mm/kasan/init.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * This file contains KASAN shadow initialization code.
   4  *
   5  * Copyright (c) 2015 Samsung Electronics Co., Ltd.
   6  * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
   7  */
   8
   9 #include <linux/memblock.h>
  10 #include <linux/init.h>
  11 #include <linux/kasan.h>
  12 #include <linux/kernel.h>
  13 #include <linux/mm.h>
  14 #include <linux/pfn.h>
  15 #include <linux/slab.h>
  16
  17 #include <asm/page.h>
  18 #include <asm/pgalloc.h>
  19
  20 #include "kasan.h"
  21
  22 /*
  23  * This page serves two purposes:
  24  *   - It used as early shadow memory. The entire shadow region populated
  25  *     with this page, before we will be able to setup normal shadow memory.
  26  *   - Latter it reused it as zero shadow to cover large ranges of memory
  27  *     that allowed to access, but not handled by kasan (vmalloc/vmemmap ...).
  28  */
  29 unsigned char kasan_early_shadow_page[PAGE_SIZE] __page_aligned_bss;
  30
  31 #if CONFIG_PGTABLE_LEVELS > 4
  32 p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D] __page_aligned_bss;
  33 static inline bool kasan_p4d_table(pgd_t pgd)
  34 {
  35         return pgd_page(pgd) == virt_to_page(lm_alias(kasan_early_shadow_p4d));
  36 }
  37 #else
  38 static inline bool kasan_p4d_table(pgd_t pgd)
  39 {
  40         return false;
  41 }
  42 #endif
  43 #if CONFIG_PGTABLE_LEVELS > 3
  44 pud_t kasan_early_shadow_pud[MAX_PTRS_PER_PUD] __page_aligned_bss;
  45 static inline bool kasan_pud_table(p4d_t p4d)
  46 {
  47         return p4d_page(p4d) == virt_to_page(lm_alias(kasan_early_shadow_pud));
  48 }
  49 #else
  50 static inline bool kasan_pud_table(p4d_t p4d)
  51 {
  52         return false;
  53 }
  54 #endif
  55 #if CONFIG_PGTABLE_LEVELS > 2
  56 pmd_t kasan_early_shadow_pmd[MAX_PTRS_PER_PMD] __page_aligned_bss;
  57 static inline bool kasan_pmd_table(pud_t pud)
  58 {
  59         return pud_page(pud) == virt_to_page(lm_alias(kasan_early_shadow_pmd));
  60 }
  61 #else
  62 static inline bool kasan_pmd_table(pud_t pud)
  63 {
  64         return false;
  65 }
  66 #endif
  67 pte_t kasan_early_shadow_pte[MAX_PTRS_PER_PTE + PTE_HWTABLE_PTRS]
  68         __page_aligned_bss;
  69
  70 static inline bool kasan_pte_table(pmd_t pmd)
  71 {
  72         return pmd_page(pmd) == virt_to_page(lm_alias(kasan_early_shadow_pte));
  73 }
  74
  75 static inline bool kasan_early_shadow_page_entry(pte_t pte)
  76 {
  77         return pte_page(pte) == virt_to_page(lm_alias(kasan_early_shadow_page));
  78 }
  79
  80 static __init void *early_alloc(size_t size, int node)
  81 {
  82         void *ptr = memblock_alloc_try_nid(size, size, __pa(MAX_DMA_ADDRESS),
  83                                            MEMBLOCK_ALLOC_ACCESSIBLE, node);
  84
  85         if (!ptr)
  86                 panic("%s: Failed to allocate %zu bytes align=%zx nid=%d from=%llx\n",
  87                       __func__, size, size, node, (u64)__pa(MAX_DMA_ADDRESS));
  88
  89         return ptr;
  90 }
  91
  92 static void __ref zero_pte_populate(pmd_t *pmd, unsigned long addr,
  93                                 unsigned long end)
  94 {
  95         pte_t *pte = pte_offset_kernel(pmd, addr);
  96         pte_t zero_pte;
  97
  98         zero_pte = pfn_pte(PFN_DOWN(__pa_symbol(kasan_early_shadow_page)),
  99                                 PAGE_KERNEL);
 100         zero_pte = pte_wrprotect(zero_pte);
 101
 102         while (addr + PAGE_SIZE <= end) {
 103                 set_pte_at(&init_mm, addr, pte, zero_pte);
 104                 addr += PAGE_SIZE;
 105                 pte = pte_offset_kernel(pmd, addr);
 106         }
 107 }
 108
 109 static int __ref zero_pmd_populate(pud_t *pud, unsigned long addr,
 110                                 unsigned long end)
 111 {
 112         pmd_t *pmd = pmd_offset(pud, addr);
 113         unsigned long next;
 114
 115         do {
 116                 next = pmd_addr_end(addr, end);
 117
 118                 if (IS_ALIGNED(addr, PMD_SIZE) && end - addr >= PMD_SIZE) {
 119                         pmd_populate_kernel(&init_mm, pmd,
 120                                         lm_alias(kasan_early_shadow_pte));
 121                         continue;
 122                 }
 123
 124                 if (pmd_none(*pmd)) {
 125                         pte_t *p;
 126
 127                         if (slab_is_available())
 128                                 p = pte_alloc_one_kernel(&init_mm);
 129                         else
 130                                 p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
 131                         if (!p)
 132                                 return -ENOMEM;
 133
 134                         pmd_populate_kernel(&init_mm, pmd, p);
 135                 }
 136                 zero_pte_populate(pmd, addr, next);
 137         } while (pmd++, addr = next, addr != end);
 138
 139         return 0;
 140 }
 141
 142 void __weak __meminit pmd_init(void *addr)
 143 {
 144 }
 145
 146 static int __ref zero_pud_populate(p4d_t *p4d, unsigned long addr,
 147                                 unsigned long end)
 148 {
 149         pud_t *pud = pud_offset(p4d, addr);
 150         unsigned long next;
 151
 152         do {
 153                 next = pud_addr_end(addr, end);
 154                 if (IS_ALIGNED(addr, PUD_SIZE) && end - addr >= PUD_SIZE) {
 155                         pmd_t *pmd;
 156
 157                         pud_populate(&init_mm, pud,
 158                                         lm_alias(kasan_early_shadow_pmd));
 159                         pmd = pmd_offset(pud, addr);
 160                         pmd_populate_kernel(&init_mm, pmd,
 161                                         lm_alias(kasan_early_shadow_pte));
 162                         continue;
 163                 }
 164
 165                 if (pud_none(*pud)) {
 166                         pmd_t *p;
 167
 168                         if (slab_is_available()) {
 169                                 p = pmd_alloc(&init_mm, pud, addr);
 170                                 if (!p)
 171                                         return -ENOMEM;
 172                         } else {
 173                                 p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
 174                                 pmd_init(p);
 175                                 pud_populate(&init_mm, pud, p);
 176                         }
 177                 }
 178                 zero_pmd_populate(pud, addr, next);
 179         } while (pud++, addr = next, addr != end);
 180
 181         return 0;
 182 }
 183
 184 void __weak __meminit pud_init(void *addr)
 185 {
 186 }
 187
 188 static int __ref zero_p4d_populate(pgd_t *pgd, unsigned long addr,
 189                                 unsigned long end)
 190 {
 191         p4d_t *p4d = p4d_offset(pgd, addr);
 192         unsigned long next;
 193
 194         do {
 195                 next = p4d_addr_end(addr, end);
 196                 if (IS_ALIGNED(addr, P4D_SIZE) && end - addr >= P4D_SIZE) {
 197                         pud_t *pud;
 198                         pmd_t *pmd;
 199
 200                         p4d_populate(&init_mm, p4d,
 201                                         lm_alias(kasan_early_shadow_pud));
 202                         pud = pud_offset(p4d, addr);
 203                         pud_populate(&init_mm, pud,
 204                                         lm_alias(kasan_early_shadow_pmd));
 205                         pmd = pmd_offset(pud, addr);
 206                         pmd_populate_kernel(&init_mm, pmd,
 207                                         lm_alias(kasan_early_shadow_pte));
 208                         continue;
 209                 }
 210
 211                 if (p4d_none(*p4d)) {
 212                         pud_t *p;
 213
 214                         if (slab_is_available()) {
 215                                 p = pud_alloc(&init_mm, p4d, addr);
 216                                 if (!p)
 217                                         return -ENOMEM;
 218                         } else {
 219                                 p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
 220                                 pud_init(p);
 221                                 p4d_populate(&init_mm, p4d, p);
 222                         }
 223                 }
 224                 zero_pud_populate(p4d, addr, next);
 225         } while (p4d++, addr = next, addr != end);
 226
 227         return 0;
 228 }
 229
 230 /**
 231  * kasan_populate_early_shadow - populate shadow memory region with
 232  *                               kasan_early_shadow_page
 233  * @shadow_start: start of the memory range to populate
 234  * @shadow_end: end of the memory range to populate
 235  */
 236 int __ref kasan_populate_early_shadow(const void *shadow_start,
 237                                         const void *shadow_end)
 238 {
 239         unsigned long addr = (unsigned long)shadow_start;
 240         unsigned long end = (unsigned long)shadow_end;
 241         pgd_t *pgd = pgd_offset_k(addr);
 242         unsigned long next;
 243
 244         do {
 245                 next = pgd_addr_end(addr, end);
 246
 247                 if (IS_ALIGNED(addr, PGDIR_SIZE) && end - addr >= PGDIR_SIZE) {
 248                         p4d_t *p4d;
 249                         pud_t *pud;
 250                         pmd_t *pmd;
 251
 252                         /*
 253                          * kasan_early_shadow_pud should be populated with pmds
 254                          * at this moment.
 255                          * [pud,pmd]_populate*() below needed only for
 256                          * 3,2 - level page tables where we don't have
 257                          * puds,pmds, so pgd_populate(), pud_populate()
 258                          * is noops.
 259                          */
 260                         pgd_populate(&init_mm, pgd,
 261                                         lm_alias(kasan_early_shadow_p4d));
 262                         p4d = p4d_offset(pgd, addr);
 263                         p4d_populate(&init_mm, p4d,
 264                                         lm_alias(kasan_early_shadow_pud));
 265                         pud = pud_offset(p4d, addr);
 266                         pud_populate(&init_mm, pud,
 267                                         lm_alias(kasan_early_shadow_pmd));
 268                         pmd = pmd_offset(pud, addr);
 269                         pmd_populate_kernel(&init_mm, pmd,
 270                                         lm_alias(kasan_early_shadow_pte));
 271                         continue;
 272                 }
 273
 274                 if (pgd_none(*pgd)) {
 275                         p4d_t *p;
 276
 277                         if (slab_is_available()) {
 278                                 p = p4d_alloc(&init_mm, pgd, addr);
 279                                 if (!p)
 280                                         return -ENOMEM;
 281                         } else {
 282                                 pgd_populate(&init_mm, pgd,
 283                                         early_alloc(PAGE_SIZE, NUMA_NO_NODE));
 284                         }
 285                 }
 286                 zero_p4d_populate(pgd, addr, next);
 287         } while (pgd++, addr = next, addr != end);
 288
 289         return 0;
 290 }
 291
 292 static void kasan_free_pte(pte_t *pte_start, pmd_t *pmd)
 293 {
 294         pte_t *pte;
 295         int i;
 296
 297         for (i = 0; i < PTRS_PER_PTE; i++) {
 298                 pte = pte_start + i;
 299                 if (!pte_none(ptep_get(pte)))
 300                         return;
 301         }
 302
 303         pte_free_kernel(&init_mm, (pte_t *)page_to_virt(pmd_page(*pmd)));
 304         pmd_clear(pmd);
 305 }
 306
 307 static void kasan_free_pmd(pmd_t *pmd_start, pud_t *pud)
 308 {
 309         pmd_t *pmd;
 310         int i;
 311
 312         for (i = 0; i < PTRS_PER_PMD; i++) {
 313                 pmd = pmd_start + i;
 314                 if (!pmd_none(*pmd))
 315                         return;
 316         }
 317
 318         pmd_free(&init_mm, (pmd_t *)page_to_virt(pud_page(*pud)));
 319         pud_clear(pud);
 320 }
 321
 322 static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d)
 323 {
 324         pud_t *pud;
 325         int i;
 326
 327         for (i = 0; i < PTRS_PER_PUD; i++) {
 328                 pud = pud_start + i;
 329                 if (!pud_none(*pud))
 330                         return;
 331         }
 332
 333         pud_free(&init_mm, (pud_t *)page_to_virt(p4d_page(*p4d)));
 334         p4d_clear(p4d);
 335 }
 336
 337 static void kasan_free_p4d(p4d_t *p4d_start, pgd_t *pgd)
 338 {
 339         p4d_t *p4d;
 340         int i;
 341
 342         for (i = 0; i < PTRS_PER_P4D; i++) {
 343                 p4d = p4d_start + i;
 344                 if (!p4d_none(*p4d))
 345                         return;
 346         }
 347
 348         p4d_free(&init_mm, (p4d_t *)page_to_virt(pgd_page(*pgd)));
 349         pgd_clear(pgd);
 350 }
 351
 352 static void kasan_remove_pte_table(pte_t *pte, unsigned long addr,
 353                                 unsigned long end)
 354 {
 355         unsigned long next;
 356         pte_t ptent;
 357
 358         for (; addr < end; addr = next, pte++) {
 359                 next = (addr + PAGE_SIZE) & PAGE_MASK;
 360                 if (next > end)
 361                         next = end;
 362
 363                 ptent = ptep_get(pte);
 364
 365                 if (!pte_present(ptent))
 366                         continue;
 367
 368                 if (WARN_ON(!kasan_early_shadow_page_entry(ptent)))
 369                         continue;
 370                 pte_clear(&init_mm, addr, pte);
 371         }
 372 }
 373
 374 static void kasan_remove_pmd_table(pmd_t *pmd, unsigned long addr,
 375                                 unsigned long end)
 376 {
 377         unsigned long next;
 378
 379         for (; addr < end; addr = next, pmd++) {
 380                 pte_t *pte;
 381
 382                 next = pmd_addr_end(addr, end);
 383
 384                 if (!pmd_present(*pmd))
 385                         continue;
 386
 387                 if (kasan_pte_table(*pmd)) {
 388                         if (IS_ALIGNED(addr, PMD_SIZE) &&
 389                             IS_ALIGNED(next, PMD_SIZE)) {
 390                                 pmd_clear(pmd);
 391                                 continue;
 392                         }
 393                 }
 394                 pte = pte_offset_kernel(pmd, addr);
 395                 kasan_remove_pte_table(pte, addr, next);
 396                 kasan_free_pte(pte_offset_kernel(pmd, 0), pmd);
 397         }
 398 }
 399
 400 static void kasan_remove_pud_table(pud_t *pud, unsigned long addr,
 401                                 unsigned long end)
 402 {
 403         unsigned long next;
 404
 405         for (; addr < end; addr = next, pud++) {
 406                 pmd_t *pmd, *pmd_base;
 407
 408                 next = pud_addr_end(addr, end);
 409
 410                 if (!pud_present(*pud))
 411                         continue;
 412
 413                 if (kasan_pmd_table(*pud)) {
 414                         if (IS_ALIGNED(addr, PUD_SIZE) &&
 415                             IS_ALIGNED(next, PUD_SIZE)) {
 416                                 pud_clear(pud);
 417                                 continue;
 418                         }
 419                 }
 420                 pmd = pmd_offset(pud, addr);
 421                 pmd_base = pmd_offset(pud, 0);
 422                 kasan_remove_pmd_table(pmd, addr, next);
 423                 kasan_free_pmd(pmd_base, pud);
 424         }
 425 }
 426
 427 static void kasan_remove_p4d_table(p4d_t *p4d, unsigned long addr,
 428                                 unsigned long end)
 429 {
 430         unsigned long next;
 431
 432         for (; addr < end; addr = next, p4d++) {
 433                 pud_t *pud;
 434
 435                 next = p4d_addr_end(addr, end);
 436
 437                 if (!p4d_present(*p4d))
 438                         continue;
 439
 440                 if (kasan_pud_table(*p4d)) {
 441                         if (IS_ALIGNED(addr, P4D_SIZE) &&
 442                             IS_ALIGNED(next, P4D_SIZE)) {
 443                                 p4d_clear(p4d);
 444                                 continue;
 445                         }
 446                 }
 447                 pud = pud_offset(p4d, addr);
 448                 kasan_remove_pud_table(pud, addr, next);
 449                 kasan_free_pud(pud_offset(p4d, 0), p4d);
 450         }
 451 }
 452
 453 void kasan_remove_zero_shadow(void *start, unsigned long size)
 454 {
 455         unsigned long addr, end, next;
 456         pgd_t *pgd;
 457
 458         addr = (unsigned long)kasan_mem_to_shadow(start);
 459         end = addr + (size >> KASAN_SHADOW_SCALE_SHIFT);
 460
 461         if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
 462             WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
 463                 return;
 464
 465         for (; addr < end; addr = next) {
 466                 p4d_t *p4d;
 467
 468                 next = pgd_addr_end(addr, end);
 469
 470                 pgd = pgd_offset_k(addr);
 471                 if (!pgd_present(*pgd))
 472                         continue;
 473
 474                 if (kasan_p4d_table(*pgd)) {
 475                         if (IS_ALIGNED(addr, PGDIR_SIZE) &&
 476                             IS_ALIGNED(next, PGDIR_SIZE)) {
 477                                 pgd_clear(pgd);
 478                                 continue;
 479                         }
 480                 }
 481
 482                 p4d = p4d_offset(pgd, addr);
 483                 kasan_remove_p4d_table(p4d, addr, next);
 484                 kasan_free_p4d(p4d_offset(pgd, 0), pgd);
 485         }
 486 }
 487
 488 int kasan_add_zero_shadow(void *start, unsigned long size)
 489 {
 490         int ret;
 491         void *shadow_start, *shadow_end;
 492
 493         shadow_start = kasan_mem_to_shadow(start);
 494         shadow_end = shadow_start + (size >> KASAN_SHADOW_SCALE_SHIFT);
 495
 496         if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
 497             WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
 498                 return -EINVAL;
 499
 500         ret = kasan_populate_early_shadow(shadow_start, shadow_end);
 501         if (ret)
 502                 kasan_remove_zero_shadow(start, size);
 503         return ret;
 504 }