1 #define __DISABLE_GUP_DEPRECATED 1
2 #include <linux/kernel.h>
3 #include <linux/errno.h>
5 #include <linux/spinlock.h>
8 #include <linux/memremap.h>
9 #include <linux/pagemap.h>
10 #include <linux/rmap.h>
11 #include <linux/swap.h>
12 #include <linux/swapops.h>
14 #include <linux/sched.h>
15 #include <linux/rwsem.h>
16 #include <linux/hugetlb.h>
18 #include <asm/mmu_context.h>
19 #include <asm/pgtable.h>
20 #include <asm/tlbflush.h>
24 static struct page *no_page_table(struct vm_area_struct *vma,
28 * When core dumping an enormous anonymous area that nobody
29 * has touched so far, we don't want to allocate unnecessary pages or
30 * page tables. Return error instead of NULL to skip handle_mm_fault,
31 * then get_dump_page() will return NULL to leave a hole in the dump.
32 * But we can only make this optimization where a hole would surely
33 * be zero-filled if handle_mm_fault() actually did handle it.
35 if ((flags & FOLL_DUMP) && (!vma->vm_ops || !vma->vm_ops->fault))
36 return ERR_PTR(-EFAULT);
40 static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address,
41 pte_t *pte, unsigned int flags)
43 /* No page to get reference */
47 if (flags & FOLL_TOUCH) {
50 if (flags & FOLL_WRITE)
51 entry = pte_mkdirty(entry);
52 entry = pte_mkyoung(entry);
54 if (!pte_same(*pte, entry)) {
55 set_pte_at(vma->vm_mm, address, pte, entry);
56 update_mmu_cache(vma, address, pte);
60 /* Proper page table entry exists, but no corresponding struct page */
64 static struct page *follow_page_pte(struct vm_area_struct *vma,
65 unsigned long address, pmd_t *pmd, unsigned int flags)
67 struct mm_struct *mm = vma->vm_mm;
68 struct dev_pagemap *pgmap = NULL;
74 if (unlikely(pmd_bad(*pmd)))
75 return no_page_table(vma, flags);
77 ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
79 if (!pte_present(pte)) {
82 * KSM's break_ksm() relies upon recognizing a ksm page
83 * even while it is being migrated, so for that case we
84 * need migration_entry_wait().
86 if (likely(!(flags & FOLL_MIGRATION)))
90 entry = pte_to_swp_entry(pte);
91 if (!is_migration_entry(entry))
93 pte_unmap_unlock(ptep, ptl);
94 migration_entry_wait(mm, pmd, address);
97 if ((flags & FOLL_NUMA) && pte_protnone(pte))
99 if ((flags & FOLL_WRITE) && !pte_write(pte)) {
100 pte_unmap_unlock(ptep, ptl);
104 page = vm_normal_page(vma, address, pte);
105 if (!page && pte_devmap(pte) && (flags & FOLL_GET)) {
107 * Only return device mapping pages in the FOLL_GET case since
108 * they are only valid while holding the pgmap reference.
110 pgmap = get_dev_pagemap(pte_pfn(pte), NULL);
112 page = pte_page(pte);
115 } else if (unlikely(!page)) {
116 if (flags & FOLL_DUMP) {
117 /* Avoid special (like zero) pages in core dumps */
118 page = ERR_PTR(-EFAULT);
122 if (is_zero_pfn(pte_pfn(pte))) {
123 page = pte_page(pte);
127 ret = follow_pfn_pte(vma, address, ptep, flags);
133 if (flags & FOLL_SPLIT && PageTransCompound(page)) {
136 pte_unmap_unlock(ptep, ptl);
138 ret = split_huge_page(page);
146 if (flags & FOLL_GET) {
149 /* drop the pgmap reference now that we hold the page */
151 put_dev_pagemap(pgmap);
155 if (flags & FOLL_TOUCH) {
156 if ((flags & FOLL_WRITE) &&
157 !pte_dirty(pte) && !PageDirty(page))
158 set_page_dirty(page);
160 * pte_mkyoung() would be more correct here, but atomic care
161 * is needed to avoid losing the dirty bit: it is easier to use
162 * mark_page_accessed().
164 mark_page_accessed(page);
166 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
167 /* Do not mlock pte-mapped THP */
168 if (PageTransCompound(page))
172 * The preliminary mapping check is mainly to avoid the
173 * pointless overhead of lock_page on the ZERO_PAGE
174 * which might bounce very badly if there is contention.
176 * If the page is already locked, we don't need to
177 * handle it now - vmscan will handle it later if and
178 * when it attempts to reclaim the page.
180 if (page->mapping && trylock_page(page)) {
181 lru_add_drain(); /* push cached pages to LRU */
183 * Because we lock page here, and migration is
184 * blocked by the pte's page reference, and we
185 * know the page is still mapped, we don't even
186 * need to check for file-cache page truncation.
188 mlock_vma_page(page);
193 pte_unmap_unlock(ptep, ptl);
196 pte_unmap_unlock(ptep, ptl);
199 return no_page_table(vma, flags);
203 * follow_page_mask - look up a page descriptor from a user-virtual address
204 * @vma: vm_area_struct mapping @address
205 * @address: virtual address to look up
206 * @flags: flags modifying lookup behaviour
207 * @page_mask: on output, *page_mask is set according to the size of the page
209 * @flags can have FOLL_ flags set, defined in <linux/mm.h>
211 * Returns the mapped (struct page *), %NULL if no mapping exists, or
212 * an error pointer if there is a mapping to something not represented
213 * by a page descriptor (see also vm_normal_page()).
215 struct page *follow_page_mask(struct vm_area_struct *vma,
216 unsigned long address, unsigned int flags,
217 unsigned int *page_mask)
224 struct mm_struct *mm = vma->vm_mm;
228 page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
230 BUG_ON(flags & FOLL_GET);
234 pgd = pgd_offset(mm, address);
235 if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
236 return no_page_table(vma, flags);
238 pud = pud_offset(pgd, address);
240 return no_page_table(vma, flags);
241 if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
242 page = follow_huge_pud(mm, address, pud, flags);
245 return no_page_table(vma, flags);
247 if (unlikely(pud_bad(*pud)))
248 return no_page_table(vma, flags);
250 pmd = pmd_offset(pud, address);
252 return no_page_table(vma, flags);
253 if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
254 page = follow_huge_pmd(mm, address, pmd, flags);
257 return no_page_table(vma, flags);
259 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
260 return no_page_table(vma, flags);
261 if (pmd_devmap(*pmd)) {
262 ptl = pmd_lock(mm, pmd);
263 page = follow_devmap_pmd(vma, address, pmd, flags);
268 if (likely(!pmd_trans_huge(*pmd)))
269 return follow_page_pte(vma, address, pmd, flags);
271 ptl = pmd_lock(mm, pmd);
272 if (unlikely(!pmd_trans_huge(*pmd))) {
274 return follow_page_pte(vma, address, pmd, flags);
276 if (flags & FOLL_SPLIT) {
278 page = pmd_page(*pmd);
279 if (is_huge_zero_page(page)) {
282 split_huge_pmd(vma, pmd, address);
287 ret = split_huge_page(page);
292 return ret ? ERR_PTR(ret) :
293 follow_page_pte(vma, address, pmd, flags);
296 page = follow_trans_huge_pmd(vma, address, pmd, flags);
298 *page_mask = HPAGE_PMD_NR - 1;
302 static int get_gate_page(struct mm_struct *mm, unsigned long address,
303 unsigned int gup_flags, struct vm_area_struct **vma,
312 /* user gate pages are read-only */
313 if (gup_flags & FOLL_WRITE)
315 if (address > TASK_SIZE)
316 pgd = pgd_offset_k(address);
318 pgd = pgd_offset_gate(mm, address);
319 BUG_ON(pgd_none(*pgd));
320 pud = pud_offset(pgd, address);
321 BUG_ON(pud_none(*pud));
322 pmd = pmd_offset(pud, address);
325 VM_BUG_ON(pmd_trans_huge(*pmd));
326 pte = pte_offset_map(pmd, address);
329 *vma = get_gate_vma(mm);
332 *page = vm_normal_page(*vma, address, *pte);
334 if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte)))
336 *page = pte_page(*pte);
347 * mmap_sem must be held on entry. If @nonblocking != NULL and
348 * *@flags does not include FOLL_NOWAIT, the mmap_sem may be released.
349 * If it is, *@nonblocking will be set to 0 and -EBUSY returned.
351 static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
352 unsigned long address, unsigned int *flags, int *nonblocking)
354 struct mm_struct *mm = vma->vm_mm;
355 unsigned int fault_flags = 0;
358 /* mlock all present pages, but do not fault in new pages */
359 if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
361 /* For mm_populate(), just skip the stack guard page. */
362 if ((*flags & FOLL_POPULATE) &&
363 (stack_guard_page_start(vma, address) ||
364 stack_guard_page_end(vma, address + PAGE_SIZE)))
366 if (*flags & FOLL_WRITE)
367 fault_flags |= FAULT_FLAG_WRITE;
369 fault_flags |= FAULT_FLAG_ALLOW_RETRY;
370 if (*flags & FOLL_NOWAIT)
371 fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
372 if (*flags & FOLL_TRIED) {
373 VM_WARN_ON_ONCE(fault_flags & FAULT_FLAG_ALLOW_RETRY);
374 fault_flags |= FAULT_FLAG_TRIED;
377 ret = handle_mm_fault(mm, vma, address, fault_flags);
378 if (ret & VM_FAULT_ERROR) {
379 if (ret & VM_FAULT_OOM)
381 if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
382 return *flags & FOLL_HWPOISON ? -EHWPOISON : -EFAULT;
383 if (ret & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV))
389 if (ret & VM_FAULT_MAJOR)
395 if (ret & VM_FAULT_RETRY) {
402 * The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when
403 * necessary, even if maybe_mkwrite decided not to set pte_write. We
404 * can thus safely do subsequent page lookups as if they were reads.
405 * But only do so when looping for pte_write is futile: in some cases
406 * userspace may also be wanting to write to the gotten user page,
407 * which a read fault here might prevent (a readonly page might get
408 * reCOWed by userspace write).
410 if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE))
411 *flags &= ~FOLL_WRITE;
415 static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
417 vm_flags_t vm_flags = vma->vm_flags;
419 if (vm_flags & (VM_IO | VM_PFNMAP))
422 if (gup_flags & FOLL_WRITE) {
423 if (!(vm_flags & VM_WRITE)) {
424 if (!(gup_flags & FOLL_FORCE))
427 * We used to let the write,force case do COW in a
428 * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could
429 * set a breakpoint in a read-only mapping of an
430 * executable, without corrupting the file (yet only
431 * when that file had been opened for writing!).
432 * Anon pages in shared mappings are surprising: now
435 if (!is_cow_mapping(vm_flags))
438 } else if (!(vm_flags & VM_READ)) {
439 if (!(gup_flags & FOLL_FORCE))
442 * Is there actually any vma we can reach here which does not
443 * have VM_MAYREAD set?
445 if (!(vm_flags & VM_MAYREAD))
448 if (!arch_vma_access_permitted(vma, (gup_flags & FOLL_WRITE)))
454 * __get_user_pages() - pin user pages in memory
455 * @tsk: task_struct of target task
456 * @mm: mm_struct of target mm
457 * @start: starting user address
458 * @nr_pages: number of pages from start to pin
459 * @gup_flags: flags modifying pin behaviour
460 * @pages: array that receives pointers to the pages pinned.
461 * Should be at least nr_pages long. Or NULL, if caller
462 * only intends to ensure the pages are faulted in.
463 * @vmas: array of pointers to vmas corresponding to each page.
464 * Or NULL if the caller does not require them.
465 * @nonblocking: whether waiting for disk IO or mmap_sem contention
467 * Returns number of pages pinned. This may be fewer than the number
468 * requested. If nr_pages is 0 or negative, returns 0. If no pages
469 * were pinned, returns -errno. Each page returned must be released
470 * with a put_page() call when it is finished with. vmas will only
471 * remain valid while mmap_sem is held.
473 * Must be called with mmap_sem held. It may be released. See below.
475 * __get_user_pages walks a process's page tables and takes a reference to
476 * each struct page that each user address corresponds to at a given
477 * instant. That is, it takes the page that would be accessed if a user
478 * thread accesses the given user virtual address at that instant.
480 * This does not guarantee that the page exists in the user mappings when
481 * __get_user_pages returns, and there may even be a completely different
482 * page there in some cases (eg. if mmapped pagecache has been invalidated
483 * and subsequently re faulted). However it does guarantee that the page
484 * won't be freed completely. And mostly callers simply care that the page
485 * contains data that was valid *at some point in time*. Typically, an IO
486 * or similar operation cannot guarantee anything stronger anyway because
487 * locks can't be held over the syscall boundary.
489 * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
490 * the page is written to, set_page_dirty (or set_page_dirty_lock, as
491 * appropriate) must be called after the page is finished with, and
492 * before put_page is called.
494 * If @nonblocking != NULL, __get_user_pages will not wait for disk IO
495 * or mmap_sem contention, and if waiting is needed to pin all pages,
496 * *@nonblocking will be set to 0. Further, if @gup_flags does not
497 * include FOLL_NOWAIT, the mmap_sem will be released via up_read() in
500 * A caller using such a combination of @nonblocking and @gup_flags
501 * must therefore hold the mmap_sem for reading only, and recognize
502 * when it's been released. Otherwise, it must be held for either
503 * reading or writing and will not be released.
505 * In most cases, get_user_pages or get_user_pages_fast should be used
506 * instead of __get_user_pages. __get_user_pages should be used only if
507 * you need some special @gup_flags.
509 long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
510 unsigned long start, unsigned long nr_pages,
511 unsigned int gup_flags, struct page **pages,
512 struct vm_area_struct **vmas, int *nonblocking)
515 unsigned int page_mask;
516 struct vm_area_struct *vma = NULL;
521 VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
524 * If FOLL_FORCE is set then do not force a full fault as the hinting
525 * fault information is unrelated to the reference behaviour of a task
526 * using the address space
528 if (!(gup_flags & FOLL_FORCE))
529 gup_flags |= FOLL_NUMA;
533 unsigned int foll_flags = gup_flags;
534 unsigned int page_increm;
536 /* first iteration or cross vma bound */
537 if (!vma || start >= vma->vm_end) {
538 vma = find_extend_vma(mm, start);
539 if (!vma && in_gate_area(mm, start)) {
541 ret = get_gate_page(mm, start & PAGE_MASK,
543 pages ? &pages[i] : NULL);
550 if (!vma || check_vma_flags(vma, gup_flags))
551 return i ? : -EFAULT;
552 if (is_vm_hugetlb_page(vma)) {
553 i = follow_hugetlb_page(mm, vma, pages, vmas,
554 &start, &nr_pages, i,
561 * If we have a pending SIGKILL, don't keep faulting pages and
562 * potentially allocating memory.
564 if (unlikely(fatal_signal_pending(current)))
565 return i ? i : -ERESTARTSYS;
567 page = follow_page_mask(vma, start, foll_flags, &page_mask);
570 ret = faultin_page(tsk, vma, start, &foll_flags,
585 } else if (PTR_ERR(page) == -EEXIST) {
587 * Proper page table entry exists, but no corresponding
591 } else if (IS_ERR(page)) {
592 return i ? i : PTR_ERR(page);
596 flush_anon_page(vma, page, start);
597 flush_dcache_page(page);
605 page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
606 if (page_increm > nr_pages)
607 page_increm = nr_pages;
609 start += page_increm * PAGE_SIZE;
610 nr_pages -= page_increm;
614 EXPORT_SYMBOL(__get_user_pages);
616 bool vma_permits_fault(struct vm_area_struct *vma, unsigned int fault_flags)
618 bool write = !!(fault_flags & FAULT_FLAG_WRITE);
619 vm_flags_t vm_flags = write ? VM_WRITE : VM_READ;
621 if (!(vm_flags & vma->vm_flags))
625 * The architecture might have a hardware protection
626 * mechanism other than read/write that can deny access
628 if (!arch_vma_access_permitted(vma, write))
635 * fixup_user_fault() - manually resolve a user page fault
636 * @tsk: the task_struct to use for page fault accounting, or
637 * NULL if faults are not to be recorded.
638 * @mm: mm_struct of target mm
639 * @address: user address
640 * @fault_flags:flags to pass down to handle_mm_fault()
641 * @unlocked: did we unlock the mmap_sem while retrying, maybe NULL if caller
642 * does not allow retry
644 * This is meant to be called in the specific scenario where for locking reasons
645 * we try to access user memory in atomic context (within a pagefault_disable()
646 * section), this returns -EFAULT, and we want to resolve the user fault before
649 * Typically this is meant to be used by the futex code.
651 * The main difference with get_user_pages() is that this function will
652 * unconditionally call handle_mm_fault() which will in turn perform all the
653 * necessary SW fixup of the dirty and young bits in the PTE, while
654 * get_user_pages() only guarantees to update these in the struct page.
656 * This is important for some architectures where those bits also gate the
657 * access permission to the page because they are maintained in software. On
658 * such architectures, gup() will not be enough to make a subsequent access
661 * This function will not return with an unlocked mmap_sem. So it has not the
662 * same semantics wrt the @mm->mmap_sem as does filemap_fault().
664 int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
665 unsigned long address, unsigned int fault_flags,
668 struct vm_area_struct *vma;
672 fault_flags |= FAULT_FLAG_ALLOW_RETRY;
675 vma = find_extend_vma(mm, address);
676 if (!vma || address < vma->vm_start)
679 if (!vma_permits_fault(vma, fault_flags))
682 ret = handle_mm_fault(mm, vma, address, fault_flags);
683 major |= ret & VM_FAULT_MAJOR;
684 if (ret & VM_FAULT_ERROR) {
685 if (ret & VM_FAULT_OOM)
687 if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
689 if (ret & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV))
694 if (ret & VM_FAULT_RETRY) {
695 down_read(&mm->mmap_sem);
696 if (!(fault_flags & FAULT_FLAG_TRIED)) {
698 fault_flags &= ~FAULT_FLAG_ALLOW_RETRY;
699 fault_flags |= FAULT_FLAG_TRIED;
713 static __always_inline long __get_user_pages_locked(struct task_struct *tsk,
714 struct mm_struct *mm,
716 unsigned long nr_pages,
717 int write, int force,
719 struct vm_area_struct **vmas,
720 int *locked, bool notify_drop,
723 long ret, pages_done;
727 /* if VM_FAULT_RETRY can be returned, vmas become invalid */
729 /* check caller initialized locked */
730 BUG_ON(*locked != 1);
741 lock_dropped = false;
743 ret = __get_user_pages(tsk, mm, start, nr_pages, flags, pages,
746 /* VM_FAULT_RETRY couldn't trigger, bypass */
749 /* VM_FAULT_RETRY cannot return errors */
752 BUG_ON(ret >= nr_pages);
756 /* If it's a prefault don't insist harder */
766 /* VM_FAULT_RETRY didn't trigger */
771 /* VM_FAULT_RETRY triggered, so seek to the faulting offset */
773 start += ret << PAGE_SHIFT;
776 * Repeat on the address that fired VM_FAULT_RETRY
777 * without FAULT_FLAG_ALLOW_RETRY but with
782 down_read(&mm->mmap_sem);
783 ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED,
798 if (notify_drop && lock_dropped && *locked) {
800 * We must let the caller know we temporarily dropped the lock
801 * and so the critical section protected by it was lost.
803 up_read(&mm->mmap_sem);
810 * We can leverage the VM_FAULT_RETRY functionality in the page fault
811 * paths better by using either get_user_pages_locked() or
812 * get_user_pages_unlocked().
814 * get_user_pages_locked() is suitable to replace the form:
816 * down_read(&mm->mmap_sem);
818 * get_user_pages(tsk, mm, ..., pages, NULL);
819 * up_read(&mm->mmap_sem);
824 * down_read(&mm->mmap_sem);
826 * get_user_pages_locked(tsk, mm, ..., pages, &locked);
828 * up_read(&mm->mmap_sem);
830 long get_user_pages_locked6(unsigned long start, unsigned long nr_pages,
831 int write, int force, struct page **pages,
834 return __get_user_pages_locked(current, current->mm, start, nr_pages,
835 write, force, pages, NULL, locked, true,
838 EXPORT_SYMBOL(get_user_pages_locked6);
841 * Same as get_user_pages_unlocked(...., FOLL_TOUCH) but it allows to
842 * pass additional gup_flags as last parameter (like FOLL_HWPOISON).
844 * NOTE: here FOLL_TOUCH is not set implicitly and must be set by the
845 * caller if required (just like with __get_user_pages). "FOLL_GET",
846 * "FOLL_WRITE" and "FOLL_FORCE" are set implicitly as needed
847 * according to the parameters "pages", "write", "force"
850 __always_inline long __get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
851 unsigned long start, unsigned long nr_pages,
852 int write, int force, struct page **pages,
853 unsigned int gup_flags)
857 down_read(&mm->mmap_sem);
858 ret = __get_user_pages_locked(tsk, mm, start, nr_pages, write, force,
859 pages, NULL, &locked, false, gup_flags);
861 up_read(&mm->mmap_sem);
864 EXPORT_SYMBOL(__get_user_pages_unlocked);
867 * get_user_pages_unlocked() is suitable to replace the form:
869 * down_read(&mm->mmap_sem);
870 * get_user_pages(tsk, mm, ..., pages, NULL);
871 * up_read(&mm->mmap_sem);
875 * get_user_pages_unlocked(tsk, mm, ..., pages);
877 * It is functionally equivalent to get_user_pages_fast so
878 * get_user_pages_fast should be used instead, if the two parameters
879 * "tsk" and "mm" are respectively equal to current and current->mm,
880 * or if "force" shall be set to 1 (get_user_pages_fast misses the
881 * "force" parameter).
883 long get_user_pages_unlocked5(unsigned long start, unsigned long nr_pages,
884 int write, int force, struct page **pages)
886 return __get_user_pages_unlocked(current, current->mm, start, nr_pages,
887 write, force, pages, FOLL_TOUCH);
889 EXPORT_SYMBOL(get_user_pages_unlocked5);
892 * get_user_pages_remote() - pin user pages in memory
893 * @tsk: the task_struct to use for page fault accounting, or
894 * NULL if faults are not to be recorded.
895 * @mm: mm_struct of target mm
896 * @start: starting user address
897 * @nr_pages: number of pages from start to pin
898 * @write: whether pages will be written to by the caller
899 * @force: whether to force access even when user mapping is currently
900 * protected (but never forces write access to shared mapping).
901 * @pages: array that receives pointers to the pages pinned.
902 * Should be at least nr_pages long. Or NULL, if caller
903 * only intends to ensure the pages are faulted in.
904 * @vmas: array of pointers to vmas corresponding to each page.
905 * Or NULL if the caller does not require them.
907 * Returns number of pages pinned. This may be fewer than the number
908 * requested. If nr_pages is 0 or negative, returns 0. If no pages
909 * were pinned, returns -errno. Each page returned must be released
910 * with a put_page() call when it is finished with. vmas will only
911 * remain valid while mmap_sem is held.
913 * Must be called with mmap_sem held for read or write.
915 * get_user_pages walks a process's page tables and takes a reference to
916 * each struct page that each user address corresponds to at a given
917 * instant. That is, it takes the page that would be accessed if a user
918 * thread accesses the given user virtual address at that instant.
920 * This does not guarantee that the page exists in the user mappings when
921 * get_user_pages returns, and there may even be a completely different
922 * page there in some cases (eg. if mmapped pagecache has been invalidated
923 * and subsequently re faulted). However it does guarantee that the page
924 * won't be freed completely. And mostly callers simply care that the page
925 * contains data that was valid *at some point in time*. Typically, an IO
926 * or similar operation cannot guarantee anything stronger anyway because
927 * locks can't be held over the syscall boundary.
929 * If write=0, the page must not be written to. If the page is written to,
930 * set_page_dirty (or set_page_dirty_lock, as appropriate) must be called
931 * after the page is finished with, and before put_page is called.
933 * get_user_pages is typically used for fewer-copy IO operations, to get a
934 * handle on the memory by some means other than accesses via the user virtual
935 * addresses. The pages may be submitted for DMA to devices or accessed via
936 * their kernel linear mapping (via the kmap APIs). Care should be taken to
937 * use the correct cache flushing APIs.
939 * See also get_user_pages_fast, for performance critical applications.
941 * get_user_pages should be phased out in favor of
942 * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
943 * should use get_user_pages because it cannot pass
944 * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
946 long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
947 unsigned long start, unsigned long nr_pages,
948 int write, int force, struct page **pages,
949 struct vm_area_struct **vmas)
951 return __get_user_pages_locked(tsk, mm, start, nr_pages, write, force,
952 pages, vmas, NULL, false,
953 FOLL_TOUCH | FOLL_REMOTE);
955 EXPORT_SYMBOL(get_user_pages_remote);
958 * This is the same as get_user_pages_remote(), just with a
959 * less-flexible calling convention where we assume that the task
960 * and mm being operated on are the current task's. We also
961 * obviously don't pass FOLL_REMOTE in here.
963 long get_user_pages6(unsigned long start, unsigned long nr_pages,
964 int write, int force, struct page **pages,
965 struct vm_area_struct **vmas)
967 return __get_user_pages_locked(current, current->mm, start, nr_pages,
968 write, force, pages, vmas, NULL, false,
971 EXPORT_SYMBOL(get_user_pages6);
974 * populate_vma_page_range() - populate a range of pages in the vma.
976 * @start: start address
980 * This takes care of mlocking the pages too if VM_LOCKED is set.
982 * return 0 on success, negative error code on error.
984 * vma->vm_mm->mmap_sem must be held.
986 * If @nonblocking is NULL, it may be held for read or write and will
989 * If @nonblocking is non-NULL, it must held for read only and may be
990 * released. If it's released, *@nonblocking will be set to 0.
992 long populate_vma_page_range(struct vm_area_struct *vma,
993 unsigned long start, unsigned long end, int *nonblocking)
995 struct mm_struct *mm = vma->vm_mm;
996 unsigned long nr_pages = (end - start) / PAGE_SIZE;
999 VM_BUG_ON(start & ~PAGE_MASK);
1000 VM_BUG_ON(end & ~PAGE_MASK);
1001 VM_BUG_ON_VMA(start < vma->vm_start, vma);
1002 VM_BUG_ON_VMA(end > vma->vm_end, vma);
1003 VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);
1005 gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK;
1006 if (vma->vm_flags & VM_LOCKONFAULT)
1007 gup_flags &= ~FOLL_POPULATE;
1009 * We want to touch writable mappings with a write fault in order
1010 * to break COW, except for shared mappings because these don't COW
1011 * and we would not want to dirty them for nothing.
1013 if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
1014 gup_flags |= FOLL_WRITE;
1017 * We want mlock to succeed for regions that have any permissions
1018 * other than PROT_NONE.
1020 if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
1021 gup_flags |= FOLL_FORCE;
1024 * We made sure addr is within a VMA, so the following will
1025 * not result in a stack expansion that recurses back here.
1027 return __get_user_pages(current, mm, start, nr_pages, gup_flags,
1028 NULL, NULL, nonblocking);
1032 * __mm_populate - populate and/or mlock pages within a range of address space.
1034 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
1035 * flags. VMAs must be already marked with the desired vm_flags, and
1036 * mmap_sem must not be held.
1038 int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
1040 struct mm_struct *mm = current->mm;
1041 unsigned long end, nstart, nend;
1042 struct vm_area_struct *vma = NULL;
1046 VM_BUG_ON(start & ~PAGE_MASK);
1047 VM_BUG_ON(len != PAGE_ALIGN(len));
1050 for (nstart = start; nstart < end; nstart = nend) {
1052 * We want to fault in pages for [nstart; end) address range.
1053 * Find first corresponding VMA.
1057 down_read(&mm->mmap_sem);
1058 vma = find_vma(mm, nstart);
1059 } else if (nstart >= vma->vm_end)
1061 if (!vma || vma->vm_start >= end)
1064 * Set [nstart; nend) to intersection of desired address
1065 * range with the first VMA. Also, skip undesirable VMA types.
1067 nend = min(end, vma->vm_end);
1068 if (vma->vm_flags & (VM_IO | VM_PFNMAP))
1070 if (nstart < vma->vm_start)
1071 nstart = vma->vm_start;
1073 * Now fault in a range of pages. populate_vma_page_range()
1074 * double checks the vma flags, so that it won't mlock pages
1075 * if the vma was already munlocked.
1077 ret = populate_vma_page_range(vma, nstart, nend, &locked);
1079 if (ignore_errors) {
1081 continue; /* continue at next VMA */
1085 nend = nstart + ret * PAGE_SIZE;
1089 up_read(&mm->mmap_sem);
1090 return ret; /* 0 or negative error code */
1094 * get_dump_page() - pin user page in memory while writing it to core dump
1095 * @addr: user address
1097 * Returns struct page pointer of user page pinned for dump,
1098 * to be freed afterwards by page_cache_release() or put_page().
1100 * Returns NULL on any kind of failure - a hole must then be inserted into
1101 * the corefile, to preserve alignment with its headers; and also returns
1102 * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
1103 * allowing a hole to be left in the corefile to save diskspace.
1105 * Called without mmap_sem, but after all other threads have been killed.
1107 #ifdef CONFIG_ELF_CORE
1108 struct page *get_dump_page(unsigned long addr)
1110 struct vm_area_struct *vma;
1113 if (__get_user_pages(current, current->mm, addr, 1,
1114 FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma,
1117 flush_cache_page(vma, addr, page_to_pfn(page));
1120 #endif /* CONFIG_ELF_CORE */
1123 * Generic RCU Fast GUP
1125 * get_user_pages_fast attempts to pin user pages by walking the page
1126 * tables directly and avoids taking locks. Thus the walker needs to be
1127 * protected from page table pages being freed from under it, and should
1128 * block any THP splits.
1130 * One way to achieve this is to have the walker disable interrupts, and
1131 * rely on IPIs from the TLB flushing code blocking before the page table
1132 * pages are freed. This is unsuitable for architectures that do not need
1133 * to broadcast an IPI when invalidating TLBs.
1135 * Another way to achieve this is to batch up page table containing pages
1136 * belonging to more than one mm_user, then rcu_sched a callback to free those
1137 * pages. Disabling interrupts will allow the fast_gup walker to both block
1138 * the rcu_sched callback, and an IPI that we broadcast for splitting THPs
1139 * (which is a relatively rare event). The code below adopts this strategy.
1141 * Before activating this code, please be aware that the following assumptions
1142 * are currently made:
1144 * *) HAVE_RCU_TABLE_FREE is enabled, and tlb_remove_table is used to free
1145 * pages containing page tables.
1147 * *) ptes can be read atomically by the architecture.
1149 * *) access_ok is sufficient to validate userspace address ranges.
1151 * The last two assumptions can be relaxed by the addition of helper functions.
1153 * This code is based heavily on the PowerPC implementation by Nick Piggin.
1155 #ifdef CONFIG_HAVE_GENERIC_RCU_GUP
1157 #ifdef __HAVE_ARCH_PTE_SPECIAL
1158 static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
1159 int write, struct page **pages, int *nr)
1164 ptem = ptep = pte_offset_map(&pmd, addr);
1167 * In the line below we are assuming that the pte can be read
1168 * atomically. If this is not the case for your architecture,
1169 * please wrap this in a helper function!
1171 * for an example see gup_get_pte in arch/x86/mm/gup.c
1173 pte_t pte = READ_ONCE(*ptep);
1174 struct page *head, *page;
1177 * Similar to the PMD case below, NUMA hinting must take slow
1178 * path using the pte_protnone check.
1180 if (!pte_present(pte) || pte_special(pte) ||
1181 pte_protnone(pte) || (write && !pte_write(pte)))
1184 if (!arch_pte_access_permitted(pte, write))
1187 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
1188 page = pte_page(pte);
1189 head = compound_head(page);
1191 if (!page_cache_get_speculative(head))
1194 if (unlikely(pte_val(pte) != pte_val(*ptep))) {
1199 VM_BUG_ON_PAGE(compound_head(page) != head, page);
1203 } while (ptep++, addr += PAGE_SIZE, addr != end);
1214 * If we can't determine whether or not a pte is special, then fail immediately
1215 * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
1218 * For a futex to be placed on a THP tail page, get_futex_key requires a
1219 * __get_user_pages_fast implementation that can pin pages. Thus it's still
1220 * useful to have gup_huge_pmd even if we can't operate on ptes.
1222 static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
1223 int write, struct page **pages, int *nr)
1227 #endif /* __HAVE_ARCH_PTE_SPECIAL */
1229 static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
1230 unsigned long end, int write, struct page **pages, int *nr)
1232 struct page *head, *page;
1235 if (write && !pmd_write(orig))
1239 head = pmd_page(orig);
1240 page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
1242 VM_BUG_ON_PAGE(compound_head(page) != head, page);
1247 } while (addr += PAGE_SIZE, addr != end);
1249 if (!page_cache_add_speculative(head, refs)) {
1254 if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
1264 static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
1265 unsigned long end, int write, struct page **pages, int *nr)
1267 struct page *head, *page;
1270 if (write && !pud_write(orig))
1274 head = pud_page(orig);
1275 page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
1277 VM_BUG_ON_PAGE(compound_head(page) != head, page);
1282 } while (addr += PAGE_SIZE, addr != end);
1284 if (!page_cache_add_speculative(head, refs)) {
1289 if (unlikely(pud_val(orig) != pud_val(*pudp))) {
1299 static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
1300 unsigned long end, int write,
1301 struct page **pages, int *nr)
1304 struct page *head, *page;
1306 if (write && !pgd_write(orig))
1310 head = pgd_page(orig);
1311 page = head + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
1313 VM_BUG_ON_PAGE(compound_head(page) != head, page);
1318 } while (addr += PAGE_SIZE, addr != end);
1320 if (!page_cache_add_speculative(head, refs)) {
1325 if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
1335 static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
1336 int write, struct page **pages, int *nr)
1341 pmdp = pmd_offset(&pud, addr);
1343 pmd_t pmd = READ_ONCE(*pmdp);
1345 next = pmd_addr_end(addr, end);
1349 if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd))) {
1351 * NUMA hinting faults need to be handled in the GUP
1352 * slowpath for accounting purposes and so that they
1353 * can be serialised against THP migration.
1355 if (pmd_protnone(pmd))
1358 if (!gup_huge_pmd(pmd, pmdp, addr, next, write,
1362 } else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) {
1364 * architecture have different format for hugetlbfs
1365 * pmd format and THP pmd format
1367 if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr,
1368 PMD_SHIFT, next, write, pages, nr))
1370 } else if (!gup_pte_range(pmd, addr, next, write, pages, nr))
1372 } while (pmdp++, addr = next, addr != end);
1377 static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
1378 int write, struct page **pages, int *nr)
1383 pudp = pud_offset(&pgd, addr);
1385 pud_t pud = READ_ONCE(*pudp);
1387 next = pud_addr_end(addr, end);
1390 if (unlikely(pud_huge(pud))) {
1391 if (!gup_huge_pud(pud, pudp, addr, next, write,
1394 } else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) {
1395 if (!gup_huge_pd(__hugepd(pud_val(pud)), addr,
1396 PUD_SHIFT, next, write, pages, nr))
1398 } else if (!gup_pmd_range(pud, addr, next, write, pages, nr))
1400 } while (pudp++, addr = next, addr != end);
1406 * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
1407 * the regular GUP. It will only return non-negative values.
1409 int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
1410 struct page **pages)
1412 struct mm_struct *mm = current->mm;
1413 unsigned long addr, len, end;
1414 unsigned long next, flags;
1420 len = (unsigned long) nr_pages << PAGE_SHIFT;
1423 if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
1428 * Disable interrupts. We use the nested form as we can already have
1429 * interrupts disabled by get_futex_key.
1431 * With interrupts disabled, we block page table pages from being
1432 * freed from under us. See mmu_gather_tlb in asm-generic/tlb.h
1435 * We do not adopt an rcu_read_lock(.) here as we also want to
1436 * block IPIs that come from THPs splitting.
1439 local_irq_save(flags);
1440 pgdp = pgd_offset(mm, addr);
1442 pgd_t pgd = READ_ONCE(*pgdp);
1444 next = pgd_addr_end(addr, end);
1447 if (unlikely(pgd_huge(pgd))) {
1448 if (!gup_huge_pgd(pgd, pgdp, addr, next, write,
1451 } else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) {
1452 if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
1453 PGDIR_SHIFT, next, write, pages, &nr))
1455 } else if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
1457 } while (pgdp++, addr = next, addr != end);
1458 local_irq_restore(flags);
1464 * get_user_pages_fast() - pin user pages in memory
1465 * @start: starting user address
1466 * @nr_pages: number of pages from start to pin
1467 * @write: whether pages will be written to
1468 * @pages: array that receives pointers to the pages pinned.
1469 * Should be at least nr_pages long.
1471 * Attempt to pin user pages in memory without taking mm->mmap_sem.
1472 * If not successful, it will fall back to taking the lock and
1473 * calling get_user_pages().
1475 * Returns number of pages pinned. This may be fewer than the number
1476 * requested. If nr_pages is 0 or negative, returns 0. If no pages
1477 * were pinned, returns -errno.
1479 int get_user_pages_fast(unsigned long start, int nr_pages, int write,
1480 struct page **pages)
1482 struct mm_struct *mm = current->mm;
1486 nr = __get_user_pages_fast(start, nr_pages, write, pages);
1489 if (nr < nr_pages) {
1490 /* Try to get the remaining pages with get_user_pages */
1491 start += nr << PAGE_SHIFT;
1494 ret = get_user_pages_unlocked(current, mm, start,
1495 nr_pages - nr, write, 0, pages);
1497 /* Have to be a bit careful with return values */
1509 #endif /* CONFIG_HAVE_GENERIC_RCU_GUP */
1511 long get_user_pages8(struct task_struct *tsk, struct mm_struct *mm,
1512 unsigned long start, unsigned long nr_pages,
1513 int write, int force, struct page **pages,
1514 struct vm_area_struct **vmas)
1516 WARN_ONCE(tsk != current, "get_user_pages() called on remote task");
1517 WARN_ONCE(mm != current->mm, "get_user_pages() called on remote mm");
1519 return get_user_pages6(start, nr_pages, write, force, pages, vmas);
1521 EXPORT_SYMBOL(get_user_pages8);
1523 long get_user_pages_locked8(struct task_struct *tsk, struct mm_struct *mm,
1524 unsigned long start, unsigned long nr_pages,
1525 int write, int force, struct page **pages, int *locked)
1527 WARN_ONCE(tsk != current, "get_user_pages_locked() called on remote task");
1528 WARN_ONCE(mm != current->mm, "get_user_pages_locked() called on remote mm");
1530 return get_user_pages_locked6(start, nr_pages, write, force, pages, locked);
1532 EXPORT_SYMBOL(get_user_pages_locked8);
1534 long get_user_pages_unlocked7(struct task_struct *tsk, struct mm_struct *mm,
1535 unsigned long start, unsigned long nr_pages,
1536 int write, int force, struct page **pages)
1538 WARN_ONCE(tsk != current, "get_user_pages_unlocked() called on remote task");
1539 WARN_ONCE(mm != current->mm, "get_user_pages_unlocked() called on remote mm");
1541 return get_user_pages_unlocked5(start, nr_pages, write, force, pages);
1543 EXPORT_SYMBOL(get_user_pages_unlocked7);