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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.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
211/**
212 * follow_page_mask - look up a page descriptor from a user-virtual address
213 * @vma: vm_area_struct mapping @address
214 * @address: virtual address to look up
215 * @flags: flags modifying lookup behaviour
216 * @page_mask: on output, *page_mask is set according to the size of the page
217 *
218 * @flags can have FOLL_ flags set, defined in <linux/mm.h>
219 *
220 * Returns the mapped (struct page *), %NULL if no mapping exists, or
221 * an error pointer if there is a mapping to something not represented
222 * by a page descriptor (see also vm_normal_page()).
223 */
224struct page *follow_page_mask(struct vm_area_struct *vma,
225 unsigned long address, unsigned int flags,
226 unsigned int *page_mask)
227{
228 pgd_t *pgd;
229 pud_t *pud;
230 pmd_t *pmd;
231 spinlock_t *ptl;
232 struct page *page;
233 struct mm_struct *mm = vma->vm_mm;
234
235 *page_mask = 0;
236
237 page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
238 if (!IS_ERR(page)) {
239 BUG_ON(flags & FOLL_GET);
240 return page;
241 }
242
243 pgd = pgd_offset(mm, address);
244 if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
245 return no_page_table(vma, flags);
246
247 pud = pud_offset(pgd, address);
248 if (pud_none(*pud))
249 return no_page_table(vma, flags);
250 if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
251 page = follow_huge_pud(mm, address, pud, flags);
252 if (page)
253 return page;
254 return no_page_table(vma, flags);
255 }
256 if (unlikely(pud_bad(*pud)))
257 return no_page_table(vma, flags);
258
259 pmd = pmd_offset(pud, address);
260 if (pmd_none(*pmd))
261 return no_page_table(vma, flags);
262 if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
263 page = follow_huge_pmd(mm, address, pmd, flags);
264 if (page)
265 return page;
266 return no_page_table(vma, flags);
267 }
268 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
269 return no_page_table(vma, flags);
270 if (pmd_devmap(*pmd)) {
271 ptl = pmd_lock(mm, pmd);
272 page = follow_devmap_pmd(vma, address, pmd, flags);
273 spin_unlock(ptl);
274 if (page)
275 return page;
276 }
277 if (likely(!pmd_trans_huge(*pmd)))
278 return follow_page_pte(vma, address, pmd, flags);
279
280 ptl = pmd_lock(mm, pmd);
281 if (unlikely(!pmd_trans_huge(*pmd))) {
282 spin_unlock(ptl);
283 return follow_page_pte(vma, address, pmd, flags);
284 }
285 if (flags & FOLL_SPLIT) {
286 int ret;
287 page = pmd_page(*pmd);
288 if (is_huge_zero_page(page)) {
289 spin_unlock(ptl);
290 ret = 0;
291 split_huge_pmd(vma, pmd, address);
292 if (pmd_trans_unstable(pmd))
293 ret = -EBUSY;
294 } else {
295 get_page(page);
296 spin_unlock(ptl);
297 lock_page(page);
298 ret = split_huge_page(page);
299 unlock_page(page);
300 put_page(page);
301 if (pmd_none(*pmd))
302 return no_page_table(vma, flags);
303 }
304
305 return ret ? ERR_PTR(ret) :
306 follow_page_pte(vma, address, pmd, flags);
307 }
308
309 page = follow_trans_huge_pmd(vma, address, pmd, flags);
310 spin_unlock(ptl);
311 *page_mask = HPAGE_PMD_NR - 1;
312 return page;
313}
314
315static int get_gate_page(struct mm_struct *mm, unsigned long address,
316 unsigned int gup_flags, struct vm_area_struct **vma,
317 struct page **page)
318{
319 pgd_t *pgd;
320 pud_t *pud;
321 pmd_t *pmd;
322 pte_t *pte;
323 int ret = -EFAULT;
324
325 /* user gate pages are read-only */
326 if (gup_flags & FOLL_WRITE)
327 return -EFAULT;
328 if (address > TASK_SIZE)
329 pgd = pgd_offset_k(address);
330 else
331 pgd = pgd_offset_gate(mm, address);
332 BUG_ON(pgd_none(*pgd));
333 pud = pud_offset(pgd, address);
334 BUG_ON(pud_none(*pud));
335 pmd = pmd_offset(pud, address);
336 if (pmd_none(*pmd))
337 return -EFAULT;
338 VM_BUG_ON(pmd_trans_huge(*pmd));
339 pte = pte_offset_map(pmd, address);
340 if (pte_none(*pte))
341 goto unmap;
342 *vma = get_gate_vma(mm);
343 if (!page)
344 goto out;
345 *page = vm_normal_page(*vma, address, *pte);
346 if (!*page) {
347 if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte)))
348 goto unmap;
349 *page = pte_page(*pte);
350 }
351 get_page(*page);
352out:
353 ret = 0;
354unmap:
355 pte_unmap(pte);
356 return ret;
357}
358
359/*
360 * mmap_sem must be held on entry. If @nonblocking != NULL and
361 * *@flags does not include FOLL_NOWAIT, the mmap_sem may be released.
362 * If it is, *@nonblocking will be set to 0 and -EBUSY returned.
363 */
364static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
365 unsigned long address, unsigned int *flags, int *nonblocking)
366{
367 unsigned int fault_flags = 0;
368 int ret;
369
370 /* mlock all present pages, but do not fault in new pages */
371 if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
372 return -ENOENT;
373 /* For mm_populate(), just skip the stack guard page. */
374 if ((*flags & FOLL_POPULATE) &&
375 (stack_guard_page_start(vma, address) ||
376 stack_guard_page_end(vma, address + PAGE_SIZE)))
377 return -ENOENT;
378 if (*flags & FOLL_WRITE)
379 fault_flags |= FAULT_FLAG_WRITE;
380 if (*flags & FOLL_REMOTE)
381 fault_flags |= FAULT_FLAG_REMOTE;
382 if (nonblocking)
383 fault_flags |= FAULT_FLAG_ALLOW_RETRY;
384 if (*flags & FOLL_NOWAIT)
385 fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
386 if (*flags & FOLL_TRIED) {
387 VM_WARN_ON_ONCE(fault_flags & FAULT_FLAG_ALLOW_RETRY);
388 fault_flags |= FAULT_FLAG_TRIED;
389 }
390
391 ret = handle_mm_fault(vma, address, fault_flags);
392 if (ret & VM_FAULT_ERROR) {
393 if (ret & VM_FAULT_OOM)
394 return -ENOMEM;
395 if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
396 return *flags & FOLL_HWPOISON ? -EHWPOISON : -EFAULT;
397 if (ret & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV))
398 return -EFAULT;
399 BUG();
400 }
401
402 if (tsk) {
403 if (ret & VM_FAULT_MAJOR)
404 tsk->maj_flt++;
405 else
406 tsk->min_flt++;
407 }
408
409 if (ret & VM_FAULT_RETRY) {
410 if (nonblocking)
411 *nonblocking = 0;
412 return -EBUSY;
413 }
414
415 /*
416 * The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when
417 * necessary, even if maybe_mkwrite decided not to set pte_write. We
418 * can thus safely do subsequent page lookups as if they were reads.
419 * But only do so when looping for pte_write is futile: in some cases
420 * userspace may also be wanting to write to the gotten user page,
421 * which a read fault here might prevent (a readonly page might get
422 * reCOWed by userspace write).
423 */
424 if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE))
425 *flags |= FOLL_COW;
426 return 0;
427}
428
429static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
430{
431 vm_flags_t vm_flags = vma->vm_flags;
432 int write = (gup_flags & FOLL_WRITE);
433 int foreign = (gup_flags & FOLL_REMOTE);
434
435 if (vm_flags & (VM_IO | VM_PFNMAP))
436 return -EFAULT;
437
438 if (write) {
439 if (!(vm_flags & VM_WRITE)) {
440 if (!(gup_flags & FOLL_FORCE))
441 return -EFAULT;
442 /*
443 * We used to let the write,force case do COW in a
444 * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could
445 * set a breakpoint in a read-only mapping of an
446 * executable, without corrupting the file (yet only
447 * when that file had been opened for writing!).
448 * Anon pages in shared mappings are surprising: now
449 * just reject it.
450 */
451 if (!is_cow_mapping(vm_flags))
452 return -EFAULT;
453 }
454 } else if (!(vm_flags & VM_READ)) {
455 if (!(gup_flags & FOLL_FORCE))
456 return -EFAULT;
457 /*
458 * Is there actually any vma we can reach here which does not
459 * have VM_MAYREAD set?
460 */
461 if (!(vm_flags & VM_MAYREAD))
462 return -EFAULT;
463 }
464 /*
465 * gups are always data accesses, not instruction
466 * fetches, so execute=false here
467 */
468 if (!arch_vma_access_permitted(vma, write, false, foreign))
469 return -EFAULT;
470 return 0;
471}
472
473/**
474 * __get_user_pages() - pin user pages in memory
475 * @tsk: task_struct of target task
476 * @mm: mm_struct of target mm
477 * @start: starting user address
478 * @nr_pages: number of pages from start to pin
479 * @gup_flags: flags modifying pin behaviour
480 * @pages: array that receives pointers to the pages pinned.
481 * Should be at least nr_pages long. Or NULL, if caller
482 * only intends to ensure the pages are faulted in.
483 * @vmas: array of pointers to vmas corresponding to each page.
484 * Or NULL if the caller does not require them.
485 * @nonblocking: whether waiting for disk IO or mmap_sem contention
486 *
487 * Returns number of pages pinned. This may be fewer than the number
488 * requested. If nr_pages is 0 or negative, returns 0. If no pages
489 * were pinned, returns -errno. Each page returned must be released
490 * with a put_page() call when it is finished with. vmas will only
491 * remain valid while mmap_sem is held.
492 *
493 * Must be called with mmap_sem held. It may be released. See below.
494 *
495 * __get_user_pages walks a process's page tables and takes a reference to
496 * each struct page that each user address corresponds to at a given
497 * instant. That is, it takes the page that would be accessed if a user
498 * thread accesses the given user virtual address at that instant.
499 *
500 * This does not guarantee that the page exists in the user mappings when
501 * __get_user_pages returns, and there may even be a completely different
502 * page there in some cases (eg. if mmapped pagecache has been invalidated
503 * and subsequently re faulted). However it does guarantee that the page
504 * won't be freed completely. And mostly callers simply care that the page
505 * contains data that was valid *at some point in time*. Typically, an IO
506 * or similar operation cannot guarantee anything stronger anyway because
507 * locks can't be held over the syscall boundary.
508 *
509 * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
510 * the page is written to, set_page_dirty (or set_page_dirty_lock, as
511 * appropriate) must be called after the page is finished with, and
512 * before put_page is called.
513 *
514 * If @nonblocking != NULL, __get_user_pages will not wait for disk IO
515 * or mmap_sem contention, and if waiting is needed to pin all pages,
516 * *@nonblocking will be set to 0. Further, if @gup_flags does not
517 * include FOLL_NOWAIT, the mmap_sem will be released via up_read() in
518 * this case.
519 *
520 * A caller using such a combination of @nonblocking and @gup_flags
521 * must therefore hold the mmap_sem for reading only, and recognize
522 * when it's been released. Otherwise, it must be held for either
523 * reading or writing and will not be released.
524 *
525 * In most cases, get_user_pages or get_user_pages_fast should be used
526 * instead of __get_user_pages. __get_user_pages should be used only if
527 * you need some special @gup_flags.
528 */
529static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
530 unsigned long start, unsigned long nr_pages,
531 unsigned int gup_flags, struct page **pages,
532 struct vm_area_struct **vmas, int *nonblocking)
533{
534 long i = 0;
535 unsigned int page_mask;
536 struct vm_area_struct *vma = NULL;
537
538 if (!nr_pages)
539 return 0;
540
541 VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
542
543 /*
544 * If FOLL_FORCE is set then do not force a full fault as the hinting
545 * fault information is unrelated to the reference behaviour of a task
546 * using the address space
547 */
548 if (!(gup_flags & FOLL_FORCE))
549 gup_flags |= FOLL_NUMA;
550
551 do {
552 struct page *page;
553 unsigned int foll_flags = gup_flags;
554 unsigned int page_increm;
555
556 /* first iteration or cross vma bound */
557 if (!vma || start >= vma->vm_end) {
558 vma = find_extend_vma(mm, start);
559 if (!vma && in_gate_area(mm, start)) {
560 int ret;
561 ret = get_gate_page(mm, start & PAGE_MASK,
562 gup_flags, &vma,
563 pages ? &pages[i] : NULL);
564 if (ret)
565 return i ? : ret;
566 page_mask = 0;
567 goto next_page;
568 }
569
570 if (!vma || check_vma_flags(vma, gup_flags))
571 return i ? : -EFAULT;
572 if (is_vm_hugetlb_page(vma)) {
573 i = follow_hugetlb_page(mm, vma, pages, vmas,
574 &start, &nr_pages, i,
575 gup_flags);
576 continue;
577 }
578 }
579retry:
580 /*
581 * If we have a pending SIGKILL, don't keep faulting pages and
582 * potentially allocating memory.
583 */
584 if (unlikely(fatal_signal_pending(current)))
585 return i ? i : -ERESTARTSYS;
586 cond_resched();
587 page = follow_page_mask(vma, start, foll_flags, &page_mask);
588 if (!page) {
589 int ret;
590 ret = faultin_page(tsk, vma, start, &foll_flags,
591 nonblocking);
592 switch (ret) {
593 case 0:
594 goto retry;
595 case -EFAULT:
596 case -ENOMEM:
597 case -EHWPOISON:
598 return i ? i : ret;
599 case -EBUSY:
600 return i;
601 case -ENOENT:
602 goto next_page;
603 }
604 BUG();
605 } else if (PTR_ERR(page) == -EEXIST) {
606 /*
607 * Proper page table entry exists, but no corresponding
608 * struct page.
609 */
610 goto next_page;
611 } else if (IS_ERR(page)) {
612 return i ? i : PTR_ERR(page);
613 }
614 if (pages) {
615 pages[i] = page;
616 flush_anon_page(vma, page, start);
617 flush_dcache_page(page);
618 page_mask = 0;
619 }
620next_page:
621 if (vmas) {
622 vmas[i] = vma;
623 page_mask = 0;
624 }
625 page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
626 if (page_increm > nr_pages)
627 page_increm = nr_pages;
628 i += page_increm;
629 start += page_increm * PAGE_SIZE;
630 nr_pages -= page_increm;
631 } while (nr_pages);
632 return i;
633}
634
635static bool vma_permits_fault(struct vm_area_struct *vma,
636 unsigned int fault_flags)
637{
638 bool write = !!(fault_flags & FAULT_FLAG_WRITE);
639 bool foreign = !!(fault_flags & FAULT_FLAG_REMOTE);
640 vm_flags_t vm_flags = write ? VM_WRITE : VM_READ;
641
642 if (!(vm_flags & vma->vm_flags))
643 return false;
644
645 /*
646 * The architecture might have a hardware protection
647 * mechanism other than read/write that can deny access.
648 *
649 * gup always represents data access, not instruction
650 * fetches, so execute=false here:
651 */
652 if (!arch_vma_access_permitted(vma, write, false, foreign))
653 return false;
654
655 return true;
656}
657
658/*
659 * fixup_user_fault() - manually resolve a user page fault
660 * @tsk: the task_struct to use for page fault accounting, or
661 * NULL if faults are not to be recorded.
662 * @mm: mm_struct of target mm
663 * @address: user address
664 * @fault_flags:flags to pass down to handle_mm_fault()
665 * @unlocked: did we unlock the mmap_sem while retrying, maybe NULL if caller
666 * does not allow retry
667 *
668 * This is meant to be called in the specific scenario where for locking reasons
669 * we try to access user memory in atomic context (within a pagefault_disable()
670 * section), this returns -EFAULT, and we want to resolve the user fault before
671 * trying again.
672 *
673 * Typically this is meant to be used by the futex code.
674 *
675 * The main difference with get_user_pages() is that this function will
676 * unconditionally call handle_mm_fault() which will in turn perform all the
677 * necessary SW fixup of the dirty and young bits in the PTE, while
678 * get_user_pages() only guarantees to update these in the struct page.
679 *
680 * This is important for some architectures where those bits also gate the
681 * access permission to the page because they are maintained in software. On
682 * such architectures, gup() will not be enough to make a subsequent access
683 * succeed.
684 *
685 * This function will not return with an unlocked mmap_sem. So it has not the
686 * same semantics wrt the @mm->mmap_sem as does filemap_fault().
687 */
688int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
689 unsigned long address, unsigned int fault_flags,
690 bool *unlocked)
691{
692 struct vm_area_struct *vma;
693 int ret, major = 0;
694
695 if (unlocked)
696 fault_flags |= FAULT_FLAG_ALLOW_RETRY;
697
698retry:
699 vma = find_extend_vma(mm, address);
700 if (!vma || address < vma->vm_start)
701 return -EFAULT;
702
703 if (!vma_permits_fault(vma, fault_flags))
704 return -EFAULT;
705
706 ret = handle_mm_fault(vma, address, fault_flags);
707 major |= ret & VM_FAULT_MAJOR;
708 if (ret & VM_FAULT_ERROR) {
709 if (ret & VM_FAULT_OOM)
710 return -ENOMEM;
711 if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
712 return -EHWPOISON;
713 if (ret & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV))
714 return -EFAULT;
715 BUG();
716 }
717
718 if (ret & VM_FAULT_RETRY) {
719 down_read(&mm->mmap_sem);
720 if (!(fault_flags & FAULT_FLAG_TRIED)) {
721 *unlocked = true;
722 fault_flags &= ~FAULT_FLAG_ALLOW_RETRY;
723 fault_flags |= FAULT_FLAG_TRIED;
724 goto retry;
725 }
726 }
727
728 if (tsk) {
729 if (major)
730 tsk->maj_flt++;
731 else
732 tsk->min_flt++;
733 }
734 return 0;
735}
736EXPORT_SYMBOL_GPL(fixup_user_fault);
737
738static __always_inline long __get_user_pages_locked(struct task_struct *tsk,
739 struct mm_struct *mm,
740 unsigned long start,
741 unsigned long nr_pages,
742 struct page **pages,
743 struct vm_area_struct **vmas,
744 int *locked, bool notify_drop,
745 unsigned int flags)
746{
747 long ret, pages_done;
748 bool lock_dropped;
749
750 if (locked) {
751 /* if VM_FAULT_RETRY can be returned, vmas become invalid */
752 BUG_ON(vmas);
753 /* check caller initialized locked */
754 BUG_ON(*locked != 1);
755 }
756
757 if (pages)
758 flags |= FOLL_GET;
759
760 pages_done = 0;
761 lock_dropped = false;
762 for (;;) {
763 ret = __get_user_pages(tsk, mm, start, nr_pages, flags, pages,
764 vmas, locked);
765 if (!locked)
766 /* VM_FAULT_RETRY couldn't trigger, bypass */
767 return ret;
768
769 /* VM_FAULT_RETRY cannot return errors */
770 if (!*locked) {
771 BUG_ON(ret < 0);
772 BUG_ON(ret >= nr_pages);
773 }
774
775 if (!pages)
776 /* If it's a prefault don't insist harder */
777 return ret;
778
779 if (ret > 0) {
780 nr_pages -= ret;
781 pages_done += ret;
782 if (!nr_pages)
783 break;
784 }
785 if (*locked) {
786 /* VM_FAULT_RETRY didn't trigger */
787 if (!pages_done)
788 pages_done = ret;
789 break;
790 }
791 /* VM_FAULT_RETRY triggered, so seek to the faulting offset */
792 pages += ret;
793 start += ret << PAGE_SHIFT;
794
795 /*
796 * Repeat on the address that fired VM_FAULT_RETRY
797 * without FAULT_FLAG_ALLOW_RETRY but with
798 * FAULT_FLAG_TRIED.
799 */
800 *locked = 1;
801 lock_dropped = true;
802 down_read(&mm->mmap_sem);
803 ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED,
804 pages, NULL, NULL);
805 if (ret != 1) {
806 BUG_ON(ret > 1);
807 if (!pages_done)
808 pages_done = ret;
809 break;
810 }
811 nr_pages--;
812 pages_done++;
813 if (!nr_pages)
814 break;
815 pages++;
816 start += PAGE_SIZE;
817 }
818 if (notify_drop && lock_dropped && *locked) {
819 /*
820 * We must let the caller know we temporarily dropped the lock
821 * and so the critical section protected by it was lost.
822 */
823 up_read(&mm->mmap_sem);
824 *locked = 0;
825 }
826 return pages_done;
827}
828
829/*
830 * We can leverage the VM_FAULT_RETRY functionality in the page fault
831 * paths better by using either get_user_pages_locked() or
832 * get_user_pages_unlocked().
833 *
834 * get_user_pages_locked() is suitable to replace the form:
835 *
836 * down_read(&mm->mmap_sem);
837 * do_something()
838 * get_user_pages(tsk, mm, ..., pages, NULL);
839 * up_read(&mm->mmap_sem);
840 *
841 * to:
842 *
843 * int locked = 1;
844 * down_read(&mm->mmap_sem);
845 * do_something()
846 * get_user_pages_locked(tsk, mm, ..., pages, &locked);
847 * if (locked)
848 * up_read(&mm->mmap_sem);
849 */
850long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
851 unsigned int gup_flags, struct page **pages,
852 int *locked)
853{
854 return __get_user_pages_locked(current, current->mm, start, nr_pages,
855 pages, NULL, locked, true,
856 gup_flags | FOLL_TOUCH);
857}
858EXPORT_SYMBOL(get_user_pages_locked);
859
860/*
861 * Same as get_user_pages_unlocked(...., FOLL_TOUCH) but it allows for
862 * tsk, mm to be specified.
863 *
864 * NOTE: here FOLL_TOUCH is not set implicitly and must be set by the
865 * caller if required (just like with __get_user_pages). "FOLL_GET"
866 * is set implicitly if "pages" is non-NULL.
867 */
868static __always_inline long __get_user_pages_unlocked(struct task_struct *tsk,
869 struct mm_struct *mm, unsigned long start,
870 unsigned long nr_pages, struct page **pages,
871 unsigned int gup_flags)
872{
873 long ret;
874 int locked = 1;
875
876 down_read(&mm->mmap_sem);
877 ret = __get_user_pages_locked(tsk, mm, start, nr_pages, pages, NULL,
878 &locked, false, gup_flags);
879 if (locked)
880 up_read(&mm->mmap_sem);
881 return ret;
882}
883
884/*
885 * get_user_pages_unlocked() is suitable to replace the form:
886 *
887 * down_read(&mm->mmap_sem);
888 * get_user_pages(tsk, mm, ..., pages, NULL);
889 * up_read(&mm->mmap_sem);
890 *
891 * with:
892 *
893 * get_user_pages_unlocked(tsk, mm, ..., pages);
894 *
895 * It is functionally equivalent to get_user_pages_fast so
896 * get_user_pages_fast should be used instead if specific gup_flags
897 * (e.g. FOLL_FORCE) are not required.
898 */
899long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
900 struct page **pages, unsigned int gup_flags)
901{
902 return __get_user_pages_unlocked(current, current->mm, start, nr_pages,
903 pages, gup_flags | FOLL_TOUCH);
904}
905EXPORT_SYMBOL(get_user_pages_unlocked);
906
907/*
908 * get_user_pages_remote() - pin user pages in memory
909 * @tsk: the task_struct to use for page fault accounting, or
910 * NULL if faults are not to be recorded.
911 * @mm: mm_struct of target mm
912 * @start: starting user address
913 * @nr_pages: number of pages from start to pin
914 * @gup_flags: flags modifying lookup behaviour
915 * @pages: array that receives pointers to the pages pinned.
916 * Should be at least nr_pages long. Or NULL, if caller
917 * only intends to ensure the pages are faulted in.
918 * @vmas: array of pointers to vmas corresponding to each page.
919 * Or NULL if the caller does not require them.
920 * @locked: pointer to lock flag indicating whether lock is held and
921 * subsequently whether VM_FAULT_RETRY functionality can be
922 * utilised. Lock must initially be held.
923 *
924 * Returns number of pages pinned. This may be fewer than the number
925 * requested. If nr_pages is 0 or negative, returns 0. If no pages
926 * were pinned, returns -errno. Each page returned must be released
927 * with a put_page() call when it is finished with. vmas will only
928 * remain valid while mmap_sem is held.
929 *
930 * Must be called with mmap_sem held for read or write.
931 *
932 * get_user_pages walks a process's page tables and takes a reference to
933 * each struct page that each user address corresponds to at a given
934 * instant. That is, it takes the page that would be accessed if a user
935 * thread accesses the given user virtual address at that instant.
936 *
937 * This does not guarantee that the page exists in the user mappings when
938 * get_user_pages returns, and there may even be a completely different
939 * page there in some cases (eg. if mmapped pagecache has been invalidated
940 * and subsequently re faulted). However it does guarantee that the page
941 * won't be freed completely. And mostly callers simply care that the page
942 * contains data that was valid *at some point in time*. Typically, an IO
943 * or similar operation cannot guarantee anything stronger anyway because
944 * locks can't be held over the syscall boundary.
945 *
946 * If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page
947 * is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must
948 * be called after the page is finished with, and before put_page is called.
949 *
950 * get_user_pages is typically used for fewer-copy IO operations, to get a
951 * handle on the memory by some means other than accesses via the user virtual
952 * addresses. The pages may be submitted for DMA to devices or accessed via
953 * their kernel linear mapping (via the kmap APIs). Care should be taken to
954 * use the correct cache flushing APIs.
955 *
956 * See also get_user_pages_fast, for performance critical applications.
957 *
958 * get_user_pages should be phased out in favor of
959 * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
960 * should use get_user_pages because it cannot pass
961 * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
962 */
963long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
964 unsigned long start, unsigned long nr_pages,
965 unsigned int gup_flags, struct page **pages,
966 struct vm_area_struct **vmas, int *locked)
967{
968 return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas,
969 locked, true,
970 gup_flags | FOLL_TOUCH | FOLL_REMOTE);
971}
972EXPORT_SYMBOL(get_user_pages_remote);
973
974/*
975 * This is the same as get_user_pages_remote(), just with a
976 * less-flexible calling convention where we assume that the task
977 * and mm being operated on are the current task's and don't allow
978 * passing of a locked parameter. We also obviously don't pass
979 * FOLL_REMOTE in here.
980 */
981long get_user_pages(unsigned long start, unsigned long nr_pages,
982 unsigned int gup_flags, struct page **pages,
983 struct vm_area_struct **vmas)
984{
985 return __get_user_pages_locked(current, current->mm, start, nr_pages,
986 pages, vmas, NULL, false,
987 gup_flags | FOLL_TOUCH);
988}
989EXPORT_SYMBOL(get_user_pages);
990
991/**
992 * populate_vma_page_range() - populate a range of pages in the vma.
993 * @vma: target vma
994 * @start: start address
995 * @end: end address
996 * @nonblocking:
997 *
998 * This takes care of mlocking the pages too if VM_LOCKED is set.
999 *
1000 * return 0 on success, negative error code on error.
1001 *
1002 * vma->vm_mm->mmap_sem must be held.
1003 *
1004 * If @nonblocking is NULL, it may be held for read or write and will
1005 * be unperturbed.
1006 *
1007 * If @nonblocking is non-NULL, it must held for read only and may be
1008 * released. If it's released, *@nonblocking will be set to 0.
1009 */
1010long populate_vma_page_range(struct vm_area_struct *vma,
1011 unsigned long start, unsigned long end, int *nonblocking)
1012{
1013 struct mm_struct *mm = vma->vm_mm;
1014 unsigned long nr_pages = (end - start) / PAGE_SIZE;
1015 int gup_flags;
1016
1017 VM_BUG_ON(start & ~PAGE_MASK);
1018 VM_BUG_ON(end & ~PAGE_MASK);
1019 VM_BUG_ON_VMA(start < vma->vm_start, vma);
1020 VM_BUG_ON_VMA(end > vma->vm_end, vma);
1021 VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);
1022
1023 gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK;
1024 if (vma->vm_flags & VM_LOCKONFAULT)
1025 gup_flags &= ~FOLL_POPULATE;
1026 /*
1027 * We want to touch writable mappings with a write fault in order
1028 * to break COW, except for shared mappings because these don't COW
1029 * and we would not want to dirty them for nothing.
1030 */
1031 if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
1032 gup_flags |= FOLL_WRITE;
1033
1034 /*
1035 * We want mlock to succeed for regions that have any permissions
1036 * other than PROT_NONE.
1037 */
1038 if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
1039 gup_flags |= FOLL_FORCE;
1040
1041 /*
1042 * We made sure addr is within a VMA, so the following will
1043 * not result in a stack expansion that recurses back here.
1044 */
1045 return __get_user_pages(current, mm, start, nr_pages, gup_flags,
1046 NULL, NULL, nonblocking);
1047}
1048
1049/*
1050 * __mm_populate - populate and/or mlock pages within a range of address space.
1051 *
1052 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
1053 * flags. VMAs must be already marked with the desired vm_flags, and
1054 * mmap_sem must not be held.
1055 */
1056int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
1057{
1058 struct mm_struct *mm = current->mm;
1059 unsigned long end, nstart, nend;
1060 struct vm_area_struct *vma = NULL;
1061 int locked = 0;
1062 long ret = 0;
1063
1064 VM_BUG_ON(start & ~PAGE_MASK);
1065 VM_BUG_ON(len != PAGE_ALIGN(len));
1066 end = start + len;
1067
1068 for (nstart = start; nstart < end; nstart = nend) {
1069 /*
1070 * We want to fault in pages for [nstart; end) address range.
1071 * Find first corresponding VMA.
1072 */
1073 if (!locked) {
1074 locked = 1;
1075 down_read(&mm->mmap_sem);
1076 vma = find_vma(mm, nstart);
1077 } else if (nstart >= vma->vm_end)
1078 vma = vma->vm_next;
1079 if (!vma || vma->vm_start >= end)
1080 break;
1081 /*
1082 * Set [nstart; nend) to intersection of desired address
1083 * range with the first VMA. Also, skip undesirable VMA types.
1084 */
1085 nend = min(end, vma->vm_end);
1086 if (vma->vm_flags & (VM_IO | VM_PFNMAP))
1087 continue;
1088 if (nstart < vma->vm_start)
1089 nstart = vma->vm_start;
1090 /*
1091 * Now fault in a range of pages. populate_vma_page_range()
1092 * double checks the vma flags, so that it won't mlock pages
1093 * if the vma was already munlocked.
1094 */
1095 ret = populate_vma_page_range(vma, nstart, nend, &locked);
1096 if (ret < 0) {
1097 if (ignore_errors) {
1098 ret = 0;
1099 continue; /* continue at next VMA */
1100 }
1101 break;
1102 }
1103 nend = nstart + ret * PAGE_SIZE;
1104 ret = 0;
1105 }
1106 if (locked)
1107 up_read(&mm->mmap_sem);
1108 return ret; /* 0 or negative error code */
1109}
1110
1111/**
1112 * get_dump_page() - pin user page in memory while writing it to core dump
1113 * @addr: user address
1114 *
1115 * Returns struct page pointer of user page pinned for dump,
1116 * to be freed afterwards by put_page().
1117 *
1118 * Returns NULL on any kind of failure - a hole must then be inserted into
1119 * the corefile, to preserve alignment with its headers; and also returns
1120 * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
1121 * allowing a hole to be left in the corefile to save diskspace.
1122 *
1123 * Called without mmap_sem, but after all other threads have been killed.
1124 */
1125#ifdef CONFIG_ELF_CORE
1126struct page *get_dump_page(unsigned long addr)
1127{
1128 struct vm_area_struct *vma;
1129 struct page *page;
1130
1131 if (__get_user_pages(current, current->mm, addr, 1,
1132 FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma,
1133 NULL) < 1)
1134 return NULL;
1135 flush_cache_page(vma, addr, page_to_pfn(page));
1136 return page;
1137}
1138#endif /* CONFIG_ELF_CORE */
1139
1140/*
1141 * Generic RCU Fast GUP
1142 *
1143 * get_user_pages_fast attempts to pin user pages by walking the page
1144 * tables directly and avoids taking locks. Thus the walker needs to be
1145 * protected from page table pages being freed from under it, and should
1146 * block any THP splits.
1147 *
1148 * One way to achieve this is to have the walker disable interrupts, and
1149 * rely on IPIs from the TLB flushing code blocking before the page table
1150 * pages are freed. This is unsuitable for architectures that do not need
1151 * to broadcast an IPI when invalidating TLBs.
1152 *
1153 * Another way to achieve this is to batch up page table containing pages
1154 * belonging to more than one mm_user, then rcu_sched a callback to free those
1155 * pages. Disabling interrupts will allow the fast_gup walker to both block
1156 * the rcu_sched callback, and an IPI that we broadcast for splitting THPs
1157 * (which is a relatively rare event). The code below adopts this strategy.
1158 *
1159 * Before activating this code, please be aware that the following assumptions
1160 * are currently made:
1161 *
1162 * *) HAVE_RCU_TABLE_FREE is enabled, and tlb_remove_table is used to free
1163 * pages containing page tables.
1164 *
1165 * *) ptes can be read atomically by the architecture.
1166 *
1167 * *) access_ok is sufficient to validate userspace address ranges.
1168 *
1169 * The last two assumptions can be relaxed by the addition of helper functions.
1170 *
1171 * This code is based heavily on the PowerPC implementation by Nick Piggin.
1172 */
1173#ifdef CONFIG_HAVE_GENERIC_RCU_GUP
1174
1175#ifdef __HAVE_ARCH_PTE_SPECIAL
1176static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
1177 int write, struct page **pages, int *nr)
1178{
1179 pte_t *ptep, *ptem;
1180 int ret = 0;
1181
1182 ptem = ptep = pte_offset_map(&pmd, addr);
1183 do {
1184 /*
1185 * In the line below we are assuming that the pte can be read
1186 * atomically. If this is not the case for your architecture,
1187 * please wrap this in a helper function!
1188 *
1189 * for an example see gup_get_pte in arch/x86/mm/gup.c
1190 */
1191 pte_t pte = READ_ONCE(*ptep);
1192 struct page *head, *page;
1193
1194 /*
1195 * Similar to the PMD case below, NUMA hinting must take slow
1196 * path using the pte_protnone check.
1197 */
1198 if (!pte_present(pte) || pte_special(pte) ||
1199 pte_protnone(pte) || (write && !pte_write(pte)))
1200 goto pte_unmap;
1201
1202 if (!arch_pte_access_permitted(pte, write))
1203 goto pte_unmap;
1204
1205 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
1206 page = pte_page(pte);
1207 head = compound_head(page);
1208
1209 if (!page_cache_get_speculative(head))
1210 goto pte_unmap;
1211
1212 if (unlikely(pte_val(pte) != pte_val(*ptep))) {
1213 put_page(head);
1214 goto pte_unmap;
1215 }
1216
1217 VM_BUG_ON_PAGE(compound_head(page) != head, page);
1218 pages[*nr] = page;
1219 (*nr)++;
1220
1221 } while (ptep++, addr += PAGE_SIZE, addr != end);
1222
1223 ret = 1;
1224
1225pte_unmap:
1226 pte_unmap(ptem);
1227 return ret;
1228}
1229#else
1230
1231/*
1232 * If we can't determine whether or not a pte is special, then fail immediately
1233 * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
1234 * to be special.
1235 *
1236 * For a futex to be placed on a THP tail page, get_futex_key requires a
1237 * __get_user_pages_fast implementation that can pin pages. Thus it's still
1238 * useful to have gup_huge_pmd even if we can't operate on ptes.
1239 */
1240static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
1241 int write, struct page **pages, int *nr)
1242{
1243 return 0;
1244}
1245#endif /* __HAVE_ARCH_PTE_SPECIAL */
1246
1247static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
1248 unsigned long end, int write, struct page **pages, int *nr)
1249{
1250 struct page *head, *page;
1251 int refs;
1252
1253 if (write && !pmd_write(orig))
1254 return 0;
1255
1256 refs = 0;
1257 head = pmd_page(orig);
1258 page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
1259 do {
1260 VM_BUG_ON_PAGE(compound_head(page) != head, page);
1261 pages[*nr] = page;
1262 (*nr)++;
1263 page++;
1264 refs++;
1265 } while (addr += PAGE_SIZE, addr != end);
1266
1267 if (!page_cache_add_speculative(head, refs)) {
1268 *nr -= refs;
1269 return 0;
1270 }
1271
1272 if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
1273 *nr -= refs;
1274 while (refs--)
1275 put_page(head);
1276 return 0;
1277 }
1278
1279 return 1;
1280}
1281
1282static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
1283 unsigned long end, int write, struct page **pages, int *nr)
1284{
1285 struct page *head, *page;
1286 int refs;
1287
1288 if (write && !pud_write(orig))
1289 return 0;
1290
1291 refs = 0;
1292 head = pud_page(orig);
1293 page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
1294 do {
1295 VM_BUG_ON_PAGE(compound_head(page) != head, page);
1296 pages[*nr] = page;
1297 (*nr)++;
1298 page++;
1299 refs++;
1300 } while (addr += PAGE_SIZE, addr != end);
1301
1302 if (!page_cache_add_speculative(head, refs)) {
1303 *nr -= refs;
1304 return 0;
1305 }
1306
1307 if (unlikely(pud_val(orig) != pud_val(*pudp))) {
1308 *nr -= refs;
1309 while (refs--)
1310 put_page(head);
1311 return 0;
1312 }
1313
1314 return 1;
1315}
1316
1317static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
1318 unsigned long end, int write,
1319 struct page **pages, int *nr)
1320{
1321 int refs;
1322 struct page *head, *page;
1323
1324 if (write && !pgd_write(orig))
1325 return 0;
1326
1327 refs = 0;
1328 head = pgd_page(orig);
1329 page = head + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
1330 do {
1331 VM_BUG_ON_PAGE(compound_head(page) != head, page);
1332 pages[*nr] = page;
1333 (*nr)++;
1334 page++;
1335 refs++;
1336 } while (addr += PAGE_SIZE, addr != end);
1337
1338 if (!page_cache_add_speculative(head, refs)) {
1339 *nr -= refs;
1340 return 0;
1341 }
1342
1343 if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
1344 *nr -= refs;
1345 while (refs--)
1346 put_page(head);
1347 return 0;
1348 }
1349
1350 return 1;
1351}
1352
1353static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
1354 int write, struct page **pages, int *nr)
1355{
1356 unsigned long next;
1357 pmd_t *pmdp;
1358
1359 pmdp = pmd_offset(&pud, addr);
1360 do {
1361 pmd_t pmd = READ_ONCE(*pmdp);
1362
1363 next = pmd_addr_end(addr, end);
1364 if (pmd_none(pmd))
1365 return 0;
1366
1367 if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd))) {
1368 /*
1369 * NUMA hinting faults need to be handled in the GUP
1370 * slowpath for accounting purposes and so that they
1371 * can be serialised against THP migration.
1372 */
1373 if (pmd_protnone(pmd))
1374 return 0;
1375
1376 if (!gup_huge_pmd(pmd, pmdp, addr, next, write,
1377 pages, nr))
1378 return 0;
1379
1380 } else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) {
1381 /*
1382 * architecture have different format for hugetlbfs
1383 * pmd format and THP pmd format
1384 */
1385 if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr,
1386 PMD_SHIFT, next, write, pages, nr))
1387 return 0;
1388 } else if (!gup_pte_range(pmd, addr, next, write, pages, nr))
1389 return 0;
1390 } while (pmdp++, addr = next, addr != end);
1391
1392 return 1;
1393}
1394
1395static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
1396 int write, struct page **pages, int *nr)
1397{
1398 unsigned long next;
1399 pud_t *pudp;
1400
1401 pudp = pud_offset(&pgd, addr);
1402 do {
1403 pud_t pud = READ_ONCE(*pudp);
1404
1405 next = pud_addr_end(addr, end);
1406 if (pud_none(pud))
1407 return 0;
1408 if (unlikely(pud_huge(pud))) {
1409 if (!gup_huge_pud(pud, pudp, addr, next, write,
1410 pages, nr))
1411 return 0;
1412 } else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) {
1413 if (!gup_huge_pd(__hugepd(pud_val(pud)), addr,
1414 PUD_SHIFT, next, write, pages, nr))
1415 return 0;
1416 } else if (!gup_pmd_range(pud, addr, next, write, pages, nr))
1417 return 0;
1418 } while (pudp++, addr = next, addr != end);
1419
1420 return 1;
1421}
1422
1423/*
1424 * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
1425 * the regular GUP. It will only return non-negative values.
1426 */
1427int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
1428 struct page **pages)
1429{
1430 struct mm_struct *mm = current->mm;
1431 unsigned long addr, len, end;
1432 unsigned long next, flags;
1433 pgd_t *pgdp;
1434 int nr = 0;
1435
1436 start &= PAGE_MASK;
1437 addr = start;
1438 len = (unsigned long) nr_pages << PAGE_SHIFT;
1439 end = start + len;
1440
1441 if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
1442 start, len)))
1443 return 0;
1444
1445 /*
1446 * Disable interrupts. We use the nested form as we can already have
1447 * interrupts disabled by get_futex_key.
1448 *
1449 * With interrupts disabled, we block page table pages from being
1450 * freed from under us. See mmu_gather_tlb in asm-generic/tlb.h
1451 * for more details.
1452 *
1453 * We do not adopt an rcu_read_lock(.) here as we also want to
1454 * block IPIs that come from THPs splitting.
1455 */
1456
1457 local_irq_save(flags);
1458 pgdp = pgd_offset(mm, addr);
1459 do {
1460 pgd_t pgd = READ_ONCE(*pgdp);
1461
1462 next = pgd_addr_end(addr, end);
1463 if (pgd_none(pgd))
1464 break;
1465 if (unlikely(pgd_huge(pgd))) {
1466 if (!gup_huge_pgd(pgd, pgdp, addr, next, write,
1467 pages, &nr))
1468 break;
1469 } else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) {
1470 if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
1471 PGDIR_SHIFT, next, write, pages, &nr))
1472 break;
1473 } else if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
1474 break;
1475 } while (pgdp++, addr = next, addr != end);
1476 local_irq_restore(flags);
1477
1478 return nr;
1479}
1480
1481/**
1482 * get_user_pages_fast() - pin user pages in memory
1483 * @start: starting user address
1484 * @nr_pages: number of pages from start to pin
1485 * @write: whether pages will be written to
1486 * @pages: array that receives pointers to the pages pinned.
1487 * Should be at least nr_pages long.
1488 *
1489 * Attempt to pin user pages in memory without taking mm->mmap_sem.
1490 * If not successful, it will fall back to taking the lock and
1491 * calling get_user_pages().
1492 *
1493 * Returns number of pages pinned. This may be fewer than the number
1494 * requested. If nr_pages is 0 or negative, returns 0. If no pages
1495 * were pinned, returns -errno.
1496 */
1497int get_user_pages_fast(unsigned long start, int nr_pages, int write,
1498 struct page **pages)
1499{
1500 int nr, ret;
1501
1502 start &= PAGE_MASK;
1503 nr = __get_user_pages_fast(start, nr_pages, write, pages);
1504 ret = nr;
1505
1506 if (nr < nr_pages) {
1507 /* Try to get the remaining pages with get_user_pages */
1508 start += nr << PAGE_SHIFT;
1509 pages += nr;
1510
1511 ret = get_user_pages_unlocked(start, nr_pages - nr, pages,
1512 write ? FOLL_WRITE : 0);
1513
1514 /* Have to be a bit careful with return values */
1515 if (nr > 0) {
1516 if (ret < 0)
1517 ret = nr;
1518 else
1519 ret += nr;
1520 }
1521 }
1522
1523 return ret;
1524}
1525
1526#endif /* CONFIG_HAVE_GENERIC_RCU_GUP */