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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/shmem_fs.h>
 29 #include <linux/profile.h>
 30 #include <linux/export.h>
 31 #include <linux/mount.h>
 32 #include <linux/mempolicy.h>
 33 #include <linux/rmap.h>
 34 #include <linux/mmu_notifier.h>
 35 #include <linux/mmdebug.h>
 36 #include <linux/perf_event.h>
 37 #include <linux/audit.h>
 38 #include <linux/khugepaged.h>
 39 #include <linux/uprobes.h>
 40 #include <linux/rbtree_augmented.h>
 41 #include <linux/notifier.h>
 42 #include <linux/memory.h>
 43 #include <linux/printk.h>
 44 #include <linux/userfaultfd_k.h>
 45 #include <linux/moduleparam.h>
 46 #include <linux/pkeys.h>
 47 #include <linux/oom.h>
 48 
 49 #include <linux/uaccess.h>
 50 #include <asm/cacheflush.h>
 51 #include <asm/tlb.h>
 52 #include <asm/mmu_context.h>
 53 
 54 #include "internal.h"
 55 
 56 #ifndef arch_mmap_check
 57 #define arch_mmap_check(addr, len, flags)       (0)
 58 #endif
 59 
 60 #ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS
 61 const int mmap_rnd_bits_min = CONFIG_ARCH_MMAP_RND_BITS_MIN;
 62 const int mmap_rnd_bits_max = CONFIG_ARCH_MMAP_RND_BITS_MAX;
 63 int mmap_rnd_bits __read_mostly = CONFIG_ARCH_MMAP_RND_BITS;
 64 #endif
 65 #ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
 66 const int mmap_rnd_compat_bits_min = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MIN;
 67 const int mmap_rnd_compat_bits_max = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MAX;
 68 int mmap_rnd_compat_bits __read_mostly = CONFIG_ARCH_MMAP_RND_COMPAT_BITS;
 69 #endif
 70 
 71 static bool ignore_rlimit_data;
 72 core_param(ignore_rlimit_data, ignore_rlimit_data, bool, 0644);
 73 
 74 static void unmap_region(struct mm_struct *mm,
 75                 struct vm_area_struct *vma, struct vm_area_struct *prev,
 76                 unsigned long start, unsigned long end);
 77 
 78 /* description of effects of mapping type and prot in current implementation.
 79  * this is due to the limited x86 page protection hardware.  The expected
 80  * behavior is in parens:
 81  *
 82  * map_type     prot
 83  *              PROT_NONE       PROT_READ       PROT_WRITE      PROT_EXEC
 84  * MAP_SHARED   r: (no) no      r: (yes) yes    r: (no) yes     r: (no) yes
 85  *              w: (no) no      w: (no) no      w: (yes) yes    w: (no) no
 86  *              x: (no) no      x: (no) yes     x: (no) yes     x: (yes) yes
 87  *
 88  * MAP_PRIVATE  r: (no) no      r: (yes) yes    r: (no) yes     r: (no) yes
 89  *              w: (no) no      w: (no) no      w: (copy) copy  w: (no) no
 90  *              x: (no) no      x: (no) yes     x: (no) yes     x: (yes) yes
 91  *
 92  * On arm64, PROT_EXEC has the following behaviour for both MAP_SHARED and
 93  * MAP_PRIVATE:
 94  *                                                              r: (no) no
 95  *                                                              w: (no) no
 96  *                                                              x: (yes) yes
 97  */
 98 pgprot_t protection_map[16] __ro_after_init = {
 99         __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
100         __S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
101 };
102 
103 #ifndef CONFIG_ARCH_HAS_FILTER_PGPROT
104 static inline pgprot_t arch_filter_pgprot(pgprot_t prot)
105 {
106         return prot;
107 }
108 #endif
109 
110 pgprot_t vm_get_page_prot(unsigned long vm_flags)
111 {
112         pgprot_t ret = __pgprot(pgprot_val(protection_map[vm_flags &
113                                 (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
114                         pgprot_val(arch_vm_get_page_prot(vm_flags)));
115 
116         return arch_filter_pgprot(ret);
117 }
118 EXPORT_SYMBOL(vm_get_page_prot);
119 
120 static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags)
121 {
122         return pgprot_modify(oldprot, vm_get_page_prot(vm_flags));
123 }
124 
125 /* Update vma->vm_page_prot to reflect vma->vm_flags. */
126 void vma_set_page_prot(struct vm_area_struct *vma)
127 {
128         unsigned long vm_flags = vma->vm_flags;
129         pgprot_t vm_page_prot;
130 
131         vm_page_prot = vm_pgprot_modify(vma->vm_page_prot, vm_flags);
132         if (vma_wants_writenotify(vma, vm_page_prot)) {
133                 vm_flags &= ~VM_SHARED;
134                 vm_page_prot = vm_pgprot_modify(vm_page_prot, vm_flags);
135         }
136         /* remove_protection_ptes reads vma->vm_page_prot without mmap_sem */
137         WRITE_ONCE(vma->vm_page_prot, vm_page_prot);
138 }
139 
140 /*
141  * Requires inode->i_mapping->i_mmap_rwsem
142  */
143 static void __remove_shared_vm_struct(struct vm_area_struct *vma,
144                 struct file *file, struct address_space *mapping)
145 {
146         if (vma->vm_flags & VM_DENYWRITE)
147                 atomic_inc(&file_inode(file)->i_writecount);
148         if (vma->vm_flags & VM_SHARED)
149                 mapping_unmap_writable(mapping);
150 
151         flush_dcache_mmap_lock(mapping);
152         vma_interval_tree_remove(vma, &mapping->i_mmap);
153         flush_dcache_mmap_unlock(mapping);
154 }
155 
156 /*
157  * Unlink a file-based vm structure from its interval tree, to hide
158  * vma from rmap and vmtruncate before freeing its page tables.
159  */
160 void unlink_file_vma(struct vm_area_struct *vma)
161 {
162         struct file *file = vma->vm_file;
163 
164         if (file) {
165                 struct address_space *mapping = file->f_mapping;
166                 i_mmap_lock_write(mapping);
167                 __remove_shared_vm_struct(vma, file, mapping);
168                 i_mmap_unlock_write(mapping);
169         }
170 }
171 
172 /*
173  * Close a vm structure and free it, returning the next.
174  */
175 static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
176 {
177         struct vm_area_struct *next = vma->vm_next;
178 
179         might_sleep();
180         if (vma->vm_ops && vma->vm_ops->close)
181                 vma->vm_ops->close(vma);
182         if (vma->vm_file)
183                 fput(vma->vm_file);
184         mpol_put(vma_policy(vma));
185         vm_area_free(vma);
186         return next;
187 }
188 
189 static int do_brk_flags(unsigned long addr, unsigned long request, unsigned long flags,
190                 struct list_head *uf);
191 SYSCALL_DEFINE1(brk, unsigned long, brk)
192 {
193         unsigned long retval;
194         unsigned long newbrk, oldbrk, origbrk;
195         struct mm_struct *mm = current->mm;
196         struct vm_area_struct *next;
197         unsigned long min_brk;
198         bool populate;
199         bool downgraded = false;
200         LIST_HEAD(uf);
201 
202         if (down_write_killable(&mm->mmap_sem))
203                 return -EINTR;
204 
205         origbrk = mm->brk;
206 
207 #ifdef CONFIG_COMPAT_BRK
208         /*
209          * CONFIG_COMPAT_BRK can still be overridden by setting
210          * randomize_va_space to 2, which will still cause mm->start_brk
211          * to be arbitrarily shifted
212          */
213         if (current->brk_randomized)
214                 min_brk = mm->start_brk;
215         else
216                 min_brk = mm->end_data;
217 #else
218         min_brk = mm->start_brk;
219 #endif
220         if (brk < min_brk)
221                 goto out;
222 
223         /*
224          * Check against rlimit here. If this check is done later after the test
225          * of oldbrk with newbrk then it can escape the test and let the data
226          * segment grow beyond its set limit the in case where the limit is
227          * not page aligned -Ram Gupta
228          */
229         if (check_data_rlimit(rlimit(RLIMIT_DATA), brk, mm->start_brk,
230                               mm->end_data, mm->start_data))
231                 goto out;
232 
233         newbrk = PAGE_ALIGN(brk);
234         oldbrk = PAGE_ALIGN(mm->brk);
235         if (oldbrk == newbrk) {
236                 mm->brk = brk;
237                 goto success;
238         }
239 
240         /*
241          * Always allow shrinking brk.
242          * __do_munmap() may downgrade mmap_sem to read.
243          */
244         if (brk <= mm->brk) {
245                 int ret;
246 
247                 /*
248                  * mm->brk must to be protected by write mmap_sem so update it
249                  * before downgrading mmap_sem. When __do_munmap() fails,
250                  * mm->brk will be restored from origbrk.
251                  */
252                 mm->brk = brk;
253                 ret = __do_munmap(mm, newbrk, oldbrk-newbrk, &uf, true);
254                 if (ret < 0) {
255                         mm->brk = origbrk;
256                         goto out;
257                 } else if (ret == 1) {
258                         downgraded = true;
259                 }
260                 goto success;
261         }
262 
263         /* Check against existing mmap mappings. */
264         next = find_vma(mm, oldbrk);
265         if (next && newbrk + PAGE_SIZE > vm_start_gap(next))
266                 goto out;
267 
268         /* Ok, looks good - let it rip. */
269         if (do_brk_flags(oldbrk, newbrk-oldbrk, 0, &uf) < 0)
270                 goto out;
271         mm->brk = brk;
272 
273 success:
274         populate = newbrk > oldbrk && (mm->def_flags & VM_LOCKED) != 0;
275         if (downgraded)
276                 up_read(&mm->mmap_sem);
277         else
278                 up_write(&mm->mmap_sem);
279         userfaultfd_unmap_complete(mm, &uf);
280         if (populate)
281                 mm_populate(oldbrk, newbrk - oldbrk);
282         return brk;
283 
284 out:
285         retval = origbrk;
286         up_write(&mm->mmap_sem);
287         return retval;
288 }
289 
290 static long vma_compute_subtree_gap(struct vm_area_struct *vma)
291 {
292         unsigned long max, prev_end, subtree_gap;
293 
294         /*
295          * Note: in the rare case of a VM_GROWSDOWN above a VM_GROWSUP, we
296          * allow two stack_guard_gaps between them here, and when choosing
297          * an unmapped area; whereas when expanding we only require one.
298          * That's a little inconsistent, but keeps the code here simpler.
299          */
300         max = vm_start_gap(vma);
301         if (vma->vm_prev) {
302                 prev_end = vm_end_gap(vma->vm_prev);
303                 if (max > prev_end)
304                         max -= prev_end;
305                 else
306                         max = 0;
307         }
308         if (vma->vm_rb.rb_left) {
309                 subtree_gap = rb_entry(vma->vm_rb.rb_left,
310                                 struct vm_area_struct, vm_rb)->rb_subtree_gap;
311                 if (subtree_gap > max)
312                         max = subtree_gap;
313         }
314         if (vma->vm_rb.rb_right) {
315                 subtree_gap = rb_entry(vma->vm_rb.rb_right,
316                                 struct vm_area_struct, vm_rb)->rb_subtree_gap;
317                 if (subtree_gap > max)
318                         max = subtree_gap;
319         }
320         return max;
321 }
322 
323 #ifdef CONFIG_DEBUG_VM_RB
324 static int browse_rb(struct mm_struct *mm)
325 {
326         struct rb_root *root = &mm->mm_rb;
327         int i = 0, j, bug = 0;
328         struct rb_node *nd, *pn = NULL;
329         unsigned long prev = 0, pend = 0;
330 
331         for (nd = rb_first(root); nd; nd = rb_next(nd)) {
332                 struct vm_area_struct *vma;
333                 vma = rb_entry(nd, struct vm_area_struct, vm_rb);
334                 if (vma->vm_start < prev) {
335                         pr_emerg("vm_start %lx < prev %lx\n",
336                                   vma->vm_start, prev);
337                         bug = 1;
338                 }
339                 if (vma->vm_start < pend) {
340                         pr_emerg("vm_start %lx < pend %lx\n",
341                                   vma->vm_start, pend);
342                         bug = 1;
343                 }
344                 if (vma->vm_start > vma->vm_end) {
345                         pr_emerg("vm_start %lx > vm_end %lx\n",
346                                   vma->vm_start, vma->vm_end);
347                         bug = 1;
348                 }
349                 spin_lock(&mm->page_table_lock);
350                 if (vma->rb_subtree_gap != vma_compute_subtree_gap(vma)) {
351                         pr_emerg("free gap %lx, correct %lx\n",
352                                vma->rb_subtree_gap,
353                                vma_compute_subtree_gap(vma));
354                         bug = 1;
355                 }
356                 spin_unlock(&mm->page_table_lock);
357                 i++;
358                 pn = nd;
359                 prev = vma->vm_start;
360                 pend = vma->vm_end;
361         }
362         j = 0;
363         for (nd = pn; nd; nd = rb_prev(nd))
364                 j++;
365         if (i != j) {
366                 pr_emerg("backwards %d, forwards %d\n", j, i);
367                 bug = 1;
368         }
369         return bug ? -1 : i;
370 }
371 
372 static void validate_mm_rb(struct rb_root *root, struct vm_area_struct *ignore)
373 {
374         struct rb_node *nd;
375 
376         for (nd = rb_first(root); nd; nd = rb_next(nd)) {
377                 struct vm_area_struct *vma;
378                 vma = rb_entry(nd, struct vm_area_struct, vm_rb);
379                 VM_BUG_ON_VMA(vma != ignore &&
380                         vma->rb_subtree_gap != vma_compute_subtree_gap(vma),
381                         vma);
382         }
383 }
384 
385 static void validate_mm(struct mm_struct *mm)
386 {
387         int bug = 0;
388         int i = 0;
389         unsigned long highest_address = 0;
390         struct vm_area_struct *vma = mm->mmap;
391 
392         while (vma) {
393                 struct anon_vma *anon_vma = vma->anon_vma;
394                 struct anon_vma_chain *avc;
395 
396                 if (anon_vma) {
397                         anon_vma_lock_read(anon_vma);
398                         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
399                                 anon_vma_interval_tree_verify(avc);
400                         anon_vma_unlock_read(anon_vma);
401                 }
402 
403                 highest_address = vm_end_gap(vma);
404                 vma = vma->vm_next;
405                 i++;
406         }
407         if (i != mm->map_count) {
408                 pr_emerg("map_count %d vm_next %d\n", mm->map_count, i);
409                 bug = 1;
410         }
411         if (highest_address != mm->highest_vm_end) {
412                 pr_emerg("mm->highest_vm_end %lx, found %lx\n",
413                           mm->highest_vm_end, highest_address);
414                 bug = 1;
415         }
416         i = browse_rb(mm);
417         if (i != mm->map_count) {
418                 if (i != -1)
419                         pr_emerg("map_count %d rb %d\n", mm->map_count, i);
420                 bug = 1;
421         }
422         VM_BUG_ON_MM(bug, mm);
423 }
424 #else
425 #define validate_mm_rb(root, ignore) do { } while (0)
426 #define validate_mm(mm) do { } while (0)
427 #endif
428 
429 RB_DECLARE_CALLBACKS(static, vma_gap_callbacks, struct vm_area_struct, vm_rb,
430                      unsigned long, rb_subtree_gap, vma_compute_subtree_gap)
431 
432 /*
433  * Update augmented rbtree rb_subtree_gap values after vma->vm_start or
434  * vma->vm_prev->vm_end values changed, without modifying the vma's position
435  * in the rbtree.
436  */
437 static void vma_gap_update(struct vm_area_struct *vma)
438 {
439         /*
440          * As it turns out, RB_DECLARE_CALLBACKS() already created a callback
441          * function that does exactly what we want.
442          */
443         vma_gap_callbacks_propagate(&vma->vm_rb, NULL);
444 }
445 
446 static inline void vma_rb_insert(struct vm_area_struct *vma,
447                                  struct rb_root *root)
448 {
449         /* All rb_subtree_gap values must be consistent prior to insertion */
450         validate_mm_rb(root, NULL);
451 
452         rb_insert_augmented(&vma->vm_rb, root, &vma_gap_callbacks);
453 }
454 
455 static void __vma_rb_erase(struct vm_area_struct *vma, struct rb_root *root)
456 {
457         /*
458          * Note rb_erase_augmented is a fairly large inline function,
459          * so make sure we instantiate it only once with our desired
460          * augmented rbtree callbacks.
461          */
462         rb_erase_augmented(&vma->vm_rb, root, &vma_gap_callbacks);
463 }
464 
465 static __always_inline void vma_rb_erase_ignore(struct vm_area_struct *vma,
466                                                 struct rb_root *root,
467                                                 struct vm_area_struct *ignore)
468 {
469         /*
470          * All rb_subtree_gap values must be consistent prior to erase,
471          * with the possible exception of the "next" vma being erased if
472          * next->vm_start was reduced.
473          */
474         validate_mm_rb(root, ignore);
475 
476         __vma_rb_erase(vma, root);
477 }
478 
479 static __always_inline void vma_rb_erase(struct vm_area_struct *vma,
480                                          struct rb_root *root)
481 {
482         /*
483          * All rb_subtree_gap values must be consistent prior to erase,
484          * with the possible exception of the vma being erased.
485          */
486         validate_mm_rb(root, vma);
487 
488         __vma_rb_erase(vma, root);
489 }
490 
491 /*
492  * vma has some anon_vma assigned, and is already inserted on that
493  * anon_vma's interval trees.
494  *
495  * Before updating the vma's vm_start / vm_end / vm_pgoff fields, the
496  * vma must be removed from the anon_vma's interval trees using
497  * anon_vma_interval_tree_pre_update_vma().
498  *
499  * After the update, the vma will be reinserted using
500  * anon_vma_interval_tree_post_update_vma().
501  *
502  * The entire update must be protected by exclusive mmap_sem and by
503  * the root anon_vma's mutex.
504  */
505 static inline void
506 anon_vma_interval_tree_pre_update_vma(struct vm_area_struct *vma)
507 {
508         struct anon_vma_chain *avc;
509 
510         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
511                 anon_vma_interval_tree_remove(avc, &avc->anon_vma->rb_root);
512 }
513 
514 static inline void
515 anon_vma_interval_tree_post_update_vma(struct vm_area_struct *vma)
516 {
517         struct anon_vma_chain *avc;
518 
519         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
520                 anon_vma_interval_tree_insert(avc, &avc->anon_vma->rb_root);
521 }
522 
523 static int find_vma_links(struct mm_struct *mm, unsigned long addr,
524                 unsigned long end, struct vm_area_struct **pprev,
525                 struct rb_node ***rb_link, struct rb_node **rb_parent)
526 {
527         struct rb_node **__rb_link, *__rb_parent, *rb_prev;
528 
529         __rb_link = &mm->mm_rb.rb_node;
530         rb_prev = __rb_parent = NULL;
531 
532         while (*__rb_link) {
533                 struct vm_area_struct *vma_tmp;
534 
535                 __rb_parent = *__rb_link;
536                 vma_tmp = rb_entry(__rb_parent, struct vm_area_struct, vm_rb);
537 
538                 if (vma_tmp->vm_end > addr) {
539                         /* Fail if an existing vma overlaps the area */
540                         if (vma_tmp->vm_start < end)
541                                 return -ENOMEM;
542                         __rb_link = &__rb_parent->rb_left;
543                 } else {
544                         rb_prev = __rb_parent;
545                         __rb_link = &__rb_parent->rb_right;
546                 }
547         }
548 
549         *pprev = NULL;
550         if (rb_prev)
551                 *pprev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
552         *rb_link = __rb_link;
553         *rb_parent = __rb_parent;
554         return 0;
555 }
556 
557 static unsigned long count_vma_pages_range(struct mm_struct *mm,
558                 unsigned long addr, unsigned long end)
559 {
560         unsigned long nr_pages = 0;
561         struct vm_area_struct *vma;
562 
563         /* Find first overlaping mapping */
564         vma = find_vma_intersection(mm, addr, end);
565         if (!vma)
566                 return 0;
567 
568         nr_pages = (min(end, vma->vm_end) -
569                 max(addr, vma->vm_start)) >> PAGE_SHIFT;
570 
571         /* Iterate over the rest of the overlaps */
572         for (vma = vma->vm_next; vma; vma = vma->vm_next) {
573                 unsigned long overlap_len;
574 
575                 if (vma->vm_start > end)
576                         break;
577 
578                 overlap_len = min(end, vma->vm_end) - vma->vm_start;
579                 nr_pages += overlap_len >> PAGE_SHIFT;
580         }
581 
582         return nr_pages;
583 }
584 
585 void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
586                 struct rb_node **rb_link, struct rb_node *rb_parent)
587 {
588         /* Update tracking information for the gap following the new vma. */
589         if (vma->vm_next)
590                 vma_gap_update(vma->vm_next);
591         else
592                 mm->highest_vm_end = vm_end_gap(vma);
593 
594         /*
595          * vma->vm_prev wasn't known when we followed the rbtree to find the
596          * correct insertion point for that vma. As a result, we could not
597          * update the vma vm_rb parents rb_subtree_gap values on the way down.
598          * So, we first insert the vma with a zero rb_subtree_gap value
599          * (to be consistent with what we did on the way down), and then
600          * immediately update the gap to the correct value. Finally we
601          * rebalance the rbtree after all augmented values have been set.
602          */
603         rb_link_node(&vma->vm_rb, rb_parent, rb_link);
604         vma->rb_subtree_gap = 0;
605         vma_gap_update(vma);
606         vma_rb_insert(vma, &mm->mm_rb);
607 }
608 
609 static void __vma_link_file(struct vm_area_struct *vma)
610 {
611         struct file *file;
612 
613         file = vma->vm_file;
614         if (file) {
615                 struct address_space *mapping = file->f_mapping;
616 
617                 if (vma->vm_flags & VM_DENYWRITE)
618                         atomic_dec(&file_inode(file)->i_writecount);
619                 if (vma->vm_flags & VM_SHARED)
620                         atomic_inc(&mapping->i_mmap_writable);
621 
622                 flush_dcache_mmap_lock(mapping);
623                 vma_interval_tree_insert(vma, &mapping->i_mmap);
624                 flush_dcache_mmap_unlock(mapping);
625         }
626 }
627 
628 static void
629 __vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
630         struct vm_area_struct *prev, struct rb_node **rb_link,
631         struct rb_node *rb_parent)
632 {
633         __vma_link_list(mm, vma, prev, rb_parent);
634         __vma_link_rb(mm, vma, rb_link, rb_parent);
635 }
636 
637 static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
638                         struct vm_area_struct *prev, struct rb_node **rb_link,
639                         struct rb_node *rb_parent)
640 {
641         struct address_space *mapping = NULL;
642 
643         if (vma->vm_file) {
644                 mapping = vma->vm_file->f_mapping;
645                 i_mmap_lock_write(mapping);
646         }
647 
648         __vma_link(mm, vma, prev, rb_link, rb_parent);
649         __vma_link_file(vma);
650 
651         if (mapping)
652                 i_mmap_unlock_write(mapping);
653 
654         mm->map_count++;
655         validate_mm(mm);
656 }
657 
658 /*
659  * Helper for vma_adjust() in the split_vma insert case: insert a vma into the
660  * mm's list and rbtree.  It has already been inserted into the interval tree.
661  */
662 static void __insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
663 {
664         struct vm_area_struct *prev;
665         struct rb_node **rb_link, *rb_parent;
666 
667         if (find_vma_links(mm, vma->vm_start, vma->vm_end,
668                            &prev, &rb_link, &rb_parent))
669                 BUG();
670         __vma_link(mm, vma, prev, rb_link, rb_parent);
671         mm->map_count++;
672 }
673 
674 static __always_inline void __vma_unlink_common(struct mm_struct *mm,
675                                                 struct vm_area_struct *vma,
676                                                 struct vm_area_struct *prev,
677                                                 bool has_prev,
678                                                 struct vm_area_struct *ignore)
679 {
680         struct vm_area_struct *next;
681 
682         vma_rb_erase_ignore(vma, &mm->mm_rb, ignore);
683         next = vma->vm_next;
684         if (has_prev)
685                 prev->vm_next = next;
686         else {
687                 prev = vma->vm_prev;
688                 if (prev)
689                         prev->vm_next = next;
690                 else
691                         mm->mmap = next;
692         }
693         if (next)
694                 next->vm_prev = prev;
695 
696         /* Kill the cache */
697         vmacache_invalidate(mm);
698 }
699 
700 static inline void __vma_unlink_prev(struct mm_struct *mm,
701                                      struct vm_area_struct *vma,
702                                      struct vm_area_struct *prev)
703 {
704         __vma_unlink_common(mm, vma, prev, true, vma);
705 }
706 
707 /*
708  * We cannot adjust vm_start, vm_end, vm_pgoff fields of a vma that
709  * is already present in an i_mmap tree without adjusting the tree.
710  * The following helper function should be used when such adjustments
711  * are necessary.  The "insert" vma (if any) is to be inserted
712  * before we drop the necessary locks.
713  */
714 int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
715         unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert,
716         struct vm_area_struct *expand)
717 {
718         struct mm_struct *mm = vma->vm_mm;
719         struct vm_area_struct *next = vma->vm_next, *orig_vma = vma;
720         struct address_space *mapping = NULL;
721         struct rb_root_cached *root = NULL;
722         struct anon_vma *anon_vma = NULL;
723         struct file *file = vma->vm_file;
724         bool start_changed = false, end_changed = false;
725         long adjust_next = 0;
726         int remove_next = 0;
727 
728         if (next && !insert) {
729                 struct vm_area_struct *exporter = NULL, *importer = NULL;
730 
731                 if (end >= next->vm_end) {
732                         /*
733                          * vma expands, overlapping all the next, and
734                          * perhaps the one after too (mprotect case 6).
735                          * The only other cases that gets here are
736                          * case 1, case 7 and case 8.
737                          */
738                         if (next == expand) {
739                                 /*
740                                  * The only case where we don't expand "vma"
741                                  * and we expand "next" instead is case 8.
742                                  */
743                                 VM_WARN_ON(end != next->vm_end);
744                                 /*
745                                  * remove_next == 3 means we're
746                                  * removing "vma" and that to do so we
747                                  * swapped "vma" and "next".
748                                  */
749                                 remove_next = 3;
750                                 VM_WARN_ON(file != next->vm_file);
751                                 swap(vma, next);
752                         } else {
753                                 VM_WARN_ON(expand != vma);
754                                 /*
755                                  * case 1, 6, 7, remove_next == 2 is case 6,
756                                  * remove_next == 1 is case 1 or 7.
757                                  */
758                                 remove_next = 1 + (end > next->vm_end);
759                                 VM_WARN_ON(remove_next == 2 &&
760                                            end != next->vm_next->vm_end);
761                                 VM_WARN_ON(remove_next == 1 &&
762                                            end != next->vm_end);
763                                 /* trim end to next, for case 6 first pass */
764                                 end = next->vm_end;
765                         }
766 
767                         exporter = next;
768                         importer = vma;
769 
770                         /*
771                          * If next doesn't have anon_vma, import from vma after
772                          * next, if the vma overlaps with it.
773                          */
774                         if (remove_next == 2 && !next->anon_vma)
775                                 exporter = next->vm_next;
776 
777                 } else if (end > next->vm_start) {
778                         /*
779                          * vma expands, overlapping part of the next:
780                          * mprotect case 5 shifting the boundary up.
781                          */
782                         adjust_next = (end - next->vm_start) >> PAGE_SHIFT;
783                         exporter = next;
784                         importer = vma;
785                         VM_WARN_ON(expand != importer);
786                 } else if (end < vma->vm_end) {
787                         /*
788                          * vma shrinks, and !insert tells it's not
789                          * split_vma inserting another: so it must be
790                          * mprotect case 4 shifting the boundary down.
791                          */
792                         adjust_next = -((vma->vm_end - end) >> PAGE_SHIFT);
793                         exporter = vma;
794                         importer = next;
795                         VM_WARN_ON(expand != importer);
796                 }
797 
798                 /*
799                  * Easily overlooked: when mprotect shifts the boundary,
800                  * make sure the expanding vma has anon_vma set if the
801                  * shrinking vma had, to cover any anon pages imported.
802                  */
803                 if (exporter && exporter->anon_vma && !importer->anon_vma) {
804                         int error;
805 
806                         importer->anon_vma = exporter->anon_vma;
807                         error = anon_vma_clone(importer, exporter);
808                         if (error)
809                                 return error;
810                 }
811         }
812 again:
813         vma_adjust_trans_huge(orig_vma, start, end, adjust_next);
814 
815         if (file) {
816                 mapping = file->f_mapping;
817                 root = &mapping->i_mmap;
818                 uprobe_munmap(vma, vma->vm_start, vma->vm_end);
819 
820                 if (adjust_next)
821                         uprobe_munmap(next, next->vm_start, next->vm_end);
822 
823                 i_mmap_lock_write(mapping);
824                 if (insert) {
825                         /*
826                          * Put into interval tree now, so instantiated pages
827                          * are visible to arm/parisc __flush_dcache_page
828                          * throughout; but we cannot insert into address
829                          * space until vma start or end is updated.
830                          */
831                         __vma_link_file(insert);
832                 }
833         }
834 
835         anon_vma = vma->anon_vma;
836         if (!anon_vma && adjust_next)
837                 anon_vma = next->anon_vma;
838         if (anon_vma) {
839                 VM_WARN_ON(adjust_next && next->anon_vma &&
840                            anon_vma != next->anon_vma);
841                 anon_vma_lock_write(anon_vma);
842                 anon_vma_interval_tree_pre_update_vma(vma);
843                 if (adjust_next)
844                         anon_vma_interval_tree_pre_update_vma(next);
845         }
846 
847         if (root) {
848                 flush_dcache_mmap_lock(mapping);
849                 vma_interval_tree_remove(vma, root);
850                 if (adjust_next)
851                         vma_interval_tree_remove(next, root);
852         }
853 
854         if (start != vma->vm_start) {
855                 vma->vm_start = start;
856                 start_changed = true;
857         }
858         if (end != vma->vm_end) {
859                 vma->vm_end = end;
860                 end_changed = true;
861         }
862         vma->vm_pgoff = pgoff;
863         if (adjust_next) {
864                 next->vm_start += adjust_next << PAGE_SHIFT;
865                 next->vm_pgoff += adjust_next;
866         }
867 
868         if (root) {
869                 if (adjust_next)
870                         vma_interval_tree_insert(next, root);
871                 vma_interval_tree_insert(vma, root);
872                 flush_dcache_mmap_unlock(mapping);
873         }
874 
875         if (remove_next) {
876                 /*
877                  * vma_merge has merged next into vma, and needs
878                  * us to remove next before dropping the locks.
879                  */
880                 if (remove_next != 3)
881                         __vma_unlink_prev(mm, next, vma);
882                 else
883                         /*
884                          * vma is not before next if they've been
885                          * swapped.
886                          *
887                          * pre-swap() next->vm_start was reduced so
888                          * tell validate_mm_rb to ignore pre-swap()
889                          * "next" (which is stored in post-swap()
890                          * "vma").
891                          */
892                         __vma_unlink_common(mm, next, NULL, false, vma);
893                 if (file)
894                         __remove_shared_vm_struct(next, file, mapping);
895         } else if (insert) {
896                 /*
897                  * split_vma has split insert from vma, and needs
898                  * us to insert it before dropping the locks
899                  * (it may either follow vma or precede it).
900                  */
901                 __insert_vm_struct(mm, insert);
902         } else {
903                 if (start_changed)
904                         vma_gap_update(vma);
905                 if (end_changed) {
906                         if (!next)
907                                 mm->highest_vm_end = vm_end_gap(vma);
908                         else if (!adjust_next)
909                                 vma_gap_update(next);
910                 }
911         }
912 
913         if (anon_vma) {
914                 anon_vma_interval_tree_post_update_vma(vma);
915                 if (adjust_next)
916                         anon_vma_interval_tree_post_update_vma(next);
917                 anon_vma_unlock_write(anon_vma);
918         }
919         if (mapping)
920                 i_mmap_unlock_write(mapping);
921 
922         if (root) {
923                 uprobe_mmap(vma);
924 
925                 if (adjust_next)
926                         uprobe_mmap(next);
927         }
928 
929         if (remove_next) {
930                 if (file) {
931                         uprobe_munmap(next, next->vm_start, next->vm_end);
932                         fput(file);
933                 }
934                 if (next->anon_vma)
935                         anon_vma_merge(vma, next);
936                 mm->map_count--;
937                 mpol_put(vma_policy(next));
938                 vm_area_free(next);
939                 /*
940                  * In mprotect's case 6 (see comments on vma_merge),
941                  * we must remove another next too. It would clutter
942                  * up the code too much to do both in one go.
943                  */
944                 if (remove_next != 3) {
945                         /*
946                          * If "next" was removed and vma->vm_end was
947                          * expanded (up) over it, in turn
948                          * "next->vm_prev->vm_end" changed and the
949                          * "vma->vm_next" gap must be updated.
950                          */
951                         next = vma->vm_next;
952                 } else {
953                         /*
954                          * For the scope of the comment "next" and
955                          * "vma" considered pre-swap(): if "vma" was
956                          * removed, next->vm_start was expanded (down)
957                          * over it and the "next" gap must be updated.
958                          * Because of the swap() the post-swap() "vma"
959                          * actually points to pre-swap() "next"
960                          * (post-swap() "next" as opposed is now a
961                          * dangling pointer).
962                          */
963                         next = vma;
964                 }
965                 if (remove_next == 2) {
966                         remove_next = 1;
967                         end = next->vm_end;
968                         goto again;
969                 }
970                 else if (next)
971                         vma_gap_update(next);
972                 else {
973                         /*
974                          * If remove_next == 2 we obviously can't
975                          * reach this path.
976                          *
977                          * If remove_next == 3 we can't reach this
978                          * path because pre-swap() next is always not
979                          * NULL. pre-swap() "next" is not being
980                          * removed and its next->vm_end is not altered
981                          * (and furthermore "end" already matches
982                          * next->vm_end in remove_next == 3).
983                          *
984                          * We reach this only in the remove_next == 1
985                          * case if the "next" vma that was removed was
986                          * the highest vma of the mm. However in such
987                          * case next->vm_end == "end" and the extended
988                          * "vma" has vma->vm_end == next->vm_end so
989                          * mm->highest_vm_end doesn't need any update
990                          * in remove_next == 1 case.
991                          */
992                         VM_WARN_ON(mm->highest_vm_end != vm_end_gap(vma));
993                 }
994         }
995         if (insert && file)
996                 uprobe_mmap(insert);
997 
998         validate_mm(mm);
999 
1000         return 0;
1001 }
1002 
1003 /*
1004  * If the vma has a ->close operation then the driver probably needs to release
1005  * per-vma resources, so we don't attempt to merge those.
1006  */
1007 static inline int is_mergeable_vma(struct vm_area_struct *vma,
1008                                 struct file *file, unsigned long vm_flags,
1009                                 struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
1010 {
1011         /*
1012          * VM_SOFTDIRTY should not prevent from VMA merging, if we
1013          * match the flags but dirty bit -- the caller should mark
1014          * merged VMA as dirty. If dirty bit won't be excluded from
1015          * comparison, we increase pressure on the memory system forcing
1016          * the kernel to generate new VMAs when old one could be
1017          * extended instead.
1018          */
1019         if ((vma->vm_flags ^ vm_flags) & ~VM_SOFTDIRTY)
1020                 return 0;
1021         if (vma->vm_file != file)
1022                 return 0;
1023         if (vma->vm_ops && vma->vm_ops->close)
1024                 return 0;
1025         if (!is_mergeable_vm_userfaultfd_ctx(vma, vm_userfaultfd_ctx))
1026                 return 0;
1027         return 1;
1028 }
1029 
1030 static inline int is_mergeable_anon_vma(struct anon_vma *anon_vma1,
1031                                         struct anon_vma *anon_vma2,
1032                                         struct vm_area_struct *vma)
1033 {
1034         /*
1035          * The list_is_singular() test is to avoid merging VMA cloned from
1036          * parents. This can improve scalability caused by anon_vma lock.
1037          */
1038         if ((!anon_vma1 || !anon_vma2) && (!vma ||
1039                 list_is_singular(&vma->anon_vma_chain)))
1040                 return 1;
1041         return anon_vma1 == anon_vma2;
1042 }
1043 
1044 /*
1045  * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
1046  * in front of (at a lower virtual address and file offset than) the vma.
1047  *
1048  * We cannot merge two vmas if they have differently assigned (non-NULL)
1049  * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
1050  *
1051  * We don't check here for the merged mmap wrapping around the end of pagecache
1052  * indices (16TB on ia32) because do_mmap_pgoff() does not permit mmap's which
1053  * wrap, nor mmaps which cover the final page at index -1UL.
1054  */
1055 static int
1056 can_vma_merge_before(struct vm_area_struct *vma, unsigned long vm_flags,
1057                      struct anon_vma *anon_vma, struct file *file,
1058                      pgoff_t vm_pgoff,
1059                      struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
1060 {
1061         if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx) &&
1062             is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
1063                 if (vma->vm_pgoff == vm_pgoff)
1064                         return 1;
1065         }
1066         return 0;
1067 }
1068 
1069 /*
1070  * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
1071  * beyond (at a higher virtual address and file offset than) the vma.
1072  *
1073  * We cannot merge two vmas if they have differently assigned (non-NULL)
1074  * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
1075  */
1076 static int
1077 can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
1078                     struct anon_vma *anon_vma, struct file *file,
1079                     pgoff_t vm_pgoff,
1080                     struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
1081 {
1082         if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx) &&
1083             is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
1084                 pgoff_t vm_pglen;
1085                 vm_pglen = vma_pages(vma);
1086                 if (vma->vm_pgoff + vm_pglen == vm_pgoff)
1087                         return 1;
1088         }
1089         return 0;
1090 }
1091 
1092 /*
1093  * Given a mapping request (addr,end,vm_flags,file,pgoff), figure out
1094  * whether that can be merged with its predecessor or its successor.
1095  * Or both (it neatly fills a hole).
1096  *
1097  * In most cases - when called for mmap, brk or mremap - [addr,end) is
1098  * certain not to be mapped by the time vma_merge is called; but when
1099  * called for mprotect, it is certain to be already mapped (either at
1100  * an offset within prev, or at the start of next), and the flags of
1101  * this area are about to be changed to vm_flags - and the no-change
1102  * case has already been eliminated.
1103  *
1104  * The following mprotect cases have to be considered, where AAAA is
1105  * the area passed down from mprotect_fixup, never extending beyond one
1106  * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
1107  *
1108  *     AAAA             AAAA                AAAA          AAAA
1109  *    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPNNNNXXXX
1110  *    cannot merge    might become    might become    might become
1111  *                    PPNNNNNNNNNN    PPPPPPPPPPNN    PPPPPPPPPPPP 6 or
1112  *    mmap, brk or    case 4 below    case 5 below    PPPPPPPPXXXX 7 or
1113  *    mremap move:                                    PPPPXXXXXXXX 8
1114  *        AAAA
1115  *    PPPP    NNNN    PPPPPPPPPPPP    PPPPPPPPNNNN    PPPPNNNNNNNN
1116  *    might become    case 1 below    case 2 below    case 3 below
1117  *
1118  * It is important for case 8 that the vma NNNN overlapping the
1119  * region AAAA is never going to extended over XXXX. Instead XXXX must
1120  * be extended in region AAAA and NNNN must be removed. This way in
1121  * all cases where vma_merge succeeds, the moment vma_adjust drops the
1122  * rmap_locks, the properties of the merged vma will be already
1123  * correct for the whole merged range. Some of those properties like
1124  * vm_page_prot/vm_flags may be accessed by rmap_walks and they must
1125  * be correct for the whole merged range immediately after the
1126  * rmap_locks are released. Otherwise if XXXX would be removed and
1127  * NNNN would be extended over the XXXX range, remove_migration_ptes
1128  * or other rmap walkers (if working on addresses beyond the "end"
1129  * parameter) may establish ptes with the wrong permissions of NNNN
1130  * instead of the right permissions of XXXX.
1131  */
1132 struct vm_area_struct *vma_merge(struct mm_struct *mm,
1133                         struct vm_area_struct *prev, unsigned long addr,
1134                         unsigned long end, unsigned long vm_flags,
1135                         struct anon_vma *anon_vma, struct file *file,
1136                         pgoff_t pgoff, struct mempolicy *policy,
1137                         struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
1138 {
1139         pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
1140         struct vm_area_struct *area, *next;
1141         int err;
1142 
1143         /*
1144          * We later require that vma->vm_flags == vm_flags,
1145          * so this tests vma->vm_flags & VM_SPECIAL, too.
1146          */
1147         if (vm_flags & VM_SPECIAL)
1148                 return NULL;
1149 
1150         if (prev)
1151                 next = prev->vm_next;
1152         else
1153                 next = mm->mmap;
1154         area = next;
1155         if (area && area->vm_end == end)                /* cases 6, 7, 8 */
1156                 next = next->vm_next;
1157 
1158         /* verify some invariant that must be enforced by the caller */
1159         VM_WARN_ON(prev && addr <= prev->vm_start);
1160         VM_WARN_ON(area && end > area->vm_end);
1161         VM_WARN_ON(addr >= end);
1162 
1163         /*
1164          * Can it merge with the predecessor?
1165          */
1166         if (prev && prev->vm_end == addr &&
1167                         mpol_equal(vma_policy(prev), policy) &&
1168                         can_vma_merge_after(prev, vm_flags,
1169                                             anon_vma, file, pgoff,
1170                                             vm_userfaultfd_ctx)) {
1171                 /*
1172                  * OK, it can.  Can we now merge in the successor as well?
1173                  */
1174                 if (next && end == next->vm_start &&
1175                                 mpol_equal(policy, vma_policy(next)) &&
1176                                 can_vma_merge_before(next, vm_flags,
1177                                                      anon_vma, file,
1178                                                      pgoff+pglen,
1179                                                      vm_userfaultfd_ctx) &&
1180                                 is_mergeable_anon_vma(prev->anon_vma,
1181                                                       next->anon_vma, NULL)) {
1182                                                         /* cases 1, 6 */
1183                         err = __vma_adjust(prev, prev->vm_start,
1184                                          next->vm_end, prev->vm_pgoff, NULL,
1185                                          prev);
1186                 } else                                  /* cases 2, 5, 7 */
1187                         err = __vma_adjust(prev, prev->vm_start,
1188                                          end, prev->vm_pgoff, NULL, prev);
1189                 if (err)
1190                         return NULL;
1191                 khugepaged_enter_vma_merge(prev, vm_flags);
1192                 return prev;
1193         }
1194 
1195         /*
1196          * Can this new request be merged in front of next?
1197          */
1198         if (next && end == next->vm_start &&
1199                         mpol_equal(policy, vma_policy(next)) &&
1200                         can_vma_merge_before(next, vm_flags,
1201                                              anon_vma, file, pgoff+pglen,
1202                                              vm_userfaultfd_ctx)) {
1203                 if (prev && addr < prev->vm_end)        /* case 4 */
1204                         err = __vma_adjust(prev, prev->vm_start,
1205                                          addr, prev->vm_pgoff, NULL, next);
1206                 else {                                  /* cases 3, 8 */
1207                         err = __vma_adjust(area, addr, next->vm_end,
1208                                          next->vm_pgoff - pglen, NULL, next);
1209                         /*
1210                          * In case 3 area is already equal to next and
1211                          * this is a noop, but in case 8 "area" has
1212                          * been removed and next was expanded over it.
1213                          */
1214                         area = next;
1215                 }
1216                 if (err)
1217                         return NULL;
1218                 khugepaged_enter_vma_merge(area, vm_flags);
1219                 return area;
1220         }
1221 
1222         return NULL;
1223 }
1224 
1225 /*
1226  * Rough compatbility check to quickly see if it's even worth looking
1227  * at sharing an anon_vma.
1228  *
1229  * They need to have the same vm_file, and the flags can only differ
1230  * in things that mprotect may change.
1231  *
1232  * NOTE! The fact that we share an anon_vma doesn't _have_ to mean that
1233  * we can merge the two vma's. For example, we refuse to merge a vma if
1234  * there is a vm_ops->close() function, because that indicates that the
1235  * driver is doing some kind of reference counting. But that doesn't
1236  * really matter for the anon_vma sharing case.
1237  */
1238 static int anon_vma_compatible(struct vm_area_struct *a, struct vm_area_struct *b)
1239 {
1240         return a->vm_end == b->vm_start &&
1241                 mpol_equal(vma_policy(a), vma_policy(b)) &&
1242                 a->vm_file == b->vm_file &&
1243                 !((a->vm_flags ^ b->vm_flags) & ~(VM_READ|VM_WRITE|VM_EXEC|VM_SOFTDIRTY)) &&
1244                 b->vm_pgoff == a->vm_pgoff + ((b->vm_start - a->vm_start) >> PAGE_SHIFT);
1245 }
1246 
1247 /*
1248  * Do some basic sanity checking to see if we can re-use the anon_vma
1249  * from 'old'. The 'a'/'b' vma's are in VM order - one of them will be
1250  * the same as 'old', the other will be the new one that is trying
1251  * to share the anon_vma.
1252  *
1253  * NOTE! This runs with mm_sem held for reading, so it is possible that
1254  * the anon_vma of 'old' is concurrently in the process of being set up
1255  * by another page fault trying to merge _that_. But that's ok: if it
1256  * is being set up, that automatically means that it will be a singleton
1257  * acceptable for merging, so we can do all of this optimistically. But
1258  * we do that READ_ONCE() to make sure that we never re-load the pointer.
1259  *
1260  * IOW: that the "list_is_singular()" test on the anon_vma_chain only
1261  * matters for the 'stable anon_vma' case (ie the thing we want to avoid
1262  * is to return an anon_vma that is "complex" due to having gone through
1263  * a fork).
1264  *
1265  * We also make sure that the two vma's are compatible (adjacent,
1266  * and with the same memory policies). That's all stable, even with just
1267  * a read lock on the mm_sem.
1268  */
1269 static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, struct vm_area_struct *a, struct vm_area_struct *b)
1270 {
1271         if (anon_vma_compatible(a, b)) {
1272                 struct anon_vma *anon_vma = READ_ONCE(old->anon_vma);
1273 
1274                 if (anon_vma && list_is_singular(&old->anon_vma_chain))
1275                         return anon_vma;
1276         }
1277         return NULL;
1278 }
1279 
1280 /*
1281  * find_mergeable_anon_vma is used by anon_vma_prepare, to check
1282  * neighbouring vmas for a suitable anon_vma, before it goes off
1283  * to allocate a new anon_vma.  It checks because a repetitive
1284  * sequence of mprotects and faults may otherwise lead to distinct
1285  * anon_vmas being allocated, preventing vma merge in subsequent
1286  * mprotect.
1287  */
1288 struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
1289 {
1290         struct anon_vma *anon_vma;
1291         struct vm_area_struct *near;
1292 
1293         near = vma->vm_next;
1294         if (!near)
1295                 goto try_prev;
1296 
1297         anon_vma = reusable_anon_vma(near, vma, near);
1298         if (anon_vma)
1299                 return anon_vma;
1300 try_prev:
1301         near = vma->vm_prev;
1302         if (!near)
1303                 goto none;
1304 
1305         anon_vma = reusable_anon_vma(near, near, vma);
1306         if (anon_vma)
1307                 return anon_vma;
1308 none:
1309         /*
1310          * There's no absolute need to look only at touching neighbours:
1311          * we could search further afield for "compatible" anon_vmas.
1312          * But it would probably just be a waste of time searching,
1313          * or lead to too many vmas hanging off the same anon_vma.
1314          * We're trying to allow mprotect remerging later on,
1315          * not trying to minimize memory used for anon_vmas.
1316          */
1317         return NULL;
1318 }
1319 
1320 /*
1321  * If a hint addr is less than mmap_min_addr change hint to be as
1322  * low as possible but still greater than mmap_min_addr
1323  */
1324 static inline unsigned long round_hint_to_min(unsigned long hint)
1325 {
1326         hint &= PAGE_MASK;
1327         if (((void *)hint != NULL) &&
1328             (hint < mmap_min_addr))
1329                 return PAGE_ALIGN(mmap_min_addr);
1330         return hint;
1331 }
1332 
1333 static inline int mlock_future_check(struct mm_struct *mm,
1334                                      unsigned long flags,
1335                                      unsigned long len)
1336 {
1337         unsigned long locked, lock_limit;
1338 
1339         /*  mlock MCL_FUTURE? */
1340         if (flags & VM_LOCKED) {
1341                 locked = len >> PAGE_SHIFT;
1342                 locked += mm->locked_vm;
1343                 lock_limit = rlimit(RLIMIT_MEMLOCK);
1344                 lock_limit >>= PAGE_SHIFT;
1345                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
1346                         return -EAGAIN;
1347         }
1348         return 0;
1349 }
1350 
1351 static inline u64 file_mmap_size_max(struct file *file, struct inode *inode)
1352 {
1353         if (S_ISREG(inode->i_mode))
1354                 return MAX_LFS_FILESIZE;
1355 
1356         if (S_ISBLK(inode->i_mode))
1357                 return MAX_LFS_FILESIZE;
1358 
1359         /* Special "we do even unsigned file positions" case */
1360         if (file->f_mode & FMODE_UNSIGNED_OFFSET)
1361                 return 0;
1362 
1363         /* Yes, random drivers might want more. But I'm tired of buggy drivers */
1364         return ULONG_MAX;
1365 }
1366 
1367 static inline bool file_mmap_ok(struct file *file, struct inode *inode,
1368                                 unsigned long pgoff, unsigned long len)
1369 {
1370         u64 maxsize = file_mmap_size_max(file, inode);
1371 
1372         if (maxsize && len > maxsize)
1373                 return false;
1374         maxsize -= len;
1375         if (pgoff > maxsize >> PAGE_SHIFT)
1376                 return false;
1377         return true;
1378 }
1379 
1380 /*
1381  * The caller must hold down_write(&current->mm->mmap_sem).
1382  */
1383 unsigned long do_mmap(struct file *file, unsigned long addr,
1384                         unsigned long len, unsigned long prot,
1385                         unsigned long flags, vm_flags_t vm_flags,
1386                         unsigned long pgoff, unsigned long *populate,
1387                         struct list_head *uf)
1388 {
1389         struct mm_struct *mm = current->mm;
1390         int pkey = 0;
1391 
1392         *populate = 0;
1393 
1394         if (!len)
1395                 return -EINVAL;
1396 
1397         /*
1398          * Does the application expect PROT_READ to imply PROT_EXEC?
1399          *
1400          * (the exception is when the underlying filesystem is noexec
1401          *  mounted, in which case we dont add PROT_EXEC.)
1402          */
1403         if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
1404                 if (!(file && path_noexec(&file->f_path)))
1405                         prot |= PROT_EXEC;
1406 
1407         /* force arch specific MAP_FIXED handling in get_unmapped_area */
1408         if (flags & MAP_FIXED_NOREPLACE)
1409                 flags |= MAP_FIXED;
1410 
1411         if (!(flags & MAP_FIXED))
1412                 addr = round_hint_to_min(addr);
1413 
1414         /* Careful about overflows.. */
1415         len = PAGE_ALIGN(len);
1416         if (!len)
1417                 return -ENOMEM;
1418 
1419         /* offset overflow? */
1420         if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
1421                 return -EOVERFLOW;
1422 
1423         /* Too many mappings? */
1424         if (mm->map_count > sysctl_max_map_count)
1425                 return -ENOMEM;
1426 
1427         /* Obtain the address to map to. we verify (or select) it and ensure
1428          * that it represents a valid section of the address space.
1429          */
1430         addr = get_unmapped_area(file, addr, len, pgoff, flags);
1431         if (offset_in_page(addr))
1432                 return addr;
1433 
1434         if (flags & MAP_FIXED_NOREPLACE) {
1435                 struct vm_area_struct *vma = find_vma(mm, addr);
1436 
1437                 if (vma && vma->vm_start < addr + len)
1438                         return -EEXIST;
1439         }
1440 
1441         if (prot == PROT_EXEC) {
1442                 pkey = execute_only_pkey(mm);
1443                 if (pkey < 0)
1444                         pkey = 0;
1445         }
1446 
1447         /* Do simple checking here so the lower-level routines won't have
1448          * to. we assume access permissions have been handled by the open
1449          * of the memory object, so we don't do any here.
1450          */
1451         vm_flags |= calc_vm_prot_bits(prot, pkey) | calc_vm_flag_bits(flags) |
1452                         mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
1453 
1454         if (flags & MAP_LOCKED)
1455                 if (!can_do_mlock())
1456                         return -EPERM;
1457 
1458         if (mlock_future_check(mm, vm_flags, len))
1459                 return -EAGAIN;
1460 
1461         if (file) {
1462                 struct inode *inode = file_inode(file);
1463                 unsigned long flags_mask;
1464 
1465                 if (!file_mmap_ok(file, inode, pgoff, len))
1466                         return -EOVERFLOW;
1467 
1468                 flags_mask = LEGACY_MAP_MASK | file->f_op->mmap_supported_flags;
1469 
1470                 switch (flags & MAP_TYPE) {
1471                 case MAP_SHARED:
1472                         /*
1473                          * Force use of MAP_SHARED_VALIDATE with non-legacy
1474                          * flags. E.g. MAP_SYNC is dangerous to use with
1475                          * MAP_SHARED as you don't know which consistency model
1476                          * you will get. We silently ignore unsupported flags
1477                          * with MAP_SHARED to preserve backward compatibility.
1478                          */
1479                         flags &= LEGACY_MAP_MASK;
1480                         /* fall through */
1481                 case MAP_SHARED_VALIDATE:
1482                         if (flags & ~flags_mask)
1483                                 return -EOPNOTSUPP;
1484                         if ((prot&PROT_WRITE) && !(file->f_mode&FMODE_WRITE))
1485                                 return -EACCES;
1486 
1487                         /*
1488                          * Make sure we don't allow writing to an append-only
1489                          * file..
1490                          */
1491                         if (IS_APPEND(inode) && (file->f_mode & FMODE_WRITE))
1492                                 return -EACCES;
1493 
1494                         /*
1495                          * Make sure there are no mandatory locks on the file.
1496                          */
1497                         if (locks_verify_locked(file))
1498                                 return -EAGAIN;
1499 
1500                         vm_flags |= VM_SHARED | VM_MAYSHARE;
1501                         if (!(file->f_mode & FMODE_WRITE))
1502                                 vm_flags &= ~(VM_MAYWRITE | VM_SHARED);
1503 
1504                         /* fall through */
1505                 case MAP_PRIVATE:
1506                         if (!(file->f_mode & FMODE_READ))
1507                                 return -EACCES;
1508                         if (path_noexec(&file->f_path)) {
1509                                 if (vm_flags & VM_EXEC)
1510                                         return -EPERM;
1511                                 vm_flags &= ~VM_MAYEXEC;
1512                         }
1513 
1514                         if (!file->f_op->mmap)
1515                                 return -ENODEV;
1516                         if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1517                                 return -EINVAL;
1518                         break;
1519 
1520                 default:
1521                         return -EINVAL;
1522                 }
1523         } else {
1524                 switch (flags & MAP_TYPE) {
1525                 case MAP_SHARED:
1526                         if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1527                                 return -EINVAL;
1528                         /*
1529                          * Ignore pgoff.
1530                          */
1531                         pgoff = 0;
1532                         vm_flags |= VM_SHARED | VM_MAYSHARE;
1533                         break;
1534                 case MAP_PRIVATE:
1535                         /*
1536                          * Set pgoff according to addr for anon_vma.
1537                          */
1538                         pgoff = addr >> PAGE_SHIFT;
1539                         break;
1540                 default:
1541                         return -EINVAL;
1542                 }
1543         }
1544 
1545         /*
1546          * Set 'VM_NORESERVE' if we should not account for the
1547          * memory use of this mapping.
1548          */
1549         if (flags & MAP_NORESERVE) {
1550                 /* We honor MAP_NORESERVE if allowed to overcommit */
1551                 if (sysctl_overcommit_memory != OVERCOMMIT_NEVER)
1552                         vm_flags |= VM_NORESERVE;
1553 
1554                 /* hugetlb applies strict overcommit unless MAP_NORESERVE */
1555                 if (file && is_file_hugepages(file))
1556                         vm_flags |= VM_NORESERVE;
1557         }
1558 
1559         addr = mmap_region(file, addr, len, vm_flags, pgoff, uf);
1560         if (!IS_ERR_VALUE(addr) &&
1561             ((vm_flags & VM_LOCKED) ||
1562              (flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE))
1563                 *populate = len;
1564         return addr;
1565 }
1566 
1567 unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
1568                               unsigned long prot, unsigned long flags,
1569                               unsigned long fd, unsigned long pgoff)
1570 {
1571         struct file *file = NULL;
1572         unsigned long retval;
1573 
1574         if (!(flags & MAP_ANONYMOUS)) {
1575                 audit_mmap_fd(fd, flags);
1576                 file = fget(fd);
1577                 if (!file)
1578                         return -EBADF;
1579                 if (is_file_hugepages(file))
1580                         len = ALIGN(len, huge_page_size(hstate_file(file)));
1581                 retval = -EINVAL;
1582                 if (unlikely(flags & MAP_HUGETLB && !is_file_hugepages(file)))
1583                         goto out_fput;
1584         } else if (flags & MAP_HUGETLB) {
1585                 struct user_struct *user = NULL;
1586                 struct hstate *hs;
1587 
1588                 hs = hstate_sizelog((flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK);
1589                 if (!hs)
1590                         return -EINVAL;
1591 
1592                 len = ALIGN(len, huge_page_size(hs));
1593                 /*
1594                  * VM_NORESERVE is used because the reservations will be
1595                  * taken when vm_ops->mmap() is called
1596                  * A dummy user value is used because we are not locking
1597                  * memory so no accounting is necessary
1598                  */
1599                 file = hugetlb_file_setup(HUGETLB_ANON_FILE, len,
1600                                 VM_NORESERVE,
1601                                 &user, HUGETLB_ANONHUGE_INODE,
1602                                 (flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK);
1603                 if (IS_ERR(file))
1604                         return PTR_ERR(file);
1605         }
1606 
1607         flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
1608 
1609         retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
1610 out_fput:
1611         if (file)
1612                 fput(file);
1613         return retval;
1614 }
1615 
1616 SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
1617                 unsigned long, prot, unsigned long, flags,
1618                 unsigned long, fd, unsigned long, pgoff)
1619 {
1620         return ksys_mmap_pgoff(addr, len, prot, flags, fd, pgoff);
1621 }
1622 
1623 #ifdef __ARCH_WANT_SYS_OLD_MMAP
1624 struct mmap_arg_struct {
1625         unsigned long addr;
1626         unsigned long len;
1627         unsigned long prot;
1628         unsigned long flags;
1629         unsigned long fd;
1630         unsigned long offset;
1631 };
1632 
1633 SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
1634 {
1635         struct mmap_arg_struct a;
1636 
1637         if (copy_from_user(&a, arg, sizeof(a)))
1638                 return -EFAULT;
1639         if (offset_in_page(a.offset))
1640                 return -EINVAL;
1641 
1642         return ksys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
1643                                a.offset >> PAGE_SHIFT);
1644 }
1645 #endif /* __ARCH_WANT_SYS_OLD_MMAP */
1646 
1647 /*
1648  * Some shared mappings will want the pages marked read-only
1649  * to track write events. If so, we'll downgrade vm_page_prot
1650  * to the private version (using protection_map[] without the
1651  * VM_SHARED bit).
1652  */
1653 int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot)
1654 {
1655         vm_flags_t vm_flags = vma->vm_flags;
1656         const struct vm_operations_struct *vm_ops = vma->vm_ops;
1657 
1658         /* If it was private or non-writable, the write bit is already clear */
1659         if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED)))
1660                 return 0;
1661 
1662         /* The backer wishes to know when pages are first written to? */
1663         if (vm_ops && (vm_ops->page_mkwrite || vm_ops->pfn_mkwrite))
1664                 return 1;
1665 
1666         /* The open routine did something to the protections that pgprot_modify
1667          * won't preserve? */
1668         if (pgprot_val(vm_page_prot) !=
1669             pgprot_val(vm_pgprot_modify(vm_page_prot, vm_flags)))
1670                 return 0;
1671 
1672         /* Do we need to track softdirty? */
1673         if (IS_ENABLED(CONFIG_MEM_SOFT_DIRTY) && !(vm_flags & VM_SOFTDIRTY))
1674                 return 1;
1675 
1676         /* Specialty mapping? */
1677         if (vm_flags & VM_PFNMAP)
1678                 return 0;
1679 
1680         /* Can the mapping track the dirty pages? */
1681         return vma->vm_file && vma->vm_file->f_mapping &&
1682                 mapping_cap_account_dirty(vma->vm_file->f_mapping);
1683 }
1684 
1685 /*
1686  * We account for memory if it's a private writeable mapping,
1687  * not hugepages and VM_NORESERVE wasn't set.
1688  */
1689 static inline int accountable_mapping(struct file *file, vm_flags_t vm_flags)
1690 {
1691         /*
1692          * hugetlb has its own accounting separate from the core VM
1693          * VM_HUGETLB may not be set yet so we cannot check for that flag.
1694          */
1695         if (file && is_file_hugepages(file))
1696                 return 0;
1697 
1698         return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE;
1699 }
1700 
1701 unsigned long mmap_region(struct file *file, unsigned long addr,
1702                 unsigned long len, vm_flags_t vm_flags, unsigned long pgoff,
1703                 struct list_head *uf)
1704 {
1705         struct mm_struct *mm = current->mm;
1706         struct vm_area_struct *vma, *prev;
1707         int error;
1708         struct rb_node **rb_link, *rb_parent;
1709         unsigned long charged = 0;
1710 
1711         /* Check against address space limit. */
1712         if (!may_expand_vm(mm, vm_flags, len >> PAGE_SHIFT)) {
1713                 unsigned long nr_pages;
1714 
1715                 /*
1716                  * MAP_FIXED may remove pages of mappings that intersects with
1717                  * requested mapping. Account for the pages it would unmap.
1718                  */
1719                 nr_pages = count_vma_pages_range(mm, addr, addr + len);
1720 
1721                 if (!may_expand_vm(mm, vm_flags,
1722                                         (len >> PAGE_SHIFT) - nr_pages))
1723                         return -ENOMEM;
1724         }
1725 
1726         /* Clear old maps */
1727         while (find_vma_links(mm, addr, addr + len, &prev, &rb_link,
1728                               &rb_parent)) {
1729                 if (do_munmap(mm, addr, len, uf))
1730                         return -ENOMEM;
1731         }
1732 
1733         /*
1734          * Private writable mapping: check memory availability
1735          */
1736         if (accountable_mapping(file, vm_flags)) {
1737                 charged = len >> PAGE_SHIFT;
1738                 if (security_vm_enough_memory_mm(mm, charged))
1739                         return -ENOMEM;
1740                 vm_flags |= VM_ACCOUNT;
1741         }
1742 
1743         /*
1744          * Can we just expand an old mapping?
1745          */
1746         vma = vma_merge(mm, prev, addr, addr + len, vm_flags,
1747                         NULL, file, pgoff, NULL, NULL_VM_UFFD_CTX);
1748         if (vma)
1749                 goto out;
1750 
1751         /*
1752          * Determine the object being mapped and call the appropriate
1753          * specific mapper. the address has already been validated, but
1754          * not unmapped, but the maps are removed from the list.
1755          */
1756         vma = vm_area_alloc(mm);
1757         if (!vma) {
1758                 error = -ENOMEM;
1759                 goto unacct_error;
1760         }
1761 
1762         vma->vm_start = addr;
1763         vma->vm_end = addr + len;
1764         vma->vm_flags = vm_flags;
1765         vma->vm_page_prot = vm_get_page_prot(vm_flags);
1766         vma->vm_pgoff = pgoff;
1767 
1768         if (file) {
1769                 if (vm_flags & VM_DENYWRITE) {
1770                         error = deny_write_access(file);
1771                         if (error)
1772                                 goto free_vma;
1773                 }
1774                 if (vm_flags & VM_SHARED) {
1775                         error = mapping_map_writable(file->f_mapping);
1776                         if (error)
1777                                 goto allow_write_and_free_vma;
1778                 }
1779 
1780                 /* ->mmap() can change vma->vm_file, but must guarantee that
1781                  * vma_link() below can deny write-access if VM_DENYWRITE is set
1782                  * and map writably if VM_SHARED is set. This usually means the
1783                  * new file must not have been exposed to user-space, yet.
1784                  */
1785                 vma->vm_file = get_file(file);
1786                 error = call_mmap(file, vma);
1787                 if (error)
1788                         goto unmap_and_free_vma;
1789 
1790                 /* Can addr have changed??
1791                  *
1792                  * Answer: Yes, several device drivers can do it in their
1793                  *         f_op->mmap method. -DaveM
1794                  * Bug: If addr is changed, prev, rb_link, rb_parent should
1795                  *      be updated for vma_link()
1796                  */
1797                 WARN_ON_ONCE(addr != vma->vm_start);
1798 
1799                 addr = vma->vm_start;
1800                 vm_flags = vma->vm_flags;
1801         } else if (vm_flags & VM_SHARED) {
1802                 error = shmem_zero_setup(vma);
1803                 if (error)
1804                         goto free_vma;
1805         } else {
1806                 vma_set_anonymous(vma);
1807         }
1808 
1809         vma_link(mm, vma, prev, rb_link, rb_parent);
1810         /* Once vma denies write, undo our temporary denial count */
1811         if (file) {
1812                 if (vm_flags & VM_SHARED)
1813                         mapping_unmap_writable(file->f_mapping);
1814                 if (vm_flags & VM_DENYWRITE)
1815                         allow_write_access(file);
1816         }
1817         file = vma->vm_file;
1818 out:
1819         perf_event_mmap(vma);
1820 
1821         vm_stat_account(mm, vm_flags, len >> PAGE_SHIFT);
1822         if (vm_flags & VM_LOCKED) {
1823                 if ((vm_flags & VM_SPECIAL) || vma_is_dax(vma) ||
1824                                         is_vm_hugetlb_page(vma) ||
1825                                         vma == get_gate_vma(current->mm))
1826                         vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
1827                 else
1828                         mm->locked_vm += (len >> PAGE_SHIFT);
1829         }
1830 
1831         if (file)
1832                 uprobe_mmap(vma);
1833 
1834         /*
1835          * New (or expanded) vma always get soft dirty status.
1836          * Otherwise user-space soft-dirty page tracker won't
1837          * be able to distinguish situation when vma area unmapped,
1838          * then new mapped in-place (which must be aimed as
1839          * a completely new data area).
1840          */
1841         vma->vm_flags |= VM_SOFTDIRTY;
1842 
1843         vma_set_page_prot(vma);
1844 
1845         return addr;
1846 
1847 unmap_and_free_vma:
1848         vma->vm_file = NULL;
1849         fput(file);
1850 
1851         /* Undo any partial mapping done by a device driver. */
1852         unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);
1853         charged = 0;
1854         if (vm_flags & VM_SHARED)
1855                 mapping_unmap_writable(file->f_mapping);
1856 allow_write_and_free_vma:
1857         if (vm_flags & VM_DENYWRITE)
1858                 allow_write_access(file);
1859 free_vma:
1860         vm_area_free(vma);
1861 unacct_error:
1862         if (charged)
1863                 vm_unacct_memory(charged);
1864         return error;
1865 }
1866 
1867 unsigned long unmapped_area(struct vm_unmapped_area_info *info)
1868 {
1869         /*
1870          * We implement the search by looking for an rbtree node that
1871          * immediately follows a suitable gap. That is,
1872          * - gap_start = vma->vm_prev->vm_end <= info->high_limit - length;
1873          * - gap_end   = vma->vm_start        >= info->low_limit  + length;
1874          * - gap_end - gap_start >= length
1875          */
1876 
1877         struct mm_struct *mm = current->mm;
1878         struct vm_area_struct *vma;
1879         unsigned long length, low_limit, high_limit, gap_start, gap_end;
1880 
1881         /* Adjust search length to account for worst case alignment overhead */
1882         length = info->length + info->align_mask;
1883         if (length < info->length)
1884                 return -ENOMEM;
1885 
1886         /* Adjust search limits by the desired length */
1887         if (info->high_limit < length)
1888                 return -ENOMEM;
1889         high_limit = info->high_limit - length;
1890 
1891         if (info->low_limit > high_limit)
1892                 return -ENOMEM;
1893         low_limit = info->low_limit + length;
1894 
1895         /* Check if rbtree root looks promising */
1896         if (RB_EMPTY_ROOT(&mm->mm_rb))
1897                 goto check_highest;
1898         vma = rb_entry(mm->mm_rb.rb_node, struct vm_area_struct, vm_rb);
1899         if (vma->rb_subtree_gap < length)
1900                 goto check_highest;
1901 
1902         while (true) {
1903                 /* Visit left subtree if it looks promising */
1904                 gap_end = vm_start_gap(vma);
1905                 if (gap_end >= low_limit && vma->vm_rb.rb_left) {
1906                         struct vm_area_struct *left =
1907                                 rb_entry(vma->vm_rb.rb_left,
1908                                          struct vm_area_struct, vm_rb);
1909                         if (left->rb_subtree_gap >= length) {
1910                                 vma = left;
1911                                 continue;
1912                         }
1913                 }
1914 
1915                 gap_start = vma->vm_prev ? vm_end_gap(vma->vm_prev) : 0;
1916 check_current:
1917                 /* Check if current node has a suitable gap */
1918                 if (gap_start > high_limit)
1919                         return -ENOMEM;
1920                 if (gap_end >= low_limit &&
1921                     gap_end > gap_start && gap_end - gap_start >= length)
1922                         goto found;
1923 
1924                 /* Visit right subtree if it looks promising */
1925                 if (vma->vm_rb.rb_right) {
1926                         struct vm_area_struct *right =
1927                                 rb_entry(vma->vm_rb.rb_right,
1928                                          struct vm_area_struct, vm_rb);
1929                         if (right->rb_subtree_gap >= length) {
1930                                 vma = right;
1931                                 continue;
1932                         }
1933                 }
1934 
1935                 /* Go back up the rbtree to find next candidate node */
1936                 while (true) {
1937                         struct rb_node *prev = &vma->vm_rb;
1938                         if (!rb_parent(prev))
1939                                 goto check_highest;
1940                         vma = rb_entry(rb_parent(prev),
1941                                        struct vm_area_struct, vm_rb);
1942                         if (prev == vma->vm_rb.rb_left) {
1943                                 gap_start = vm_end_gap(vma->vm_prev);
1944                                 gap_end = vm_start_gap(vma);
1945                                 goto check_current;
1946                         }
1947                 }
1948         }
1949 
1950 check_highest:
1951         /* Check highest gap, which does not precede any rbtree node */
1952         gap_start = mm->highest_vm_end;
1953         gap_end = ULONG_MAX;  /* Only for VM_BUG_ON below */
1954         if (gap_start > high_limit)
1955                 return -ENOMEM;
1956 
1957 found:
1958         /* We found a suitable gap. Clip it with the original low_limit. */
1959         if (gap_start < info->low_limit)
1960                 gap_start = info->low_limit;
1961 
1962         /* Adjust gap address to the desired alignment */
1963         gap_start += (info->align_offset - gap_start) & info->align_mask;
1964 
1965         VM_BUG_ON(gap_start + info->length > info->high_limit);
1966         VM_BUG_ON(gap_start + info->length > gap_end);
1967         return gap_start;
1968 }
1969 
1970 unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
1971 {
1972         struct mm_struct *mm = current->mm;
1973         struct vm_area_struct *vma;
1974         unsigned long length, low_limit, high_limit, gap_start, gap_end;
1975 
1976         /* Adjust search length to account for worst case alignment overhead */
1977         length = info->length + info->align_mask;
1978         if (length < info->length)
1979                 return -ENOMEM;
1980 
1981         /*
1982          * Adjust search limits by the desired length.
1983          * See implementation comment at top of unmapped_area().
1984          */
1985         gap_end = info->high_limit;
1986         if (gap_end < length)
1987                 return -ENOMEM;
1988         high_limit = gap_end - length;
1989 
1990         if (info->low_limit > high_limit)
1991                 return -ENOMEM;
1992         low_limit = info->low_limit + length;
1993 
1994         /* Check highest gap, which does not precede any rbtree node */
1995         gap_start = mm->highest_vm_end;
1996         if (gap_start <= high_limit)
1997                 goto found_highest;
1998 
1999         /* Check if rbtree root looks promising */
2000         if (RB_EMPTY_ROOT(&mm->mm_rb))
2001                 return -ENOMEM;
2002         vma = rb_entry(mm->mm_rb.rb_node, struct vm_area_struct, vm_rb);
2003         if (vma->rb_subtree_gap < length)
2004                 return -ENOMEM;
2005 
2006         while (true) {
2007                 /* Visit right subtree if it looks promising */
2008                 gap_start = vma->vm_prev ? vm_end_gap(vma->vm_prev) : 0;
2009                 if (gap_start <= high_limit && vma->vm_rb.rb_right) {
2010                         struct vm_area_struct *right =
2011                                 rb_entry(vma->vm_rb.rb_right,
2012                                          struct vm_area_struct, vm_rb);
2013                         if (right->rb_subtree_gap >= length) {
2014                                 vma = right;
2015                                 continue;
2016                         }
2017                 }
2018 
2019 check_current:
2020                 /* Check if current node has a suitable gap */
2021                 gap_end = vm_start_gap(vma);
2022                 if (gap_end < low_limit)
2023                         return -ENOMEM;
2024                 if (gap_start <= high_limit &&
2025                     gap_end > gap_start && gap_end - gap_start >= length)
2026                         goto found;
2027 
2028                 /* Visit left subtree if it looks promising */
2029                 if (vma->vm_rb.rb_left) {
2030                         struct vm_area_struct *left =
2031                                 rb_entry(vma->vm_rb.rb_left,
2032                                          struct vm_area_struct, vm_rb);
2033                         if (left->rb_subtree_gap >= length) {
2034                                 vma = left;
2035                                 continue;
2036                         }
2037                 }
2038 
2039                 /* Go back up the rbtree to find next candidate node */
2040                 while (true) {
2041                         struct rb_node *prev = &vma->vm_rb;
2042                         if (!rb_parent(prev))
2043                                 return -ENOMEM;
2044                         vma = rb_entry(rb_parent(prev),
2045                                        struct vm_area_struct, vm_rb);
2046                         if (prev == vma->vm_rb.rb_right) {
2047                                 gap_start = vma->vm_prev ?
2048                                         vm_end_gap(vma->vm_prev) : 0;
2049                                 goto check_current;
2050                         }
2051                 }
2052         }
2053 
2054 found:
2055         /* We found a suitable gap. Clip it with the original high_limit. */
2056         if (gap_end > info->high_limit)
2057                 gap_end = info->high_limit;
2058 
2059 found_highest:
2060         /* Compute highest gap address at the desired alignment */
2061         gap_end -= info->length;
2062         gap_end -= (gap_end - info->align_offset) & info->align_mask;
2063 
2064         VM_BUG_ON(gap_end < info->low_limit);
2065         VM_BUG_ON(gap_end < gap_start);
2066         return gap_end;
2067 }
2068 
2069 
2070 #ifndef arch_get_mmap_end
2071 #define arch_get_mmap_end(addr) (TASK_SIZE)
2072 #endif
2073 
2074 #ifndef arch_get_mmap_base
2075 #define arch_get_mmap_base(addr, base) (base)
2076 #endif
2077 
2078 /* Get an address range which is currently unmapped.
2079  * For shmat() with addr=0.
2080  *
2081  * Ugly calling convention alert:
2082  * Return value with the low bits set means error value,
2083  * ie
2084  *      if (ret & ~PAGE_MASK)
2085  *              error = ret;
2086  *
2087  * This function "knows" that -ENOMEM has the bits set.
2088  */
2089 #ifndef HAVE_ARCH_UNMAPPED_AREA
2090 unsigned long
2091 arch_get_unmapped_area(struct file *filp, unsigned long addr,
2092                 unsigned long len, unsigned long pgoff, unsigned long flags)
2093 {
2094         struct mm_struct *mm = current->mm;
2095         struct vm_area_struct *vma, *prev;
2096         struct vm_unmapped_area_info info;
2097         const unsigned long mmap_end = arch_get_mmap_end(addr);
2098 
2099         if (len > mmap_end - mmap_min_addr)
2100                 return -ENOMEM;
2101 
2102         if (flags & MAP_FIXED)
2103                 return addr;
2104 
2105         if (addr) {
2106                 addr = PAGE_ALIGN(addr);
2107                 vma = find_vma_prev(mm, addr, &prev);
2108                 if (mmap_end - len >= addr && addr >= mmap_min_addr &&
2109                     (!vma || addr + len <= vm_start_gap(vma)) &&
2110                     (!prev || addr >= vm_end_gap(prev)))
2111                         return addr;
2112         }
2113 
2114         info.flags = 0;
2115         info.length = len;
2116         info.low_limit = mm->mmap_base;
2117         info.high_limit = mmap_end;
2118         info.align_mask = 0;
2119         return vm_unmapped_area(&info);
2120 }
2121 #endif
2122 
2123 /*
2124  * This mmap-allocator allocates new areas top-down from below the
2125  * stack's low limit (the base):
2126  */
2127 #ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
2128 unsigned long
2129 arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
2130                           unsigned long len, unsigned long pgoff,
2131                           unsigned long flags)
2132 {
2133         struct vm_area_struct *vma, *prev;
2134         struct mm_struct *mm = current->mm;
2135         struct vm_unmapped_area_info info;
2136         const unsigned long mmap_end = arch_get_mmap_end(addr);
2137 
2138         /* requested length too big for entire address space */
2139         if (len > mmap_end - mmap_min_addr)
2140                 return -ENOMEM;
2141 
2142         if (flags & MAP_FIXED)
2143                 return addr;
2144 
2145         /* requesting a specific address */
2146         if (addr) {
2147                 addr = PAGE_ALIGN(addr);
2148                 vma = find_vma_prev(mm, addr, &prev);
2149                 if (mmap_end - len >= addr && addr >= mmap_min_addr &&
2150                                 (!vma || addr + len <= vm_start_gap(vma)) &&
2151                                 (!prev || addr >= vm_end_gap(prev)))
2152                         return addr;
2153         }
2154 
2155         info.flags = VM_UNMAPPED_AREA_TOPDOWN;
2156         info.length = len;
2157         info.low_limit = max(PAGE_SIZE, mmap_min_addr);
2158         info.high_limit = arch_get_mmap_base(addr, mm->mmap_base);
2159         info.align_mask = 0;
2160         addr = vm_unmapped_area(&info);
2161 
2162         /*
2163          * A failed mmap() very likely causes application failure,
2164          * so fall back to the bottom-up function here. This scenario
2165          * can happen with large stack limits and large mmap()
2166          * allocations.
2167          */
2168         if (offset_in_page(addr)) {
2169                 VM_BUG_ON(addr != -ENOMEM);
2170                 info.flags = 0;
2171                 info.low_limit = TASK_UNMAPPED_BASE;
2172                 info.high_limit = mmap_end;
2173                 addr = vm_unmapped_area(&info);
2174         }
2175 
2176         return addr;
2177 }
2178 #endif
2179 
2180 unsigned long
2181 get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
2182                 unsigned long pgoff, unsigned long flags)
2183 {
2184         unsigned long (*get_area)(struct file *, unsigned long,
2185                                   unsigned long, unsigned long, unsigned long);
2186 
2187         unsigned long error = arch_mmap_check(addr, len, flags);
2188         if (error)
2189                 return error;
2190 
2191         /* Careful about overflows.. */
2192         if (len > TASK_SIZE)
2193                 return -ENOMEM;
2194 
2195         get_area = current->mm->get_unmapped_area;
2196         if (file) {
2197                 if (file->f_op->get_unmapped_area)
2198                         get_area = file->f_op->get_unmapped_area;
2199         } else if (flags & MAP_SHARED) {
2200                 /*
2201                  * mmap_region() will call shmem_zero_setup() to create a file,
2202                  * so use shmem's get_unmapped_area in case it can be huge.
2203                  * do_mmap_pgoff() will clear pgoff, so match alignment.
2204                  */
2205                 pgoff = 0;
2206                 get_area = shmem_get_unmapped_area;
2207         }
2208 
2209         addr = get_area(file, addr, len, pgoff, flags);
2210         if (IS_ERR_VALUE(addr))
2211                 return addr;
2212 
2213         if (addr > TASK_SIZE - len)
2214                 return -ENOMEM;
2215         if (offset_in_page(addr))
2216                 return -EINVAL;
2217 
2218         error = security_mmap_addr(addr);
2219         return error ? error : addr;
2220 }
2221 
2222 EXPORT_SYMBOL(get_unmapped_area);
2223 
2224 /* Look up the first VMA which satisfies  addr < vm_end,  NULL if none. */
2225 struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
2226 {
2227         struct rb_node *rb_node;
2228         struct vm_area_struct *vma;
2229 
2230         /* Check the cache first. */
2231         vma = vmacache_find(mm, addr);
2232         if (likely(vma))
2233                 return vma;
2234 
2235         rb_node = mm->mm_rb.rb_node;
2236 
2237         while (rb_node) {
2238                 struct vm_area_struct *tmp;
2239 
2240                 tmp = rb_entry(rb_node, struct vm_area_struct, vm_rb);
2241 
2242                 if (tmp->vm_end > addr) {
2243                         vma = tmp;
2244                         if (tmp->vm_start <= addr)
2245                                 break;
2246                         rb_node = rb_node->rb_left;
2247                 } else
2248                         rb_node = rb_node->rb_right;
2249         }
2250 
2251         if (vma)
2252                 vmacache_update(addr, vma);
2253         return vma;
2254 }
2255 
2256 EXPORT_SYMBOL(find_vma);
2257 
2258 /*
2259  * Same as find_vma, but also return a pointer to the previous VMA in *pprev.
2260  */
2261 struct vm_area_struct *
2262 find_vma_prev(struct mm_struct *mm, unsigned long addr,
2263                         struct vm_area_struct **pprev)
2264 {
2265         struct vm_area_struct *vma;
2266 
2267         vma = find_vma(mm, addr);
2268         if (vma) {
2269                 *pprev = vma->vm_prev;
2270         } else {
2271                 struct rb_node *rb_node = mm->mm_rb.rb_node;
2272                 *pprev = NULL;
2273                 while (rb_node) {
2274                         *pprev = rb_entry(rb_node, struct vm_area_struct, vm_rb);
2275                         rb_node = rb_node->rb_right;
2276                 }
2277         }
2278         return vma;
2279 }
2280 
2281 /*
2282  * Verify that the stack growth is acceptable and
2283  * update accounting. This is shared with both the
2284  * grow-up and grow-down cases.
2285  */
2286 static int acct_stack_growth(struct vm_area_struct *vma,
2287                              unsigned long size, unsigned long grow)
2288 {
2289         struct mm_struct *mm = vma->vm_mm;
2290         unsigned long new_start;
2291 
2292         /* address space limit tests */
2293         if (!may_expand_vm(mm, vma->vm_flags, grow))
2294                 return -ENOMEM;
2295 
2296         /* Stack limit test */
2297         if (size > rlimit(RLIMIT_STACK))
2298                 return -ENOMEM;
2299 
2300         /* mlock limit tests */
2301         if (vma->vm_flags & VM_LOCKED) {
2302                 unsigned long locked;
2303                 unsigned long limit;
2304                 locked = mm->locked_vm + grow;
2305                 limit = rlimit(RLIMIT_MEMLOCK);
2306                 limit >>= PAGE_SHIFT;
2307                 if (locked > limit && !capable(CAP_IPC_LOCK))
2308                         return -ENOMEM;
2309         }
2310 
2311         /* Check to ensure the stack will not grow into a hugetlb-only region */
2312         new_start = (vma->vm_flags & VM_GROWSUP) ? vma->vm_start :
2313                         vma->vm_end - size;
2314         if (is_hugepage_only_range(vma->vm_mm, new_start, size))
2315                 return -EFAULT;
2316 
2317         /*
2318          * Overcommit..  This must be the final test, as it will
2319          * update security statistics.
2320          */
2321         if (security_vm_enough_memory_mm(mm, grow))
2322                 return -ENOMEM;
2323 
2324         return 0;
2325 }
2326 
2327 #if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
2328 /*
2329  * PA-RISC uses this for its stack; IA64 for its Register Backing Store.
2330  * vma is the last one with address > vma->vm_end.  Have to extend vma.
2331  */
2332 int expand_upwards(struct vm_area_struct *vma, unsigned long address)
2333 {
2334         struct mm_struct *mm = vma->vm_mm;
2335         struct vm_area_struct *next;
2336         unsigned long gap_addr;
2337         int error = 0;
2338 
2339         if (!(vma->vm_flags & VM_GROWSUP))
2340                 return -EFAULT;
2341 
2342         /* Guard against exceeding limits of the address space. */
2343         address &= PAGE_MASK;
2344         if (address >= (TASK_SIZE & PAGE_MASK))
2345                 return -ENOMEM;
2346         address += PAGE_SIZE;
2347 
2348         /* Enforce stack_guard_gap */
2349         gap_addr = address + stack_guard_gap;
2350 
2351         /* Guard against overflow */
2352         if (gap_addr < address || gap_addr > TASK_SIZE)
2353                 gap_addr = TASK_SIZE;
2354 
2355         next = vma->vm_next;
2356         if (next && next->vm_start < gap_addr &&
2357                         (next->vm_flags & (VM_WRITE|VM_READ|VM_EXEC))) {
2358                 if (!(next->vm_flags & VM_GROWSUP))
2359                         return -ENOMEM;
2360                 /* Check that both stack segments have the same anon_vma? */
2361         }
2362 
2363         /* We must make sure the anon_vma is allocated. */
2364         if (unlikely(anon_vma_prepare(vma)))
2365                 return -ENOMEM;
2366 
2367         /*
2368          * vma->vm_start/vm_end cannot change under us because the caller
2369          * is required to hold the mmap_sem in read mode.  We need the
2370          * anon_vma lock to serialize against concurrent expand_stacks.
2371          */
2372         anon_vma_lock_write(vma->anon_vma);
2373 
2374         /* Somebody else might have raced and expanded it already */
2375         if (address > vma->vm_end) {
2376                 unsigned long size, grow;
2377 
2378                 size = address - vma->vm_start;
2379                 grow = (address - vma->vm_end) >> PAGE_SHIFT;
2380 
2381                 error = -ENOMEM;
2382                 if (vma->vm_pgoff + (size >> PAGE_SHIFT) >= vma->vm_pgoff) {
2383                         error = acct_stack_growth(vma, size, grow);
2384                         if (!error) {
2385                                 /*
2386                                  * vma_gap_update() doesn't support concurrent
2387                                  * updates, but we only hold a shared mmap_sem
2388                                  * lock here, so we need to protect against
2389                                  * concurrent vma expansions.
2390                                  * anon_vma_lock_write() doesn't help here, as
2391                                  * we don't guarantee that all growable vmas
2392                                  * in a mm share the same root anon vma.
2393                                  * So, we reuse mm->page_table_lock to guard
2394                                  * against concurrent vma expansions.
2395                                  */
2396                                 spin_lock(&mm->page_table_lock);
2397                                 if (vma->vm_flags & VM_LOCKED)
2398                                         mm->locked_vm += grow;
2399                                 vm_stat_account(mm, vma->vm_flags, grow);
2400                                 anon_vma_interval_tree_pre_update_vma(vma);
2401                                 vma->vm_end = address;
2402                                 anon_vma_interval_tree_post_update_vma(vma);
2403                                 if (vma->vm_next)
2404                                         vma_gap_update(vma->vm_next);
2405                                 else
2406                                         mm->highest_vm_end = vm_end_gap(vma);
2407                                 spin_unlock(&mm->page_table_lock);
2408 
2409                                 perf_event_mmap(vma);
2410                         }
2411                 }
2412         }
2413         anon_vma_unlock_write(vma->anon_vma);
2414         khugepaged_enter_vma_merge(vma, vma->vm_flags);
2415         validate_mm(mm);
2416         return error;
2417 }
2418 #endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
2419 
2420 /*
2421  * vma is the first one with address < vma->vm_start.  Have to extend vma.
2422  */
2423 int expand_downwards(struct vm_area_struct *vma,
2424                                    unsigned long address)
2425 {
2426         struct mm_struct *mm = vma->vm_mm;
2427         struct vm_area_struct *prev;
2428         int error = 0;
2429 
2430         address &= PAGE_MASK;
2431         if (address < mmap_min_addr)
2432                 return -EPERM;
2433 
2434         /* Enforce stack_guard_gap */
2435         prev = vma->vm_prev;
2436         /* Check that both stack segments have the same anon_vma? */
2437         if (prev && !(prev->vm_flags & VM_GROWSDOWN) &&
2438                         (prev->vm_flags & (VM_WRITE|VM_READ|VM_EXEC))) {
2439                 if (address - prev->vm_end < stack_guard_gap)
2440                         return -ENOMEM;
2441         }
2442 
2443         /* We must make sure the anon_vma is allocated. */
2444         if (unlikely(anon_vma_prepare(vma)))
2445                 return -ENOMEM;
2446 
2447         /*
2448          * vma->vm_start/vm_end cannot change under us because the caller
2449          * is required to hold the mmap_sem in read mode.  We need the
2450          * anon_vma lock to serialize against concurrent expand_stacks.
2451          */
2452         anon_vma_lock_write(vma->anon_vma);
2453 
2454         /* Somebody else might have raced and expanded it already */
2455         if (address < vma->vm_start) {
2456                 unsigned long size, grow;
2457 
2458                 size = vma->vm_end - address;
2459                 grow = (vma->vm_start - address) >> PAGE_SHIFT;
2460 
2461                 error = -ENOMEM;
2462                 if (grow <= vma->vm_pgoff) {
2463                         error = acct_stack_growth(vma, size, grow);
2464                         if (!error) {
2465                                 /*
2466                                  * vma_gap_update() doesn't support concurrent
2467                                  * updates, but we only hold a shared mmap_sem
2468                                  * lock here, so we need to protect against
2469                                  * concurrent vma expansions.
2470                                  * anon_vma_lock_write() doesn't help here, as
2471                                  * we don't guarantee that all growable vmas
2472                                  * in a mm share the same root anon vma.
2473                                  * So, we reuse mm->page_table_lock to guard
2474                                  * against concurrent vma expansions.
2475                                  */
2476                                 spin_lock(&mm->page_table_lock);
2477                                 if (vma->vm_flags & VM_LOCKED)
2478                                         mm->locked_vm += grow;
2479                                 vm_stat_account(mm, vma->vm_flags, grow);
2480                                 anon_vma_interval_tree_pre_update_vma(vma);
2481                                 vma->vm_start = address;
2482                                 vma->vm_pgoff -= grow;
2483                                 anon_vma_interval_tree_post_update_vma(vma);
2484                                 vma_gap_update(vma);
2485                                 spin_unlock(&mm->page_table_lock);
2486 
2487                                 perf_event_mmap(vma);
2488                         }
2489                 }
2490         }
2491         anon_vma_unlock_write(vma->anon_vma);
2492         khugepaged_enter_vma_merge(vma, vma->vm_flags);
2493         validate_mm(mm);
2494         return error;
2495 }
2496 
2497 /* enforced gap between the expanding stack and other mappings. */
2498 unsigned long stack_guard_gap = 256UL<<PAGE_SHIFT;
2499 
2500 static int __init cmdline_parse_stack_guard_gap(char *p)
2501 {
2502         unsigned long val;
2503         char *endptr;
2504 
2505         val = simple_strtoul(p, &endptr, 10);
2506         if (!*endptr)
2507                 stack_guard_gap = val << PAGE_SHIFT;
2508 
2509         return 0;
2510 }
2511 __setup("stack_guard_gap=", cmdline_parse_stack_guard_gap);
2512 
2513 #ifdef CONFIG_STACK_GROWSUP
2514 int expand_stack(struct vm_area_struct *vma, unsigned long address)
2515 {
2516         return expand_upwards(vma, address);
2517 }
2518 
2519 struct vm_area_struct *
2520 find_extend_vma(struct mm_struct *mm, unsigned long addr)
2521 {
2522         struct vm_area_struct *vma, *prev;
2523 
2524         addr &= PAGE_MASK;
2525         vma = find_vma_prev(mm, addr, &prev);
2526         if (vma && (vma->vm_start <= addr))
2527                 return vma;
2528         if (!prev || expand_stack(prev, addr))
2529                 return NULL;
2530         if (prev->vm_flags & VM_LOCKED)
2531                 populate_vma_page_range(prev, addr, prev->vm_end, NULL);
2532         return prev;
2533 }
2534 #else
2535 int expand_stack(struct vm_area_struct *vma, unsigned long address)
2536 {
2537         return expand_downwards(vma, address);
2538 }
2539 
2540 struct vm_area_struct *
2541 find_extend_vma(struct mm_struct *mm, unsigned long addr)
2542 {
2543         struct vm_area_struct *vma;
2544         unsigned long start;
2545 
2546         addr &= PAGE_MASK;
2547         vma = find_vma(mm, addr);
2548         if (!vma)
2549                 return NULL;
2550         if (vma->vm_start <= addr)
2551                 return vma;
2552         if (!(vma->vm_flags & VM_GROWSDOWN))
2553                 return NULL;
2554         start = vma->vm_start;
2555         if (expand_stack(vma, addr))
2556                 return NULL;
2557         if (vma->vm_flags & VM_LOCKED)
2558                 populate_vma_page_range(vma, addr, start, NULL);
2559         return vma;
2560 }
2561 #endif
2562 
2563 EXPORT_SYMBOL_GPL(find_extend_vma);
2564 
2565 /*
2566  * Ok - we have the memory areas we should free on the vma list,
2567  * so release them, and do the vma updates.
2568  *
2569  * Called with the mm semaphore held.
2570  */
2571 static void remove_vma_list(struct mm_struct *mm, struct vm_area_struct *vma)
2572 {
2573         unsigned long nr_accounted = 0;
2574 
2575         /* Update high watermark before we lower total_vm */
2576         update_hiwater_vm(mm);
2577         do {
2578                 long nrpages = vma_pages(vma);
2579 
2580                 if (vma->vm_flags & VM_ACCOUNT)
2581                         nr_accounted += nrpages;
2582                 vm_stat_account(mm, vma->vm_flags, -nrpages);
2583                 vma = remove_vma(vma);
2584         } while (vma);
2585         vm_unacct_memory(nr_accounted);
2586         validate_mm(mm);
2587 }
2588 
2589 /*
2590  * Get rid of page table information in the indicated region.
2591  *
2592  * Called with the mm semaphore held.
2593  */
2594 static void unmap_region(struct mm_struct *mm,
2595                 struct vm_area_struct *vma, struct vm_area_struct *prev,
2596                 unsigned long start, unsigned long end)
2597 {
2598         struct vm_area_struct *next = prev ? prev->vm_next : mm->mmap;
2599         struct mmu_gather tlb;
2600 
2601         lru_add_drain();
2602         tlb_gather_mmu(&tlb, mm, start, end);
2603         update_hiwater_rss(mm);
2604         unmap_vmas(&tlb, vma, start, end);
2605         free_pgtables(&tlb, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
2606                                  next ? next->vm_start : USER_PGTABLES_CEILING);
2607         tlb_finish_mmu(&tlb, start, end);
2608 }
2609 
2610 /*
2611  * Create a list of vma's touched by the unmap, removing them from the mm's
2612  * vma list as we go..
2613  */
2614 static void
2615 detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
2616         struct vm_area_struct *prev, unsigned long end)
2617 {
2618         struct vm_area_struct **insertion_point;
2619         struct vm_area_struct *tail_vma = NULL;
2620 
2621         insertion_point = (prev ? &prev->vm_next : &mm->mmap);
2622         vma->vm_prev = NULL;
2623         do {
2624                 vma_rb_erase(vma, &mm->mm_rb);
2625                 mm->map_count--;
2626                 tail_vma = vma;
2627                 vma = vma->vm_next;
2628         } while (vma && vma->vm_start < end);
2629         *insertion_point = vma;
2630         if (vma) {
2631                 vma->vm_prev = prev;
2632                 vma_gap_update(vma);
2633         } else
2634                 mm->highest_vm_end = prev ? vm_end_gap(prev) : 0;
2635         tail_vma->vm_next = NULL;
2636 
2637         /* Kill the cache */
2638         vmacache_invalidate(mm);
2639 }
2640 
2641 /*
2642  * __split_vma() bypasses sysctl_max_map_count checking.  We use this where it
2643  * has already been checked or doesn't make sense to fail.
2644  */
2645 int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
2646                 unsigned long addr, int new_below)
2647 {
2648         struct vm_area_struct *new;
2649         int err;
2650 
2651         if (vma->vm_ops && vma->vm_ops->split) {
2652                 err = vma->vm_ops->split(vma, addr);
2653                 if (err)
2654                         return err;
2655         }
2656 
2657         new = vm_area_dup(vma);
2658         if (!new)
2659                 return -ENOMEM;
2660 
2661         if (new_below)
2662                 new->vm_end = addr;
2663         else {
2664                 new->vm_start = addr;
2665                 new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
2666         }
2667 
2668         err = vma_dup_policy(vma, new);
2669         if (err)
2670                 goto out_free_vma;
2671 
2672         err = anon_vma_clone(new, vma);
2673         if (err)
2674                 goto out_free_mpol;
2675 
2676         if (new->vm_file)
2677                 get_file(new->vm_file);
2678 
2679         if (new->vm_ops && new->vm_ops->open)
2680                 new->vm_ops->open(new);
2681 
2682         if (new_below)
2683                 err = vma_adjust(vma, addr, vma->vm_end, vma->vm_pgoff +
2684                         ((addr - new->vm_start) >> PAGE_SHIFT), new);
2685         else
2686                 err = vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new);
2687 
2688         /* Success. */
2689         if (!err)
2690                 return 0;
2691 
2692         /* Clean everything up if vma_adjust failed. */
2693         if (new->vm_ops && new->vm_ops->close)
2694                 new->vm_ops->close(new);
2695         if (new->vm_file)
2696                 fput(new->vm_file);
2697         unlink_anon_vmas(new);
2698  out_free_mpol:
2699         mpol_put(vma_policy(new));
2700  out_free_vma:
2701         vm_area_free(new);
2702         return err;
2703 }
2704 
2705 /*
2706  * Split a vma into two pieces at address 'addr', a new vma is allocated
2707  * either for the first part or the tail.
2708  */
2709 int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
2710               unsigned long addr, int new_below)
2711 {
2712         if (mm->map_count >= sysctl_max_map_count)
2713                 return -ENOMEM;
2714 
2715         return __split_vma(mm, vma, addr, new_below);
2716 }
2717 
2718 /* Munmap is split into 2 main parts -- this part which finds
2719  * what needs doing, and the areas themselves, which do the
2720  * work.  This now handles partial unmappings.
2721  * Jeremy Fitzhardinge <jeremy@goop.org>
2722  */
2723 int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
2724                 struct list_head *uf, bool downgrade)
2725 {
2726         unsigned long end;
2727         struct vm_area_struct *vma, *prev, *last;
2728 
2729         if ((offset_in_page(start)) || start > TASK_SIZE || len > TASK_SIZE-start)
2730                 return -EINVAL;
2731 
2732         len = PAGE_ALIGN(len);
2733         if (len == 0)
2734                 return -EINVAL;
2735 
2736         /* Find the first overlapping VMA */
2737         vma = find_vma(mm, start);
2738         if (!vma)
2739                 return 0;
2740         prev = vma->vm_prev;
2741         /* we have  start < vma->vm_end  */
2742 
2743         /* if it doesn't overlap, we have nothing.. */
2744         end = start + len;
2745         if (vma->vm_start >= end)
2746                 return 0;
2747 
2748         /*
2749          * If we need to split any vma, do it now to save pain later.
2750          *
2751          * Note: mremap's move_vma VM_ACCOUNT handling assumes a partially
2752          * unmapped vm_area_struct will remain in use: so lower split_vma
2753          * places tmp vma above, and higher split_vma places tmp vma below.
2754          */
2755         if (start > vma->vm_start) {
2756                 int error;
2757 
2758                 /*
2759                  * Make sure that map_count on return from munmap() will
2760                  * not exceed its limit; but let map_count go just above
2761                  * its limit temporarily, to help free resources as expected.
2762                  */
2763                 if (end < vma->vm_end && mm->map_count >= sysctl_max_map_count)
2764                         return -ENOMEM;
2765 
2766                 error = __split_vma(mm, vma, start, 0);
2767                 if (error)
2768                         return error;
2769                 prev = vma;
2770         }
2771 
2772         /* Does it split the last one? */
2773         last = find_vma(mm, end);
2774         if (last && end > last->vm_start) {
2775                 int error = __split_vma(mm, last, end, 1);
2776                 if (error)
2777                         return error;
2778         }
2779         vma = prev ? prev->vm_next : mm->mmap;
2780 
2781         if (unlikely(uf)) {
2782                 /*
2783                  * If userfaultfd_unmap_prep returns an error the vmas
2784                  * will remain splitted, but userland will get a
2785                  * highly unexpected error anyway. This is no
2786                  * different than the case where the first of the two
2787                  * __split_vma fails, but we don't undo the first
2788                  * split, despite we could. This is unlikely enough
2789                  * failure that it's not worth optimizing it for.
2790                  */
2791                 int error = userfaultfd_unmap_prep(vma, start, end, uf);
2792                 if (error)
2793                         return error;
2794         }
2795 
2796         /*
2797          * unlock any mlock()ed ranges before detaching vmas
2798          */
2799         if (mm->locked_vm) {
2800                 struct vm_area_struct *tmp = vma;
2801                 while (tmp && tmp->vm_start < end) {
2802                         if (tmp->vm_flags & VM_LOCKED) {
2803                                 mm->locked_vm -= vma_pages(tmp);
2804                                 munlock_vma_pages_all(tmp);
2805                         }
2806 
2807                         tmp = tmp->vm_next;
2808                 }
2809         }
2810 
2811         /* Detach vmas from rbtree */
2812         detach_vmas_to_be_unmapped(mm, vma, prev, end);
2813 
2814         /*
2815          * mpx unmap needs to be called with mmap_sem held for write.
2816          * It is safe to call it before unmap_region().
2817          */
2818         arch_unmap(mm, vma, start, end);
2819 
2820         if (downgrade)
2821                 downgrade_write(&mm->mmap_sem);
2822 
2823         unmap_region(mm, vma, prev, start, end);
2824 
2825         /* Fix up all other VM information */
2826         remove_vma_list(mm, vma);
2827 
2828         return downgrade ? 1 : 0;
2829 }
2830 
2831 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
2832               struct list_head *uf)
2833 {
2834         return __do_munmap(mm, start, len, uf, false);
2835 }
2836 
2837 static int __vm_munmap(unsigned long start, size_t len, bool downgrade)
2838 {
2839         int ret;
2840         struct mm_struct *mm = current->mm;
2841         LIST_HEAD(uf);
2842 
2843         if (down_write_killable(&mm->mmap_sem))
2844                 return -EINTR;
2845 
2846         ret = __do_munmap(mm, start, len, &uf, downgrade);
2847         /*
2848          * Returning 1 indicates mmap_sem is downgraded.
2849          * But 1 is not legal return value of vm_munmap() and munmap(), reset
2850          * it to 0 before return.
2851          */
2852         if (ret == 1) {
2853                 up_read(&mm->mmap_sem);
2854                 ret = 0;
2855         } else
2856                 up_write(&mm->mmap_sem);
2857 
2858         userfaultfd_unmap_complete(mm, &uf);
2859         return ret;
2860 }
2861 
2862 int vm_munmap(unsigned long start, size_t len)
2863 {
2864         return __vm_munmap(start, len, false);
2865 }
2866 EXPORT_SYMBOL(vm_munmap);
2867 
2868 SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
2869 {
2870         profile_munmap(addr);
2871         return __vm_munmap(addr, len, true);
2872 }
2873 
2874 
2875 /*
2876  * Emulation of deprecated remap_file_pages() syscall.
2877  */
2878 SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
2879                 unsigned long, prot, unsigned long, pgoff, unsigned long, flags)
2880 {
2881 
2882         struct mm_struct *mm = current->mm;
2883         struct vm_area_struct *vma;
2884         unsigned long populate = 0;
2885         unsigned long ret = -EINVAL;
2886         struct file *file;
2887 
2888         pr_warn_once("%s (%d) uses deprecated remap_file_pages() syscall. See Documentation/vm/remap_file_pages.rst.\n",
2889                      current->comm, current->pid);
2890 
2891         if (prot)
2892                 return ret;
2893         start = start & PAGE_MASK;
2894         size = size & PAGE_MASK;
2895 
2896         if (start + size <= start)
2897                 return ret;
2898 
2899         /* Does pgoff wrap? */
2900         if (pgoff + (size >> PAGE_SHIFT) < pgoff)
2901                 return ret;
2902 
2903         if (down_write_killable(&mm->mmap_sem))
2904                 return -EINTR;
2905 
2906         vma = find_vma(mm, start);
2907 
2908         if (!vma || !(vma->vm_flags & VM_SHARED))
2909                 goto out;
2910 
2911         if (start < vma->vm_start)
2912                 goto out;
2913 
2914         if (start + size > vma->vm_end) {
2915                 struct vm_area_struct *next;
2916 
2917                 for (next = vma->vm_next; next; next = next->vm_next) {
2918                         /* hole between vmas ? */
2919                         if (next->vm_start != next->vm_prev->vm_end)
2920                                 goto out;
2921 
2922                         if (next->vm_file != vma->vm_file)
2923                                 goto out;
2924 
2925                         if (next->vm_flags != vma->vm_flags)
2926                                 goto out;
2927 
2928                         if (start + size <= next->vm_end)
2929                                 break;
2930                 }
2931 
2932                 if (!next)
2933                         goto out;
2934         }
2935 
2936         prot |= vma->vm_flags & VM_READ ? PROT_READ : 0;
2937         prot |= vma->vm_flags & VM_WRITE ? PROT_WRITE : 0;
2938         prot |= vma->vm_flags & VM_EXEC ? PROT_EXEC : 0;
2939 
2940         flags &= MAP_NONBLOCK;
2941         flags |= MAP_SHARED | MAP_FIXED | MAP_POPULATE;
2942         if (vma->vm_flags & VM_LOCKED) {
2943                 struct vm_area_struct *tmp;
2944                 flags |= MAP_LOCKED;
2945 
2946                 /* drop PG_Mlocked flag for over-mapped range */
2947                 for (tmp = vma; tmp->vm_start >= start + size;
2948                                 tmp = tmp->vm_next) {
2949                         /*
2950                          * Split pmd and munlock page on the border
2951                          * of the range.
2952                          */
2953                         vma_adjust_trans_huge(tmp, start, start + size, 0);
2954 
2955                         munlock_vma_pages_range(tmp,
2956                                         max(tmp->vm_start, start),
2957                                         min(tmp->vm_end, start + size));
2958                 }
2959         }
2960 
2961         file = get_file(vma->vm_file);
2962         ret = do_mmap_pgoff(vma->vm_file, start, size,
2963                         prot, flags, pgoff, &populate, NULL);
2964         fput(file);
2965 out:
2966         up_write(&mm->mmap_sem);
2967         if (populate)
2968                 mm_populate(ret, populate);
2969         if (!IS_ERR_VALUE(ret))
2970                 ret = 0;
2971         return ret;
2972 }
2973 
2974 /*
2975  *  this is really a simplified "do_mmap".  it only handles
2976  *  anonymous maps.  eventually we may be able to do some
2977  *  brk-specific accounting here.
2978  */
2979 static int do_brk_flags(unsigned long addr, unsigned long len, unsigned long flags, struct list_head *uf)
2980 {
2981         struct mm_struct *mm = current->mm;
2982         struct vm_area_struct *vma, *prev;
2983         struct rb_node **rb_link, *rb_parent;
2984         pgoff_t pgoff = addr >> PAGE_SHIFT;
2985         int error;
2986 
2987         /* Until we need other flags, refuse anything except VM_EXEC. */
2988         if ((flags & (~VM_EXEC)) != 0)
2989                 return -EINVAL;
2990         flags |= VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
2991 
2992         error = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
2993         if (offset_in_page(error))
2994                 return error;
2995 
2996         error = mlock_future_check(mm, mm->def_flags, len);
2997         if (error)
2998                 return error;
2999 
3000         /*
3001          * Clear old maps.  this also does some error checking for us
3002          */
3003         while (find_vma_links(mm, addr, addr + len, &prev, &rb_link,
3004                               &rb_parent)) {
3005                 if (do_munmap(mm, addr, len, uf))
3006                         return -ENOMEM;
3007         }
3008 
3009         /* Check against address space limits *after* clearing old maps... */
3010         if (!may_expand_vm(mm, flags, len >> PAGE_SHIFT))
3011                 return -ENOMEM;
3012 
3013         if (mm->map_count > sysctl_max_map_count)
3014                 return -ENOMEM;
3015 
3016         if (security_vm_enough_memory_mm(mm, len >> PAGE_SHIFT))
3017                 return -ENOMEM;
3018 
3019         /* Can we just expand an old private anonymous mapping? */
3020         vma = vma_merge(mm, prev, addr, addr + len, flags,
3021                         NULL, NULL, pgoff, NULL, NULL_VM_UFFD_CTX);
3022         if (vma)
3023                 goto out;
3024 
3025         /*
3026          * create a vma struct for an anonymous mapping
3027          */
3028         vma = vm_area_alloc(mm);
3029         if (!vma) {
3030                 vm_unacct_memory(len >> PAGE_SHIFT);
3031                 return -ENOMEM;
3032         }
3033 
3034         vma_set_anonymous(vma);
3035         vma->vm_start = addr;
3036         vma->vm_end = addr + len;
3037         vma->vm_pgoff = pgoff;
3038         vma->vm_flags = flags;
3039         vma->vm_page_prot = vm_get_page_prot(flags);
3040         vma_link(mm, vma, prev, rb_link, rb_parent);
3041 out:
3042         perf_event_mmap(vma);
3043         mm->total_vm += len >> PAGE_SHIFT;
3044         mm->data_vm += len >> PAGE_SHIFT;
3045         if (flags & VM_LOCKED)
3046                 mm->locked_vm += (len >> PAGE_SHIFT);
3047         vma->vm_flags |= VM_SOFTDIRTY;
3048         return 0;
3049 }
3050 
3051 int vm_brk_flags(unsigned long addr, unsigned long request, unsigned long flags)
3052 {
3053         struct mm_struct *mm = current->mm;
3054         unsigned long len;
3055         int ret;
3056         bool populate;
3057         LIST_HEAD(uf);
3058 
3059         len = PAGE_ALIGN(request);
3060         if (len < request)
3061                 return -ENOMEM;
3062         if (!len)
3063                 return 0;
3064 
3065         if (down_write_killable(&mm->mmap_sem))
3066                 return -EINTR;
3067 
3068         ret = do_brk_flags(addr, len, flags, &uf);
3069         populate = ((mm->def_flags & VM_LOCKED) != 0);
3070         up_write(&mm->mmap_sem);
3071         userfaultfd_unmap_complete(mm, &uf);
3072         if (populate && !ret)
3073                 mm_populate(addr, len);
3074         return ret;
3075 }
3076 EXPORT_SYMBOL(vm_brk_flags);
3077 
3078 int vm_brk(unsigned long addr, unsigned long len)
3079 {
3080         return vm_brk_flags(addr, len, 0);
3081 }
3082 EXPORT_SYMBOL(vm_brk);
3083 
3084 /* Release all mmaps. */
3085 void exit_mmap(struct mm_struct *mm)
3086 {
3087         struct mmu_gather tlb;
3088         struct vm_area_struct *vma;
3089         unsigned long nr_accounted = 0;
3090 
3091         /* mm's last user has gone, and its about to be pulled down */
3092         mmu_notifier_release(mm);
3093 
3094         if (unlikely(mm_is_oom_victim(mm))) {
3095                 /*
3096                  * Manually reap the mm to free as much memory as possible.
3097                  * Then, as the oom reaper does, set MMF_OOM_SKIP to disregard
3098                  * this mm from further consideration.  Taking mm->mmap_sem for
3099                  * write after setting MMF_OOM_SKIP will guarantee that the oom
3100                  * reaper will not run on this mm again after mmap_sem is
3101                  * dropped.
3102                  *
3103                  * Nothing can be holding mm->mmap_sem here and the above call
3104                  * to mmu_notifier_release(mm) ensures mmu notifier callbacks in
3105                  * __oom_reap_task_mm() will not block.
3106                  *
3107                  * This needs to be done before calling munlock_vma_pages_all(),
3108                  * which clears VM_LOCKED, otherwise the oom reaper cannot
3109                  * reliably test it.
3110                  */
3111                 (void)__oom_reap_task_mm(mm);
3112 
3113                 set_bit(MMF_OOM_SKIP, &mm->flags);
3114                 down_write(&mm->mmap_sem);
3115                 up_write(&mm->mmap_sem);
3116         }
3117 
3118         if (mm->locked_vm) {
3119                 vma = mm->mmap;
3120                 while (vma) {
3121                         if (vma->vm_flags & VM_LOCKED)
3122                                 munlock_vma_pages_all(vma);
3123                         vma = vma->vm_next;
3124                 }
3125         }
3126 
3127         arch_exit_mmap(mm);
3128 
3129         vma = mm->mmap;
3130         if (!vma)       /* Can happen if dup_mmap() received an OOM */
3131                 return;
3132 
3133         lru_add_drain();
3134         flush_cache_mm(mm);
3135         tlb_gather_mmu(&tlb, mm, 0, -1);
3136         /* update_hiwater_rss(mm) here? but nobody should be looking */
3137         /* Use -1 here to ensure all VMAs in the mm are unmapped */
3138         unmap_vmas(&tlb, vma, 0, -1);
3139         free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, USER_PGTABLES_CEILING);
3140         tlb_finish_mmu(&tlb, 0, -1);
3141 
3142         /*
3143          * Walk the list again, actually closing and freeing it,
3144          * with preemption enabled, without holding any MM locks.
3145          */
3146         while (vma) {
3147                 if (vma->vm_flags & VM_ACCOUNT)
3148                         nr_accounted += vma_pages(vma);
3149                 vma = remove_vma(vma);
3150         }
3151         vm_unacct_memory(nr_accounted);
3152 }
3153 
3154 /* Insert vm structure into process list sorted by address
3155  * and into the inode's i_mmap tree.  If vm_file is non-NULL
3156  * then i_mmap_rwsem is taken here.
3157  */
3158 int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
3159 {
3160         struct vm_area_struct *prev;
3161         struct rb_node **rb_link, *rb_parent;
3162 
3163         if (find_vma_links(mm, vma->vm_start, vma->vm_end,
3164                            &prev, &rb_link, &rb_parent))
3165                 return -ENOMEM;
3166         if ((vma->vm_flags & VM_ACCOUNT) &&
3167              security_vm_enough_memory_mm(mm, vma_pages(vma)))
3168                 return -ENOMEM;
3169 
3170         /*
3171          * The vm_pgoff of a purely anonymous vma should be irrelevant
3172          * until its first write fault, when page's anon_vma and index
3173          * are set.  But now set the vm_pgoff it will almost certainly
3174          * end up with (unless mremap moves it elsewhere before that
3175          * first wfault), so /proc/pid/maps tells a consistent story.
3176          *
3177          * By setting it to reflect the virtual start address of the
3178          * vma, merges and splits can happen in a seamless way, just
3179          * using the existing file pgoff checks and manipulations.
3180          * Similarly in do_mmap_pgoff and in do_brk.
3181          */
3182         if (vma_is_anonymous(vma)) {
3183                 BUG_ON(vma->anon_vma);
3184                 vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;
3185         }
3186 
3187         vma_link(mm, vma, prev, rb_link, rb_parent);
3188         return 0;
3189 }
3190 
3191 /*
3192  * Copy the vma structure to a new location in the same mm,
3193  * prior to moving page table entries, to effect an mremap move.
3194  */
3195 struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
3196         unsigned long addr, unsigned long len, pgoff_t pgoff,
3197         bool *need_rmap_locks)
3198 {
3199         struct vm_area_struct *vma = *vmap;
3200         unsigned long vma_start = vma->vm_start;
3201         struct mm_struct *mm = vma->vm_mm;
3202         struct vm_area_struct *new_vma, *prev;
3203         struct rb_node **rb_link, *rb_parent;
3204         bool faulted_in_anon_vma = true;
3205 
3206         /*
3207          * If anonymous vma has not yet been faulted, update new pgoff
3208          * to match new location, to increase its chance of merging.
3209          */
3210         if (unlikely(vma_is_anonymous(vma) && !vma->anon_vma)) {
3211                 pgoff = addr >> PAGE_SHIFT;
3212                 faulted_in_anon_vma = false;
3213         }
3214 
3215         if (find_vma_links(mm, addr, addr + len, &prev, &rb_link, &rb_parent))
3216                 return NULL;    /* should never get here */
3217         new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags,
3218                             vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
3219                             vma->vm_userfaultfd_ctx);
3220         if (new_vma) {
3221                 /*
3222                  * Source vma may have been merged into new_vma
3223                  */
3224                 if (unlikely(vma_start >= new_vma->vm_start &&
3225                              vma_start < new_vma->vm_end)) {
3226                         /*
3227                          * The only way we can get a vma_merge with
3228                          * self during an mremap is if the vma hasn't
3229                          * been faulted in yet and we were allowed to
3230                          * reset the dst vma->vm_pgoff to the
3231                          * destination address of the mremap to allow
3232                          * the merge to happen. mremap must change the
3233                          * vm_pgoff linearity between src and dst vmas
3234                          * (in turn preventing a vma_merge) to be
3235                          * safe. It is only safe to keep the vm_pgoff
3236                          * linear if there are no pages mapped yet.
3237                          */
3238                         VM_BUG_ON_VMA(faulted_in_anon_vma, new_vma);
3239                         *vmap = vma = new_vma;
3240                 }
3241                 *need_rmap_locks = (new_vma->vm_pgoff <= vma->vm_pgoff);
3242         } else {
3243                 new_vma = vm_area_dup(vma);
3244                 if (!new_vma)
3245                         goto out;
3246                 new_vma->vm_start = addr;
3247                 new_vma->vm_end = addr + len;
3248                 new_vma->vm_pgoff = pgoff;
3249                 if (vma_dup_policy(vma, new_vma))
3250                         goto out_free_vma;
3251                 if (anon_vma_clone(new_vma, vma))
3252                         goto out_free_mempol;
3253                 if (new_vma->vm_file)
3254                         get_file(new_vma->vm_file);
3255                 if (new_vma->vm_ops && new_vma->vm_ops->open)
3256                         new_vma->vm_ops->open(new_vma);
3257                 vma_link(mm, new_vma, prev, rb_link, rb_parent);
3258                 *need_rmap_locks = false;
3259         }
3260         return new_vma;
3261 
3262 out_free_mempol:
3263         mpol_put(vma_policy(new_vma));
3264 out_free_vma:
3265         vm_area_free(new_vma);
3266 out:
3267         return NULL;
3268 }
3269 
3270 /*
3271  * Return true if the calling process may expand its vm space by the passed
3272  * number of pages
3273  */
3274 bool may_expand_vm(struct mm_struct *mm, vm_flags_t flags, unsigned long npages)
3275 {
3276         if (mm->total_vm + npages > rlimit(RLIMIT_AS) >> PAGE_SHIFT)
3277                 return false;
3278 
3279         if (is_data_mapping(flags) &&
3280             mm->data_vm + npages > rlimit(RLIMIT_DATA) >> PAGE_SHIFT) {
3281                 /* Workaround for Valgrind */
3282                 if (rlimit(RLIMIT_DATA) == 0 &&
3283                     mm->data_vm + npages <= rlimit_max(RLIMIT_DATA) >> PAGE_SHIFT)
3284                         return true;
3285 
3286                 pr_warn_once("%s (%d): VmData %lu exceed data ulimit %lu. Update limits%s.\n",
3287                              current->comm, current->pid,
3288                              (mm->data_vm + npages) << PAGE_SHIFT,
3289                              rlimit(RLIMIT_DATA),
3290                              ignore_rlimit_data ? "" : " or use boot option ignore_rlimit_data");
3291 
3292                 if (!ignore_rlimit_data)
3293                         return false;
3294         }
3295 
3296         return true;
3297 }
3298 
3299 void vm_stat_account(struct mm_struct *mm, vm_flags_t flags, long npages)
3300 {
3301         mm->total_vm += npages;
3302 
3303         if (is_exec_mapping(flags))
3304                 mm->exec_vm += npages;
3305         else if (is_stack_mapping(flags))
3306                 mm->stack_vm += npages;
3307         else if (is_data_mapping(flags))
3308                 mm->data_vm += npages;
3309 }
3310 
3311 static vm_fault_t special_mapping_fault(struct vm_fault *vmf);
3312 
3313 /*
3314  * Having a close hook prevents vma merging regardless of flags.
3315  */
3316 static void special_mapping_close(struct vm_area_struct *vma)
3317 {
3318 }
3319 
3320 static const char *special_mapping_name(struct vm_area_struct *vma)
3321 {
3322         return ((struct vm_special_mapping *)vma->vm_private_data)->name;
3323 }
3324 
3325 static int special_mapping_mremap(struct vm_area_struct *new_vma)
3326 {
3327         struct vm_special_mapping *sm = new_vma->vm_private_data;
3328 
3329         if (WARN_ON_ONCE(current->mm != new_vma->vm_mm))
3330                 return -EFAULT;
3331 
3332         if (sm->mremap)
3333                 return sm->mremap(sm, new_vma);
3334 
3335         return 0;
3336 }
3337 
3338 static const struct vm_operations_struct special_mapping_vmops = {
3339         .close = special_mapping_close,
3340         .fault = special_mapping_fault,
3341         .mremap = special_mapping_mremap,
3342         .name = special_mapping_name,
3343 };
3344 
3345 static const struct vm_operations_struct legacy_special_mapping_vmops = {
3346         .close = special_mapping_close,
3347         .fault = special_mapping_fault,
3348 };
3349 
3350 static vm_fault_t special_mapping_fault(struct vm_fault *vmf)
3351 {
3352         struct vm_area_struct *vma = vmf->vma;
3353         pgoff_t pgoff;
3354         struct page **pages;
3355 
3356         if (vma->vm_ops == &legacy_special_mapping_vmops) {
3357                 pages = vma->vm_private_data;
3358         } else {
3359                 struct vm_special_mapping *sm = vma->vm_private_data;
3360 
3361                 if (sm->fault)
3362                         return sm->fault(sm, vmf->vma, vmf);
3363 
3364                 pages = sm->pages;
3365         }
3366 
3367         for (pgoff = vmf->pgoff; pgoff && *pages; ++pages)
3368                 pgoff--;
3369 
3370         if (*pages) {
3371                 struct page *page = *pages;
3372                 get_page(page);
3373                 vmf->page = page;
3374                 return 0;
3375         }
3376 
3377         return VM_FAULT_SIGBUS;
3378 }
3379 
3380 static struct vm_area_struct *__install_special_mapping(
3381         struct mm_struct *mm,
3382         unsigned long addr, unsigned long len,
3383         unsigned long vm_flags, void *priv,
3384         const struct vm_operations_struct *ops)
3385 {
3386         int ret;
3387         struct vm_area_struct *vma;
3388 
3389         vma = vm_area_alloc(mm);
3390         if (unlikely(vma == NULL))
3391                 return ERR_PTR(-ENOMEM);
3392 
3393         vma->vm_start = addr;
3394         vma->vm_end = addr + len;
3395 
3396         vma->vm_flags = vm_flags | mm->def_flags | VM_DONTEXPAND | VM_SOFTDIRTY;
3397         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
3398 
3399         vma->vm_ops = ops;
3400         vma->vm_private_data = priv;
3401 
3402         ret = insert_vm_struct(mm, vma);
3403         if (ret)
3404                 goto out;
3405 
3406         vm_stat_account(mm, vma->vm_flags, len >> PAGE_SHIFT);
3407 
3408         perf_event_mmap(vma);
3409 
3410         return vma;
3411 
3412 out:
3413         vm_area_free(vma);
3414         return ERR_PTR(ret);
3415 }
3416 
3417 bool vma_is_special_mapping(const struct vm_area_struct *vma,
3418         const struct vm_special_mapping *sm)
3419 {
3420         return vma->vm_private_data == sm &&
3421                 (vma->vm_ops == &special_mapping_vmops ||
3422                  vma->vm_ops == &legacy_special_mapping_vmops);
3423 }
3424 
3425 /*
3426  * Called with mm->mmap_sem held for writing.
3427  * Insert a new vma covering the given region, with the given flags.
3428  * Its pages are supplied by the given array of struct page *.
3429  * The array can be shorter than len >> PAGE_SHIFT if it's null-terminated.
3430  * The region past the last page supplied will always produce SIGBUS.
3431  * The array pointer and the pages it points to are assumed to stay alive
3432  * for as long as this mapping might exist.
3433  */
3434 struct vm_area_struct *_install_special_mapping(
3435         struct mm_struct *mm,
3436         unsigned long addr, unsigned long len,
3437         unsigned long vm_flags, const struct vm_special_mapping *spec)
3438 {
3439         return __install_special_mapping(mm, addr, len, vm_flags, (void *)spec,
3440                                         &special_mapping_vmops);
3441 }
3442 
3443 int install_special_mapping(struct mm_struct *mm,
3444                             unsigned long addr, unsigned long len,
3445                             unsigned long vm_flags, struct page **pages)
3446 {
3447         struct vm_area_struct *vma = __install_special_mapping(
3448                 mm, addr, len, vm_flags, (void *)pages,
3449                 &legacy_special_mapping_vmops);
3450 
3451         return PTR_ERR_OR_ZERO(vma);
3452 }
3453 
3454 static DEFINE_MUTEX(mm_all_locks_mutex);
3455 
3456 static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma)
3457 {
3458         if (!test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_root.rb_node)) {
3459                 /*
3460                  * The LSB of head.next can't change from under us
3461                  * because we hold the mm_all_locks_mutex.
3462                  */
3463                 down_write_nest_lock(&anon_vma->root->rwsem, &mm->mmap_sem);
3464                 /*
3465                  * We can safely modify head.next after taking the
3466                  * anon_vma->root->rwsem. If some other vma in this mm shares
3467                  * the same anon_vma we won't take it again.
3468                  *
3469                  * No need of atomic instructions here, head.next
3470                  * can't change from under us thanks to the
3471                  * anon_vma->root->rwsem.
3472                  */
3473                 if (__test_and_set_bit(0, (unsigned long *)
3474                                        &anon_vma->root->rb_root.rb_root.rb_node))
3475                         BUG();
3476         }
3477 }
3478 
3479 static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping)
3480 {
3481         if (!test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
3482                 /*
3483                  * AS_MM_ALL_LOCKS can't change from under us because
3484                  * we hold the mm_all_locks_mutex.
3485                  *
3486                  * Operations on ->flags have to be atomic because
3487                  * even if AS_MM_ALL_LOCKS is stable thanks to the
3488                  * mm_all_locks_mutex, there may be other cpus
3489                  * changing other bitflags in parallel to us.
3490                  */
3491                 if (test_and_set_bit(AS_MM_ALL_LOCKS, &mapping->flags))
3492                         BUG();
3493                 down_write_nest_lock(&mapping->i_mmap_rwsem, &mm->mmap_sem);
3494         }
3495 }
3496 
3497 /*
3498  * This operation locks against the VM for all pte/vma/mm related
3499  * operations that could ever happen on a certain mm. This includes
3500  * vmtruncate, try_to_unmap, and all page faults.
3501  *
3502  * The caller must take the mmap_sem in write mode before calling
3503  * mm_take_all_locks(). The caller isn't allowed to release the
3504  * mmap_sem until mm_drop_all_locks() returns.
3505  *
3506  * mmap_sem in write mode is required in order to block all operations
3507  * that could modify pagetables and free pages without need of
3508  * altering the vma layout. It's also needed in write mode to avoid new
3509  * anon_vmas to be associated with existing vmas.
3510  *
3511  * A single task can't take more than one mm_take_all_locks() in a row
3512  * or it would deadlock.
3513  *
3514  * The LSB in anon_vma->rb_root.rb_node and the AS_MM_ALL_LOCKS bitflag in
3515  * mapping->flags avoid to take the same lock twice, if more than one
3516  * vma in this mm is backed by the same anon_vma or address_space.
3517  *
3518  * We take locks in following order, accordingly to comment at beginning
3519  * of mm/rmap.c:
3520  *   - all hugetlbfs_i_mmap_rwsem_key locks (aka mapping->i_mmap_rwsem for
3521  *     hugetlb mapping);
3522  *   - all i_mmap_rwsem locks;
3523  *   - all anon_vma->rwseml
3524  *
3525  * We can take all locks within these types randomly because the VM code
3526  * doesn't nest them and we protected from parallel mm_take_all_locks() by
3527  * mm_all_locks_mutex.
3528  *
3529  * mm_take_all_locks() and mm_drop_all_locks are expensive operations
3530  * that may have to take thousand of locks.
3531  *
3532  * mm_take_all_locks() can fail if it's interrupted by signals.
3533  */
3534 int mm_take_all_locks(struct mm_struct *mm)
3535 {
3536         struct vm_area_struct *vma;
3537         struct anon_vma_chain *avc;
3538 
3539         BUG_ON(down_read_trylock(&mm->mmap_sem));
3540 
3541         mutex_lock(&mm_all_locks_mutex);
3542 
3543         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3544                 if (signal_pending(current))
3545                         goto out_unlock;
3546                 if (vma->vm_file && vma->vm_file->f_mapping &&
3547                                 is_vm_hugetlb_page(vma))
3548                         vm_lock_mapping(mm, vma->vm_file->f_mapping);
3549         }
3550 
3551         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3552                 if (signal_pending(current))
3553                         goto out_unlock;
3554                 if (vma->vm_file && vma->vm_file->f_mapping &&
3555                                 !is_vm_hugetlb_page(vma))
3556                         vm_lock_mapping(mm, vma->vm_file->f_mapping);
3557         }
3558 
3559         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3560                 if (signal_pending(current))
3561                         goto out_unlock;
3562                 if (vma->anon_vma)
3563                         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
3564                                 vm_lock_anon_vma(mm, avc->anon_vma);
3565         }
3566 
3567         return 0;
3568 
3569 out_unlock:
3570         mm_drop_all_locks(mm);
3571         return -EINTR;
3572 }
3573 
3574 static void vm_unlock_anon_vma(struct anon_vma *anon_vma)
3575 {
3576         if (test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_root.rb_node)) {
3577                 /*
3578                  * The LSB of head.next can't change to 0 from under
3579                  * us because we hold the mm_all_locks_mutex.
3580                  *
3581                  * We must however clear the bitflag before unlocking
3582                  * the vma so the users using the anon_vma->rb_root will
3583                  * never see our bitflag.
3584                  *
3585                  * No need of atomic instructions here, head.next
3586                  * can't change from under us until we release the
3587                  * anon_vma->root->rwsem.
3588                  */
3589                 if (!__test_and_clear_bit(0, (unsigned long *)
3590                                           &anon_vma->root->rb_root.rb_root.rb_node))
3591                         BUG();
3592                 anon_vma_unlock_write(anon_vma);
3593         }
3594 }
3595 
3596 static void vm_unlock_mapping(struct address_space *mapping)
3597 {
3598         if (test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
3599                 /*
3600                  * AS_MM_ALL_LOCKS can't change to 0 from under us
3601                  * because we hold the mm_all_locks_mutex.
3602                  */
3603                 i_mmap_unlock_write(mapping);
3604                 if (!test_and_clear_bit(AS_MM_ALL_LOCKS,
3605                                         &mapping->flags))
3606                         BUG();
3607         }
3608 }
3609 
3610 /*
3611  * The mmap_sem cannot be released by the caller until
3612  * mm_drop_all_locks() returns.
3613  */
3614 void mm_drop_all_locks(struct mm_struct *mm)
3615 {
3616         struct vm_area_struct *vma;
3617         struct anon_vma_chain *avc;
3618 
3619         BUG_ON(down_read_trylock(&mm->mmap_sem));
3620         BUG_ON(!mutex_is_locked(&mm_all_locks_mutex));
3621 
3622         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3623                 if (vma->anon_vma)
3624                         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
3625                                 vm_unlock_anon_vma(avc->anon_vma);
3626                 if (vma->vm_file && vma->vm_file->f_mapping)
3627                         vm_unlock_mapping(vma->vm_file->f_mapping);
3628         }
3629 
3630         mutex_unlock(&mm_all_locks_mutex);
3631 }
3632 
3633 /*
3634  * initialise the percpu counter for VM
3635  */
3636 void __init mmap_init(void)
3637 {
3638         int ret;
3639 
3640         ret = percpu_counter_init(&vm_committed_as, 0, GFP_KERNEL);
3641         VM_BUG_ON(ret);
3642 }
3643 
3644 /*
3645  * Initialise sysctl_user_reserve_kbytes.
3646  *
3647  * This is intended to prevent a user from starting a single memory hogging
3648  * process, such that they cannot recover (kill the hog) in OVERCOMMIT_NEVER
3649  * mode.
3650  *
3651  * The default value is min(3% of free memory, 128MB)
3652  * 128MB is enough to recover with sshd/login, bash, and top/kill.
3653  */
3654 static int init_user_reserve(void)
3655 {
3656         unsigned long free_kbytes;
3657 
3658         free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
3659 
3660         sysctl_user_reserve_kbytes = min(free_kbytes / 32, 1UL << 17);
3661         return 0;
3662 }
3663 subsys_initcall(init_user_reserve);
3664 
3665 /*
3666  * Initialise sysctl_admin_reserve_kbytes.
3667  *
3668  * The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin
3669  * to log in and kill a memory hogging process.
3670  *
3671  * Systems with more than 256MB will reserve 8MB, enough to recover
3672  * with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will
3673  * only reserve 3% of free pages by default.
3674  */
3675 static int init_admin_reserve(void)
3676 {
3677         unsigned long free_kbytes;
3678 
3679         free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
3680 
3681         sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13);
3682         return 0;
3683 }
3684 subsys_initcall(init_admin_reserve);
3685 
3686 /*
3687  * Reinititalise user and admin reserves if memory is added or removed.
3688  *
3689  * The default user reserve max is 128MB, and the default max for the
3690  * admin reserve is 8MB. These are usually, but not always, enough to
3691  * enable recovery from a memory hogging process using login/sshd, a shell,
3692  * and tools like top. It may make sense to increase or even disable the
3693  * reserve depending on the existence of swap or variations in the recovery
3694  * tools. So, the admin may have changed them.
3695  *
3696  * If memory is added and the reserves have been eliminated or increased above
3697  * the default max, then we'll trust the admin.
3698  *
3699  * If memory is removed and there isn't enough free memory, then we
3700  * need to reset the reserves.
3701  *
3702  * Otherwise keep the reserve set by the admin.
3703  */
3704 static int reserve_mem_notifier(struct notifier_block *nb,
3705                              unsigned long action, void *data)
3706 {
3707         unsigned long tmp, free_kbytes;
3708 
3709         switch (action) {
3710         case MEM_ONLINE:
3711                 /* Default max is 128MB. Leave alone if modified by operator. */
3712                 tmp = sysctl_user_reserve_kbytes;
3713                 if (0 < tmp && tmp < (1UL << 17))
3714                         init_user_reserve();
3715 
3716                 /* Default max is 8MB.  Leave alone if modified by operator. */
3717                 tmp = sysctl_admin_reserve_kbytes;
3718                 if (0 < tmp && tmp < (1UL << 13))
3719                         init_admin_reserve();
3720 
3721                 break;
3722         case MEM_OFFLINE:
3723                 free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
3724 
3725                 if (sysctl_user_reserve_kbytes > free_kbytes) {
3726                         init_user_reserve();
3727                         pr_info("vm.user_reserve_kbytes reset to %lu\n",
3728                                 sysctl_user_reserve_kbytes);
3729                 }
3730 
3731                 if (sysctl_admin_reserve_kbytes > free_kbytes) {
3732                         init_admin_reserve();
3733                         pr_info("vm.admin_reserve_kbytes reset to %lu\n",
3734                                 sysctl_admin_reserve_kbytes);
3735                 }
3736                 break;
3737         default:
3738                 break;
3739         }
3740         return NOTIFY_OK;
3741 }
3742 
3743 static struct notifier_block reserve_mem_nb = {
3744         .notifier_call = reserve_mem_notifier,
3745 };
3746 
3747 static int __meminit init_reserve_notifier(void)
3748 {
3749         if (register_hotmemory_notifier(&reserve_mem_nb))
3750                 pr_err("Failed registering memory add/remove notifier for admin reserve\n");
3751 
3752         return 0;
3753 }
3754 subsys_initcall(init_reserve_notifier);
3755 

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