arch/arm64/mm/kasan_init.c

   1 /*
   2  * This file contains kasan initialization code for ARM64.
   3  *
   4  * Copyright (c) 2015 Samsung Electronics Co., Ltd.
   5  * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  */
  12
  13 #define pr_fmt(fmt) "kasan: " fmt
  14 #include <linux/kasan.h>
  15 #include <linux/kernel.h>
  16 #include <linux/memblock.h>
  17 #include <linux/start_kernel.h>
  18
  19 #include <asm/page.h>
  20 #include <asm/pgalloc.h>
  21 #include <asm/pgtable.h>
  22 #include <asm/tlbflush.h>
  23
  24 static pgd_t tmp_pg_dir[PTRS_PER_PGD] __initdata __aligned(PGD_SIZE);
  25
  26 static void __init kasan_early_pte_populate(pmd_t *pmd, unsigned long addr,
  27                                         unsigned long end)
  28 {
  29         pte_t *pte;
  30         unsigned long next;
  31
  32         if (pmd_none(*pmd))
  33                 pmd_populate_kernel(&init_mm, pmd, kasan_zero_pte);
  34
  35         pte = pte_offset_kernel(pmd, addr);
  36         do {
  37                 next = addr + PAGE_SIZE;
  38                 set_pte(pte, pfn_pte(virt_to_pfn(kasan_zero_page),
  39                                         PAGE_KERNEL));
  40         } while (pte++, addr = next, addr != end && pte_none(*pte));
  41 }
  42
  43 static void __init kasan_early_pmd_populate(pud_t *pud,
  44                                         unsigned long addr,
  45                                         unsigned long end)
  46 {
  47         pmd_t *pmd;
  48         unsigned long next;
  49
  50         if (pud_none(*pud))
  51                 pud_populate(&init_mm, pud, kasan_zero_pmd);
  52
  53         pmd = pmd_offset(pud, addr);
  54         do {
  55                 next = pmd_addr_end(addr, end);
  56                 kasan_early_pte_populate(pmd, addr, next);
  57         } while (pmd++, addr = next, addr != end && pmd_none(*pmd));
  58 }
  59
  60 static void __init kasan_early_pud_populate(pgd_t *pgd,
  61                                         unsigned long addr,
  62                                         unsigned long end)
  63 {
  64         pud_t *pud;
  65         unsigned long next;
  66
  67         if (pgd_none(*pgd))
  68                 pgd_populate(&init_mm, pgd, kasan_zero_pud);
  69
  70         pud = pud_offset(pgd, addr);
  71         do {
  72                 next = pud_addr_end(addr, end);
  73                 kasan_early_pmd_populate(pud, addr, next);
  74         } while (pud++, addr = next, addr != end && pud_none(*pud));
  75 }
  76
  77 static void __init kasan_map_early_shadow(void)
  78 {
  79         unsigned long addr = KASAN_SHADOW_START;
  80         unsigned long end = KASAN_SHADOW_END;
  81         unsigned long next;
  82         pgd_t *pgd;
  83
  84         pgd = pgd_offset_k(addr);
  85         do {
  86                 next = pgd_addr_end(addr, end);
  87                 kasan_early_pud_populate(pgd, addr, next);
  88         } while (pgd++, addr = next, addr != end);
  89 }
  90
  91 asmlinkage void __init kasan_early_init(void)
  92 {
  93         BUILD_BUG_ON(KASAN_SHADOW_OFFSET != KASAN_SHADOW_END - (1UL << 61));
  94         BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, PGDIR_SIZE));
  95         BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, PGDIR_SIZE));
  96         kasan_map_early_shadow();
  97 }
  98
  99 static void __init clear_pgds(unsigned long start,
 100                         unsigned long end)
 101 {
 102         /*
 103          * Remove references to kasan page tables from
 104          * swapper_pg_dir. pgd_clear() can't be used
 105          * here because it's nop on 2,3-level pagetable setups
 106          */
 107         for (; start < end; start += PGDIR_SIZE)
 108                 set_pgd(pgd_offset_k(start), __pgd(0));
 109 }
 110
 111 static void __init cpu_set_ttbr1(unsigned long ttbr1)
 112 {
 113         asm(
 114         "       msr     ttbr1_el1, %0\n"
 115         "       isb"
 116         :
 117         : "r" (ttbr1));
 118 }
 119
 120 void __init kasan_init(void)
 121 {
 122         struct memblock_region *reg;
 123         int i;
 124
 125         /*
 126          * We are going to perform proper setup of shadow memory.
 127          * At first we should unmap early shadow (clear_pgds() call bellow).
 128          * However, instrumented code couldn't execute without shadow memory.
 129          * tmp_pg_dir used to keep early shadow mapped until full shadow
 130          * setup will be finished.
 131          */
 132         memcpy(tmp_pg_dir, swapper_pg_dir, sizeof(tmp_pg_dir));
 133         cpu_set_ttbr1(__pa(tmp_pg_dir));
 134         flush_tlb_all();
 135
 136         clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
 137
 138         kasan_populate_zero_shadow((void *)KASAN_SHADOW_START,
 139                         kasan_mem_to_shadow((void *)MODULES_VADDR));
 140
 141         for_each_memblock(memory, reg) {
 142                 void *start = (void *)__phys_to_virt(reg->base);
 143                 void *end = (void *)__phys_to_virt(reg->base + reg->size);
 144
 145                 if (start >= end)
 146                         break;
 147
 148                 /*
 149                  * end + 1 here is intentional. We check several shadow bytes in
 150                  * advance to slightly speed up fastpath. In some rare cases
 151                  * we could cross boundary of mapped shadow, so we just map
 152                  * some more here.
 153                  */
 154                 vmemmap_populate((unsigned long)kasan_mem_to_shadow(start),
 155                                 (unsigned long)kasan_mem_to_shadow(end) + 1,
 156                                 pfn_to_nid(virt_to_pfn(start)));
 157         }
 158
 159         /*
 160          * KAsan may reuse the contents of kasan_zero_pte directly, so we
 161          * should make sure that it maps the zero page read-only.
 162          */
 163         for (i = 0; i < PTRS_PER_PTE; i++)
 164                 set_pte(&kasan_zero_pte[i],
 165                         pfn_pte(virt_to_pfn(kasan_zero_page), PAGE_KERNEL_RO));
 166
 167         memset(kasan_zero_page, 0, PAGE_SIZE);
 168         cpu_set_ttbr1(__pa(swapper_pg_dir));
 169         flush_tlb_all();
 170
 171         /* At this point kasan is fully initialized. Enable error messages */
 172         init_task.kasan_depth = 0;
 173         pr_info("KernelAddressSanitizer initialized\n");
 174 }