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