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