Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris...
[linux-3.10.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/highmem.h>
19 #include <linux/security.h>
20 #include <linux/syscalls.h>
21 #include <linux/mmu_notifier.h>
22
23 #include <asm/uaccess.h>
24 #include <asm/cacheflush.h>
25 #include <asm/tlbflush.h>
26
27 #include "internal.h"
28
29 static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
30 {
31         pgd_t *pgd;
32         pud_t *pud;
33         pmd_t *pmd;
34
35         pgd = pgd_offset(mm, addr);
36         if (pgd_none_or_clear_bad(pgd))
37                 return NULL;
38
39         pud = pud_offset(pgd, addr);
40         if (pud_none_or_clear_bad(pud))
41                 return NULL;
42
43         pmd = pmd_offset(pud, addr);
44         if (pmd_none(*pmd))
45                 return NULL;
46
47         return pmd;
48 }
49
50 static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
51                             unsigned long addr)
52 {
53         pgd_t *pgd;
54         pud_t *pud;
55         pmd_t *pmd;
56
57         pgd = pgd_offset(mm, addr);
58         pud = pud_alloc(mm, pgd, addr);
59         if (!pud)
60                 return NULL;
61
62         pmd = pmd_alloc(mm, pud, addr);
63         if (!pmd)
64                 return NULL;
65
66         VM_BUG_ON(pmd_trans_huge(*pmd));
67
68         return pmd;
69 }
70
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)
75 {
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;
81
82         /*
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...
87          *
88          * When need_rmap_locks is false, we use other ways to avoid
89          * such races:
90          *
91          * - During exec() shift_arg_pages(), we use a specially tagged vma
92          *   which rmap call sites look for using is_vma_temporary_stack().
93          *
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).
99          */
100         if (need_rmap_locks) {
101                 if (vma->vm_file) {
102                         mapping = vma->vm_file->f_mapping;
103                         mutex_lock(&mapping->i_mmap_mutex);
104                 }
105                 if (vma->anon_vma) {
106                         anon_vma = vma->anon_vma;
107                         anon_vma_lock_write(anon_vma);
108                 }
109         }
110
111         /*
112          * We don't have to worry about the ordering of src and dst
113          * pte locks because exclusive mmap_sem prevents deadlock.
114          */
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();
121
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))
125                         continue;
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);
129         }
130
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);
136         if (anon_vma)
137                 anon_vma_unlock(anon_vma);
138         if (mapping)
139                 mutex_unlock(&mapping->i_mmap_mutex);
140 }
141
142 #define LATENCY_LIMIT   (64 * PAGE_SIZE)
143
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)
148 {
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 */
154
155         old_end = old_addr + len;
156         flush_cache_range(vma, old_addr, old_end);
157
158         mmun_start = old_addr;
159         mmun_end   = old_end;
160         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
161
162         for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
163                 cond_resched();
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);
170                 if (!old_pmd)
171                         continue;
172                 new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr);
173                 if (!new_pmd)
174                         break;
175                 if (pmd_trans_huge(*old_pmd)) {
176                         int err = 0;
177                         if (extent == HPAGE_PMD_SIZE)
178                                 err = move_huge_pmd(vma, new_vma, old_addr,
179                                                     new_addr, old_end,
180                                                     old_pmd, new_pmd);
181                         if (err > 0) {
182                                 need_flush = true;
183                                 continue;
184                         } else if (!err) {
185                                 split_huge_page_pmd(vma, old_addr, old_pmd);
186                         }
187                         VM_BUG_ON(pmd_trans_huge(*old_pmd));
188                 }
189                 if (pmd_none(*new_pmd) && __pte_alloc(new_vma->vm_mm, new_vma,
190                                                       new_pmd, new_addr))
191                         break;
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);
199                 need_flush = true;
200         }
201         if (likely(need_flush))
202                 flush_tlb_range(vma, old_end-len, old_addr);
203
204         mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
205
206         return len + old_addr - old_end;        /* how much done */
207 }
208
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)
212 {
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;
220         int split = 0;
221         int err;
222         bool need_rmap_locks;
223
224         /*
225          * We'd prefer to avoid failure later on in do_munmap:
226          * which may split one vma into three before unmapping.
227          */
228         if (mm->map_count >= sysctl_max_map_count - 3)
229                 return -ENOMEM;
230
231         /*
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.
237          */
238         err = ksm_madvise(vma, old_addr, old_addr + old_len,
239                                                 MADV_UNMERGEABLE, &vm_flags);
240         if (err)
241                 return err;
242
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,
245                            &need_rmap_locks);
246         if (!new_vma)
247                 return -ENOMEM;
248
249         moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len,
250                                      need_rmap_locks);
251         if (moved_len < old_len) {
252                 /*
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.
256                  */
257                 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len,
258                                  true);
259                 vma = new_vma;
260                 old_len = new_len;
261                 old_addr = new_addr;
262                 new_addr = -ENOMEM;
263         }
264
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)
271                         split = 1;
272         }
273
274         /*
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.
277          *
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().
282          */
283         hiwater_vm = mm->hiwater_vm;
284         vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
285
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);
289                 excess = 0;
290         }
291         mm->hiwater_vm = hiwater_vm;
292
293         /* Restore VM_ACCOUNT if one or two pieces of vma left */
294         if (excess) {
295                 vma->vm_flags |= VM_ACCOUNT;
296                 if (split)
297                         vma->vm_next->vm_flags |= VM_ACCOUNT;
298         }
299
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,
304                                                        new_addr + new_len);
305         }
306
307         return new_addr;
308 }
309
310 static struct vm_area_struct *vma_to_resize(unsigned long addr,
311         unsigned long old_len, unsigned long new_len, unsigned long *p)
312 {
313         struct mm_struct *mm = current->mm;
314         struct vm_area_struct *vma = find_vma(mm, addr);
315
316         if (!vma || vma->vm_start > addr)
317                 goto Efault;
318
319         if (is_vm_hugetlb_page(vma))
320                 goto Einval;
321
322         /* We can't remap across vm area boundaries */
323         if (old_len > vma->vm_end - addr)
324                 goto Efault;
325
326         /* Need to be careful about a growing mapping */
327         if (new_len > old_len) {
328                 unsigned long pgoff;
329
330                 if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
331                         goto Efault;
332                 pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
333                 pgoff += vma->vm_pgoff;
334                 if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
335                         goto Einval;
336         }
337
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))
344                         goto Eagain;
345         }
346
347         if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT))
348                 goto Enomem;
349
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))
353                         goto Efault;
354                 *p = charged;
355         }
356
357         return vma;
358
359 Efault: /* very odd choice for most of the cases, but... */
360         return ERR_PTR(-EFAULT);
361 Einval:
362         return ERR_PTR(-EINVAL);
363 Enomem:
364         return ERR_PTR(-ENOMEM);
365 Eagain:
366         return ERR_PTR(-EAGAIN);
367 }
368
369 static unsigned long mremap_to(unsigned long addr,
370         unsigned long old_len, unsigned long new_addr,
371         unsigned long new_len)
372 {
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;
378
379         if (new_addr & ~PAGE_MASK)
380                 goto out;
381
382         if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
383                 goto out;
384
385         /* Check if the location we're moving into overlaps the
386          * old location at all, and fail if it does.
387          */
388         if ((new_addr <= addr) && (new_addr+new_len) > addr)
389                 goto out;
390
391         if ((addr <= new_addr) && (addr+old_len) > new_addr)
392                 goto out;
393
394         ret = do_munmap(mm, new_addr, new_len);
395         if (ret)
396                 goto out;
397
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)
401                         goto out;
402                 old_len = new_len;
403         }
404
405         vma = vma_to_resize(addr, old_len, new_len, &charged);
406         if (IS_ERR(vma)) {
407                 ret = PTR_ERR(vma);
408                 goto out;
409         }
410
411         map_flags = MAP_FIXED;
412         if (vma->vm_flags & VM_MAYSHARE)
413                 map_flags |= MAP_SHARED;
414
415         ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
416                                 ((addr - vma->vm_start) >> PAGE_SHIFT),
417                                 map_flags);
418         if (ret & ~PAGE_MASK)
419                 goto out1;
420
421         ret = move_vma(vma, addr, old_len, new_len, new_addr);
422         if (!(ret & ~PAGE_MASK))
423                 goto out;
424 out1:
425         vm_unacct_memory(charged);
426
427 out:
428         return ret;
429 }
430
431 static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
432 {
433         unsigned long end = vma->vm_end + delta;
434         if (end < vma->vm_end) /* overflow */
435                 return 0;
436         if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */
437                 return 0;
438         if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
439                               0, MAP_FIXED) & ~PAGE_MASK)
440                 return 0;
441         return 1;
442 }
443
444 /*
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)
447  *
448  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
449  * This option implies MREMAP_MAYMOVE.
450  */
451 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
452                 unsigned long, new_len, unsigned long, flags,
453                 unsigned long, new_addr)
454 {
455         struct mm_struct *mm = current->mm;
456         struct vm_area_struct *vma;
457         unsigned long ret = -EINVAL;
458         unsigned long charged = 0;
459
460         down_write(&current->mm->mmap_sem);
461
462         if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
463                 goto out;
464
465         if (addr & ~PAGE_MASK)
466                 goto out;
467
468         old_len = PAGE_ALIGN(old_len);
469         new_len = PAGE_ALIGN(new_len);
470
471         /*
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.
475          */
476         if (!new_len)
477                 goto out;
478
479         if (flags & MREMAP_FIXED) {
480                 if (flags & MREMAP_MAYMOVE)
481                         ret = mremap_to(addr, old_len, new_addr, new_len);
482                 goto out;
483         }
484
485         /*
486          * Always allow a shrinking remap: that just unmaps
487          * the unnecessary pages..
488          * do_munmap does all the needed commit accounting
489          */
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)
493                         goto out;
494                 ret = addr;
495                 goto out;
496         }
497
498         /*
499          * Ok, we need to grow..
500          */
501         vma = vma_to_resize(addr, old_len, new_len, &charged);
502         if (IS_ERR(vma)) {
503                 ret = PTR_ERR(vma);
504                 goto out;
505         }
506
507         /* old_len exactly to the end of the area..
508          */
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;
513
514                         if (vma_adjust(vma, vma->vm_start, addr + new_len,
515                                        vma->vm_pgoff, NULL)) {
516                                 ret = -ENOMEM;
517                                 goto out;
518                         }
519
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,
524                                                    addr + new_len);
525                         }
526                         ret = addr;
527                         goto out;
528                 }
529         }
530
531         /*
532          * We weren't able to just expand or shrink the area,
533          * we need to create a new one and move it..
534          */
535         ret = -ENOMEM;
536         if (flags & MREMAP_MAYMOVE) {
537                 unsigned long map_flags = 0;
538                 if (vma->vm_flags & VM_MAYSHARE)
539                         map_flags |= MAP_SHARED;
540
541                 new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
542                                         vma->vm_pgoff +
543                                         ((addr - vma->vm_start) >> PAGE_SHIFT),
544                                         map_flags);
545                 if (new_addr & ~PAGE_MASK) {
546                         ret = new_addr;
547                         goto out;
548                 }
549
550                 ret = move_vma(vma, addr, old_len, new_len, new_addr);
551         }
552 out:
553         if (ret & ~PAGE_MASK)
554                 vm_unacct_memory(charged);
555         up_write(&current->mm->mmap_sem);
556         return ret;
557 }