]> git.proxmox.com Git - mirror_ubuntu-jammy-kernel.git/blob - mm/gup.c
arm64: Ensure execute-only permissions are not allowed without EPAN
[mirror_ubuntu-jammy-kernel.git] / mm / gup.c
1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/kernel.h>
3 #include <linux/errno.h>
4 #include <linux/err.h>
5 #include <linux/spinlock.h>
6
7 #include <linux/mm.h>
8 #include <linux/memremap.h>
9 #include <linux/pagemap.h>
10 #include <linux/rmap.h>
11 #include <linux/swap.h>
12 #include <linux/swapops.h>
13 #include <linux/secretmem.h>
14
15 #include <linux/sched/signal.h>
16 #include <linux/rwsem.h>
17 #include <linux/hugetlb.h>
18 #include <linux/migrate.h>
19 #include <linux/mm_inline.h>
20 #include <linux/sched/mm.h>
21
22 #include <asm/mmu_context.h>
23 #include <asm/tlbflush.h>
24
25 #include "internal.h"
26
27 struct follow_page_context {
28 struct dev_pagemap *pgmap;
29 unsigned int page_mask;
30 };
31
32 static void hpage_pincount_add(struct page *page, int refs)
33 {
34 VM_BUG_ON_PAGE(!hpage_pincount_available(page), page);
35 VM_BUG_ON_PAGE(page != compound_head(page), page);
36
37 atomic_add(refs, compound_pincount_ptr(page));
38 }
39
40 static void hpage_pincount_sub(struct page *page, int refs)
41 {
42 VM_BUG_ON_PAGE(!hpage_pincount_available(page), page);
43 VM_BUG_ON_PAGE(page != compound_head(page), page);
44
45 atomic_sub(refs, compound_pincount_ptr(page));
46 }
47
48 /* Equivalent to calling put_page() @refs times. */
49 static void put_page_refs(struct page *page, int refs)
50 {
51 #ifdef CONFIG_DEBUG_VM
52 if (VM_WARN_ON_ONCE_PAGE(page_ref_count(page) < refs, page))
53 return;
54 #endif
55
56 /*
57 * Calling put_page() for each ref is unnecessarily slow. Only the last
58 * ref needs a put_page().
59 */
60 if (refs > 1)
61 page_ref_sub(page, refs - 1);
62 put_page(page);
63 }
64
65 /*
66 * Return the compound head page with ref appropriately incremented,
67 * or NULL if that failed.
68 */
69 static inline struct page *try_get_compound_head(struct page *page, int refs)
70 {
71 struct page *head = compound_head(page);
72
73 if (WARN_ON_ONCE(page_ref_count(head) < 0))
74 return NULL;
75 if (unlikely(!page_cache_add_speculative(head, refs)))
76 return NULL;
77
78 /*
79 * At this point we have a stable reference to the head page; but it
80 * could be that between the compound_head() lookup and the refcount
81 * increment, the compound page was split, in which case we'd end up
82 * holding a reference on a page that has nothing to do with the page
83 * we were given anymore.
84 * So now that the head page is stable, recheck that the pages still
85 * belong together.
86 */
87 if (unlikely(compound_head(page) != head)) {
88 put_page_refs(head, refs);
89 return NULL;
90 }
91
92 return head;
93 }
94
95 /**
96 * try_grab_compound_head() - attempt to elevate a page's refcount, by a
97 * flags-dependent amount.
98 *
99 * Even though the name includes "compound_head", this function is still
100 * appropriate for callers that have a non-compound @page to get.
101 *
102 * @page: pointer to page to be grabbed
103 * @refs: the value to (effectively) add to the page's refcount
104 * @flags: gup flags: these are the FOLL_* flag values.
105 *
106 * "grab" names in this file mean, "look at flags to decide whether to use
107 * FOLL_PIN or FOLL_GET behavior, when incrementing the page's refcount.
108 *
109 * Either FOLL_PIN or FOLL_GET (or neither) must be set, but not both at the
110 * same time. (That's true throughout the get_user_pages*() and
111 * pin_user_pages*() APIs.) Cases:
112 *
113 * FOLL_GET: page's refcount will be incremented by @refs.
114 *
115 * FOLL_PIN on compound pages that are > two pages long: page's refcount will
116 * be incremented by @refs, and page[2].hpage_pinned_refcount will be
117 * incremented by @refs * GUP_PIN_COUNTING_BIAS.
118 *
119 * FOLL_PIN on normal pages, or compound pages that are two pages long:
120 * page's refcount will be incremented by @refs * GUP_PIN_COUNTING_BIAS.
121 *
122 * Return: head page (with refcount appropriately incremented) for success, or
123 * NULL upon failure. If neither FOLL_GET nor FOLL_PIN was set, that's
124 * considered failure, and furthermore, a likely bug in the caller, so a warning
125 * is also emitted.
126 */
127 __maybe_unused struct page *try_grab_compound_head(struct page *page,
128 int refs, unsigned int flags)
129 {
130 if (flags & FOLL_GET)
131 return try_get_compound_head(page, refs);
132 else if (flags & FOLL_PIN) {
133 /*
134 * Can't do FOLL_LONGTERM + FOLL_PIN gup fast path if not in a
135 * right zone, so fail and let the caller fall back to the slow
136 * path.
137 */
138 if (unlikely((flags & FOLL_LONGTERM) &&
139 !is_pinnable_page(page)))
140 return NULL;
141
142 /*
143 * CAUTION: Don't use compound_head() on the page before this
144 * point, the result won't be stable.
145 */
146 page = try_get_compound_head(page, refs);
147 if (!page)
148 return NULL;
149
150 /*
151 * When pinning a compound page of order > 1 (which is what
152 * hpage_pincount_available() checks for), use an exact count to
153 * track it, via hpage_pincount_add/_sub().
154 *
155 * However, be sure to *also* increment the normal page refcount
156 * field at least once, so that the page really is pinned.
157 * That's why the refcount from the earlier
158 * try_get_compound_head() is left intact.
159 */
160 if (hpage_pincount_available(page))
161 hpage_pincount_add(page, refs);
162 else
163 page_ref_add(page, refs * (GUP_PIN_COUNTING_BIAS - 1));
164
165 mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_ACQUIRED,
166 refs);
167
168 return page;
169 }
170
171 WARN_ON_ONCE(1);
172 return NULL;
173 }
174
175 static void put_compound_head(struct page *page, int refs, unsigned int flags)
176 {
177 if (flags & FOLL_PIN) {
178 mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_RELEASED,
179 refs);
180
181 if (hpage_pincount_available(page))
182 hpage_pincount_sub(page, refs);
183 else
184 refs *= GUP_PIN_COUNTING_BIAS;
185 }
186
187 put_page_refs(page, refs);
188 }
189
190 /**
191 * try_grab_page() - elevate a page's refcount by a flag-dependent amount
192 *
193 * This might not do anything at all, depending on the flags argument.
194 *
195 * "grab" names in this file mean, "look at flags to decide whether to use
196 * FOLL_PIN or FOLL_GET behavior, when incrementing the page's refcount.
197 *
198 * @page: pointer to page to be grabbed
199 * @flags: gup flags: these are the FOLL_* flag values.
200 *
201 * Either FOLL_PIN or FOLL_GET (or neither) may be set, but not both at the same
202 * time. Cases: please see the try_grab_compound_head() documentation, with
203 * "refs=1".
204 *
205 * Return: true for success, or if no action was required (if neither FOLL_PIN
206 * nor FOLL_GET was set, nothing is done). False for failure: FOLL_GET or
207 * FOLL_PIN was set, but the page could not be grabbed.
208 */
209 bool __must_check try_grab_page(struct page *page, unsigned int flags)
210 {
211 WARN_ON_ONCE((flags & (FOLL_GET | FOLL_PIN)) == (FOLL_GET | FOLL_PIN));
212
213 if (flags & FOLL_GET)
214 return try_get_page(page);
215 else if (flags & FOLL_PIN) {
216 int refs = 1;
217
218 page = compound_head(page);
219
220 if (WARN_ON_ONCE(page_ref_count(page) <= 0))
221 return false;
222
223 if (hpage_pincount_available(page))
224 hpage_pincount_add(page, 1);
225 else
226 refs = GUP_PIN_COUNTING_BIAS;
227
228 /*
229 * Similar to try_grab_compound_head(): even if using the
230 * hpage_pincount_add/_sub() routines, be sure to
231 * *also* increment the normal page refcount field at least
232 * once, so that the page really is pinned.
233 */
234 page_ref_add(page, refs);
235
236 mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_ACQUIRED, 1);
237 }
238
239 return true;
240 }
241
242 /**
243 * unpin_user_page() - release a dma-pinned page
244 * @page: pointer to page to be released
245 *
246 * Pages that were pinned via pin_user_pages*() must be released via either
247 * unpin_user_page(), or one of the unpin_user_pages*() routines. This is so
248 * that such pages can be separately tracked and uniquely handled. In
249 * particular, interactions with RDMA and filesystems need special handling.
250 */
251 void unpin_user_page(struct page *page)
252 {
253 put_compound_head(compound_head(page), 1, FOLL_PIN);
254 }
255 EXPORT_SYMBOL(unpin_user_page);
256
257 static inline void compound_range_next(unsigned long i, unsigned long npages,
258 struct page **list, struct page **head,
259 unsigned int *ntails)
260 {
261 struct page *next, *page;
262 unsigned int nr = 1;
263
264 if (i >= npages)
265 return;
266
267 next = *list + i;
268 page = compound_head(next);
269 if (PageCompound(page) && compound_order(page) >= 1)
270 nr = min_t(unsigned int,
271 page + compound_nr(page) - next, npages - i);
272
273 *head = page;
274 *ntails = nr;
275 }
276
277 #define for_each_compound_range(__i, __list, __npages, __head, __ntails) \
278 for (__i = 0, \
279 compound_range_next(__i, __npages, __list, &(__head), &(__ntails)); \
280 __i < __npages; __i += __ntails, \
281 compound_range_next(__i, __npages, __list, &(__head), &(__ntails)))
282
283 static inline void compound_next(unsigned long i, unsigned long npages,
284 struct page **list, struct page **head,
285 unsigned int *ntails)
286 {
287 struct page *page;
288 unsigned int nr;
289
290 if (i >= npages)
291 return;
292
293 page = compound_head(list[i]);
294 for (nr = i + 1; nr < npages; nr++) {
295 if (compound_head(list[nr]) != page)
296 break;
297 }
298
299 *head = page;
300 *ntails = nr - i;
301 }
302
303 #define for_each_compound_head(__i, __list, __npages, __head, __ntails) \
304 for (__i = 0, \
305 compound_next(__i, __npages, __list, &(__head), &(__ntails)); \
306 __i < __npages; __i += __ntails, \
307 compound_next(__i, __npages, __list, &(__head), &(__ntails)))
308
309 /**
310 * unpin_user_pages_dirty_lock() - release and optionally dirty gup-pinned pages
311 * @pages: array of pages to be maybe marked dirty, and definitely released.
312 * @npages: number of pages in the @pages array.
313 * @make_dirty: whether to mark the pages dirty
314 *
315 * "gup-pinned page" refers to a page that has had one of the get_user_pages()
316 * variants called on that page.
317 *
318 * For each page in the @pages array, make that page (or its head page, if a
319 * compound page) dirty, if @make_dirty is true, and if the page was previously
320 * listed as clean. In any case, releases all pages using unpin_user_page(),
321 * possibly via unpin_user_pages(), for the non-dirty case.
322 *
323 * Please see the unpin_user_page() documentation for details.
324 *
325 * set_page_dirty_lock() is used internally. If instead, set_page_dirty() is
326 * required, then the caller should a) verify that this is really correct,
327 * because _lock() is usually required, and b) hand code it:
328 * set_page_dirty_lock(), unpin_user_page().
329 *
330 */
331 void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages,
332 bool make_dirty)
333 {
334 unsigned long index;
335 struct page *head;
336 unsigned int ntails;
337
338 if (!make_dirty) {
339 unpin_user_pages(pages, npages);
340 return;
341 }
342
343 for_each_compound_head(index, pages, npages, head, ntails) {
344 /*
345 * Checking PageDirty at this point may race with
346 * clear_page_dirty_for_io(), but that's OK. Two key
347 * cases:
348 *
349 * 1) This code sees the page as already dirty, so it
350 * skips the call to set_page_dirty(). That could happen
351 * because clear_page_dirty_for_io() called
352 * page_mkclean(), followed by set_page_dirty().
353 * However, now the page is going to get written back,
354 * which meets the original intention of setting it
355 * dirty, so all is well: clear_page_dirty_for_io() goes
356 * on to call TestClearPageDirty(), and write the page
357 * back.
358 *
359 * 2) This code sees the page as clean, so it calls
360 * set_page_dirty(). The page stays dirty, despite being
361 * written back, so it gets written back again in the
362 * next writeback cycle. This is harmless.
363 */
364 if (!PageDirty(head))
365 set_page_dirty_lock(head);
366 put_compound_head(head, ntails, FOLL_PIN);
367 }
368 }
369 EXPORT_SYMBOL(unpin_user_pages_dirty_lock);
370
371 /**
372 * unpin_user_page_range_dirty_lock() - release and optionally dirty
373 * gup-pinned page range
374 *
375 * @page: the starting page of a range maybe marked dirty, and definitely released.
376 * @npages: number of consecutive pages to release.
377 * @make_dirty: whether to mark the pages dirty
378 *
379 * "gup-pinned page range" refers to a range of pages that has had one of the
380 * pin_user_pages() variants called on that page.
381 *
382 * For the page ranges defined by [page .. page+npages], make that range (or
383 * its head pages, if a compound page) dirty, if @make_dirty is true, and if the
384 * page range was previously listed as clean.
385 *
386 * set_page_dirty_lock() is used internally. If instead, set_page_dirty() is
387 * required, then the caller should a) verify that this is really correct,
388 * because _lock() is usually required, and b) hand code it:
389 * set_page_dirty_lock(), unpin_user_page().
390 *
391 */
392 void unpin_user_page_range_dirty_lock(struct page *page, unsigned long npages,
393 bool make_dirty)
394 {
395 unsigned long index;
396 struct page *head;
397 unsigned int ntails;
398
399 for_each_compound_range(index, &page, npages, head, ntails) {
400 if (make_dirty && !PageDirty(head))
401 set_page_dirty_lock(head);
402 put_compound_head(head, ntails, FOLL_PIN);
403 }
404 }
405 EXPORT_SYMBOL(unpin_user_page_range_dirty_lock);
406
407 /**
408 * unpin_user_pages() - release an array of gup-pinned pages.
409 * @pages: array of pages to be marked dirty and released.
410 * @npages: number of pages in the @pages array.
411 *
412 * For each page in the @pages array, release the page using unpin_user_page().
413 *
414 * Please see the unpin_user_page() documentation for details.
415 */
416 void unpin_user_pages(struct page **pages, unsigned long npages)
417 {
418 unsigned long index;
419 struct page *head;
420 unsigned int ntails;
421
422 /*
423 * If this WARN_ON() fires, then the system *might* be leaking pages (by
424 * leaving them pinned), but probably not. More likely, gup/pup returned
425 * a hard -ERRNO error to the caller, who erroneously passed it here.
426 */
427 if (WARN_ON(IS_ERR_VALUE(npages)))
428 return;
429
430 for_each_compound_head(index, pages, npages, head, ntails)
431 put_compound_head(head, ntails, FOLL_PIN);
432 }
433 EXPORT_SYMBOL(unpin_user_pages);
434
435 /*
436 * Set the MMF_HAS_PINNED if not set yet; after set it'll be there for the mm's
437 * lifecycle. Avoid setting the bit unless necessary, or it might cause write
438 * cache bouncing on large SMP machines for concurrent pinned gups.
439 */
440 static inline void mm_set_has_pinned_flag(unsigned long *mm_flags)
441 {
442 if (!test_bit(MMF_HAS_PINNED, mm_flags))
443 set_bit(MMF_HAS_PINNED, mm_flags);
444 }
445
446 #ifdef CONFIG_MMU
447 static struct page *no_page_table(struct vm_area_struct *vma,
448 unsigned int flags)
449 {
450 /*
451 * When core dumping an enormous anonymous area that nobody
452 * has touched so far, we don't want to allocate unnecessary pages or
453 * page tables. Return error instead of NULL to skip handle_mm_fault,
454 * then get_dump_page() will return NULL to leave a hole in the dump.
455 * But we can only make this optimization where a hole would surely
456 * be zero-filled if handle_mm_fault() actually did handle it.
457 */
458 if ((flags & FOLL_DUMP) &&
459 (vma_is_anonymous(vma) || !vma->vm_ops->fault))
460 return ERR_PTR(-EFAULT);
461 return NULL;
462 }
463
464 static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address,
465 pte_t *pte, unsigned int flags)
466 {
467 /* No page to get reference */
468 if (flags & FOLL_GET)
469 return -EFAULT;
470
471 if (flags & FOLL_TOUCH) {
472 pte_t entry = *pte;
473
474 if (flags & FOLL_WRITE)
475 entry = pte_mkdirty(entry);
476 entry = pte_mkyoung(entry);
477
478 if (!pte_same(*pte, entry)) {
479 set_pte_at(vma->vm_mm, address, pte, entry);
480 update_mmu_cache(vma, address, pte);
481 }
482 }
483
484 /* Proper page table entry exists, but no corresponding struct page */
485 return -EEXIST;
486 }
487
488 /*
489 * FOLL_FORCE can write to even unwritable pte's, but only
490 * after we've gone through a COW cycle and they are dirty.
491 */
492 static inline bool can_follow_write_pte(pte_t pte, unsigned int flags)
493 {
494 return pte_write(pte) ||
495 ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte));
496 }
497
498 static struct page *follow_page_pte(struct vm_area_struct *vma,
499 unsigned long address, pmd_t *pmd, unsigned int flags,
500 struct dev_pagemap **pgmap)
501 {
502 struct mm_struct *mm = vma->vm_mm;
503 struct page *page;
504 spinlock_t *ptl;
505 pte_t *ptep, pte;
506 int ret;
507
508 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
509 if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
510 (FOLL_PIN | FOLL_GET)))
511 return ERR_PTR(-EINVAL);
512 retry:
513 if (unlikely(pmd_bad(*pmd)))
514 return no_page_table(vma, flags);
515
516 ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
517 pte = *ptep;
518 if (!pte_present(pte)) {
519 swp_entry_t entry;
520 /*
521 * KSM's break_ksm() relies upon recognizing a ksm page
522 * even while it is being migrated, so for that case we
523 * need migration_entry_wait().
524 */
525 if (likely(!(flags & FOLL_MIGRATION)))
526 goto no_page;
527 if (pte_none(pte))
528 goto no_page;
529 entry = pte_to_swp_entry(pte);
530 if (!is_migration_entry(entry))
531 goto no_page;
532 pte_unmap_unlock(ptep, ptl);
533 migration_entry_wait(mm, pmd, address);
534 goto retry;
535 }
536 if ((flags & FOLL_NUMA) && pte_protnone(pte))
537 goto no_page;
538 if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, flags)) {
539 pte_unmap_unlock(ptep, ptl);
540 return NULL;
541 }
542
543 page = vm_normal_page(vma, address, pte);
544 if (!page && pte_devmap(pte) && (flags & (FOLL_GET | FOLL_PIN))) {
545 /*
546 * Only return device mapping pages in the FOLL_GET or FOLL_PIN
547 * case since they are only valid while holding the pgmap
548 * reference.
549 */
550 *pgmap = get_dev_pagemap(pte_pfn(pte), *pgmap);
551 if (*pgmap)
552 page = pte_page(pte);
553 else
554 goto no_page;
555 } else if (unlikely(!page)) {
556 if (flags & FOLL_DUMP) {
557 /* Avoid special (like zero) pages in core dumps */
558 page = ERR_PTR(-EFAULT);
559 goto out;
560 }
561
562 if (is_zero_pfn(pte_pfn(pte))) {
563 page = pte_page(pte);
564 } else {
565 ret = follow_pfn_pte(vma, address, ptep, flags);
566 page = ERR_PTR(ret);
567 goto out;
568 }
569 }
570
571 /* try_grab_page() does nothing unless FOLL_GET or FOLL_PIN is set. */
572 if (unlikely(!try_grab_page(page, flags))) {
573 page = ERR_PTR(-ENOMEM);
574 goto out;
575 }
576 /*
577 * We need to make the page accessible if and only if we are going
578 * to access its content (the FOLL_PIN case). Please see
579 * Documentation/core-api/pin_user_pages.rst for details.
580 */
581 if (flags & FOLL_PIN) {
582 ret = arch_make_page_accessible(page);
583 if (ret) {
584 unpin_user_page(page);
585 page = ERR_PTR(ret);
586 goto out;
587 }
588 }
589 if (flags & FOLL_TOUCH) {
590 if ((flags & FOLL_WRITE) &&
591 !pte_dirty(pte) && !PageDirty(page))
592 set_page_dirty(page);
593 /*
594 * pte_mkyoung() would be more correct here, but atomic care
595 * is needed to avoid losing the dirty bit: it is easier to use
596 * mark_page_accessed().
597 */
598 mark_page_accessed(page);
599 }
600 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
601 /* Do not mlock pte-mapped THP */
602 if (PageTransCompound(page))
603 goto out;
604
605 /*
606 * The preliminary mapping check is mainly to avoid the
607 * pointless overhead of lock_page on the ZERO_PAGE
608 * which might bounce very badly if there is contention.
609 *
610 * If the page is already locked, we don't need to
611 * handle it now - vmscan will handle it later if and
612 * when it attempts to reclaim the page.
613 */
614 if (page->mapping && trylock_page(page)) {
615 lru_add_drain(); /* push cached pages to LRU */
616 /*
617 * Because we lock page here, and migration is
618 * blocked by the pte's page reference, and we
619 * know the page is still mapped, we don't even
620 * need to check for file-cache page truncation.
621 */
622 mlock_vma_page(page);
623 unlock_page(page);
624 }
625 }
626 out:
627 pte_unmap_unlock(ptep, ptl);
628 return page;
629 no_page:
630 pte_unmap_unlock(ptep, ptl);
631 if (!pte_none(pte))
632 return NULL;
633 return no_page_table(vma, flags);
634 }
635
636 static struct page *follow_pmd_mask(struct vm_area_struct *vma,
637 unsigned long address, pud_t *pudp,
638 unsigned int flags,
639 struct follow_page_context *ctx)
640 {
641 pmd_t *pmd, pmdval;
642 spinlock_t *ptl;
643 struct page *page;
644 struct mm_struct *mm = vma->vm_mm;
645
646 pmd = pmd_offset(pudp, address);
647 /*
648 * The READ_ONCE() will stabilize the pmdval in a register or
649 * on the stack so that it will stop changing under the code.
650 */
651 pmdval = READ_ONCE(*pmd);
652 if (pmd_none(pmdval))
653 return no_page_table(vma, flags);
654 if (pmd_huge(pmdval) && is_vm_hugetlb_page(vma)) {
655 page = follow_huge_pmd(mm, address, pmd, flags);
656 if (page)
657 return page;
658 return no_page_table(vma, flags);
659 }
660 if (is_hugepd(__hugepd(pmd_val(pmdval)))) {
661 page = follow_huge_pd(vma, address,
662 __hugepd(pmd_val(pmdval)), flags,
663 PMD_SHIFT);
664 if (page)
665 return page;
666 return no_page_table(vma, flags);
667 }
668 retry:
669 if (!pmd_present(pmdval)) {
670 if (likely(!(flags & FOLL_MIGRATION)))
671 return no_page_table(vma, flags);
672 VM_BUG_ON(thp_migration_supported() &&
673 !is_pmd_migration_entry(pmdval));
674 if (is_pmd_migration_entry(pmdval))
675 pmd_migration_entry_wait(mm, pmd);
676 pmdval = READ_ONCE(*pmd);
677 /*
678 * MADV_DONTNEED may convert the pmd to null because
679 * mmap_lock is held in read mode
680 */
681 if (pmd_none(pmdval))
682 return no_page_table(vma, flags);
683 goto retry;
684 }
685 if (pmd_devmap(pmdval)) {
686 ptl = pmd_lock(mm, pmd);
687 page = follow_devmap_pmd(vma, address, pmd, flags, &ctx->pgmap);
688 spin_unlock(ptl);
689 if (page)
690 return page;
691 }
692 if (likely(!pmd_trans_huge(pmdval)))
693 return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
694
695 if ((flags & FOLL_NUMA) && pmd_protnone(pmdval))
696 return no_page_table(vma, flags);
697
698 retry_locked:
699 ptl = pmd_lock(mm, pmd);
700 if (unlikely(pmd_none(*pmd))) {
701 spin_unlock(ptl);
702 return no_page_table(vma, flags);
703 }
704 if (unlikely(!pmd_present(*pmd))) {
705 spin_unlock(ptl);
706 if (likely(!(flags & FOLL_MIGRATION)))
707 return no_page_table(vma, flags);
708 pmd_migration_entry_wait(mm, pmd);
709 goto retry_locked;
710 }
711 if (unlikely(!pmd_trans_huge(*pmd))) {
712 spin_unlock(ptl);
713 return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
714 }
715 if (flags & FOLL_SPLIT_PMD) {
716 int ret;
717 page = pmd_page(*pmd);
718 if (is_huge_zero_page(page)) {
719 spin_unlock(ptl);
720 ret = 0;
721 split_huge_pmd(vma, pmd, address);
722 if (pmd_trans_unstable(pmd))
723 ret = -EBUSY;
724 } else {
725 spin_unlock(ptl);
726 split_huge_pmd(vma, pmd, address);
727 ret = pte_alloc(mm, pmd) ? -ENOMEM : 0;
728 }
729
730 return ret ? ERR_PTR(ret) :
731 follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
732 }
733 page = follow_trans_huge_pmd(vma, address, pmd, flags);
734 spin_unlock(ptl);
735 ctx->page_mask = HPAGE_PMD_NR - 1;
736 return page;
737 }
738
739 static struct page *follow_pud_mask(struct vm_area_struct *vma,
740 unsigned long address, p4d_t *p4dp,
741 unsigned int flags,
742 struct follow_page_context *ctx)
743 {
744 pud_t *pud;
745 spinlock_t *ptl;
746 struct page *page;
747 struct mm_struct *mm = vma->vm_mm;
748
749 pud = pud_offset(p4dp, address);
750 if (pud_none(*pud))
751 return no_page_table(vma, flags);
752 if (pud_huge(*pud) && is_vm_hugetlb_page(vma)) {
753 page = follow_huge_pud(mm, address, pud, flags);
754 if (page)
755 return page;
756 return no_page_table(vma, flags);
757 }
758 if (is_hugepd(__hugepd(pud_val(*pud)))) {
759 page = follow_huge_pd(vma, address,
760 __hugepd(pud_val(*pud)), flags,
761 PUD_SHIFT);
762 if (page)
763 return page;
764 return no_page_table(vma, flags);
765 }
766 if (pud_devmap(*pud)) {
767 ptl = pud_lock(mm, pud);
768 page = follow_devmap_pud(vma, address, pud, flags, &ctx->pgmap);
769 spin_unlock(ptl);
770 if (page)
771 return page;
772 }
773 if (unlikely(pud_bad(*pud)))
774 return no_page_table(vma, flags);
775
776 return follow_pmd_mask(vma, address, pud, flags, ctx);
777 }
778
779 static struct page *follow_p4d_mask(struct vm_area_struct *vma,
780 unsigned long address, pgd_t *pgdp,
781 unsigned int flags,
782 struct follow_page_context *ctx)
783 {
784 p4d_t *p4d;
785 struct page *page;
786
787 p4d = p4d_offset(pgdp, address);
788 if (p4d_none(*p4d))
789 return no_page_table(vma, flags);
790 BUILD_BUG_ON(p4d_huge(*p4d));
791 if (unlikely(p4d_bad(*p4d)))
792 return no_page_table(vma, flags);
793
794 if (is_hugepd(__hugepd(p4d_val(*p4d)))) {
795 page = follow_huge_pd(vma, address,
796 __hugepd(p4d_val(*p4d)), flags,
797 P4D_SHIFT);
798 if (page)
799 return page;
800 return no_page_table(vma, flags);
801 }
802 return follow_pud_mask(vma, address, p4d, flags, ctx);
803 }
804
805 /**
806 * follow_page_mask - look up a page descriptor from a user-virtual address
807 * @vma: vm_area_struct mapping @address
808 * @address: virtual address to look up
809 * @flags: flags modifying lookup behaviour
810 * @ctx: contains dev_pagemap for %ZONE_DEVICE memory pinning and a
811 * pointer to output page_mask
812 *
813 * @flags can have FOLL_ flags set, defined in <linux/mm.h>
814 *
815 * When getting pages from ZONE_DEVICE memory, the @ctx->pgmap caches
816 * the device's dev_pagemap metadata to avoid repeating expensive lookups.
817 *
818 * On output, the @ctx->page_mask is set according to the size of the page.
819 *
820 * Return: the mapped (struct page *), %NULL if no mapping exists, or
821 * an error pointer if there is a mapping to something not represented
822 * by a page descriptor (see also vm_normal_page()).
823 */
824 static struct page *follow_page_mask(struct vm_area_struct *vma,
825 unsigned long address, unsigned int flags,
826 struct follow_page_context *ctx)
827 {
828 pgd_t *pgd;
829 struct page *page;
830 struct mm_struct *mm = vma->vm_mm;
831
832 ctx->page_mask = 0;
833
834 /* make this handle hugepd */
835 page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
836 if (!IS_ERR(page)) {
837 WARN_ON_ONCE(flags & (FOLL_GET | FOLL_PIN));
838 return page;
839 }
840
841 pgd = pgd_offset(mm, address);
842
843 if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
844 return no_page_table(vma, flags);
845
846 if (pgd_huge(*pgd)) {
847 page = follow_huge_pgd(mm, address, pgd, flags);
848 if (page)
849 return page;
850 return no_page_table(vma, flags);
851 }
852 if (is_hugepd(__hugepd(pgd_val(*pgd)))) {
853 page = follow_huge_pd(vma, address,
854 __hugepd(pgd_val(*pgd)), flags,
855 PGDIR_SHIFT);
856 if (page)
857 return page;
858 return no_page_table(vma, flags);
859 }
860
861 return follow_p4d_mask(vma, address, pgd, flags, ctx);
862 }
863
864 struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
865 unsigned int foll_flags)
866 {
867 struct follow_page_context ctx = { NULL };
868 struct page *page;
869
870 if (vma_is_secretmem(vma))
871 return NULL;
872
873 page = follow_page_mask(vma, address, foll_flags, &ctx);
874 if (ctx.pgmap)
875 put_dev_pagemap(ctx.pgmap);
876 return page;
877 }
878
879 static int get_gate_page(struct mm_struct *mm, unsigned long address,
880 unsigned int gup_flags, struct vm_area_struct **vma,
881 struct page **page)
882 {
883 pgd_t *pgd;
884 p4d_t *p4d;
885 pud_t *pud;
886 pmd_t *pmd;
887 pte_t *pte;
888 int ret = -EFAULT;
889
890 /* user gate pages are read-only */
891 if (gup_flags & FOLL_WRITE)
892 return -EFAULT;
893 if (address > TASK_SIZE)
894 pgd = pgd_offset_k(address);
895 else
896 pgd = pgd_offset_gate(mm, address);
897 if (pgd_none(*pgd))
898 return -EFAULT;
899 p4d = p4d_offset(pgd, address);
900 if (p4d_none(*p4d))
901 return -EFAULT;
902 pud = pud_offset(p4d, address);
903 if (pud_none(*pud))
904 return -EFAULT;
905 pmd = pmd_offset(pud, address);
906 if (!pmd_present(*pmd))
907 return -EFAULT;
908 VM_BUG_ON(pmd_trans_huge(*pmd));
909 pte = pte_offset_map(pmd, address);
910 if (pte_none(*pte))
911 goto unmap;
912 *vma = get_gate_vma(mm);
913 if (!page)
914 goto out;
915 *page = vm_normal_page(*vma, address, *pte);
916 if (!*page) {
917 if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte)))
918 goto unmap;
919 *page = pte_page(*pte);
920 }
921 if (unlikely(!try_grab_page(*page, gup_flags))) {
922 ret = -ENOMEM;
923 goto unmap;
924 }
925 out:
926 ret = 0;
927 unmap:
928 pte_unmap(pte);
929 return ret;
930 }
931
932 /*
933 * mmap_lock must be held on entry. If @locked != NULL and *@flags
934 * does not include FOLL_NOWAIT, the mmap_lock may be released. If it
935 * is, *@locked will be set to 0 and -EBUSY returned.
936 */
937 static int faultin_page(struct vm_area_struct *vma,
938 unsigned long address, unsigned int *flags, int *locked)
939 {
940 unsigned int fault_flags = 0;
941 vm_fault_t ret;
942
943 /* mlock all present pages, but do not fault in new pages */
944 if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
945 return -ENOENT;
946 if (*flags & FOLL_WRITE)
947 fault_flags |= FAULT_FLAG_WRITE;
948 if (*flags & FOLL_REMOTE)
949 fault_flags |= FAULT_FLAG_REMOTE;
950 if (locked)
951 fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
952 if (*flags & FOLL_NOWAIT)
953 fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
954 if (*flags & FOLL_TRIED) {
955 /*
956 * Note: FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_TRIED
957 * can co-exist
958 */
959 fault_flags |= FAULT_FLAG_TRIED;
960 }
961
962 ret = handle_mm_fault(vma, address, fault_flags, NULL);
963 if (ret & VM_FAULT_ERROR) {
964 int err = vm_fault_to_errno(ret, *flags);
965
966 if (err)
967 return err;
968 BUG();
969 }
970
971 if (ret & VM_FAULT_RETRY) {
972 if (locked && !(fault_flags & FAULT_FLAG_RETRY_NOWAIT))
973 *locked = 0;
974 return -EBUSY;
975 }
976
977 /*
978 * The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when
979 * necessary, even if maybe_mkwrite decided not to set pte_write. We
980 * can thus safely do subsequent page lookups as if they were reads.
981 * But only do so when looping for pte_write is futile: in some cases
982 * userspace may also be wanting to write to the gotten user page,
983 * which a read fault here might prevent (a readonly page might get
984 * reCOWed by userspace write).
985 */
986 if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE))
987 *flags |= FOLL_COW;
988 return 0;
989 }
990
991 static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
992 {
993 vm_flags_t vm_flags = vma->vm_flags;
994 int write = (gup_flags & FOLL_WRITE);
995 int foreign = (gup_flags & FOLL_REMOTE);
996
997 if (vm_flags & (VM_IO | VM_PFNMAP))
998 return -EFAULT;
999
1000 if (gup_flags & FOLL_ANON && !vma_is_anonymous(vma))
1001 return -EFAULT;
1002
1003 if ((gup_flags & FOLL_LONGTERM) && vma_is_fsdax(vma))
1004 return -EOPNOTSUPP;
1005
1006 if (vma_is_secretmem(vma))
1007 return -EFAULT;
1008
1009 if (write) {
1010 if (!(vm_flags & VM_WRITE)) {
1011 if (!(gup_flags & FOLL_FORCE))
1012 return -EFAULT;
1013 /*
1014 * We used to let the write,force case do COW in a
1015 * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could
1016 * set a breakpoint in a read-only mapping of an
1017 * executable, without corrupting the file (yet only
1018 * when that file had been opened for writing!).
1019 * Anon pages in shared mappings are surprising: now
1020 * just reject it.
1021 */
1022 if (!is_cow_mapping(vm_flags))
1023 return -EFAULT;
1024 }
1025 } else if (!(vm_flags & VM_READ)) {
1026 if (!(gup_flags & FOLL_FORCE))
1027 return -EFAULT;
1028 /*
1029 * Is there actually any vma we can reach here which does not
1030 * have VM_MAYREAD set?
1031 */
1032 if (!(vm_flags & VM_MAYREAD))
1033 return -EFAULT;
1034 }
1035 /*
1036 * gups are always data accesses, not instruction
1037 * fetches, so execute=false here
1038 */
1039 if (!arch_vma_access_permitted(vma, write, false, foreign))
1040 return -EFAULT;
1041 return 0;
1042 }
1043
1044 /**
1045 * __get_user_pages() - pin user pages in memory
1046 * @mm: mm_struct of target mm
1047 * @start: starting user address
1048 * @nr_pages: number of pages from start to pin
1049 * @gup_flags: flags modifying pin behaviour
1050 * @pages: array that receives pointers to the pages pinned.
1051 * Should be at least nr_pages long. Or NULL, if caller
1052 * only intends to ensure the pages are faulted in.
1053 * @vmas: array of pointers to vmas corresponding to each page.
1054 * Or NULL if the caller does not require them.
1055 * @locked: whether we're still with the mmap_lock held
1056 *
1057 * Returns either number of pages pinned (which may be less than the
1058 * number requested), or an error. Details about the return value:
1059 *
1060 * -- If nr_pages is 0, returns 0.
1061 * -- If nr_pages is >0, but no pages were pinned, returns -errno.
1062 * -- If nr_pages is >0, and some pages were pinned, returns the number of
1063 * pages pinned. Again, this may be less than nr_pages.
1064 * -- 0 return value is possible when the fault would need to be retried.
1065 *
1066 * The caller is responsible for releasing returned @pages, via put_page().
1067 *
1068 * @vmas are valid only as long as mmap_lock is held.
1069 *
1070 * Must be called with mmap_lock held. It may be released. See below.
1071 *
1072 * __get_user_pages walks a process's page tables and takes a reference to
1073 * each struct page that each user address corresponds to at a given
1074 * instant. That is, it takes the page that would be accessed if a user
1075 * thread accesses the given user virtual address at that instant.
1076 *
1077 * This does not guarantee that the page exists in the user mappings when
1078 * __get_user_pages returns, and there may even be a completely different
1079 * page there in some cases (eg. if mmapped pagecache has been invalidated
1080 * and subsequently re faulted). However it does guarantee that the page
1081 * won't be freed completely. And mostly callers simply care that the page
1082 * contains data that was valid *at some point in time*. Typically, an IO
1083 * or similar operation cannot guarantee anything stronger anyway because
1084 * locks can't be held over the syscall boundary.
1085 *
1086 * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
1087 * the page is written to, set_page_dirty (or set_page_dirty_lock, as
1088 * appropriate) must be called after the page is finished with, and
1089 * before put_page is called.
1090 *
1091 * If @locked != NULL, *@locked will be set to 0 when mmap_lock is
1092 * released by an up_read(). That can happen if @gup_flags does not
1093 * have FOLL_NOWAIT.
1094 *
1095 * A caller using such a combination of @locked and @gup_flags
1096 * must therefore hold the mmap_lock for reading only, and recognize
1097 * when it's been released. Otherwise, it must be held for either
1098 * reading or writing and will not be released.
1099 *
1100 * In most cases, get_user_pages or get_user_pages_fast should be used
1101 * instead of __get_user_pages. __get_user_pages should be used only if
1102 * you need some special @gup_flags.
1103 */
1104 static long __get_user_pages(struct mm_struct *mm,
1105 unsigned long start, unsigned long nr_pages,
1106 unsigned int gup_flags, struct page **pages,
1107 struct vm_area_struct **vmas, int *locked)
1108 {
1109 long ret = 0, i = 0;
1110 struct vm_area_struct *vma = NULL;
1111 struct follow_page_context ctx = { NULL };
1112
1113 if (!nr_pages)
1114 return 0;
1115
1116 start = untagged_addr(start);
1117
1118 VM_BUG_ON(!!pages != !!(gup_flags & (FOLL_GET | FOLL_PIN)));
1119
1120 /*
1121 * If FOLL_FORCE is set then do not force a full fault as the hinting
1122 * fault information is unrelated to the reference behaviour of a task
1123 * using the address space
1124 */
1125 if (!(gup_flags & FOLL_FORCE))
1126 gup_flags |= FOLL_NUMA;
1127
1128 do {
1129 struct page *page;
1130 unsigned int foll_flags = gup_flags;
1131 unsigned int page_increm;
1132
1133 /* first iteration or cross vma bound */
1134 if (!vma || start >= vma->vm_end) {
1135 vma = find_extend_vma(mm, start);
1136 if (!vma && in_gate_area(mm, start)) {
1137 ret = get_gate_page(mm, start & PAGE_MASK,
1138 gup_flags, &vma,
1139 pages ? &pages[i] : NULL);
1140 if (ret)
1141 goto out;
1142 ctx.page_mask = 0;
1143 goto next_page;
1144 }
1145
1146 if (!vma) {
1147 ret = -EFAULT;
1148 goto out;
1149 }
1150 ret = check_vma_flags(vma, gup_flags);
1151 if (ret)
1152 goto out;
1153
1154 if (is_vm_hugetlb_page(vma)) {
1155 i = follow_hugetlb_page(mm, vma, pages, vmas,
1156 &start, &nr_pages, i,
1157 gup_flags, locked);
1158 if (locked && *locked == 0) {
1159 /*
1160 * We've got a VM_FAULT_RETRY
1161 * and we've lost mmap_lock.
1162 * We must stop here.
1163 */
1164 BUG_ON(gup_flags & FOLL_NOWAIT);
1165 goto out;
1166 }
1167 continue;
1168 }
1169 }
1170 retry:
1171 /*
1172 * If we have a pending SIGKILL, don't keep faulting pages and
1173 * potentially allocating memory.
1174 */
1175 if (fatal_signal_pending(current)) {
1176 ret = -EINTR;
1177 goto out;
1178 }
1179 cond_resched();
1180
1181 page = follow_page_mask(vma, start, foll_flags, &ctx);
1182 if (!page) {
1183 ret = faultin_page(vma, start, &foll_flags, locked);
1184 switch (ret) {
1185 case 0:
1186 goto retry;
1187 case -EBUSY:
1188 ret = 0;
1189 fallthrough;
1190 case -EFAULT:
1191 case -ENOMEM:
1192 case -EHWPOISON:
1193 goto out;
1194 case -ENOENT:
1195 goto next_page;
1196 }
1197 BUG();
1198 } else if (PTR_ERR(page) == -EEXIST) {
1199 /*
1200 * Proper page table entry exists, but no corresponding
1201 * struct page.
1202 */
1203 goto next_page;
1204 } else if (IS_ERR(page)) {
1205 ret = PTR_ERR(page);
1206 goto out;
1207 }
1208 if (pages) {
1209 pages[i] = page;
1210 flush_anon_page(vma, page, start);
1211 flush_dcache_page(page);
1212 ctx.page_mask = 0;
1213 }
1214 next_page:
1215 if (vmas) {
1216 vmas[i] = vma;
1217 ctx.page_mask = 0;
1218 }
1219 page_increm = 1 + (~(start >> PAGE_SHIFT) & ctx.page_mask);
1220 if (page_increm > nr_pages)
1221 page_increm = nr_pages;
1222 i += page_increm;
1223 start += page_increm * PAGE_SIZE;
1224 nr_pages -= page_increm;
1225 } while (nr_pages);
1226 out:
1227 if (ctx.pgmap)
1228 put_dev_pagemap(ctx.pgmap);
1229 return i ? i : ret;
1230 }
1231
1232 static bool vma_permits_fault(struct vm_area_struct *vma,
1233 unsigned int fault_flags)
1234 {
1235 bool write = !!(fault_flags & FAULT_FLAG_WRITE);
1236 bool foreign = !!(fault_flags & FAULT_FLAG_REMOTE);
1237 vm_flags_t vm_flags = write ? VM_WRITE : VM_READ;
1238
1239 if (!(vm_flags & vma->vm_flags))
1240 return false;
1241
1242 /*
1243 * The architecture might have a hardware protection
1244 * mechanism other than read/write that can deny access.
1245 *
1246 * gup always represents data access, not instruction
1247 * fetches, so execute=false here:
1248 */
1249 if (!arch_vma_access_permitted(vma, write, false, foreign))
1250 return false;
1251
1252 return true;
1253 }
1254
1255 /**
1256 * fixup_user_fault() - manually resolve a user page fault
1257 * @mm: mm_struct of target mm
1258 * @address: user address
1259 * @fault_flags:flags to pass down to handle_mm_fault()
1260 * @unlocked: did we unlock the mmap_lock while retrying, maybe NULL if caller
1261 * does not allow retry. If NULL, the caller must guarantee
1262 * that fault_flags does not contain FAULT_FLAG_ALLOW_RETRY.
1263 *
1264 * This is meant to be called in the specific scenario where for locking reasons
1265 * we try to access user memory in atomic context (within a pagefault_disable()
1266 * section), this returns -EFAULT, and we want to resolve the user fault before
1267 * trying again.
1268 *
1269 * Typically this is meant to be used by the futex code.
1270 *
1271 * The main difference with get_user_pages() is that this function will
1272 * unconditionally call handle_mm_fault() which will in turn perform all the
1273 * necessary SW fixup of the dirty and young bits in the PTE, while
1274 * get_user_pages() only guarantees to update these in the struct page.
1275 *
1276 * This is important for some architectures where those bits also gate the
1277 * access permission to the page because they are maintained in software. On
1278 * such architectures, gup() will not be enough to make a subsequent access
1279 * succeed.
1280 *
1281 * This function will not return with an unlocked mmap_lock. So it has not the
1282 * same semantics wrt the @mm->mmap_lock as does filemap_fault().
1283 */
1284 int fixup_user_fault(struct mm_struct *mm,
1285 unsigned long address, unsigned int fault_flags,
1286 bool *unlocked)
1287 {
1288 struct vm_area_struct *vma;
1289 vm_fault_t ret;
1290
1291 address = untagged_addr(address);
1292
1293 if (unlocked)
1294 fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
1295
1296 retry:
1297 vma = find_extend_vma(mm, address);
1298 if (!vma || address < vma->vm_start)
1299 return -EFAULT;
1300
1301 if (!vma_permits_fault(vma, fault_flags))
1302 return -EFAULT;
1303
1304 if ((fault_flags & FAULT_FLAG_KILLABLE) &&
1305 fatal_signal_pending(current))
1306 return -EINTR;
1307
1308 ret = handle_mm_fault(vma, address, fault_flags, NULL);
1309 if (ret & VM_FAULT_ERROR) {
1310 int err = vm_fault_to_errno(ret, 0);
1311
1312 if (err)
1313 return err;
1314 BUG();
1315 }
1316
1317 if (ret & VM_FAULT_RETRY) {
1318 mmap_read_lock(mm);
1319 *unlocked = true;
1320 fault_flags |= FAULT_FLAG_TRIED;
1321 goto retry;
1322 }
1323
1324 return 0;
1325 }
1326 EXPORT_SYMBOL_GPL(fixup_user_fault);
1327
1328 /*
1329 * Please note that this function, unlike __get_user_pages will not
1330 * return 0 for nr_pages > 0 without FOLL_NOWAIT
1331 */
1332 static __always_inline long __get_user_pages_locked(struct mm_struct *mm,
1333 unsigned long start,
1334 unsigned long nr_pages,
1335 struct page **pages,
1336 struct vm_area_struct **vmas,
1337 int *locked,
1338 unsigned int flags)
1339 {
1340 long ret, pages_done;
1341 bool lock_dropped;
1342
1343 if (locked) {
1344 /* if VM_FAULT_RETRY can be returned, vmas become invalid */
1345 BUG_ON(vmas);
1346 /* check caller initialized locked */
1347 BUG_ON(*locked != 1);
1348 }
1349
1350 if (flags & FOLL_PIN)
1351 mm_set_has_pinned_flag(&mm->flags);
1352
1353 /*
1354 * FOLL_PIN and FOLL_GET are mutually exclusive. Traditional behavior
1355 * is to set FOLL_GET if the caller wants pages[] filled in (but has
1356 * carelessly failed to specify FOLL_GET), so keep doing that, but only
1357 * for FOLL_GET, not for the newer FOLL_PIN.
1358 *
1359 * FOLL_PIN always expects pages to be non-null, but no need to assert
1360 * that here, as any failures will be obvious enough.
1361 */
1362 if (pages && !(flags & FOLL_PIN))
1363 flags |= FOLL_GET;
1364
1365 pages_done = 0;
1366 lock_dropped = false;
1367 for (;;) {
1368 ret = __get_user_pages(mm, start, nr_pages, flags, pages,
1369 vmas, locked);
1370 if (!locked)
1371 /* VM_FAULT_RETRY couldn't trigger, bypass */
1372 return ret;
1373
1374 /* VM_FAULT_RETRY cannot return errors */
1375 if (!*locked) {
1376 BUG_ON(ret < 0);
1377 BUG_ON(ret >= nr_pages);
1378 }
1379
1380 if (ret > 0) {
1381 nr_pages -= ret;
1382 pages_done += ret;
1383 if (!nr_pages)
1384 break;
1385 }
1386 if (*locked) {
1387 /*
1388 * VM_FAULT_RETRY didn't trigger or it was a
1389 * FOLL_NOWAIT.
1390 */
1391 if (!pages_done)
1392 pages_done = ret;
1393 break;
1394 }
1395 /*
1396 * VM_FAULT_RETRY triggered, so seek to the faulting offset.
1397 * For the prefault case (!pages) we only update counts.
1398 */
1399 if (likely(pages))
1400 pages += ret;
1401 start += ret << PAGE_SHIFT;
1402 lock_dropped = true;
1403
1404 retry:
1405 /*
1406 * Repeat on the address that fired VM_FAULT_RETRY
1407 * with both FAULT_FLAG_ALLOW_RETRY and
1408 * FAULT_FLAG_TRIED. Note that GUP can be interrupted
1409 * by fatal signals, so we need to check it before we
1410 * start trying again otherwise it can loop forever.
1411 */
1412
1413 if (fatal_signal_pending(current)) {
1414 if (!pages_done)
1415 pages_done = -EINTR;
1416 break;
1417 }
1418
1419 ret = mmap_read_lock_killable(mm);
1420 if (ret) {
1421 BUG_ON(ret > 0);
1422 if (!pages_done)
1423 pages_done = ret;
1424 break;
1425 }
1426
1427 *locked = 1;
1428 ret = __get_user_pages(mm, start, 1, flags | FOLL_TRIED,
1429 pages, NULL, locked);
1430 if (!*locked) {
1431 /* Continue to retry until we succeeded */
1432 BUG_ON(ret != 0);
1433 goto retry;
1434 }
1435 if (ret != 1) {
1436 BUG_ON(ret > 1);
1437 if (!pages_done)
1438 pages_done = ret;
1439 break;
1440 }
1441 nr_pages--;
1442 pages_done++;
1443 if (!nr_pages)
1444 break;
1445 if (likely(pages))
1446 pages++;
1447 start += PAGE_SIZE;
1448 }
1449 if (lock_dropped && *locked) {
1450 /*
1451 * We must let the caller know we temporarily dropped the lock
1452 * and so the critical section protected by it was lost.
1453 */
1454 mmap_read_unlock(mm);
1455 *locked = 0;
1456 }
1457 return pages_done;
1458 }
1459
1460 /**
1461 * populate_vma_page_range() - populate a range of pages in the vma.
1462 * @vma: target vma
1463 * @start: start address
1464 * @end: end address
1465 * @locked: whether the mmap_lock is still held
1466 *
1467 * This takes care of mlocking the pages too if VM_LOCKED is set.
1468 *
1469 * Return either number of pages pinned in the vma, or a negative error
1470 * code on error.
1471 *
1472 * vma->vm_mm->mmap_lock must be held.
1473 *
1474 * If @locked is NULL, it may be held for read or write and will
1475 * be unperturbed.
1476 *
1477 * If @locked is non-NULL, it must held for read only and may be
1478 * released. If it's released, *@locked will be set to 0.
1479 */
1480 long populate_vma_page_range(struct vm_area_struct *vma,
1481 unsigned long start, unsigned long end, int *locked)
1482 {
1483 struct mm_struct *mm = vma->vm_mm;
1484 unsigned long nr_pages = (end - start) / PAGE_SIZE;
1485 int gup_flags;
1486
1487 VM_BUG_ON(!PAGE_ALIGNED(start));
1488 VM_BUG_ON(!PAGE_ALIGNED(end));
1489 VM_BUG_ON_VMA(start < vma->vm_start, vma);
1490 VM_BUG_ON_VMA(end > vma->vm_end, vma);
1491 mmap_assert_locked(mm);
1492
1493 gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK;
1494 if (vma->vm_flags & VM_LOCKONFAULT)
1495 gup_flags &= ~FOLL_POPULATE;
1496 /*
1497 * We want to touch writable mappings with a write fault in order
1498 * to break COW, except for shared mappings because these don't COW
1499 * and we would not want to dirty them for nothing.
1500 */
1501 if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
1502 gup_flags |= FOLL_WRITE;
1503
1504 /*
1505 * We want mlock to succeed for regions that have any permissions
1506 * other than PROT_NONE.
1507 */
1508 if (vma_is_accessible(vma))
1509 gup_flags |= FOLL_FORCE;
1510
1511 /*
1512 * We made sure addr is within a VMA, so the following will
1513 * not result in a stack expansion that recurses back here.
1514 */
1515 return __get_user_pages(mm, start, nr_pages, gup_flags,
1516 NULL, NULL, locked);
1517 }
1518
1519 /*
1520 * faultin_vma_page_range() - populate (prefault) page tables inside the
1521 * given VMA range readable/writable
1522 *
1523 * This takes care of mlocking the pages, too, if VM_LOCKED is set.
1524 *
1525 * @vma: target vma
1526 * @start: start address
1527 * @end: end address
1528 * @write: whether to prefault readable or writable
1529 * @locked: whether the mmap_lock is still held
1530 *
1531 * Returns either number of processed pages in the vma, or a negative error
1532 * code on error (see __get_user_pages()).
1533 *
1534 * vma->vm_mm->mmap_lock must be held. The range must be page-aligned and
1535 * covered by the VMA.
1536 *
1537 * If @locked is NULL, it may be held for read or write and will be unperturbed.
1538 *
1539 * If @locked is non-NULL, it must held for read only and may be released. If
1540 * it's released, *@locked will be set to 0.
1541 */
1542 long faultin_vma_page_range(struct vm_area_struct *vma, unsigned long start,
1543 unsigned long end, bool write, int *locked)
1544 {
1545 struct mm_struct *mm = vma->vm_mm;
1546 unsigned long nr_pages = (end - start) / PAGE_SIZE;
1547 int gup_flags;
1548
1549 VM_BUG_ON(!PAGE_ALIGNED(start));
1550 VM_BUG_ON(!PAGE_ALIGNED(end));
1551 VM_BUG_ON_VMA(start < vma->vm_start, vma);
1552 VM_BUG_ON_VMA(end > vma->vm_end, vma);
1553 mmap_assert_locked(mm);
1554
1555 /*
1556 * FOLL_TOUCH: Mark page accessed and thereby young; will also mark
1557 * the page dirty with FOLL_WRITE -- which doesn't make a
1558 * difference with !FOLL_FORCE, because the page is writable
1559 * in the page table.
1560 * FOLL_HWPOISON: Return -EHWPOISON instead of -EFAULT when we hit
1561 * a poisoned page.
1562 * FOLL_POPULATE: Always populate memory with VM_LOCKONFAULT.
1563 * !FOLL_FORCE: Require proper access permissions.
1564 */
1565 gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK | FOLL_HWPOISON;
1566 if (write)
1567 gup_flags |= FOLL_WRITE;
1568
1569 /*
1570 * We want to report -EINVAL instead of -EFAULT for any permission
1571 * problems or incompatible mappings.
1572 */
1573 if (check_vma_flags(vma, gup_flags))
1574 return -EINVAL;
1575
1576 return __get_user_pages(mm, start, nr_pages, gup_flags,
1577 NULL, NULL, locked);
1578 }
1579
1580 /*
1581 * __mm_populate - populate and/or mlock pages within a range of address space.
1582 *
1583 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
1584 * flags. VMAs must be already marked with the desired vm_flags, and
1585 * mmap_lock must not be held.
1586 */
1587 int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
1588 {
1589 struct mm_struct *mm = current->mm;
1590 unsigned long end, nstart, nend;
1591 struct vm_area_struct *vma = NULL;
1592 int locked = 0;
1593 long ret = 0;
1594
1595 end = start + len;
1596
1597 for (nstart = start; nstart < end; nstart = nend) {
1598 /*
1599 * We want to fault in pages for [nstart; end) address range.
1600 * Find first corresponding VMA.
1601 */
1602 if (!locked) {
1603 locked = 1;
1604 mmap_read_lock(mm);
1605 vma = find_vma(mm, nstart);
1606 } else if (nstart >= vma->vm_end)
1607 vma = vma->vm_next;
1608 if (!vma || vma->vm_start >= end)
1609 break;
1610 /*
1611 * Set [nstart; nend) to intersection of desired address
1612 * range with the first VMA. Also, skip undesirable VMA types.
1613 */
1614 nend = min(end, vma->vm_end);
1615 if (vma->vm_flags & (VM_IO | VM_PFNMAP))
1616 continue;
1617 if (nstart < vma->vm_start)
1618 nstart = vma->vm_start;
1619 /*
1620 * Now fault in a range of pages. populate_vma_page_range()
1621 * double checks the vma flags, so that it won't mlock pages
1622 * if the vma was already munlocked.
1623 */
1624 ret = populate_vma_page_range(vma, nstart, nend, &locked);
1625 if (ret < 0) {
1626 if (ignore_errors) {
1627 ret = 0;
1628 continue; /* continue at next VMA */
1629 }
1630 break;
1631 }
1632 nend = nstart + ret * PAGE_SIZE;
1633 ret = 0;
1634 }
1635 if (locked)
1636 mmap_read_unlock(mm);
1637 return ret; /* 0 or negative error code */
1638 }
1639 #else /* CONFIG_MMU */
1640 static long __get_user_pages_locked(struct mm_struct *mm, unsigned long start,
1641 unsigned long nr_pages, struct page **pages,
1642 struct vm_area_struct **vmas, int *locked,
1643 unsigned int foll_flags)
1644 {
1645 struct vm_area_struct *vma;
1646 unsigned long vm_flags;
1647 long i;
1648
1649 /* calculate required read or write permissions.
1650 * If FOLL_FORCE is set, we only require the "MAY" flags.
1651 */
1652 vm_flags = (foll_flags & FOLL_WRITE) ?
1653 (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
1654 vm_flags &= (foll_flags & FOLL_FORCE) ?
1655 (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
1656
1657 for (i = 0; i < nr_pages; i++) {
1658 vma = find_vma(mm, start);
1659 if (!vma)
1660 goto finish_or_fault;
1661
1662 /* protect what we can, including chardevs */
1663 if ((vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
1664 !(vm_flags & vma->vm_flags))
1665 goto finish_or_fault;
1666
1667 if (pages) {
1668 pages[i] = virt_to_page(start);
1669 if (pages[i])
1670 get_page(pages[i]);
1671 }
1672 if (vmas)
1673 vmas[i] = vma;
1674 start = (start + PAGE_SIZE) & PAGE_MASK;
1675 }
1676
1677 return i;
1678
1679 finish_or_fault:
1680 return i ? : -EFAULT;
1681 }
1682 #endif /* !CONFIG_MMU */
1683
1684 /**
1685 * get_dump_page() - pin user page in memory while writing it to core dump
1686 * @addr: user address
1687 *
1688 * Returns struct page pointer of user page pinned for dump,
1689 * to be freed afterwards by put_page().
1690 *
1691 * Returns NULL on any kind of failure - a hole must then be inserted into
1692 * the corefile, to preserve alignment with its headers; and also returns
1693 * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
1694 * allowing a hole to be left in the corefile to save disk space.
1695 *
1696 * Called without mmap_lock (takes and releases the mmap_lock by itself).
1697 */
1698 #ifdef CONFIG_ELF_CORE
1699 struct page *get_dump_page(unsigned long addr)
1700 {
1701 struct mm_struct *mm = current->mm;
1702 struct page *page;
1703 int locked = 1;
1704 int ret;
1705
1706 if (mmap_read_lock_killable(mm))
1707 return NULL;
1708 ret = __get_user_pages_locked(mm, addr, 1, &page, NULL, &locked,
1709 FOLL_FORCE | FOLL_DUMP | FOLL_GET);
1710 if (locked)
1711 mmap_read_unlock(mm);
1712 return (ret == 1) ? page : NULL;
1713 }
1714 #endif /* CONFIG_ELF_CORE */
1715
1716 #ifdef CONFIG_MIGRATION
1717 /*
1718 * Check whether all pages are pinnable, if so return number of pages. If some
1719 * pages are not pinnable, migrate them, and unpin all pages. Return zero if
1720 * pages were migrated, or if some pages were not successfully isolated.
1721 * Return negative error if migration fails.
1722 */
1723 static long check_and_migrate_movable_pages(unsigned long nr_pages,
1724 struct page **pages,
1725 unsigned int gup_flags)
1726 {
1727 unsigned long i;
1728 unsigned long isolation_error_count = 0;
1729 bool drain_allow = true;
1730 LIST_HEAD(movable_page_list);
1731 long ret = 0;
1732 struct page *prev_head = NULL;
1733 struct page *head;
1734 struct migration_target_control mtc = {
1735 .nid = NUMA_NO_NODE,
1736 .gfp_mask = GFP_USER | __GFP_NOWARN,
1737 };
1738
1739 for (i = 0; i < nr_pages; i++) {
1740 head = compound_head(pages[i]);
1741 if (head == prev_head)
1742 continue;
1743 prev_head = head;
1744 /*
1745 * If we get a movable page, since we are going to be pinning
1746 * these entries, try to move them out if possible.
1747 */
1748 if (!is_pinnable_page(head)) {
1749 if (PageHuge(head)) {
1750 if (!isolate_huge_page(head, &movable_page_list))
1751 isolation_error_count++;
1752 } else {
1753 if (!PageLRU(head) && drain_allow) {
1754 lru_add_drain_all();
1755 drain_allow = false;
1756 }
1757
1758 if (isolate_lru_page(head)) {
1759 isolation_error_count++;
1760 continue;
1761 }
1762 list_add_tail(&head->lru, &movable_page_list);
1763 mod_node_page_state(page_pgdat(head),
1764 NR_ISOLATED_ANON +
1765 page_is_file_lru(head),
1766 thp_nr_pages(head));
1767 }
1768 }
1769 }
1770
1771 /*
1772 * If list is empty, and no isolation errors, means that all pages are
1773 * in the correct zone.
1774 */
1775 if (list_empty(&movable_page_list) && !isolation_error_count)
1776 return nr_pages;
1777
1778 if (gup_flags & FOLL_PIN) {
1779 unpin_user_pages(pages, nr_pages);
1780 } else {
1781 for (i = 0; i < nr_pages; i++)
1782 put_page(pages[i]);
1783 }
1784 if (!list_empty(&movable_page_list)) {
1785 ret = migrate_pages(&movable_page_list, alloc_migration_target,
1786 NULL, (unsigned long)&mtc, MIGRATE_SYNC,
1787 MR_LONGTERM_PIN, NULL);
1788 if (ret && !list_empty(&movable_page_list))
1789 putback_movable_pages(&movable_page_list);
1790 }
1791
1792 return ret > 0 ? -ENOMEM : ret;
1793 }
1794 #else
1795 static long check_and_migrate_movable_pages(unsigned long nr_pages,
1796 struct page **pages,
1797 unsigned int gup_flags)
1798 {
1799 return nr_pages;
1800 }
1801 #endif /* CONFIG_MIGRATION */
1802
1803 /*
1804 * __gup_longterm_locked() is a wrapper for __get_user_pages_locked which
1805 * allows us to process the FOLL_LONGTERM flag.
1806 */
1807 static long __gup_longterm_locked(struct mm_struct *mm,
1808 unsigned long start,
1809 unsigned long nr_pages,
1810 struct page **pages,
1811 struct vm_area_struct **vmas,
1812 unsigned int gup_flags)
1813 {
1814 unsigned int flags;
1815 long rc;
1816
1817 if (!(gup_flags & FOLL_LONGTERM))
1818 return __get_user_pages_locked(mm, start, nr_pages, pages, vmas,
1819 NULL, gup_flags);
1820 flags = memalloc_pin_save();
1821 do {
1822 rc = __get_user_pages_locked(mm, start, nr_pages, pages, vmas,
1823 NULL, gup_flags);
1824 if (rc <= 0)
1825 break;
1826 rc = check_and_migrate_movable_pages(rc, pages, gup_flags);
1827 } while (!rc);
1828 memalloc_pin_restore(flags);
1829
1830 return rc;
1831 }
1832
1833 static bool is_valid_gup_flags(unsigned int gup_flags)
1834 {
1835 /*
1836 * FOLL_PIN must only be set internally by the pin_user_pages*() APIs,
1837 * never directly by the caller, so enforce that with an assertion:
1838 */
1839 if (WARN_ON_ONCE(gup_flags & FOLL_PIN))
1840 return false;
1841 /*
1842 * FOLL_PIN is a prerequisite to FOLL_LONGTERM. Another way of saying
1843 * that is, FOLL_LONGTERM is a specific case, more restrictive case of
1844 * FOLL_PIN.
1845 */
1846 if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
1847 return false;
1848
1849 return true;
1850 }
1851
1852 #ifdef CONFIG_MMU
1853 static long __get_user_pages_remote(struct mm_struct *mm,
1854 unsigned long start, unsigned long nr_pages,
1855 unsigned int gup_flags, struct page **pages,
1856 struct vm_area_struct **vmas, int *locked)
1857 {
1858 /*
1859 * Parts of FOLL_LONGTERM behavior are incompatible with
1860 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
1861 * vmas. However, this only comes up if locked is set, and there are
1862 * callers that do request FOLL_LONGTERM, but do not set locked. So,
1863 * allow what we can.
1864 */
1865 if (gup_flags & FOLL_LONGTERM) {
1866 if (WARN_ON_ONCE(locked))
1867 return -EINVAL;
1868 /*
1869 * This will check the vmas (even if our vmas arg is NULL)
1870 * and return -ENOTSUPP if DAX isn't allowed in this case:
1871 */
1872 return __gup_longterm_locked(mm, start, nr_pages, pages,
1873 vmas, gup_flags | FOLL_TOUCH |
1874 FOLL_REMOTE);
1875 }
1876
1877 return __get_user_pages_locked(mm, start, nr_pages, pages, vmas,
1878 locked,
1879 gup_flags | FOLL_TOUCH | FOLL_REMOTE);
1880 }
1881
1882 /**
1883 * get_user_pages_remote() - pin user pages in memory
1884 * @mm: mm_struct of target mm
1885 * @start: starting user address
1886 * @nr_pages: number of pages from start to pin
1887 * @gup_flags: flags modifying lookup behaviour
1888 * @pages: array that receives pointers to the pages pinned.
1889 * Should be at least nr_pages long. Or NULL, if caller
1890 * only intends to ensure the pages are faulted in.
1891 * @vmas: array of pointers to vmas corresponding to each page.
1892 * Or NULL if the caller does not require them.
1893 * @locked: pointer to lock flag indicating whether lock is held and
1894 * subsequently whether VM_FAULT_RETRY functionality can be
1895 * utilised. Lock must initially be held.
1896 *
1897 * Returns either number of pages pinned (which may be less than the
1898 * number requested), or an error. Details about the return value:
1899 *
1900 * -- If nr_pages is 0, returns 0.
1901 * -- If nr_pages is >0, but no pages were pinned, returns -errno.
1902 * -- If nr_pages is >0, and some pages were pinned, returns the number of
1903 * pages pinned. Again, this may be less than nr_pages.
1904 *
1905 * The caller is responsible for releasing returned @pages, via put_page().
1906 *
1907 * @vmas are valid only as long as mmap_lock is held.
1908 *
1909 * Must be called with mmap_lock held for read or write.
1910 *
1911 * get_user_pages_remote walks a process's page tables and takes a reference
1912 * to each struct page that each user address corresponds to at a given
1913 * instant. That is, it takes the page that would be accessed if a user
1914 * thread accesses the given user virtual address at that instant.
1915 *
1916 * This does not guarantee that the page exists in the user mappings when
1917 * get_user_pages_remote returns, and there may even be a completely different
1918 * page there in some cases (eg. if mmapped pagecache has been invalidated
1919 * and subsequently re faulted). However it does guarantee that the page
1920 * won't be freed completely. And mostly callers simply care that the page
1921 * contains data that was valid *at some point in time*. Typically, an IO
1922 * or similar operation cannot guarantee anything stronger anyway because
1923 * locks can't be held over the syscall boundary.
1924 *
1925 * If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page
1926 * is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must
1927 * be called after the page is finished with, and before put_page is called.
1928 *
1929 * get_user_pages_remote is typically used for fewer-copy IO operations,
1930 * to get a handle on the memory by some means other than accesses
1931 * via the user virtual addresses. The pages may be submitted for
1932 * DMA to devices or accessed via their kernel linear mapping (via the
1933 * kmap APIs). Care should be taken to use the correct cache flushing APIs.
1934 *
1935 * See also get_user_pages_fast, for performance critical applications.
1936 *
1937 * get_user_pages_remote should be phased out in favor of
1938 * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
1939 * should use get_user_pages_remote because it cannot pass
1940 * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
1941 */
1942 long get_user_pages_remote(struct mm_struct *mm,
1943 unsigned long start, unsigned long nr_pages,
1944 unsigned int gup_flags, struct page **pages,
1945 struct vm_area_struct **vmas, int *locked)
1946 {
1947 if (!is_valid_gup_flags(gup_flags))
1948 return -EINVAL;
1949
1950 return __get_user_pages_remote(mm, start, nr_pages, gup_flags,
1951 pages, vmas, locked);
1952 }
1953 EXPORT_SYMBOL(get_user_pages_remote);
1954
1955 #else /* CONFIG_MMU */
1956 long get_user_pages_remote(struct mm_struct *mm,
1957 unsigned long start, unsigned long nr_pages,
1958 unsigned int gup_flags, struct page **pages,
1959 struct vm_area_struct **vmas, int *locked)
1960 {
1961 return 0;
1962 }
1963
1964 static long __get_user_pages_remote(struct mm_struct *mm,
1965 unsigned long start, unsigned long nr_pages,
1966 unsigned int gup_flags, struct page **pages,
1967 struct vm_area_struct **vmas, int *locked)
1968 {
1969 return 0;
1970 }
1971 #endif /* !CONFIG_MMU */
1972
1973 /**
1974 * get_user_pages() - pin user pages in memory
1975 * @start: starting user address
1976 * @nr_pages: number of pages from start to pin
1977 * @gup_flags: flags modifying lookup behaviour
1978 * @pages: array that receives pointers to the pages pinned.
1979 * Should be at least nr_pages long. Or NULL, if caller
1980 * only intends to ensure the pages are faulted in.
1981 * @vmas: array of pointers to vmas corresponding to each page.
1982 * Or NULL if the caller does not require them.
1983 *
1984 * This is the same as get_user_pages_remote(), just with a less-flexible
1985 * calling convention where we assume that the mm being operated on belongs to
1986 * the current task, and doesn't allow passing of a locked parameter. We also
1987 * obviously don't pass FOLL_REMOTE in here.
1988 */
1989 long get_user_pages(unsigned long start, unsigned long nr_pages,
1990 unsigned int gup_flags, struct page **pages,
1991 struct vm_area_struct **vmas)
1992 {
1993 if (!is_valid_gup_flags(gup_flags))
1994 return -EINVAL;
1995
1996 return __gup_longterm_locked(current->mm, start, nr_pages,
1997 pages, vmas, gup_flags | FOLL_TOUCH);
1998 }
1999 EXPORT_SYMBOL(get_user_pages);
2000
2001 /**
2002 * get_user_pages_locked() - variant of get_user_pages()
2003 *
2004 * @start: starting user address
2005 * @nr_pages: number of pages from start to pin
2006 * @gup_flags: flags modifying lookup behaviour
2007 * @pages: array that receives pointers to the pages pinned.
2008 * Should be at least nr_pages long. Or NULL, if caller
2009 * only intends to ensure the pages are faulted in.
2010 * @locked: pointer to lock flag indicating whether lock is held and
2011 * subsequently whether VM_FAULT_RETRY functionality can be
2012 * utilised. Lock must initially be held.
2013 *
2014 * It is suitable to replace the form:
2015 *
2016 * mmap_read_lock(mm);
2017 * do_something()
2018 * get_user_pages(mm, ..., pages, NULL);
2019 * mmap_read_unlock(mm);
2020 *
2021 * to:
2022 *
2023 * int locked = 1;
2024 * mmap_read_lock(mm);
2025 * do_something()
2026 * get_user_pages_locked(mm, ..., pages, &locked);
2027 * if (locked)
2028 * mmap_read_unlock(mm);
2029 *
2030 * We can leverage the VM_FAULT_RETRY functionality in the page fault
2031 * paths better by using either get_user_pages_locked() or
2032 * get_user_pages_unlocked().
2033 *
2034 */
2035 long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
2036 unsigned int gup_flags, struct page **pages,
2037 int *locked)
2038 {
2039 /*
2040 * FIXME: Current FOLL_LONGTERM behavior is incompatible with
2041 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
2042 * vmas. As there are no users of this flag in this call we simply
2043 * disallow this option for now.
2044 */
2045 if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
2046 return -EINVAL;
2047 /*
2048 * FOLL_PIN must only be set internally by the pin_user_pages*() APIs,
2049 * never directly by the caller, so enforce that:
2050 */
2051 if (WARN_ON_ONCE(gup_flags & FOLL_PIN))
2052 return -EINVAL;
2053
2054 return __get_user_pages_locked(current->mm, start, nr_pages,
2055 pages, NULL, locked,
2056 gup_flags | FOLL_TOUCH);
2057 }
2058 EXPORT_SYMBOL(get_user_pages_locked);
2059
2060 /*
2061 * get_user_pages_unlocked() is suitable to replace the form:
2062 *
2063 * mmap_read_lock(mm);
2064 * get_user_pages(mm, ..., pages, NULL);
2065 * mmap_read_unlock(mm);
2066 *
2067 * with:
2068 *
2069 * get_user_pages_unlocked(mm, ..., pages);
2070 *
2071 * It is functionally equivalent to get_user_pages_fast so
2072 * get_user_pages_fast should be used instead if specific gup_flags
2073 * (e.g. FOLL_FORCE) are not required.
2074 */
2075 long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
2076 struct page **pages, unsigned int gup_flags)
2077 {
2078 struct mm_struct *mm = current->mm;
2079 int locked = 1;
2080 long ret;
2081
2082 /*
2083 * FIXME: Current FOLL_LONGTERM behavior is incompatible with
2084 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
2085 * vmas. As there are no users of this flag in this call we simply
2086 * disallow this option for now.
2087 */
2088 if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
2089 return -EINVAL;
2090
2091 mmap_read_lock(mm);
2092 ret = __get_user_pages_locked(mm, start, nr_pages, pages, NULL,
2093 &locked, gup_flags | FOLL_TOUCH);
2094 if (locked)
2095 mmap_read_unlock(mm);
2096 return ret;
2097 }
2098 EXPORT_SYMBOL(get_user_pages_unlocked);
2099
2100 /*
2101 * Fast GUP
2102 *
2103 * get_user_pages_fast attempts to pin user pages by walking the page
2104 * tables directly and avoids taking locks. Thus the walker needs to be
2105 * protected from page table pages being freed from under it, and should
2106 * block any THP splits.
2107 *
2108 * One way to achieve this is to have the walker disable interrupts, and
2109 * rely on IPIs from the TLB flushing code blocking before the page table
2110 * pages are freed. This is unsuitable for architectures that do not need
2111 * to broadcast an IPI when invalidating TLBs.
2112 *
2113 * Another way to achieve this is to batch up page table containing pages
2114 * belonging to more than one mm_user, then rcu_sched a callback to free those
2115 * pages. Disabling interrupts will allow the fast_gup walker to both block
2116 * the rcu_sched callback, and an IPI that we broadcast for splitting THPs
2117 * (which is a relatively rare event). The code below adopts this strategy.
2118 *
2119 * Before activating this code, please be aware that the following assumptions
2120 * are currently made:
2121 *
2122 * *) Either MMU_GATHER_RCU_TABLE_FREE is enabled, and tlb_remove_table() is used to
2123 * free pages containing page tables or TLB flushing requires IPI broadcast.
2124 *
2125 * *) ptes can be read atomically by the architecture.
2126 *
2127 * *) access_ok is sufficient to validate userspace address ranges.
2128 *
2129 * The last two assumptions can be relaxed by the addition of helper functions.
2130 *
2131 * This code is based heavily on the PowerPC implementation by Nick Piggin.
2132 */
2133 #ifdef CONFIG_HAVE_FAST_GUP
2134
2135 static void __maybe_unused undo_dev_pagemap(int *nr, int nr_start,
2136 unsigned int flags,
2137 struct page **pages)
2138 {
2139 while ((*nr) - nr_start) {
2140 struct page *page = pages[--(*nr)];
2141
2142 ClearPageReferenced(page);
2143 if (flags & FOLL_PIN)
2144 unpin_user_page(page);
2145 else
2146 put_page(page);
2147 }
2148 }
2149
2150 #ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
2151 static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
2152 unsigned int flags, struct page **pages, int *nr)
2153 {
2154 struct dev_pagemap *pgmap = NULL;
2155 int nr_start = *nr, ret = 0;
2156 pte_t *ptep, *ptem;
2157
2158 ptem = ptep = pte_offset_map(&pmd, addr);
2159 do {
2160 pte_t pte = ptep_get_lockless(ptep);
2161 struct page *head, *page;
2162
2163 /*
2164 * Similar to the PMD case below, NUMA hinting must take slow
2165 * path using the pte_protnone check.
2166 */
2167 if (pte_protnone(pte))
2168 goto pte_unmap;
2169
2170 if (!pte_access_permitted(pte, flags & FOLL_WRITE))
2171 goto pte_unmap;
2172
2173 if (pte_devmap(pte)) {
2174 if (unlikely(flags & FOLL_LONGTERM))
2175 goto pte_unmap;
2176
2177 pgmap = get_dev_pagemap(pte_pfn(pte), pgmap);
2178 if (unlikely(!pgmap)) {
2179 undo_dev_pagemap(nr, nr_start, flags, pages);
2180 goto pte_unmap;
2181 }
2182 } else if (pte_special(pte))
2183 goto pte_unmap;
2184
2185 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
2186 page = pte_page(pte);
2187
2188 head = try_grab_compound_head(page, 1, flags);
2189 if (!head)
2190 goto pte_unmap;
2191
2192 if (unlikely(page_is_secretmem(page))) {
2193 put_compound_head(head, 1, flags);
2194 goto pte_unmap;
2195 }
2196
2197 if (unlikely(pte_val(pte) != pte_val(*ptep))) {
2198 put_compound_head(head, 1, flags);
2199 goto pte_unmap;
2200 }
2201
2202 VM_BUG_ON_PAGE(compound_head(page) != head, page);
2203
2204 /*
2205 * We need to make the page accessible if and only if we are
2206 * going to access its content (the FOLL_PIN case). Please
2207 * see Documentation/core-api/pin_user_pages.rst for
2208 * details.
2209 */
2210 if (flags & FOLL_PIN) {
2211 ret = arch_make_page_accessible(page);
2212 if (ret) {
2213 unpin_user_page(page);
2214 goto pte_unmap;
2215 }
2216 }
2217 SetPageReferenced(page);
2218 pages[*nr] = page;
2219 (*nr)++;
2220
2221 } while (ptep++, addr += PAGE_SIZE, addr != end);
2222
2223 ret = 1;
2224
2225 pte_unmap:
2226 if (pgmap)
2227 put_dev_pagemap(pgmap);
2228 pte_unmap(ptem);
2229 return ret;
2230 }
2231 #else
2232
2233 /*
2234 * If we can't determine whether or not a pte is special, then fail immediately
2235 * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
2236 * to be special.
2237 *
2238 * For a futex to be placed on a THP tail page, get_futex_key requires a
2239 * get_user_pages_fast_only implementation that can pin pages. Thus it's still
2240 * useful to have gup_huge_pmd even if we can't operate on ptes.
2241 */
2242 static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
2243 unsigned int flags, struct page **pages, int *nr)
2244 {
2245 return 0;
2246 }
2247 #endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
2248
2249 #if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
2250 static int __gup_device_huge(unsigned long pfn, unsigned long addr,
2251 unsigned long end, unsigned int flags,
2252 struct page **pages, int *nr)
2253 {
2254 int nr_start = *nr;
2255 struct dev_pagemap *pgmap = NULL;
2256 int ret = 1;
2257
2258 do {
2259 struct page *page = pfn_to_page(pfn);
2260
2261 pgmap = get_dev_pagemap(pfn, pgmap);
2262 if (unlikely(!pgmap)) {
2263 undo_dev_pagemap(nr, nr_start, flags, pages);
2264 ret = 0;
2265 break;
2266 }
2267 SetPageReferenced(page);
2268 pages[*nr] = page;
2269 if (unlikely(!try_grab_page(page, flags))) {
2270 undo_dev_pagemap(nr, nr_start, flags, pages);
2271 ret = 0;
2272 break;
2273 }
2274 (*nr)++;
2275 pfn++;
2276 } while (addr += PAGE_SIZE, addr != end);
2277
2278 put_dev_pagemap(pgmap);
2279 return ret;
2280 }
2281
2282 static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
2283 unsigned long end, unsigned int flags,
2284 struct page **pages, int *nr)
2285 {
2286 unsigned long fault_pfn;
2287 int nr_start = *nr;
2288
2289 fault_pfn = pmd_pfn(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
2290 if (!__gup_device_huge(fault_pfn, addr, end, flags, pages, nr))
2291 return 0;
2292
2293 if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
2294 undo_dev_pagemap(nr, nr_start, flags, pages);
2295 return 0;
2296 }
2297 return 1;
2298 }
2299
2300 static int __gup_device_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
2301 unsigned long end, unsigned int flags,
2302 struct page **pages, int *nr)
2303 {
2304 unsigned long fault_pfn;
2305 int nr_start = *nr;
2306
2307 fault_pfn = pud_pfn(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
2308 if (!__gup_device_huge(fault_pfn, addr, end, flags, pages, nr))
2309 return 0;
2310
2311 if (unlikely(pud_val(orig) != pud_val(*pudp))) {
2312 undo_dev_pagemap(nr, nr_start, flags, pages);
2313 return 0;
2314 }
2315 return 1;
2316 }
2317 #else
2318 static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
2319 unsigned long end, unsigned int flags,
2320 struct page **pages, int *nr)
2321 {
2322 BUILD_BUG();
2323 return 0;
2324 }
2325
2326 static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr,
2327 unsigned long end, unsigned int flags,
2328 struct page **pages, int *nr)
2329 {
2330 BUILD_BUG();
2331 return 0;
2332 }
2333 #endif
2334
2335 static int record_subpages(struct page *page, unsigned long addr,
2336 unsigned long end, struct page **pages)
2337 {
2338 int nr;
2339
2340 for (nr = 0; addr != end; addr += PAGE_SIZE)
2341 pages[nr++] = page++;
2342
2343 return nr;
2344 }
2345
2346 #ifdef CONFIG_ARCH_HAS_HUGEPD
2347 static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end,
2348 unsigned long sz)
2349 {
2350 unsigned long __boundary = (addr + sz) & ~(sz-1);
2351 return (__boundary - 1 < end - 1) ? __boundary : end;
2352 }
2353
2354 static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
2355 unsigned long end, unsigned int flags,
2356 struct page **pages, int *nr)
2357 {
2358 unsigned long pte_end;
2359 struct page *head, *page;
2360 pte_t pte;
2361 int refs;
2362
2363 pte_end = (addr + sz) & ~(sz-1);
2364 if (pte_end < end)
2365 end = pte_end;
2366
2367 pte = huge_ptep_get(ptep);
2368
2369 if (!pte_access_permitted(pte, flags & FOLL_WRITE))
2370 return 0;
2371
2372 /* hugepages are never "special" */
2373 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
2374
2375 head = pte_page(pte);
2376 page = head + ((addr & (sz-1)) >> PAGE_SHIFT);
2377 refs = record_subpages(page, addr, end, pages + *nr);
2378
2379 head = try_grab_compound_head(head, refs, flags);
2380 if (!head)
2381 return 0;
2382
2383 if (unlikely(pte_val(pte) != pte_val(*ptep))) {
2384 put_compound_head(head, refs, flags);
2385 return 0;
2386 }
2387
2388 *nr += refs;
2389 SetPageReferenced(head);
2390 return 1;
2391 }
2392
2393 static int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
2394 unsigned int pdshift, unsigned long end, unsigned int flags,
2395 struct page **pages, int *nr)
2396 {
2397 pte_t *ptep;
2398 unsigned long sz = 1UL << hugepd_shift(hugepd);
2399 unsigned long next;
2400
2401 ptep = hugepte_offset(hugepd, addr, pdshift);
2402 do {
2403 next = hugepte_addr_end(addr, end, sz);
2404 if (!gup_hugepte(ptep, sz, addr, end, flags, pages, nr))
2405 return 0;
2406 } while (ptep++, addr = next, addr != end);
2407
2408 return 1;
2409 }
2410 #else
2411 static inline int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
2412 unsigned int pdshift, unsigned long end, unsigned int flags,
2413 struct page **pages, int *nr)
2414 {
2415 return 0;
2416 }
2417 #endif /* CONFIG_ARCH_HAS_HUGEPD */
2418
2419 static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
2420 unsigned long end, unsigned int flags,
2421 struct page **pages, int *nr)
2422 {
2423 struct page *head, *page;
2424 int refs;
2425
2426 if (!pmd_access_permitted(orig, flags & FOLL_WRITE))
2427 return 0;
2428
2429 if (pmd_devmap(orig)) {
2430 if (unlikely(flags & FOLL_LONGTERM))
2431 return 0;
2432 return __gup_device_huge_pmd(orig, pmdp, addr, end, flags,
2433 pages, nr);
2434 }
2435
2436 page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
2437 refs = record_subpages(page, addr, end, pages + *nr);
2438
2439 head = try_grab_compound_head(pmd_page(orig), refs, flags);
2440 if (!head)
2441 return 0;
2442
2443 if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
2444 put_compound_head(head, refs, flags);
2445 return 0;
2446 }
2447
2448 *nr += refs;
2449 SetPageReferenced(head);
2450 return 1;
2451 }
2452
2453 static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
2454 unsigned long end, unsigned int flags,
2455 struct page **pages, int *nr)
2456 {
2457 struct page *head, *page;
2458 int refs;
2459
2460 if (!pud_access_permitted(orig, flags & FOLL_WRITE))
2461 return 0;
2462
2463 if (pud_devmap(orig)) {
2464 if (unlikely(flags & FOLL_LONGTERM))
2465 return 0;
2466 return __gup_device_huge_pud(orig, pudp, addr, end, flags,
2467 pages, nr);
2468 }
2469
2470 page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
2471 refs = record_subpages(page, addr, end, pages + *nr);
2472
2473 head = try_grab_compound_head(pud_page(orig), refs, flags);
2474 if (!head)
2475 return 0;
2476
2477 if (unlikely(pud_val(orig) != pud_val(*pudp))) {
2478 put_compound_head(head, refs, flags);
2479 return 0;
2480 }
2481
2482 *nr += refs;
2483 SetPageReferenced(head);
2484 return 1;
2485 }
2486
2487 static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
2488 unsigned long end, unsigned int flags,
2489 struct page **pages, int *nr)
2490 {
2491 int refs;
2492 struct page *head, *page;
2493
2494 if (!pgd_access_permitted(orig, flags & FOLL_WRITE))
2495 return 0;
2496
2497 BUILD_BUG_ON(pgd_devmap(orig));
2498
2499 page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
2500 refs = record_subpages(page, addr, end, pages + *nr);
2501
2502 head = try_grab_compound_head(pgd_page(orig), refs, flags);
2503 if (!head)
2504 return 0;
2505
2506 if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
2507 put_compound_head(head, refs, flags);
2508 return 0;
2509 }
2510
2511 *nr += refs;
2512 SetPageReferenced(head);
2513 return 1;
2514 }
2515
2516 static int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr, unsigned long end,
2517 unsigned int flags, struct page **pages, int *nr)
2518 {
2519 unsigned long next;
2520 pmd_t *pmdp;
2521
2522 pmdp = pmd_offset_lockless(pudp, pud, addr);
2523 do {
2524 pmd_t pmd = READ_ONCE(*pmdp);
2525
2526 next = pmd_addr_end(addr, end);
2527 if (!pmd_present(pmd))
2528 return 0;
2529
2530 if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd) ||
2531 pmd_devmap(pmd))) {
2532 /*
2533 * NUMA hinting faults need to be handled in the GUP
2534 * slowpath for accounting purposes and so that they
2535 * can be serialised against THP migration.
2536 */
2537 if (pmd_protnone(pmd))
2538 return 0;
2539
2540 if (!gup_huge_pmd(pmd, pmdp, addr, next, flags,
2541 pages, nr))
2542 return 0;
2543
2544 } else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) {
2545 /*
2546 * architecture have different format for hugetlbfs
2547 * pmd format and THP pmd format
2548 */
2549 if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr,
2550 PMD_SHIFT, next, flags, pages, nr))
2551 return 0;
2552 } else if (!gup_pte_range(pmd, addr, next, flags, pages, nr))
2553 return 0;
2554 } while (pmdp++, addr = next, addr != end);
2555
2556 return 1;
2557 }
2558
2559 static int gup_pud_range(p4d_t *p4dp, p4d_t p4d, unsigned long addr, unsigned long end,
2560 unsigned int flags, struct page **pages, int *nr)
2561 {
2562 unsigned long next;
2563 pud_t *pudp;
2564
2565 pudp = pud_offset_lockless(p4dp, p4d, addr);
2566 do {
2567 pud_t pud = READ_ONCE(*pudp);
2568
2569 next = pud_addr_end(addr, end);
2570 if (unlikely(!pud_present(pud)))
2571 return 0;
2572 if (unlikely(pud_huge(pud))) {
2573 if (!gup_huge_pud(pud, pudp, addr, next, flags,
2574 pages, nr))
2575 return 0;
2576 } else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) {
2577 if (!gup_huge_pd(__hugepd(pud_val(pud)), addr,
2578 PUD_SHIFT, next, flags, pages, nr))
2579 return 0;
2580 } else if (!gup_pmd_range(pudp, pud, addr, next, flags, pages, nr))
2581 return 0;
2582 } while (pudp++, addr = next, addr != end);
2583
2584 return 1;
2585 }
2586
2587 static int gup_p4d_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr, unsigned long end,
2588 unsigned int flags, struct page **pages, int *nr)
2589 {
2590 unsigned long next;
2591 p4d_t *p4dp;
2592
2593 p4dp = p4d_offset_lockless(pgdp, pgd, addr);
2594 do {
2595 p4d_t p4d = READ_ONCE(*p4dp);
2596
2597 next = p4d_addr_end(addr, end);
2598 if (p4d_none(p4d))
2599 return 0;
2600 BUILD_BUG_ON(p4d_huge(p4d));
2601 if (unlikely(is_hugepd(__hugepd(p4d_val(p4d))))) {
2602 if (!gup_huge_pd(__hugepd(p4d_val(p4d)), addr,
2603 P4D_SHIFT, next, flags, pages, nr))
2604 return 0;
2605 } else if (!gup_pud_range(p4dp, p4d, addr, next, flags, pages, nr))
2606 return 0;
2607 } while (p4dp++, addr = next, addr != end);
2608
2609 return 1;
2610 }
2611
2612 static void gup_pgd_range(unsigned long addr, unsigned long end,
2613 unsigned int flags, struct page **pages, int *nr)
2614 {
2615 unsigned long next;
2616 pgd_t *pgdp;
2617
2618 pgdp = pgd_offset(current->mm, addr);
2619 do {
2620 pgd_t pgd = READ_ONCE(*pgdp);
2621
2622 next = pgd_addr_end(addr, end);
2623 if (pgd_none(pgd))
2624 return;
2625 if (unlikely(pgd_huge(pgd))) {
2626 if (!gup_huge_pgd(pgd, pgdp, addr, next, flags,
2627 pages, nr))
2628 return;
2629 } else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) {
2630 if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
2631 PGDIR_SHIFT, next, flags, pages, nr))
2632 return;
2633 } else if (!gup_p4d_range(pgdp, pgd, addr, next, flags, pages, nr))
2634 return;
2635 } while (pgdp++, addr = next, addr != end);
2636 }
2637 #else
2638 static inline void gup_pgd_range(unsigned long addr, unsigned long end,
2639 unsigned int flags, struct page **pages, int *nr)
2640 {
2641 }
2642 #endif /* CONFIG_HAVE_FAST_GUP */
2643
2644 #ifndef gup_fast_permitted
2645 /*
2646 * Check if it's allowed to use get_user_pages_fast_only() for the range, or
2647 * we need to fall back to the slow version:
2648 */
2649 static bool gup_fast_permitted(unsigned long start, unsigned long end)
2650 {
2651 return true;
2652 }
2653 #endif
2654
2655 static int __gup_longterm_unlocked(unsigned long start, int nr_pages,
2656 unsigned int gup_flags, struct page **pages)
2657 {
2658 int ret;
2659
2660 /*
2661 * FIXME: FOLL_LONGTERM does not work with
2662 * get_user_pages_unlocked() (see comments in that function)
2663 */
2664 if (gup_flags & FOLL_LONGTERM) {
2665 mmap_read_lock(current->mm);
2666 ret = __gup_longterm_locked(current->mm,
2667 start, nr_pages,
2668 pages, NULL, gup_flags);
2669 mmap_read_unlock(current->mm);
2670 } else {
2671 ret = get_user_pages_unlocked(start, nr_pages,
2672 pages, gup_flags);
2673 }
2674
2675 return ret;
2676 }
2677
2678 static unsigned long lockless_pages_from_mm(unsigned long start,
2679 unsigned long end,
2680 unsigned int gup_flags,
2681 struct page **pages)
2682 {
2683 unsigned long flags;
2684 int nr_pinned = 0;
2685 unsigned seq;
2686
2687 if (!IS_ENABLED(CONFIG_HAVE_FAST_GUP) ||
2688 !gup_fast_permitted(start, end))
2689 return 0;
2690
2691 if (gup_flags & FOLL_PIN) {
2692 seq = raw_read_seqcount(&current->mm->write_protect_seq);
2693 if (seq & 1)
2694 return 0;
2695 }
2696
2697 /*
2698 * Disable interrupts. The nested form is used, in order to allow full,
2699 * general purpose use of this routine.
2700 *
2701 * With interrupts disabled, we block page table pages from being freed
2702 * from under us. See struct mmu_table_batch comments in
2703 * include/asm-generic/tlb.h for more details.
2704 *
2705 * We do not adopt an rcu_read_lock() here as we also want to block IPIs
2706 * that come from THPs splitting.
2707 */
2708 local_irq_save(flags);
2709 gup_pgd_range(start, end, gup_flags, pages, &nr_pinned);
2710 local_irq_restore(flags);
2711
2712 /*
2713 * When pinning pages for DMA there could be a concurrent write protect
2714 * from fork() via copy_page_range(), in this case always fail fast GUP.
2715 */
2716 if (gup_flags & FOLL_PIN) {
2717 if (read_seqcount_retry(&current->mm->write_protect_seq, seq)) {
2718 unpin_user_pages(pages, nr_pinned);
2719 return 0;
2720 }
2721 }
2722 return nr_pinned;
2723 }
2724
2725 static int internal_get_user_pages_fast(unsigned long start,
2726 unsigned long nr_pages,
2727 unsigned int gup_flags,
2728 struct page **pages)
2729 {
2730 unsigned long len, end;
2731 unsigned long nr_pinned;
2732 int ret;
2733
2734 if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM |
2735 FOLL_FORCE | FOLL_PIN | FOLL_GET |
2736 FOLL_FAST_ONLY)))
2737 return -EINVAL;
2738
2739 if (gup_flags & FOLL_PIN)
2740 mm_set_has_pinned_flag(&current->mm->flags);
2741
2742 if (!(gup_flags & FOLL_FAST_ONLY))
2743 might_lock_read(&current->mm->mmap_lock);
2744
2745 start = untagged_addr(start) & PAGE_MASK;
2746 len = nr_pages << PAGE_SHIFT;
2747 if (check_add_overflow(start, len, &end))
2748 return 0;
2749 if (unlikely(!access_ok((void __user *)start, len)))
2750 return -EFAULT;
2751
2752 nr_pinned = lockless_pages_from_mm(start, end, gup_flags, pages);
2753 if (nr_pinned == nr_pages || gup_flags & FOLL_FAST_ONLY)
2754 return nr_pinned;
2755
2756 /* Slow path: try to get the remaining pages with get_user_pages */
2757 start += nr_pinned << PAGE_SHIFT;
2758 pages += nr_pinned;
2759 ret = __gup_longterm_unlocked(start, nr_pages - nr_pinned, gup_flags,
2760 pages);
2761 if (ret < 0) {
2762 /*
2763 * The caller has to unpin the pages we already pinned so
2764 * returning -errno is not an option
2765 */
2766 if (nr_pinned)
2767 return nr_pinned;
2768 return ret;
2769 }
2770 return ret + nr_pinned;
2771 }
2772
2773 /**
2774 * get_user_pages_fast_only() - pin user pages in memory
2775 * @start: starting user address
2776 * @nr_pages: number of pages from start to pin
2777 * @gup_flags: flags modifying pin behaviour
2778 * @pages: array that receives pointers to the pages pinned.
2779 * Should be at least nr_pages long.
2780 *
2781 * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
2782 * the regular GUP.
2783 * Note a difference with get_user_pages_fast: this always returns the
2784 * number of pages pinned, 0 if no pages were pinned.
2785 *
2786 * If the architecture does not support this function, simply return with no
2787 * pages pinned.
2788 *
2789 * Careful, careful! COW breaking can go either way, so a non-write
2790 * access can get ambiguous page results. If you call this function without
2791 * 'write' set, you'd better be sure that you're ok with that ambiguity.
2792 */
2793 int get_user_pages_fast_only(unsigned long start, int nr_pages,
2794 unsigned int gup_flags, struct page **pages)
2795 {
2796 int nr_pinned;
2797 /*
2798 * Internally (within mm/gup.c), gup fast variants must set FOLL_GET,
2799 * because gup fast is always a "pin with a +1 page refcount" request.
2800 *
2801 * FOLL_FAST_ONLY is required in order to match the API description of
2802 * this routine: no fall back to regular ("slow") GUP.
2803 */
2804 gup_flags |= FOLL_GET | FOLL_FAST_ONLY;
2805
2806 nr_pinned = internal_get_user_pages_fast(start, nr_pages, gup_flags,
2807 pages);
2808
2809 /*
2810 * As specified in the API description above, this routine is not
2811 * allowed to return negative values. However, the common core
2812 * routine internal_get_user_pages_fast() *can* return -errno.
2813 * Therefore, correct for that here:
2814 */
2815 if (nr_pinned < 0)
2816 nr_pinned = 0;
2817
2818 return nr_pinned;
2819 }
2820 EXPORT_SYMBOL_GPL(get_user_pages_fast_only);
2821
2822 /**
2823 * get_user_pages_fast() - pin user pages in memory
2824 * @start: starting user address
2825 * @nr_pages: number of pages from start to pin
2826 * @gup_flags: flags modifying pin behaviour
2827 * @pages: array that receives pointers to the pages pinned.
2828 * Should be at least nr_pages long.
2829 *
2830 * Attempt to pin user pages in memory without taking mm->mmap_lock.
2831 * If not successful, it will fall back to taking the lock and
2832 * calling get_user_pages().
2833 *
2834 * Returns number of pages pinned. This may be fewer than the number requested.
2835 * If nr_pages is 0 or negative, returns 0. If no pages were pinned, returns
2836 * -errno.
2837 */
2838 int get_user_pages_fast(unsigned long start, int nr_pages,
2839 unsigned int gup_flags, struct page **pages)
2840 {
2841 if (!is_valid_gup_flags(gup_flags))
2842 return -EINVAL;
2843
2844 /*
2845 * The caller may or may not have explicitly set FOLL_GET; either way is
2846 * OK. However, internally (within mm/gup.c), gup fast variants must set
2847 * FOLL_GET, because gup fast is always a "pin with a +1 page refcount"
2848 * request.
2849 */
2850 gup_flags |= FOLL_GET;
2851 return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
2852 }
2853 EXPORT_SYMBOL_GPL(get_user_pages_fast);
2854
2855 /**
2856 * pin_user_pages_fast() - pin user pages in memory without taking locks
2857 *
2858 * @start: starting user address
2859 * @nr_pages: number of pages from start to pin
2860 * @gup_flags: flags modifying pin behaviour
2861 * @pages: array that receives pointers to the pages pinned.
2862 * Should be at least nr_pages long.
2863 *
2864 * Nearly the same as get_user_pages_fast(), except that FOLL_PIN is set. See
2865 * get_user_pages_fast() for documentation on the function arguments, because
2866 * the arguments here are identical.
2867 *
2868 * FOLL_PIN means that the pages must be released via unpin_user_page(). Please
2869 * see Documentation/core-api/pin_user_pages.rst for further details.
2870 */
2871 int pin_user_pages_fast(unsigned long start, int nr_pages,
2872 unsigned int gup_flags, struct page **pages)
2873 {
2874 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
2875 if (WARN_ON_ONCE(gup_flags & FOLL_GET))
2876 return -EINVAL;
2877
2878 gup_flags |= FOLL_PIN;
2879 return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
2880 }
2881 EXPORT_SYMBOL_GPL(pin_user_pages_fast);
2882
2883 /*
2884 * This is the FOLL_PIN equivalent of get_user_pages_fast_only(). Behavior
2885 * is the same, except that this one sets FOLL_PIN instead of FOLL_GET.
2886 *
2887 * The API rules are the same, too: no negative values may be returned.
2888 */
2889 int pin_user_pages_fast_only(unsigned long start, int nr_pages,
2890 unsigned int gup_flags, struct page **pages)
2891 {
2892 int nr_pinned;
2893
2894 /*
2895 * FOLL_GET and FOLL_PIN are mutually exclusive. Note that the API
2896 * rules require returning 0, rather than -errno:
2897 */
2898 if (WARN_ON_ONCE(gup_flags & FOLL_GET))
2899 return 0;
2900 /*
2901 * FOLL_FAST_ONLY is required in order to match the API description of
2902 * this routine: no fall back to regular ("slow") GUP.
2903 */
2904 gup_flags |= (FOLL_PIN | FOLL_FAST_ONLY);
2905 nr_pinned = internal_get_user_pages_fast(start, nr_pages, gup_flags,
2906 pages);
2907 /*
2908 * This routine is not allowed to return negative values. However,
2909 * internal_get_user_pages_fast() *can* return -errno. Therefore,
2910 * correct for that here:
2911 */
2912 if (nr_pinned < 0)
2913 nr_pinned = 0;
2914
2915 return nr_pinned;
2916 }
2917 EXPORT_SYMBOL_GPL(pin_user_pages_fast_only);
2918
2919 /**
2920 * pin_user_pages_remote() - pin pages of a remote process
2921 *
2922 * @mm: mm_struct of target mm
2923 * @start: starting user address
2924 * @nr_pages: number of pages from start to pin
2925 * @gup_flags: flags modifying lookup behaviour
2926 * @pages: array that receives pointers to the pages pinned.
2927 * Should be at least nr_pages long. Or NULL, if caller
2928 * only intends to ensure the pages are faulted in.
2929 * @vmas: array of pointers to vmas corresponding to each page.
2930 * Or NULL if the caller does not require them.
2931 * @locked: pointer to lock flag indicating whether lock is held and
2932 * subsequently whether VM_FAULT_RETRY functionality can be
2933 * utilised. Lock must initially be held.
2934 *
2935 * Nearly the same as get_user_pages_remote(), except that FOLL_PIN is set. See
2936 * get_user_pages_remote() for documentation on the function arguments, because
2937 * the arguments here are identical.
2938 *
2939 * FOLL_PIN means that the pages must be released via unpin_user_page(). Please
2940 * see Documentation/core-api/pin_user_pages.rst for details.
2941 */
2942 long pin_user_pages_remote(struct mm_struct *mm,
2943 unsigned long start, unsigned long nr_pages,
2944 unsigned int gup_flags, struct page **pages,
2945 struct vm_area_struct **vmas, int *locked)
2946 {
2947 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
2948 if (WARN_ON_ONCE(gup_flags & FOLL_GET))
2949 return -EINVAL;
2950
2951 gup_flags |= FOLL_PIN;
2952 return __get_user_pages_remote(mm, start, nr_pages, gup_flags,
2953 pages, vmas, locked);
2954 }
2955 EXPORT_SYMBOL(pin_user_pages_remote);
2956
2957 /**
2958 * pin_user_pages() - pin user pages in memory for use by other devices
2959 *
2960 * @start: starting user address
2961 * @nr_pages: number of pages from start to pin
2962 * @gup_flags: flags modifying lookup behaviour
2963 * @pages: array that receives pointers to the pages pinned.
2964 * Should be at least nr_pages long. Or NULL, if caller
2965 * only intends to ensure the pages are faulted in.
2966 * @vmas: array of pointers to vmas corresponding to each page.
2967 * Or NULL if the caller does not require them.
2968 *
2969 * Nearly the same as get_user_pages(), except that FOLL_TOUCH is not set, and
2970 * FOLL_PIN is set.
2971 *
2972 * FOLL_PIN means that the pages must be released via unpin_user_page(). Please
2973 * see Documentation/core-api/pin_user_pages.rst for details.
2974 */
2975 long pin_user_pages(unsigned long start, unsigned long nr_pages,
2976 unsigned int gup_flags, struct page **pages,
2977 struct vm_area_struct **vmas)
2978 {
2979 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
2980 if (WARN_ON_ONCE(gup_flags & FOLL_GET))
2981 return -EINVAL;
2982
2983 gup_flags |= FOLL_PIN;
2984 return __gup_longterm_locked(current->mm, start, nr_pages,
2985 pages, vmas, gup_flags);
2986 }
2987 EXPORT_SYMBOL(pin_user_pages);
2988
2989 /*
2990 * pin_user_pages_unlocked() is the FOLL_PIN variant of
2991 * get_user_pages_unlocked(). Behavior is the same, except that this one sets
2992 * FOLL_PIN and rejects FOLL_GET.
2993 */
2994 long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
2995 struct page **pages, unsigned int gup_flags)
2996 {
2997 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
2998 if (WARN_ON_ONCE(gup_flags & FOLL_GET))
2999 return -EINVAL;
3000
3001 gup_flags |= FOLL_PIN;
3002 return get_user_pages_unlocked(start, nr_pages, pages, gup_flags);
3003 }
3004 EXPORT_SYMBOL(pin_user_pages_unlocked);
3005
3006 /*
3007 * pin_user_pages_locked() is the FOLL_PIN variant of get_user_pages_locked().
3008 * Behavior is the same, except that this one sets FOLL_PIN and rejects
3009 * FOLL_GET.
3010 */
3011 long pin_user_pages_locked(unsigned long start, unsigned long nr_pages,
3012 unsigned int gup_flags, struct page **pages,
3013 int *locked)
3014 {
3015 /*
3016 * FIXME: Current FOLL_LONGTERM behavior is incompatible with
3017 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
3018 * vmas. As there are no users of this flag in this call we simply
3019 * disallow this option for now.
3020 */
3021 if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
3022 return -EINVAL;
3023
3024 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
3025 if (WARN_ON_ONCE(gup_flags & FOLL_GET))
3026 return -EINVAL;
3027
3028 gup_flags |= FOLL_PIN;
3029 return __get_user_pages_locked(current->mm, start, nr_pages,
3030 pages, NULL, locked,
3031 gup_flags | FOLL_TOUCH);
3032 }
3033 EXPORT_SYMBOL(pin_user_pages_locked);