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TOMOYO Linux Cross Reference
Linux/mm/mmap.c

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  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/sched/sysctl.h>
 41 #include <linux/notifier.h>
 42 #include <linux/memory.h>
 43 #include <linux/printk.h>
 44 #include <linux/userfaultfd_k.h>
 45 
 46 #include <asm/uaccess.h>
 47 #include <asm/cacheflush.h>
 48 #include <asm/tlb.h>
 49 #include <asm/mmu_context.h>
 50 
 51 #include "internal.h"
 52 
 53 #ifndef arch_mmap_check
 54 #define arch_mmap_check(addr, len, flags)       (0)
 55 #endif
 56 
 57 #ifndef arch_rebalance_pgtables
 58 #define arch_rebalance_pgtables(addr, len)              (addr)
 59 #endif
 60 
 61 static void unmap_region(struct mm_struct *mm,
 62                 struct vm_area_struct *vma, struct vm_area_struct *prev,
 63                 unsigned long start, unsigned long end);
 64 
 65 /* description of effects of mapping type and prot in current implementation.
 66  * this is due to the limited x86 page protection hardware.  The expected
 67  * behavior is in parens:
 68  *
 69  * map_type     prot
 70  *              PROT_NONE       PROT_READ       PROT_WRITE      PROT_EXEC
 71  * MAP_SHARED   r: (no) no      r: (yes) yes    r: (no) yes     r: (no) yes
 72  *              w: (no) no      w: (no) no      w: (yes) yes    w: (no) no
 73  *              x: (no) no      x: (no) yes     x: (no) yes     x: (yes) yes
 74  *
 75  * MAP_PRIVATE  r: (no) no      r: (yes) yes    r: (no) yes     r: (no) yes
 76  *              w: (no) no      w: (no) no      w: (copy) copy  w: (no) no
 77  *              x: (no) no      x: (no) yes     x: (no) yes     x: (yes) yes
 78  *
 79  */
 80 pgprot_t protection_map[16] = {
 81         __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
 82         __S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
 83 };
 84 
 85 pgprot_t vm_get_page_prot(unsigned long vm_flags)
 86 {
 87         return __pgprot(pgprot_val(protection_map[vm_flags &
 88                                 (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
 89                         pgprot_val(arch_vm_get_page_prot(vm_flags)));
 90 }
 91 EXPORT_SYMBOL(vm_get_page_prot);
 92 
 93 static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags)
 94 {
 95         return pgprot_modify(oldprot, vm_get_page_prot(vm_flags));
 96 }
 97 
 98 /* Update vma->vm_page_prot to reflect vma->vm_flags. */
 99 void vma_set_page_prot(struct vm_area_struct *vma)
100 {
101         unsigned long vm_flags = vma->vm_flags;
102 
103         vma->vm_page_prot = vm_pgprot_modify(vma->vm_page_prot, vm_flags);
104         if (vma_wants_writenotify(vma)) {
105                 vm_flags &= ~VM_SHARED;
106                 vma->vm_page_prot = vm_pgprot_modify(vma->vm_page_prot,
107                                                      vm_flags);
108         }
109 }
110 
111 
112 int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS;  /* heuristic overcommit */
113 int sysctl_overcommit_ratio __read_mostly = 50; /* default is 50% */
114 unsigned long sysctl_overcommit_kbytes __read_mostly;
115 int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
116 unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */
117 unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */
118 /*
119  * Make sure vm_committed_as in one cacheline and not cacheline shared with
120  * other variables. It can be updated by several CPUs frequently.
121  */
122 struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
123 
124 /*
125  * The global memory commitment made in the system can be a metric
126  * that can be used to drive ballooning decisions when Linux is hosted
127  * as a guest. On Hyper-V, the host implements a policy engine for dynamically
128  * balancing memory across competing virtual machines that are hosted.
129  * Several metrics drive this policy engine including the guest reported
130  * memory commitment.
131  */
132 unsigned long vm_memory_committed(void)
133 {
134         return percpu_counter_read_positive(&vm_committed_as);
135 }
136 EXPORT_SYMBOL_GPL(vm_memory_committed);
137 
138 /*
139  * Check that a process has enough memory to allocate a new virtual
140  * mapping. 0 means there is enough memory for the allocation to
141  * succeed and -ENOMEM implies there is not.
142  *
143  * We currently support three overcommit policies, which are set via the
144  * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-accounting
145  *
146  * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
147  * Additional code 2002 Jul 20 by Robert Love.
148  *
149  * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
150  *
151  * Note this is a helper function intended to be used by LSMs which
152  * wish to use this logic.
153  */
154 int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
155 {
156         long free, allowed, reserve;
157 
158         VM_WARN_ONCE(percpu_counter_read(&vm_committed_as) <
159                         -(s64)vm_committed_as_batch * num_online_cpus(),
160                         "memory commitment underflow");
161 
162         vm_acct_memory(pages);
163 
164         /*
165          * Sometimes we want to use more memory than we have
166          */
167         if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
168                 return 0;
169 
170         if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
171                 free = global_page_state(NR_FREE_PAGES);
172                 free += global_page_state(NR_FILE_PAGES);
173 
174                 /*
175                  * shmem pages shouldn't be counted as free in this
176                  * case, they can't be purged, only swapped out, and
177                  * that won't affect the overall amount of available
178                  * memory in the system.
179                  */
180                 free -= global_page_state(NR_SHMEM);
181 
182                 free += get_nr_swap_pages();
183 
184                 /*
185                  * Any slabs which are created with the
186                  * SLAB_RECLAIM_ACCOUNT flag claim to have contents
187                  * which are reclaimable, under pressure.  The dentry
188                  * cache and most inode caches should fall into this
189                  */
190                 free += global_page_state(NR_SLAB_RECLAIMABLE);
191 
192                 /*
193                  * Leave reserved pages. The pages are not for anonymous pages.
194                  */
195                 if (free <= totalreserve_pages)
196                         goto error;
197                 else
198                         free -= totalreserve_pages;
199 
200                 /*
201                  * Reserve some for root
202                  */
203                 if (!cap_sys_admin)
204                         free -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
205 
206                 if (free > pages)
207                         return 0;
208 
209                 goto error;
210         }
211 
212         allowed = vm_commit_limit();
213         /*
214          * Reserve some for root
215          */
216         if (!cap_sys_admin)
217                 allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
218 
219         /*
220          * Don't let a single process grow so big a user can't recover
221          */
222         if (mm) {
223                 reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10);
224                 allowed -= min_t(long, mm->total_vm / 32, reserve);
225         }
226 
227         if (percpu_counter_read_positive(&vm_committed_as) < allowed)
228                 return 0;
229 error:
230         vm_unacct_memory(pages);
231 
232         return -ENOMEM;
233 }
234 
235 /*
236  * Requires inode->i_mapping->i_mmap_rwsem
237  */
238 static void __remove_shared_vm_struct(struct vm_area_struct *vma,
239                 struct file *file, struct address_space *mapping)
240 {
241         if (vma->vm_flags & VM_DENYWRITE)
242                 atomic_inc(&file_inode(file)->i_writecount);
243         if (vma->vm_flags & VM_SHARED)
244                 mapping_unmap_writable(mapping);
245 
246         flush_dcache_mmap_lock(mapping);
247         vma_interval_tree_remove(vma, &mapping->i_mmap);
248         flush_dcache_mmap_unlock(mapping);
249 }
250 
251 /*
252  * Unlink a file-based vm structure from its interval tree, to hide
253  * vma from rmap and vmtruncate before freeing its page tables.
254  */
255 void unlink_file_vma(struct vm_area_struct *vma)
256 {
257         struct file *file = vma->vm_file;
258 
259         if (file) {
260                 struct address_space *mapping = file->f_mapping;
261                 i_mmap_lock_write(mapping);
262                 __remove_shared_vm_struct(vma, file, mapping);
263                 i_mmap_unlock_write(mapping);
264         }
265 }
266 
267 /*
268  * Close a vm structure and free it, returning the next.
269  */
270 static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
271 {
272         struct vm_area_struct *next = vma->vm_next;
273 
274         might_sleep();
275         if (vma->vm_ops && vma->vm_ops->close)
276                 vma->vm_ops->close(vma);
277         if (vma->vm_file)
278                 fput(vma->vm_file);
279         mpol_put(vma_policy(vma));
280         kmem_cache_free(vm_area_cachep, vma);
281         return next;
282 }
283 
284 static unsigned long do_brk(unsigned long addr, unsigned long len);
285 
286 SYSCALL_DEFINE1(brk, unsigned long, brk)
287 {
288         unsigned long retval;
289         unsigned long newbrk, oldbrk;
290         struct mm_struct *mm = current->mm;
291         unsigned long min_brk;
292         bool populate;
293 
294         down_write(&mm->mmap_sem);
295 
296 #ifdef CONFIG_COMPAT_BRK
297         /*
298          * CONFIG_COMPAT_BRK can still be overridden by setting
299          * randomize_va_space to 2, which will still cause mm->start_brk
300          * to be arbitrarily shifted
301          */
302         if (current->brk_randomized)
303                 min_brk = mm->start_brk;
304         else
305                 min_brk = mm->end_data;
306 #else
307         min_brk = mm->start_brk;
308 #endif
309         if (brk < min_brk)
310                 goto out;
311 
312         /*
313          * Check against rlimit here. If this check is done later after the test
314          * of oldbrk with newbrk then it can escape the test and let the data
315          * segment grow beyond its set limit the in case where the limit is
316          * not page aligned -Ram Gupta
317          */
318         if (check_data_rlimit(rlimit(RLIMIT_DATA), brk, mm->start_brk,
319                               mm->end_data, mm->start_data))
320                 goto out;
321 
322         newbrk = PAGE_ALIGN(brk);
323         oldbrk = PAGE_ALIGN(mm->brk);
324         if (oldbrk == newbrk)
325                 goto set_brk;
326 
327         /* Always allow shrinking brk. */
328         if (brk <= mm->brk) {
329                 if (!do_munmap(mm, newbrk, oldbrk-newbrk))
330                         goto set_brk;
331                 goto out;
332         }
333 
334         /* Check against existing mmap mappings. */
335         if (find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE))
336                 goto out;
337 
338         /* Ok, looks good - let it rip. */
339         if (do_brk(oldbrk, newbrk-oldbrk) != oldbrk)
340                 goto out;
341 
342 set_brk:
343         mm->brk = brk;
344         populate = newbrk > oldbrk && (mm->def_flags & VM_LOCKED) != 0;
345         up_write(&mm->mmap_sem);
346         if (populate)
347                 mm_populate(oldbrk, newbrk - oldbrk);
348         return brk;
349 
350 out:
351         retval = mm->brk;
352         up_write(&mm->mmap_sem);
353         return retval;
354 }
355 
356 static long vma_compute_subtree_gap(struct vm_area_struct *vma)
357 {
358         unsigned long max, subtree_gap;
359         max = vma->vm_start;
360         if (vma->vm_prev)
361                 max -= vma->vm_prev->vm_end;
362         if (vma->vm_rb.rb_left) {
363                 subtree_gap = rb_entry(vma->vm_rb.rb_left,
364                                 struct vm_area_struct, vm_rb)->rb_subtree_gap;
365                 if (subtree_gap > max)
366                         max = subtree_gap;
367         }
368         if (vma->vm_rb.rb_right) {
369                 subtree_gap = rb_entry(vma->vm_rb.rb_right,
370                                 struct vm_area_struct, vm_rb)->rb_subtree_gap;
371                 if (subtree_gap > max)
372                         max = subtree_gap;
373         }
374         return max;
375 }
376 
377 #ifdef CONFIG_DEBUG_VM_RB
378 static int browse_rb(struct rb_root *root)
379 {
380         int i = 0, j, bug = 0;
381         struct rb_node *nd, *pn = NULL;
382         unsigned long prev = 0, pend = 0;
383 
384         for (nd = rb_first(root); nd; nd = rb_next(nd)) {
385                 struct vm_area_struct *vma;
386                 vma = rb_entry(nd, struct vm_area_struct, vm_rb);
387                 if (vma->vm_start < prev) {
388                         pr_emerg("vm_start %lx < prev %lx\n",
389                                   vma->vm_start, prev);
390                         bug = 1;
391                 }
392                 if (vma->vm_start < pend) {
393                         pr_emerg("vm_start %lx < pend %lx\n",
394                                   vma->vm_start, pend);
395                         bug = 1;
396                 }
397                 if (vma->vm_start > vma->vm_end) {
398                         pr_emerg("vm_start %lx > vm_end %lx\n",
399                                   vma->vm_start, vma->vm_end);
400                         bug = 1;
401                 }
402                 if (vma->rb_subtree_gap != vma_compute_subtree_gap(vma)) {
403                         pr_emerg("free gap %lx, correct %lx\n",
404                                vma->rb_subtree_gap,
405                                vma_compute_subtree_gap(vma));
406                         bug = 1;
407                 }
408                 i++;
409                 pn = nd;
410                 prev = vma->vm_start;
411                 pend = vma->vm_end;
412         }
413         j = 0;
414         for (nd = pn; nd; nd = rb_prev(nd))
415                 j++;
416         if (i != j) {
417                 pr_emerg("backwards %d, forwards %d\n", j, i);
418                 bug = 1;
419         }
420         return bug ? -1 : i;
421 }
422 
423 static void validate_mm_rb(struct rb_root *root, struct vm_area_struct *ignore)
424 {
425         struct rb_node *nd;
426 
427         for (nd = rb_first(root); nd; nd = rb_next(nd)) {
428                 struct vm_area_struct *vma;
429                 vma = rb_entry(nd, struct vm_area_struct, vm_rb);
430                 VM_BUG_ON_VMA(vma != ignore &&
431                         vma->rb_subtree_gap != vma_compute_subtree_gap(vma),
432                         vma);
433         }
434 }
435 
436 static void validate_mm(struct mm_struct *mm)
437 {
438         int bug = 0;
439         int i = 0;
440         unsigned long highest_address = 0;
441         struct vm_area_struct *vma = mm->mmap;
442 
443         while (vma) {
444                 struct anon_vma_chain *avc;
445 
446                 vma_lock_anon_vma(vma);
447                 list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
448                         anon_vma_interval_tree_verify(avc);
449                 vma_unlock_anon_vma(vma);
450                 highest_address = vma->vm_end;
451                 vma = vma->vm_next;
452                 i++;
453         }
454         if (i != mm->map_count) {
455                 pr_emerg("map_count %d vm_next %d\n", mm->map_count, i);
456                 bug = 1;
457         }
458         if (highest_address != mm->highest_vm_end) {
459                 pr_emerg("mm->highest_vm_end %lx, found %lx\n",
460                           mm->highest_vm_end, highest_address);
461                 bug = 1;
462         }
463         i = browse_rb(&mm->mm_rb);
464         if (i != mm->map_count) {
465                 if (i != -1)
466                         pr_emerg("map_count %d rb %d\n", mm->map_count, i);
467                 bug = 1;
468         }
469         VM_BUG_ON_MM(bug, mm);
470 }
471 #else
472 #define validate_mm_rb(root, ignore) do { } while (0)
473 #define validate_mm(mm) do { } while (0)
474 #endif
475 
476 RB_DECLARE_CALLBACKS(static, vma_gap_callbacks, struct vm_area_struct, vm_rb,
477                      unsigned long, rb_subtree_gap, vma_compute_subtree_gap)
478 
479 /*
480  * Update augmented rbtree rb_subtree_gap values after vma->vm_start or
481  * vma->vm_prev->vm_end values changed, without modifying the vma's position
482  * in the rbtree.
483  */
484 static void vma_gap_update(struct vm_area_struct *vma)
485 {
486         /*
487          * As it turns out, RB_DECLARE_CALLBACKS() already created a callback
488          * function that does exacltly what we want.
489          */
490         vma_gap_callbacks_propagate(&vma->vm_rb, NULL);
491 }
492 
493 static inline void vma_rb_insert(struct vm_area_struct *vma,
494                                  struct rb_root *root)
495 {
496         /* All rb_subtree_gap values must be consistent prior to insertion */
497         validate_mm_rb(root, NULL);
498 
499         rb_insert_augmented(&vma->vm_rb, root, &vma_gap_callbacks);
500 }
501 
502 static void vma_rb_erase(struct vm_area_struct *vma, struct rb_root *root)
503 {
504         /*
505          * All rb_subtree_gap values must be consistent prior to erase,
506          * with the possible exception of the vma being erased.
507          */
508         validate_mm_rb(root, vma);
509 
510         /*
511          * Note rb_erase_augmented is a fairly large inline function,
512          * so make sure we instantiate it only once with our desired
513          * augmented rbtree callbacks.
514          */
515         rb_erase_augmented(&vma->vm_rb, root, &vma_gap_callbacks);
516 }
517 
518 /*
519  * vma has some anon_vma assigned, and is already inserted on that
520  * anon_vma's interval trees.
521  *
522  * Before updating the vma's vm_start / vm_end / vm_pgoff fields, the
523  * vma must be removed from the anon_vma's interval trees using
524  * anon_vma_interval_tree_pre_update_vma().
525  *
526  * After the update, the vma will be reinserted using
527  * anon_vma_interval_tree_post_update_vma().
528  *
529  * The entire update must be protected by exclusive mmap_sem and by
530  * the root anon_vma's mutex.
531  */
532 static inline void
533 anon_vma_interval_tree_pre_update_vma(struct vm_area_struct *vma)
534 {
535         struct anon_vma_chain *avc;
536 
537         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
538                 anon_vma_interval_tree_remove(avc, &avc->anon_vma->rb_root);
539 }
540 
541 static inline void
542 anon_vma_interval_tree_post_update_vma(struct vm_area_struct *vma)
543 {
544         struct anon_vma_chain *avc;
545 
546         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
547                 anon_vma_interval_tree_insert(avc, &avc->anon_vma->rb_root);
548 }
549 
550 static int find_vma_links(struct mm_struct *mm, unsigned long addr,
551                 unsigned long end, struct vm_area_struct **pprev,
552                 struct rb_node ***rb_link, struct rb_node **rb_parent)
553 {
554         struct rb_node **__rb_link, *__rb_parent, *rb_prev;
555 
556         __rb_link = &mm->mm_rb.rb_node;
557         rb_prev = __rb_parent = NULL;
558 
559         while (*__rb_link) {
560                 struct vm_area_struct *vma_tmp;
561 
562                 __rb_parent = *__rb_link;
563                 vma_tmp = rb_entry(__rb_parent, struct vm_area_struct, vm_rb);
564 
565                 if (vma_tmp->vm_end > addr) {
566                         /* Fail if an existing vma overlaps the area */
567                         if (vma_tmp->vm_start < end)
568                                 return -ENOMEM;
569                         __rb_link = &__rb_parent->rb_left;
570                 } else {
571                         rb_prev = __rb_parent;
572                         __rb_link = &__rb_parent->rb_right;
573                 }
574         }
575 
576         *pprev = NULL;
577         if (rb_prev)
578                 *pprev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
579         *rb_link = __rb_link;
580         *rb_parent = __rb_parent;
581         return 0;
582 }
583 
584 static unsigned long count_vma_pages_range(struct mm_struct *mm,
585                 unsigned long addr, unsigned long end)
586 {
587         unsigned long nr_pages = 0;
588         struct vm_area_struct *vma;
589 
590         /* Find first overlaping mapping */
591         vma = find_vma_intersection(mm, addr, end);
592         if (!vma)
593                 return 0;
594 
595         nr_pages = (min(end, vma->vm_end) -
596                 max(addr, vma->vm_start)) >> PAGE_SHIFT;
597 
598         /* Iterate over the rest of the overlaps */
599         for (vma = vma->vm_next; vma; vma = vma->vm_next) {
600                 unsigned long overlap_len;
601 
602                 if (vma->vm_start > end)
603                         break;
604 
605                 overlap_len = min(end, vma->vm_end) - vma->vm_start;
606                 nr_pages += overlap_len >> PAGE_SHIFT;
607         }
608 
609         return nr_pages;
610 }
611 
612 void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
613                 struct rb_node **rb_link, struct rb_node *rb_parent)
614 {
615         /* Update tracking information for the gap following the new vma. */
616         if (vma->vm_next)
617                 vma_gap_update(vma->vm_next);
618         else
619                 mm->highest_vm_end = vma->vm_end;
620 
621         /*
622          * vma->vm_prev wasn't known when we followed the rbtree to find the
623          * correct insertion point for that vma. As a result, we could not
624          * update the vma vm_rb parents rb_subtree_gap values on the way down.
625          * So, we first insert the vma with a zero rb_subtree_gap value
626          * (to be consistent with what we did on the way down), and then
627          * immediately update the gap to the correct value. Finally we
628          * rebalance the rbtree after all augmented values have been set.
629          */
630         rb_link_node(&vma->vm_rb, rb_parent, rb_link);
631         vma->rb_subtree_gap = 0;
632         vma_gap_update(vma);
633         vma_rb_insert(vma, &mm->mm_rb);
634 }
635 
636 static void __vma_link_file(struct vm_area_struct *vma)
637 {
638         struct file *file;
639 
640         file = vma->vm_file;
641         if (file) {
642                 struct address_space *mapping = file->f_mapping;
643 
644                 if (vma->vm_flags & VM_DENYWRITE)
645                         atomic_dec(&file_inode(file)->i_writecount);
646                 if (vma->vm_flags & VM_SHARED)
647                         atomic_inc(&mapping->i_mmap_writable);
648 
649                 flush_dcache_mmap_lock(mapping);
650                 vma_interval_tree_insert(vma, &mapping->i_mmap);
651                 flush_dcache_mmap_unlock(mapping);
652         }
653 }
654 
655 static void
656 __vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
657         struct vm_area_struct *prev, struct rb_node **rb_link,
658         struct rb_node *rb_parent)
659 {
660         __vma_link_list(mm, vma, prev, rb_parent);
661         __vma_link_rb(mm, vma, rb_link, rb_parent);
662 }
663 
664 static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
665                         struct vm_area_struct *prev, struct rb_node **rb_link,
666                         struct rb_node *rb_parent)
667 {
668         struct address_space *mapping = NULL;
669 
670         if (vma->vm_file) {
671                 mapping = vma->vm_file->f_mapping;
672                 i_mmap_lock_write(mapping);
673         }
674 
675         __vma_link(mm, vma, prev, rb_link, rb_parent);
676         __vma_link_file(vma);
677 
678         if (mapping)
679                 i_mmap_unlock_write(mapping);
680 
681         mm->map_count++;
682         validate_mm(mm);
683 }
684 
685 /*
686  * Helper for vma_adjust() in the split_vma insert case: insert a vma into the
687  * mm's list and rbtree.  It has already been inserted into the interval tree.
688  */
689 static void __insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
690 {
691         struct vm_area_struct *prev;
692         struct rb_node **rb_link, *rb_parent;
693 
694         if (find_vma_links(mm, vma->vm_start, vma->vm_end,
695                            &prev, &rb_link, &rb_parent))
696                 BUG();
697         __vma_link(mm, vma, prev, rb_link, rb_parent);
698         mm->map_count++;
699 }
700 
701 static inline void
702 __vma_unlink(struct mm_struct *mm, struct vm_area_struct *vma,
703                 struct vm_area_struct *prev)
704 {
705         struct vm_area_struct *next;
706 
707         vma_rb_erase(vma, &mm->mm_rb);
708         prev->vm_next = next = vma->vm_next;
709         if (next)
710                 next->vm_prev = prev;
711 
712         /* Kill the cache */
713         vmacache_invalidate(mm);
714 }
715 
716 /*
717  * We cannot adjust vm_start, vm_end, vm_pgoff fields of a vma that
718  * is already present in an i_mmap tree without adjusting the tree.
719  * The following helper function should be used when such adjustments
720  * are necessary.  The "insert" vma (if any) is to be inserted
721  * before we drop the necessary locks.
722  */
723 int vma_adjust(struct vm_area_struct *vma, unsigned long start,
724         unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert)
725 {
726         struct mm_struct *mm = vma->vm_mm;
727         struct vm_area_struct *next = vma->vm_next;
728         struct vm_area_struct *importer = NULL;
729         struct address_space *mapping = NULL;
730         struct rb_root *root = NULL;
731         struct anon_vma *anon_vma = NULL;
732         struct file *file = vma->vm_file;
733         bool start_changed = false, end_changed = false;
734         long adjust_next = 0;
735         int remove_next = 0;
736 
737         if (next && !insert) {
738                 struct vm_area_struct *exporter = NULL;
739 
740                 if (end >= next->vm_end) {
741                         /*
742                          * vma expands, overlapping all the next, and
743                          * perhaps the one after too (mprotect case 6).
744                          */
745 again:                  remove_next = 1 + (end > next->vm_end);
746                         end = next->vm_end;
747                         exporter = next;
748                         importer = vma;
749                 } else if (end > next->vm_start) {
750                         /*
751                          * vma expands, overlapping part of the next:
752                          * mprotect case 5 shifting the boundary up.
753                          */
754                         adjust_next = (end - next->vm_start) >> PAGE_SHIFT;
755                         exporter = next;
756                         importer = vma;
757                 } else if (end < vma->vm_end) {
758                         /*
759                          * vma shrinks, and !insert tells it's not
760                          * split_vma inserting another: so it must be
761                          * mprotect case 4 shifting the boundary down.
762                          */
763                         adjust_next = -((vma->vm_end - end) >> PAGE_SHIFT);
764                         exporter = vma;
765                         importer = next;
766                 }
767 
768                 /*
769                  * Easily overlooked: when mprotect shifts the boundary,
770                  * make sure the expanding vma has anon_vma set if the
771                  * shrinking vma had, to cover any anon pages imported.
772                  */
773                 if (exporter && exporter->anon_vma && !importer->anon_vma) {
774                         int error;
775 
776                         importer->anon_vma = exporter->anon_vma;
777                         error = anon_vma_clone(importer, exporter);
778                         if (error)
779                                 return error;
780                 }
781         }
782 
783         if (file) {
784                 mapping = file->f_mapping;
785                 root = &mapping->i_mmap;
786                 uprobe_munmap(vma, vma->vm_start, vma->vm_end);
787 
788                 if (adjust_next)
789                         uprobe_munmap(next, next->vm_start, next->vm_end);
790 
791                 i_mmap_lock_write(mapping);
792                 if (insert) {
793                         /*
794                          * Put into interval tree now, so instantiated pages
795                          * are visible to arm/parisc __flush_dcache_page
796                          * throughout; but we cannot insert into address
797                          * space until vma start or end is updated.
798                          */
799                         __vma_link_file(insert);
800                 }
801         }
802 
803         vma_adjust_trans_huge(vma, start, end, adjust_next);
804 
805         anon_vma = vma->anon_vma;
806         if (!anon_vma && adjust_next)
807                 anon_vma = next->anon_vma;
808         if (anon_vma) {
809                 VM_BUG_ON_VMA(adjust_next && next->anon_vma &&
810                           anon_vma != next->anon_vma, next);
811                 anon_vma_lock_write(anon_vma);
812                 anon_vma_interval_tree_pre_update_vma(vma);
813                 if (adjust_next)
814                         anon_vma_interval_tree_pre_update_vma(next);
815         }
816 
817         if (root) {
818                 flush_dcache_mmap_lock(mapping);
819                 vma_interval_tree_remove(vma, root);
820                 if (adjust_next)
821                         vma_interval_tree_remove(next, root);
822         }
823 
824         if (start != vma->vm_start) {
825                 vma->vm_start = start;
826                 start_changed = true;
827         }
828         if (end != vma->vm_end) {
829                 vma->vm_end = end;
830                 end_changed = true;
831         }
832         vma->vm_pgoff = pgoff;
833         if (adjust_next) {
834                 next->vm_start += adjust_next << PAGE_SHIFT;
835                 next->vm_pgoff += adjust_next;
836         }
837 
838         if (root) {
839                 if (adjust_next)
840                         vma_interval_tree_insert(next, root);
841                 vma_interval_tree_insert(vma, root);
842                 flush_dcache_mmap_unlock(mapping);
843         }
844 
845         if (remove_next) {
846                 /*
847                  * vma_merge has merged next into vma, and needs
848                  * us to remove next before dropping the locks.
849                  */
850                 __vma_unlink(mm, next, vma);
851                 if (file)
852                         __remove_shared_vm_struct(next, file, mapping);
853         } else if (insert) {
854                 /*
855                  * split_vma has split insert from vma, and needs
856                  * us to insert it before dropping the locks
857                  * (it may either follow vma or precede it).
858                  */
859                 __insert_vm_struct(mm, insert);
860         } else {
861                 if (start_changed)
862                         vma_gap_update(vma);
863                 if (end_changed) {
864                         if (!next)
865                                 mm->highest_vm_end = end;
866                         else if (!adjust_next)
867                                 vma_gap_update(next);
868                 }
869         }
870 
871         if (anon_vma) {
872                 anon_vma_interval_tree_post_update_vma(vma);
873                 if (adjust_next)
874                         anon_vma_interval_tree_post_update_vma(next);
875                 anon_vma_unlock_write(anon_vma);
876         }
877         if (mapping)
878                 i_mmap_unlock_write(mapping);
879 
880         if (root) {
881                 uprobe_mmap(vma);
882 
883                 if (adjust_next)
884                         uprobe_mmap(next);
885         }
886 
887         if (remove_next) {
888                 if (file) {
889                         uprobe_munmap(next, next->vm_start, next->vm_end);
890                         fput(file);
891                 }
892                 if (next->anon_vma)
893                         anon_vma_merge(vma, next);
894                 mm->map_count--;
895                 mpol_put(vma_policy(next));
896                 kmem_cache_free(vm_area_cachep, next);
897                 /*
898                  * In mprotect's case 6 (see comments on vma_merge),
899                  * we must remove another next too. It would clutter
900                  * up the code too much to do both in one go.
901                  */
902                 next = vma->vm_next;
903                 if (remove_next == 2)
904                         goto again;
905                 else if (next)
906                         vma_gap_update(next);
907                 else
908                         mm->highest_vm_end = end;
909         }
910         if (insert && file)
911                 uprobe_mmap(insert);
912 
913         validate_mm(mm);
914 
915         return 0;
916 }
917 
918 /*
919  * If the vma has a ->close operation then the driver probably needs to release
920  * per-vma resources, so we don't attempt to merge those.
921  */
922 static inline int is_mergeable_vma(struct vm_area_struct *vma,
923                                 struct file *file, unsigned long vm_flags,
924                                 struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
925 {
926         /*
927          * VM_SOFTDIRTY should not prevent from VMA merging, if we
928          * match the flags but dirty bit -- the caller should mark
929          * merged VMA as dirty. If dirty bit won't be excluded from
930          * comparison, we increase pressue on the memory system forcing
931          * the kernel to generate new VMAs when old one could be
932          * extended instead.
933          */
934         if ((vma->vm_flags ^ vm_flags) & ~VM_SOFTDIRTY)
935                 return 0;
936         if (vma->vm_file != file)
937                 return 0;
938         if (vma->vm_ops && vma->vm_ops->close)
939                 return 0;
940         if (!is_mergeable_vm_userfaultfd_ctx(vma, vm_userfaultfd_ctx))
941                 return 0;
942         return 1;
943 }
944 
945 static inline int is_mergeable_anon_vma(struct anon_vma *anon_vma1,
946                                         struct anon_vma *anon_vma2,
947                                         struct vm_area_struct *vma)
948 {
949         /*
950          * The list_is_singular() test is to avoid merging VMA cloned from
951          * parents. This can improve scalability caused by anon_vma lock.
952          */
953         if ((!anon_vma1 || !anon_vma2) && (!vma ||
954                 list_is_singular(&vma->anon_vma_chain)))
955                 return 1;
956         return anon_vma1 == anon_vma2;
957 }
958 
959 /*
960  * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
961  * in front of (at a lower virtual address and file offset than) the vma.
962  *
963  * We cannot merge two vmas if they have differently assigned (non-NULL)
964  * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
965  *
966  * We don't check here for the merged mmap wrapping around the end of pagecache
967  * indices (16TB on ia32) because do_mmap_pgoff() does not permit mmap's which
968  * wrap, nor mmaps which cover the final page at index -1UL.
969  */
970 static int
971 can_vma_merge_before(struct vm_area_struct *vma, unsigned long vm_flags,
972                      struct anon_vma *anon_vma, struct file *file,
973                      pgoff_t vm_pgoff,
974                      struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
975 {
976         if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx) &&
977             is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
978                 if (vma->vm_pgoff == vm_pgoff)
979                         return 1;
980         }
981         return 0;
982 }
983 
984 /*
985  * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
986  * beyond (at a higher virtual address and file offset than) the vma.
987  *
988  * We cannot merge two vmas if they have differently assigned (non-NULL)
989  * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
990  */
991 static int
992 can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
993                     struct anon_vma *anon_vma, struct file *file,
994                     pgoff_t vm_pgoff,
995                     struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
996 {
997         if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx) &&
998             is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
999                 pgoff_t vm_pglen;
1000                 vm_pglen = vma_pages(vma);
1001                 if (vma->vm_pgoff + vm_pglen == vm_pgoff)
1002                         return 1;
1003         }
1004         return 0;
1005 }
1006 
1007 /*
1008  * Given a mapping request (addr,end,vm_flags,file,pgoff), figure out
1009  * whether that can be merged with its predecessor or its successor.
1010  * Or both (it neatly fills a hole).
1011  *
1012  * In most cases - when called for mmap, brk or mremap - [addr,end) is
1013  * certain not to be mapped by the time vma_merge is called; but when
1014  * called for mprotect, it is certain to be already mapped (either at
1015  * an offset within prev, or at the start of next), and the flags of
1016  * this area are about to be changed to vm_flags - and the no-change
1017  * case has already been eliminated.
1018  *
1019  * The following mprotect cases have to be considered, where AAAA is
1020  * the area passed down from mprotect_fixup, never extending beyond one
1021  * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
1022  *
1023  *     AAAA             AAAA                AAAA          AAAA
1024  *    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPNNNNXXXX
1025  *    cannot merge    might become    might become    might become
1026  *                    PPNNNNNNNNNN    PPPPPPPPPPNN    PPPPPPPPPPPP 6 or
1027  *    mmap, brk or    case 4 below    case 5 below    PPPPPPPPXXXX 7 or
1028  *    mremap move:                                    PPPPNNNNNNNN 8
1029  *        AAAA
1030  *    PPPP    NNNN    PPPPPPPPPPPP    PPPPPPPPNNNN    PPPPNNNNNNNN
1031  *    might become    case 1 below    case 2 below    case 3 below
1032  *
1033  * Odd one out? Case 8, because it extends NNNN but needs flags of XXXX:
1034  * mprotect_fixup updates vm_flags & vm_page_prot on successful return.
1035  */
1036 struct vm_area_struct *vma_merge(struct mm_struct *mm,
1037                         struct vm_area_struct *prev, unsigned long addr,
1038                         unsigned long end, unsigned long vm_flags,
1039                         struct anon_vma *anon_vma, struct file *file,
1040                         pgoff_t pgoff, struct mempolicy *policy,
1041                         struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
1042 {
1043         pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
1044         struct vm_area_struct *area, *next;
1045         int err;
1046 
1047         /*
1048          * We later require that vma->vm_flags == vm_flags,
1049          * so this tests vma->vm_flags & VM_SPECIAL, too.
1050          */
1051         if (vm_flags & VM_SPECIAL)
1052                 return NULL;
1053 
1054         if (prev)
1055                 next = prev->vm_next;
1056         else
1057                 next = mm->mmap;
1058         area = next;
1059         if (next && next->vm_end == end)                /* cases 6, 7, 8 */
1060                 next = next->vm_next;
1061 
1062         /*
1063          * Can it merge with the predecessor?
1064          */
1065         if (prev && prev->vm_end == addr &&
1066                         mpol_equal(vma_policy(prev), policy) &&
1067                         can_vma_merge_after(prev, vm_flags,
1068                                             anon_vma, file, pgoff,
1069                                             vm_userfaultfd_ctx)) {
1070                 /*
1071                  * OK, it can.  Can we now merge in the successor as well?
1072                  */
1073                 if (next && end == next->vm_start &&
1074                                 mpol_equal(policy, vma_policy(next)) &&
1075                                 can_vma_merge_before(next, vm_flags,
1076                                                      anon_vma, file,
1077                                                      pgoff+pglen,
1078                                                      vm_userfaultfd_ctx) &&
1079                                 is_mergeable_anon_vma(prev->anon_vma,
1080                                                       next->anon_vma, NULL)) {
1081                                                         /* cases 1, 6 */
1082                         err = vma_adjust(prev, prev->vm_start,
1083                                 next->vm_end, prev->vm_pgoff, NULL);
1084                 } else                                  /* cases 2, 5, 7 */
1085                         err = vma_adjust(prev, prev->vm_start,
1086                                 end, prev->vm_pgoff, NULL);
1087                 if (err)
1088                         return NULL;
1089                 khugepaged_enter_vma_merge(prev, vm_flags);
1090                 return prev;
1091         }
1092 
1093         /*
1094          * Can this new request be merged in front of next?
1095          */
1096         if (next && end == next->vm_start &&
1097                         mpol_equal(policy, vma_policy(next)) &&
1098                         can_vma_merge_before(next, vm_flags,
1099                                              anon_vma, file, pgoff+pglen,
1100                                              vm_userfaultfd_ctx)) {
1101                 if (prev && addr < prev->vm_end)        /* case 4 */
1102                         err = vma_adjust(prev, prev->vm_start,
1103                                 addr, prev->vm_pgoff, NULL);
1104                 else                                    /* cases 3, 8 */
1105                         err = vma_adjust(area, addr, next->vm_end,
1106                                 next->vm_pgoff - pglen, NULL);
1107                 if (err)
1108                         return NULL;
1109                 khugepaged_enter_vma_merge(area, vm_flags);
1110                 return area;
1111         }
1112 
1113         return NULL;
1114 }
1115 
1116 /*
1117  * Rough compatbility check to quickly see if it's even worth looking
1118  * at sharing an anon_vma.
1119  *
1120  * They need to have the same vm_file, and the flags can only differ
1121  * in things that mprotect may change.
1122  *
1123  * NOTE! The fact that we share an anon_vma doesn't _have_ to mean that
1124  * we can merge the two vma's. For example, we refuse to merge a vma if
1125  * there is a vm_ops->close() function, because that indicates that the
1126  * driver is doing some kind of reference counting. But that doesn't
1127  * really matter for the anon_vma sharing case.
1128  */
1129 static int anon_vma_compatible(struct vm_area_struct *a, struct vm_area_struct *b)
1130 {
1131         return a->vm_end == b->vm_start &&
1132                 mpol_equal(vma_policy(a), vma_policy(b)) &&
1133                 a->vm_file == b->vm_file &&
1134                 !((a->vm_flags ^ b->vm_flags) & ~(VM_READ|VM_WRITE|VM_EXEC|VM_SOFTDIRTY)) &&
1135                 b->vm_pgoff == a->vm_pgoff + ((b->vm_start - a->vm_start) >> PAGE_SHIFT);
1136 }
1137 
1138 /*
1139  * Do some basic sanity checking to see if we can re-use the anon_vma
1140  * from 'old'. The 'a'/'b' vma's are in VM order - one of them will be
1141  * the same as 'old', the other will be the new one that is trying
1142  * to share the anon_vma.
1143  *
1144  * NOTE! This runs with mm_sem held for reading, so it is possible that
1145  * the anon_vma of 'old' is concurrently in the process of being set up
1146  * by another page fault trying to merge _that_. But that's ok: if it
1147  * is being set up, that automatically means that it will be a singleton
1148  * acceptable for merging, so we can do all of this optimistically. But
1149  * we do that READ_ONCE() to make sure that we never re-load the pointer.
1150  *
1151  * IOW: that the "list_is_singular()" test on the anon_vma_chain only
1152  * matters for the 'stable anon_vma' case (ie the thing we want to avoid
1153  * is to return an anon_vma that is "complex" due to having gone through
1154  * a fork).
1155  *
1156  * We also make sure that the two vma's are compatible (adjacent,
1157  * and with the same memory policies). That's all stable, even with just
1158  * a read lock on the mm_sem.
1159  */
1160 static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, struct vm_area_struct *a, struct vm_area_struct *b)
1161 {
1162         if (anon_vma_compatible(a, b)) {
1163                 struct anon_vma *anon_vma = READ_ONCE(old->anon_vma);
1164 
1165                 if (anon_vma && list_is_singular(&old->anon_vma_chain))
1166                         return anon_vma;
1167         }
1168         return NULL;
1169 }
1170 
1171 /*
1172  * find_mergeable_anon_vma is used by anon_vma_prepare, to check
1173  * neighbouring vmas for a suitable anon_vma, before it goes off
1174  * to allocate a new anon_vma.  It checks because a repetitive
1175  * sequence of mprotects and faults may otherwise lead to distinct
1176  * anon_vmas being allocated, preventing vma merge in subsequent
1177  * mprotect.
1178  */
1179 struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
1180 {
1181         struct anon_vma *anon_vma;
1182         struct vm_area_struct *near;
1183 
1184         near = vma->vm_next;
1185         if (!near)
1186                 goto try_prev;
1187 
1188         anon_vma = reusable_anon_vma(near, vma, near);
1189         if (anon_vma)
1190                 return anon_vma;
1191 try_prev:
1192         near = vma->vm_prev;
1193         if (!near)
1194                 goto none;
1195 
1196         anon_vma = reusable_anon_vma(near, near, vma);
1197         if (anon_vma)
1198                 return anon_vma;
1199 none:
1200         /*
1201          * There's no absolute need to look only at touching neighbours:
1202          * we could search further afield for "compatible" anon_vmas.
1203          * But it would probably just be a waste of time searching,
1204          * or lead to too many vmas hanging off the same anon_vma.
1205          * We're trying to allow mprotect remerging later on,
1206          * not trying to minimize memory used for anon_vmas.
1207          */
1208         return NULL;
1209 }
1210 
1211 #ifdef CONFIG_PROC_FS
1212 void vm_stat_account(struct mm_struct *mm, unsigned long flags,
1213                                                 struct file *file, long pages)
1214 {
1215         const unsigned long stack_flags
1216                 = VM_STACK_FLAGS & (VM_GROWSUP|VM_GROWSDOWN);
1217 
1218         mm->total_vm += pages;
1219 
1220         if (file) {
1221                 mm->shared_vm += pages;
1222                 if ((flags & (VM_EXEC|VM_WRITE)) == VM_EXEC)
1223                         mm->exec_vm += pages;
1224         } else if (flags & stack_flags)
1225                 mm->stack_vm += pages;
1226 }
1227 #endif /* CONFIG_PROC_FS */
1228 
1229 /*
1230  * If a hint addr is less than mmap_min_addr change hint to be as
1231  * low as possible but still greater than mmap_min_addr
1232  */
1233 static inline unsigned long round_hint_to_min(unsigned long hint)
1234 {
1235         hint &= PAGE_MASK;
1236         if (((void *)hint != NULL) &&
1237             (hint < mmap_min_addr))
1238                 return PAGE_ALIGN(mmap_min_addr);
1239         return hint;
1240 }
1241 
1242 static inline int mlock_future_check(struct mm_struct *mm,
1243                                      unsigned long flags,
1244                                      unsigned long len)
1245 {
1246         unsigned long locked, lock_limit;
1247 
1248         /*  mlock MCL_FUTURE? */
1249         if (flags & VM_LOCKED) {
1250                 locked = len >> PAGE_SHIFT;
1251                 locked += mm->locked_vm;
1252                 lock_limit = rlimit(RLIMIT_MEMLOCK);
1253                 lock_limit >>= PAGE_SHIFT;
1254                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
1255                         return -EAGAIN;
1256         }
1257         return 0;
1258 }
1259 
1260 /*
1261  * The caller must hold down_write(&current->mm->mmap_sem).
1262  */
1263 unsigned long do_mmap(struct file *file, unsigned long addr,
1264                         unsigned long len, unsigned long prot,
1265                         unsigned long flags, vm_flags_t vm_flags,
1266                         unsigned long pgoff, unsigned long *populate)
1267 {
1268         struct mm_struct *mm = current->mm;
1269 
1270         *populate = 0;
1271 
1272         if (!len)
1273                 return -EINVAL;
1274 
1275         /*
1276          * Does the application expect PROT_READ to imply PROT_EXEC?
1277          *
1278          * (the exception is when the underlying filesystem is noexec
1279          *  mounted, in which case we dont add PROT_EXEC.)
1280          */
1281         if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
1282                 if (!(file && path_noexec(&file->f_path)))
1283                         prot |= PROT_EXEC;
1284 
1285         if (!(flags & MAP_FIXED))
1286                 addr = round_hint_to_min(addr);
1287 
1288         /* Careful about overflows.. */
1289         len = PAGE_ALIGN(len);
1290         if (!len)
1291                 return -ENOMEM;
1292 
1293         /* offset overflow? */
1294         if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
1295                 return -EOVERFLOW;
1296 
1297         /* Too many mappings? */
1298         if (mm->map_count > sysctl_max_map_count)
1299                 return -ENOMEM;
1300 
1301         /* Obtain the address to map to. we verify (or select) it and ensure
1302          * that it represents a valid section of the address space.
1303          */
1304         addr = get_unmapped_area(file, addr, len, pgoff, flags);
1305         if (addr & ~PAGE_MASK)
1306                 return addr;
1307 
1308         /* Do simple checking here so the lower-level routines won't have
1309          * to. we assume access permissions have been handled by the open
1310          * of the memory object, so we don't do any here.
1311          */
1312         vm_flags |= calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags) |
1313                         mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
1314 
1315         if (flags & MAP_LOCKED)
1316                 if (!can_do_mlock())
1317                         return -EPERM;
1318 
1319         if (mlock_future_check(mm, vm_flags, len))
1320                 return -EAGAIN;
1321 
1322         if (file) {
1323                 struct inode *inode = file_inode(file);
1324 
1325                 switch (flags & MAP_TYPE) {
1326                 case MAP_SHARED:
1327                         if ((prot&PROT_WRITE) && !(file->f_mode&FMODE_WRITE))
1328                                 return -EACCES;
1329 
1330                         /*
1331                          * Make sure we don't allow writing to an append-only
1332                          * file..
1333                          */
1334                         if (IS_APPEND(inode) && (file->f_mode & FMODE_WRITE))
1335                                 return -EACCES;
1336 
1337                         /*
1338                          * Make sure there are no mandatory locks on the file.
1339                          */
1340                         if (locks_verify_locked(file))
1341                                 return -EAGAIN;
1342 
1343                         vm_flags |= VM_SHARED | VM_MAYSHARE;
1344                         if (!(file->f_mode & FMODE_WRITE))
1345                                 vm_flags &= ~(VM_MAYWRITE | VM_SHARED);
1346 
1347                         /* fall through */
1348                 case MAP_PRIVATE:
1349                         if (!(file->f_mode & FMODE_READ))
1350                                 return -EACCES;
1351                         if (path_noexec(&file->f_path)) {
1352                                 if (vm_flags & VM_EXEC)
1353                                         return -EPERM;
1354                                 vm_flags &= ~VM_MAYEXEC;
1355                         }
1356 
1357                         if (!file->f_op->mmap)
1358                                 return -ENODEV;
1359                         if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1360                                 return -EINVAL;
1361                         break;
1362 
1363                 default:
1364                         return -EINVAL;
1365                 }
1366         } else {
1367                 switch (flags & MAP_TYPE) {
1368                 case MAP_SHARED:
1369                         if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1370                                 return -EINVAL;
1371                         /*
1372                          * Ignore pgoff.
1373                          */
1374                         pgoff = 0;
1375                         vm_flags |= VM_SHARED | VM_MAYSHARE;
1376                         break;
1377                 case MAP_PRIVATE:
1378                         /*
1379                          * Set pgoff according to addr for anon_vma.
1380                          */
1381                         pgoff = addr >> PAGE_SHIFT;
1382                         break;
1383                 default:
1384                         return -EINVAL;
1385                 }
1386         }
1387 
1388         /*
1389          * Set 'VM_NORESERVE' if we should not account for the
1390          * memory use of this mapping.
1391          */
1392         if (flags & MAP_NORESERVE) {
1393                 /* We honor MAP_NORESERVE if allowed to overcommit */
1394                 if (sysctl_overcommit_memory != OVERCOMMIT_NEVER)
1395                         vm_flags |= VM_NORESERVE;
1396 
1397                 /* hugetlb applies strict overcommit unless MAP_NORESERVE */
1398                 if (file && is_file_hugepages(file))
1399                         vm_flags |= VM_NORESERVE;
1400         }
1401 
1402         addr = mmap_region(file, addr, len, vm_flags, pgoff);
1403         if (!IS_ERR_VALUE(addr) &&
1404             ((vm_flags & VM_LOCKED) ||
1405              (flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE))
1406                 *populate = len;
1407         return addr;
1408 }
1409 
1410 SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
1411                 unsigned long, prot, unsigned long, flags,
1412                 unsigned long, fd, unsigned long, pgoff)
1413 {
1414         struct file *file = NULL;
1415         unsigned long retval = -EBADF;
1416 
1417         if (!(flags & MAP_ANONYMOUS)) {
1418                 audit_mmap_fd(fd, flags);
1419                 file = fget(fd);
1420                 if (!file)
1421                         goto out;
1422                 if (is_file_hugepages(file))
1423                         len = ALIGN(len, huge_page_size(hstate_file(file)));
1424                 retval = -EINVAL;
1425                 if (unlikely(flags & MAP_HUGETLB && !is_file_hugepages(file)))
1426                         goto out_fput;
1427         } else if (flags & MAP_HUGETLB) {
1428                 struct user_struct *user = NULL;
1429                 struct hstate *hs;
1430 
1431                 hs = hstate_sizelog((flags >> MAP_HUGE_SHIFT) & SHM_HUGE_MASK);
1432                 if (!hs)
1433                         return -EINVAL;
1434 
1435                 len = ALIGN(len, huge_page_size(hs));
1436                 /*
1437                  * VM_NORESERVE is used because the reservations will be
1438                  * taken when vm_ops->mmap() is called
1439                  * A dummy user value is used because we are not locking
1440                  * memory so no accounting is necessary
1441                  */
1442                 file = hugetlb_file_setup(HUGETLB_ANON_FILE, len,
1443                                 VM_NORESERVE,
1444                                 &user, HUGETLB_ANONHUGE_INODE,
1445                                 (flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK);
1446                 if (IS_ERR(file))
1447                         return PTR_ERR(file);
1448         }
1449 
1450         flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
1451 
1452         retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
1453 out_fput:
1454         if (file)
1455                 fput(file);
1456 out:
1457         return retval;
1458 }
1459 
1460 #ifdef __ARCH_WANT_SYS_OLD_MMAP
1461 struct mmap_arg_struct {
1462         unsigned long addr;
1463         unsigned long len;
1464         unsigned long prot;
1465         unsigned long flags;
1466         unsigned long fd;
1467         unsigned long offset;
1468 };
1469 
1470 SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
1471 {
1472         struct mmap_arg_struct a;
1473 
1474         if (copy_from_user(&a, arg, sizeof(a)))
1475                 return -EFAULT;
1476         if (a.offset & ~PAGE_MASK)
1477                 return -EINVAL;
1478 
1479         return sys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
1480                               a.offset >> PAGE_SHIFT);
1481 }
1482 #endif /* __ARCH_WANT_SYS_OLD_MMAP */
1483 
1484 /*
1485  * Some shared mappigns will want the pages marked read-only
1486  * to track write events. If so, we'll downgrade vm_page_prot
1487  * to the private version (using protection_map[] without the
1488  * VM_SHARED bit).
1489  */
1490 int vma_wants_writenotify(struct vm_area_struct *vma)
1491 {
1492         vm_flags_t vm_flags = vma->vm_flags;
1493         const struct vm_operations_struct *vm_ops = vma->vm_ops;
1494 
1495         /* If it was private or non-writable, the write bit is already clear */
1496         if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED)))
1497                 return 0;
1498 
1499         /* The backer wishes to know when pages are first written to? */
1500         if (vm_ops && (vm_ops->page_mkwrite || vm_ops->pfn_mkwrite))
1501                 return 1;
1502 
1503         /* The open routine did something to the protections that pgprot_modify
1504          * won't preserve? */
1505         if (pgprot_val(vma->vm_page_prot) !=
1506             pgprot_val(vm_pgprot_modify(vma->vm_page_prot, vm_flags)))
1507                 return 0;
1508 
1509         /* Do we need to track softdirty? */
1510         if (IS_ENABLED(CONFIG_MEM_SOFT_DIRTY) && !(vm_flags & VM_SOFTDIRTY))
1511                 return 1;
1512 
1513         /* Specialty mapping? */
1514         if (vm_flags & VM_PFNMAP)
1515                 return 0;
1516 
1517         /* Can the mapping track the dirty pages? */
1518         return vma->vm_file && vma->vm_file->f_mapping &&
1519                 mapping_cap_account_dirty(vma->vm_file->f_mapping);
1520 }
1521 
1522 /*
1523  * We account for memory if it's a private writeable mapping,
1524  * not hugepages and VM_NORESERVE wasn't set.
1525  */
1526 static inline int accountable_mapping(struct file *file, vm_flags_t vm_flags)
1527 {
1528         /*
1529          * hugetlb has its own accounting separate from the core VM
1530          * VM_HUGETLB may not be set yet so we cannot check for that flag.
1531          */
1532         if (file && is_file_hugepages(file))
1533                 return 0;
1534 
1535         return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE;
1536 }
1537 
1538 unsigned long mmap_region(struct file *file, unsigned long addr,
1539                 unsigned long len, vm_flags_t vm_flags, unsigned long pgoff)
1540 {
1541         struct mm_struct *mm = current->mm;
1542         struct vm_area_struct *vma, *prev;
1543         int error;
1544         struct rb_node **rb_link, *rb_parent;
1545         unsigned long charged = 0;
1546 
1547         /* Check against address space limit. */
1548         if (!may_expand_vm(mm, len >> PAGE_SHIFT)) {
1549                 unsigned long nr_pages;
1550 
1551                 /*
1552                  * MAP_FIXED may remove pages of mappings that intersects with
1553                  * requested mapping. Account for the pages it would unmap.
1554                  */
1555                 if (!(vm_flags & MAP_FIXED))
1556                         return -ENOMEM;
1557 
1558                 nr_pages = count_vma_pages_range(mm, addr, addr + len);
1559 
1560                 if (!may_expand_vm(mm, (len >> PAGE_SHIFT) - nr_pages))
1561                         return -ENOMEM;
1562         }
1563 
1564         /* Clear old maps */
1565         error = -ENOMEM;
1566         while (find_vma_links(mm, addr, addr + len, &prev, &rb_link,
1567                               &rb_parent)) {
1568                 if (do_munmap(mm, addr, len))
1569                         return -ENOMEM;
1570         }
1571 
1572         /*
1573          * Private writable mapping: check memory availability
1574          */
1575         if (accountable_mapping(file, vm_flags)) {
1576                 charged = len >> PAGE_SHIFT;
1577                 if (security_vm_enough_memory_mm(mm, charged))
1578                         return -ENOMEM;
1579                 vm_flags |= VM_ACCOUNT;
1580         }
1581 
1582         /*
1583          * Can we just expand an old mapping?
1584          */
1585         vma = vma_merge(mm, prev, addr, addr + len, vm_flags,
1586                         NULL, file, pgoff, NULL, NULL_VM_UFFD_CTX);
1587         if (vma)
1588                 goto out;
1589 
1590         /*
1591          * Determine the object being mapped and call the appropriate
1592          * specific mapper. the address has already been validated, but
1593          * not unmapped, but the maps are removed from the list.
1594          */
1595         vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
1596         if (!vma) {
1597                 error = -ENOMEM;
1598                 goto unacct_error;
1599         }
1600 
1601         vma->vm_mm = mm;
1602         vma->vm_start = addr;
1603         vma->vm_end = addr + len;
1604         vma->vm_flags = vm_flags;
1605         vma->vm_page_prot = vm_get_page_prot(vm_flags);
1606         vma->vm_pgoff = pgoff;
1607         INIT_LIST_HEAD(&vma->anon_vma_chain);
1608 
1609         if (file) {
1610                 if (vm_flags & VM_DENYWRITE) {
1611                         error = deny_write_access(file);
1612                         if (error)
1613                                 goto free_vma;
1614                 }
1615                 if (vm_flags & VM_SHARED) {
1616                         error = mapping_map_writable(file->f_mapping);
1617                         if (error)
1618                                 goto allow_write_and_free_vma;
1619                 }
1620 
1621                 /* ->mmap() can change vma->vm_file, but must guarantee that
1622                  * vma_link() below can deny write-access if VM_DENYWRITE is set
1623                  * and map writably if VM_SHARED is set. This usually means the
1624                  * new file must not have been exposed to user-space, yet.
1625                  */
1626                 vma->vm_file = get_file(file);
1627                 error = file->f_op->mmap(file, vma);
1628                 if (error)
1629                         goto unmap_and_free_vma;
1630 
1631                 /* Can addr have changed??
1632                  *
1633                  * Answer: Yes, several device drivers can do it in their
1634                  *         f_op->mmap method. -DaveM
1635                  * Bug: If addr is changed, prev, rb_link, rb_parent should
1636                  *      be updated for vma_link()
1637                  */
1638                 WARN_ON_ONCE(addr != vma->vm_start);
1639 
1640                 addr = vma->vm_start;
1641                 vm_flags = vma->vm_flags;
1642         } else if (vm_flags & VM_SHARED) {
1643                 error = shmem_zero_setup(vma);
1644                 if (error)
1645                         goto free_vma;
1646         }
1647 
1648         vma_link(mm, vma, prev, rb_link, rb_parent);
1649         /* Once vma denies write, undo our temporary denial count */
1650         if (file) {
1651                 if (vm_flags & VM_SHARED)
1652                         mapping_unmap_writable(file->f_mapping);
1653                 if (vm_flags & VM_DENYWRITE)
1654                         allow_write_access(file);
1655         }
1656         file = vma->vm_file;
1657 out:
1658         perf_event_mmap(vma);
1659 
1660         vm_stat_account(mm, vm_flags, file, len >> PAGE_SHIFT);
1661         if (vm_flags & VM_LOCKED) {
1662                 if (!((vm_flags & VM_SPECIAL) || is_vm_hugetlb_page(vma) ||
1663                                         vma == get_gate_vma(current->mm)))
1664                         mm->locked_vm += (len >> PAGE_SHIFT);
1665                 else
1666                         vma->vm_flags &= ~VM_LOCKED;
1667         }
1668 
1669         if (file)
1670                 uprobe_mmap(vma);
1671 
1672         /*
1673          * New (or expanded) vma always get soft dirty status.
1674          * Otherwise user-space soft-dirty page tracker won't
1675          * be able to distinguish situation when vma area unmapped,
1676          * then new mapped in-place (which must be aimed as
1677          * a completely new data area).
1678          */
1679         vma->vm_flags |= VM_SOFTDIRTY;
1680 
1681         vma_set_page_prot(vma);
1682 
1683         return addr;
1684 
1685 unmap_and_free_vma:
1686         vma->vm_file = NULL;
1687         fput(file);
1688 
1689         /* Undo any partial mapping done by a device driver. */
1690         unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);
1691         charged = 0;
1692         if (vm_flags & VM_SHARED)
1693                 mapping_unmap_writable(file->f_mapping);
1694 allow_write_and_free_vma:
1695         if (vm_flags & VM_DENYWRITE)
1696                 allow_write_access(file);
1697 free_vma:
1698         kmem_cache_free(vm_area_cachep, vma);
1699 unacct_error:
1700         if (charged)
1701                 vm_unacct_memory(charged);
1702         return error;
1703 }
1704 
1705 unsigned long unmapped_area(struct vm_unmapped_area_info *info)
1706 {
1707         /*
1708          * We implement the search by looking for an rbtree node that
1709          * immediately follows a suitable gap. That is,
1710          * - gap_start = vma->vm_prev->vm_end <= info->high_limit - length;
1711          * - gap_end   = vma->vm_start        >= info->low_limit  + length;
1712          * - gap_end - gap_start >= length
1713          */
1714 
1715         struct mm_struct *mm = current->mm;
1716         struct vm_area_struct *vma;
1717         unsigned long length, low_limit, high_limit, gap_start, gap_end;
1718 
1719         /* Adjust search length to account for worst case alignment overhead */
1720         length = info->length + info->align_mask;
1721         if (length < info->length)
1722                 return -ENOMEM;
1723 
1724         /* Adjust search limits by the desired length */
1725         if (info->high_limit < length)
1726                 return -ENOMEM;
1727         high_limit = info->high_limit - length;
1728 
1729         if (info->low_limit > high_limit)
1730                 return -ENOMEM;
1731         low_limit = info->low_limit + length;
1732 
1733         /* Check if rbtree root looks promising */
1734         if (RB_EMPTY_ROOT(&mm->mm_rb))
1735                 goto check_highest;
1736         vma = rb_entry(mm->mm_rb.rb_node, struct vm_area_struct, vm_rb);
1737         if (vma->rb_subtree_gap < length)
1738                 goto check_highest;
1739 
1740         while (true) {
1741                 /* Visit left subtree if it looks promising */
1742                 gap_end = vma->vm_start;
1743                 if (gap_end >= low_limit && vma->vm_rb.rb_left) {
1744                         struct vm_area_struct *left =
1745                                 rb_entry(vma->vm_rb.rb_left,
1746                                          struct vm_area_struct, vm_rb);
1747                         if (left->rb_subtree_gap >= length) {
1748                                 vma = left;
1749                                 continue;
1750                         }
1751                 }
1752 
1753                 gap_start = vma->vm_prev ? vma->vm_prev->vm_end : 0;
1754 check_current:
1755                 /* Check if current node has a suitable gap */
1756                 if (gap_start > high_limit)
1757                         return -ENOMEM;
1758                 if (gap_end >= low_limit && gap_end - gap_start >= length)
1759                         goto found;
1760 
1761                 /* Visit right subtree if it looks promising */
1762                 if (vma->vm_rb.rb_right) {
1763                         struct vm_area_struct *right =
1764                                 rb_entry(vma->vm_rb.rb_right,
1765                                          struct vm_area_struct, vm_rb);
1766                         if (right->rb_subtree_gap >= length) {
1767                                 vma = right;
1768                                 continue;
1769                         }
1770                 }
1771 
1772                 /* Go back up the rbtree to find next candidate node */
1773                 while (true) {
1774                         struct rb_node *prev = &vma->vm_rb;
1775                         if (!rb_parent(prev))
1776                                 goto check_highest;
1777                         vma = rb_entry(rb_parent(prev),
1778                                        struct vm_area_struct, vm_rb);
1779                         if (prev == vma->vm_rb.rb_left) {
1780                                 gap_start = vma->vm_prev->vm_end;
1781                                 gap_end = vma->vm_start;
1782                                 goto check_current;
1783                         }
1784                 }
1785         }
1786 
1787 check_highest:
1788         /* Check highest gap, which does not precede any rbtree node */
1789         gap_start = mm->highest_vm_end;
1790         gap_end = ULONG_MAX;  /* Only for VM_BUG_ON below */
1791         if (gap_start > high_limit)
1792                 return -ENOMEM;
1793 
1794 found:
1795         /* We found a suitable gap. Clip it with the original low_limit. */
1796         if (gap_start < info->low_limit)
1797                 gap_start = info->low_limit;
1798 
1799         /* Adjust gap address to the desired alignment */
1800         gap_start += (info->align_offset - gap_start) & info->align_mask;
1801 
1802         VM_BUG_ON(gap_start + info->length > info->high_limit);
1803         VM_BUG_ON(gap_start + info->length > gap_end);
1804         return gap_start;
1805 }
1806 
1807 unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
1808 {
1809         struct mm_struct *mm = current->mm;
1810         struct vm_area_struct *vma;
1811         unsigned long length, low_limit, high_limit, gap_start, gap_end;
1812 
1813         /* Adjust search length to account for worst case alignment overhead */
1814         length = info->length + info->align_mask;
1815         if (length < info->length)
1816                 return -ENOMEM;
1817 
1818         /*
1819          * Adjust search limits by the desired length.
1820          * See implementation comment at top of unmapped_area().
1821          */
1822         gap_end = info->high_limit;
1823         if (gap_end < length)
1824                 return -ENOMEM;
1825         high_limit = gap_end - length;
1826 
1827         if (info->low_limit > high_limit)
1828                 return -ENOMEM;
1829         low_limit = info->low_limit + length;
1830 
1831         /* Check highest gap, which does not precede any rbtree node */
1832         gap_start = mm->highest_vm_end;
1833         if (gap_start <= high_limit)
1834                 goto found_highest;
1835 
1836         /* Check if rbtree root looks promising */
1837         if (RB_EMPTY_ROOT(&mm->mm_rb))
1838                 return -ENOMEM;
1839         vma = rb_entry(mm->mm_rb.rb_node, struct vm_area_struct, vm_rb);
1840         if (vma->rb_subtree_gap < length)
1841                 return -ENOMEM;
1842 
1843         while (true) {
1844                 /* Visit right subtree if it looks promising */
1845                 gap_start = vma->vm_prev ? vma->vm_prev->vm_end : 0;
1846                 if (gap_start <= high_limit && vma->vm_rb.rb_right) {
1847                         struct vm_area_struct *right =
1848                                 rb_entry(vma->vm_rb.rb_right,
1849                                          struct vm_area_struct, vm_rb);
1850                         if (right->rb_subtree_gap >= length) {
1851                                 vma = right;
1852                                 continue;
1853                         }
1854                 }
1855 
1856 check_current:
1857                 /* Check if current node has a suitable gap */
1858                 gap_end = vma->vm_start;
1859                 if (gap_end < low_limit)
1860                         return -ENOMEM;
1861                 if (gap_start <= high_limit && gap_end - gap_start >= length)
1862                         goto found;
1863 
1864                 /* Visit left subtree if it looks promising */
1865                 if (vma->vm_rb.rb_left) {
1866                         struct vm_area_struct *left =
1867                                 rb_entry(vma->vm_rb.rb_left,
1868                                          struct vm_area_struct, vm_rb);
1869                         if (left->rb_subtree_gap >= length) {
1870                                 vma = left;
1871                                 continue;
1872                         }
1873                 }
1874 
1875                 /* Go back up the rbtree to find next candidate node */
1876                 while (true) {
1877                         struct rb_node *prev = &vma->vm_rb;
1878                         if (!rb_parent(prev))
1879                                 return -ENOMEM;
1880                         vma = rb_entry(rb_parent(prev),
1881                                        struct vm_area_struct, vm_rb);
1882                         if (prev == vma->vm_rb.rb_right) {
1883                                 gap_start = vma->vm_prev ?
1884                                         vma->vm_prev->vm_end : 0;
1885                                 goto check_current;
1886                         }
1887                 }
1888         }
1889 
1890 found:
1891         /* We found a suitable gap. Clip it with the original high_limit. */
1892         if (gap_end > info->high_limit)
1893                 gap_end = info->high_limit;
1894 
1895 found_highest:
1896         /* Compute highest gap address at the desired alignment */
1897         gap_end -= info->length;
1898         gap_end -= (gap_end - info->align_offset) & info->align_mask;
1899 
1900         VM_BUG_ON(gap_end < info->low_limit);
1901         VM_BUG_ON(gap_end < gap_start);
1902         return gap_end;
1903 }
1904 
1905 /* Get an address range which is currently unmapped.
1906  * For shmat() with addr=0.
1907  *
1908  * Ugly calling convention alert:
1909  * Return value with the low bits set means error value,
1910  * ie
1911  *      if (ret & ~PAGE_MASK)
1912  *              error = ret;
1913  *
1914  * This function "knows" that -ENOMEM has the bits set.
1915  */
1916 #ifndef HAVE_ARCH_UNMAPPED_AREA
1917 unsigned long
1918 arch_get_unmapped_area(struct file *filp, unsigned long addr,
1919                 unsigned long len, unsigned long pgoff, unsigned long flags)
1920 {
1921         struct mm_struct *mm = current->mm;
1922         struct vm_area_struct *vma;
1923         struct vm_unmapped_area_info info;
1924 
1925         if (len > TASK_SIZE - mmap_min_addr)
1926                 return -ENOMEM;
1927 
1928         if (flags & MAP_FIXED)
1929                 return addr;
1930 
1931         if (addr) {
1932                 addr = PAGE_ALIGN(addr);
1933                 vma = find_vma(mm, addr);
1934                 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
1935                     (!vma || addr + len <= vma->vm_start))
1936                         return addr;
1937         }
1938 
1939         info.flags = 0;
1940         info.length = len;
1941         info.low_limit = mm->mmap_base;
1942         info.high_limit = TASK_SIZE;
1943         info.align_mask = 0;
1944         return vm_unmapped_area(&info);
1945 }
1946 #endif
1947 
1948 /*
1949  * This mmap-allocator allocates new areas top-down from below the
1950  * stack's low limit (the base):
1951  */
1952 #ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
1953 unsigned long
1954 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
1955                           const unsigned long len, const unsigned long pgoff,
1956                           const unsigned long flags)
1957 {
1958         struct vm_area_struct *vma;
1959         struct mm_struct *mm = current->mm;
1960         unsigned long addr = addr0;
1961         struct vm_unmapped_area_info info;
1962 
1963         /* requested length too big for entire address space */
1964         if (len > TASK_SIZE - mmap_min_addr)
1965                 return -ENOMEM;
1966 
1967         if (flags & MAP_FIXED)
1968                 return addr;
1969 
1970         /* requesting a specific address */
1971         if (addr) {
1972                 addr = PAGE_ALIGN(addr);
1973                 vma = find_vma(mm, addr);
1974                 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
1975                                 (!vma || addr + len <= vma->vm_start))
1976                         return addr;
1977         }
1978 
1979         info.flags = VM_UNMAPPED_AREA_TOPDOWN;
1980         info.length = len;
1981         info.low_limit = max(PAGE_SIZE, mmap_min_addr);
1982         info.high_limit = mm->mmap_base;
1983         info.align_mask = 0;
1984         addr = vm_unmapped_area(&info);
1985 
1986         /*
1987          * A failed mmap() very likely causes application failure,
1988          * so fall back to the bottom-up function here. This scenario
1989          * can happen with large stack limits and large mmap()
1990          * allocations.
1991          */
1992         if (addr & ~PAGE_MASK) {
1993                 VM_BUG_ON(addr != -ENOMEM);
1994                 info.flags = 0;
1995                 info.low_limit = TASK_UNMAPPED_BASE;
1996                 info.high_limit = TASK_SIZE;
1997                 addr = vm_unmapped_area(&info);
1998         }
1999 
2000         return addr;
2001 }
2002 #endif
2003 
2004 unsigned long
2005 get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
2006                 unsigned long pgoff, unsigned long flags)
2007 {
2008         unsigned long (*get_area)(struct file *, unsigned long,
2009                                   unsigned long, unsigned long, unsigned long);
2010 
2011         unsigned long error = arch_mmap_check(addr, len, flags);
2012         if (error)
2013                 return error;
2014 
2015         /* Careful about overflows.. */
2016         if (len > TASK_SIZE)
2017                 return -ENOMEM;
2018 
2019         get_area = current->mm->get_unmapped_area;
2020         if (file && file->f_op->get_unmapped_area)
2021                 get_area = file->f_op->get_unmapped_area;
2022         addr = get_area(file, addr, len, pgoff, flags);
2023         if (IS_ERR_VALUE(addr))
2024                 return addr;
2025 
2026         if (addr > TASK_SIZE - len)
2027                 return -ENOMEM;
2028         if (addr & ~PAGE_MASK)
2029                 return -EINVAL;
2030 
2031         addr = arch_rebalance_pgtables(addr, len);
2032         error = security_mmap_addr(addr);
2033         return error ? error : addr;
2034 }
2035 
2036 EXPORT_SYMBOL(get_unmapped_area);
2037 
2038 /* Look up the first VMA which satisfies  addr < vm_end,  NULL if none. */
2039 struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
2040 {
2041         struct rb_node *rb_node;
2042         struct vm_area_struct *vma;
2043 
2044         /* Check the cache first. */
2045         vma = vmacache_find(mm, addr);
2046         if (likely(vma))
2047                 return vma;
2048 
2049         rb_node = mm->mm_rb.rb_node;
2050         vma = NULL;
2051 
2052         while (rb_node) {
2053                 struct vm_area_struct *tmp;
2054 
2055                 tmp = rb_entry(rb_node, struct vm_area_struct, vm_rb);
2056 
2057                 if (tmp->vm_end > addr) {
2058                         vma = tmp;
2059                         if (tmp->vm_start <= addr)
2060                                 break;
2061                         rb_node = rb_node->rb_left;
2062                 } else
2063                         rb_node = rb_node->rb_right;
2064         }
2065 
2066         if (vma)
2067                 vmacache_update(addr, vma);
2068         return vma;
2069 }
2070 
2071 EXPORT_SYMBOL(find_vma);
2072 
2073 /*
2074  * Same as find_vma, but also return a pointer to the previous VMA in *pprev.
2075  */
2076 struct vm_area_struct *
2077 find_vma_prev(struct mm_struct *mm, unsigned long addr,
2078                         struct vm_area_struct **pprev)
2079 {
2080         struct vm_area_struct *vma;
2081 
2082         vma = find_vma(mm, addr);
2083         if (vma) {
2084                 *pprev = vma->vm_prev;
2085         } else {
2086                 struct rb_node *rb_node = mm->mm_rb.rb_node;
2087                 *pprev = NULL;
2088                 while (rb_node) {
2089                         *pprev = rb_entry(rb_node, struct vm_area_struct, vm_rb);
2090                         rb_node = rb_node->rb_right;
2091                 }
2092         }
2093         return vma;
2094 }
2095 
2096 /*
2097  * Verify that the stack growth is acceptable and
2098  * update accounting. This is shared with both the
2099  * grow-up and grow-down cases.
2100  */
2101 static int acct_stack_growth(struct vm_area_struct *vma, unsigned long size, unsigned long grow)
2102 {
2103         struct mm_struct *mm = vma->vm_mm;
2104         struct rlimit *rlim = current->signal->rlim;
2105         unsigned long new_start, actual_size;
2106 
2107         /* address space limit tests */
2108         if (!may_expand_vm(mm, grow))
2109                 return -ENOMEM;
2110 
2111         /* Stack limit test */
2112         actual_size = size;
2113         if (size && (vma->vm_flags & (VM_GROWSUP | VM_GROWSDOWN)))
2114                 actual_size -= PAGE_SIZE;
2115         if (actual_size > READ_ONCE(rlim[RLIMIT_STACK].rlim_cur))
2116                 return -ENOMEM;
2117 
2118         /* mlock limit tests */
2119         if (vma->vm_flags & VM_LOCKED) {
2120                 unsigned long locked;
2121                 unsigned long limit;
2122                 locked = mm->locked_vm + grow;
2123                 limit = READ_ONCE(rlim[RLIMIT_MEMLOCK].rlim_cur);
2124                 limit >>= PAGE_SHIFT;
2125                 if (locked > limit && !capable(CAP_IPC_LOCK))
2126                         return -ENOMEM;
2127         }
2128 
2129         /* Check to ensure the stack will not grow into a hugetlb-only region */
2130         new_start = (vma->vm_flags & VM_GROWSUP) ? vma->vm_start :
2131                         vma->vm_end - size;
2132         if (is_hugepage_only_range(vma->vm_mm, new_start, size))
2133                 return -EFAULT;
2134 
2135         /*
2136          * Overcommit..  This must be the final test, as it will
2137          * update security statistics.
2138          */
2139         if (security_vm_enough_memory_mm(mm, grow))
2140                 return -ENOMEM;
2141 
2142         /* Ok, everything looks good - let it rip */
2143         if (vma->vm_flags & VM_LOCKED)
2144                 mm->locked_vm += grow;
2145         vm_stat_account(mm, vma->vm_flags, vma->vm_file, grow);
2146         return 0;
2147 }
2148 
2149 #if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
2150 /*
2151  * PA-RISC uses this for its stack; IA64 for its Register Backing Store.
2152  * vma is the last one with address > vma->vm_end.  Have to extend vma.
2153  */
2154 int expand_upwards(struct vm_area_struct *vma, unsigned long address)
2155 {
2156         int error;
2157 
2158         if (!(vma->vm_flags & VM_GROWSUP))
2159                 return -EFAULT;
2160 
2161         /*
2162          * We must make sure the anon_vma is allocated
2163          * so that the anon_vma locking is not a noop.
2164          */
2165         if (unlikely(anon_vma_prepare(vma)))
2166                 return -ENOMEM;
2167         vma_lock_anon_vma(vma);
2168 
2169         /*
2170          * vma->vm_start/vm_end cannot change under us because the caller
2171          * is required to hold the mmap_sem in read mode.  We need the
2172          * anon_vma lock to serialize against concurrent expand_stacks.
2173          * Also guard against wrapping around to address 0.
2174          */
2175         if (address < PAGE_ALIGN(address+4))
2176                 address = PAGE_ALIGN(address+4);
2177         else {
2178                 vma_unlock_anon_vma(vma);
2179                 return -ENOMEM;
2180         }
2181         error = 0;
2182 
2183         /* Somebody else might have raced and expanded it already */
2184         if (address > vma->vm_end) {
2185                 unsigned long size, grow;
2186 
2187                 size = address - vma->vm_start;
2188                 grow = (address - vma->vm_end) >> PAGE_SHIFT;
2189 
2190                 error = -ENOMEM;
2191                 if (vma->vm_pgoff + (size >> PAGE_SHIFT) >= vma->vm_pgoff) {
2192                         error = acct_stack_growth(vma, size, grow);
2193                         if (!error) {
2194                                 /*
2195                                  * vma_gap_update() doesn't support concurrent
2196                                  * updates, but we only hold a shared mmap_sem
2197                                  * lock here, so we need to protect against
2198                                  * concurrent vma expansions.
2199                                  * vma_lock_anon_vma() doesn't help here, as
2200                                  * we don't guarantee that all growable vmas
2201                                  * in a mm share the same root anon vma.
2202                                  * So, we reuse mm->page_table_lock to guard
2203                                  * against concurrent vma expansions.
2204                                  */
2205                                 spin_lock(&vma->vm_mm->page_table_lock);
2206                                 anon_vma_interval_tree_pre_update_vma(vma);
2207                                 vma->vm_end = address;
2208                                 anon_vma_interval_tree_post_update_vma(vma);
2209                                 if (vma->vm_next)
2210                                         vma_gap_update(vma->vm_next);
2211                                 else
2212                                         vma->vm_mm->highest_vm_end = address;
2213                                 spin_unlock(&vma->vm_mm->page_table_lock);
2214 
2215                                 perf_event_mmap(vma);
2216                         }
2217                 }
2218         }
2219         vma_unlock_anon_vma(vma);
2220         khugepaged_enter_vma_merge(vma, vma->vm_flags);
2221         validate_mm(vma->vm_mm);
2222         return error;
2223 }
2224 #endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
2225 
2226 /*
2227  * vma is the first one with address < vma->vm_start.  Have to extend vma.
2228  */
2229 int expand_downwards(struct vm_area_struct *vma,
2230                                    unsigned long address)
2231 {
2232         int error;
2233 
2234         /*
2235          * We must make sure the anon_vma is allocated
2236          * so that the anon_vma locking is not a noop.
2237          */
2238         if (unlikely(anon_vma_prepare(vma)))
2239                 return -ENOMEM;
2240 
2241         address &= PAGE_MASK;
2242         error = security_mmap_addr(address);
2243         if (error)
2244                 return error;
2245 
2246         vma_lock_anon_vma(vma);
2247 
2248         /*
2249          * vma->vm_start/vm_end cannot change under us because the caller
2250          * is required to hold the mmap_sem in read mode.  We need the
2251          * anon_vma lock to serialize against concurrent expand_stacks.
2252          */
2253 
2254         /* Somebody else might have raced and expanded it already */
2255         if (address < vma->vm_start) {
2256                 unsigned long size, grow;
2257 
2258                 size = vma->vm_end - address;
2259                 grow = (vma->vm_start - address) >> PAGE_SHIFT;
2260 
2261                 error = -ENOMEM;
2262                 if (grow <= vma->vm_pgoff) {
2263                         error = acct_stack_growth(vma, size, grow);
2264                         if (!error) {
2265                                 /*
2266                                  * vma_gap_update() doesn't support concurrent
2267                                  * updates, but we only hold a shared mmap_sem
2268                                  * lock here, so we need to protect against
2269                                  * concurrent vma expansions.
2270                                  * vma_lock_anon_vma() doesn't help here, as
2271                                  * we don't guarantee that all growable vmas
2272                                  * in a mm share the same root anon vma.
2273                                  * So, we reuse mm->page_table_lock to guard
2274                                  * against concurrent vma expansions.
2275                                  */
2276                                 spin_lock(&vma->vm_mm->page_table_lock);
2277                                 anon_vma_interval_tree_pre_update_vma(vma);
2278                                 vma->vm_start = address;
2279                                 vma->vm_pgoff -= grow;
2280                                 anon_vma_interval_tree_post_update_vma(vma);
2281                                 vma_gap_update(vma);
2282                                 spin_unlock(&vma->vm_mm->page_table_lock);
2283 
2284                                 perf_event_mmap(vma);
2285                         }
2286                 }
2287         }
2288         vma_unlock_anon_vma(vma);
2289         khugepaged_enter_vma_merge(vma, vma->vm_flags);
2290         validate_mm(vma->vm_mm);
2291         return error;
2292 }
2293 
2294 /*
2295  * Note how expand_stack() refuses to expand the stack all the way to
2296  * abut the next virtual mapping, *unless* that mapping itself is also
2297  * a stack mapping. We want to leave room for a guard page, after all
2298  * (the guard page itself is not added here, that is done by the
2299  * actual page faulting logic)
2300  *
2301  * This matches the behavior of the guard page logic (see mm/memory.c:
2302  * check_stack_guard_page()), which only allows the guard page to be
2303  * removed under these circumstances.
2304  */
2305 #ifdef CONFIG_STACK_GROWSUP
2306 int expand_stack(struct vm_area_struct *vma, unsigned long address)
2307 {
2308         struct vm_area_struct *next;
2309 
2310         address &= PAGE_MASK;
2311         next = vma->vm_next;
2312         if (next && next->vm_start == address + PAGE_SIZE) {
2313                 if (!(next->vm_flags & VM_GROWSUP))
2314                         return -ENOMEM;
2315         }
2316         return expand_upwards(vma, address);
2317 }
2318 
2319 struct vm_area_struct *
2320 find_extend_vma(struct mm_struct *mm, unsigned long addr)
2321 {
2322         struct vm_area_struct *vma, *prev;
2323 
2324         addr &= PAGE_MASK;
2325         vma = find_vma_prev(mm, addr, &prev);
2326         if (vma && (vma->vm_start <= addr))
2327                 return vma;
2328         if (!prev || expand_stack(prev, addr))
2329                 return NULL;
2330         if (prev->vm_flags & VM_LOCKED)
2331                 populate_vma_page_range(prev, addr, prev->vm_end, NULL);
2332         return prev;
2333 }
2334 #else
2335 int expand_stack(struct vm_area_struct *vma, unsigned long address)
2336 {
2337         struct vm_area_struct *prev;
2338 
2339         address &= PAGE_MASK;
2340         prev = vma->vm_prev;
2341         if (prev && prev->vm_end == address) {
2342                 if (!(prev->vm_flags & VM_GROWSDOWN))
2343                         return -ENOMEM;
2344         }
2345         return expand_downwards(vma, address);
2346 }
2347 
2348 struct vm_area_struct *
2349 find_extend_vma(struct mm_struct *mm, unsigned long addr)
2350 {
2351         struct vm_area_struct *vma;
2352         unsigned long start;
2353 
2354         addr &= PAGE_MASK;
2355         vma = find_vma(mm, addr);
2356         if (!vma)
2357                 return NULL;
2358         if (vma->vm_start <= addr)
2359                 return vma;
2360         if (!(vma->vm_flags & VM_GROWSDOWN))
2361                 return NULL;
2362         start = vma->vm_start;
2363         if (expand_stack(vma, addr))
2364                 return NULL;
2365         if (vma->vm_flags & VM_LOCKED)
2366                 populate_vma_page_range(vma, addr, start, NULL);
2367         return vma;
2368 }
2369 #endif
2370 
2371 EXPORT_SYMBOL_GPL(find_extend_vma);
2372 
2373 /*
2374  * Ok - we have the memory areas we should free on the vma list,
2375  * so release them, and do the vma updates.
2376  *
2377  * Called with the mm semaphore held.
2378  */
2379 static void remove_vma_list(struct mm_struct *mm, struct vm_area_struct *vma)
2380 {
2381         unsigned long nr_accounted = 0;
2382 
2383         /* Update high watermark before we lower total_vm */
2384         update_hiwater_vm(mm);
2385         do {
2386                 long nrpages = vma_pages(vma);
2387 
2388                 if (vma->vm_flags & VM_ACCOUNT)
2389                         nr_accounted += nrpages;
2390                 vm_stat_account(mm, vma->vm_flags, vma->vm_file, -nrpages);
2391                 vma = remove_vma(vma);
2392         } while (vma);
2393         vm_unacct_memory(nr_accounted);
2394         validate_mm(mm);
2395 }
2396 
2397 /*
2398  * Get rid of page table information in the indicated region.
2399  *
2400  * Called with the mm semaphore held.
2401  */
2402 static void unmap_region(struct mm_struct *mm,
2403                 struct vm_area_struct *vma, struct vm_area_struct *prev,
2404                 unsigned long start, unsigned long end)
2405 {
2406         struct vm_area_struct *next = prev ? prev->vm_next : mm->mmap;
2407         struct mmu_gather tlb;
2408 
2409         lru_add_drain();
2410         tlb_gather_mmu(&tlb, mm, start, end);
2411         update_hiwater_rss(mm);
2412         unmap_vmas(&tlb, vma, start, end);
2413         free_pgtables(&tlb, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
2414                                  next ? next->vm_start : USER_PGTABLES_CEILING);
2415         tlb_finish_mmu(&tlb, start, end);
2416 }
2417 
2418 /*
2419  * Create a list of vma's touched by the unmap, removing them from the mm's
2420  * vma list as we go..
2421  */
2422 static void
2423 detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
2424         struct vm_area_struct *prev, unsigned long end)
2425 {
2426         struct vm_area_struct **insertion_point;
2427         struct vm_area_struct *tail_vma = NULL;
2428 
2429         insertion_point = (prev ? &prev->vm_next : &mm->mmap);
2430         vma->vm_prev = NULL;
2431         do {
2432                 vma_rb_erase(vma, &mm->mm_rb);
2433                 mm->map_count--;
2434                 tail_vma = vma;
2435                 vma = vma->vm_next;
2436         } while (vma && vma->vm_start < end);
2437         *insertion_point = vma;
2438         if (vma) {
2439                 vma->vm_prev = prev;
2440                 vma_gap_update(vma);
2441         } else
2442                 mm->highest_vm_end = prev ? prev->vm_end : 0;
2443         tail_vma->vm_next = NULL;
2444 
2445         /* Kill the cache */
2446         vmacache_invalidate(mm);
2447 }
2448 
2449 /*
2450  * __split_vma() bypasses sysctl_max_map_count checking.  We use this on the
2451  * munmap path where it doesn't make sense to fail.
2452  */
2453 static int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
2454               unsigned long addr, int new_below)
2455 {
2456         struct vm_area_struct *new;
2457         int err;
2458 
2459         if (is_vm_hugetlb_page(vma) && (addr &
2460                                         ~(huge_page_mask(hstate_vma(vma)))))
2461                 return -EINVAL;
2462 
2463         new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
2464         if (!new)
2465                 return -ENOMEM;
2466 
2467         /* most fields are the same, copy all, and then fixup */
2468         *new = *vma;
2469 
2470         INIT_LIST_HEAD(&new->anon_vma_chain);
2471 
2472         if (new_below)
2473                 new->vm_end = addr;
2474         else {
2475                 new->vm_start = addr;
2476                 new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
2477         }
2478 
2479         err = vma_dup_policy(vma, new);
2480         if (err)
2481                 goto out_free_vma;
2482 
2483         err = anon_vma_clone(new, vma);
2484         if (err)
2485                 goto out_free_mpol;
2486 
2487         if (new->vm_file)
2488                 get_file(new->vm_file);
2489 
2490         if (new->vm_ops && new->vm_ops->open)
2491                 new->vm_ops->open(new);
2492 
2493         if (new_below)
2494                 err = vma_adjust(vma, addr, vma->vm_end, vma->vm_pgoff +
2495                         ((addr - new->vm_start) >> PAGE_SHIFT), new);
2496         else
2497                 err = vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new);
2498 
2499         /* Success. */
2500         if (!err)
2501                 return 0;
2502 
2503         /* Clean everything up if vma_adjust failed. */
2504         if (new->vm_ops && new->vm_ops->close)
2505                 new->vm_ops->close(new);
2506         if (new->vm_file)
2507                 fput(new->vm_file);
2508         unlink_anon_vmas(new);
2509  out_free_mpol:
2510         mpol_put(vma_policy(new));
2511  out_free_vma:
2512         kmem_cache_free(vm_area_cachep, new);
2513         return err;
2514 }
2515 
2516 /*
2517  * Split a vma into two pieces at address 'addr', a new vma is allocated
2518  * either for the first part or the tail.
2519  */
2520 int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
2521               unsigned long addr, int new_below)
2522 {
2523         if (mm->map_count >= sysctl_max_map_count)
2524                 return -ENOMEM;
2525 
2526         return __split_vma(mm, vma, addr, new_below);
2527 }
2528 
2529 /* Munmap is split into 2 main parts -- this part which finds
2530  * what needs doing, and the areas themselves, which do the
2531  * work.  This now handles partial unmappings.
2532  * Jeremy Fitzhardinge <jeremy@goop.org>
2533  */
2534 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
2535 {
2536         unsigned long end;
2537         struct vm_area_struct *vma, *prev, *last;
2538 
2539         if ((start & ~PAGE_MASK) || start > TASK_SIZE || len > TASK_SIZE-start)
2540                 return -EINVAL;
2541 
2542         len = PAGE_ALIGN(len);
2543         if (len == 0)
2544                 return -EINVAL;
2545 
2546         /* Find the first overlapping VMA */
2547         vma = find_vma(mm, start);
2548         if (!vma)
2549                 return 0;
2550         prev = vma->vm_prev;
2551         /* we have  start < vma->vm_end  */
2552 
2553         /* if it doesn't overlap, we have nothing.. */
2554         end = start + len;
2555         if (vma->vm_start >= end)
2556                 return 0;
2557 
2558         /*
2559          * If we need to split any vma, do it now to save pain later.
2560          *
2561          * Note: mremap's move_vma VM_ACCOUNT handling assumes a partially
2562          * unmapped vm_area_struct will remain in use: so lower split_vma
2563          * places tmp vma above, and higher split_vma places tmp vma below.
2564          */
2565         if (start > vma->vm_start) {
2566                 int error;
2567 
2568                 /*
2569                  * Make sure that map_count on return from munmap() will
2570                  * not exceed its limit; but let map_count go just above
2571                  * its limit temporarily, to help free resources as expected.
2572                  */
2573                 if (end < vma->vm_end && mm->map_count >= sysctl_max_map_count)
2574                         return -ENOMEM;
2575 
2576                 error = __split_vma(mm, vma, start, 0);
2577                 if (error)
2578                         return error;
2579                 prev = vma;
2580         }
2581 
2582         /* Does it split the last one? */
2583         last = find_vma(mm, end);
2584         if (last && end > last->vm_start) {
2585                 int error = __split_vma(mm, last, end, 1);
2586                 if (error)
2587                         return error;
2588         }
2589         vma = prev ? prev->vm_next : mm->mmap;
2590 
2591         /*
2592          * unlock any mlock()ed ranges before detaching vmas
2593          */
2594         if (mm->locked_vm) {
2595                 struct vm_area_struct *tmp = vma;
2596                 while (tmp && tmp->vm_start < end) {
2597                         if (tmp->vm_flags & VM_LOCKED) {
2598                                 mm->locked_vm -= vma_pages(tmp);
2599                                 munlock_vma_pages_all(tmp);
2600                         }
2601                         tmp = tmp->vm_next;
2602                 }
2603         }
2604 
2605         /*
2606          * Remove the vma's, and unmap the actual pages
2607          */
2608         detach_vmas_to_be_unmapped(mm, vma, prev, end);
2609         unmap_region(mm, vma, prev, start, end);
2610 
2611         arch_unmap(mm, vma, start, end);
2612 
2613         /* Fix up all other VM information */
2614         remove_vma_list(mm, vma);
2615 
2616         return 0;
2617 }
2618 
2619 int vm_munmap(unsigned long start, size_t len)
2620 {
2621         int ret;
2622         struct mm_struct *mm = current->mm;
2623 
2624         down_write(&mm->mmap_sem);
2625         ret = do_munmap(mm, start, len);
2626         up_write(&mm->mmap_sem);
2627         return ret;
2628 }
2629 EXPORT_SYMBOL(vm_munmap);
2630 
2631 SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
2632 {
2633         profile_munmap(addr);
2634         return vm_munmap(addr, len);
2635 }
2636 
2637 
2638 /*
2639  * Emulation of deprecated remap_file_pages() syscall.
2640  */
2641 SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
2642                 unsigned long, prot, unsigned long, pgoff, unsigned long, flags)
2643 {
2644 
2645         struct mm_struct *mm = current->mm;
2646         struct vm_area_struct *vma;
2647         unsigned long populate = 0;
2648         unsigned long ret = -EINVAL;
2649         struct file *file;
2650 
2651         pr_warn_once("%s (%d) uses deprecated remap_file_pages() syscall. "
2652                         "See Documentation/vm/remap_file_pages.txt.\n",
2653                         current->comm, current->pid);
2654 
2655         if (prot)
2656                 return ret;
2657         start = start & PAGE_MASK;
2658         size = size & PAGE_MASK;
2659 
2660         if (start + size <= start)
2661                 return ret;
2662 
2663         /* Does pgoff wrap? */
2664         if (pgoff + (size >> PAGE_SHIFT) < pgoff)
2665                 return ret;
2666 
2667         down_write(&mm->mmap_sem);
2668         vma = find_vma(mm, start);
2669 
2670         if (!vma || !(vma->vm_flags & VM_SHARED))
2671                 goto out;
2672 
2673         if (start < vma->vm_start || start + size > vma->vm_end)
2674                 goto out;
2675 
2676         if (pgoff == linear_page_index(vma, start)) {
2677                 ret = 0;
2678                 goto out;
2679         }
2680 
2681         prot |= vma->vm_flags & VM_READ ? PROT_READ : 0;
2682         prot |= vma->vm_flags & VM_WRITE ? PROT_WRITE : 0;
2683         prot |= vma->vm_flags & VM_EXEC ? PROT_EXEC : 0;
2684 
2685         flags &= MAP_NONBLOCK;
2686         flags |= MAP_SHARED | MAP_FIXED | MAP_POPULATE;
2687         if (vma->vm_flags & VM_LOCKED) {
2688                 flags |= MAP_LOCKED;
2689                 /* drop PG_Mlocked flag for over-mapped range */
2690                 munlock_vma_pages_range(vma, start, start + size);
2691         }
2692 
2693         file = get_file(vma->vm_file);
2694         ret = do_mmap_pgoff(vma->vm_file, start, size,
2695                         prot, flags, pgoff, &populate);
2696         fput(file);
2697 out:
2698         up_write(&mm->mmap_sem);
2699         if (populate)
2700                 mm_populate(ret, populate);
2701         if (!IS_ERR_VALUE(ret))
2702                 ret = 0;
2703         return ret;
2704 }
2705 
2706 static inline void verify_mm_writelocked(struct mm_struct *mm)
2707 {
2708 #ifdef CONFIG_DEBUG_VM
2709         if (unlikely(down_read_trylock(&mm->mmap_sem))) {
2710                 WARN_ON(1);
2711                 up_read(&mm->mmap_sem);
2712         }
2713 #endif
2714 }
2715 
2716 /*
2717  *  this is really a simplified "do_mmap".  it only handles
2718  *  anonymous maps.  eventually we may be able to do some
2719  *  brk-specific accounting here.
2720  */
2721 static unsigned long do_brk(unsigned long addr, unsigned long len)
2722 {
2723         struct mm_struct *mm = current->mm;
2724         struct vm_area_struct *vma, *prev;
2725         unsigned long flags;
2726         struct rb_node **rb_link, *rb_parent;
2727         pgoff_t pgoff = addr >> PAGE_SHIFT;
2728         int error;
2729 
2730         len = PAGE_ALIGN(len);
2731         if (!len)
2732                 return addr;
2733 
2734         flags = VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
2735 
2736         error = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
2737         if (error & ~PAGE_MASK)
2738                 return error;
2739 
2740         error = mlock_future_check(mm, mm->def_flags, len);
2741         if (error)
2742                 return error;
2743 
2744         /*
2745          * mm->mmap_sem is required to protect against another thread
2746          * changing the mappings in case we sleep.
2747          */
2748         verify_mm_writelocked(mm);
2749 
2750         /*
2751          * Clear old maps.  this also does some error checking for us
2752          */
2753         while (find_vma_links(mm, addr, addr + len, &prev, &rb_link,
2754                               &rb_parent)) {
2755                 if (do_munmap(mm, addr, len))
2756                         return -ENOMEM;
2757         }
2758 
2759         /* Check against address space limits *after* clearing old maps... */
2760         if (!may_expand_vm(mm, len >> PAGE_SHIFT))
2761                 return -ENOMEM;
2762 
2763         if (mm->map_count > sysctl_max_map_count)
2764                 return -ENOMEM;
2765 
2766         if (security_vm_enough_memory_mm(mm, len >> PAGE_SHIFT))
2767                 return -ENOMEM;
2768 
2769         /* Can we just expand an old private anonymous mapping? */
2770         vma = vma_merge(mm, prev, addr, addr + len, flags,
2771                         NULL, NULL, pgoff, NULL, NULL_VM_UFFD_CTX);
2772         if (vma)
2773                 goto out;
2774 
2775         /*
2776          * create a vma struct for an anonymous mapping
2777          */
2778         vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
2779         if (!vma) {
2780                 vm_unacct_memory(len >> PAGE_SHIFT);
2781                 return -ENOMEM;
2782         }
2783 
2784         INIT_LIST_HEAD(&vma->anon_vma_chain);
2785         vma->vm_mm = mm;
2786         vma->vm_start = addr;
2787         vma->vm_end = addr + len;
2788         vma->vm_pgoff = pgoff;
2789         vma->vm_flags = flags;
2790         vma->vm_page_prot = vm_get_page_prot(flags);
2791         vma_link(mm, vma, prev, rb_link, rb_parent);
2792 out:
2793         perf_event_mmap(vma);
2794         mm->total_vm += len >> PAGE_SHIFT;
2795         if (flags & VM_LOCKED)
2796                 mm->locked_vm += (len >> PAGE_SHIFT);
2797         vma->vm_flags |= VM_SOFTDIRTY;
2798         return addr;
2799 }
2800 
2801 unsigned long vm_brk(unsigned long addr, unsigned long len)
2802 {
2803         struct mm_struct *mm = current->mm;
2804         unsigned long ret;
2805         bool populate;
2806 
2807         down_write(&mm->mmap_sem);
2808         ret = do_brk(addr, len);
2809         populate = ((mm->def_flags & VM_LOCKED) != 0);
2810         up_write(&mm->mmap_sem);
2811         if (populate)
2812                 mm_populate(addr, len);
2813         return ret;
2814 }
2815 EXPORT_SYMBOL(vm_brk);
2816 
2817 /* Release all mmaps. */
2818 void exit_mmap(struct mm_struct *mm)
2819 {
2820         struct mmu_gather tlb;
2821         struct vm_area_struct *vma;
2822         unsigned long nr_accounted = 0;
2823 
2824         /* mm's last user has gone, and its about to be pulled down */
2825         mmu_notifier_release(mm);
2826 
2827         if (mm->locked_vm) {
2828                 vma = mm->mmap;
2829                 while (vma) {
2830                         if (vma->vm_flags & VM_LOCKED)
2831                                 munlock_vma_pages_all(vma);
2832                         vma = vma->vm_next;
2833                 }
2834         }
2835 
2836         arch_exit_mmap(mm);
2837 
2838         vma = mm->mmap;
2839         if (!vma)       /* Can happen if dup_mmap() received an OOM */
2840                 return;
2841 
2842         lru_add_drain();
2843         flush_cache_mm(mm);
2844         tlb_gather_mmu(&tlb, mm, 0, -1);
2845         /* update_hiwater_rss(mm) here? but nobody should be looking */
2846         /* Use -1 here to ensure all VMAs in the mm are unmapped */
2847         unmap_vmas(&tlb, vma, 0, -1);
2848 
2849         free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, USER_PGTABLES_CEILING);
2850         tlb_finish_mmu(&tlb, 0, -1);
2851 
2852         /*
2853          * Walk the list again, actually closing and freeing it,
2854          * with preemption enabled, without holding any MM locks.
2855          */
2856         while (vma) {
2857                 if (vma->vm_flags & VM_ACCOUNT)
2858                         nr_accounted += vma_pages(vma);
2859                 vma = remove_vma(vma);
2860         }
2861         vm_unacct_memory(nr_accounted);
2862 }
2863 
2864 /* Insert vm structure into process list sorted by address
2865  * and into the inode's i_mmap tree.  If vm_file is non-NULL
2866  * then i_mmap_rwsem is taken here.
2867  */
2868 int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
2869 {
2870         struct vm_area_struct *prev;
2871         struct rb_node **rb_link, *rb_parent;
2872 
2873         if (find_vma_links(mm, vma->vm_start, vma->vm_end,
2874                            &prev, &rb_link, &rb_parent))
2875                 return -ENOMEM;
2876         if ((vma->vm_flags & VM_ACCOUNT) &&
2877              security_vm_enough_memory_mm(mm, vma_pages(vma)))
2878                 return -ENOMEM;
2879 
2880         /*
2881          * The vm_pgoff of a purely anonymous vma should be irrelevant
2882          * until its first write fault, when page's anon_vma and index
2883          * are set.  But now set the vm_pgoff it will almost certainly
2884          * end up with (unless mremap moves it elsewhere before that
2885          * first wfault), so /proc/pid/maps tells a consistent story.
2886          *
2887          * By setting it to reflect the virtual start address of the
2888          * vma, merges and splits can happen in a seamless way, just
2889          * using the existing file pgoff checks and manipulations.
2890          * Similarly in do_mmap_pgoff and in do_brk.
2891          */
2892         if (vma_is_anonymous(vma)) {
2893                 BUG_ON(vma->anon_vma);
2894                 vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;
2895         }
2896 
2897         vma_link(mm, vma, prev, rb_link, rb_parent);
2898         return 0;
2899 }
2900 
2901 /*
2902  * Copy the vma structure to a new location in the same mm,
2903  * prior to moving page table entries, to effect an mremap move.
2904  */
2905 struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
2906         unsigned long addr, unsigned long len, pgoff_t pgoff,
2907         bool *need_rmap_locks)
2908 {
2909         struct vm_area_struct *vma = *vmap;
2910         unsigned long vma_start = vma->vm_start;
2911         struct mm_struct *mm = vma->vm_mm;
2912         struct vm_area_struct *new_vma, *prev;
2913         struct rb_node **rb_link, *rb_parent;
2914         bool faulted_in_anon_vma = true;
2915 
2916         /*
2917          * If anonymous vma has not yet been faulted, update new pgoff
2918          * to match new location, to increase its chance of merging.
2919          */
2920         if (unlikely(vma_is_anonymous(vma) && !vma->anon_vma)) {
2921                 pgoff = addr >> PAGE_SHIFT;
2922                 faulted_in_anon_vma = false;
2923         }
2924 
2925         if (find_vma_links(mm, addr, addr + len, &prev, &rb_link, &rb_parent))
2926                 return NULL;    /* should never get here */
2927         new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags,
2928                             vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
2929                             vma->vm_userfaultfd_ctx);
2930         if (new_vma) {
2931                 /*
2932                  * Source vma may have been merged into new_vma
2933                  */
2934                 if (unlikely(vma_start >= new_vma->vm_start &&
2935                              vma_start < new_vma->vm_end)) {
2936                         /*
2937                          * The only way we can get a vma_merge with
2938                          * self during an mremap is if the vma hasn't
2939                          * been faulted in yet and we were allowed to
2940                          * reset the dst vma->vm_pgoff to the
2941                          * destination address of the mremap to allow
2942                          * the merge to happen. mremap must change the
2943                          * vm_pgoff linearity between src and dst vmas
2944                          * (in turn preventing a vma_merge) to be
2945                          * safe. It is only safe to keep the vm_pgoff
2946                          * linear if there are no pages mapped yet.
2947                          */
2948                         VM_BUG_ON_VMA(faulted_in_anon_vma, new_vma);
2949                         *vmap = vma = new_vma;
2950                 }
2951                 *need_rmap_locks = (new_vma->vm_pgoff <= vma->vm_pgoff);
2952         } else {
2953                 new_vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
2954                 if (!new_vma)
2955                         goto out;
2956                 *new_vma = *vma;
2957                 new_vma->vm_start = addr;
2958                 new_vma->vm_end = addr + len;
2959                 new_vma->vm_pgoff = pgoff;
2960                 if (vma_dup_policy(vma, new_vma))
2961                         goto out_free_vma;
2962                 INIT_LIST_HEAD(&new_vma->anon_vma_chain);
2963                 if (anon_vma_clone(new_vma, vma))
2964                         goto out_free_mempol;
2965                 if (new_vma->vm_file)
2966                         get_file(new_vma->vm_file);
2967                 if (new_vma->vm_ops && new_vma->vm_ops->open)
2968                         new_vma->vm_ops->open(new_vma);
2969                 vma_link(mm, new_vma, prev, rb_link, rb_parent);
2970                 *need_rmap_locks = false;
2971         }
2972         return new_vma;
2973 
2974 out_free_mempol:
2975         mpol_put(vma_policy(new_vma));
2976 out_free_vma:
2977         kmem_cache_free(vm_area_cachep, new_vma);
2978 out:
2979         return NULL;
2980 }
2981 
2982 /*
2983  * Return true if the calling process may expand its vm space by the passed
2984  * number of pages
2985  */
2986 int may_expand_vm(struct mm_struct *mm, unsigned long npages)
2987 {
2988         unsigned long cur = mm->total_vm;       /* pages */
2989         unsigned long lim;
2990 
2991         lim = rlimit(RLIMIT_AS) >> PAGE_SHIFT;
2992 
2993         if (cur + npages > lim)
2994                 return 0;
2995         return 1;
2996 }
2997 
2998 static int special_mapping_fault(struct vm_area_struct *vma,
2999                                  struct vm_fault *vmf);
3000 
3001 /*
3002  * Having a close hook prevents vma merging regardless of flags.
3003  */
3004 static void special_mapping_close(struct vm_area_struct *vma)
3005 {
3006 }
3007 
3008 static const char *special_mapping_name(struct vm_area_struct *vma)
3009 {
3010         return ((struct vm_special_mapping *)vma->vm_private_data)->name;
3011 }
3012 
3013 static const struct vm_operations_struct special_mapping_vmops = {
3014         .close = special_mapping_close,
3015         .fault = special_mapping_fault,
3016         .name = special_mapping_name,
3017 };
3018 
3019 static const struct vm_operations_struct legacy_special_mapping_vmops = {
3020         .close = special_mapping_close,
3021         .fault = special_mapping_fault,
3022 };
3023 
3024 static int special_mapping_fault(struct vm_area_struct *vma,
3025                                 struct vm_fault *vmf)
3026 {
3027         pgoff_t pgoff;
3028         struct page **pages;
3029 
3030         if (vma->vm_ops == &legacy_special_mapping_vmops)
3031                 pages = vma->vm_private_data;
3032         else
3033                 pages = ((struct vm_special_mapping *)vma->vm_private_data)->
3034                         pages;
3035 
3036         for (pgoff = vmf->pgoff; pgoff && *pages; ++pages)
3037                 pgoff--;
3038 
3039         if (*pages) {
3040                 struct page *page = *pages;
3041                 get_page(page);
3042                 vmf->page = page;
3043                 return 0;
3044         }
3045 
3046         return VM_FAULT_SIGBUS;
3047 }
3048 
3049 static struct vm_area_struct *__install_special_mapping(
3050         struct mm_struct *mm,
3051         unsigned long addr, unsigned long len,
3052         unsigned long vm_flags, const struct vm_operations_struct *ops,
3053         void *priv)
3054 {
3055         int ret;
3056         struct vm_area_struct *vma;
3057 
3058         vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
3059         if (unlikely(vma == NULL))
3060                 return ERR_PTR(-ENOMEM);
3061 
3062         INIT_LIST_HEAD(&vma->anon_vma_chain);
3063         vma->vm_mm = mm;
3064         vma->vm_start = addr;
3065         vma->vm_end = addr + len;
3066 
3067         vma->vm_flags = vm_flags | mm->def_flags | VM_DONTEXPAND | VM_SOFTDIRTY;
3068         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
3069 
3070         vma->vm_ops = ops;
3071         vma->vm_private_data = priv;
3072 
3073         ret = insert_vm_struct(mm, vma);
3074         if (ret)
3075                 goto out;
3076 
3077         mm->total_vm += len >> PAGE_SHIFT;
3078 
3079         perf_event_mmap(vma);
3080 
3081         return vma;
3082 
3083 out:
3084         kmem_cache_free(vm_area_cachep, vma);
3085         return ERR_PTR(ret);
3086 }
3087 
3088 /*
3089  * Called with mm->mmap_sem held for writing.
3090  * Insert a new vma covering the given region, with the given flags.
3091  * Its pages are supplied by the given array of struct page *.
3092  * The array can be shorter than len >> PAGE_SHIFT if it's null-terminated.
3093  * The region past the last page supplied will always produce SIGBUS.
3094  * The array pointer and the pages it points to are assumed to stay alive
3095  * for as long as this mapping might exist.
3096  */
3097 struct vm_area_struct *_install_special_mapping(
3098         struct mm_struct *mm,
3099         unsigned long addr, unsigned long len,
3100         unsigned long vm_flags, const struct vm_special_mapping *spec)
3101 {
3102         return __install_special_mapping(mm, addr, len, vm_flags,
3103                                          &special_mapping_vmops, (void *)spec);
3104 }
3105 
3106 int install_special_mapping(struct mm_struct *mm,
3107                             unsigned long addr, unsigned long len,
3108                             unsigned long vm_flags, struct page **pages)
3109 {
3110         struct vm_area_struct *vma = __install_special_mapping(
3111                 mm, addr, len, vm_flags, &legacy_special_mapping_vmops,
3112                 (void *)pages);
3113 
3114         return PTR_ERR_OR_ZERO(vma);
3115 }
3116 
3117 static DEFINE_MUTEX(mm_all_locks_mutex);
3118 
3119 static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma)
3120 {
3121         if (!test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_node)) {
3122                 /*
3123                  * The LSB of head.next can't change from under us
3124                  * because we hold the mm_all_locks_mutex.
3125                  */
3126                 down_write_nest_lock(&anon_vma->root->rwsem, &mm->mmap_sem);
3127                 /*
3128                  * We can safely modify head.next after taking the
3129                  * anon_vma->root->rwsem. If some other vma in this mm shares
3130                  * the same anon_vma we won't take it again.
3131                  *
3132                  * No need of atomic instructions here, head.next
3133                  * can't change from under us thanks to the
3134                  * anon_vma->root->rwsem.
3135                  */
3136                 if (__test_and_set_bit(0, (unsigned long *)
3137                                        &anon_vma->root->rb_root.rb_node))
3138                         BUG();
3139         }
3140 }
3141 
3142 static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping)
3143 {
3144         if (!test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
3145                 /*
3146                  * AS_MM_ALL_LOCKS can't change from under us because
3147                  * we hold the mm_all_locks_mutex.
3148                  *
3149                  * Operations on ->flags have to be atomic because
3150                  * even if AS_MM_ALL_LOCKS is stable thanks to the
3151                  * mm_all_locks_mutex, there may be other cpus
3152                  * changing other bitflags in parallel to us.
3153                  */
3154                 if (test_and_set_bit(AS_MM_ALL_LOCKS, &mapping->flags))
3155                         BUG();
3156                 down_write_nest_lock(&mapping->i_mmap_rwsem, &mm->mmap_sem);
3157         }
3158 }
3159 
3160 /*
3161  * This operation locks against the VM for all pte/vma/mm related
3162  * operations that could ever happen on a certain mm. This includes
3163  * vmtruncate, try_to_unmap, and all page faults.
3164  *
3165  * The caller must take the mmap_sem in write mode before calling
3166  * mm_take_all_locks(). The caller isn't allowed to release the
3167  * mmap_sem until mm_drop_all_locks() returns.
3168  *
3169  * mmap_sem in write mode is required in order to block all operations
3170  * that could modify pagetables and free pages without need of
3171  * altering the vma layout. It's also needed in write mode to avoid new
3172  * anon_vmas to be associated with existing vmas.
3173  *
3174  * A single task can't take more than one mm_take_all_locks() in a row
3175  * or it would deadlock.
3176  *
3177  * The LSB in anon_vma->rb_root.rb_node and the AS_MM_ALL_LOCKS bitflag in
3178  * mapping->flags avoid to take the same lock twice, if more than one
3179  * vma in this mm is backed by the same anon_vma or address_space.
3180  *
3181  * We can take all the locks in random order because the VM code
3182  * taking i_mmap_rwsem or anon_vma->rwsem outside the mmap_sem never
3183  * takes more than one of them in a row. Secondly we're protected
3184  * against a concurrent mm_take_all_locks() by the mm_all_locks_mutex.
3185  *
3186  * mm_take_all_locks() and mm_drop_all_locks are expensive operations
3187  * that may have to take thousand of locks.
3188  *
3189  * mm_take_all_locks() can fail if it's interrupted by signals.
3190  */
3191 int mm_take_all_locks(struct mm_struct *mm)
3192 {
3193         struct vm_area_struct *vma;
3194         struct anon_vma_chain *avc;
3195 
3196         BUG_ON(down_read_trylock(&mm->mmap_sem));
3197 
3198         mutex_lock(&mm_all_locks_mutex);
3199 
3200         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3201                 if (signal_pending(current))
3202                         goto out_unlock;
3203                 if (vma->vm_file && vma->vm_file->f_mapping)
3204                         vm_lock_mapping(mm, vma->vm_file->f_mapping);
3205         }
3206 
3207         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3208                 if (signal_pending(current))
3209                         goto out_unlock;
3210                 if (vma->anon_vma)
3211                         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
3212                                 vm_lock_anon_vma(mm, avc->anon_vma);
3213         }
3214 
3215         return 0;
3216 
3217 out_unlock:
3218         mm_drop_all_locks(mm);
3219         return -EINTR;
3220 }
3221 
3222 static void vm_unlock_anon_vma(struct anon_vma *anon_vma)
3223 {
3224         if (test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_node)) {
3225                 /*
3226                  * The LSB of head.next can't change to 0 from under
3227                  * us because we hold the mm_all_locks_mutex.
3228                  *
3229                  * We must however clear the bitflag before unlocking
3230                  * the vma so the users using the anon_vma->rb_root will
3231                  * never see our bitflag.
3232                  *
3233                  * No need of atomic instructions here, head.next
3234                  * can't change from under us until we release the
3235                  * anon_vma->root->rwsem.
3236                  */
3237                 if (!__test_and_clear_bit(0, (unsigned long *)
3238                                           &anon_vma->root->rb_root.rb_node))
3239                         BUG();
3240                 anon_vma_unlock_write(anon_vma);
3241         }
3242 }
3243 
3244 static void vm_unlock_mapping(struct address_space *mapping)
3245 {
3246         if (test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
3247                 /*
3248                  * AS_MM_ALL_LOCKS can't change to 0 from under us
3249                  * because we hold the mm_all_locks_mutex.
3250                  */
3251                 i_mmap_unlock_write(mapping);
3252                 if (!test_and_clear_bit(AS_MM_ALL_LOCKS,
3253                                         &mapping->flags))
3254                         BUG();
3255         }
3256 }
3257 
3258 /*
3259  * The mmap_sem cannot be released by the caller until
3260  * mm_drop_all_locks() returns.
3261  */
3262 void mm_drop_all_locks(struct mm_struct *mm)
3263 {
3264         struct vm_area_struct *vma;
3265         struct anon_vma_chain *avc;
3266 
3267         BUG_ON(down_read_trylock(&mm->mmap_sem));
3268         BUG_ON(!mutex_is_locked(&mm_all_locks_mutex));
3269 
3270         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3271                 if (vma->anon_vma)
3272                         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
3273                                 vm_unlock_anon_vma(avc->anon_vma);
3274                 if (vma->vm_file && vma->vm_file->f_mapping)
3275                         vm_unlock_mapping(vma->vm_file->f_mapping);
3276         }
3277 
3278         mutex_unlock(&mm_all_locks_mutex);
3279 }
3280 
3281 /*
3282  * initialise the VMA slab
3283  */
3284 void __init mmap_init(void)
3285 {
3286         int ret;
3287 
3288         ret = percpu_counter_init(&vm_committed_as, 0, GFP_KERNEL);
3289         VM_BUG_ON(ret);
3290 }
3291 
3292 /*
3293  * Initialise sysctl_user_reserve_kbytes.
3294  *
3295  * This is intended to prevent a user from starting a single memory hogging
3296  * process, such that they cannot recover (kill the hog) in OVERCOMMIT_NEVER
3297  * mode.
3298  *
3299  * The default value is min(3% of free memory, 128MB)
3300  * 128MB is enough to recover with sshd/login, bash, and top/kill.
3301  */
3302 static int init_user_reserve(void)
3303 {
3304         unsigned long free_kbytes;
3305 
3306         free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
3307 
3308         sysctl_user_reserve_kbytes = min(free_kbytes / 32, 1UL << 17);
3309         return 0;
3310 }
3311 subsys_initcall(init_user_reserve);
3312 
3313 /*
3314  * Initialise sysctl_admin_reserve_kbytes.
3315  *
3316  * The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin
3317  * to log in and kill a memory hogging process.
3318  *
3319  * Systems with more than 256MB will reserve 8MB, enough to recover
3320  * with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will
3321  * only reserve 3% of free pages by default.
3322  */
3323 static int init_admin_reserve(void)
3324 {
3325         unsigned long free_kbytes;
3326 
3327         free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
3328 
3329         sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13);
3330         return 0;
3331 }
3332 subsys_initcall(init_admin_reserve);
3333 
3334 /*
3335  * Reinititalise user and admin reserves if memory is added or removed.
3336  *
3337  * The default user reserve max is 128MB, and the default max for the
3338  * admin reserve is 8MB. These are usually, but not always, enough to
3339  * enable recovery from a memory hogging process using login/sshd, a shell,
3340  * and tools like top. It may make sense to increase or even disable the
3341  * reserve depending on the existence of swap or variations in the recovery
3342  * tools. So, the admin may have changed them.
3343  *
3344  * If memory is added and the reserves have been eliminated or increased above
3345  * the default max, then we'll trust the admin.
3346  *
3347  * If memory is removed and there isn't enough free memory, then we
3348  * need to reset the reserves.
3349  *
3350  * Otherwise keep the reserve set by the admin.
3351  */
3352 static int reserve_mem_notifier(struct notifier_block *nb,
3353                              unsigned long action, void *data)
3354 {
3355         unsigned long tmp, free_kbytes;
3356 
3357         switch (action) {
3358         case MEM_ONLINE:
3359                 /* Default max is 128MB. Leave alone if modified by operator. */
3360                 tmp = sysctl_user_reserve_kbytes;
3361                 if (0 < tmp && tmp < (1UL << 17))
3362                         init_user_reserve();
3363 
3364                 /* Default max is 8MB.  Leave alone if modified by operator. */
3365                 tmp = sysctl_admin_reserve_kbytes;
3366                 if (0 < tmp && tmp < (1UL << 13))
3367                         init_admin_reserve();
3368 
3369                 break;
3370         case MEM_OFFLINE:
3371                 free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
3372 
3373                 if (sysctl_user_reserve_kbytes > free_kbytes) {
3374                         init_user_reserve();
3375                         pr_info("vm.user_reserve_kbytes reset to %lu\n",
3376                                 sysctl_user_reserve_kbytes);
3377                 }
3378 
3379                 if (sysctl_admin_reserve_kbytes > free_kbytes) {
3380                         init_admin_reserve();
3381                         pr_info("vm.admin_reserve_kbytes reset to %lu\n",
3382                                 sysctl_admin_reserve_kbytes);
3383                 }
3384                 break;
3385         default:
3386                 break;
3387         }
3388         return NOTIFY_OK;
3389 }
3390 
3391 static struct notifier_block reserve_mem_nb = {
3392         .notifier_call = reserve_mem_notifier,
3393 };
3394 
3395 static int __meminit init_reserve_notifier(void)
3396 {
3397         if (register_hotmemory_notifier(&reserve_mem_nb))
3398                 pr_err("Failed registering memory add/remove notifier for admin reserve\n");
3399 
3400         return 0;
3401 }
3402 subsys_initcall(init_reserve_notifier);
3403 

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