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git.proxmox.com Git - mirror_ubuntu-bionic-kernel.git/blob - mm/mremap.c
4 * (C) Copyright 1996 Linus Torvalds
6 * Address space accounting code <alan@lxorguk.ukuu.org.uk>
7 * (C) Copyright 2002 Red Hat Inc, All Rights Reserved
11 #include <linux/hugetlb.h>
12 #include <linux/shm.h>
13 #include <linux/ksm.h>
14 #include <linux/mman.h>
15 #include <linux/swap.h>
16 #include <linux/capability.h>
18 #include <linux/highmem.h>
19 #include <linux/security.h>
20 #include <linux/syscalls.h>
21 #include <linux/mmu_notifier.h>
23 #include <asm/uaccess.h>
24 #include <asm/cacheflush.h>
25 #include <asm/tlbflush.h>
29 static pmd_t
*get_old_pmd(struct mm_struct
*mm
, unsigned long addr
)
35 pgd
= pgd_offset(mm
, addr
);
36 if (pgd_none_or_clear_bad(pgd
))
39 pud
= pud_offset(pgd
, addr
);
40 if (pud_none_or_clear_bad(pud
))
43 pmd
= pmd_offset(pud
, addr
);
50 static pmd_t
*alloc_new_pmd(struct mm_struct
*mm
, struct vm_area_struct
*vma
,
57 pgd
= pgd_offset(mm
, addr
);
58 pud
= pud_alloc(mm
, pgd
, addr
);
62 pmd
= pmd_alloc(mm
, pud
, addr
);
66 VM_BUG_ON(pmd_trans_huge(*pmd
));
71 static void move_ptes(struct vm_area_struct
*vma
, pmd_t
*old_pmd
,
72 unsigned long old_addr
, unsigned long old_end
,
73 struct vm_area_struct
*new_vma
, pmd_t
*new_pmd
,
74 unsigned long new_addr
, bool need_rmap_locks
)
76 struct address_space
*mapping
= NULL
;
77 struct anon_vma
*anon_vma
= NULL
;
78 struct mm_struct
*mm
= vma
->vm_mm
;
79 pte_t
*old_pte
, *new_pte
, pte
;
80 spinlock_t
*old_ptl
, *new_ptl
;
83 * When need_rmap_locks is true, we take the i_mmap_mutex and anon_vma
84 * locks to ensure that rmap will always observe either the old or the
85 * new ptes. This is the easiest way to avoid races with
86 * truncate_pagecache(), page migration, etc...
88 * When need_rmap_locks is false, we use other ways to avoid
91 * - During exec() shift_arg_pages(), we use a specially tagged vma
92 * which rmap call sites look for using is_vma_temporary_stack().
94 * - During mremap(), new_vma is often known to be placed after vma
95 * in rmap traversal order. This ensures rmap will always observe
96 * either the old pte, or the new pte, or both (the page table locks
97 * serialize access to individual ptes, but only rmap traversal
98 * order guarantees that we won't miss both the old and new ptes).
100 if (need_rmap_locks
) {
102 mapping
= vma
->vm_file
->f_mapping
;
103 mutex_lock(&mapping
->i_mmap_mutex
);
106 anon_vma
= vma
->anon_vma
;
107 anon_vma_lock_write(anon_vma
);
112 * We don't have to worry about the ordering of src and dst
113 * pte locks because exclusive mmap_sem prevents deadlock.
115 old_pte
= pte_offset_map_lock(mm
, old_pmd
, old_addr
, &old_ptl
);
116 new_pte
= pte_offset_map(new_pmd
, new_addr
);
117 new_ptl
= pte_lockptr(mm
, new_pmd
);
118 if (new_ptl
!= old_ptl
)
119 spin_lock_nested(new_ptl
, SINGLE_DEPTH_NESTING
);
120 arch_enter_lazy_mmu_mode();
122 for (; old_addr
< old_end
; old_pte
++, old_addr
+= PAGE_SIZE
,
123 new_pte
++, new_addr
+= PAGE_SIZE
) {
124 if (pte_none(*old_pte
))
126 pte
= ptep_get_and_clear(mm
, old_addr
, old_pte
);
127 pte
= move_pte(pte
, new_vma
->vm_page_prot
, old_addr
, new_addr
);
128 set_pte_at(mm
, new_addr
, new_pte
, pte
);
131 arch_leave_lazy_mmu_mode();
132 if (new_ptl
!= old_ptl
)
133 spin_unlock(new_ptl
);
134 pte_unmap(new_pte
- 1);
135 pte_unmap_unlock(old_pte
- 1, old_ptl
);
137 anon_vma_unlock(anon_vma
);
139 mutex_unlock(&mapping
->i_mmap_mutex
);
142 #define LATENCY_LIMIT (64 * PAGE_SIZE)
144 unsigned long move_page_tables(struct vm_area_struct
*vma
,
145 unsigned long old_addr
, struct vm_area_struct
*new_vma
,
146 unsigned long new_addr
, unsigned long len
,
147 bool need_rmap_locks
)
149 unsigned long extent
, next
, old_end
;
150 pmd_t
*old_pmd
, *new_pmd
;
151 bool need_flush
= false;
152 unsigned long mmun_start
; /* For mmu_notifiers */
153 unsigned long mmun_end
; /* For mmu_notifiers */
155 old_end
= old_addr
+ len
;
156 flush_cache_range(vma
, old_addr
, old_end
);
158 mmun_start
= old_addr
;
160 mmu_notifier_invalidate_range_start(vma
->vm_mm
, mmun_start
, mmun_end
);
162 for (; old_addr
< old_end
; old_addr
+= extent
, new_addr
+= extent
) {
164 next
= (old_addr
+ PMD_SIZE
) & PMD_MASK
;
165 /* even if next overflowed, extent below will be ok */
166 extent
= next
- old_addr
;
167 if (extent
> old_end
- old_addr
)
168 extent
= old_end
- old_addr
;
169 old_pmd
= get_old_pmd(vma
->vm_mm
, old_addr
);
172 new_pmd
= alloc_new_pmd(vma
->vm_mm
, vma
, new_addr
);
175 if (pmd_trans_huge(*old_pmd
)) {
177 if (extent
== HPAGE_PMD_SIZE
)
178 err
= move_huge_pmd(vma
, new_vma
, old_addr
,
185 split_huge_page_pmd(vma
, old_addr
, old_pmd
);
187 VM_BUG_ON(pmd_trans_huge(*old_pmd
));
189 if (pmd_none(*new_pmd
) && __pte_alloc(new_vma
->vm_mm
, new_vma
,
192 next
= (new_addr
+ PMD_SIZE
) & PMD_MASK
;
193 if (extent
> next
- new_addr
)
194 extent
= next
- new_addr
;
195 if (extent
> LATENCY_LIMIT
)
196 extent
= LATENCY_LIMIT
;
197 move_ptes(vma
, old_pmd
, old_addr
, old_addr
+ extent
,
198 new_vma
, new_pmd
, new_addr
, need_rmap_locks
);
201 if (likely(need_flush
))
202 flush_tlb_range(vma
, old_end
-len
, old_addr
);
204 mmu_notifier_invalidate_range_end(vma
->vm_mm
, mmun_start
, mmun_end
);
206 return len
+ old_addr
- old_end
; /* how much done */
209 static unsigned long move_vma(struct vm_area_struct
*vma
,
210 unsigned long old_addr
, unsigned long old_len
,
211 unsigned long new_len
, unsigned long new_addr
)
213 struct mm_struct
*mm
= vma
->vm_mm
;
214 struct vm_area_struct
*new_vma
;
215 unsigned long vm_flags
= vma
->vm_flags
;
216 unsigned long new_pgoff
;
217 unsigned long moved_len
;
218 unsigned long excess
= 0;
219 unsigned long hiwater_vm
;
222 bool need_rmap_locks
;
225 * We'd prefer to avoid failure later on in do_munmap:
226 * which may split one vma into three before unmapping.
228 if (mm
->map_count
>= sysctl_max_map_count
- 3)
232 * Advise KSM to break any KSM pages in the area to be moved:
233 * it would be confusing if they were to turn up at the new
234 * location, where they happen to coincide with different KSM
235 * pages recently unmapped. But leave vma->vm_flags as it was,
236 * so KSM can come around to merge on vma and new_vma afterwards.
238 err
= ksm_madvise(vma
, old_addr
, old_addr
+ old_len
,
239 MADV_UNMERGEABLE
, &vm_flags
);
243 new_pgoff
= vma
->vm_pgoff
+ ((old_addr
- vma
->vm_start
) >> PAGE_SHIFT
);
244 new_vma
= copy_vma(&vma
, new_addr
, new_len
, new_pgoff
,
249 moved_len
= move_page_tables(vma
, old_addr
, new_vma
, new_addr
, old_len
,
251 if (moved_len
< old_len
) {
253 * On error, move entries back from new area to old,
254 * which will succeed since page tables still there,
255 * and then proceed to unmap new area instead of old.
257 move_page_tables(new_vma
, new_addr
, vma
, old_addr
, moved_len
,
265 /* Conceal VM_ACCOUNT so old reservation is not undone */
266 if (vm_flags
& VM_ACCOUNT
) {
267 vma
->vm_flags
&= ~VM_ACCOUNT
;
268 excess
= vma
->vm_end
- vma
->vm_start
- old_len
;
269 if (old_addr
> vma
->vm_start
&&
270 old_addr
+ old_len
< vma
->vm_end
)
275 * If we failed to move page tables we still do total_vm increment
276 * since do_munmap() will decrement it by old_len == new_len.
278 * Since total_vm is about to be raised artificially high for a
279 * moment, we need to restore high watermark afterwards: if stats
280 * are taken meanwhile, total_vm and hiwater_vm appear too high.
281 * If this were a serious issue, we'd add a flag to do_munmap().
283 hiwater_vm
= mm
->hiwater_vm
;
284 vm_stat_account(mm
, vma
->vm_flags
, vma
->vm_file
, new_len
>>PAGE_SHIFT
);
286 if (do_munmap(mm
, old_addr
, old_len
) < 0) {
287 /* OOM: unable to split vma, just get accounts right */
288 vm_unacct_memory(excess
>> PAGE_SHIFT
);
291 mm
->hiwater_vm
= hiwater_vm
;
293 /* Restore VM_ACCOUNT if one or two pieces of vma left */
295 vma
->vm_flags
|= VM_ACCOUNT
;
297 vma
->vm_next
->vm_flags
|= VM_ACCOUNT
;
300 if (vm_flags
& VM_LOCKED
) {
301 mm
->locked_vm
+= new_len
>> PAGE_SHIFT
;
302 if (new_len
> old_len
)
303 mlock_vma_pages_range(new_vma
, new_addr
+ old_len
,
310 static struct vm_area_struct
*vma_to_resize(unsigned long addr
,
311 unsigned long old_len
, unsigned long new_len
, unsigned long *p
)
313 struct mm_struct
*mm
= current
->mm
;
314 struct vm_area_struct
*vma
= find_vma(mm
, addr
);
316 if (!vma
|| vma
->vm_start
> addr
)
319 if (is_vm_hugetlb_page(vma
))
322 /* We can't remap across vm area boundaries */
323 if (old_len
> vma
->vm_end
- addr
)
326 /* Need to be careful about a growing mapping */
327 if (new_len
> old_len
) {
330 if (vma
->vm_flags
& (VM_DONTEXPAND
| VM_PFNMAP
))
332 pgoff
= (addr
- vma
->vm_start
) >> PAGE_SHIFT
;
333 pgoff
+= vma
->vm_pgoff
;
334 if (pgoff
+ (new_len
>> PAGE_SHIFT
) < pgoff
)
338 if (vma
->vm_flags
& VM_LOCKED
) {
339 unsigned long locked
, lock_limit
;
340 locked
= mm
->locked_vm
<< PAGE_SHIFT
;
341 lock_limit
= rlimit(RLIMIT_MEMLOCK
);
342 locked
+= new_len
- old_len
;
343 if (locked
> lock_limit
&& !capable(CAP_IPC_LOCK
))
347 if (!may_expand_vm(mm
, (new_len
- old_len
) >> PAGE_SHIFT
))
350 if (vma
->vm_flags
& VM_ACCOUNT
) {
351 unsigned long charged
= (new_len
- old_len
) >> PAGE_SHIFT
;
352 if (security_vm_enough_memory_mm(mm
, charged
))
359 Efault
: /* very odd choice for most of the cases, but... */
360 return ERR_PTR(-EFAULT
);
362 return ERR_PTR(-EINVAL
);
364 return ERR_PTR(-ENOMEM
);
366 return ERR_PTR(-EAGAIN
);
369 static unsigned long mremap_to(unsigned long addr
,
370 unsigned long old_len
, unsigned long new_addr
,
371 unsigned long new_len
)
373 struct mm_struct
*mm
= current
->mm
;
374 struct vm_area_struct
*vma
;
375 unsigned long ret
= -EINVAL
;
376 unsigned long charged
= 0;
377 unsigned long map_flags
;
379 if (new_addr
& ~PAGE_MASK
)
382 if (new_len
> TASK_SIZE
|| new_addr
> TASK_SIZE
- new_len
)
385 /* Check if the location we're moving into overlaps the
386 * old location at all, and fail if it does.
388 if ((new_addr
<= addr
) && (new_addr
+new_len
) > addr
)
391 if ((addr
<= new_addr
) && (addr
+old_len
) > new_addr
)
394 ret
= do_munmap(mm
, new_addr
, new_len
);
398 if (old_len
>= new_len
) {
399 ret
= do_munmap(mm
, addr
+new_len
, old_len
- new_len
);
400 if (ret
&& old_len
!= new_len
)
405 vma
= vma_to_resize(addr
, old_len
, new_len
, &charged
);
411 map_flags
= MAP_FIXED
;
412 if (vma
->vm_flags
& VM_MAYSHARE
)
413 map_flags
|= MAP_SHARED
;
415 ret
= get_unmapped_area(vma
->vm_file
, new_addr
, new_len
, vma
->vm_pgoff
+
416 ((addr
- vma
->vm_start
) >> PAGE_SHIFT
),
418 if (ret
& ~PAGE_MASK
)
421 ret
= move_vma(vma
, addr
, old_len
, new_len
, new_addr
);
422 if (!(ret
& ~PAGE_MASK
))
425 vm_unacct_memory(charged
);
431 static int vma_expandable(struct vm_area_struct
*vma
, unsigned long delta
)
433 unsigned long end
= vma
->vm_end
+ delta
;
434 if (end
< vma
->vm_end
) /* overflow */
436 if (vma
->vm_next
&& vma
->vm_next
->vm_start
< end
) /* intersection */
438 if (get_unmapped_area(NULL
, vma
->vm_start
, end
- vma
->vm_start
,
439 0, MAP_FIXED
) & ~PAGE_MASK
)
445 * Expand (or shrink) an existing mapping, potentially moving it at the
446 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
448 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
449 * This option implies MREMAP_MAYMOVE.
451 SYSCALL_DEFINE5(mremap
, unsigned long, addr
, unsigned long, old_len
,
452 unsigned long, new_len
, unsigned long, flags
,
453 unsigned long, new_addr
)
455 struct mm_struct
*mm
= current
->mm
;
456 struct vm_area_struct
*vma
;
457 unsigned long ret
= -EINVAL
;
458 unsigned long charged
= 0;
460 down_write(¤t
->mm
->mmap_sem
);
462 if (flags
& ~(MREMAP_FIXED
| MREMAP_MAYMOVE
))
465 if (addr
& ~PAGE_MASK
)
468 old_len
= PAGE_ALIGN(old_len
);
469 new_len
= PAGE_ALIGN(new_len
);
472 * We allow a zero old-len as a special case
473 * for DOS-emu "duplicate shm area" thing. But
474 * a zero new-len is nonsensical.
479 if (flags
& MREMAP_FIXED
) {
480 if (flags
& MREMAP_MAYMOVE
)
481 ret
= mremap_to(addr
, old_len
, new_addr
, new_len
);
486 * Always allow a shrinking remap: that just unmaps
487 * the unnecessary pages..
488 * do_munmap does all the needed commit accounting
490 if (old_len
>= new_len
) {
491 ret
= do_munmap(mm
, addr
+new_len
, old_len
- new_len
);
492 if (ret
&& old_len
!= new_len
)
499 * Ok, we need to grow..
501 vma
= vma_to_resize(addr
, old_len
, new_len
, &charged
);
507 /* old_len exactly to the end of the area..
509 if (old_len
== vma
->vm_end
- addr
) {
510 /* can we just expand the current mapping? */
511 if (vma_expandable(vma
, new_len
- old_len
)) {
512 int pages
= (new_len
- old_len
) >> PAGE_SHIFT
;
514 if (vma_adjust(vma
, vma
->vm_start
, addr
+ new_len
,
515 vma
->vm_pgoff
, NULL
)) {
520 vm_stat_account(mm
, vma
->vm_flags
, vma
->vm_file
, pages
);
521 if (vma
->vm_flags
& VM_LOCKED
) {
522 mm
->locked_vm
+= pages
;
523 mlock_vma_pages_range(vma
, addr
+ old_len
,
532 * We weren't able to just expand or shrink the area,
533 * we need to create a new one and move it..
536 if (flags
& MREMAP_MAYMOVE
) {
537 unsigned long map_flags
= 0;
538 if (vma
->vm_flags
& VM_MAYSHARE
)
539 map_flags
|= MAP_SHARED
;
541 new_addr
= get_unmapped_area(vma
->vm_file
, 0, new_len
,
543 ((addr
- vma
->vm_start
) >> PAGE_SHIFT
),
545 if (new_addr
& ~PAGE_MASK
) {
550 ret
= move_vma(vma
, addr
, old_len
, new_len
, new_addr
);
553 if (ret
& ~PAGE_MASK
)
554 vm_unacct_memory(charged
);
555 up_write(¤t
->mm
->mmap_sem
);