();
 208
 209         /*
 210          * kasan_zero_page has been used as early shadow memory, thus it may
 211          * contain some garbage. Now we can clear and write protect it, since
 212          * after the TLB flush no one should write to it.
 213          */
 214         memset(kasan_zero_page, 0, PAGE_SIZE);
 215         for (i = 0; i < PTRS_PER_PTE; i++) {
 216                 pte_t pte = __pte(__pa(kasan_zero_page) | __PAGE_KERNEL_RO | _PAGE_ENC);
 217                 set_pte(&kasan_zero_pte[i], pte);
 218         }
 219         /* Flush TLBs again to be sure that write protection applied. */
 220         __flush_tlb_all();
 221
 222         init_task.kasan_depth = 0;
 223         pr_info("KernelAddressSanitizer initialized\n");
 224 }