Merge branch 'drm-fixes-3.18' of git://people.freedesktop.org/~agd5f/linux into drm...
[linux-2.6-microblaze.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 #include <linux/uaccess.h>
25
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                                 VM_BUG_ON_VMA(vma->vm_file || !vma->anon_vma,
199                                               vma);
200                                 /* See comment in move_ptes() */
201                                 if (need_rmap_locks)
202                                         anon_vma_lock_write(vma->anon_vma);
203                                 err = move_huge_pmd(vma, new_vma, old_addr,
204                                                     new_addr, old_end,
205                                                     old_pmd, new_pmd);
206                                 if (need_rmap_locks)
207                                         anon_vma_unlock_write(vma->anon_vma);
208                         }
209                         if (err > 0) {
210                                 need_flush = true;
211                                 continue;
212                         } else if (!err) {
213                                 split_huge_page_pmd(vma, old_addr, old_pmd);
214                         }
215                         VM_BUG_ON(pmd_trans_huge(*old_pmd));
216                 }
217                 if (pmd_none(*new_pmd) && __pte_alloc(new_vma->vm_mm, new_vma,
218                                                       new_pmd, new_addr))
219                         break;
220                 next = (new_addr + PMD_SIZE) & PMD_MASK;
221                 if (extent > next - new_addr)
222                         extent = next - new_addr;
223                 if (extent > LATENCY_LIMIT)
224                         extent = LATENCY_LIMIT;
225                 move_ptes(vma, old_pmd, old_addr, old_addr + extent,
226                           new_vma, new_pmd, new_addr, need_rmap_locks);
227                 need_flush = true;
228         }
229         if (likely(need_flush))
230                 flush_tlb_range(vma, old_end-len, old_addr);
231
232         mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
233
234         return len + old_addr - old_end;        /* how much done */
235 }
236
237 static unsigned long move_vma(struct vm_area_struct *vma,
238                 unsigned long old_addr, unsigned long old_len,
239                 unsigned long new_len, unsigned long new_addr, bool *locked)
240 {
241         struct mm_struct *mm = vma->vm_mm;
242         struct vm_area_struct *new_vma;
243         unsigned long vm_flags = vma->vm_flags;
244         unsigned long new_pgoff;
245         unsigned long moved_len;
246         unsigned long excess = 0;
247         unsigned long hiwater_vm;
248         int split = 0;
249         int err;
250         bool need_rmap_locks;
251
252         /*
253          * We'd prefer to avoid failure later on in do_munmap:
254          * which may split one vma into three before unmapping.
255          */
256         if (mm->map_count >= sysctl_max_map_count - 3)
257                 return -ENOMEM;
258
259         /*
260          * Advise KSM to break any KSM pages in the area to be moved:
261          * it would be confusing if they were to turn up at the new
262          * location, where they happen to coincide with different KSM
263          * pages recently unmapped.  But leave vma->vm_flags as it was,
264          * so KSM can come around to merge on vma and new_vma afterwards.
265          */
266         err = ksm_madvise(vma, old_addr, old_addr + old_len,
267                                                 MADV_UNMERGEABLE, &vm_flags);
268         if (err)
269                 return err;
270
271         new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
272         new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff,
273                            &need_rmap_locks);
274         if (!new_vma)
275                 return -ENOMEM;
276
277         moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len,
278                                      need_rmap_locks);
279         if (moved_len < old_len) {
280                 /*
281                  * On error, move entries back from new area to old,
282                  * which will succeed since page tables still there,
283                  * and then proceed to unmap new area instead of old.
284                  */
285                 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len,
286                                  true);
287                 vma = new_vma;
288                 old_len = new_len;
289                 old_addr = new_addr;
290                 new_addr = -ENOMEM;
291         }
292
293         /* Conceal VM_ACCOUNT so old reservation is not undone */
294         if (vm_flags & VM_ACCOUNT) {
295                 vma->vm_flags &= ~VM_ACCOUNT;
296                 excess = vma->vm_end - vma->vm_start - old_len;
297                 if (old_addr > vma->vm_start &&
298                     old_addr + old_len < vma->vm_end)
299                         split = 1;
300         }
301
302         /*
303          * If we failed to move page tables we still do total_vm increment
304          * since do_munmap() will decrement it by old_len == new_len.
305          *
306          * Since total_vm is about to be raised artificially high for a
307          * moment, we need to restore high watermark afterwards: if stats
308          * are taken meanwhile, total_vm and hiwater_vm appear too high.
309          * If this were a serious issue, we'd add a flag to do_munmap().
310          */
311         hiwater_vm = mm->hiwater_vm;
312         vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
313
314         if (do_munmap(mm, old_addr, old_len) < 0) {
315                 /* OOM: unable to split vma, just get accounts right */
316                 vm_unacct_memory(excess >> PAGE_SHIFT);
317                 excess = 0;
318         }
319         mm->hiwater_vm = hiwater_vm;
320
321         /* Restore VM_ACCOUNT if one or two pieces of vma left */
322         if (excess) {
323                 vma->vm_flags |= VM_ACCOUNT;
324                 if (split)
325                         vma->vm_next->vm_flags |= VM_ACCOUNT;
326         }
327
328         if (vm_flags & VM_LOCKED) {
329                 mm->locked_vm += new_len >> PAGE_SHIFT;
330                 *locked = true;
331         }
332
333         return new_addr;
334 }
335
336 static struct vm_area_struct *vma_to_resize(unsigned long addr,
337         unsigned long old_len, unsigned long new_len, unsigned long *p)
338 {
339         struct mm_struct *mm = current->mm;
340         struct vm_area_struct *vma = find_vma(mm, addr);
341
342         if (!vma || vma->vm_start > addr)
343                 goto Efault;
344
345         if (is_vm_hugetlb_page(vma))
346                 goto Einval;
347
348         /* We can't remap across vm area boundaries */
349         if (old_len > vma->vm_end - addr)
350                 goto Efault;
351
352         /* Need to be careful about a growing mapping */
353         if (new_len > old_len) {
354                 unsigned long pgoff;
355
356                 if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
357                         goto Efault;
358                 pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
359                 pgoff += vma->vm_pgoff;
360                 if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
361                         goto Einval;
362         }
363
364         if (vma->vm_flags & VM_LOCKED) {
365                 unsigned long locked, lock_limit;
366                 locked = mm->locked_vm << PAGE_SHIFT;
367                 lock_limit = rlimit(RLIMIT_MEMLOCK);
368                 locked += new_len - old_len;
369                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
370                         goto Eagain;
371         }
372
373         if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT))
374                 goto Enomem;
375
376         if (vma->vm_flags & VM_ACCOUNT) {
377                 unsigned long charged = (new_len - old_len) >> PAGE_SHIFT;
378                 if (security_vm_enough_memory_mm(mm, charged))
379                         goto Efault;
380                 *p = charged;
381         }
382
383         return vma;
384
385 Efault: /* very odd choice for most of the cases, but... */
386         return ERR_PTR(-EFAULT);
387 Einval:
388         return ERR_PTR(-EINVAL);
389 Enomem:
390         return ERR_PTR(-ENOMEM);
391 Eagain:
392         return ERR_PTR(-EAGAIN);
393 }
394
395 static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
396                 unsigned long new_addr, unsigned long new_len, bool *locked)
397 {
398         struct mm_struct *mm = current->mm;
399         struct vm_area_struct *vma;
400         unsigned long ret = -EINVAL;
401         unsigned long charged = 0;
402         unsigned long map_flags;
403
404         if (new_addr & ~PAGE_MASK)
405                 goto out;
406
407         if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
408                 goto out;
409
410         /* Check if the location we're moving into overlaps the
411          * old location at all, and fail if it does.
412          */
413         if ((new_addr <= addr) && (new_addr+new_len) > addr)
414                 goto out;
415
416         if ((addr <= new_addr) && (addr+old_len) > new_addr)
417                 goto out;
418
419         ret = do_munmap(mm, new_addr, new_len);
420         if (ret)
421                 goto out;
422
423         if (old_len >= new_len) {
424                 ret = do_munmap(mm, addr+new_len, old_len - new_len);
425                 if (ret && old_len != new_len)
426                         goto out;
427                 old_len = new_len;
428         }
429
430         vma = vma_to_resize(addr, old_len, new_len, &charged);
431         if (IS_ERR(vma)) {
432                 ret = PTR_ERR(vma);
433                 goto out;
434         }
435
436         map_flags = MAP_FIXED;
437         if (vma->vm_flags & VM_MAYSHARE)
438                 map_flags |= MAP_SHARED;
439
440         ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
441                                 ((addr - vma->vm_start) >> PAGE_SHIFT),
442                                 map_flags);
443         if (ret & ~PAGE_MASK)
444                 goto out1;
445
446         ret = move_vma(vma, addr, old_len, new_len, new_addr, locked);
447         if (!(ret & ~PAGE_MASK))
448                 goto out;
449 out1:
450         vm_unacct_memory(charged);
451
452 out:
453         return ret;
454 }
455
456 static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
457 {
458         unsigned long end = vma->vm_end + delta;
459         if (end < vma->vm_end) /* overflow */
460                 return 0;
461         if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */
462                 return 0;
463         if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
464                               0, MAP_FIXED) & ~PAGE_MASK)
465                 return 0;
466         return 1;
467 }
468
469 /*
470  * Expand (or shrink) an existing mapping, potentially moving it at the
471  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
472  *
473  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
474  * This option implies MREMAP_MAYMOVE.
475  */
476 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
477                 unsigned long, new_len, unsigned long, flags,
478                 unsigned long, new_addr)
479 {
480         struct mm_struct *mm = current->mm;
481         struct vm_area_struct *vma;
482         unsigned long ret = -EINVAL;
483         unsigned long charged = 0;
484         bool locked = false;
485
486         if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
487                 return ret;
488
489         if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE))
490                 return ret;
491
492         if (addr & ~PAGE_MASK)
493                 return ret;
494
495         old_len = PAGE_ALIGN(old_len);
496         new_len = PAGE_ALIGN(new_len);
497
498         /*
499          * We allow a zero old-len as a special case
500          * for DOS-emu "duplicate shm area" thing. But
501          * a zero new-len is nonsensical.
502          */
503         if (!new_len)
504                 return ret;
505
506         down_write(&current->mm->mmap_sem);
507
508         if (flags & MREMAP_FIXED) {
509                 ret = mremap_to(addr, old_len, new_addr, new_len,
510                                 &locked);
511                 goto out;
512         }
513
514         /*
515          * Always allow a shrinking remap: that just unmaps
516          * the unnecessary pages..
517          * do_munmap does all the needed commit accounting
518          */
519         if (old_len >= new_len) {
520                 ret = do_munmap(mm, addr+new_len, old_len - new_len);
521                 if (ret && old_len != new_len)
522                         goto out;
523                 ret = addr;
524                 goto out;
525         }
526
527         /*
528          * Ok, we need to grow..
529          */
530         vma = vma_to_resize(addr, old_len, new_len, &charged);
531         if (IS_ERR(vma)) {
532                 ret = PTR_ERR(vma);
533                 goto out;
534         }
535
536         /* old_len exactly to the end of the area..
537          */
538         if (old_len == vma->vm_end - addr) {
539                 /* can we just expand the current mapping? */
540                 if (vma_expandable(vma, new_len - old_len)) {
541                         int pages = (new_len - old_len) >> PAGE_SHIFT;
542
543                         if (vma_adjust(vma, vma->vm_start, addr + new_len,
544                                        vma->vm_pgoff, NULL)) {
545                                 ret = -ENOMEM;
546                                 goto out;
547                         }
548
549                         vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
550                         if (vma->vm_flags & VM_LOCKED) {
551                                 mm->locked_vm += pages;
552                                 locked = true;
553                                 new_addr = addr;
554                         }
555                         ret = addr;
556                         goto out;
557                 }
558         }
559
560         /*
561          * We weren't able to just expand or shrink the area,
562          * we need to create a new one and move it..
563          */
564         ret = -ENOMEM;
565         if (flags & MREMAP_MAYMOVE) {
566                 unsigned long map_flags = 0;
567                 if (vma->vm_flags & VM_MAYSHARE)
568                         map_flags |= MAP_SHARED;
569
570                 new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
571                                         vma->vm_pgoff +
572                                         ((addr - vma->vm_start) >> PAGE_SHIFT),
573                                         map_flags);
574                 if (new_addr & ~PAGE_MASK) {
575                         ret = new_addr;
576                         goto out;
577                 }
578
579                 ret = move_vma(vma, addr, old_len, new_len, new_addr, &locked);
580         }
581 out:
582         if (ret & ~PAGE_MASK)
583                 vm_unacct_memory(charged);
584         up_write(&current->mm->mmap_sem);
585         if (locked && new_len > old_len)
586                 mm_populate(new_addr + old_len, new_len - old_len);
587         return ret;
588 }