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