1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/pagewalk.h> 3 #include <linux/highmem.h> 4 #include <linux/sched.h> 5 #include <linux/hugetlb.h> 6 7 /* 8 * We want to know the real level where a entry is located ignoring any 9 * folding of levels which may be happening. For example if p4d is folded then 10 * a missing entry found at level 1 (p4d) is actually at level 0 (pgd). 11 */ 12 static int real_depth(int depth) 13 { 14 if (depth == 3 && PTRS_PER_PMD == 1) 15 depth = 2; 16 if (depth == 2 && PTRS_PER_PUD == 1) 17 depth = 1; 18 if (depth == 1 && PTRS_PER_P4D == 1) 19 depth = 0; 20 return depth; 21 } 22 23 static int walk_pte_range_inner(pte_t *pte, unsigned long addr, 24 unsigned long end, struct mm_walk *walk) 25 { 26 const struct mm_walk_ops *ops = walk->ops; 27 int err = 0; 28 29 for (;;) { 30 err = ops->pte_entry(pte, addr, addr + PAGE_SIZE, walk); 31 if (err) 32 break; 33 if (addr >= end - PAGE_SIZE) 34 break; 35 addr += PAGE_SIZE; 36 pte++; 37 } 38 return err; 39 } 40 41 static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, 42 struct mm_walk *walk) 43 { 44 pte_t *pte; 45 int err = 0; 46 spinlock_t *ptl; 47 48 if (walk->no_vma) { 49 /* 50 * pte_offset_map() might apply user-specific validation. 51 */ 52 if (walk->mm == &init_mm) 53 pte = pte_offset_kernel(pmd, addr); 54 else 55 pte = pte_offset_map(pmd, addr); 56 if (pte) { 57 err = walk_pte_range_inner(pte, addr, end, walk); 58 if (walk->mm != &init_mm) 59 pte_unmap(pte); 60 } 61 } else { 62 pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); 63 if (pte) { 64 err = walk_pte_range_inner(pte, addr, end, walk); 65 pte_unmap_unlock(pte, ptl); 66 } 67 } 68 if (!pte) 69 walk->action = ACTION_AGAIN; 70 return err; 71 } 72 73 #ifdef CONFIG_ARCH_HAS_HUGEPD 74 static int walk_hugepd_range(hugepd_t *phpd, unsigned long addr, 75 unsigned long end, struct mm_walk *walk, int pdshift) 76 { 77 int err = 0; 78 const struct mm_walk_ops *ops = walk->ops; 79 int shift = hugepd_shift(*phpd); 80 int page_size = 1 << shift; 81 82 if (!ops->pte_entry) 83 return 0; 84 85 if (addr & (page_size - 1)) 86 return 0; 87 88 for (;;) { 89 pte_t *pte; 90 91 spin_lock(&walk->mm->page_table_lock); 92 pte = hugepte_offset(*phpd, addr, pdshift); 93 err = ops->pte_entry(pte, addr, addr + page_size, walk); 94 spin_unlock(&walk->mm->page_table_lock); 95 96 if (err) 97 break; 98 if (addr >= end - page_size) 99 break; 100 addr += page_size; 101 } 102 return err; 103 } 104 #else 105 static int walk_hugepd_range(hugepd_t *phpd, unsigned long addr, 106 unsigned long end, struct mm_walk *walk, int pdshift) 107 { 108 return 0; 109 } 110 #endif 111 112 static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end, 113 struct mm_walk *walk) 114 { 115 pmd_t *pmd; 116 unsigned long next; 117 const struct mm_walk_ops *ops = walk->ops; 118 int err = 0; 119 int depth = real_depth(3); 120 121 pmd = pmd_offset(pud, addr); 122 do { 123 again: 124 next = pmd_addr_end(addr, end); 125 if (pmd_none(*pmd)) { 126 if (ops->pte_hole) 127 err = ops->pte_hole(addr, next, depth, walk); 128 if (err) 129 break; 130 continue; 131 } 132 133 walk->action = ACTION_SUBTREE; 134 135 /* 136 * This implies that each ->pmd_entry() handler 137 * needs to know about pmd_trans_huge() pmds 138 */ 139 if (ops->pmd_entry) 140 err = ops->pmd_entry(pmd, addr, next, walk); 141 if (err) 142 break; 143 144 if (walk->action == ACTION_AGAIN) 145 goto again; 146 147 /* 148 * Check this here so we only break down trans_huge 149 * pages when we _need_ to 150 */ 151 if ((!walk->vma && (pmd_leaf(*pmd) || !pmd_present(*pmd))) || 152 walk->action == ACTION_CONTINUE || 153 !(ops->pte_entry)) 154 continue; 155 156 if (walk->vma) 157 split_huge_pmd(walk->vma, pmd, addr); 158 159 if (is_hugepd(__hugepd(pmd_val(*pmd)))) 160 err = walk_hugepd_range((hugepd_t *)pmd, addr, next, walk, PMD_SHIFT); 161 else 162 err = walk_pte_range(pmd, addr, next, walk); 163 if (err) 164 break; 165 166 if (walk->action == ACTION_AGAIN) 167 goto again; 168 169 } while (pmd++, addr = next, addr != end); 170 171 return err; 172 } 173 174 static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end, 175 struct mm_walk *walk) 176 { 177 pud_t *pud; 178 unsigned long next; 179 const struct mm_walk_ops *ops = walk->ops; 180 int err = 0; 181 int depth = real_depth(2); 182 183 pud = pud_offset(p4d, addr); 184 do { 185 again: 186 next = pud_addr_end(addr, end); 187 if (pud_none(*pud)) { 188 if (ops->pte_hole) 189 err = ops->pte_hole(addr, next, depth, walk); 190 if (err) 191 break; 192 continue; 193 } 194 195 walk->action = ACTION_SUBTREE; 196 197 if (ops->pud_entry) 198 err = ops->pud_entry(pud, addr, next, walk); 199 if (err) 200 break; 201 202 if (walk->action == ACTION_AGAIN) 203 goto again; 204 205 if ((!walk->vma && (pud_leaf(*pud) || !pud_present(*pud))) || 206 walk->action == ACTION_CONTINUE || 207 !(ops->pmd_entry || ops->pte_entry)) 208 continue; 209 210 if (walk->vma) 211 split_huge_pud(walk->vma, pud, addr); 212 if (pud_none(*pud)) 213 goto again; 214 215 if (is_hugepd(__hugepd(pud_val(*pud)))) 216 err = walk_hugepd_range((hugepd_t *)pud, addr, next, walk, PUD_SHIFT); 217 else 218 err = walk_pmd_range(pud, addr, next, walk); 219 if (err) 220 break; 221 } while (pud++, addr = next, addr != end); 222 223 return err; 224 } 225 226 static int walk_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end, 227 struct mm_walk *walk) 228 { 229 p4d_t *p4d; 230 unsigned long next; 231 const struct mm_walk_ops *ops = walk->ops; 232 int err = 0; 233 int depth = real_depth(1); 234 235 p4d = p4d_offset(pgd, addr); 236 do { 237 next = p4d_addr_end(addr, end); 238 if (p4d_none_or_clear_bad(p4d)) { 239 if (ops->pte_hole) 240 err = ops->pte_hole(addr, next, depth, walk); 241 if (err) 242 break; 243 continue; 244 } 245 if (ops->p4d_entry) { 246 err = ops->p4d_entry(p4d, addr, next, walk); 247 if (err) 248 break; 249 } 250 if (is_hugepd(__hugepd(p4d_val(*p4d)))) 251 err = walk_hugepd_range((hugepd_t *)p4d, addr, next, walk, P4D_SHIFT); 252 else if (ops->pud_entry || ops->pmd_entry || ops->pte_entry) 253 err = walk_pud_range(p4d, addr, next, walk); 254 if (err) 255 break; 256 } while (p4d++, addr = next, addr != end); 257 258 return err; 259 } 260 261 static int walk_pgd_range(unsigned long addr, unsigned long end, 262 struct mm_walk *walk) 263 { 264 pgd_t *pgd; 265 unsigned long next; 266 const struct mm_walk_ops *ops = walk->ops; 267 int err = 0; 268 269 if (walk->pgd) 270 pgd = walk->pgd + pgd_index(addr); 271 else 272 pgd = pgd_offset(walk->mm, addr); 273 do { 274 next = pgd_addr_end(addr, end); 275 if (pgd_none_or_clear_bad(pgd)) { 276 if (ops->pte_hole) 277 err = ops->pte_hole(addr, next, 0, walk); 278 if (err) 279 break; 280 continue; 281 } 282 if (ops->pgd_entry) { 283 err = ops->pgd_entry(pgd, addr, next, walk); 284 if (err) 285 break; 286 } 287 if (is_hugepd(__hugepd(pgd_val(*pgd)))) 288 err = walk_hugepd_range((hugepd_t *)pgd, addr, next, walk, PGDIR_SHIFT); 289 else if (ops->p4d_entry || ops->pud_entry || ops->pmd_entry || ops->pte_entry) 290 err = walk_p4d_range(pgd, addr, next, walk); 291 if (err) 292 break; 293 } while (pgd++, addr = next, addr != end); 294 295 return err; 296 } 297 298 #ifdef CONFIG_HUGETLB_PAGE 299 static unsigned long hugetlb_entry_end(struct hstate *h, unsigned long addr, 300 unsigned long end) 301 { 302 unsigned long boundary = (addr & huge_page_mask(h)) + huge_page_size(h); 303 return boundary < end ? boundary : end; 304 } 305 306 static int walk_hugetlb_range(unsigned long addr, unsigned long end, 307 struct mm_walk *walk) 308 { 309 struct vm_area_struct *vma = walk->vma; 310 struct hstate *h = hstate_vma(vma); 311 unsigned long next; 312 unsigned long hmask = huge_page_mask(h); 313 unsigned long sz = huge_page_size(h); 314 pte_t *pte; 315 const struct mm_walk_ops *ops = walk->ops; 316 int err = 0; 317 318 hugetlb_vma_lock_read(vma); 319 do { 320 next = hugetlb_entry_end(h, addr, end); 321 pte = hugetlb_walk(vma, addr & hmask, sz); 322 if (pte) 323 err = ops->hugetlb_entry(pte, hmask, addr, next, walk); 324 else if (ops->pte_hole) 325 err = ops->pte_hole(addr, next, -1, walk); 326 if (err) 327 break; 328 } while (addr = next, addr != end); 329 hugetlb_vma_unlock_read(vma); 330 331 return err; 332 } 333 334 #else /* CONFIG_HUGETLB_PAGE */ 335 static int walk_hugetlb_range(unsigned long addr, unsigned long end, 336 struct mm_walk *walk) 337 { 338 return 0; 339 } 340 341 #endif /* CONFIG_HUGETLB_PAGE */ 342 343 /* 344 * Decide whether we really walk over the current vma on [@start, @end) 345 * or skip it via the returned value. Return 0 if we do walk over the 346 * current vma, and return 1 if we skip the vma. Negative values means 347 * error, where we abort the current walk. 348 */ 349 static int walk_page_test(unsigned long start, unsigned long end, 350 struct mm_walk *walk) 351 { 352 struct vm_area_struct *vma = walk->vma; 353 const struct mm_walk_ops *ops = walk->ops; 354 355 if (ops->test_walk) 356 return ops->test_walk(start, end, walk); 357 358 /* 359 * vma(VM_PFNMAP) doesn't have any valid struct pages behind VM_PFNMAP 360 * range, so we don't walk over it as we do for normal vmas. However, 361 * Some callers are interested in handling hole range and they don't 362 * want to just ignore any single address range. Such users certainly 363 * define their ->pte_hole() callbacks, so let's delegate them to handle 364 * vma(VM_PFNMAP). 365 */ 366 if (vma->vm_flags & VM_PFNMAP) { 367 int err = 1; 368 if (ops->pte_hole) 369 err = ops->pte_hole(start, end, -1, walk); 370 return err ? err : 1; 371 } 372 return 0; 373 } 374 375 static int __walk_page_range(unsigned long start, unsigned long end, 376 struct mm_walk *walk) 377 { 378 int err = 0; 379 struct vm_area_struct *vma = walk->vma; 380 const struct mm_walk_ops *ops = walk->ops; 381 382 if (ops->pre_vma) { 383 err = ops->pre_vma(start, end, walk); 384 if (err) 385 return err; 386 } 387 388 if (is_vm_hugetlb_page(vma)) { 389 if (ops->hugetlb_entry) 390 err = walk_hugetlb_range(start, end, walk); 391 } else 392 err = walk_pgd_range(start, end, walk); 393 394 if (ops->post_vma) 395 ops->post_vma(walk); 396 397 return err; 398 } 399 400 /** 401 * walk_page_range - walk page table with caller specific callbacks 402 * @mm: mm_struct representing the target process of page table walk 403 * @start: start address of the virtual address range 404 * @end: end address of the virtual address range 405 * @ops: operation to call during the walk 406 * @private: private data for callbacks' usage 407 * 408 * Recursively walk the page table tree of the process represented by @mm 409 * within the virtual address range [@start, @end). During walking, we can do 410 * some caller-specific works for each entry, by setting up pmd_entry(), 411 * pte_entry(), and/or hugetlb_entry(). If you don't set up for some of these 412 * callbacks, the associated entries/pages are just ignored. 413 * The return values of these callbacks are commonly defined like below: 414 * 415 * - 0 : succeeded to handle the current entry, and if you don't reach the 416 * end address yet, continue to walk. 417 * - >0 : succeeded to handle the current entry, and return to the caller 418 * with caller specific value. 419 * - <0 : failed to handle the current entry, and return to the caller 420 * with error code. 421 * 422 * Before starting to walk page table, some callers want to check whether 423 * they really want to walk over the current vma, typically by checking 424 * its vm_flags. walk_page_test() and @ops->test_walk() are used for this 425 * purpose. 426 * 427 * If operations need to be staged before and committed after a vma is walked, 428 * there are two callbacks, pre_vma() and post_vma(). Note that post_vma(), 429 * since it is intended to handle commit-type operations, can't return any 430 * errors. 431 * 432 * struct mm_walk keeps current values of some common data like vma and pmd, 433 * which are useful for the access from callbacks. If you want to pass some 434 * caller-specific data to callbacks, @private should be helpful. 435 * 436 * Locking: 437 * Callers of walk_page_range() and walk_page_vma() should hold @mm->mmap_lock, 438 * because these function traverse vma list and/or access to vma's data. 439 */ 440 int walk_page_range(struct mm_struct *mm, unsigned long start, 441 unsigned long end, const struct mm_walk_ops *ops, 442 void *private) 443 { 444 int err = 0; 445 unsigned long next; 446 struct vm_area_struct *vma; 447 struct mm_walk walk = { 448 .ops = ops, 449 .mm = mm, 450 .private = private, 451 }; 452 453 if (start >= end) 454 return -EINVAL; 455 456 if (!walk.mm) 457 return -EINVAL; 458 459 mmap_assert_locked(walk.mm); 460 461 vma = find_vma(walk.mm, start); 462 do { 463 if (!vma) { /* after the last vma */ 464 walk.vma = NULL; 465 next = end; 466 if (ops->pte_hole) 467 err = ops->pte_hole(start, next, -1, &walk); 468 } else if (start < vma->vm_start) { /* outside vma */ 469 walk.vma = NULL; 470 next = min(end, vma->vm_start); 471 if (ops->pte_hole) 472 err = ops->pte_hole(start, next, -1, &walk); 473 } else { /* inside vma */ 474 walk.vma = vma; 475 next = min(end, vma->vm_end); 476 vma = find_vma(mm, vma->vm_end); 477 478 err = walk_page_test(start, next, &walk); 479 if (err > 0) { 480 /* 481 * positive return values are purely for 482 * controlling the pagewalk, so should never 483 * be passed to the callers. 484 */ 485 err = 0; 486 continue; 487 } 488 if (err < 0) 489 break; 490 err = __walk_page_range(start, next, &walk); 491 } 492 if (err) 493 break; 494 } while (start = next, start < end); 495 return err; 496 } 497 498 /** 499 * walk_page_range_novma - walk a range of pagetables not backed by a vma 500 * @mm: mm_struct representing the target process of page table walk 501 * @start: start address of the virtual address range 502 * @end: end address of the virtual address range 503 * @ops: operation to call during the walk 504 * @pgd: pgd to walk if different from mm->pgd 505 * @private: private data for callbacks' usage 506 * 507 * Similar to walk_page_range() but can walk any page tables even if they are 508 * not backed by VMAs. Because 'unusual' entries may be walked this function 509 * will also not lock the PTEs for the pte_entry() callback. This is useful for 510 * walking the kernel pages tables or page tables for firmware. 511 */ 512 int walk_page_range_novma(struct mm_struct *mm, unsigned long start, 513 unsigned long end, const struct mm_walk_ops *ops, 514 pgd_t *pgd, 515 void *private) 516 { 517 struct mm_walk walk = { 518 .ops = ops, 519 .mm = mm, 520 .pgd = pgd, 521 .private = private, 522 .no_vma = true 523 }; 524 525 if (start >= end || !walk.mm) 526 return -EINVAL; 527 528 mmap_assert_write_locked(walk.mm); 529 530 return walk_pgd_range(start, end, &walk); 531 } 532 533 int walk_page_range_vma(struct vm_area_struct *vma, unsigned long start, 534 unsigned long end, const struct mm_walk_ops *ops, 535 void *private) 536 { 537 struct mm_walk walk = { 538 .ops = ops, 539 .mm = vma->vm_mm, 540 .vma = vma, 541 .private = private, 542 }; 543 544 if (start >= end || !walk.mm) 545 return -EINVAL; 546 if (start < vma->vm_start || end > vma->vm_end) 547 return -EINVAL; 548 549 mmap_assert_locked(walk.mm); 550 return __walk_page_range(start, end, &walk); 551 } 552 553 int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops, 554 void *private) 555 { 556 struct mm_walk walk = { 557 .ops = ops, 558 .mm = vma->vm_mm, 559 .vma = vma, 560 .private = private, 561 }; 562 563 if (!walk.mm) 564 return -EINVAL; 565 566 mmap_assert_locked(walk.mm); 567 return __walk_page_range(vma->vm_start, vma->vm_end, &walk); 568 } 569 570 /** 571 * walk_page_mapping - walk all memory areas mapped into a struct address_space. 572 * @mapping: Pointer to the struct address_space 573 * @first_index: First page offset in the address_space 574 * @nr: Number of incremental page offsets to cover 575 * @ops: operation to call during the walk 576 * @private: private data for callbacks' usage 577 * 578 * This function walks all memory areas mapped into a struct address_space. 579 * The walk is limited to only the given page-size index range, but if 580 * the index boundaries cross a huge page-table entry, that entry will be 581 * included. 582 * 583 * Also see walk_page_range() for additional information. 584 * 585 * Locking: 586 * This function can't require that the struct mm_struct::mmap_lock is held, 587 * since @mapping may be mapped by multiple processes. Instead 588 * @mapping->i_mmap_rwsem must be held. This might have implications in the 589 * callbacks, and it's up tho the caller to ensure that the 590 * struct mm_struct::mmap_lock is not needed. 591 * 592 * Also this means that a caller can't rely on the struct 593 * vm_area_struct::vm_flags to be constant across a call, 594 * except for immutable flags. Callers requiring this shouldn't use 595 * this function. 596 * 597 * Return: 0 on success, negative error code on failure, positive number on 598 * caller defined premature termination. 599 */ 600 int walk_page_mapping(struct address_space *mapping, pgoff_t first_index, 601 pgoff_t nr, const struct mm_walk_ops *ops, 602 void *private) 603 { 604 struct mm_walk walk = { 605 .ops = ops, 606 .private = private, 607 }; 608 struct vm_area_struct *vma; 609 pgoff_t vba, vea, cba, cea; 610 unsigned long start_addr, end_addr; 611 int err = 0; 612 613 lockdep_assert_held(&mapping->i_mmap_rwsem); 614 vma_interval_tree_foreach(vma, &mapping->i_mmap, first_index, 615 first_index + nr - 1) { 616 /* Clip to the vma */ 617 vba = vma->vm_pgoff; 618 vea = vba + vma_pages(vma); 619 cba = first_index; 620 cba = max(cba, vba); 621 cea = first_index + nr; 622 cea = min(cea, vea); 623 624 start_addr = ((cba - vba) << PAGE_SHIFT) + vma->vm_start; 625 end_addr = ((cea - vba) << PAGE_SHIFT) + vma->vm_start; 626 if (start_addr >= end_addr) 627 continue; 628 629 walk.vma = vma; 630 walk.mm = vma->vm_mm; 631 632 err = walk_page_test(vma->vm_start, vma->vm_end, &walk); 633 if (err > 0) { 634 err = 0; 635 break; 636 } else if (err < 0) 637 break; 638 639 err = __walk_page_range(start_addr, end_addr, &walk); 640 if (err) 641 break; 642 } 643 644 return err; 645 } 646