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/mmu_context.h>
  20 #include <asm/kernel-pgtable.h>
  21 #include <asm/page.h>
  22 #include <asm/pgalloc.h>
  23 #include <asm/pgtable.h>
  24 #include <asm/sections.h>
  25 #include <asm/tlbflush.h>
  26
  27 static pgd_t tmp_pg_dir[PTRS_PER_PGD] __initdata __aligned(PGD_SIZE);
  28
  29 static void __init kasan_early_pte_populate(pmd_t *pmd, unsigned long addr,
  30                                         unsigned long end)
  31 {
  32         pte_t *pte;
  33         unsigned long next;
  34
  35         if (pmd_none(*pmd))
  36                 pmd_populate_kernel(&init_mm, pmd, kasan_zero_pte);
  37
  38         pte = pte_offset_kimg(pmd, addr);
  39         do {
  40                 next = addr + PAGE_SIZE;
  41                 set_pte(pte, pfn_pte(virt_to_pfn(kasan_zero_page),
  42                                         PAGE_KERNEL));
  43         } while (pte++, addr = next, addr != end && pte_none(*pte));
  44 }
  45
  46 static void __init kasan_early_pmd_populate(pud_t *pud,
  47                                         unsigned long addr,
  48                                         unsigned long end)
  49 {
  50         pmd_t *pmd;
  51         unsigned long next;
  52
  53         if (pud_none(*pud))
  54                 pud_populate(&init_mm, pud, kasan_zero_pmd);
  55
  56         pmd = pmd_offset_kimg(pud, addr);
  57         do {
  58                 next = pmd_addr_end(addr, end);
  59                 kasan_early_pte_populate(pmd, addr, next);
  60         } while (pmd++, addr = next, addr != end && pmd_none(*pmd));
  61 }
  62
  63 static void __init kasan_early_pud_populate(pgd_t *pgd,
  64                                         unsigned long addr,
  65                                         unsigned long end)
  66 {
  67         pud_t *pud;
  68         unsigned long next;
  69
  70         if (pgd_none(*pgd))
  71                 pgd_populate(&init_mm, pgd, kasan_zero_pud);
  72
  73         pud = pud_offset_kimg(pgd, addr);
  74         do {
  75                 next = pud_addr_end(addr, end);
  76                 kasan_early_pmd_populate(pud, addr, next);
  77         } while (pud++, addr = next, addr != end && pud_none(*pud));
  78 }
  79
  80 static void __init kasan_map_early_shadow(void)
  81 {
  82         unsigned long addr = KASAN_SHADOW_START;
  83         unsigned long end = KASAN_SHADOW_END;
  84         unsigned long next;
  85         pgd_t *pgd;
  86
  87         pgd = pgd_offset_k(addr);
  88         do {
  89                 next = pgd_addr_end(addr, end);
  90                 kasan_early_pud_populate(pgd, addr, next);
  91         } while (pgd++, addr = next, addr != end);
  92 }
  93
  94 asmlinkage void __init kasan_early_init(void)
  95 {
  96         BUILD_BUG_ON(KASAN_SHADOW_OFFSET != KASAN_SHADOW_END - (1UL << 61));
  97         BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, PGDIR_SIZE));
  98         BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, PGDIR_SIZE));
  99         kasan_map_early_shadow();
 100 }
 101
 102 /*
 103  * Copy the current shadow region into a new pgdir.
 104  */
 105 void __init kasan_copy_shadow(pgd_t *pgdir)
 106 {
 107         pgd_t *pgd, *pgd_new, *pgd_end;
 108
 109         pgd = pgd_offset_k(KASAN_SHADOW_START);
 110         pgd_end = pgd_offset_k(KASAN_SHADOW_END);
 111         pgd_new = pgd_offset_raw(pgdir, KASAN_SHADOW_START);
 112         do {
 113                 set_pgd(pgd_new, *pgd);
 114         } while (pgd++, pgd_new++, pgd != pgd_end);
 115 }
 116
 117 static void __init clear_pgds(unsigned long start,
 118                         unsigned long end)
 119 {
 120         /*
 121          * Remove references to kasan page tables from
 122          * swapper_pg_dir. pgd_clear() can't be used
 123          * here because it's nop on 2,3-level pagetable setups
 124          */
 125         for (; start < end; start += PGDIR_SIZE)
 126                 set_pgd(pgd_offset_k(start), __pgd(0));
 127 }
 128
 129 void __init kasan_init(void)
 130 {
 131         u64 kimg_shadow_start, kimg_shadow_end;
 132         u64 mod_shadow_start, mod_shadow_end;
 133         struct memblock_region *reg;
 134         int i;
 135
 136         kimg_shadow_start = (u64)kasan_mem_to_shadow(_text);
 137         kimg_shadow_end = (u64)kasan_mem_to_shadow(_end);
 138
 139         mod_shadow_start = (u64)kasan_mem_to_shadow((void *)MODULES_VADDR);
 140         mod_shadow_end = (u64)kasan_mem_to_shadow((void *)MODULES_END);
 141
 142         /*
 143          * We are going to perform proper setup of shadow memory.
 144          * At first we should unmap early shadow (clear_pgds() call bellow).
 145          * However, instrumented code couldn't execute without shadow memory.
 146          * tmp_pg_dir used to keep early shadow mapped until full shadow
 147          * setup will be finished.
 148          */
 149         memcpy(tmp_pg_dir, swapper_pg_dir, sizeof(tmp_pg_dir));
 150         dsb(ishst);
 151         cpu_replace_ttbr1(tmp_pg_dir);
 152
 153         clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
 154
 155         vmemmap_populate(kimg_shadow_start, kimg_shadow_end,
 156                          pfn_to_nid(virt_to_pfn(_text)));
 157
 158         /*
 159          * vmemmap_populate() has populated the shadow region that covers the
 160          * kernel image with SWAPPER_BLOCK_SIZE mappings, so we have to round
 161          * the start and end addresses to SWAPPER_BLOCK_SIZE as well, to prevent
 162          * kasan_populate_zero_shadow() from replacing the page table entries
 163          * (PMD or PTE) at the edges of the shadow region for the kernel
 164          * image.
 165          */
 166         kimg_shadow_start = round_down(kimg_shadow_start, SWAPPER_BLOCK_SIZE);
 167         kimg_shadow_end = round_up(kimg_shadow_end, SWAPPER_BLOCK_SIZE);
 168
 169         kasan_populate_zero_shadow((void *)KASAN_SHADOW_START,
 170                                    (void *)mod_shadow_start);
 171         kasan_populate_zero_shadow((void *)kimg_shadow_end,
 172                                    kasan_mem_to_shadow((void *)PAGE_OFFSET));
 173
 174         if (kimg_shadow_start > mod_shadow_end)
 175                 kasan_populate_zero_shadow((void *)mod_shadow_end,
 176                                            (void *)kimg_shadow_start);
 177
 178         for_each_memblock(memory, reg) {
 179                 void *start = (void *)__phys_to_virt(reg->base);
 180                 void *end = (void *)__phys_to_virt(reg->base + reg->size);
 181
 182                 if (start >= end)
 183                         break;
 184
 185                 /*
 186                  * end + 1 here is intentional. We check several shadow bytes in
 187                  * advance to slightly speed up fastpath. In some rare cases
 188                  * we could cross boundary of mapped shadow, so we just map
 189                  * some more here.
 190                  */
 191                 vmemmap_populate((unsigned long)kasan_mem_to_shadow(start),
 192                                 (unsigned long)kasan_mem_to_shadow(end) + 1,
 193                                 pfn_to_nid(virt_to_pfn(start)));
 194         }
 195
 196         /*
 197          * KAsan may reuse the contents of kasan_zero_pte directly, so we
 198          * should make sure that it maps the zero page read-only.
 199          */
 200         for (i = 0; i < PTRS_PER_PTE; i++)
 201                 set_pte(&kasan_zero_pte[i],
 202                         pfn_pte(virt_to_pfn(kasan_zero_page), PAGE_KERNEL_RO));
 203
 204         memset(kasan_zero_page, 0, PAGE_SIZE);
 205         cpu_replace_ttbr1(swapper_pg_dir);
 206
 207         /* At this point kasan is fully initialized. Enable error messages */
 208         init_task.kasan_depth = 0;
 209         pr_info("KernelAddressSanitizer initialized\n");
 210 }