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#include <linux/mmu_context.h>
7#include <linux/swap.h>
8#include <linux/swapops.h>
9
10#include <asm/tlbflush.h>
11
12#include "internal.h"
13
14/*
15 * We want to know the real level where a entry is located ignoring any
16 * folding of levels which may be happening. For example if p4d is folded then
17 * a missing entry found at level 1 (p4d) is actually at level 0 (pgd).
18 */
19static int real_depth(int depth)
20{
21 if (depth == 3 && PTRS_PER_PMD == 1)
22 depth = 2;
23 if (depth == 2 && PTRS_PER_PUD == 1)
24 depth = 1;
25 if (depth == 1 && PTRS_PER_P4D == 1)
26 depth = 0;
27 return depth;
28}
29
30static int walk_pte_range_inner(pte_t *pte, unsigned long addr,
31 unsigned long end, struct mm_walk *walk)
32{
33 const struct mm_walk_ops *ops = walk->ops;
34 int err = 0;
35
36 for (;;) {
37 if (ops->install_pte && pte_none(pte: ptep_get(ptep: pte))) {
38 pte_t new_pte;
39
40 err = ops->install_pte(addr, addr + PAGE_SIZE, &new_pte,
41 walk);
42 if (err)
43 break;
44
45 set_pte_at(walk->mm, addr, pte, new_pte);
46 /* Non-present before, so for arches that need it. */
47 if (!WARN_ON_ONCE(walk->no_vma))
48 update_mmu_cache(vma: walk->vma, addr, ptep: pte);
49 } else {
50 err = ops->pte_entry(pte, addr, addr + PAGE_SIZE, walk);
51 if (err)
52 break;
53 }
54 if (addr >= end - PAGE_SIZE)
55 break;
56 addr += PAGE_SIZE;
57 pte++;
58 }
59 return err;
60}
61
62static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
63 struct mm_walk *walk)
64{
65 pte_t *pte;
66 int err = 0;
67 spinlock_t *ptl;
68
69 if (walk->no_vma) {
70 /*
71 * pte_offset_map() might apply user-specific validation.
72 * Indeed, on x86_64 the pmd entries set up by init_espfix_ap()
73 * fit its pmd_bad() check (_PAGE_NX set and _PAGE_RW clear),
74 * and CONFIG_EFI_PGT_DUMP efi_mm goes so far as to walk them.
75 */
76 if (walk->mm == &init_mm || addr >= TASK_SIZE)
77 pte = pte_offset_kernel(pmd, address: addr);
78 else
79 pte = pte_offset_map(pmd, addr);
80 if (pte) {
81 err = walk_pte_range_inner(pte, addr, end, walk);
82 if (walk->mm != &init_mm && addr < TASK_SIZE)
83 pte_unmap(pte);
84 }
85 } else {
86 pte = pte_offset_map_lock(mm: walk->mm, pmd, addr, ptlp: &ptl);
87 if (pte) {
88 err = walk_pte_range_inner(pte, addr, end, walk);
89 pte_unmap_unlock(pte, ptl);
90 }
91 }
92 if (!pte)
93 walk->action = ACTION_AGAIN;
94 return err;
95}
96
97static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
98 struct mm_walk *walk)
99{
100 pmd_t *pmd;
101 unsigned long next;
102 const struct mm_walk_ops *ops = walk->ops;
103 bool has_handler = ops->pte_entry;
104 bool has_install = ops->install_pte;
105 int err = 0;
106 int depth = real_depth(depth: 3);
107
108 pmd = pmd_offset(pud, address: addr);
109 do {
110again:
111 next = pmd_addr_end(addr, end);
112 if (pmd_none(pmd: *pmd)) {
113 if (has_install)
114 err = __pte_alloc(mm: walk->mm, pmd);
115 else if (ops->pte_hole)
116 err = ops->pte_hole(addr, next, depth, walk);
117 if (err)
118 break;
119 if (!has_install)
120 continue;
121 }
122
123 walk->action = ACTION_SUBTREE;
124
125 /*
126 * This implies that each ->pmd_entry() handler
127 * needs to know about pmd_trans_huge() pmds
128 */
129 if (ops->pmd_entry)
130 err = ops->pmd_entry(pmd, addr, next, walk);
131 if (err)
132 break;
133
134 if (walk->action == ACTION_AGAIN)
135 goto again;
136 if (walk->action == ACTION_CONTINUE)
137 continue;
138
139 if (!has_handler) { /* No handlers for lower page tables. */
140 if (!has_install)
141 continue; /* Nothing to do. */
142 /*
143 * We are ONLY installing, so avoid unnecessarily
144 * splitting a present huge page.
145 */
146 if (pmd_present(pmd: *pmd) && pmd_trans_huge(pmd: *pmd))
147 continue;
148 }
149
150 if (walk->vma)
151 split_huge_pmd(walk->vma, pmd, addr);
152 else if (pmd_leaf(pte: *pmd) || !pmd_present(pmd: *pmd))
153 continue; /* Nothing to do. */
154
155 err = walk_pte_range(pmd, addr, end: next, walk);
156 if (err)
157 break;
158
159 if (walk->action == ACTION_AGAIN)
160 goto again;
161
162 } while (pmd++, addr = next, addr != end);
163
164 return err;
165}
166
167static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
168 struct mm_walk *walk)
169{
170 pud_t *pud;
171 unsigned long next;
172 const struct mm_walk_ops *ops = walk->ops;
173 bool has_handler = ops->pmd_entry || ops->pte_entry;
174 bool has_install = ops->install_pte;
175 int err = 0;
176 int depth = real_depth(depth: 2);
177
178 pud = pud_offset(p4d, address: addr);
179 do {
180 again:
181 next = pud_addr_end(addr, end);
182 if (pud_none(pud: *pud)) {
183 if (has_install)
184 err = __pmd_alloc(mm: walk->mm, pud, address: addr);
185 else if (ops->pte_hole)
186 err = ops->pte_hole(addr, next, depth, walk);
187 if (err)
188 break;
189 if (!has_install)
190 continue;
191 }
192
193 walk->action = ACTION_SUBTREE;
194
195 if (ops->pud_entry)
196 err = ops->pud_entry(pud, addr, next, walk);
197 if (err)
198 break;
199
200 if (walk->action == ACTION_AGAIN)
201 goto again;
202 if (walk->action == ACTION_CONTINUE)
203 continue;
204
205 if (!has_handler) { /* No handlers for lower page tables. */
206 if (!has_install)
207 continue; /* Nothing to do. */
208 /*
209 * We are ONLY installing, so avoid unnecessarily
210 * splitting a present huge page.
211 */
212 if (pud_present(pud: *pud) && pud_trans_huge(pud: *pud))
213 continue;
214 }
215
216 if (walk->vma)
217 split_huge_pud(walk->vma, pud, addr);
218 else if (pud_leaf(pud: *pud) || !pud_present(pud: *pud))
219 continue; /* Nothing to do. */
220
221 if (pud_none(pud: *pud))
222 goto again;
223
224 err = walk_pmd_range(pud, addr, end: next, walk);
225 if (err)
226 break;
227 } while (pud++, addr = next, addr != end);
228
229 return err;
230}
231
232static int walk_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,
233 struct mm_walk *walk)
234{
235 p4d_t *p4d;
236 unsigned long next;
237 const struct mm_walk_ops *ops = walk->ops;
238 bool has_handler = ops->pud_entry || ops->pmd_entry || ops->pte_entry;
239 bool has_install = ops->install_pte;
240 int err = 0;
241 int depth = real_depth(depth: 1);
242
243 p4d = p4d_offset(pgd, address: addr);
244 do {
245 next = p4d_addr_end(addr, end);
246 if (p4d_none_or_clear_bad(p4d)) {
247 if (has_install)
248 err = __pud_alloc(mm: walk->mm, p4d, address: addr);
249 else if (ops->pte_hole)
250 err = ops->pte_hole(addr, next, depth, walk);
251 if (err)
252 break;
253 if (!has_install)
254 continue;
255 }
256 if (ops->p4d_entry) {
257 err = ops->p4d_entry(p4d, addr, next, walk);
258 if (err)
259 break;
260 }
261 if (has_handler || has_install)
262 err = walk_pud_range(p4d, addr, end: next, walk);
263 if (err)
264 break;
265 } while (p4d++, addr = next, addr != end);
266
267 return err;
268}
269
270static int walk_pgd_range(unsigned long addr, unsigned long end,
271 struct mm_walk *walk)
272{
273 pgd_t *pgd;
274 unsigned long next;
275 const struct mm_walk_ops *ops = walk->ops;
276 bool has_handler = ops->p4d_entry || ops->pud_entry || ops->pmd_entry ||
277 ops->pte_entry;
278 bool has_install = ops->install_pte;
279 int err = 0;
280
281 if (walk->pgd)
282 pgd = walk->pgd + pgd_index(addr);
283 else
284 pgd = pgd_offset(walk->mm, addr);
285 do {
286 next = pgd_addr_end(addr, end);
287 if (pgd_none_or_clear_bad(pgd)) {
288 if (has_install)
289 err = __p4d_alloc(mm: walk->mm, pgd, address: addr);
290 else if (ops->pte_hole)
291 err = ops->pte_hole(addr, next, 0, walk);
292 if (err)
293 break;
294 if (!has_install)
295 continue;
296 }
297 if (ops->pgd_entry) {
298 err = ops->pgd_entry(pgd, addr, next, walk);
299 if (err)
300 break;
301 }
302 if (has_handler || has_install)
303 err = walk_p4d_range(pgd, addr, end: next, walk);
304 if (err)
305 break;
306 } while (pgd++, addr = next, addr != end);
307
308 return err;
309}
310
311#ifdef CONFIG_HUGETLB_PAGE
312static unsigned long hugetlb_entry_end(struct hstate *h, unsigned long addr,
313 unsigned long end)
314{
315 unsigned long boundary = (addr & huge_page_mask(h)) + huge_page_size(h);
316 return boundary < end ? boundary : end;
317}
318
319static int walk_hugetlb_range(unsigned long addr, unsigned long end,
320 struct mm_walk *walk)
321{
322 struct vm_area_struct *vma = walk->vma;
323 struct hstate *h = hstate_vma(vma);
324 unsigned long next;
325 unsigned long hmask = huge_page_mask(h);
326 unsigned long sz = huge_page_size(h);
327 pte_t *pte;
328 const struct mm_walk_ops *ops = walk->ops;
329 int err = 0;
330
331 hugetlb_vma_lock_read(vma);
332 do {
333 next = hugetlb_entry_end(h, addr, end);
334 pte = hugetlb_walk(vma, addr: addr & hmask, sz);
335 if (pte)
336 err = ops->hugetlb_entry(pte, hmask, addr, next, walk);
337 else if (ops->pte_hole)
338 err = ops->pte_hole(addr, next, -1, walk);
339 if (err)
340 break;
341 } while (addr = next, addr != end);
342 hugetlb_vma_unlock_read(vma);
343
344 return err;
345}
346
347#else /* CONFIG_HUGETLB_PAGE */
348static int walk_hugetlb_range(unsigned long addr, unsigned long end,
349 struct mm_walk *walk)
350{
351 return 0;
352}
353
354#endif /* CONFIG_HUGETLB_PAGE */
355
356/*
357 * Decide whether we really walk over the current vma on [@start, @end)
358 * or skip it via the returned value. Return 0 if we do walk over the
359 * current vma, and return 1 if we skip the vma. Negative values means
360 * error, where we abort the current walk.
361 */
362static int walk_page_test(unsigned long start, unsigned long end,
363 struct mm_walk *walk)
364{
365 struct vm_area_struct *vma = walk->vma;
366 const struct mm_walk_ops *ops = walk->ops;
367
368 if (ops->test_walk)
369 return ops->test_walk(start, end, walk);
370
371 /*
372 * vma(VM_PFNMAP) doesn't have any valid struct pages behind VM_PFNMAP
373 * range, so we don't walk over it as we do for normal vmas. However,
374 * Some callers are interested in handling hole range and they don't
375 * want to just ignore any single address range. Such users certainly
376 * define their ->pte_hole() callbacks, so let's delegate them to handle
377 * vma(VM_PFNMAP).
378 */
379 if (vma->vm_flags & VM_PFNMAP) {
380 int err = 1;
381 if (ops->pte_hole)
382 err = ops->pte_hole(start, end, -1, walk);
383 return err ? err : 1;
384 }
385 return 0;
386}
387
388static int __walk_page_range(unsigned long start, unsigned long end,
389 struct mm_walk *walk)
390{
391 int err = 0;
392 struct vm_area_struct *vma = walk->vma;
393 const struct mm_walk_ops *ops = walk->ops;
394 bool is_hugetlb = is_vm_hugetlb_page(vma);
395
396 /* We do not support hugetlb PTE installation. */
397 if (ops->install_pte && is_hugetlb)
398 return -EINVAL;
399
400 if (ops->pre_vma) {
401 err = ops->pre_vma(start, end, walk);
402 if (err)
403 return err;
404 }
405
406 if (is_hugetlb) {
407 if (ops->hugetlb_entry)
408 err = walk_hugetlb_range(addr: start, end, walk);
409 } else
410 err = walk_pgd_range(addr: start, end, walk);
411
412 if (ops->post_vma)
413 ops->post_vma(walk);
414
415 return err;
416}
417
418static inline void process_mm_walk_lock(struct mm_struct *mm,
419 enum page_walk_lock walk_lock)
420{
421 if (walk_lock == PGWALK_RDLOCK)
422 mmap_assert_locked(mm);
423 else if (walk_lock != PGWALK_VMA_RDLOCK_VERIFY)
424 mmap_assert_write_locked(mm);
425}
426
427static inline void process_vma_walk_lock(struct vm_area_struct *vma,
428 enum page_walk_lock walk_lock)
429{
430#ifdef CONFIG_PER_VMA_LOCK
431 switch (walk_lock) {
432 case PGWALK_WRLOCK:
433 vma_start_write(vma);
434 break;
435 case PGWALK_WRLOCK_VERIFY:
436 vma_assert_write_locked(vma);
437 break;
438 case PGWALK_VMA_RDLOCK_VERIFY:
439 vma_assert_locked(vma);
440 break;
441 case PGWALK_RDLOCK:
442 /* PGWALK_RDLOCK is handled by process_mm_walk_lock */
443 break;
444 }
445#endif
446}
447
448/*
449 * See the comment for walk_page_range(), this performs the heavy lifting of the
450 * operation, only sets no restrictions on how the walk proceeds.
451 *
452 * We usually restrict the ability to install PTEs, but this functionality is
453 * available to internal memory management code and provided in mm/internal.h.
454 */
455int walk_page_range_mm(struct mm_struct *mm, unsigned long start,
456 unsigned long end, const struct mm_walk_ops *ops,
457 void *private)
458{
459 int err = 0;
460 unsigned long next;
461 struct vm_area_struct *vma;
462 struct mm_walk walk = {
463 .ops = ops,
464 .mm = mm,
465 .private = private,
466 };
467
468 if (start >= end)
469 return -EINVAL;
470
471 if (!walk.mm)
472 return -EINVAL;
473
474 process_mm_walk_lock(mm: walk.mm, walk_lock: ops->walk_lock);
475
476 vma = find_vma(mm: walk.mm, addr: start);
477 do {
478 if (!vma) { /* after the last vma */
479 walk.vma = NULL;
480 next = end;
481 if (ops->pte_hole)
482 err = ops->pte_hole(start, next, -1, &walk);
483 } else if (start < vma->vm_start) { /* outside vma */
484 walk.vma = NULL;
485 next = min(end, vma->vm_start);
486 if (ops->pte_hole)
487 err = ops->pte_hole(start, next, -1, &walk);
488 } else { /* inside vma */
489 process_vma_walk_lock(vma, walk_lock: ops->walk_lock);
490 walk.vma = vma;
491 next = min(end, vma->vm_end);
492 vma = find_vma(mm, addr: vma->vm_end);
493
494 err = walk_page_test(start, end: next, walk: &walk);
495 if (err > 0) {
496 /*
497 * positive return values are purely for
498 * controlling the pagewalk, so should never
499 * be passed to the callers.
500 */
501 err = 0;
502 continue;
503 }
504 if (err < 0)
505 break;
506 err = __walk_page_range(start, end: next, walk: &walk);
507 }
508 if (err)
509 break;
510 } while (start = next, start < end);
511 return err;
512}
513
514/*
515 * Determine if the walk operations specified are permitted to be used for a
516 * page table walk.
517 *
518 * This check is performed on all functions which are parameterised by walk
519 * operations and exposed in include/linux/pagewalk.h.
520 *
521 * Internal memory management code can use the walk_page_range_mm() function to
522 * be able to use all page walking operations.
523 */
524static bool check_ops_valid(const struct mm_walk_ops *ops)
525{
526 /*
527 * The installation of PTEs is solely under the control of memory
528 * management logic and subject to many subtle locking, security and
529 * cache considerations so we cannot permit other users to do so, and
530 * certainly not for exported symbols.
531 */
532 if (ops->install_pte)
533 return false;
534
535 return true;
536}
537
538/**
539 * walk_page_range - walk page table with caller specific callbacks
540 * @mm: mm_struct representing the target process of page table walk
541 * @start: start address of the virtual address range
542 * @end: end address of the virtual address range
543 * @ops: operation to call during the walk
544 * @private: private data for callbacks' usage
545 *
546 * Recursively walk the page table tree of the process represented by @mm
547 * within the virtual address range [@start, @end). During walking, we can do
548 * some caller-specific works for each entry, by setting up pmd_entry(),
549 * pte_entry(), and/or hugetlb_entry(). If you don't set up for some of these
550 * callbacks, the associated entries/pages are just ignored.
551 * The return values of these callbacks are commonly defined like below:
552 *
553 * - 0 : succeeded to handle the current entry, and if you don't reach the
554 * end address yet, continue to walk.
555 * - >0 : succeeded to handle the current entry, and return to the caller
556 * with caller specific value.
557 * - <0 : failed to handle the current entry, and return to the caller
558 * with error code.
559 *
560 * Before starting to walk page table, some callers want to check whether
561 * they really want to walk over the current vma, typically by checking
562 * its vm_flags. walk_page_test() and @ops->test_walk() are used for this
563 * purpose.
564 *
565 * If operations need to be staged before and committed after a vma is walked,
566 * there are two callbacks, pre_vma() and post_vma(). Note that post_vma(),
567 * since it is intended to handle commit-type operations, can't return any
568 * errors.
569 *
570 * struct mm_walk keeps current values of some common data like vma and pmd,
571 * which are useful for the access from callbacks. If you want to pass some
572 * caller-specific data to callbacks, @private should be helpful.
573 *
574 * Locking:
575 * Callers of walk_page_range() and walk_page_vma() should hold @mm->mmap_lock,
576 * because these function traverse vma list and/or access to vma's data.
577 */
578int walk_page_range(struct mm_struct *mm, unsigned long start,
579 unsigned long end, const struct mm_walk_ops *ops,
580 void *private)
581{
582 if (!check_ops_valid(ops))
583 return -EINVAL;
584
585 return walk_page_range_mm(mm, start, end, ops, private);
586}
587
588/**
589 * walk_kernel_page_table_range - walk a range of kernel pagetables.
590 * @start: start address of the virtual address range
591 * @end: end address of the virtual address range
592 * @ops: operation to call during the walk
593 * @pgd: pgd to walk if different from mm->pgd
594 * @private: private data for callbacks' usage
595 *
596 * Similar to walk_page_range() but can walk any page tables even if they are
597 * not backed by VMAs. Because 'unusual' entries may be walked this function
598 * will also not lock the PTEs for the pte_entry() callback. This is useful for
599 * walking kernel pages tables or page tables for firmware.
600 *
601 * Note: Be careful to walk the kernel pages tables, the caller may be need to
602 * take other effective approaches (mmap lock may be insufficient) to prevent
603 * the intermediate kernel page tables belonging to the specified address range
604 * from being freed (e.g. memory hot-remove).
605 */
606int walk_kernel_page_table_range(unsigned long start, unsigned long end,
607 const struct mm_walk_ops *ops, pgd_t *pgd, void *private)
608{
609 /*
610 * Kernel intermediate page tables are usually not freed, so the mmap
611 * read lock is sufficient. But there are some exceptions.
612 * E.g. memory hot-remove. In which case, the mmap lock is insufficient
613 * to prevent the intermediate kernel pages tables belonging to the
614 * specified address range from being freed. The caller should take
615 * other actions to prevent this race.
616 */
617 mmap_assert_locked(mm: &init_mm);
618
619 return walk_kernel_page_table_range_lockless(start, end, ops, pgd,
620 private);
621}
622
623/*
624 * Use this function to walk the kernel page tables locklessly. It should be
625 * guaranteed that the caller has exclusive access over the range they are
626 * operating on - that there should be no concurrent access, for example,
627 * changing permissions for vmalloc objects.
628 */
629int walk_kernel_page_table_range_lockless(unsigned long start, unsigned long end,
630 const struct mm_walk_ops *ops, pgd_t *pgd, void *private)
631{
632 struct mm_walk walk = {
633 .ops = ops,
634 .mm = &init_mm,
635 .pgd = pgd,
636 .private = private,
637 .no_vma = true
638 };
639
640 if (start >= end)
641 return -EINVAL;
642 if (!check_ops_valid(ops))
643 return -EINVAL;
644
645 return walk_pgd_range(addr: start, end, walk: &walk);
646}
647
648/**
649 * walk_page_range_debug - walk a range of pagetables not backed by a vma
650 * @mm: mm_struct representing the target process of page table walk
651 * @start: start address of the virtual address range
652 * @end: end address of the virtual address range
653 * @ops: operation to call during the walk
654 * @pgd: pgd to walk if different from mm->pgd
655 * @private: private data for callbacks' usage
656 *
657 * Similar to walk_page_range() but can walk any page tables even if they are
658 * not backed by VMAs. Because 'unusual' entries may be walked this function
659 * will also not lock the PTEs for the pte_entry() callback.
660 *
661 * This is for debugging purposes ONLY.
662 */
663int walk_page_range_debug(struct mm_struct *mm, unsigned long start,
664 unsigned long end, const struct mm_walk_ops *ops,
665 pgd_t *pgd, void *private)
666{
667 struct mm_walk walk = {
668 .ops = ops,
669 .mm = mm,
670 .pgd = pgd,
671 .private = private,
672 .no_vma = true
673 };
674
675 /* For convenience, we allow traversal of kernel mappings. */
676 if (mm == &init_mm)
677 return walk_kernel_page_table_range(start, end, ops,
678 pgd, private);
679 if (start >= end || !walk.mm)
680 return -EINVAL;
681 if (!check_ops_valid(ops))
682 return -EINVAL;
683
684 /*
685 * The mmap lock protects the page walker from changes to the page
686 * tables during the walk. However a read lock is insufficient to
687 * protect those areas which don't have a VMA as munmap() detaches
688 * the VMAs before downgrading to a read lock and actually tearing
689 * down PTEs/page tables. In which case, the mmap write lock should
690 * be held.
691 */
692 mmap_assert_write_locked(mm);
693
694 return walk_pgd_range(addr: start, end, walk: &walk);
695}
696
697int walk_page_range_vma(struct vm_area_struct *vma, unsigned long start,
698 unsigned long end, const struct mm_walk_ops *ops,
699 void *private)
700{
701 struct mm_walk walk = {
702 .ops = ops,
703 .mm = vma->vm_mm,
704 .vma = vma,
705 .private = private,
706 };
707
708 if (start >= end || !walk.mm)
709 return -EINVAL;
710 if (start < vma->vm_start || end > vma->vm_end)
711 return -EINVAL;
712 if (!check_ops_valid(ops))
713 return -EINVAL;
714
715 process_mm_walk_lock(mm: walk.mm, walk_lock: ops->walk_lock);
716 process_vma_walk_lock(vma, walk_lock: ops->walk_lock);
717 return __walk_page_range(start, end, walk: &walk);
718}
719
720int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
721 void *private)
722{
723 struct mm_walk walk = {
724 .ops = ops,
725 .mm = vma->vm_mm,
726 .vma = vma,
727 .private = private,
728 };
729
730 if (!walk.mm)
731 return -EINVAL;
732 if (!check_ops_valid(ops))
733 return -EINVAL;
734
735 process_mm_walk_lock(mm: walk.mm, walk_lock: ops->walk_lock);
736 process_vma_walk_lock(vma, walk_lock: ops->walk_lock);
737 return __walk_page_range(start: vma->vm_start, end: vma->vm_end, walk: &walk);
738}
739
740/**
741 * walk_page_mapping - walk all memory areas mapped into a struct address_space.
742 * @mapping: Pointer to the struct address_space
743 * @first_index: First page offset in the address_space
744 * @nr: Number of incremental page offsets to cover
745 * @ops: operation to call during the walk
746 * @private: private data for callbacks' usage
747 *
748 * This function walks all memory areas mapped into a struct address_space.
749 * The walk is limited to only the given page-size index range, but if
750 * the index boundaries cross a huge page-table entry, that entry will be
751 * included.
752 *
753 * Also see walk_page_range() for additional information.
754 *
755 * Locking:
756 * This function can't require that the struct mm_struct::mmap_lock is held,
757 * since @mapping may be mapped by multiple processes. Instead
758 * @mapping->i_mmap_rwsem must be held. This might have implications in the
759 * callbacks, and it's up tho the caller to ensure that the
760 * struct mm_struct::mmap_lock is not needed.
761 *
762 * Also this means that a caller can't rely on the struct
763 * vm_area_struct::vm_flags to be constant across a call,
764 * except for immutable flags. Callers requiring this shouldn't use
765 * this function.
766 *
767 * Return: 0 on success, negative error code on failure, positive number on
768 * caller defined premature termination.
769 */
770int walk_page_mapping(struct address_space *mapping, pgoff_t first_index,
771 pgoff_t nr, const struct mm_walk_ops *ops,
772 void *private)
773{
774 struct mm_walk walk = {
775 .ops = ops,
776 .private = private,
777 };
778 struct vm_area_struct *vma;
779 pgoff_t vba, vea, cba, cea;
780 unsigned long start_addr, end_addr;
781 int err = 0;
782
783 if (!check_ops_valid(ops))
784 return -EINVAL;
785
786 lockdep_assert_held(&mapping->i_mmap_rwsem);
787 vma_interval_tree_foreach(vma, &mapping->i_mmap, first_index,
788 first_index + nr - 1) {
789 /* Clip to the vma */
790 vba = vma->vm_pgoff;
791 vea = vba + vma_pages(vma);
792 cba = first_index;
793 cba = max(cba, vba);
794 cea = first_index + nr;
795 cea = min(cea, vea);
796
797 start_addr = ((cba - vba) << PAGE_SHIFT) + vma->vm_start;
798 end_addr = ((cea - vba) << PAGE_SHIFT) + vma->vm_start;
799 if (start_addr >= end_addr)
800 continue;
801
802 walk.vma = vma;
803 walk.mm = vma->vm_mm;
804
805 err = walk_page_test(start: vma->vm_start, end: vma->vm_end, walk: &walk);
806 if (err > 0) {
807 err = 0;
808 break;
809 } else if (err < 0)
810 break;
811
812 err = __walk_page_range(start: start_addr, end: end_addr, walk: &walk);
813 if (err)
814 break;
815 }
816
817 return err;
818}
819
820/**
821 * folio_walk_start - walk the page tables to a folio
822 * @fw: filled with information on success.
823 * @vma: the VMA.
824 * @addr: the virtual address to use for the page table walk.
825 * @flags: flags modifying which folios to walk to.
826 *
827 * Walk the page tables using @addr in a given @vma to a mapped folio and
828 * return the folio, making sure that the page table entry referenced by
829 * @addr cannot change until folio_walk_end() was called.
830 *
831 * As default, this function returns only folios that are not special (e.g., not
832 * the zeropage) and never returns folios that are supposed to be ignored by the
833 * VM as documented by vm_normal_page(). If requested, zeropages will be
834 * returned as well.
835 *
836 * As default, this function only considers present page table entries.
837 * If requested, it will also consider migration entries.
838 *
839 * If this function returns NULL it might either indicate "there is nothing" or
840 * "there is nothing suitable".
841 *
842 * On success, @fw is filled and the function returns the folio while the PTL
843 * is still held and folio_walk_end() must be called to clean up,
844 * releasing any held locks. The returned folio must *not* be used after the
845 * call to folio_walk_end(), unless a short-term folio reference is taken before
846 * that call.
847 *
848 * @fw->page will correspond to the page that is effectively referenced by
849 * @addr. However, for migration entries and shared zeropages @fw->page is
850 * set to NULL. Note that large folios might be mapped by multiple page table
851 * entries, and this function will always only lookup a single entry as
852 * specified by @addr, which might or might not cover more than a single page of
853 * the returned folio.
854 *
855 * This function must *not* be used as a naive replacement for
856 * get_user_pages() / pin_user_pages(), especially not to perform DMA or
857 * to carelessly modify page content. This function may *only* be used to grab
858 * short-term folio references, never to grab long-term folio references.
859 *
860 * Using the page table entry pointers in @fw for reading or modifying the
861 * entry should be avoided where possible: however, there might be valid
862 * use cases.
863 *
864 * WARNING: Modifying page table entries in hugetlb VMAs requires a lot of care.
865 * For example, PMD page table sharing might require prior unsharing. Also,
866 * logical hugetlb entries might span multiple physical page table entries,
867 * which *must* be modified in a single operation (set_huge_pte_at(),
868 * huge_ptep_set_*, ...). Note that the page table entry stored in @fw might
869 * not correspond to the first physical entry of a logical hugetlb entry.
870 *
871 * The mmap lock must be held in read mode.
872 *
873 * Return: folio pointer on success, otherwise NULL.
874 */
875struct folio *folio_walk_start(struct folio_walk *fw,
876 struct vm_area_struct *vma, unsigned long addr,
877 folio_walk_flags_t flags)
878{
879 unsigned long entry_size;
880 bool expose_page = true;
881 struct page *page;
882 pud_t *pudp, pud;
883 pmd_t *pmdp, pmd;
884 pte_t *ptep, pte;
885 spinlock_t *ptl;
886 pgd_t *pgdp;
887 p4d_t *p4dp;
888
889 mmap_assert_locked(mm: vma->vm_mm);
890 vma_pgtable_walk_begin(vma);
891
892 if (WARN_ON_ONCE(addr < vma->vm_start || addr >= vma->vm_end))
893 goto not_found;
894
895 pgdp = pgd_offset(vma->vm_mm, addr);
896 if (pgd_none_or_clear_bad(pgd: pgdp))
897 goto not_found;
898
899 p4dp = p4d_offset(pgd: pgdp, address: addr);
900 if (p4d_none_or_clear_bad(p4d: p4dp))
901 goto not_found;
902
903 pudp = pud_offset(p4d: p4dp, address: addr);
904 pud = pudp_get(pudp);
905 if (pud_none(pud))
906 goto not_found;
907 if (IS_ENABLED(CONFIG_PGTABLE_HAS_HUGE_LEAVES) &&
908 (!pud_present(pud) || pud_leaf(pud))) {
909 ptl = pud_lock(mm: vma->vm_mm, pud: pudp);
910 pud = pudp_get(pudp);
911
912 entry_size = PUD_SIZE;
913 fw->level = FW_LEVEL_PUD;
914 fw->pudp = pudp;
915 fw->pud = pud;
916
917 if (pud_none(pud)) {
918 spin_unlock(lock: ptl);
919 goto not_found;
920 } else if (pud_present(pud) && !pud_leaf(pud)) {
921 spin_unlock(lock: ptl);
922 goto pmd_table;
923 } else if (pud_present(pud)) {
924 page = vm_normal_page_pud(vma, addr, pud);
925 if (page)
926 goto found;
927 }
928 /*
929 * TODO: FW_MIGRATION support for PUD migration entries
930 * once there are relevant users.
931 */
932 spin_unlock(lock: ptl);
933 goto not_found;
934 }
935
936pmd_table:
937 VM_WARN_ON_ONCE(!pud_present(pud) || pud_leaf(pud));
938 pmdp = pmd_offset(pud: pudp, address: addr);
939 pmd = pmdp_get_lockless(pmdp);
940 if (pmd_none(pmd))
941 goto not_found;
942 if (IS_ENABLED(CONFIG_PGTABLE_HAS_HUGE_LEAVES) &&
943 (!pmd_present(pmd) || pmd_leaf(pte: pmd))) {
944 ptl = pmd_lock(mm: vma->vm_mm, pmd: pmdp);
945 pmd = pmdp_get(pmdp);
946
947 entry_size = PMD_SIZE;
948 fw->level = FW_LEVEL_PMD;
949 fw->pmdp = pmdp;
950 fw->pmd = pmd;
951
952 if (pmd_none(pmd)) {
953 spin_unlock(lock: ptl);
954 goto not_found;
955 } else if (pmd_present(pmd) && !pmd_leaf(pte: pmd)) {
956 spin_unlock(lock: ptl);
957 goto pte_table;
958 } else if (pmd_present(pmd)) {
959 page = vm_normal_page_pmd(vma, addr, pmd);
960 if (page) {
961 goto found;
962 } else if ((flags & FW_ZEROPAGE) &&
963 is_huge_zero_pmd(pmd)) {
964 page = pfn_to_page(pmd_pfn(pmd));
965 expose_page = false;
966 goto found;
967 }
968 } else if ((flags & FW_MIGRATION) &&
969 is_pmd_migration_entry(pmd)) {
970 swp_entry_t entry = pmd_to_swp_entry(pmd);
971
972 page = pfn_swap_entry_to_page(entry);
973 expose_page = false;
974 goto found;
975 }
976 spin_unlock(lock: ptl);
977 goto not_found;
978 }
979
980pte_table:
981 VM_WARN_ON_ONCE(!pmd_present(pmd) || pmd_leaf(pmd));
982 ptep = pte_offset_map_lock(mm: vma->vm_mm, pmd: pmdp, addr, ptlp: &ptl);
983 if (!ptep)
984 goto not_found;
985 pte = ptep_get(ptep);
986
987 entry_size = PAGE_SIZE;
988 fw->level = FW_LEVEL_PTE;
989 fw->ptep = ptep;
990 fw->pte = pte;
991
992 if (pte_present(a: pte)) {
993 page = vm_normal_page(vma, addr, pte);
994 if (page)
995 goto found;
996 if ((flags & FW_ZEROPAGE) &&
997 is_zero_pfn(pfn: pte_pfn(pte))) {
998 page = pfn_to_page(pte_pfn(pte));
999 expose_page = false;
1000 goto found;
1001 }
1002 } else if (!pte_none(pte)) {
1003 swp_entry_t entry = pte_to_swp_entry(pte);
1004
1005 if ((flags & FW_MIGRATION) &&
1006 is_migration_entry(entry)) {
1007 page = pfn_swap_entry_to_page(entry);
1008 expose_page = false;
1009 goto found;
1010 }
1011 }
1012 pte_unmap_unlock(ptep, ptl);
1013not_found:
1014 vma_pgtable_walk_end(vma);
1015 return NULL;
1016found:
1017 if (expose_page)
1018 /* Note: Offset from the mapped page, not the folio start. */
1019 fw->page = page + ((addr & (entry_size - 1)) >> PAGE_SHIFT);
1020 else
1021 fw->page = NULL;
1022 fw->ptl = ptl;
1023 return page_folio(page);
1024}
1025