mm/mmap.c

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This source file includes following definitions.
arch_filter_pgprot
vm_get_page_prot
vm_pgprot_modify
vma_set_page_prot
__remove_shared_vm_struct
unlink_file_vma
remove_vma
SYSCALL_DEFINE1
vma_compute_gap
vma_compute_subtree_gap
browse_rb
validate_mm_rb
validate_mm
RB_DECLARE_CALLBACKS_MAX
vma_rb_insert
__vma_rb_erase
vma_rb_erase_ignore
vma_rb_erase
anon_vma_interval_tree_pre_update_vma
anon_vma_interval_tree_post_update_vma
find_vma_links
count_vma_pages_range
__vma_link_rb
__vma_link_file
__vma_link
vma_link
__insert_vm_struct
__vma_unlink_common
__vma_unlink_prev
__vma_adjust
is_mergeable_vma
is_mergeable_anon_vma
can_vma_merge_before
can_vma_merge_after
vma_merge
anon_vma_compatible
reusable_anon_vma
find_mergeable_anon_vma
round_hint_to_min
mlock_future_check
file_mmap_size_max
file_mmap_ok
do_mmap
ksys_mmap_pgoff
SYSCALL_DEFINE6
SYSCALL_DEFINE1
vma_wants_writenotify
accountable_mapping
mmap_region
unmapped_area
unmapped_area_topdown
arch_get_unmapped_area
arch_get_unmapped_area_topdown
get_unmapped_area
find_vma
find_vma_prev
acct_stack_growth
expand_upwards
expand_downwards
cmdline_parse_stack_guard_gap
expand_stack
find_extend_vma
expand_stack
find_extend_vma
remove_vma_list
unmap_region
detach_vmas_to_be_unmapped
__split_vma
split_vma
__do_munmap
do_munmap
__vm_munmap
vm_munmap
SYSCALL_DEFINE2
SYSCALL_DEFINE5
do_brk_flags
vm_brk_flags
vm_brk
exit_mmap
insert_vm_struct
copy_vma
may_expand_vm
vm_stat_account
special_mapping_close
special_mapping_name
special_mapping_mremap
special_mapping_fault
__install_special_mapping
vma_is_special_mapping
_install_special_mapping
install_special_mapping
vm_lock_anon_vma
vm_lock_mapping
mm_take_all_locks
vm_unlock_anon_vma
vm_unlock_mapping
mm_drop_all_locks
mmap_init
init_user_reserve
init_admin_reserve
reserve_mem_notifier
init_reserve_notifier
   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * mm/mmap.c
   4  *
   5  * Written by obz.
   6  *
   7  * Address space accounting code        <alan@lxorguk.ukuu.org.uk>
   8  */
   9 
  10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  11 
  12 #include <linux/kernel.h>
  13 #include <linux/slab.h>
  14 #include <linux/backing-dev.h>
  15 #include <linux/mm.h>
  16 #include <linux/vmacache.h>
  17 #include <linux/shm.h>
  18 #include <linux/mman.h>
  19 #include <linux/pagemap.h>
  20 #include <linux/swap.h>
  21 #include <linux/syscalls.h>
  22 #include <linux/capability.h>
  23 #include <linux/init.h>
  24 #include <linux/file.h>
  25 #include <linux/fs.h>
  26 #include <linux/personality.h>
  27 #include <linux/security.h>
  28 #include <linux/hugetlb.h>
  29 #include <linux/shmem_fs.h>
  30 #include <linux/profile.h>
  31 #include <linux/export.h>
  32 #include <linux/mount.h>
  33 #include <linux/mempolicy.h>
  34 #include <linux/rmap.h>
  35 #include <linux/mmu_notifier.h>
  36 #include <linux/mmdebug.h>
  37 #include <linux/perf_event.h>
  38 #include <linux/audit.h>
  39 #include <linux/khugepaged.h>
  40 #include <linux/uprobes.h>
  41 #include <linux/rbtree_augmented.h>
  42 #include <linux/notifier.h>
  43 #include <linux/memory.h>
  44 #include <linux/printk.h>
  45 #include <linux/userfaultfd_k.h>
  46 #include <linux/moduleparam.h>
  47 #include <linux/pkeys.h>
  48 #include <linux/oom.h>
  49 #include <linux/sched/mm.h>
  50 
  51 #include <linux/uaccess.h>
  52 #include <asm/cacheflush.h>
  53 #include <asm/tlb.h>
  54 #include <asm/mmu_context.h>
  55 
  56 #include "internal.h"
  57 
  58 #ifndef arch_mmap_check
  59 #define arch_mmap_check(addr, len, flags)       (0)
  60 #endif
  61 
  62 #ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS
  63 const int mmap_rnd_bits_min = CONFIG_ARCH_MMAP_RND_BITS_MIN;
  64 const int mmap_rnd_bits_max = CONFIG_ARCH_MMAP_RND_BITS_MAX;
  65 int mmap_rnd_bits __read_mostly = CONFIG_ARCH_MMAP_RND_BITS;
  66 #endif
  67 #ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
  68 const int mmap_rnd_compat_bits_min = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MIN;
  69 const int mmap_rnd_compat_bits_max = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MAX;
  70 int mmap_rnd_compat_bits __read_mostly = CONFIG_ARCH_MMAP_RND_COMPAT_BITS;
  71 #endif
  72 
  73 static bool ignore_rlimit_data;
  74 core_param(ignore_rlimit_data, ignore_rlimit_data, bool, 0644);
  75 
  76 static void unmap_region(struct mm_struct *mm,
  77                 struct vm_area_struct *vma, struct vm_area_struct *prev,
  78                 unsigned long start, unsigned long end);
  79 
  80 /* description of effects of mapping type and prot in current implementation.
  81  * this is due to the limited x86 page protection hardware.  The expected
  82  * behavior is in parens:
  83  *
  84  * map_type     prot
  85  *              PROT_NONE       PROT_READ       PROT_WRITE      PROT_EXEC
  86  * MAP_SHARED   r: (no) no      r: (yes) yes    r: (no) yes     r: (no) yes
  87  *              w: (no) no      w: (no) no      w: (yes) yes    w: (no) no
  88  *              x: (no) no      x: (no) yes     x: (no) yes     x: (yes) yes
  89  *
  90  * MAP_PRIVATE  r: (no) no      r: (yes) yes    r: (no) yes     r: (no) yes
  91  *              w: (no) no      w: (no) no      w: (copy) copy  w: (no) no
  92  *              x: (no) no      x: (no) yes     x: (no) yes     x: (yes) yes
  93  */
  94 pgprot_t protection_map[16] __ro_after_init = {
  95         __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
  96         __S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
  97 };
  98 
  99 #ifndef CONFIG_ARCH_HAS_FILTER_PGPROT
 100 static inline pgprot_t arch_filter_pgprot(pgprot_t prot)
 101 {
 102         return prot;
 103 }
 104 #endif
 105 
 106 pgprot_t vm_get_page_prot(unsigned long vm_flags)
 107 {
 108         pgprot_t ret = __pgprot(pgprot_val(protection_map[vm_flags &
 109                                 (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
 110                         pgprot_val(arch_vm_get_page_prot(vm_flags)));
 111 
 112         return arch_filter_pgprot(ret);
 113 }
 114 EXPORT_SYMBOL(vm_get_page_prot);
 115 
 116 static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags)
 117 {
 118         return pgprot_modify(oldprot, vm_get_page_prot(vm_flags));
 119 }
 120 
 121 /* Update vma->vm_page_prot to reflect vma->vm_flags. */
 122 void vma_set_page_prot(struct vm_area_struct *vma)
 123 {
 124         unsigned long vm_flags = vma->vm_flags;
 125         pgprot_t vm_page_prot;
 126 
 127         vm_page_prot = vm_pgprot_modify(vma->vm_page_prot, vm_flags);
 128         if (vma_wants_writenotify(vma, vm_page_prot)) {
 129                 vm_flags &= ~VM_SHARED;
 130                 vm_page_prot = vm_pgprot_modify(vm_page_prot, vm_flags);
 131         }
 132         /* remove_protection_ptes reads vma->vm_page_prot without mmap_sem */
 133         WRITE_ONCE(vma->vm_page_prot, vm_page_prot);
 134 }
 135 
 136 /*
 137  * Requires inode->i_mapping->i_mmap_rwsem
 138  */
 139 static void __remove_shared_vm_struct(struct vm_area_struct *vma,
 140                 struct file *file, struct address_space *mapping)
 141 {
 142         if (vma->vm_flags & VM_DENYWRITE)
 143                 atomic_inc(&file_inode(file)->i_writecount);
 144         if (vma->vm_flags & VM_SHARED)
 145                 mapping_unmap_writable(mapping);
 146 
 147         flush_dcache_mmap_lock(mapping);
 148         vma_interval_tree_remove(vma, &mapping->i_mmap);
 149         flush_dcache_mmap_unlock(mapping);
 150 }
 151 
 152 /*
 153  * Unlink a file-based vm structure from its interval tree, to hide
 154  * vma from rmap and vmtruncate before freeing its page tables.
 155  */
 156 void unlink_file_vma(struct vm_area_struct *vma)
 157 {
 158         struct file *file = vma->vm_file;
 159 
 160         if (file) {
 161                 struct address_space *mapping = file->f_mapping;
 162                 i_mmap_lock_write(mapping);
 163                 __remove_shared_vm_struct(vma, file, mapping);
 164                 i_mmap_unlock_write(mapping);
 165         }
 166 }
 167 
 168 /*
 169  * Close a vm structure and free it, returning the next.
 170  */
 171 static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
 172 {
 173         struct vm_area_struct *next = vma->vm_next;
 174 
 175         might_sleep();
 176         if (vma->vm_ops && vma->vm_ops->close)
 177                 vma->vm_ops->close(vma);
 178         if (vma->vm_file)
 179                 fput(vma->vm_file);
 180         mpol_put(vma_policy(vma));
 181         vm_area_free(vma);
 182         return next;
 183 }
 184 
 185 static int do_brk_flags(unsigned long addr, unsigned long request, unsigned long flags,
 186                 struct list_head *uf);
 187 SYSCALL_DEFINE1(brk, unsigned long, brk)
 188 {
 189         unsigned long retval;
 190         unsigned long newbrk, oldbrk, origbrk;
 191         struct mm_struct *mm = current->mm;
 192         struct vm_area_struct *next;
 193         unsigned long min_brk;
 194         bool populate;
 195         bool downgraded = false;
 196         LIST_HEAD(uf);
 197 
 198         if (down_write_killable(&mm->mmap_sem))
 199                 return -EINTR;
 200 
 201         origbrk = mm->brk;
 202 
 203 #ifdef CONFIG_COMPAT_BRK
 204         /*
 205          * CONFIG_COMPAT_BRK can still be overridden by setting
 206          * randomize_va_space to 2, which will still cause mm->start_brk
 207          * to be arbitrarily shifted
 208          */
 209         if (current->brk_randomized)
 210                 min_brk = mm->start_brk;
 211         else
 212                 min_brk = mm->end_data;
 213 #else
 214         min_brk = mm->start_brk;
 215 #endif
 216         if (brk < min_brk)
 217                 goto out;
 218 
 219         /*
 220          * Check against rlimit here. If this check is done later after the test
 221          * of oldbrk with newbrk then it can escape the test and let the data
 222          * segment grow beyond its set limit the in case where the limit is
 223          * not page aligned -Ram Gupta
 224          */
 225         if (check_data_rlimit(rlimit(RLIMIT_DATA), brk, mm->start_brk,
 226                               mm->end_data, mm->start_data))
 227                 goto out;
 228 
 229         newbrk = PAGE_ALIGN(brk);
 230         oldbrk = PAGE_ALIGN(mm->brk);
 231         if (oldbrk == newbrk) {
 232                 mm->brk = brk;
 233                 goto success;
 234         }
 235 
 236         /*
 237          * Always allow shrinking brk.
 238          * __do_munmap() may downgrade mmap_sem to read.
 239          */
 240         if (brk <= mm->brk) {
 241                 int ret;
 242 
 243                 /*
 244                  * mm->brk must to be protected by write mmap_sem so update it
 245                  * before downgrading mmap_sem. When __do_munmap() fails,
 246                  * mm->brk will be restored from origbrk.
 247                  */
 248                 mm->brk = brk;
 249                 ret = __do_munmap(mm, newbrk, oldbrk-newbrk, &uf, true);
 250                 if (ret < 0) {
 251                         mm->brk = origbrk;
 252                         goto out;
 253                 } else if (ret == 1) {
 254                         downgraded = true;
 255                 }
 256                 goto success;
 257         }
 258 
 259         /* Check against existing mmap mappings. */
 260         next = find_vma(mm, oldbrk);
 261         if (next && newbrk + PAGE_SIZE > vm_start_gap(next))
 262                 goto out;
 263 
 264         /* Ok, looks good - let it rip. */
 265         if (do_brk_flags(oldbrk, newbrk-oldbrk, 0, &uf) < 0)
 266                 goto out;
 267         mm->brk = brk;
 268 
 269 success:
 270         populate = newbrk > oldbrk && (mm->def_flags & VM_LOCKED) != 0;
 271         if (downgraded)
 272                 up_read(&mm->mmap_sem);
 273         else
 274                 up_write(&mm->mmap_sem);
 275         userfaultfd_unmap_complete(mm, &uf);
 276         if (populate)
 277                 mm_populate(oldbrk, newbrk - oldbrk);
 278         return brk;
 279 
 280 out:
 281         retval = origbrk;
 282         up_write(&mm->mmap_sem);
 283         return retval;
 284 }
 285 
 286 static inline unsigned long vma_compute_gap(struct vm_area_struct *vma)
 287 {
 288         unsigned long gap, prev_end;
 289 
 290         /*
 291          * Note: in the rare case of a VM_GROWSDOWN above a VM_GROWSUP, we
 292          * allow two stack_guard_gaps between them here, and when choosing
 293          * an unmapped area; whereas when expanding we only require one.
 294          * That's a little inconsistent, but keeps the code here simpler.
 295          */
 296         gap = vm_start_gap(vma);
 297         if (vma->vm_prev) {
 298                 prev_end = vm_end_gap(vma->vm_prev);
 299                 if (gap > prev_end)
 300                         gap -= prev_end;
 301                 else
 302                         gap = 0;
 303         }
 304         return gap;
 305 }
 306 
 307 #ifdef CONFIG_DEBUG_VM_RB
 308 static unsigned long vma_compute_subtree_gap(struct vm_area_struct *vma)
 309 {
 310         unsigned long max = vma_compute_gap(vma), subtree_gap;
 311         if (vma->vm_rb.rb_left) {
 312                 subtree_gap = rb_entry(vma->vm_rb.rb_left,
 313                                 struct vm_area_struct, vm_rb)->rb_subtree_gap;
 314                 if (subtree_gap > max)
 315                         max = subtree_gap;
 316         }
 317         if (vma->vm_rb.rb_right) {
 318                 subtree_gap = rb_entry(vma->vm_rb.rb_right,
 319                                 struct vm_area_struct, vm_rb)->rb_subtree_gap;
 320                 if (subtree_gap > max)
 321                         max = subtree_gap;
 322         }
 323         return max;
 324 }
 325 
 326 static int browse_rb(struct mm_struct *mm)
 327 {
 328         struct rb_root *root = &mm->mm_rb;
 329         int i = 0, j, bug = 0;
 330         struct rb_node *nd, *pn = NULL;
 331         unsigned long prev = 0, pend = 0;
 332 
 333         for (nd = rb_first(root); nd; nd = rb_next(nd)) {
 334                 struct vm_area_struct *vma;
 335                 vma = rb_entry(nd, struct vm_area_struct, vm_rb);
 336                 if (vma->vm_start < prev) {
 337                         pr_emerg("vm_start %lx < prev %lx\n",
 338                                   vma->vm_start, prev);
 339                         bug = 1;
 340                 }
 341                 if (vma->vm_start < pend) {
 342                         pr_emerg("vm_start %lx < pend %lx\n",
 343                                   vma->vm_start, pend);
 344                         bug = 1;
 345                 }
 346                 if (vma->vm_start > vma->vm_end) {
 347                         pr_emerg("vm_start %lx > vm_end %lx\n",
 348                                   vma->vm_start, vma->vm_end);
 349                         bug = 1;
 350                 }
 351                 spin_lock(&mm->page_table_lock);
 352                 if (vma->rb_subtree_gap != vma_compute_subtree_gap(vma)) {
 353                         pr_emerg("free gap %lx, correct %lx\n",
 354                                vma->rb_subtree_gap,
 355                                vma_compute_subtree_gap(vma));
 356                         bug = 1;
 357                 }
 358                 spin_unlock(&mm->page_table_lock);
 359                 i++;
 360                 pn = nd;
 361                 prev = vma->vm_start;
 362                 pend = vma->vm_end;
 363         }
 364         j = 0;
 365         for (nd = pn; nd; nd = rb_prev(nd))
 366                 j++;
 367         if (i != j) {
 368                 pr_emerg("backwards %d, forwards %d\n", j, i);
 369                 bug = 1;
 370         }
 371         return bug ? -1 : i;
 372 }
 373 
 374 static void validate_mm_rb(struct rb_root *root, struct vm_area_struct *ignore)
 375 {
 376         struct rb_node *nd;
 377 
 378         for (nd = rb_first(root); nd; nd = rb_next(nd)) {
 379                 struct vm_area_struct *vma;
 380                 vma = rb_entry(nd, struct vm_area_struct, vm_rb);
 381                 VM_BUG_ON_VMA(vma != ignore &&
 382                         vma->rb_subtree_gap != vma_compute_subtree_gap(vma),
 383                         vma);
 384         }
 385 }
 386 
 387 static void validate_mm(struct mm_struct *mm)
 388 {
 389         int bug = 0;
 390         int i = 0;
 391         unsigned long highest_address = 0;
 392         struct vm_area_struct *vma = mm->mmap;
 393 
 394         while (vma) {
 395                 struct anon_vma *anon_vma = vma->anon_vma;
 396                 struct anon_vma_chain *avc;
 397 
 398                 if (anon_vma) {
 399                         anon_vma_lock_read(anon_vma);
 400                         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
 401                                 anon_vma_interval_tree_verify(avc);
 402                         anon_vma_unlock_read(anon_vma);
 403                 }
 404 
 405                 highest_address = vm_end_gap(vma);
 406                 vma = vma->vm_next;
 407                 i++;
 408         }
 409         if (i != mm->map_count) {
 410                 pr_emerg("map_count %d vm_next %d\n", mm->map_count, i);
 411                 bug = 1;
 412         }
 413         if (highest_address != mm->highest_vm_end) {
 414                 pr_emerg("mm->highest_vm_end %lx, found %lx\n",
 415                           mm->highest_vm_end, highest_address);
 416                 bug = 1;
 417         }
 418         i = browse_rb(mm);
 419         if (i != mm->map_count) {
 420                 if (i != -1)
 421                         pr_emerg("map_count %d rb %d\n", mm->map_count, i);
 422                 bug = 1;
 423         }
 424         VM_BUG_ON_MM(bug, mm);
 425 }
 426 #else
 427 #define validate_mm_rb(root, ignore) do { } while (0)
 428 #define validate_mm(mm) do { } while (0)
 429 #endif
 430 
 431 RB_DECLARE_CALLBACKS_MAX(static, vma_gap_callbacks,
 432                          struct vm_area_struct, vm_rb,
 433                          unsigned long, rb_subtree_gap, vma_compute_gap)
 434 
 435 /*
 436  * Update augmented rbtree rb_subtree_gap values after vma->vm_start or
 437  * vma->vm_prev->vm_end values changed, without modifying the vma's position
 438  * in the rbtree.
 439  */
 440 static void vma_gap_update(struct vm_area_struct *vma)
 441 {
 442         /*
 443          * As it turns out, RB_DECLARE_CALLBACKS_MAX() already created
 444          * a callback function that does exactly what we want.
 445          */
 446         vma_gap_callbacks_propagate(&vma->vm_rb, NULL);
 447 }
 448 
 449 static inline void vma_rb_insert(struct vm_area_struct *vma,
 450                                  struct rb_root *root)
 451 {
 452         /* All rb_subtree_gap values must be consistent prior to insertion */
 453         validate_mm_rb(root, NULL);
 454 
 455         rb_insert_augmented(&vma->vm_rb, root, &vma_gap_callbacks);
 456 }
 457 
 458 static void __vma_rb_erase(struct vm_area_struct *vma, struct rb_root *root)
 459 {
 460         /*
 461          * Note rb_erase_augmented is a fairly large inline function,
 462          * so make sure we instantiate it only once with our desired
 463          * augmented rbtree callbacks.
 464          */
 465         rb_erase_augmented(&vma->vm_rb, root, &vma_gap_callbacks);
 466 }
 467 
 468 static __always_inline void vma_rb_erase_ignore(struct vm_area_struct *vma,
 469                                                 struct rb_root *root,
 470                                                 struct vm_area_struct *ignore)
 471 {
 472         /*
 473          * All rb_subtree_gap values must be consistent prior to erase,
 474          * with the possible exception of the "next" vma being erased if
 475          * next->vm_start was reduced.
 476          */
 477         validate_mm_rb(root, ignore);
 478 
 479         __vma_rb_erase(vma, root);
 480 }
 481 
 482 static __always_inline void vma_rb_erase(struct vm_area_struct *vma,
 483                                          struct rb_root *root)
 484 {
 485         /*
 486          * All rb_subtree_gap values must be consistent prior to erase,
 487          * with the possible exception of the vma being erased.
 488          */
 489         validate_mm_rb(root, vma);
 490 
 491         __vma_rb_erase(vma, root);
 492 }
 493 
 494 /*
 495  * vma has some anon_vma assigned, and is already inserted on that
 496  * anon_vma's interval trees.
 497  *
 498  * Before updating the vma's vm_start / vm_end / vm_pgoff fields, the
 499  * vma must be removed from the anon_vma's interval trees using
 500  * anon_vma_interval_tree_pre_update_vma().
 501  *
 502  * After the update, the vma will be reinserted using
 503  * anon_vma_interval_tree_post_update_vma().
 504  *
 505  * The entire update must be protected by exclusive mmap_sem and by
 506  * the root anon_vma's mutex.
 507  */
 508 static inline void
 509 anon_vma_interval_tree_pre_update_vma(struct vm_area_struct *vma)
 510 {
 511         struct anon_vma_chain *avc;
 512 
 513         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
 514                 anon_vma_interval_tree_remove(avc, &avc->anon_vma->rb_root);
 515 }
 516 
 517 static inline void
 518 anon_vma_interval_tree_post_update_vma(struct vm_area_struct *vma)
 519 {
 520         struct anon_vma_chain *avc;
 521 
 522         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
 523                 anon_vma_interval_tree_insert(avc, &avc->anon_vma->rb_root);
 524 }
 525 
 526 static int find_vma_links(struct mm_struct *mm, unsigned long addr,
 527                 unsigned long end, struct vm_area_struct **pprev,
 528                 struct rb_node ***rb_link, struct rb_node **rb_parent)
 529 {
 530         struct rb_node **__rb_link, *__rb_parent, *rb_prev;
 531 
 532         __rb_link = &mm->mm_rb.rb_node;
 533         rb_prev = __rb_parent = NULL;
 534 
 535         while (*__rb_link) {
 536                 struct vm_area_struct *vma_tmp;
 537 
 538                 __rb_parent = *__rb_link;
 539                 vma_tmp = rb_entry(__rb_parent, struct vm_area_struct, vm_rb);
 540 
 541                 if (vma_tmp->vm_end > addr) {
 542                         /* Fail if an existing vma overlaps the area */
 543                         if (vma_tmp->vm_start < end)
 544                                 return -ENOMEM;
 545                         __rb_link = &__rb_parent->rb_left;
 546                 } else {
 547                         rb_prev = __rb_parent;
 548                         __rb_link = &__rb_parent->rb_right;
 549                 }
 550         }
 551 
 552         *pprev = NULL;
 553         if (rb_prev)
 554                 *pprev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
 555         *rb_link = __rb_link;
 556         *rb_parent = __rb_parent;
 557         return 0;
 558 }
 559 
 560 static unsigned long count_vma_pages_range(struct mm_struct *mm,
 561                 unsigned long addr, unsigned long end)
 562 {
 563         unsigned long nr_pages = 0;
 564         struct vm_area_struct *vma;
 565 
 566         /* Find first overlaping mapping */
 567         vma = find_vma_intersection(mm, addr, end);
 568         if (!vma)
 569                 return 0;
 570 
 571         nr_pages = (min(end, vma->vm_end) -
 572                 max(addr, vma->vm_start)) >> PAGE_SHIFT;
 573 
 574         /* Iterate over the rest of the overlaps */
 575         for (vma = vma->vm_next; vma; vma = vma->vm_next) {
 576                 unsigned long overlap_len;
 577 
 578                 if (vma->vm_start > end)
 579                         break;
 580 
 581                 overlap_len = min(end, vma->vm_end) - vma->vm_start;
 582                 nr_pages += overlap_len >> PAGE_SHIFT;
 583         }
 584 
 585         return nr_pages;
 586 }
 587 
 588 void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
 589                 struct rb_node **rb_link, struct rb_node *rb_parent)
 590 {
 591         /* Update tracking information for the gap following the new vma. */
 592         if (vma->vm_next)
 593                 vma_gap_update(vma->vm_next);
 594         else
 595                 mm->highest_vm_end = vm_end_gap(vma);
 596 
 597         /*
 598          * vma->vm_prev wasn't known when we followed the rbtree to find the
 599          * correct insertion point for that vma. As a result, we could not
 600          * update the vma vm_rb parents rb_subtree_gap values on the way down.
 601          * So, we first insert the vma with a zero rb_subtree_gap value
 602          * (to be consistent with what we did on the way down), and then
 603          * immediately update the gap to the correct value. Finally we
 604          * rebalance the rbtree after all augmented values have been set.
 605          */
 606         rb_link_node(&vma->vm_rb, rb_parent, rb_link);
 607         vma->rb_subtree_gap = 0;
 608         vma_gap_update(vma);
 609         vma_rb_insert(vma, &mm->mm_rb);
 610 }
 611 
 612 static void __vma_link_file(struct vm_area_struct *vma)
 613 {
 614         struct file *file;
 615 
 616         file = vma->vm_file;
 617         if (file) {
 618                 struct address_space *mapping = file->f_mapping;
 619 
 620                 if (vma->vm_flags & VM_DENYWRITE)
 621                         atomic_dec(&file_inode(file)->i_writecount);
 622                 if (vma->vm_flags & VM_SHARED)
 623                         atomic_inc(&mapping->i_mmap_writable);
 624 
 625                 flush_dcache_mmap_lock(mapping);
 626                 vma_interval_tree_insert(vma, &mapping->i_mmap);
 627                 flush_dcache_mmap_unlock(mapping);
 628         }
 629 }
 630 
 631 static void
 632 __vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
 633         struct vm_area_struct *prev, struct rb_node **rb_link,
 634         struct rb_node *rb_parent)
 635 {
 636         __vma_link_list(mm, vma, prev, rb_parent);
 637         __vma_link_rb(mm, vma, rb_link, rb_parent);
 638 }
 639 
 640 static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
 641                         struct vm_area_struct *prev, struct rb_node **rb_link,
 642                         struct rb_node *rb_parent)
 643 {
 644         struct address_space *mapping = NULL;
 645 
 646         if (vma->vm_file) {
 647                 mapping = vma->vm_file->f_mapping;
 648                 i_mmap_lock_write(mapping);
 649         }
 650 
 651         __vma_link(mm, vma, prev, rb_link, rb_parent);
 652         __vma_link_file(vma);
 653 
 654         if (mapping)
 655                 i_mmap_unlock_write(mapping);
 656 
 657         mm->map_count++;
 658         validate_mm(mm);
 659 }
 660 
 661 /*
 662  * Helper for vma_adjust() in the split_vma insert case: insert a vma into the
 663  * mm's list and rbtree.  It has already been inserted into the interval tree.
 664  */
 665 static void __insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
 666 {
 667         struct vm_area_struct *prev;
 668         struct rb_node **rb_link, *rb_parent;
 669 
 670         if (find_vma_links(mm, vma->vm_start, vma->vm_end,
 671                            &prev, &rb_link, &rb_parent))
 672                 BUG();
 673         __vma_link(mm, vma, prev, rb_link, rb_parent);
 674         mm->map_count++;
 675 }
 676 
 677 static __always_inline void __vma_unlink_common(struct mm_struct *mm,
 678                                                 struct vm_area_struct *vma,
 679                                                 struct vm_area_struct *prev,
 680                                                 bool has_prev,
 681                                                 struct vm_area_struct *ignore)
 682 {
 683         struct vm_area_struct *next;
 684 
 685         vma_rb_erase_ignore(vma, &mm->mm_rb, ignore);
 686         next = vma->vm_next;
 687         if (has_prev)
 688                 prev->vm_next = next;
 689         else {
 690                 prev = vma->vm_prev;
 691                 if (prev)
 692                         prev->vm_next = next;
 693                 else
 694                         mm->mmap = next;
 695         }
 696         if (next)
 697                 next->vm_prev = prev;
 698 
 699         /* Kill the cache */
 700         vmacache_invalidate(mm);
 701 }
 702 
 703 static inline void __vma_unlink_prev(struct mm_struct *mm,
 704                                      struct vm_area_struct *vma,
 705                                      struct vm_area_struct *prev)
 706 {
 707         __vma_unlink_common(mm, vma, prev, true, vma);
 708 }
 709 
 710 /*
 711  * We cannot adjust vm_start, vm_end, vm_pgoff fields of a vma that
 712  * is already present in an i_mmap tree without adjusting the tree.
 713  * The following helper function should be used when such adjustments
 714  * are necessary.  The "insert" vma (if any) is to be inserted
 715  * before we drop the necessary locks.
 716  */
 717 int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
 718         unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert,
 719         struct vm_area_struct *expand)
 720 {
 721         struct mm_struct *mm = vma->vm_mm;
 722         struct vm_area_struct *next = vma->vm_next, *orig_vma = vma;
 723         struct address_space *mapping = NULL;
 724         struct rb_root_cached *root = NULL;
 725         struct anon_vma *anon_vma = NULL;
 726         struct file *file = vma->vm_file;
 727         bool start_changed = false, end_changed = false;
 728         long adjust_next = 0;
 729         int remove_next = 0;
 730 
 731         if (next && !insert) {
 732                 struct vm_area_struct *exporter = NULL, *importer = NULL;
 733 
 734                 if (end >= next->vm_end) {
 735                         /*
 736                          * vma expands, overlapping all the next, and
 737                          * perhaps the one after too (mprotect case 6).
 738                          * The only other cases that gets here are
 739                          * case 1, case 7 and case 8.
 740                          */
 741                         if (next == expand) {
 742                                 /*
 743                                  * The only case where we don't expand "vma"
 744                                  * and we expand "next" instead is case 8.
 745                                  */
 746                                 VM_WARN_ON(end != next->vm_end);
 747                                 /*
 748                                  * remove_next == 3 means we're
 749                                  * removing "vma" and that to do so we
 750                                  * swapped "vma" and "next".
 751                                  */
 752                                 remove_next = 3;
 753                                 VM_WARN_ON(file != next->vm_file);
 754                                 swap(vma, next);
 755                         } else {
 756                                 VM_WARN_ON(expand != vma);
 757                                 /*
 758                                  * case 1, 6, 7, remove_next == 2 is case 6,
 759                                  * remove_next == 1 is case 1 or 7.
 760                                  */
 761                                 remove_next = 1 + (end > next->vm_end);
 762                                 VM_WARN_ON(remove_next == 2 &&
 763                                            end != next->vm_next->vm_end);
 764                                 VM_WARN_ON(remove_next == 1 &&
 765                                            end != next->vm_end);
 766                                 /* trim end to next, for case 6 first pass */
 767                                 end = next->vm_end;
 768                         }
 769 
 770                         exporter = next;
 771                         importer = vma;
 772 
 773                         /*
 774                          * If next doesn't have anon_vma, import from vma after
 775                          * next, if the vma overlaps with it.
 776                          */
 777                         if (remove_next == 2 && !next->anon_vma)
 778                                 exporter = next->vm_next;
 779 
 780                 } else if (end > next->vm_start) {
 781                         /*
 782                          * vma expands, overlapping part of the next:
 783                          * mprotect case 5 shifting the boundary up.
 784                          */
 785                         adjust_next = (end - next->vm_start) >> PAGE_SHIFT;
 786                         exporter = next;
 787                         importer = vma;
 788                         VM_WARN_ON(expand != importer);
 789                 } else if (end < vma->vm_end) {
 790                         /*
 791                          * vma shrinks, and !insert tells it's not
 792                          * split_vma inserting another: so it must be
 793                          * mprotect case 4 shifting the boundary down.
 794                          */
 795                         adjust_next = -((vma->vm_end - end) >> PAGE_SHIFT);
 796                         exporter = vma;
 797                         importer = next;
 798                         VM_WARN_ON(expand != importer);
 799                 }
 800 
 801                 /*
 802                  * Easily overlooked: when mprotect shifts the boundary,
 803                  * make sure the expanding vma has anon_vma set if the
 804                  * shrinking vma had, to cover any anon pages imported.
 805                  */
 806                 if (exporter && exporter->anon_vma && !importer->anon_vma) {
 807                         int error;
 808 
 809                         importer->anon_vma = exporter->anon_vma;
 810                         error = anon_vma_clone(importer, exporter);
 811                         if (error)
 812                                 return error;
 813                 }
 814         }
 815 again:
 816         vma_adjust_trans_huge(orig_vma, start, end, adjust_next);
 817 
 818         if (file) {
 819                 mapping = file->f_mapping;
 820                 root = &mapping->i_mmap;
 821                 uprobe_munmap(vma, vma->vm_start, vma->vm_end);
 822 
 823                 if (adjust_next)
 824                         uprobe_munmap(next, next->vm_start, next->vm_end);
 825 
 826                 i_mmap_lock_write(mapping);
 827                 if (insert) {
 828                         /*
 829                          * Put into interval tree now, so instantiated pages
 830                          * are visible to arm/parisc __flush_dcache_page
 831                          * throughout; but we cannot insert into address
 832                          * space until vma start or end is updated.
 833                          */
 834                         __vma_link_file(insert);
 835                 }
 836         }
 837 
 838         anon_vma = vma->anon_vma;
 839         if (!anon_vma && adjust_next)
 840                 anon_vma = next->anon_vma;
 841         if (anon_vma) {
 842                 VM_WARN_ON(adjust_next && next->anon_vma &&
 843                            anon_vma != next->anon_vma);
 844                 anon_vma_lock_write(anon_vma);
 845                 anon_vma_interval_tree_pre_update_vma(vma);
 846                 if (adjust_next)
 847                         anon_vma_interval_tree_pre_update_vma(next);
 848         }
 849 
 850         if (root) {
 851                 flush_dcache_mmap_lock(mapping);
 852                 vma_interval_tree_remove(vma, root);
 853                 if (adjust_next)
 854                         vma_interval_tree_remove(next, root);
 855         }
 856 
 857         if (start != vma->vm_start) {
 858                 vma->vm_start = start;
 859                 start_changed = true;
 860         }
 861         if (end != vma->vm_end) {
 862                 vma->vm_end = end;
 863                 end_changed = true;
 864         }
 865         vma->vm_pgoff = pgoff;
 866         if (adjust_next) {
 867                 next->vm_start += adjust_next << PAGE_SHIFT;
 868                 next->vm_pgoff += adjust_next;
 869         }
 870 
 871         if (root) {
 872                 if (adjust_next)
 873                         vma_interval_tree_insert(next, root);
 874                 vma_interval_tree_insert(vma, root);
 875                 flush_dcache_mmap_unlock(mapping);
 876         }
 877 
 878         if (remove_next) {
 879                 /*
 880                  * vma_merge has merged next into vma, and needs
 881                  * us to remove next before dropping the locks.
 882                  */
 883                 if (remove_next != 3)
 884                         __vma_unlink_prev(mm, next, vma);
 885                 else
 886                         /*
 887                          * vma is not before next if they've been
 888                          * swapped.
 889                          *
 890                          * pre-swap() next->vm_start was reduced so
 891                          * tell validate_mm_rb to ignore pre-swap()
 892                          * "next" (which is stored in post-swap()
 893                          * "vma").
 894                          */
 895                         __vma_unlink_common(mm, next, NULL, false, vma);
 896                 if (file)
 897                         __remove_shared_vm_struct(next, file, mapping);
 898         } else if (insert) {
 899                 /*
 900                  * split_vma has split insert from vma, and needs
 901                  * us to insert it before dropping the locks
 902                  * (it may either follow vma or precede it).
 903                  */
 904                 __insert_vm_struct(mm, insert);
 905         } else {
 906                 if (start_changed)
 907                         vma_gap_update(vma);
 908                 if (end_changed) {
 909                         if (!next)
 910                                 mm->highest_vm_end = vm_end_gap(vma);
 911                         else if (!adjust_next)
 912                                 vma_gap_update(next);
 913                 }
 914         }
 915 
 916         if (anon_vma) {
 917                 anon_vma_interval_tree_post_update_vma(vma);
 918                 if (adjust_next)
 919                         anon_vma_interval_tree_post_update_vma(next);
 920                 anon_vma_unlock_write(anon_vma);
 921         }
 922         if (mapping)
 923                 i_mmap_unlock_write(mapping);
 924 
 925         if (root) {
 926                 uprobe_mmap(vma);
 927 
 928                 if (adjust_next)
 929                         uprobe_mmap(next);
 930         }
 931 
 932         if (remove_next) {
 933                 if (file) {
 934                         uprobe_munmap(next, next->vm_start, next->vm_end);
 935                         fput(file);
 936                 }
 937                 if (next->anon_vma)
 938                         anon_vma_merge(vma, next);
 939                 mm->map_count--;
 940                 mpol_put(vma_policy(next));
 941                 vm_area_free(next);
 942                 /*
 943                  * In mprotect's case 6 (see comments on vma_merge),
 944                  * we must remove another next too. It would clutter
 945                  * up the code too much to do both in one go.
 946                  */
 947                 if (remove_next != 3) {
 948                         /*
 949                          * If "next" was removed and vma->vm_end was
 950                          * expanded (up) over it, in turn
 951                          * "next->vm_prev->vm_end" changed and the
 952                          * "vma->vm_next" gap must be updated.
 953                          */
 954                         next = vma->vm_next;
 955                 } else {
 956                         /*
 957                          * For the scope of the comment "next" and
 958                          * "vma" considered pre-swap(): if "vma" was
 959                          * removed, next->vm_start was expanded (down)
 960                          * over it and the "next" gap must be updated.
 961                          * Because of the swap() the post-swap() "vma"
 962                          * actually points to pre-swap() "next"
 963                          * (post-swap() "next" as opposed is now a
 964                          * dangling pointer).
 965                          */
 966                         next = vma;
 967                 }
 968                 if (remove_next == 2) {
 969                         remove_next = 1;
 970                         end = next->vm_end;
 971                         goto again;
 972                 }
 973                 else if (next)
 974                         vma_gap_update(next);
 975                 else {
 976                         /*
 977                          * If remove_next == 2 we obviously can't
 978                          * reach this path.
 979                          *
 980                          * If remove_next == 3 we can't reach this
 981                          * path because pre-swap() next is always not
 982                          * NULL. pre-swap() "next" is not being
 983                          * removed and its next->vm_end is not altered
 984                          * (and furthermore "end" already matches
 985                          * next->vm_end in remove_next == 3).
 986                          *
 987                          * We reach this only in the remove_next == 1
 988                          * case if the "next" vma that was removed was
 989                          * the highest vma of the mm. However in such
 990                          * case next->vm_end == "end" and the extended
 991                          * "vma" has vma->vm_end == next->vm_end so
 992                          * mm->highest_vm_end doesn't need any update
 993                          * in remove_next == 1 case.
 994                          */
 995                         VM_WARN_ON(mm->highest_vm_end != vm_end_gap(vma));
 996                 }
 997         }
 998         if (insert && file)
 999                 uprobe_mmap(insert);
1000 
1001         validate_mm(mm);
1002 
1003         return 0;
1004 }
1005 
1006 /*
1007  * If the vma has a ->close operation then the driver probably needs to release
1008  * per-vma resources, so we don't attempt to merge those.
1009  */
1010 static inline int is_mergeable_vma(struct vm_area_struct *vma,
1011                                 struct file *file, unsigned long vm_flags,
1012                                 struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
1013 {
1014         /*
1015          * VM_SOFTDIRTY should not prevent from VMA merging, if we
1016          * match the flags but dirty bit -- the caller should mark
1017          * merged VMA as dirty. If dirty bit won't be excluded from
1018          * comparison, we increase pressure on the memory system forcing
1019          * the kernel to generate new VMAs when old one could be
1020          * extended instead.
1021          */
1022         if ((vma->vm_flags ^ vm_flags) & ~VM_SOFTDIRTY)
1023                 return 0;
1024         if (vma->vm_file != file)
1025                 return 0;
1026         if (vma->vm_ops && vma->vm_ops->close)
1027                 return 0;
1028         if (!is_mergeable_vm_userfaultfd_ctx(vma, vm_userfaultfd_ctx))
1029                 return 0;
1030         return 1;
1031 }
1032 
1033 static inline int is_mergeable_anon_vma(struct anon_vma *anon_vma1,
1034                                         struct anon_vma *anon_vma2,
1035                                         struct vm_area_struct *vma)
1036 {
1037         /*
1038          * The list_is_singular() test is to avoid merging VMA cloned from
1039          * parents. This can improve scalability caused by anon_vma lock.
1040          */
1041         if ((!anon_vma1 || !anon_vma2) && (!vma ||
1042                 list_is_singular(&vma->anon_vma_chain)))
1043                 return 1;
1044         return anon_vma1 == anon_vma2;
1045 }
1046 
1047 /*
1048  * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
1049  * in front of (at a lower virtual address and file offset than) the vma.
1050  *
1051  * We cannot merge two vmas if they have differently assigned (non-NULL)
1052  * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
1053  *
1054  * We don't check here for the merged mmap wrapping around the end of pagecache
1055  * indices (16TB on ia32) because do_mmap_pgoff() does not permit mmap's which
1056  * wrap, nor mmaps which cover the final page at index -1UL.
1057  */
1058 static int
1059 can_vma_merge_before(struct vm_area_struct *vma, unsigned long vm_flags,
1060                      struct anon_vma *anon_vma, struct file *file,
1061                      pgoff_t vm_pgoff,
1062                      struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
1063 {
1064         if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx) &&
1065             is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
1066                 if (vma->vm_pgoff == vm_pgoff)
1067                         return 1;
1068         }
1069         return 0;
1070 }
1071 
1072 /*
1073  * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
1074  * beyond (at a higher virtual address and file offset than) the vma.
1075  *
1076  * We cannot merge two vmas if they have differently assigned (non-NULL)
1077  * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
1078  */
1079 static int
1080 can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
1081                     struct anon_vma *anon_vma, struct file *file,
1082                     pgoff_t vm_pgoff,
1083                     struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
1084 {
1085         if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx) &&
1086             is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
1087                 pgoff_t vm_pglen;
1088                 vm_pglen = vma_pages(vma);
1089                 if (vma->vm_pgoff + vm_pglen == vm_pgoff)
1090                         return 1;
1091         }
1092         return 0;
1093 }
1094 
1095 /*
1096  * Given a mapping request (addr,end,vm_flags,file,pgoff), figure out
1097  * whether that can be merged with its predecessor or its successor.
1098  * Or both (it neatly fills a hole).
1099  *
1100  * In most cases - when called for mmap, brk or mremap - [addr,end) is
1101  * certain not to be mapped by the time vma_merge is called; but when
1102  * called for mprotect, it is certain to be already mapped (either at
1103  * an offset within prev, or at the start of next), and the flags of
1104  * this area are about to be changed to vm_flags - and the no-change
1105  * case has already been eliminated.
1106  *
1107  * The following mprotect cases have to be considered, where AAAA is
1108  * the area passed down from mprotect_fixup, never extending beyond one
1109  * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
1110  *
1111  *     AAAA             AAAA                AAAA          AAAA
1112  *    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPNNNNXXXX
1113  *    cannot merge    might become    might become    might become
1114  *                    PPNNNNNNNNNN    PPPPPPPPPPNN    PPPPPPPPPPPP 6 or
1115  *    mmap, brk or    case 4 below    case 5 below    PPPPPPPPXXXX 7 or
1116  *    mremap move:                                    PPPPXXXXXXXX 8
1117  *        AAAA
1118  *    PPPP    NNNN    PPPPPPPPPPPP    PPPPPPPPNNNN    PPPPNNNNNNNN
1119  *    might become    case 1 below    case 2 below    case 3 below
1120  *
1121  * It is important for case 8 that the vma NNNN overlapping the
1122  * region AAAA is never going to extended over XXXX. Instead XXXX must
1123  * be extended in region AAAA and NNNN must be removed. This way in
1124  * all cases where vma_merge succeeds, the moment vma_adjust drops the
1125  * rmap_locks, the properties of the merged vma will be already
1126  * correct for the whole merged range. Some of those properties like
1127  * vm_page_prot/vm_flags may be accessed by rmap_walks and they must
1128  * be correct for the whole merged range immediately after the
1129  * rmap_locks are released. Otherwise if XXXX would be removed and
1130  * NNNN would be extended over the XXXX range, remove_migration_ptes
1131  * or other rmap walkers (if working on addresses beyond the "end"
1132  * parameter) may establish ptes with the wrong permissions of NNNN
1133  * instead of the right permissions of XXXX.
1134  */
1135 struct vm_area_struct *vma_merge(struct mm_struct *mm,
1136                         struct vm_area_struct *prev, unsigned long addr,
1137                         unsigned long end, unsigned long vm_flags,
1138                         struct anon_vma *anon_vma, struct file *file,
1139                         pgoff_t pgoff, struct mempolicy *policy,
1140                         struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
1141 {
1142         pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
1143         struct vm_area_struct *area, *next;
1144         int err;
1145 
1146         /*
1147          * We later require that vma->vm_flags == vm_flags,
1148          * so this tests vma->vm_flags & VM_SPECIAL, too.
1149          */
1150         if (vm_flags & VM_SPECIAL)
1151                 return NULL;
1152 
1153         if (prev)
1154                 next = prev->vm_next;
1155         else
1156                 next = mm->mmap;
1157         area = next;
1158         if (area && area->vm_end == end)                /* cases 6, 7, 8 */
1159                 next = next->vm_next;
1160 
1161         /* verify some invariant that must be enforced by the caller */
1162         VM_WARN_ON(prev && addr <= prev->vm_start);
1163         VM_WARN_ON(area && end > area->vm_end);
1164         VM_WARN_ON(addr >= end);
1165 
1166         /*
1167          * Can it merge with the predecessor?
1168          */
1169         if (prev && prev->vm_end == addr &&
1170                         mpol_equal(vma_policy(prev), policy) &&
1171                         can_vma_merge_after(prev, vm_flags,
1172                                             anon_vma, file, pgoff,
1173                                             vm_userfaultfd_ctx)) {
1174                 /*
1175                  * OK, it can.  Can we now merge in the successor as well?
1176                  */
1177                 if (next && end == next->vm_start &&
1178                                 mpol_equal(policy, vma_policy(next)) &&
1179                                 can_vma_merge_before(next, vm_flags,
1180                                                      anon_vma, file,
1181                                                      pgoff+pglen,
1182                                                      vm_userfaultfd_ctx) &&
1183                                 is_mergeable_anon_vma(prev->anon_vma,
1184                                                       next->anon_vma, NULL)) {
1185                                                         /* cases 1, 6 */
1186                         err = __vma_adjust(prev, prev->vm_start,
1187                                          next->vm_end, prev->vm_pgoff, NULL,
1188                                          prev);
1189                 } else                                  /* cases 2, 5, 7 */
1190                         err = __vma_adjust(prev, prev->vm_start,
1191                                          end, prev->vm_pgoff, NULL, prev);
1192                 if (err)
1193                         return NULL;
1194                 khugepaged_enter_vma_merge(prev, vm_flags);
1195                 return prev;
1196         }
1197 
1198         /*
1199          * Can this new request be merged in front of next?
1200          */
1201         if (next && end == next->vm_start &&
1202                         mpol_equal(policy, vma_policy(next)) &&
1203                         can_vma_merge_before(next, vm_flags,
1204                                              anon_vma, file, pgoff+pglen,
1205                                              vm_userfaultfd_ctx)) {
1206                 if (prev && addr < prev->vm_end)        /* case 4 */
1207                         err = __vma_adjust(prev, prev->vm_start,
1208                                          addr, prev->vm_pgoff, NULL, next);
1209                 else {                                  /* cases 3, 8 */
1210                         err = __vma_adjust(area, addr, next->vm_end,
1211                                          next->vm_pgoff - pglen, NULL, next);
1212                         /*
1213                          * In case 3 area is already equal to next and
1214                          * this is a noop, but in case 8 "area" has
1215                          * been removed and next was expanded over it.
1216                          */
1217                         area = next;
1218                 }
1219                 if (err)
1220                         return NULL;
1221                 khugepaged_enter_vma_merge(area, vm_flags);
1222                 return area;
1223         }
1224 
1225         return NULL;
1226 }
1227 
1228 /*
1229  * Rough compatbility check to quickly see if it's even worth looking
1230  * at sharing an anon_vma.
1231  *
1232  * They need to have the same vm_file, and the flags can only differ
1233  * in things that mprotect may change.
1234  *
1235  * NOTE! The fact that we share an anon_vma doesn't _have_ to mean that
1236  * we can merge the two vma's. For example, we refuse to merge a vma if
1237  * there is a vm_ops->close() function, because that indicates that the
1238  * driver is doing some kind of reference counting. But that doesn't
1239  * really matter for the anon_vma sharing case.
1240  */
1241 static int anon_vma_compatible(struct vm_area_struct *a, struct vm_area_struct *b)
1242 {
1243         return a->vm_end == b->vm_start &&
1244                 mpol_equal(vma_policy(a), vma_policy(b)) &&
1245                 a->vm_file == b->vm_file &&
1246                 !((a->vm_flags ^ b->vm_flags) & ~(VM_READ|VM_WRITE|VM_EXEC|VM_SOFTDIRTY)) &&
1247                 b->vm_pgoff == a->vm_pgoff + ((b->vm_start - a->vm_start) >> PAGE_SHIFT);
1248 }
1249 
1250 /*
1251  * Do some basic sanity checking to see if we can re-use the anon_vma
1252  * from 'old'. The 'a'/'b' vma's are in VM order - one of them will be
1253  * the same as 'old', the other will be the new one that is trying
1254  * to share the anon_vma.
1255  *
1256  * NOTE! This runs with mm_sem held for reading, so it is possible that
1257  * the anon_vma of 'old' is concurrently in the process of being set up
1258  * by another page fault trying to merge _that_. But that's ok: if it
1259  * is being set up, that automatically means that it will be a singleton
1260  * acceptable for merging, so we can do all of this optimistically. But
1261  * we do that READ_ONCE() to make sure that we never re-load the pointer.
1262  *
1263  * IOW: that the "list_is_singular()" test on the anon_vma_chain only
1264  * matters for the 'stable anon_vma' case (ie the thing we want to avoid
1265  * is to return an anon_vma that is "complex" due to having gone through
1266  * a fork).
1267  *
1268  * We also make sure that the two vma's are compatible (adjacent,
1269  * and with the same memory policies). That's all stable, even with just
1270  * a read lock on the mm_sem.
1271  */
1272 static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, struct vm_area_struct *a, struct vm_area_struct *b)
1273 {
1274         if (anon_vma_compatible(a, b)) {
1275                 struct anon_vma *anon_vma = READ_ONCE(old->anon_vma);
1276 
1277                 if (anon_vma && list_is_singular(&old->anon_vma_chain))
1278                         return anon_vma;
1279         }
1280         return NULL;
1281 }
1282 
1283 /*
1284  * find_mergeable_anon_vma is used by anon_vma_prepare, to check
1285  * neighbouring vmas for a suitable anon_vma, before it goes off
1286  * to allocate a new anon_vma.  It checks because a repetitive
1287  * sequence of mprotects and faults may otherwise lead to distinct
1288  * anon_vmas being allocated, preventing vma merge in subsequent
1289  * mprotect.
1290  */
1291 struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
1292 {
1293         struct anon_vma *anon_vma;
1294         struct vm_area_struct *near;
1295 
1296         near = vma->vm_next;
1297         if (!near)
1298                 goto try_prev;
1299 
1300         anon_vma = reusable_anon_vma(near, vma, near);
1301         if (anon_vma)
1302                 return anon_vma;
1303 try_prev:
1304         near = vma->vm_prev;
1305         if (!near)
1306                 goto none;
1307 
1308         anon_vma = reusable_anon_vma(near, near, vma);
1309         if (anon_vma)
1310                 return anon_vma;
1311 none:
1312         /*
1313          * There's no absolute need to look only at touching neighbours:
1314          * we could search further afield for "compatible" anon_vmas.
1315          * But it would probably just be a waste of time searching,
1316          * or lead to too many vmas hanging off the same anon_vma.
1317          * We're trying to allow mprotect remerging later on,
1318          * not trying to minimize memory used for anon_vmas.
1319          */
1320         return NULL;
1321 }
1322 
1323 /*
1324  * If a hint addr is less than mmap_min_addr change hint to be as
1325  * low as possible but still greater than mmap_min_addr
1326  */
1327 static inline unsigned long round_hint_to_min(unsigned long hint)
1328 {
1329         hint &= PAGE_MASK;
1330         if (((void *)hint != NULL) &&
1331             (hint < mmap_min_addr))
1332                 return PAGE_ALIGN(mmap_min_addr);
1333         return hint;
1334 }
1335 
1336 static inline int mlock_future_check(struct mm_struct *mm,
1337                                      unsigned long flags,
1338                                      unsigned long len)
1339 {
1340         unsigned long locked, lock_limit;
1341 
1342         /*  mlock MCL_FUTURE? */
1343         if (flags & VM_LOCKED) {
1344                 locked = len >> PAGE_SHIFT;
1345                 locked += mm->locked_vm;
1346                 lock_limit = rlimit(RLIMIT_MEMLOCK);
1347                 lock_limit >>= PAGE_SHIFT;
1348                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
1349                         return -EAGAIN;
1350         }
1351         return 0;
1352 }
1353 
1354 static inline u64 file_mmap_size_max(struct file *file, struct inode *inode)
1355 {
1356         if (S_ISREG(inode->i_mode))
1357                 return MAX_LFS_FILESIZE;
1358 
1359         if (S_ISBLK(inode->i_mode))
1360                 return MAX_LFS_FILESIZE;
1361 
1362         if (S_ISSOCK(inode->i_mode))
1363                 return MAX_LFS_FILESIZE;
1364 
1365         /* Special "we do even unsigned file positions" case */
1366         if (file->f_mode & FMODE_UNSIGNED_OFFSET)
1367                 return 0;
1368 
1369         /* Yes, random drivers might want more. But I'm tired of buggy drivers */
1370         return ULONG_MAX;
1371 }
1372 
1373 static inline bool file_mmap_ok(struct file *file, struct inode *inode,
1374                                 unsigned long pgoff, unsigned long len)
1375 {
1376         u64 maxsize = file_mmap_size_max(file, inode);
1377 
1378         if (maxsize && len > maxsize)
1379                 return false;
1380         maxsize -= len;
1381         if (pgoff > maxsize >> PAGE_SHIFT)
1382                 return false;
1383         return true;
1384 }
1385 
1386 /*
1387  * The caller must hold down_write(&current->mm->mmap_sem).
1388  */
1389 unsigned long do_mmap(struct file *file, unsigned long addr,
1390                         unsigned long len, unsigned long prot,
1391                         unsigned long flags, vm_flags_t vm_flags,
1392                         unsigned long pgoff, unsigned long *populate,
1393                         struct list_head *uf)
1394 {
1395         struct mm_struct *mm = current->mm;
1396         int pkey = 0;
1397 
1398         *populate = 0;
1399 
1400         if (!len)
1401                 return -EINVAL;
1402 
1403         /*
1404          * Does the application expect PROT_READ to imply PROT_EXEC?
1405          *
1406          * (the exception is when the underlying filesystem is noexec
1407          *  mounted, in which case we dont add PROT_EXEC.)
1408          */
1409         if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
1410                 if (!(file && path_noexec(&file->f_path)))
1411                         prot |= PROT_EXEC;
1412 
1413         /* force arch specific MAP_FIXED handling in get_unmapped_area */
1414         if (flags & MAP_FIXED_NOREPLACE)
1415                 flags |= MAP_FIXED;
1416 
1417         if (!(flags & MAP_FIXED))
1418                 addr = round_hint_to_min(addr);
1419 
1420         /* Careful about overflows.. */
1421         len = PAGE_ALIGN(len);
1422         if (!len)
1423                 return -ENOMEM;
1424 
1425         /* offset overflow? */
1426         if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
1427                 return -EOVERFLOW;
1428 
1429         /* Too many mappings? */
1430         if (mm->map_count > sysctl_max_map_count)
1431                 return -ENOMEM;
1432 
1433         /* Obtain the address to map to. we verify (or select) it and ensure
1434          * that it represents a valid section of the address space.
1435          */
1436         addr = get_unmapped_area(file, addr, len, pgoff, flags);
1437         if (offset_in_page(addr))
1438                 return addr;
1439 
1440         if (flags & MAP_FIXED_NOREPLACE) {
1441                 struct vm_area_struct *vma = find_vma(mm, addr);
1442 
1443                 if (vma && vma->vm_start < addr + len)
1444                         return -EEXIST;
1445         }
1446 
1447         if (prot == PROT_EXEC) {
1448                 pkey = execute_only_pkey(mm);
1449                 if (pkey < 0)
1450                         pkey = 0;
1451         }
1452 
1453         /* Do simple checking here so the lower-level routines won't have
1454          * to. we assume access permissions have been handled by the open
1455          * of the memory object, so we don't do any here.
1456          */
1457         vm_flags |= calc_vm_prot_bits(prot, pkey) | calc_vm_flag_bits(flags) |
1458                         mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
1459 
1460         if (flags & MAP_LOCKED)
1461                 if (!can_do_mlock())
1462                         return -EPERM;
1463 
1464         if (mlock_future_check(mm, vm_flags, len))
1465                 return -EAGAIN;
1466 
1467         if (file) {
1468                 struct inode *inode = file_inode(file);
1469                 unsigned long flags_mask;
1470 
1471                 if (!file_mmap_ok(file, inode, pgoff, len))
1472                         return -EOVERFLOW;
1473 
1474                 flags_mask = LEGACY_MAP_MASK | file->f_op->mmap_supported_flags;
1475 
1476                 switch (flags & MAP_TYPE) {
1477                 case MAP_SHARED:
1478                         /*
1479                          * Force use of MAP_SHARED_VALIDATE with non-legacy
1480                          * flags. E.g. MAP_SYNC is dangerous to use with
1481                          * MAP_SHARED as you don't know which consistency model
1482                          * you will get. We silently ignore unsupported flags
1483                          * with MAP_SHARED to preserve backward compatibility.
1484                          */
1485                         flags &= LEGACY_MAP_MASK;
1486                         /* fall through */
1487                 case MAP_SHARED_VALIDATE:
1488                         if (flags & ~flags_mask)
1489                                 return -EOPNOTSUPP;
1490                         if (prot & PROT_WRITE) {
1491                                 if (!(file->f_mode & FMODE_WRITE))
1492                                         return -EACCES;
1493                                 if (IS_SWAPFILE(file->f_mapping->host))
1494                                         return -ETXTBSY;
1495                         }
1496 
1497                         /*
1498                          * Make sure we don't allow writing to an append-only
1499                          * file..
1500                          */
1501                         if (IS_APPEND(inode) && (file->f_mode & FMODE_WRITE))
1502                                 return -EACCES;
1503 
1504                         /*
1505                          * Make sure there are no mandatory locks on the file.
1506                          */
1507                         if (locks_verify_locked(file))
1508                                 return -EAGAIN;
1509 
1510                         vm_flags |= VM_SHARED | VM_MAYSHARE;
1511                         if (!(file->f_mode & FMODE_WRITE))
1512                                 vm_flags &= ~(VM_MAYWRITE | VM_SHARED);
1513 
1514                         /* fall through */
1515                 case MAP_PRIVATE:
1516                         if (!(file->f_mode & FMODE_READ))
1517                                 return -EACCES;
1518                         if (path_noexec(&file->f_path)) {
1519                                 if (vm_flags & VM_EXEC)
1520                                         return -EPERM;
1521                                 vm_flags &= ~VM_MAYEXEC;
1522                         }
1523 
1524                         if (!file->f_op->mmap)
1525                                 return -ENODEV;
1526                         if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1527                                 return -EINVAL;
1528                         break;
1529 
1530                 default:
1531                         return -EINVAL;
1532                 }
1533         } else {
1534                 switch (flags & MAP_TYPE) {
1535                 case MAP_SHARED:
1536                         if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1537                                 return -EINVAL;
1538                         /*
1539                          * Ignore pgoff.
1540                          */
1541                         pgoff = 0;
1542                         vm_flags |= VM_SHARED | VM_MAYSHARE;
1543                         break;
1544                 case MAP_PRIVATE:
1545                         /*
1546                          * Set pgoff according to addr for anon_vma.
1547                          */
1548                         pgoff = addr >> PAGE_SHIFT;
1549                         break;
1550                 default:
1551                         return -EINVAL;
1552                 }
1553         }
1554 
1555         /*
1556          * Set 'VM_NORESERVE' if we should not account for the
1557          * memory use of this mapping.
1558          */
1559         if (flags & MAP_NORESERVE) {
1560                 /* We honor MAP_NORESERVE if allowed to overcommit */
1561                 if (sysctl_overcommit_memory != OVERCOMMIT_NEVER)
1562                         vm_flags |= VM_NORESERVE;
1563 
1564                 /* hugetlb applies strict overcommit unless MAP_NORESERVE */
1565                 if (file && is_file_hugepages(file))
1566                         vm_flags |= VM_NORESERVE;
1567         }
1568 
1569         addr = mmap_region(file, addr, len, vm_flags, pgoff, uf);
1570         if (!IS_ERR_VALUE(addr) &&
1571             ((vm_flags & VM_LOCKED) ||
1572              (flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE))
1573                 *populate = len;
1574         return addr;
1575 }
1576 
1577 unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
1578                               unsigned long prot, unsigned long flags,
1579                               unsigned long fd, unsigned long pgoff)
1580 {
1581         struct file *file = NULL;
1582         unsigned long retval;
1583 
1584         if (!(flags & MAP_ANONYMOUS)) {
1585                 audit_mmap_fd(fd, flags);
1586                 file = fget(fd);
1587                 if (!file)
1588                         return -EBADF;
1589                 if (is_file_hugepages(file))
1590                         len = ALIGN(len, huge_page_size(hstate_file(file)));
1591                 retval = -EINVAL;
1592                 if (unlikely(flags & MAP_HUGETLB && !is_file_hugepages(file)))
1593                         goto out_fput;
1594         } else if (flags & MAP_HUGETLB) {
1595                 struct user_struct *user = NULL;
1596                 struct hstate *hs;
1597 
1598                 hs = hstate_sizelog((flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK);
1599                 if (!hs)
1600                         return -EINVAL;
1601 
1602                 len = ALIGN(len, huge_page_size(hs));
1603                 /*
1604                  * VM_NORESERVE is used because the reservations will be
1605                  * taken when vm_ops->mmap() is called
1606                  * A dummy user value is used because we are not locking
1607                  * memory so no accounting is necessary
1608                  */
1609                 file = hugetlb_file_setup(HUGETLB_ANON_FILE, len,
1610                                 VM_NORESERVE,
1611                                 &user, HUGETLB_ANONHUGE_INODE,
1612                                 (flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK);
1613                 if (IS_ERR(file))
1614                         return PTR_ERR(file);
1615         }
1616 
1617         flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
1618 
1619         retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
1620 out_fput:
1621         if (file)
1622                 fput(file);
1623         return retval;
1624 }
1625 
1626 SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
1627                 unsigned long, prot, unsigned long, flags,
1628                 unsigned long, fd, unsigned long, pgoff)
1629 {
1630         return ksys_mmap_pgoff(addr, len, prot, flags, fd, pgoff);
1631 }
1632 
1633 #ifdef __ARCH_WANT_SYS_OLD_MMAP
1634 struct mmap_arg_struct {
1635         unsigned long addr;
1636         unsigned long len;
1637         unsigned long prot;
1638         unsigned long flags;
1639         unsigned long fd;
1640         unsigned long offset;
1641 };
1642 
1643 SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
1644 {
1645         struct mmap_arg_struct a;
1646 
1647         if (copy_from_user(&a, arg, sizeof(a)))
1648                 return -EFAULT;
1649         if (offset_in_page(a.offset))
1650                 return -EINVAL;
1651 
1652         return ksys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
1653                                a.offset >> PAGE_SHIFT);
1654 }
1655 #endif /* __ARCH_WANT_SYS_OLD_MMAP */
1656 
1657 /*
1658  * Some shared mappings will want the pages marked read-only
1659  * to track write events. If so, we'll downgrade vm_page_prot
1660  * to the private version (using protection_map[] without the
1661  * VM_SHARED bit).
1662  */
1663 int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot)
1664 {
1665         vm_flags_t vm_flags = vma->vm_flags;
1666         const struct vm_operations_struct *vm_ops = vma->vm_ops;
1667 
1668         /* If it was private or non-writable, the write bit is already clear */
1669         if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED)))
1670                 return 0;
1671 
1672         /* The backer wishes to know when pages are first written to? */
1673         if (vm_ops && (vm_ops->page_mkwrite || vm_ops->pfn_mkwrite))
1674                 return 1;
1675 
1676         /* The open routine did something to the protections that pgprot_modify
1677          * won't preserve? */
1678         if (pgprot_val(vm_page_prot) !=
1679             pgprot_val(vm_pgprot_modify(vm_page_prot, vm_flags)))
1680                 return 0;
1681 
1682         /* Do we need to track softdirty? */
1683         if (IS_ENABLED(CONFIG_MEM_SOFT_DIRTY) && !(vm_flags & VM_SOFTDIRTY))
1684                 return 1;
1685 
1686         /* Specialty mapping? */
1687         if (vm_flags & VM_PFNMAP)
1688                 return 0;
1689 
1690         /* Can the mapping track the dirty pages? */
1691         return vma->vm_file && vma->vm_file->f_mapping &&
1692                 mapping_cap_account_dirty(vma->vm_file->f_mapping);
1693 }
1694 
1695 /*
1696  * We account for memory if it's a private writeable mapping,
1697  * not hugepages and VM_NORESERVE wasn't set.
1698  */
1699 static inline int accountable_mapping(struct file *file, vm_flags_t vm_flags)
1700 {
1701         /*
1702          * hugetlb has its own accounting separate from the core VM
1703          * VM_HUGETLB may not be set yet so we cannot check for that flag.
1704          */
1705         if (file && is_file_hugepages(file))
1706                 return 0;
1707 
1708         return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE;
1709 }
1710 
1711 unsigned long mmap_region(struct file *file, unsigned long addr,
1712                 unsigned long len, vm_flags_t vm_flags, unsigned long pgoff,
1713                 struct list_head *uf)
1714 {
1715         struct mm_struct *mm = current->mm;
1716         struct vm_area_struct *vma, *prev;
1717         int error;
1718         struct rb_node **rb_link, *rb_parent;
1719         unsigned long charged = 0;
1720 
1721         /* Check against address space limit. */
1722         if (!may_expand_vm(mm, vm_flags, len >> PAGE_SHIFT)) {
1723                 unsigned long nr_pages;
1724 
1725                 /*
1726                  * MAP_FIXED may remove pages of mappings that intersects with
1727                  * requested mapping. Account for the pages it would unmap.
1728                  */
1729                 nr_pages = count_vma_pages_range(mm, addr, addr + len);
1730 
1731                 if (!may_expand_vm(mm, vm_flags,
1732                                         (len >> PAGE_SHIFT) - nr_pages))
1733                         return -ENOMEM;
1734         }
1735 
1736         /* Clear old maps */
1737         while (find_vma_links(mm, addr, addr + len, &prev, &rb_link,
1738                               &rb_parent)) {
1739                 if (do_munmap(mm, addr, len, uf))
1740                         return -ENOMEM;
1741         }
1742 
1743         /*
1744          * Private writable mapping: check memory availability
1745          */
1746         if (accountable_mapping(file, vm_flags)) {
1747                 charged = len >> PAGE_SHIFT;
1748                 if (security_vm_enough_memory_mm(mm, charged))
1749                         return -ENOMEM;
1750                 vm_flags |= VM_ACCOUNT;
1751         }
1752 
1753         /*
1754          * Can we just expand an old mapping?
1755          */
1756         vma = vma_merge(mm, prev, addr, addr + len, vm_flags,
1757                         NULL, file, pgoff, NULL, NULL_VM_UFFD_CTX);
1758         if (vma)
1759                 goto out;
1760 
1761         /*
1762          * Determine the object being mapped and call the appropriate
1763          * specific mapper. the address has already been validated, but
1764          * not unmapped, but the maps are removed from the list.
1765          */
1766         vma = vm_area_alloc(mm);
1767         if (!vma) {
1768                 error = -ENOMEM;
1769                 goto unacct_error;
1770         }
1771 
1772         vma->vm_start = addr;
1773         vma->vm_end = addr + len;
1774         vma->vm_flags = vm_flags;
1775         vma->vm_page_prot = vm_get_page_prot(vm_flags);
1776         vma->vm_pgoff = pgoff;
1777 
1778         if (file) {
1779                 if (vm_flags & VM_DENYWRITE) {
1780                         error = deny_write_access(file);
1781                         if (error)
1782                                 goto free_vma;
1783                 }
1784                 if (vm_flags & VM_SHARED) {
1785                         error = mapping_map_writable(file->f_mapping);
1786                         if (error)
1787                                 goto allow_write_and_free_vma;
1788                 }
1789 
1790                 /* ->mmap() can change vma->vm_file, but must guarantee that
1791                  * vma_link() below can deny write-access if VM_DENYWRITE is set
1792                  * and map writably if VM_SHARED is set. This usually means the
1793                  * new file must not have been exposed to user-space, yet.
1794                  */
1795                 vma->vm_file = get_file(file);
1796                 error = call_mmap(file, vma);
1797                 if (error)
1798                         goto unmap_and_free_vma;
1799 
1800                 /* Can addr have changed??
1801                  *
1802                  * Answer: Yes, several device drivers can do it in their
1803                  *         f_op->mmap method. -DaveM
1804                  * Bug: If addr is changed, prev, rb_link, rb_parent should
1805                  *      be updated for vma_link()
1806                  */
1807                 WARN_ON_ONCE(addr != vma->vm_start);
1808 
1809                 addr = vma->vm_start;
1810                 vm_flags = vma->vm_flags;
1811         } else if (vm_flags & VM_SHARED) {
1812                 error = shmem_zero_setup(vma);
1813                 if (error)
1814                         goto free_vma;
1815         } else {
1816                 vma_set_anonymous(vma);
1817         }
1818 
1819         vma_link(mm, vma, prev, rb_link, rb_parent);
1820         /* Once vma denies write, undo our temporary denial count */
1821         if (file) {
1822                 if (vm_flags & VM_SHARED)
1823                         mapping_unmap_writable(file->f_mapping);
1824                 if (vm_flags & VM_DENYWRITE)
1825                         allow_write_access(file);
1826         }
1827         file = vma->vm_file;
1828 out:
1829         perf_event_mmap(vma);
1830 
1831         vm_stat_account(mm, vm_flags, len >> PAGE_SHIFT);
1832         if (vm_flags & VM_LOCKED) {
1833                 if ((vm_flags & VM_SPECIAL) || vma_is_dax(vma) ||
1834                                         is_vm_hugetlb_page(vma) ||
1835                                         vma == get_gate_vma(current->mm))
1836                         vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
1837                 else
1838                         mm->locked_vm += (len >> PAGE_SHIFT);
1839         }
1840 
1841         if (file)
1842                 uprobe_mmap(vma);
1843 
1844         /*
1845          * New (or expanded) vma always get soft dirty status.
1846          * Otherwise user-space soft-dirty page tracker won't
1847          * be able to distinguish situation when vma area unmapped,
1848          * then new mapped in-place (which must be aimed as
1849          * a completely new data area).
1850          */
1851         vma->vm_flags |= VM_SOFTDIRTY;
1852 
1853         vma_set_page_prot(vma);
1854 
1855         return addr;
1856 
1857 unmap_and_free_vma:
1858         vma->vm_file = NULL;
1859         fput(file);
1860 
1861         /* Undo any partial mapping done by a device driver. */
1862         unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);
1863         charged = 0;
1864         if (vm_flags & VM_SHARED)
1865                 mapping_unmap_writable(file->f_mapping);
1866 allow_write_and_free_vma:
1867         if (vm_flags & VM_DENYWRITE)
1868                 allow_write_access(file);
1869 free_vma:
1870         vm_area_free(vma);
1871 unacct_error:
1872         if (charged)
1873                 vm_unacct_memory(charged);
1874         return error;
1875 }
1876 
1877 unsigned long unmapped_area(struct vm_unmapped_area_info *info)
1878 {
1879         /*
1880          * We implement the search by looking for an rbtree node that
1881          * immediately follows a suitable gap. That is,
1882          * - gap_start = vma->vm_prev->vm_end <= info->high_limit - length;
1883          * - gap_end   = vma->vm_start        >= info->low_limit  + length;
1884          * - gap_end - gap_start >= length
1885          */
1886 
1887         struct mm_struct *mm = current->mm;
1888         struct vm_area_struct *vma;
1889         unsigned long length, low_limit, high_limit, gap_start, gap_end;
1890 
1891         /* Adjust search length to account for worst case alignment overhead */
1892         length = info->length + info->align_mask;
1893         if (length < info->length)
1894                 return -ENOMEM;
1895 
1896         /* Adjust search limits by the desired length */
1897         if (info->high_limit < length)
1898                 return -ENOMEM;
1899         high_limit = info->high_limit - length;
1900 
1901         if (info->low_limit > high_limit)
1902                 return -ENOMEM;
1903         low_limit = info->low_limit + length;
1904 
1905         /* Check if rbtree root looks promising */
1906         if (RB_EMPTY_ROOT(&mm->mm_rb))
1907                 goto check_highest;
1908         vma = rb_entry(mm->mm_rb.rb_node, struct vm_area_struct, vm_rb);
1909         if (vma->rb_subtree_gap < length)
1910                 goto check_highest;
1911 
1912         while (true) {
1913                 /* Visit left subtree if it looks promising */
1914                 gap_end = vm_start_gap(vma);
1915                 if (gap_end >= low_limit && vma->vm_rb.rb_left) {
1916                         struct vm_area_struct *left =
1917                                 rb_entry(vma->vm_rb.rb_left,
1918                                          struct vm_area_struct, vm_rb);
1919                         if (left->rb_subtree_gap >= length) {
1920                                 vma = left;
1921                                 continue;
1922                         }
1923                 }
1924 
1925                 gap_start = vma->vm_prev ? vm_end_gap(vma->vm_prev) : 0;
1926 check_current:
1927                 /* Check if current node has a suitable gap */
1928                 if (gap_start > high_limit)
1929                         return -ENOMEM;
1930                 if (gap_end >= low_limit &&
1931                     gap_end > gap_start && gap_end - gap_start >= length)
1932                         goto found;
1933 
1934                 /* Visit right subtree if it looks promising */
1935                 if (vma->vm_rb.rb_right) {
1936                         struct vm_area_struct *right =
1937                                 rb_entry(vma->vm_rb.rb_right,
1938                                          struct vm_area_struct, vm_rb);
1939                         if (right->rb_subtree_gap >= length) {
1940                                 vma = right;
1941                                 continue;
1942                         }
1943                 }
1944 
1945                 /* Go back up the rbtree to find next candidate node */
1946                 while (true) {
1947                         struct rb_node *prev = &vma->vm_rb;
1948                         if (!rb_parent(prev))
1949                                 goto check_highest;
1950                         vma = rb_entry(rb_parent(prev),
1951                                        struct vm_area_struct, vm_rb);
1952                         if (prev == vma->vm_rb.rb_left) {
1953                                 gap_start = vm_end_gap(vma->vm_prev);
1954                                 gap_end = vm_start_gap(vma);
1955                                 goto check_current;
1956                         }
1957                 }
1958         }
1959 
1960 check_highest:
1961         /* Check highest gap, which does not precede any rbtree node */
1962         gap_start = mm->highest_vm_end;
1963         gap_end = ULONG_MAX;  /* Only for VM_BUG_ON below */
1964         if (gap_start > high_limit)
1965                 return -ENOMEM;
1966 
1967 found:
1968         /* We found a suitable gap. Clip it with the original low_limit. */
1969         if (gap_start < info->low_limit)
1970                 gap_start = info->low_limit;
1971 
1972         /* Adjust gap address to the desired alignment */
1973         gap_start += (info->align_offset - gap_start) & info->align_mask;
1974 
1975         VM_BUG_ON(gap_start + info->length > info->high_limit);
1976         VM_BUG_ON(gap_start + info->length > gap_end);
1977         return gap_start;
1978 }
1979 
1980 unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
1981 {
1982         struct mm_struct *mm = current->mm;
1983         struct vm_area_struct *vma;
1984         unsigned long length, low_limit, high_limit, gap_start, gap_end;
1985 
1986         /* Adjust search length to account for worst case alignment overhead */
1987         length = info->length + info->align_mask;
1988         if (length < info->length)
1989                 return -ENOMEM;
1990 
1991         /*
1992          * Adjust search limits by the desired length.
1993          * See implementation comment at top of unmapped_area().
1994          */
1995         gap_end = info->high_limit;
1996         if (gap_end < length)
1997                 return -ENOMEM;
1998         high_limit = gap_end - length;
1999 
2000         if (info->low_limit > high_limit)
2001                 return -ENOMEM;
2002         low_limit = info->low_limit + length;
2003 
2004         /* Check highest gap, which does not precede any rbtree node */
2005         gap_start = mm->highest_vm_end;
2006         if (gap_start <= high_limit)
2007                 goto found_highest;
2008 
2009         /* Check if rbtree root looks promising */
2010         if (RB_EMPTY_ROOT(&mm->mm_rb))
2011                 return -ENOMEM;
2012         vma = rb_entry(mm->mm_rb.rb_node, struct vm_area_struct, vm_rb);
2013         if (vma->rb_subtree_gap < length)
2014                 return -ENOMEM;
2015 
2016         while (true) {
2017                 /* Visit right subtree if it looks promising */
2018                 gap_start = vma->vm_prev ? vm_end_gap(vma->vm_prev) : 0;
2019                 if (gap_start <= high_limit && vma->vm_rb.rb_right) {
2020                         struct vm_area_struct *right =
2021                                 rb_entry(vma->vm_rb.rb_right,
2022                                          struct vm_area_struct, vm_rb);
2023                         if (right->rb_subtree_gap >= length) {
2024                                 vma = right;
2025                                 continue;
2026                         }
2027                 }
2028 
2029 check_current:
2030                 /* Check if current node has a suitable gap */
2031                 gap_end = vm_start_gap(vma);
2032                 if (gap_end < low_limit)
2033                         return -ENOMEM;
2034                 if (gap_start <= high_limit &&
2035                     gap_end > gap_start && gap_end - gap_start >= length)
2036                         goto found;
2037 
2038                 /* Visit left subtree if it looks promising */
2039                 if (vma->vm_rb.rb_left) {
2040                         struct vm_area_struct *left =
2041                                 rb_entry(vma->vm_rb.rb_left,
2042                                          struct vm_area_struct, vm_rb);
2043                         if (left->rb_subtree_gap >= length) {
2044                                 vma = left;
2045                                 continue;
2046                         }
2047                 }
2048 
2049                 /* Go back up the rbtree to find next candidate node */
2050                 while (true) {
2051                         struct rb_node *prev = &vma->vm_rb;
2052                         if (!rb_parent(prev))
2053                                 return -ENOMEM;
2054                         vma = rb_entry(rb_parent(prev),
2055                                        struct vm_area_struct, vm_rb);
2056                         if (prev == vma->vm_rb.rb_right) {
2057                                 gap_start = vma->vm_prev ?
2058                                         vm_end_gap(vma->vm_prev) : 0;
2059                                 goto check_current;
2060                         }
2061                 }
2062         }
2063 
2064 found:
2065         /* We found a suitable gap. Clip it with the original high_limit. */
2066         if (gap_end > info->high_limit)
2067                 gap_end = info->high_limit;
2068 
2069 found_highest:
2070         /* Compute highest gap address at the desired alignment */
2071         gap_end -= info->length;
2072         gap_end -= (gap_end - info->align_offset) & info->align_mask;
2073 
2074         VM_BUG_ON(gap_end < info->low_limit);
2075         VM_BUG_ON(gap_end < gap_start);
2076         return gap_end;
2077 }
2078 
2079 
2080 #ifndef arch_get_mmap_end
2081 #define arch_get_mmap_end(addr) (TASK_SIZE)
2082 #endif
2083 
2084 #ifndef arch_get_mmap_base
2085 #define arch_get_mmap_base(addr, base) (base)
2086 #endif
2087 
2088 /* Get an address range which is currently unmapped.
2089  * For shmat() with addr=0.
2090  *
2091  * Ugly calling convention alert:
2092  * Return value with the low bits set means error value,
2093  * ie
2094  *      if (ret & ~PAGE_MASK)
2095  *              error = ret;
2096  *
2097  * This function "knows" that -ENOMEM has the bits set.
2098  */
2099 #ifndef HAVE_ARCH_UNMAPPED_AREA
2100 unsigned long
2101 arch_get_unmapped_area(struct file *filp, unsigned long addr,
2102                 unsigned long len, unsigned long pgoff, unsigned long flags)
2103 {
2104         struct mm_struct *mm = current->mm;
2105         struct vm_area_struct *vma, *prev;
2106         struct vm_unmapped_area_info info;
2107         const unsigned long mmap_end = arch_get_mmap_end(addr);
2108 
2109         if (len > mmap_end - mmap_min_addr)
2110                 return -ENOMEM;
2111 
2112         if (flags & MAP_FIXED)
2113                 return addr;
2114 
2115         if (addr) {
2116                 addr = PAGE_ALIGN(addr);
2117                 vma = find_vma_prev(mm, addr, &prev);
2118                 if (mmap_end - len >= addr && addr >= mmap_min_addr &&
2119                     (!vma || addr + len <= vm_start_gap(vma)) &&
2120                     (!prev || addr >= vm_end_gap(prev)))
2121                         return addr;
2122         }
2123 
2124         info.flags = 0;
2125         info.length = len;
2126         info.low_limit = mm->mmap_base;
2127         info.high_limit = mmap_end;
2128         info.align_mask = 0;
2129         return vm_unmapped_area(&info);
2130 }
2131 #endif
2132 
2133 /*
2134  * This mmap-allocator allocates new areas top-down from below the
2135  * stack's low limit (the base):
2136  */
2137 #ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
2138 unsigned long
2139 arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
2140                           unsigned long len, unsigned long pgoff,
2141                           unsigned long flags)
2142 {
2143         struct vm_area_struct *vma, *prev;
2144         struct mm_struct *mm = current->mm;
2145         struct vm_unmapped_area_info info;
2146         const unsigned long mmap_end = arch_get_mmap_end(addr);
2147 
2148         /* requested length too big for entire address space */
2149         if (len > mmap_end - mmap_min_addr)
2150                 return -ENOMEM;
2151 
2152         if (flags & MAP_FIXED)
2153                 return addr;
2154 
2155         /* requesting a specific address */
2156         if (addr) {
2157                 addr = PAGE_ALIGN(addr);
2158                 vma = find_vma_prev(mm, addr, &prev);
2159                 if (mmap_end - len >= addr && addr >= mmap_min_addr &&
2160                                 (!vma || addr + len <= vm_start_gap(vma)) &&
2161                                 (!prev || addr >= vm_end_gap(prev)))
2162                         return addr;
2163         }
2164 
2165         info.flags = VM_UNMAPPED_AREA_TOPDOWN;
2166         info.length = len;
2167         info.low_limit = max(PAGE_SIZE, mmap_min_addr);
2168         info.high_limit = arch_get_mmap_base(addr, mm->mmap_base);
2169         info.align_mask = 0;
2170         addr = vm_unmapped_area(&info);
2171 
2172         /*
2173          * A failed mmap() very likely causes application failure,
2174          * so fall back to the bottom-up function here. This scenario
2175          * can happen with large stack limits and large mmap()
2176          * allocations.
2177          */
2178         if (offset_in_page(addr)) {
2179                 VM_BUG_ON(addr != -ENOMEM);
2180                 info.flags = 0;
2181                 info.low_limit = TASK_UNMAPPED_BASE;
2182                 info.high_limit = mmap_end;
2183                 addr = vm_unmapped_area(&info);
2184         }
2185 
2186         return addr;
2187 }
2188 #endif
2189 
2190 unsigned long
2191 get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
2192                 unsigned long pgoff, unsigned long flags)
2193 {
2194         unsigned long (*get_area)(struct file *, unsigned long,
2195                                   unsigned long, unsigned long, unsigned long);
2196 
2197         unsigned long error = arch_mmap_check(addr, len, flags);
2198         if (error)
2199                 return error;
2200 
2201         /* Careful about overflows.. */
2202         if (len > TASK_SIZE)
2203                 return -ENOMEM;
2204 
2205         get_area = current->mm->get_unmapped_area;
2206         if (file) {
2207                 if (file->f_op->get_unmapped_area)
2208                         get_area = file->f_op->get_unmapped_area;
2209         } else if (flags & MAP_SHARED) {
2210                 /*
2211                  * mmap_region() will call shmem_zero_setup() to create a file,
2212                  * so use shmem's get_unmapped_area in case it can be huge.
2213                  * do_mmap_pgoff() will clear pgoff, so match alignment.
2214                  */
2215                 pgoff = 0;
2216                 get_area = shmem_get_unmapped_area;
2217         }
2218 
2219         addr = get_area(file, addr, len, pgoff, flags);
2220         if (IS_ERR_VALUE(addr))
2221                 return addr;
2222 
2223         if (addr > TASK_SIZE - len)
2224                 return -ENOMEM;
2225         if (offset_in_page(addr))
2226                 return -EINVAL;
2227 
2228         error = security_mmap_addr(addr);
2229         return error ? error : addr;
2230 }
2231 
2232 EXPORT_SYMBOL(get_unmapped_area);
2233 
2234 /* Look up the first VMA which satisfies  addr < vm_end,  NULL if none. */
2235 struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
2236 {
2237         struct rb_node *rb_node;
2238         struct vm_area_struct *vma;
2239 
2240         /* Check the cache first. */
2241         vma = vmacache_find(mm, addr);
2242         if (likely(vma))
2243                 return vma;
2244 
2245         rb_node = mm->mm_rb.rb_node;
2246 
2247         while (rb_node) {
2248                 struct vm_area_struct *tmp;
2249 
2250                 tmp = rb_entry(rb_node, struct vm_area_struct, vm_rb);
2251 
2252                 if (tmp->vm_end > addr) {
2253                         vma = tmp;
2254                         if (tmp->vm_start <= addr)
2255                                 break;
2256                         rb_node = rb_node->rb_left;
2257                 } else
2258                         rb_node = rb_node->rb_right;
2259         }
2260 
2261         if (vma)
2262                 vmacache_update(addr, vma);
2263         return vma;
2264 }
2265 
2266 EXPORT_SYMBOL(find_vma);
2267 
2268 /*
2269  * Same as find_vma, but also return a pointer to the previous VMA in *pprev.
2270  */
2271 struct vm_area_struct *
2272 find_vma_prev(struct mm_struct *mm, unsigned long addr,
2273                         struct vm_area_struct **pprev)
2274 {
2275         struct vm_area_struct *vma;
2276 
2277         vma = find_vma(mm, addr);
2278         if (vma) {
2279                 *pprev = vma->vm_prev;
2280         } else {
2281                 struct rb_node *rb_node = rb_last(&mm->mm_rb);
2282 
2283                 *pprev = rb_node ? rb_entry(rb_node, struct vm_area_struct, vm_rb) : NULL;
2284         }
2285         return vma;
2286 }
2287 
2288 /*
2289  * Verify that the stack growth is acceptable and
2290  * update accounting. This is shared with both the
2291  * grow-up and grow-down cases.
2292  */
2293 static int acct_stack_growth(struct vm_area_struct *vma,
2294                              unsigned long size, unsigned long grow)
2295 {
2296         struct mm_struct *mm = vma->vm_mm;
2297         unsigned long new_start;
2298 
2299         /* address space limit tests */
2300         if (!may_expand_vm(mm, vma->vm_flags, grow))
2301                 return -ENOMEM;
2302 
2303         /* Stack limit test */
2304         if (size > rlimit(RLIMIT_STACK))
2305                 return -ENOMEM;
2306 
2307         /* mlock limit tests */
2308         if (vma->vm_flags & VM_LOCKED) {
2309                 unsigned long locked;
2310                 unsigned long limit;
2311                 locked = mm->locked_vm + grow;
2312                 limit = rlimit(RLIMIT_MEMLOCK);
2313                 limit >>= PAGE_SHIFT;
2314                 if (locked > limit && !capable(CAP_IPC_LOCK))
2315                         return -ENOMEM;
2316         }
2317 
2318         /* Check to ensure the stack will not grow into a hugetlb-only region */
2319         new_start = (vma->vm_flags & VM_GROWSUP) ? vma->vm_start :
2320                         vma->vm_end - size;
2321         if (is_hugepage_only_range(vma->vm_mm, new_start, size))
2322                 return -EFAULT;
2323 
2324         /*
2325          * Overcommit..  This must be the final test, as it will
2326          * update security statistics.
2327          */
2328         if (security_vm_enough_memory_mm(mm, grow))
2329                 return -ENOMEM;
2330 
2331         return 0;
2332 }
2333 
2334 #if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
2335 /*
2336  * PA-RISC uses this for its stack; IA64 for its Register Backing Store.
2337  * vma is the last one with address > vma->vm_end.  Have to extend vma.
2338  */
2339 int expand_upwards(struct vm_area_struct *vma, unsigned long address)
2340 {
2341         struct mm_struct *mm = vma->vm_mm;
2342         struct vm_area_struct *next;
2343         unsigned long gap_addr;
2344         int error = 0;
2345 
2346         if (!(vma->vm_flags & VM_GROWSUP))
2347                 return -EFAULT;
2348 
2349         /* Guard against exceeding limits of the address space. */
2350         address &= PAGE_MASK;
2351         if (address >= (TASK_SIZE & PAGE_MASK))
2352                 return -ENOMEM;
2353         address += PAGE_SIZE;
2354 
2355         /* Enforce stack_guard_gap */
2356         gap_addr = address + stack_guard_gap;
2357 
2358         /* Guard against overflow */
2359         if (gap_addr < address || gap_addr > TASK_SIZE)
2360                 gap_addr = TASK_SIZE;
2361 
2362         next = vma->vm_next;
2363         if (next && next->vm_start < gap_addr &&
2364                         (next->vm_flags & (VM_WRITE|VM_READ|VM_EXEC))) {
2365                 if (!(next->vm_flags & VM_GROWSUP))
2366                         return -ENOMEM;
2367                 /* Check that both stack segments have the same anon_vma? */
2368         }
2369 
2370         /* We must make sure the anon_vma is allocated. */
2371         if (unlikely(anon_vma_prepare(vma)))
2372                 return -ENOMEM;
2373 
2374         /*
2375          * vma->vm_start/vm_end cannot change under us because the caller
2376          * is required to hold the mmap_sem in read mode.  We need the
2377          * anon_vma lock to serialize against concurrent expand_stacks.
2378          */
2379         anon_vma_lock_write(vma->anon_vma);
2380 
2381         /* Somebody else might have raced and expanded it already */
2382         if (address > vma->vm_end) {
2383                 unsigned long size, grow;
2384 
2385                 size = address - vma->vm_start;
2386                 grow = (address - vma->vm_end) >> PAGE_SHIFT;
2387 
2388                 error = -ENOMEM;
2389                 if (vma->vm_pgoff + (size >> PAGE_SHIFT) >= vma->vm_pgoff) {
2390                         error = acct_stack_growth(vma, size, grow);
2391                         if (!error) {
2392                                 /*
2393                                  * vma_gap_update() doesn't support concurrent
2394                                  * updates, but we only hold a shared mmap_sem
2395                                  * lock here, so we need to protect against
2396                                  * concurrent vma expansions.
2397                                  * anon_vma_lock_write() doesn't help here, as
2398                                  * we don't guarantee that all growable vmas
2399                                  * in a mm share the same root anon vma.
2400                                  * So, we reuse mm->page_table_lock to guard
2401                                  * against concurrent vma expansions.
2402                                  */
2403                                 spin_lock(&mm->page_table_lock);
2404                                 if (vma->vm_flags & VM_LOCKED)
2405                                         mm->locked_vm += grow;
2406                                 vm_stat_account(mm, vma->vm_flags, grow);
2407                                 anon_vma_interval_tree_pre_update_vma(vma);
2408                                 vma->vm_end = address;
2409                                 anon_vma_interval_tree_post_update_vma(vma);
2410                                 if (vma->vm_next)
2411                                         vma_gap_update(vma->vm_next);
2412                                 else
2413                                         mm->highest_vm_end = vm_end_gap(vma);
2414                                 spin_unlock(&mm->page_table_lock);
2415 
2416                                 perf_event_mmap(vma);
2417                         }
2418                 }
2419         }
2420         anon_vma_unlock_write(vma->anon_vma);
2421         khugepaged_enter_vma_merge(vma, vma->vm_flags);
2422         validate_mm(mm);
2423         return error;
2424 }
2425 #endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
2426 
2427 /*
2428  * vma is the first one with address < vma->vm_start.  Have to extend vma.
2429  */
2430 int expand_downwards(struct vm_area_struct *vma,
2431                                    unsigned long address)
2432 {
2433         struct mm_struct *mm = vma->vm_mm;
2434         struct vm_area_struct *prev;
2435         int error = 0;
2436 
2437         address &= PAGE_MASK;
2438         if (address < mmap_min_addr)
2439                 return -EPERM;
2440 
2441         /* Enforce stack_guard_gap */
2442         prev = vma->vm_prev;
2443         /* Check that both stack segments have the same anon_vma? */
2444         if (prev && !(prev->vm_flags & VM_GROWSDOWN) &&
2445                         (prev->vm_flags & (VM_WRITE|VM_READ|VM_EXEC))) {
2446                 if (address - prev->vm_end < stack_guard_gap)
2447                         return -ENOMEM;
2448         }
2449 
2450         /* We must make sure the anon_vma is allocated. */
2451         if (unlikely(anon_vma_prepare(vma)))
2452                 return -ENOMEM;
2453 
2454         /*
2455          * vma->vm_start/vm_end cannot change under us because the caller
2456          * is required to hold the mmap_sem in read mode.  We need the
2457          * anon_vma lock to serialize against concurrent expand_stacks.
2458          */
2459         anon_vma_lock_write(vma->anon_vma);
2460 
2461         /* Somebody else might have raced and expanded it already */
2462         if (address < vma->vm_start) {
2463                 unsigned long size, grow;
2464 
2465                 size = vma->vm_end - address;
2466                 grow = (vma->vm_start - address) >> PAGE_SHIFT;
2467 
2468                 error = -ENOMEM;
2469                 if (grow <= vma->vm_pgoff) {
2470                         error = acct_stack_growth(vma, size, grow);
2471                         if (!error) {
2472                                 /*
2473                                  * vma_gap_update() doesn't support concurrent
2474                                  * updates, but we only hold a shared mmap_sem
2475                                  * lock here, so we need to protect against
2476                                  * concurrent vma expansions.
2477                                  * anon_vma_lock_write() doesn't help here, as
2478                                  * we don't guarantee that all growable vmas
2479                                  * in a mm share the same root anon vma.
2480                                  * So, we reuse mm->page_table_lock to guard
2481                                  * against concurrent vma expansions.
2482                                  */
2483                                 spin_lock(&mm->page_table_lock);
2484                                 if (vma->vm_flags & VM_LOCKED)
2485                                         mm->locked_vm += grow;
2486                                 vm_stat_account(mm, vma->vm_flags, grow);
2487                                 anon_vma_interval_tree_pre_update_vma(vma);
2488                                 vma->vm_start = address;
2489                                 vma->vm_pgoff -= grow;
2490                                 anon_vma_interval_tree_post_update_vma(vma);
2491                                 vma_gap_update(vma);
2492                                 spin_unlock(&mm->page_table_lock);
2493 
2494                                 perf_event_mmap(vma);
2495                         }
2496                 }
2497         }
2498         anon_vma_unlock_write(vma->anon_vma);
2499         khugepaged_enter_vma_merge(vma, vma->vm_flags);
2500         validate_mm(mm);
2501         return error;
2502 }
2503 
2504 /* enforced gap between the expanding stack and other mappings. */
2505 unsigned long stack_guard_gap = 256UL<<PAGE_SHIFT;
2506 
2507 static int __init cmdline_parse_stack_guard_gap(char *p)
2508 {
2509         unsigned long val;
2510         char *endptr;
2511 
2512         val = simple_strtoul(p, &endptr, 10);
2513         if (!*endptr)
2514                 stack_guard_gap = val << PAGE_SHIFT;
2515 
2516         return 0;
2517 }
2518 __setup("stack_guard_gap=", cmdline_parse_stack_guard_gap);
2519 
2520 #ifdef CONFIG_STACK_GROWSUP
2521 int expand_stack(struct vm_area_struct *vma, unsigned long address)
2522 {
2523         return expand_upwards(vma, address);
2524 }
2525 
2526 struct vm_area_struct *
2527 find_extend_vma(struct mm_struct *mm, unsigned long addr)
2528 {
2529         struct vm_area_struct *vma, *prev;
2530 
2531         addr &= PAGE_MASK;
2532         vma = find_vma_prev(mm, addr, &prev);
2533         if (vma && (vma->vm_start <= addr))
2534                 return vma;
2535         /* don't alter vm_end if the coredump is running */
2536         if (!prev || !mmget_still_valid(mm) || expand_stack(prev, addr))
2537                 return NULL;
2538         if (prev->vm_flags & VM_LOCKED)
2539                 populate_vma_page_range(prev, addr, prev->vm_end, NULL);
2540         return prev;
2541 }
2542 #else
2543 int expand_stack(struct vm_area_struct *vma, unsigned long address)
2544 {
2545         return expand_downwards(vma, address);
2546 }
2547 
2548 struct vm_area_struct *
2549 find_extend_vma(struct mm_struct *mm, unsigned long addr)
2550 {
2551         struct vm_area_struct *vma;
2552         unsigned long start;
2553 
2554         addr &= PAGE_MASK;
2555         vma = find_vma(mm, addr);
2556         if (!vma)
2557                 return NULL;
2558         if (vma->vm_start <= addr)
2559                 return vma;
2560         if (!(vma->vm_flags & VM_GROWSDOWN))
2561                 return NULL;
2562         /* don't alter vm_start if the coredump is running */
2563         if (!mmget_still_valid(mm))
2564                 return NULL;
2565         start = vma->vm_start;
2566         if (expand_stack(vma, addr))
2567                 return NULL;
2568         if (vma->vm_flags & VM_LOCKED)
2569                 populate_vma_page_range(vma, addr, start, NULL);
2570         return vma;
2571 }
2572 #endif
2573 
2574 EXPORT_SYMBOL_GPL(find_extend_vma);
2575 
2576 /*
2577  * Ok - we have the memory areas we should free on the vma list,
2578  * so release them, and do the vma updates.
2579  *
2580  * Called with the mm semaphore held.
2581  */
2582 static void remove_vma_list(struct mm_struct *mm, struct vm_area_struct *vma)
2583 {
2584         unsigned long nr_accounted = 0;
2585 
2586         /* Update high watermark before we lower total_vm */
2587         update_hiwater_vm(mm);
2588         do {
2589                 long nrpages = vma_pages(vma);
2590 
2591                 if (vma->vm_flags & VM_ACCOUNT)
2592                         nr_accounted += nrpages;
2593                 vm_stat_account(mm, vma->vm_flags, -nrpages);
2594                 vma = remove_vma(vma);
2595         } while (vma);
2596         vm_unacct_memory(nr_accounted);
2597         validate_mm(mm);
2598 }
2599 
2600 /*
2601  * Get rid of page table information in the indicated region.
2602  *
2603  * Called with the mm semaphore held.
2604  */
2605 static void unmap_region(struct mm_struct *mm,
2606                 struct vm_area_struct *vma, struct vm_area_struct *prev,
2607                 unsigned long start, unsigned long end)
2608 {
2609         struct vm_area_struct *next = prev ? prev->vm_next : mm->mmap;
2610         struct mmu_gather tlb;
2611 
2612         lru_add_drain();
2613         tlb_gather_mmu(&tlb, mm, start, end);
2614         update_hiwater_rss(mm);
2615         unmap_vmas(&tlb, vma, start, end);
2616         free_pgtables(&tlb, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
2617                                  next ? next->vm_start : USER_PGTABLES_CEILING);
2618         tlb_finish_mmu(&tlb, start, end);
2619 }
2620 
2621 /*
2622  * Create a list of vma's touched by the unmap, removing them from the mm's
2623  * vma list as we go..
2624  */
2625 static void
2626 detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
2627         struct vm_area_struct *prev, unsigned long end)
2628 {
2629         struct vm_area_struct **insertion_point;
2630         struct vm_area_struct *tail_vma = NULL;
2631 
2632         insertion_point = (prev ? &prev->vm_next : &mm->mmap);
2633         vma->vm_prev = NULL;
2634         do {
2635                 vma_rb_erase(vma, &mm->mm_rb);
2636                 mm->map_count--;
2637                 tail_vma = vma;
2638                 vma = vma->vm_next;
2639         } while (vma && vma->vm_start < end);
2640         *insertion_point = vma;
2641         if (vma) {
2642                 vma->vm_prev = prev;
2643                 vma_gap_update(vma);
2644         } else
2645                 mm->highest_vm_end = prev ? vm_end_gap(prev) : 0;
2646         tail_vma->vm_next = NULL;
2647 
2648         /* Kill the cache */
2649         vmacache_invalidate(mm);
2650 }
2651 
2652 /*
2653  * __split_vma() bypasses sysctl_max_map_count checking.  We use this where it
2654  * has already been checked or doesn't make sense to fail.
2655  */
2656 int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
2657                 unsigned long addr, int new_below)
2658 {
2659         struct vm_area_struct *new;
2660         int err;
2661 
2662         if (vma->vm_ops && vma->vm_ops->split) {
2663                 err = vma->vm_ops->split(vma, addr);
2664                 if (err)
2665                         return err;
2666         }
2667 
2668         new = vm_area_dup(vma);
2669         if (!new)
2670                 return -ENOMEM;
2671 
2672         if (new_below)
2673                 new->vm_end = addr;
2674         else {
2675                 new->vm_start = addr;
2676                 new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
2677         }
2678 
2679         err = vma_dup_policy(vma, new);
2680         if (err)
2681                 goto out_free_vma;
2682 
2683         err = anon_vma_clone(new, vma);
2684         if (err)
2685                 goto out_free_mpol;
2686 
2687         if (new->vm_file)
2688                 get_file(new->vm_file);
2689 
2690         if (new->vm_ops && new->vm_ops->open)
2691                 new->vm_ops->open(new);
2692 
2693         if (new_below)
2694                 err = vma_adjust(vma, addr, vma->vm_end, vma->vm_pgoff +
2695                         ((addr - new->vm_start) >> PAGE_SHIFT), new);
2696         else
2697                 err = vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new);
2698 
2699         /* Success. */
2700         if (!err)
2701                 return 0;
2702 
2703         /* Clean everything up if vma_adjust failed. */
2704         if (new->vm_ops && new->vm_ops->close)
2705                 new->vm_ops->close(new);
2706         if (new->vm_file)
2707                 fput(new->vm_file);
2708         unlink_anon_vmas(new);
2709  out_free_mpol:
2710         mpol_put(vma_policy(new));
2711  out_free_vma:
2712         vm_area_free(new);
2713         return err;
2714 }
2715 
2716 /*
2717  * Split a vma into two pieces at address 'addr', a new vma is allocated
2718  * either for the first part or the tail.
2719  */
2720 int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
2721               unsigned long addr, int new_below)
2722 {
2723         if (mm->map_count >= sysctl_max_map_count)
2724                 return -ENOMEM;
2725 
2726         return __split_vma(mm, vma, addr, new_below);
2727 }
2728 
2729 /* Munmap is split into 2 main parts -- this part which finds
2730  * what needs doing, and the areas themselves, which do the
2731  * work.  This now handles partial unmappings.
2732  * Jeremy Fitzhardinge <jeremy@goop.org>
2733  */
2734 int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
2735                 struct list_head *uf, bool downgrade)
2736 {
2737         unsigned long end;
2738         struct vm_area_struct *vma, *prev, *last;
2739 
2740         if ((offset_in_page(start)) || start > TASK_SIZE || len > TASK_SIZE-start)
2741                 return -EINVAL;
2742 
2743         len = PAGE_ALIGN(len);
2744         end = start + len;
2745         if (len == 0)
2746                 return -EINVAL;
2747 
2748         /*
2749          * arch_unmap() might do unmaps itself.  It must be called
2750          * and finish any rbtree manipulation before this code
2751          * runs and also starts to manipulate the rbtree.
2752          */
2753         arch_unmap(mm, start, end);
2754 
2755         /* Find the first overlapping VMA */
2756         vma = find_vma(mm, start);
2757         if (!vma)
2758                 return 0;
2759         prev = vma->vm_prev;
2760         /* we have  start < vma->vm_end  */
2761 
2762         /* if it doesn't overlap, we have nothing.. */
2763         if (vma->vm_start >= end)
2764                 return 0;
2765 
2766         /*
2767          * If we need to split any vma, do it now to save pain later.
2768          *
2769          * Note: mremap's move_vma VM_ACCOUNT handling assumes a partially
2770          * unmapped vm_area_struct will remain in use: so lower split_vma
2771          * places tmp vma above, and higher split_vma places tmp vma below.
2772          */
2773         if (start > vma->vm_start) {
2774                 int error;
2775 
2776                 /*
2777                  * Make sure that map_count on return from munmap() will
2778                  * not exceed its limit; but let map_count go just above
2779                  * its limit temporarily, to help free resources as expected.
2780                  */
2781                 if (end < vma->vm_end && mm->map_count >= sysctl_max_map_count)
2782                         return -ENOMEM;
2783 
2784                 error = __split_vma(mm, vma, start, 0);
2785                 if (error)
2786                         return error;
2787                 prev = vma;
2788         }
2789 
2790         /* Does it split the last one? */
2791         last = find_vma(mm, end);
2792         if (last && end > last->vm_start) {
2793                 int error = __split_vma(mm, last, end, 1);
2794                 if (error)
2795                         return error;
2796         }
2797         vma = prev ? prev->vm_next : mm->mmap;
2798 
2799         if (unlikely(uf)) {
2800                 /*
2801                  * If userfaultfd_unmap_prep returns an error the vmas
2802                  * will remain splitted, but userland will get a
2803                  * highly unexpected error anyway. This is no
2804                  * different than the case where the first of the two
2805                  * __split_vma fails, but we don't undo the first
2806                  * split, despite we could. This is unlikely enough
2807                  * failure that it's not worth optimizing it for.
2808                  */
2809                 int error = userfaultfd_unmap_prep(vma, start, end, uf);
2810                 if (error)
2811                         return error;
2812         }
2813 
2814         /*
2815          * unlock any mlock()ed ranges before detaching vmas
2816          */
2817         if (mm->locked_vm) {
2818                 struct vm_area_struct *tmp = vma;
2819                 while (tmp && tmp->vm_start < end) {
2820                         if (tmp->vm_flags & VM_LOCKED) {
2821                                 mm->locked_vm -= vma_pages(tmp);
2822                                 munlock_vma_pages_all(tmp);
2823                         }
2824 
2825                         tmp = tmp->vm_next;
2826                 }
2827         }
2828 
2829         /* Detach vmas from rbtree */
2830         detach_vmas_to_be_unmapped(mm, vma, prev, end);
2831 
2832         if (downgrade)
2833                 downgrade_write(&mm->mmap_sem);
2834 
2835         unmap_region(mm, vma, prev, start, end);
2836 
2837         /* Fix up all other VM information */
2838         remove_vma_list(mm, vma);
2839 
2840         return downgrade ? 1 : 0;
2841 }
2842 
2843 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
2844               struct list_head *uf)
2845 {
2846         return __do_munmap(mm, start, len, uf, false);
2847 }
2848 
2849 static int __vm_munmap(unsigned long start, size_t len, bool downgrade)
2850 {
2851         int ret;
2852         struct mm_struct *mm = current->mm;
2853         LIST_HEAD(uf);
2854 
2855         if (down_write_killable(&mm->mmap_sem))
2856                 return -EINTR;
2857 
2858         ret = __do_munmap(mm, start, len, &uf, downgrade);
2859         /*
2860          * Returning 1 indicates mmap_sem is downgraded.
2861          * But 1 is not legal return value of vm_munmap() and munmap(), reset
2862          * it to 0 before return.
2863          */
2864         if (ret == 1) {
2865                 up_read(&mm->mmap_sem);
2866                 ret = 0;
2867         } else
2868                 up_write(&mm->mmap_sem);
2869 
2870         userfaultfd_unmap_complete(mm, &uf);
2871         return ret;
2872 }
2873 
2874 int vm_munmap(unsigned long start, size_t len)
2875 {
2876         return __vm_munmap(start, len, false);
2877 }
2878 EXPORT_SYMBOL(vm_munmap);
2879 
2880 SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
2881 {
2882         addr = untagged_addr(addr);
2883         profile_munmap(addr);
2884         return __vm_munmap(addr, len, true);
2885 }
2886 
2887 
2888 /*
2889  * Emulation of deprecated remap_file_pages() syscall.
2890  */
2891 SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
2892                 unsigned long, prot, unsigned long, pgoff, unsigned long, flags)
2893 {
2894 
2895         struct mm_struct *mm = current->mm;
2896         struct vm_area_struct *vma;
2897         unsigned long populate = 0;
2898         unsigned long ret = -EINVAL;
2899         struct file *file;
2900 
2901         pr_warn_once("%s (%d) uses deprecated remap_file_pages() syscall. See Documentation/vm/remap_file_pages.rst.\n",
2902                      current->comm, current->pid);
2903 
2904         if (prot)
2905                 return ret;
2906         start = start & PAGE_MASK;
2907         size = size & PAGE_MASK;
2908 
2909         if (start + size <= start)
2910                 return ret;
2911 
2912         /* Does pgoff wrap? */
2913         if (pgoff + (size >> PAGE_SHIFT) < pgoff)
2914                 return ret;
2915 
2916         if (down_write_killable(&mm->mmap_sem))
2917                 return -EINTR;
2918 
2919         vma = find_vma(mm, start);
2920 
2921         if (!vma || !(vma->vm_flags & VM_SHARED))
2922                 goto out;
2923 
2924         if (start < vma->vm_start)
2925                 goto out;
2926 
2927         if (start + size > vma->vm_end) {
2928                 struct vm_area_struct *next;
2929 
2930                 for (next = vma->vm_next; next; next = next->vm_next) {
2931                         /* hole between vmas ? */
2932                         if (next->vm_start != next->vm_prev->vm_end)
2933                                 goto out;
2934 
2935                         if (next->vm_file != vma->vm_file)
2936                                 goto out;
2937 
2938                         if (next->vm_flags != vma->vm_flags)
2939                                 goto out;
2940 
2941                         if (start + size <= next->vm_end)
2942                                 break;
2943                 }
2944 
2945                 if (!next)
2946                         goto out;
2947         }
2948 
2949         prot |= vma->vm_flags & VM_READ ? PROT_READ : 0;
2950         prot |= vma->vm_flags & VM_WRITE ? PROT_WRITE : 0;
2951         prot |= vma->vm_flags & VM_EXEC ? PROT_EXEC : 0;
2952 
2953         flags &= MAP_NONBLOCK;
2954         flags |= MAP_SHARED | MAP_FIXED | MAP_POPULATE;
2955         if (vma->vm_flags & VM_LOCKED) {
2956                 struct vm_area_struct *tmp;
2957                 flags |= MAP_LOCKED;
2958 
2959                 /* drop PG_Mlocked flag for over-mapped range */
2960                 for (tmp = vma; tmp->vm_start >= start + size;
2961                                 tmp = tmp->vm_next) {
2962                         /*
2963                          * Split pmd and munlock page on the border
2964                          * of the range.
2965                          */
2966                         vma_adjust_trans_huge(tmp, start, start + size, 0);
2967 
2968                         munlock_vma_pages_range(tmp,
2969                                         max(tmp->vm_start, start),
2970                                         min(tmp->vm_end, start + size));
2971                 }
2972         }
2973 
2974         file = get_file(vma->vm_file);
2975         ret = do_mmap_pgoff(vma->vm_file, start, size,
2976                         prot, flags, pgoff, &populate, NULL);
2977         fput(file);
2978 out:
2979         up_write(&mm->mmap_sem);
2980         if (populate)
2981                 mm_populate(ret, populate);
2982         if (!IS_ERR_VALUE(ret))
2983                 ret = 0;
2984         return ret;
2985 }
2986 
2987 /*
2988  *  this is really a simplified "do_mmap".  it only handles
2989  *  anonymous maps.  eventually we may be able to do some
2990  *  brk-specific accounting here.
2991  */
2992 static int do_brk_flags(unsigned long addr, unsigned long len, unsigned long flags, struct list_head *uf)
2993 {
2994         struct mm_struct *mm = current->mm;
2995         struct vm_area_struct *vma, *prev;
2996         struct rb_node **rb_link, *rb_parent;
2997         pgoff_t pgoff = addr >> PAGE_SHIFT;
2998         int error;
2999 
3000         /* Until we need other flags, refuse anything except VM_EXEC. */
3001         if ((flags & (~VM_EXEC)) != 0)
3002                 return -EINVAL;
3003         flags |= VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
3004 
3005         error = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
3006         if (offset_in_page(error))
3007                 return error;
3008 
3009         error = mlock_future_check(mm, mm->def_flags, len);
3010         if (error)
3011                 return error;
3012 
3013         /*
3014          * Clear old maps.  this also does some error checking for us
3015          */
3016         while (find_vma_links(mm, addr, addr + len, &prev, &rb_link,
3017                               &rb_parent)) {
3018                 if (do_munmap(mm, addr, len, uf))
3019                         return -ENOMEM;
3020         }
3021 
3022         /* Check against address space limits *after* clearing old maps... */
3023         if (!may_expand_vm(mm, flags, len >> PAGE_SHIFT))
3024                 return -ENOMEM;
3025 
3026         if (mm->map_count > sysctl_max_map_count)
3027                 return -ENOMEM;
3028 
3029         if (security_vm_enough_memory_mm(mm, len >> PAGE_SHIFT))
3030                 return -ENOMEM;
3031 
3032         /* Can we just expand an old private anonymous mapping? */
3033         vma = vma_merge(mm, prev, addr, addr + len, flags,
3034                         NULL, NULL, pgoff, NULL, NULL_VM_UFFD_CTX);
3035         if (vma)
3036                 goto out;
3037 
3038         /*
3039          * create a vma struct for an anonymous mapping
3040          */
3041         vma = vm_area_alloc(mm);
3042         if (!vma) {
3043                 vm_unacct_memory(len >> PAGE_SHIFT);
3044                 return -ENOMEM;
3045         }
3046 
3047         vma_set_anonymous(vma);
3048         vma->vm_start = addr;
3049         vma->vm_end = addr + len;
3050         vma->vm_pgoff = pgoff;
3051         vma->vm_flags = flags;
3052         vma->vm_page_prot = vm_get_page_prot(flags);
3053         vma_link(mm, vma, prev, rb_link, rb_parent);
3054 out:
3055         perf_event_mmap(vma);
3056         mm->total_vm += len >> PAGE_SHIFT;
3057         mm->data_vm += len >> PAGE_SHIFT;
3058         if (flags & VM_LOCKED)
3059                 mm->locked_vm += (len >> PAGE_SHIFT);
3060         vma->vm_flags |= VM_SOFTDIRTY;
3061         return 0;
3062 }
3063 
3064 int vm_brk_flags(unsigned long addr, unsigned long request, unsigned long flags)
3065 {
3066         struct mm_struct *mm = current->mm;
3067         unsigned long len;
3068         int ret;
3069         bool populate;
3070         LIST_HEAD(uf);
3071 
3072         len = PAGE_ALIGN(request);
3073         if (len < request)
3074                 return -ENOMEM;
3075         if (!len)
3076                 return 0;
3077 
3078         if (down_write_killable(&mm->mmap_sem))
3079                 return -EINTR;
3080 
3081         ret = do_brk_flags(addr, len, flags, &uf);
3082         populate = ((mm->def_flags & VM_LOCKED) != 0);
3083         up_write(&mm->mmap_sem);
3084         userfaultfd_unmap_complete(mm, &uf);
3085         if (populate && !ret)
3086                 mm_populate(addr, len);
3087         return ret;
3088 }
3089 EXPORT_SYMBOL(vm_brk_flags);
3090 
3091 int vm_brk(unsigned long addr, unsigned long len)
3092 {
3093         return vm_brk_flags(addr, len, 0);
3094 }
3095 EXPORT_SYMBOL(vm_brk);
3096 
3097 /* Release all mmaps. */
3098 void exit_mmap(struct mm_struct *mm)
3099 {
3100         struct mmu_gather tlb;
3101         struct vm_area_struct *vma;
3102         unsigned long nr_accounted = 0;
3103 
3104         /* mm's last user has gone, and its about to be pulled down */
3105         mmu_notifier_release(mm);
3106 
3107         if (unlikely(mm_is_oom_victim(mm))) {
3108                 /*
3109                  * Manually reap the mm to free as much memory as possible.
3110                  * Then, as the oom reaper does, set MMF_OOM_SKIP to disregard
3111                  * this mm from further consideration.  Taking mm->mmap_sem for
3112                  * write after setting MMF_OOM_SKIP will guarantee that the oom
3113                  * reaper will not run on this mm again after mmap_sem is
3114                  * dropped.
3115                  *
3116                  * Nothing can be holding mm->mmap_sem here and the above call
3117                  * to mmu_notifier_release(mm) ensures mmu notifier callbacks in
3118                  * __oom_reap_task_mm() will not block.
3119                  *
3120                  * This needs to be done before calling munlock_vma_pages_all(),
3121                  * which clears VM_LOCKED, otherwise the oom reaper cannot
3122                  * reliably test it.
3123                  */
3124                 (void)__oom_reap_task_mm(mm);
3125 
3126                 set_bit(MMF_OOM_SKIP, &mm->flags);
3127                 down_write(&mm->mmap_sem);
3128                 up_write(&mm->mmap_sem);
3129         }
3130 
3131         if (mm->locked_vm) {
3132                 vma = mm->mmap;
3133                 while (vma) {
3134                         if (vma->vm_flags & VM_LOCKED)
3135                                 munlock_vma_pages_all(vma);
3136                         vma = vma->vm_next;
3137                 }
3138         }
3139 
3140         arch_exit_mmap(mm);
3141 
3142         vma = mm->mmap;
3143         if (!vma)       /* Can happen if dup_mmap() received an OOM */
3144                 return;
3145 
3146         lru_add_drain();
3147         flush_cache_mm(mm);
3148         tlb_gather_mmu(&tlb, mm, 0, -1);
3149         /* update_hiwater_rss(mm) here? but nobody should be looking */
3150         /* Use -1 here to ensure all VMAs in the mm are unmapped */
3151         unmap_vmas(&tlb, vma, 0, -1);
3152         free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, USER_PGTABLES_CEILING);
3153         tlb_finish_mmu(&tlb, 0, -1);
3154 
3155         /*
3156          * Walk the list again, actually closing and freeing it,
3157          * with preemption enabled, without holding any MM locks.
3158          */
3159         while (vma) {
3160                 if (vma->vm_flags & VM_ACCOUNT)
3161                         nr_accounted += vma_pages(vma);
3162                 vma = remove_vma(vma);
3163         }
3164         vm_unacct_memory(nr_accounted);
3165 }
3166 
3167 /* Insert vm structure into process list sorted by address
3168  * and into the inode's i_mmap tree.  If vm_file is non-NULL
3169  * then i_mmap_rwsem is taken here.
3170  */
3171 int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
3172 {
3173         struct vm_area_struct *prev;
3174         struct rb_node **rb_link, *rb_parent;
3175 
3176         if (find_vma_links(mm, vma->vm_start, vma->vm_end,
3177                            &prev, &rb_link, &rb_parent))
3178                 return -ENOMEM;
3179         if ((vma->vm_flags & VM_ACCOUNT) &&
3180              security_vm_enough_memory_mm(mm, vma_pages(vma)))
3181                 return -ENOMEM;
3182 
3183         /*
3184          * The vm_pgoff of a purely anonymous vma should be irrelevant
3185          * until its first write fault, when page's anon_vma and index
3186          * are set.  But now set the vm_pgoff it will almost certainly
3187          * end up with (unless mremap moves it elsewhere before that
3188          * first wfault), so /proc/pid/maps tells a consistent story.
3189          *
3190          * By setting it to reflect the virtual start address of the
3191          * vma, merges and splits can happen in a seamless way, just
3192          * using the existing file pgoff checks and manipulations.
3193          * Similarly in do_mmap_pgoff and in do_brk.
3194          */
3195         if (vma_is_anonymous(vma)) {
3196                 BUG_ON(vma->anon_vma);
3197                 vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;
3198         }
3199 
3200         vma_link(mm, vma, prev, rb_link, rb_parent);
3201         return 0;
3202 }
3203 
3204 /*
3205  * Copy the vma structure to a new location in the same mm,
3206  * prior to moving page table entries, to effect an mremap move.
3207  */
3208 struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
3209         unsigned long addr, unsigned long len, pgoff_t pgoff,
3210         bool *need_rmap_locks)
3211 {
3212         struct vm_area_struct *vma = *vmap;
3213         unsigned long vma_start = vma->vm_start;
3214         struct mm_struct *mm = vma->vm_mm;
3215         struct vm_area_struct *new_vma, *prev;
3216         struct rb_node **rb_link, *rb_parent;
3217         bool faulted_in_anon_vma = true;
3218 
3219         /*
3220          * If anonymous vma has not yet been faulted, update new pgoff
3221          * to match new location, to increase its chance of merging.
3222          */
3223         if (unlikely(vma_is_anonymous(vma) && !vma->anon_vma)) {
3224                 pgoff = addr >> PAGE_SHIFT;
3225                 faulted_in_anon_vma = false;
3226         }
3227 
3228         if (find_vma_links(mm, addr, addr + len, &prev, &rb_link, &rb_parent))
3229                 return NULL;    /* should never get here */
3230         new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags,
3231                             vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
3232                             vma->vm_userfaultfd_ctx);
3233         if (new_vma) {
3234                 /*
3235                  * Source vma may have been merged into new_vma
3236                  */
3237                 if (unlikely(vma_start >= new_vma->vm_start &&
3238                              vma_start < new_vma->vm_end)) {
3239                         /*
3240                          * The only way we can get a vma_merge with
3241                          * self during an mremap is if the vma hasn't
3242                          * been faulted in yet and we were allowed to
3243                          * reset the dst vma->vm_pgoff to the
3244                          * destination address of the mremap to allow
3245                          * the merge to happen. mremap must change the
3246                          * vm_pgoff linearity between src and dst vmas
3247                          * (in turn preventing a vma_merge) to be
3248                          * safe. It is only safe to keep the vm_pgoff
3249                          * linear if there are no pages mapped yet.
3250                          */
3251                         VM_BUG_ON_VMA(faulted_in_anon_vma, new_vma);
3252                         *vmap = vma = new_vma;
3253                 }
3254                 *need_rmap_locks = (new_vma->vm_pgoff <= vma->vm_pgoff);
3255         } else {
3256                 new_vma = vm_area_dup(vma);
3257                 if (!new_vma)
3258                         goto out;
3259                 new_vma->vm_start = addr;
3260                 new_vma->vm_end = addr + len;
3261                 new_vma->vm_pgoff = pgoff;
3262                 if (vma_dup_policy(vma, new_vma))
3263                         goto out_free_vma;
3264                 if (anon_vma_clone(new_vma, vma))
3265                         goto out_free_mempol;
3266                 if (new_vma->vm_file)
3267                         get_file(new_vma->vm_file);
3268                 if (new_vma->vm_ops && new_vma->vm_ops->open)
3269                         new_vma->vm_ops->open(new_vma);
3270                 vma_link(mm, new_vma, prev, rb_link, rb_parent);
3271                 *need_rmap_locks = false;
3272         }
3273         return new_vma;
3274 
3275 out_free_mempol:
3276         mpol_put(vma_policy(new_vma));
3277 out_free_vma:
3278         vm_area_free(new_vma);
3279 out:
3280         return NULL;
3281 }
3282 
3283 /*
3284  * Return true if the calling process may expand its vm space by the passed
3285  * number of pages
3286  */
3287 bool may_expand_vm(struct mm_struct *mm, vm_flags_t flags, unsigned long npages)
3288 {
3289         if (mm->total_vm + npages > rlimit(RLIMIT_AS) >> PAGE_SHIFT)
3290                 return false;
3291 
3292         if (is_data_mapping(flags) &&
3293             mm->data_vm + npages > rlimit(RLIMIT_DATA) >> PAGE_SHIFT) {
3294                 /* Workaround for Valgrind */
3295                 if (rlimit(RLIMIT_DATA) == 0 &&
3296                     mm->data_vm + npages <= rlimit_max(RLIMIT_DATA) >> PAGE_SHIFT)
3297                         return true;
3298 
3299                 pr_warn_once("%s (%d): VmData %lu exceed data ulimit %lu. Update limits%s.\n",
3300                              current->comm, current->pid,
3301                              (mm->data_vm + npages) << PAGE_SHIFT,
3302                              rlimit(RLIMIT_DATA),
3303                              ignore_rlimit_data ? "" : " or use boot option ignore_rlimit_data");
3304 
3305                 if (!ignore_rlimit_data)
3306                         return false;
3307         }
3308 
3309         return true;
3310 }
3311 
3312 void vm_stat_account(struct mm_struct *mm, vm_flags_t flags, long npages)
3313 {
3314         mm->total_vm += npages;
3315 
3316         if (is_exec_mapping(flags))
3317                 mm->exec_vm += npages;
3318         else if (is_stack_mapping(flags))
3319                 mm->stack_vm += npages;
3320         else if (is_data_mapping(flags))
3321                 mm->data_vm += npages;
3322 }
3323 
3324 static vm_fault_t special_mapping_fault(struct vm_fault *vmf);
3325 
3326 /*
3327  * Having a close hook prevents vma merging regardless of flags.
3328  */
3329 static void special_mapping_close(struct vm_area_struct *vma)
3330 {
3331 }
3332 
3333 static const char *special_mapping_name(struct vm_area_struct *vma)
3334 {
3335         return ((struct vm_special_mapping *)vma->vm_private_data)->name;
3336 }
3337 
3338 static int special_mapping_mremap(struct vm_area_struct *new_vma)
3339 {
3340         struct vm_special_mapping *sm = new_vma->vm_private_data;
3341 
3342         if (WARN_ON_ONCE(current->mm != new_vma->vm_mm))
3343                 return -EFAULT;
3344 
3345         if (sm->mremap)
3346                 return sm->mremap(sm, new_vma);
3347 
3348         return 0;
3349 }
3350 
3351 static const struct vm_operations_struct special_mapping_vmops = {
3352         .close = special_mapping_close,
3353         .fault = special_mapping_fault,
3354         .mremap = special_mapping_mremap,
3355         .name = special_mapping_name,
3356 };
3357 
3358 static const struct vm_operations_struct legacy_special_mapping_vmops = {
3359         .close = special_mapping_close,
3360         .fault = special_mapping_fault,
3361 };
3362 
3363 static vm_fault_t special_mapping_fault(struct vm_fault *vmf)
3364 {
3365         struct vm_area_struct *vma = vmf->vma;
3366         pgoff_t pgoff;
3367         struct page **pages;
3368 
3369         if (vma->vm_ops == &legacy_special_mapping_vmops) {
3370                 pages = vma->vm_private_data;
3371         } else {
3372                 struct vm_special_mapping *sm = vma->vm_private_data;
3373 
3374                 if (sm->fault)
3375                         return sm->fault(sm, vmf->vma, vmf);
3376 
3377                 pages = sm->pages;
3378         }
3379 
3380         for (pgoff = vmf->pgoff; pgoff && *pages; ++pages)
3381                 pgoff--;
3382 
3383         if (*pages) {
3384                 struct page *page = *pages;
3385                 get_page(page);
3386                 vmf->page = page;
3387                 return 0;
3388         }
3389 
3390         return VM_FAULT_SIGBUS;
3391 }
3392 
3393 static struct vm_area_struct *__install_special_mapping(
3394         struct mm_struct *mm,
3395         unsigned long addr, unsigned long len,
3396         unsigned long vm_flags, void *priv,
3397         const struct vm_operations_struct *ops)
3398 {
3399         int ret;
3400         struct vm_area_struct *vma;
3401 
3402         vma = vm_area_alloc(mm);
3403         if (unlikely(vma == NULL))
3404                 return ERR_PTR(-ENOMEM);
3405 
3406         vma->vm_start = addr;
3407         vma->vm_end = addr + len;
3408 
3409         vma->vm_flags = vm_flags | mm->def_flags | VM_DONTEXPAND | VM_SOFTDIRTY;
3410         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
3411 
3412         vma->vm_ops = ops;
3413         vma->vm_private_data = priv;
3414 
3415         ret = insert_vm_struct(mm, vma);
3416         if (ret)
3417                 goto out;
3418 
3419         vm_stat_account(mm, vma->vm_flags, len >> PAGE_SHIFT);
3420 
3421         perf_event_mmap(vma);
3422 
3423         return vma;
3424 
3425 out:
3426         vm_area_free(vma);
3427         return ERR_PTR(ret);
3428 }
3429 
3430 bool vma_is_special_mapping(const struct vm_area_struct *vma,
3431         const struct vm_special_mapping *sm)
3432 {
3433         return vma->vm_private_data == sm &&
3434                 (vma->vm_ops == &special_mapping_vmops ||
3435                  vma->vm_ops == &legacy_special_mapping_vmops);
3436 }
3437 
3438 /*
3439  * Called with mm->mmap_sem held for writing.
3440  * Insert a new vma covering the given region, with the given flags.
3441  * Its pages are supplied by the given array of struct page *.
3442  * The array can be shorter than len >> PAGE_SHIFT if it's null-terminated.
3443  * The region past the last page supplied will always produce SIGBUS.
3444  * The array pointer and the pages it points to are assumed to stay alive
3445  * for as long as this mapping might exist.
3446  */
3447 struct vm_area_struct *_install_special_mapping(
3448         struct mm_struct *mm,
3449         unsigned long addr, unsigned long len,
3450         unsigned long vm_flags, const struct vm_special_mapping *spec)
3451 {
3452         return __install_special_mapping(mm, addr, len, vm_flags, (void *)spec,
3453                                         &special_mapping_vmops);
3454 }
3455 
3456 int install_special_mapping(struct mm_struct *mm,
3457                             unsigned long addr, unsigned long len,
3458                             unsigned long vm_flags, struct page **pages)
3459 {
3460         struct vm_area_struct *vma = __install_special_mapping(
3461                 mm, addr, len, vm_flags, (void *)pages,
3462                 &legacy_special_mapping_vmops);
3463 
3464         return PTR_ERR_OR_ZERO(vma);
3465 }
3466 
3467 static DEFINE_MUTEX(mm_all_locks_mutex);
3468 
3469 static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma)
3470 {
3471         if (!test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_root.rb_node)) {
3472                 /*
3473                  * The LSB of head.next can't change from under us
3474                  * because we hold the mm_all_locks_mutex.
3475                  */
3476                 down_write_nest_lock(&anon_vma->root->rwsem, &mm->mmap_sem);
3477                 /*
3478                  * We can safely modify head.next after taking the
3479                  * anon_vma->root->rwsem. If some other vma in this mm shares
3480                  * the same anon_vma we won't take it again.
3481                  *
3482                  * No need of atomic instructions here, head.next
3483                  * can't change from under us thanks to the
3484                  * anon_vma->root->rwsem.
3485                  */
3486                 if (__test_and_set_bit(0, (unsigned long *)
3487                                        &anon_vma->root->rb_root.rb_root.rb_node))
3488                         BUG();
3489         }
3490 }
3491 
3492 static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping)
3493 {
3494         if (!test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
3495                 /*
3496                  * AS_MM_ALL_LOCKS can't change from under us because
3497                  * we hold the mm_all_locks_mutex.
3498                  *
3499                  * Operations on ->flags have to be atomic because
3500                  * even if AS_MM_ALL_LOCKS is stable thanks to the
3501                  * mm_all_locks_mutex, there may be other cpus
3502                  * changing other bitflags in parallel to us.
3503                  */
3504                 if (test_and_set_bit(AS_MM_ALL_LOCKS, &mapping->flags))
3505                         BUG();
3506                 down_write_nest_lock(&mapping->i_mmap_rwsem, &mm->mmap_sem);
3507         }
3508 }
3509 
3510 /*
3511  * This operation locks against the VM for all pte/vma/mm related
3512  * operations that could ever happen on a certain mm. This includes
3513  * vmtruncate, try_to_unmap, and all page faults.
3514  *
3515  * The caller must take the mmap_sem in write mode before calling
3516  * mm_take_all_locks(). The caller isn't allowed to release the
3517  * mmap_sem until mm_drop_all_locks() returns.
3518  *
3519  * mmap_sem in write mode is required in order to block all operations
3520  * that could modify pagetables and free pages without need of
3521  * altering the vma layout. It's also needed in write mode to avoid new
3522  * anon_vmas to be associated with existing vmas.
3523  *
3524  * A single task can't take more than one mm_take_all_locks() in a row
3525  * or it would deadlock.
3526  *
3527  * The LSB in anon_vma->rb_root.rb_node and the AS_MM_ALL_LOCKS bitflag in
3528  * mapping->flags avoid to take the same lock twice, if more than one
3529  * vma in this mm is backed by the same anon_vma or address_space.
3530  *
3531  * We take locks in following order, accordingly to comment at beginning
3532  * of mm/rmap.c:
3533  *   - all hugetlbfs_i_mmap_rwsem_key locks (aka mapping->i_mmap_rwsem for
3534  *     hugetlb mapping);
3535  *   - all i_mmap_rwsem locks;
3536  *   - all anon_vma->rwseml
3537  *
3538  * We can take all locks within these types randomly because the VM code
3539  * doesn't nest them and we protected from parallel mm_take_all_locks() by
3540  * mm_all_locks_mutex.
3541  *
3542  * mm_take_all_locks() and mm_drop_all_locks are expensive operations
3543  * that may have to take thousand of locks.
3544  *
3545  * mm_take_all_locks() can fail if it's interrupted by signals.
3546  */
3547 int mm_take_all_locks(struct mm_struct *mm)
3548 {
3549         struct vm_area_struct *vma;
3550         struct anon_vma_chain *avc;
3551 
3552         BUG_ON(down_read_trylock(&mm->mmap_sem));
3553 
3554         mutex_lock(&mm_all_locks_mutex);
3555 
3556         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3557                 if (signal_pending(current))
3558                         goto out_unlock;
3559                 if (vma->vm_file && vma->vm_file->f_mapping &&
3560                                 is_vm_hugetlb_page(vma))
3561                         vm_lock_mapping(mm, vma->vm_file->f_mapping);
3562         }
3563 
3564         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3565                 if (signal_pending(current))
3566                         goto out_unlock;
3567                 if (vma->vm_file && vma->vm_file->f_mapping &&
3568                                 !is_vm_hugetlb_page(vma))
3569                         vm_lock_mapping(mm, vma->vm_file->f_mapping);
3570         }
3571 
3572         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3573                 if (signal_pending(current))
3574                         goto out_unlock;
3575                 if (vma->anon_vma)
3576                         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
3577                                 vm_lock_anon_vma(mm, avc->anon_vma);
3578         }
3579 
3580         return 0;
3581 
3582 out_unlock:
3583         mm_drop_all_locks(mm);
3584         return -EINTR;
3585 }
3586 
3587 static void vm_unlock_anon_vma(struct anon_vma *anon_vma)
3588 {
3589         if (test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_root.rb_node)) {
3590                 /*
3591                  * The LSB of head.next can't change to 0 from under
3592                  * us because we hold the mm_all_locks_mutex.
3593                  *
3594                  * We must however clear the bitflag before unlocking
3595                  * the vma so the users using the anon_vma->rb_root will
3596                  * never see our bitflag.
3597                  *
3598                  * No need of atomic instructions here, head.next
3599                  * can't change from under us until we release the
3600                  * anon_vma->root->rwsem.
3601                  */
3602                 if (!__test_and_clear_bit(0, (unsigned long *)
3603                                           &anon_vma->root->rb_root.rb_root.rb_node))
3604                         BUG();
3605                 anon_vma_unlock_write(anon_vma);
3606         }
3607 }
3608 
3609 static void vm_unlock_mapping(struct address_space *mapping)
3610 {
3611         if (test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
3612                 /*
3613                  * AS_MM_ALL_LOCKS can't change to 0 from under us
3614                  * because we hold the mm_all_locks_mutex.
3615                  */
3616                 i_mmap_unlock_write(mapping);
3617                 if (!test_and_clear_bit(AS_MM_ALL_LOCKS,
3618                                         &mapping->flags))
3619                         BUG();
3620         }
3621 }
3622 
3623 /*
3624  * The mmap_sem cannot be released by the caller until
3625  * mm_drop_all_locks() returns.
3626  */
3627 void mm_drop_all_locks(struct mm_struct *mm)
3628 {
3629         struct vm_area_struct *vma;
3630         struct anon_vma_chain *avc;
3631 
3632         BUG_ON(down_read_trylock(&mm->mmap_sem));
3633         BUG_ON(!mutex_is_locked(&mm_all_locks_mutex));
3634 
3635         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3636                 if (vma->anon_vma)
3637                         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
3638                                 vm_unlock_anon_vma(avc->anon_vma);
3639                 if (vma->vm_file && vma->vm_file->f_mapping)
3640                         vm_unlock_mapping(vma->vm_file->f_mapping);
3641         }
3642 
3643         mutex_unlock(&mm_all_locks_mutex);
3644 }
3645 
3646 /*
3647  * initialise the percpu counter for VM
3648  */
3649 void __init mmap_init(void)
3650 {
3651         int ret;
3652 
3653         ret = percpu_counter_init(&vm_committed_as, 0, GFP_KERNEL);
3654         VM_BUG_ON(ret);
3655 }
3656 
3657 /*
3658  * Initialise sysctl_user_reserve_kbytes.
3659  *
3660  * This is intended to prevent a user from starting a single memory hogging
3661  * process, such that they cannot recover (kill the hog) in OVERCOMMIT_NEVER
3662  * mode.
3663  *
3664  * The default value is min(3% of free memory, 128MB)
3665  * 128MB is enough to recover with sshd/login, bash, and top/kill.
3666  */
3667 static int init_user_reserve(void)
3668 {
3669         unsigned long free_kbytes;
3670 
3671         free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
3672 
3673         sysctl_user_reserve_kbytes = min(free_kbytes / 32, 1UL << 17);
3674         return 0;
3675 }
3676 subsys_initcall(init_user_reserve);
3677 
3678 /*
3679  * Initialise sysctl_admin_reserve_kbytes.
3680  *
3681  * The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin
3682  * to log in and kill a memory hogging process.
3683  *
3684  * Systems with more than 256MB will reserve 8MB, enough to recover
3685  * with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will
3686  * only reserve 3% of free pages by default.
3687  */
3688 static int init_admin_reserve(void)
3689 {
3690         unsigned long free_kbytes;
3691 
3692         free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
3693 
3694         sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13);
3695         return 0;
3696 }
3697 subsys_initcall(init_admin_reserve);
3698 
3699 /*
3700  * Reinititalise user and admin reserves if memory is added or removed.
3701  *
3702  * The default user reserve max is 128MB, and the default max for the
3703  * admin reserve is 8MB. These are usually, but not always, enough to
3704  * enable recovery from a memory hogging process using login/sshd, a shell,
3705  * and tools like top. It may make sense to increase or even disable the
3706  * reserve depending on the existence of swap or variations in the recovery
3707  * tools. So, the admin may have changed them.
3708  *
3709  * If memory is added and the reserves have been eliminated or increased above
3710  * the default max, then we'll trust the admin.
3711  *
3712  * If memory is removed and there isn't enough free memory, then we
3713  * need to reset the reserves.
3714  *
3715  * Otherwise keep the reserve set by the admin.
3716  */
3717 static int reserve_mem_notifier(struct notifier_block *nb,
3718                              unsigned long action, void *data)
3719 {
3720         unsigned long tmp, free_kbytes;
3721 
3722         switch (action) {
3723         case MEM_ONLINE:
3724                 /* Default max is 128MB. Leave alone if modified by operator. */
3725                 tmp = sysctl_user_reserve_kbytes;
3726                 if (0 < tmp && tmp < (1UL << 17))
3727                         init_user_reserve();
3728 
3729                 /* Default max is 8MB.  Leave alone if modified by operator. */
3730                 tmp = sysctl_admin_reserve_kbytes;
3731                 if (0 < tmp && tmp < (1UL << 13))
3732                         init_admin_reserve();
3733 
3734                 break;
3735         case MEM_OFFLINE:
3736                 free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
3737 
3738                 if (sysctl_user_reserve_kbytes > free_kbytes) {
3739                         init_user_reserve();
3740                         pr_info("vm.user_reserve_kbytes reset to %lu\n",
3741                                 sysctl_user_reserve_kbytes);
3742                 }
3743 
3744                 if (sysctl_admin_reserve_kbytes > free_kbytes) {
3745                         init_admin_reserve();
3746                         pr_info("vm.admin_reserve_kbytes reset to %lu\n",
3747                                 sysctl_admin_reserve_kbytes);
3748                 }
3749                 break;
3750         default:
3751                 break;
3752         }
3753         return NOTIFY_OK;
3754 }
3755 
3756 static struct notifier_block reserve_mem_nb = {
3757         .notifier_call = reserve_mem_notifier,
3758 };
3759 
3760 static int __meminit init_reserve_notifier(void)
3761 {
3762         if (register_hotmemory_notifier(&reserve_mem_nb))
3763                 pr_err("Failed registering memory add/remove notifier for admin reserve\n");
3764 
3765         return 0;
3766 }
3767 subsys_initcall(init_reserve_notifier);
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root/mm/mmap.c

DEFINITIONS
