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1#include <linux/kernel.h>
2#include <linux/errno.h>
3#include <linux/err.h>
4#include <linux/spinlock.h>
5
6#include <linux/mm.h>
7#include <linux/memremap.h>
8#include <linux/pagemap.h>
9#include <linux/rmap.h>
10#include <linux/swap.h>
11#include <linux/swapops.h>
12
13#include <linux/sched/signal.h>
14#include <linux/rwsem.h>
15#include <linux/hugetlb.h>
16
17#include <asm/mmu_context.h>
18#include <asm/pgtable.h>
19#include <asm/tlbflush.h>
20
21#include "internal.h"
22
23static struct page *no_page_table(struct vm_area_struct *vma,
24 unsigned int flags)
25{
26 /*
27 * When core dumping an enormous anonymous area that nobody
28 * has touched so far, we don't want to allocate unnecessary pages or
29 * page tables. Return error instead of NULL to skip handle_mm_fault,
30 * then get_dump_page() will return NULL to leave a hole in the dump.
31 * But we can only make this optimization where a hole would surely
32 * be zero-filled if handle_mm_fault() actually did handle it.
33 */
34 if ((flags & FOLL_DUMP) && (!vma->vm_ops || !vma->vm_ops->fault))
35 return ERR_PTR(-EFAULT);
36 return NULL;
37}
38
39static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address,
40 pte_t *pte, unsigned int flags)
41{
42 /* No page to get reference */
43 if (flags & FOLL_GET)
44 return -EFAULT;
45
46 if (flags & FOLL_TOUCH) {
47 pte_t entry = *pte;
48
49 if (flags & FOLL_WRITE)
50 entry = pte_mkdirty(entry);
51 entry = pte_mkyoung(entry);
52
53 if (!pte_same(*pte, entry)) {
54 set_pte_at(vma->vm_mm, address, pte, entry);
55 update_mmu_cache(vma, address, pte);
56 }
57 }
58
59 /* Proper page table entry exists, but no corresponding struct page */
60 return -EEXIST;
61}
62
63/*
64 * FOLL_FORCE can write to even unwritable pte's, but only
65 * after we've gone through a COW cycle and they are dirty.
66 */
67static inline bool can_follow_write_pte(pte_t pte, unsigned int flags)
68{
69 return pte_write(pte) ||
70 ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte));
71}
72
73static struct page *follow_page_pte(struct vm_area_struct *vma,
74 unsigned long address, pmd_t *pmd, unsigned int flags)
75{
76 struct mm_struct *mm = vma->vm_mm;
77 struct dev_pagemap *pgmap = NULL;
78 struct page *page;
79 spinlock_t *ptl;
80 pte_t *ptep, pte;
81
82retry:
83 if (unlikely(pmd_bad(*pmd)))
84 return no_page_table(vma, flags);
85
86 ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
87 pte = *ptep;
88 if (!pte_present(pte)) {
89 swp_entry_t entry;
90 /*
91 * KSM's break_ksm() relies upon recognizing a ksm page
92 * even while it is being migrated, so for that case we
93 * need migration_entry_wait().
94 */
95 if (likely(!(flags & FOLL_MIGRATION)))
96 goto no_page;
97 if (pte_none(pte))
98 goto no_page;
99 entry = pte_to_swp_entry(pte);
100 if (!is_migration_entry(entry))
101 goto no_page;
102 pte_unmap_unlock(ptep, ptl);
103 migration_entry_wait(mm, pmd, address);
104 goto retry;
105 }
106 if ((flags & FOLL_NUMA) && pte_protnone(pte))
107 goto no_page;
108 if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, flags)) {
109 pte_unmap_unlock(ptep, ptl);
110 return NULL;
111 }
112
113 page = vm_normal_page(vma, address, pte);
114 if (!page && pte_devmap(pte) && (flags & FOLL_GET)) {
115 /*
116 * Only return device mapping pages in the FOLL_GET case since
117 * they are only valid while holding the pgmap reference.
118 */
119 pgmap = get_dev_pagemap(pte_pfn(pte), NULL);
120 if (pgmap)
121 page = pte_page(pte);
122 else
123 goto no_page;
124 } else if (unlikely(!page)) {
125 if (flags & FOLL_DUMP) {
126 /* Avoid special (like zero) pages in core dumps */
127 page = ERR_PTR(-EFAULT);
128 goto out;
129 }
130
131 if (is_zero_pfn(pte_pfn(pte))) {
132 page = pte_page(pte);
133 } else {
134 int ret;
135
136 ret = follow_pfn_pte(vma, address, ptep, flags);
137 page = ERR_PTR(ret);
138 goto out;
139 }
140 }
141
142 if (flags & FOLL_SPLIT && PageTransCompound(page)) {
143 int ret;
144 get_page(page);
145 pte_unmap_unlock(ptep, ptl);
146 lock_page(page);
147 ret = split_huge_page(page);
148 unlock_page(page);
149 put_page(page);
150 if (ret)
151 return ERR_PTR(ret);
152 goto retry;
153 }
154
155 if (flags & FOLL_GET) {
156 get_page(page);
157
158 /* drop the pgmap reference now that we hold the page */
159 if (pgmap) {
160 put_dev_pagemap(pgmap);
161 pgmap = NULL;
162 }
163 }
164 if (flags & FOLL_TOUCH) {
165 if ((flags & FOLL_WRITE) &&
166 !pte_dirty(pte) && !PageDirty(page))
167 set_page_dirty(page);
168 /*
169 * pte_mkyoung() would be more correct here, but atomic care
170 * is needed to avoid losing the dirty bit: it is easier to use
171 * mark_page_accessed().
172 */
173 mark_page_accessed(page);
174 }
175 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
176 /* Do not mlock pte-mapped THP */
177 if (PageTransCompound(page))
178 goto out;
179
180 /*
181 * The preliminary mapping check is mainly to avoid the
182 * pointless overhead of lock_page on the ZERO_PAGE
183 * which might bounce very badly if there is contention.
184 *
185 * If the page is already locked, we don't need to
186 * handle it now - vmscan will handle it later if and
187 * when it attempts to reclaim the page.
188 */
189 if (page->mapping && trylock_page(page)) {
190 lru_add_drain(); /* push cached pages to LRU */
191 /*
192 * Because we lock page here, and migration is
193 * blocked by the pte's page reference, and we
194 * know the page is still mapped, we don't even
195 * need to check for file-cache page truncation.
196 */
197 mlock_vma_page(page);
198 unlock_page(page);
199 }
200 }
201out:
202 pte_unmap_unlock(ptep, ptl);
203 return page;
204no_page:
205 pte_unmap_unlock(ptep, ptl);
206 if (!pte_none(pte))
207 return NULL;
208 return no_page_table(vma, flags);
209}
210
211static struct page *follow_pmd_mask(struct vm_area_struct *vma,
212 unsigned long address, pud_t *pudp,
213 unsigned int flags, unsigned int *page_mask)
214{
215 pmd_t *pmd;
216 spinlock_t *ptl;
217 struct page *page;
218 struct mm_struct *mm = vma->vm_mm;
219
220 pmd = pmd_offset(pudp, address);
221 if (pmd_none(*pmd))
222 return no_page_table(vma, flags);
223 if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
224 page = follow_huge_pmd(mm, address, pmd, flags);
225 if (page)
226 return page;
227 return no_page_table(vma, flags);
228 }
229 if (is_hugepd(__hugepd(pmd_val(*pmd)))) {
230 page = follow_huge_pd(vma, address,
231 __hugepd(pmd_val(*pmd)), flags,
232 PMD_SHIFT);
233 if (page)
234 return page;
235 return no_page_table(vma, flags);
236 }
237retry:
238 if (!pmd_present(*pmd)) {
239 if (likely(!(flags & FOLL_MIGRATION)))
240 return no_page_table(vma, flags);
241 VM_BUG_ON(thp_migration_supported() &&
242 !is_pmd_migration_entry(*pmd));
243 if (is_pmd_migration_entry(*pmd))
244 pmd_migration_entry_wait(mm, pmd);
245 goto retry;
246 }
247 if (pmd_devmap(*pmd)) {
248 ptl = pmd_lock(mm, pmd);
249 page = follow_devmap_pmd(vma, address, pmd, flags);
250 spin_unlock(ptl);
251 if (page)
252 return page;
253 }
254 if (likely(!pmd_trans_huge(*pmd)))
255 return follow_page_pte(vma, address, pmd, flags);
256
257 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
258 return no_page_table(vma, flags);
259
260retry_locked:
261 ptl = pmd_lock(mm, pmd);
262 if (unlikely(!pmd_present(*pmd))) {
263 spin_unlock(ptl);
264 if (likely(!(flags & FOLL_MIGRATION)))
265 return no_page_table(vma, flags);
266 pmd_migration_entry_wait(mm, pmd);
267 goto retry_locked;
268 }
269 if (unlikely(!pmd_trans_huge(*pmd))) {
270 spin_unlock(ptl);
271 return follow_page_pte(vma, address, pmd, flags);
272 }
273 if (flags & FOLL_SPLIT) {
274 int ret;
275 page = pmd_page(*pmd);
276 if (is_huge_zero_page(page)) {
277 spin_unlock(ptl);
278 ret = 0;
279 split_huge_pmd(vma, pmd, address);
280 if (pmd_trans_unstable(pmd))
281 ret = -EBUSY;
282 } else {
283 get_page(page);
284 spin_unlock(ptl);
285 lock_page(page);
286 ret = split_huge_page(page);
287 unlock_page(page);
288 put_page(page);
289 if (pmd_none(*pmd))
290 return no_page_table(vma, flags);
291 }
292
293 return ret ? ERR_PTR(ret) :
294 follow_page_pte(vma, address, pmd, flags);
295 }
296 page = follow_trans_huge_pmd(vma, address, pmd, flags);
297 spin_unlock(ptl);
298 *page_mask = HPAGE_PMD_NR - 1;
299 return page;
300}
301
302
303static struct page *follow_pud_mask(struct vm_area_struct *vma,
304 unsigned long address, p4d_t *p4dp,
305 unsigned int flags, unsigned int *page_mask)
306{
307 pud_t *pud;
308 spinlock_t *ptl;
309 struct page *page;
310 struct mm_struct *mm = vma->vm_mm;
311
312 pud = pud_offset(p4dp, address);
313 if (pud_none(*pud))
314 return no_page_table(vma, flags);
315 if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
316 page = follow_huge_pud(mm, address, pud, flags);
317 if (page)
318 return page;
319 return no_page_table(vma, flags);
320 }
321 if (is_hugepd(__hugepd(pud_val(*pud)))) {
322 page = follow_huge_pd(vma, address,
323 __hugepd(pud_val(*pud)), flags,
324 PUD_SHIFT);
325 if (page)
326 return page;
327 return no_page_table(vma, flags);
328 }
329 if (pud_devmap(*pud)) {
330 ptl = pud_lock(mm, pud);
331 page = follow_devmap_pud(vma, address, pud, flags);
332 spin_unlock(ptl);
333 if (page)
334 return page;
335 }
336 if (unlikely(pud_bad(*pud)))
337 return no_page_table(vma, flags);
338
339 return follow_pmd_mask(vma, address, pud, flags, page_mask);
340}
341
342
343static struct page *follow_p4d_mask(struct vm_area_struct *vma,
344 unsigned long address, pgd_t *pgdp,
345 unsigned int flags, unsigned int *page_mask)
346{
347 p4d_t *p4d;
348 struct page *page;
349
350 p4d = p4d_offset(pgdp, address);
351 if (p4d_none(*p4d))
352 return no_page_table(vma, flags);
353 BUILD_BUG_ON(p4d_huge(*p4d));
354 if (unlikely(p4d_bad(*p4d)))
355 return no_page_table(vma, flags);
356
357 if (is_hugepd(__hugepd(p4d_val(*p4d)))) {
358 page = follow_huge_pd(vma, address,
359 __hugepd(p4d_val(*p4d)), flags,
360 P4D_SHIFT);
361 if (page)
362 return page;
363 return no_page_table(vma, flags);
364 }
365 return follow_pud_mask(vma, address, p4d, flags, page_mask);
366}
367
368/**
369 * follow_page_mask - look up a page descriptor from a user-virtual address
370 * @vma: vm_area_struct mapping @address
371 * @address: virtual address to look up
372 * @flags: flags modifying lookup behaviour
373 * @page_mask: on output, *page_mask is set according to the size of the page
374 *
375 * @flags can have FOLL_ flags set, defined in <linux/mm.h>
376 *
377 * Returns the mapped (struct page *), %NULL if no mapping exists, or
378 * an error pointer if there is a mapping to something not represented
379 * by a page descriptor (see also vm_normal_page()).
380 */
381struct page *follow_page_mask(struct vm_area_struct *vma,
382 unsigned long address, unsigned int flags,
383 unsigned int *page_mask)
384{
385 pgd_t *pgd;
386 struct page *page;
387 struct mm_struct *mm = vma->vm_mm;
388
389 *page_mask = 0;
390
391 /* make this handle hugepd */
392 page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
393 if (!IS_ERR(page)) {
394 BUG_ON(flags & FOLL_GET);
395 return page;
396 }
397
398 pgd = pgd_offset(mm, address);
399
400 if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
401 return no_page_table(vma, flags);
402
403 if (pgd_huge(*pgd)) {
404 page = follow_huge_pgd(mm, address, pgd, flags);
405 if (page)
406 return page;
407 return no_page_table(vma, flags);
408 }
409 if (is_hugepd(__hugepd(pgd_val(*pgd)))) {
410 page = follow_huge_pd(vma, address,
411 __hugepd(pgd_val(*pgd)), flags,
412 PGDIR_SHIFT);
413 if (page)
414 return page;
415 return no_page_table(vma, flags);
416 }
417
418 return follow_p4d_mask(vma, address, pgd, flags, page_mask);
419}
420
421static int get_gate_page(struct mm_struct *mm, unsigned long address,
422 unsigned int gup_flags, struct vm_area_struct **vma,
423 struct page **page)
424{
425 pgd_t *pgd;
426 p4d_t *p4d;
427 pud_t *pud;
428 pmd_t *pmd;
429 pte_t *pte;
430 int ret = -EFAULT;
431
432 /* user gate pages are read-only */
433 if (gup_flags & FOLL_WRITE)
434 return -EFAULT;
435 if (address > TASK_SIZE)
436 pgd = pgd_offset_k(address);
437 else
438 pgd = pgd_offset_gate(mm, address);
439 BUG_ON(pgd_none(*pgd));
440 p4d = p4d_offset(pgd, address);
441 BUG_ON(p4d_none(*p4d));
442 pud = pud_offset(p4d, address);
443 BUG_ON(pud_none(*pud));
444 pmd = pmd_offset(pud, address);
445 if (!pmd_present(*pmd))
446 return -EFAULT;
447 VM_BUG_ON(pmd_trans_huge(*pmd));
448 pte = pte_offset_map(pmd, address);
449 if (pte_none(*pte))
450 goto unmap;
451 *vma = get_gate_vma(mm);
452 if (!page)
453 goto out;
454 *page = vm_normal_page(*vma, address, *pte);
455 if (!*page) {
456 if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte)))
457 goto unmap;
458 *page = pte_page(*pte);
459
460 /*
461 * This should never happen (a device public page in the gate
462 * area).
463 */
464 if (is_device_public_page(*page))
465 goto unmap;
466 }
467 get_page(*page);
468out:
469 ret = 0;
470unmap:
471 pte_unmap(pte);
472 return ret;
473}
474
475/*
476 * mmap_sem must be held on entry. If @nonblocking != NULL and
477 * *@flags does not include FOLL_NOWAIT, the mmap_sem may be released.
478 * If it is, *@nonblocking will be set to 0 and -EBUSY returned.
479 */
480static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
481 unsigned long address, unsigned int *flags, int *nonblocking)
482{
483 unsigned int fault_flags = 0;
484 int ret;
485
486 /* mlock all present pages, but do not fault in new pages */
487 if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
488 return -ENOENT;
489 if (*flags & FOLL_WRITE)
490 fault_flags |= FAULT_FLAG_WRITE;
491 if (*flags & FOLL_REMOTE)
492 fault_flags |= FAULT_FLAG_REMOTE;
493 if (nonblocking)
494 fault_flags |= FAULT_FLAG_ALLOW_RETRY;
495 if (*flags & FOLL_NOWAIT)
496 fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
497 if (*flags & FOLL_TRIED) {
498 VM_WARN_ON_ONCE(fault_flags & FAULT_FLAG_ALLOW_RETRY);
499 fault_flags |= FAULT_FLAG_TRIED;
500 }
501
502 ret = handle_mm_fault(vma, address, fault_flags);
503 if (ret & VM_FAULT_ERROR) {
504 int err = vm_fault_to_errno(ret, *flags);
505
506 if (err)
507 return err;
508 BUG();
509 }
510
511 if (tsk) {
512 if (ret & VM_FAULT_MAJOR)
513 tsk->maj_flt++;
514 else
515 tsk->min_flt++;
516 }
517
518 if (ret & VM_FAULT_RETRY) {
519 if (nonblocking && !(fault_flags & FAULT_FLAG_RETRY_NOWAIT))
520 *nonblocking = 0;
521 return -EBUSY;
522 }
523
524 /*
525 * The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when
526 * necessary, even if maybe_mkwrite decided not to set pte_write. We
527 * can thus safely do subsequent page lookups as if they were reads.
528 * But only do so when looping for pte_write is futile: in some cases
529 * userspace may also be wanting to write to the gotten user page,
530 * which a read fault here might prevent (a readonly page might get
531 * reCOWed by userspace write).
532 */
533 if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE))
534 *flags |= FOLL_COW;
535 return 0;
536}
537
538static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
539{
540 vm_flags_t vm_flags = vma->vm_flags;
541 int write = (gup_flags & FOLL_WRITE);
542 int foreign = (gup_flags & FOLL_REMOTE);
543
544 if (vm_flags & (VM_IO | VM_PFNMAP))
545 return -EFAULT;
546
547 if (gup_flags & FOLL_ANON && !vma_is_anonymous(vma))
548 return -EFAULT;
549
550 if (write) {
551 if (!(vm_flags & VM_WRITE)) {
552 if (!(gup_flags & FOLL_FORCE))
553 return -EFAULT;
554 /*
555 * We used to let the write,force case do COW in a
556 * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could
557 * set a breakpoint in a read-only mapping of an
558 * executable, without corrupting the file (yet only
559 * when that file had been opened for writing!).
560 * Anon pages in shared mappings are surprising: now
561 * just reject it.
562 */
563 if (!is_cow_mapping(vm_flags))
564 return -EFAULT;
565 }
566 } else if (!(vm_flags & VM_READ)) {
567 if (!(gup_flags & FOLL_FORCE))
568 return -EFAULT;
569 /*
570 * Is there actually any vma we can reach here which does not
571 * have VM_MAYREAD set?
572 */
573 if (!(vm_flags & VM_MAYREAD))
574 return -EFAULT;
575 }
576 /*
577 * gups are always data accesses, not instruction
578 * fetches, so execute=false here
579 */
580 if (!arch_vma_access_permitted(vma, write, false, foreign))
581 return -EFAULT;
582 return 0;
583}
584
585/**
586 * __get_user_pages() - pin user pages in memory
587 * @tsk: task_struct of target task
588 * @mm: mm_struct of target mm
589 * @start: starting user address
590 * @nr_pages: number of pages from start to pin
591 * @gup_flags: flags modifying pin behaviour
592 * @pages: array that receives pointers to the pages pinned.
593 * Should be at least nr_pages long. Or NULL, if caller
594 * only intends to ensure the pages are faulted in.
595 * @vmas: array of pointers to vmas corresponding to each page.
596 * Or NULL if the caller does not require them.
597 * @nonblocking: whether waiting for disk IO or mmap_sem contention
598 *
599 * Returns number of pages pinned. This may be fewer than the number
600 * requested. If nr_pages is 0 or negative, returns 0. If no pages
601 * were pinned, returns -errno. Each page returned must be released
602 * with a put_page() call when it is finished with. vmas will only
603 * remain valid while mmap_sem is held.
604 *
605 * Must be called with mmap_sem held. It may be released. See below.
606 *
607 * __get_user_pages walks a process's page tables and takes a reference to
608 * each struct page that each user address corresponds to at a given
609 * instant. That is, it takes the page that would be accessed if a user
610 * thread accesses the given user virtual address at that instant.
611 *
612 * This does not guarantee that the page exists in the user mappings when
613 * __get_user_pages returns, and there may even be a completely different
614 * page there in some cases (eg. if mmapped pagecache has been invalidated
615 * and subsequently re faulted). However it does guarantee that the page
616 * won't be freed completely. And mostly callers simply care that the page
617 * contains data that was valid *at some point in time*. Typically, an IO
618 * or similar operation cannot guarantee anything stronger anyway because
619 * locks can't be held over the syscall boundary.
620 *
621 * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
622 * the page is written to, set_page_dirty (or set_page_dirty_lock, as
623 * appropriate) must be called after the page is finished with, and
624 * before put_page is called.
625 *
626 * If @nonblocking != NULL, __get_user_pages will not wait for disk IO
627 * or mmap_sem contention, and if waiting is needed to pin all pages,
628 * *@nonblocking will be set to 0. Further, if @gup_flags does not
629 * include FOLL_NOWAIT, the mmap_sem will be released via up_read() in
630 * this case.
631 *
632 * A caller using such a combination of @nonblocking and @gup_flags
633 * must therefore hold the mmap_sem for reading only, and recognize
634 * when it's been released. Otherwise, it must be held for either
635 * reading or writing and will not be released.
636 *
637 * In most cases, get_user_pages or get_user_pages_fast should be used
638 * instead of __get_user_pages. __get_user_pages should be used only if
639 * you need some special @gup_flags.
640 */
641static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
642 unsigned long start, unsigned long nr_pages,
643 unsigned int gup_flags, struct page **pages,
644 struct vm_area_struct **vmas, int *nonblocking)
645{
646 long i = 0;
647 unsigned int page_mask;
648 struct vm_area_struct *vma = NULL;
649
650 if (!nr_pages)
651 return 0;
652
653 VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
654
655 /*
656 * If FOLL_FORCE is set then do not force a full fault as the hinting
657 * fault information is unrelated to the reference behaviour of a task
658 * using the address space
659 */
660 if (!(gup_flags & FOLL_FORCE))
661 gup_flags |= FOLL_NUMA;
662
663 do {
664 struct page *page;
665 unsigned int foll_flags = gup_flags;
666 unsigned int page_increm;
667
668 /* first iteration or cross vma bound */
669 if (!vma || start >= vma->vm_end) {
670 vma = find_extend_vma(mm, start);
671 if (!vma && in_gate_area(mm, start)) {
672 int ret;
673 ret = get_gate_page(mm, start & PAGE_MASK,
674 gup_flags, &vma,
675 pages ? &pages[i] : NULL);
676 if (ret)
677 return i ? : ret;
678 page_mask = 0;
679 goto next_page;
680 }
681
682 if (!vma || check_vma_flags(vma, gup_flags))
683 return i ? : -EFAULT;
684 if (is_vm_hugetlb_page(vma)) {
685 i = follow_hugetlb_page(mm, vma, pages, vmas,
686 &start, &nr_pages, i,
687 gup_flags, nonblocking);
688 continue;
689 }
690 }
691retry:
692 /*
693 * If we have a pending SIGKILL, don't keep faulting pages and
694 * potentially allocating memory.
695 */
696 if (unlikely(fatal_signal_pending(current)))
697 return i ? i : -ERESTARTSYS;
698 cond_resched();
699 page = follow_page_mask(vma, start, foll_flags, &page_mask);
700 if (!page) {
701 int ret;
702 ret = faultin_page(tsk, vma, start, &foll_flags,
703 nonblocking);
704 switch (ret) {
705 case 0:
706 goto retry;
707 case -EFAULT:
708 case -ENOMEM:
709 case -EHWPOISON:
710 return i ? i : ret;
711 case -EBUSY:
712 return i;
713 case -ENOENT:
714 goto next_page;
715 }
716 BUG();
717 } else if (PTR_ERR(page) == -EEXIST) {
718 /*
719 * Proper page table entry exists, but no corresponding
720 * struct page.
721 */
722 goto next_page;
723 } else if (IS_ERR(page)) {
724 return i ? i : PTR_ERR(page);
725 }
726 if (pages) {
727 pages[i] = page;
728 flush_anon_page(vma, page, start);
729 flush_dcache_page(page);
730 page_mask = 0;
731 }
732next_page:
733 if (vmas) {
734 vmas[i] = vma;
735 page_mask = 0;
736 }
737 page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
738 if (page_increm > nr_pages)
739 page_increm = nr_pages;
740 i += page_increm;
741 start += page_increm * PAGE_SIZE;
742 nr_pages -= page_increm;
743 } while (nr_pages);
744 return i;
745}
746
747static bool vma_permits_fault(struct vm_area_struct *vma,
748 unsigned int fault_flags)
749{
750 bool write = !!(fault_flags & FAULT_FLAG_WRITE);
751 bool foreign = !!(fault_flags & FAULT_FLAG_REMOTE);
752 vm_flags_t vm_flags = write ? VM_WRITE : VM_READ;
753
754 if (!(vm_flags & vma->vm_flags))
755 return false;
756
757 /*
758 * The architecture might have a hardware protection
759 * mechanism other than read/write that can deny access.
760 *
761 * gup always represents data access, not instruction
762 * fetches, so execute=false here:
763 */
764 if (!arch_vma_access_permitted(vma, write, false, foreign))
765 return false;
766
767 return true;
768}
769
770/*
771 * fixup_user_fault() - manually resolve a user page fault
772 * @tsk: the task_struct to use for page fault accounting, or
773 * NULL if faults are not to be recorded.
774 * @mm: mm_struct of target mm
775 * @address: user address
776 * @fault_flags:flags to pass down to handle_mm_fault()
777 * @unlocked: did we unlock the mmap_sem while retrying, maybe NULL if caller
778 * does not allow retry
779 *
780 * This is meant to be called in the specific scenario where for locking reasons
781 * we try to access user memory in atomic context (within a pagefault_disable()
782 * section), this returns -EFAULT, and we want to resolve the user fault before
783 * trying again.
784 *
785 * Typically this is meant to be used by the futex code.
786 *
787 * The main difference with get_user_pages() is that this function will
788 * unconditionally call handle_mm_fault() which will in turn perform all the
789 * necessary SW fixup of the dirty and young bits in the PTE, while
790 * get_user_pages() only guarantees to update these in the struct page.
791 *
792 * This is important for some architectures where those bits also gate the
793 * access permission to the page because they are maintained in software. On
794 * such architectures, gup() will not be enough to make a subsequent access
795 * succeed.
796 *
797 * This function will not return with an unlocked mmap_sem. So it has not the
798 * same semantics wrt the @mm->mmap_sem as does filemap_fault().
799 */
800int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
801 unsigned long address, unsigned int fault_flags,
802 bool *unlocked)
803{
804 struct vm_area_struct *vma;
805 int ret, major = 0;
806
807 if (unlocked)
808 fault_flags |= FAULT_FLAG_ALLOW_RETRY;
809
810retry:
811 vma = find_extend_vma(mm, address);
812 if (!vma || address < vma->vm_start)
813 return -EFAULT;
814
815 if (!vma_permits_fault(vma, fault_flags))
816 return -EFAULT;
817
818 ret = handle_mm_fault(vma, address, fault_flags);
819 major |= ret & VM_FAULT_MAJOR;
820 if (ret & VM_FAULT_ERROR) {
821 int err = vm_fault_to_errno(ret, 0);
822
823 if (err)
824 return err;
825 BUG();
826 }
827
828 if (ret & VM_FAULT_RETRY) {
829 down_read(&mm->mmap_sem);
830 if (!(fault_flags & FAULT_FLAG_TRIED)) {
831 *unlocked = true;
832 fault_flags &= ~FAULT_FLAG_ALLOW_RETRY;
833 fault_flags |= FAULT_FLAG_TRIED;
834 goto retry;
835 }
836 }
837
838 if (tsk) {
839 if (major)
840 tsk->maj_flt++;
841 else
842 tsk->min_flt++;
843 }
844 return 0;
845}
846EXPORT_SYMBOL_GPL(fixup_user_fault);
847
848static __always_inline long __get_user_pages_locked(struct task_struct *tsk,
849 struct mm_struct *mm,
850 unsigned long start,
851 unsigned long nr_pages,
852 struct page **pages,
853 struct vm_area_struct **vmas,
854 int *locked,
855 unsigned int flags)
856{
857 long ret, pages_done;
858 bool lock_dropped;
859
860 if (locked) {
861 /* if VM_FAULT_RETRY can be returned, vmas become invalid */
862 BUG_ON(vmas);
863 /* check caller initialized locked */
864 BUG_ON(*locked != 1);
865 }
866
867 if (pages)
868 flags |= FOLL_GET;
869
870 pages_done = 0;
871 lock_dropped = false;
872 for (;;) {
873 ret = __get_user_pages(tsk, mm, start, nr_pages, flags, pages,
874 vmas, locked);
875 if (!locked)
876 /* VM_FAULT_RETRY couldn't trigger, bypass */
877 return ret;
878
879 /* VM_FAULT_RETRY cannot return errors */
880 if (!*locked) {
881 BUG_ON(ret < 0);
882 BUG_ON(ret >= nr_pages);
883 }
884
885 if (!pages)
886 /* If it's a prefault don't insist harder */
887 return ret;
888
889 if (ret > 0) {
890 nr_pages -= ret;
891 pages_done += ret;
892 if (!nr_pages)
893 break;
894 }
895 if (*locked) {
896 /*
897 * VM_FAULT_RETRY didn't trigger or it was a
898 * FOLL_NOWAIT.
899 */
900 if (!pages_done)
901 pages_done = ret;
902 break;
903 }
904 /* VM_FAULT_RETRY triggered, so seek to the faulting offset */
905 pages += ret;
906 start += ret << PAGE_SHIFT;
907
908 /*
909 * Repeat on the address that fired VM_FAULT_RETRY
910 * without FAULT_FLAG_ALLOW_RETRY but with
911 * FAULT_FLAG_TRIED.
912 */
913 *locked = 1;
914 lock_dropped = true;
915 down_read(&mm->mmap_sem);
916 ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED,
917 pages, NULL, NULL);
918 if (ret != 1) {
919 BUG_ON(ret > 1);
920 if (!pages_done)
921 pages_done = ret;
922 break;
923 }
924 nr_pages--;
925 pages_done++;
926 if (!nr_pages)
927 break;
928 pages++;
929 start += PAGE_SIZE;
930 }
931 if (lock_dropped && *locked) {
932 /*
933 * We must let the caller know we temporarily dropped the lock
934 * and so the critical section protected by it was lost.
935 */
936 up_read(&mm->mmap_sem);
937 *locked = 0;
938 }
939 return pages_done;
940}
941
942/*
943 * We can leverage the VM_FAULT_RETRY functionality in the page fault
944 * paths better by using either get_user_pages_locked() or
945 * get_user_pages_unlocked().
946 *
947 * get_user_pages_locked() is suitable to replace the form:
948 *
949 * down_read(&mm->mmap_sem);
950 * do_something()
951 * get_user_pages(tsk, mm, ..., pages, NULL);
952 * up_read(&mm->mmap_sem);
953 *
954 * to:
955 *
956 * int locked = 1;
957 * down_read(&mm->mmap_sem);
958 * do_something()
959 * get_user_pages_locked(tsk, mm, ..., pages, &locked);
960 * if (locked)
961 * up_read(&mm->mmap_sem);
962 */
963long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
964 unsigned int gup_flags, struct page **pages,
965 int *locked)
966{
967 return __get_user_pages_locked(current, current->mm, start, nr_pages,
968 pages, NULL, locked,
969 gup_flags | FOLL_TOUCH);
970}
971EXPORT_SYMBOL(get_user_pages_locked);
972
973/*
974 * get_user_pages_unlocked() is suitable to replace the form:
975 *
976 * down_read(&mm->mmap_sem);
977 * get_user_pages(tsk, mm, ..., pages, NULL);
978 * up_read(&mm->mmap_sem);
979 *
980 * with:
981 *
982 * get_user_pages_unlocked(tsk, mm, ..., pages);
983 *
984 * It is functionally equivalent to get_user_pages_fast so
985 * get_user_pages_fast should be used instead if specific gup_flags
986 * (e.g. FOLL_FORCE) are not required.
987 */
988long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
989 struct page **pages, unsigned int gup_flags)
990{
991 struct mm_struct *mm = current->mm;
992 int locked = 1;
993 long ret;
994
995 down_read(&mm->mmap_sem);
996 ret = __get_user_pages_locked(current, mm, start, nr_pages, pages, NULL,
997 &locked, gup_flags | FOLL_TOUCH);
998 if (locked)
999 up_read(&mm->mmap_sem);
1000 return ret;
1001}
1002EXPORT_SYMBOL(get_user_pages_unlocked);
1003
1004/*
1005 * get_user_pages_remote() - pin user pages in memory
1006 * @tsk: the task_struct to use for page fault accounting, or
1007 * NULL if faults are not to be recorded.
1008 * @mm: mm_struct of target mm
1009 * @start: starting user address
1010 * @nr_pages: number of pages from start to pin
1011 * @gup_flags: flags modifying lookup behaviour
1012 * @pages: array that receives pointers to the pages pinned.
1013 * Should be at least nr_pages long. Or NULL, if caller
1014 * only intends to ensure the pages are faulted in.
1015 * @vmas: array of pointers to vmas corresponding to each page.
1016 * Or NULL if the caller does not require them.
1017 * @locked: pointer to lock flag indicating whether lock is held and
1018 * subsequently whether VM_FAULT_RETRY functionality can be
1019 * utilised. Lock must initially be held.
1020 *
1021 * Returns number of pages pinned. This may be fewer than the number
1022 * requested. If nr_pages is 0 or negative, returns 0. If no pages
1023 * were pinned, returns -errno. Each page returned must be released
1024 * with a put_page() call when it is finished with. vmas will only
1025 * remain valid while mmap_sem is held.
1026 *
1027 * Must be called with mmap_sem held for read or write.
1028 *
1029 * get_user_pages walks a process's page tables and takes a reference to
1030 * each struct page that each user address corresponds to at a given
1031 * instant. That is, it takes the page that would be accessed if a user
1032 * thread accesses the given user virtual address at that instant.
1033 *
1034 * This does not guarantee that the page exists in the user mappings when
1035 * get_user_pages returns, and there may even be a completely different
1036 * page there in some cases (eg. if mmapped pagecache has been invalidated
1037 * and subsequently re faulted). However it does guarantee that the page
1038 * won't be freed completely. And mostly callers simply care that the page
1039 * contains data that was valid *at some point in time*. Typically, an IO
1040 * or similar operation cannot guarantee anything stronger anyway because
1041 * locks can't be held over the syscall boundary.
1042 *
1043 * If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page
1044 * is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must
1045 * be called after the page is finished with, and before put_page is called.
1046 *
1047 * get_user_pages is typically used for fewer-copy IO operations, to get a
1048 * handle on the memory by some means other than accesses via the user virtual
1049 * addresses. The pages may be submitted for DMA to devices or accessed via
1050 * their kernel linear mapping (via the kmap APIs). Care should be taken to
1051 * use the correct cache flushing APIs.
1052 *
1053 * See also get_user_pages_fast, for performance critical applications.
1054 *
1055 * get_user_pages should be phased out in favor of
1056 * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
1057 * should use get_user_pages because it cannot pass
1058 * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
1059 */
1060long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
1061 unsigned long start, unsigned long nr_pages,
1062 unsigned int gup_flags, struct page **pages,
1063 struct vm_area_struct **vmas, int *locked)
1064{
1065 return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas,
1066 locked,
1067 gup_flags | FOLL_TOUCH | FOLL_REMOTE);
1068}
1069EXPORT_SYMBOL(get_user_pages_remote);
1070
1071/*
1072 * This is the same as get_user_pages_remote(), just with a
1073 * less-flexible calling convention where we assume that the task
1074 * and mm being operated on are the current task's and don't allow
1075 * passing of a locked parameter. We also obviously don't pass
1076 * FOLL_REMOTE in here.
1077 */
1078long get_user_pages(unsigned long start, unsigned long nr_pages,
1079 unsigned int gup_flags, struct page **pages,
1080 struct vm_area_struct **vmas)
1081{
1082 return __get_user_pages_locked(current, current->mm, start, nr_pages,
1083 pages, vmas, NULL,
1084 gup_flags | FOLL_TOUCH);
1085}
1086EXPORT_SYMBOL(get_user_pages);
1087
1088#ifdef CONFIG_FS_DAX
1089/*
1090 * This is the same as get_user_pages() in that it assumes we are
1091 * operating on the current task's mm, but it goes further to validate
1092 * that the vmas associated with the address range are suitable for
1093 * longterm elevated page reference counts. For example, filesystem-dax
1094 * mappings are subject to the lifetime enforced by the filesystem and
1095 * we need guarantees that longterm users like RDMA and V4L2 only
1096 * establish mappings that have a kernel enforced revocation mechanism.
1097 *
1098 * "longterm" == userspace controlled elevated page count lifetime.
1099 * Contrast this to iov_iter_get_pages() usages which are transient.
1100 */
1101long get_user_pages_longterm(unsigned long start, unsigned long nr_pages,
1102 unsigned int gup_flags, struct page **pages,
1103 struct vm_area_struct **vmas_arg)
1104{
1105 struct vm_area_struct **vmas = vmas_arg;
1106 struct vm_area_struct *vma_prev = NULL;
1107 long rc, i;
1108
1109 if (!pages)
1110 return -EINVAL;
1111
1112 if (!vmas) {
1113 vmas = kcalloc(nr_pages, sizeof(struct vm_area_struct *),
1114 GFP_KERNEL);
1115 if (!vmas)
1116 return -ENOMEM;
1117 }
1118
1119 rc = get_user_pages(start, nr_pages, gup_flags, pages, vmas);
1120
1121 for (i = 0; i < rc; i++) {
1122 struct vm_area_struct *vma = vmas[i];
1123
1124 if (vma == vma_prev)
1125 continue;
1126
1127 vma_prev = vma;
1128
1129 if (vma_is_fsdax(vma))
1130 break;
1131 }
1132
1133 /*
1134 * Either get_user_pages() failed, or the vma validation
1135 * succeeded, in either case we don't need to put_page() before
1136 * returning.
1137 */
1138 if (i >= rc)
1139 goto out;
1140
1141 for (i = 0; i < rc; i++)
1142 put_page(pages[i]);
1143 rc = -EOPNOTSUPP;
1144out:
1145 if (vmas != vmas_arg)
1146 kfree(vmas);
1147 return rc;
1148}
1149EXPORT_SYMBOL(get_user_pages_longterm);
1150#endif /* CONFIG_FS_DAX */
1151
1152/**
1153 * populate_vma_page_range() - populate a range of pages in the vma.
1154 * @vma: target vma
1155 * @start: start address
1156 * @end: end address
1157 * @nonblocking:
1158 *
1159 * This takes care of mlocking the pages too if VM_LOCKED is set.
1160 *
1161 * return 0 on success, negative error code on error.
1162 *
1163 * vma->vm_mm->mmap_sem must be held.
1164 *
1165 * If @nonblocking is NULL, it may be held for read or write and will
1166 * be unperturbed.
1167 *
1168 * If @nonblocking is non-NULL, it must held for read only and may be
1169 * released. If it's released, *@nonblocking will be set to 0.
1170 */
1171long populate_vma_page_range(struct vm_area_struct *vma,
1172 unsigned long start, unsigned long end, int *nonblocking)
1173{
1174 struct mm_struct *mm = vma->vm_mm;
1175 unsigned long nr_pages = (end - start) / PAGE_SIZE;
1176 int gup_flags;
1177
1178 VM_BUG_ON(start & ~PAGE_MASK);
1179 VM_BUG_ON(end & ~PAGE_MASK);
1180 VM_BUG_ON_VMA(start < vma->vm_start, vma);
1181 VM_BUG_ON_VMA(end > vma->vm_end, vma);
1182 VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);
1183
1184 gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK;
1185 if (vma->vm_flags & VM_LOCKONFAULT)
1186 gup_flags &= ~FOLL_POPULATE;
1187 /*
1188 * We want to touch writable mappings with a write fault in order
1189 * to break COW, except for shared mappings because these don't COW
1190 * and we would not want to dirty them for nothing.
1191 */
1192 if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
1193 gup_flags |= FOLL_WRITE;
1194
1195 /*
1196 * We want mlock to succeed for regions that have any permissions
1197 * other than PROT_NONE.
1198 */
1199 if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
1200 gup_flags |= FOLL_FORCE;
1201
1202 /*
1203 * We made sure addr is within a VMA, so the following will
1204 * not result in a stack expansion that recurses back here.
1205 */
1206 return __get_user_pages(current, mm, start, nr_pages, gup_flags,
1207 NULL, NULL, nonblocking);
1208}
1209
1210/*
1211 * __mm_populate - populate and/or mlock pages within a range of address space.
1212 *
1213 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
1214 * flags. VMAs must be already marked with the desired vm_flags, and
1215 * mmap_sem must not be held.
1216 */
1217int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
1218{
1219 struct mm_struct *mm = current->mm;
1220 unsigned long end, nstart, nend;
1221 struct vm_area_struct *vma = NULL;
1222 int locked = 0;
1223 long ret = 0;
1224
1225 VM_BUG_ON(start & ~PAGE_MASK);
1226 VM_BUG_ON(len != PAGE_ALIGN(len));
1227 end = start + len;
1228
1229 for (nstart = start; nstart < end; nstart = nend) {
1230 /*
1231 * We want to fault in pages for [nstart; end) address range.
1232 * Find first corresponding VMA.
1233 */
1234 if (!locked) {
1235 locked = 1;
1236 down_read(&mm->mmap_sem);
1237 vma = find_vma(mm, nstart);
1238 } else if (nstart >= vma->vm_end)
1239 vma = vma->vm_next;
1240 if (!vma || vma->vm_start >= end)
1241 break;
1242 /*
1243 * Set [nstart; nend) to intersection of desired address
1244 * range with the first VMA. Also, skip undesirable VMA types.
1245 */
1246 nend = min(end, vma->vm_end);
1247 if (vma->vm_flags & (VM_IO | VM_PFNMAP))
1248 continue;
1249 if (nstart < vma->vm_start)
1250 nstart = vma->vm_start;
1251 /*
1252 * Now fault in a range of pages. populate_vma_page_range()
1253 * double checks the vma flags, so that it won't mlock pages
1254 * if the vma was already munlocked.
1255 */
1256 ret = populate_vma_page_range(vma, nstart, nend, &locked);
1257 if (ret < 0) {
1258 if (ignore_errors) {
1259 ret = 0;
1260 continue; /* continue at next VMA */
1261 }
1262 break;
1263 }
1264 nend = nstart + ret * PAGE_SIZE;
1265 ret = 0;
1266 }
1267 if (locked)
1268 up_read(&mm->mmap_sem);
1269 return ret; /* 0 or negative error code */
1270}
1271
1272/**
1273 * get_dump_page() - pin user page in memory while writing it to core dump
1274 * @addr: user address
1275 *
1276 * Returns struct page pointer of user page pinned for dump,
1277 * to be freed afterwards by put_page().
1278 *
1279 * Returns NULL on any kind of failure - a hole must then be inserted into
1280 * the corefile, to preserve alignment with its headers; and also returns
1281 * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
1282 * allowing a hole to be left in the corefile to save diskspace.
1283 *
1284 * Called without mmap_sem, but after all other threads have been killed.
1285 */
1286#ifdef CONFIG_ELF_CORE
1287struct page *get_dump_page(unsigned long addr)
1288{
1289 struct vm_area_struct *vma;
1290 struct page *page;
1291
1292 if (__get_user_pages(current, current->mm, addr, 1,
1293 FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma,
1294 NULL) < 1)
1295 return NULL;
1296 flush_cache_page(vma, addr, page_to_pfn(page));
1297 return page;
1298}
1299#endif /* CONFIG_ELF_CORE */
1300
1301/*
1302 * Generic Fast GUP
1303 *
1304 * get_user_pages_fast attempts to pin user pages by walking the page
1305 * tables directly and avoids taking locks. Thus the walker needs to be
1306 * protected from page table pages being freed from under it, and should
1307 * block any THP splits.
1308 *
1309 * One way to achieve this is to have the walker disable interrupts, and
1310 * rely on IPIs from the TLB flushing code blocking before the page table
1311 * pages are freed. This is unsuitable for architectures that do not need
1312 * to broadcast an IPI when invalidating TLBs.
1313 *
1314 * Another way to achieve this is to batch up page table containing pages
1315 * belonging to more than one mm_user, then rcu_sched a callback to free those
1316 * pages. Disabling interrupts will allow the fast_gup walker to both block
1317 * the rcu_sched callback, and an IPI that we broadcast for splitting THPs
1318 * (which is a relatively rare event). The code below adopts this strategy.
1319 *
1320 * Before activating this code, please be aware that the following assumptions
1321 * are currently made:
1322 *
1323 * *) Either HAVE_RCU_TABLE_FREE is enabled, and tlb_remove_table() is used to
1324 * free pages containing page tables or TLB flushing requires IPI broadcast.
1325 *
1326 * *) ptes can be read atomically by the architecture.
1327 *
1328 * *) access_ok is sufficient to validate userspace address ranges.
1329 *
1330 * The last two assumptions can be relaxed by the addition of helper functions.
1331 *
1332 * This code is based heavily on the PowerPC implementation by Nick Piggin.
1333 */
1334#ifdef CONFIG_HAVE_GENERIC_GUP
1335
1336#ifndef gup_get_pte
1337/*
1338 * We assume that the PTE can be read atomically. If this is not the case for
1339 * your architecture, please provide the helper.
1340 */
1341static inline pte_t gup_get_pte(pte_t *ptep)
1342{
1343 return READ_ONCE(*ptep);
1344}
1345#endif
1346
1347static void undo_dev_pagemap(int *nr, int nr_start, struct page **pages)
1348{
1349 while ((*nr) - nr_start) {
1350 struct page *page = pages[--(*nr)];
1351
1352 ClearPageReferenced(page);
1353 put_page(page);
1354 }
1355}
1356
1357#ifdef __HAVE_ARCH_PTE_SPECIAL
1358static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
1359 int write, struct page **pages, int *nr)
1360{
1361 struct dev_pagemap *pgmap = NULL;
1362 int nr_start = *nr, ret = 0;
1363 pte_t *ptep, *ptem;
1364
1365 ptem = ptep = pte_offset_map(&pmd, addr);
1366 do {
1367 pte_t pte = gup_get_pte(ptep);
1368 struct page *head, *page;
1369
1370 /*
1371 * Similar to the PMD case below, NUMA hinting must take slow
1372 * path using the pte_protnone check.
1373 */
1374 if (pte_protnone(pte))
1375 goto pte_unmap;
1376
1377 if (!pte_access_permitted(pte, write))
1378 goto pte_unmap;
1379
1380 if (pte_devmap(pte)) {
1381 pgmap = get_dev_pagemap(pte_pfn(pte), pgmap);
1382 if (unlikely(!pgmap)) {
1383 undo_dev_pagemap(nr, nr_start, pages);
1384 goto pte_unmap;
1385 }
1386 } else if (pte_special(pte))
1387 goto pte_unmap;
1388
1389 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
1390 page = pte_page(pte);
1391 head = compound_head(page);
1392
1393 if (!page_cache_get_speculative(head))
1394 goto pte_unmap;
1395
1396 if (unlikely(pte_val(pte) != pte_val(*ptep))) {
1397 put_page(head);
1398 goto pte_unmap;
1399 }
1400
1401 VM_BUG_ON_PAGE(compound_head(page) != head, page);
1402
1403 SetPageReferenced(page);
1404 pages[*nr] = page;
1405 (*nr)++;
1406
1407 } while (ptep++, addr += PAGE_SIZE, addr != end);
1408
1409 ret = 1;
1410
1411pte_unmap:
1412 if (pgmap)
1413 put_dev_pagemap(pgmap);
1414 pte_unmap(ptem);
1415 return ret;
1416}
1417#else
1418
1419/*
1420 * If we can't determine whether or not a pte is special, then fail immediately
1421 * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
1422 * to be special.
1423 *
1424 * For a futex to be placed on a THP tail page, get_futex_key requires a
1425 * __get_user_pages_fast implementation that can pin pages. Thus it's still
1426 * useful to have gup_huge_pmd even if we can't operate on ptes.
1427 */
1428static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
1429 int write, struct page **pages, int *nr)
1430{
1431 return 0;
1432}
1433#endif /* __HAVE_ARCH_PTE_SPECIAL */
1434
1435#if defined(__HAVE_ARCH_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
1436static int __gup_device_huge(unsigned long pfn, unsigned long addr,
1437 unsigned long end, struct page **pages, int *nr)
1438{
1439 int nr_start = *nr;
1440 struct dev_pagemap *pgmap = NULL;
1441
1442 do {
1443 struct page *page = pfn_to_page(pfn);
1444
1445 pgmap = get_dev_pagemap(pfn, pgmap);
1446 if (unlikely(!pgmap)) {
1447 undo_dev_pagemap(nr, nr_start, pages);
1448 return 0;
1449 }
1450 SetPageReferenced(page);
1451 pages[*nr] = page;
1452 get_page(page);
1453 (*nr)++;
1454 pfn++;
1455 } while (addr += PAGE_SIZE, addr != end);
1456
1457 if (pgmap)
1458 put_dev_pagemap(pgmap);
1459 return 1;
1460}
1461
1462static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr,
1463 unsigned long end, struct page **pages, int *nr)
1464{
1465 unsigned long fault_pfn;
1466
1467 fault_pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
1468 return __gup_device_huge(fault_pfn, addr, end, pages, nr);
1469}
1470
1471static int __gup_device_huge_pud(pud_t pud, unsigned long addr,
1472 unsigned long end, struct page **pages, int *nr)
1473{
1474 unsigned long fault_pfn;
1475
1476 fault_pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
1477 return __gup_device_huge(fault_pfn, addr, end, pages, nr);
1478}
1479#else
1480static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr,
1481 unsigned long end, struct page **pages, int *nr)
1482{
1483 BUILD_BUG();
1484 return 0;
1485}
1486
1487static int __gup_device_huge_pud(pud_t pud, unsigned long addr,
1488 unsigned long end, struct page **pages, int *nr)
1489{
1490 BUILD_BUG();
1491 return 0;
1492}
1493#endif
1494
1495static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
1496 unsigned long end, int write, struct page **pages, int *nr)
1497{
1498 struct page *head, *page;
1499 int refs;
1500
1501 if (!pmd_access_permitted(orig, write))
1502 return 0;
1503
1504 if (pmd_devmap(orig))
1505 return __gup_device_huge_pmd(orig, addr, end, pages, nr);
1506
1507 refs = 0;
1508 page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
1509 do {
1510 pages[*nr] = page;
1511 (*nr)++;
1512 page++;
1513 refs++;
1514 } while (addr += PAGE_SIZE, addr != end);
1515
1516 head = compound_head(pmd_page(orig));
1517 if (!page_cache_add_speculative(head, refs)) {
1518 *nr -= refs;
1519 return 0;
1520 }
1521
1522 if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
1523 *nr -= refs;
1524 while (refs--)
1525 put_page(head);
1526 return 0;
1527 }
1528
1529 SetPageReferenced(head);
1530 return 1;
1531}
1532
1533static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
1534 unsigned long end, int write, struct page **pages, int *nr)
1535{
1536 struct page *head, *page;
1537 int refs;
1538
1539 if (!pud_access_permitted(orig, write))
1540 return 0;
1541
1542 if (pud_devmap(orig))
1543 return __gup_device_huge_pud(orig, addr, end, pages, nr);
1544
1545 refs = 0;
1546 page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
1547 do {
1548 pages[*nr] = page;
1549 (*nr)++;
1550 page++;
1551 refs++;
1552 } while (addr += PAGE_SIZE, addr != end);
1553
1554 head = compound_head(pud_page(orig));
1555 if (!page_cache_add_speculative(head, refs)) {
1556 *nr -= refs;
1557 return 0;
1558 }
1559
1560 if (unlikely(pud_val(orig) != pud_val(*pudp))) {
1561 *nr -= refs;
1562 while (refs--)
1563 put_page(head);
1564 return 0;
1565 }
1566
1567 SetPageReferenced(head);
1568 return 1;
1569}
1570
1571static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
1572 unsigned long end, int write,
1573 struct page **pages, int *nr)
1574{
1575 int refs;
1576 struct page *head, *page;
1577
1578 if (!pgd_access_permitted(orig, write))
1579 return 0;
1580
1581 BUILD_BUG_ON(pgd_devmap(orig));
1582 refs = 0;
1583 page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
1584 do {
1585 pages[*nr] = page;
1586 (*nr)++;
1587 page++;
1588 refs++;
1589 } while (addr += PAGE_SIZE, addr != end);
1590
1591 head = compound_head(pgd_page(orig));
1592 if (!page_cache_add_speculative(head, refs)) {
1593 *nr -= refs;
1594 return 0;
1595 }
1596
1597 if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
1598 *nr -= refs;
1599 while (refs--)
1600 put_page(head);
1601 return 0;
1602 }
1603
1604 SetPageReferenced(head);
1605 return 1;
1606}
1607
1608static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
1609 int write, struct page **pages, int *nr)
1610{
1611 unsigned long next;
1612 pmd_t *pmdp;
1613
1614 pmdp = pmd_offset(&pud, addr);
1615 do {
1616 pmd_t pmd = READ_ONCE(*pmdp);
1617
1618 next = pmd_addr_end(addr, end);
1619 if (!pmd_present(pmd))
1620 return 0;
1621
1622 if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd))) {
1623 /*
1624 * NUMA hinting faults need to be handled in the GUP
1625 * slowpath for accounting purposes and so that they
1626 * can be serialised against THP migration.
1627 */
1628 if (pmd_protnone(pmd))
1629 return 0;
1630
1631 if (!gup_huge_pmd(pmd, pmdp, addr, next, write,
1632 pages, nr))
1633 return 0;
1634
1635 } else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) {
1636 /*
1637 * architecture have different format for hugetlbfs
1638 * pmd format and THP pmd format
1639 */
1640 if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr,
1641 PMD_SHIFT, next, write, pages, nr))
1642 return 0;
1643 } else if (!gup_pte_range(pmd, addr, next, write, pages, nr))
1644 return 0;
1645 } while (pmdp++, addr = next, addr != end);
1646
1647 return 1;
1648}
1649
1650static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end,
1651 int write, struct page **pages, int *nr)
1652{
1653 unsigned long next;
1654 pud_t *pudp;
1655
1656 pudp = pud_offset(&p4d, addr);
1657 do {
1658 pud_t pud = READ_ONCE(*pudp);
1659
1660 next = pud_addr_end(addr, end);
1661 if (pud_none(pud))
1662 return 0;
1663 if (unlikely(pud_huge(pud))) {
1664 if (!gup_huge_pud(pud, pudp, addr, next, write,
1665 pages, nr))
1666 return 0;
1667 } else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) {
1668 if (!gup_huge_pd(__hugepd(pud_val(pud)), addr,
1669 PUD_SHIFT, next, write, pages, nr))
1670 return 0;
1671 } else if (!gup_pmd_range(pud, addr, next, write, pages, nr))
1672 return 0;
1673 } while (pudp++, addr = next, addr != end);
1674
1675 return 1;
1676}
1677
1678static int gup_p4d_range(pgd_t pgd, unsigned long addr, unsigned long end,
1679 int write, struct page **pages, int *nr)
1680{
1681 unsigned long next;
1682 p4d_t *p4dp;
1683
1684 p4dp = p4d_offset(&pgd, addr);
1685 do {
1686 p4d_t p4d = READ_ONCE(*p4dp);
1687
1688 next = p4d_addr_end(addr, end);
1689 if (p4d_none(p4d))
1690 return 0;
1691 BUILD_BUG_ON(p4d_huge(p4d));
1692 if (unlikely(is_hugepd(__hugepd(p4d_val(p4d))))) {
1693 if (!gup_huge_pd(__hugepd(p4d_val(p4d)), addr,
1694 P4D_SHIFT, next, write, pages, nr))
1695 return 0;
1696 } else if (!gup_pud_range(p4d, addr, next, write, pages, nr))
1697 return 0;
1698 } while (p4dp++, addr = next, addr != end);
1699
1700 return 1;
1701}
1702
1703static void gup_pgd_range(unsigned long addr, unsigned long end,
1704 int write, struct page **pages, int *nr)
1705{
1706 unsigned long next;
1707 pgd_t *pgdp;
1708
1709 pgdp = pgd_offset(current->mm, addr);
1710 do {
1711 pgd_t pgd = READ_ONCE(*pgdp);
1712
1713 next = pgd_addr_end(addr, end);
1714 if (pgd_none(pgd))
1715 return;
1716 if (unlikely(pgd_huge(pgd))) {
1717 if (!gup_huge_pgd(pgd, pgdp, addr, next, write,
1718 pages, nr))
1719 return;
1720 } else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) {
1721 if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
1722 PGDIR_SHIFT, next, write, pages, nr))
1723 return;
1724 } else if (!gup_p4d_range(pgd, addr, next, write, pages, nr))
1725 return;
1726 } while (pgdp++, addr = next, addr != end);
1727}
1728
1729#ifndef gup_fast_permitted
1730/*
1731 * Check if it's allowed to use __get_user_pages_fast() for the range, or
1732 * we need to fall back to the slow version:
1733 */
1734bool gup_fast_permitted(unsigned long start, int nr_pages, int write)
1735{
1736 unsigned long len, end;
1737
1738 len = (unsigned long) nr_pages << PAGE_SHIFT;
1739 end = start + len;
1740 return end >= start;
1741}
1742#endif
1743
1744/*
1745 * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
1746 * the regular GUP.
1747 * Note a difference with get_user_pages_fast: this always returns the
1748 * number of pages pinned, 0 if no pages were pinned.
1749 */
1750int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
1751 struct page **pages)
1752{
1753 unsigned long addr, len, end;
1754 unsigned long flags;
1755 int nr = 0;
1756
1757 start &= PAGE_MASK;
1758 addr = start;
1759 len = (unsigned long) nr_pages << PAGE_SHIFT;
1760 end = start + len;
1761
1762 if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
1763 (void __user *)start, len)))
1764 return 0;
1765
1766 /*
1767 * Disable interrupts. We use the nested form as we can already have
1768 * interrupts disabled by get_futex_key.
1769 *
1770 * With interrupts disabled, we block page table pages from being
1771 * freed from under us. See mmu_gather_tlb in asm-generic/tlb.h
1772 * for more details.
1773 *
1774 * We do not adopt an rcu_read_lock(.) here as we also want to
1775 * block IPIs that come from THPs splitting.
1776 */
1777
1778 if (gup_fast_permitted(start, nr_pages, write)) {
1779 local_irq_save(flags);
1780 gup_pgd_range(addr, end, write, pages, &nr);
1781 local_irq_restore(flags);
1782 }
1783
1784 return nr;
1785}
1786
1787/**
1788 * get_user_pages_fast() - pin user pages in memory
1789 * @start: starting user address
1790 * @nr_pages: number of pages from start to pin
1791 * @write: whether pages will be written to
1792 * @pages: array that receives pointers to the pages pinned.
1793 * Should be at least nr_pages long.
1794 *
1795 * Attempt to pin user pages in memory without taking mm->mmap_sem.
1796 * If not successful, it will fall back to taking the lock and
1797 * calling get_user_pages().
1798 *
1799 * Returns number of pages pinned. This may be fewer than the number
1800 * requested. If nr_pages is 0 or negative, returns 0. If no pages
1801 * were pinned, returns -errno.
1802 */
1803int get_user_pages_fast(unsigned long start, int nr_pages, int write,
1804 struct page **pages)
1805{
1806 unsigned long addr, len, end;
1807 int nr = 0, ret = 0;
1808
1809 start &= PAGE_MASK;
1810 addr = start;
1811 len = (unsigned long) nr_pages << PAGE_SHIFT;
1812 end = start + len;
1813
1814 if (nr_pages <= 0)
1815 return 0;
1816
1817 if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
1818 (void __user *)start, len)))
1819 return -EFAULT;
1820
1821 if (gup_fast_permitted(start, nr_pages, write)) {
1822 local_irq_disable();
1823 gup_pgd_range(addr, end, write, pages, &nr);
1824 local_irq_enable();
1825 ret = nr;
1826 }
1827
1828 if (nr < nr_pages) {
1829 /* Try to get the remaining pages with get_user_pages */
1830 start += nr << PAGE_SHIFT;
1831 pages += nr;
1832
1833 ret = get_user_pages_unlocked(start, nr_pages - nr, pages,
1834 write ? FOLL_WRITE : 0);
1835
1836 /* Have to be a bit careful with return values */
1837 if (nr > 0) {
1838 if (ret < 0)
1839 ret = nr;
1840 else
1841 ret += nr;
1842 }
1843 }
1844
1845 return ret;
1846}
1847
1848#endif /* CONFIG_HAVE_GENERIC_GUP */