]>
git.proxmox.com Git - mirror_ubuntu-zesty-kernel.git/blob - mm/gup.c
1 #include <linux/kernel.h>
2 #include <linux/errno.h>
4 #include <linux/spinlock.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>
13 #include <linux/sched.h>
14 #include <linux/rwsem.h>
15 #include <linux/hugetlb.h>
17 #include <asm/mmu_context.h>
18 #include <asm/pgtable.h>
19 #include <asm/tlbflush.h>
23 static struct page
*no_page_table(struct vm_area_struct
*vma
,
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.
34 if ((flags
& FOLL_DUMP
) && (!vma
->vm_ops
|| !vma
->vm_ops
->fault
))
35 return ERR_PTR(-EFAULT
);
39 static int follow_pfn_pte(struct vm_area_struct
*vma
, unsigned long address
,
40 pte_t
*pte
, unsigned int flags
)
42 /* No page to get reference */
46 if (flags
& FOLL_TOUCH
) {
49 if (flags
& FOLL_WRITE
)
50 entry
= pte_mkdirty(entry
);
51 entry
= pte_mkyoung(entry
);
53 if (!pte_same(*pte
, entry
)) {
54 set_pte_at(vma
->vm_mm
, address
, pte
, entry
);
55 update_mmu_cache(vma
, address
, pte
);
59 /* Proper page table entry exists, but no corresponding struct page */
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.
67 static inline bool can_follow_write_pte(pte_t pte
, unsigned int flags
)
69 return pte_write(pte
) ||
70 ((flags
& FOLL_FORCE
) && (flags
& FOLL_COW
) && pte_dirty(pte
));
73 static struct page
*follow_page_pte(struct vm_area_struct
*vma
,
74 unsigned long address
, pmd_t
*pmd
, unsigned int flags
)
76 struct mm_struct
*mm
= vma
->vm_mm
;
77 struct dev_pagemap
*pgmap
= NULL
;
83 if (unlikely(pmd_bad(*pmd
)))
84 return no_page_table(vma
, flags
);
86 ptep
= pte_offset_map_lock(mm
, pmd
, address
, &ptl
);
88 if (!pte_present(pte
)) {
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().
95 if (likely(!(flags
& FOLL_MIGRATION
)))
99 entry
= pte_to_swp_entry(pte
);
100 if (!is_migration_entry(entry
))
102 pte_unmap_unlock(ptep
, ptl
);
103 migration_entry_wait(mm
, pmd
, address
);
106 if ((flags
& FOLL_NUMA
) && pte_protnone(pte
))
108 if ((flags
& FOLL_WRITE
) && !can_follow_write_pte(pte
, flags
)) {
109 pte_unmap_unlock(ptep
, ptl
);
113 page
= vm_normal_page(vma
, address
, pte
);
114 if (!page
&& pte_devmap(pte
) && (flags
& FOLL_GET
)) {
116 * Only return device mapping pages in the FOLL_GET case since
117 * they are only valid while holding the pgmap reference.
119 pgmap
= get_dev_pagemap(pte_pfn(pte
), NULL
);
121 page
= pte_page(pte
);
124 } else if (unlikely(!page
)) {
125 if (flags
& FOLL_DUMP
) {
126 /* Avoid special (like zero) pages in core dumps */
127 page
= ERR_PTR(-EFAULT
);
131 if (is_zero_pfn(pte_pfn(pte
))) {
132 page
= pte_page(pte
);
136 ret
= follow_pfn_pte(vma
, address
, ptep
, flags
);
142 if (flags
& FOLL_SPLIT
&& PageTransCompound(page
)) {
145 pte_unmap_unlock(ptep
, ptl
);
147 ret
= split_huge_page(page
);
155 if (flags
& FOLL_GET
) {
158 /* drop the pgmap reference now that we hold the page */
160 put_dev_pagemap(pgmap
);
164 if (flags
& FOLL_TOUCH
) {
165 if ((flags
& FOLL_WRITE
) &&
166 !pte_dirty(pte
) && !PageDirty(page
))
167 set_page_dirty(page
);
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().
173 mark_page_accessed(page
);
175 if ((flags
& FOLL_MLOCK
) && (vma
->vm_flags
& VM_LOCKED
)) {
176 /* Do not mlock pte-mapped THP */
177 if (PageTransCompound(page
))
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.
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.
189 if (page
->mapping
&& trylock_page(page
)) {
190 lru_add_drain(); /* push cached pages to LRU */
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.
197 mlock_vma_page(page
);
202 pte_unmap_unlock(ptep
, ptl
);
205 pte_unmap_unlock(ptep
, ptl
);
208 return no_page_table(vma
, flags
);
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
218 * @flags can have FOLL_ flags set, defined in <linux/mm.h>
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()).
224 struct page
*follow_page_mask(struct vm_area_struct
*vma
,
225 unsigned long address
, unsigned int flags
,
226 unsigned int *page_mask
)
233 struct mm_struct
*mm
= vma
->vm_mm
;
237 page
= follow_huge_addr(mm
, address
, flags
& FOLL_WRITE
);
239 BUG_ON(flags
& FOLL_GET
);
243 pgd
= pgd_offset(mm
, address
);
244 if (pgd_none(*pgd
) || unlikely(pgd_bad(*pgd
)))
245 return no_page_table(vma
, flags
);
247 pud
= pud_offset(pgd
, address
);
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
);
254 return no_page_table(vma
, flags
);
256 if (unlikely(pud_bad(*pud
)))
257 return no_page_table(vma
, flags
);
259 pmd
= pmd_offset(pud
, address
);
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
);
266 return no_page_table(vma
, flags
);
268 if (pmd_devmap(*pmd
)) {
269 ptl
= pmd_lock(mm
, pmd
);
270 page
= follow_devmap_pmd(vma
, address
, pmd
, flags
);
275 if (likely(!pmd_trans_huge(*pmd
)))
276 return follow_page_pte(vma
, address
, pmd
, flags
);
278 if ((flags
& FOLL_NUMA
) && pmd_protnone(*pmd
))
279 return no_page_table(vma
, flags
);
281 ptl
= pmd_lock(mm
, pmd
);
282 if (unlikely(!pmd_trans_huge(*pmd
))) {
284 return follow_page_pte(vma
, address
, pmd
, flags
);
286 if (flags
& FOLL_SPLIT
) {
288 page
= pmd_page(*pmd
);
289 if (is_huge_zero_page(page
)) {
292 split_huge_pmd(vma
, pmd
, address
);
293 if (pmd_trans_unstable(pmd
))
299 ret
= split_huge_page(page
);
303 return no_page_table(vma
, flags
);
306 return ret
? ERR_PTR(ret
) :
307 follow_page_pte(vma
, address
, pmd
, flags
);
310 page
= follow_trans_huge_pmd(vma
, address
, pmd
, flags
);
312 *page_mask
= HPAGE_PMD_NR
- 1;
316 static int get_gate_page(struct mm_struct
*mm
, unsigned long address
,
317 unsigned int gup_flags
, struct vm_area_struct
**vma
,
326 /* user gate pages are read-only */
327 if (gup_flags
& FOLL_WRITE
)
329 if (address
> TASK_SIZE
)
330 pgd
= pgd_offset_k(address
);
332 pgd
= pgd_offset_gate(mm
, address
);
333 BUG_ON(pgd_none(*pgd
));
334 pud
= pud_offset(pgd
, address
);
335 BUG_ON(pud_none(*pud
));
336 pmd
= pmd_offset(pud
, address
);
339 VM_BUG_ON(pmd_trans_huge(*pmd
));
340 pte
= pte_offset_map(pmd
, address
);
343 *vma
= get_gate_vma(mm
);
346 *page
= vm_normal_page(*vma
, address
, *pte
);
348 if ((gup_flags
& FOLL_DUMP
) || !is_zero_pfn(pte_pfn(*pte
)))
350 *page
= pte_page(*pte
);
361 * mmap_sem must be held on entry. If @nonblocking != NULL and
362 * *@flags does not include FOLL_NOWAIT, the mmap_sem may be released.
363 * If it is, *@nonblocking will be set to 0 and -EBUSY returned.
365 static int faultin_page(struct task_struct
*tsk
, struct vm_area_struct
*vma
,
366 unsigned long address
, unsigned int *flags
, int *nonblocking
)
368 unsigned int fault_flags
= 0;
371 /* mlock all present pages, but do not fault in new pages */
372 if ((*flags
& (FOLL_POPULATE
| FOLL_MLOCK
)) == FOLL_MLOCK
)
374 if (*flags
& FOLL_WRITE
)
375 fault_flags
|= FAULT_FLAG_WRITE
;
376 if (*flags
& FOLL_REMOTE
)
377 fault_flags
|= FAULT_FLAG_REMOTE
;
379 fault_flags
|= FAULT_FLAG_ALLOW_RETRY
;
380 if (*flags
& FOLL_NOWAIT
)
381 fault_flags
|= FAULT_FLAG_ALLOW_RETRY
| FAULT_FLAG_RETRY_NOWAIT
;
382 if (*flags
& FOLL_TRIED
) {
383 VM_WARN_ON_ONCE(fault_flags
& FAULT_FLAG_ALLOW_RETRY
);
384 fault_flags
|= FAULT_FLAG_TRIED
;
387 ret
= handle_mm_fault(vma
, address
, fault_flags
);
388 if (ret
& VM_FAULT_ERROR
) {
389 if (ret
& VM_FAULT_OOM
)
391 if (ret
& (VM_FAULT_HWPOISON
| VM_FAULT_HWPOISON_LARGE
))
392 return *flags
& FOLL_HWPOISON
? -EHWPOISON
: -EFAULT
;
393 if (ret
& (VM_FAULT_SIGBUS
| VM_FAULT_SIGSEGV
))
399 if (ret
& VM_FAULT_MAJOR
)
405 if (ret
& VM_FAULT_RETRY
) {
412 * The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when
413 * necessary, even if maybe_mkwrite decided not to set pte_write. We
414 * can thus safely do subsequent page lookups as if they were reads.
415 * But only do so when looping for pte_write is futile: in some cases
416 * userspace may also be wanting to write to the gotten user page,
417 * which a read fault here might prevent (a readonly page might get
418 * reCOWed by userspace write).
420 if ((ret
& VM_FAULT_WRITE
) && !(vma
->vm_flags
& VM_WRITE
))
425 static int check_vma_flags(struct vm_area_struct
*vma
, unsigned long gup_flags
)
427 vm_flags_t vm_flags
= vma
->vm_flags
;
428 int write
= (gup_flags
& FOLL_WRITE
);
429 int foreign
= (gup_flags
& FOLL_REMOTE
);
431 if (vm_flags
& (VM_IO
| VM_PFNMAP
))
435 if (!(vm_flags
& VM_WRITE
)) {
436 if (!(gup_flags
& FOLL_FORCE
))
439 * We used to let the write,force case do COW in a
440 * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could
441 * set a breakpoint in a read-only mapping of an
442 * executable, without corrupting the file (yet only
443 * when that file had been opened for writing!).
444 * Anon pages in shared mappings are surprising: now
447 if (!is_cow_mapping(vm_flags
))
450 } else if (!(vm_flags
& VM_READ
)) {
451 if (!(gup_flags
& FOLL_FORCE
))
454 * Is there actually any vma we can reach here which does not
455 * have VM_MAYREAD set?
457 if (!(vm_flags
& VM_MAYREAD
))
461 * gups are always data accesses, not instruction
462 * fetches, so execute=false here
464 if (!arch_vma_access_permitted(vma
, write
, false, foreign
))
470 * __get_user_pages() - pin user pages in memory
471 * @tsk: task_struct of target task
472 * @mm: mm_struct of target mm
473 * @start: starting user address
474 * @nr_pages: number of pages from start to pin
475 * @gup_flags: flags modifying pin behaviour
476 * @pages: array that receives pointers to the pages pinned.
477 * Should be at least nr_pages long. Or NULL, if caller
478 * only intends to ensure the pages are faulted in.
479 * @vmas: array of pointers to vmas corresponding to each page.
480 * Or NULL if the caller does not require them.
481 * @nonblocking: whether waiting for disk IO or mmap_sem contention
483 * Returns number of pages pinned. This may be fewer than the number
484 * requested. If nr_pages is 0 or negative, returns 0. If no pages
485 * were pinned, returns -errno. Each page returned must be released
486 * with a put_page() call when it is finished with. vmas will only
487 * remain valid while mmap_sem is held.
489 * Must be called with mmap_sem held. It may be released. See below.
491 * __get_user_pages walks a process's page tables and takes a reference to
492 * each struct page that each user address corresponds to at a given
493 * instant. That is, it takes the page that would be accessed if a user
494 * thread accesses the given user virtual address at that instant.
496 * This does not guarantee that the page exists in the user mappings when
497 * __get_user_pages returns, and there may even be a completely different
498 * page there in some cases (eg. if mmapped pagecache has been invalidated
499 * and subsequently re faulted). However it does guarantee that the page
500 * won't be freed completely. And mostly callers simply care that the page
501 * contains data that was valid *at some point in time*. Typically, an IO
502 * or similar operation cannot guarantee anything stronger anyway because
503 * locks can't be held over the syscall boundary.
505 * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
506 * the page is written to, set_page_dirty (or set_page_dirty_lock, as
507 * appropriate) must be called after the page is finished with, and
508 * before put_page is called.
510 * If @nonblocking != NULL, __get_user_pages will not wait for disk IO
511 * or mmap_sem contention, and if waiting is needed to pin all pages,
512 * *@nonblocking will be set to 0. Further, if @gup_flags does not
513 * include FOLL_NOWAIT, the mmap_sem will be released via up_read() in
516 * A caller using such a combination of @nonblocking and @gup_flags
517 * must therefore hold the mmap_sem for reading only, and recognize
518 * when it's been released. Otherwise, it must be held for either
519 * reading or writing and will not be released.
521 * In most cases, get_user_pages or get_user_pages_fast should be used
522 * instead of __get_user_pages. __get_user_pages should be used only if
523 * you need some special @gup_flags.
525 static long __get_user_pages(struct task_struct
*tsk
, struct mm_struct
*mm
,
526 unsigned long start
, unsigned long nr_pages
,
527 unsigned int gup_flags
, struct page
**pages
,
528 struct vm_area_struct
**vmas
, int *nonblocking
)
531 unsigned int page_mask
;
532 struct vm_area_struct
*vma
= NULL
;
537 VM_BUG_ON(!!pages
!= !!(gup_flags
& FOLL_GET
));
540 * If FOLL_FORCE is set then do not force a full fault as the hinting
541 * fault information is unrelated to the reference behaviour of a task
542 * using the address space
544 if (!(gup_flags
& FOLL_FORCE
))
545 gup_flags
|= FOLL_NUMA
;
549 unsigned int foll_flags
= gup_flags
;
550 unsigned int page_increm
;
552 /* first iteration or cross vma bound */
553 if (!vma
|| start
>= vma
->vm_end
) {
554 vma
= find_extend_vma(mm
, start
);
555 if (!vma
&& in_gate_area(mm
, start
)) {
557 ret
= get_gate_page(mm
, start
& PAGE_MASK
,
559 pages
? &pages
[i
] : NULL
);
566 if (!vma
|| check_vma_flags(vma
, gup_flags
))
567 return i
? : -EFAULT
;
568 if (is_vm_hugetlb_page(vma
)) {
569 i
= follow_hugetlb_page(mm
, vma
, pages
, vmas
,
570 &start
, &nr_pages
, i
,
577 * If we have a pending SIGKILL, don't keep faulting pages and
578 * potentially allocating memory.
580 if (unlikely(fatal_signal_pending(current
)))
581 return i
? i
: -ERESTARTSYS
;
583 page
= follow_page_mask(vma
, start
, foll_flags
, &page_mask
);
586 ret
= faultin_page(tsk
, vma
, start
, &foll_flags
,
601 } else if (PTR_ERR(page
) == -EEXIST
) {
603 * Proper page table entry exists, but no corresponding
607 } else if (IS_ERR(page
)) {
608 return i
? i
: PTR_ERR(page
);
612 flush_anon_page(vma
, page
, start
);
613 flush_dcache_page(page
);
621 page_increm
= 1 + (~(start
>> PAGE_SHIFT
) & page_mask
);
622 if (page_increm
> nr_pages
)
623 page_increm
= nr_pages
;
625 start
+= page_increm
* PAGE_SIZE
;
626 nr_pages
-= page_increm
;
631 static bool vma_permits_fault(struct vm_area_struct
*vma
,
632 unsigned int fault_flags
)
634 bool write
= !!(fault_flags
& FAULT_FLAG_WRITE
);
635 bool foreign
= !!(fault_flags
& FAULT_FLAG_REMOTE
);
636 vm_flags_t vm_flags
= write
? VM_WRITE
: VM_READ
;
638 if (!(vm_flags
& vma
->vm_flags
))
642 * The architecture might have a hardware protection
643 * mechanism other than read/write that can deny access.
645 * gup always represents data access, not instruction
646 * fetches, so execute=false here:
648 if (!arch_vma_access_permitted(vma
, write
, false, foreign
))
655 * fixup_user_fault() - manually resolve a user page fault
656 * @tsk: the task_struct to use for page fault accounting, or
657 * NULL if faults are not to be recorded.
658 * @mm: mm_struct of target mm
659 * @address: user address
660 * @fault_flags:flags to pass down to handle_mm_fault()
661 * @unlocked: did we unlock the mmap_sem while retrying, maybe NULL if caller
662 * does not allow retry
664 * This is meant to be called in the specific scenario where for locking reasons
665 * we try to access user memory in atomic context (within a pagefault_disable()
666 * section), this returns -EFAULT, and we want to resolve the user fault before
669 * Typically this is meant to be used by the futex code.
671 * The main difference with get_user_pages() is that this function will
672 * unconditionally call handle_mm_fault() which will in turn perform all the
673 * necessary SW fixup of the dirty and young bits in the PTE, while
674 * get_user_pages() only guarantees to update these in the struct page.
676 * This is important for some architectures where those bits also gate the
677 * access permission to the page because they are maintained in software. On
678 * such architectures, gup() will not be enough to make a subsequent access
681 * This function will not return with an unlocked mmap_sem. So it has not the
682 * same semantics wrt the @mm->mmap_sem as does filemap_fault().
684 int fixup_user_fault(struct task_struct
*tsk
, struct mm_struct
*mm
,
685 unsigned long address
, unsigned int fault_flags
,
688 struct vm_area_struct
*vma
;
692 fault_flags
|= FAULT_FLAG_ALLOW_RETRY
;
695 vma
= find_extend_vma(mm
, address
);
696 if (!vma
|| address
< vma
->vm_start
)
699 if (!vma_permits_fault(vma
, fault_flags
))
702 ret
= handle_mm_fault(vma
, address
, fault_flags
);
703 major
|= ret
& VM_FAULT_MAJOR
;
704 if (ret
& VM_FAULT_ERROR
) {
705 if (ret
& VM_FAULT_OOM
)
707 if (ret
& (VM_FAULT_HWPOISON
| VM_FAULT_HWPOISON_LARGE
))
709 if (ret
& (VM_FAULT_SIGBUS
| VM_FAULT_SIGSEGV
))
714 if (ret
& VM_FAULT_RETRY
) {
715 down_read(&mm
->mmap_sem
);
716 if (!(fault_flags
& FAULT_FLAG_TRIED
)) {
718 fault_flags
&= ~FAULT_FLAG_ALLOW_RETRY
;
719 fault_flags
|= FAULT_FLAG_TRIED
;
732 EXPORT_SYMBOL_GPL(fixup_user_fault
);
734 static __always_inline
long __get_user_pages_locked(struct task_struct
*tsk
,
735 struct mm_struct
*mm
,
737 unsigned long nr_pages
,
739 struct vm_area_struct
**vmas
,
740 int *locked
, bool notify_drop
,
743 long ret
, pages_done
;
747 /* if VM_FAULT_RETRY can be returned, vmas become invalid */
749 /* check caller initialized locked */
750 BUG_ON(*locked
!= 1);
757 lock_dropped
= false;
759 ret
= __get_user_pages(tsk
, mm
, start
, nr_pages
, flags
, pages
,
762 /* VM_FAULT_RETRY couldn't trigger, bypass */
765 /* VM_FAULT_RETRY cannot return errors */
768 BUG_ON(ret
>= nr_pages
);
772 /* If it's a prefault don't insist harder */
782 /* VM_FAULT_RETRY didn't trigger */
787 /* VM_FAULT_RETRY triggered, so seek to the faulting offset */
789 start
+= ret
<< PAGE_SHIFT
;
792 * Repeat on the address that fired VM_FAULT_RETRY
793 * without FAULT_FLAG_ALLOW_RETRY but with
798 down_read(&mm
->mmap_sem
);
799 ret
= __get_user_pages(tsk
, mm
, start
, 1, flags
| FOLL_TRIED
,
814 if (notify_drop
&& lock_dropped
&& *locked
) {
816 * We must let the caller know we temporarily dropped the lock
817 * and so the critical section protected by it was lost.
819 up_read(&mm
->mmap_sem
);
826 * We can leverage the VM_FAULT_RETRY functionality in the page fault
827 * paths better by using either get_user_pages_locked() or
828 * get_user_pages_unlocked().
830 * get_user_pages_locked() is suitable to replace the form:
832 * down_read(&mm->mmap_sem);
834 * get_user_pages(tsk, mm, ..., pages, NULL);
835 * up_read(&mm->mmap_sem);
840 * down_read(&mm->mmap_sem);
842 * get_user_pages_locked(tsk, mm, ..., pages, &locked);
844 * up_read(&mm->mmap_sem);
846 long get_user_pages_locked(unsigned long start
, unsigned long nr_pages
,
847 unsigned int gup_flags
, struct page
**pages
,
850 return __get_user_pages_locked(current
, current
->mm
, start
, nr_pages
,
851 pages
, NULL
, locked
, true,
852 gup_flags
| FOLL_TOUCH
);
854 EXPORT_SYMBOL(get_user_pages_locked
);
857 * Same as get_user_pages_unlocked(...., FOLL_TOUCH) but it allows for
858 * tsk, mm to be specified.
860 * NOTE: here FOLL_TOUCH is not set implicitly and must be set by the
861 * caller if required (just like with __get_user_pages). "FOLL_GET"
862 * is set implicitly if "pages" is non-NULL.
864 static __always_inline
long __get_user_pages_unlocked(struct task_struct
*tsk
,
865 struct mm_struct
*mm
, unsigned long start
,
866 unsigned long nr_pages
, struct page
**pages
,
867 unsigned int gup_flags
)
872 down_read(&mm
->mmap_sem
);
873 ret
= __get_user_pages_locked(tsk
, mm
, start
, nr_pages
, pages
, NULL
,
874 &locked
, false, gup_flags
);
876 up_read(&mm
->mmap_sem
);
881 * get_user_pages_unlocked() is suitable to replace the form:
883 * down_read(&mm->mmap_sem);
884 * get_user_pages(tsk, mm, ..., pages, NULL);
885 * up_read(&mm->mmap_sem);
889 * get_user_pages_unlocked(tsk, mm, ..., pages);
891 * It is functionally equivalent to get_user_pages_fast so
892 * get_user_pages_fast should be used instead if specific gup_flags
893 * (e.g. FOLL_FORCE) are not required.
895 long get_user_pages_unlocked(unsigned long start
, unsigned long nr_pages
,
896 struct page
**pages
, unsigned int gup_flags
)
898 return __get_user_pages_unlocked(current
, current
->mm
, start
, nr_pages
,
899 pages
, gup_flags
| FOLL_TOUCH
);
901 EXPORT_SYMBOL(get_user_pages_unlocked
);
904 * get_user_pages_remote() - pin user pages in memory
905 * @tsk: the task_struct to use for page fault accounting, or
906 * NULL if faults are not to be recorded.
907 * @mm: mm_struct of target mm
908 * @start: starting user address
909 * @nr_pages: number of pages from start to pin
910 * @gup_flags: flags modifying lookup behaviour
911 * @pages: array that receives pointers to the pages pinned.
912 * Should be at least nr_pages long. Or NULL, if caller
913 * only intends to ensure the pages are faulted in.
914 * @vmas: array of pointers to vmas corresponding to each page.
915 * Or NULL if the caller does not require them.
916 * @locked: pointer to lock flag indicating whether lock is held and
917 * subsequently whether VM_FAULT_RETRY functionality can be
918 * utilised. Lock must initially be held.
920 * Returns number of pages pinned. This may be fewer than the number
921 * requested. If nr_pages is 0 or negative, returns 0. If no pages
922 * were pinned, returns -errno. Each page returned must be released
923 * with a put_page() call when it is finished with. vmas will only
924 * remain valid while mmap_sem is held.
926 * Must be called with mmap_sem held for read or write.
928 * get_user_pages walks a process's page tables and takes a reference to
929 * each struct page that each user address corresponds to at a given
930 * instant. That is, it takes the page that would be accessed if a user
931 * thread accesses the given user virtual address at that instant.
933 * This does not guarantee that the page exists in the user mappings when
934 * get_user_pages returns, and there may even be a completely different
935 * page there in some cases (eg. if mmapped pagecache has been invalidated
936 * and subsequently re faulted). However it does guarantee that the page
937 * won't be freed completely. And mostly callers simply care that the page
938 * contains data that was valid *at some point in time*. Typically, an IO
939 * or similar operation cannot guarantee anything stronger anyway because
940 * locks can't be held over the syscall boundary.
942 * If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page
943 * is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must
944 * be called after the page is finished with, and before put_page is called.
946 * get_user_pages is typically used for fewer-copy IO operations, to get a
947 * handle on the memory by some means other than accesses via the user virtual
948 * addresses. The pages may be submitted for DMA to devices or accessed via
949 * their kernel linear mapping (via the kmap APIs). Care should be taken to
950 * use the correct cache flushing APIs.
952 * See also get_user_pages_fast, for performance critical applications.
954 * get_user_pages should be phased out in favor of
955 * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
956 * should use get_user_pages because it cannot pass
957 * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
959 long get_user_pages_remote(struct task_struct
*tsk
, struct mm_struct
*mm
,
960 unsigned long start
, unsigned long nr_pages
,
961 unsigned int gup_flags
, struct page
**pages
,
962 struct vm_area_struct
**vmas
, int *locked
)
964 return __get_user_pages_locked(tsk
, mm
, start
, nr_pages
, pages
, vmas
,
966 gup_flags
| FOLL_TOUCH
| FOLL_REMOTE
);
968 EXPORT_SYMBOL(get_user_pages_remote
);
971 * This is the same as get_user_pages_remote(), just with a
972 * less-flexible calling convention where we assume that the task
973 * and mm being operated on are the current task's and don't allow
974 * passing of a locked parameter. We also obviously don't pass
975 * FOLL_REMOTE in here.
977 long get_user_pages(unsigned long start
, unsigned long nr_pages
,
978 unsigned int gup_flags
, struct page
**pages
,
979 struct vm_area_struct
**vmas
)
981 return __get_user_pages_locked(current
, current
->mm
, start
, nr_pages
,
982 pages
, vmas
, NULL
, false,
983 gup_flags
| FOLL_TOUCH
);
985 EXPORT_SYMBOL(get_user_pages
);
988 * populate_vma_page_range() - populate a range of pages in the vma.
990 * @start: start address
994 * This takes care of mlocking the pages too if VM_LOCKED is set.
996 * return 0 on success, negative error code on error.
998 * vma->vm_mm->mmap_sem must be held.
1000 * If @nonblocking is NULL, it may be held for read or write and will
1003 * If @nonblocking is non-NULL, it must held for read only and may be
1004 * released. If it's released, *@nonblocking will be set to 0.
1006 long populate_vma_page_range(struct vm_area_struct
*vma
,
1007 unsigned long start
, unsigned long end
, int *nonblocking
)
1009 struct mm_struct
*mm
= vma
->vm_mm
;
1010 unsigned long nr_pages
= (end
- start
) / PAGE_SIZE
;
1013 VM_BUG_ON(start
& ~PAGE_MASK
);
1014 VM_BUG_ON(end
& ~PAGE_MASK
);
1015 VM_BUG_ON_VMA(start
< vma
->vm_start
, vma
);
1016 VM_BUG_ON_VMA(end
> vma
->vm_end
, vma
);
1017 VM_BUG_ON_MM(!rwsem_is_locked(&mm
->mmap_sem
), mm
);
1019 gup_flags
= FOLL_TOUCH
| FOLL_POPULATE
| FOLL_MLOCK
;
1020 if (vma
->vm_flags
& VM_LOCKONFAULT
)
1021 gup_flags
&= ~FOLL_POPULATE
;
1023 * We want to touch writable mappings with a write fault in order
1024 * to break COW, except for shared mappings because these don't COW
1025 * and we would not want to dirty them for nothing.
1027 if ((vma
->vm_flags
& (VM_WRITE
| VM_SHARED
)) == VM_WRITE
)
1028 gup_flags
|= FOLL_WRITE
;
1031 * We want mlock to succeed for regions that have any permissions
1032 * other than PROT_NONE.
1034 if (vma
->vm_flags
& (VM_READ
| VM_WRITE
| VM_EXEC
))
1035 gup_flags
|= FOLL_FORCE
;
1038 * We made sure addr is within a VMA, so the following will
1039 * not result in a stack expansion that recurses back here.
1041 return __get_user_pages(current
, mm
, start
, nr_pages
, gup_flags
,
1042 NULL
, NULL
, nonblocking
);
1046 * __mm_populate - populate and/or mlock pages within a range of address space.
1048 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
1049 * flags. VMAs must be already marked with the desired vm_flags, and
1050 * mmap_sem must not be held.
1052 int __mm_populate(unsigned long start
, unsigned long len
, int ignore_errors
)
1054 struct mm_struct
*mm
= current
->mm
;
1055 unsigned long end
, nstart
, nend
;
1056 struct vm_area_struct
*vma
= NULL
;
1060 VM_BUG_ON(start
& ~PAGE_MASK
);
1061 VM_BUG_ON(len
!= PAGE_ALIGN(len
));
1064 for (nstart
= start
; nstart
< end
; nstart
= nend
) {
1066 * We want to fault in pages for [nstart; end) address range.
1067 * Find first corresponding VMA.
1071 down_read(&mm
->mmap_sem
);
1072 vma
= find_vma(mm
, nstart
);
1073 } else if (nstart
>= vma
->vm_end
)
1075 if (!vma
|| vma
->vm_start
>= end
)
1078 * Set [nstart; nend) to intersection of desired address
1079 * range with the first VMA. Also, skip undesirable VMA types.
1081 nend
= min(end
, vma
->vm_end
);
1082 if (vma
->vm_flags
& (VM_IO
| VM_PFNMAP
))
1084 if (nstart
< vma
->vm_start
)
1085 nstart
= vma
->vm_start
;
1087 * Now fault in a range of pages. populate_vma_page_range()
1088 * double checks the vma flags, so that it won't mlock pages
1089 * if the vma was already munlocked.
1091 ret
= populate_vma_page_range(vma
, nstart
, nend
, &locked
);
1093 if (ignore_errors
) {
1095 continue; /* continue at next VMA */
1099 nend
= nstart
+ ret
* PAGE_SIZE
;
1103 up_read(&mm
->mmap_sem
);
1104 return ret
; /* 0 or negative error code */
1108 * get_dump_page() - pin user page in memory while writing it to core dump
1109 * @addr: user address
1111 * Returns struct page pointer of user page pinned for dump,
1112 * to be freed afterwards by put_page().
1114 * Returns NULL on any kind of failure - a hole must then be inserted into
1115 * the corefile, to preserve alignment with its headers; and also returns
1116 * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
1117 * allowing a hole to be left in the corefile to save diskspace.
1119 * Called without mmap_sem, but after all other threads have been killed.
1121 #ifdef CONFIG_ELF_CORE
1122 struct page
*get_dump_page(unsigned long addr
)
1124 struct vm_area_struct
*vma
;
1127 if (__get_user_pages(current
, current
->mm
, addr
, 1,
1128 FOLL_FORCE
| FOLL_DUMP
| FOLL_GET
, &page
, &vma
,
1131 flush_cache_page(vma
, addr
, page_to_pfn(page
));
1134 #endif /* CONFIG_ELF_CORE */
1137 * Generic RCU Fast GUP
1139 * get_user_pages_fast attempts to pin user pages by walking the page
1140 * tables directly and avoids taking locks. Thus the walker needs to be
1141 * protected from page table pages being freed from under it, and should
1142 * block any THP splits.
1144 * One way to achieve this is to have the walker disable interrupts, and
1145 * rely on IPIs from the TLB flushing code blocking before the page table
1146 * pages are freed. This is unsuitable for architectures that do not need
1147 * to broadcast an IPI when invalidating TLBs.
1149 * Another way to achieve this is to batch up page table containing pages
1150 * belonging to more than one mm_user, then rcu_sched a callback to free those
1151 * pages. Disabling interrupts will allow the fast_gup walker to both block
1152 * the rcu_sched callback, and an IPI that we broadcast for splitting THPs
1153 * (which is a relatively rare event). The code below adopts this strategy.
1155 * Before activating this code, please be aware that the following assumptions
1156 * are currently made:
1158 * *) HAVE_RCU_TABLE_FREE is enabled, and tlb_remove_table is used to free
1159 * pages containing page tables.
1161 * *) ptes can be read atomically by the architecture.
1163 * *) access_ok is sufficient to validate userspace address ranges.
1165 * The last two assumptions can be relaxed by the addition of helper functions.
1167 * This code is based heavily on the PowerPC implementation by Nick Piggin.
1169 #ifdef CONFIG_HAVE_GENERIC_RCU_GUP
1171 #ifdef __HAVE_ARCH_PTE_SPECIAL
1172 static int gup_pte_range(pmd_t pmd
, unsigned long addr
, unsigned long end
,
1173 int write
, struct page
**pages
, int *nr
)
1178 ptem
= ptep
= pte_offset_map(&pmd
, addr
);
1181 * In the line below we are assuming that the pte can be read
1182 * atomically. If this is not the case for your architecture,
1183 * please wrap this in a helper function!
1185 * for an example see gup_get_pte in arch/x86/mm/gup.c
1187 pte_t pte
= READ_ONCE(*ptep
);
1188 struct page
*head
, *page
;
1191 * Similar to the PMD case below, NUMA hinting must take slow
1192 * path using the pte_protnone check.
1194 if (!pte_present(pte
) || pte_special(pte
) ||
1195 pte_protnone(pte
) || (write
&& !pte_write(pte
)))
1198 if (!arch_pte_access_permitted(pte
, write
))
1201 VM_BUG_ON(!pfn_valid(pte_pfn(pte
)));
1202 page
= pte_page(pte
);
1203 head
= compound_head(page
);
1205 if (!page_cache_get_speculative(head
))
1208 if (unlikely(pte_val(pte
) != pte_val(*ptep
))) {
1213 VM_BUG_ON_PAGE(compound_head(page
) != head
, page
);
1217 } while (ptep
++, addr
+= PAGE_SIZE
, addr
!= end
);
1228 * If we can't determine whether or not a pte is special, then fail immediately
1229 * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
1232 * For a futex to be placed on a THP tail page, get_futex_key requires a
1233 * __get_user_pages_fast implementation that can pin pages. Thus it's still
1234 * useful to have gup_huge_pmd even if we can't operate on ptes.
1236 static int gup_pte_range(pmd_t pmd
, unsigned long addr
, unsigned long end
,
1237 int write
, struct page
**pages
, int *nr
)
1241 #endif /* __HAVE_ARCH_PTE_SPECIAL */
1243 static int gup_huge_pmd(pmd_t orig
, pmd_t
*pmdp
, unsigned long addr
,
1244 unsigned long end
, int write
, struct page
**pages
, int *nr
)
1246 struct page
*head
, *page
;
1249 if (write
&& !pmd_write(orig
))
1253 head
= pmd_page(orig
);
1254 page
= head
+ ((addr
& ~PMD_MASK
) >> PAGE_SHIFT
);
1256 VM_BUG_ON_PAGE(compound_head(page
) != head
, page
);
1261 } while (addr
+= PAGE_SIZE
, addr
!= end
);
1263 if (!page_cache_add_speculative(head
, refs
)) {
1268 if (unlikely(pmd_val(orig
) != pmd_val(*pmdp
))) {
1278 static int gup_huge_pud(pud_t orig
, pud_t
*pudp
, unsigned long addr
,
1279 unsigned long end
, int write
, struct page
**pages
, int *nr
)
1281 struct page
*head
, *page
;
1284 if (write
&& !pud_write(orig
))
1288 head
= pud_page(orig
);
1289 page
= head
+ ((addr
& ~PUD_MASK
) >> PAGE_SHIFT
);
1291 VM_BUG_ON_PAGE(compound_head(page
) != head
, page
);
1296 } while (addr
+= PAGE_SIZE
, addr
!= end
);
1298 if (!page_cache_add_speculative(head
, refs
)) {
1303 if (unlikely(pud_val(orig
) != pud_val(*pudp
))) {
1313 static int gup_huge_pgd(pgd_t orig
, pgd_t
*pgdp
, unsigned long addr
,
1314 unsigned long end
, int write
,
1315 struct page
**pages
, int *nr
)
1318 struct page
*head
, *page
;
1320 if (write
&& !pgd_write(orig
))
1324 head
= pgd_page(orig
);
1325 page
= head
+ ((addr
& ~PGDIR_MASK
) >> PAGE_SHIFT
);
1327 VM_BUG_ON_PAGE(compound_head(page
) != head
, page
);
1332 } while (addr
+= PAGE_SIZE
, addr
!= end
);
1334 if (!page_cache_add_speculative(head
, refs
)) {
1339 if (unlikely(pgd_val(orig
) != pgd_val(*pgdp
))) {
1349 static int gup_pmd_range(pud_t pud
, unsigned long addr
, unsigned long end
,
1350 int write
, struct page
**pages
, int *nr
)
1355 pmdp
= pmd_offset(&pud
, addr
);
1357 pmd_t pmd
= READ_ONCE(*pmdp
);
1359 next
= pmd_addr_end(addr
, end
);
1363 if (unlikely(pmd_trans_huge(pmd
) || pmd_huge(pmd
))) {
1365 * NUMA hinting faults need to be handled in the GUP
1366 * slowpath for accounting purposes and so that they
1367 * can be serialised against THP migration.
1369 if (pmd_protnone(pmd
))
1372 if (!gup_huge_pmd(pmd
, pmdp
, addr
, next
, write
,
1376 } else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd
))))) {
1378 * architecture have different format for hugetlbfs
1379 * pmd format and THP pmd format
1381 if (!gup_huge_pd(__hugepd(pmd_val(pmd
)), addr
,
1382 PMD_SHIFT
, next
, write
, pages
, nr
))
1384 } else if (!gup_pte_range(pmd
, addr
, next
, write
, pages
, nr
))
1386 } while (pmdp
++, addr
= next
, addr
!= end
);
1391 static int gup_pud_range(pgd_t pgd
, unsigned long addr
, unsigned long end
,
1392 int write
, struct page
**pages
, int *nr
)
1397 pudp
= pud_offset(&pgd
, addr
);
1399 pud_t pud
= READ_ONCE(*pudp
);
1401 next
= pud_addr_end(addr
, end
);
1404 if (unlikely(pud_huge(pud
))) {
1405 if (!gup_huge_pud(pud
, pudp
, addr
, next
, write
,
1408 } else if (unlikely(is_hugepd(__hugepd(pud_val(pud
))))) {
1409 if (!gup_huge_pd(__hugepd(pud_val(pud
)), addr
,
1410 PUD_SHIFT
, next
, write
, pages
, nr
))
1412 } else if (!gup_pmd_range(pud
, addr
, next
, write
, pages
, nr
))
1414 } while (pudp
++, addr
= next
, addr
!= end
);
1420 * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
1421 * the regular GUP. It will only return non-negative values.
1423 int __get_user_pages_fast(unsigned long start
, int nr_pages
, int write
,
1424 struct page
**pages
)
1426 struct mm_struct
*mm
= current
->mm
;
1427 unsigned long addr
, len
, end
;
1428 unsigned long next
, flags
;
1434 len
= (unsigned long) nr_pages
<< PAGE_SHIFT
;
1437 if (unlikely(!access_ok(write
? VERIFY_WRITE
: VERIFY_READ
,
1442 * Disable interrupts. We use the nested form as we can already have
1443 * interrupts disabled by get_futex_key.
1445 * With interrupts disabled, we block page table pages from being
1446 * freed from under us. See mmu_gather_tlb in asm-generic/tlb.h
1449 * We do not adopt an rcu_read_lock(.) here as we also want to
1450 * block IPIs that come from THPs splitting.
1453 local_irq_save(flags
);
1454 pgdp
= pgd_offset(mm
, addr
);
1456 pgd_t pgd
= READ_ONCE(*pgdp
);
1458 next
= pgd_addr_end(addr
, end
);
1461 if (unlikely(pgd_huge(pgd
))) {
1462 if (!gup_huge_pgd(pgd
, pgdp
, addr
, next
, write
,
1465 } else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd
))))) {
1466 if (!gup_huge_pd(__hugepd(pgd_val(pgd
)), addr
,
1467 PGDIR_SHIFT
, next
, write
, pages
, &nr
))
1469 } else if (!gup_pud_range(pgd
, addr
, next
, write
, pages
, &nr
))
1471 } while (pgdp
++, addr
= next
, addr
!= end
);
1472 local_irq_restore(flags
);
1478 * get_user_pages_fast() - pin user pages in memory
1479 * @start: starting user address
1480 * @nr_pages: number of pages from start to pin
1481 * @write: whether pages will be written to
1482 * @pages: array that receives pointers to the pages pinned.
1483 * Should be at least nr_pages long.
1485 * Attempt to pin user pages in memory without taking mm->mmap_sem.
1486 * If not successful, it will fall back to taking the lock and
1487 * calling get_user_pages().
1489 * Returns number of pages pinned. This may be fewer than the number
1490 * requested. If nr_pages is 0 or negative, returns 0. If no pages
1491 * were pinned, returns -errno.
1493 int get_user_pages_fast(unsigned long start
, int nr_pages
, int write
,
1494 struct page
**pages
)
1499 nr
= __get_user_pages_fast(start
, nr_pages
, write
, pages
);
1502 if (nr
< nr_pages
) {
1503 /* Try to get the remaining pages with get_user_pages */
1504 start
+= nr
<< PAGE_SHIFT
;
1507 ret
= get_user_pages_unlocked(start
, nr_pages
- nr
, pages
,
1508 write
? FOLL_WRITE
: 0);
1510 /* Have to be a bit careful with return values */
1522 #endif /* CONFIG_HAVE_GENERIC_RCU_GUP */