Version:  2.0.40 2.2.26 2.4.37 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4 4.5 4.6

Linux/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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 10 
 11 #include <linux/kernel.h>
 12 #include <linux/slab.h>
 13 #include <linux/backing-dev.h>
 14 #include <linux/mm.h>
 15 #include <linux/vmacache.h>
 16 #include <linux/shm.h>
 17 #include <linux/mman.h>
 18 #include <linux/pagemap.h>
 19 #include <linux/swap.h>
 20 #include <linux/syscalls.h>
 21 #include <linux/capability.h>
 22 #include <linux/init.h>
 23 #include <linux/file.h>
 24 #include <linux/fs.h>
 25 #include <linux/personality.h>
 26 #include <linux/security.h>
 27 #include <linux/hugetlb.h>
 28 #include <linux/profile.h>
 29 #include <linux/export.h>
 30 #include <linux/mount.h>
 31 #include <linux/mempolicy.h>
 32 #include <linux/rmap.h>
 33 #include <linux/mmu_notifier.h>
 34 #include <linux/mmdebug.h>
 35 #include <linux/perf_event.h>
 36 #include <linux/audit.h>
 37 #include <linux/khugepaged.h>
 38 #include <linux/uprobes.h>
 39 #include <linux/rbtree_augmented.h>
 40 #include <linux/notifier.h>
 41 #include <linux/memory.h>
 42 #include <linux/printk.h>
 43 #include <linux/userfaultfd_k.h>
 44 #include <linux/moduleparam.h>
 45 #include <linux/pkeys.h>
 46 
 47 #include <asm/uaccess.h>
 48 #include <asm/cacheflush.h>
 49 #include <asm/tlb.h>
 50 #include <asm/mmu_context.h>
 51 
 52 #include "internal.h"
 53 
 54 #ifndef arch_mmap_check
 55 #define arch_mmap_check(addr, len, flags)       (0)
 56 #endif
 57 
 58 #ifndef arch_rebalance_pgtables
 59 #define arch_rebalance_pgtables(addr, len)              (addr)
 60 #endif
 61 
 62 #ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS
 63 const int mmap_rnd_bits_min = CONFIG_ARCH_MMAP_RND_BITS_MIN;
 64 const int mmap_rnd_bits_max = CONFIG_ARCH_MMAP_RND_BITS_MAX;
 65 int mmap_rnd_bits __read_mostly = CONFIG_ARCH_MMAP_RND_BITS;
 66 #endif
 67 #ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
 68 const int mmap_rnd_compat_bits_min = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MIN;
 69 const int mmap_rnd_compat_bits_max = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MAX;
 70 int mmap_rnd_compat_bits __read_mostly = CONFIG_ARCH_MMAP_RND_COMPAT_BITS;
 71 #endif
 72 
 73 static bool ignore_rlimit_data = true;
 74 core_param(ignore_rlimit_data, ignore_rlimit_data, bool, 0644);
 75 
 76 static void unmap_region(struct mm_struct *mm,
 77                 struct vm_area_struct *vma, struct vm_area_struct *prev,
 78                 unsigned long start, unsigned long end);
 79 
 80 /* description of effects of mapping type and prot in current implementation.
 81  * this is due to the limited x86 page protection hardware.  The expected
 82  * behavior is in parens:
 83  *
 84  * map_type     prot
 85  *              PROT_NONE       PROT_READ       PROT_WRITE      PROT_EXEC
 86  * MAP_SHARED   r: (no) no      r: (yes) yes    r: (no) yes     r: (no) yes
 87  *              w: (no) no      w: (no) no      w: (yes) yes    w: (no) no
 88  *              x: (no) no      x: (no) yes     x: (no) yes     x: (yes) yes
 89  *
 90  * MAP_PRIVATE  r: (no) no      r: (yes) yes    r: (no) yes     r: (no) yes
 91  *              w: (no) no      w: (no) no      w: (copy) copy  w: (no) no
 92  *              x: (no) no      x: (no) yes     x: (no) yes     x: (yes) yes
 93  *
 94  */
 95 pgprot_t protection_map[16] = {
 96         __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
 97         __S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
 98 };
 99 
100 pgprot_t vm_get_page_prot(unsigned long vm_flags)
101 {
102         return __pgprot(pgprot_val(protection_map[vm_flags &
103                                 (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
104                         pgprot_val(arch_vm_get_page_prot(vm_flags)));
105 }
106 EXPORT_SYMBOL(vm_get_page_prot);
107 
108 static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags)
109 {
110         return pgprot_modify(oldprot, vm_get_page_prot(vm_flags));
111 }
112 
113 /* Update vma->vm_page_prot to reflect vma->vm_flags. */
114 void vma_set_page_prot(struct vm_area_struct *vma)
115 {
116         unsigned long vm_flags = vma->vm_flags;
117 
118         vma->vm_page_prot = vm_pgprot_modify(vma->vm_page_prot, vm_flags);
119         if (vma_wants_writenotify(vma)) {
120                 vm_flags &= ~VM_SHARED;
121                 vma->vm_page_prot = vm_pgprot_modify(vma->vm_page_prot,
122                                                      vm_flags);
123         }
124 }
125 
126 /*
127  * Requires inode->i_mapping->i_mmap_rwsem
128  */
129 static void __remove_shared_vm_struct(struct vm_area_struct *vma,
130                 struct file *file, struct address_space *mapping)
131 {
132         if (vma->vm_flags & VM_DENYWRITE)
133                 atomic_inc(&file_inode(file)->i_writecount);
134         if (vma->vm_flags & VM_SHARED)
135                 mapping_unmap_writable(mapping);
136 
137         flush_dcache_mmap_lock(mapping);
138         vma_interval_tree_remove(vma, &mapping->i_mmap);
139         flush_dcache_mmap_unlock(mapping);
140 }
141 
142 /*
143  * Unlink a file-based vm structure from its interval tree, to hide
144  * vma from rmap and vmtruncate before freeing its page tables.
145  */
146 void unlink_file_vma(struct vm_area_struct *vma)
147 {
148         struct file *file = vma->vm_file;
149 
150         if (file) {
151                 struct address_space *mapping = file->f_mapping;
152                 i_mmap_lock_write(mapping);
153                 __remove_shared_vm_struct(vma, file, mapping);
154                 i_mmap_unlock_write(mapping);
155         }
156 }
157 
158 /*
159  * Close a vm structure and free it, returning the next.
160  */
161 static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
162 {
163         struct vm_area_struct *next = vma->vm_next;
164 
165         might_sleep();
166         if (vma->vm_ops && vma->vm_ops->close)
167                 vma->vm_ops->close(vma);
168         if (vma->vm_file)
169                 fput(vma->vm_file);
170         mpol_put(vma_policy(vma));
171         kmem_cache_free(vm_area_cachep, vma);
172         return next;
173 }
174 
175 static unsigned long do_brk(unsigned long addr, unsigned long len);
176 
177 SYSCALL_DEFINE1(brk, unsigned long, brk)
178 {
179         unsigned long retval;
180         unsigned long newbrk, oldbrk;
181         struct mm_struct *mm = current->mm;
182         unsigned long min_brk;
183         bool populate;
184 
185         down_write(&mm->mmap_sem);
186 
187 #ifdef CONFIG_COMPAT_BRK
188         /*
189          * CONFIG_COMPAT_BRK can still be overridden by setting
190          * randomize_va_space to 2, which will still cause mm->start_brk
191          * to be arbitrarily shifted
192          */
193         if (current->brk_randomized)
194                 min_brk = mm->start_brk;
195         else
196                 min_brk = mm->end_data;
197 #else
198         min_brk = mm->start_brk;
199 #endif
200         if (brk < min_brk)
201                 goto out;
202 
203         /*
204          * Check against rlimit here. If this check is done later after the test
205          * of oldbrk with newbrk then it can escape the test and let the data
206          * segment grow beyond its set limit the in case where the limit is
207          * not page aligned -Ram Gupta
208          */
209         if (check_data_rlimit(rlimit(RLIMIT_DATA), brk, mm->start_brk,
210                               mm->end_data, mm->start_data))
211                 goto out;
212 
213         newbrk = PAGE_ALIGN(brk);
214         oldbrk = PAGE_ALIGN(mm->brk);
215         if (oldbrk == newbrk)
216                 goto set_brk;
217 
218         /* Always allow shrinking brk. */
219         if (brk <= mm->brk) {
220                 if (!do_munmap(mm, newbrk, oldbrk-newbrk))
221                         goto set_brk;
222                 goto out;
223         }
224 
225         /* Check against existing mmap mappings. */
226         if (find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE))
227                 goto out;
228 
229         /* Ok, looks good - let it rip. */
230         if (do_brk(oldbrk, newbrk-oldbrk) != oldbrk)
231                 goto out;
232 
233 set_brk:
234         mm->brk = brk;
235         populate = newbrk > oldbrk && (mm->def_flags & VM_LOCKED) != 0;
236         up_write(&mm->mmap_sem);
237         if (populate)
238                 mm_populate(oldbrk, newbrk - oldbrk);
239         return brk;
240 
241 out:
242         retval = mm->brk;
243         up_write(&mm->mmap_sem);
244         return retval;
245 }
246 
247 static long vma_compute_subtree_gap(struct vm_area_struct *vma)
248 {
249         unsigned long max, subtree_gap;
250         max = vma->vm_start;
251         if (vma->vm_prev)
252                 max -= vma->vm_prev->vm_end;
253         if (vma->vm_rb.rb_left) {
254                 subtree_gap = rb_entry(vma->vm_rb.rb_left,
255                                 struct vm_area_struct, vm_rb)->rb_subtree_gap;
256                 if (subtree_gap > max)
257                         max = subtree_gap;
258         }
259         if (vma->vm_rb.rb_right) {
260                 subtree_gap = rb_entry(vma->vm_rb.rb_right,
261                                 struct vm_area_struct, vm_rb)->rb_subtree_gap;
262                 if (subtree_gap > max)
263                         max = subtree_gap;
264         }
265         return max;
266 }
267 
268 #ifdef CONFIG_DEBUG_VM_RB
269 static int browse_rb(struct mm_struct *mm)
270 {
271         struct rb_root *root = &mm->mm_rb;
272         int i = 0, j, bug = 0;
273         struct rb_node *nd, *pn = NULL;
274         unsigned long prev = 0, pend = 0;
275 
276         for (nd = rb_first(root); nd; nd = rb_next(nd)) {
277                 struct vm_area_struct *vma;
278                 vma = rb_entry(nd, struct vm_area_struct, vm_rb);
279                 if (vma->vm_start < prev) {
280                         pr_emerg("vm_start %lx < prev %lx\n",
281                                   vma->vm_start, prev);
282                         bug = 1;
283                 }
284                 if (vma->vm_start < pend) {
285                         pr_emerg("vm_start %lx < pend %lx\n",
286                                   vma->vm_start, pend);
287                         bug = 1;
288                 }
289                 if (vma->vm_start > vma->vm_end) {
290                         pr_emerg("vm_start %lx > vm_end %lx\n",
291                                   vma->vm_start, vma->vm_end);
292                         bug = 1;
293                 }
294                 spin_lock(&mm->page_table_lock);
295                 if (vma->rb_subtree_gap != vma_compute_subtree_gap(vma)) {
296                         pr_emerg("free gap %lx, correct %lx\n",
297                                vma->rb_subtree_gap,
298                                vma_compute_subtree_gap(vma));
299                         bug = 1;
300                 }
301                 spin_unlock(&mm->page_table_lock);
302                 i++;
303                 pn = nd;
304                 prev = vma->vm_start;
305                 pend = vma->vm_end;
306         }
307         j = 0;
308         for (nd = pn; nd; nd = rb_prev(nd))
309                 j++;
310         if (i != j) {
311                 pr_emerg("backwards %d, forwards %d\n", j, i);
312                 bug = 1;
313         }
314         return bug ? -1 : i;
315 }
316 
317 static void validate_mm_rb(struct rb_root *root, struct vm_area_struct *ignore)
318 {
319         struct rb_node *nd;
320 
321         for (nd = rb_first(root); nd; nd = rb_next(nd)) {
322                 struct vm_area_struct *vma;
323                 vma = rb_entry(nd, struct vm_area_struct, vm_rb);
324                 VM_BUG_ON_VMA(vma != ignore &&
325                         vma->rb_subtree_gap != vma_compute_subtree_gap(vma),
326                         vma);
327         }
328 }
329 
330 static void validate_mm(struct mm_struct *mm)
331 {
332         int bug = 0;
333         int i = 0;
334         unsigned long highest_address = 0;
335         struct vm_area_struct *vma = mm->mmap;
336 
337         while (vma) {
338                 struct anon_vma *anon_vma = vma->anon_vma;
339                 struct anon_vma_chain *avc;
340 
341                 if (anon_vma) {
342                         anon_vma_lock_read(anon_vma);
343                         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
344                                 anon_vma_interval_tree_verify(avc);
345                         anon_vma_unlock_read(anon_vma);
346                 }
347 
348                 highest_address = vma->vm_end;
349                 vma = vma->vm_next;
350                 i++;
351         }
352         if (i != mm->map_count) {
353                 pr_emerg("map_count %d vm_next %d\n", mm->map_count, i);
354                 bug = 1;
355         }
356         if (highest_address != mm->highest_vm_end) {
357                 pr_emerg("mm->highest_vm_end %lx, found %lx\n",
358                           mm->highest_vm_end, highest_address);
359                 bug = 1;
360         }
361         i = browse_rb(mm);
362         if (i != mm->map_count) {
363                 if (i != -1)
364                         pr_emerg("map_count %d rb %d\n", mm->map_count, i);
365                 bug = 1;
366         }
367         VM_BUG_ON_MM(bug, mm);
368 }
369 #else
370 #define validate_mm_rb(root, ignore) do { } while (0)
371 #define validate_mm(mm) do { } while (0)
372 #endif
373 
374 RB_DECLARE_CALLBACKS(static, vma_gap_callbacks, struct vm_area_struct, vm_rb,
375                      unsigned long, rb_subtree_gap, vma_compute_subtree_gap)
376 
377 /*
378  * Update augmented rbtree rb_subtree_gap values after vma->vm_start or
379  * vma->vm_prev->vm_end values changed, without modifying the vma's position
380  * in the rbtree.
381  */
382 static void vma_gap_update(struct vm_area_struct *vma)
383 {
384         /*
385          * As it turns out, RB_DECLARE_CALLBACKS() already created a callback
386          * function that does exacltly what we want.
387          */
388         vma_gap_callbacks_propagate(&vma->vm_rb, NULL);
389 }
390 
391 static inline void vma_rb_insert(struct vm_area_struct *vma,
392                                  struct rb_root *root)
393 {
394         /* All rb_subtree_gap values must be consistent prior to insertion */
395         validate_mm_rb(root, NULL);
396 
397         rb_insert_augmented(&vma->vm_rb, root, &vma_gap_callbacks);
398 }
399 
400 static void vma_rb_erase(struct vm_area_struct *vma, struct rb_root *root)
401 {
402         /*
403          * All rb_subtree_gap values must be consistent prior to erase,
404          * with the possible exception of the vma being erased.
405          */
406         validate_mm_rb(root, vma);
407 
408         /*
409          * Note rb_erase_augmented is a fairly large inline function,
410          * so make sure we instantiate it only once with our desired
411          * augmented rbtree callbacks.
412          */
413         rb_erase_augmented(&vma->vm_rb, root, &vma_gap_callbacks);
414 }
415 
416 /*
417  * vma has some anon_vma assigned, and is already inserted on that
418  * anon_vma's interval trees.
419  *
420  * Before updating the vma's vm_start / vm_end / vm_pgoff fields, the
421  * vma must be removed from the anon_vma's interval trees using
422  * anon_vma_interval_tree_pre_update_vma().
423  *
424  * After the update, the vma will be reinserted using
425  * anon_vma_interval_tree_post_update_vma().
426  *
427  * The entire update must be protected by exclusive mmap_sem and by
428  * the root anon_vma's mutex.
429  */
430 static inline void
431 anon_vma_interval_tree_pre_update_vma(struct vm_area_struct *vma)
432 {
433         struct anon_vma_chain *avc;
434 
435         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
436                 anon_vma_interval_tree_remove(avc, &avc->anon_vma->rb_root);
437 }
438 
439 static inline void
440 anon_vma_interval_tree_post_update_vma(struct vm_area_struct *vma)
441 {
442         struct anon_vma_chain *avc;
443 
444         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
445                 anon_vma_interval_tree_insert(avc, &avc->anon_vma->rb_root);
446 }
447 
448 static int find_vma_links(struct mm_struct *mm, unsigned long addr,
449                 unsigned long end, struct vm_area_struct **pprev,
450                 struct rb_node ***rb_link, struct rb_node **rb_parent)
451 {
452         struct rb_node **__rb_link, *__rb_parent, *rb_prev;
453 
454         __rb_link = &mm->mm_rb.rb_node;
455         rb_prev = __rb_parent = NULL;
456 
457         while (*__rb_link) {
458                 struct vm_area_struct *vma_tmp;
459 
460                 __rb_parent = *__rb_link;
461                 vma_tmp = rb_entry(__rb_parent, struct vm_area_struct, vm_rb);
462 
463                 if (vma_tmp->vm_end > addr) {
464                         /* Fail if an existing vma overlaps the area */
465                         if (vma_tmp->vm_start < end)
466                                 return -ENOMEM;
467                         __rb_link = &__rb_parent->rb_left;
468                 } else {
469                         rb_prev = __rb_parent;
470                         __rb_link = &__rb_parent->rb_right;
471                 }
472         }
473 
474         *pprev = NULL;
475         if (rb_prev)
476                 *pprev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
477         *rb_link = __rb_link;
478         *rb_parent = __rb_parent;
479         return 0;
480 }
481 
482 static unsigned long count_vma_pages_range(struct mm_struct *mm,
483                 unsigned long addr, unsigned long end)
484 {
485         unsigned long nr_pages = 0;
486         struct vm_area_struct *vma;
487 
488         /* Find first overlaping mapping */
489         vma = find_vma_intersection(mm, addr, end);
490         if (!vma)
491                 return 0;
492 
493         nr_pages = (min(end, vma->vm_end) -
494                 max(addr, vma->vm_start)) >> PAGE_SHIFT;
495 
496         /* Iterate over the rest of the overlaps */
497         for (vma = vma->vm_next; vma; vma = vma->vm_next) {
498                 unsigned long overlap_len;
499 
500                 if (vma->vm_start > end)
501                         break;
502 
503                 overlap_len = min(end, vma->vm_end) - vma->vm_start;
504                 nr_pages += overlap_len >> PAGE_SHIFT;
505         }
506 
507         return nr_pages;
508 }
509 
510 void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
511                 struct rb_node **rb_link, struct rb_node *rb_parent)
512 {
513         /* Update tracking information for the gap following the new vma. */
514         if (vma->vm_next)
515                 vma_gap_update(vma->vm_next);
516         else
517                 mm->highest_vm_end = vma->vm_end;
518 
519         /*
520          * vma->vm_prev wasn't known when we followed the rbtree to find the
521          * correct insertion point for that vma. As a result, we could not
522          * update the vma vm_rb parents rb_subtree_gap values on the way down.
523          * So, we first insert the vma with a zero rb_subtree_gap value
524          * (to be consistent with what we did on the way down), and then
525          * immediately update the gap to the correct value. Finally we
526          * rebalance the rbtree after all augmented values have been set.
527          */
528         rb_link_node(&vma->vm_rb, rb_parent, rb_link);
529         vma->rb_subtree_gap = 0;
530         vma_gap_update(vma);
531         vma_rb_insert(vma, &mm->mm_rb);
532 }
533 
534 static void __vma_link_file(struct vm_area_struct *vma)
535 {
536         struct file *file;
537 
538         file = vma->vm_file;
539         if (file) {
540                 struct address_space *mapping = file->f_mapping;
541 
542                 if (vma->vm_flags & VM_DENYWRITE)
543                         atomic_dec(&file_inode(file)->i_writecount);
544                 if (vma->vm_flags & VM_SHARED)
545                         atomic_inc(&mapping->i_mmap_writable);
546 
547                 flush_dcache_mmap_lock(mapping);
548                 vma_interval_tree_insert(vma, &mapping->i_mmap);
549                 flush_dcache_mmap_unlock(mapping);
550         }
551 }
552 
553 static void
554 __vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
555         struct vm_area_struct *prev, struct rb_node **rb_link,
556         struct rb_node *rb_parent)
557 {
558         __vma_link_list(mm, vma, prev, rb_parent);
559         __vma_link_rb(mm, vma, rb_link, rb_parent);
560 }
561 
562 static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
563                         struct vm_area_struct *prev, struct rb_node **rb_link,
564                         struct rb_node *rb_parent)
565 {
566         struct address_space *mapping = NULL;
567 
568         if (vma->vm_file) {
569                 mapping = vma->vm_file->f_mapping;
570                 i_mmap_lock_write(mapping);
571         }
572 
573         __vma_link(mm, vma, prev, rb_link, rb_parent);
574         __vma_link_file(vma);
575 
576         if (mapping)
577                 i_mmap_unlock_write(mapping);
578 
579         mm->map_count++;
580         validate_mm(mm);
581 }
582 
583 /*
584  * Helper for vma_adjust() in the split_vma insert case: insert a vma into the
585  * mm's list and rbtree.  It has already been inserted into the interval tree.
586  */
587 static void __insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
588 {
589         struct vm_area_struct *prev;
590         struct rb_node **rb_link, *rb_parent;
591 
592         if (find_vma_links(mm, vma->vm_start, vma->vm_end,
593                            &prev, &rb_link, &rb_parent))
594                 BUG();
595         __vma_link(mm, vma, prev, rb_link, rb_parent);
596         mm->map_count++;
597 }
598 
599 static inline void
600 __vma_unlink(struct mm_struct *mm, struct vm_area_struct *vma,
601                 struct vm_area_struct *prev)
602 {
603         struct vm_area_struct *next;
604 
605         vma_rb_erase(vma, &mm->mm_rb);
606         prev->vm_next = next = vma->vm_next;
607         if (next)
608                 next->vm_prev = prev;
609 
610         /* Kill the cache */
611         vmacache_invalidate(mm);
612 }
613 
614 /*
615  * We cannot adjust vm_start, vm_end, vm_pgoff fields of a vma that
616  * is already present in an i_mmap tree without adjusting the tree.
617  * The following helper function should be used when such adjustments
618  * are necessary.  The "insert" vma (if any) is to be inserted
619  * before we drop the necessary locks.
620  */
621 int vma_adjust(struct vm_area_struct *vma, unsigned long start,
622         unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert)
623 {
624         struct mm_struct *mm = vma->vm_mm;
625         struct vm_area_struct *next = vma->vm_next;
626         struct vm_area_struct *importer = NULL;
627         struct address_space *mapping = NULL;
628         struct rb_root *root = NULL;
629         struct anon_vma *anon_vma = NULL;
630         struct file *file = vma->vm_file;
631         bool start_changed = false, end_changed = false;
632         long adjust_next = 0;
633         int remove_next = 0;
634 
635         if (next && !insert) {
636                 struct vm_area_struct *exporter = NULL;
637 
638                 if (end >= next->vm_end) {
639                         /*
640                          * vma expands, overlapping all the next, and
641                          * perhaps the one after too (mprotect case 6).
642                          */
643 again:                  remove_next = 1 + (end > next->vm_end);
644                         end = next->vm_end;
645                         exporter = next;
646                         importer = vma;
647                 } else if (end > next->vm_start) {
648                         /*
649                          * vma expands, overlapping part of the next:
650                          * mprotect case 5 shifting the boundary up.
651                          */
652                         adjust_next = (end - next->vm_start) >> PAGE_SHIFT;
653                         exporter = next;
654                         importer = vma;
655                 } else if (end < vma->vm_end) {
656                         /*
657                          * vma shrinks, and !insert tells it's not
658                          * split_vma inserting another: so it must be
659                          * mprotect case 4 shifting the boundary down.
660                          */
661                         adjust_next = -((vma->vm_end - end) >> PAGE_SHIFT);
662                         exporter = vma;
663                         importer = next;
664                 }
665 
666                 /*
667                  * Easily overlooked: when mprotect shifts the boundary,
668                  * make sure the expanding vma has anon_vma set if the
669                  * shrinking vma had, to cover any anon pages imported.
670                  */
671                 if (exporter && exporter->anon_vma && !importer->anon_vma) {
672                         int error;
673 
674                         importer->anon_vma = exporter->anon_vma;
675                         error = anon_vma_clone(importer, exporter);
676                         if (error)
677                                 return error;
678                 }
679         }
680 
681         if (file) {
682                 mapping = file->f_mapping;
683                 root = &mapping->i_mmap;
684                 uprobe_munmap(vma, vma->vm_start, vma->vm_end);
685 
686                 if (adjust_next)
687                         uprobe_munmap(next, next->vm_start, next->vm_end);
688 
689                 i_mmap_lock_write(mapping);
690                 if (insert) {
691                         /*
692                          * Put into interval tree now, so instantiated pages
693                          * are visible to arm/parisc __flush_dcache_page
694                          * throughout; but we cannot insert into address
695                          * space until vma start or end is updated.
696                          */
697                         __vma_link_file(insert);
698                 }
699         }
700 
701         vma_adjust_trans_huge(vma, start, end, adjust_next);
702 
703         anon_vma = vma->anon_vma;
704         if (!anon_vma && adjust_next)
705                 anon_vma = next->anon_vma;
706         if (anon_vma) {
707                 VM_BUG_ON_VMA(adjust_next && next->anon_vma &&
708                           anon_vma != next->anon_vma, next);
709                 anon_vma_lock_write(anon_vma);
710                 anon_vma_interval_tree_pre_update_vma(vma);
711                 if (adjust_next)
712                         anon_vma_interval_tree_pre_update_vma(next);
713         }
714 
715         if (root) {
716                 flush_dcache_mmap_lock(mapping);
717                 vma_interval_tree_remove(vma, root);
718                 if (adjust_next)
719                         vma_interval_tree_remove(next, root);
720         }
721 
722         if (start != vma->vm_start) {
723                 vma->vm_start = start;
724                 start_changed = true;
725         }
726         if (end != vma->vm_end) {
727                 vma->vm_end = end;
728                 end_changed = true;
729         }
730         vma->vm_pgoff = pgoff;
731         if (adjust_next) {
732                 next->vm_start += adjust_next << PAGE_SHIFT;
733                 next->vm_pgoff += adjust_next;
734         }
735 
736         if (root) {
737                 if (adjust_next)
738                         vma_interval_tree_insert(next, root);
739                 vma_interval_tree_insert(vma, root);
740                 flush_dcache_mmap_unlock(mapping);
741         }
742 
743         if (remove_next) {
744                 /*
745                  * vma_merge has merged next into vma, and needs
746                  * us to remove next before dropping the locks.
747                  */
748                 __vma_unlink(mm, next, vma);
749                 if (file)
750                         __remove_shared_vm_struct(next, file, mapping);
751         } else if (insert) {
752                 /*
753                  * split_vma has split insert from vma, and needs
754                  * us to insert it before dropping the locks
755                  * (it may either follow vma or precede it).
756                  */
757                 __insert_vm_struct(mm, insert);
758         } else {
759                 if (start_changed)
760                         vma_gap_update(vma);
761                 if (end_changed) {
762                         if (!next)
763                                 mm->highest_vm_end = end;
764                         else if (!adjust_next)
765                                 vma_gap_update(next);
766                 }
767         }
768 
769         if (anon_vma) {
770                 anon_vma_interval_tree_post_update_vma(vma);
771                 if (adjust_next)
772                         anon_vma_interval_tree_post_update_vma(next);
773                 anon_vma_unlock_write(anon_vma);
774         }
775         if (mapping)
776                 i_mmap_unlock_write(mapping);
777 
778         if (root) {
779                 uprobe_mmap(vma);
780 
781                 if (adjust_next)
782                         uprobe_mmap(next);
783         }
784 
785         if (remove_next) {
786                 if (file) {
787                         uprobe_munmap(next, next->vm_start, next->vm_end);
788                         fput(file);
789                 }
790                 if (next->anon_vma)
791                         anon_vma_merge(vma, next);
792                 mm->map_count--;
793                 mpol_put(vma_policy(next));
794                 kmem_cache_free(vm_area_cachep, next);
795                 /*
796                  * In mprotect's case 6 (see comments on vma_merge),
797                  * we must remove another next too. It would clutter
798                  * up the code too much to do both in one go.
799                  */
800                 next = vma->vm_next;
801                 if (remove_next == 2)
802                         goto again;
803                 else if (next)
804                         vma_gap_update(next);
805                 else
806                         mm->highest_vm_end = end;
807         }
808         if (insert && file)
809                 uprobe_mmap(insert);
810 
811         validate_mm(mm);
812 
813         return 0;
814 }
815 
816 /*
817  * If the vma has a ->close operation then the driver probably needs to release
818  * per-vma resources, so we don't attempt to merge those.
819  */
820 static inline int is_mergeable_vma(struct vm_area_struct *vma,
821                                 struct file *file, unsigned long vm_flags,
822                                 struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
823 {
824         /*
825          * VM_SOFTDIRTY should not prevent from VMA merging, if we
826          * match the flags but dirty bit -- the caller should mark
827          * merged VMA as dirty. If dirty bit won't be excluded from
828          * comparison, we increase pressue on the memory system forcing
829          * the kernel to generate new VMAs when old one could be
830          * extended instead.
831          */
832         if ((vma->vm_flags ^ vm_flags) & ~VM_SOFTDIRTY)
833                 return 0;
834         if (vma->vm_file != file)
835                 return 0;
836         if (vma->vm_ops && vma->vm_ops->close)
837                 return 0;
838         if (!is_mergeable_vm_userfaultfd_ctx(vma, vm_userfaultfd_ctx))
839                 return 0;
840         return 1;
841 }
842 
843 static inline int is_mergeable_anon_vma(struct anon_vma *anon_vma1,
844                                         struct anon_vma *anon_vma2,
845                                         struct vm_area_struct *vma)
846 {
847         /*
848          * The list_is_singular() test is to avoid merging VMA cloned from
849          * parents. This can improve scalability caused by anon_vma lock.
850          */
851         if ((!anon_vma1 || !anon_vma2) && (!vma ||
852                 list_is_singular(&vma->anon_vma_chain)))
853                 return 1;
854         return anon_vma1 == anon_vma2;
855 }
856 
857 /*
858  * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
859  * in front of (at a lower virtual address and file offset than) the vma.
860  *
861  * We cannot merge two vmas if they have differently assigned (non-NULL)
862  * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
863  *
864  * We don't check here for the merged mmap wrapping around the end of pagecache
865  * indices (16TB on ia32) because do_mmap_pgoff() does not permit mmap's which
866  * wrap, nor mmaps which cover the final page at index -1UL.
867  */
868 static int
869 can_vma_merge_before(struct vm_area_struct *vma, unsigned long vm_flags,
870                      struct anon_vma *anon_vma, struct file *file,
871                      pgoff_t vm_pgoff,
872                      struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
873 {
874         if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx) &&
875             is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
876                 if (vma->vm_pgoff == vm_pgoff)
877                         return 1;
878         }
879         return 0;
880 }
881 
882 /*
883  * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
884  * beyond (at a higher virtual address and file offset than) the vma.
885  *
886  * We cannot merge two vmas if they have differently assigned (non-NULL)
887  * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
888  */
889 static int
890 can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
891                     struct anon_vma *anon_vma, struct file *file,
892                     pgoff_t vm_pgoff,
893                     struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
894 {
895         if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx) &&
896             is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
897                 pgoff_t vm_pglen;
898                 vm_pglen = vma_pages(vma);
899                 if (vma->vm_pgoff + vm_pglen == vm_pgoff)
900                         return 1;
901         }
902         return 0;
903 }
904 
905 /*
906  * Given a mapping request (addr,end,vm_flags,file,pgoff), figure out
907  * whether that can be merged with its predecessor or its successor.
908  * Or both (it neatly fills a hole).
909  *
910  * In most cases - when called for mmap, brk or mremap - [addr,end) is
911  * certain not to be mapped by the time vma_merge is called; but when
912  * called for mprotect, it is certain to be already mapped (either at
913  * an offset within prev, or at the start of next), and the flags of
914  * this area are about to be changed to vm_flags - and the no-change
915  * case has already been eliminated.
916  *
917  * The following mprotect cases have to be considered, where AAAA is
918  * the area passed down from mprotect_fixup, never extending beyond one
919  * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
920  *
921  *     AAAA             AAAA                AAAA          AAAA
922  *    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPNNNNXXXX
923  *    cannot merge    might become    might become    might become
924  *                    PPNNNNNNNNNN    PPPPPPPPPPNN    PPPPPPPPPPPP 6 or
925  *    mmap, brk or    case 4 below    case 5 below    PPPPPPPPXXXX 7 or
926  *    mremap move:                                    PPPPNNNNNNNN 8
927  *        AAAA
928  *    PPPP    NNNN    PPPPPPPPPPPP    PPPPPPPPNNNN    PPPPNNNNNNNN
929  *    might become    case 1 below    case 2 below    case 3 below
930  *
931  * Odd one out? Case 8, because it extends NNNN but needs flags of XXXX:
932  * mprotect_fixup updates vm_flags & vm_page_prot on successful return.
933  */
934 struct vm_area_struct *vma_merge(struct mm_struct *mm,
935                         struct vm_area_struct *prev, unsigned long addr,
936                         unsigned long end, unsigned long vm_flags,
937                         struct anon_vma *anon_vma, struct file *file,
938                         pgoff_t pgoff, struct mempolicy *policy,
939                         struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
940 {
941         pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
942         struct vm_area_struct *area, *next;
943         int err;
944 
945         /*
946          * We later require that vma->vm_flags == vm_flags,
947          * so this tests vma->vm_flags & VM_SPECIAL, too.
948          */
949         if (vm_flags & VM_SPECIAL)
950                 return NULL;
951 
952         if (prev)
953                 next = prev->vm_next;
954         else
955                 next = mm->mmap;
956         area = next;
957         if (next && next->vm_end == end)                /* cases 6, 7, 8 */
958                 next = next->vm_next;
959 
960         /*
961          * Can it merge with the predecessor?
962          */
963         if (prev && prev->vm_end == addr &&
964                         mpol_equal(vma_policy(prev), policy) &&
965                         can_vma_merge_after(prev, vm_flags,
966                                             anon_vma, file, pgoff,
967                                             vm_userfaultfd_ctx)) {
968                 /*
969                  * OK, it can.  Can we now merge in the successor as well?
970                  */
971                 if (next && end == next->vm_start &&
972                                 mpol_equal(policy, vma_policy(next)) &&
973                                 can_vma_merge_before(next, vm_flags,
974                                                      anon_vma, file,
975                                                      pgoff+pglen,
976                                                      vm_userfaultfd_ctx) &&
977                                 is_mergeable_anon_vma(prev->anon_vma,
978                                                       next->anon_vma, NULL)) {
979                                                         /* cases 1, 6 */
980                         err = vma_adjust(prev, prev->vm_start,
981                                 next->vm_end, prev->vm_pgoff, NULL);
982                 } else                                  /* cases 2, 5, 7 */
983                         err = vma_adjust(prev, prev->vm_start,
984                                 end, prev->vm_pgoff, NULL);
985                 if (err)
986                         return NULL;
987                 khugepaged_enter_vma_merge(prev, vm_flags);
988                 return prev;
989         }
990 
991         /*
992          * Can this new request be merged in front of next?
993          */
994         if (next && end == next->vm_start &&
995                         mpol_equal(policy, vma_policy(next)) &&
996                         can_vma_merge_before(next, vm_flags,
997                                              anon_vma, file, pgoff+pglen,
998                                              vm_userfaultfd_ctx)) {
999                 if (prev && addr < prev->vm_end)        /* case 4 */
1000                         err = vma_adjust(prev, prev->vm_start,
1001                                 addr, prev->vm_pgoff, NULL);
1002                 else                                    /* cases 3, 8 */
1003                         err = vma_adjust(area, addr, next->vm_end,
1004                                 next->vm_pgoff - pglen, NULL);
1005                 if (err)
1006                         return NULL;
1007                 khugepaged_enter_vma_merge(area, vm_flags);
1008                 return area;
1009         }
1010 
1011         return NULL;
1012 }
1013 
1014 /*
1015  * Rough compatbility check to quickly see if it's even worth looking
1016  * at sharing an anon_vma.
1017  *
1018  * They need to have the same vm_file, and the flags can only differ
1019  * in things that mprotect may change.
1020  *
1021  * NOTE! The fact that we share an anon_vma doesn't _have_ to mean that
1022  * we can merge the two vma's. For example, we refuse to merge a vma if
1023  * there is a vm_ops->close() function, because that indicates that the
1024  * driver is doing some kind of reference counting. But that doesn't
1025  * really matter for the anon_vma sharing case.
1026  */
1027 static int anon_vma_compatible(struct vm_area_struct *a, struct vm_area_struct *b)
1028 {
1029         return a->vm_end == b->vm_start &&
1030                 mpol_equal(vma_policy(a), vma_policy(b)) &&
1031                 a->vm_file == b->vm_file &&
1032                 !((a->vm_flags ^ b->vm_flags) & ~(VM_READ|VM_WRITE|VM_EXEC|VM_SOFTDIRTY)) &&
1033                 b->vm_pgoff == a->vm_pgoff + ((b->vm_start - a->vm_start) >> PAGE_SHIFT);
1034 }
1035 
1036 /*
1037  * Do some basic sanity checking to see if we can re-use the anon_vma
1038  * from 'old'. The 'a'/'b' vma's are in VM order - one of them will be
1039  * the same as 'old', the other will be the new one that is trying
1040  * to share the anon_vma.
1041  *
1042  * NOTE! This runs with mm_sem held for reading, so it is possible that
1043  * the anon_vma of 'old' is concurrently in the process of being set up
1044  * by another page fault trying to merge _that_. But that's ok: if it
1045  * is being set up, that automatically means that it will be a singleton
1046  * acceptable for merging, so we can do all of this optimistically. But
1047  * we do that READ_ONCE() to make sure that we never re-load the pointer.
1048  *
1049  * IOW: that the "list_is_singular()" test on the anon_vma_chain only
1050  * matters for the 'stable anon_vma' case (ie the thing we want to avoid
1051  * is to return an anon_vma that is "complex" due to having gone through
1052  * a fork).
1053  *
1054  * We also make sure that the two vma's are compatible (adjacent,
1055  * and with the same memory policies). That's all stable, even with just
1056  * a read lock on the mm_sem.
1057  */
1058 static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, struct vm_area_struct *a, struct vm_area_struct *b)
1059 {
1060         if (anon_vma_compatible(a, b)) {
1061                 struct anon_vma *anon_vma = READ_ONCE(old->anon_vma);
1062 
1063                 if (anon_vma && list_is_singular(&old->anon_vma_chain))
1064                         return anon_vma;
1065         }
1066         return NULL;
1067 }
1068 
1069 /*
1070  * find_mergeable_anon_vma is used by anon_vma_prepare, to check
1071  * neighbouring vmas for a suitable anon_vma, before it goes off
1072  * to allocate a new anon_vma.  It checks because a repetitive
1073  * sequence of mprotects and faults may otherwise lead to distinct
1074  * anon_vmas being allocated, preventing vma merge in subsequent
1075  * mprotect.
1076  */
1077 struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
1078 {
1079         struct anon_vma *anon_vma;
1080         struct vm_area_struct *near;
1081 
1082         near = vma->vm_next;
1083         if (!near)
1084                 goto try_prev;
1085 
1086         anon_vma = reusable_anon_vma(near, vma, near);
1087         if (anon_vma)
1088                 return anon_vma;
1089 try_prev:
1090         near = vma->vm_prev;
1091         if (!near)
1092                 goto none;
1093 
1094         anon_vma = reusable_anon_vma(near, near, vma);
1095         if (anon_vma)
1096                 return anon_vma;
1097 none:
1098         /*
1099          * There's no absolute need to look only at touching neighbours:
1100          * we could search further afield for "compatible" anon_vmas.
1101          * But it would probably just be a waste of time searching,
1102          * or lead to too many vmas hanging off the same anon_vma.
1103          * We're trying to allow mprotect remerging later on,
1104          * not trying to minimize memory used for anon_vmas.
1105          */
1106         return NULL;
1107 }
1108 
1109 /*
1110  * If a hint addr is less than mmap_min_addr change hint to be as
1111  * low as possible but still greater than mmap_min_addr
1112  */
1113 static inline unsigned long round_hint_to_min(unsigned long hint)
1114 {
1115         hint &= PAGE_MASK;
1116         if (((void *)hint != NULL) &&
1117             (hint < mmap_min_addr))
1118                 return PAGE_ALIGN(mmap_min_addr);
1119         return hint;
1120 }
1121 
1122 static inline int mlock_future_check(struct mm_struct *mm,
1123                                      unsigned long flags,
1124                                      unsigned long len)
1125 {
1126         unsigned long locked, lock_limit;
1127 
1128         /*  mlock MCL_FUTURE? */
1129         if (flags & VM_LOCKED) {
1130                 locked = len >> PAGE_SHIFT;
1131                 locked += mm->locked_vm;
1132                 lock_limit = rlimit(RLIMIT_MEMLOCK);
1133                 lock_limit >>= PAGE_SHIFT;
1134                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
1135                         return -EAGAIN;
1136         }
1137         return 0;
1138 }
1139 
1140 /*
1141  * The caller must hold down_write(&current->mm->mmap_sem).
1142  */
1143 unsigned long do_mmap(struct file *file, unsigned long addr,
1144                         unsigned long len, unsigned long prot,
1145                         unsigned long flags, vm_flags_t vm_flags,
1146                         unsigned long pgoff, unsigned long *populate)
1147 {
1148         struct mm_struct *mm = current->mm;
1149         int pkey = 0;
1150 
1151         *populate = 0;
1152 
1153         if (!len)
1154                 return -EINVAL;
1155 
1156         /*
1157          * Does the application expect PROT_READ to imply PROT_EXEC?
1158          *
1159          * (the exception is when the underlying filesystem is noexec
1160          *  mounted, in which case we dont add PROT_EXEC.)
1161          */
1162         if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
1163                 if (!(file && path_noexec(&file->f_path)))
1164                         prot |= PROT_EXEC;
1165 
1166         if (!(flags & MAP_FIXED))
1167                 addr = round_hint_to_min(addr);
1168 
1169         /* Careful about overflows.. */
1170         len = PAGE_ALIGN(len);
1171         if (!len)
1172                 return -ENOMEM;
1173 
1174         /* offset overflow? */
1175         if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
1176                 return -EOVERFLOW;
1177 
1178         /* Too many mappings? */
1179         if (mm->map_count > sysctl_max_map_count)
1180                 return -ENOMEM;
1181 
1182         /* Obtain the address to map to. we verify (or select) it and ensure
1183          * that it represents a valid section of the address space.
1184          */
1185         addr = get_unmapped_area(file, addr, len, pgoff, flags);
1186         if (offset_in_page(addr))
1187                 return addr;
1188 
1189         if (prot == PROT_EXEC) {
1190                 pkey = execute_only_pkey(mm);
1191                 if (pkey < 0)
1192                         pkey = 0;
1193         }
1194 
1195         /* Do simple checking here so the lower-level routines won't have
1196          * to. we assume access permissions have been handled by the open
1197          * of the memory object, so we don't do any here.
1198          */
1199         vm_flags |= calc_vm_prot_bits(prot, pkey) | calc_vm_flag_bits(flags) |
1200                         mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
1201 
1202         if (flags & MAP_LOCKED)
1203                 if (!can_do_mlock())
1204                         return -EPERM;
1205 
1206         if (mlock_future_check(mm, vm_flags, len))
1207                 return -EAGAIN;
1208 
1209         if (file) {
1210                 struct inode *inode = file_inode(file);
1211 
1212                 switch (flags & MAP_TYPE) {
1213                 case MAP_SHARED:
1214                         if ((prot&PROT_WRITE) && !(file->f_mode&FMODE_WRITE))
1215                                 return -EACCES;
1216 
1217                         /*
1218                          * Make sure we don't allow writing to an append-only
1219                          * file..
1220                          */
1221                         if (IS_APPEND(inode) && (file->f_mode & FMODE_WRITE))
1222                                 return -EACCES;
1223 
1224                         /*
1225                          * Make sure there are no mandatory locks on the file.
1226                          */
1227                         if (locks_verify_locked(file))
1228                                 return -EAGAIN;
1229 
1230                         vm_flags |= VM_SHARED | VM_MAYSHARE;
1231                         if (!(file->f_mode & FMODE_WRITE))
1232                                 vm_flags &= ~(VM_MAYWRITE | VM_SHARED);
1233 
1234                         /* fall through */
1235                 case MAP_PRIVATE:
1236                         if (!(file->f_mode & FMODE_READ))
1237                                 return -EACCES;
1238                         if (path_noexec(&file->f_path)) {
1239                                 if (vm_flags & VM_EXEC)
1240                                         return -EPERM;
1241                                 vm_flags &= ~VM_MAYEXEC;
1242                         }
1243 
1244                         if (!file->f_op->mmap)
1245                                 return -ENODEV;
1246                         if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1247                                 return -EINVAL;
1248                         break;
1249 
1250                 default:
1251                         return -EINVAL;
1252                 }
1253         } else {
1254                 switch (flags & MAP_TYPE) {
1255                 case MAP_SHARED:
1256                         if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1257                                 return -EINVAL;
1258                         /*
1259                          * Ignore pgoff.
1260                          */
1261                         pgoff = 0;
1262                         vm_flags |= VM_SHARED | VM_MAYSHARE;
1263                         break;
1264                 case MAP_PRIVATE:
1265                         /*
1266                          * Set pgoff according to addr for anon_vma.
1267                          */
1268                         pgoff = addr >> PAGE_SHIFT;
1269                         break;
1270                 default:
1271                         return -EINVAL;
1272                 }
1273         }
1274 
1275         /*
1276          * Set 'VM_NORESERVE' if we should not account for the
1277          * memory use of this mapping.
1278          */
1279         if (flags & MAP_NORESERVE) {
1280                 /* We honor MAP_NORESERVE if allowed to overcommit */
1281                 if (sysctl_overcommit_memory != OVERCOMMIT_NEVER)
1282                         vm_flags |= VM_NORESERVE;
1283 
1284                 /* hugetlb applies strict overcommit unless MAP_NORESERVE */
1285                 if (file && is_file_hugepages(file))
1286                         vm_flags |= VM_NORESERVE;
1287         }
1288 
1289         addr = mmap_region(file, addr, len, vm_flags, pgoff);
1290         if (!IS_ERR_VALUE(addr) &&
1291             ((vm_flags & VM_LOCKED) ||
1292              (flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE))
1293                 *populate = len;
1294         return addr;
1295 }
1296 
1297 SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
1298                 unsigned long, prot, unsigned long, flags,
1299                 unsigned long, fd, unsigned long, pgoff)
1300 {
1301         struct file *file = NULL;
1302         unsigned long retval;
1303 
1304         if (!(flags & MAP_ANONYMOUS)) {
1305                 audit_mmap_fd(fd, flags);
1306                 file = fget(fd);
1307                 if (!file)
1308                         return -EBADF;
1309                 if (is_file_hugepages(file))
1310                         len = ALIGN(len, huge_page_size(hstate_file(file)));
1311                 retval = -EINVAL;
1312                 if (unlikely(flags & MAP_HUGETLB && !is_file_hugepages(file)))
1313                         goto out_fput;
1314         } else if (flags & MAP_HUGETLB) {
1315                 struct user_struct *user = NULL;
1316                 struct hstate *hs;
1317 
1318                 hs = hstate_sizelog((flags >> MAP_HUGE_SHIFT) & SHM_HUGE_MASK);
1319                 if (!hs)
1320                         return -EINVAL;
1321 
1322                 len = ALIGN(len, huge_page_size(hs));
1323                 /*
1324                  * VM_NORESERVE is used because the reservations will be
1325                  * taken when vm_ops->mmap() is called
1326                  * A dummy user value is used because we are not locking
1327                  * memory so no accounting is necessary
1328                  */
1329                 file = hugetlb_file_setup(HUGETLB_ANON_FILE, len,
1330                                 VM_NORESERVE,
1331                                 &user, HUGETLB_ANONHUGE_INODE,
1332                                 (flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK);
1333                 if (IS_ERR(file))
1334                         return PTR_ERR(file);
1335         }
1336 
1337         flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
1338 
1339         retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
1340 out_fput:
1341         if (file)
1342                 fput(file);
1343         return retval;
1344 }
1345 
1346 #ifdef __ARCH_WANT_SYS_OLD_MMAP
1347 struct mmap_arg_struct {
1348         unsigned long addr;
1349         unsigned long len;
1350         unsigned long prot;
1351         unsigned long flags;
1352         unsigned long fd;
1353         unsigned long offset;
1354 };
1355 
1356 SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
1357 {
1358         struct mmap_arg_struct a;
1359 
1360         if (copy_from_user(&a, arg, sizeof(a)))
1361                 return -EFAULT;
1362         if (offset_in_page(a.offset))
1363                 return -EINVAL;
1364 
1365         return sys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
1366                               a.offset >> PAGE_SHIFT);
1367 }
1368 #endif /* __ARCH_WANT_SYS_OLD_MMAP */
1369 
1370 /*
1371  * Some shared mappigns will want the pages marked read-only
1372  * to track write events. If so, we'll downgrade vm_page_prot
1373  * to the private version (using protection_map[] without the
1374  * VM_SHARED bit).
1375  */
1376 int vma_wants_writenotify(struct vm_area_struct *vma)
1377 {
1378         vm_flags_t vm_flags = vma->vm_flags;
1379         const struct vm_operations_struct *vm_ops = vma->vm_ops;
1380 
1381         /* If it was private or non-writable, the write bit is already clear */
1382         if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED)))
1383                 return 0;
1384 
1385         /* The backer wishes to know when pages are first written to? */
1386         if (vm_ops && (vm_ops->page_mkwrite || vm_ops->pfn_mkwrite))
1387                 return 1;
1388 
1389         /* The open routine did something to the protections that pgprot_modify
1390          * won't preserve? */
1391         if (pgprot_val(vma->vm_page_prot) !=
1392             pgprot_val(vm_pgprot_modify(vma->vm_page_prot, vm_flags)))
1393                 return 0;
1394 
1395         /* Do we need to track softdirty? */
1396         if (IS_ENABLED(CONFIG_MEM_SOFT_DIRTY) && !(vm_flags & VM_SOFTDIRTY))
1397                 return 1;
1398 
1399         /* Specialty mapping? */
1400         if (vm_flags & VM_PFNMAP)
1401                 return 0;
1402 
1403         /* Can the mapping track the dirty pages? */
1404         return vma->vm_file && vma->vm_file->f_mapping &&
1405                 mapping_cap_account_dirty(vma->vm_file->f_mapping);
1406 }
1407 
1408 /*
1409  * We account for memory if it's a private writeable mapping,
1410  * not hugepages and VM_NORESERVE wasn't set.
1411  */
1412 static inline int accountable_mapping(struct file *file, vm_flags_t vm_flags)
1413 {
1414         /*
1415          * hugetlb has its own accounting separate from the core VM
1416          * VM_HUGETLB may not be set yet so we cannot check for that flag.
1417          */
1418         if (file && is_file_hugepages(file))
1419                 return 0;
1420 
1421         return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE;
1422 }
1423 
1424 unsigned long mmap_region(struct file *file, unsigned long addr,
1425                 unsigned long len, vm_flags_t vm_flags, unsigned long pgoff)
1426 {
1427         struct mm_struct *mm = current->mm;
1428         struct vm_area_struct *vma, *prev;
1429         int error;
1430         struct rb_node **rb_link, *rb_parent;
1431         unsigned long charged = 0;
1432 
1433         /* Check against address space limit. */
1434         if (!may_expand_vm(mm, vm_flags, len >> PAGE_SHIFT)) {
1435                 unsigned long nr_pages;
1436 
1437                 /*
1438                  * MAP_FIXED may remove pages of mappings that intersects with
1439                  * requested mapping. Account for the pages it would unmap.
1440                  */
1441                 nr_pages = count_vma_pages_range(mm, addr, addr + len);
1442 
1443                 if (!may_expand_vm(mm, vm_flags,
1444                                         (len >> PAGE_SHIFT) - nr_pages))
1445                         return -ENOMEM;
1446         }
1447 
1448         /* Clear old maps */
1449         while (find_vma_links(mm, addr, addr + len, &prev, &rb_link,
1450                               &rb_parent)) {
1451                 if (do_munmap(mm, addr, len))
1452                         return -ENOMEM;
1453         }
1454 
1455         /*
1456          * Private writable mapping: check memory availability
1457          */
1458         if (accountable_mapping(file, vm_flags)) {
1459                 charged = len >> PAGE_SHIFT;
1460                 if (security_vm_enough_memory_mm(mm, charged))
1461                         return -ENOMEM;
1462                 vm_flags |= VM_ACCOUNT;
1463         }
1464 
1465         /*
1466          * Can we just expand an old mapping?
1467          */
1468         vma = vma_merge(mm, prev, addr, addr + len, vm_flags,
1469                         NULL, file, pgoff, NULL, NULL_VM_UFFD_CTX);
1470         if (vma)
1471                 goto out;
1472 
1473         /*
1474          * Determine the object being mapped and call the appropriate
1475          * specific mapper. the address has already been validated, but
1476          * not unmapped, but the maps are removed from the list.
1477          */
1478         vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
1479         if (!vma) {
1480                 error = -ENOMEM;
1481                 goto unacct_error;
1482         }
1483 
1484         vma->vm_mm = mm;
1485         vma->vm_start = addr;
1486         vma->vm_end = addr + len;
1487         vma->vm_flags = vm_flags;
1488         vma->vm_page_prot = vm_get_page_prot(vm_flags);
1489         vma->vm_pgoff = pgoff;
1490         INIT_LIST_HEAD(&vma->anon_vma_chain);
1491 
1492         if (file) {
1493                 if (vm_flags & VM_DENYWRITE) {
1494                         error = deny_write_access(file);
1495                         if (error)
1496                                 goto free_vma;
1497                 }
1498                 if (vm_flags & VM_SHARED) {
1499                         error = mapping_map_writable(file->f_mapping);
1500                         if (error)
1501                                 goto allow_write_and_free_vma;
1502                 }
1503 
1504                 /* ->mmap() can change vma->vm_file, but must guarantee that
1505                  * vma_link() below can deny write-access if VM_DENYWRITE is set
1506                  * and map writably if VM_SHARED is set. This usually means the
1507                  * new file must not have been exposed to user-space, yet.
1508                  */
1509                 vma->vm_file = get_file(file);
1510                 error = file->f_op->mmap(file, vma);
1511                 if (error)
1512                         goto unmap_and_free_vma;
1513 
1514                 /* Can addr have changed??
1515                  *
1516                  * Answer: Yes, several device drivers can do it in their
1517                  *         f_op->mmap method. -DaveM
1518                  * Bug: If addr is changed, prev, rb_link, rb_parent should
1519                  *      be updated for vma_link()
1520                  */
1521                 WARN_ON_ONCE(addr != vma->vm_start);
1522 
1523                 addr = vma->vm_start;
1524                 vm_flags = vma->vm_flags;
1525         } else if (vm_flags & VM_SHARED) {
1526                 error = shmem_zero_setup(vma);
1527                 if (error)
1528                         goto free_vma;
1529         }
1530 
1531         vma_link(mm, vma, prev, rb_link, rb_parent);
1532         /* Once vma denies write, undo our temporary denial count */
1533         if (file) {
1534                 if (vm_flags & VM_SHARED)
1535                         mapping_unmap_writable(file->f_mapping);
1536                 if (vm_flags & VM_DENYWRITE)
1537                         allow_write_access(file);
1538         }
1539         file = vma->vm_file;
1540 out:
1541         perf_event_mmap(vma);
1542 
1543         vm_stat_account(mm, vm_flags, len >> PAGE_SHIFT);
1544         if (vm_flags & VM_LOCKED) {
1545                 if (!((vm_flags & VM_SPECIAL) || is_vm_hugetlb_page(vma) ||
1546                                         vma == get_gate_vma(current->mm)))
1547                         mm->locked_vm += (len >> PAGE_SHIFT);
1548                 else
1549                         vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
1550         }
1551 
1552         if (file)
1553                 uprobe_mmap(vma);
1554 
1555         /*
1556          * New (or expanded) vma always get soft dirty status.
1557          * Otherwise user-space soft-dirty page tracker won't
1558          * be able to distinguish situation when vma area unmapped,
1559          * then new mapped in-place (which must be aimed as
1560          * a completely new data area).
1561          */
1562         vma->vm_flags |= VM_SOFTDIRTY;
1563 
1564         vma_set_page_prot(vma);
1565 
1566         return addr;
1567 
1568 unmap_and_free_vma:
1569         vma->vm_file = NULL;
1570         fput(file);
1571 
1572         /* Undo any partial mapping done by a device driver. */
1573         unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);
1574         charged = 0;
1575         if (vm_flags & VM_SHARED)
1576                 mapping_unmap_writable(file->f_mapping);
1577 allow_write_and_free_vma:
1578         if (vm_flags & VM_DENYWRITE)
1579                 allow_write_access(file);
1580 free_vma:
1581         kmem_cache_free(vm_area_cachep, vma);
1582 unacct_error:
1583         if (charged)
1584                 vm_unacct_memory(charged);
1585         return error;
1586 }
1587 
1588 unsigned long unmapped_area(struct vm_unmapped_area_info *info)
1589 {
1590         /*
1591          * We implement the search by looking for an rbtree node that
1592          * immediately follows a suitable gap. That is,
1593          * - gap_start = vma->vm_prev->vm_end <= info->high_limit - length;
1594          * - gap_end   = vma->vm_start        >= info->low_limit  + length;
1595          * - gap_end - gap_start >= length
1596          */
1597 
1598         struct mm_struct *mm = current->mm;
1599         struct vm_area_struct *vma;
1600         unsigned long length, low_limit, high_limit, gap_start, gap_end;
1601 
1602         /* Adjust search length to account for worst case alignment overhead */
1603         length = info->length + info->align_mask;
1604         if (length < info->length)
1605                 return -ENOMEM;
1606 
1607         /* Adjust search limits by the desired length */
1608         if (info->high_limit < length)
1609                 return -ENOMEM;
1610         high_limit = info->high_limit - length;
1611 
1612         if (info->low_limit > high_limit)
1613                 return -ENOMEM;
1614         low_limit = info->low_limit + length;
1615 
1616         /* Check if rbtree root looks promising */
1617         if (RB_EMPTY_ROOT(&mm->mm_rb))
1618                 goto check_highest;
1619         vma = rb_entry(mm->mm_rb.rb_node, struct vm_area_struct, vm_rb);
1620         if (vma->rb_subtree_gap < length)
1621                 goto check_highest;
1622 
1623         while (true) {
1624                 /* Visit left subtree if it looks promising */
1625                 gap_end = vma->vm_start;
1626                 if (gap_end >= low_limit && vma->vm_rb.rb_left) {
1627                         struct vm_area_struct *left =
1628                                 rb_entry(vma->vm_rb.rb_left,
1629                                          struct vm_area_struct, vm_rb);
1630                         if (left->rb_subtree_gap >= length) {
1631                                 vma = left;
1632                                 continue;
1633                         }
1634                 }
1635 
1636                 gap_start = vma->vm_prev ? vma->vm_prev->vm_end : 0;
1637 check_current:
1638                 /* Check if current node has a suitable gap */
1639                 if (gap_start > high_limit)
1640                         return -ENOMEM;
1641                 if (gap_end >= low_limit && gap_end - gap_start >= length)
1642                         goto found;
1643 
1644                 /* Visit right subtree if it looks promising */
1645                 if (vma->vm_rb.rb_right) {
1646                         struct vm_area_struct *right =
1647                                 rb_entry(vma->vm_rb.rb_right,
1648                                          struct vm_area_struct, vm_rb);
1649                         if (right->rb_subtree_gap >= length) {
1650                                 vma = right;
1651                                 continue;
1652                         }
1653                 }
1654 
1655                 /* Go back up the rbtree to find next candidate node */
1656                 while (true) {
1657                         struct rb_node *prev = &vma->vm_rb;
1658                         if (!rb_parent(prev))
1659                                 goto check_highest;
1660                         vma = rb_entry(rb_parent(prev),
1661                                        struct vm_area_struct, vm_rb);
1662                         if (prev == vma->vm_rb.rb_left) {
1663                                 gap_start = vma->vm_prev->vm_end;
1664                                 gap_end = vma->vm_start;
1665                                 goto check_current;
1666                         }
1667                 }
1668         }
1669 
1670 check_highest:
1671         /* Check highest gap, which does not precede any rbtree node */
1672         gap_start = mm->highest_vm_end;
1673         gap_end = ULONG_MAX;  /* Only for VM_BUG_ON below */
1674         if (gap_start > high_limit)
1675                 return -ENOMEM;
1676 
1677 found:
1678         /* We found a suitable gap. Clip it with the original low_limit. */
1679         if (gap_start < info->low_limit)
1680                 gap_start = info->low_limit;
1681 
1682         /* Adjust gap address to the desired alignment */
1683         gap_start += (info->align_offset - gap_start) & info->align_mask;
1684 
1685         VM_BUG_ON(gap_start + info->length > info->high_limit);
1686         VM_BUG_ON(gap_start + info->length > gap_end);
1687         return gap_start;
1688 }
1689 
1690 unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
1691 {
1692         struct mm_struct *mm = current->mm;
1693         struct vm_area_struct *vma;
1694         unsigned long length, low_limit, high_limit, gap_start, gap_end;
1695 
1696         /* Adjust search length to account for worst case alignment overhead */
1697         length = info->length + info->align_mask;
1698         if (length < info->length)
1699                 return -ENOMEM;
1700 
1701         /*
1702          * Adjust search limits by the desired length.
1703          * See implementation comment at top of unmapped_area().
1704          */
1705         gap_end = info->high_limit;
1706         if (gap_end < length)
1707                 return -ENOMEM;
1708         high_limit = gap_end - length;
1709 
1710         if (info->low_limit > high_limit)
1711                 return -ENOMEM;
1712         low_limit = info->low_limit + length;
1713 
1714         /* Check highest gap, which does not precede any rbtree node */
1715         gap_start = mm->highest_vm_end;
1716         if (gap_start <= high_limit)
1717                 goto found_highest;
1718 
1719         /* Check if rbtree root looks promising */
1720         if (RB_EMPTY_ROOT(&mm->mm_rb))
1721                 return -ENOMEM;
1722         vma = rb_entry(mm->mm_rb.rb_node, struct vm_area_struct, vm_rb);
1723         if (vma->rb_subtree_gap < length)
1724                 return -ENOMEM;
1725 
1726         while (true) {
1727                 /* Visit right subtree if it looks promising */
1728                 gap_start = vma->vm_prev ? vma->vm_prev->vm_end : 0;
1729                 if (gap_start <= high_limit && vma->vm_rb.rb_right) {
1730                         struct vm_area_struct *right =
1731                                 rb_entry(vma->vm_rb.rb_right,
1732                                          struct vm_area_struct, vm_rb);
1733                         if (right->rb_subtree_gap >= length) {
1734                                 vma = right;
1735                                 continue;
1736                         }
1737                 }
1738 
1739 check_current:
1740                 /* Check if current node has a suitable gap */
1741                 gap_end = vma->vm_start;
1742                 if (gap_end < low_limit)
1743                         return -ENOMEM;
1744                 if (gap_start <= high_limit && gap_end - gap_start >= length)
1745                         goto found;
1746 
1747                 /* Visit left subtree if it looks promising */
1748                 if (vma->vm_rb.rb_left) {
1749                         struct vm_area_struct *left =
1750                                 rb_entry(vma->vm_rb.rb_left,
1751                                          struct vm_area_struct, vm_rb);
1752                         if (left->rb_subtree_gap >= length) {
1753                                 vma = left;
1754                                 continue;
1755                         }
1756                 }
1757 
1758                 /* Go back up the rbtree to find next candidate node */
1759                 while (true) {
1760                         struct rb_node *prev = &vma->vm_rb;
1761                         if (!rb_parent(prev))
1762                                 return -ENOMEM;
1763                         vma = rb_entry(rb_parent(prev),
1764                                        struct vm_area_struct, vm_rb);
1765                         if (prev == vma->vm_rb.rb_right) {
1766                                 gap_start = vma->vm_prev ?
1767                                         vma->vm_prev->vm_end : 0;
1768                                 goto check_current;
1769                         }
1770                 }
1771         }
1772 
1773 found:
1774         /* We found a suitable gap. Clip it with the original high_limit. */
1775         if (gap_end > info->high_limit)
1776                 gap_end = info->high_limit;
1777 
1778 found_highest:
1779         /* Compute highest gap address at the desired alignment */
1780         gap_end -= info->length;
1781         gap_end -= (gap_end - info->align_offset) & info->align_mask;
1782 
1783         VM_BUG_ON(gap_end < info->low_limit);
1784         VM_BUG_ON(gap_end < gap_start);
1785         return gap_end;
1786 }
1787 
1788 /* Get an address range which is currently unmapped.
1789  * For shmat() with addr=0.
1790  *
1791  * Ugly calling convention alert:
1792  * Return value with the low bits set means error value,
1793  * ie
1794  *      if (ret & ~PAGE_MASK)
1795  *              error = ret;
1796  *
1797  * This function "knows" that -ENOMEM has the bits set.
1798  */
1799 #ifndef HAVE_ARCH_UNMAPPED_AREA
1800 unsigned long
1801 arch_get_unmapped_area(struct file *filp, unsigned long addr,
1802                 unsigned long len, unsigned long pgoff, unsigned long flags)
1803 {
1804         struct mm_struct *mm = current->mm;
1805         struct vm_area_struct *vma;
1806         struct vm_unmapped_area_info info;
1807 
1808         if (len > TASK_SIZE - mmap_min_addr)
1809                 return -ENOMEM;
1810 
1811         if (flags & MAP_FIXED)
1812                 return addr;
1813 
1814         if (addr) {
1815                 addr = PAGE_ALIGN(addr);
1816                 vma = find_vma(mm, addr);
1817                 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
1818                     (!vma || addr + len <= vma->vm_start))
1819                         return addr;
1820         }
1821 
1822         info.flags = 0;
1823         info.length = len;
1824         info.low_limit = mm->mmap_base;
1825         info.high_limit = TASK_SIZE;
1826         info.align_mask = 0;
1827         return vm_unmapped_area(&info);
1828 }
1829 #endif
1830 
1831 /*
1832  * This mmap-allocator allocates new areas top-down from below the
1833  * stack's low limit (the base):
1834  */
1835 #ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
1836 unsigned long
1837 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
1838                           const unsigned long len, const unsigned long pgoff,
1839                           const unsigned long flags)
1840 {
1841         struct vm_area_struct *vma;
1842         struct mm_struct *mm = current->mm;
1843         unsigned long addr = addr0;
1844         struct vm_unmapped_area_info info;
1845 
1846         /* requested length too big for entire address space */
1847         if (len > TASK_SIZE - mmap_min_addr)
1848                 return -ENOMEM;
1849 
1850         if (flags & MAP_FIXED)
1851                 return addr;
1852 
1853         /* requesting a specific address */
1854         if (addr) {
1855                 addr = PAGE_ALIGN(addr);
1856                 vma = find_vma(mm, addr);
1857                 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
1858                                 (!vma || addr + len <= vma->vm_start))
1859                         return addr;
1860         }
1861 
1862         info.flags = VM_UNMAPPED_AREA_TOPDOWN;
1863         info.length = len;
1864         info.low_limit = max(PAGE_SIZE, mmap_min_addr);
1865         info.high_limit = mm->mmap_base;
1866         info.align_mask = 0;
1867         addr = vm_unmapped_area(&info);
1868 
1869         /*
1870          * A failed mmap() very likely causes application failure,
1871          * so fall back to the bottom-up function here. This scenario
1872          * can happen with large stack limits and large mmap()
1873          * allocations.
1874          */
1875         if (offset_in_page(addr)) {
1876                 VM_BUG_ON(addr != -ENOMEM);
1877                 info.flags = 0;
1878                 info.low_limit = TASK_UNMAPPED_BASE;
1879                 info.high_limit = TASK_SIZE;
1880                 addr = vm_unmapped_area(&info);
1881         }
1882 
1883         return addr;
1884 }
1885 #endif
1886 
1887 unsigned long
1888 get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
1889                 unsigned long pgoff, unsigned long flags)
1890 {
1891         unsigned long (*get_area)(struct file *, unsigned long,
1892                                   unsigned long, unsigned long, unsigned long);
1893 
1894         unsigned long error = arch_mmap_check(addr, len, flags);
1895         if (error)
1896                 return error;
1897 
1898         /* Careful about overflows.. */
1899         if (len > TASK_SIZE)
1900                 return -ENOMEM;
1901 
1902         get_area = current->mm->get_unmapped_area;
1903         if (file && file->f_op->get_unmapped_area)
1904                 get_area = file->f_op->get_unmapped_area;
1905         addr = get_area(file, addr, len, pgoff, flags);
1906         if (IS_ERR_VALUE(addr))
1907                 return addr;
1908 
1909         if (addr > TASK_SIZE - len)
1910                 return -ENOMEM;
1911         if (offset_in_page(addr))
1912                 return -EINVAL;
1913 
1914         addr = arch_rebalance_pgtables(addr, len);
1915         error = security_mmap_addr(addr);
1916         return error ? error : addr;
1917 }
1918 
1919 EXPORT_SYMBOL(get_unmapped_area);
1920 
1921 /* Look up the first VMA which satisfies  addr < vm_end,  NULL if none. */
1922 struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
1923 {
1924         struct rb_node *rb_node;
1925         struct vm_area_struct *vma;
1926 
1927         /* Check the cache first. */
1928         vma = vmacache_find(mm, addr);
1929         if (likely(vma))
1930                 return vma;
1931 
1932         rb_node = mm->mm_rb.rb_node;
1933 
1934         while (rb_node) {
1935                 struct vm_area_struct *tmp;
1936 
1937                 tmp = rb_entry(rb_node, struct vm_area_struct, vm_rb);
1938 
1939                 if (tmp->vm_end > addr) {
1940                         vma = tmp;
1941                         if (tmp->vm_start <= addr)
1942                                 break;
1943                         rb_node = rb_node->rb_left;
1944                 } else
1945                         rb_node = rb_node->rb_right;
1946         }
1947 
1948         if (vma)
1949                 vmacache_update(addr, vma);
1950         return vma;
1951 }
1952 
1953 EXPORT_SYMBOL(find_vma);
1954 
1955 /*
1956  * Same as find_vma, but also return a pointer to the previous VMA in *pprev.
1957  */
1958 struct vm_area_struct *
1959 find_vma_prev(struct mm_struct *mm, unsigned long addr,
1960                         struct vm_area_struct **pprev)
1961 {
1962         struct vm_area_struct *vma;
1963 
1964         vma = find_vma(mm, addr);
1965         if (vma) {
1966                 *pprev = vma->vm_prev;
1967         } else {
1968                 struct rb_node *rb_node = mm->mm_rb.rb_node;
1969                 *pprev = NULL;
1970                 while (rb_node) {
1971                         *pprev = rb_entry(rb_node, struct vm_area_struct, vm_rb);
1972                         rb_node = rb_node->rb_right;
1973                 }
1974         }
1975         return vma;
1976 }
1977 
1978 /*
1979  * Verify that the stack growth is acceptable and
1980  * update accounting. This is shared with both the
1981  * grow-up and grow-down cases.
1982  */
1983 static int acct_stack_growth(struct vm_area_struct *vma, unsigned long size, unsigned long grow)
1984 {
1985         struct mm_struct *mm = vma->vm_mm;
1986         struct rlimit *rlim = current->signal->rlim;
1987         unsigned long new_start, actual_size;
1988 
1989         /* address space limit tests */
1990         if (!may_expand_vm(mm, vma->vm_flags, grow))
1991                 return -ENOMEM;
1992 
1993         /* Stack limit test */
1994         actual_size = size;
1995         if (size && (vma->vm_flags & (VM_GROWSUP | VM_GROWSDOWN)))
1996                 actual_size -= PAGE_SIZE;
1997         if (actual_size > READ_ONCE(rlim[RLIMIT_STACK].rlim_cur))
1998                 return -ENOMEM;
1999 
2000         /* mlock limit tests */
2001         if (vma->vm_flags & VM_LOCKED) {
2002                 unsigned long locked;
2003                 unsigned long limit;
2004                 locked = mm->locked_vm + grow;
2005                 limit = READ_ONCE(rlim[RLIMIT_MEMLOCK].rlim_cur);
2006                 limit >>= PAGE_SHIFT;
2007                 if (locked > limit && !capable(CAP_IPC_LOCK))
2008                         return -ENOMEM;
2009         }
2010 
2011         /* Check to ensure the stack will not grow into a hugetlb-only region */
2012         new_start = (vma->vm_flags & VM_GROWSUP) ? vma->vm_start :
2013                         vma->vm_end - size;
2014         if (is_hugepage_only_range(vma->vm_mm, new_start, size))
2015                 return -EFAULT;
2016 
2017         /*
2018          * Overcommit..  This must be the final test, as it will
2019          * update security statistics.
2020          */
2021         if (security_vm_enough_memory_mm(mm, grow))
2022                 return -ENOMEM;
2023 
2024         return 0;
2025 }
2026 
2027 #if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
2028 /*
2029  * PA-RISC uses this for its stack; IA64 for its Register Backing Store.
2030  * vma is the last one with address > vma->vm_end.  Have to extend vma.
2031  */
2032 int expand_upwards(struct vm_area_struct *vma, unsigned long address)
2033 {
2034         struct mm_struct *mm = vma->vm_mm;
2035         int error = 0;
2036 
2037         if (!(vma->vm_flags & VM_GROWSUP))
2038                 return -EFAULT;
2039 
2040         /* Guard against wrapping around to address 0. */
2041         if (address < PAGE_ALIGN(address+4))
2042                 address = PAGE_ALIGN(address+4);
2043         else
2044                 return -ENOMEM;
2045 
2046         /* We must make sure the anon_vma is allocated. */
2047         if (unlikely(anon_vma_prepare(vma)))
2048                 return -ENOMEM;
2049 
2050         /*
2051          * vma->vm_start/vm_end cannot change under us because the caller
2052          * is required to hold the mmap_sem in read mode.  We need the
2053          * anon_vma lock to serialize against concurrent expand_stacks.
2054          */
2055         anon_vma_lock_write(vma->anon_vma);
2056 
2057         /* Somebody else might have raced and expanded it already */
2058         if (address > vma->vm_end) {
2059                 unsigned long size, grow;
2060 
2061                 size = address - vma->vm_start;
2062                 grow = (address - vma->vm_end) >> PAGE_SHIFT;
2063 
2064                 error = -ENOMEM;
2065                 if (vma->vm_pgoff + (size >> PAGE_SHIFT) >= vma->vm_pgoff) {
2066                         error = acct_stack_growth(vma, size, grow);
2067                         if (!error) {
2068                                 /*
2069                                  * vma_gap_update() doesn't support concurrent
2070                                  * updates, but we only hold a shared mmap_sem
2071                                  * lock here, so we need to protect against
2072                                  * concurrent vma expansions.
2073                                  * anon_vma_lock_write() doesn't help here, as
2074                                  * we don't guarantee that all growable vmas
2075                                  * in a mm share the same root anon vma.
2076                                  * So, we reuse mm->page_table_lock to guard
2077                                  * against concurrent vma expansions.
2078                                  */
2079                                 spin_lock(&mm->page_table_lock);
2080                                 if (vma->vm_flags & VM_LOCKED)
2081                                         mm->locked_vm += grow;
2082                                 vm_stat_account(mm, vma->vm_flags, grow);
2083                                 anon_vma_interval_tree_pre_update_vma(vma);
2084                                 vma->vm_end = address;
2085                                 anon_vma_interval_tree_post_update_vma(vma);
2086                                 if (vma->vm_next)
2087                                         vma_gap_update(vma->vm_next);
2088                                 else
2089                                         mm->highest_vm_end = address;
2090                                 spin_unlock(&mm->page_table_lock);
2091 
2092                                 perf_event_mmap(vma);
2093                         }
2094                 }
2095         }
2096         anon_vma_unlock_write(vma->anon_vma);
2097         khugepaged_enter_vma_merge(vma, vma->vm_flags);
2098         validate_mm(mm);
2099         return error;
2100 }
2101 #endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
2102 
2103 /*
2104  * vma is the first one with address < vma->vm_start.  Have to extend vma.
2105  */
2106 int expand_downwards(struct vm_area_struct *vma,
2107                                    unsigned long address)
2108 {
2109         struct mm_struct *mm = vma->vm_mm;
2110         int error;
2111 
2112         address &= PAGE_MASK;
2113         error = security_mmap_addr(address);
2114         if (error)
2115                 return error;
2116 
2117         /* We must make sure the anon_vma is allocated. */
2118         if (unlikely(anon_vma_prepare(vma)))
2119                 return -ENOMEM;
2120 
2121         /*
2122          * vma->vm_start/vm_end cannot change under us because the caller
2123          * is required to hold the mmap_sem in read mode.  We need the
2124          * anon_vma lock to serialize against concurrent expand_stacks.
2125          */
2126         anon_vma_lock_write(vma->anon_vma);
2127 
2128         /* Somebody else might have raced and expanded it already */
2129         if (address < vma->vm_start) {
2130                 unsigned long size, grow;
2131 
2132                 size = vma->vm_end - address;
2133                 grow = (vma->vm_start - address) >> PAGE_SHIFT;
2134 
2135                 error = -ENOMEM;
2136                 if (grow <= vma->vm_pgoff) {
2137                         error = acct_stack_growth(vma, size, grow);
2138                         if (!error) {
2139                                 /*
2140                                  * vma_gap_update() doesn't support concurrent
2141                                  * updates, but we only hold a shared mmap_sem
2142                                  * lock here, so we need to protect against
2143                                  * concurrent vma expansions.
2144                                  * anon_vma_lock_write() doesn't help here, as
2145                                  * we don't guarantee that all growable vmas
2146                                  * in a mm share the same root anon vma.
2147                                  * So, we reuse mm->page_table_lock to guard
2148                                  * against concurrent vma expansions.
2149                                  */
2150                                 spin_lock(&mm->page_table_lock);
2151                                 if (vma->vm_flags & VM_LOCKED)
2152                                         mm->locked_vm += grow;
2153                                 vm_stat_account(mm, vma->vm_flags, grow);
2154                                 anon_vma_interval_tree_pre_update_vma(vma);
2155                                 vma->vm_start = address;
2156                                 vma->vm_pgoff -= grow;
2157                                 anon_vma_interval_tree_post_update_vma(vma);
2158                                 vma_gap_update(vma);
2159                                 spin_unlock(&mm->page_table_lock);
2160 
2161                                 perf_event_mmap(vma);
2162                         }
2163                 }
2164         }
2165         anon_vma_unlock_write(vma->anon_vma);
2166         khugepaged_enter_vma_merge(vma, vma->vm_flags);
2167         validate_mm(mm);
2168         return error;
2169 }
2170 
2171 /*
2172  * Note how expand_stack() refuses to expand the stack all the way to
2173  * abut the next virtual mapping, *unless* that mapping itself is also
2174  * a stack mapping. We want to leave room for a guard page, after all
2175  * (the guard page itself is not added here, that is done by the
2176  * actual page faulting logic)
2177  *
2178  * This matches the behavior of the guard page logic (see mm/memory.c:
2179  * check_stack_guard_page()), which only allows the guard page to be
2180  * removed under these circumstances.
2181  */
2182 #ifdef CONFIG_STACK_GROWSUP
2183 int expand_stack(struct vm_area_struct *vma, unsigned long address)
2184 {
2185         struct vm_area_struct *next;
2186 
2187         address &= PAGE_MASK;
2188         next = vma->vm_next;
2189         if (next && next->vm_start == address + PAGE_SIZE) {
2190                 if (!(next->vm_flags & VM_GROWSUP))
2191                         return -ENOMEM;
2192         }
2193         return expand_upwards(vma, address);
2194 }
2195 
2196 struct vm_area_struct *
2197 find_extend_vma(struct mm_struct *mm, unsigned long addr)
2198 {
2199         struct vm_area_struct *vma, *prev;
2200 
2201         addr &= PAGE_MASK;
2202         vma = find_vma_prev(mm, addr, &prev);
2203         if (vma && (vma->vm_start <= addr))
2204                 return vma;
2205         if (!prev || expand_stack(prev, addr))
2206                 return NULL;
2207         if (prev->vm_flags & VM_LOCKED)
2208                 populate_vma_page_range(prev, addr, prev->vm_end, NULL);
2209         return prev;
2210 }
2211 #else
2212 int expand_stack(struct vm_area_struct *vma, unsigned long address)
2213 {
2214         struct vm_area_struct *prev;
2215 
2216         address &= PAGE_MASK;
2217         prev = vma->vm_prev;
2218         if (prev && prev->vm_end == address) {
2219                 if (!(prev->vm_flags & VM_GROWSDOWN))
2220                         return -ENOMEM;
2221         }
2222         return expand_downwards(vma, address);
2223 }
2224 
2225 struct vm_area_struct *
2226 find_extend_vma(struct mm_struct *mm, unsigned long addr)
2227 {
2228         struct vm_area_struct *vma;
2229         unsigned long start;
2230 
2231         addr &= PAGE_MASK;
2232         vma = find_vma(mm, addr);
2233         if (!vma)
2234                 return NULL;
2235         if (vma->vm_start <= addr)
2236                 return vma;
2237         if (!(vma->vm_flags & VM_GROWSDOWN))
2238                 return NULL;
2239         start = vma->vm_start;
2240         if (expand_stack(vma, addr))
2241                 return NULL;
2242         if (vma->vm_flags & VM_LOCKED)
2243                 populate_vma_page_range(vma, addr, start, NULL);
2244         return vma;
2245 }
2246 #endif
2247 
2248 EXPORT_SYMBOL_GPL(find_extend_vma);
2249 
2250 /*
2251  * Ok - we have the memory areas we should free on the vma list,
2252  * so release them, and do the vma updates.
2253  *
2254  * Called with the mm semaphore held.
2255  */
2256 static void remove_vma_list(struct mm_struct *mm, struct vm_area_struct *vma)
2257 {
2258         unsigned long nr_accounted = 0;
2259 
2260         /* Update high watermark before we lower total_vm */
2261         update_hiwater_vm(mm);
2262         do {
2263                 long nrpages = vma_pages(vma);
2264 
2265                 if (vma->vm_flags & VM_ACCOUNT)
2266                         nr_accounted += nrpages;
2267                 vm_stat_account(mm, vma->vm_flags, -nrpages);
2268                 vma = remove_vma(vma);
2269         } while (vma);
2270         vm_unacct_memory(nr_accounted);
2271         validate_mm(mm);
2272 }
2273 
2274 /*
2275  * Get rid of page table information in the indicated region.
2276  *
2277  * Called with the mm semaphore held.
2278  */
2279 static void unmap_region(struct mm_struct *mm,
2280                 struct vm_area_struct *vma, struct vm_area_struct *prev,
2281                 unsigned long start, unsigned long end)
2282 {
2283         struct vm_area_struct *next = prev ? prev->vm_next : mm->mmap;
2284         struct mmu_gather tlb;
2285 
2286         lru_add_drain();
2287         tlb_gather_mmu(&tlb, mm, start, end);
2288         update_hiwater_rss(mm);
2289         unmap_vmas(&tlb, vma, start, end);
2290         free_pgtables(&tlb, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
2291                                  next ? next->vm_start : USER_PGTABLES_CEILING);
2292         tlb_finish_mmu(&tlb, start, end);
2293 }
2294 
2295 /*
2296  * Create a list of vma's touched by the unmap, removing them from the mm's
2297  * vma list as we go..
2298  */
2299 static void
2300 detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
2301         struct vm_area_struct *prev, unsigned long end)
2302 {
2303         struct vm_area_struct **insertion_point;
2304         struct vm_area_struct *tail_vma = NULL;
2305 
2306         insertion_point = (prev ? &prev->vm_next : &mm->mmap);
2307         vma->vm_prev = NULL;
2308         do {
2309                 vma_rb_erase(vma, &mm->mm_rb);
2310                 mm->map_count--;
2311                 tail_vma = vma;
2312                 vma = vma->vm_next;
2313         } while (vma && vma->vm_start < end);
2314         *insertion_point = vma;
2315         if (vma) {
2316                 vma->vm_prev = prev;
2317                 vma_gap_update(vma);
2318         } else
2319                 mm->highest_vm_end = prev ? prev->vm_end : 0;
2320         tail_vma->vm_next = NULL;
2321 
2322         /* Kill the cache */
2323         vmacache_invalidate(mm);
2324 }
2325 
2326 /*
2327  * __split_vma() bypasses sysctl_max_map_count checking.  We use this on the
2328  * munmap path where it doesn't make sense to fail.
2329  */
2330 static int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
2331               unsigned long addr, int new_below)
2332 {
2333         struct vm_area_struct *new;
2334         int err;
2335 
2336         if (is_vm_hugetlb_page(vma) && (addr &
2337                                         ~(huge_page_mask(hstate_vma(vma)))))
2338                 return -EINVAL;
2339 
2340         new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
2341         if (!new)
2342                 return -ENOMEM;
2343 
2344         /* most fields are the same, copy all, and then fixup */
2345         *new = *vma;
2346 
2347         INIT_LIST_HEAD(&new->anon_vma_chain);
2348 
2349         if (new_below)
2350                 new->vm_end = addr;
2351         else {
2352                 new->vm_start = addr;
2353                 new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
2354         }
2355 
2356         err = vma_dup_policy(vma, new);
2357         if (err)
2358                 goto out_free_vma;
2359 
2360         err = anon_vma_clone(new, vma);
2361         if (err)
2362                 goto out_free_mpol;
2363 
2364         if (new->vm_file)
2365                 get_file(new->vm_file);
2366 
2367         if (new->vm_ops && new->vm_ops->open)
2368                 new->vm_ops->open(new);
2369 
2370         if (new_below)
2371                 err = vma_adjust(vma, addr, vma->vm_end, vma->vm_pgoff +
2372                         ((addr - new->vm_start) >> PAGE_SHIFT), new);
2373         else
2374                 err = vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new);
2375 
2376         /* Success. */
2377         if (!err)
2378                 return 0;
2379 
2380         /* Clean everything up if vma_adjust failed. */
2381         if (new->vm_ops && new->vm_ops->close)
2382                 new->vm_ops->close(new);
2383         if (new->vm_file)
2384                 fput(new->vm_file);
2385         unlink_anon_vmas(new);
2386  out_free_mpol:
2387         mpol_put(vma_policy(new));
2388  out_free_vma:
2389         kmem_cache_free(vm_area_cachep, new);
2390         return err;
2391 }
2392 
2393 /*
2394  * Split a vma into two pieces at address 'addr', a new vma is allocated
2395  * either for the first part or the tail.
2396  */
2397 int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
2398               unsigned long addr, int new_below)
2399 {
2400         if (mm->map_count >= sysctl_max_map_count)
2401                 return -ENOMEM;
2402 
2403         return __split_vma(mm, vma, addr, new_below);
2404 }
2405 
2406 /* Munmap is split into 2 main parts -- this part which finds
2407  * what needs doing, and the areas themselves, which do the
2408  * work.  This now handles partial unmappings.
2409  * Jeremy Fitzhardinge <jeremy@goop.org>
2410  */
2411 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
2412 {
2413         unsigned long end;
2414         struct vm_area_struct *vma, *prev, *last;
2415 
2416         if ((offset_in_page(start)) || start > TASK_SIZE || len > TASK_SIZE-start)
2417                 return -EINVAL;
2418 
2419         len = PAGE_ALIGN(len);
2420         if (len == 0)
2421                 return -EINVAL;
2422 
2423         /* Find the first overlapping VMA */
2424         vma = find_vma(mm, start);
2425         if (!vma)
2426                 return 0;
2427         prev = vma->vm_prev;
2428         /* we have  start < vma->vm_end  */
2429 
2430         /* if it doesn't overlap, we have nothing.. */
2431         end = start + len;
2432         if (vma->vm_start >= end)
2433                 return 0;
2434 
2435         /*
2436          * If we need to split any vma, do it now to save pain later.
2437          *
2438          * Note: mremap's move_vma VM_ACCOUNT handling assumes a partially
2439          * unmapped vm_area_struct will remain in use: so lower split_vma
2440          * places tmp vma above, and higher split_vma places tmp vma below.
2441          */
2442         if (start > vma->vm_start) {
2443                 int error;
2444 
2445                 /*
2446                  * Make sure that map_count on return from munmap() will
2447                  * not exceed its limit; but let map_count go just above
2448                  * its limit temporarily, to help free resources as expected.
2449                  */
2450                 if (end < vma->vm_end && mm->map_count >= sysctl_max_map_count)
2451                         return -ENOMEM;
2452 
2453                 error = __split_vma(mm, vma, start, 0);
2454                 if (error)
2455                         return error;
2456                 prev = vma;
2457         }
2458 
2459         /* Does it split the last one? */
2460         last = find_vma(mm, end);
2461         if (last && end > last->vm_start) {
2462                 int error = __split_vma(mm, last, end, 1);
2463                 if (error)
2464                         return error;
2465         }
2466         vma = prev ? prev->vm_next : mm->mmap;
2467 
2468         /*
2469          * unlock any mlock()ed ranges before detaching vmas
2470          */
2471         if (mm->locked_vm) {
2472                 struct vm_area_struct *tmp = vma;
2473                 while (tmp && tmp->vm_start < end) {
2474                         if (tmp->vm_flags & VM_LOCKED) {
2475                                 mm->locked_vm -= vma_pages(tmp);
2476                                 munlock_vma_pages_all(tmp);
2477                         }
2478                         tmp = tmp->vm_next;
2479                 }
2480         }
2481 
2482         /*
2483          * Remove the vma's, and unmap the actual pages
2484          */
2485         detach_vmas_to_be_unmapped(mm, vma, prev, end);
2486         unmap_region(mm, vma, prev, start, end);
2487 
2488         arch_unmap(mm, vma, start, end);
2489 
2490         /* Fix up all other VM information */
2491         remove_vma_list(mm, vma);
2492 
2493         return 0;
2494 }
2495 
2496 int vm_munmap(unsigned long start, size_t len)
2497 {
2498         int ret;
2499         struct mm_struct *mm = current->mm;
2500 
2501         down_write(&mm->mmap_sem);
2502         ret = do_munmap(mm, start, len);
2503         up_write(&mm->mmap_sem);
2504         return ret;
2505 }
2506 EXPORT_SYMBOL(vm_munmap);
2507 
2508 SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
2509 {
2510         profile_munmap(addr);
2511         return vm_munmap(addr, len);
2512 }
2513 
2514 
2515 /*
2516  * Emulation of deprecated remap_file_pages() syscall.
2517  */
2518 SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
2519                 unsigned long, prot, unsigned long, pgoff, unsigned long, flags)
2520 {
2521 
2522         struct mm_struct *mm = current->mm;
2523         struct vm_area_struct *vma;
2524         unsigned long populate = 0;
2525         unsigned long ret = -EINVAL;
2526         struct file *file;
2527 
2528         pr_warn_once("%s (%d) uses deprecated remap_file_pages() syscall. See Documentation/vm/remap_file_pages.txt.\n",
2529                      current->comm, current->pid);
2530 
2531         if (prot)
2532                 return ret;
2533         start = start & PAGE_MASK;
2534         size = size & PAGE_MASK;
2535 
2536         if (start + size <= start)
2537                 return ret;
2538 
2539         /* Does pgoff wrap? */
2540         if (pgoff + (size >> PAGE_SHIFT) < pgoff)
2541                 return ret;
2542 
2543         down_write(&mm->mmap_sem);
2544         vma = find_vma(mm, start);
2545 
2546         if (!vma || !(vma->vm_flags & VM_SHARED))
2547                 goto out;
2548 
2549         if (start < vma->vm_start)
2550                 goto out;
2551 
2552         if (start + size > vma->vm_end) {
2553                 struct vm_area_struct *next;
2554 
2555                 for (next = vma->vm_next; next; next = next->vm_next) {
2556                         /* hole between vmas ? */
2557                         if (next->vm_start != next->vm_prev->vm_end)
2558                                 goto out;
2559 
2560                         if (next->vm_file != vma->vm_file)
2561                                 goto out;
2562 
2563                         if (next->vm_flags != vma->vm_flags)
2564                                 goto out;
2565 
2566                         if (start + size <= next->vm_end)
2567                                 break;
2568                 }
2569 
2570                 if (!next)
2571                         goto out;
2572         }
2573 
2574         prot |= vma->vm_flags & VM_READ ? PROT_READ : 0;
2575         prot |= vma->vm_flags & VM_WRITE ? PROT_WRITE : 0;
2576         prot |= vma->vm_flags & VM_EXEC ? PROT_EXEC : 0;
2577 
2578         flags &= MAP_NONBLOCK;
2579         flags |= MAP_SHARED | MAP_FIXED | MAP_POPULATE;
2580         if (vma->vm_flags & VM_LOCKED) {
2581                 struct vm_area_struct *tmp;
2582                 flags |= MAP_LOCKED;
2583 
2584                 /* drop PG_Mlocked flag for over-mapped range */
2585                 for (tmp = vma; tmp->vm_start >= start + size;
2586                                 tmp = tmp->vm_next) {
2587                         munlock_vma_pages_range(tmp,
2588                                         max(tmp->vm_start, start),
2589                                         min(tmp->vm_end, start + size));
2590                 }
2591         }
2592 
2593         file = get_file(vma->vm_file);
2594         ret = do_mmap_pgoff(vma->vm_file, start, size,
2595                         prot, flags, pgoff, &populate);
2596         fput(file);
2597 out:
2598         up_write(&mm->mmap_sem);
2599         if (populate)
2600                 mm_populate(ret, populate);
2601         if (!IS_ERR_VALUE(ret))
2602                 ret = 0;
2603         return ret;
2604 }
2605 
2606 static inline void verify_mm_writelocked(struct mm_struct *mm)
2607 {
2608 #ifdef CONFIG_DEBUG_VM
2609         if (unlikely(down_read_trylock(&mm->mmap_sem))) {
2610                 WARN_ON(1);
2611                 up_read(&mm->mmap_sem);
2612         }
2613 #endif
2614 }
2615 
2616 /*
2617  *  this is really a simplified "do_mmap".  it only handles
2618  *  anonymous maps.  eventually we may be able to do some
2619  *  brk-specific accounting here.
2620  */
2621 static unsigned long do_brk(unsigned long addr, unsigned long len)
2622 {
2623         struct mm_struct *mm = current->mm;
2624         struct vm_area_struct *vma, *prev;
2625         unsigned long flags;
2626         struct rb_node **rb_link, *rb_parent;
2627         pgoff_t pgoff = addr >> PAGE_SHIFT;
2628         int error;
2629 
2630         len = PAGE_ALIGN(len);
2631         if (!len)
2632                 return addr;
2633 
2634         flags = VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
2635 
2636         error = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
2637         if (offset_in_page(error))
2638                 return error;
2639 
2640         error = mlock_future_check(mm, mm->def_flags, len);
2641         if (error)
2642                 return error;
2643 
2644         /*
2645          * mm->mmap_sem is required to protect against another thread
2646          * changing the mappings in case we sleep.
2647          */
2648         verify_mm_writelocked(mm);
2649 
2650         /*
2651          * Clear old maps.  this also does some error checking for us
2652          */
2653         while (find_vma_links(mm, addr, addr + len, &prev, &rb_link,
2654                               &rb_parent)) {
2655                 if (do_munmap(mm, addr, len))
2656                         return -ENOMEM;
2657         }
2658 
2659         /* Check against address space limits *after* clearing old maps... */
2660         if (!may_expand_vm(mm, flags, len >> PAGE_SHIFT))
2661                 return -ENOMEM;
2662 
2663         if (mm->map_count > sysctl_max_map_count)
2664                 return -ENOMEM;
2665 
2666         if (security_vm_enough_memory_mm(mm, len >> PAGE_SHIFT))
2667                 return -ENOMEM;
2668 
2669         /* Can we just expand an old private anonymous mapping? */
2670         vma = vma_merge(mm, prev, addr, addr + len, flags,
2671                         NULL, NULL, pgoff, NULL, NULL_VM_UFFD_CTX);
2672         if (vma)
2673                 goto out;
2674 
2675         /*
2676          * create a vma struct for an anonymous mapping
2677          */
2678         vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
2679         if (!vma) {
2680                 vm_unacct_memory(len >> PAGE_SHIFT);
2681                 return -ENOMEM;
2682         }
2683 
2684         INIT_LIST_HEAD(&vma->anon_vma_chain);
2685         vma->vm_mm = mm;
2686         vma->vm_start = addr;
2687         vma->vm_end = addr + len;
2688         vma->vm_pgoff = pgoff;
2689         vma->vm_flags = flags;
2690         vma->vm_page_prot = vm_get_page_prot(flags);
2691         vma_link(mm, vma, prev, rb_link, rb_parent);
2692 out:
2693         perf_event_mmap(vma);
2694         mm->total_vm += len >> PAGE_SHIFT;
2695         mm->data_vm += len >> PAGE_SHIFT;
2696         if (flags & VM_LOCKED)
2697                 mm->locked_vm += (len >> PAGE_SHIFT);
2698         vma->vm_flags |= VM_SOFTDIRTY;
2699         return addr;
2700 }
2701 
2702 unsigned long vm_brk(unsigned long addr, unsigned long len)
2703 {
2704         struct mm_struct *mm = current->mm;
2705         unsigned long ret;
2706         bool populate;
2707 
2708         down_write(&mm->mmap_sem);
2709         ret = do_brk(addr, len);
2710         populate = ((mm->def_flags & VM_LOCKED) != 0);
2711         up_write(&mm->mmap_sem);
2712         if (populate)
2713                 mm_populate(addr, len);
2714         return ret;
2715 }
2716 EXPORT_SYMBOL(vm_brk);
2717 
2718 /* Release all mmaps. */
2719 void exit_mmap(struct mm_struct *mm)
2720 {
2721         struct mmu_gather tlb;
2722         struct vm_area_struct *vma;
2723         unsigned long nr_accounted = 0;
2724 
2725         /* mm's last user has gone, and its about to be pulled down */
2726         mmu_notifier_release(mm);
2727 
2728         if (mm->locked_vm) {
2729                 vma = mm->mmap;
2730                 while (vma) {
2731                         if (vma->vm_flags & VM_LOCKED)
2732                                 munlock_vma_pages_all(vma);
2733                         vma = vma->vm_next;
2734                 }
2735         }
2736 
2737         arch_exit_mmap(mm);
2738 
2739         vma = mm->mmap;
2740         if (!vma)       /* Can happen if dup_mmap() received an OOM */
2741                 return;
2742 
2743         lru_add_drain();
2744         flush_cache_mm(mm);
2745         tlb_gather_mmu(&tlb, mm, 0, -1);
2746         /* update_hiwater_rss(mm) here? but nobody should be looking */
2747         /* Use -1 here to ensure all VMAs in the mm are unmapped */
2748         unmap_vmas(&tlb, vma, 0, -1);
2749 
2750         free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, USER_PGTABLES_CEILING);
2751         tlb_finish_mmu(&tlb, 0, -1);
2752 
2753         /*
2754          * Walk the list again, actually closing and freeing it,
2755          * with preemption enabled, without holding any MM locks.
2756          */
2757         while (vma) {
2758                 if (vma->vm_flags & VM_ACCOUNT)
2759                         nr_accounted += vma_pages(vma);
2760                 vma = remove_vma(vma);
2761         }
2762         vm_unacct_memory(nr_accounted);
2763 }
2764 
2765 /* Insert vm structure into process list sorted by address
2766  * and into the inode's i_mmap tree.  If vm_file is non-NULL
2767  * then i_mmap_rwsem is taken here.
2768  */
2769 int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
2770 {
2771         struct vm_area_struct *prev;
2772         struct rb_node **rb_link, *rb_parent;
2773 
2774         if (find_vma_links(mm, vma->vm_start, vma->vm_end,
2775                            &prev, &rb_link, &rb_parent))
2776                 return -ENOMEM;
2777         if ((vma->vm_flags & VM_ACCOUNT) &&
2778              security_vm_enough_memory_mm(mm, vma_pages(vma)))
2779                 return -ENOMEM;
2780 
2781         /*
2782          * The vm_pgoff of a purely anonymous vma should be irrelevant
2783          * until its first write fault, when page's anon_vma and index
2784          * are set.  But now set the vm_pgoff it will almost certainly
2785          * end up with (unless mremap moves it elsewhere before that
2786          * first wfault), so /proc/pid/maps tells a consistent story.
2787          *
2788          * By setting it to reflect the virtual start address of the
2789          * vma, merges and splits can happen in a seamless way, just
2790          * using the existing file pgoff checks and manipulations.
2791          * Similarly in do_mmap_pgoff and in do_brk.
2792          */
2793         if (vma_is_anonymous(vma)) {
2794                 BUG_ON(vma->anon_vma);
2795                 vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;
2796         }
2797 
2798         vma_link(mm, vma, prev, rb_link, rb_parent);
2799         return 0;
2800 }
2801 
2802 /*
2803  * Copy the vma structure to a new location in the same mm,
2804  * prior to moving page table entries, to effect an mremap move.
2805  */
2806 struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
2807         unsigned long addr, unsigned long len, pgoff_t pgoff,
2808         bool *need_rmap_locks)
2809 {
2810         struct vm_area_struct *vma = *vmap;
2811         unsigned long vma_start = vma->vm_start;
2812         struct mm_struct *mm = vma->vm_mm;
2813         struct vm_area_struct *new_vma, *prev;
2814         struct rb_node **rb_link, *rb_parent;
2815         bool faulted_in_anon_vma = true;
2816 
2817         /*
2818          * If anonymous vma has not yet been faulted, update new pgoff
2819          * to match new location, to increase its chance of merging.
2820          */
2821         if (unlikely(vma_is_anonymous(vma) && !vma->anon_vma)) {
2822                 pgoff = addr >> PAGE_SHIFT;
2823                 faulted_in_anon_vma = false;
2824         }
2825 
2826         if (find_vma_links(mm, addr, addr + len, &prev, &rb_link, &rb_parent))
2827                 return NULL;    /* should never get here */
2828         new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags,
2829                             vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
2830                             vma->vm_userfaultfd_ctx);
2831         if (new_vma) {
2832                 /*
2833                  * Source vma may have been merged into new_vma
2834                  */
2835                 if (unlikely(vma_start >= new_vma->vm_start &&
2836                              vma_start < new_vma->vm_end)) {
2837                         /*
2838                          * The only way we can get a vma_merge with
2839                          * self during an mremap is if the vma hasn't
2840                          * been faulted in yet and we were allowed to
2841                          * reset the dst vma->vm_pgoff to the
2842                          * destination address of the mremap to allow
2843                          * the merge to happen. mremap must change the
2844                          * vm_pgoff linearity between src and dst vmas
2845                          * (in turn preventing a vma_merge) to be
2846                          * safe. It is only safe to keep the vm_pgoff
2847                          * linear if there are no pages mapped yet.
2848                          */
2849                         VM_BUG_ON_VMA(faulted_in_anon_vma, new_vma);
2850                         *vmap = vma = new_vma;
2851                 }
2852                 *need_rmap_locks = (new_vma->vm_pgoff <= vma->vm_pgoff);
2853         } else {
2854                 new_vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
2855                 if (!new_vma)
2856                         goto out;
2857                 *new_vma = *vma;
2858                 new_vma->vm_start = addr;
2859                 new_vma->vm_end = addr + len;
2860                 new_vma->vm_pgoff = pgoff;
2861                 if (vma_dup_policy(vma, new_vma))
2862                         goto out_free_vma;
2863                 INIT_LIST_HEAD(&new_vma->anon_vma_chain);
2864                 if (anon_vma_clone(new_vma, vma))
2865                         goto out_free_mempol;
2866                 if (new_vma->vm_file)
2867                         get_file(new_vma->vm_file);
2868                 if (new_vma->vm_ops && new_vma->vm_ops->open)
2869                         new_vma->vm_ops->open(new_vma);
2870                 vma_link(mm, new_vma, prev, rb_link, rb_parent);
2871                 *need_rmap_locks = false;
2872         }
2873         return new_vma;
2874 
2875 out_free_mempol:
2876         mpol_put(vma_policy(new_vma));
2877 out_free_vma:
2878         kmem_cache_free(vm_area_cachep, new_vma);
2879 out:
2880         return NULL;
2881 }
2882 
2883 /*
2884  * Return true if the calling process may expand its vm space by the passed
2885  * number of pages
2886  */
2887 bool may_expand_vm(struct mm_struct *mm, vm_flags_t flags, unsigned long npages)
2888 {
2889         if (mm->total_vm + npages > rlimit(RLIMIT_AS) >> PAGE_SHIFT)
2890                 return false;
2891 
2892         if (is_data_mapping(flags) &&
2893             mm->data_vm + npages > rlimit(RLIMIT_DATA) >> PAGE_SHIFT) {
2894                 if (ignore_rlimit_data)
2895                         pr_warn_once("%s (%d): VmData %lu exceed data ulimit %lu. Will be forbidden soon.\n",
2896                                      current->comm, current->pid,
2897                                      (mm->data_vm + npages) << PAGE_SHIFT,
2898                                      rlimit(RLIMIT_DATA));
2899                 else
2900                         return false;
2901         }
2902 
2903         return true;
2904 }
2905 
2906 void vm_stat_account(struct mm_struct *mm, vm_flags_t flags, long npages)
2907 {
2908         mm->total_vm += npages;
2909 
2910         if (is_exec_mapping(flags))
2911                 mm->exec_vm += npages;
2912         else if (is_stack_mapping(flags))
2913                 mm->stack_vm += npages;
2914         else if (is_data_mapping(flags))
2915                 mm->data_vm += npages;
2916 }
2917 
2918 static int special_mapping_fault(struct vm_area_struct *vma,
2919                                  struct vm_fault *vmf);
2920 
2921 /*
2922  * Having a close hook prevents vma merging regardless of flags.
2923  */
2924 static void special_mapping_close(struct vm_area_struct *vma)
2925 {
2926 }
2927 
2928 static const char *special_mapping_name(struct vm_area_struct *vma)
2929 {
2930         return ((struct vm_special_mapping *)vma->vm_private_data)->name;
2931 }
2932 
2933 static const struct vm_operations_struct special_mapping_vmops = {
2934         .close = special_mapping_close,
2935         .fault = special_mapping_fault,
2936         .name = special_mapping_name,
2937 };
2938 
2939 static const struct vm_operations_struct legacy_special_mapping_vmops = {
2940         .close = special_mapping_close,
2941         .fault = special_mapping_fault,
2942 };
2943 
2944 static int special_mapping_fault(struct vm_area_struct *vma,
2945                                 struct vm_fault *vmf)
2946 {
2947         pgoff_t pgoff;
2948         struct page **pages;
2949 
2950         if (vma->vm_ops == &legacy_special_mapping_vmops) {
2951                 pages = vma->vm_private_data;
2952         } else {
2953                 struct vm_special_mapping *sm = vma->vm_private_data;
2954 
2955                 if (sm->fault)
2956                         return sm->fault(sm, vma, vmf);
2957 
2958                 pages = sm->pages;
2959         }
2960 
2961         for (pgoff = vmf->pgoff; pgoff && *pages; ++pages)
2962                 pgoff--;
2963 
2964         if (*pages) {
2965                 struct page *page = *pages;
2966                 get_page(page);
2967                 vmf->page = page;
2968                 return 0;
2969         }
2970 
2971         return VM_FAULT_SIGBUS;
2972 }
2973 
2974 static struct vm_area_struct *__install_special_mapping(
2975         struct mm_struct *mm,
2976         unsigned long addr, unsigned long len,
2977         unsigned long vm_flags, void *priv,
2978         const struct vm_operations_struct *ops)
2979 {
2980         int ret;
2981         struct vm_area_struct *vma;
2982 
2983         vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
2984         if (unlikely(vma == NULL))
2985                 return ERR_PTR(-ENOMEM);
2986 
2987         INIT_LIST_HEAD(&vma->anon_vma_chain);
2988         vma->vm_mm = mm;
2989         vma->vm_start = addr;
2990         vma->vm_end = addr + len;
2991 
2992         vma->vm_flags = vm_flags | mm->def_flags | VM_DONTEXPAND | VM_SOFTDIRTY;
2993         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
2994 
2995         vma->vm_ops = ops;
2996         vma->vm_private_data = priv;
2997 
2998         ret = insert_vm_struct(mm, vma);
2999         if (ret)
3000                 goto out;
3001 
3002         vm_stat_account(mm, vma->vm_flags, len >> PAGE_SHIFT);
3003 
3004         perf_event_mmap(vma);
3005 
3006         return vma;
3007 
3008 out:
3009         kmem_cache_free(vm_area_cachep, vma);
3010         return ERR_PTR(ret);
3011 }
3012 
3013 /*
3014  * Called with mm->mmap_sem held for writing.
3015  * Insert a new vma covering the given region, with the given flags.
3016  * Its pages are supplied by the given array of struct page *.
3017  * The array can be shorter than len >> PAGE_SHIFT if it's null-terminated.
3018  * The region past the last page supplied will always produce SIGBUS.
3019  * The array pointer and the pages it points to are assumed to stay alive
3020  * for as long as this mapping might exist.
3021  */
3022 struct vm_area_struct *_install_special_mapping(
3023         struct mm_struct *mm,
3024         unsigned long addr, unsigned long len,
3025         unsigned long vm_flags, const struct vm_special_mapping *spec)
3026 {
3027         return __install_special_mapping(mm, addr, len, vm_flags, (void *)spec,
3028                                         &special_mapping_vmops);
3029 }
3030 
3031 int install_special_mapping(struct mm_struct *mm,
3032                             unsigned long addr, unsigned long len,
3033                             unsigned long vm_flags, struct page **pages)
3034 {
3035         struct vm_area_struct *vma = __install_special_mapping(
3036                 mm, addr, len, vm_flags, (void *)pages,
3037                 &legacy_special_mapping_vmops);
3038 
3039         return PTR_ERR_OR_ZERO(vma);
3040 }
3041 
3042 static DEFINE_MUTEX(mm_all_locks_mutex);
3043 
3044 static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma)
3045 {
3046         if (!test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_node)) {
3047                 /*
3048                  * The LSB of head.next can't change from under us
3049                  * because we hold the mm_all_locks_mutex.
3050                  */
3051                 down_write_nest_lock(&anon_vma->root->rwsem, &mm->mmap_sem);
3052                 /*
3053                  * We can safely modify head.next after taking the
3054                  * anon_vma->root->rwsem. If some other vma in this mm shares
3055                  * the same anon_vma we won't take it again.
3056                  *
3057                  * No need of atomic instructions here, head.next
3058                  * can't change from under us thanks to the
3059                  * anon_vma->root->rwsem.
3060                  */
3061                 if (__test_and_set_bit(0, (unsigned long *)
3062                                        &anon_vma->root->rb_root.rb_node))
3063                         BUG();
3064         }
3065 }
3066 
3067 static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping)
3068 {
3069         if (!test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
3070                 /*
3071                  * AS_MM_ALL_LOCKS can't change from under us because
3072                  * we hold the mm_all_locks_mutex.
3073                  *
3074                  * Operations on ->flags have to be atomic because
3075                  * even if AS_MM_ALL_LOCKS is stable thanks to the
3076                  * mm_all_locks_mutex, there may be other cpus
3077                  * changing other bitflags in parallel to us.
3078                  */
3079                 if (test_and_set_bit(AS_MM_ALL_LOCKS, &mapping->flags))
3080                         BUG();
3081                 down_write_nest_lock(&mapping->i_mmap_rwsem, &mm->mmap_sem);
3082         }
3083 }
3084 
3085 /*
3086  * This operation locks against the VM for all pte/vma/mm related
3087  * operations that could ever happen on a certain mm. This includes
3088  * vmtruncate, try_to_unmap, and all page faults.
3089  *
3090  * The caller must take the mmap_sem in write mode before calling
3091  * mm_take_all_locks(). The caller isn't allowed to release the
3092  * mmap_sem until mm_drop_all_locks() returns.
3093  *
3094  * mmap_sem in write mode is required in order to block all operations
3095  * that could modify pagetables and free pages without need of
3096  * altering the vma layout. It's also needed in write mode to avoid new
3097  * anon_vmas to be associated with existing vmas.
3098  *
3099  * A single task can't take more than one mm_take_all_locks() in a row
3100  * or it would deadlock.
3101  *
3102  * The LSB in anon_vma->rb_root.rb_node and the AS_MM_ALL_LOCKS bitflag in
3103  * mapping->flags avoid to take the same lock twice, if more than one
3104  * vma in this mm is backed by the same anon_vma or address_space.
3105  *
3106  * We take locks in following order, accordingly to comment at beginning
3107  * of mm/rmap.c:
3108  *   - all hugetlbfs_i_mmap_rwsem_key locks (aka mapping->i_mmap_rwsem for
3109  *     hugetlb mapping);
3110  *   - all i_mmap_rwsem locks;
3111  *   - all anon_vma->rwseml
3112  *
3113  * We can take all locks within these types randomly because the VM code
3114  * doesn't nest them and we protected from parallel mm_take_all_locks() by
3115  * mm_all_locks_mutex.
3116  *
3117  * mm_take_all_locks() and mm_drop_all_locks are expensive operations
3118  * that may have to take thousand of locks.
3119  *
3120  * mm_take_all_locks() can fail if it's interrupted by signals.
3121  */
3122 int mm_take_all_locks(struct mm_struct *mm)
3123 {
3124         struct vm_area_struct *vma;
3125         struct anon_vma_chain *avc;
3126 
3127         BUG_ON(down_read_trylock(&mm->mmap_sem));
3128 
3129         mutex_lock(&mm_all_locks_mutex);
3130 
3131         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3132                 if (signal_pending(current))
3133                         goto out_unlock;
3134                 if (vma->vm_file && vma->vm_file->f_mapping &&
3135                                 is_vm_hugetlb_page(vma))
3136                         vm_lock_mapping(mm, vma->vm_file->f_mapping);
3137         }
3138 
3139         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3140                 if (signal_pending(current))
3141                         goto out_unlock;
3142                 if (vma->vm_file && vma->vm_file->f_mapping &&
3143                                 !is_vm_hugetlb_page(vma))
3144                         vm_lock_mapping(mm, vma->vm_file->f_mapping);
3145         }
3146 
3147         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3148                 if (signal_pending(current))
3149                         goto out_unlock;
3150                 if (vma->anon_vma)
3151                         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
3152                                 vm_lock_anon_vma(mm, avc->anon_vma);
3153         }
3154 
3155         return 0;
3156 
3157 out_unlock:
3158         mm_drop_all_locks(mm);
3159         return -EINTR;
3160 }
3161 
3162 static void vm_unlock_anon_vma(struct anon_vma *anon_vma)
3163 {
3164         if (test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_node)) {
3165                 /*
3166                  * The LSB of head.next can't change to 0 from under
3167                  * us because we hold the mm_all_locks_mutex.
3168                  *
3169                  * We must however clear the bitflag before unlocking
3170                  * the vma so the users using the anon_vma->rb_root will
3171                  * never see our bitflag.
3172                  *
3173                  * No need of atomic instructions here, head.next
3174                  * can't change from under us until we release the
3175                  * anon_vma->root->rwsem.
3176                  */
3177                 if (!__test_and_clear_bit(0, (unsigned long *)
3178                                           &anon_vma->root->rb_root.rb_node))
3179                         BUG();
3180                 anon_vma_unlock_write(anon_vma);
3181         }
3182 }
3183 
3184 static void vm_unlock_mapping(struct address_space *mapping)
3185 {
3186         if (test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
3187                 /*
3188                  * AS_MM_ALL_LOCKS can't change to 0 from under us
3189                  * because we hold the mm_all_locks_mutex.
3190                  */
3191                 i_mmap_unlock_write(mapping);
3192                 if (!test_and_clear_bit(AS_MM_ALL_LOCKS,
3193                                         &mapping->flags))
3194                         BUG();
3195         }
3196 }
3197 
3198 /*
3199  * The mmap_sem cannot be released by the caller until
3200  * mm_drop_all_locks() returns.
3201  */
3202 void mm_drop_all_locks(struct mm_struct *mm)
3203 {
3204         struct vm_area_struct *vma;
3205         struct anon_vma_chain *avc;
3206 
3207         BUG_ON(down_read_trylock(&mm->mmap_sem));
3208         BUG_ON(!mutex_is_locked(&mm_all_locks_mutex));
3209 
3210         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3211                 if (vma->anon_vma)
3212                         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
3213                                 vm_unlock_anon_vma(avc->anon_vma);
3214                 if (vma->vm_file && vma->vm_file->f_mapping)
3215                         vm_unlock_mapping(vma->vm_file->f_mapping);
3216         }
3217 
3218         mutex_unlock(&mm_all_locks_mutex);
3219 }
3220 
3221 /*
3222  * initialise the VMA slab
3223  */
3224 void __init mmap_init(void)
3225 {
3226         int ret;
3227 
3228         ret = percpu_counter_init(&vm_committed_as, 0, GFP_KERNEL);
3229         VM_BUG_ON(ret);
3230 }
3231 
3232 /*
3233  * Initialise sysctl_user_reserve_kbytes.
3234  *
3235  * This is intended to prevent a user from starting a single memory hogging
3236  * process, such that they cannot recover (kill the hog) in OVERCOMMIT_NEVER
3237  * mode.
3238  *
3239  * The default value is min(3% of free memory, 128MB)
3240  * 128MB is enough to recover with sshd/login, bash, and top/kill.
3241  */
3242 static int init_user_reserve(void)
3243 {
3244         unsigned long free_kbytes;
3245 
3246         free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
3247 
3248         sysctl_user_reserve_kbytes = min(free_kbytes / 32, 1UL << 17);
3249         return 0;
3250 }
3251 subsys_initcall(init_user_reserve);
3252 
3253 /*
3254  * Initialise sysctl_admin_reserve_kbytes.
3255  *
3256  * The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin
3257  * to log in and kill a memory hogging process.
3258  *
3259  * Systems with more than 256MB will reserve 8MB, enough to recover
3260  * with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will
3261  * only reserve 3% of free pages by default.
3262  */
3263 static int init_admin_reserve(void)
3264 {
3265         unsigned long free_kbytes;
3266 
3267         free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
3268 
3269         sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13);
3270         return 0;
3271 }
3272 subsys_initcall(init_admin_reserve);
3273 
3274 /*
3275  * Reinititalise user and admin reserves if memory is added or removed.
3276  *
3277  * The default user reserve max is 128MB, and the default max for the
3278  * admin reserve is 8MB. These are usually, but not always, enough to
3279  * enable recovery from a memory hogging process using login/sshd, a shell,
3280  * and tools like top. It may make sense to increase or even disable the
3281  * reserve depending on the existence of swap or variations in the recovery
3282  * tools. So, the admin may have changed them.
3283  *
3284  * If memory is added and the reserves have been eliminated or increased above
3285  * the default max, then we'll trust the admin.
3286  *
3287  * If memory is removed and there isn't enough free memory, then we
3288  * need to reset the reserves.
3289  *
3290  * Otherwise keep the reserve set by the admin.
3291  */
3292 static int reserve_mem_notifier(struct notifier_block *nb,
3293                              unsigned long action, void *data)
3294 {
3295         unsigned long tmp, free_kbytes;
3296 
3297         switch (action) {
3298         case MEM_ONLINE:
3299                 /* Default max is 128MB. Leave alone if modified by operator. */
3300                 tmp = sysctl_user_reserve_kbytes;
3301                 if (0 < tmp && tmp < (1UL << 17))
3302                         init_user_reserve();
3303 
3304                 /* Default max is 8MB.  Leave alone if modified by operator. */
3305                 tmp = sysctl_admin_reserve_kbytes;
3306                 if (0 < tmp && tmp < (1UL << 13))
3307                         init_admin_reserve();
3308 
3309                 break;
3310         case MEM_OFFLINE:
3311                 free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
3312 
3313                 if (sysctl_user_reserve_kbytes > free_kbytes) {
3314                         init_user_reserve();
3315                         pr_info("vm.user_reserve_kbytes reset to %lu\n",
3316                                 sysctl_user_reserve_kbytes);
3317                 }
3318 
3319                 if (sysctl_admin_reserve_kbytes > free_kbytes) {
3320                         init_admin_reserve();
3321                         pr_info("vm.admin_reserve_kbytes reset to %lu\n",
3322                                 sysctl_admin_reserve_kbytes);
3323                 }
3324                 break;
3325         default:
3326                 break;
3327         }
3328         return NOTIFY_OK;
3329 }
3330 
3331 static struct notifier_block reserve_mem_nb = {
3332         .notifier_call = reserve_mem_notifier,
3333 };
3334 
3335 static int __meminit init_reserve_notifier(void)
3336 {
3337         if (register_hotmemory_notifier(&reserve_mem_nb))
3338                 pr_err("Failed registering memory add/remove notifier for admin reserve\n");
3339 
3340         return 0;
3341 }
3342 subsys_initcall(init_reserve_notifier);
3343 

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