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1/*
2 * mm/mremap.c
3 *
4 * (C) Copyright 1996 Linus Torvalds
5 *
6 * Address space accounting code <alan@lxorguk.ukuu.org.uk>
7 * (C) Copyright 2002 Red Hat Inc, All Rights Reserved
8 */
9
10#include <linux/mm.h>
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>
17#include <linux/fs.h>
18#include <linux/swapops.h>
19#include <linux/highmem.h>
20#include <linux/security.h>
21#include <linux/syscalls.h>
22#include <linux/mmu_notifier.h>
23#include <linux/sched/sysctl.h>
24
25#include <asm/uaccess.h>
26#include <asm/cacheflush.h>
27#include <asm/tlbflush.h>
28
29#include "internal.h"
30
31static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
32{
33 pgd_t *pgd;
34 pud_t *pud;
35 pmd_t *pmd;
36
37 pgd = pgd_offset(mm, addr);
38 if (pgd_none_or_clear_bad(pgd))
39 return NULL;
40
41 pud = pud_offset(pgd, addr);
42 if (pud_none_or_clear_bad(pud))
43 return NULL;
44
45 pmd = pmd_offset(pud, addr);
46 if (pmd_none(*pmd))
47 return NULL;
48
49 return pmd;
50}
51
52static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
53 unsigned long addr)
54{
55 pgd_t *pgd;
56 pud_t *pud;
57 pmd_t *pmd;
58
59 pgd = pgd_offset(mm, addr);
60 pud = pud_alloc(mm, pgd, addr);
61 if (!pud)
62 return NULL;
63
64 pmd = pmd_alloc(mm, pud, addr);
65 if (!pmd)
66 return NULL;
67
68 VM_BUG_ON(pmd_trans_huge(*pmd));
69
70 return pmd;
71}
72
73static pte_t move_soft_dirty_pte(pte_t pte)
74{
75 /*
76 * Set soft dirty bit so we can notice
77 * in userspace the ptes were moved.
78 */
79#ifdef CONFIG_MEM_SOFT_DIRTY
80 if (pte_present(pte))
81 pte = pte_mksoft_dirty(pte);
82 else if (is_swap_pte(pte))
83 pte = pte_swp_mksoft_dirty(pte);
84 else if (pte_file(pte))
85 pte = pte_file_mksoft_dirty(pte);
86#endif
87 return pte;
88}
89
90static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
91 unsigned long old_addr, unsigned long old_end,
92 struct vm_area_struct *new_vma, pmd_t *new_pmd,
93 unsigned long new_addr, bool need_rmap_locks)
94{
95 struct address_space *mapping = NULL;
96 struct anon_vma *anon_vma = NULL;
97 struct mm_struct *mm = vma->vm_mm;
98 pte_t *old_pte, *new_pte, pte;
99 spinlock_t *old_ptl, *new_ptl;
100
101 /*
102 * When need_rmap_locks is true, we take the i_mmap_mutex and anon_vma
103 * locks to ensure that rmap will always observe either the old or the
104 * new ptes. This is the easiest way to avoid races with
105 * truncate_pagecache(), page migration, etc...
106 *
107 * When need_rmap_locks is false, we use other ways to avoid
108 * such races:
109 *
110 * - During exec() shift_arg_pages(), we use a specially tagged vma
111 * which rmap call sites look for using is_vma_temporary_stack().
112 *
113 * - During mremap(), new_vma is often known to be placed after vma
114 * in rmap traversal order. This ensures rmap will always observe
115 * either the old pte, or the new pte, or both (the page table locks
116 * serialize access to individual ptes, but only rmap traversal
117 * order guarantees that we won't miss both the old and new ptes).
118 */
119 if (need_rmap_locks) {
120 if (vma->vm_file) {
121 mapping = vma->vm_file->f_mapping;
122 mutex_lock(&mapping->i_mmap_mutex);
123 }
124 if (vma->anon_vma) {
125 anon_vma = vma->anon_vma;
126 anon_vma_lock_write(anon_vma);
127 }
128 }
129
130 /*
131 * We don't have to worry about the ordering of src and dst
132 * pte locks because exclusive mmap_sem prevents deadlock.
133 */
134 old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
135 new_pte = pte_offset_map(new_pmd, new_addr);
136 new_ptl = pte_lockptr(mm, new_pmd);
137 if (new_ptl != old_ptl)
138 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
139 arch_enter_lazy_mmu_mode();
140
141 for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
142 new_pte++, new_addr += PAGE_SIZE) {
143 if (pte_none(*old_pte))
144 continue;
145 pte = ptep_get_and_clear(mm, old_addr, old_pte);
146 pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
147 pte = move_soft_dirty_pte(pte);
148 set_pte_at(mm, new_addr, new_pte, pte);
149 }
150
151 arch_leave_lazy_mmu_mode();
152 if (new_ptl != old_ptl)
153 spin_unlock(new_ptl);
154 pte_unmap(new_pte - 1);
155 pte_unmap_unlock(old_pte - 1, old_ptl);
156 if (anon_vma)
157 anon_vma_unlock_write(anon_vma);
158 if (mapping)
159 mutex_unlock(&mapping->i_mmap_mutex);
160}
161
162#define LATENCY_LIMIT (64 * PAGE_SIZE)
163
164unsigned long move_page_tables(struct vm_area_struct *vma,
165 unsigned long old_addr, struct vm_area_struct *new_vma,
166 unsigned long new_addr, unsigned long len,
167 bool need_rmap_locks)
168{
169 unsigned long extent, next, old_end;
170 pmd_t *old_pmd, *new_pmd;
171 bool need_flush = false;
172 unsigned long mmun_start; /* For mmu_notifiers */
173 unsigned long mmun_end; /* For mmu_notifiers */
174
175 old_end = old_addr + len;
176 flush_cache_range(vma, old_addr, old_end);
177
178 mmun_start = old_addr;
179 mmun_end = old_end;
180 mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
181
182 for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
183 cond_resched();
184 next = (old_addr + PMD_SIZE) & PMD_MASK;
185 /* even if next overflowed, extent below will be ok */
186 extent = next - old_addr;
187 if (extent > old_end - old_addr)
188 extent = old_end - old_addr;
189 old_pmd = get_old_pmd(vma->vm_mm, old_addr);
190 if (!old_pmd)
191 continue;
192 new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr);
193 if (!new_pmd)
194 break;
195 if (pmd_trans_huge(*old_pmd)) {
196 int err = 0;
197 if (extent == HPAGE_PMD_SIZE) {
198 VM_BUG_ON(vma->vm_file || !vma->anon_vma);
199 /* See comment in move_ptes() */
200 if (need_rmap_locks)
201 anon_vma_lock_write(vma->anon_vma);
202 err = move_huge_pmd(vma, new_vma, old_addr,
203 new_addr, old_end,
204 old_pmd, new_pmd);
205 if (need_rmap_locks)
206 anon_vma_unlock_write(vma->anon_vma);
207 }
208 if (err > 0) {
209 need_flush = true;
210 continue;
211 } else if (!err) {
212 split_huge_page_pmd(vma, old_addr, old_pmd);
213 }
214 VM_BUG_ON(pmd_trans_huge(*old_pmd));
215 }
216 if (pmd_none(*new_pmd) && __pte_alloc(new_vma->vm_mm, new_vma,
217 new_pmd, new_addr))
218 break;
219 next = (new_addr + PMD_SIZE) & PMD_MASK;
220 if (extent > next - new_addr)
221 extent = next - new_addr;
222 if (extent > LATENCY_LIMIT)
223 extent = LATENCY_LIMIT;
224 move_ptes(vma, old_pmd, old_addr, old_addr + extent,
225 new_vma, new_pmd, new_addr, need_rmap_locks);
226 need_flush = true;
227 }
228 if (likely(need_flush))
229 flush_tlb_range(vma, old_end-len, old_addr);
230
231 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
232
233 return len + old_addr - old_end; /* how much done */
234}
235
236static unsigned long move_vma(struct vm_area_struct *vma,
237 unsigned long old_addr, unsigned long old_len,
238 unsigned long new_len, unsigned long new_addr, bool *locked)
239{
240 struct mm_struct *mm = vma->vm_mm;
241 struct vm_area_struct *new_vma;
242 unsigned long vm_flags = vma->vm_flags;
243 unsigned long new_pgoff;
244 unsigned long moved_len;
245 unsigned long excess = 0;
246 unsigned long hiwater_vm;
247 int split = 0;
248 int err;
249 bool need_rmap_locks;
250
251 /*
252 * We'd prefer to avoid failure later on in do_munmap:
253 * which may split one vma into three before unmapping.
254 */
255 if (mm->map_count >= sysctl_max_map_count - 3)
256 return -ENOMEM;
257
258 /*
259 * Advise KSM to break any KSM pages in the area to be moved:
260 * it would be confusing if they were to turn up at the new
261 * location, where they happen to coincide with different KSM
262 * pages recently unmapped. But leave vma->vm_flags as it was,
263 * so KSM can come around to merge on vma and new_vma afterwards.
264 */
265 err = ksm_madvise(vma, old_addr, old_addr + old_len,
266 MADV_UNMERGEABLE, &vm_flags);
267 if (err)
268 return err;
269
270 new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
271 new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff,
272 &need_rmap_locks);
273 if (!new_vma)
274 return -ENOMEM;
275
276 moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len,
277 need_rmap_locks);
278 if (moved_len < old_len) {
279 /*
280 * On error, move entries back from new area to old,
281 * which will succeed since page tables still there,
282 * and then proceed to unmap new area instead of old.
283 */
284 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len,
285 true);
286 vma = new_vma;
287 old_len = new_len;
288 old_addr = new_addr;
289 new_addr = -ENOMEM;
290 }
291
292 /* Conceal VM_ACCOUNT so old reservation is not undone */
293 if (vm_flags & VM_ACCOUNT) {
294 vma->vm_flags &= ~VM_ACCOUNT;
295 excess = vma->vm_end - vma->vm_start - old_len;
296 if (old_addr > vma->vm_start &&
297 old_addr + old_len < vma->vm_end)
298 split = 1;
299 }
300
301 /*
302 * If we failed to move page tables we still do total_vm increment
303 * since do_munmap() will decrement it by old_len == new_len.
304 *
305 * Since total_vm is about to be raised artificially high for a
306 * moment, we need to restore high watermark afterwards: if stats
307 * are taken meanwhile, total_vm and hiwater_vm appear too high.
308 * If this were a serious issue, we'd add a flag to do_munmap().
309 */
310 hiwater_vm = mm->hiwater_vm;
311 vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
312
313 if (do_munmap(mm, old_addr, old_len) < 0) {
314 /* OOM: unable to split vma, just get accounts right */
315 vm_unacct_memory(excess >> PAGE_SHIFT);
316 excess = 0;
317 }
318 mm->hiwater_vm = hiwater_vm;
319
320 /* Restore VM_ACCOUNT if one or two pieces of vma left */
321 if (excess) {
322 vma->vm_flags |= VM_ACCOUNT;
323 if (split)
324 vma->vm_next->vm_flags |= VM_ACCOUNT;
325 }
326
327 if (vm_flags & VM_LOCKED) {
328 mm->locked_vm += new_len >> PAGE_SHIFT;
329 *locked = true;
330 }
331
332 return new_addr;
333}
334
335static struct vm_area_struct *vma_to_resize(unsigned long addr,
336 unsigned long old_len, unsigned long new_len, unsigned long *p)
337{
338 struct mm_struct *mm = current->mm;
339 struct vm_area_struct *vma = find_vma(mm, addr);
340
341 if (!vma || vma->vm_start > addr)
342 goto Efault;
343
344 if (is_vm_hugetlb_page(vma))
345 goto Einval;
346
347 /* We can't remap across vm area boundaries */
348 if (old_len > vma->vm_end - addr)
349 goto Efault;
350
351 /* Need to be careful about a growing mapping */
352 if (new_len > old_len) {
353 unsigned long pgoff;
354
355 if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
356 goto Efault;
357 pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
358 pgoff += vma->vm_pgoff;
359 if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
360 goto Einval;
361 }
362
363 if (vma->vm_flags & VM_LOCKED) {
364 unsigned long locked, lock_limit;
365 locked = mm->locked_vm << PAGE_SHIFT;
366 lock_limit = rlimit(RLIMIT_MEMLOCK);
367 locked += new_len - old_len;
368 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
369 goto Eagain;
370 }
371
372 if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT))
373 goto Enomem;
374
375 if (vma->vm_flags & VM_ACCOUNT) {
376 unsigned long charged = (new_len - old_len) >> PAGE_SHIFT;
377 if (security_vm_enough_memory_mm(mm, charged))
378 goto Efault;
379 *p = charged;
380 }
381
382 return vma;
383
384Efault: /* very odd choice for most of the cases, but... */
385 return ERR_PTR(-EFAULT);
386Einval:
387 return ERR_PTR(-EINVAL);
388Enomem:
389 return ERR_PTR(-ENOMEM);
390Eagain:
391 return ERR_PTR(-EAGAIN);
392}
393
394static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
395 unsigned long new_addr, unsigned long new_len, bool *locked)
396{
397 struct mm_struct *mm = current->mm;
398 struct vm_area_struct *vma;
399 unsigned long ret = -EINVAL;
400 unsigned long charged = 0;
401 unsigned long map_flags;
402
403 if (new_addr & ~PAGE_MASK)
404 goto out;
405
406 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
407 goto out;
408
409 /* Check if the location we're moving into overlaps the
410 * old location at all, and fail if it does.
411 */
412 if ((new_addr <= addr) && (new_addr+new_len) > addr)
413 goto out;
414
415 if ((addr <= new_addr) && (addr+old_len) > new_addr)
416 goto out;
417
418 ret = do_munmap(mm, new_addr, new_len);
419 if (ret)
420 goto out;
421
422 if (old_len >= new_len) {
423 ret = do_munmap(mm, addr+new_len, old_len - new_len);
424 if (ret && old_len != new_len)
425 goto out;
426 old_len = new_len;
427 }
428
429 vma = vma_to_resize(addr, old_len, new_len, &charged);
430 if (IS_ERR(vma)) {
431 ret = PTR_ERR(vma);
432 goto out;
433 }
434
435 map_flags = MAP_FIXED;
436 if (vma->vm_flags & VM_MAYSHARE)
437 map_flags |= MAP_SHARED;
438
439 ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
440 ((addr - vma->vm_start) >> PAGE_SHIFT),
441 map_flags);
442 if (ret & ~PAGE_MASK)
443 goto out1;
444
445 ret = move_vma(vma, addr, old_len, new_len, new_addr, locked);
446 if (!(ret & ~PAGE_MASK))
447 goto out;
448out1:
449 vm_unacct_memory(charged);
450
451out:
452 return ret;
453}
454
455static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
456{
457 unsigned long end = vma->vm_end + delta;
458 if (end < vma->vm_end) /* overflow */
459 return 0;
460 if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */
461 return 0;
462 if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
463 0, MAP_FIXED) & ~PAGE_MASK)
464 return 0;
465 return 1;
466}
467
468/*
469 * Expand (or shrink) an existing mapping, potentially moving it at the
470 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
471 *
472 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
473 * This option implies MREMAP_MAYMOVE.
474 */
475SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
476 unsigned long, new_len, unsigned long, flags,
477 unsigned long, new_addr)
478{
479 struct mm_struct *mm = current->mm;
480 struct vm_area_struct *vma;
481 unsigned long ret = -EINVAL;
482 unsigned long charged = 0;
483 bool locked = false;
484
485 if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
486 return ret;
487
488 if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE))
489 return ret;
490
491 if (addr & ~PAGE_MASK)
492 return ret;
493
494 old_len = PAGE_ALIGN(old_len);
495 new_len = PAGE_ALIGN(new_len);
496
497 /*
498 * We allow a zero old-len as a special case
499 * for DOS-emu "duplicate shm area" thing. But
500 * a zero new-len is nonsensical.
501 */
502 if (!new_len)
503 return ret;
504
505 down_write(¤t->mm->mmap_sem);
506
507 if (flags & MREMAP_FIXED) {
508 ret = mremap_to(addr, old_len, new_addr, new_len,
509 &locked);
510 goto out;
511 }
512
513 /*
514 * Always allow a shrinking remap: that just unmaps
515 * the unnecessary pages..
516 * do_munmap does all the needed commit accounting
517 */
518 if (old_len >= new_len) {
519 ret = do_munmap(mm, addr+new_len, old_len - new_len);
520 if (ret && old_len != new_len)
521 goto out;
522 ret = addr;
523 goto out;
524 }
525
526 /*
527 * Ok, we need to grow..
528 */
529 vma = vma_to_resize(addr, old_len, new_len, &charged);
530 if (IS_ERR(vma)) {
531 ret = PTR_ERR(vma);
532 goto out;
533 }
534
535 /* old_len exactly to the end of the area..
536 */
537 if (old_len == vma->vm_end - addr) {
538 /* can we just expand the current mapping? */
539 if (vma_expandable(vma, new_len - old_len)) {
540 int pages = (new_len - old_len) >> PAGE_SHIFT;
541
542 if (vma_adjust(vma, vma->vm_start, addr + new_len,
543 vma->vm_pgoff, NULL)) {
544 ret = -ENOMEM;
545 goto out;
546 }
547
548 vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
549 if (vma->vm_flags & VM_LOCKED) {
550 mm->locked_vm += pages;
551 locked = true;
552 new_addr = addr;
553 }
554 ret = addr;
555 goto out;
556 }
557 }
558
559 /*
560 * We weren't able to just expand or shrink the area,
561 * we need to create a new one and move it..
562 */
563 ret = -ENOMEM;
564 if (flags & MREMAP_MAYMOVE) {
565 unsigned long map_flags = 0;
566 if (vma->vm_flags & VM_MAYSHARE)
567 map_flags |= MAP_SHARED;
568
569 new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
570 vma->vm_pgoff +
571 ((addr - vma->vm_start) >> PAGE_SHIFT),
572 map_flags);
573 if (new_addr & ~PAGE_MASK) {
574 ret = new_addr;
575 goto out;
576 }
577
578 ret = move_vma(vma, addr, old_len, new_len, new_addr, &locked);
579 }
580out:
581 if (ret & ~PAGE_MASK)
582 vm_unacct_memory(charged);
583 up_write(¤t->mm->mmap_sem);
584 if (locked && new_len > old_len)
585 mm_populate(new_addr + old_len, new_len - old_len);
586 return ret;
587}
1/*
2 * mm/mremap.c
3 *
4 * (C) Copyright 1996 Linus Torvalds
5 *
6 * Address space accounting code <alan@lxorguk.ukuu.org.uk>
7 * (C) Copyright 2002 Red Hat Inc, All Rights Reserved
8 */
9
10#include <linux/mm.h>
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>
17#include <linux/fs.h>
18#include <linux/swapops.h>
19#include <linux/highmem.h>
20#include <linux/security.h>
21#include <linux/syscalls.h>
22#include <linux/mmu_notifier.h>
23#include <linux/uaccess.h>
24#include <linux/mm-arch-hooks.h>
25
26#include <asm/cacheflush.h>
27#include <asm/tlbflush.h>
28
29#include "internal.h"
30
31static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
32{
33 pgd_t *pgd;
34 pud_t *pud;
35 pmd_t *pmd;
36
37 pgd = pgd_offset(mm, addr);
38 if (pgd_none_or_clear_bad(pgd))
39 return NULL;
40
41 pud = pud_offset(pgd, addr);
42 if (pud_none_or_clear_bad(pud))
43 return NULL;
44
45 pmd = pmd_offset(pud, addr);
46 if (pmd_none(*pmd))
47 return NULL;
48
49 return pmd;
50}
51
52static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
53 unsigned long addr)
54{
55 pgd_t *pgd;
56 pud_t *pud;
57 pmd_t *pmd;
58
59 pgd = pgd_offset(mm, addr);
60 pud = pud_alloc(mm, pgd, addr);
61 if (!pud)
62 return NULL;
63
64 pmd = pmd_alloc(mm, pud, addr);
65 if (!pmd)
66 return NULL;
67
68 VM_BUG_ON(pmd_trans_huge(*pmd));
69
70 return pmd;
71}
72
73static pte_t move_soft_dirty_pte(pte_t pte)
74{
75 /*
76 * Set soft dirty bit so we can notice
77 * in userspace the ptes were moved.
78 */
79#ifdef CONFIG_MEM_SOFT_DIRTY
80 if (pte_present(pte))
81 pte = pte_mksoft_dirty(pte);
82 else if (is_swap_pte(pte))
83 pte = pte_swp_mksoft_dirty(pte);
84#endif
85 return pte;
86}
87
88static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
89 unsigned long old_addr, unsigned long old_end,
90 struct vm_area_struct *new_vma, pmd_t *new_pmd,
91 unsigned long new_addr, bool need_rmap_locks)
92{
93 struct address_space *mapping = NULL;
94 struct anon_vma *anon_vma = NULL;
95 struct mm_struct *mm = vma->vm_mm;
96 pte_t *old_pte, *new_pte, pte;
97 spinlock_t *old_ptl, *new_ptl;
98
99 /*
100 * When need_rmap_locks is true, we take the i_mmap_rwsem and anon_vma
101 * locks to ensure that rmap will always observe either the old or the
102 * new ptes. This is the easiest way to avoid races with
103 * truncate_pagecache(), page migration, etc...
104 *
105 * When need_rmap_locks is false, we use other ways to avoid
106 * such races:
107 *
108 * - During exec() shift_arg_pages(), we use a specially tagged vma
109 * which rmap call sites look for using is_vma_temporary_stack().
110 *
111 * - During mremap(), new_vma is often known to be placed after vma
112 * in rmap traversal order. This ensures rmap will always observe
113 * either the old pte, or the new pte, or both (the page table locks
114 * serialize access to individual ptes, but only rmap traversal
115 * order guarantees that we won't miss both the old and new ptes).
116 */
117 if (need_rmap_locks) {
118 if (vma->vm_file) {
119 mapping = vma->vm_file->f_mapping;
120 i_mmap_lock_write(mapping);
121 }
122 if (vma->anon_vma) {
123 anon_vma = vma->anon_vma;
124 anon_vma_lock_write(anon_vma);
125 }
126 }
127
128 /*
129 * We don't have to worry about the ordering of src and dst
130 * pte locks because exclusive mmap_sem prevents deadlock.
131 */
132 old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
133 new_pte = pte_offset_map(new_pmd, new_addr);
134 new_ptl = pte_lockptr(mm, new_pmd);
135 if (new_ptl != old_ptl)
136 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
137 arch_enter_lazy_mmu_mode();
138
139 for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
140 new_pte++, new_addr += PAGE_SIZE) {
141 if (pte_none(*old_pte))
142 continue;
143 pte = ptep_get_and_clear(mm, old_addr, old_pte);
144 pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
145 pte = move_soft_dirty_pte(pte);
146 set_pte_at(mm, new_addr, new_pte, pte);
147 }
148
149 arch_leave_lazy_mmu_mode();
150 if (new_ptl != old_ptl)
151 spin_unlock(new_ptl);
152 pte_unmap(new_pte - 1);
153 pte_unmap_unlock(old_pte - 1, old_ptl);
154 if (anon_vma)
155 anon_vma_unlock_write(anon_vma);
156 if (mapping)
157 i_mmap_unlock_write(mapping);
158}
159
160#define LATENCY_LIMIT (64 * PAGE_SIZE)
161
162unsigned long move_page_tables(struct vm_area_struct *vma,
163 unsigned long old_addr, struct vm_area_struct *new_vma,
164 unsigned long new_addr, unsigned long len,
165 bool need_rmap_locks)
166{
167 unsigned long extent, next, old_end;
168 pmd_t *old_pmd, *new_pmd;
169 bool need_flush = false;
170 unsigned long mmun_start; /* For mmu_notifiers */
171 unsigned long mmun_end; /* For mmu_notifiers */
172
173 old_end = old_addr + len;
174 flush_cache_range(vma, old_addr, old_end);
175
176 mmun_start = old_addr;
177 mmun_end = old_end;
178 mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
179
180 for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
181 cond_resched();
182 next = (old_addr + PMD_SIZE) & PMD_MASK;
183 /* even if next overflowed, extent below will be ok */
184 extent = next - old_addr;
185 if (extent > old_end - old_addr)
186 extent = old_end - old_addr;
187 old_pmd = get_old_pmd(vma->vm_mm, old_addr);
188 if (!old_pmd)
189 continue;
190 new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr);
191 if (!new_pmd)
192 break;
193 if (pmd_trans_huge(*old_pmd)) {
194 if (extent == HPAGE_PMD_SIZE) {
195 bool moved;
196 VM_BUG_ON_VMA(vma->vm_file || !vma->anon_vma,
197 vma);
198 /* See comment in move_ptes() */
199 if (need_rmap_locks)
200 anon_vma_lock_write(vma->anon_vma);
201 moved = move_huge_pmd(vma, new_vma, old_addr,
202 new_addr, old_end,
203 old_pmd, new_pmd);
204 if (need_rmap_locks)
205 anon_vma_unlock_write(vma->anon_vma);
206 if (moved) {
207 need_flush = true;
208 continue;
209 }
210 }
211 split_huge_pmd(vma, old_pmd, old_addr);
212 if (pmd_none(*old_pmd))
213 continue;
214 VM_BUG_ON(pmd_trans_huge(*old_pmd));
215 }
216 if (pte_alloc(new_vma->vm_mm, new_pmd, new_addr))
217 break;
218 next = (new_addr + PMD_SIZE) & PMD_MASK;
219 if (extent > next - new_addr)
220 extent = next - new_addr;
221 if (extent > LATENCY_LIMIT)
222 extent = LATENCY_LIMIT;
223 move_ptes(vma, old_pmd, old_addr, old_addr + extent,
224 new_vma, new_pmd, new_addr, need_rmap_locks);
225 need_flush = true;
226 }
227 if (likely(need_flush))
228 flush_tlb_range(vma, old_end-len, old_addr);
229
230 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
231
232 return len + old_addr - old_end; /* how much done */
233}
234
235static unsigned long move_vma(struct vm_area_struct *vma,
236 unsigned long old_addr, unsigned long old_len,
237 unsigned long new_len, unsigned long new_addr, bool *locked)
238{
239 struct mm_struct *mm = vma->vm_mm;
240 struct vm_area_struct *new_vma;
241 unsigned long vm_flags = vma->vm_flags;
242 unsigned long new_pgoff;
243 unsigned long moved_len;
244 unsigned long excess = 0;
245 unsigned long hiwater_vm;
246 int split = 0;
247 int err;
248 bool need_rmap_locks;
249
250 /*
251 * We'd prefer to avoid failure later on in do_munmap:
252 * which may split one vma into three before unmapping.
253 */
254 if (mm->map_count >= sysctl_max_map_count - 3)
255 return -ENOMEM;
256
257 /*
258 * Advise KSM to break any KSM pages in the area to be moved:
259 * it would be confusing if they were to turn up at the new
260 * location, where they happen to coincide with different KSM
261 * pages recently unmapped. But leave vma->vm_flags as it was,
262 * so KSM can come around to merge on vma and new_vma afterwards.
263 */
264 err = ksm_madvise(vma, old_addr, old_addr + old_len,
265 MADV_UNMERGEABLE, &vm_flags);
266 if (err)
267 return err;
268
269 new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
270 new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff,
271 &need_rmap_locks);
272 if (!new_vma)
273 return -ENOMEM;
274
275 moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len,
276 need_rmap_locks);
277 if (moved_len < old_len) {
278 err = -ENOMEM;
279 } else if (vma->vm_ops && vma->vm_ops->mremap) {
280 err = vma->vm_ops->mremap(new_vma);
281 }
282
283 if (unlikely(err)) {
284 /*
285 * On error, move entries back from new area to old,
286 * which will succeed since page tables still there,
287 * and then proceed to unmap new area instead of old.
288 */
289 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len,
290 true);
291 vma = new_vma;
292 old_len = new_len;
293 old_addr = new_addr;
294 new_addr = err;
295 } else {
296 arch_remap(mm, old_addr, old_addr + old_len,
297 new_addr, new_addr + new_len);
298 }
299
300 /* Conceal VM_ACCOUNT so old reservation is not undone */
301 if (vm_flags & VM_ACCOUNT) {
302 vma->vm_flags &= ~VM_ACCOUNT;
303 excess = vma->vm_end - vma->vm_start - old_len;
304 if (old_addr > vma->vm_start &&
305 old_addr + old_len < vma->vm_end)
306 split = 1;
307 }
308
309 /*
310 * If we failed to move page tables we still do total_vm increment
311 * since do_munmap() will decrement it by old_len == new_len.
312 *
313 * Since total_vm is about to be raised artificially high for a
314 * moment, we need to restore high watermark afterwards: if stats
315 * are taken meanwhile, total_vm and hiwater_vm appear too high.
316 * If this were a serious issue, we'd add a flag to do_munmap().
317 */
318 hiwater_vm = mm->hiwater_vm;
319 vm_stat_account(mm, vma->vm_flags, new_len >> PAGE_SHIFT);
320
321 /* Tell pfnmap has moved from this vma */
322 if (unlikely(vma->vm_flags & VM_PFNMAP))
323 untrack_pfn_moved(vma);
324
325 if (do_munmap(mm, old_addr, old_len) < 0) {
326 /* OOM: unable to split vma, just get accounts right */
327 vm_unacct_memory(excess >> PAGE_SHIFT);
328 excess = 0;
329 }
330 mm->hiwater_vm = hiwater_vm;
331
332 /* Restore VM_ACCOUNT if one or two pieces of vma left */
333 if (excess) {
334 vma->vm_flags |= VM_ACCOUNT;
335 if (split)
336 vma->vm_next->vm_flags |= VM_ACCOUNT;
337 }
338
339 if (vm_flags & VM_LOCKED) {
340 mm->locked_vm += new_len >> PAGE_SHIFT;
341 *locked = true;
342 }
343
344 return new_addr;
345}
346
347static struct vm_area_struct *vma_to_resize(unsigned long addr,
348 unsigned long old_len, unsigned long new_len, unsigned long *p)
349{
350 struct mm_struct *mm = current->mm;
351 struct vm_area_struct *vma = find_vma(mm, addr);
352 unsigned long pgoff;
353
354 if (!vma || vma->vm_start > addr)
355 return ERR_PTR(-EFAULT);
356
357 if (is_vm_hugetlb_page(vma))
358 return ERR_PTR(-EINVAL);
359
360 /* We can't remap across vm area boundaries */
361 if (old_len > vma->vm_end - addr)
362 return ERR_PTR(-EFAULT);
363
364 if (new_len == old_len)
365 return vma;
366
367 /* Need to be careful about a growing mapping */
368 pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
369 pgoff += vma->vm_pgoff;
370 if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
371 return ERR_PTR(-EINVAL);
372
373 if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
374 return ERR_PTR(-EFAULT);
375
376 if (vma->vm_flags & VM_LOCKED) {
377 unsigned long locked, lock_limit;
378 locked = mm->locked_vm << PAGE_SHIFT;
379 lock_limit = rlimit(RLIMIT_MEMLOCK);
380 locked += new_len - old_len;
381 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
382 return ERR_PTR(-EAGAIN);
383 }
384
385 if (!may_expand_vm(mm, vma->vm_flags,
386 (new_len - old_len) >> PAGE_SHIFT))
387 return ERR_PTR(-ENOMEM);
388
389 if (vma->vm_flags & VM_ACCOUNT) {
390 unsigned long charged = (new_len - old_len) >> PAGE_SHIFT;
391 if (security_vm_enough_memory_mm(mm, charged))
392 return ERR_PTR(-ENOMEM);
393 *p = charged;
394 }
395
396 return vma;
397}
398
399static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
400 unsigned long new_addr, unsigned long new_len, bool *locked)
401{
402 struct mm_struct *mm = current->mm;
403 struct vm_area_struct *vma;
404 unsigned long ret = -EINVAL;
405 unsigned long charged = 0;
406 unsigned long map_flags;
407
408 if (offset_in_page(new_addr))
409 goto out;
410
411 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
412 goto out;
413
414 /* Ensure the old/new locations do not overlap */
415 if (addr + old_len > new_addr && new_addr + new_len > addr)
416 goto out;
417
418 ret = do_munmap(mm, new_addr, new_len);
419 if (ret)
420 goto out;
421
422 if (old_len >= new_len) {
423 ret = do_munmap(mm, addr+new_len, old_len - new_len);
424 if (ret && old_len != new_len)
425 goto out;
426 old_len = new_len;
427 }
428
429 vma = vma_to_resize(addr, old_len, new_len, &charged);
430 if (IS_ERR(vma)) {
431 ret = PTR_ERR(vma);
432 goto out;
433 }
434
435 map_flags = MAP_FIXED;
436 if (vma->vm_flags & VM_MAYSHARE)
437 map_flags |= MAP_SHARED;
438
439 ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
440 ((addr - vma->vm_start) >> PAGE_SHIFT),
441 map_flags);
442 if (offset_in_page(ret))
443 goto out1;
444
445 ret = move_vma(vma, addr, old_len, new_len, new_addr, locked);
446 if (!(offset_in_page(ret)))
447 goto out;
448out1:
449 vm_unacct_memory(charged);
450
451out:
452 return ret;
453}
454
455static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
456{
457 unsigned long end = vma->vm_end + delta;
458 if (end < vma->vm_end) /* overflow */
459 return 0;
460 if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */
461 return 0;
462 if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
463 0, MAP_FIXED) & ~PAGE_MASK)
464 return 0;
465 return 1;
466}
467
468/*
469 * Expand (or shrink) an existing mapping, potentially moving it at the
470 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
471 *
472 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
473 * This option implies MREMAP_MAYMOVE.
474 */
475SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
476 unsigned long, new_len, unsigned long, flags,
477 unsigned long, new_addr)
478{
479 struct mm_struct *mm = current->mm;
480 struct vm_area_struct *vma;
481 unsigned long ret = -EINVAL;
482 unsigned long charged = 0;
483 bool locked = false;
484
485 if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
486 return ret;
487
488 if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE))
489 return ret;
490
491 if (offset_in_page(addr))
492 return ret;
493
494 old_len = PAGE_ALIGN(old_len);
495 new_len = PAGE_ALIGN(new_len);
496
497 /*
498 * We allow a zero old-len as a special case
499 * for DOS-emu "duplicate shm area" thing. But
500 * a zero new-len is nonsensical.
501 */
502 if (!new_len)
503 return ret;
504
505 down_write(¤t->mm->mmap_sem);
506
507 if (flags & MREMAP_FIXED) {
508 ret = mremap_to(addr, old_len, new_addr, new_len,
509 &locked);
510 goto out;
511 }
512
513 /*
514 * Always allow a shrinking remap: that just unmaps
515 * the unnecessary pages..
516 * do_munmap does all the needed commit accounting
517 */
518 if (old_len >= new_len) {
519 ret = do_munmap(mm, addr+new_len, old_len - new_len);
520 if (ret && old_len != new_len)
521 goto out;
522 ret = addr;
523 goto out;
524 }
525
526 /*
527 * Ok, we need to grow..
528 */
529 vma = vma_to_resize(addr, old_len, new_len, &charged);
530 if (IS_ERR(vma)) {
531 ret = PTR_ERR(vma);
532 goto out;
533 }
534
535 /* old_len exactly to the end of the area..
536 */
537 if (old_len == vma->vm_end - addr) {
538 /* can we just expand the current mapping? */
539 if (vma_expandable(vma, new_len - old_len)) {
540 int pages = (new_len - old_len) >> PAGE_SHIFT;
541
542 if (vma_adjust(vma, vma->vm_start, addr + new_len,
543 vma->vm_pgoff, NULL)) {
544 ret = -ENOMEM;
545 goto out;
546 }
547
548 vm_stat_account(mm, vma->vm_flags, pages);
549 if (vma->vm_flags & VM_LOCKED) {
550 mm->locked_vm += pages;
551 locked = true;
552 new_addr = addr;
553 }
554 ret = addr;
555 goto out;
556 }
557 }
558
559 /*
560 * We weren't able to just expand or shrink the area,
561 * we need to create a new one and move it..
562 */
563 ret = -ENOMEM;
564 if (flags & MREMAP_MAYMOVE) {
565 unsigned long map_flags = 0;
566 if (vma->vm_flags & VM_MAYSHARE)
567 map_flags |= MAP_SHARED;
568
569 new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
570 vma->vm_pgoff +
571 ((addr - vma->vm_start) >> PAGE_SHIFT),
572 map_flags);
573 if (offset_in_page(new_addr)) {
574 ret = new_addr;
575 goto out;
576 }
577
578 ret = move_vma(vma, addr, old_len, new_len, new_addr, &locked);
579 }
580out:
581 if (offset_in_page(ret)) {
582 vm_unacct_memory(charged);
583 locked = 0;
584 }
585 up_write(¤t->mm->mmap_sem);
586 if (locked && new_len > old_len)
587 mm_populate(new_addr + old_len, new_len - old_len);
588 return ret;
589}