Root/mm/mmap.c

1/*
2 * mm/mmap.c
3 *
4 * Written by obz.
5 *
6 * Address space accounting code <alan@lxorguk.ukuu.org.uk>
7 */
8
9#include <linux/slab.h>
10#include <linux/backing-dev.h>
11#include <linux/mm.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>
20#include <linux/fs.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>
33#include <linux/uprobes.h>
34
35#include <asm/uaccess.h>
36#include <asm/cacheflush.h>
37#include <asm/tlb.h>
38#include <asm/mmu_context.h>
39
40#include "internal.h"
41
42#ifndef arch_mmap_check
43#define arch_mmap_check(addr, len, flags) (0)
44#endif
45
46#ifndef arch_rebalance_pgtables
47#define arch_rebalance_pgtables(addr, len) (addr)
48#endif
49
50static void unmap_region(struct mm_struct *mm,
51        struct vm_area_struct *vma, struct vm_area_struct *prev,
52        unsigned long start, unsigned long end);
53
54/*
55 * WARNING: the debugging will use recursive algorithms so never enable this
56 * unless you know what you are doing.
57 */
58#undef DEBUG_MM_RB
59
60/* description of effects of mapping type and prot in current implementation.
61 * this is due to the limited x86 page protection hardware. The expected
62 * behavior is in parens:
63 *
64 * map_type prot
65 * PROT_NONE PROT_READ PROT_WRITE PROT_EXEC
66 * MAP_SHARED r: (no) no r: (yes) yes r: (no) yes r: (no) yes
67 * w: (no) no w: (no) no w: (yes) yes w: (no) no
68 * x: (no) no x: (no) yes x: (no) yes x: (yes) yes
69 *
70 * MAP_PRIVATE r: (no) no r: (yes) yes r: (no) yes r: (no) yes
71 * w: (no) no w: (no) no w: (copy) copy w: (no) no
72 * x: (no) no x: (no) yes x: (no) yes x: (yes) yes
73 *
74 */
75pgprot_t protection_map[16] = {
76    __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
77    __S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
78};
79
80pgprot_t vm_get_page_prot(unsigned long vm_flags)
81{
82    return __pgprot(pgprot_val(protection_map[vm_flags &
83                (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
84            pgprot_val(arch_vm_get_page_prot(vm_flags)));
85}
86EXPORT_SYMBOL(vm_get_page_prot);
87
88int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS; /* heuristic overcommit */
89int sysctl_overcommit_ratio __read_mostly = 50; /* default is 50% */
90int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
91/*
92 * Make sure vm_committed_as in one cacheline and not cacheline shared with
93 * other variables. It can be updated by several CPUs frequently.
94 */
95struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
96
97/*
98 * Check that a process has enough memory to allocate a new virtual
99 * mapping. 0 means there is enough memory for the allocation to
100 * succeed and -ENOMEM implies there is not.
101 *
102 * We currently support three overcommit policies, which are set via the
103 * vm.overcommit_memory sysctl. See Documentation/vm/overcommit-accounting
104 *
105 * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
106 * Additional code 2002 Jul 20 by Robert Love.
107 *
108 * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
109 *
110 * Note this is a helper function intended to be used by LSMs which
111 * wish to use this logic.
112 */
113int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
114{
115    unsigned long free, allowed;
116
117    vm_acct_memory(pages);
118
119    /*
120     * Sometimes we want to use more memory than we have
121     */
122    if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
123        return 0;
124
125    if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
126        free = global_page_state(NR_FREE_PAGES);
127        free += global_page_state(NR_FILE_PAGES);
128
129        /*
130         * shmem pages shouldn't be counted as free in this
131         * case, they can't be purged, only swapped out, and
132         * that won't affect the overall amount of available
133         * memory in the system.
134         */
135        free -= global_page_state(NR_SHMEM);
136
137        free += nr_swap_pages;
138
139        /*
140         * Any slabs which are created with the
141         * SLAB_RECLAIM_ACCOUNT flag claim to have contents
142         * which are reclaimable, under pressure. The dentry
143         * cache and most inode caches should fall into this
144         */
145        free += global_page_state(NR_SLAB_RECLAIMABLE);
146
147        /*
148         * Leave reserved pages. The pages are not for anonymous pages.
149         */
150        if (free <= totalreserve_pages)
151            goto error;
152        else
153            free -= totalreserve_pages;
154
155        /*
156         * Leave the last 3% for root
157         */
158        if (!cap_sys_admin)
159            free -= free / 32;
160
161        if (free > pages)
162            return 0;
163
164        goto error;
165    }
166
167    allowed = (totalram_pages - hugetlb_total_pages())
168               * sysctl_overcommit_ratio / 100;
169    /*
170     * Leave the last 3% for root
171     */
172    if (!cap_sys_admin)
173        allowed -= allowed / 32;
174    allowed += total_swap_pages;
175
176    /* Don't let a single process grow too big:
177       leave 3% of the size of this process for other processes */
178    if (mm)
179        allowed -= mm->total_vm / 32;
180
181    if (percpu_counter_read_positive(&vm_committed_as) < allowed)
182        return 0;
183error:
184    vm_unacct_memory(pages);
185
186    return -ENOMEM;
187}
188
189/*
190 * Requires inode->i_mapping->i_mmap_mutex
191 */
192static void __remove_shared_vm_struct(struct vm_area_struct *vma,
193        struct file *file, struct address_space *mapping)
194{
195    if (vma->vm_flags & VM_DENYWRITE)
196        atomic_inc(&file->f_path.dentry->d_inode->i_writecount);
197    if (vma->vm_flags & VM_SHARED)
198        mapping->i_mmap_writable--;
199
200    flush_dcache_mmap_lock(mapping);
201    if (unlikely(vma->vm_flags & VM_NONLINEAR))
202        list_del_init(&vma->shared.vm_set.list);
203    else
204        vma_prio_tree_remove(vma, &mapping->i_mmap);
205    flush_dcache_mmap_unlock(mapping);
206}
207
208/*
209 * Unlink a file-based vm structure from its prio_tree, to hide
210 * vma from rmap and vmtruncate before freeing its page tables.
211 */
212void unlink_file_vma(struct vm_area_struct *vma)
213{
214    struct file *file = vma->vm_file;
215
216    if (file) {
217        struct address_space *mapping = file->f_mapping;
218        mutex_lock(&mapping->i_mmap_mutex);
219        __remove_shared_vm_struct(vma, file, mapping);
220        mutex_unlock(&mapping->i_mmap_mutex);
221    }
222}
223
224/*
225 * Close a vm structure and free it, returning the next.
226 */
227static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
228{
229    struct vm_area_struct *next = vma->vm_next;
230
231    might_sleep();
232    if (vma->vm_ops && vma->vm_ops->close)
233        vma->vm_ops->close(vma);
234    if (vma->vm_file) {
235        fput(vma->vm_file);
236        if (vma->vm_flags & VM_EXECUTABLE)
237            removed_exe_file_vma(vma->vm_mm);
238    }
239    mpol_put(vma_policy(vma));
240    kmem_cache_free(vm_area_cachep, vma);
241    return next;
242}
243
244static unsigned long do_brk(unsigned long addr, unsigned long len);
245
246SYSCALL_DEFINE1(brk, unsigned long, brk)
247{
248    unsigned long rlim, retval;
249    unsigned long newbrk, oldbrk;
250    struct mm_struct *mm = current->mm;
251    unsigned long min_brk;
252
253    down_write(&mm->mmap_sem);
254
255#ifdef CONFIG_COMPAT_BRK
256    /*
257     * CONFIG_COMPAT_BRK can still be overridden by setting
258     * randomize_va_space to 2, which will still cause mm->start_brk
259     * to be arbitrarily shifted
260     */
261    if (current->brk_randomized)
262        min_brk = mm->start_brk;
263    else
264        min_brk = mm->end_data;
265#else
266    min_brk = mm->start_brk;
267#endif
268    if (brk < min_brk)
269        goto out;
270
271    /*
272     * Check against rlimit here. If this check is done later after the test
273     * of oldbrk with newbrk then it can escape the test and let the data
274     * segment grow beyond its set limit the in case where the limit is
275     * not page aligned -Ram Gupta
276     */
277    rlim = rlimit(RLIMIT_DATA);
278    if (rlim < RLIM_INFINITY && (brk - mm->start_brk) +
279            (mm->end_data - mm->start_data) > rlim)
280        goto out;
281
282    newbrk = PAGE_ALIGN(brk);
283    oldbrk = PAGE_ALIGN(mm->brk);
284    if (oldbrk == newbrk)
285        goto set_brk;
286
287    /* Always allow shrinking brk. */
288    if (brk <= mm->brk) {
289        if (!do_munmap(mm, newbrk, oldbrk-newbrk))
290            goto set_brk;
291        goto out;
292    }
293
294    /* Check against existing mmap mappings. */
295    if (find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE))
296        goto out;
297
298    /* Ok, looks good - let it rip. */
299    if (do_brk(oldbrk, newbrk-oldbrk) != oldbrk)
300        goto out;
301set_brk:
302    mm->brk = brk;
303out:
304    retval = mm->brk;
305    up_write(&mm->mmap_sem);
306    return retval;
307}
308
309#ifdef DEBUG_MM_RB
310static int browse_rb(struct rb_root *root)
311{
312    int i = 0, j;
313    struct rb_node *nd, *pn = NULL;
314    unsigned long prev = 0, pend = 0;
315
316    for (nd = rb_first(root); nd; nd = rb_next(nd)) {
317        struct vm_area_struct *vma;
318        vma = rb_entry(nd, struct vm_area_struct, vm_rb);
319        if (vma->vm_start < prev)
320            printk("vm_start %lx prev %lx\n", vma->vm_start, prev), i = -1;
321        if (vma->vm_start < pend)
322            printk("vm_start %lx pend %lx\n", vma->vm_start, pend);
323        if (vma->vm_start > vma->vm_end)
324            printk("vm_end %lx < vm_start %lx\n", vma->vm_end, vma->vm_start);
325        i++;
326        pn = nd;
327        prev = vma->vm_start;
328        pend = vma->vm_end;
329    }
330    j = 0;
331    for (nd = pn; nd; nd = rb_prev(nd)) {
332        j++;
333    }
334    if (i != j)
335        printk("backwards %d, forwards %d\n", j, i), i = 0;
336    return i;
337}
338
339void validate_mm(struct mm_struct *mm)
340{
341    int bug = 0;
342    int i = 0;
343    struct vm_area_struct *tmp = mm->mmap;
344    while (tmp) {
345        tmp = tmp->vm_next;
346        i++;
347    }
348    if (i != mm->map_count)
349        printk("map_count %d vm_next %d\n", mm->map_count, i), bug = 1;
350    i = browse_rb(&mm->mm_rb);
351    if (i != mm->map_count)
352        printk("map_count %d rb %d\n", mm->map_count, i), bug = 1;
353    BUG_ON(bug);
354}
355#else
356#define validate_mm(mm) do { } while (0)
357#endif
358
359static struct vm_area_struct *
360find_vma_prepare(struct mm_struct *mm, unsigned long addr,
361        struct vm_area_struct **pprev, struct rb_node ***rb_link,
362        struct rb_node ** rb_parent)
363{
364    struct vm_area_struct * vma;
365    struct rb_node ** __rb_link, * __rb_parent, * rb_prev;
366
367    __rb_link = &mm->mm_rb.rb_node;
368    rb_prev = __rb_parent = NULL;
369    vma = NULL;
370
371    while (*__rb_link) {
372        struct vm_area_struct *vma_tmp;
373
374        __rb_parent = *__rb_link;
375        vma_tmp = rb_entry(__rb_parent, struct vm_area_struct, vm_rb);
376
377        if (vma_tmp->vm_end > addr) {
378            vma = vma_tmp;
379            if (vma_tmp->vm_start <= addr)
380                break;
381            __rb_link = &__rb_parent->rb_left;
382        } else {
383            rb_prev = __rb_parent;
384            __rb_link = &__rb_parent->rb_right;
385        }
386    }
387
388    *pprev = NULL;
389    if (rb_prev)
390        *pprev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
391    *rb_link = __rb_link;
392    *rb_parent = __rb_parent;
393    return vma;
394}
395
396void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
397        struct rb_node **rb_link, struct rb_node *rb_parent)
398{
399    rb_link_node(&vma->vm_rb, rb_parent, rb_link);
400    rb_insert_color(&vma->vm_rb, &mm->mm_rb);
401}
402
403static void __vma_link_file(struct vm_area_struct *vma)
404{
405    struct file *file;
406
407    file = vma->vm_file;
408    if (file) {
409        struct address_space *mapping = file->f_mapping;
410
411        if (vma->vm_flags & VM_DENYWRITE)
412            atomic_dec(&file->f_path.dentry->d_inode->i_writecount);
413        if (vma->vm_flags & VM_SHARED)
414            mapping->i_mmap_writable++;
415
416        flush_dcache_mmap_lock(mapping);
417        if (unlikely(vma->vm_flags & VM_NONLINEAR))
418            vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
419        else
420            vma_prio_tree_insert(vma, &mapping->i_mmap);
421        flush_dcache_mmap_unlock(mapping);
422    }
423}
424
425static void
426__vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
427    struct vm_area_struct *prev, struct rb_node **rb_link,
428    struct rb_node *rb_parent)
429{
430    __vma_link_list(mm, vma, prev, rb_parent);
431    __vma_link_rb(mm, vma, rb_link, rb_parent);
432}
433
434static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
435            struct vm_area_struct *prev, struct rb_node **rb_link,
436            struct rb_node *rb_parent)
437{
438    struct address_space *mapping = NULL;
439
440    if (vma->vm_file)
441        mapping = vma->vm_file->f_mapping;
442
443    if (mapping)
444        mutex_lock(&mapping->i_mmap_mutex);
445
446    __vma_link(mm, vma, prev, rb_link, rb_parent);
447    __vma_link_file(vma);
448
449    if (mapping)
450        mutex_unlock(&mapping->i_mmap_mutex);
451
452    mm->map_count++;
453    validate_mm(mm);
454}
455
456/*
457 * Helper for vma_adjust() in the split_vma insert case: insert a vma into the
458 * mm's list and rbtree. It has already been inserted into the prio_tree.
459 */
460static void __insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
461{
462    struct vm_area_struct *__vma, *prev;
463    struct rb_node **rb_link, *rb_parent;
464
465    __vma = find_vma_prepare(mm, vma->vm_start,&prev, &rb_link, &rb_parent);
466    BUG_ON(__vma && __vma->vm_start < vma->vm_end);
467    __vma_link(mm, vma, prev, rb_link, rb_parent);
468    mm->map_count++;
469}
470
471static inline void
472__vma_unlink(struct mm_struct *mm, struct vm_area_struct *vma,
473        struct vm_area_struct *prev)
474{
475    struct vm_area_struct *next = vma->vm_next;
476
477    prev->vm_next = next;
478    if (next)
479        next->vm_prev = prev;
480    rb_erase(&vma->vm_rb, &mm->mm_rb);
481    if (mm->mmap_cache == vma)
482        mm->mmap_cache = prev;
483}
484
485/*
486 * We cannot adjust vm_start, vm_end, vm_pgoff fields of a vma that
487 * is already present in an i_mmap tree without adjusting the tree.
488 * The following helper function should be used when such adjustments
489 * are necessary. The "insert" vma (if any) is to be inserted
490 * before we drop the necessary locks.
491 */
492int vma_adjust(struct vm_area_struct *vma, unsigned long start,
493    unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert)
494{
495    struct mm_struct *mm = vma->vm_mm;
496    struct vm_area_struct *next = vma->vm_next;
497    struct vm_area_struct *importer = NULL;
498    struct address_space *mapping = NULL;
499    struct prio_tree_root *root = NULL;
500    struct anon_vma *anon_vma = NULL;
501    struct file *file = vma->vm_file;
502    long adjust_next = 0;
503    int remove_next = 0;
504
505    if (next && !insert) {
506        struct vm_area_struct *exporter = NULL;
507
508        if (end >= next->vm_end) {
509            /*
510             * vma expands, overlapping all the next, and
511             * perhaps the one after too (mprotect case 6).
512             */
513again: remove_next = 1 + (end > next->vm_end);
514            end = next->vm_end;
515            exporter = next;
516            importer = vma;
517        } else if (end > next->vm_start) {
518            /*
519             * vma expands, overlapping part of the next:
520             * mprotect case 5 shifting the boundary up.
521             */
522            adjust_next = (end - next->vm_start) >> PAGE_SHIFT;
523            exporter = next;
524            importer = vma;
525        } else if (end < vma->vm_end) {
526            /*
527             * vma shrinks, and !insert tells it's not
528             * split_vma inserting another: so it must be
529             * mprotect case 4 shifting the boundary down.
530             */
531            adjust_next = - ((vma->vm_end - end) >> PAGE_SHIFT);
532            exporter = vma;
533            importer = next;
534        }
535
536        /*
537         * Easily overlooked: when mprotect shifts the boundary,
538         * make sure the expanding vma has anon_vma set if the
539         * shrinking vma had, to cover any anon pages imported.
540         */
541        if (exporter && exporter->anon_vma && !importer->anon_vma) {
542            if (anon_vma_clone(importer, exporter))
543                return -ENOMEM;
544            importer->anon_vma = exporter->anon_vma;
545        }
546    }
547
548    if (file) {
549        mapping = file->f_mapping;
550        if (!(vma->vm_flags & VM_NONLINEAR)) {
551            root = &mapping->i_mmap;
552            uprobe_munmap(vma, vma->vm_start, vma->vm_end);
553
554            if (adjust_next)
555                uprobe_munmap(next, next->vm_start,
556                            next->vm_end);
557        }
558
559        mutex_lock(&mapping->i_mmap_mutex);
560        if (insert) {
561            /*
562             * Put into prio_tree now, so instantiated pages
563             * are visible to arm/parisc __flush_dcache_page
564             * throughout; but we cannot insert into address
565             * space until vma start or end is updated.
566             */
567            __vma_link_file(insert);
568        }
569    }
570
571    vma_adjust_trans_huge(vma, start, end, adjust_next);
572
573    /*
574     * When changing only vma->vm_end, we don't really need anon_vma
575     * lock. This is a fairly rare case by itself, but the anon_vma
576     * lock may be shared between many sibling processes. Skipping
577     * the lock for brk adjustments makes a difference sometimes.
578     */
579    if (vma->anon_vma && (importer || start != vma->vm_start)) {
580        anon_vma = vma->anon_vma;
581        anon_vma_lock(anon_vma);
582    }
583
584    if (root) {
585        flush_dcache_mmap_lock(mapping);
586        vma_prio_tree_remove(vma, root);
587        if (adjust_next)
588            vma_prio_tree_remove(next, root);
589    }
590
591    vma->vm_start = start;
592    vma->vm_end = end;
593    vma->vm_pgoff = pgoff;
594    if (adjust_next) {
595        next->vm_start += adjust_next << PAGE_SHIFT;
596        next->vm_pgoff += adjust_next;
597    }
598
599    if (root) {
600        if (adjust_next)
601            vma_prio_tree_insert(next, root);
602        vma_prio_tree_insert(vma, root);
603        flush_dcache_mmap_unlock(mapping);
604    }
605
606    if (remove_next) {
607        /*
608         * vma_merge has merged next into vma, and needs
609         * us to remove next before dropping the locks.
610         */
611        __vma_unlink(mm, next, vma);
612        if (file)
613            __remove_shared_vm_struct(next, file, mapping);
614    } else if (insert) {
615        /*
616         * split_vma has split insert from vma, and needs
617         * us to insert it before dropping the locks
618         * (it may either follow vma or precede it).
619         */
620        __insert_vm_struct(mm, insert);
621    }
622
623    if (anon_vma)
624        anon_vma_unlock(anon_vma);
625    if (mapping)
626        mutex_unlock(&mapping->i_mmap_mutex);
627
628    if (root) {
629        uprobe_mmap(vma);
630
631        if (adjust_next)
632            uprobe_mmap(next);
633    }
634
635    if (remove_next) {
636        if (file) {
637            uprobe_munmap(next, next->vm_start, next->vm_end);
638            fput(file);
639            if (next->vm_flags & VM_EXECUTABLE)
640                removed_exe_file_vma(mm);
641        }
642        if (next->anon_vma)
643            anon_vma_merge(vma, next);
644        mm->map_count--;
645        mpol_put(vma_policy(next));
646        kmem_cache_free(vm_area_cachep, next);
647        /*
648         * In mprotect's case 6 (see comments on vma_merge),
649         * we must remove another next too. It would clutter
650         * up the code too much to do both in one go.
651         */
652        if (remove_next == 2) {
653            next = vma->vm_next;
654            goto again;
655        }
656    }
657    if (insert && file)
658        uprobe_mmap(insert);
659
660    validate_mm(mm);
661
662    return 0;
663}
664
665/*
666 * If the vma has a ->close operation then the driver probably needs to release
667 * per-vma resources, so we don't attempt to merge those.
668 */
669static inline int is_mergeable_vma(struct vm_area_struct *vma,
670            struct file *file, unsigned long vm_flags)
671{
672    /* VM_CAN_NONLINEAR may get set later by f_op->mmap() */
673    if ((vma->vm_flags ^ vm_flags) & ~VM_CAN_NONLINEAR)
674        return 0;
675    if (vma->vm_file != file)
676        return 0;
677    if (vma->vm_ops && vma->vm_ops->close)
678        return 0;
679    return 1;
680}
681
682static inline int is_mergeable_anon_vma(struct anon_vma *anon_vma1,
683                    struct anon_vma *anon_vma2,
684                    struct vm_area_struct *vma)
685{
686    /*
687     * The list_is_singular() test is to avoid merging VMA cloned from
688     * parents. This can improve scalability caused by anon_vma lock.
689     */
690    if ((!anon_vma1 || !anon_vma2) && (!vma ||
691        list_is_singular(&vma->anon_vma_chain)))
692        return 1;
693    return anon_vma1 == anon_vma2;
694}
695
696/*
697 * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
698 * in front of (at a lower virtual address and file offset than) the vma.
699 *
700 * We cannot merge two vmas if they have differently assigned (non-NULL)
701 * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
702 *
703 * We don't check here for the merged mmap wrapping around the end of pagecache
704 * indices (16TB on ia32) because do_mmap_pgoff() does not permit mmap's which
705 * wrap, nor mmaps which cover the final page at index -1UL.
706 */
707static int
708can_vma_merge_before(struct vm_area_struct *vma, unsigned long vm_flags,
709    struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff)
710{
711    if (is_mergeable_vma(vma, file, vm_flags) &&
712        is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
713        if (vma->vm_pgoff == vm_pgoff)
714            return 1;
715    }
716    return 0;
717}
718
719/*
720 * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
721 * beyond (at a higher virtual address and file offset than) the vma.
722 *
723 * We cannot merge two vmas if they have differently assigned (non-NULL)
724 * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
725 */
726static int
727can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
728    struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff)
729{
730    if (is_mergeable_vma(vma, file, vm_flags) &&
731        is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
732        pgoff_t vm_pglen;
733        vm_pglen = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
734        if (vma->vm_pgoff + vm_pglen == vm_pgoff)
735            return 1;
736    }
737    return 0;
738}
739
740/*
741 * Given a mapping request (addr,end,vm_flags,file,pgoff), figure out
742 * whether that can be merged with its predecessor or its successor.
743 * Or both (it neatly fills a hole).
744 *
745 * In most cases - when called for mmap, brk or mremap - [addr,end) is
746 * certain not to be mapped by the time vma_merge is called; but when
747 * called for mprotect, it is certain to be already mapped (either at
748 * an offset within prev, or at the start of next), and the flags of
749 * this area are about to be changed to vm_flags - and the no-change
750 * case has already been eliminated.
751 *
752 * The following mprotect cases have to be considered, where AAAA is
753 * the area passed down from mprotect_fixup, never extending beyond one
754 * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
755 *
756 * AAAA AAAA AAAA AAAA
757 * PPPPPPNNNNNN PPPPPPNNNNNN PPPPPPNNNNNN PPPPNNNNXXXX
758 * cannot merge might become might become might become
759 * PPNNNNNNNNNN PPPPPPPPPPNN PPPPPPPPPPPP 6 or
760 * mmap, brk or case 4 below case 5 below PPPPPPPPXXXX 7 or
761 * mremap move: PPPPNNNNNNNN 8
762 * AAAA
763 * PPPP NNNN PPPPPPPPPPPP PPPPPPPPNNNN PPPPNNNNNNNN
764 * might become case 1 below case 2 below case 3 below
765 *
766 * Odd one out? Case 8, because it extends NNNN but needs flags of XXXX:
767 * mprotect_fixup updates vm_flags & vm_page_prot on successful return.
768 */
769struct vm_area_struct *vma_merge(struct mm_struct *mm,
770            struct vm_area_struct *prev, unsigned long addr,
771            unsigned long end, unsigned long vm_flags,
772                 struct anon_vma *anon_vma, struct file *file,
773            pgoff_t pgoff, struct mempolicy *policy)
774{
775    pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
776    struct vm_area_struct *area, *next;
777    int err;
778
779    /*
780     * We later require that vma->vm_flags == vm_flags,
781     * so this tests vma->vm_flags & VM_SPECIAL, too.
782     */
783    if (vm_flags & VM_SPECIAL)
784        return NULL;
785
786    if (prev)
787        next = prev->vm_next;
788    else
789        next = mm->mmap;
790    area = next;
791    if (next && next->vm_end == end) /* cases 6, 7, 8 */
792        next = next->vm_next;
793
794    /*
795     * Can it merge with the predecessor?
796     */
797    if (prev && prev->vm_end == addr &&
798              mpol_equal(vma_policy(prev), policy) &&
799            can_vma_merge_after(prev, vm_flags,
800                        anon_vma, file, pgoff)) {
801        /*
802         * OK, it can. Can we now merge in the successor as well?
803         */
804        if (next && end == next->vm_start &&
805                mpol_equal(policy, vma_policy(next)) &&
806                can_vma_merge_before(next, vm_flags,
807                    anon_vma, file, pgoff+pglen) &&
808                is_mergeable_anon_vma(prev->anon_vma,
809                              next->anon_vma, NULL)) {
810                            /* cases 1, 6 */
811            err = vma_adjust(prev, prev->vm_start,
812                next->vm_end, prev->vm_pgoff, NULL);
813        } else /* cases 2, 5, 7 */
814            err = vma_adjust(prev, prev->vm_start,
815                end, prev->vm_pgoff, NULL);
816        if (err)
817            return NULL;
818        khugepaged_enter_vma_merge(prev);
819        return prev;
820    }
821
822    /*
823     * Can this new request be merged in front of next?
824     */
825    if (next && end == next->vm_start &&
826             mpol_equal(policy, vma_policy(next)) &&
827            can_vma_merge_before(next, vm_flags,
828                    anon_vma, file, pgoff+pglen)) {
829        if (prev && addr < prev->vm_end) /* case 4 */
830            err = vma_adjust(prev, prev->vm_start,
831                addr, prev->vm_pgoff, NULL);
832        else /* cases 3, 8 */
833            err = vma_adjust(area, addr, next->vm_end,
834                next->vm_pgoff - pglen, NULL);
835        if (err)
836            return NULL;
837        khugepaged_enter_vma_merge(area);
838        return area;
839    }
840
841    return NULL;
842}
843
844/*
845 * Rough compatbility check to quickly see if it's even worth looking
846 * at sharing an anon_vma.
847 *
848 * They need to have the same vm_file, and the flags can only differ
849 * in things that mprotect may change.
850 *
851 * NOTE! The fact that we share an anon_vma doesn't _have_ to mean that
852 * we can merge the two vma's. For example, we refuse to merge a vma if
853 * there is a vm_ops->close() function, because that indicates that the
854 * driver is doing some kind of reference counting. But that doesn't
855 * really matter for the anon_vma sharing case.
856 */
857static int anon_vma_compatible(struct vm_area_struct *a, struct vm_area_struct *b)
858{
859    return a->vm_end == b->vm_start &&
860        mpol_equal(vma_policy(a), vma_policy(b)) &&
861        a->vm_file == b->vm_file &&
862        !((a->vm_flags ^ b->vm_flags) & ~(VM_READ|VM_WRITE|VM_EXEC)) &&
863        b->vm_pgoff == a->vm_pgoff + ((b->vm_start - a->vm_start) >> PAGE_SHIFT);
864}
865
866/*
867 * Do some basic sanity checking to see if we can re-use the anon_vma
868 * from 'old'. The 'a'/'b' vma's are in VM order - one of them will be
869 * the same as 'old', the other will be the new one that is trying
870 * to share the anon_vma.
871 *
872 * NOTE! This runs with mm_sem held for reading, so it is possible that
873 * the anon_vma of 'old' is concurrently in the process of being set up
874 * by another page fault trying to merge _that_. But that's ok: if it
875 * is being set up, that automatically means that it will be a singleton
876 * acceptable for merging, so we can do all of this optimistically. But
877 * we do that ACCESS_ONCE() to make sure that we never re-load the pointer.
878 *
879 * IOW: that the "list_is_singular()" test on the anon_vma_chain only
880 * matters for the 'stable anon_vma' case (ie the thing we want to avoid
881 * is to return an anon_vma that is "complex" due to having gone through
882 * a fork).
883 *
884 * We also make sure that the two vma's are compatible (adjacent,
885 * and with the same memory policies). That's all stable, even with just
886 * a read lock on the mm_sem.
887 */
888static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, struct vm_area_struct *a, struct vm_area_struct *b)
889{
890    if (anon_vma_compatible(a, b)) {
891        struct anon_vma *anon_vma = ACCESS_ONCE(old->anon_vma);
892
893        if (anon_vma && list_is_singular(&old->anon_vma_chain))
894            return anon_vma;
895    }
896    return NULL;
897}
898
899/*
900 * find_mergeable_anon_vma is used by anon_vma_prepare, to check
901 * neighbouring vmas for a suitable anon_vma, before it goes off
902 * to allocate a new anon_vma. It checks because a repetitive
903 * sequence of mprotects and faults may otherwise lead to distinct
904 * anon_vmas being allocated, preventing vma merge in subsequent
905 * mprotect.
906 */
907struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
908{
909    struct anon_vma *anon_vma;
910    struct vm_area_struct *near;
911
912    near = vma->vm_next;
913    if (!near)
914        goto try_prev;
915
916    anon_vma = reusable_anon_vma(near, vma, near);
917    if (anon_vma)
918        return anon_vma;
919try_prev:
920    near = vma->vm_prev;
921    if (!near)
922        goto none;
923
924    anon_vma = reusable_anon_vma(near, near, vma);
925    if (anon_vma)
926        return anon_vma;
927none:
928    /*
929     * There's no absolute need to look only at touching neighbours:
930     * we could search further afield for "compatible" anon_vmas.
931     * But it would probably just be a waste of time searching,
932     * or lead to too many vmas hanging off the same anon_vma.
933     * We're trying to allow mprotect remerging later on,
934     * not trying to minimize memory used for anon_vmas.
935     */
936    return NULL;
937}
938
939#ifdef CONFIG_PROC_FS
940void vm_stat_account(struct mm_struct *mm, unsigned long flags,
941                        struct file *file, long pages)
942{
943    const unsigned long stack_flags
944        = VM_STACK_FLAGS & (VM_GROWSUP|VM_GROWSDOWN);
945
946    mm->total_vm += pages;
947
948    if (file) {
949        mm->shared_vm += pages;
950        if ((flags & (VM_EXEC|VM_WRITE)) == VM_EXEC)
951            mm->exec_vm += pages;
952    } else if (flags & stack_flags)
953        mm->stack_vm += pages;
954    if (flags & (VM_RESERVED|VM_IO))
955        mm->reserved_vm += pages;
956}
957#endif /* CONFIG_PROC_FS */
958
959/*
960 * If a hint addr is less than mmap_min_addr change hint to be as
961 * low as possible but still greater than mmap_min_addr
962 */
963static inline unsigned long round_hint_to_min(unsigned long hint)
964{
965    hint &= PAGE_MASK;
966    if (((void *)hint != NULL) &&
967        (hint < mmap_min_addr))
968        return PAGE_ALIGN(mmap_min_addr);
969    return hint;
970}
971
972/*
973 * The caller must hold down_write(&current->mm->mmap_sem).
974 */
975
976unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
977            unsigned long len, unsigned long prot,
978            unsigned long flags, unsigned long pgoff)
979{
980    struct mm_struct * mm = current->mm;
981    struct inode *inode;
982    vm_flags_t vm_flags;
983
984    /*
985     * Does the application expect PROT_READ to imply PROT_EXEC?
986     *
987     * (the exception is when the underlying filesystem is noexec
988     * mounted, in which case we dont add PROT_EXEC.)
989     */
990    if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
991        if (!(file && (file->f_path.mnt->mnt_flags & MNT_NOEXEC)))
992            prot |= PROT_EXEC;
993
994    if (!len)
995        return -EINVAL;
996
997    if (!(flags & MAP_FIXED))
998        addr = round_hint_to_min(addr);
999
1000    /* Careful about overflows.. */
1001    len = PAGE_ALIGN(len);
1002    if (!len)
1003        return -ENOMEM;
1004
1005    /* offset overflow? */
1006    if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
1007               return -EOVERFLOW;
1008
1009    /* Too many mappings? */
1010    if (mm->map_count > sysctl_max_map_count)
1011        return -ENOMEM;
1012
1013    /* Obtain the address to map to. we verify (or select) it and ensure
1014     * that it represents a valid section of the address space.
1015     */
1016    addr = get_unmapped_area(file, addr, len, pgoff, flags);
1017    if (addr & ~PAGE_MASK)
1018        return addr;
1019
1020    /* Do simple checking here so the lower-level routines won't have
1021     * to. we assume access permissions have been handled by the open
1022     * of the memory object, so we don't do any here.
1023     */
1024    vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags) |
1025            mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
1026
1027    if (flags & MAP_LOCKED)
1028        if (!can_do_mlock())
1029            return -EPERM;
1030
1031    /* mlock MCL_FUTURE? */
1032    if (vm_flags & VM_LOCKED) {
1033        unsigned long locked, lock_limit;
1034        locked = len >> PAGE_SHIFT;
1035        locked += mm->locked_vm;
1036        lock_limit = rlimit(RLIMIT_MEMLOCK);
1037        lock_limit >>= PAGE_SHIFT;
1038        if (locked > lock_limit && !capable(CAP_IPC_LOCK))
1039            return -EAGAIN;
1040    }
1041
1042    inode = file ? file->f_path.dentry->d_inode : NULL;
1043
1044    if (file) {
1045        switch (flags & MAP_TYPE) {
1046        case MAP_SHARED:
1047            if ((prot&PROT_WRITE) && !(file->f_mode&FMODE_WRITE))
1048                return -EACCES;
1049
1050            /*
1051             * Make sure we don't allow writing to an append-only
1052             * file..
1053             */
1054            if (IS_APPEND(inode) && (file->f_mode & FMODE_WRITE))
1055                return -EACCES;
1056
1057            /*
1058             * Make sure there are no mandatory locks on the file.
1059             */
1060            if (locks_verify_locked(inode))
1061                return -EAGAIN;
1062
1063            vm_flags |= VM_SHARED | VM_MAYSHARE;
1064            if (!(file->f_mode & FMODE_WRITE))
1065                vm_flags &= ~(VM_MAYWRITE | VM_SHARED);
1066
1067            /* fall through */
1068        case MAP_PRIVATE:
1069            if (!(file->f_mode & FMODE_READ))
1070                return -EACCES;
1071            if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) {
1072                if (vm_flags & VM_EXEC)
1073                    return -EPERM;
1074                vm_flags &= ~VM_MAYEXEC;
1075            }
1076
1077            if (!file->f_op || !file->f_op->mmap)
1078                return -ENODEV;
1079            break;
1080
1081        default:
1082            return -EINVAL;
1083        }
1084    } else {
1085        switch (flags & MAP_TYPE) {
1086        case MAP_SHARED:
1087            /*
1088             * Ignore pgoff.
1089             */
1090            pgoff = 0;
1091            vm_flags |= VM_SHARED | VM_MAYSHARE;
1092            break;
1093        case MAP_PRIVATE:
1094            /*
1095             * Set pgoff according to addr for anon_vma.
1096             */
1097            pgoff = addr >> PAGE_SHIFT;
1098            break;
1099        default:
1100            return -EINVAL;
1101        }
1102    }
1103
1104    return mmap_region(file, addr, len, flags, vm_flags, pgoff);
1105}
1106
1107SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
1108        unsigned long, prot, unsigned long, flags,
1109        unsigned long, fd, unsigned long, pgoff)
1110{
1111    struct file *file = NULL;
1112    unsigned long retval = -EBADF;
1113
1114    if (!(flags & MAP_ANONYMOUS)) {
1115        audit_mmap_fd(fd, flags);
1116        if (unlikely(flags & MAP_HUGETLB))
1117            return -EINVAL;
1118        file = fget(fd);
1119        if (!file)
1120            goto out;
1121    } else if (flags & MAP_HUGETLB) {
1122        struct user_struct *user = NULL;
1123        /*
1124         * VM_NORESERVE is used because the reservations will be
1125         * taken when vm_ops->mmap() is called
1126         * A dummy user value is used because we are not locking
1127         * memory so no accounting is necessary
1128         */
1129        file = hugetlb_file_setup(HUGETLB_ANON_FILE, addr, len,
1130                        VM_NORESERVE, &user,
1131                        HUGETLB_ANONHUGE_INODE);
1132        if (IS_ERR(file))
1133            return PTR_ERR(file);
1134    }
1135
1136    flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
1137
1138    retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
1139    if (file)
1140        fput(file);
1141out:
1142    return retval;
1143}
1144
1145#ifdef __ARCH_WANT_SYS_OLD_MMAP
1146struct mmap_arg_struct {
1147    unsigned long addr;
1148    unsigned long len;
1149    unsigned long prot;
1150    unsigned long flags;
1151    unsigned long fd;
1152    unsigned long offset;
1153};
1154
1155SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
1156{
1157    struct mmap_arg_struct a;
1158
1159    if (copy_from_user(&a, arg, sizeof(a)))
1160        return -EFAULT;
1161    if (a.offset & ~PAGE_MASK)
1162        return -EINVAL;
1163
1164    return sys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
1165                  a.offset >> PAGE_SHIFT);
1166}
1167#endif /* __ARCH_WANT_SYS_OLD_MMAP */
1168
1169/*
1170 * Some shared mappigns will want the pages marked read-only
1171 * to track write events. If so, we'll downgrade vm_page_prot
1172 * to the private version (using protection_map[] without the
1173 * VM_SHARED bit).
1174 */
1175int vma_wants_writenotify(struct vm_area_struct *vma)
1176{
1177    vm_flags_t vm_flags = vma->vm_flags;
1178
1179    /* If it was private or non-writable, the write bit is already clear */
1180    if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED)))
1181        return 0;
1182
1183    /* The backer wishes to know when pages are first written to? */
1184    if (vma->vm_ops && vma->vm_ops->page_mkwrite)
1185        return 1;
1186
1187    /* The open routine did something to the protections already? */
1188    if (pgprot_val(vma->vm_page_prot) !=
1189        pgprot_val(vm_get_page_prot(vm_flags)))
1190        return 0;
1191
1192    /* Specialty mapping? */
1193    if (vm_flags & (VM_PFNMAP|VM_INSERTPAGE))
1194        return 0;
1195
1196    /* Can the mapping track the dirty pages? */
1197    return vma->vm_file && vma->vm_file->f_mapping &&
1198        mapping_cap_account_dirty(vma->vm_file->f_mapping);
1199}
1200
1201/*
1202 * We account for memory if it's a private writeable mapping,
1203 * not hugepages and VM_NORESERVE wasn't set.
1204 */
1205static inline int accountable_mapping(struct file *file, vm_flags_t vm_flags)
1206{
1207    /*
1208     * hugetlb has its own accounting separate from the core VM
1209     * VM_HUGETLB may not be set yet so we cannot check for that flag.
1210     */
1211    if (file && is_file_hugepages(file))
1212        return 0;
1213
1214    return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE;
1215}
1216
1217unsigned long mmap_region(struct file *file, unsigned long addr,
1218              unsigned long len, unsigned long flags,
1219              vm_flags_t vm_flags, unsigned long pgoff)
1220{
1221    struct mm_struct *mm = current->mm;
1222    struct vm_area_struct *vma, *prev;
1223    int correct_wcount = 0;
1224    int error;
1225    struct rb_node **rb_link, *rb_parent;
1226    unsigned long charged = 0;
1227    struct inode *inode = file ? file->f_path.dentry->d_inode : NULL;
1228
1229    /* Clear old maps */
1230    error = -ENOMEM;
1231munmap_back:
1232    vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
1233    if (vma && vma->vm_start < addr + len) {
1234        if (do_munmap(mm, addr, len))
1235            return -ENOMEM;
1236        goto munmap_back;
1237    }
1238
1239    /* Check against address space limit. */
1240    if (!may_expand_vm(mm, len >> PAGE_SHIFT))
1241        return -ENOMEM;
1242
1243    /*
1244     * Set 'VM_NORESERVE' if we should not account for the
1245     * memory use of this mapping.
1246     */
1247    if ((flags & MAP_NORESERVE)) {
1248        /* We honor MAP_NORESERVE if allowed to overcommit */
1249        if (sysctl_overcommit_memory != OVERCOMMIT_NEVER)
1250            vm_flags |= VM_NORESERVE;
1251
1252        /* hugetlb applies strict overcommit unless MAP_NORESERVE */
1253        if (file && is_file_hugepages(file))
1254            vm_flags |= VM_NORESERVE;
1255    }
1256
1257    /*
1258     * Private writable mapping: check memory availability
1259     */
1260    if (accountable_mapping(file, vm_flags)) {
1261        charged = len >> PAGE_SHIFT;
1262        if (security_vm_enough_memory_mm(mm, charged))
1263            return -ENOMEM;
1264        vm_flags |= VM_ACCOUNT;
1265    }
1266
1267    /*
1268     * Can we just expand an old mapping?
1269     */
1270    vma = vma_merge(mm, prev, addr, addr + len, vm_flags, NULL, file, pgoff, NULL);
1271    if (vma)
1272        goto out;
1273
1274    /*
1275     * Determine the object being mapped and call the appropriate
1276     * specific mapper. the address has already been validated, but
1277     * not unmapped, but the maps are removed from the list.
1278     */
1279    vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
1280    if (!vma) {
1281        error = -ENOMEM;
1282        goto unacct_error;
1283    }
1284
1285    vma->vm_mm = mm;
1286    vma->vm_start = addr;
1287    vma->vm_end = addr + len;
1288    vma->vm_flags = vm_flags;
1289    vma->vm_page_prot = vm_get_page_prot(vm_flags);
1290    vma->vm_pgoff = pgoff;
1291    INIT_LIST_HEAD(&vma->anon_vma_chain);
1292
1293    error = -EINVAL; /* when rejecting VM_GROWSDOWN|VM_GROWSUP */
1294
1295    if (file) {
1296        if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1297            goto free_vma;
1298        if (vm_flags & VM_DENYWRITE) {
1299            error = deny_write_access(file);
1300            if (error)
1301                goto free_vma;
1302            correct_wcount = 1;
1303        }
1304        vma->vm_file = file;
1305        get_file(file);
1306        error = file->f_op->mmap(file, vma);
1307        if (error)
1308            goto unmap_and_free_vma;
1309        if (vm_flags & VM_EXECUTABLE)
1310            added_exe_file_vma(mm);
1311
1312        /* Can addr have changed??
1313         *
1314         * Answer: Yes, several device drivers can do it in their
1315         * f_op->mmap method. -DaveM
1316         */
1317        addr = vma->vm_start;
1318        pgoff = vma->vm_pgoff;
1319        vm_flags = vma->vm_flags;
1320    } else if (vm_flags & VM_SHARED) {
1321        if (unlikely(vm_flags & (VM_GROWSDOWN|VM_GROWSUP)))
1322            goto free_vma;
1323        error = shmem_zero_setup(vma);
1324        if (error)
1325            goto free_vma;
1326    }
1327
1328    if (vma_wants_writenotify(vma)) {
1329        pgprot_t pprot = vma->vm_page_prot;
1330
1331        /* Can vma->vm_page_prot have changed??
1332         *
1333         * Answer: Yes, drivers may have changed it in their
1334         * f_op->mmap method.
1335         *
1336         * Ensures that vmas marked as uncached stay that way.
1337         */
1338        vma->vm_page_prot = vm_get_page_prot(vm_flags & ~VM_SHARED);
1339        if (pgprot_val(pprot) == pgprot_val(pgprot_noncached(pprot)))
1340            vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
1341    }
1342
1343    vma_link(mm, vma, prev, rb_link, rb_parent);
1344    file = vma->vm_file;
1345
1346    /* Once vma denies write, undo our temporary denial count */
1347    if (correct_wcount)
1348        atomic_inc(&inode->i_writecount);
1349out:
1350    perf_event_mmap(vma);
1351
1352    vm_stat_account(mm, vm_flags, file, len >> PAGE_SHIFT);
1353    if (vm_flags & VM_LOCKED) {
1354        if (!mlock_vma_pages_range(vma, addr, addr + len))
1355            mm->locked_vm += (len >> PAGE_SHIFT);
1356    } else if ((flags & MAP_POPULATE) && !(flags & MAP_NONBLOCK))
1357        make_pages_present(addr, addr + len);
1358
1359    if (file && uprobe_mmap(vma))
1360        /* matching probes but cannot insert */
1361        goto unmap_and_free_vma;
1362
1363    return addr;
1364
1365unmap_and_free_vma:
1366    if (correct_wcount)
1367        atomic_inc(&inode->i_writecount);
1368    vma->vm_file = NULL;
1369    fput(file);
1370
1371    /* Undo any partial mapping done by a device driver. */
1372    unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);
1373    charged = 0;
1374free_vma:
1375    kmem_cache_free(vm_area_cachep, vma);
1376unacct_error:
1377    if (charged)
1378        vm_unacct_memory(charged);
1379    return error;
1380}
1381
1382/* Get an address range which is currently unmapped.
1383 * For shmat() with addr=0.
1384 *
1385 * Ugly calling convention alert:
1386 * Return value with the low bits set means error value,
1387 * ie
1388 * if (ret & ~PAGE_MASK)
1389 * error = ret;
1390 *
1391 * This function "knows" that -ENOMEM has the bits set.
1392 */
1393#ifndef HAVE_ARCH_UNMAPPED_AREA
1394unsigned long
1395arch_get_unmapped_area(struct file *filp, unsigned long addr,
1396        unsigned long len, unsigned long pgoff, unsigned long flags)
1397{
1398    struct mm_struct *mm = current->mm;
1399    struct vm_area_struct *vma;
1400    unsigned long start_addr;
1401
1402    if (len > TASK_SIZE)
1403        return -ENOMEM;
1404
1405    if (flags & MAP_FIXED)
1406        return addr;
1407
1408    if (addr) {
1409        addr = PAGE_ALIGN(addr);
1410        vma = find_vma(mm, addr);
1411        if (TASK_SIZE - len >= addr &&
1412            (!vma || addr + len <= vma->vm_start))
1413            return addr;
1414    }
1415    if (len > mm->cached_hole_size) {
1416            start_addr = addr = mm->free_area_cache;
1417    } else {
1418            start_addr = addr = TASK_UNMAPPED_BASE;
1419            mm->cached_hole_size = 0;
1420    }
1421
1422full_search:
1423    for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
1424        /* At this point: (!vma || addr < vma->vm_end). */
1425        if (TASK_SIZE - len < addr) {
1426            /*
1427             * Start a new search - just in case we missed
1428             * some holes.
1429             */
1430            if (start_addr != TASK_UNMAPPED_BASE) {
1431                addr = TASK_UNMAPPED_BASE;
1432                    start_addr = addr;
1433                mm->cached_hole_size = 0;
1434                goto full_search;
1435            }
1436            return -ENOMEM;
1437        }
1438        if (!vma || addr + len <= vma->vm_start) {
1439            /*
1440             * Remember the place where we stopped the search:
1441             */
1442            mm->free_area_cache = addr + len;
1443            return addr;
1444        }
1445        if (addr + mm->cached_hole_size < vma->vm_start)
1446                mm->cached_hole_size = vma->vm_start - addr;
1447        addr = vma->vm_end;
1448    }
1449}
1450#endif
1451
1452void arch_unmap_area(struct mm_struct *mm, unsigned long addr)
1453{
1454    /*
1455     * Is this a new hole at the lowest possible address?
1456     */
1457    if (addr >= TASK_UNMAPPED_BASE && addr < mm->free_area_cache)
1458        mm->free_area_cache = addr;
1459}
1460
1461/*
1462 * This mmap-allocator allocates new areas top-down from below the
1463 * stack's low limit (the base):
1464 */
1465#ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
1466unsigned long
1467arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
1468              const unsigned long len, const unsigned long pgoff,
1469              const unsigned long flags)
1470{
1471    struct vm_area_struct *vma;
1472    struct mm_struct *mm = current->mm;
1473    unsigned long addr = addr0, start_addr;
1474
1475    /* requested length too big for entire address space */
1476    if (len > TASK_SIZE)
1477        return -ENOMEM;
1478
1479    if (flags & MAP_FIXED)
1480        return addr;
1481
1482    /* requesting a specific address */
1483    if (addr) {
1484        addr = PAGE_ALIGN(addr);
1485        vma = find_vma(mm, addr);
1486        if (TASK_SIZE - len >= addr &&
1487                (!vma || addr + len <= vma->vm_start))
1488            return addr;
1489    }
1490
1491    /* check if free_area_cache is useful for us */
1492    if (len <= mm->cached_hole_size) {
1493             mm->cached_hole_size = 0;
1494         mm->free_area_cache = mm->mmap_base;
1495     }
1496
1497try_again:
1498    /* either no address requested or can't fit in requested address hole */
1499    start_addr = addr = mm->free_area_cache;
1500
1501    if (addr < len)
1502        goto fail;
1503
1504    addr -= len;
1505    do {
1506        /*
1507         * Lookup failure means no vma is above this address,
1508         * else if new region fits below vma->vm_start,
1509         * return with success:
1510         */
1511        vma = find_vma(mm, addr);
1512        if (!vma || addr+len <= vma->vm_start)
1513            /* remember the address as a hint for next time */
1514            return (mm->free_area_cache = addr);
1515
1516         /* remember the largest hole we saw so far */
1517         if (addr + mm->cached_hole_size < vma->vm_start)
1518                 mm->cached_hole_size = vma->vm_start - addr;
1519
1520        /* try just below the current vma->vm_start */
1521        addr = vma->vm_start-len;
1522    } while (len < vma->vm_start);
1523
1524fail:
1525    /*
1526     * if hint left us with no space for the requested
1527     * mapping then try again:
1528     *
1529     * Note: this is different with the case of bottomup
1530     * which does the fully line-search, but we use find_vma
1531     * here that causes some holes skipped.
1532     */
1533    if (start_addr != mm->mmap_base) {
1534        mm->free_area_cache = mm->mmap_base;
1535        mm->cached_hole_size = 0;
1536        goto try_again;
1537    }
1538
1539    /*
1540     * A failed mmap() very likely causes application failure,
1541     * so fall back to the bottom-up function here. This scenario
1542     * can happen with large stack limits and large mmap()
1543     * allocations.
1544     */
1545    mm->cached_hole_size = ~0UL;
1546      mm->free_area_cache = TASK_UNMAPPED_BASE;
1547    addr = arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
1548    /*
1549     * Restore the topdown base:
1550     */
1551    mm->free_area_cache = mm->mmap_base;
1552    mm->cached_hole_size = ~0UL;
1553
1554    return addr;
1555}
1556#endif
1557
1558void arch_unmap_area_topdown(struct mm_struct *mm, unsigned long addr)
1559{
1560    /*
1561     * Is this a new hole at the highest possible address?
1562     */
1563    if (addr > mm->free_area_cache)
1564        mm->free_area_cache = addr;
1565
1566    /* dont allow allocations above current base */
1567    if (mm->free_area_cache > mm->mmap_base)
1568        mm->free_area_cache = mm->mmap_base;
1569}
1570
1571unsigned long
1572get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
1573        unsigned long pgoff, unsigned long flags)
1574{
1575    unsigned long (*get_area)(struct file *, unsigned long,
1576                  unsigned long, unsigned long, unsigned long);
1577
1578    unsigned long error = arch_mmap_check(addr, len, flags);
1579    if (error)
1580        return error;
1581
1582    /* Careful about overflows.. */
1583    if (len > TASK_SIZE)
1584        return -ENOMEM;
1585
1586    get_area = current->mm->get_unmapped_area;
1587    if (file && file->f_op && file->f_op->get_unmapped_area)
1588        get_area = file->f_op->get_unmapped_area;
1589    addr = get_area(file, addr, len, pgoff, flags);
1590    if (IS_ERR_VALUE(addr))
1591        return addr;
1592
1593    if (addr > TASK_SIZE - len)
1594        return -ENOMEM;
1595    if (addr & ~PAGE_MASK)
1596        return -EINVAL;
1597
1598    addr = arch_rebalance_pgtables(addr, len);
1599    error = security_mmap_addr(addr);
1600    return error ? error : addr;
1601}
1602
1603EXPORT_SYMBOL(get_unmapped_area);
1604
1605/* Look up the first VMA which satisfies addr < vm_end, NULL if none. */
1606struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
1607{
1608    struct vm_area_struct *vma = NULL;
1609
1610    if (WARN_ON_ONCE(!mm)) /* Remove this in linux-3.6 */
1611        return NULL;
1612
1613    /* Check the cache first. */
1614    /* (Cache hit rate is typically around 35%.) */
1615    vma = mm->mmap_cache;
1616    if (!(vma && vma->vm_end > addr && vma->vm_start <= addr)) {
1617        struct rb_node *rb_node;
1618
1619        rb_node = mm->mm_rb.rb_node;
1620        vma = NULL;
1621
1622        while (rb_node) {
1623            struct vm_area_struct *vma_tmp;
1624
1625            vma_tmp = rb_entry(rb_node,
1626                       struct vm_area_struct, vm_rb);
1627
1628            if (vma_tmp->vm_end > addr) {
1629                vma = vma_tmp;
1630                if (vma_tmp->vm_start <= addr)
1631                    break;
1632                rb_node = rb_node->rb_left;
1633            } else
1634                rb_node = rb_node->rb_right;
1635        }
1636        if (vma)
1637            mm->mmap_cache = vma;
1638    }
1639    return vma;
1640}
1641
1642EXPORT_SYMBOL(find_vma);
1643
1644/*
1645 * Same as find_vma, but also return a pointer to the previous VMA in *pprev.
1646 */
1647struct vm_area_struct *
1648find_vma_prev(struct mm_struct *mm, unsigned long addr,
1649            struct vm_area_struct **pprev)
1650{
1651    struct vm_area_struct *vma;
1652
1653    vma = find_vma(mm, addr);
1654    if (vma) {
1655        *pprev = vma->vm_prev;
1656    } else {
1657        struct rb_node *rb_node = mm->mm_rb.rb_node;
1658        *pprev = NULL;
1659        while (rb_node) {
1660            *pprev = rb_entry(rb_node, struct vm_area_struct, vm_rb);
1661            rb_node = rb_node->rb_right;
1662        }
1663    }
1664    return vma;
1665}
1666
1667/*
1668 * Verify that the stack growth is acceptable and
1669 * update accounting. This is shared with both the
1670 * grow-up and grow-down cases.
1671 */
1672static int acct_stack_growth(struct vm_area_struct *vma, unsigned long size, unsigned long grow)
1673{
1674    struct mm_struct *mm = vma->vm_mm;
1675    struct rlimit *rlim = current->signal->rlim;
1676    unsigned long new_start;
1677
1678    /* address space limit tests */
1679    if (!may_expand_vm(mm, grow))
1680        return -ENOMEM;
1681
1682    /* Stack limit test */
1683    if (size > ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur))
1684        return -ENOMEM;
1685
1686    /* mlock limit tests */
1687    if (vma->vm_flags & VM_LOCKED) {
1688        unsigned long locked;
1689        unsigned long limit;
1690        locked = mm->locked_vm + grow;
1691        limit = ACCESS_ONCE(rlim[RLIMIT_MEMLOCK].rlim_cur);
1692        limit >>= PAGE_SHIFT;
1693        if (locked > limit && !capable(CAP_IPC_LOCK))
1694            return -ENOMEM;
1695    }
1696
1697    /* Check to ensure the stack will not grow into a hugetlb-only region */
1698    new_start = (vma->vm_flags & VM_GROWSUP) ? vma->vm_start :
1699            vma->vm_end - size;
1700    if (is_hugepage_only_range(vma->vm_mm, new_start, size))
1701        return -EFAULT;
1702
1703    /*
1704     * Overcommit.. This must be the final test, as it will
1705     * update security statistics.
1706     */
1707    if (security_vm_enough_memory_mm(mm, grow))
1708        return -ENOMEM;
1709
1710    /* Ok, everything looks good - let it rip */
1711    if (vma->vm_flags & VM_LOCKED)
1712        mm->locked_vm += grow;
1713    vm_stat_account(mm, vma->vm_flags, vma->vm_file, grow);
1714    return 0;
1715}
1716
1717#if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
1718/*
1719 * PA-RISC uses this for its stack; IA64 for its Register Backing Store.
1720 * vma is the last one with address > vma->vm_end. Have to extend vma.
1721 */
1722int expand_upwards(struct vm_area_struct *vma, unsigned long address)
1723{
1724    int error;
1725
1726    if (!(vma->vm_flags & VM_GROWSUP))
1727        return -EFAULT;
1728
1729    /*
1730     * We must make sure the anon_vma is allocated
1731     * so that the anon_vma locking is not a noop.
1732     */
1733    if (unlikely(anon_vma_prepare(vma)))
1734        return -ENOMEM;
1735    vma_lock_anon_vma(vma);
1736
1737    /*
1738     * vma->vm_start/vm_end cannot change under us because the caller
1739     * is required to hold the mmap_sem in read mode. We need the
1740     * anon_vma lock to serialize against concurrent expand_stacks.
1741     * Also guard against wrapping around to address 0.
1742     */
1743    if (address < PAGE_ALIGN(address+4))
1744        address = PAGE_ALIGN(address+4);
1745    else {
1746        vma_unlock_anon_vma(vma);
1747        return -ENOMEM;
1748    }
1749    error = 0;
1750
1751    /* Somebody else might have raced and expanded it already */
1752    if (address > vma->vm_end) {
1753        unsigned long size, grow;
1754
1755        size = address - vma->vm_start;
1756        grow = (address - vma->vm_end) >> PAGE_SHIFT;
1757
1758        error = -ENOMEM;
1759        if (vma->vm_pgoff + (size >> PAGE_SHIFT) >= vma->vm_pgoff) {
1760            error = acct_stack_growth(vma, size, grow);
1761            if (!error) {
1762                vma->vm_end = address;
1763                perf_event_mmap(vma);
1764            }
1765        }
1766    }
1767    vma_unlock_anon_vma(vma);
1768    khugepaged_enter_vma_merge(vma);
1769    return error;
1770}
1771#endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
1772
1773/*
1774 * vma is the first one with address < vma->vm_start. Have to extend vma.
1775 */
1776int expand_downwards(struct vm_area_struct *vma,
1777                   unsigned long address)
1778{
1779    int error;
1780
1781    /*
1782     * We must make sure the anon_vma is allocated
1783     * so that the anon_vma locking is not a noop.
1784     */
1785    if (unlikely(anon_vma_prepare(vma)))
1786        return -ENOMEM;
1787
1788    address &= PAGE_MASK;
1789    error = security_mmap_addr(address);
1790    if (error)
1791        return error;
1792
1793    vma_lock_anon_vma(vma);
1794
1795    /*
1796     * vma->vm_start/vm_end cannot change under us because the caller
1797     * is required to hold the mmap_sem in read mode. We need the
1798     * anon_vma lock to serialize against concurrent expand_stacks.
1799     */
1800
1801    /* Somebody else might have raced and expanded it already */
1802    if (address < vma->vm_start) {
1803        unsigned long size, grow;
1804
1805        size = vma->vm_end - address;
1806        grow = (vma->vm_start - address) >> PAGE_SHIFT;
1807
1808        error = -ENOMEM;
1809        if (grow <= vma->vm_pgoff) {
1810            error = acct_stack_growth(vma, size, grow);
1811            if (!error) {
1812                vma->vm_start = address;
1813                vma->vm_pgoff -= grow;
1814                perf_event_mmap(vma);
1815            }
1816        }
1817    }
1818    vma_unlock_anon_vma(vma);
1819    khugepaged_enter_vma_merge(vma);
1820    return error;
1821}
1822
1823#ifdef CONFIG_STACK_GROWSUP
1824int expand_stack(struct vm_area_struct *vma, unsigned long address)
1825{
1826    return expand_upwards(vma, address);
1827}
1828
1829struct vm_area_struct *
1830find_extend_vma(struct mm_struct *mm, unsigned long addr)
1831{
1832    struct vm_area_struct *vma, *prev;
1833
1834    addr &= PAGE_MASK;
1835    vma = find_vma_prev(mm, addr, &prev);
1836    if (vma && (vma->vm_start <= addr))
1837        return vma;
1838    if (!prev || expand_stack(prev, addr))
1839        return NULL;
1840    if (prev->vm_flags & VM_LOCKED) {
1841        mlock_vma_pages_range(prev, addr, prev->vm_end);
1842    }
1843    return prev;
1844}
1845#else
1846int expand_stack(struct vm_area_struct *vma, unsigned long address)
1847{
1848    return expand_downwards(vma, address);
1849}
1850
1851struct vm_area_struct *
1852find_extend_vma(struct mm_struct * mm, unsigned long addr)
1853{
1854    struct vm_area_struct * vma;
1855    unsigned long start;
1856
1857    addr &= PAGE_MASK;
1858    vma = find_vma(mm,addr);
1859    if (!vma)
1860        return NULL;
1861    if (vma->vm_start <= addr)
1862        return vma;
1863    if (!(vma->vm_flags & VM_GROWSDOWN))
1864        return NULL;
1865    start = vma->vm_start;
1866    if (expand_stack(vma, addr))
1867        return NULL;
1868    if (vma->vm_flags & VM_LOCKED) {
1869        mlock_vma_pages_range(vma, addr, start);
1870    }
1871    return vma;
1872}
1873#endif
1874
1875/*
1876 * Ok - we have the memory areas we should free on the vma list,
1877 * so release them, and do the vma updates.
1878 *
1879 * Called with the mm semaphore held.
1880 */
1881static void remove_vma_list(struct mm_struct *mm, struct vm_area_struct *vma)
1882{
1883    unsigned long nr_accounted = 0;
1884
1885    /* Update high watermark before we lower total_vm */
1886    update_hiwater_vm(mm);
1887    do {
1888        long nrpages = vma_pages(vma);
1889
1890        if (vma->vm_flags & VM_ACCOUNT)
1891            nr_accounted += nrpages;
1892        vm_stat_account(mm, vma->vm_flags, vma->vm_file, -nrpages);
1893        vma = remove_vma(vma);
1894    } while (vma);
1895    vm_unacct_memory(nr_accounted);
1896    validate_mm(mm);
1897}
1898
1899/*
1900 * Get rid of page table information in the indicated region.
1901 *
1902 * Called with the mm semaphore held.
1903 */
1904static void unmap_region(struct mm_struct *mm,
1905        struct vm_area_struct *vma, struct vm_area_struct *prev,
1906        unsigned long start, unsigned long end)
1907{
1908    struct vm_area_struct *next = prev? prev->vm_next: mm->mmap;
1909    struct mmu_gather tlb;
1910
1911    lru_add_drain();
1912    tlb_gather_mmu(&tlb, mm, 0);
1913    update_hiwater_rss(mm);
1914    unmap_vmas(&tlb, vma, start, end);
1915    free_pgtables(&tlb, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
1916                 next ? next->vm_start : 0);
1917    tlb_finish_mmu(&tlb, start, end);
1918}
1919
1920/*
1921 * Create a list of vma's touched by the unmap, removing them from the mm's
1922 * vma list as we go..
1923 */
1924static void
1925detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
1926    struct vm_area_struct *prev, unsigned long end)
1927{
1928    struct vm_area_struct **insertion_point;
1929    struct vm_area_struct *tail_vma = NULL;
1930    unsigned long addr;
1931
1932    insertion_point = (prev ? &prev->vm_next : &mm->mmap);
1933    vma->vm_prev = NULL;
1934    do {
1935        rb_erase(&vma->vm_rb, &mm->mm_rb);
1936        mm->map_count--;
1937        tail_vma = vma;
1938        vma = vma->vm_next;
1939    } while (vma && vma->vm_start < end);
1940    *insertion_point = vma;
1941    if (vma)
1942        vma->vm_prev = prev;
1943    tail_vma->vm_next = NULL;
1944    if (mm->unmap_area == arch_unmap_area)
1945        addr = prev ? prev->vm_end : mm->mmap_base;
1946    else
1947        addr = vma ? vma->vm_start : mm->mmap_base;
1948    mm->unmap_area(mm, addr);
1949    mm->mmap_cache = NULL; /* Kill the cache. */
1950}
1951
1952/*
1953 * __split_vma() bypasses sysctl_max_map_count checking. We use this on the
1954 * munmap path where it doesn't make sense to fail.
1955 */
1956static int __split_vma(struct mm_struct * mm, struct vm_area_struct * vma,
1957          unsigned long addr, int new_below)
1958{
1959    struct mempolicy *pol;
1960    struct vm_area_struct *new;
1961    int err = -ENOMEM;
1962
1963    if (is_vm_hugetlb_page(vma) && (addr &
1964                    ~(huge_page_mask(hstate_vma(vma)))))
1965        return -EINVAL;
1966
1967    new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
1968    if (!new)
1969        goto out_err;
1970
1971    /* most fields are the same, copy all, and then fixup */
1972    *new = *vma;
1973
1974    INIT_LIST_HEAD(&new->anon_vma_chain);
1975
1976    if (new_below)
1977        new->vm_end = addr;
1978    else {
1979        new->vm_start = addr;
1980        new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
1981    }
1982
1983    pol = mpol_dup(vma_policy(vma));
1984    if (IS_ERR(pol)) {
1985        err = PTR_ERR(pol);
1986        goto out_free_vma;
1987    }
1988    vma_set_policy(new, pol);
1989
1990    if (anon_vma_clone(new, vma))
1991        goto out_free_mpol;
1992
1993    if (new->vm_file) {
1994        get_file(new->vm_file);
1995        if (vma->vm_flags & VM_EXECUTABLE)
1996            added_exe_file_vma(mm);
1997    }
1998
1999    if (new->vm_ops && new->vm_ops->open)
2000        new->vm_ops->open(new);
2001
2002    if (new_below)
2003        err = vma_adjust(vma, addr, vma->vm_end, vma->vm_pgoff +
2004            ((addr - new->vm_start) >> PAGE_SHIFT), new);
2005    else
2006        err = vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new);
2007
2008    /* Success. */
2009    if (!err)
2010        return 0;
2011
2012    /* Clean everything up if vma_adjust failed. */
2013    if (new->vm_ops && new->vm_ops->close)
2014        new->vm_ops->close(new);
2015    if (new->vm_file) {
2016        if (vma->vm_flags & VM_EXECUTABLE)
2017            removed_exe_file_vma(mm);
2018        fput(new->vm_file);
2019    }
2020    unlink_anon_vmas(new);
2021 out_free_mpol:
2022    mpol_put(pol);
2023 out_free_vma:
2024    kmem_cache_free(vm_area_cachep, new);
2025 out_err:
2026    return err;
2027}
2028
2029/*
2030 * Split a vma into two pieces at address 'addr', a new vma is allocated
2031 * either for the first part or the tail.
2032 */
2033int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
2034          unsigned long addr, int new_below)
2035{
2036    if (mm->map_count >= sysctl_max_map_count)
2037        return -ENOMEM;
2038
2039    return __split_vma(mm, vma, addr, new_below);
2040}
2041
2042/* Munmap is split into 2 main parts -- this part which finds
2043 * what needs doing, and the areas themselves, which do the
2044 * work. This now handles partial unmappings.
2045 * Jeremy Fitzhardinge <jeremy@goop.org>
2046 */
2047int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
2048{
2049    unsigned long end;
2050    struct vm_area_struct *vma, *prev, *last;
2051
2052    if ((start & ~PAGE_MASK) || start > TASK_SIZE || len > TASK_SIZE-start)
2053        return -EINVAL;
2054
2055    if ((len = PAGE_ALIGN(len)) == 0)
2056        return -EINVAL;
2057
2058    /* Find the first overlapping VMA */
2059    vma = find_vma(mm, start);
2060    if (!vma)
2061        return 0;
2062    prev = vma->vm_prev;
2063    /* we have start < vma->vm_end */
2064
2065    /* if it doesn't overlap, we have nothing.. */
2066    end = start + len;
2067    if (vma->vm_start >= end)
2068        return 0;
2069
2070    /*
2071     * If we need to split any vma, do it now to save pain later.
2072     *
2073     * Note: mremap's move_vma VM_ACCOUNT handling assumes a partially
2074     * unmapped vm_area_struct will remain in use: so lower split_vma
2075     * places tmp vma above, and higher split_vma places tmp vma below.
2076     */
2077    if (start > vma->vm_start) {
2078        int error;
2079
2080        /*
2081         * Make sure that map_count on return from munmap() will
2082         * not exceed its limit; but let map_count go just above
2083         * its limit temporarily, to help free resources as expected.
2084         */
2085        if (end < vma->vm_end && mm->map_count >= sysctl_max_map_count)
2086            return -ENOMEM;
2087
2088        error = __split_vma(mm, vma, start, 0);
2089        if (error)
2090            return error;
2091        prev = vma;
2092    }
2093
2094    /* Does it split the last one? */
2095    last = find_vma(mm, end);
2096    if (last && end > last->vm_start) {
2097        int error = __split_vma(mm, last, end, 1);
2098        if (error)
2099            return error;
2100    }
2101    vma = prev? prev->vm_next: mm->mmap;
2102
2103    /*
2104     * unlock any mlock()ed ranges before detaching vmas
2105     */
2106    if (mm->locked_vm) {
2107        struct vm_area_struct *tmp = vma;
2108        while (tmp && tmp->vm_start < end) {
2109            if (tmp->vm_flags & VM_LOCKED) {
2110                mm->locked_vm -= vma_pages(tmp);
2111                munlock_vma_pages_all(tmp);
2112            }
2113            tmp = tmp->vm_next;
2114        }
2115    }
2116
2117    /*
2118     * Remove the vma's, and unmap the actual pages
2119     */
2120    detach_vmas_to_be_unmapped(mm, vma, prev, end);
2121    unmap_region(mm, vma, prev, start, end);
2122
2123    /* Fix up all other VM information */
2124    remove_vma_list(mm, vma);
2125
2126    return 0;
2127}
2128
2129int vm_munmap(unsigned long start, size_t len)
2130{
2131    int ret;
2132    struct mm_struct *mm = current->mm;
2133
2134    down_write(&mm->mmap_sem);
2135    ret = do_munmap(mm, start, len);
2136    up_write(&mm->mmap_sem);
2137    return ret;
2138}
2139EXPORT_SYMBOL(vm_munmap);
2140
2141SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
2142{
2143    profile_munmap(addr);
2144    return vm_munmap(addr, len);
2145}
2146
2147static inline void verify_mm_writelocked(struct mm_struct *mm)
2148{
2149#ifdef CONFIG_DEBUG_VM
2150    if (unlikely(down_read_trylock(&mm->mmap_sem))) {
2151        WARN_ON(1);
2152        up_read(&mm->mmap_sem);
2153    }
2154#endif
2155}
2156
2157/*
2158 * this is really a simplified "do_mmap". it only handles
2159 * anonymous maps. eventually we may be able to do some
2160 * brk-specific accounting here.
2161 */
2162static unsigned long do_brk(unsigned long addr, unsigned long len)
2163{
2164    struct mm_struct * mm = current->mm;
2165    struct vm_area_struct * vma, * prev;
2166    unsigned long flags;
2167    struct rb_node ** rb_link, * rb_parent;
2168    pgoff_t pgoff = addr >> PAGE_SHIFT;
2169    int error;
2170
2171    len = PAGE_ALIGN(len);
2172    if (!len)
2173        return addr;
2174
2175    flags = VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
2176
2177    error = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
2178    if (error & ~PAGE_MASK)
2179        return error;
2180
2181    /*
2182     * mlock MCL_FUTURE?
2183     */
2184    if (mm->def_flags & VM_LOCKED) {
2185        unsigned long locked, lock_limit;
2186        locked = len >> PAGE_SHIFT;
2187        locked += mm->locked_vm;
2188        lock_limit = rlimit(RLIMIT_MEMLOCK);
2189        lock_limit >>= PAGE_SHIFT;
2190        if (locked > lock_limit && !capable(CAP_IPC_LOCK))
2191            return -EAGAIN;
2192    }
2193
2194    /*
2195     * mm->mmap_sem is required to protect against another thread
2196     * changing the mappings in case we sleep.
2197     */
2198    verify_mm_writelocked(mm);
2199
2200    /*
2201     * Clear old maps. this also does some error checking for us
2202     */
2203 munmap_back:
2204    vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
2205    if (vma && vma->vm_start < addr + len) {
2206        if (do_munmap(mm, addr, len))
2207            return -ENOMEM;
2208        goto munmap_back;
2209    }
2210
2211    /* Check against address space limits *after* clearing old maps... */
2212    if (!may_expand_vm(mm, len >> PAGE_SHIFT))
2213        return -ENOMEM;
2214
2215    if (mm->map_count > sysctl_max_map_count)
2216        return -ENOMEM;
2217
2218    if (security_vm_enough_memory_mm(mm, len >> PAGE_SHIFT))
2219        return -ENOMEM;
2220
2221    /* Can we just expand an old private anonymous mapping? */
2222    vma = vma_merge(mm, prev, addr, addr + len, flags,
2223                    NULL, NULL, pgoff, NULL);
2224    if (vma)
2225        goto out;
2226
2227    /*
2228     * create a vma struct for an anonymous mapping
2229     */
2230    vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
2231    if (!vma) {
2232        vm_unacct_memory(len >> PAGE_SHIFT);
2233        return -ENOMEM;
2234    }
2235
2236    INIT_LIST_HEAD(&vma->anon_vma_chain);
2237    vma->vm_mm = mm;
2238    vma->vm_start = addr;
2239    vma->vm_end = addr + len;
2240    vma->vm_pgoff = pgoff;
2241    vma->vm_flags = flags;
2242    vma->vm_page_prot = vm_get_page_prot(flags);
2243    vma_link(mm, vma, prev, rb_link, rb_parent);
2244out:
2245    perf_event_mmap(vma);
2246    mm->total_vm += len >> PAGE_SHIFT;
2247    if (flags & VM_LOCKED) {
2248        if (!mlock_vma_pages_range(vma, addr, addr + len))
2249            mm->locked_vm += (len >> PAGE_SHIFT);
2250    }
2251    return addr;
2252}
2253
2254unsigned long vm_brk(unsigned long addr, unsigned long len)
2255{
2256    struct mm_struct *mm = current->mm;
2257    unsigned long ret;
2258
2259    down_write(&mm->mmap_sem);
2260    ret = do_brk(addr, len);
2261    up_write(&mm->mmap_sem);
2262    return ret;
2263}
2264EXPORT_SYMBOL(vm_brk);
2265
2266/* Release all mmaps. */
2267void exit_mmap(struct mm_struct *mm)
2268{
2269    struct mmu_gather tlb;
2270    struct vm_area_struct *vma;
2271    unsigned long nr_accounted = 0;
2272
2273    /* mm's last user has gone, and its about to be pulled down */
2274    mmu_notifier_release(mm);
2275
2276    if (mm->locked_vm) {
2277        vma = mm->mmap;
2278        while (vma) {
2279            if (vma->vm_flags & VM_LOCKED)
2280                munlock_vma_pages_all(vma);
2281            vma = vma->vm_next;
2282        }
2283    }
2284
2285    arch_exit_mmap(mm);
2286
2287    vma = mm->mmap;
2288    if (!vma) /* Can happen if dup_mmap() received an OOM */
2289        return;
2290
2291    lru_add_drain();
2292    flush_cache_mm(mm);
2293    tlb_gather_mmu(&tlb, mm, 1);
2294    /* update_hiwater_rss(mm) here? but nobody should be looking */
2295    /* Use -1 here to ensure all VMAs in the mm are unmapped */
2296    unmap_vmas(&tlb, vma, 0, -1);
2297
2298    free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, 0);
2299    tlb_finish_mmu(&tlb, 0, -1);
2300
2301    /*
2302     * Walk the list again, actually closing and freeing it,
2303     * with preemption enabled, without holding any MM locks.
2304     */
2305    while (vma) {
2306        if (vma->vm_flags & VM_ACCOUNT)
2307            nr_accounted += vma_pages(vma);
2308        vma = remove_vma(vma);
2309    }
2310    vm_unacct_memory(nr_accounted);
2311
2312    BUG_ON(mm->nr_ptes > (FIRST_USER_ADDRESS+PMD_SIZE-1)>>PMD_SHIFT);
2313}
2314
2315/* Insert vm structure into process list sorted by address
2316 * and into the inode's i_mmap tree. If vm_file is non-NULL
2317 * then i_mmap_mutex is taken here.
2318 */
2319int insert_vm_struct(struct mm_struct * mm, struct vm_area_struct * vma)
2320{
2321    struct vm_area_struct * __vma, * prev;
2322    struct rb_node ** rb_link, * rb_parent;
2323
2324    /*
2325     * The vm_pgoff of a purely anonymous vma should be irrelevant
2326     * until its first write fault, when page's anon_vma and index
2327     * are set. But now set the vm_pgoff it will almost certainly
2328     * end up with (unless mremap moves it elsewhere before that
2329     * first wfault), so /proc/pid/maps tells a consistent story.
2330     *
2331     * By setting it to reflect the virtual start address of the
2332     * vma, merges and splits can happen in a seamless way, just
2333     * using the existing file pgoff checks and manipulations.
2334     * Similarly in do_mmap_pgoff and in do_brk.
2335     */
2336    if (!vma->vm_file) {
2337        BUG_ON(vma->anon_vma);
2338        vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;
2339    }
2340    __vma = find_vma_prepare(mm,vma->vm_start,&prev,&rb_link,&rb_parent);
2341    if (__vma && __vma->vm_start < vma->vm_end)
2342        return -ENOMEM;
2343    if ((vma->vm_flags & VM_ACCOUNT) &&
2344         security_vm_enough_memory_mm(mm, vma_pages(vma)))
2345        return -ENOMEM;
2346
2347    vma_link(mm, vma, prev, rb_link, rb_parent);
2348    return 0;
2349}
2350
2351/*
2352 * Copy the vma structure to a new location in the same mm,
2353 * prior to moving page table entries, to effect an mremap move.
2354 */
2355struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
2356    unsigned long addr, unsigned long len, pgoff_t pgoff)
2357{
2358    struct vm_area_struct *vma = *vmap;
2359    unsigned long vma_start = vma->vm_start;
2360    struct mm_struct *mm = vma->vm_mm;
2361    struct vm_area_struct *new_vma, *prev;
2362    struct rb_node **rb_link, *rb_parent;
2363    struct mempolicy *pol;
2364    bool faulted_in_anon_vma = true;
2365
2366    /*
2367     * If anonymous vma has not yet been faulted, update new pgoff
2368     * to match new location, to increase its chance of merging.
2369     */
2370    if (unlikely(!vma->vm_file && !vma->anon_vma)) {
2371        pgoff = addr >> PAGE_SHIFT;
2372        faulted_in_anon_vma = false;
2373    }
2374
2375    find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
2376    new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags,
2377            vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma));
2378    if (new_vma) {
2379        /*
2380         * Source vma may have been merged into new_vma
2381         */
2382        if (unlikely(vma_start >= new_vma->vm_start &&
2383                 vma_start < new_vma->vm_end)) {
2384            /*
2385             * The only way we can get a vma_merge with
2386             * self during an mremap is if the vma hasn't
2387             * been faulted in yet and we were allowed to
2388             * reset the dst vma->vm_pgoff to the
2389             * destination address of the mremap to allow
2390             * the merge to happen. mremap must change the
2391             * vm_pgoff linearity between src and dst vmas
2392             * (in turn preventing a vma_merge) to be
2393             * safe. It is only safe to keep the vm_pgoff
2394             * linear if there are no pages mapped yet.
2395             */
2396            VM_BUG_ON(faulted_in_anon_vma);
2397            *vmap = new_vma;
2398        } else
2399            anon_vma_moveto_tail(new_vma);
2400    } else {
2401        new_vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
2402        if (new_vma) {
2403            *new_vma = *vma;
2404            pol = mpol_dup(vma_policy(vma));
2405            if (IS_ERR(pol))
2406                goto out_free_vma;
2407            INIT_LIST_HEAD(&new_vma->anon_vma_chain);
2408            if (anon_vma_clone(new_vma, vma))
2409                goto out_free_mempol;
2410            vma_set_policy(new_vma, pol);
2411            new_vma->vm_start = addr;
2412            new_vma->vm_end = addr + len;
2413            new_vma->vm_pgoff = pgoff;
2414            if (new_vma->vm_file) {
2415                get_file(new_vma->vm_file);
2416
2417                if (vma->vm_flags & VM_EXECUTABLE)
2418                    added_exe_file_vma(mm);
2419            }
2420            if (new_vma->vm_ops && new_vma->vm_ops->open)
2421                new_vma->vm_ops->open(new_vma);
2422            vma_link(mm, new_vma, prev, rb_link, rb_parent);
2423        }
2424    }
2425    return new_vma;
2426
2427 out_free_mempol:
2428    mpol_put(pol);
2429 out_free_vma:
2430    kmem_cache_free(vm_area_cachep, new_vma);
2431    return NULL;
2432}
2433
2434/*
2435 * Return true if the calling process may expand its vm space by the passed
2436 * number of pages
2437 */
2438int may_expand_vm(struct mm_struct *mm, unsigned long npages)
2439{
2440    unsigned long cur = mm->total_vm; /* pages */
2441    unsigned long lim;
2442
2443    lim = rlimit(RLIMIT_AS) >> PAGE_SHIFT;
2444
2445    if (cur + npages > lim)
2446        return 0;
2447    return 1;
2448}
2449
2450
2451static int special_mapping_fault(struct vm_area_struct *vma,
2452                struct vm_fault *vmf)
2453{
2454    pgoff_t pgoff;
2455    struct page **pages;
2456
2457    /*
2458     * special mappings have no vm_file, and in that case, the mm
2459     * uses vm_pgoff internally. So we have to subtract it from here.
2460     * We are allowed to do this because we are the mm; do not copy
2461     * this code into drivers!
2462     */
2463    pgoff = vmf->pgoff - vma->vm_pgoff;
2464
2465    for (pages = vma->vm_private_data; pgoff && *pages; ++pages)
2466        pgoff--;
2467
2468    if (*pages) {
2469        struct page *page = *pages;
2470        get_page(page);
2471        vmf->page = page;
2472        return 0;
2473    }
2474
2475    return VM_FAULT_SIGBUS;
2476}
2477
2478/*
2479 * Having a close hook prevents vma merging regardless of flags.
2480 */
2481static void special_mapping_close(struct vm_area_struct *vma)
2482{
2483}
2484
2485static const struct vm_operations_struct special_mapping_vmops = {
2486    .close = special_mapping_close,
2487    .fault = special_mapping_fault,
2488};
2489
2490/*
2491 * Called with mm->mmap_sem held for writing.
2492 * Insert a new vma covering the given region, with the given flags.
2493 * Its pages are supplied by the given array of struct page *.
2494 * The array can be shorter than len >> PAGE_SHIFT if it's null-terminated.
2495 * The region past the last page supplied will always produce SIGBUS.
2496 * The array pointer and the pages it points to are assumed to stay alive
2497 * for as long as this mapping might exist.
2498 */
2499int install_special_mapping(struct mm_struct *mm,
2500                unsigned long addr, unsigned long len,
2501                unsigned long vm_flags, struct page **pages)
2502{
2503    int ret;
2504    struct vm_area_struct *vma;
2505
2506    vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
2507    if (unlikely(vma == NULL))
2508        return -ENOMEM;
2509
2510    INIT_LIST_HEAD(&vma->anon_vma_chain);
2511    vma->vm_mm = mm;
2512    vma->vm_start = addr;
2513    vma->vm_end = addr + len;
2514
2515    vma->vm_flags = vm_flags | mm->def_flags | VM_DONTEXPAND;
2516    vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
2517
2518    vma->vm_ops = &special_mapping_vmops;
2519    vma->vm_private_data = pages;
2520
2521    ret = insert_vm_struct(mm, vma);
2522    if (ret)
2523        goto out;
2524
2525    mm->total_vm += len >> PAGE_SHIFT;
2526
2527    perf_event_mmap(vma);
2528
2529    return 0;
2530
2531out:
2532    kmem_cache_free(vm_area_cachep, vma);
2533    return ret;
2534}
2535
2536static DEFINE_MUTEX(mm_all_locks_mutex);
2537
2538static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma)
2539{
2540    if (!test_bit(0, (unsigned long *) &anon_vma->root->head.next)) {
2541        /*
2542         * The LSB of head.next can't change from under us
2543         * because we hold the mm_all_locks_mutex.
2544         */
2545        mutex_lock_nest_lock(&anon_vma->root->mutex, &mm->mmap_sem);
2546        /*
2547         * We can safely modify head.next after taking the
2548         * anon_vma->root->mutex. If some other vma in this mm shares
2549         * the same anon_vma we won't take it again.
2550         *
2551         * No need of atomic instructions here, head.next
2552         * can't change from under us thanks to the
2553         * anon_vma->root->mutex.
2554         */
2555        if (__test_and_set_bit(0, (unsigned long *)
2556                       &anon_vma->root->head.next))
2557            BUG();
2558    }
2559}
2560
2561static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping)
2562{
2563    if (!test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
2564        /*
2565         * AS_MM_ALL_LOCKS can't change from under us because
2566         * we hold the mm_all_locks_mutex.
2567         *
2568         * Operations on ->flags have to be atomic because
2569         * even if AS_MM_ALL_LOCKS is stable thanks to the
2570         * mm_all_locks_mutex, there may be other cpus
2571         * changing other bitflags in parallel to us.
2572         */
2573        if (test_and_set_bit(AS_MM_ALL_LOCKS, &mapping->flags))
2574            BUG();
2575        mutex_lock_nest_lock(&mapping->i_mmap_mutex, &mm->mmap_sem);
2576    }
2577}
2578
2579/*
2580 * This operation locks against the VM for all pte/vma/mm related
2581 * operations that could ever happen on a certain mm. This includes
2582 * vmtruncate, try_to_unmap, and all page faults.
2583 *
2584 * The caller must take the mmap_sem in write mode before calling
2585 * mm_take_all_locks(). The caller isn't allowed to release the
2586 * mmap_sem until mm_drop_all_locks() returns.
2587 *
2588 * mmap_sem in write mode is required in order to block all operations
2589 * that could modify pagetables and free pages without need of
2590 * altering the vma layout (for example populate_range() with
2591 * nonlinear vmas). It's also needed in write mode to avoid new
2592 * anon_vmas to be associated with existing vmas.
2593 *
2594 * A single task can't take more than one mm_take_all_locks() in a row
2595 * or it would deadlock.
2596 *
2597 * The LSB in anon_vma->head.next and the AS_MM_ALL_LOCKS bitflag in
2598 * mapping->flags avoid to take the same lock twice, if more than one
2599 * vma in this mm is backed by the same anon_vma or address_space.
2600 *
2601 * We can take all the locks in random order because the VM code
2602 * taking i_mmap_mutex or anon_vma->mutex outside the mmap_sem never
2603 * takes more than one of them in a row. Secondly we're protected
2604 * against a concurrent mm_take_all_locks() by the mm_all_locks_mutex.
2605 *
2606 * mm_take_all_locks() and mm_drop_all_locks are expensive operations
2607 * that may have to take thousand of locks.
2608 *
2609 * mm_take_all_locks() can fail if it's interrupted by signals.
2610 */
2611int mm_take_all_locks(struct mm_struct *mm)
2612{
2613    struct vm_area_struct *vma;
2614    struct anon_vma_chain *avc;
2615
2616    BUG_ON(down_read_trylock(&mm->mmap_sem));
2617
2618    mutex_lock(&mm_all_locks_mutex);
2619
2620    for (vma = mm->mmap; vma; vma = vma->vm_next) {
2621        if (signal_pending(current))
2622            goto out_unlock;
2623        if (vma->vm_file && vma->vm_file->f_mapping)
2624            vm_lock_mapping(mm, vma->vm_file->f_mapping);
2625    }
2626
2627    for (vma = mm->mmap; vma; vma = vma->vm_next) {
2628        if (signal_pending(current))
2629            goto out_unlock;
2630        if (vma->anon_vma)
2631            list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
2632                vm_lock_anon_vma(mm, avc->anon_vma);
2633    }
2634
2635    return 0;
2636
2637out_unlock:
2638    mm_drop_all_locks(mm);
2639    return -EINTR;
2640}
2641
2642static void vm_unlock_anon_vma(struct anon_vma *anon_vma)
2643{
2644    if (test_bit(0, (unsigned long *) &anon_vma->root->head.next)) {
2645        /*
2646         * The LSB of head.next can't change to 0 from under
2647         * us because we hold the mm_all_locks_mutex.
2648         *
2649         * We must however clear the bitflag before unlocking
2650         * the vma so the users using the anon_vma->head will
2651         * never see our bitflag.
2652         *
2653         * No need of atomic instructions here, head.next
2654         * can't change from under us until we release the
2655         * anon_vma->root->mutex.
2656         */
2657        if (!__test_and_clear_bit(0, (unsigned long *)
2658                      &anon_vma->root->head.next))
2659            BUG();
2660        anon_vma_unlock(anon_vma);
2661    }
2662}
2663
2664static void vm_unlock_mapping(struct address_space *mapping)
2665{
2666    if (test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
2667        /*
2668         * AS_MM_ALL_LOCKS can't change to 0 from under us
2669         * because we hold the mm_all_locks_mutex.
2670         */
2671        mutex_unlock(&mapping->i_mmap_mutex);
2672        if (!test_and_clear_bit(AS_MM_ALL_LOCKS,
2673                    &mapping->flags))
2674            BUG();
2675    }
2676}
2677
2678/*
2679 * The mmap_sem cannot be released by the caller until
2680 * mm_drop_all_locks() returns.
2681 */
2682void mm_drop_all_locks(struct mm_struct *mm)
2683{
2684    struct vm_area_struct *vma;
2685    struct anon_vma_chain *avc;
2686
2687    BUG_ON(down_read_trylock(&mm->mmap_sem));
2688    BUG_ON(!mutex_is_locked(&mm_all_locks_mutex));
2689
2690    for (vma = mm->mmap; vma; vma = vma->vm_next) {
2691        if (vma->anon_vma)
2692            list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
2693                vm_unlock_anon_vma(avc->anon_vma);
2694        if (vma->vm_file && vma->vm_file->f_mapping)
2695            vm_unlock_mapping(vma->vm_file->f_mapping);
2696    }
2697
2698    mutex_unlock(&mm_all_locks_mutex);
2699}
2700
2701/*
2702 * initialise the VMA slab
2703 */
2704void __init mmap_init(void)
2705{
2706    int ret;
2707
2708    ret = percpu_counter_init(&vm_committed_as, 0);
2709    VM_BUG_ON(ret);
2710}
2711

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