// SPDX-License-Identifier: GPL-2.0-only
      /*
       * mm/mmap.c
       *
       * Written by obz.
       *
       * Address space accounting code        <alan@lxorguk.ukuu.org.uk>
       */
      
      #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
      
      #include <linux/kernel.h>
      #include <linux/slab.h>
      #include <linux/backing-dev.h>
      #include <linux/mm.h>
      #include <linux/vmacache.h>
      #include <linux/shm.h>
      #include <linux/mman.h>
      #include <linux/pagemap.h>
      #include <linux/swap.h>
      #include <linux/syscalls.h>
      #include <linux/capability.h>
      #include <linux/init.h>
      #include <linux/file.h>
      #include <linux/fs.h>
      #include <linux/personality.h>
      #include <linux/security.h>
      #include <linux/hugetlb.h>
      #include <linux/shmem_fs.h>
      #include <linux/profile.h>
      #include <linux/export.h>
      #include <linux/mount.h>
      #include <linux/mempolicy.h>
      #include <linux/rmap.h>
      #include <linux/mmu_notifier.h>
      #include <linux/mmdebug.h>
      #include <linux/perf_event.h>
      #include <linux/audit.h>
      #include <linux/khugepaged.h>
      #include <linux/uprobes.h>
      #include <linux/rbtree_augmented.h>
      #include <linux/notifier.h>
      #include <linux/memory.h>
      #include <linux/printk.h>
      #include <linux/userfaultfd_k.h>
      #include <linux/moduleparam.h>
      #include <linux/pkeys.h>
      #include <linux/oom.h>
      #include <linux/sched/mm.h>
      
      #include <linux/uaccess.h>
      #include <asm/cacheflush.h>
      #include <asm/tlb.h>
      #include <asm/mmu_context.h>
      
      #include "internal.h"
      
      #ifndef arch_mmap_check
      #define arch_mmap_check(addr, len, flags)        (0)
      #endif
      
      #ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS
      const int mmap_rnd_bits_min = CONFIG_ARCH_MMAP_RND_BITS_MIN;
      const int mmap_rnd_bits_max = CONFIG_ARCH_MMAP_RND_BITS_MAX;
      int mmap_rnd_bits __read_mostly = CONFIG_ARCH_MMAP_RND_BITS;
      #endif
      #ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
      const int mmap_rnd_compat_bits_min = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MIN;
      const int mmap_rnd_compat_bits_max = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MAX;
      int mmap_rnd_compat_bits __read_mostly = CONFIG_ARCH_MMAP_RND_COMPAT_BITS;
      #endif
      
      static bool ignore_rlimit_data;
      core_param(ignore_rlimit_data, ignore_rlimit_data, bool, 0644);
      
      static void unmap_region(struct mm_struct *mm,
                      struct vm_area_struct *vma, struct vm_area_struct *prev,
                      unsigned long start, unsigned long end);
      
      /* description of effects of mapping type and prot in current implementation.
       * this is due to the limited x86 page protection hardware.  The expected
       * behavior is in parens:
       *
       * map_type        prot
       *                PROT_NONE        PROT_READ        PROT_WRITE        PROT_EXEC
       * MAP_SHARED        r: (no) no        r: (yes) yes        r: (no) yes        r: (no) yes
       *                w: (no) no        w: (no) no        w: (yes) yes        w: (no) no
       *                x: (no) no        x: (no) yes        x: (no) yes        x: (yes) yes
       *
       * MAP_PRIVATE        r: (no) no        r: (yes) yes        r: (no) yes        r: (no) yes
       *                w: (no) no        w: (no) no        w: (copy) copy        w: (no) no
       *                x: (no) no        x: (no) yes        x: (no) yes        x: (yes) yes
       */
      pgprot_t protection_map[16] __ro_after_init = {
              __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
              __S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
      };
      
      #ifndef CONFIG_ARCH_HAS_FILTER_PGPROT
      static inline pgprot_t arch_filter_pgprot(pgprot_t prot)
      {
              return prot;
      }
      #endif
      
      pgprot_t vm_get_page_prot(unsigned long vm_flags)
      {
  129         pgprot_t ret = __pgprot(pgprot_val(protection_map[vm_flags &
                                      (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
                              pgprot_val(arch_vm_get_page_prot(vm_flags)));
      
  558         return arch_filter_pgprot(ret);
      }
      EXPORT_SYMBOL(vm_get_page_prot);
      
      static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags)
      {
  632         return pgprot_modify(oldprot, vm_get_page_prot(vm_flags));
      }
      
      /* Update vma->vm_page_prot to reflect vma->vm_flags. */
      void vma_set_page_prot(struct vm_area_struct *vma)
      {
  632         unsigned long vm_flags = vma->vm_flags;
              pgprot_t vm_page_prot;
      
  632         vm_page_prot = vm_pgprot_modify(vma->vm_page_prot, vm_flags);
              if (vma_wants_writenotify(vma, vm_page_prot)) {
                      vm_flags &= ~VM_SHARED;
  129                 vm_page_prot = vm_pgprot_modify(vm_page_prot, vm_flags);
              }
              /* remove_protection_ptes reads vma->vm_page_prot without mmap_sem */
  632         WRITE_ONCE(vma->vm_page_prot, vm_page_prot);
      }
      
      /*
       * Requires inode->i_mapping->i_mmap_rwsem
       */
      static void __remove_shared_vm_struct(struct vm_area_struct *vma,
                      struct file *file, struct address_space *mapping)
      {
   86         if (vma->vm_flags & VM_DENYWRITE)
                      atomic_inc(&file_inode(file)->i_writecount);
   86         if (vma->vm_flags & VM_SHARED)
   69                 mapping_unmap_writable(mapping);
      
              flush_dcache_mmap_lock(mapping);
   86         vma_interval_tree_remove(vma, &mapping->i_mmap);
              flush_dcache_mmap_unlock(mapping);
      }
      
      /*
       * Unlink a file-based vm structure from its interval tree, to hide
       * vma from rmap and vmtruncate before freeing its page tables.
       */
      void unlink_file_vma(struct vm_area_struct *vma)
      {
  687         struct file *file = vma->vm_file;
      
              if (file) {
   86                 struct address_space *mapping = file->f_mapping;
                      i_mmap_lock_write(mapping);
                      __remove_shared_vm_struct(vma, file, mapping);
                      i_mmap_unlock_write(mapping);
              }
  687 }
      
      /*
       * Close a vm structure and free it, returning the next.
       */
      static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
      {
  679         struct vm_area_struct *next = vma->vm_next;
      
              might_sleep();
   83         if (vma->vm_ops && vma->vm_ops->close)
   11                 vma->vm_ops->close(vma);
  679         if (vma->vm_file)
   83                 fput(vma->vm_file);
  679         mpol_put(vma_policy(vma));
  679         vm_area_free(vma);
              return next;
      }
      
      static int do_brk_flags(unsigned long addr, unsigned long request, unsigned long flags,
                      struct list_head *uf);
      SYSCALL_DEFINE1(brk, unsigned long, brk)
      {
              unsigned long retval;
              unsigned long newbrk, oldbrk, origbrk;
              struct mm_struct *mm = current->mm;
              struct vm_area_struct *next;
              unsigned long min_brk;
              bool populate;
              bool downgraded = false;
              LIST_HEAD(uf);
      
              brk = untagged_addr(brk);
      
              if (down_write_killable(&mm->mmap_sem))
                      return -EINTR;
      
              origbrk = mm->brk;
      
      #ifdef CONFIG_COMPAT_BRK
              /*
               * CONFIG_COMPAT_BRK can still be overridden by setting
               * randomize_va_space to 2, which will still cause mm->start_brk
               * to be arbitrarily shifted
               */
              if (current->brk_randomized)
                      min_brk = mm->start_brk;
              else
                      min_brk = mm->end_data;
      #else
              min_brk = mm->start_brk;
      #endif
              if (brk < min_brk)
                      goto out;
      
              /*
               * Check against rlimit here. If this check is done later after the test
               * of oldbrk with newbrk then it can escape the test and let the data
               * segment grow beyond its set limit the in case where the limit is
               * not page aligned -Ram Gupta
               */
              if (check_data_rlimit(rlimit(RLIMIT_DATA), brk, mm->start_brk,
                                    mm->end_data, mm->start_data))
                      goto out;
      
              newbrk = PAGE_ALIGN(brk);
              oldbrk = PAGE_ALIGN(mm->brk);
              if (oldbrk == newbrk) {
                      mm->brk = brk;
                      goto success;
              }
      
              /*
               * Always allow shrinking brk.
               * __do_munmap() may downgrade mmap_sem to read.
               */
              if (brk <= mm->brk) {
                      int ret;
      
                      /*
                       * mm->brk must to be protected by write mmap_sem so update it
                       * before downgrading mmap_sem. When __do_munmap() fails,
                       * mm->brk will be restored from origbrk.
                       */
                      mm->brk = brk;
                      ret = __do_munmap(mm, newbrk, oldbrk-newbrk, &uf, true);
                      if (ret < 0) {
                              mm->brk = origbrk;
                              goto out;
                      } else if (ret == 1) {
                              downgraded = true;
                      }
                      goto success;
              }
      
              /* Check against existing mmap mappings. */
              next = find_vma(mm, oldbrk);
              if (next && newbrk + PAGE_SIZE > vm_start_gap(next))
                      goto out;
      
              /* Ok, looks good - let it rip. */
              if (do_brk_flags(oldbrk, newbrk-oldbrk, 0, &uf) < 0)
                      goto out;
              mm->brk = brk;
      
      success:
              populate = newbrk > oldbrk && (mm->def_flags & VM_LOCKED) != 0;
              if (downgraded)
                      up_read(&mm->mmap_sem);
              else
                      up_write(&mm->mmap_sem);
              userfaultfd_unmap_complete(mm, &uf);
              if (populate)
                      mm_populate(oldbrk, newbrk - oldbrk);
              return brk;
      
      out:
              retval = origbrk;
              up_write(&mm->mmap_sem);
              return retval;
      }
      
      static inline unsigned long vma_compute_gap(struct vm_area_struct *vma)
      {
              unsigned long gap, prev_end;
      
              /*
               * Note: in the rare case of a VM_GROWSDOWN above a VM_GROWSUP, we
               * allow two stack_guard_gaps between them here, and when choosing
               * an unmapped area; whereas when expanding we only require one.
               * That's a little inconsistent, but keeps the code here simpler.
               */
  754         gap = vm_start_gap(vma);
  754         if (vma->vm_prev) {
  754                 prev_end = vm_end_gap(vma->vm_prev);
                      if (gap > prev_end)
  754                         gap -= prev_end;
                      else
                              gap = 0;
              }
              return gap;
      }
      
      #ifdef CONFIG_DEBUG_VM_RB
      static unsigned long vma_compute_subtree_gap(struct vm_area_struct *vma)
      {
  753         unsigned long max = vma_compute_gap(vma), subtree_gap;
  753         if (vma->vm_rb.rb_left) {
  753                 subtree_gap = rb_entry(vma->vm_rb.rb_left,
                                      struct vm_area_struct, vm_rb)->rb_subtree_gap;
                      if (subtree_gap > max)
                              max = subtree_gap;
              }
  753         if (vma->vm_rb.rb_right) {
  753                 subtree_gap = rb_entry(vma->vm_rb.rb_right,
                                      struct vm_area_struct, vm_rb)->rb_subtree_gap;
                      if (subtree_gap > max)
                              max = subtree_gap;
              }
  753         return max;
      }
      
      static int browse_rb(struct mm_struct *mm)
      {
  748         struct rb_root *root = &mm->mm_rb;
              int i = 0, j, bug = 0;
              struct rb_node *nd, *pn = NULL;
              unsigned long prev = 0, pend = 0;
      
              for (nd = rb_first(root); nd; nd = rb_next(nd)) {
                      struct vm_area_struct *vma;
  748                 vma = rb_entry(nd, struct vm_area_struct, vm_rb);
                      if (vma->vm_start < prev) {
                              pr_emerg("vm_start %lx < prev %lx\n",
                                        vma->vm_start, prev);
                              bug = 1;
                      }
  748                 if (vma->vm_start < pend) {
                              pr_emerg("vm_start %lx < pend %lx\n",
                                        vma->vm_start, pend);
                              bug = 1;
                      }
  748                 if (vma->vm_start > vma->vm_end) {
                              pr_emerg("vm_start %lx > vm_end %lx\n",
                                        vma->vm_start, vma->vm_end);
                              bug = 1;
                      }
  748                 spin_lock(&mm->page_table_lock);
                      if (vma->rb_subtree_gap != vma_compute_subtree_gap(vma)) {
                              pr_emerg("free gap %lx, correct %lx\n",
                                     vma->rb_subtree_gap,
                                     vma_compute_subtree_gap(vma));
                              bug = 1;
                      }
  748                 spin_unlock(&mm->page_table_lock);
                      i++;
                      pn = nd;
                      prev = vma->vm_start;
                      pend = vma->vm_end;
              }
              j = 0;
  743         for (nd = pn; nd; nd = rb_prev(nd))
  743                 j++;
  743         if (i != j) {
                      pr_emerg("backwards %d, forwards %d\n", j, i);
                      bug = 1;
              }
  743         return bug ? -1 : i;
      }
      
      static void validate_mm_rb(struct rb_root *root, struct vm_area_struct *ignore)
      {
              struct rb_node *nd;
      
  726         for (nd = rb_first(root); nd; nd = rb_next(nd)) {
                      struct vm_area_struct *vma;
  725                 vma = rb_entry(nd, struct vm_area_struct, vm_rb);
  725                 VM_BUG_ON_VMA(vma != ignore &&
                              vma->rb_subtree_gap != vma_compute_subtree_gap(vma),
                              vma);
              }
  725 }
      
      static void validate_mm(struct mm_struct *mm)
      {
              int bug = 0;
              int i = 0;
              unsigned long highest_address = 0;
  748         struct vm_area_struct *vma = mm->mmap;
      
              while (vma) {
  748                 struct anon_vma *anon_vma = vma->anon_vma;
                      struct anon_vma_chain *avc;
      
                      if (anon_vma) {
  748                         anon_vma_lock_read(anon_vma);
                              list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
  748                                 anon_vma_interval_tree_verify(avc);
  748                         anon_vma_unlock_read(anon_vma);
                      }
      
  748                 highest_address = vm_end_gap(vma);
  748                 vma = vma->vm_next;
                      i++;
              }
  748         if (i != mm->map_count) {
                      pr_emerg("map_count %d vm_next %d\n", mm->map_count, i);
                      bug = 1;
              }
  748         if (highest_address != mm->highest_vm_end) {
                      pr_emerg("mm->highest_vm_end %lx, found %lx\n",
                                mm->highest_vm_end, highest_address);
                      bug = 1;
              }
  748         i = browse_rb(mm);
  743         if (i != mm->map_count) {
                      if (i != -1)
                              pr_emerg("map_count %d rb %d\n", mm->map_count, i);
                      bug = 1;
              }
  743         VM_BUG_ON_MM(bug, mm);
  743 }
      #else
      #define validate_mm_rb(root, ignore) do { } while (0)
      #define validate_mm(mm) do { } while (0)
      #endif
      
  752 RB_DECLARE_CALLBACKS_MAX(static, vma_gap_callbacks,
                               struct vm_area_struct, vm_rb,
                               unsigned long, rb_subtree_gap, vma_compute_gap)
      
      /*
       * Update augmented rbtree rb_subtree_gap values after vma->vm_start or
       * vma->vm_prev->vm_end values changed, without modifying the vma's position
       * in the rbtree.
       */
      static void vma_gap_update(struct vm_area_struct *vma)
      {
              /*
               * As it turns out, RB_DECLARE_CALLBACKS_MAX() already created
               * a callback function that does exactly what we want.
               */
  752         vma_gap_callbacks_propagate(&vma->vm_rb, NULL);
      }
      
      static inline void vma_rb_insert(struct vm_area_struct *vma,
                                       struct rb_root *root)
      {
              /* All rb_subtree_gap values must be consistent prior to insertion */
              validate_mm_rb(root, NULL);
      
              rb_insert_augmented(&vma->vm_rb, root, &vma_gap_callbacks);
      }
      
      static void __vma_rb_erase(struct vm_area_struct *vma, struct rb_root *root)
      {
              /*
               * Note rb_erase_augmented is a fairly large inline function,
               * so make sure we instantiate it only once with our desired
               * augmented rbtree callbacks.
               */
  689         rb_erase_augmented(&vma->vm_rb, root, &vma_gap_callbacks);
  689 }
      
      static __always_inline void vma_rb_erase_ignore(struct vm_area_struct *vma,
                                                      struct rb_root *root,
                                                      struct vm_area_struct *ignore)
      {
              /*
               * All rb_subtree_gap values must be consistent prior to erase,
               * with the possible exception of the "next" vma being erased if
               * next->vm_start was reduced.
               */
    7         validate_mm_rb(root, ignore);
      
              __vma_rb_erase(vma, root);
      }
      
      static __always_inline void vma_rb_erase(struct vm_area_struct *vma,
                                               struct rb_root *root)
      {
              /*
               * All rb_subtree_gap values must be consistent prior to erase,
               * with the possible exception of the vma being erased.
               */
  689         validate_mm_rb(root, vma);
      
              __vma_rb_erase(vma, root);
      }
      
      /*
       * vma has some anon_vma assigned, and is already inserted on that
       * anon_vma's interval trees.
       *
       * Before updating the vma's vm_start / vm_end / vm_pgoff fields, the
       * vma must be removed from the anon_vma's interval trees using
       * anon_vma_interval_tree_pre_update_vma().
       *
       * After the update, the vma will be reinserted using
       * anon_vma_interval_tree_post_update_vma().
       *
       * The entire update must be protected by exclusive mmap_sem and by
       * the root anon_vma's mutex.
       */
      static inline void
      anon_vma_interval_tree_pre_update_vma(struct vm_area_struct *vma)
      {
              struct anon_vma_chain *avc;
      
   36         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
  427                 anon_vma_interval_tree_remove(avc, &avc->anon_vma->rb_root);
      }
      
      static inline void
      anon_vma_interval_tree_post_update_vma(struct vm_area_struct *vma)
      {
              struct anon_vma_chain *avc;
      
  391         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
  426                 anon_vma_interval_tree_insert(avc, &avc->anon_vma->rb_root);
      }
      
      static int find_vma_links(struct mm_struct *mm, unsigned long addr,
                      unsigned long end, struct vm_area_struct **pprev,
                      struct rb_node ***rb_link, struct rb_node **rb_parent)
      {
              struct rb_node **__rb_link, *__rb_parent, *rb_prev;
      
              __rb_link = &mm->mm_rb.rb_node;
              rb_prev = __rb_parent = NULL;
      
  733         while (*__rb_link) {
                      struct vm_area_struct *vma_tmp;
      
                      __rb_parent = *__rb_link;
                      vma_tmp = rb_entry(__rb_parent, struct vm_area_struct, vm_rb);
      
  733                 if (vma_tmp->vm_end > addr) {
                              /* Fail if an existing vma overlaps the area */
  733                         if (vma_tmp->vm_start < end)
                                      return -ENOMEM;
  733                         __rb_link = &__rb_parent->rb_left;
                      } else {
                              rb_prev = __rb_parent;
  733                         __rb_link = &__rb_parent->rb_right;
                      }
              }
      
              *pprev = NULL;
  722         if (rb_prev)
  722                 *pprev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
              *rb_link = __rb_link;
              *rb_parent = __rb_parent;
              return 0;
      }
      
      static unsigned long count_vma_pages_range(struct mm_struct *mm,
                      unsigned long addr, unsigned long end)
      {
              unsigned long nr_pages = 0;
              struct vm_area_struct *vma;
      
              /* Find first overlaping mapping */
    4         vma = find_vma_intersection(mm, addr, end);
              if (!vma)
                      return 0;
      
    2         nr_pages = (min(end, vma->vm_end) -
                      max(addr, vma->vm_start)) >> PAGE_SHIFT;
      
              /* Iterate over the rest of the overlaps */
              for (vma = vma->vm_next; vma; vma = vma->vm_next) {
                      unsigned long overlap_len;
      
    2                 if (vma->vm_start > end)
                              break;
      
    1                 overlap_len = min(end, vma->vm_end) - vma->vm_start;
                      nr_pages += overlap_len >> PAGE_SHIFT;
              }
      
              return nr_pages;
      }
      
      void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
                      struct rb_node **rb_link, struct rb_node *rb_parent)
      {
              /* Update tracking information for the gap following the new vma. */
  655         if (vma->vm_next)
  655                 vma_gap_update(vma->vm_next);
              else
                      mm->highest_vm_end = vm_end_gap(vma);
      
              /*
               * vma->vm_prev wasn't known when we followed the rbtree to find the
               * correct insertion point for that vma. As a result, we could not
               * update the vma vm_rb parents rb_subtree_gap values on the way down.
               * So, we first insert the vma with a zero rb_subtree_gap value
               * (to be consistent with what we did on the way down), and then
               * immediately update the gap to the correct value. Finally we
               * rebalance the rbtree after all augmented values have been set.
               */
  655         rb_link_node(&vma->vm_rb, rb_parent, rb_link);
              vma->rb_subtree_gap = 0;
  655         vma_gap_update(vma);
  655         vma_rb_insert(vma, &mm->mm_rb);
      }
      
      static void __vma_link_file(struct vm_area_struct *vma)
      {
              struct file *file;
      
  630         file = vma->vm_file;
              if (file) {
  563                 struct address_space *mapping = file->f_mapping;
      
                      if (vma->vm_flags & VM_DENYWRITE)
                              atomic_dec(&file_inode(file)->i_writecount);
  563                 if (vma->vm_flags & VM_SHARED)
  443                         atomic_inc(&mapping->i_mmap_writable);
      
                      flush_dcache_mmap_lock(mapping);
  563                 vma_interval_tree_insert(vma, &mapping->i_mmap);
                      flush_dcache_mmap_unlock(mapping);
              }
  630 }
      
      static void
      __vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
              struct vm_area_struct *prev, struct rb_node **rb_link,
              struct rb_node *rb_parent)
      {
  643         __vma_link_list(mm, vma, prev);
              __vma_link_rb(mm, vma, rb_link, rb_parent);
      }
      
      static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
                              struct vm_area_struct *prev, struct rb_node **rb_link,
                              struct rb_node *rb_parent)
      {
              struct address_space *mapping = NULL;
      
  625         if (vma->vm_file) {
  554                 mapping = vma->vm_file->f_mapping;
                      i_mmap_lock_write(mapping);
              }
      
   78         __vma_link(mm, vma, prev, rb_link, rb_parent);
              __vma_link_file(vma);
      
              if (mapping)
  554                 i_mmap_unlock_write(mapping);
      
  625         mm->map_count++;
              validate_mm(mm);
      }
      
      /*
       * Helper for vma_adjust() in the split_vma insert case: insert a vma into the
       * mm's list and rbtree.  It has already been inserted into the interval tree.
       */
      static void __insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
      {
              struct vm_area_struct *prev;
              struct rb_node **rb_link, *rb_parent;
      
  609         if (find_vma_links(mm, vma->vm_start, vma->vm_end,
                                 &prev, &rb_link, &rb_parent))
                      BUG();
  609         __vma_link(mm, vma, prev, rb_link, rb_parent);
              mm->map_count++;
      }
      
      static __always_inline void __vma_unlink_common(struct mm_struct *mm,
                                                      struct vm_area_struct *vma,
                                                      struct vm_area_struct *ignore)
      {
    7         vma_rb_erase_ignore(vma, &mm->mm_rb, ignore);
              __vma_unlink_list(mm, vma);
              /* Kill the cache */
              vmacache_invalidate(mm);
      }
      
      /*
       * We cannot adjust vm_start, vm_end, vm_pgoff fields of a vma that
       * is already present in an i_mmap tree without adjusting the tree.
       * The following helper function should be used when such adjustments
       * are necessary.  The "insert" vma (if any) is to be inserted
       * before we drop the necessary locks.
       */
      int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
              unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert,
              struct vm_area_struct *expand)
      {
  614         struct mm_struct *mm = vma->vm_mm;
              struct vm_area_struct *next = vma->vm_next, *orig_vma = vma;
              struct address_space *mapping = NULL;
              struct rb_root_cached *root = NULL;
              struct anon_vma *anon_vma = NULL;
              struct file *file = vma->vm_file;
              bool start_changed = false, end_changed = false;
              long adjust_next = 0;
              int remove_next = 0;
      
  614         if (next && !insert) {
                      struct vm_area_struct *exporter = NULL, *importer = NULL;
      
   16                 if (end >= next->vm_end) {
                              /*
                               * vma expands, overlapping all the next, and
                               * perhaps the one after too (mprotect case 6).
                               * The only other cases that gets here are
                               * case 1, case 7 and case 8.
                               */
    7                         if (next == expand) {
                                      /*
                                       * The only case where we don't expand "vma"
                                       * and we expand "next" instead is case 8.
                                       */
                                      VM_WARN_ON(end != next->vm_end);
                                      /*
                                       * remove_next == 3 means we're
                                       * removing "vma" and that to do so we
                                       * swapped "vma" and "next".
                                       */
                                      remove_next = 3;
                                      VM_WARN_ON(file != next->vm_file);
                                      swap(vma, next);
                              } else {
    7                                 VM_WARN_ON(expand != vma);
                                      /*
                                       * case 1, 6, 7, remove_next == 2 is case 6,
                                       * remove_next == 1 is case 1 or 7.
                                       */
    7                                 remove_next = 1 + (end > next->vm_end);
                                      VM_WARN_ON(remove_next == 2 &&
                                                 end != next->vm_next->vm_end);
                                      /* trim end to next, for case 6 first pass */
                                      end = next->vm_end;
                              }
      
                              exporter = next;
                              importer = vma;
      
                              /*
                               * If next doesn't have anon_vma, import from vma after
                               * next, if the vma overlaps with it.
                               */
                              if (remove_next == 2 && !next->anon_vma)
                                      exporter = next->vm_next;
      
   10                 } else if (end > next->vm_start) {
                              /*
                               * vma expands, overlapping part of the next:
                               * mprotect case 5 shifting the boundary up.
                               */
                              adjust_next = (end - next->vm_start) >> PAGE_SHIFT;
                              exporter = next;
                              importer = vma;
                              VM_WARN_ON(expand != importer);
   10                 } else if (end < vma->vm_end) {
                              /*
                               * vma shrinks, and !insert tells it's not
                               * split_vma inserting another: so it must be
                               * mprotect case 4 shifting the boundary down.
                               */
                              adjust_next = -((vma->vm_end - end) >> PAGE_SHIFT);
                              exporter = vma;
                              importer = next;
                              VM_WARN_ON(expand != importer);
                      }
      
                      /*
                       * Easily overlooked: when mprotect shifts the boundary,
                       * make sure the expanding vma has anon_vma set if the
                       * shrinking vma had, to cover any anon pages imported.
                       */
    7                 if (exporter && exporter->anon_vma && !importer->anon_vma) {
                              int error;
      
    1                         importer->anon_vma = exporter->anon_vma;
                              error = anon_vma_clone(importer, exporter);
                              if (error)
                                      return error;
                      }
              }
      again:
  614         vma_adjust_trans_huge(orig_vma, start, end, adjust_next);
      
              if (file) {
   65                 mapping = file->f_mapping;
                      root = &mapping->i_mmap;
                      uprobe_munmap(vma, vma->vm_start, vma->vm_end);
      
                      if (adjust_next)
                              uprobe_munmap(next, next->vm_start, next->vm_end);
      
   65                 i_mmap_lock_write(mapping);
                      if (insert) {
                              /*
                               * Put into interval tree now, so instantiated pages
                               * are visible to arm/parisc __flush_dcache_page
                               * throughout; but we cannot insert into address
                               * space until vma start or end is updated.
                               */
   65                         __vma_link_file(insert);
                      }
              }
      
  610         anon_vma = vma->anon_vma;
  253         if (!anon_vma && adjust_next)
                      anon_vma = next->anon_vma;
              if (anon_vma) {
  392                 VM_WARN_ON(adjust_next && next->anon_vma &&
                                 anon_vma != next->anon_vma);
  392                 anon_vma_lock_write(anon_vma);
  392                 anon_vma_interval_tree_pre_update_vma(vma);
  392                 if (adjust_next)
                              anon_vma_interval_tree_pre_update_vma(next);
              }
      
  610         if (root) {
                      flush_dcache_mmap_lock(mapping);
   65                 vma_interval_tree_remove(vma, root);
                      if (adjust_next)
                              vma_interval_tree_remove(next, root);
              }
      
  610         if (start != vma->vm_start) {
  554                 vma->vm_start = start;
                      start_changed = true;
              }
  610         if (end != vma->vm_end) {
  208                 vma->vm_end = end;
                      end_changed = true;
              }
  610         vma->vm_pgoff = pgoff;
              if (adjust_next) {
                      next->vm_start += adjust_next << PAGE_SHIFT;
                      next->vm_pgoff += adjust_next;
              }
      
  610         if (root) {
                      if (adjust_next)
                              vma_interval_tree_insert(next, root);
   65                 vma_interval_tree_insert(vma, root);
                      flush_dcache_mmap_unlock(mapping);
              }
      
  610         if (remove_next) {
                      /*
                       * vma_merge has merged next into vma, and needs
                       * us to remove next before dropping the locks.
                       */
    7                 if (remove_next != 3)
    7                         __vma_unlink_common(mm, next, next);
                      else
                              /*
                               * vma is not before next if they've been
                               * swapped.
                               *
                               * pre-swap() next->vm_start was reduced so
                               * tell validate_mm_rb to ignore pre-swap()
                               * "next" (which is stored in post-swap()
                               * "vma").
                               */
                              __vma_unlink_common(mm, next, vma);
    7                 if (file)
    1                         __remove_shared_vm_struct(next, file, mapping);
  609         } else if (insert) {
                      /*
                       * split_vma has split insert from vma, and needs
                       * us to insert it before dropping the locks
                       * (it may either follow vma or precede it).
                       */
  609                 __insert_vm_struct(mm, insert);
              } else {
   10                 if (start_changed)
    4                         vma_gap_update(vma);
   10                 if (end_changed) {
    6                         if (!next)
                                      mm->highest_vm_end = vm_end_gap(vma);
    6                         else if (!adjust_next)
    6                                 vma_gap_update(next);
                      }
              }
      
  609         if (anon_vma) {
  391                 anon_vma_interval_tree_post_update_vma(vma);
  391                 if (adjust_next)
                              anon_vma_interval_tree_post_update_vma(next);
  391                 anon_vma_unlock_write(anon_vma);
              }
  609         if (mapping)
   65                 i_mmap_unlock_write(mapping);
      
  609         if (root) {
   65                 uprobe_mmap(vma);
      
                      if (adjust_next)
                              uprobe_mmap(next);
              }
      
  609         if (remove_next) {
    7                 if (file) {
    1                         uprobe_munmap(next, next->vm_start, next->vm_end);
                              fput(file);
                      }
    7                 if (next->anon_vma)
    5                         anon_vma_merge(vma, next);
    7                 mm->map_count--;
                      mpol_put(vma_policy(next));
    7                 vm_area_free(next);
                      /*
                       * In mprotect's case 6 (see comments on vma_merge),
                       * we must remove another next too. It would clutter
                       * up the code too much to do both in one go.
                       */
                      if (remove_next != 3) {
                              /*
                               * If "next" was removed and vma->vm_end was
                               * expanded (up) over it, in turn
                               * "next->vm_prev->vm_end" changed and the
                               * "vma->vm_next" gap must be updated.
                               */
    7                         next = vma->vm_next;
                      } else {
                              /*
                               * For the scope of the comment "next" and
                               * "vma" considered pre-swap(): if "vma" was
                               * removed, next->vm_start was expanded (down)
                               * over it and the "next" gap must be updated.
                               * Because of the swap() the post-swap() "vma"
                               * actually points to pre-swap() "next"
                               * (post-swap() "next" as opposed is now a
                               * dangling pointer).
                               */
                              next = vma;
                      }
                      if (remove_next == 2) {
                              remove_next = 1;
                              end = next->vm_end;
                              goto again;
                      }
    7                 else if (next)
    7                         vma_gap_update(next);
                      else {
                              /*
                               * If remove_next == 2 we obviously can't
                               * reach this path.
                               *
                               * If remove_next == 3 we can't reach this
                               * path because pre-swap() next is always not
                               * NULL. pre-swap() "next" is not being
                               * removed and its next->vm_end is not altered
                               * (and furthermore "end" already matches
                               * next->vm_end in remove_next == 3).
                               *
                               * We reach this only in the remove_next == 1
                               * case if the "next" vma that was removed was
                               * the highest vma of the mm. However in such
                               * case next->vm_end == "end" and the extended
                               * "vma" has vma->vm_end == next->vm_end so
                               * mm->highest_vm_end doesn't need any update
                               * in remove_next == 1 case.
                               */
                              VM_WARN_ON(mm->highest_vm_end != vm_end_gap(vma));
                      }
              }
  609         if (insert && file)
   65                 uprobe_mmap(insert);
      
  609         validate_mm(mm);
      
  609         return 0;
      }
      
      /*
       * If the vma has a ->close operation then the driver probably needs to release
       * per-vma resources, so we don't attempt to merge those.
       */
      static inline int is_mergeable_vma(struct vm_area_struct *vma,
                                      struct file *file, unsigned long vm_flags,
                                      struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
      {
              /*
               * VM_SOFTDIRTY should not prevent from VMA merging, if we
               * match the flags but dirty bit -- the caller should mark
               * merged VMA as dirty. If dirty bit won't be excluded from
               * comparison, we increase pressure on the memory system forcing
               * the kernel to generate new VMAs when old one could be
               * extended instead.
               */
  606         if ((vma->vm_flags ^ vm_flags) & ~VM_SOFTDIRTY)
                      return 0;
   21         if (vma->vm_file != file)
                      return 0;
   18         if (vma->vm_ops && vma->vm_ops->close)
                      return 0;
              if (!is_mergeable_vm_userfaultfd_ctx(vma, vm_userfaultfd_ctx))
                      return 0;
              return 1;
      }
      
      static inline int is_mergeable_anon_vma(struct anon_vma *anon_vma1,
                                              struct anon_vma *anon_vma2,
                                              struct vm_area_struct *vma)
      {
              /*
               * The list_is_singular() test is to avoid merging VMA cloned from
               * parents. This can improve scalability caused by anon_vma lock.
               */
   13         if ((!anon_vma1 || !anon_vma2) && (!vma ||
   18                 list_is_singular(&vma->anon_vma_chain)))
                      return 1;
              return anon_vma1 == anon_vma2;
      }
      
      /*
       * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
       * in front of (at a lower virtual address and file offset than) the vma.
       *
       * We cannot merge two vmas if they have differently assigned (non-NULL)
       * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
       *
       * We don't check here for the merged mmap wrapping around the end of pagecache
       * indices (16TB on ia32) because do_mmap_pgoff() does not permit mmap's which
       * wrap, nor mmaps which cover the final page at index -1UL.
       */
      static int
   13 can_vma_merge_before(struct vm_area_struct *vma, unsigned long vm_flags,
                           struct anon_vma *anon_vma, struct file *file,
                           pgoff_t vm_pgoff,
                           struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
      {
  551         if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx) &&
   13             is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
   13                 if (vma->vm_pgoff == vm_pgoff)
                              return 1;
              }
  551         return 0;
      }
      
      /*
       * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
       * beyond (at a higher virtual address and file offset than) the vma.
       *
       * We cannot merge two vmas if they have differently assigned (non-NULL)
       * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
       */
      static int
      can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
                          struct anon_vma *anon_vma, struct file *file,
                          pgoff_t vm_pgoff,
                          struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
      {
  206         if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx) &&
   15             is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
                      pgoff_t vm_pglen;
   15                 vm_pglen = vma_pages(vma);
                      if (vma->vm_pgoff + vm_pglen == vm_pgoff)
                              return 1;
              }
              return 0;
      }
      
      /*
       * Given a mapping request (addr,end,vm_flags,file,pgoff), figure out
       * whether that can be merged with its predecessor or its successor.
       * Or both (it neatly fills a hole).
       *
       * In most cases - when called for mmap, brk or mremap - [addr,end) is
       * certain not to be mapped by the time vma_merge is called; but when
       * called for mprotect, it is certain to be already mapped (either at
       * an offset within prev, or at the start of next), and the flags of
       * this area are about to be changed to vm_flags - and the no-change
       * case has already been eliminated.
       *
       * The following mprotect cases have to be considered, where AAAA is
       * the area passed down from mprotect_fixup, never extending beyond one
       * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
       *
       *     AAAA             AAAA                   AAAA
       *    PPPPPPNNNNNN    PPPPPPNNNNNN       PPPPPPNNNNNN
       *    cannot merge    might become       might become
       *                    PPNNNNNNNNNN       PPPPPPPPPPNN
       *    mmap, brk or    case 4 below       case 5 below
       *    mremap move:
       *                        AAAA               AAAA
       *                    PPPP    NNNN       PPPPNNNNXXXX
       *                    might become       might become
       *                    PPPPPPPPPPPP 1 or  PPPPPPPPPPPP 6 or
       *                    PPPPPPPPNNNN 2 or  PPPPPPPPXXXX 7 or
       *                    PPPPNNNNNNNN 3     PPPPXXXXXXXX 8
       *
       * It is important for case 8 that the vma NNNN overlapping the
       * region AAAA is never going to extended over XXXX. Instead XXXX must
       * be extended in region AAAA and NNNN must be removed. This way in
       * all cases where vma_merge succeeds, the moment vma_adjust drops the
       * rmap_locks, the properties of the merged vma will be already
       * correct for the whole merged range. Some of those properties like
       * vm_page_prot/vm_flags may be accessed by rmap_walks and they must
       * be correct for the whole merged range immediately after the
       * rmap_locks are released. Otherwise if XXXX would be removed and
       * NNNN would be extended over the XXXX range, remove_migration_ptes
       * or other rmap walkers (if working on addresses beyond the "end"
       * parameter) may establish ptes with the wrong permissions of NNNN
       * instead of the right permissions of XXXX.
       */
      struct vm_area_struct *vma_merge(struct mm_struct *mm,
                              struct vm_area_struct *prev, unsigned long addr,
                              unsigned long end, unsigned long vm_flags,
                              struct anon_vma *anon_vma, struct file *file,
                              pgoff_t pgoff, struct mempolicy *policy,
                              struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
      {
  715         pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
              struct vm_area_struct *area, *next;
              int err;
      
              /*
               * We later require that vma->vm_flags == vm_flags,
               * so this tests vma->vm_flags & VM_SPECIAL, too.
               */
              if (vm_flags & VM_SPECIAL)
  715                 return NULL;
      
  715         if (prev)
  715                 next = prev->vm_next;
              else
                      next = mm->mmap;
              area = next;
  715         if (area && area->vm_end == end)                /* cases 6, 7, 8 */
                      next = next->vm_next;
      
              /* verify some invariant that must be enforced by the caller */
  715         VM_WARN_ON(prev && addr <= prev->vm_start);
  715         VM_WARN_ON(area && end > area->vm_end);
  715         VM_WARN_ON(addr >= end);
      
              /*
               * Can it merge with the predecessor?
               */
  715         if (prev && prev->vm_end == addr &&
  206                         mpol_equal(vma_policy(prev), policy) &&
  206                         can_vma_merge_after(prev, vm_flags,
                                                  anon_vma, file, pgoff,
                                                  vm_userfaultfd_ctx)) {
                      /*
                       * OK, it can.  Can we now merge in the successor as well?
                       */
   13                 if (next && end == next->vm_start &&
   11                                 mpol_equal(policy, vma_policy(next)) &&
   11                                 can_vma_merge_before(next, vm_flags,
                                                           anon_vma, file,
                                                           pgoff+pglen,
    5                                                      vm_userfaultfd_ctx) &&
    8                                 is_mergeable_anon_vma(prev->anon_vma,
                                                            next->anon_vma, NULL)) {
                                                              /* cases 1, 6 */
    7                         err = __vma_adjust(prev, prev->vm_start,
                                               next->vm_end, prev->vm_pgoff, NULL,
                                               prev);
                      } else                                        /* cases 2, 5, 7 */
    6                         err = __vma_adjust(prev, prev->vm_start,
                                               end, prev->vm_pgoff, NULL, prev);
   13                 if (err)
                              return NULL;
   13                 khugepaged_enter_vma_merge(prev, vm_flags);
                      return prev;
              }
      
              /*
               * Can this new request be merged in front of next?
               */
  709         if (next && end == next->vm_start &&
  545                         mpol_equal(policy, vma_policy(next)) &&
  545                         can_vma_merge_before(next, vm_flags,
                                                   anon_vma, file, pgoff+pglen,
                                                   vm_userfaultfd_ctx)) {
    4                 if (prev && addr < prev->vm_end)        /* case 4 */
                              err = __vma_adjust(prev, prev->vm_start,
                                               addr, prev->vm_pgoff, NULL, next);
                      else {                                        /* cases 3, 8 */
                              err = __vma_adjust(area, addr, next->vm_end,
    4                                          next->vm_pgoff - pglen, NULL, next);
                              /*
                               * In case 3 area is already equal to next and
                               * this is a noop, but in case 8 "area" has
                               * been removed and next was expanded over it.
                               */
                              area = next;
                      }
    4                 if (err)
                              return NULL;
    4                 khugepaged_enter_vma_merge(area, vm_flags);
                      return area;
              }
      
              return NULL;
      }
      
      /*
       * Rough compatbility check to quickly see if it's even worth looking
       * at sharing an anon_vma.
       *
       * They need to have the same vm_file, and the flags can only differ
       * in things that mprotect may change.
       *
       * NOTE! The fact that we share an anon_vma doesn't _have_ to mean that
       * we can merge the two vma's. For example, we refuse to merge a vma if
       * there is a vm_ops->close() function, because that indicates that the
       * driver is doing some kind of reference counting. But that doesn't
       * really matter for the anon_vma sharing case.
       */
      static int anon_vma_compatible(struct vm_area_struct *a, struct vm_area_struct *b)
      {
  350         return a->vm_end == b->vm_start &&
  100                 mpol_equal(vma_policy(a), vma_policy(b)) &&
  100                 a->vm_file == b->vm_file &&
  350                 !((a->vm_flags ^ b->vm_flags) & ~(VM_READ|VM_WRITE|VM_EXEC|VM_SOFTDIRTY)) &&
   30                 b->vm_pgoff == a->vm_pgoff + ((b->vm_start - a->vm_start) >> PAGE_SHIFT);
      }
      
      /*
       * Do some basic sanity checking to see if we can re-use the anon_vma
       * from 'old'. The 'a'/'b' vma's are in VM order - one of them will be
       * the same as 'old', the other will be the new one that is trying
       * to share the anon_vma.
       *
       * NOTE! This runs with mm_sem held for reading, so it is possible that
       * the anon_vma of 'old' is concurrently in the process of being set up
       * by another page fault trying to merge _that_. But that's ok: if it
       * is being set up, that automatically means that it will be a singleton
       * acceptable for merging, so we can do all of this optimistically. But
       * we do that READ_ONCE() to make sure that we never re-load the pointer.
       *
       * IOW: that the "list_is_singular()" test on the anon_vma_chain only
       * matters for the 'stable anon_vma' case (ie the thing we want to avoid
       * is to return an anon_vma that is "complex" due to having gone through
       * a fork).
       *
       * We also make sure that the two vma's are compatible (adjacent,
       * and with the same memory policies). That's all stable, even with just
       * a read lock on the mm_sem.
       */
      static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, struct vm_area_struct *a, struct vm_area_struct *b)
      {
  350         if (anon_vma_compatible(a, b)) {
   30                 struct anon_vma *anon_vma = READ_ONCE(old->anon_vma);
      
   29                 if (anon_vma && list_is_singular(&old->anon_vma_chain))
                              return anon_vma;
              }
              return NULL;
      }
      
      /*
       * find_mergeable_anon_vma is used by anon_vma_prepare, to check
       * neighbouring vmas for a suitable anon_vma, before it goes off
       * to allocate a new anon_vma.  It checks because a repetitive
       * sequence of mprotects and faults may otherwise lead to distinct
       * anon_vmas being allocated, preventing vma merge in subsequent
       * mprotect.
       */
      struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
  350 {
              struct anon_vma *anon_vma = NULL;
      
              /* Try next first. */
  350         if (vma->vm_next) {
  350                 anon_vma = reusable_anon_vma(vma->vm_next, vma, vma->vm_next);
                      if (anon_vma)
                              return anon_vma;
              }
      
              /* Try prev next. */
  324         if (vma->vm_prev)
  324                 anon_vma = reusable_anon_vma(vma->vm_prev, vma->vm_prev, vma);
      
              /*
               * We might reach here with anon_vma == NULL if we can't find
               * any reusable anon_vma.
               * There's no absolute need to look only at touching neighbours:
               * we could search further afield for "compatible" anon_vmas.
               * But it would probably just be a waste of time searching,
               * or lead to too many vmas hanging off the same anon_vma.
               * We're trying to allow mprotect remerging later on,
               * not trying to minimize memory used for anon_vmas.
               */
              return anon_vma;
      }
      
      /*
       * If a hint addr is less than mmap_min_addr change hint to be as
       * low as possible but still greater than mmap_min_addr
       */
      static inline unsigned long round_hint_to_min(unsigned long hint)
      {
              hint &= PAGE_MASK;
              if (((void *)hint != NULL) &&
                  (hint < mmap_min_addr))
                      return PAGE_ALIGN(mmap_min_addr);
              return hint;
      }
      
    5 static inline int mlock_future_check(struct mm_struct *mm,
                                           unsigned long flags,
                                           unsigned long len)
      {
              unsigned long locked, lock_limit;
      
              /*  mlock MCL_FUTURE? */
  751         if (flags & VM_LOCKED) {