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Merge branch 'x86-spinlocks-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...
[karo-tx-linux.git] / mm / mremap.c
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
31 static 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
52 static 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
73 static 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
90 static 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
164 unsigned 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                                 err = move_huge_pmd(vma, new_vma, old_addr,
199                                                     new_addr, old_end,
200                                                     old_pmd, new_pmd);
201                         if (err > 0) {
202                                 need_flush = true;
203                                 continue;
204                         } else if (!err) {
205                                 split_huge_page_pmd(vma, old_addr, old_pmd);
206                         }
207                         VM_BUG_ON(pmd_trans_huge(*old_pmd));
208                 }
209                 if (pmd_none(*new_pmd) && __pte_alloc(new_vma->vm_mm, new_vma,
210                                                       new_pmd, new_addr))
211                         break;
212                 next = (new_addr + PMD_SIZE) & PMD_MASK;
213                 if (extent > next - new_addr)
214                         extent = next - new_addr;
215                 if (extent > LATENCY_LIMIT)
216                         extent = LATENCY_LIMIT;
217                 move_ptes(vma, old_pmd, old_addr, old_addr + extent,
218                           new_vma, new_pmd, new_addr, need_rmap_locks);
219                 need_flush = true;
220         }
221         if (likely(need_flush))
222                 flush_tlb_range(vma, old_end-len, old_addr);
223
224         mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
225
226         return len + old_addr - old_end;        /* how much done */
227 }
228
229 static unsigned long move_vma(struct vm_area_struct *vma,
230                 unsigned long old_addr, unsigned long old_len,
231                 unsigned long new_len, unsigned long new_addr, bool *locked)
232 {
233         struct mm_struct *mm = vma->vm_mm;
234         struct vm_area_struct *new_vma;
235         unsigned long vm_flags = vma->vm_flags;
236         unsigned long new_pgoff;
237         unsigned long moved_len;
238         unsigned long excess = 0;
239         unsigned long hiwater_vm;
240         int split = 0;
241         int err;
242         bool need_rmap_locks;
243
244         /*
245          * We'd prefer to avoid failure later on in do_munmap:
246          * which may split one vma into three before unmapping.
247          */
248         if (mm->map_count >= sysctl_max_map_count - 3)
249                 return -ENOMEM;
250
251         /*
252          * Advise KSM to break any KSM pages in the area to be moved:
253          * it would be confusing if they were to turn up at the new
254          * location, where they happen to coincide with different KSM
255          * pages recently unmapped.  But leave vma->vm_flags as it was,
256          * so KSM can come around to merge on vma and new_vma afterwards.
257          */
258         err = ksm_madvise(vma, old_addr, old_addr + old_len,
259                                                 MADV_UNMERGEABLE, &vm_flags);
260         if (err)
261                 return err;
262
263         new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
264         new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff,
265                            &need_rmap_locks);
266         if (!new_vma)
267                 return -ENOMEM;
268
269         moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len,
270                                      need_rmap_locks);
271         if (moved_len < old_len) {
272                 /*
273                  * On error, move entries back from new area to old,
274                  * which will succeed since page tables still there,
275                  * and then proceed to unmap new area instead of old.
276                  */
277                 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len,
278                                  true);
279                 vma = new_vma;
280                 old_len = new_len;
281                 old_addr = new_addr;
282                 new_addr = -ENOMEM;
283         }
284
285         /* Conceal VM_ACCOUNT so old reservation is not undone */
286         if (vm_flags & VM_ACCOUNT) {
287                 vma->vm_flags &= ~VM_ACCOUNT;
288                 excess = vma->vm_end - vma->vm_start - old_len;
289                 if (old_addr > vma->vm_start &&
290                     old_addr + old_len < vma->vm_end)
291                         split = 1;
292         }
293
294         /*
295          * If we failed to move page tables we still do total_vm increment
296          * since do_munmap() will decrement it by old_len == new_len.
297          *
298          * Since total_vm is about to be raised artificially high for a
299          * moment, we need to restore high watermark afterwards: if stats
300          * are taken meanwhile, total_vm and hiwater_vm appear too high.
301          * If this were a serious issue, we'd add a flag to do_munmap().
302          */
303         hiwater_vm = mm->hiwater_vm;
304         vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
305
306         if (do_munmap(mm, old_addr, old_len) < 0) {
307                 /* OOM: unable to split vma, just get accounts right */
308                 vm_unacct_memory(excess >> PAGE_SHIFT);
309                 excess = 0;
310         }
311         mm->hiwater_vm = hiwater_vm;
312
313         /* Restore VM_ACCOUNT if one or two pieces of vma left */
314         if (excess) {
315                 vma->vm_flags |= VM_ACCOUNT;
316                 if (split)
317                         vma->vm_next->vm_flags |= VM_ACCOUNT;
318         }
319
320         if (vm_flags & VM_LOCKED) {
321                 mm->locked_vm += new_len >> PAGE_SHIFT;
322                 *locked = true;
323         }
324
325         return new_addr;
326 }
327
328 static struct vm_area_struct *vma_to_resize(unsigned long addr,
329         unsigned long old_len, unsigned long new_len, unsigned long *p)
330 {
331         struct mm_struct *mm = current->mm;
332         struct vm_area_struct *vma = find_vma(mm, addr);
333
334         if (!vma || vma->vm_start > addr)
335                 goto Efault;
336
337         if (is_vm_hugetlb_page(vma))
338                 goto Einval;
339
340         /* We can't remap across vm area boundaries */
341         if (old_len > vma->vm_end - addr)
342                 goto Efault;
343
344         /* Need to be careful about a growing mapping */
345         if (new_len > old_len) {
346                 unsigned long pgoff;
347
348                 if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
349                         goto Efault;
350                 pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
351                 pgoff += vma->vm_pgoff;
352                 if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
353                         goto Einval;
354         }
355
356         if (vma->vm_flags & VM_LOCKED) {
357                 unsigned long locked, lock_limit;
358                 locked = mm->locked_vm << PAGE_SHIFT;
359                 lock_limit = rlimit(RLIMIT_MEMLOCK);
360                 locked += new_len - old_len;
361                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
362                         goto Eagain;
363         }
364
365         if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT))
366                 goto Enomem;
367
368         if (vma->vm_flags & VM_ACCOUNT) {
369                 unsigned long charged = (new_len - old_len) >> PAGE_SHIFT;
370                 if (security_vm_enough_memory_mm(mm, charged))
371                         goto Efault;
372                 *p = charged;
373         }
374
375         return vma;
376
377 Efault: /* very odd choice for most of the cases, but... */
378         return ERR_PTR(-EFAULT);
379 Einval:
380         return ERR_PTR(-EINVAL);
381 Enomem:
382         return ERR_PTR(-ENOMEM);
383 Eagain:
384         return ERR_PTR(-EAGAIN);
385 }
386
387 static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
388                 unsigned long new_addr, unsigned long new_len, bool *locked)
389 {
390         struct mm_struct *mm = current->mm;
391         struct vm_area_struct *vma;
392         unsigned long ret = -EINVAL;
393         unsigned long charged = 0;
394         unsigned long map_flags;
395
396         if (new_addr & ~PAGE_MASK)
397                 goto out;
398
399         if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
400                 goto out;
401
402         /* Check if the location we're moving into overlaps the
403          * old location at all, and fail if it does.
404          */
405         if ((new_addr <= addr) && (new_addr+new_len) > addr)
406                 goto out;
407
408         if ((addr <= new_addr) && (addr+old_len) > new_addr)
409                 goto out;
410
411         ret = do_munmap(mm, new_addr, new_len);
412         if (ret)
413                 goto out;
414
415         if (old_len >= new_len) {
416                 ret = do_munmap(mm, addr+new_len, old_len - new_len);
417                 if (ret && old_len != new_len)
418                         goto out;
419                 old_len = new_len;
420         }
421
422         vma = vma_to_resize(addr, old_len, new_len, &charged);
423         if (IS_ERR(vma)) {
424                 ret = PTR_ERR(vma);
425                 goto out;
426         }
427
428         map_flags = MAP_FIXED;
429         if (vma->vm_flags & VM_MAYSHARE)
430                 map_flags |= MAP_SHARED;
431
432         ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
433                                 ((addr - vma->vm_start) >> PAGE_SHIFT),
434                                 map_flags);
435         if (ret & ~PAGE_MASK)
436                 goto out1;
437
438         ret = move_vma(vma, addr, old_len, new_len, new_addr, locked);
439         if (!(ret & ~PAGE_MASK))
440                 goto out;
441 out1:
442         vm_unacct_memory(charged);
443
444 out:
445         return ret;
446 }
447
448 static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
449 {
450         unsigned long end = vma->vm_end + delta;
451         if (end < vma->vm_end) /* overflow */
452                 return 0;
453         if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */
454                 return 0;
455         if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
456                               0, MAP_FIXED) & ~PAGE_MASK)
457                 return 0;
458         return 1;
459 }
460
461 /*
462  * Expand (or shrink) an existing mapping, potentially moving it at the
463  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
464  *
465  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
466  * This option implies MREMAP_MAYMOVE.
467  */
468 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
469                 unsigned long, new_len, unsigned long, flags,
470                 unsigned long, new_addr)
471 {
472         struct mm_struct *mm = current->mm;
473         struct vm_area_struct *vma;
474         unsigned long ret = -EINVAL;
475         unsigned long charged = 0;
476         bool locked = false;
477
478         if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
479                 return ret;
480
481         if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE))
482                 return ret;
483
484         if (addr & ~PAGE_MASK)
485                 return ret;
486
487         old_len = PAGE_ALIGN(old_len);
488         new_len = PAGE_ALIGN(new_len);
489
490         /*
491          * We allow a zero old-len as a special case
492          * for DOS-emu "duplicate shm area" thing. But
493          * a zero new-len is nonsensical.
494          */
495         if (!new_len)
496                 return ret;
497
498         down_write(&current->mm->mmap_sem);
499
500         if (flags & MREMAP_FIXED) {
501                 ret = mremap_to(addr, old_len, new_addr, new_len,
502                                 &locked);
503                 goto out;
504         }
505
506         /*
507          * Always allow a shrinking remap: that just unmaps
508          * the unnecessary pages..
509          * do_munmap does all the needed commit accounting
510          */
511         if (old_len >= new_len) {
512                 ret = do_munmap(mm, addr+new_len, old_len - new_len);
513                 if (ret && old_len != new_len)
514                         goto out;
515                 ret = addr;
516                 goto out;
517         }
518
519         /*
520          * Ok, we need to grow..
521          */
522         vma = vma_to_resize(addr, old_len, new_len, &charged);
523         if (IS_ERR(vma)) {
524                 ret = PTR_ERR(vma);
525                 goto out;
526         }
527
528         /* old_len exactly to the end of the area..
529          */
530         if (old_len == vma->vm_end - addr) {
531                 /* can we just expand the current mapping? */
532                 if (vma_expandable(vma, new_len - old_len)) {
533                         int pages = (new_len - old_len) >> PAGE_SHIFT;
534
535                         if (vma_adjust(vma, vma->vm_start, addr + new_len,
536                                        vma->vm_pgoff, NULL)) {
537                                 ret = -ENOMEM;
538                                 goto out;
539                         }
540
541                         vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
542                         if (vma->vm_flags & VM_LOCKED) {
543                                 mm->locked_vm += pages;
544                                 locked = true;
545                                 new_addr = addr;
546                         }
547                         ret = addr;
548                         goto out;
549                 }
550         }
551
552         /*
553          * We weren't able to just expand or shrink the area,
554          * we need to create a new one and move it..
555          */
556         ret = -ENOMEM;
557         if (flags & MREMAP_MAYMOVE) {
558                 unsigned long map_flags = 0;
559                 if (vma->vm_flags & VM_MAYSHARE)
560                         map_flags |= MAP_SHARED;
561
562                 new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
563                                         vma->vm_pgoff +
564                                         ((addr - vma->vm_start) >> PAGE_SHIFT),
565                                         map_flags);
566                 if (new_addr & ~PAGE_MASK) {
567                         ret = new_addr;
568                         goto out;
569                 }
570
571                 ret = move_vma(vma, addr, old_len, new_len, new_addr, &locked);
572         }
573 out:
574         if (ret & ~PAGE_MASK)
575                 vm_unacct_memory(charged);
576         up_write(&current->mm->mmap_sem);
577         if (locked && new_len > old_len)
578                 mm_populate(new_addr + old_len, new_len - old_len);
579         return ret;
580 }