1 // SPDX-License-Identifier: GPL-2.0
5 * (C) Copyright 1996 Linus Torvalds
7 * Address space accounting code <alan@lxorguk.ukuu.org.uk>
8 * (C) Copyright 2002 Red Hat Inc, All Rights Reserved
12 #include <linux/hugetlb.h>
13 #include <linux/shm.h>
14 #include <linux/ksm.h>
15 #include <linux/mman.h>
16 #include <linux/swap.h>
17 #include <linux/capability.h>
19 #include <linux/swapops.h>
20 #include <linux/highmem.h>
21 #include <linux/security.h>
22 #include <linux/syscalls.h>
23 #include <linux/mmu_notifier.h>
24 #include <linux/uaccess.h>
25 #include <linux/mm-arch-hooks.h>
26 #include <linux/userfaultfd_k.h>
28 #include <asm/cacheflush.h>
29 #include <asm/tlbflush.h>
33 static pud_t
*get_old_pud(struct mm_struct
*mm
, unsigned long addr
)
39 pgd
= pgd_offset(mm
, addr
);
40 if (pgd_none_or_clear_bad(pgd
))
43 p4d
= p4d_offset(pgd
, addr
);
44 if (p4d_none_or_clear_bad(p4d
))
47 pud
= pud_offset(p4d
, addr
);
48 if (pud_none_or_clear_bad(pud
))
54 static pmd_t
*get_old_pmd(struct mm_struct
*mm
, unsigned long addr
)
59 pud
= get_old_pud(mm
, addr
);
63 pmd
= pmd_offset(pud
, addr
);
70 static pud_t
*alloc_new_pud(struct mm_struct
*mm
, struct vm_area_struct
*vma
,
76 pgd
= pgd_offset(mm
, addr
);
77 p4d
= p4d_alloc(mm
, pgd
, addr
);
81 return pud_alloc(mm
, p4d
, addr
);
84 static pmd_t
*alloc_new_pmd(struct mm_struct
*mm
, struct vm_area_struct
*vma
,
90 pud
= alloc_new_pud(mm
, vma
, addr
);
94 pmd
= pmd_alloc(mm
, pud
, addr
);
98 VM_BUG_ON(pmd_trans_huge(*pmd
));
103 static void take_rmap_locks(struct vm_area_struct
*vma
)
106 i_mmap_lock_write(vma
->vm_file
->f_mapping
);
108 anon_vma_lock_write(vma
->anon_vma
);
111 static void drop_rmap_locks(struct vm_area_struct
*vma
)
114 anon_vma_unlock_write(vma
->anon_vma
);
116 i_mmap_unlock_write(vma
->vm_file
->f_mapping
);
119 static pte_t
move_soft_dirty_pte(pte_t pte
)
122 * Set soft dirty bit so we can notice
123 * in userspace the ptes were moved.
125 #ifdef CONFIG_MEM_SOFT_DIRTY
126 if (pte_present(pte
))
127 pte
= pte_mksoft_dirty(pte
);
128 else if (is_swap_pte(pte
))
129 pte
= pte_swp_mksoft_dirty(pte
);
134 static void move_ptes(struct vm_area_struct
*vma
, pmd_t
*old_pmd
,
135 unsigned long old_addr
, unsigned long old_end
,
136 struct vm_area_struct
*new_vma
, pmd_t
*new_pmd
,
137 unsigned long new_addr
, bool need_rmap_locks
)
139 struct mm_struct
*mm
= vma
->vm_mm
;
140 pte_t
*old_pte
, *new_pte
, pte
;
141 spinlock_t
*old_ptl
, *new_ptl
;
142 bool force_flush
= false;
143 unsigned long len
= old_end
- old_addr
;
146 * When need_rmap_locks is true, we take the i_mmap_rwsem and anon_vma
147 * locks to ensure that rmap will always observe either the old or the
148 * new ptes. This is the easiest way to avoid races with
149 * truncate_pagecache(), page migration, etc...
151 * When need_rmap_locks is false, we use other ways to avoid
154 * - During exec() shift_arg_pages(), we use a specially tagged vma
155 * which rmap call sites look for using vma_is_temporary_stack().
157 * - During mremap(), new_vma is often known to be placed after vma
158 * in rmap traversal order. This ensures rmap will always observe
159 * either the old pte, or the new pte, or both (the page table locks
160 * serialize access to individual ptes, but only rmap traversal
161 * order guarantees that we won't miss both the old and new ptes).
164 take_rmap_locks(vma
);
167 * We don't have to worry about the ordering of src and dst
168 * pte locks because exclusive mmap_lock prevents deadlock.
170 old_pte
= pte_offset_map_lock(mm
, old_pmd
, old_addr
, &old_ptl
);
171 new_pte
= pte_offset_map(new_pmd
, new_addr
);
172 new_ptl
= pte_lockptr(mm
, new_pmd
);
173 if (new_ptl
!= old_ptl
)
174 spin_lock_nested(new_ptl
, SINGLE_DEPTH_NESTING
);
175 flush_tlb_batched_pending(vma
->vm_mm
);
176 arch_enter_lazy_mmu_mode();
178 for (; old_addr
< old_end
; old_pte
++, old_addr
+= PAGE_SIZE
,
179 new_pte
++, new_addr
+= PAGE_SIZE
) {
180 if (pte_none(*old_pte
))
183 pte
= ptep_get_and_clear(mm
, old_addr
, old_pte
);
185 * If we are remapping a valid PTE, make sure
186 * to flush TLB before we drop the PTL for the
189 * NOTE! Both old and new PTL matter: the old one
190 * for racing with page_mkclean(), the new one to
191 * make sure the physical page stays valid until
192 * the TLB entry for the old mapping has been
195 if (pte_present(pte
))
197 pte
= move_pte(pte
, new_vma
->vm_page_prot
, old_addr
, new_addr
);
198 pte
= move_soft_dirty_pte(pte
);
199 set_pte_at(mm
, new_addr
, new_pte
, pte
);
202 arch_leave_lazy_mmu_mode();
204 flush_tlb_range(vma
, old_end
- len
, old_end
);
205 if (new_ptl
!= old_ptl
)
206 spin_unlock(new_ptl
);
207 pte_unmap(new_pte
- 1);
208 pte_unmap_unlock(old_pte
- 1, old_ptl
);
210 drop_rmap_locks(vma
);
213 #ifdef CONFIG_HAVE_MOVE_PMD
214 static bool move_normal_pmd(struct vm_area_struct
*vma
, unsigned long old_addr
,
215 unsigned long new_addr
, pmd_t
*old_pmd
, pmd_t
*new_pmd
)
217 spinlock_t
*old_ptl
, *new_ptl
;
218 struct mm_struct
*mm
= vma
->vm_mm
;
222 * The destination pmd shouldn't be established, free_pgtables()
223 * should have released it.
225 * However, there's a case during execve() where we use mremap
226 * to move the initial stack, and in that case the target area
227 * may overlap the source area (always moving down).
229 * If everything is PMD-aligned, that works fine, as moving
230 * each pmd down will clear the source pmd. But if we first
231 * have a few 4kB-only pages that get moved down, and then
232 * hit the "now the rest is PMD-aligned, let's do everything
233 * one pmd at a time", we will still have the old (now empty
234 * of any 4kB pages, but still there) PMD in the page table
237 * Warn on it once - because we really should try to figure
238 * out how to do this better - but then say "I won't move
241 * One alternative might be to just unmap the target pmd at
242 * this point, and verify that it really is empty. We'll see.
244 if (WARN_ON_ONCE(!pmd_none(*new_pmd
)))
248 * We don't have to worry about the ordering of src and dst
249 * ptlocks because exclusive mmap_lock prevents deadlock.
251 old_ptl
= pmd_lock(vma
->vm_mm
, old_pmd
);
252 new_ptl
= pmd_lockptr(mm
, new_pmd
);
253 if (new_ptl
!= old_ptl
)
254 spin_lock_nested(new_ptl
, SINGLE_DEPTH_NESTING
);
260 VM_BUG_ON(!pmd_none(*new_pmd
));
262 /* Set the new pmd */
263 set_pmd_at(mm
, new_addr
, new_pmd
, pmd
);
264 flush_tlb_range(vma
, old_addr
, old_addr
+ PMD_SIZE
);
265 if (new_ptl
!= old_ptl
)
266 spin_unlock(new_ptl
);
267 spin_unlock(old_ptl
);
272 static inline bool move_normal_pmd(struct vm_area_struct
*vma
,
273 unsigned long old_addr
, unsigned long new_addr
, pmd_t
*old_pmd
,
280 #ifdef CONFIG_HAVE_MOVE_PUD
281 static bool move_normal_pud(struct vm_area_struct
*vma
, unsigned long old_addr
,
282 unsigned long new_addr
, pud_t
*old_pud
, pud_t
*new_pud
)
284 spinlock_t
*old_ptl
, *new_ptl
;
285 struct mm_struct
*mm
= vma
->vm_mm
;
289 * The destination pud shouldn't be established, free_pgtables()
290 * should have released it.
292 if (WARN_ON_ONCE(!pud_none(*new_pud
)))
296 * We don't have to worry about the ordering of src and dst
297 * ptlocks because exclusive mmap_lock prevents deadlock.
299 old_ptl
= pud_lock(vma
->vm_mm
, old_pud
);
300 new_ptl
= pud_lockptr(mm
, new_pud
);
301 if (new_ptl
!= old_ptl
)
302 spin_lock_nested(new_ptl
, SINGLE_DEPTH_NESTING
);
308 VM_BUG_ON(!pud_none(*new_pud
));
310 /* Set the new pud */
311 set_pud_at(mm
, new_addr
, new_pud
, pud
);
312 flush_tlb_range(vma
, old_addr
, old_addr
+ PUD_SIZE
);
313 if (new_ptl
!= old_ptl
)
314 spin_unlock(new_ptl
);
315 spin_unlock(old_ptl
);
320 static inline bool move_normal_pud(struct vm_area_struct
*vma
,
321 unsigned long old_addr
, unsigned long new_addr
, pud_t
*old_pud
,
335 * Returns an extent of the corresponding size for the pgt_entry specified if
336 * valid. Else returns a smaller extent bounded by the end of the source and
337 * destination pgt_entry.
339 static __always_inline
unsigned long get_extent(enum pgt_entry entry
,
340 unsigned long old_addr
, unsigned long old_end
,
341 unsigned long new_addr
)
343 unsigned long next
, extent
, mask
, size
;
360 next
= (old_addr
+ size
) & mask
;
361 /* even if next overflowed, extent below will be ok */
362 extent
= next
- old_addr
;
363 if (extent
> old_end
- old_addr
)
364 extent
= old_end
- old_addr
;
365 next
= (new_addr
+ size
) & mask
;
366 if (extent
> next
- new_addr
)
367 extent
= next
- new_addr
;
372 * Attempts to speedup the move by moving entry at the level corresponding to
373 * pgt_entry. Returns true if the move was successful, else false.
375 static bool move_pgt_entry(enum pgt_entry entry
, struct vm_area_struct
*vma
,
376 unsigned long old_addr
, unsigned long new_addr
,
377 void *old_entry
, void *new_entry
, bool need_rmap_locks
)
381 /* See comment in move_ptes() */
383 take_rmap_locks(vma
);
387 moved
= move_normal_pmd(vma
, old_addr
, new_addr
, old_entry
,
391 moved
= move_normal_pud(vma
, old_addr
, new_addr
, old_entry
,
395 moved
= IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE
) &&
396 move_huge_pmd(vma
, old_addr
, new_addr
, old_entry
,
405 drop_rmap_locks(vma
);
410 unsigned long move_page_tables(struct vm_area_struct
*vma
,
411 unsigned long old_addr
, struct vm_area_struct
*new_vma
,
412 unsigned long new_addr
, unsigned long len
,
413 bool need_rmap_locks
)
415 unsigned long extent
, old_end
;
416 struct mmu_notifier_range range
;
417 pmd_t
*old_pmd
, *new_pmd
;
419 old_end
= old_addr
+ len
;
420 flush_cache_range(vma
, old_addr
, old_end
);
422 mmu_notifier_range_init(&range
, MMU_NOTIFY_UNMAP
, 0, vma
, vma
->vm_mm
,
424 mmu_notifier_invalidate_range_start(&range
);
426 for (; old_addr
< old_end
; old_addr
+= extent
, new_addr
+= extent
) {
429 * If extent is PUD-sized try to speed up the move by moving at the
430 * PUD level if possible.
432 extent
= get_extent(NORMAL_PUD
, old_addr
, old_end
, new_addr
);
433 if (IS_ENABLED(CONFIG_HAVE_MOVE_PUD
) && extent
== PUD_SIZE
) {
434 pud_t
*old_pud
, *new_pud
;
436 old_pud
= get_old_pud(vma
->vm_mm
, old_addr
);
439 new_pud
= alloc_new_pud(vma
->vm_mm
, vma
, new_addr
);
442 if (move_pgt_entry(NORMAL_PUD
, vma
, old_addr
, new_addr
,
443 old_pud
, new_pud
, need_rmap_locks
))
447 extent
= get_extent(NORMAL_PMD
, old_addr
, old_end
, new_addr
);
448 old_pmd
= get_old_pmd(vma
->vm_mm
, old_addr
);
451 new_pmd
= alloc_new_pmd(vma
->vm_mm
, vma
, new_addr
);
454 if (is_swap_pmd(*old_pmd
) || pmd_trans_huge(*old_pmd
) ||
455 pmd_devmap(*old_pmd
)) {
456 if (extent
== HPAGE_PMD_SIZE
&&
457 move_pgt_entry(HPAGE_PMD
, vma
, old_addr
, new_addr
,
458 old_pmd
, new_pmd
, need_rmap_locks
))
460 split_huge_pmd(vma
, old_pmd
, old_addr
);
461 if (pmd_trans_unstable(old_pmd
))
463 } else if (IS_ENABLED(CONFIG_HAVE_MOVE_PMD
) &&
464 extent
== PMD_SIZE
) {
466 * If the extent is PMD-sized, try to speed the move by
467 * moving at the PMD level if possible.
469 if (move_pgt_entry(NORMAL_PMD
, vma
, old_addr
, new_addr
,
470 old_pmd
, new_pmd
, need_rmap_locks
))
474 if (pte_alloc(new_vma
->vm_mm
, new_pmd
))
476 move_ptes(vma
, old_pmd
, old_addr
, old_addr
+ extent
, new_vma
,
477 new_pmd
, new_addr
, need_rmap_locks
);
480 mmu_notifier_invalidate_range_end(&range
);
482 return len
+ old_addr
- old_end
; /* how much done */
485 static unsigned long move_vma(struct vm_area_struct
*vma
,
486 unsigned long old_addr
, unsigned long old_len
,
487 unsigned long new_len
, unsigned long new_addr
,
488 bool *locked
, unsigned long flags
,
489 struct vm_userfaultfd_ctx
*uf
, struct list_head
*uf_unmap
)
491 struct mm_struct
*mm
= vma
->vm_mm
;
492 struct vm_area_struct
*new_vma
;
493 unsigned long vm_flags
= vma
->vm_flags
;
494 unsigned long new_pgoff
;
495 unsigned long moved_len
;
496 unsigned long excess
= 0;
497 unsigned long hiwater_vm
;
500 bool need_rmap_locks
;
503 * We'd prefer to avoid failure later on in do_munmap:
504 * which may split one vma into three before unmapping.
506 if (mm
->map_count
>= sysctl_max_map_count
- 3)
509 if (vma
->vm_ops
&& vma
->vm_ops
->may_split
) {
510 if (vma
->vm_start
!= old_addr
)
511 err
= vma
->vm_ops
->may_split(vma
, old_addr
);
512 if (!err
&& vma
->vm_end
!= old_addr
+ old_len
)
513 err
= vma
->vm_ops
->may_split(vma
, old_addr
+ old_len
);
519 * Advise KSM to break any KSM pages in the area to be moved:
520 * it would be confusing if they were to turn up at the new
521 * location, where they happen to coincide with different KSM
522 * pages recently unmapped. But leave vma->vm_flags as it was,
523 * so KSM can come around to merge on vma and new_vma afterwards.
525 err
= ksm_madvise(vma
, old_addr
, old_addr
+ old_len
,
526 MADV_UNMERGEABLE
, &vm_flags
);
530 if (unlikely(flags
& MREMAP_DONTUNMAP
&& vm_flags
& VM_ACCOUNT
)) {
531 if (security_vm_enough_memory_mm(mm
, new_len
>> PAGE_SHIFT
))
535 new_pgoff
= vma
->vm_pgoff
+ ((old_addr
- vma
->vm_start
) >> PAGE_SHIFT
);
536 new_vma
= copy_vma(&vma
, new_addr
, new_len
, new_pgoff
,
539 if (unlikely(flags
& MREMAP_DONTUNMAP
&& vm_flags
& VM_ACCOUNT
))
540 vm_unacct_memory(new_len
>> PAGE_SHIFT
);
544 moved_len
= move_page_tables(vma
, old_addr
, new_vma
, new_addr
, old_len
,
546 if (moved_len
< old_len
) {
548 } else if (vma
->vm_ops
&& vma
->vm_ops
->mremap
) {
549 err
= vma
->vm_ops
->mremap(new_vma
, flags
);
554 * On error, move entries back from new area to old,
555 * which will succeed since page tables still there,
556 * and then proceed to unmap new area instead of old.
558 move_page_tables(new_vma
, new_addr
, vma
, old_addr
, moved_len
,
565 mremap_userfaultfd_prep(new_vma
, uf
);
566 arch_remap(mm
, old_addr
, old_addr
+ old_len
,
567 new_addr
, new_addr
+ new_len
);
570 /* Conceal VM_ACCOUNT so old reservation is not undone */
571 if (vm_flags
& VM_ACCOUNT
&& !(flags
& MREMAP_DONTUNMAP
)) {
572 vma
->vm_flags
&= ~VM_ACCOUNT
;
573 excess
= vma
->vm_end
- vma
->vm_start
- old_len
;
574 if (old_addr
> vma
->vm_start
&&
575 old_addr
+ old_len
< vma
->vm_end
)
580 * If we failed to move page tables we still do total_vm increment
581 * since do_munmap() will decrement it by old_len == new_len.
583 * Since total_vm is about to be raised artificially high for a
584 * moment, we need to restore high watermark afterwards: if stats
585 * are taken meanwhile, total_vm and hiwater_vm appear too high.
586 * If this were a serious issue, we'd add a flag to do_munmap().
588 hiwater_vm
= mm
->hiwater_vm
;
589 vm_stat_account(mm
, vma
->vm_flags
, new_len
>> PAGE_SHIFT
);
591 /* Tell pfnmap has moved from this vma */
592 if (unlikely(vma
->vm_flags
& VM_PFNMAP
))
593 untrack_pfn_moved(vma
);
595 if (unlikely(!err
&& (flags
& MREMAP_DONTUNMAP
))) {
596 /* We always clear VM_LOCKED[ONFAULT] on the old vma */
597 vma
->vm_flags
&= VM_LOCKED_CLEAR_MASK
;
599 /* Because we won't unmap we don't need to touch locked_vm */
603 if (do_munmap(mm
, old_addr
, old_len
, uf_unmap
) < 0) {
604 /* OOM: unable to split vma, just get accounts right */
605 if (vm_flags
& VM_ACCOUNT
&& !(flags
& MREMAP_DONTUNMAP
))
606 vm_acct_memory(new_len
>> PAGE_SHIFT
);
610 if (vm_flags
& VM_LOCKED
) {
611 mm
->locked_vm
+= new_len
>> PAGE_SHIFT
;
615 mm
->hiwater_vm
= hiwater_vm
;
617 /* Restore VM_ACCOUNT if one or two pieces of vma left */
619 vma
->vm_flags
|= VM_ACCOUNT
;
621 vma
->vm_next
->vm_flags
|= VM_ACCOUNT
;
627 static struct vm_area_struct
*vma_to_resize(unsigned long addr
,
628 unsigned long old_len
, unsigned long new_len
, unsigned long flags
,
631 struct mm_struct
*mm
= current
->mm
;
632 struct vm_area_struct
*vma
= find_vma(mm
, addr
);
635 if (!vma
|| vma
->vm_start
> addr
)
636 return ERR_PTR(-EFAULT
);
639 * !old_len is a special case where an attempt is made to 'duplicate'
640 * a mapping. This makes no sense for private mappings as it will
641 * instead create a fresh/new mapping unrelated to the original. This
642 * is contrary to the basic idea of mremap which creates new mappings
643 * based on the original. There are no known use cases for this
644 * behavior. As a result, fail such attempts.
646 if (!old_len
&& !(vma
->vm_flags
& (VM_SHARED
| VM_MAYSHARE
))) {
647 pr_warn_once("%s (%d): attempted to duplicate a private mapping with mremap. This is not supported.\n", current
->comm
, current
->pid
);
648 return ERR_PTR(-EINVAL
);
651 if (flags
& MREMAP_DONTUNMAP
&& (!vma_is_anonymous(vma
) ||
652 vma
->vm_flags
& VM_SHARED
))
653 return ERR_PTR(-EINVAL
);
655 if (is_vm_hugetlb_page(vma
))
656 return ERR_PTR(-EINVAL
);
658 /* We can't remap across vm area boundaries */
659 if (old_len
> vma
->vm_end
- addr
)
660 return ERR_PTR(-EFAULT
);
662 if (new_len
== old_len
)
665 /* Need to be careful about a growing mapping */
666 pgoff
= (addr
- vma
->vm_start
) >> PAGE_SHIFT
;
667 pgoff
+= vma
->vm_pgoff
;
668 if (pgoff
+ (new_len
>> PAGE_SHIFT
) < pgoff
)
669 return ERR_PTR(-EINVAL
);
671 if (vma
->vm_flags
& (VM_DONTEXPAND
| VM_PFNMAP
))
672 return ERR_PTR(-EFAULT
);
674 if (vma
->vm_flags
& VM_LOCKED
) {
675 unsigned long locked
, lock_limit
;
676 locked
= mm
->locked_vm
<< PAGE_SHIFT
;
677 lock_limit
= rlimit(RLIMIT_MEMLOCK
);
678 locked
+= new_len
- old_len
;
679 if (locked
> lock_limit
&& !capable(CAP_IPC_LOCK
))
680 return ERR_PTR(-EAGAIN
);
683 if (!may_expand_vm(mm
, vma
->vm_flags
,
684 (new_len
- old_len
) >> PAGE_SHIFT
))
685 return ERR_PTR(-ENOMEM
);
687 if (vma
->vm_flags
& VM_ACCOUNT
) {
688 unsigned long charged
= (new_len
- old_len
) >> PAGE_SHIFT
;
689 if (security_vm_enough_memory_mm(mm
, charged
))
690 return ERR_PTR(-ENOMEM
);
697 static unsigned long mremap_to(unsigned long addr
, unsigned long old_len
,
698 unsigned long new_addr
, unsigned long new_len
, bool *locked
,
699 unsigned long flags
, struct vm_userfaultfd_ctx
*uf
,
700 struct list_head
*uf_unmap_early
,
701 struct list_head
*uf_unmap
)
703 struct mm_struct
*mm
= current
->mm
;
704 struct vm_area_struct
*vma
;
705 unsigned long ret
= -EINVAL
;
706 unsigned long charged
= 0;
707 unsigned long map_flags
= 0;
709 if (offset_in_page(new_addr
))
712 if (new_len
> TASK_SIZE
|| new_addr
> TASK_SIZE
- new_len
)
715 /* Ensure the old/new locations do not overlap */
716 if (addr
+ old_len
> new_addr
&& new_addr
+ new_len
> addr
)
720 * move_vma() need us to stay 4 maps below the threshold, otherwise
721 * it will bail out at the very beginning.
722 * That is a problem if we have already unmaped the regions here
723 * (new_addr, and old_addr), because userspace will not know the
724 * state of the vma's after it gets -ENOMEM.
725 * So, to avoid such scenario we can pre-compute if the whole
726 * operation has high chances to success map-wise.
727 * Worst-scenario case is when both vma's (new_addr and old_addr) get
728 * split in 3 before unmaping it.
729 * That means 2 more maps (1 for each) to the ones we already hold.
730 * Check whether current map count plus 2 still leads us to 4 maps below
731 * the threshold, otherwise return -ENOMEM here to be more safe.
733 if ((mm
->map_count
+ 2) >= sysctl_max_map_count
- 3)
736 if (flags
& MREMAP_FIXED
) {
737 ret
= do_munmap(mm
, new_addr
, new_len
, uf_unmap_early
);
742 if (old_len
>= new_len
) {
743 ret
= do_munmap(mm
, addr
+new_len
, old_len
- new_len
, uf_unmap
);
744 if (ret
&& old_len
!= new_len
)
749 vma
= vma_to_resize(addr
, old_len
, new_len
, flags
, &charged
);
755 /* MREMAP_DONTUNMAP expands by old_len since old_len == new_len */
756 if (flags
& MREMAP_DONTUNMAP
&&
757 !may_expand_vm(mm
, vma
->vm_flags
, old_len
>> PAGE_SHIFT
)) {
762 if (flags
& MREMAP_FIXED
)
763 map_flags
|= MAP_FIXED
;
765 if (vma
->vm_flags
& VM_MAYSHARE
)
766 map_flags
|= MAP_SHARED
;
768 ret
= get_unmapped_area(vma
->vm_file
, new_addr
, new_len
, vma
->vm_pgoff
+
769 ((addr
- vma
->vm_start
) >> PAGE_SHIFT
),
771 if (IS_ERR_VALUE(ret
))
774 /* We got a new mapping */
775 if (!(flags
& MREMAP_FIXED
))
778 ret
= move_vma(vma
, addr
, old_len
, new_len
, new_addr
, locked
, flags
, uf
,
781 if (!(offset_in_page(ret
)))
785 vm_unacct_memory(charged
);
791 static int vma_expandable(struct vm_area_struct
*vma
, unsigned long delta
)
793 unsigned long end
= vma
->vm_end
+ delta
;
794 if (end
< vma
->vm_end
) /* overflow */
796 if (vma
->vm_next
&& vma
->vm_next
->vm_start
< end
) /* intersection */
798 if (get_unmapped_area(NULL
, vma
->vm_start
, end
- vma
->vm_start
,
799 0, MAP_FIXED
) & ~PAGE_MASK
)
805 * Expand (or shrink) an existing mapping, potentially moving it at the
806 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
808 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
809 * This option implies MREMAP_MAYMOVE.
811 SYSCALL_DEFINE5(mremap
, unsigned long, addr
, unsigned long, old_len
,
812 unsigned long, new_len
, unsigned long, flags
,
813 unsigned long, new_addr
)
815 struct mm_struct
*mm
= current
->mm
;
816 struct vm_area_struct
*vma
;
817 unsigned long ret
= -EINVAL
;
818 unsigned long charged
= 0;
820 bool downgraded
= false;
821 struct vm_userfaultfd_ctx uf
= NULL_VM_UFFD_CTX
;
822 LIST_HEAD(uf_unmap_early
);
826 * There is a deliberate asymmetry here: we strip the pointer tag
827 * from the old address but leave the new address alone. This is
828 * for consistency with mmap(), where we prevent the creation of
829 * aliasing mappings in userspace by leaving the tag bits of the
830 * mapping address intact. A non-zero tag will cause the subsequent
831 * range checks to reject the address as invalid.
833 * See Documentation/arm64/tagged-address-abi.rst for more information.
835 addr
= untagged_addr(addr
);
837 if (flags
& ~(MREMAP_FIXED
| MREMAP_MAYMOVE
| MREMAP_DONTUNMAP
))
840 if (flags
& MREMAP_FIXED
&& !(flags
& MREMAP_MAYMOVE
))
844 * MREMAP_DONTUNMAP is always a move and it does not allow resizing
847 if (flags
& MREMAP_DONTUNMAP
&&
848 (!(flags
& MREMAP_MAYMOVE
) || old_len
!= new_len
))
852 if (offset_in_page(addr
))
855 old_len
= PAGE_ALIGN(old_len
);
856 new_len
= PAGE_ALIGN(new_len
);
859 * We allow a zero old-len as a special case
860 * for DOS-emu "duplicate shm area" thing. But
861 * a zero new-len is nonsensical.
866 if (mmap_write_lock_killable(current
->mm
))
869 if (flags
& (MREMAP_FIXED
| MREMAP_DONTUNMAP
)) {
870 ret
= mremap_to(addr
, old_len
, new_addr
, new_len
,
871 &locked
, flags
, &uf
, &uf_unmap_early
,
877 * Always allow a shrinking remap: that just unmaps
878 * the unnecessary pages..
879 * __do_munmap does all the needed commit accounting, and
880 * downgrades mmap_lock to read if so directed.
882 if (old_len
>= new_len
) {
885 retval
= __do_munmap(mm
, addr
+new_len
, old_len
- new_len
,
887 if (retval
< 0 && old_len
!= new_len
) {
890 /* Returning 1 indicates mmap_lock is downgraded to read. */
891 } else if (retval
== 1)
898 * Ok, we need to grow..
900 vma
= vma_to_resize(addr
, old_len
, new_len
, flags
, &charged
);
906 /* old_len exactly to the end of the area..
908 if (old_len
== vma
->vm_end
- addr
) {
909 /* can we just expand the current mapping? */
910 if (vma_expandable(vma
, new_len
- old_len
)) {
911 int pages
= (new_len
- old_len
) >> PAGE_SHIFT
;
913 if (vma_adjust(vma
, vma
->vm_start
, addr
+ new_len
,
914 vma
->vm_pgoff
, NULL
)) {
919 vm_stat_account(mm
, vma
->vm_flags
, pages
);
920 if (vma
->vm_flags
& VM_LOCKED
) {
921 mm
->locked_vm
+= pages
;
931 * We weren't able to just expand or shrink the area,
932 * we need to create a new one and move it..
935 if (flags
& MREMAP_MAYMOVE
) {
936 unsigned long map_flags
= 0;
937 if (vma
->vm_flags
& VM_MAYSHARE
)
938 map_flags
|= MAP_SHARED
;
940 new_addr
= get_unmapped_area(vma
->vm_file
, 0, new_len
,
942 ((addr
- vma
->vm_start
) >> PAGE_SHIFT
),
944 if (IS_ERR_VALUE(new_addr
)) {
949 ret
= move_vma(vma
, addr
, old_len
, new_len
, new_addr
,
950 &locked
, flags
, &uf
, &uf_unmap
);
953 if (offset_in_page(ret
)) {
954 vm_unacct_memory(charged
);
958 mmap_read_unlock(current
->mm
);
960 mmap_write_unlock(current
->mm
);
961 if (locked
&& new_len
> old_len
)
962 mm_populate(new_addr
+ old_len
, new_len
- old_len
);
963 userfaultfd_unmap_complete(mm
, &uf_unmap_early
);
964 mremap_userfaultfd_complete(&uf
, addr
, ret
, old_len
);
965 userfaultfd_unmap_complete(mm
, &uf_unmap
);