arch/arm64/mm/kasan_init.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * This file contains kasan initialization code for ARM64.
   4  *
   5  * Copyright (c) 2015 Samsung Electronics Co., Ltd.
   6  * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
   7  */
   8
   9 #define pr_fmt(fmt) "kasan: " fmt
  10 #include <linux/kasan.h>
  11 #include <linux/kernel.h>
  12 #include <linux/sched/task.h>
  13 #include <linux/memblock.h>
  14 #include <linux/start_kernel.h>
  15 #include <linux/mm.h>
  16
  17 #include <asm/mmu_context.h>
  18 #include <asm/kernel-pgtable.h>
  19 #include <asm/page.h>
  20 #include <asm/pgalloc.h>
  21 #include <asm/sections.h>
  22 #include <asm/tlbflush.h>
  23
  24 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
  25
  26 static pgd_t tmp_pg_dir[PTRS_PER_PTE] __initdata __aligned(PAGE_SIZE);
  27
  28 /*
  29  * The p*d_populate functions call virt_to_phys implicitly so they can't be used
  30  * directly on kernel symbols (bm_p*d). All the early functions are called too
  31  * early to use lm_alias so __p*d_populate functions must be used to populate
  32  * with the physical address from __pa_symbol.
  33  */
  34
  35 static phys_addr_t __init kasan_alloc_zeroed_page(int node)
  36 {
  37         void *p = memblock_alloc_try_nid(PAGE_SIZE, PAGE_SIZE,
  38                                               __pa(MAX_DMA_ADDRESS),
  39                                               MEMBLOCK_ALLOC_NOLEAKTRACE, node);
  40         if (!p)
  41                 panic("%s: Failed to allocate %lu bytes align=0x%lx nid=%d from=%llx\n",
  42                       __func__, PAGE_SIZE, PAGE_SIZE, node,
  43                       __pa(MAX_DMA_ADDRESS));
  44
  45         return __pa(p);
  46 }
  47
  48 static phys_addr_t __init kasan_alloc_raw_page(int node)
  49 {
  50         void *p = memblock_alloc_try_nid_raw(PAGE_SIZE, PAGE_SIZE,
  51                                                 __pa(MAX_DMA_ADDRESS),
  52                                                 MEMBLOCK_ALLOC_NOLEAKTRACE,
  53                                                 node);
  54         if (!p)
  55                 panic("%s: Failed to allocate %lu bytes align=0x%lx nid=%d from=%llx\n",
  56                       __func__, PAGE_SIZE, PAGE_SIZE, node,
  57                       __pa(MAX_DMA_ADDRESS));
  58
  59         return __pa(p);
  60 }
  61
  62 static pte_t *__init kasan_pte_offset(pmd_t *pmdp, unsigned long addr, int node,
  63                                       bool early)
  64 {
  65         if (pmd_none(READ_ONCE(*pmdp))) {
  66                 phys_addr_t pte_phys = early ?
  67                                 __pa_symbol(kasan_early_shadow_pte)
  68                                         : kasan_alloc_zeroed_page(node);
  69                 __pmd_populate(pmdp, pte_phys, PMD_TYPE_TABLE);
  70         }
  71
  72         return early ? pte_offset_kimg(pmdp, addr)
  73                      : pte_offset_kernel(pmdp, addr);
  74 }
  75
  76 static pmd_t *__init kasan_pmd_offset(pud_t *pudp, unsigned long addr, int node,
  77                                       bool early)
  78 {
  79         if (pud_none(READ_ONCE(*pudp))) {
  80                 phys_addr_t pmd_phys = early ?
  81                                 __pa_symbol(kasan_early_shadow_pmd)
  82                                         : kasan_alloc_zeroed_page(node);
  83                 __pud_populate(pudp, pmd_phys, PUD_TYPE_TABLE);
  84         }
  85
  86         return early ? pmd_offset_kimg(pudp, addr) : pmd_offset(pudp, addr);
  87 }
  88
  89 static pud_t *__init kasan_pud_offset(p4d_t *p4dp, unsigned long addr, int node,
  90                                       bool early)
  91 {
  92         if (p4d_none(READ_ONCE(*p4dp))) {
  93                 phys_addr_t pud_phys = early ?
  94                                 __pa_symbol(kasan_early_shadow_pud)
  95                                         : kasan_alloc_zeroed_page(node);
  96                 __p4d_populate(p4dp, pud_phys, P4D_TYPE_TABLE);
  97         }
  98
  99         return early ? pud_offset_kimg(p4dp, addr) : pud_offset(p4dp, addr);
 100 }
 101
 102 static p4d_t *__init kasan_p4d_offset(pgd_t *pgdp, unsigned long addr, int node,
 103                                       bool early)
 104 {
 105         if (pgd_none(READ_ONCE(*pgdp))) {
 106                 phys_addr_t p4d_phys = early ?
 107                                 __pa_symbol(kasan_early_shadow_p4d)
 108                                         : kasan_alloc_zeroed_page(node);
 109                 __pgd_populate(pgdp, p4d_phys, PGD_TYPE_TABLE);
 110         }
 111
 112         return early ? p4d_offset_kimg(pgdp, addr) : p4d_offset(pgdp, addr);
 113 }
 114
 115 static void __init kasan_pte_populate(pmd_t *pmdp, unsigned long addr,
 116                                       unsigned long end, int node, bool early)
 117 {
 118         unsigned long next;
 119         pte_t *ptep = kasan_pte_offset(pmdp, addr, node, early);
 120
 121         do {
 122                 phys_addr_t page_phys = early ?
 123                                 __pa_symbol(kasan_early_shadow_page)
 124                                         : kasan_alloc_raw_page(node);
 125                 if (!early)
 126                         memset(__va(page_phys), KASAN_SHADOW_INIT, PAGE_SIZE);
 127                 next = addr + PAGE_SIZE;
 128                 __set_pte(ptep, pfn_pte(__phys_to_pfn(page_phys), PAGE_KERNEL));
 129         } while (ptep++, addr = next, addr != end && pte_none(__ptep_get(ptep)));
 130 }
 131
 132 static void __init kasan_pmd_populate(pud_t *pudp, unsigned long addr,
 133                                       unsigned long end, int node, bool early)
 134 {
 135         unsigned long next;
 136         pmd_t *pmdp = kasan_pmd_offset(pudp, addr, node, early);
 137
 138         do {
 139                 next = pmd_addr_end(addr, end);
 140                 kasan_pte_populate(pmdp, addr, next, node, early);
 141         } while (pmdp++, addr = next, addr != end && pmd_none(READ_ONCE(*pmdp)));
 142 }
 143
 144 static void __init kasan_pud_populate(p4d_t *p4dp, unsigned long addr,
 145                                       unsigned long end, int node, bool early)
 146 {
 147         unsigned long next;
 148         pud_t *pudp = kasan_pud_offset(p4dp, addr, node, early);
 149
 150         do {
 151                 next = pud_addr_end(addr, end);
 152                 kasan_pmd_populate(pudp, addr, next, node, early);
 153         } while (pudp++, addr = next, addr != end && pud_none(READ_ONCE(*pudp)));
 154 }
 155
 156 static void __init kasan_p4d_populate(pgd_t *pgdp, unsigned long addr,
 157                                       unsigned long end, int node, bool early)
 158 {
 159         unsigned long next;
 160         p4d_t *p4dp = kasan_p4d_offset(pgdp, addr, node, early);
 161
 162         do {
 163                 next = p4d_addr_end(addr, end);
 164                 kasan_pud_populate(p4dp, addr, next, node, early);
 165         } while (p4dp++, addr = next, addr != end && p4d_none(READ_ONCE(*p4dp)));
 166 }
 167
 168 static void __init kasan_pgd_populate(unsigned long addr, unsigned long end,
 169                                       int node, bool early)
 170 {
 171         unsigned long next;
 172         pgd_t *pgdp;
 173
 174         pgdp = pgd_offset_k(addr);
 175         do {
 176                 next = pgd_addr_end(addr, end);
 177                 kasan_p4d_populate(pgdp, addr, next, node, early);
 178         } while (pgdp++, addr = next, addr != end);
 179 }
 180
 181 #if defined(CONFIG_ARM64_64K_PAGES) || CONFIG_PGTABLE_LEVELS > 4
 182 #define SHADOW_ALIGN    P4D_SIZE
 183 #else
 184 #define SHADOW_ALIGN    PUD_SIZE
 185 #endif
 186
 187 /*
 188  * Return whether 'addr' is aligned to the size covered by a root level
 189  * descriptor.
 190  */
 191 static bool __init root_level_aligned(u64 addr)
 192 {
 193         int shift = (ARM64_HW_PGTABLE_LEVELS(vabits_actual) - 1) * (PAGE_SHIFT - 3);
 194
 195         return (addr % (PAGE_SIZE << shift)) == 0;
 196 }
 197
 198 /* The early shadow maps everything to a single page of zeroes */
 199 asmlinkage void __init kasan_early_init(void)
 200 {
 201         BUILD_BUG_ON(KASAN_SHADOW_OFFSET !=
 202                 KASAN_SHADOW_END - (1UL << (64 - KASAN_SHADOW_SCALE_SHIFT)));
 203         BUILD_BUG_ON(!IS_ALIGNED(_KASAN_SHADOW_START(VA_BITS), SHADOW_ALIGN));
 204         BUILD_BUG_ON(!IS_ALIGNED(_KASAN_SHADOW_START(VA_BITS_MIN), SHADOW_ALIGN));
 205         BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, SHADOW_ALIGN));
 206
 207         if (!root_level_aligned(KASAN_SHADOW_START)) {
 208                 /*
 209                  * The start address is misaligned, and so the next level table
 210                  * will be shared with the linear region. This can happen with
 211                  * 4 or 5 level paging, so install a generic pte_t[] as the
 212                  * next level. This prevents the kasan_pgd_populate call below
 213                  * from inserting an entry that refers to the shared KASAN zero
 214                  * shadow pud_t[]/p4d_t[], which could end up getting corrupted
 215                  * when the linear region is mapped.
 216                  */
 217                 static pte_t tbl[PTRS_PER_PTE] __page_aligned_bss;
 218                 pgd_t *pgdp = pgd_offset_k(KASAN_SHADOW_START);
 219
 220                 set_pgd(pgdp, __pgd(__pa_symbol(tbl) | PGD_TYPE_TABLE));
 221         }
 222
 223         kasan_pgd_populate(KASAN_SHADOW_START, KASAN_SHADOW_END, NUMA_NO_NODE,
 224                            true);
 225 }
 226
 227 /* Set up full kasan mappings, ensuring that the mapped pages are zeroed */
 228 static void __init kasan_map_populate(unsigned long start, unsigned long end,
 229                                       int node)
 230 {
 231         kasan_pgd_populate(start & PAGE_MASK, PAGE_ALIGN(end), node, false);
 232 }
 233
 234 /*
 235  * Return the descriptor index of 'addr' in the root level table
 236  */
 237 static int __init root_level_idx(u64 addr)
 238 {
 239         /*
 240          * On 64k pages, the TTBR1 range root tables are extended for 52-bit
 241          * virtual addressing, and TTBR1 will simply point to the pgd_t entry
 242          * that covers the start of the 48-bit addressable VA space if LVA is
 243          * not implemented. This means we need to index the table as usual,
 244          * instead of masking off bits based on vabits_actual.
 245          */
 246         u64 vabits = IS_ENABLED(CONFIG_ARM64_64K_PAGES) ? VA_BITS
 247                                                         : vabits_actual;
 248         int shift = (ARM64_HW_PGTABLE_LEVELS(vabits) - 1) * (PAGE_SHIFT - 3);
 249
 250         return (addr & ~_PAGE_OFFSET(vabits)) >> (shift + PAGE_SHIFT);
 251 }
 252
 253 /*
 254  * Clone a next level table from swapper_pg_dir into tmp_pg_dir
 255  */
 256 static void __init clone_next_level(u64 addr, pgd_t *tmp_pg_dir, pud_t *pud)
 257 {
 258         int idx = root_level_idx(addr);
 259         pgd_t pgd = READ_ONCE(swapper_pg_dir[idx]);
 260         pud_t *pudp = (pud_t *)__phys_to_kimg(__pgd_to_phys(pgd));
 261
 262         memcpy(pud, pudp, PAGE_SIZE);
 263         tmp_pg_dir[idx] = __pgd(__phys_to_pgd_val(__pa_symbol(pud)) |
 264                                 PUD_TYPE_TABLE);
 265 }
 266
 267 /*
 268  * Return the descriptor index of 'addr' in the next level table
 269  */
 270 static int __init next_level_idx(u64 addr)
 271 {
 272         int shift = (ARM64_HW_PGTABLE_LEVELS(vabits_actual) - 2) * (PAGE_SHIFT - 3);
 273
 274         return (addr >> (shift + PAGE_SHIFT)) % PTRS_PER_PTE;
 275 }
 276
 277 /*
 278  * Dereference the table descriptor at 'pgd_idx' and clear the entries from
 279  * 'start' to 'end' (exclusive) from the table.
 280  */
 281 static void __init clear_next_level(int pgd_idx, int start, int end)
 282 {
 283         pgd_t pgd = READ_ONCE(swapper_pg_dir[pgd_idx]);
 284         pud_t *pudp = (pud_t *)__phys_to_kimg(__pgd_to_phys(pgd));
 285
 286         memset(&pudp[start], 0, (end - start) * sizeof(pud_t));
 287 }
 288
 289 static void __init clear_shadow(u64 start, u64 end)
 290 {
 291         int l = root_level_idx(start), m = root_level_idx(end);
 292
 293         if (!root_level_aligned(start))
 294                 clear_next_level(l++, next_level_idx(start), PTRS_PER_PTE);
 295         if (!root_level_aligned(end))
 296                 clear_next_level(m, 0, next_level_idx(end));
 297         memset(&swapper_pg_dir[l], 0, (m - l) * sizeof(pgd_t));
 298 }
 299
 300 static void __init kasan_init_shadow(void)
 301 {
 302         static pud_t pud[2][PTRS_PER_PUD] __initdata __aligned(PAGE_SIZE);
 303         u64 kimg_shadow_start, kimg_shadow_end;
 304         u64 mod_shadow_start;
 305         u64 vmalloc_shadow_end;
 306         phys_addr_t pa_start, pa_end;
 307         u64 i;
 308
 309         kimg_shadow_start = (u64)kasan_mem_to_shadow(KERNEL_START) & PAGE_MASK;
 310         kimg_shadow_end = PAGE_ALIGN((u64)kasan_mem_to_shadow(KERNEL_END));
 311
 312         mod_shadow_start = (u64)kasan_mem_to_shadow((void *)MODULES_VADDR);
 313
 314         vmalloc_shadow_end = (u64)kasan_mem_to_shadow((void *)VMALLOC_END);
 315
 316         /*
 317          * We are going to perform proper setup of shadow memory.
 318          * At first we should unmap early shadow (clear_pgds() call below).
 319          * However, instrumented code couldn't execute without shadow memory.
 320          * tmp_pg_dir used to keep early shadow mapped until full shadow
 321          * setup will be finished.
 322          */
 323         memcpy(tmp_pg_dir, swapper_pg_dir, sizeof(tmp_pg_dir));
 324
 325         /*
 326          * If the start or end address of the shadow region is not aligned to
 327          * the root level size, we have to allocate a temporary next-level table
 328          * in each case, clone the next level of descriptors, and install the
 329          * table into tmp_pg_dir. Note that with 5 levels of paging, the next
 330          * level will in fact be p4d_t, but that makes no difference in this
 331          * case.
 332          */
 333         if (!root_level_aligned(KASAN_SHADOW_START))
 334                 clone_next_level(KASAN_SHADOW_START, tmp_pg_dir, pud[0]);
 335         if (!root_level_aligned(KASAN_SHADOW_END))
 336                 clone_next_level(KASAN_SHADOW_END, tmp_pg_dir, pud[1]);
 337         dsb(ishst);
 338         cpu_replace_ttbr1(lm_alias(tmp_pg_dir));
 339
 340         clear_shadow(KASAN_SHADOW_START, KASAN_SHADOW_END);
 341
 342         kasan_map_populate(kimg_shadow_start, kimg_shadow_end,
 343                            early_pfn_to_nid(virt_to_pfn(lm_alias(KERNEL_START))));
 344
 345         kasan_populate_early_shadow(kasan_mem_to_shadow((void *)PAGE_END),
 346                                    (void *)mod_shadow_start);
 347
 348         BUILD_BUG_ON(VMALLOC_START != MODULES_END);
 349         kasan_populate_early_shadow((void *)vmalloc_shadow_end,
 350                                     (void *)KASAN_SHADOW_END);
 351
 352         for_each_mem_range(i, &pa_start, &pa_end) {
 353                 void *start = (void *)__phys_to_virt(pa_start);
 354                 void *end = (void *)__phys_to_virt(pa_end);
 355
 356                 if (start >= end)
 357                         break;
 358
 359                 kasan_map_populate((unsigned long)kasan_mem_to_shadow(start),
 360                                    (unsigned long)kasan_mem_to_shadow(end),
 361                                    early_pfn_to_nid(virt_to_pfn(start)));
 362         }
 363
 364         /*
 365          * KAsan may reuse the contents of kasan_early_shadow_pte directly,
 366          * so we should make sure that it maps the zero page read-only.
 367          */
 368         for (i = 0; i < PTRS_PER_PTE; i++)
 369                 __set_pte(&kasan_early_shadow_pte[i],
 370                         pfn_pte(sym_to_pfn(kasan_early_shadow_page),
 371                                 PAGE_KERNEL_RO));
 372
 373         memset(kasan_early_shadow_page, KASAN_SHADOW_INIT, PAGE_SIZE);
 374         cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
 375 }
 376
 377 static void __init kasan_init_depth(void)
 378 {
 379         init_task.kasan_depth = 0;
 380 }
 381
 382 #ifdef CONFIG_KASAN_VMALLOC
 383 void __init kasan_populate_early_vm_area_shadow(void *start, unsigned long size)
 384 {
 385         unsigned long shadow_start, shadow_end;
 386
 387         if (!is_vmalloc_or_module_addr(start))
 388                 return;
 389
 390         shadow_start = (unsigned long)kasan_mem_to_shadow(start);
 391         shadow_start = ALIGN_DOWN(shadow_start, PAGE_SIZE);
 392         shadow_end = (unsigned long)kasan_mem_to_shadow(start + size);
 393         shadow_end = ALIGN(shadow_end, PAGE_SIZE);
 394         kasan_map_populate(shadow_start, shadow_end, NUMA_NO_NODE);
 395 }
 396 #endif
 397
 398 void __init kasan_init(void)
 399 {
 400         kasan_init_shadow();
 401         kasan_init_depth();
 402 #if defined(CONFIG_KASAN_GENERIC)
 403         /*
 404          * Generic KASAN is now fully initialized.
 405          * Software and Hardware Tag-Based modes still require
 406          * kasan_init_sw_tags() and kasan_init_hw_tags() correspondingly.
 407          */
 408         pr_info("KernelAddressSanitizer initialized (generic)\n");
 409 #endif
 410 }
 411
 412 #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */