Line data Source code
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 0 : depth = 1;
18 : if (depth == 1 && PTRS_PER_P4D == 1)
19 0 : 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 0 : const struct mm_walk_ops *ops = walk->ops;
27 0 : int err = 0;
28 :
29 : for (;;) {
30 0 : err = ops->pte_entry(pte, addr, addr + PAGE_SIZE, walk);
31 0 : if (err)
32 : break;
33 0 : if (addr >= end - PAGE_SIZE)
34 : break;
35 0 : addr += PAGE_SIZE;
36 0 : pte++;
37 : }
38 : return err;
39 : }
40 :
41 0 : 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 0 : int err = 0;
46 : spinlock_t *ptl;
47 :
48 0 : if (walk->no_vma) {
49 0 : pte = pte_offset_map(pmd, addr);
50 : err = walk_pte_range_inner(pte, addr, end, walk);
51 : pte_unmap(pte);
52 : } else {
53 0 : pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
54 0 : err = walk_pte_range_inner(pte, addr, end, walk);
55 0 : pte_unmap_unlock(pte, ptl);
56 : }
57 :
58 0 : 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 0 : 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 0 : const struct mm_walk_ops *ops = walk->ops;
106 0 : int err = 0;
107 0 : int depth = real_depth(3);
108 :
109 0 : pmd = pmd_offset(pud, addr);
110 : do {
111 : again:
112 0 : next = pmd_addr_end(addr, end);
113 0 : if (pmd_none(*pmd)) {
114 0 : if (ops->pte_hole)
115 0 : err = ops->pte_hole(addr, next, depth, walk);
116 0 : if (err)
117 : break;
118 0 : continue;
119 : }
120 :
121 0 : 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 0 : if (ops->pmd_entry)
128 0 : err = ops->pmd_entry(pmd, addr, next, walk);
129 0 : if (err)
130 : break;
131 :
132 0 : 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 0 : if ((!walk->vma && (pmd_leaf(*pmd) || !pmd_present(*pmd))) ||
140 0 : walk->action == ACTION_CONTINUE ||
141 0 : !(ops->pte_entry))
142 0 : 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 0 : err = walk_pte_range(pmd, addr, next, walk);
154 0 : if (err)
155 : break;
156 0 : } while (pmd++, addr = next, addr != end);
157 :
158 0 : return err;
159 : }
160 :
161 0 : 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 0 : const struct mm_walk_ops *ops = walk->ops;
167 0 : int err = 0;
168 0 : int depth = real_depth(2);
169 :
170 0 : pud = pud_offset(p4d, addr);
171 : do {
172 : again:
173 0 : next = pud_addr_end(addr, end);
174 0 : if (pud_none(*pud)) {
175 0 : if (ops->pte_hole)
176 0 : err = ops->pte_hole(addr, next, depth, walk);
177 0 : if (err)
178 : break;
179 0 : continue;
180 : }
181 :
182 0 : walk->action = ACTION_SUBTREE;
183 :
184 0 : if (ops->pud_entry)
185 0 : err = ops->pud_entry(pud, addr, next, walk);
186 0 : if (err)
187 : break;
188 :
189 0 : if (walk->action == ACTION_AGAIN)
190 : goto again;
191 :
192 0 : if ((!walk->vma && (pud_leaf(*pud) || !pud_present(*pud))) ||
193 0 : walk->action == ACTION_CONTINUE ||
194 0 : !(ops->pmd_entry || ops->pte_entry))
195 0 : continue;
196 :
197 : if (walk->vma)
198 : split_huge_pud(walk->vma, pud, addr);
199 0 : 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 0 : err = walk_pmd_range(pud, addr, next, walk);
206 0 : if (err)
207 : break;
208 0 : } while (pud++, addr = next, addr != end);
209 :
210 0 : return err;
211 : }
212 :
213 0 : 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 0 : const struct mm_walk_ops *ops = walk->ops;
219 0 : int err = 0;
220 0 : int depth = real_depth(1);
221 :
222 0 : p4d = p4d_offset(pgd, addr);
223 : do {
224 0 : next = p4d_addr_end(addr, end);
225 0 : 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 0 : if (ops->p4d_entry) {
233 0 : err = ops->p4d_entry(p4d, addr, next, walk);
234 0 : 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 0 : else if (ops->pud_entry || ops->pmd_entry || ops->pte_entry)
240 0 : err = walk_pud_range(p4d, addr, next, walk);
241 : if (err)
242 : break;
243 : } while (p4d++, addr = next, addr != end);
244 :
245 0 : return err;
246 : }
247 :
248 0 : 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 0 : const struct mm_walk_ops *ops = walk->ops;
254 0 : int err = 0;
255 :
256 0 : if (walk->pgd)
257 0 : pgd = walk->pgd + pgd_index(addr);
258 : else
259 0 : pgd = pgd_offset(walk->mm, addr);
260 : do {
261 0 : next = pgd_addr_end(addr, end);
262 0 : 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 0 : if (ops->pgd_entry) {
270 0 : err = ops->pgd_entry(pgd, addr, next, walk);
271 0 : 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 0 : else if (ops->p4d_entry || ops->pud_entry || ops->pmd_entry || ops->pte_entry)
277 0 : err = walk_p4d_range(pgd, addr, next, walk);
278 0 : if (err)
279 : break;
280 0 : } while (pgd++, addr = next, addr != end);
281 :
282 0 : 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 : hugetlb_vma_lock_read(vma);
306 : do {
307 : next = hugetlb_entry_end(h, addr, end);
308 : pte = hugetlb_walk(vma, addr & hmask, sz);
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 : if (err)
314 : break;
315 : } while (addr = next, addr != end);
316 : hugetlb_vma_unlock_read(vma);
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 0 : static int walk_page_test(unsigned long start, unsigned long end,
337 : struct mm_walk *walk)
338 : {
339 0 : struct vm_area_struct *vma = walk->vma;
340 0 : const struct mm_walk_ops *ops = walk->ops;
341 :
342 0 : if (ops->test_walk)
343 0 : 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 0 : if (vma->vm_flags & VM_PFNMAP) {
354 0 : int err = 1;
355 0 : if (ops->pte_hole)
356 0 : err = ops->pte_hole(start, end, -1, walk);
357 0 : return err ? err : 1;
358 : }
359 : return 0;
360 : }
361 :
362 0 : static int __walk_page_range(unsigned long start, unsigned long end,
363 : struct mm_walk *walk)
364 : {
365 0 : int err = 0;
366 0 : struct vm_area_struct *vma = walk->vma;
367 0 : const struct mm_walk_ops *ops = walk->ops;
368 :
369 0 : if (ops->pre_vma) {
370 0 : err = ops->pre_vma(start, end, walk);
371 0 : if (err)
372 : return err;
373 : }
374 :
375 0 : if (is_vm_hugetlb_page(vma)) {
376 : if (ops->hugetlb_entry)
377 : err = walk_hugetlb_range(start, end, walk);
378 : } else
379 0 : err = walk_pgd_range(start, end, walk);
380 :
381 0 : if (ops->post_vma)
382 0 : 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 0 : 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 0 : int err = 0;
432 : unsigned long next;
433 : struct vm_area_struct *vma;
434 0 : struct mm_walk walk = {
435 : .ops = ops,
436 : .mm = mm,
437 : .private = private,
438 : };
439 :
440 0 : if (start >= end)
441 : return -EINVAL;
442 :
443 0 : if (!walk.mm)
444 : return -EINVAL;
445 :
446 0 : mmap_assert_locked(walk.mm);
447 :
448 0 : vma = find_vma(walk.mm, start);
449 : do {
450 0 : if (!vma) { /* after the last vma */
451 0 : walk.vma = NULL;
452 0 : next = end;
453 0 : if (ops->pte_hole)
454 0 : err = ops->pte_hole(start, next, -1, &walk);
455 0 : } else if (start < vma->vm_start) { /* outside vma */
456 0 : walk.vma = NULL;
457 0 : next = min(end, vma->vm_start);
458 0 : if (ops->pte_hole)
459 0 : err = ops->pte_hole(start, next, -1, &walk);
460 : } else { /* inside vma */
461 0 : walk.vma = vma;
462 0 : next = min(end, vma->vm_end);
463 0 : vma = find_vma(mm, vma->vm_end);
464 :
465 0 : err = walk_page_test(start, next, &walk);
466 0 : 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 0 : err = 0;
473 0 : continue;
474 : }
475 0 : if (err < 0)
476 : break;
477 0 : err = __walk_page_range(start, next, &walk);
478 : }
479 0 : if (err)
480 : break;
481 0 : } 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 0 : 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 0 : struct mm_walk walk = {
505 : .ops = ops,
506 : .mm = mm,
507 : .pgd = pgd,
508 : .private = private,
509 : .no_vma = true
510 : };
511 :
512 0 : if (start >= end || !walk.mm)
513 : return -EINVAL;
514 :
515 0 : mmap_assert_write_locked(walk.mm);
516 :
517 0 : return walk_pgd_range(start, end, &walk);
518 : }
519 :
520 0 : 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 0 : struct mm_walk walk = {
525 : .ops = ops,
526 0 : .mm = vma->vm_mm,
527 : .vma = vma,
528 : .private = private,
529 : };
530 :
531 0 : if (start >= end || !walk.mm)
532 : return -EINVAL;
533 0 : if (start < vma->vm_start || end > vma->vm_end)
534 : return -EINVAL;
535 :
536 0 : mmap_assert_locked(walk.mm);
537 0 : return __walk_page_range(start, end, &walk);
538 : }
539 :
540 0 : int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
541 : void *private)
542 : {
543 0 : struct mm_walk walk = {
544 : .ops = ops,
545 0 : .mm = vma->vm_mm,
546 : .vma = vma,
547 : .private = private,
548 : };
549 :
550 0 : if (!walk.mm)
551 : return -EINVAL;
552 :
553 0 : mmap_assert_locked(walk.mm);
554 0 : 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 0 : 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 0 : 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 0 : int err = 0;
599 :
600 : lockdep_assert_held(&mapping->i_mmap_rwsem);
601 0 : vma_interval_tree_foreach(vma, &mapping->i_mmap, first_index,
602 : first_index + nr - 1) {
603 : /* Clip to the vma */
604 0 : vba = vma->vm_pgoff;
605 0 : vea = vba + vma_pages(vma);
606 0 : cba = first_index;
607 0 : cba = max(cba, vba);
608 0 : cea = first_index + nr;
609 0 : cea = min(cea, vea);
610 :
611 0 : start_addr = ((cba - vba) << PAGE_SHIFT) + vma->vm_start;
612 0 : end_addr = ((cea - vba) << PAGE_SHIFT) + vma->vm_start;
613 0 : if (start_addr >= end_addr)
614 0 : continue;
615 :
616 0 : walk.vma = vma;
617 0 : walk.mm = vma->vm_mm;
618 :
619 0 : err = walk_page_test(vma->vm_start, vma->vm_end, &walk);
620 0 : if (err > 0) {
621 : err = 0;
622 : break;
623 0 : } else if (err < 0)
624 : break;
625 :
626 0 : err = __walk_page_range(start_addr, end_addr, &walk);
627 0 : if (err)
628 : break;
629 : }
630 :
631 0 : return err;
632 : }
|
