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/sched/task.h>
  17 #include <linux/memblock.h>
  18 #include <linux/start_kernel.h>
  19 #include <linux/mm.h>
  20
  21 #include <asm/mmu_context.h>
  22 #include <asm/kernel-pgtable.h>
  23 #include <asm/page.h>
  24 #include <asm/pgalloc.h>
  25 #include <asm/pgtable.h>
  26 #include <asm/sections.h>
  27 #include <asm/tlbflush.h>
  28
  29 static pgd_t tmp_pg_dir[PTRS_PER_PGD] __initdata __aligned(PGD_SIZE);
  30
  31 /*
  32  * The p*d_populate functions call virt_to_phys implicitly so they can't be used
  33  * directly on kernel symbols (bm_p*d). All the early functions are called too
  34  * early to use lm_alias so __p*d_populate functions must be used to populate
  35  * with the physical address from __pa_symbol.
  36  */
  37
  38 static phys_addr_t __init kasan_alloc_zeroed_page(int node)
  39 {
  40         void *p = memblock_alloc_try_nid(PAGE_SIZE, PAGE_SIZE,
  41                                               __pa(MAX_DMA_ADDRESS),
  42                                               MEMBLOCK_ALLOC_KASAN, node);
  43         return __pa(p);
  44 }
  45
  46 static phys_addr_t __init kasan_alloc_raw_page(int node)
  47 {
  48         void *p = memblock_alloc_try_nid_raw(PAGE_SIZE, PAGE_SIZE,
  49                                                 __pa(MAX_DMA_ADDRESS),
  50                                                 MEMBLOCK_ALLOC_KASAN, node);
  51         return __pa(p);
  52 }
  53
  54 static pte_t *__init kasan_pte_offset(pmd_t *pmdp, unsigned long addr, int node,
  55                                       bool early)
  56 {
  57         if (pmd_none(READ_ONCE(*pmdp))) {
  58                 phys_addr_t pte_phys = early ?
  59                                 __pa_symbol(kasan_early_shadow_pte)
  60                                         : kasan_alloc_zeroed_page(node);
  61                 __pmd_populate(pmdp, pte_phys, PMD_TYPE_TABLE);
  62         }
  63
  64         return early ? pte_offset_kimg(pmdp, addr)
  65                      : pte_offset_kernel(pmdp, addr);
  66 }
  67
  68 static pmd_t *__init kasan_pmd_offset(pud_t *pudp, unsigned long addr, int node,
  69                                       bool early)
  70 {
  71         if (pud_none(READ_ONCE(*pudp))) {
  72                 phys_addr_t pmd_phys = early ?
  73                                 __pa_symbol(kasan_early_shadow_pmd)
  74                                         : kasan_alloc_zeroed_page(node);
  75                 __pud_populate(pudp, pmd_phys, PMD_TYPE_TABLE);
  76         }
  77
  78         return early ? pmd_offset_kimg(pudp, addr) : pmd_offset(pudp, addr);
  79 }
  80
  81 static pud_t *__init kasan_pud_offset(pgd_t *pgdp, unsigned long addr, int node,
  82                                       bool early)
  83 {
  84         if (pgd_none(READ_ONCE(*pgdp))) {
  85                 phys_addr_t pud_phys = early ?
  86                                 __pa_symbol(kasan_early_shadow_pud)
  87                                         : kasan_alloc_zeroed_page(node);
  88                 __pgd_populate(pgdp, pud_phys, PMD_TYPE_TABLE);
  89         }
  90
  91         return early ? pud_offset_kimg(pgdp, addr) : pud_offset(pgdp, addr);
  92 }
  93
  94 static void __init kasan_pte_populate(pmd_t *pmdp, unsigned long addr,
  95                                       unsigned long end, int node, bool early)
  96 {
  97         unsigned long next;
  98         pte_t *ptep = kasan_pte_offset(pmdp, addr, node, early);
  99
 100         do {
 101                 phys_addr_t page_phys = early ?
 102                                 __pa_symbol(kasan_early_shadow_page)
 103                                         : kasan_alloc_raw_page(node);
 104                 if (!early)
 105                         memset(__va(page_phys), KASAN_SHADOW_INIT, PAGE_SIZE);
 106                 next = addr + PAGE_SIZE;
 107                 set_pte(ptep, pfn_pte(__phys_to_pfn(page_phys), PAGE_KERNEL));
 108         } while (ptep++, addr = next, addr != end && pte_none(READ_ONCE(*ptep)));
 109 }
 110
 111 static void __init kasan_pmd_populate(pud_t *pudp, unsigned long addr,
 112                                       unsigned long end, int node, bool early)
 113 {
 114         unsigned long next;
 115         pmd_t *pmdp = kasan_pmd_offset(pudp, addr, node, early);
 116
 117         do {
 118                 next = pmd_addr_end(addr, end);
 119                 kasan_pte_populate(pmdp, addr, next, node, early);
 120         } while (pmdp++, addr = next, addr != end && pmd_none(READ_ONCE(*pmdp)));
 121 }
 122
 123 static void __init kasan_pud_populate(pgd_t *pgdp, unsigned long addr,
 124                                       unsigned long end, int node, bool early)
 125 {
 126         unsigned long next;
 127         pud_t *pudp = kasan_pud_offset(pgdp, addr, node, early);
 128
 129         do {
 130                 next = pud_addr_end(addr, end);
 131                 kasan_pmd_populate(pudp, addr, next, node, early);
 132         } while (pudp++, addr = next, addr != end && pud_none(READ_ONCE(*pudp)));
 133 }
 134
 135 static void __init kasan_pgd_populate(unsigned long addr, unsigned long end,
 136                                       int node, bool early)
 137 {
 138         unsigned long next;
 139         pgd_t *pgdp;
 140
 141         pgdp = pgd_offset_k(addr);
 142         do {
 143                 next = pgd_addr_end(addr, end);
 144                 kasan_pud_populate(pgdp, addr, next, node, early);
 145         } while (pgdp++, addr = next, addr != end);
 146 }
 147
 148 /* The early shadow maps everything to a single page of zeroes */
 149 asmlinkage void __init kasan_early_init(void)
 150 {
 151         BUILD_BUG_ON(KASAN_SHADOW_OFFSET !=
 152                 KASAN_SHADOW_END - (1UL << (64 - KASAN_SHADOW_SCALE_SHIFT)));
 153         BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, PGDIR_SIZE));
 154         BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, PGDIR_SIZE));
 155         kasan_pgd_populate(KASAN_SHADOW_START, KASAN_SHADOW_END, NUMA_NO_NODE,
 156                            true);
 157 }
 158
 159 /* Set up full kasan mappings, ensuring that the mapped pages are zeroed */
 160 static void __init kasan_map_populate(unsigned long start, unsigned long end,
 161                                       int node)
 162 {
 163         kasan_pgd_populate(start & PAGE_MASK, PAGE_ALIGN(end), node, false);
 164 }
 165
 166 /*
 167  * Copy the current shadow region into a new pgdir.
 168  */
 169 void __init kasan_copy_shadow(pgd_t *pgdir)
 170 {
 171         pgd_t *pgdp, *pgdp_new, *pgdp_end;
 172
 173         pgdp = pgd_offset_k(KASAN_SHADOW_START);
 174         pgdp_end = pgd_offset_k(KASAN_SHADOW_END);
 175         pgdp_new = pgd_offset_raw(pgdir, KASAN_SHADOW_START);
 176         do {
 177                 set_pgd(pgdp_new, READ_ONCE(*pgdp));
 178         } while (pgdp++, pgdp_new++, pgdp != pgdp_end);
 179 }
 180
 181 static void __init clear_pgds(unsigned long start,
 182                         unsigned long end)
 183 {
 184         /*
 185          * Remove references to kasan page tables from
 186          * swapper_pg_dir. pgd_clear() can't be used
 187          * here because it's nop on 2,3-level pagetable setups
 188          */
 189         for (; start < end; start += PGDIR_SIZE)
 190                 set_pgd(pgd_offset_k(start), __pgd(0));
 191 }
 192
 193 void __init kasan_init(void)
 194 {
 195         u64 kimg_shadow_start, kimg_shadow_end;
 196         u64 mod_shadow_start, mod_shadow_end;
 197         struct memblock_region *reg;
 198         int i;
 199
 200         kimg_shadow_start = (u64)kasan_mem_to_shadow(_text) & PAGE_MASK;
 201         kimg_shadow_end = PAGE_ALIGN((u64)kasan_mem_to_shadow(_end));
 202
 203         mod_shadow_start = (u64)kasan_mem_to_shadow((void *)MODULES_VADDR);
 204         mod_shadow_end = (u64)kasan_mem_to_shadow((void *)MODULES_END);
 205
 206         /*
 207          * We are going to perform proper setup of shadow memory.
 208          * At first we should unmap early shadow (clear_pgds() call below).
 209          * However, instrumented code couldn't execute without shadow memory.
 210          * tmp_pg_dir used to keep early shadow mapped until full shadow
 211          * setup will be finished.
 212          */
 213         memcpy(tmp_pg_dir, swapper_pg_dir, sizeof(tmp_pg_dir));
 214         dsb(ishst);
 215         cpu_replace_ttbr1(lm_alias(tmp_pg_dir));
 216
 217         clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
 218
 219         kasan_map_populate(kimg_shadow_start, kimg_shadow_end,
 220                            early_pfn_to_nid(virt_to_pfn(lm_alias(_text))));
 221
 222         kasan_populate_early_shadow((void *)KASAN_SHADOW_START,
 223                                     (void *)mod_shadow_start);
 224         kasan_populate_early_shadow((void *)kimg_shadow_end,
 225                                     kasan_mem_to_shadow((void *)PAGE_OFFSET));
 226
 227         if (kimg_shadow_start > mod_shadow_end)
 228                 kasan_populate_early_shadow((void *)mod_shadow_end,
 229                                             (void *)kimg_shadow_start);
 230
 231         for_each_memblock(memory, reg) {
 232                 void *start = (void *)__phys_to_virt(reg->base);
 233                 void *end = (void *)__phys_to_virt(reg->base + reg->size);
 234
 235                 if (start >= end)
 236                         break;
 237
 238                 kasan_map_populate((unsigned long)kasan_mem_to_shadow(start),
 239                                    (unsigned long)kasan_mem_to_shadow(end),
 240                                    early_pfn_to_nid(virt_to_pfn(start)));
 241         }
 242
 243         /*
 244          * KAsan may reuse the contents of kasan_early_shadow_pte directly,
 245          * so we should make sure that it maps the zero page read-only.
 246          */
 247         for (i = 0; i < PTRS_PER_PTE; i++)
 248                 set_pte(&kasan_early_shadow_pte[i],
 249                         pfn_pte(sym_to_pfn(kasan_early_shadow_page),
 250                                 PAGE_KERNEL_RO));
 251
 252         memset(kasan_early_shadow_page, KASAN_SHADOW_INIT, PAGE_SIZE);
 253         cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
 254
 255         /* At this point kasan is fully initialized. Enable error messages */
 256         init_task.kasan_depth = 0;
 257         pr_info("KernelAddressSanitizer initialized\n");
 258 }