6 * Address space accounting code <alan@lxorguk.ukuu.org.uk>
9 #include <linux/slab.h>
10 #include <linux/backing-dev.h>
12 #include <linux/shm.h>
13 #include <linux/mman.h>
14 #include <linux/pagemap.h>
15 #include <linux/swap.h>
16 #include <linux/syscalls.h>
17 #include <linux/capability.h>
18 #include <linux/init.h>
19 #include <linux/file.h>
21 #include <linux/personality.h>
22 #include <linux/security.h>
23 #include <linux/hugetlb.h>
24 #include <linux/profile.h>
25 #include <linux/export.h>
26 #include <linux/mount.h>
27 #include <linux/mempolicy.h>
28 #include <linux/rmap.h>
29 #include <linux/mmu_notifier.h>
30 #include <linux/perf_event.h>
31 #include <linux/audit.h>
32 #include <linux/khugepaged.h>
34 #include <asm/uaccess.h>
35 #include <asm/cacheflush.h>
37 #include <asm/mmu_context.h>
41 #ifndef arch_mmap_check
42 #define arch_mmap_check(addr, len, flags) (0)
45 #ifndef arch_rebalance_pgtables
46 #define arch_rebalance_pgtables(addr, len) (addr)
49 static void unmap_region(struct mm_struct *mm,
50 struct vm_area_struct *vma, struct vm_area_struct *prev,
51 unsigned long start, unsigned long end);
54 * WARNING: the debugging will use recursive algorithms so never enable this
55 * unless you know what you are doing.
59 /* description of effects of mapping type and prot in current implementation.
60 * this is due to the limited x86 page protection hardware. The expected
61 * behavior is in parens:
64 * PROT_NONE PROT_READ PROT_WRITE PROT_EXEC
65 * MAP_SHARED r: (no) no r: (yes) yes r: (no) yes r: (no) yes
66 * w: (no) no w: (no) no w: (yes) yes w: (no) no
67 * x: (no) no x: (no) yes x: (no) yes x: (yes) yes
69 * MAP_PRIVATE r: (no) no r: (yes) yes r: (no) yes r: (no) yes
70 * w: (no) no w: (no) no w: (copy) copy w: (no) no
71 * x: (no) no x: (no) yes x: (no) yes x: (yes) yes
74 pgprot_t protection_map[16] = {
75 __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
76 __S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
79 pgprot_t vm_get_page_prot(unsigned long vm_flags)
81 return __pgprot(pgprot_val(protection_map[vm_flags &
82 (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
83 pgprot_val(arch_vm_get_page_prot(vm_flags)));
85 EXPORT_SYMBOL(vm_get_page_prot);
87 int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS; /* heuristic overcommit */
88 int sysctl_overcommit_ratio __read_mostly = 50; /* default is 50% */
89 int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
91 * Make sure vm_committed_as in one cacheline and not cacheline shared with
92 * other variables. It can be updated by several CPUs frequently.
94 struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
97 * Check that a process has enough memory to allocate a new virtual
98 * mapping. 0 means there is enough memory for the allocation to
99 * succeed and -ENOMEM implies there is not.
101 * We currently support three overcommit policies, which are set via the
102 * vm.overcommit_memory sysctl. See Documentation/vm/overcommit-accounting
104 * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
105 * Additional code 2002 Jul 20 by Robert Love.
107 * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
109 * Note this is a helper function intended to be used by LSMs which
110 * wish to use this logic.
112 int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
114 unsigned long free, allowed;
116 vm_acct_memory(pages);
119 * Sometimes we want to use more memory than we have
121 if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
124 if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
125 free = global_page_state(NR_FREE_PAGES);
126 free += global_page_state(NR_FILE_PAGES);
129 * shmem pages shouldn't be counted as free in this
130 * case, they can't be purged, only swapped out, and
131 * that won't affect the overall amount of available
132 * memory in the system.
134 free -= global_page_state(NR_SHMEM);
136 free += nr_swap_pages;
139 * Any slabs which are created with the
140 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
141 * which are reclaimable, under pressure. The dentry
142 * cache and most inode caches should fall into this
144 free += global_page_state(NR_SLAB_RECLAIMABLE);
147 * Leave reserved pages. The pages are not for anonymous pages.
149 if (free <= totalreserve_pages)
152 free -= totalreserve_pages;
155 * Leave the last 3% for root
166 allowed = (totalram_pages - hugetlb_total_pages())
167 * sysctl_overcommit_ratio / 100;
169 * Leave the last 3% for root
172 allowed -= allowed / 32;
173 allowed += total_swap_pages;
175 /* Don't let a single process grow too big:
176 leave 3% of the size of this process for other processes */
178 allowed -= mm->total_vm / 32;
180 if (percpu_counter_read_positive(&vm_committed_as) < allowed)
183 vm_unacct_memory(pages);
189 * Requires inode->i_mapping->i_mmap_mutex
191 static void __remove_shared_vm_struct(struct vm_area_struct *vma,
192 struct file *file, struct address_space *mapping)
194 if (vma->vm_flags & VM_DENYWRITE)
195 atomic_inc(&file->f_path.dentry->d_inode->i_writecount);
196 if (vma->vm_flags & VM_SHARED)
197 mapping->i_mmap_writable--;
199 flush_dcache_mmap_lock(mapping);
200 if (unlikely(vma->vm_flags & VM_NONLINEAR))
201 list_del_init(&vma->shared.vm_set.list);
203 vma_prio_tree_remove(vma, &mapping->i_mmap);
204 flush_dcache_mmap_unlock(mapping);
208 * Unlink a file-based vm structure from its prio_tree, to hide
209 * vma from rmap and vmtruncate before freeing its page tables.
211 void unlink_file_vma(struct vm_area_struct *vma)
213 struct file *file = vma->vm_file;
216 struct address_space *mapping = file->f_mapping;
217 mutex_lock(&mapping->i_mmap_mutex);
218 __remove_shared_vm_struct(vma, file, mapping);
219 mutex_unlock(&mapping->i_mmap_mutex);
224 * Close a vm structure and free it, returning the next.
226 static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
228 struct vm_area_struct *next = vma->vm_next;
231 if (vma->vm_ops && vma->vm_ops->close)
232 vma->vm_ops->close(vma);
235 if (vma->vm_flags & VM_EXECUTABLE)
236 removed_exe_file_vma(vma->vm_mm);
238 mpol_put(vma_policy(vma));
239 kmem_cache_free(vm_area_cachep, vma);
243 SYSCALL_DEFINE1(brk, unsigned long, brk)
245 unsigned long rlim, retval;
246 unsigned long newbrk, oldbrk;
247 struct mm_struct *mm = current->mm;
248 unsigned long min_brk;
250 down_write(&mm->mmap_sem);
252 #ifdef CONFIG_COMPAT_BRK
254 * CONFIG_COMPAT_BRK can still be overridden by setting
255 * randomize_va_space to 2, which will still cause mm->start_brk
256 * to be arbitrarily shifted
258 if (current->brk_randomized)
259 min_brk = mm->start_brk;
261 min_brk = mm->end_data;
263 min_brk = mm->start_brk;
269 * Check against rlimit here. If this check is done later after the test
270 * of oldbrk with newbrk then it can escape the test and let the data
271 * segment grow beyond its set limit the in case where the limit is
272 * not page aligned -Ram Gupta
274 rlim = rlimit(RLIMIT_DATA);
275 if (rlim < RLIM_INFINITY && (brk - mm->start_brk) +
276 (mm->end_data - mm->start_data) > rlim)
279 newbrk = PAGE_ALIGN(brk);
280 oldbrk = PAGE_ALIGN(mm->brk);
281 if (oldbrk == newbrk)
284 /* Always allow shrinking brk. */
285 if (brk <= mm->brk) {
286 if (!do_munmap(mm, newbrk, oldbrk-newbrk))
291 /* Check against existing mmap mappings. */
292 if (find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE))
295 /* Ok, looks good - let it rip. */
296 if (do_brk(oldbrk, newbrk-oldbrk) != oldbrk)
302 up_write(&mm->mmap_sem);
307 static int browse_rb(struct rb_root *root)
310 struct rb_node *nd, *pn = NULL;
311 unsigned long prev = 0, pend = 0;
313 for (nd = rb_first(root); nd; nd = rb_next(nd)) {
314 struct vm_area_struct *vma;
315 vma = rb_entry(nd, struct vm_area_struct, vm_rb);
316 if (vma->vm_start < prev)
317 printk("vm_start %lx prev %lx\n", vma->vm_start, prev), i = -1;
318 if (vma->vm_start < pend)
319 printk("vm_start %lx pend %lx\n", vma->vm_start, pend);
320 if (vma->vm_start > vma->vm_end)
321 printk("vm_end %lx < vm_start %lx\n", vma->vm_end, vma->vm_start);
324 prev = vma->vm_start;
328 for (nd = pn; nd; nd = rb_prev(nd)) {
332 printk("backwards %d, forwards %d\n", j, i), i = 0;
336 void validate_mm(struct mm_struct *mm)
340 struct vm_area_struct *tmp = mm->mmap;
345 if (i != mm->map_count)
346 printk("map_count %d vm_next %d\n", mm->map_count, i), bug = 1;
347 i = browse_rb(&mm->mm_rb);
348 if (i != mm->map_count)
349 printk("map_count %d rb %d\n", mm->map_count, i), bug = 1;
353 #define validate_mm(mm) do { } while (0)
356 static struct vm_area_struct *
357 find_vma_prepare(struct mm_struct *mm, unsigned long addr,
358 struct vm_area_struct **pprev, struct rb_node ***rb_link,
359 struct rb_node ** rb_parent)
361 struct vm_area_struct * vma;
362 struct rb_node ** __rb_link, * __rb_parent, * rb_prev;
364 __rb_link = &mm->mm_rb.rb_node;
365 rb_prev = __rb_parent = NULL;
369 struct vm_area_struct *vma_tmp;
371 __rb_parent = *__rb_link;
372 vma_tmp = rb_entry(__rb_parent, struct vm_area_struct, vm_rb);
374 if (vma_tmp->vm_end > addr) {
376 if (vma_tmp->vm_start <= addr)
378 __rb_link = &__rb_parent->rb_left;
380 rb_prev = __rb_parent;
381 __rb_link = &__rb_parent->rb_right;
387 *pprev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
388 *rb_link = __rb_link;
389 *rb_parent = __rb_parent;
393 void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
394 struct rb_node **rb_link, struct rb_node *rb_parent)
396 rb_link_node(&vma->vm_rb, rb_parent, rb_link);
397 rb_insert_color(&vma->vm_rb, &mm->mm_rb);
400 static void __vma_link_file(struct vm_area_struct *vma)
406 struct address_space *mapping = file->f_mapping;
408 if (vma->vm_flags & VM_DENYWRITE)
409 atomic_dec(&file->f_path.dentry->d_inode->i_writecount);
410 if (vma->vm_flags & VM_SHARED)
411 mapping->i_mmap_writable++;
413 flush_dcache_mmap_lock(mapping);
414 if (unlikely(vma->vm_flags & VM_NONLINEAR))
415 vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
417 vma_prio_tree_insert(vma, &mapping->i_mmap);
418 flush_dcache_mmap_unlock(mapping);
423 __vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
424 struct vm_area_struct *prev, struct rb_node **rb_link,
425 struct rb_node *rb_parent)
427 __vma_link_list(mm, vma, prev, rb_parent);
428 __vma_link_rb(mm, vma, rb_link, rb_parent);
431 static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
432 struct vm_area_struct *prev, struct rb_node **rb_link,
433 struct rb_node *rb_parent)
435 struct address_space *mapping = NULL;
438 mapping = vma->vm_file->f_mapping;
441 mutex_lock(&mapping->i_mmap_mutex);
443 __vma_link(mm, vma, prev, rb_link, rb_parent);
444 __vma_link_file(vma);
447 mutex_unlock(&mapping->i_mmap_mutex);
454 * Helper for vma_adjust in the split_vma insert case:
455 * insert vm structure into list and rbtree and anon_vma,
456 * but it has already been inserted into prio_tree earlier.
458 static void __insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
460 struct vm_area_struct *__vma, *prev;
461 struct rb_node **rb_link, *rb_parent;
463 __vma = find_vma_prepare(mm, vma->vm_start,&prev, &rb_link, &rb_parent);
464 BUG_ON(__vma && __vma->vm_start < vma->vm_end);
465 __vma_link(mm, vma, prev, rb_link, rb_parent);
470 __vma_unlink(struct mm_struct *mm, struct vm_area_struct *vma,
471 struct vm_area_struct *prev)
473 struct vm_area_struct *next = vma->vm_next;
475 prev->vm_next = next;
477 next->vm_prev = prev;
478 rb_erase(&vma->vm_rb, &mm->mm_rb);
479 if (mm->mmap_cache == vma)
480 mm->mmap_cache = prev;
484 * We cannot adjust vm_start, vm_end, vm_pgoff fields of a vma that
485 * is already present in an i_mmap tree without adjusting the tree.
486 * The following helper function should be used when such adjustments
487 * are necessary. The "insert" vma (if any) is to be inserted
488 * before we drop the necessary locks.
490 int vma_adjust(struct vm_area_struct *vma, unsigned long start,
491 unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert)
493 struct mm_struct *mm = vma->vm_mm;
494 struct vm_area_struct *next = vma->vm_next;
495 struct vm_area_struct *importer = NULL;
496 struct address_space *mapping = NULL;
497 struct prio_tree_root *root = NULL;
498 struct anon_vma *anon_vma = NULL;
499 struct file *file = vma->vm_file;
500 long adjust_next = 0;
503 if (next && !insert) {
504 struct vm_area_struct *exporter = NULL;
506 if (end >= next->vm_end) {
508 * vma expands, overlapping all the next, and
509 * perhaps the one after too (mprotect case 6).
511 again: remove_next = 1 + (end > next->vm_end);
515 } else if (end > next->vm_start) {
517 * vma expands, overlapping part of the next:
518 * mprotect case 5 shifting the boundary up.
520 adjust_next = (end - next->vm_start) >> PAGE_SHIFT;
523 } else if (end < vma->vm_end) {
525 * vma shrinks, and !insert tells it's not
526 * split_vma inserting another: so it must be
527 * mprotect case 4 shifting the boundary down.
529 adjust_next = - ((vma->vm_end - end) >> PAGE_SHIFT);
535 * Easily overlooked: when mprotect shifts the boundary,
536 * make sure the expanding vma has anon_vma set if the
537 * shrinking vma had, to cover any anon pages imported.
539 if (exporter && exporter->anon_vma && !importer->anon_vma) {
542 importer->anon_vma = exporter->anon_vma;
543 error = anon_vma_clone(importer, exporter);
545 importer->anon_vma = NULL;
552 mapping = file->f_mapping;
553 if (!(vma->vm_flags & VM_NONLINEAR))
554 root = &mapping->i_mmap;
555 mutex_lock(&mapping->i_mmap_mutex);
558 * Put into prio_tree now, so instantiated pages
559 * are visible to arm/parisc __flush_dcache_page
560 * throughout; but we cannot insert into address
561 * space until vma start or end is updated.
563 __vma_link_file(insert);
567 vma_adjust_trans_huge(vma, start, end, adjust_next);
570 * When changing only vma->vm_end, we don't really need anon_vma
571 * lock. This is a fairly rare case by itself, but the anon_vma
572 * lock may be shared between many sibling processes. Skipping
573 * the lock for brk adjustments makes a difference sometimes.
575 if (vma->anon_vma && (importer || start != vma->vm_start)) {
576 anon_vma = vma->anon_vma;
577 anon_vma_lock(anon_vma);
581 flush_dcache_mmap_lock(mapping);
582 vma_prio_tree_remove(vma, root);
584 vma_prio_tree_remove(next, root);
587 vma->vm_start = start;
589 vma->vm_pgoff = pgoff;
591 next->vm_start += adjust_next << PAGE_SHIFT;
592 next->vm_pgoff += adjust_next;
597 vma_prio_tree_insert(next, root);
598 vma_prio_tree_insert(vma, root);
599 flush_dcache_mmap_unlock(mapping);
604 * vma_merge has merged next into vma, and needs
605 * us to remove next before dropping the locks.
607 __vma_unlink(mm, next, vma);
609 __remove_shared_vm_struct(next, file, mapping);
612 * split_vma has split insert from vma, and needs
613 * us to insert it before dropping the locks
614 * (it may either follow vma or precede it).
616 __insert_vm_struct(mm, insert);
620 anon_vma_unlock(anon_vma);
622 mutex_unlock(&mapping->i_mmap_mutex);
627 if (next->vm_flags & VM_EXECUTABLE)
628 removed_exe_file_vma(mm);
631 anon_vma_merge(vma, next);
633 mpol_put(vma_policy(next));
634 kmem_cache_free(vm_area_cachep, next);
636 * In mprotect's case 6 (see comments on vma_merge),
637 * we must remove another next too. It would clutter
638 * up the code too much to do both in one go.
640 if (remove_next == 2) {
652 * If the vma has a ->close operation then the driver probably needs to release
653 * per-vma resources, so we don't attempt to merge those.
655 static inline int is_mergeable_vma(struct vm_area_struct *vma,
656 struct file *file, unsigned long vm_flags)
658 /* VM_CAN_NONLINEAR may get set later by f_op->mmap() */
659 if ((vma->vm_flags ^ vm_flags) & ~VM_CAN_NONLINEAR)
661 if (vma->vm_file != file)
663 if (vma->vm_ops && vma->vm_ops->close)
668 static inline int is_mergeable_anon_vma(struct anon_vma *anon_vma1,
669 struct anon_vma *anon_vma2,
670 struct vm_area_struct *vma)
673 * The list_is_singular() test is to avoid merging VMA cloned from
674 * parents. This can improve scalability caused by anon_vma lock.
676 if ((!anon_vma1 || !anon_vma2) && (!vma ||
677 list_is_singular(&vma->anon_vma_chain)))
679 return anon_vma1 == anon_vma2;
683 * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
684 * in front of (at a lower virtual address and file offset than) the vma.
686 * We cannot merge two vmas if they have differently assigned (non-NULL)
687 * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
689 * We don't check here for the merged mmap wrapping around the end of pagecache
690 * indices (16TB on ia32) because do_mmap_pgoff() does not permit mmap's which
691 * wrap, nor mmaps which cover the final page at index -1UL.
694 can_vma_merge_before(struct vm_area_struct *vma, unsigned long vm_flags,
695 struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff)
697 if (is_mergeable_vma(vma, file, vm_flags) &&
698 is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
699 if (vma->vm_pgoff == vm_pgoff)
706 * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
707 * beyond (at a higher virtual address and file offset than) the vma.
709 * We cannot merge two vmas if they have differently assigned (non-NULL)
710 * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
713 can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
714 struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff)
716 if (is_mergeable_vma(vma, file, vm_flags) &&
717 is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
719 vm_pglen = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
720 if (vma->vm_pgoff + vm_pglen == vm_pgoff)
727 * Given a mapping request (addr,end,vm_flags,file,pgoff), figure out
728 * whether that can be merged with its predecessor or its successor.
729 * Or both (it neatly fills a hole).
731 * In most cases - when called for mmap, brk or mremap - [addr,end) is
732 * certain not to be mapped by the time vma_merge is called; but when
733 * called for mprotect, it is certain to be already mapped (either at
734 * an offset within prev, or at the start of next), and the flags of
735 * this area are about to be changed to vm_flags - and the no-change
736 * case has already been eliminated.
738 * The following mprotect cases have to be considered, where AAAA is
739 * the area passed down from mprotect_fixup, never extending beyond one
740 * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
742 * AAAA AAAA AAAA AAAA
743 * PPPPPPNNNNNN PPPPPPNNNNNN PPPPPPNNNNNN PPPPNNNNXXXX
744 * cannot merge might become might become might become
745 * PPNNNNNNNNNN PPPPPPPPPPNN PPPPPPPPPPPP 6 or
746 * mmap, brk or case 4 below case 5 below PPPPPPPPXXXX 7 or
747 * mremap move: PPPPNNNNNNNN 8
749 * PPPP NNNN PPPPPPPPPPPP PPPPPPPPNNNN PPPPNNNNNNNN
750 * might become case 1 below case 2 below case 3 below
752 * Odd one out? Case 8, because it extends NNNN but needs flags of XXXX:
753 * mprotect_fixup updates vm_flags & vm_page_prot on successful return.
755 struct vm_area_struct *vma_merge(struct mm_struct *mm,
756 struct vm_area_struct *prev, unsigned long addr,
757 unsigned long end, unsigned long vm_flags,
758 struct anon_vma *anon_vma, struct file *file,
759 pgoff_t pgoff, struct mempolicy *policy)
761 pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
762 struct vm_area_struct *area, *next;
766 * We later require that vma->vm_flags == vm_flags,
767 * so this tests vma->vm_flags & VM_SPECIAL, too.
769 if (vm_flags & VM_SPECIAL)
773 next = prev->vm_next;
777 if (next && next->vm_end == end) /* cases 6, 7, 8 */
778 next = next->vm_next;
781 * Can it merge with the predecessor?
783 if (prev && prev->vm_end == addr &&
784 mpol_equal(vma_policy(prev), policy) &&
785 can_vma_merge_after(prev, vm_flags,
786 anon_vma, file, pgoff)) {
788 * OK, it can. Can we now merge in the successor as well?
790 if (next && end == next->vm_start &&
791 mpol_equal(policy, vma_policy(next)) &&
792 can_vma_merge_before(next, vm_flags,
793 anon_vma, file, pgoff+pglen) &&
794 is_mergeable_anon_vma(prev->anon_vma,
795 next->anon_vma, NULL)) {
797 err = vma_adjust(prev, prev->vm_start,
798 next->vm_end, prev->vm_pgoff, NULL);
799 } else /* cases 2, 5, 7 */
800 err = vma_adjust(prev, prev->vm_start,
801 end, prev->vm_pgoff, NULL);
804 khugepaged_enter_vma_merge(prev, vm_flags);
809 * Can this new request be merged in front of next?
811 if (next && end == next->vm_start &&
812 mpol_equal(policy, vma_policy(next)) &&
813 can_vma_merge_before(next, vm_flags,
814 anon_vma, file, pgoff+pglen)) {
815 if (prev && addr < prev->vm_end) /* case 4 */
816 err = vma_adjust(prev, prev->vm_start,
817 addr, prev->vm_pgoff, NULL);
818 else /* cases 3, 8 */
819 err = vma_adjust(area, addr, next->vm_end,
820 next->vm_pgoff - pglen, NULL);
823 khugepaged_enter_vma_merge(area, vm_flags);
831 * Rough compatbility check to quickly see if it's even worth looking
832 * at sharing an anon_vma.
834 * They need to have the same vm_file, and the flags can only differ
835 * in things that mprotect may change.
837 * NOTE! The fact that we share an anon_vma doesn't _have_ to mean that
838 * we can merge the two vma's. For example, we refuse to merge a vma if
839 * there is a vm_ops->close() function, because that indicates that the
840 * driver is doing some kind of reference counting. But that doesn't
841 * really matter for the anon_vma sharing case.
843 static int anon_vma_compatible(struct vm_area_struct *a, struct vm_area_struct *b)
845 return a->vm_end == b->vm_start &&
846 mpol_equal(vma_policy(a), vma_policy(b)) &&
847 a->vm_file == b->vm_file &&
848 !((a->vm_flags ^ b->vm_flags) & ~(VM_READ|VM_WRITE|VM_EXEC)) &&
849 b->vm_pgoff == a->vm_pgoff + ((b->vm_start - a->vm_start) >> PAGE_SHIFT);
853 * Do some basic sanity checking to see if we can re-use the anon_vma
854 * from 'old'. The 'a'/'b' vma's are in VM order - one of them will be
855 * the same as 'old', the other will be the new one that is trying
856 * to share the anon_vma.
858 * NOTE! This runs with mm_sem held for reading, so it is possible that
859 * the anon_vma of 'old' is concurrently in the process of being set up
860 * by another page fault trying to merge _that_. But that's ok: if it
861 * is being set up, that automatically means that it will be a singleton
862 * acceptable for merging, so we can do all of this optimistically. But
863 * we do that ACCESS_ONCE() to make sure that we never re-load the pointer.
865 * IOW: that the "list_is_singular()" test on the anon_vma_chain only
866 * matters for the 'stable anon_vma' case (ie the thing we want to avoid
867 * is to return an anon_vma that is "complex" due to having gone through
870 * We also make sure that the two vma's are compatible (adjacent,
871 * and with the same memory policies). That's all stable, even with just
872 * a read lock on the mm_sem.
874 static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, struct vm_area_struct *a, struct vm_area_struct *b)
876 if (anon_vma_compatible(a, b)) {
877 struct anon_vma *anon_vma = ACCESS_ONCE(old->anon_vma);
879 if (anon_vma && list_is_singular(&old->anon_vma_chain))
886 * find_mergeable_anon_vma is used by anon_vma_prepare, to check
887 * neighbouring vmas for a suitable anon_vma, before it goes off
888 * to allocate a new anon_vma. It checks because a repetitive
889 * sequence of mprotects and faults may otherwise lead to distinct
890 * anon_vmas being allocated, preventing vma merge in subsequent
893 struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
895 struct anon_vma *anon_vma;
896 struct vm_area_struct *near;
902 anon_vma = reusable_anon_vma(near, vma, near);
910 anon_vma = reusable_anon_vma(near, near, vma);
915 * There's no absolute need to look only at touching neighbours:
916 * we could search further afield for "compatible" anon_vmas.
917 * But it would probably just be a waste of time searching,
918 * or lead to too many vmas hanging off the same anon_vma.
919 * We're trying to allow mprotect remerging later on,
920 * not trying to minimize memory used for anon_vmas.
925 #ifdef CONFIG_PROC_FS
926 void vm_stat_account(struct mm_struct *mm, unsigned long flags,
927 struct file *file, long pages)
929 const unsigned long stack_flags
930 = VM_STACK_FLAGS & (VM_GROWSUP|VM_GROWSDOWN);
933 mm->shared_vm += pages;
934 if ((flags & (VM_EXEC|VM_WRITE)) == VM_EXEC)
935 mm->exec_vm += pages;
936 } else if (flags & stack_flags)
937 mm->stack_vm += pages;
938 if (flags & (VM_RESERVED|VM_IO))
939 mm->reserved_vm += pages;
941 #endif /* CONFIG_PROC_FS */
944 * The caller must hold down_write(¤t->mm->mmap_sem).
947 unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
948 unsigned long len, unsigned long prot,
949 unsigned long flags, unsigned long pgoff)
951 struct mm_struct * mm = current->mm;
955 unsigned long reqprot = prot;
958 * Does the application expect PROT_READ to imply PROT_EXEC?
960 * (the exception is when the underlying filesystem is noexec
961 * mounted, in which case we dont add PROT_EXEC.)
963 if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
964 if (!(file && (file->f_path.mnt->mnt_flags & MNT_NOEXEC)))
970 if (!(flags & MAP_FIXED))
971 addr = round_hint_to_min(addr);
973 /* Careful about overflows.. */
974 len = PAGE_ALIGN(len);
978 /* offset overflow? */
979 if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
982 /* Too many mappings? */
983 if (mm->map_count > sysctl_max_map_count)
986 /* Obtain the address to map to. we verify (or select) it and ensure
987 * that it represents a valid section of the address space.
989 addr = get_unmapped_area(file, addr, len, pgoff, flags);
990 if (addr & ~PAGE_MASK)
993 /* Do simple checking here so the lower-level routines won't have
994 * to. we assume access permissions have been handled by the open
995 * of the memory object, so we don't do any here.
997 vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags) |
998 mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
1000 if (flags & MAP_LOCKED)
1001 if (!can_do_mlock())
1004 /* mlock MCL_FUTURE? */
1005 if (vm_flags & VM_LOCKED) {
1006 unsigned long locked, lock_limit;
1007 locked = len >> PAGE_SHIFT;
1008 locked += mm->locked_vm;
1009 lock_limit = rlimit(RLIMIT_MEMLOCK);
1010 lock_limit >>= PAGE_SHIFT;
1011 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
1015 inode = file ? file->f_path.dentry->d_inode : NULL;
1018 switch (flags & MAP_TYPE) {
1020 if ((prot&PROT_WRITE) && !(file->f_mode&FMODE_WRITE))
1024 * Make sure we don't allow writing to an append-only
1027 if (IS_APPEND(inode) && (file->f_mode & FMODE_WRITE))
1031 * Make sure there are no mandatory locks on the file.
1033 if (locks_verify_locked(inode))
1036 vm_flags |= VM_SHARED | VM_MAYSHARE;
1037 if (!(file->f_mode & FMODE_WRITE))
1038 vm_flags &= ~(VM_MAYWRITE | VM_SHARED);
1042 if (!(file->f_mode & FMODE_READ))
1044 if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) {
1045 if (vm_flags & VM_EXEC)
1047 vm_flags &= ~VM_MAYEXEC;
1050 if (!file->f_op || !file->f_op->mmap)
1058 switch (flags & MAP_TYPE) {
1064 vm_flags |= VM_SHARED | VM_MAYSHARE;
1068 * Set pgoff according to addr for anon_vma.
1070 pgoff = addr >> PAGE_SHIFT;
1077 error = security_file_mmap(file, reqprot, prot, flags, addr, 0);
1081 return mmap_region(file, addr, len, flags, vm_flags, pgoff);
1083 EXPORT_SYMBOL(do_mmap_pgoff);
1085 SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
1086 unsigned long, prot, unsigned long, flags,
1087 unsigned long, fd, unsigned long, pgoff)
1089 struct file *file = NULL;
1090 unsigned long retval = -EBADF;
1092 if (!(flags & MAP_ANONYMOUS)) {
1093 audit_mmap_fd(fd, flags);
1094 if (unlikely(flags & MAP_HUGETLB))
1099 } else if (flags & MAP_HUGETLB) {
1100 struct user_struct *user = NULL;
1102 * VM_NORESERVE is used because the reservations will be
1103 * taken when vm_ops->mmap() is called
1104 * A dummy user value is used because we are not locking
1105 * memory so no accounting is necessary
1107 len = ALIGN(len, huge_page_size(&default_hstate));
1108 file = hugetlb_file_setup(HUGETLB_ANON_FILE, len, VM_NORESERVE,
1109 &user, HUGETLB_ANONHUGE_INODE);
1111 return PTR_ERR(file);
1114 flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
1116 down_write(¤t->mm->mmap_sem);
1117 retval = do_mmap_pgoff(file, addr, len, prot, flags, pgoff);
1118 up_write(¤t->mm->mmap_sem);
1126 #ifdef __ARCH_WANT_SYS_OLD_MMAP
1127 struct mmap_arg_struct {
1131 unsigned long flags;
1133 unsigned long offset;
1136 SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
1138 struct mmap_arg_struct a;
1140 if (copy_from_user(&a, arg, sizeof(a)))
1142 if (a.offset & ~PAGE_MASK)
1145 return sys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
1146 a.offset >> PAGE_SHIFT);
1148 #endif /* __ARCH_WANT_SYS_OLD_MMAP */
1151 * Some shared mappigns will want the pages marked read-only
1152 * to track write events. If so, we'll downgrade vm_page_prot
1153 * to the private version (using protection_map[] without the
1156 int vma_wants_writenotify(struct vm_area_struct *vma)
1158 vm_flags_t vm_flags = vma->vm_flags;
1160 /* If it was private or non-writable, the write bit is already clear */
1161 if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED)))
1164 /* The backer wishes to know when pages are first written to? */
1165 if (vma->vm_ops && vma->vm_ops->page_mkwrite)
1168 /* The open routine did something to the protections already? */
1169 if (pgprot_val(vma->vm_page_prot) !=
1170 pgprot_val(vm_get_page_prot(vm_flags)))
1173 /* Specialty mapping? */
1174 if (vm_flags & (VM_PFNMAP|VM_INSERTPAGE))
1177 /* Can the mapping track the dirty pages? */
1178 return vma->vm_file && vma->vm_file->f_mapping &&
1179 mapping_cap_account_dirty(vma->vm_file->f_mapping);
1183 * We account for memory if it's a private writeable mapping,
1184 * not hugepages and VM_NORESERVE wasn't set.
1186 static inline int accountable_mapping(struct file *file, vm_flags_t vm_flags)
1189 * hugetlb has its own accounting separate from the core VM
1190 * VM_HUGETLB may not be set yet so we cannot check for that flag.
1192 if (file && is_file_hugepages(file))
1195 return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE;
1198 unsigned long mmap_region(struct file *file, unsigned long addr,
1199 unsigned long len, unsigned long flags,
1200 vm_flags_t vm_flags, unsigned long pgoff)
1202 struct mm_struct *mm = current->mm;
1203 struct vm_area_struct *vma, *prev;
1204 int correct_wcount = 0;
1206 struct rb_node **rb_link, *rb_parent;
1207 unsigned long charged = 0;
1208 struct inode *inode = file ? file->f_path.dentry->d_inode : NULL;
1210 /* Clear old maps */
1213 vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
1214 if (vma && vma->vm_start < addr + len) {
1215 if (do_munmap(mm, addr, len))
1220 /* Check against address space limit. */
1221 if (!may_expand_vm(mm, len >> PAGE_SHIFT))
1225 * Set 'VM_NORESERVE' if we should not account for the
1226 * memory use of this mapping.
1228 if ((flags & MAP_NORESERVE)) {
1229 /* We honor MAP_NORESERVE if allowed to overcommit */
1230 if (sysctl_overcommit_memory != OVERCOMMIT_NEVER)
1231 vm_flags |= VM_NORESERVE;
1233 /* hugetlb applies strict overcommit unless MAP_NORESERVE */
1234 if (file && is_file_hugepages(file))
1235 vm_flags |= VM_NORESERVE;
1239 * Private writable mapping: check memory availability
1241 if (accountable_mapping(file, vm_flags)) {
1242 charged = len >> PAGE_SHIFT;
1243 if (security_vm_enough_memory(charged))
1245 vm_flags |= VM_ACCOUNT;
1249 * Can we just expand an old mapping?
1251 vma = vma_merge(mm, prev, addr, addr + len, vm_flags, NULL, file, pgoff, NULL);
1256 * Determine the object being mapped and call the appropriate
1257 * specific mapper. the address has already been validated, but
1258 * not unmapped, but the maps are removed from the list.
1260 vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
1267 vma->vm_start = addr;
1268 vma->vm_end = addr + len;
1269 vma->vm_flags = vm_flags;
1270 vma->vm_page_prot = vm_get_page_prot(vm_flags);
1271 vma->vm_pgoff = pgoff;
1272 INIT_LIST_HEAD(&vma->anon_vma_chain);
1276 if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1278 if (vm_flags & VM_DENYWRITE) {
1279 error = deny_write_access(file);
1284 vma->vm_file = file;
1286 error = file->f_op->mmap(file, vma);
1288 goto unmap_and_free_vma;
1289 if (vm_flags & VM_EXECUTABLE)
1290 added_exe_file_vma(mm);
1292 /* Can addr have changed??
1294 * Answer: Yes, several device drivers can do it in their
1295 * f_op->mmap method. -DaveM
1297 addr = vma->vm_start;
1298 pgoff = vma->vm_pgoff;
1299 vm_flags = vma->vm_flags;
1300 } else if (vm_flags & VM_SHARED) {
1301 error = shmem_zero_setup(vma);
1306 if (vma_wants_writenotify(vma)) {
1307 pgprot_t pprot = vma->vm_page_prot;
1309 /* Can vma->vm_page_prot have changed??
1311 * Answer: Yes, drivers may have changed it in their
1312 * f_op->mmap method.
1314 * Ensures that vmas marked as uncached stay that way.
1316 vma->vm_page_prot = vm_get_page_prot(vm_flags & ~VM_SHARED);
1317 if (pgprot_val(pprot) == pgprot_val(pgprot_noncached(pprot)))
1318 vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
1321 vma_link(mm, vma, prev, rb_link, rb_parent);
1322 file = vma->vm_file;
1324 /* Once vma denies write, undo our temporary denial count */
1326 atomic_inc(&inode->i_writecount);
1328 perf_event_mmap(vma);
1330 mm->total_vm += len >> PAGE_SHIFT;
1331 vm_stat_account(mm, vm_flags, file, len >> PAGE_SHIFT);
1332 if (vm_flags & VM_LOCKED) {
1333 if (!mlock_vma_pages_range(vma, addr, addr + len))
1334 mm->locked_vm += (len >> PAGE_SHIFT);
1335 } else if ((flags & MAP_POPULATE) && !(flags & MAP_NONBLOCK))
1336 make_pages_present(addr, addr + len);
1341 atomic_inc(&inode->i_writecount);
1342 vma->vm_file = NULL;
1345 /* Undo any partial mapping done by a device driver. */
1346 unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);
1349 kmem_cache_free(vm_area_cachep, vma);
1352 vm_unacct_memory(charged);
1356 /* Get an address range which is currently unmapped.
1357 * For shmat() with addr=0.
1359 * Ugly calling convention alert:
1360 * Return value with the low bits set means error value,
1362 * if (ret & ~PAGE_MASK)
1365 * This function "knows" that -ENOMEM has the bits set.
1367 #ifndef HAVE_ARCH_UNMAPPED_AREA
1369 arch_get_unmapped_area(struct file *filp, unsigned long addr,
1370 unsigned long len, unsigned long pgoff, unsigned long flags)
1372 struct mm_struct *mm = current->mm;
1373 struct vm_area_struct *vma;
1374 unsigned long start_addr;
1376 if (len > TASK_SIZE - mmap_min_addr)
1379 if (flags & MAP_FIXED)
1383 addr = PAGE_ALIGN(addr);
1384 vma = find_vma(mm, addr);
1385 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
1386 (!vma || addr + len <= vma->vm_start))
1389 if (len > mm->cached_hole_size) {
1390 start_addr = addr = mm->free_area_cache;
1392 start_addr = addr = TASK_UNMAPPED_BASE;
1393 mm->cached_hole_size = 0;
1397 for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
1398 /* At this point: (!vma || addr < vma->vm_end). */
1399 if (TASK_SIZE - len < addr) {
1401 * Start a new search - just in case we missed
1404 if (start_addr != TASK_UNMAPPED_BASE) {
1405 addr = TASK_UNMAPPED_BASE;
1407 mm->cached_hole_size = 0;
1412 if (!vma || addr + len <= vma->vm_start) {
1414 * Remember the place where we stopped the search:
1416 mm->free_area_cache = addr + len;
1419 if (addr + mm->cached_hole_size < vma->vm_start)
1420 mm->cached_hole_size = vma->vm_start - addr;
1426 void arch_unmap_area(struct mm_struct *mm, unsigned long addr)
1429 * Is this a new hole at the lowest possible address?
1431 if (addr >= TASK_UNMAPPED_BASE && addr < mm->free_area_cache) {
1432 mm->free_area_cache = addr;
1433 mm->cached_hole_size = ~0UL;
1438 * This mmap-allocator allocates new areas top-down from below the
1439 * stack's low limit (the base):
1441 #ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
1443 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
1444 const unsigned long len, const unsigned long pgoff,
1445 const unsigned long flags)
1447 struct vm_area_struct *vma;
1448 struct mm_struct *mm = current->mm;
1449 unsigned long addr = addr0;
1450 unsigned long low_limit = max(PAGE_SIZE, mmap_min_addr);
1452 /* requested length too big for entire address space */
1453 if (len > TASK_SIZE - mmap_min_addr)
1456 if (flags & MAP_FIXED)
1459 /* requesting a specific address */
1461 addr = PAGE_ALIGN(addr);
1462 vma = find_vma(mm, addr);
1463 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
1464 (!vma || addr + len <= vma->vm_start))
1468 /* check if free_area_cache is useful for us */
1469 if (len <= mm->cached_hole_size) {
1470 mm->cached_hole_size = 0;
1471 mm->free_area_cache = mm->mmap_base;
1474 /* either no address requested or can't fit in requested address hole */
1475 addr = mm->free_area_cache;
1477 /* make sure it can fit in the remaining address space */
1478 if (addr >= low_limit + len) {
1479 vma = find_vma(mm, addr-len);
1480 if (!vma || addr <= vma->vm_start)
1481 /* remember the address as a hint for next time */
1482 return (mm->free_area_cache = addr-len);
1485 if (mm->mmap_base < low_limit + len)
1488 addr = mm->mmap_base-len;
1492 * Lookup failure means no vma is above this address,
1493 * else if new region fits below vma->vm_start,
1494 * return with success:
1496 vma = find_vma(mm, addr);
1497 if (!vma || addr+len <= vma->vm_start)
1498 /* remember the address as a hint for next time */
1499 return (mm->free_area_cache = addr);
1501 /* remember the largest hole we saw so far */
1502 if (addr + mm->cached_hole_size < vma->vm_start)
1503 mm->cached_hole_size = vma->vm_start - addr;
1505 /* try just below the current vma->vm_start */
1506 addr = vma->vm_start-len;
1507 } while (vma->vm_start >= low_limit + len);
1511 * A failed mmap() very likely causes application failure,
1512 * so fall back to the bottom-up function here. This scenario
1513 * can happen with large stack limits and large mmap()
1516 mm->cached_hole_size = ~0UL;
1517 mm->free_area_cache = TASK_UNMAPPED_BASE;
1518 addr = arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
1520 * Restore the topdown base:
1522 mm->free_area_cache = mm->mmap_base;
1523 mm->cached_hole_size = ~0UL;
1529 void arch_unmap_area_topdown(struct mm_struct *mm, unsigned long addr)
1532 * Is this a new hole at the highest possible address?
1534 if (addr > mm->free_area_cache)
1535 mm->free_area_cache = addr;
1537 /* dont allow allocations above current base */
1538 if (mm->free_area_cache > mm->mmap_base)
1539 mm->free_area_cache = mm->mmap_base;
1543 get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
1544 unsigned long pgoff, unsigned long flags)
1546 unsigned long (*get_area)(struct file *, unsigned long,
1547 unsigned long, unsigned long, unsigned long);
1549 unsigned long error = arch_mmap_check(addr, len, flags);
1553 /* Careful about overflows.. */
1554 if (len > TASK_SIZE)
1557 get_area = current->mm->get_unmapped_area;
1558 if (file && file->f_op && file->f_op->get_unmapped_area)
1559 get_area = file->f_op->get_unmapped_area;
1560 addr = get_area(file, addr, len, pgoff, flags);
1561 if (IS_ERR_VALUE(addr))
1564 if (addr > TASK_SIZE - len)
1566 if (addr & ~PAGE_MASK)
1569 return arch_rebalance_pgtables(addr, len);
1572 EXPORT_SYMBOL(get_unmapped_area);
1574 /* Look up the first VMA which satisfies addr < vm_end, NULL if none. */
1575 struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
1577 struct vm_area_struct *vma = NULL;
1580 /* Check the cache first. */
1581 /* (Cache hit rate is typically around 35%.) */
1582 vma = ACCESS_ONCE(mm->mmap_cache);
1583 if (!(vma && vma->vm_end > addr && vma->vm_start <= addr)) {
1584 struct rb_node * rb_node;
1586 rb_node = mm->mm_rb.rb_node;
1590 struct vm_area_struct * vma_tmp;
1592 vma_tmp = rb_entry(rb_node,
1593 struct vm_area_struct, vm_rb);
1595 if (vma_tmp->vm_end > addr) {
1597 if (vma_tmp->vm_start <= addr)
1599 rb_node = rb_node->rb_left;
1601 rb_node = rb_node->rb_right;
1604 mm->mmap_cache = vma;
1610 EXPORT_SYMBOL(find_vma);
1612 /* Same as find_vma, but also return a pointer to the previous VMA in *pprev. */
1613 struct vm_area_struct *
1614 find_vma_prev(struct mm_struct *mm, unsigned long addr,
1615 struct vm_area_struct **pprev)
1617 struct vm_area_struct *vma = NULL, *prev = NULL;
1618 struct rb_node *rb_node;
1622 /* Guard against addr being lower than the first VMA */
1625 /* Go through the RB tree quickly. */
1626 rb_node = mm->mm_rb.rb_node;
1629 struct vm_area_struct *vma_tmp;
1630 vma_tmp = rb_entry(rb_node, struct vm_area_struct, vm_rb);
1632 if (addr < vma_tmp->vm_end) {
1633 rb_node = rb_node->rb_left;
1636 if (!prev->vm_next || (addr < prev->vm_next->vm_end))
1638 rb_node = rb_node->rb_right;
1644 return prev ? prev->vm_next : vma;
1648 * Verify that the stack growth is acceptable and
1649 * update accounting. This is shared with both the
1650 * grow-up and grow-down cases.
1652 static int acct_stack_growth(struct vm_area_struct *vma, unsigned long size, unsigned long grow)
1654 struct mm_struct *mm = vma->vm_mm;
1655 struct rlimit *rlim = current->signal->rlim;
1656 unsigned long new_start, actual_size;
1658 /* address space limit tests */
1659 if (!may_expand_vm(mm, grow))
1662 /* Stack limit test */
1664 if (size && (vma->vm_flags & (VM_GROWSUP | VM_GROWSDOWN)))
1665 actual_size -= PAGE_SIZE;
1666 if (actual_size > ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur))
1669 /* mlock limit tests */
1670 if (vma->vm_flags & VM_LOCKED) {
1671 unsigned long locked;
1672 unsigned long limit;
1673 locked = mm->locked_vm + grow;
1674 limit = ACCESS_ONCE(rlim[RLIMIT_MEMLOCK].rlim_cur);
1675 limit >>= PAGE_SHIFT;
1676 if (locked > limit && !capable(CAP_IPC_LOCK))
1680 /* Check to ensure the stack will not grow into a hugetlb-only region */
1681 new_start = (vma->vm_flags & VM_GROWSUP) ? vma->vm_start :
1683 if (is_hugepage_only_range(vma->vm_mm, new_start, size))
1687 * Overcommit.. This must be the final test, as it will
1688 * update security statistics.
1690 if (security_vm_enough_memory_mm(mm, grow))
1693 /* Ok, everything looks good - let it rip */
1694 mm->total_vm += grow;
1695 if (vma->vm_flags & VM_LOCKED)
1696 mm->locked_vm += grow;
1697 vm_stat_account(mm, vma->vm_flags, vma->vm_file, grow);
1701 #if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
1703 * PA-RISC uses this for its stack; IA64 for its Register Backing Store.
1704 * vma is the last one with address > vma->vm_end. Have to extend vma.
1706 int expand_upwards(struct vm_area_struct *vma, unsigned long address)
1710 if (!(vma->vm_flags & VM_GROWSUP))
1714 * We must make sure the anon_vma is allocated
1715 * so that the anon_vma locking is not a noop.
1717 if (unlikely(anon_vma_prepare(vma)))
1719 vma_lock_anon_vma(vma);
1722 * vma->vm_start/vm_end cannot change under us because the caller
1723 * is required to hold the mmap_sem in read mode. We need the
1724 * anon_vma lock to serialize against concurrent expand_stacks.
1725 * Also guard against wrapping around to address 0.
1727 if (address < PAGE_ALIGN(address+4))
1728 address = PAGE_ALIGN(address+4);
1730 vma_unlock_anon_vma(vma);
1735 /* Somebody else might have raced and expanded it already */
1736 if (address > vma->vm_end) {
1737 unsigned long size, grow;
1739 size = address - vma->vm_start;
1740 grow = (address - vma->vm_end) >> PAGE_SHIFT;
1743 if (vma->vm_pgoff + (size >> PAGE_SHIFT) >= vma->vm_pgoff) {
1744 error = acct_stack_growth(vma, size, grow);
1746 vma->vm_end = address;
1747 perf_event_mmap(vma);
1751 vma_unlock_anon_vma(vma);
1752 khugepaged_enter_vma_merge(vma, vma->vm_flags);
1755 #endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
1758 * vma is the first one with address < vma->vm_start. Have to extend vma.
1760 int expand_downwards(struct vm_area_struct *vma,
1761 unsigned long address)
1766 * We must make sure the anon_vma is allocated
1767 * so that the anon_vma locking is not a noop.
1769 if (unlikely(anon_vma_prepare(vma)))
1772 address &= PAGE_MASK;
1773 error = security_file_mmap(NULL, 0, 0, 0, address, 1);
1777 vma_lock_anon_vma(vma);
1780 * vma->vm_start/vm_end cannot change under us because the caller
1781 * is required to hold the mmap_sem in read mode. We need the
1782 * anon_vma lock to serialize against concurrent expand_stacks.
1785 /* Somebody else might have raced and expanded it already */
1786 if (address < vma->vm_start) {
1787 unsigned long size, grow;
1789 size = vma->vm_end - address;
1790 grow = (vma->vm_start - address) >> PAGE_SHIFT;
1793 if (grow <= vma->vm_pgoff) {
1794 error = acct_stack_growth(vma, size, grow);
1796 vma->vm_start = address;
1797 vma->vm_pgoff -= grow;
1798 perf_event_mmap(vma);
1802 vma_unlock_anon_vma(vma);
1803 khugepaged_enter_vma_merge(vma, vma->vm_flags);
1807 #ifdef CONFIG_STACK_GROWSUP
1808 int expand_stack(struct vm_area_struct *vma, unsigned long address)
1810 return expand_upwards(vma, address);
1813 struct vm_area_struct *
1814 find_extend_vma(struct mm_struct *mm, unsigned long addr)
1816 struct vm_area_struct *vma, *prev;
1819 vma = find_vma_prev(mm, addr, &prev);
1820 if (vma && (vma->vm_start <= addr))
1822 if (!prev || expand_stack(prev, addr))
1824 if (prev->vm_flags & VM_LOCKED) {
1825 mlock_vma_pages_range(prev, addr, prev->vm_end);
1830 int expand_stack(struct vm_area_struct *vma, unsigned long address)
1832 return expand_downwards(vma, address);
1835 struct vm_area_struct *
1836 find_extend_vma(struct mm_struct * mm, unsigned long addr)
1838 struct vm_area_struct * vma;
1839 unsigned long start;
1842 vma = find_vma(mm,addr);
1845 if (vma->vm_start <= addr)
1847 if (!(vma->vm_flags & VM_GROWSDOWN))
1849 start = vma->vm_start;
1850 if (expand_stack(vma, addr))
1852 if (vma->vm_flags & VM_LOCKED) {
1853 mlock_vma_pages_range(vma, addr, start);
1860 * Ok - we have the memory areas we should free on the vma list,
1861 * so release them, and do the vma updates.
1863 * Called with the mm semaphore held.
1865 static void remove_vma_list(struct mm_struct *mm, struct vm_area_struct *vma)
1867 /* Update high watermark before we lower total_vm */
1868 update_hiwater_vm(mm);
1870 long nrpages = vma_pages(vma);
1872 mm->total_vm -= nrpages;
1873 vm_stat_account(mm, vma->vm_flags, vma->vm_file, -nrpages);
1874 vma = remove_vma(vma);
1880 * Get rid of page table information in the indicated region.
1882 * Called with the mm semaphore held.
1884 static void unmap_region(struct mm_struct *mm,
1885 struct vm_area_struct *vma, struct vm_area_struct *prev,
1886 unsigned long start, unsigned long end)
1888 struct vm_area_struct *next = prev? prev->vm_next: mm->mmap;
1889 struct mmu_gather tlb;
1890 unsigned long nr_accounted = 0;
1893 tlb_gather_mmu(&tlb, mm, 0);
1894 update_hiwater_rss(mm);
1895 unmap_vmas(&tlb, vma, start, end, &nr_accounted, NULL);
1896 vm_unacct_memory(nr_accounted);
1897 free_pgtables(&tlb, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
1898 next ? next->vm_start : 0);
1899 tlb_finish_mmu(&tlb, start, end);
1903 * Create a list of vma's touched by the unmap, removing them from the mm's
1904 * vma list as we go..
1907 detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
1908 struct vm_area_struct *prev, unsigned long end)
1910 struct vm_area_struct **insertion_point;
1911 struct vm_area_struct *tail_vma = NULL;
1914 insertion_point = (prev ? &prev->vm_next : &mm->mmap);
1915 vma->vm_prev = NULL;
1917 rb_erase(&vma->vm_rb, &mm->mm_rb);
1921 } while (vma && vma->vm_start < end);
1922 *insertion_point = vma;
1924 vma->vm_prev = prev;
1925 tail_vma->vm_next = NULL;
1926 if (mm->unmap_area == arch_unmap_area)
1927 addr = prev ? prev->vm_end : mm->mmap_base;
1929 addr = vma ? vma->vm_start : mm->mmap_base;
1930 mm->unmap_area(mm, addr);
1931 mm->mmap_cache = NULL; /* Kill the cache. */
1935 * __split_vma() bypasses sysctl_max_map_count checking. We use this on the
1936 * munmap path where it doesn't make sense to fail.
1938 static int __split_vma(struct mm_struct * mm, struct vm_area_struct * vma,
1939 unsigned long addr, int new_below)
1941 struct mempolicy *pol;
1942 struct vm_area_struct *new;
1945 if (is_vm_hugetlb_page(vma) && (addr &
1946 ~(huge_page_mask(hstate_vma(vma)))))
1949 new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
1953 /* most fields are the same, copy all, and then fixup */
1956 INIT_LIST_HEAD(&new->anon_vma_chain);
1961 new->vm_start = addr;
1962 new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
1965 pol = mpol_dup(vma_policy(vma));
1970 vma_set_policy(new, pol);
1972 if (anon_vma_clone(new, vma))
1976 get_file(new->vm_file);
1977 if (vma->vm_flags & VM_EXECUTABLE)
1978 added_exe_file_vma(mm);
1981 if (new->vm_ops && new->vm_ops->open)
1982 new->vm_ops->open(new);
1985 err = vma_adjust(vma, addr, vma->vm_end, vma->vm_pgoff +
1986 ((addr - new->vm_start) >> PAGE_SHIFT), new);
1988 err = vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new);
1994 /* Clean everything up if vma_adjust failed. */
1995 if (new->vm_ops && new->vm_ops->close)
1996 new->vm_ops->close(new);
1998 if (vma->vm_flags & VM_EXECUTABLE)
1999 removed_exe_file_vma(mm);
2002 unlink_anon_vmas(new);
2006 kmem_cache_free(vm_area_cachep, new);
2012 * Split a vma into two pieces at address 'addr', a new vma is allocated
2013 * either for the first part or the tail.
2015 int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
2016 unsigned long addr, int new_below)
2018 if (mm->map_count >= sysctl_max_map_count)
2021 return __split_vma(mm, vma, addr, new_below);
2024 /* Munmap is split into 2 main parts -- this part which finds
2025 * what needs doing, and the areas themselves, which do the
2026 * work. This now handles partial unmappings.
2027 * Jeremy Fitzhardinge <jeremy@goop.org>
2029 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
2032 struct vm_area_struct *vma, *prev, *last;
2034 if ((start & ~PAGE_MASK) || start > TASK_SIZE || len > TASK_SIZE-start)
2037 if ((len = PAGE_ALIGN(len)) == 0)
2040 /* Find the first overlapping VMA */
2041 vma = find_vma(mm, start);
2044 prev = vma->vm_prev;
2045 /* we have start < vma->vm_end */
2047 /* if it doesn't overlap, we have nothing.. */
2049 if (vma->vm_start >= end)
2053 * If we need to split any vma, do it now to save pain later.
2055 * Note: mremap's move_vma VM_ACCOUNT handling assumes a partially
2056 * unmapped vm_area_struct will remain in use: so lower split_vma
2057 * places tmp vma above, and higher split_vma places tmp vma below.
2059 if (start > vma->vm_start) {
2063 * Make sure that map_count on return from munmap() will
2064 * not exceed its limit; but let map_count go just above
2065 * its limit temporarily, to help free resources as expected.
2067 if (end < vma->vm_end && mm->map_count >= sysctl_max_map_count)
2070 error = __split_vma(mm, vma, start, 0);
2076 /* Does it split the last one? */
2077 last = find_vma(mm, end);
2078 if (last && end > last->vm_start) {
2079 int error = __split_vma(mm, last, end, 1);
2083 vma = prev? prev->vm_next: mm->mmap;
2086 * unlock any mlock()ed ranges before detaching vmas
2088 if (mm->locked_vm) {
2089 struct vm_area_struct *tmp = vma;
2090 while (tmp && tmp->vm_start < end) {
2091 if (tmp->vm_flags & VM_LOCKED) {
2092 mm->locked_vm -= vma_pages(tmp);
2093 munlock_vma_pages_all(tmp);
2100 * Remove the vma's, and unmap the actual pages
2102 detach_vmas_to_be_unmapped(mm, vma, prev, end);
2103 unmap_region(mm, vma, prev, start, end);
2105 /* Fix up all other VM information */
2106 remove_vma_list(mm, vma);
2111 EXPORT_SYMBOL(do_munmap);
2113 SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
2116 struct mm_struct *mm = current->mm;
2118 profile_munmap(addr);
2120 down_write(&mm->mmap_sem);
2121 ret = do_munmap(mm, addr, len);
2122 up_write(&mm->mmap_sem);
2126 static inline void verify_mm_writelocked(struct mm_struct *mm)
2128 #ifdef CONFIG_DEBUG_VM
2129 if (unlikely(down_read_trylock(&mm->mmap_sem))) {
2131 up_read(&mm->mmap_sem);
2137 * this is really a simplified "do_mmap". it only handles
2138 * anonymous maps. eventually we may be able to do some
2139 * brk-specific accounting here.
2141 unsigned long do_brk(unsigned long addr, unsigned long len)
2143 struct mm_struct * mm = current->mm;
2144 struct vm_area_struct * vma, * prev;
2145 unsigned long flags;
2146 struct rb_node ** rb_link, * rb_parent;
2147 pgoff_t pgoff = addr >> PAGE_SHIFT;
2150 len = PAGE_ALIGN(len);
2154 error = security_file_mmap(NULL, 0, 0, 0, addr, 1);
2158 flags = VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
2160 error = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
2161 if (error & ~PAGE_MASK)
2167 if (mm->def_flags & VM_LOCKED) {
2168 unsigned long locked, lock_limit;
2169 locked = len >> PAGE_SHIFT;
2170 locked += mm->locked_vm;
2171 lock_limit = rlimit(RLIMIT_MEMLOCK);
2172 lock_limit >>= PAGE_SHIFT;
2173 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
2178 * mm->mmap_sem is required to protect against another thread
2179 * changing the mappings in case we sleep.
2181 verify_mm_writelocked(mm);
2184 * Clear old maps. this also does some error checking for us
2187 vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
2188 if (vma && vma->vm_start < addr + len) {
2189 if (do_munmap(mm, addr, len))
2194 /* Check against address space limits *after* clearing old maps... */
2195 if (!may_expand_vm(mm, len >> PAGE_SHIFT))
2198 if (mm->map_count > sysctl_max_map_count)
2201 if (security_vm_enough_memory(len >> PAGE_SHIFT))
2204 /* Can we just expand an old private anonymous mapping? */
2205 vma = vma_merge(mm, prev, addr, addr + len, flags,
2206 NULL, NULL, pgoff, NULL);
2211 * create a vma struct for an anonymous mapping
2213 vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
2215 vm_unacct_memory(len >> PAGE_SHIFT);
2219 INIT_LIST_HEAD(&vma->anon_vma_chain);
2221 vma->vm_start = addr;
2222 vma->vm_end = addr + len;
2223 vma->vm_pgoff = pgoff;
2224 vma->vm_flags = flags;
2225 vma->vm_page_prot = vm_get_page_prot(flags);
2226 vma_link(mm, vma, prev, rb_link, rb_parent);
2228 perf_event_mmap(vma);
2229 mm->total_vm += len >> PAGE_SHIFT;
2230 if (flags & VM_LOCKED) {
2231 if (!mlock_vma_pages_range(vma, addr, addr + len))
2232 mm->locked_vm += (len >> PAGE_SHIFT);
2237 EXPORT_SYMBOL(do_brk);
2239 /* Release all mmaps. */
2240 void exit_mmap(struct mm_struct *mm)
2242 struct mmu_gather tlb;
2243 struct vm_area_struct *vma;
2244 unsigned long nr_accounted = 0;
2247 /* mm's last user has gone, and its about to be pulled down */
2248 mmu_notifier_release(mm);
2250 if (mm->locked_vm) {
2253 if (vma->vm_flags & VM_LOCKED)
2254 munlock_vma_pages_all(vma);
2262 if (!vma) /* Can happen if dup_mmap() received an OOM */
2267 tlb_gather_mmu(&tlb, mm, 1);
2268 /* update_hiwater_rss(mm) here? but nobody should be looking */
2269 /* Use -1 here to ensure all VMAs in the mm are unmapped */
2270 end = unmap_vmas(&tlb, vma, 0, -1, &nr_accounted, NULL);
2271 vm_unacct_memory(nr_accounted);
2273 free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, 0);
2274 tlb_finish_mmu(&tlb, 0, end);
2277 * Walk the list again, actually closing and freeing it,
2278 * with preemption enabled, without holding any MM locks.
2281 vma = remove_vma(vma);
2283 BUG_ON(mm->nr_ptes > (FIRST_USER_ADDRESS+PMD_SIZE-1)>>PMD_SHIFT);
2286 /* Insert vm structure into process list sorted by address
2287 * and into the inode's i_mmap tree. If vm_file is non-NULL
2288 * then i_mmap_mutex is taken here.
2290 int insert_vm_struct(struct mm_struct * mm, struct vm_area_struct * vma)
2292 struct vm_area_struct * __vma, * prev;
2293 struct rb_node ** rb_link, * rb_parent;
2296 * The vm_pgoff of a purely anonymous vma should be irrelevant
2297 * until its first write fault, when page's anon_vma and index
2298 * are set. But now set the vm_pgoff it will almost certainly
2299 * end up with (unless mremap moves it elsewhere before that
2300 * first wfault), so /proc/pid/maps tells a consistent story.
2302 * By setting it to reflect the virtual start address of the
2303 * vma, merges and splits can happen in a seamless way, just
2304 * using the existing file pgoff checks and manipulations.
2305 * Similarly in do_mmap_pgoff and in do_brk.
2307 if (!vma->vm_file) {
2308 BUG_ON(vma->anon_vma);
2309 vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;
2311 __vma = find_vma_prepare(mm,vma->vm_start,&prev,&rb_link,&rb_parent);
2312 if (__vma && __vma->vm_start < vma->vm_end)
2314 if ((vma->vm_flags & VM_ACCOUNT) &&
2315 security_vm_enough_memory_mm(mm, vma_pages(vma)))
2317 vma_link(mm, vma, prev, rb_link, rb_parent);
2322 * Copy the vma structure to a new location in the same mm,
2323 * prior to moving page table entries, to effect an mremap move.
2325 struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
2326 unsigned long addr, unsigned long len, pgoff_t pgoff)
2328 struct vm_area_struct *vma = *vmap;
2329 unsigned long vma_start = vma->vm_start;
2330 struct mm_struct *mm = vma->vm_mm;
2331 struct vm_area_struct *new_vma, *prev;
2332 struct rb_node **rb_link, *rb_parent;
2333 struct mempolicy *pol;
2336 * If anonymous vma has not yet been faulted, update new pgoff
2337 * to match new location, to increase its chance of merging.
2339 if (!vma->vm_file && !vma->anon_vma)
2340 pgoff = addr >> PAGE_SHIFT;
2342 find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
2343 new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags,
2344 vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma));
2347 * Source vma may have been merged into new_vma
2349 if (vma_start >= new_vma->vm_start &&
2350 vma_start < new_vma->vm_end)
2353 new_vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
2356 pol = mpol_dup(vma_policy(vma));
2359 INIT_LIST_HEAD(&new_vma->anon_vma_chain);
2360 if (anon_vma_clone(new_vma, vma))
2361 goto out_free_mempol;
2362 vma_set_policy(new_vma, pol);
2363 new_vma->vm_start = addr;
2364 new_vma->vm_end = addr + len;
2365 new_vma->vm_pgoff = pgoff;
2366 if (new_vma->vm_file) {
2367 get_file(new_vma->vm_file);
2368 if (vma->vm_flags & VM_EXECUTABLE)
2369 added_exe_file_vma(mm);
2371 if (new_vma->vm_ops && new_vma->vm_ops->open)
2372 new_vma->vm_ops->open(new_vma);
2373 vma_link(mm, new_vma, prev, rb_link, rb_parent);
2381 kmem_cache_free(vm_area_cachep, new_vma);
2386 * Return true if the calling process may expand its vm space by the passed
2389 int may_expand_vm(struct mm_struct *mm, unsigned long npages)
2391 unsigned long cur = mm->total_vm; /* pages */
2394 lim = rlimit(RLIMIT_AS) >> PAGE_SHIFT;
2396 if (cur + npages > lim)
2402 static int special_mapping_fault(struct vm_area_struct *vma,
2403 struct vm_fault *vmf)
2406 struct page **pages;
2409 * special mappings have no vm_file, and in that case, the mm
2410 * uses vm_pgoff internally. So we have to subtract it from here.
2411 * We are allowed to do this because we are the mm; do not copy
2412 * this code into drivers!
2414 pgoff = vmf->pgoff - vma->vm_pgoff;
2416 for (pages = vma->vm_private_data; pgoff && *pages; ++pages)
2420 struct page *page = *pages;
2426 return VM_FAULT_SIGBUS;
2430 * Having a close hook prevents vma merging regardless of flags.
2432 static void special_mapping_close(struct vm_area_struct *vma)
2436 static const struct vm_operations_struct special_mapping_vmops = {
2437 .close = special_mapping_close,
2438 .fault = special_mapping_fault,
2442 * Called with mm->mmap_sem held for writing.
2443 * Insert a new vma covering the given region, with the given flags.
2444 * Its pages are supplied by the given array of struct page *.
2445 * The array can be shorter than len >> PAGE_SHIFT if it's null-terminated.
2446 * The region past the last page supplied will always produce SIGBUS.
2447 * The array pointer and the pages it points to are assumed to stay alive
2448 * for as long as this mapping might exist.
2450 int install_special_mapping(struct mm_struct *mm,
2451 unsigned long addr, unsigned long len,
2452 unsigned long vm_flags, struct page **pages)
2455 struct vm_area_struct *vma;
2457 vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
2458 if (unlikely(vma == NULL))
2461 INIT_LIST_HEAD(&vma->anon_vma_chain);
2463 vma->vm_start = addr;
2464 vma->vm_end = addr + len;
2466 vma->vm_flags = vm_flags | mm->def_flags | VM_DONTEXPAND;
2467 vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
2469 vma->vm_ops = &special_mapping_vmops;
2470 vma->vm_private_data = pages;
2472 ret = security_file_mmap(NULL, 0, 0, 0, vma->vm_start, 1);
2476 ret = insert_vm_struct(mm, vma);
2480 mm->total_vm += len >> PAGE_SHIFT;
2482 perf_event_mmap(vma);
2487 kmem_cache_free(vm_area_cachep, vma);
2491 static DEFINE_MUTEX(mm_all_locks_mutex);
2493 static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma)
2495 if (!test_bit(0, (unsigned long *) &anon_vma->root->head.next)) {
2497 * The LSB of head.next can't change from under us
2498 * because we hold the mm_all_locks_mutex.
2500 mutex_lock_nest_lock(&anon_vma->root->mutex, &mm->mmap_sem);
2502 * We can safely modify head.next after taking the
2503 * anon_vma->root->mutex. If some other vma in this mm shares
2504 * the same anon_vma we won't take it again.
2506 * No need of atomic instructions here, head.next
2507 * can't change from under us thanks to the
2508 * anon_vma->root->mutex.
2510 if (__test_and_set_bit(0, (unsigned long *)
2511 &anon_vma->root->head.next))
2516 static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping)
2518 if (!test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
2520 * AS_MM_ALL_LOCKS can't change from under us because
2521 * we hold the mm_all_locks_mutex.
2523 * Operations on ->flags have to be atomic because
2524 * even if AS_MM_ALL_LOCKS is stable thanks to the
2525 * mm_all_locks_mutex, there may be other cpus
2526 * changing other bitflags in parallel to us.
2528 if (test_and_set_bit(AS_MM_ALL_LOCKS, &mapping->flags))
2530 mutex_lock_nest_lock(&mapping->i_mmap_mutex, &mm->mmap_sem);
2535 * This operation locks against the VM for all pte/vma/mm related
2536 * operations that could ever happen on a certain mm. This includes
2537 * vmtruncate, try_to_unmap, and all page faults.
2539 * The caller must take the mmap_sem in write mode before calling
2540 * mm_take_all_locks(). The caller isn't allowed to release the
2541 * mmap_sem until mm_drop_all_locks() returns.
2543 * mmap_sem in write mode is required in order to block all operations
2544 * that could modify pagetables and free pages without need of
2545 * altering the vma layout (for example populate_range() with
2546 * nonlinear vmas). It's also needed in write mode to avoid new
2547 * anon_vmas to be associated with existing vmas.
2549 * A single task can't take more than one mm_take_all_locks() in a row
2550 * or it would deadlock.
2552 * The LSB in anon_vma->head.next and the AS_MM_ALL_LOCKS bitflag in
2553 * mapping->flags avoid to take the same lock twice, if more than one
2554 * vma in this mm is backed by the same anon_vma or address_space.
2556 * We can take all the locks in random order because the VM code
2557 * taking i_mmap_mutex or anon_vma->mutex outside the mmap_sem never
2558 * takes more than one of them in a row. Secondly we're protected
2559 * against a concurrent mm_take_all_locks() by the mm_all_locks_mutex.
2561 * mm_take_all_locks() and mm_drop_all_locks are expensive operations
2562 * that may have to take thousand of locks.
2564 * mm_take_all_locks() can fail if it's interrupted by signals.
2566 int mm_take_all_locks(struct mm_struct *mm)
2568 struct vm_area_struct *vma;
2569 struct anon_vma_chain *avc;
2571 BUG_ON(down_read_trylock(&mm->mmap_sem));
2573 mutex_lock(&mm_all_locks_mutex);
2575 for (vma = mm->mmap; vma; vma = vma->vm_next) {
2576 if (signal_pending(current))
2578 if (vma->vm_file && vma->vm_file->f_mapping)
2579 vm_lock_mapping(mm, vma->vm_file->f_mapping);
2582 for (vma = mm->mmap; vma; vma = vma->vm_next) {
2583 if (signal_pending(current))
2586 list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
2587 vm_lock_anon_vma(mm, avc->anon_vma);
2593 mm_drop_all_locks(mm);
2597 static void vm_unlock_anon_vma(struct anon_vma *anon_vma)
2599 if (test_bit(0, (unsigned long *) &anon_vma->root->head.next)) {
2601 * The LSB of head.next can't change to 0 from under
2602 * us because we hold the mm_all_locks_mutex.
2604 * We must however clear the bitflag before unlocking
2605 * the vma so the users using the anon_vma->head will
2606 * never see our bitflag.
2608 * No need of atomic instructions here, head.next
2609 * can't change from under us until we release the
2610 * anon_vma->root->mutex.
2612 if (!__test_and_clear_bit(0, (unsigned long *)
2613 &anon_vma->root->head.next))
2615 anon_vma_unlock(anon_vma);
2619 static void vm_unlock_mapping(struct address_space *mapping)
2621 if (test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
2623 * AS_MM_ALL_LOCKS can't change to 0 from under us
2624 * because we hold the mm_all_locks_mutex.
2626 mutex_unlock(&mapping->i_mmap_mutex);
2627 if (!test_and_clear_bit(AS_MM_ALL_LOCKS,
2634 * The mmap_sem cannot be released by the caller until
2635 * mm_drop_all_locks() returns.
2637 void mm_drop_all_locks(struct mm_struct *mm)
2639 struct vm_area_struct *vma;
2640 struct anon_vma_chain *avc;
2642 BUG_ON(down_read_trylock(&mm->mmap_sem));
2643 BUG_ON(!mutex_is_locked(&mm_all_locks_mutex));
2645 for (vma = mm->mmap; vma; vma = vma->vm_next) {
2647 list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
2648 vm_unlock_anon_vma(avc->anon_vma);
2649 if (vma->vm_file && vma->vm_file->f_mapping)
2650 vm_unlock_mapping(vma->vm_file->f_mapping);
2653 mutex_unlock(&mm_all_locks_mutex);
2657 * initialise the VMA slab
2659 void __init mmap_init(void)
2663 ret = percpu_counter_init(&vm_committed_as, 0);