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 */
63 static struct page
*follow_page_pte(struct vm_area_struct
*vma
,
64 unsigned long address
, pmd_t
*pmd
, unsigned int flags
)
66 struct mm_struct
*mm
= vma
->vm_mm
;
67 struct dev_pagemap
*pgmap
= NULL
;
73 if (unlikely(pmd_bad(*pmd
)))
74 return no_page_table(vma
, flags
);
76 ptep
= pte_offset_map_lock(mm
, pmd
, address
, &ptl
);
78 if (!pte_present(pte
)) {
81 * KSM's break_ksm() relies upon recognizing a ksm page
82 * even while it is being migrated, so for that case we
83 * need migration_entry_wait().
85 if (likely(!(flags
& FOLL_MIGRATION
)))
89 entry
= pte_to_swp_entry(pte
);
90 if (!is_migration_entry(entry
))
92 pte_unmap_unlock(ptep
, ptl
);
93 migration_entry_wait(mm
, pmd
, address
);
96 if ((flags
& FOLL_NUMA
) && pte_protnone(pte
))
98 if ((flags
& FOLL_WRITE
) && !pte_write(pte
)) {
99 pte_unmap_unlock(ptep
, ptl
);
103 page
= vm_normal_page(vma
, address
, pte
);
104 if (!page
&& pte_devmap(pte
) && (flags
& FOLL_GET
)) {
106 * Only return device mapping pages in the FOLL_GET case since
107 * they are only valid while holding the pgmap reference.
109 pgmap
= get_dev_pagemap(pte_pfn(pte
), NULL
);
111 page
= pte_page(pte
);
114 } else if (unlikely(!page
)) {
115 if (flags
& FOLL_DUMP
) {
116 /* Avoid special (like zero) pages in core dumps */
117 page
= ERR_PTR(-EFAULT
);
121 if (is_zero_pfn(pte_pfn(pte
))) {
122 page
= pte_page(pte
);
126 ret
= follow_pfn_pte(vma
, address
, ptep
, flags
);
132 if (flags
& FOLL_SPLIT
&& PageTransCompound(page
)) {
135 pte_unmap_unlock(ptep
, ptl
);
137 ret
= split_huge_page(page
);
145 if (flags
& FOLL_GET
) {
148 /* drop the pgmap reference now that we hold the page */
150 put_dev_pagemap(pgmap
);
154 if (flags
& FOLL_TOUCH
) {
155 if ((flags
& FOLL_WRITE
) &&
156 !pte_dirty(pte
) && !PageDirty(page
))
157 set_page_dirty(page
);
159 * pte_mkyoung() would be more correct here, but atomic care
160 * is needed to avoid losing the dirty bit: it is easier to use
161 * mark_page_accessed().
163 mark_page_accessed(page
);
165 if ((flags
& FOLL_MLOCK
) && (vma
->vm_flags
& VM_LOCKED
)) {
166 /* Do not mlock pte-mapped THP */
167 if (PageTransCompound(page
))
171 * The preliminary mapping check is mainly to avoid the
172 * pointless overhead of lock_page on the ZERO_PAGE
173 * which might bounce very badly if there is contention.
175 * If the page is already locked, we don't need to
176 * handle it now - vmscan will handle it later if and
177 * when it attempts to reclaim the page.
179 if (page
->mapping
&& trylock_page(page
)) {
180 lru_add_drain(); /* push cached pages to LRU */
182 * Because we lock page here, and migration is
183 * blocked by the pte's page reference, and we
184 * know the page is still mapped, we don't even
185 * need to check for file-cache page truncation.
187 mlock_vma_page(page
);
192 pte_unmap_unlock(ptep
, ptl
);
195 pte_unmap_unlock(ptep
, ptl
);
198 return no_page_table(vma
, flags
);
202 * follow_page_mask - look up a page descriptor from a user-virtual address
203 * @vma: vm_area_struct mapping @address
204 * @address: virtual address to look up
205 * @flags: flags modifying lookup behaviour
206 * @page_mask: on output, *page_mask is set according to the size of the page
208 * @flags can have FOLL_ flags set, defined in <linux/mm.h>
210 * Returns the mapped (struct page *), %NULL if no mapping exists, or
211 * an error pointer if there is a mapping to something not represented
212 * by a page descriptor (see also vm_normal_page()).
214 struct page
*follow_page_mask(struct vm_area_struct
*vma
,
215 unsigned long address
, unsigned int flags
,
216 unsigned int *page_mask
)
223 struct mm_struct
*mm
= vma
->vm_mm
;
227 page
= follow_huge_addr(mm
, address
, flags
& FOLL_WRITE
);
229 BUG_ON(flags
& FOLL_GET
);
233 pgd
= pgd_offset(mm
, address
);
234 if (pgd_none(*pgd
) || unlikely(pgd_bad(*pgd
)))
235 return no_page_table(vma
, flags
);
237 pud
= pud_offset(pgd
, address
);
239 return no_page_table(vma
, flags
);
240 if (pud_huge(*pud
) && vma
->vm_flags
& VM_HUGETLB
) {
241 page
= follow_huge_pud(mm
, address
, pud
, flags
);
244 return no_page_table(vma
, flags
);
246 if (unlikely(pud_bad(*pud
)))
247 return no_page_table(vma
, flags
);
249 pmd
= pmd_offset(pud
, address
);
251 return no_page_table(vma
, flags
);
252 if (pmd_huge(*pmd
) && vma
->vm_flags
& VM_HUGETLB
) {
253 page
= follow_huge_pmd(mm
, address
, pmd
, flags
);
256 return no_page_table(vma
, flags
);
258 if ((flags
& FOLL_NUMA
) && pmd_protnone(*pmd
))
259 return no_page_table(vma
, flags
);
260 if (pmd_devmap(*pmd
)) {
261 ptl
= pmd_lock(mm
, pmd
);
262 page
= follow_devmap_pmd(vma
, address
, pmd
, flags
);
267 if (likely(!pmd_trans_huge(*pmd
)))
268 return follow_page_pte(vma
, address
, pmd
, flags
);
270 ptl
= pmd_lock(mm
, pmd
);
271 if (unlikely(!pmd_trans_huge(*pmd
))) {
273 return follow_page_pte(vma
, address
, pmd
, flags
);
275 if (flags
& FOLL_SPLIT
) {
277 page
= pmd_page(*pmd
);
278 if (is_huge_zero_page(page
)) {
281 split_huge_pmd(vma
, pmd
, address
);
286 ret
= split_huge_page(page
);
291 return ret
? ERR_PTR(ret
) :
292 follow_page_pte(vma
, address
, pmd
, flags
);
295 page
= follow_trans_huge_pmd(vma
, address
, pmd
, flags
);
297 *page_mask
= HPAGE_PMD_NR
- 1;
301 static int get_gate_page(struct mm_struct
*mm
, unsigned long address
,
302 unsigned int gup_flags
, struct vm_area_struct
**vma
,
311 /* user gate pages are read-only */
312 if (gup_flags
& FOLL_WRITE
)
314 if (address
> TASK_SIZE
)
315 pgd
= pgd_offset_k(address
);
317 pgd
= pgd_offset_gate(mm
, address
);
318 BUG_ON(pgd_none(*pgd
));
319 pud
= pud_offset(pgd
, address
);
320 BUG_ON(pud_none(*pud
));
321 pmd
= pmd_offset(pud
, address
);
324 VM_BUG_ON(pmd_trans_huge(*pmd
));
325 pte
= pte_offset_map(pmd
, address
);
328 *vma
= get_gate_vma(mm
);
331 *page
= vm_normal_page(*vma
, address
, *pte
);
333 if ((gup_flags
& FOLL_DUMP
) || !is_zero_pfn(pte_pfn(*pte
)))
335 *page
= pte_page(*pte
);
346 * mmap_sem must be held on entry. If @nonblocking != NULL and
347 * *@flags does not include FOLL_NOWAIT, the mmap_sem may be released.
348 * If it is, *@nonblocking will be set to 0 and -EBUSY returned.
350 static int faultin_page(struct task_struct
*tsk
, struct vm_area_struct
*vma
,
351 unsigned long address
, unsigned int *flags
, int *nonblocking
)
353 struct mm_struct
*mm
= vma
->vm_mm
;
354 unsigned int fault_flags
= 0;
357 /* mlock all present pages, but do not fault in new pages */
358 if ((*flags
& (FOLL_POPULATE
| FOLL_MLOCK
)) == FOLL_MLOCK
)
360 /* For mm_populate(), just skip the stack guard page. */
361 if ((*flags
& FOLL_POPULATE
) &&
362 (stack_guard_page_start(vma
, address
) ||
363 stack_guard_page_end(vma
, address
+ PAGE_SIZE
)))
365 if (*flags
& FOLL_WRITE
)
366 fault_flags
|= FAULT_FLAG_WRITE
;
367 if (*flags
& FOLL_REMOTE
)
368 fault_flags
|= FAULT_FLAG_REMOTE
;
370 fault_flags
|= FAULT_FLAG_ALLOW_RETRY
;
371 if (*flags
& FOLL_NOWAIT
)
372 fault_flags
|= FAULT_FLAG_ALLOW_RETRY
| FAULT_FLAG_RETRY_NOWAIT
;
373 if (*flags
& FOLL_TRIED
) {
374 VM_WARN_ON_ONCE(fault_flags
& FAULT_FLAG_ALLOW_RETRY
);
375 fault_flags
|= FAULT_FLAG_TRIED
;
378 ret
= handle_mm_fault(mm
, vma
, address
, fault_flags
);
379 if (ret
& VM_FAULT_ERROR
) {
380 if (ret
& VM_FAULT_OOM
)
382 if (ret
& (VM_FAULT_HWPOISON
| VM_FAULT_HWPOISON_LARGE
))
383 return *flags
& FOLL_HWPOISON
? -EHWPOISON
: -EFAULT
;
384 if (ret
& (VM_FAULT_SIGBUS
| VM_FAULT_SIGSEGV
))
390 if (ret
& VM_FAULT_MAJOR
)
396 if (ret
& VM_FAULT_RETRY
) {
403 * The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when
404 * necessary, even if maybe_mkwrite decided not to set pte_write. We
405 * can thus safely do subsequent page lookups as if they were reads.
406 * But only do so when looping for pte_write is futile: in some cases
407 * userspace may also be wanting to write to the gotten user page,
408 * which a read fault here might prevent (a readonly page might get
409 * reCOWed by userspace write).
411 if ((ret
& VM_FAULT_WRITE
) && !(vma
->vm_flags
& VM_WRITE
))
412 *flags
&= ~FOLL_WRITE
;
416 static int check_vma_flags(struct vm_area_struct
*vma
, unsigned long gup_flags
)
418 vm_flags_t vm_flags
= vma
->vm_flags
;
419 int write
= (gup_flags
& FOLL_WRITE
);
420 int foreign
= (gup_flags
& FOLL_REMOTE
);
422 if (vm_flags
& (VM_IO
| VM_PFNMAP
))
426 if (!(vm_flags
& VM_WRITE
)) {
427 if (!(gup_flags
& FOLL_FORCE
))
430 * We used to let the write,force case do COW in a
431 * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could
432 * set a breakpoint in a read-only mapping of an
433 * executable, without corrupting the file (yet only
434 * when that file had been opened for writing!).
435 * Anon pages in shared mappings are surprising: now
438 if (!is_cow_mapping(vm_flags
))
441 } else if (!(vm_flags
& VM_READ
)) {
442 if (!(gup_flags
& FOLL_FORCE
))
445 * Is there actually any vma we can reach here which does not
446 * have VM_MAYREAD set?
448 if (!(vm_flags
& VM_MAYREAD
))
452 * gups are always data accesses, not instruction
453 * fetches, so execute=false here
455 if (!arch_vma_access_permitted(vma
, write
, false, foreign
))
461 * __get_user_pages() - pin user pages in memory
462 * @tsk: task_struct of target task
463 * @mm: mm_struct of target mm
464 * @start: starting user address
465 * @nr_pages: number of pages from start to pin
466 * @gup_flags: flags modifying pin behaviour
467 * @pages: array that receives pointers to the pages pinned.
468 * Should be at least nr_pages long. Or NULL, if caller
469 * only intends to ensure the pages are faulted in.
470 * @vmas: array of pointers to vmas corresponding to each page.
471 * Or NULL if the caller does not require them.
472 * @nonblocking: whether waiting for disk IO or mmap_sem contention
474 * Returns number of pages pinned. This may be fewer than the number
475 * requested. If nr_pages is 0 or negative, returns 0. If no pages
476 * were pinned, returns -errno. Each page returned must be released
477 * with a put_page() call when it is finished with. vmas will only
478 * remain valid while mmap_sem is held.
480 * Must be called with mmap_sem held. It may be released. See below.
482 * __get_user_pages walks a process's page tables and takes a reference to
483 * each struct page that each user address corresponds to at a given
484 * instant. That is, it takes the page that would be accessed if a user
485 * thread accesses the given user virtual address at that instant.
487 * This does not guarantee that the page exists in the user mappings when
488 * __get_user_pages returns, and there may even be a completely different
489 * page there in some cases (eg. if mmapped pagecache has been invalidated
490 * and subsequently re faulted). However it does guarantee that the page
491 * won't be freed completely. And mostly callers simply care that the page
492 * contains data that was valid *at some point in time*. Typically, an IO
493 * or similar operation cannot guarantee anything stronger anyway because
494 * locks can't be held over the syscall boundary.
496 * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
497 * the page is written to, set_page_dirty (or set_page_dirty_lock, as
498 * appropriate) must be called after the page is finished with, and
499 * before put_page is called.
501 * If @nonblocking != NULL, __get_user_pages will not wait for disk IO
502 * or mmap_sem contention, and if waiting is needed to pin all pages,
503 * *@nonblocking will be set to 0. Further, if @gup_flags does not
504 * include FOLL_NOWAIT, the mmap_sem will be released via up_read() in
507 * A caller using such a combination of @nonblocking and @gup_flags
508 * must therefore hold the mmap_sem for reading only, and recognize
509 * when it's been released. Otherwise, it must be held for either
510 * reading or writing and will not be released.
512 * In most cases, get_user_pages or get_user_pages_fast should be used
513 * instead of __get_user_pages. __get_user_pages should be used only if
514 * you need some special @gup_flags.
516 long __get_user_pages(struct task_struct
*tsk
, struct mm_struct
*mm
,
517 unsigned long start
, unsigned long nr_pages
,
518 unsigned int gup_flags
, struct page
**pages
,
519 struct vm_area_struct
**vmas
, int *nonblocking
)
522 unsigned int page_mask
;
523 struct vm_area_struct
*vma
= NULL
;
528 VM_BUG_ON(!!pages
!= !!(gup_flags
& FOLL_GET
));
531 * If FOLL_FORCE is set then do not force a full fault as the hinting
532 * fault information is unrelated to the reference behaviour of a task
533 * using the address space
535 if (!(gup_flags
& FOLL_FORCE
))
536 gup_flags
|= FOLL_NUMA
;
540 unsigned int foll_flags
= gup_flags
;
541 unsigned int page_increm
;
543 /* first iteration or cross vma bound */
544 if (!vma
|| start
>= vma
->vm_end
) {
545 vma
= find_extend_vma(mm
, start
);
546 if (!vma
&& in_gate_area(mm
, start
)) {
548 ret
= get_gate_page(mm
, start
& PAGE_MASK
,
550 pages
? &pages
[i
] : NULL
);
557 if (!vma
|| check_vma_flags(vma
, gup_flags
))
558 return i
? : -EFAULT
;
559 if (is_vm_hugetlb_page(vma
)) {
560 i
= follow_hugetlb_page(mm
, vma
, pages
, vmas
,
561 &start
, &nr_pages
, i
,
568 * If we have a pending SIGKILL, don't keep faulting pages and
569 * potentially allocating memory.
571 if (unlikely(fatal_signal_pending(current
)))
572 return i
? i
: -ERESTARTSYS
;
574 page
= follow_page_mask(vma
, start
, foll_flags
, &page_mask
);
577 ret
= faultin_page(tsk
, vma
, start
, &foll_flags
,
592 } else if (PTR_ERR(page
) == -EEXIST
) {
594 * Proper page table entry exists, but no corresponding
598 } else if (IS_ERR(page
)) {
599 return i
? i
: PTR_ERR(page
);
603 flush_anon_page(vma
, page
, start
);
604 flush_dcache_page(page
);
612 page_increm
= 1 + (~(start
>> PAGE_SHIFT
) & page_mask
);
613 if (page_increm
> nr_pages
)
614 page_increm
= nr_pages
;
616 start
+= page_increm
* PAGE_SIZE
;
617 nr_pages
-= page_increm
;
621 EXPORT_SYMBOL(__get_user_pages
);
623 bool vma_permits_fault(struct vm_area_struct
*vma
, unsigned int fault_flags
)
625 bool write
= !!(fault_flags
& FAULT_FLAG_WRITE
);
626 bool foreign
= !!(fault_flags
& FAULT_FLAG_REMOTE
);
627 vm_flags_t vm_flags
= write
? VM_WRITE
: VM_READ
;
629 if (!(vm_flags
& vma
->vm_flags
))
633 * The architecture might have a hardware protection
634 * mechanism other than read/write that can deny access.
636 * gup always represents data access, not instruction
637 * fetches, so execute=false here:
639 if (!arch_vma_access_permitted(vma
, write
, false, foreign
))
646 * fixup_user_fault() - manually resolve a user page fault
647 * @tsk: the task_struct to use for page fault accounting, or
648 * NULL if faults are not to be recorded.
649 * @mm: mm_struct of target mm
650 * @address: user address
651 * @fault_flags:flags to pass down to handle_mm_fault()
652 * @unlocked: did we unlock the mmap_sem while retrying, maybe NULL if caller
653 * does not allow retry
655 * This is meant to be called in the specific scenario where for locking reasons
656 * we try to access user memory in atomic context (within a pagefault_disable()
657 * section), this returns -EFAULT, and we want to resolve the user fault before
660 * Typically this is meant to be used by the futex code.
662 * The main difference with get_user_pages() is that this function will
663 * unconditionally call handle_mm_fault() which will in turn perform all the
664 * necessary SW fixup of the dirty and young bits in the PTE, while
665 * get_user_pages() only guarantees to update these in the struct page.
667 * This is important for some architectures where those bits also gate the
668 * access permission to the page because they are maintained in software. On
669 * such architectures, gup() will not be enough to make a subsequent access
672 * This function will not return with an unlocked mmap_sem. So it has not the
673 * same semantics wrt the @mm->mmap_sem as does filemap_fault().
675 int fixup_user_fault(struct task_struct
*tsk
, struct mm_struct
*mm
,
676 unsigned long address
, unsigned int fault_flags
,
679 struct vm_area_struct
*vma
;
683 fault_flags
|= FAULT_FLAG_ALLOW_RETRY
;
686 vma
= find_extend_vma(mm
, address
);
687 if (!vma
|| address
< vma
->vm_start
)
690 if (!vma_permits_fault(vma
, fault_flags
))
693 ret
= handle_mm_fault(mm
, vma
, address
, fault_flags
);
694 major
|= ret
& VM_FAULT_MAJOR
;
695 if (ret
& VM_FAULT_ERROR
) {
696 if (ret
& VM_FAULT_OOM
)
698 if (ret
& (VM_FAULT_HWPOISON
| VM_FAULT_HWPOISON_LARGE
))
700 if (ret
& (VM_FAULT_SIGBUS
| VM_FAULT_SIGSEGV
))
705 if (ret
& VM_FAULT_RETRY
) {
706 down_read(&mm
->mmap_sem
);
707 if (!(fault_flags
& FAULT_FLAG_TRIED
)) {
709 fault_flags
&= ~FAULT_FLAG_ALLOW_RETRY
;
710 fault_flags
|= FAULT_FLAG_TRIED
;
723 EXPORT_SYMBOL_GPL(fixup_user_fault
);
725 static __always_inline
long __get_user_pages_locked(struct task_struct
*tsk
,
726 struct mm_struct
*mm
,
728 unsigned long nr_pages
,
729 int write
, int force
,
731 struct vm_area_struct
**vmas
,
732 int *locked
, bool notify_drop
,
735 long ret
, pages_done
;
739 /* if VM_FAULT_RETRY can be returned, vmas become invalid */
741 /* check caller initialized locked */
742 BUG_ON(*locked
!= 1);
753 lock_dropped
= false;
755 ret
= __get_user_pages(tsk
, mm
, start
, nr_pages
, flags
, pages
,
758 /* VM_FAULT_RETRY couldn't trigger, bypass */
761 /* VM_FAULT_RETRY cannot return errors */
764 BUG_ON(ret
>= nr_pages
);
768 /* If it's a prefault don't insist harder */
778 /* VM_FAULT_RETRY didn't trigger */
783 /* VM_FAULT_RETRY triggered, so seek to the faulting offset */
785 start
+= ret
<< PAGE_SHIFT
;
788 * Repeat on the address that fired VM_FAULT_RETRY
789 * without FAULT_FLAG_ALLOW_RETRY but with
794 down_read(&mm
->mmap_sem
);
795 ret
= __get_user_pages(tsk
, mm
, start
, 1, flags
| FOLL_TRIED
,
810 if (notify_drop
&& lock_dropped
&& *locked
) {
812 * We must let the caller know we temporarily dropped the lock
813 * and so the critical section protected by it was lost.
815 up_read(&mm
->mmap_sem
);
822 * We can leverage the VM_FAULT_RETRY functionality in the page fault
823 * paths better by using either get_user_pages_locked() or
824 * get_user_pages_unlocked().
826 * get_user_pages_locked() is suitable to replace the form:
828 * down_read(&mm->mmap_sem);
830 * get_user_pages(tsk, mm, ..., pages, NULL);
831 * up_read(&mm->mmap_sem);
836 * down_read(&mm->mmap_sem);
838 * get_user_pages_locked(tsk, mm, ..., pages, &locked);
840 * up_read(&mm->mmap_sem);
842 long get_user_pages_locked(unsigned long start
, unsigned long nr_pages
,
843 int write
, int force
, struct page
**pages
,
846 return __get_user_pages_locked(current
, current
->mm
, start
, nr_pages
,
847 write
, force
, pages
, NULL
, locked
, true,
850 EXPORT_SYMBOL(get_user_pages_locked
);
853 * Same as get_user_pages_unlocked(...., FOLL_TOUCH) but it allows to
854 * pass additional gup_flags as last parameter (like FOLL_HWPOISON).
856 * NOTE: here FOLL_TOUCH is not set implicitly and must be set by the
857 * caller if required (just like with __get_user_pages). "FOLL_GET",
858 * "FOLL_WRITE" and "FOLL_FORCE" are set implicitly as needed
859 * according to the parameters "pages", "write", "force"
862 __always_inline
long __get_user_pages_unlocked(struct task_struct
*tsk
, struct mm_struct
*mm
,
863 unsigned long start
, unsigned long nr_pages
,
864 int write
, int force
, struct page
**pages
,
865 unsigned int gup_flags
)
869 down_read(&mm
->mmap_sem
);
870 ret
= __get_user_pages_locked(tsk
, mm
, start
, nr_pages
, write
, force
,
871 pages
, NULL
, &locked
, false, gup_flags
);
873 up_read(&mm
->mmap_sem
);
876 EXPORT_SYMBOL(__get_user_pages_unlocked
);
879 * get_user_pages_unlocked() is suitable to replace the form:
881 * down_read(&mm->mmap_sem);
882 * get_user_pages(tsk, mm, ..., pages, NULL);
883 * up_read(&mm->mmap_sem);
887 * get_user_pages_unlocked(tsk, mm, ..., pages);
889 * It is functionally equivalent to get_user_pages_fast so
890 * get_user_pages_fast should be used instead, if the two parameters
891 * "tsk" and "mm" are respectively equal to current and current->mm,
892 * or if "force" shall be set to 1 (get_user_pages_fast misses the
893 * "force" parameter).
895 long get_user_pages_unlocked(unsigned long start
, unsigned long nr_pages
,
896 int write
, int force
, struct page
**pages
)
898 return __get_user_pages_unlocked(current
, current
->mm
, start
, nr_pages
,
899 write
, force
, pages
, 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 * @write: whether pages will be written to by the caller
911 * @force: whether to force access even when user mapping is currently
912 * protected (but never forces write access to shared mapping).
913 * @pages: array that receives pointers to the pages pinned.
914 * Should be at least nr_pages long. Or NULL, if caller
915 * only intends to ensure the pages are faulted in.
916 * @vmas: array of pointers to vmas corresponding to each page.
917 * Or NULL if the caller does not require them.
919 * Returns number of pages pinned. This may be fewer than the number
920 * requested. If nr_pages is 0 or negative, returns 0. If no pages
921 * were pinned, returns -errno. Each page returned must be released
922 * with a put_page() call when it is finished with. vmas will only
923 * remain valid while mmap_sem is held.
925 * Must be called with mmap_sem held for read or write.
927 * get_user_pages walks a process's page tables and takes a reference to
928 * each struct page that each user address corresponds to at a given
929 * instant. That is, it takes the page that would be accessed if a user
930 * thread accesses the given user virtual address at that instant.
932 * This does not guarantee that the page exists in the user mappings when
933 * get_user_pages returns, and there may even be a completely different
934 * page there in some cases (eg. if mmapped pagecache has been invalidated
935 * and subsequently re faulted). However it does guarantee that the page
936 * won't be freed completely. And mostly callers simply care that the page
937 * contains data that was valid *at some point in time*. Typically, an IO
938 * or similar operation cannot guarantee anything stronger anyway because
939 * locks can't be held over the syscall boundary.
941 * If write=0, the page must not be written to. If the page is written to,
942 * set_page_dirty (or set_page_dirty_lock, as appropriate) must be called
943 * after the page is finished with, and before put_page is called.
945 * get_user_pages is typically used for fewer-copy IO operations, to get a
946 * handle on the memory by some means other than accesses via the user virtual
947 * addresses. The pages may be submitted for DMA to devices or accessed via
948 * their kernel linear mapping (via the kmap APIs). Care should be taken to
949 * use the correct cache flushing APIs.
951 * See also get_user_pages_fast, for performance critical applications.
953 * get_user_pages should be phased out in favor of
954 * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
955 * should use get_user_pages because it cannot pass
956 * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
958 long get_user_pages_remote(struct task_struct
*tsk
, struct mm_struct
*mm
,
959 unsigned long start
, unsigned long nr_pages
,
960 int write
, int force
, struct page
**pages
,
961 struct vm_area_struct
**vmas
)
963 return __get_user_pages_locked(tsk
, mm
, start
, nr_pages
, write
, force
,
964 pages
, vmas
, NULL
, false,
965 FOLL_TOUCH
| FOLL_REMOTE
);
967 EXPORT_SYMBOL(get_user_pages_remote
);
970 * This is the same as get_user_pages_remote(), just with a
971 * less-flexible calling convention where we assume that the task
972 * and mm being operated on are the current task's. We also
973 * obviously don't pass FOLL_REMOTE in here.
975 long get_user_pages(unsigned long start
, unsigned long nr_pages
,
976 int write
, int force
, struct page
**pages
,
977 struct vm_area_struct
**vmas
)
979 return __get_user_pages_locked(current
, current
->mm
, start
, nr_pages
,
980 write
, force
, pages
, vmas
, NULL
, false,
983 EXPORT_SYMBOL(get_user_pages
);
986 * populate_vma_page_range() - populate a range of pages in the vma.
988 * @start: start address
992 * This takes care of mlocking the pages too if VM_LOCKED is set.
994 * return 0 on success, negative error code on error.
996 * vma->vm_mm->mmap_sem must be held.
998 * If @nonblocking is NULL, it may be held for read or write and will
1001 * If @nonblocking is non-NULL, it must held for read only and may be
1002 * released. If it's released, *@nonblocking will be set to 0.
1004 long populate_vma_page_range(struct vm_area_struct
*vma
,
1005 unsigned long start
, unsigned long end
, int *nonblocking
)
1007 struct mm_struct
*mm
= vma
->vm_mm
;
1008 unsigned long nr_pages
= (end
- start
) / PAGE_SIZE
;
1011 VM_BUG_ON(start
& ~PAGE_MASK
);
1012 VM_BUG_ON(end
& ~PAGE_MASK
);
1013 VM_BUG_ON_VMA(start
< vma
->vm_start
, vma
);
1014 VM_BUG_ON_VMA(end
> vma
->vm_end
, vma
);
1015 VM_BUG_ON_MM(!rwsem_is_locked(&mm
->mmap_sem
), mm
);
1017 gup_flags
= FOLL_TOUCH
| FOLL_POPULATE
| FOLL_MLOCK
;
1018 if (vma
->vm_flags
& VM_LOCKONFAULT
)
1019 gup_flags
&= ~FOLL_POPULATE
;
1021 * We want to touch writable mappings with a write fault in order
1022 * to break COW, except for shared mappings because these don't COW
1023 * and we would not want to dirty them for nothing.
1025 if ((vma
->vm_flags
& (VM_WRITE
| VM_SHARED
)) == VM_WRITE
)
1026 gup_flags
|= FOLL_WRITE
;
1029 * We want mlock to succeed for regions that have any permissions
1030 * other than PROT_NONE.
1032 if (vma
->vm_flags
& (VM_READ
| VM_WRITE
| VM_EXEC
))
1033 gup_flags
|= FOLL_FORCE
;
1036 * We made sure addr is within a VMA, so the following will
1037 * not result in a stack expansion that recurses back here.
1039 return __get_user_pages(current
, mm
, start
, nr_pages
, gup_flags
,
1040 NULL
, NULL
, nonblocking
);
1044 * __mm_populate - populate and/or mlock pages within a range of address space.
1046 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
1047 * flags. VMAs must be already marked with the desired vm_flags, and
1048 * mmap_sem must not be held.
1050 int __mm_populate(unsigned long start
, unsigned long len
, int ignore_errors
)
1052 struct mm_struct
*mm
= current
->mm
;
1053 unsigned long end
, nstart
, nend
;
1054 struct vm_area_struct
*vma
= NULL
;
1058 VM_BUG_ON(start
& ~PAGE_MASK
);
1059 VM_BUG_ON(len
!= PAGE_ALIGN(len
));
1062 for (nstart
= start
; nstart
< end
; nstart
= nend
) {
1064 * We want to fault in pages for [nstart; end) address range.
1065 * Find first corresponding VMA.
1069 down_read(&mm
->mmap_sem
);
1070 vma
= find_vma(mm
, nstart
);
1071 } else if (nstart
>= vma
->vm_end
)
1073 if (!vma
|| vma
->vm_start
>= end
)
1076 * Set [nstart; nend) to intersection of desired address
1077 * range with the first VMA. Also, skip undesirable VMA types.
1079 nend
= min(end
, vma
->vm_end
);
1080 if (vma
->vm_flags
& (VM_IO
| VM_PFNMAP
))
1082 if (nstart
< vma
->vm_start
)
1083 nstart
= vma
->vm_start
;
1085 * Now fault in a range of pages. populate_vma_page_range()
1086 * double checks the vma flags, so that it won't mlock pages
1087 * if the vma was already munlocked.
1089 ret
= populate_vma_page_range(vma
, nstart
, nend
, &locked
);
1091 if (ignore_errors
) {
1093 continue; /* continue at next VMA */
1097 nend
= nstart
+ ret
* PAGE_SIZE
;
1101 up_read(&mm
->mmap_sem
);
1102 return ret
; /* 0 or negative error code */
1106 * get_dump_page() - pin user page in memory while writing it to core dump
1107 * @addr: user address
1109 * Returns struct page pointer of user page pinned for dump,
1110 * to be freed afterwards by put_page().
1112 * Returns NULL on any kind of failure - a hole must then be inserted into
1113 * the corefile, to preserve alignment with its headers; and also returns
1114 * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
1115 * allowing a hole to be left in the corefile to save diskspace.
1117 * Called without mmap_sem, but after all other threads have been killed.
1119 #ifdef CONFIG_ELF_CORE
1120 struct page
*get_dump_page(unsigned long addr
)
1122 struct vm_area_struct
*vma
;
1125 if (__get_user_pages(current
, current
->mm
, addr
, 1,
1126 FOLL_FORCE
| FOLL_DUMP
| FOLL_GET
, &page
, &vma
,
1129 flush_cache_page(vma
, addr
, page_to_pfn(page
));
1132 #endif /* CONFIG_ELF_CORE */
1135 * Generic RCU Fast GUP
1137 * get_user_pages_fast attempts to pin user pages by walking the page
1138 * tables directly and avoids taking locks. Thus the walker needs to be
1139 * protected from page table pages being freed from under it, and should
1140 * block any THP splits.
1142 * One way to achieve this is to have the walker disable interrupts, and
1143 * rely on IPIs from the TLB flushing code blocking before the page table
1144 * pages are freed. This is unsuitable for architectures that do not need
1145 * to broadcast an IPI when invalidating TLBs.
1147 * Another way to achieve this is to batch up page table containing pages
1148 * belonging to more than one mm_user, then rcu_sched a callback to free those
1149 * pages. Disabling interrupts will allow the fast_gup walker to both block
1150 * the rcu_sched callback, and an IPI that we broadcast for splitting THPs
1151 * (which is a relatively rare event). The code below adopts this strategy.
1153 * Before activating this code, please be aware that the following assumptions
1154 * are currently made:
1156 * *) HAVE_RCU_TABLE_FREE is enabled, and tlb_remove_table is used to free
1157 * pages containing page tables.
1159 * *) ptes can be read atomically by the architecture.
1161 * *) access_ok is sufficient to validate userspace address ranges.
1163 * The last two assumptions can be relaxed by the addition of helper functions.
1165 * This code is based heavily on the PowerPC implementation by Nick Piggin.
1167 #ifdef CONFIG_HAVE_GENERIC_RCU_GUP
1169 #ifdef __HAVE_ARCH_PTE_SPECIAL
1170 static int gup_pte_range(pmd_t pmd
, unsigned long addr
, unsigned long end
,
1171 int write
, struct page
**pages
, int *nr
)
1176 ptem
= ptep
= pte_offset_map(&pmd
, addr
);
1179 * In the line below we are assuming that the pte can be read
1180 * atomically. If this is not the case for your architecture,
1181 * please wrap this in a helper function!
1183 * for an example see gup_get_pte in arch/x86/mm/gup.c
1185 pte_t pte
= READ_ONCE(*ptep
);
1186 struct page
*head
, *page
;
1189 * Similar to the PMD case below, NUMA hinting must take slow
1190 * path using the pte_protnone check.
1192 if (!pte_present(pte
) || pte_special(pte
) ||
1193 pte_protnone(pte
) || (write
&& !pte_write(pte
)))
1196 if (!arch_pte_access_permitted(pte
, write
))
1199 VM_BUG_ON(!pfn_valid(pte_pfn(pte
)));
1200 page
= pte_page(pte
);
1201 head
= compound_head(page
);
1203 if (!page_cache_get_speculative(head
))
1206 if (unlikely(pte_val(pte
) != pte_val(*ptep
))) {
1211 VM_BUG_ON_PAGE(compound_head(page
) != head
, page
);
1215 } while (ptep
++, addr
+= PAGE_SIZE
, addr
!= end
);
1226 * If we can't determine whether or not a pte is special, then fail immediately
1227 * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
1230 * For a futex to be placed on a THP tail page, get_futex_key requires a
1231 * __get_user_pages_fast implementation that can pin pages. Thus it's still
1232 * useful to have gup_huge_pmd even if we can't operate on ptes.
1234 static int gup_pte_range(pmd_t pmd
, unsigned long addr
, unsigned long end
,
1235 int write
, struct page
**pages
, int *nr
)
1239 #endif /* __HAVE_ARCH_PTE_SPECIAL */
1241 static int gup_huge_pmd(pmd_t orig
, pmd_t
*pmdp
, unsigned long addr
,
1242 unsigned long end
, int write
, struct page
**pages
, int *nr
)
1244 struct page
*head
, *page
;
1247 if (write
&& !pmd_write(orig
))
1251 head
= pmd_page(orig
);
1252 page
= head
+ ((addr
& ~PMD_MASK
) >> PAGE_SHIFT
);
1254 VM_BUG_ON_PAGE(compound_head(page
) != head
, page
);
1259 } while (addr
+= PAGE_SIZE
, addr
!= end
);
1261 if (!page_cache_add_speculative(head
, refs
)) {
1266 if (unlikely(pmd_val(orig
) != pmd_val(*pmdp
))) {
1276 static int gup_huge_pud(pud_t orig
, pud_t
*pudp
, unsigned long addr
,
1277 unsigned long end
, int write
, struct page
**pages
, int *nr
)
1279 struct page
*head
, *page
;
1282 if (write
&& !pud_write(orig
))
1286 head
= pud_page(orig
);
1287 page
= head
+ ((addr
& ~PUD_MASK
) >> PAGE_SHIFT
);
1289 VM_BUG_ON_PAGE(compound_head(page
) != head
, page
);
1294 } while (addr
+= PAGE_SIZE
, addr
!= end
);
1296 if (!page_cache_add_speculative(head
, refs
)) {
1301 if (unlikely(pud_val(orig
) != pud_val(*pudp
))) {
1311 static int gup_huge_pgd(pgd_t orig
, pgd_t
*pgdp
, unsigned long addr
,
1312 unsigned long end
, int write
,
1313 struct page
**pages
, int *nr
)
1316 struct page
*head
, *page
;
1318 if (write
&& !pgd_write(orig
))
1322 head
= pgd_page(orig
);
1323 page
= head
+ ((addr
& ~PGDIR_MASK
) >> PAGE_SHIFT
);
1325 VM_BUG_ON_PAGE(compound_head(page
) != head
, page
);
1330 } while (addr
+= PAGE_SIZE
, addr
!= end
);
1332 if (!page_cache_add_speculative(head
, refs
)) {
1337 if (unlikely(pgd_val(orig
) != pgd_val(*pgdp
))) {
1347 static int gup_pmd_range(pud_t pud
, unsigned long addr
, unsigned long end
,
1348 int write
, struct page
**pages
, int *nr
)
1353 pmdp
= pmd_offset(&pud
, addr
);
1355 pmd_t pmd
= READ_ONCE(*pmdp
);
1357 next
= pmd_addr_end(addr
, end
);
1361 if (unlikely(pmd_trans_huge(pmd
) || pmd_huge(pmd
))) {
1363 * NUMA hinting faults need to be handled in the GUP
1364 * slowpath for accounting purposes and so that they
1365 * can be serialised against THP migration.
1367 if (pmd_protnone(pmd
))
1370 if (!gup_huge_pmd(pmd
, pmdp
, addr
, next
, write
,
1374 } else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd
))))) {
1376 * architecture have different format for hugetlbfs
1377 * pmd format and THP pmd format
1379 if (!gup_huge_pd(__hugepd(pmd_val(pmd
)), addr
,
1380 PMD_SHIFT
, next
, write
, pages
, nr
))
1382 } else if (!gup_pte_range(pmd
, addr
, next
, write
, pages
, nr
))
1384 } while (pmdp
++, addr
= next
, addr
!= end
);
1389 static int gup_pud_range(pgd_t pgd
, unsigned long addr
, unsigned long end
,
1390 int write
, struct page
**pages
, int *nr
)
1395 pudp
= pud_offset(&pgd
, addr
);
1397 pud_t pud
= READ_ONCE(*pudp
);
1399 next
= pud_addr_end(addr
, end
);
1402 if (unlikely(pud_huge(pud
))) {
1403 if (!gup_huge_pud(pud
, pudp
, addr
, next
, write
,
1406 } else if (unlikely(is_hugepd(__hugepd(pud_val(pud
))))) {
1407 if (!gup_huge_pd(__hugepd(pud_val(pud
)), addr
,
1408 PUD_SHIFT
, next
, write
, pages
, nr
))
1410 } else if (!gup_pmd_range(pud
, addr
, next
, write
, pages
, nr
))
1412 } while (pudp
++, addr
= next
, addr
!= end
);
1418 * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
1419 * the regular GUP. It will only return non-negative values.
1421 int __get_user_pages_fast(unsigned long start
, int nr_pages
, int write
,
1422 struct page
**pages
)
1424 struct mm_struct
*mm
= current
->mm
;
1425 unsigned long addr
, len
, end
;
1426 unsigned long next
, flags
;
1432 len
= (unsigned long) nr_pages
<< PAGE_SHIFT
;
1435 if (unlikely(!access_ok(write
? VERIFY_WRITE
: VERIFY_READ
,
1440 * Disable interrupts. We use the nested form as we can already have
1441 * interrupts disabled by get_futex_key.
1443 * With interrupts disabled, we block page table pages from being
1444 * freed from under us. See mmu_gather_tlb in asm-generic/tlb.h
1447 * We do not adopt an rcu_read_lock(.) here as we also want to
1448 * block IPIs that come from THPs splitting.
1451 local_irq_save(flags
);
1452 pgdp
= pgd_offset(mm
, addr
);
1454 pgd_t pgd
= READ_ONCE(*pgdp
);
1456 next
= pgd_addr_end(addr
, end
);
1459 if (unlikely(pgd_huge(pgd
))) {
1460 if (!gup_huge_pgd(pgd
, pgdp
, addr
, next
, write
,
1463 } else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd
))))) {
1464 if (!gup_huge_pd(__hugepd(pgd_val(pgd
)), addr
,
1465 PGDIR_SHIFT
, next
, write
, pages
, &nr
))
1467 } else if (!gup_pud_range(pgd
, addr
, next
, write
, pages
, &nr
))
1469 } while (pgdp
++, addr
= next
, addr
!= end
);
1470 local_irq_restore(flags
);
1476 * get_user_pages_fast() - pin user pages in memory
1477 * @start: starting user address
1478 * @nr_pages: number of pages from start to pin
1479 * @write: whether pages will be written to
1480 * @pages: array that receives pointers to the pages pinned.
1481 * Should be at least nr_pages long.
1483 * Attempt to pin user pages in memory without taking mm->mmap_sem.
1484 * If not successful, it will fall back to taking the lock and
1485 * calling get_user_pages().
1487 * Returns number of pages pinned. This may be fewer than the number
1488 * requested. If nr_pages is 0 or negative, returns 0. If no pages
1489 * were pinned, returns -errno.
1491 int get_user_pages_fast(unsigned long start
, int nr_pages
, int write
,
1492 struct page
**pages
)
1497 nr
= __get_user_pages_fast(start
, nr_pages
, write
, pages
);
1500 if (nr
< nr_pages
) {
1501 /* Try to get the remaining pages with get_user_pages */
1502 start
+= nr
<< PAGE_SHIFT
;
1505 ret
= get_user_pages_unlocked(start
, nr_pages
- nr
, write
, 0, pages
);
1507 /* Have to be a bit careful with return values */
1519 #endif /* CONFIG_HAVE_GENERIC_RCU_GUP */