linux/mm/mmap.c
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   1/*
   2 * mm/mmap.c
   3 *
   4 * Written by obz.
   5 *
   6 * Address space accounting code        <alan@lxorguk.ukuu.org.uk>
   7 */
   8
   9#include <linux/slab.h>
  10#include <linux/backing-dev.h>
  11#include <linux/mm.h>
  12#include <linux/shm.h>
  13#include <linux/mman.h>
  14#include <linux/pagemap.h>
  15#include <linux/swap.h>
  16#include <linux/syscalls.h>
  17#include <linux/capability.h>
  18#include <linux/init.h>
  19#include <linux/file.h>
  20#include <linux/fs.h>
  21#include <linux/personality.h>
  22#include <linux/security.h>
  23#include <linux/hugetlb.h>
  24#include <linux/profile.h>
  25#include <linux/export.h>
  26#include <linux/mount.h>
  27#include <linux/mempolicy.h>
  28#include <linux/rmap.h>
  29#include <linux/mmu_notifier.h>
  30#include <linux/perf_event.h>
  31#include <linux/audit.h>
  32#include <linux/khugepaged.h>
  33#include <linux/uprobes.h>
  34
  35#include <asm/uaccess.h>
  36#include <asm/cacheflush.h>
  37#include <asm/tlb.h>
  38#include <asm/mmu_context.h>
  39
  40#include "internal.h"
  41
  42#ifndef arch_mmap_check
  43#define arch_mmap_check(addr, len, flags)       (0)
  44#endif
  45
  46#ifndef arch_rebalance_pgtables
  47#define arch_rebalance_pgtables(addr, len)              (addr)
  48#endif
  49
  50static void unmap_region(struct mm_struct *mm,
  51                struct vm_area_struct *vma, struct vm_area_struct *prev,
  52                unsigned long start, unsigned long end);
  53
  54/* description of effects of mapping type and prot in current implementation.
  55 * this is due to the limited x86 page protection hardware.  The expected
  56 * behavior is in parens:
  57 *
  58 * map_type     prot
  59 *              PROT_NONE       PROT_READ       PROT_WRITE      PROT_EXEC
  60 * MAP_SHARED   r: (no) no      r: (yes) yes    r: (no) yes     r: (no) yes
  61 *              w: (no) no      w: (no) no      w: (yes) yes    w: (no) no
  62 *              x: (no) no      x: (no) yes     x: (no) yes     x: (yes) yes
  63 *              
  64 * MAP_PRIVATE  r: (no) no      r: (yes) yes    r: (no) yes     r: (no) yes
  65 *              w: (no) no      w: (no) no      w: (copy) copy  w: (no) no
  66 *              x: (no) no      x: (no) yes     x: (no) yes     x: (yes) yes
  67 *
  68 */
  69pgprot_t protection_map[16] = {
  70        __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
  71        __S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
  72};
  73
  74pgprot_t vm_get_page_prot(unsigned long vm_flags)
  75{
  76        return __pgprot(pgprot_val(protection_map[vm_flags &
  77                                (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
  78                        pgprot_val(arch_vm_get_page_prot(vm_flags)));
  79}
  80EXPORT_SYMBOL(vm_get_page_prot);
  81
  82int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS;  /* heuristic overcommit */
  83int sysctl_overcommit_ratio __read_mostly = 50; /* default is 50% */
  84int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
  85/*
  86 * Make sure vm_committed_as in one cacheline and not cacheline shared with
  87 * other variables. It can be updated by several CPUs frequently.
  88 */
  89struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
  90
  91/*
  92 * Check that a process has enough memory to allocate a new virtual
  93 * mapping. 0 means there is enough memory for the allocation to
  94 * succeed and -ENOMEM implies there is not.
  95 *
  96 * We currently support three overcommit policies, which are set via the
  97 * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-accounting
  98 *
  99 * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
 100 * Additional code 2002 Jul 20 by Robert Love.
 101 *
 102 * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
 103 *
 104 * Note this is a helper function intended to be used by LSMs which
 105 * wish to use this logic.
 106 */
 107int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
 108{
 109        unsigned long free, allowed;
 110
 111        vm_acct_memory(pages);
 112
 113        /*
 114         * Sometimes we want to use more memory than we have
 115         */
 116        if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
 117                return 0;
 118
 119        if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
 120                free = global_page_state(NR_FREE_PAGES);
 121                free += global_page_state(NR_FILE_PAGES);
 122
 123                /*
 124                 * shmem pages shouldn't be counted as free in this
 125                 * case, they can't be purged, only swapped out, and
 126                 * that won't affect the overall amount of available
 127                 * memory in the system.
 128                 */
 129                free -= global_page_state(NR_SHMEM);
 130
 131                free += nr_swap_pages;
 132
 133                /*
 134                 * Any slabs which are created with the
 135                 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
 136                 * which are reclaimable, under pressure.  The dentry
 137                 * cache and most inode caches should fall into this
 138                 */
 139                free += global_page_state(NR_SLAB_RECLAIMABLE);
 140
 141                /*
 142                 * Leave reserved pages. The pages are not for anonymous pages.
 143                 */
 144                if (free <= totalreserve_pages)
 145                        goto error;
 146                else
 147                        free -= totalreserve_pages;
 148
 149                /*
 150                 * Leave the last 3% for root
 151                 */
 152                if (!cap_sys_admin)
 153                        free -= free / 32;
 154
 155                if (free > pages)
 156                        return 0;
 157
 158                goto error;
 159        }
 160
 161        allowed = (totalram_pages - hugetlb_total_pages())
 162                * sysctl_overcommit_ratio / 100;
 163        /*
 164         * Leave the last 3% for root
 165         */
 166        if (!cap_sys_admin)
 167                allowed -= allowed / 32;
 168        allowed += total_swap_pages;
 169
 170        /* Don't let a single process grow too big:
 171           leave 3% of the size of this process for other processes */
 172        if (mm)
 173                allowed -= mm->total_vm / 32;
 174
 175        if (percpu_counter_read_positive(&vm_committed_as) < allowed)
 176                return 0;
 177error:
 178        vm_unacct_memory(pages);
 179
 180        return -ENOMEM;
 181}
 182
 183/*
 184 * Requires inode->i_mapping->i_mmap_mutex
 185 */
 186static void __remove_shared_vm_struct(struct vm_area_struct *vma,
 187                struct file *file, struct address_space *mapping)
 188{
 189        if (vma->vm_flags & VM_DENYWRITE)
 190                atomic_inc(&file->f_path.dentry->d_inode->i_writecount);
 191        if (vma->vm_flags & VM_SHARED)
 192                mapping->i_mmap_writable--;
 193
 194        flush_dcache_mmap_lock(mapping);
 195        if (unlikely(vma->vm_flags & VM_NONLINEAR))
 196                list_del_init(&vma->shared.nonlinear);
 197        else
 198                vma_interval_tree_remove(vma, &mapping->i_mmap);
 199        flush_dcache_mmap_unlock(mapping);
 200}
 201
 202/*
 203 * Unlink a file-based vm structure from its interval tree, to hide
 204 * vma from rmap and vmtruncate before freeing its page tables.
 205 */
 206void unlink_file_vma(struct vm_area_struct *vma)
 207{
 208        struct file *file = vma->vm_file;
 209
 210        if (file) {
 211                struct address_space *mapping = file->f_mapping;
 212                mutex_lock(&mapping->i_mmap_mutex);
 213                __remove_shared_vm_struct(vma, file, mapping);
 214                mutex_unlock(&mapping->i_mmap_mutex);
 215        }
 216}
 217
 218/*
 219 * Close a vm structure and free it, returning the next.
 220 */
 221static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
 222{
 223        struct vm_area_struct *next = vma->vm_next;
 224
 225        might_sleep();
 226        if (vma->vm_ops && vma->vm_ops->close)
 227                vma->vm_ops->close(vma);
 228        if (vma->vm_file)
 229                fput(vma->vm_file);
 230        mpol_put(vma_policy(vma));
 231        kmem_cache_free(vm_area_cachep, vma);
 232        return next;
 233}
 234
 235static unsigned long do_brk(unsigned long addr, unsigned long len);
 236
 237SYSCALL_DEFINE1(brk, unsigned long, brk)
 238{
 239        unsigned long rlim, retval;
 240        unsigned long newbrk, oldbrk;
 241        struct mm_struct *mm = current->mm;
 242        unsigned long min_brk;
 243
 244        down_write(&mm->mmap_sem);
 245
 246#ifdef CONFIG_COMPAT_BRK
 247        /*
 248         * CONFIG_COMPAT_BRK can still be overridden by setting
 249         * randomize_va_space to 2, which will still cause mm->start_brk
 250         * to be arbitrarily shifted
 251         */
 252        if (current->brk_randomized)
 253                min_brk = mm->start_brk;
 254        else
 255                min_brk = mm->end_data;
 256#else
 257        min_brk = mm->start_brk;
 258#endif
 259        if (brk < min_brk)
 260                goto out;
 261
 262        /*
 263         * Check against rlimit here. If this check is done later after the test
 264         * of oldbrk with newbrk then it can escape the test and let the data
 265         * segment grow beyond its set limit the in case where the limit is
 266         * not page aligned -Ram Gupta
 267         */
 268        rlim = rlimit(RLIMIT_DATA);
 269        if (rlim < RLIM_INFINITY && (brk - mm->start_brk) +
 270                        (mm->end_data - mm->start_data) > rlim)
 271                goto out;
 272
 273        newbrk = PAGE_ALIGN(brk);
 274        oldbrk = PAGE_ALIGN(mm->brk);
 275        if (oldbrk == newbrk)
 276                goto set_brk;
 277
 278        /* Always allow shrinking brk. */
 279        if (brk <= mm->brk) {
 280                if (!do_munmap(mm, newbrk, oldbrk-newbrk))
 281                        goto set_brk;
 282                goto out;
 283        }
 284
 285        /* Check against existing mmap mappings. */
 286        if (find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE))
 287                goto out;
 288
 289        /* Ok, looks good - let it rip. */
 290        if (do_brk(oldbrk, newbrk-oldbrk) != oldbrk)
 291                goto out;
 292set_brk:
 293        mm->brk = brk;
 294out:
 295        retval = mm->brk;
 296        up_write(&mm->mmap_sem);
 297        return retval;
 298}
 299
 300#ifdef CONFIG_DEBUG_VM_RB
 301static int browse_rb(struct rb_root *root)
 302{
 303        int i = 0, j;
 304        struct rb_node *nd, *pn = NULL;
 305        unsigned long prev = 0, pend = 0;
 306
 307        for (nd = rb_first(root); nd; nd = rb_next(nd)) {
 308                struct vm_area_struct *vma;
 309                vma = rb_entry(nd, struct vm_area_struct, vm_rb);
 310                if (vma->vm_start < prev)
 311                        printk("vm_start %lx prev %lx\n", vma->vm_start, prev), i = -1;
 312                if (vma->vm_start < pend)
 313                        printk("vm_start %lx pend %lx\n", vma->vm_start, pend);
 314                if (vma->vm_start > vma->vm_end)
 315                        printk("vm_end %lx < vm_start %lx\n", vma->vm_end, vma->vm_start);
 316                i++;
 317                pn = nd;
 318                prev = vma->vm_start;
 319                pend = vma->vm_end;
 320        }
 321        j = 0;
 322        for (nd = pn; nd; nd = rb_prev(nd)) {
 323                j++;
 324        }
 325        if (i != j)
 326                printk("backwards %d, forwards %d\n", j, i), i = 0;
 327        return i;
 328}
 329
 330void validate_mm(struct mm_struct *mm)
 331{
 332        int bug = 0;
 333        int i = 0;
 334        struct vm_area_struct *vma = mm->mmap;
 335        while (vma) {
 336                struct anon_vma_chain *avc;
 337                vma_lock_anon_vma(vma);
 338                list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
 339                        anon_vma_interval_tree_verify(avc);
 340                vma_unlock_anon_vma(vma);
 341                vma = vma->vm_next;
 342                i++;
 343        }
 344        if (i != mm->map_count)
 345                printk("map_count %d vm_next %d\n", mm->map_count, i), bug = 1;
 346        i = browse_rb(&mm->mm_rb);
 347        if (i != mm->map_count)
 348                printk("map_count %d rb %d\n", mm->map_count, i), bug = 1;
 349        BUG_ON(bug);
 350}
 351#else
 352#define validate_mm(mm) do { } while (0)
 353#endif
 354
 355/*
 356 * vma has some anon_vma assigned, and is already inserted on that
 357 * anon_vma's interval trees.
 358 *
 359 * Before updating the vma's vm_start / vm_end / vm_pgoff fields, the
 360 * vma must be removed from the anon_vma's interval trees using
 361 * anon_vma_interval_tree_pre_update_vma().
 362 *
 363 * After the update, the vma will be reinserted using
 364 * anon_vma_interval_tree_post_update_vma().
 365 *
 366 * The entire update must be protected by exclusive mmap_sem and by
 367 * the root anon_vma's mutex.
 368 */
 369static inline void
 370anon_vma_interval_tree_pre_update_vma(struct vm_area_struct *vma)
 371{
 372        struct anon_vma_chain *avc;
 373
 374        list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
 375                anon_vma_interval_tree_remove(avc, &avc->anon_vma->rb_root);
 376}
 377
 378static inline void
 379anon_vma_interval_tree_post_update_vma(struct vm_area_struct *vma)
 380{
 381        struct anon_vma_chain *avc;
 382
 383        list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
 384                anon_vma_interval_tree_insert(avc, &avc->anon_vma->rb_root);
 385}
 386
 387static int find_vma_links(struct mm_struct *mm, unsigned long addr,
 388                unsigned long end, struct vm_area_struct **pprev,
 389                struct rb_node ***rb_link, struct rb_node **rb_parent)
 390{
 391        struct rb_node **__rb_link, *__rb_parent, *rb_prev;
 392
 393        __rb_link = &mm->mm_rb.rb_node;
 394        rb_prev = __rb_parent = NULL;
 395
 396        while (*__rb_link) {
 397                struct vm_area_struct *vma_tmp;
 398
 399                __rb_parent = *__rb_link;
 400                vma_tmp = rb_entry(__rb_parent, struct vm_area_struct, vm_rb);
 401
 402                if (vma_tmp->vm_end > addr) {
 403                        /* Fail if an existing vma overlaps the area */
 404                        if (vma_tmp->vm_start < end)
 405                                return -ENOMEM;
 406                        __rb_link = &__rb_parent->rb_left;
 407                } else {
 408                        rb_prev = __rb_parent;
 409                        __rb_link = &__rb_parent->rb_right;
 410                }
 411        }
 412
 413        *pprev = NULL;
 414        if (rb_prev)
 415                *pprev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
 416        *rb_link = __rb_link;
 417        *rb_parent = __rb_parent;
 418        return 0;
 419}
 420
 421void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
 422                struct rb_node **rb_link, struct rb_node *rb_parent)
 423{
 424        rb_link_node(&vma->vm_rb, rb_parent, rb_link);
 425        rb_insert_color(&vma->vm_rb, &mm->mm_rb);
 426}
 427
 428static void __vma_link_file(struct vm_area_struct *vma)
 429{
 430        struct file *file;
 431
 432        file = vma->vm_file;
 433        if (file) {
 434                struct address_space *mapping = file->f_mapping;
 435
 436                if (vma->vm_flags & VM_DENYWRITE)
 437                        atomic_dec(&file->f_path.dentry->d_inode->i_writecount);
 438                if (vma->vm_flags & VM_SHARED)
 439                        mapping->i_mmap_writable++;
 440
 441                flush_dcache_mmap_lock(mapping);
 442                if (unlikely(vma->vm_flags & VM_NONLINEAR))
 443                        vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
 444                else
 445                        vma_interval_tree_insert(vma, &mapping->i_mmap);
 446                flush_dcache_mmap_unlock(mapping);
 447        }
 448}
 449
 450static void
 451__vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
 452        struct vm_area_struct *prev, struct rb_node **rb_link,
 453        struct rb_node *rb_parent)
 454{
 455        __vma_link_list(mm, vma, prev, rb_parent);
 456        __vma_link_rb(mm, vma, rb_link, rb_parent);
 457}
 458
 459static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
 460                        struct vm_area_struct *prev, struct rb_node **rb_link,
 461                        struct rb_node *rb_parent)
 462{
 463        struct address_space *mapping = NULL;
 464
 465        if (vma->vm_file)
 466                mapping = vma->vm_file->f_mapping;
 467
 468        if (mapping)
 469                mutex_lock(&mapping->i_mmap_mutex);
 470
 471        __vma_link(mm, vma, prev, rb_link, rb_parent);
 472        __vma_link_file(vma);
 473
 474        if (mapping)
 475                mutex_unlock(&mapping->i_mmap_mutex);
 476
 477        mm->map_count++;
 478        validate_mm(mm);
 479}
 480
 481/*
 482 * Helper for vma_adjust() in the split_vma insert case: insert a vma into the
 483 * mm's list and rbtree.  It has already been inserted into the interval tree.
 484 */
 485static void __insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
 486{
 487        struct vm_area_struct *prev;
 488        struct rb_node **rb_link, *rb_parent;
 489
 490        if (find_vma_links(mm, vma->vm_start, vma->vm_end,
 491                           &prev, &rb_link, &rb_parent))
 492                BUG();
 493        __vma_link(mm, vma, prev, rb_link, rb_parent);
 494        mm->map_count++;
 495}
 496
 497static inline void
 498__vma_unlink(struct mm_struct *mm, struct vm_area_struct *vma,
 499                struct vm_area_struct *prev)
 500{
 501        struct vm_area_struct *next = vma->vm_next;
 502
 503        prev->vm_next = next;
 504        if (next)
 505                next->vm_prev = prev;
 506        rb_erase(&vma->vm_rb, &mm->mm_rb);
 507        if (mm->mmap_cache == vma)
 508                mm->mmap_cache = prev;
 509}
 510
 511/*
 512 * We cannot adjust vm_start, vm_end, vm_pgoff fields of a vma that
 513 * is already present in an i_mmap tree without adjusting the tree.
 514 * The following helper function should be used when such adjustments
 515 * are necessary.  The "insert" vma (if any) is to be inserted
 516 * before we drop the necessary locks.
 517 */
 518int vma_adjust(struct vm_area_struct *vma, unsigned long start,
 519        unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert)
 520{
 521        struct mm_struct *mm = vma->vm_mm;
 522        struct vm_area_struct *next = vma->vm_next;
 523        struct vm_area_struct *importer = NULL;
 524        struct address_space *mapping = NULL;
 525        struct rb_root *root = NULL;
 526        struct anon_vma *anon_vma = NULL;
 527        struct file *file = vma->vm_file;
 528        long adjust_next = 0;
 529        int remove_next = 0;
 530
 531        if (next && !insert) {
 532                struct vm_area_struct *exporter = NULL;
 533
 534                if (end >= next->vm_end) {
 535                        /*
 536                         * vma expands, overlapping all the next, and
 537                         * perhaps the one after too (mprotect case 6).
 538                         */
 539again:                  remove_next = 1 + (end > next->vm_end);
 540                        end = next->vm_end;
 541                        exporter = next;
 542                        importer = vma;
 543                } else if (end > next->vm_start) {
 544                        /*
 545                         * vma expands, overlapping part of the next:
 546                         * mprotect case 5 shifting the boundary up.
 547                         */
 548                        adjust_next = (end - next->vm_start) >> PAGE_SHIFT;
 549                        exporter = next;
 550                        importer = vma;
 551                } else if (end < vma->vm_end) {
 552                        /*
 553                         * vma shrinks, and !insert tells it's not
 554                         * split_vma inserting another: so it must be
 555                         * mprotect case 4 shifting the boundary down.
 556                         */
 557                        adjust_next = - ((vma->vm_end - end) >> PAGE_SHIFT);
 558                        exporter = vma;
 559                        importer = next;
 560                }
 561
 562                /*
 563                 * Easily overlooked: when mprotect shifts the boundary,
 564                 * make sure the expanding vma has anon_vma set if the
 565                 * shrinking vma had, to cover any anon pages imported.
 566                 */
 567                if (exporter && exporter->anon_vma && !importer->anon_vma) {
 568                        if (anon_vma_clone(importer, exporter))
 569                                return -ENOMEM;
 570                        importer->anon_vma = exporter->anon_vma;
 571                }
 572        }
 573
 574        if (file) {
 575                mapping = file->f_mapping;
 576                if (!(vma->vm_flags & VM_NONLINEAR)) {
 577                        root = &mapping->i_mmap;
 578                        uprobe_munmap(vma, vma->vm_start, vma->vm_end);
 579
 580                        if (adjust_next)
 581                                uprobe_munmap(next, next->vm_start,
 582                                                        next->vm_end);
 583                }
 584
 585                mutex_lock(&mapping->i_mmap_mutex);
 586                if (insert) {
 587                        /*
 588                         * Put into interval tree now, so instantiated pages
 589                         * are visible to arm/parisc __flush_dcache_page
 590                         * throughout; but we cannot insert into address
 591                         * space until vma start or end is updated.
 592                         */
 593                        __vma_link_file(insert);
 594                }
 595        }
 596
 597        vma_adjust_trans_huge(vma, start, end, adjust_next);
 598
 599        anon_vma = vma->anon_vma;
 600        if (!anon_vma && adjust_next)
 601                anon_vma = next->anon_vma;
 602        if (anon_vma) {
 603                VM_BUG_ON(adjust_next && next->anon_vma &&
 604                          anon_vma != next->anon_vma);
 605                anon_vma_lock(anon_vma);
 606                anon_vma_interval_tree_pre_update_vma(vma);
 607                if (adjust_next)
 608                        anon_vma_interval_tree_pre_update_vma(next);
 609        }
 610
 611        if (root) {
 612                flush_dcache_mmap_lock(mapping);
 613                vma_interval_tree_remove(vma, root);
 614                if (adjust_next)
 615                        vma_interval_tree_remove(next, root);
 616        }
 617
 618        vma->vm_start = start;
 619        vma->vm_end = end;
 620        vma->vm_pgoff = pgoff;
 621        if (adjust_next) {
 622                next->vm_start += adjust_next << PAGE_SHIFT;
 623                next->vm_pgoff += adjust_next;
 624        }
 625
 626        if (root) {
 627                if (adjust_next)
 628                        vma_interval_tree_insert(next, root);
 629                vma_interval_tree_insert(vma, root);
 630                flush_dcache_mmap_unlock(mapping);
 631        }
 632
 633        if (remove_next) {
 634                /*
 635                 * vma_merge has merged next into vma, and needs
 636                 * us to remove next before dropping the locks.
 637                 */
 638                __vma_unlink(mm, next, vma);
 639                if (file)
 640                        __remove_shared_vm_struct(next, file, mapping);
 641        } else if (insert) {
 642                /*
 643                 * split_vma has split insert from vma, and needs
 644                 * us to insert it before dropping the locks
 645                 * (it may either follow vma or precede it).
 646                 */
 647                __insert_vm_struct(mm, insert);
 648        }
 649
 650        if (anon_vma) {
 651                anon_vma_interval_tree_post_update_vma(vma);
 652                if (adjust_next)
 653                        anon_vma_interval_tree_post_update_vma(next);
 654                anon_vma_unlock(anon_vma);
 655        }
 656        if (mapping)
 657                mutex_unlock(&mapping->i_mmap_mutex);
 658
 659        if (root) {
 660                uprobe_mmap(vma);
 661
 662                if (adjust_next)
 663                        uprobe_mmap(next);
 664        }
 665
 666        if (remove_next) {
 667                if (file) {
 668                        uprobe_munmap(next, next->vm_start, next->vm_end);
 669                        fput(file);
 670                }
 671                if (next->anon_vma)
 672                        anon_vma_merge(vma, next);
 673                mm->map_count--;
 674                mpol_put(vma_policy(next));
 675                kmem_cache_free(vm_area_cachep, next);
 676                /*
 677                 * In mprotect's case 6 (see comments on vma_merge),
 678                 * we must remove another next too. It would clutter
 679                 * up the code too much to do both in one go.
 680                 */
 681                if (remove_next == 2) {
 682                        next = vma->vm_next;
 683                        goto again;
 684                }
 685        }
 686        if (insert && file)
 687                uprobe_mmap(insert);
 688
 689        validate_mm(mm);
 690
 691        return 0;
 692}
 693
 694/*
 695 * If the vma has a ->close operation then the driver probably needs to release
 696 * per-vma resources, so we don't attempt to merge those.
 697 */
 698static inline int is_mergeable_vma(struct vm_area_struct *vma,
 699                        struct file *file, unsigned long vm_flags)
 700{
 701        if (vma->vm_flags ^ vm_flags)
 702                return 0;
 703        if (vma->vm_file != file)
 704                return 0;
 705        if (vma->vm_ops && vma->vm_ops->close)
 706                return 0;
 707        return 1;
 708}
 709
 710static inline int is_mergeable_anon_vma(struct anon_vma *anon_vma1,
 711                                        struct anon_vma *anon_vma2,
 712                                        struct vm_area_struct *vma)
 713{
 714        /*
 715         * The list_is_singular() test is to avoid merging VMA cloned from
 716         * parents. This can improve scalability caused by anon_vma lock.
 717         */
 718        if ((!anon_vma1 || !anon_vma2) && (!vma ||
 719                list_is_singular(&vma->anon_vma_chain)))
 720                return 1;
 721        return anon_vma1 == anon_vma2;
 722}
 723
 724/*
 725 * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
 726 * in front of (at a lower virtual address and file offset than) the vma.
 727 *
 728 * We cannot merge two vmas if they have differently assigned (non-NULL)
 729 * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
 730 *
 731 * We don't check here for the merged mmap wrapping around the end of pagecache
 732 * indices (16TB on ia32) because do_mmap_pgoff() does not permit mmap's which
 733 * wrap, nor mmaps which cover the final page at index -1UL.
 734 */
 735static int
 736can_vma_merge_before(struct vm_area_struct *vma, unsigned long vm_flags,
 737        struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff)
 738{
 739        if (is_mergeable_vma(vma, file, vm_flags) &&
 740            is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
 741                if (vma->vm_pgoff == vm_pgoff)
 742                        return 1;
 743        }
 744        return 0;
 745}
 746
 747/*
 748 * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
 749 * beyond (at a higher virtual address and file offset than) the vma.
 750 *
 751 * We cannot merge two vmas if they have differently assigned (non-NULL)
 752 * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
 753 */
 754static int
 755can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
 756        struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff)
 757{
 758        if (is_mergeable_vma(vma, file, vm_flags) &&
 759            is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
 760                pgoff_t vm_pglen;
 761                vm_pglen = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
 762                if (vma->vm_pgoff + vm_pglen == vm_pgoff)
 763                        return 1;
 764        }
 765        return 0;
 766}
 767
 768/*
 769 * Given a mapping request (addr,end,vm_flags,file,pgoff), figure out
 770 * whether that can be merged with its predecessor or its successor.
 771 * Or both (it neatly fills a hole).
 772 *
 773 * In most cases - when called for mmap, brk or mremap - [addr,end) is
 774 * certain not to be mapped by the time vma_merge is called; but when
 775 * called for mprotect, it is certain to be already mapped (either at
 776 * an offset within prev, or at the start of next), and the flags of
 777 * this area are about to be changed to vm_flags - and the no-change
 778 * case has already been eliminated.
 779 *
 780 * The following mprotect cases have to be considered, where AAAA is
 781 * the area passed down from mprotect_fixup, never extending beyond one
 782 * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
 783 *
 784 *     AAAA             AAAA                AAAA          AAAA
 785 *    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPNNNNXXXX
 786 *    cannot merge    might become    might become    might become
 787 *                    PPNNNNNNNNNN    PPPPPPPPPPNN    PPPPPPPPPPPP 6 or
 788 *    mmap, brk or    case 4 below    case 5 below    PPPPPPPPXXXX 7 or
 789 *    mremap move:                                    PPPPNNNNNNNN 8
 790 *        AAAA
 791 *    PPPP    NNNN    PPPPPPPPPPPP    PPPPPPPPNNNN    PPPPNNNNNNNN
 792 *    might become    case 1 below    case 2 below    case 3 below
 793 *
 794 * Odd one out? Case 8, because it extends NNNN but needs flags of XXXX:
 795 * mprotect_fixup updates vm_flags & vm_page_prot on successful return.
 796 */
 797struct vm_area_struct *vma_merge(struct mm_struct *mm,
 798                        struct vm_area_struct *prev, unsigned long addr,
 799                        unsigned long end, unsigned long vm_flags,
 800                        struct anon_vma *anon_vma, struct file *file,
 801                        pgoff_t pgoff, struct mempolicy *policy)
 802{
 803        pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
 804        struct vm_area_struct *area, *next;
 805        int err;
 806
 807        /*
 808         * We later require that vma->vm_flags == vm_flags,
 809         * so this tests vma->vm_flags & VM_SPECIAL, too.
 810         */
 811        if (vm_flags & VM_SPECIAL)
 812                return NULL;
 813
 814        if (prev)
 815                next = prev->vm_next;
 816        else
 817                next = mm->mmap;
 818        area = next;
 819        if (next && next->vm_end == end)                /* cases 6, 7, 8 */
 820                next = next->vm_next;
 821
 822        /*
 823         * Can it merge with the predecessor?
 824         */
 825        if (prev && prev->vm_end == addr &&
 826                        mpol_equal(vma_policy(prev), policy) &&
 827                        can_vma_merge_after(prev, vm_flags,
 828                                                anon_vma, file, pgoff)) {
 829                /*
 830                 * OK, it can.  Can we now merge in the successor as well?
 831                 */
 832                if (next && end == next->vm_start &&
 833                                mpol_equal(policy, vma_policy(next)) &&
 834                                can_vma_merge_before(next, vm_flags,
 835                                        anon_vma, file, pgoff+pglen) &&
 836                                is_mergeable_anon_vma(prev->anon_vma,
 837                                                      next->anon_vma, NULL)) {
 838                                                        /* cases 1, 6 */
 839                        err = vma_adjust(prev, prev->vm_start,
 840                                next->vm_end, prev->vm_pgoff, NULL);
 841                } else                                  /* cases 2, 5, 7 */
 842                        err = vma_adjust(prev, prev->vm_start,
 843                                end, prev->vm_pgoff, NULL);
 844                if (err)
 845                        return NULL;
 846                khugepaged_enter_vma_merge(prev);
 847                return prev;
 848        }
 849
 850        /*
 851         * Can this new request be merged in front of next?
 852         */
 853        if (next && end == next->vm_start &&
 854                        mpol_equal(policy, vma_policy(next)) &&
 855                        can_vma_merge_before(next, vm_flags,
 856                                        anon_vma, file, pgoff+pglen)) {
 857                if (prev && addr < prev->vm_end)        /* case 4 */
 858                        err = vma_adjust(prev, prev->vm_start,
 859                                addr, prev->vm_pgoff, NULL);
 860                else                                    /* cases 3, 8 */
 861                        err = vma_adjust(area, addr, next->vm_end,
 862                                next->vm_pgoff - pglen, NULL);
 863                if (err)
 864                        return NULL;
 865                khugepaged_enter_vma_merge(area);
 866                return area;
 867        }
 868
 869        return NULL;
 870}
 871
 872/*
 873 * Rough compatbility check to quickly see if it's even worth looking
 874 * at sharing an anon_vma.
 875 *
 876 * They need to have the same vm_file, and the flags can only differ
 877 * in things that mprotect may change.
 878 *
 879 * NOTE! The fact that we share an anon_vma doesn't _have_ to mean that
 880 * we can merge the two vma's. For example, we refuse to merge a vma if
 881 * there is a vm_ops->close() function, because that indicates that the
 882 * driver is doing some kind of reference counting. But that doesn't
 883 * really matter for the anon_vma sharing case.
 884 */
 885static int anon_vma_compatible(struct vm_area_struct *a, struct vm_area_struct *b)
 886{
 887        return a->vm_end == b->vm_start &&
 888                mpol_equal(vma_policy(a), vma_policy(b)) &&
 889                a->vm_file == b->vm_file &&
 890                !((a->vm_flags ^ b->vm_flags) & ~(VM_READ|VM_WRITE|VM_EXEC)) &&
 891                b->vm_pgoff == a->vm_pgoff + ((b->vm_start - a->vm_start) >> PAGE_SHIFT);
 892}
 893
 894/*
 895 * Do some basic sanity checking to see if we can re-use the anon_vma
 896 * from 'old'. The 'a'/'b' vma's are in VM order - one of them will be
 897 * the same as 'old', the other will be the new one that is trying
 898 * to share the anon_vma.
 899 *
 900 * NOTE! This runs with mm_sem held for reading, so it is possible that
 901 * the anon_vma of 'old' is concurrently in the process of being set up
 902 * by another page fault trying to merge _that_. But that's ok: if it
 903 * is being set up, that automatically means that it will be a singleton
 904 * acceptable for merging, so we can do all of this optimistically. But
 905 * we do that ACCESS_ONCE() to make sure that we never re-load the pointer.
 906 *
 907 * IOW: that the "list_is_singular()" test on the anon_vma_chain only
 908 * matters for the 'stable anon_vma' case (ie the thing we want to avoid
 909 * is to return an anon_vma that is "complex" due to having gone through
 910 * a fork).
 911 *
 912 * We also make sure that the two vma's are compatible (adjacent,
 913 * and with the same memory policies). That's all stable, even with just
 914 * a read lock on the mm_sem.
 915 */
 916static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, struct vm_area_struct *a, struct vm_area_struct *b)
 917{
 918        if (anon_vma_compatible(a, b)) {
 919                struct anon_vma *anon_vma = ACCESS_ONCE(old->anon_vma);
 920
 921                if (anon_vma && list_is_singular(&old->anon_vma_chain))
 922                        return anon_vma;
 923        }
 924        return NULL;
 925}
 926
 927/*
 928 * find_mergeable_anon_vma is used by anon_vma_prepare, to check
 929 * neighbouring vmas for a suitable anon_vma, before it goes off
 930 * to allocate a new anon_vma.  It checks because a repetitive
 931 * sequence of mprotects and faults may otherwise lead to distinct
 932 * anon_vmas being allocated, preventing vma merge in subsequent
 933 * mprotect.
 934 */
 935struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
 936{
 937        struct anon_vma *anon_vma;
 938        struct vm_area_struct *near;
 939
 940        near = vma->vm_next;
 941        if (!near)
 942                goto try_prev;
 943
 944        anon_vma = reusable_anon_vma(near, vma, near);
 945        if (anon_vma)
 946                return anon_vma;
 947try_prev:
 948        near = vma->vm_prev;
 949        if (!near)
 950                goto none;
 951
 952        anon_vma = reusable_anon_vma(near, near, vma);
 953        if (anon_vma)
 954                return anon_vma;
 955none:
 956        /*
 957         * There's no absolute need to look only at touching neighbours:
 958         * we could search further afield for "compatible" anon_vmas.
 959         * But it would probably just be a waste of time searching,
 960         * or lead to too many vmas hanging off the same anon_vma.
 961         * We're trying to allow mprotect remerging later on,
 962         * not trying to minimize memory used for anon_vmas.
 963         */
 964        return NULL;
 965}
 966
 967#ifdef CONFIG_PROC_FS
 968void vm_stat_account(struct mm_struct *mm, unsigned long flags,
 969                                                struct file *file, long pages)
 970{
 971        const unsigned long stack_flags
 972                = VM_STACK_FLAGS & (VM_GROWSUP|VM_GROWSDOWN);
 973
 974        mm->total_vm += pages;
 975
 976        if (file) {
 977                mm->shared_vm += pages;
 978                if ((flags & (VM_EXEC|VM_WRITE)) == VM_EXEC)
 979                        mm->exec_vm += pages;
 980        } else if (flags & stack_flags)
 981                mm->stack_vm += pages;
 982}
 983#endif /* CONFIG_PROC_FS */
 984
 985/*
 986 * If a hint addr is less than mmap_min_addr change hint to be as
 987 * low as possible but still greater than mmap_min_addr
 988 */
 989static inline unsigned long round_hint_to_min(unsigned long hint)
 990{
 991        hint &= PAGE_MASK;
 992        if (((void *)hint != NULL) &&
 993            (hint < mmap_min_addr))
 994                return PAGE_ALIGN(mmap_min_addr);
 995        return hint;
 996}
 997
 998/*
 999 * The caller must hold down_write(&current->mm->mmap_sem).
1000 */
1001
1002unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
1003                        unsigned long len, unsigned long prot,
1004                        unsigned long flags, unsigned long pgoff)
1005{
1006        struct mm_struct * mm = current->mm;
1007        struct inode *inode;
1008        vm_flags_t vm_flags;
1009
1010        /*
1011         * Does the application expect PROT_READ to imply PROT_EXEC?
1012         *
1013         * (the exception is when the underlying filesystem is noexec
1014         *  mounted, in which case we dont add PROT_EXEC.)
1015         */
1016        if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
1017                if (!(file && (file->f_path.mnt->mnt_flags & MNT_NOEXEC)))
1018                        prot |= PROT_EXEC;
1019
1020        if (!len)
1021                return -EINVAL;
1022
1023        if (!(flags & MAP_FIXED))
1024                addr = round_hint_to_min(addr);
1025
1026        /* Careful about overflows.. */
1027        len = PAGE_ALIGN(len);
1028        if (!len)
1029                return -ENOMEM;
1030
1031        /* offset overflow? */
1032        if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
1033               return -EOVERFLOW;
1034
1035        /* Too many mappings? */
1036        if (mm->map_count > sysctl_max_map_count)
1037                return -ENOMEM;
1038
1039        /* Obtain the address to map to. we verify (or select) it and ensure
1040         * that it represents a valid section of the address space.
1041         */
1042        addr = get_unmapped_area(file, addr, len, pgoff, flags);
1043        if (addr & ~PAGE_MASK)
1044                return addr;
1045
1046        /* Do simple checking here so the lower-level routines won't have
1047         * to. we assume access permissions have been handled by the open
1048         * of the memory object, so we don't do any here.
1049         */
1050        vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags) |
1051                        mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
1052
1053        if (flags & MAP_LOCKED)
1054                if (!can_do_mlock())
1055                        return -EPERM;
1056
1057        /* mlock MCL_FUTURE? */
1058        if (vm_flags & VM_LOCKED) {
1059                unsigned long locked, lock_limit;
1060                locked = len >> PAGE_SHIFT;
1061                locked += mm->locked_vm;
1062                lock_limit = rlimit(RLIMIT_MEMLOCK);
1063                lock_limit >>= PAGE_SHIFT;
1064                if (locked > lock_limit && !capable(CAP_IPC_LOCK))
1065                        return -EAGAIN;
1066        }
1067
1068        inode = file ? file->f_path.dentry->d_inode : NULL;
1069
1070        if (file) {
1071                switch (flags & MAP_TYPE) {
1072                case MAP_SHARED:
1073                        if ((prot&PROT_WRITE) && !(file->f_mode&FMODE_WRITE))
1074                                return -EACCES;
1075
1076                        /*
1077                         * Make sure we don't allow writing to an append-only
1078                         * file..
1079                         */
1080                        if (IS_APPEND(inode) && (file->f_mode & FMODE_WRITE))
1081                                return -EACCES;
1082
1083                        /*
1084                         * Make sure there are no mandatory locks on the file.
1085                         */
1086                        if (locks_verify_locked(inode))
1087                                return -EAGAIN;
1088
1089                        vm_flags |= VM_SHARED | VM_MAYSHARE;
1090                        if (!(file->f_mode & FMODE_WRITE))
1091                                vm_flags &= ~(VM_MAYWRITE | VM_SHARED);
1092
1093                        /* fall through */
1094                case MAP_PRIVATE:
1095                        if (!(file->f_mode & FMODE_READ))
1096                                return -EACCES;
1097                        if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) {
1098                                if (vm_flags & VM_EXEC)
1099                                        return -EPERM;
1100                                vm_flags &= ~VM_MAYEXEC;
1101                        }
1102
1103                        if (!file->f_op || !file->f_op->mmap)
1104                                return -ENODEV;
1105                        break;
1106
1107                default:
1108                        return -EINVAL;
1109                }
1110        } else {
1111                switch (flags & MAP_TYPE) {
1112                case MAP_SHARED:
1113                        /*
1114                         * Ignore pgoff.
1115                         */
1116                        pgoff = 0;
1117                        vm_flags |= VM_SHARED | VM_MAYSHARE;
1118                        break;
1119                case MAP_PRIVATE:
1120                        /*
1121                         * Set pgoff according to addr for anon_vma.
1122                         */
1123                        pgoff = addr >> PAGE_SHIFT;
1124                        break;
1125                default:
1126                        return -EINVAL;
1127                }
1128        }
1129
1130        return mmap_region(file, addr, len, flags, vm_flags, pgoff);
1131}
1132
1133SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
1134                unsigned long, prot, unsigned long, flags,
1135                unsigned long, fd, unsigned long, pgoff)
1136{
1137        struct file *file = NULL;
1138        unsigned long retval = -EBADF;
1139
1140        if (!(flags & MAP_ANONYMOUS)) {
1141                audit_mmap_fd(fd, flags);
1142                if (unlikely(flags & MAP_HUGETLB))
1143                        return -EINVAL;
1144                file = fget(fd);
1145                if (!file)
1146                        goto out;
1147        } else if (flags & MAP_HUGETLB) {
1148                struct user_struct *user = NULL;
1149                /*
1150                 * VM_NORESERVE is used because the reservations will be
1151                 * taken when vm_ops->mmap() is called
1152                 * A dummy user value is used because we are not locking
1153                 * memory so no accounting is necessary
1154                 */
1155                file = hugetlb_file_setup(HUGETLB_ANON_FILE, addr, len,
1156                                                VM_NORESERVE, &user,
1157                                                HUGETLB_ANONHUGE_INODE);
1158                if (IS_ERR(file))
1159                        return PTR_ERR(file);
1160        }
1161
1162        flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
1163
1164        retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
1165        if (file)
1166                fput(file);
1167out:
1168        return retval;
1169}
1170
1171#ifdef __ARCH_WANT_SYS_OLD_MMAP
1172struct mmap_arg_struct {
1173        unsigned long addr;
1174        unsigned long len;
1175        unsigned long prot;
1176        unsigned long flags;
1177        unsigned long fd;
1178        unsigned long offset;
1179};
1180
1181SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
1182{
1183        struct mmap_arg_struct a;
1184
1185        if (copy_from_user(&a, arg, sizeof(a)))
1186                return -EFAULT;
1187        if (a.offset & ~PAGE_MASK)
1188                return -EINVAL;
1189
1190        return sys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
1191                              a.offset >> PAGE_SHIFT);
1192}
1193#endif /* __ARCH_WANT_SYS_OLD_MMAP */
1194
1195/*
1196 * Some shared mappigns will want the pages marked read-only
1197 * to track write events. If so, we'll downgrade vm_page_prot
1198 * to the private version (using protection_map[] without the
1199 * VM_SHARED bit).
1200 */
1201int vma_wants_writenotify(struct vm_area_struct *vma)
1202{
1203        vm_flags_t vm_flags = vma->vm_flags;
1204
1205        /* If it was private or non-writable, the write bit is already clear */
1206        if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED)))
1207                return 0;
1208
1209        /* The backer wishes to know when pages are first written to? */
1210        if (vma->vm_ops && vma->vm_ops->page_mkwrite)
1211                return 1;
1212
1213        /* The open routine did something to the protections already? */
1214        if (pgprot_val(vma->vm_page_prot) !=
1215            pgprot_val(vm_get_page_prot(vm_flags)))
1216                return 0;
1217
1218        /* Specialty mapping? */
1219        if (vm_flags & VM_PFNMAP)
1220                return 0;
1221
1222        /* Can the mapping track the dirty pages? */
1223        return vma->vm_file && vma->vm_file->f_mapping &&
1224                mapping_cap_account_dirty(vma->vm_file->f_mapping);
1225}
1226
1227/*
1228 * We account for memory if it's a private writeable mapping,
1229 * not hugepages and VM_NORESERVE wasn't set.
1230 */
1231static inline int accountable_mapping(struct file *file, vm_flags_t vm_flags)
1232{
1233        /*
1234         * hugetlb has its own accounting separate from the core VM
1235         * VM_HUGETLB may not be set yet so we cannot check for that flag.
1236         */
1237        if (file && is_file_hugepages(file))
1238                return 0;
1239
1240        return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE;
1241}
1242
1243unsigned long mmap_region(struct file *file, unsigned long addr,
1244                          unsigned long len, unsigned long flags,
1245                          vm_flags_t vm_flags, unsigned long pgoff)
1246{
1247        struct mm_struct *mm = current->mm;
1248        struct vm_area_struct *vma, *prev;
1249        int correct_wcount = 0;
1250        int error;
1251        struct rb_node **rb_link, *rb_parent;
1252        unsigned long charged = 0;
1253        struct inode *inode =  file ? file->f_path.dentry->d_inode : NULL;
1254
1255        /* Clear old maps */
1256        error = -ENOMEM;
1257munmap_back:
1258        if (find_vma_links(mm, addr, addr + len, &prev, &rb_link, &rb_parent)) {
1259                if (do_munmap(mm, addr, len))
1260                        return -ENOMEM;
1261                goto munmap_back;
1262        }
1263
1264        /* Check against address space limit. */
1265        if (!may_expand_vm(mm, len >> PAGE_SHIFT))
1266                return -ENOMEM;
1267
1268        /*
1269         * Set 'VM_NORESERVE' if we should not account for the
1270         * memory use of this mapping.
1271         */
1272        if ((flags & MAP_NORESERVE)) {
1273                /* We honor MAP_NORESERVE if allowed to overcommit */
1274                if (sysctl_overcommit_memory != OVERCOMMIT_NEVER)
1275                        vm_flags |= VM_NORESERVE;
1276
1277                /* hugetlb applies strict overcommit unless MAP_NORESERVE */
1278                if (file && is_file_hugepages(file))
1279                        vm_flags |= VM_NORESERVE;
1280        }
1281
1282        /*
1283         * Private writable mapping: check memory availability
1284         */
1285        if (accountable_mapping(file, vm_flags)) {
1286                charged = len >> PAGE_SHIFT;
1287                if (security_vm_enough_memory_mm(mm, charged))
1288                        return -ENOMEM;
1289                vm_flags |= VM_ACCOUNT;
1290        }
1291
1292        /*
1293         * Can we just expand an old mapping?
1294         */
1295        vma = vma_merge(mm, prev, addr, addr + len, vm_flags, NULL, file, pgoff, NULL);
1296        if (vma)
1297                goto out;
1298
1299        /*
1300         * Determine the object being mapped and call the appropriate
1301         * specific mapper. the address has already been validated, but
1302         * not unmapped, but the maps are removed from the list.
1303         */
1304        vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
1305        if (!vma) {
1306                error = -ENOMEM;
1307                goto unacct_error;
1308        }
1309
1310        vma->vm_mm = mm;
1311        vma->vm_start = addr;
1312        vma->vm_end = addr + len;
1313        vma->vm_flags = vm_flags;
1314        vma->vm_page_prot = vm_get_page_prot(vm_flags);
1315        vma->vm_pgoff = pgoff;
1316        INIT_LIST_HEAD(&vma->anon_vma_chain);
1317
1318        error = -EINVAL;        /* when rejecting VM_GROWSDOWN|VM_GROWSUP */
1319
1320        if (file) {
1321                if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1322                        goto free_vma;
1323                if (vm_flags & VM_DENYWRITE) {
1324                        error = deny_write_access(file);
1325                        if (error)
1326                                goto free_vma;
1327                        correct_wcount = 1;
1328                }
1329                vma->vm_file = get_file(file);
1330                error = file->f_op->mmap(file, vma);
1331                if (error)
1332                        goto unmap_and_free_vma;
1333
1334                /* Can addr have changed??
1335                 *
1336                 * Answer: Yes, several device drivers can do it in their
1337                 *         f_op->mmap method. -DaveM
1338                 */
1339                addr = vma->vm_start;
1340                pgoff = vma->vm_pgoff;
1341                vm_flags = vma->vm_flags;
1342        } else if (vm_flags & VM_SHARED) {
1343                if (unlikely(vm_flags & (VM_GROWSDOWN|VM_GROWSUP)))
1344                        goto free_vma;
1345                error = shmem_zero_setup(vma);
1346                if (error)
1347                        goto free_vma;
1348        }
1349
1350        if (vma_wants_writenotify(vma)) {
1351                pgprot_t pprot = vma->vm_page_prot;
1352
1353                /* Can vma->vm_page_prot have changed??
1354                 *
1355                 * Answer: Yes, drivers may have changed it in their
1356                 *         f_op->mmap method.
1357                 *
1358                 * Ensures that vmas marked as uncached stay that way.
1359                 */
1360                vma->vm_page_prot = vm_get_page_prot(vm_flags & ~VM_SHARED);
1361                if (pgprot_val(pprot) == pgprot_val(pgprot_noncached(pprot)))
1362                        vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
1363        }
1364
1365        vma_link(mm, vma, prev, rb_link, rb_parent);
1366        file = vma->vm_file;
1367
1368        /* Once vma denies write, undo our temporary denial count */
1369        if (correct_wcount)
1370                atomic_inc(&inode->i_writecount);
1371out:
1372        perf_event_mmap(vma);
1373
1374        vm_stat_account(mm, vm_flags, file, len >> PAGE_SHIFT);
1375        if (vm_flags & VM_LOCKED) {
1376                if (!mlock_vma_pages_range(vma, addr, addr + len))
1377                        mm->locked_vm += (len >> PAGE_SHIFT);
1378        } else if ((flags & MAP_POPULATE) && !(flags & MAP_NONBLOCK))
1379                make_pages_present(addr, addr + len);
1380
1381        if (file)
1382                uprobe_mmap(vma);
1383
1384        return addr;
1385
1386unmap_and_free_vma:
1387        if (correct_wcount)
1388                atomic_inc(&inode->i_writecount);
1389        vma->vm_file = NULL;
1390        fput(file);
1391
1392        /* Undo any partial mapping done by a device driver. */
1393        unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);
1394        charged = 0;
1395free_vma:
1396        kmem_cache_free(vm_area_cachep, vma);
1397unacct_error:
1398        if (charged)
1399                vm_unacct_memory(charged);
1400        return error;
1401}
1402
1403/* Get an address range which is currently unmapped.
1404 * For shmat() with addr=0.
1405 *
1406 * Ugly calling convention alert:
1407 * Return value with the low bits set means error value,
1408 * ie
1409 *      if (ret & ~PAGE_MASK)
1410 *              error = ret;
1411 *
1412 * This function "knows" that -ENOMEM has the bits set.
1413 */
1414#ifndef HAVE_ARCH_UNMAPPED_AREA
1415unsigned long
1416arch_get_unmapped_area(struct file *filp, unsigned long addr,
1417                unsigned long len, unsigned long pgoff, unsigned long flags)
1418{
1419        struct mm_struct *mm = current->mm;
1420        struct vm_area_struct *vma;
1421        unsigned long start_addr;
1422
1423        if (len > TASK_SIZE)
1424                return -ENOMEM;
1425
1426        if (flags & MAP_FIXED)
1427                return addr;
1428
1429        if (addr) {
1430                addr = PAGE_ALIGN(addr);
1431                vma = find_vma(mm, addr);
1432                if (TASK_SIZE - len >= addr &&
1433                    (!vma || addr + len <= vma->vm_start))
1434                        return addr;
1435        }
1436        if (len > mm->cached_hole_size) {
1437                start_addr = addr = mm->free_area_cache;
1438        } else {
1439                start_addr = addr = TASK_UNMAPPED_BASE;
1440                mm->cached_hole_size = 0;
1441        }
1442
1443full_search:
1444        for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
1445                /* At this point:  (!vma || addr < vma->vm_end). */
1446                if (TASK_SIZE - len < addr) {
1447                        /*
1448                         * Start a new search - just in case we missed
1449                         * some holes.
1450                         */
1451                        if (start_addr != TASK_UNMAPPED_BASE) {
1452                                addr = TASK_UNMAPPED_BASE;
1453                                start_addr = addr;
1454                                mm->cached_hole_size = 0;
1455                                goto full_search;
1456                        }
1457                        return -ENOMEM;
1458                }
1459                if (!vma || addr + len <= vma->vm_start) {
1460                        /*
1461                         * Remember the place where we stopped the search:
1462                         */
1463                        mm->free_area_cache = addr + len;
1464                        return addr;
1465                }
1466                if (addr + mm->cached_hole_size < vma->vm_start)
1467                        mm->cached_hole_size = vma->vm_start - addr;
1468                addr = vma->vm_end;
1469        }
1470}
1471#endif  
1472
1473void arch_unmap_area(struct mm_struct *mm, unsigned long addr)
1474{
1475        /*
1476         * Is this a new hole at the lowest possible address?
1477         */
1478        if (addr >= TASK_UNMAPPED_BASE && addr < mm->free_area_cache)
1479                mm->free_area_cache = addr;
1480}
1481
1482/*
1483 * This mmap-allocator allocates new areas top-down from below the
1484 * stack's low limit (the base):
1485 */
1486#ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
1487unsigned long
1488arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
1489                          const unsigned long len, const unsigned long pgoff,
1490                          const unsigned long flags)
1491{
1492        struct vm_area_struct *vma;
1493        struct mm_struct *mm = current->mm;
1494        unsigned long addr = addr0, start_addr;
1495
1496        /* requested length too big for entire address space */
1497        if (len > TASK_SIZE)
1498                return -ENOMEM;
1499
1500        if (flags & MAP_FIXED)
1501                return addr;
1502
1503        /* requesting a specific address */
1504        if (addr) {
1505                addr = PAGE_ALIGN(addr);
1506                vma = find_vma(mm, addr);
1507                if (TASK_SIZE - len >= addr &&
1508                                (!vma || addr + len <= vma->vm_start))
1509                        return addr;
1510        }
1511
1512        /* check if free_area_cache is useful for us */
1513        if (len <= mm->cached_hole_size) {
1514                mm->cached_hole_size = 0;
1515                mm->free_area_cache = mm->mmap_base;
1516        }
1517
1518try_again:
1519        /* either no address requested or can't fit in requested address hole */
1520        start_addr = addr = mm->free_area_cache;
1521
1522        if (addr < len)
1523                goto fail;
1524
1525        addr -= len;
1526        do {
1527                /*
1528                 * Lookup failure means no vma is above this address,
1529                 * else if new region fits below vma->vm_start,
1530                 * return with success:
1531                 */
1532                vma = find_vma(mm, addr);
1533                if (!vma || addr+len <= vma->vm_start)
1534                        /* remember the address as a hint for next time */
1535                        return (mm->free_area_cache = addr);
1536
1537                /* remember the largest hole we saw so far */
1538                if (addr + mm->cached_hole_size < vma->vm_start)
1539                        mm->cached_hole_size = vma->vm_start - addr;
1540
1541                /* try just below the current vma->vm_start */
1542                addr = vma->vm_start-len;
1543        } while (len < vma->vm_start);
1544
1545fail:
1546        /*
1547         * if hint left us with no space for the requested
1548         * mapping then try again:
1549         *
1550         * Note: this is different with the case of bottomup
1551         * which does the fully line-search, but we use find_vma
1552         * here that causes some holes skipped.
1553         */
1554        if (start_addr != mm->mmap_base) {
1555                mm->free_area_cache = mm->mmap_base;
1556                mm->cached_hole_size = 0;
1557                goto try_again;
1558        }
1559
1560        /*
1561         * A failed mmap() very likely causes application failure,
1562         * so fall back to the bottom-up function here. This scenario
1563         * can happen with large stack limits and large mmap()
1564         * allocations.
1565         */
1566        mm->cached_hole_size = ~0UL;
1567        mm->free_area_cache = TASK_UNMAPPED_BASE;
1568        addr = arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
1569        /*
1570         * Restore the topdown base:
1571         */
1572        mm->free_area_cache = mm->mmap_base;
1573        mm->cached_hole_size = ~0UL;
1574
1575        return addr;
1576}
1577#endif
1578
1579void arch_unmap_area_topdown(struct mm_struct *mm, unsigned long addr)
1580{
1581        /*
1582         * Is this a new hole at the highest possible address?
1583         */
1584        if (addr > mm->free_area_cache)
1585                mm->free_area_cache = addr;
1586
1587        /* dont allow allocations above current base */
1588        if (mm->free_area_cache > mm->mmap_base)
1589                mm->free_area_cache = mm->mmap_base;
1590}
1591
1592unsigned long
1593get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
1594                unsigned long pgoff, unsigned long flags)
1595{
1596        unsigned long (*get_area)(struct file *, unsigned long,
1597                                  unsigned long, unsigned long, unsigned long);
1598
1599        unsigned long error = arch_mmap_check(addr, len, flags);
1600        if (error)
1601                return error;
1602
1603        /* Careful about overflows.. */
1604        if (len > TASK_SIZE)
1605                return -ENOMEM;
1606
1607        get_area = current->mm->get_unmapped_area;
1608        if (file && file->f_op && file->f_op->get_unmapped_area)
1609                get_area = file->f_op->get_unmapped_area;
1610        addr = get_area(file, addr, len, pgoff, flags);
1611        if (IS_ERR_VALUE(addr))
1612                return addr;
1613
1614        if (addr > TASK_SIZE - len)
1615                return -ENOMEM;
1616        if (addr & ~PAGE_MASK)
1617                return -EINVAL;
1618
1619        addr = arch_rebalance_pgtables(addr, len);
1620        error = security_mmap_addr(addr);
1621        return error ? error : addr;
1622}
1623
1624EXPORT_SYMBOL(get_unmapped_area);
1625
1626/* Look up the first VMA which satisfies  addr < vm_end,  NULL if none. */
1627struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
1628{
1629        struct vm_area_struct *vma = NULL;
1630
1631        if (WARN_ON_ONCE(!mm))          /* Remove this in linux-3.6 */
1632                return NULL;
1633
1634        /* Check the cache first. */
1635        /* (Cache hit rate is typically around 35%.) */
1636        vma = mm->mmap_cache;
1637        if (!(vma && vma->vm_end > addr && vma->vm_start <= addr)) {
1638                struct rb_node *rb_node;
1639
1640                rb_node = mm->mm_rb.rb_node;
1641                vma = NULL;
1642
1643                while (rb_node) {
1644                        struct vm_area_struct *vma_tmp;
1645
1646                        vma_tmp = rb_entry(rb_node,
1647                                           struct vm_area_struct, vm_rb);
1648
1649                        if (vma_tmp->vm_end > addr) {
1650                                vma = vma_tmp;
1651                                if (vma_tmp->vm_start <= addr)
1652                                        break;
1653                                rb_node = rb_node->rb_left;
1654                        } else
1655                                rb_node = rb_node->rb_right;
1656                }
1657                if (vma)
1658                        mm->mmap_cache = vma;
1659        }
1660        return vma;
1661}
1662
1663EXPORT_SYMBOL(find_vma);
1664
1665/*
1666 * Same as find_vma, but also return a pointer to the previous VMA in *pprev.
1667 */
1668struct vm_area_struct *
1669find_vma_prev(struct mm_struct *mm, unsigned long addr,
1670                        struct vm_area_struct **pprev)
1671{
1672        struct vm_area_struct *vma;
1673
1674        vma = find_vma(mm, addr);
1675        if (vma) {
1676                *pprev = vma->vm_prev;
1677        } else {
1678                struct rb_node *rb_node = mm->mm_rb.rb_node;
1679                *pprev = NULL;
1680                while (rb_node) {
1681                        *pprev = rb_entry(rb_node, struct vm_area_struct, vm_rb);
1682                        rb_node = rb_node->rb_right;
1683                }
1684        }
1685        return vma;
1686}
1687
1688/*
1689 * Verify that the stack growth is acceptable and
1690 * update accounting. This is shared with both the
1691 * grow-up and grow-down cases.
1692 */
1693static int acct_stack_growth(struct vm_area_struct *vma, unsigned long size, unsigned long grow)
1694{
1695        struct mm_struct *mm = vma->vm_mm;
1696        struct rlimit *rlim = current->signal->rlim;
1697        unsigned long new_start;
1698
1699        /* address space limit tests */
1700        if (!may_expand_vm(mm, grow))
1701                return -ENOMEM;
1702
1703        /* Stack limit test */
1704        if (size > ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur))
1705                return -ENOMEM;
1706
1707        /* mlock limit tests */
1708        if (vma->vm_flags & VM_LOCKED) {
1709                unsigned long locked;
1710                unsigned long limit;
1711                locked = mm->locked_vm + grow;
1712                limit = ACCESS_ONCE(rlim[RLIMIT_MEMLOCK].rlim_cur);
1713                limit >>= PAGE_SHIFT;
1714                if (locked > limit && !capable(CAP_IPC_LOCK))
1715                        return -ENOMEM;
1716        }
1717
1718        /* Check to ensure the stack will not grow into a hugetlb-only region */
1719        new_start = (vma->vm_flags & VM_GROWSUP) ? vma->vm_start :
1720                        vma->vm_end - size;
1721        if (is_hugepage_only_range(vma->vm_mm, new_start, size))
1722                return -EFAULT;
1723
1724        /*
1725         * Overcommit..  This must be the final test, as it will
1726         * update security statistics.
1727         */
1728        if (security_vm_enough_memory_mm(mm, grow))
1729                return -ENOMEM;
1730
1731        /* Ok, everything looks good - let it rip */
1732        if (vma->vm_flags & VM_LOCKED)
1733                mm->locked_vm += grow;
1734        vm_stat_account(mm, vma->vm_flags, vma->vm_file, grow);
1735        return 0;
1736}
1737
1738#if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
1739/*
1740 * PA-RISC uses this for its stack; IA64 for its Register Backing Store.
1741 * vma is the last one with address > vma->vm_end.  Have to extend vma.
1742 */
1743int expand_upwards(struct vm_area_struct *vma, unsigned long address)
1744{
1745        int error;
1746
1747        if (!(vma->vm_flags & VM_GROWSUP))
1748                return -EFAULT;
1749
1750        /*
1751         * We must make sure the anon_vma is allocated
1752         * so that the anon_vma locking is not a noop.
1753         */
1754        if (unlikely(anon_vma_prepare(vma)))
1755                return -ENOMEM;
1756        vma_lock_anon_vma(vma);
1757
1758        /*
1759         * vma->vm_start/vm_end cannot change under us because the caller
1760         * is required to hold the mmap_sem in read mode.  We need the
1761         * anon_vma lock to serialize against concurrent expand_stacks.
1762         * Also guard against wrapping around to address 0.
1763         */
1764        if (address < PAGE_ALIGN(address+4))
1765                address = PAGE_ALIGN(address+4);
1766        else {
1767                vma_unlock_anon_vma(vma);
1768                return -ENOMEM;
1769        }
1770        error = 0;
1771
1772        /* Somebody else might have raced and expanded it already */
1773        if (address > vma->vm_end) {
1774                unsigned long size, grow;
1775
1776                size = address - vma->vm_start;
1777                grow = (address - vma->vm_end) >> PAGE_SHIFT;
1778
1779                error = -ENOMEM;
1780                if (vma->vm_pgoff + (size >> PAGE_SHIFT) >= vma->vm_pgoff) {
1781                        error = acct_stack_growth(vma, size, grow);
1782                        if (!error) {
1783                                anon_vma_interval_tree_pre_update_vma(vma);
1784                                vma->vm_end = address;
1785                                anon_vma_interval_tree_post_update_vma(vma);
1786                                perf_event_mmap(vma);
1787                        }
1788                }
1789        }
1790        vma_unlock_anon_vma(vma);
1791        khugepaged_enter_vma_merge(vma);
1792        validate_mm(vma->vm_mm);
1793        return error;
1794}
1795#endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
1796
1797/*
1798 * vma is the first one with address < vma->vm_start.  Have to extend vma.
1799 */
1800int expand_downwards(struct vm_area_struct *vma,
1801                                   unsigned long address)
1802{
1803        int error;
1804
1805        /*
1806         * We must make sure the anon_vma is allocated
1807         * so that the anon_vma locking is not a noop.
1808         */
1809        if (unlikely(anon_vma_prepare(vma)))
1810                return -ENOMEM;
1811
1812        address &= PAGE_MASK;
1813        error = security_mmap_addr(address);
1814        if (error)
1815                return error;
1816
1817        vma_lock_anon_vma(vma);
1818
1819        /*
1820         * vma->vm_start/vm_end cannot change under us because the caller
1821         * is required to hold the mmap_sem in read mode.  We need the
1822         * anon_vma lock to serialize against concurrent expand_stacks.
1823         */
1824
1825        /* Somebody else might have raced and expanded it already */
1826        if (address < vma->vm_start) {
1827                unsigned long size, grow;
1828
1829                size = vma->vm_end - address;
1830                grow = (vma->vm_start - address) >> PAGE_SHIFT;
1831
1832                error = -ENOMEM;
1833                if (grow <= vma->vm_pgoff) {
1834                        error = acct_stack_growth(vma, size, grow);
1835                        if (!error) {
1836                                anon_vma_interval_tree_pre_update_vma(vma);
1837                                vma->vm_start = address;
1838                                vma->vm_pgoff -= grow;
1839                                anon_vma_interval_tree_post_update_vma(vma);
1840                                perf_event_mmap(vma);
1841                        }
1842                }
1843        }
1844        vma_unlock_anon_vma(vma);
1845        khugepaged_enter_vma_merge(vma);
1846        validate_mm(vma->vm_mm);
1847        return error;
1848}
1849
1850#ifdef CONFIG_STACK_GROWSUP
1851int expand_stack(struct vm_area_struct *vma, unsigned long address)
1852{
1853        return expand_upwards(vma, address);
1854}
1855
1856struct vm_area_struct *
1857find_extend_vma(struct mm_struct *mm, unsigned long addr)
1858{
1859        struct vm_area_struct *vma, *prev;
1860
1861        addr &= PAGE_MASK;
1862        vma = find_vma_prev(mm, addr, &prev);
1863        if (vma && (vma->vm_start <= addr))
1864                return vma;
1865        if (!prev || expand_stack(prev, addr))
1866                return NULL;
1867        if (prev->vm_flags & VM_LOCKED) {
1868                mlock_vma_pages_range(prev, addr, prev->vm_end);
1869        }
1870        return prev;
1871}
1872#else
1873int expand_stack(struct vm_area_struct *vma, unsigned long address)
1874{
1875        return expand_downwards(vma, address);
1876}
1877
1878struct vm_area_struct *
1879find_extend_vma(struct mm_struct * mm, unsigned long addr)
1880{
1881        struct vm_area_struct * vma;
1882        unsigned long start;
1883
1884        addr &= PAGE_MASK;
1885        vma = find_vma(mm,addr);
1886        if (!vma)
1887                return NULL;
1888        if (vma->vm_start <= addr)
1889                return vma;
1890        if (!(vma->vm_flags & VM_GROWSDOWN))
1891                return NULL;
1892        start = vma->vm_start;
1893        if (expand_stack(vma, addr))
1894                return NULL;
1895        if (vma->vm_flags & VM_LOCKED) {
1896                mlock_vma_pages_range(vma, addr, start);
1897        }
1898        return vma;
1899}
1900#endif
1901
1902/*
1903 * Ok - we have the memory areas we should free on the vma list,
1904 * so release them, and do the vma updates.
1905 *
1906 * Called with the mm semaphore held.
1907 */
1908static void remove_vma_list(struct mm_struct *mm, struct vm_area_struct *vma)
1909{
1910        unsigned long nr_accounted = 0;
1911
1912        /* Update high watermark before we lower total_vm */
1913        update_hiwater_vm(mm);
1914        do {
1915                long nrpages = vma_pages(vma);
1916
1917                if (vma->vm_flags & VM_ACCOUNT)
1918                        nr_accounted += nrpages;
1919                vm_stat_account(mm, vma->vm_flags, vma->vm_file, -nrpages);
1920                vma = remove_vma(vma);
1921        } while (vma);
1922        vm_unacct_memory(nr_accounted);
1923        validate_mm(mm);
1924}
1925
1926/*
1927 * Get rid of page table information in the indicated region.
1928 *
1929 * Called with the mm semaphore held.
1930 */
1931static void unmap_region(struct mm_struct *mm,
1932                struct vm_area_struct *vma, struct vm_area_struct *prev,
1933                unsigned long start, unsigned long end)
1934{
1935        struct vm_area_struct *next = prev? prev->vm_next: mm->mmap;
1936        struct mmu_gather tlb;
1937
1938        lru_add_drain();
1939        tlb_gather_mmu(&tlb, mm, 0);
1940        update_hiwater_rss(mm);
1941        unmap_vmas(&tlb, vma, start, end);
1942        free_pgtables(&tlb, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
1943                                 next ? next->vm_start : 0);
1944        tlb_finish_mmu(&tlb, start, end);
1945}
1946
1947/*
1948 * Create a list of vma's touched by the unmap, removing them from the mm's
1949 * vma list as we go..
1950 */
1951static void
1952detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
1953        struct vm_area_struct *prev, unsigned long end)
1954{
1955        struct vm_area_struct **insertion_point;
1956        struct vm_area_struct *tail_vma = NULL;
1957        unsigned long addr;
1958
1959        insertion_point = (prev ? &prev->vm_next : &mm->mmap);
1960        vma->vm_prev = NULL;
1961        do {
1962                rb_erase(&vma->vm_rb, &mm->mm_rb);
1963                mm->map_count--;
1964                tail_vma = vma;
1965                vma = vma->vm_next;
1966        } while (vma && vma->vm_start < end);
1967        *insertion_point = vma;
1968        if (vma)
1969                vma->vm_prev = prev;
1970        tail_vma->vm_next = NULL;
1971        if (mm->unmap_area == arch_unmap_area)
1972                addr = prev ? prev->vm_end : mm->mmap_base;
1973        else
1974                addr = vma ?  vma->vm_start : mm->mmap_base;
1975        mm->unmap_area(mm, addr);
1976        mm->mmap_cache = NULL;          /* Kill the cache. */
1977}
1978
1979/*
1980 * __split_vma() bypasses sysctl_max_map_count checking.  We use this on the
1981 * munmap path where it doesn't make sense to fail.
1982 */
1983static int __split_vma(struct mm_struct * mm, struct vm_area_struct * vma,
1984              unsigned long addr, int new_below)
1985{
1986        struct mempolicy *pol;
1987        struct vm_area_struct *new;
1988        int err = -ENOMEM;
1989
1990        if (is_vm_hugetlb_page(vma) && (addr &
1991                                        ~(huge_page_mask(hstate_vma(vma)))))
1992                return -EINVAL;
1993
1994        new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
1995        if (!new)
1996                goto out_err;
1997
1998        /* most fields are the same, copy all, and then fixup */
1999        *new = *vma;
2000
2001        INIT_LIST_HEAD(&new->anon_vma_chain);
2002
2003        if (new_below)
2004                new->vm_end = addr;
2005        else {
2006                new->vm_start = addr;
2007                new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
2008        }
2009
2010        pol = mpol_dup(vma_policy(vma));
2011        if (IS_ERR(pol)) {
2012                err = PTR_ERR(pol);
2013                goto out_free_vma;
2014        }
2015        vma_set_policy(new, pol);
2016
2017        if (anon_vma_clone(new, vma))
2018                goto out_free_mpol;
2019
2020        if (new->vm_file)
2021                get_file(new->vm_file);
2022
2023        if (new->vm_ops && new->vm_ops->open)
2024                new->vm_ops->open(new);
2025
2026        if (new_below)
2027                err = vma_adjust(vma, addr, vma->vm_end, vma->vm_pgoff +
2028                        ((addr - new->vm_start) >> PAGE_SHIFT), new);
2029        else
2030                err = vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new);
2031
2032        /* Success. */
2033        if (!err)
2034                return 0;
2035
2036        /* Clean everything up if vma_adjust failed. */
2037        if (new->vm_ops && new->vm_ops->close)
2038                new->vm_ops->close(new);
2039        if (new->vm_file)
2040                fput(new->vm_file);
2041        unlink_anon_vmas(new);
2042 out_free_mpol:
2043        mpol_put(pol);
2044 out_free_vma:
2045        kmem_cache_free(vm_area_cachep, new);
2046 out_err:
2047        return err;
2048}
2049
2050/*
2051 * Split a vma into two pieces at address 'addr', a new vma is allocated
2052 * either for the first part or the tail.
2053 */
2054int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
2055              unsigned long addr, int new_below)
2056{
2057        if (mm->map_count >= sysctl_max_map_count)
2058                return -ENOMEM;
2059
2060        return __split_vma(mm, vma, addr, new_below);
2061}
2062
2063/* Munmap is split into 2 main parts -- this part which finds
2064 * what needs doing, and the areas themselves, which do the
2065 * work.  This now handles partial unmappings.
2066 * Jeremy Fitzhardinge <jeremy@goop.org>
2067 */
2068int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
2069{
2070        unsigned long end;
2071        struct vm_area_struct *vma, *prev, *last;
2072
2073        if ((start & ~PAGE_MASK) || start > TASK_SIZE || len > TASK_SIZE-start)
2074                return -EINVAL;
2075
2076        if ((len = PAGE_ALIGN(len)) == 0)
2077                return -EINVAL;
2078
2079        /* Find the first overlapping VMA */
2080        vma = find_vma(mm, start);
2081        if (!vma)
2082                return 0;
2083        prev = vma->vm_prev;
2084        /* we have  start < vma->vm_end  */
2085
2086        /* if it doesn't overlap, we have nothing.. */
2087        end = start + len;
2088        if (vma->vm_start >= end)
2089                return 0;
2090
2091        /*
2092         * If we need to split any vma, do it now to save pain later.
2093         *
2094         * Note: mremap's move_vma VM_ACCOUNT handling assumes a partially
2095         * unmapped vm_area_struct will remain in use: so lower split_vma
2096         * places tmp vma above, and higher split_vma places tmp vma below.
2097         */
2098        if (start > vma->vm_start) {
2099                int error;
2100
2101                /*
2102                 * Make sure that map_count on return from munmap() will
2103                 * not exceed its limit; but let map_count go just above
2104                 * its limit temporarily, to help free resources as expected.
2105                 */
2106                if (end < vma->vm_end && mm->map_count >= sysctl_max_map_count)
2107                        return -ENOMEM;
2108
2109                error = __split_vma(mm, vma, start, 0);
2110                if (error)
2111                        return error;
2112                prev = vma;
2113        }
2114
2115        /* Does it split the last one? */
2116        last = find_vma(mm, end);
2117        if (last && end > last->vm_start) {
2118                int error = __split_vma(mm, last, end, 1);
2119                if (error)
2120                        return error;
2121        }
2122        vma = prev? prev->vm_next: mm->mmap;
2123
2124        /*
2125         * unlock any mlock()ed ranges before detaching vmas
2126         */
2127        if (mm->locked_vm) {
2128                struct vm_area_struct *tmp = vma;
2129                while (tmp && tmp->vm_start < end) {
2130                        if (tmp->vm_flags & VM_LOCKED) {
2131                                mm->locked_vm -= vma_pages(tmp);
2132                                munlock_vma_pages_all(tmp);
2133                        }
2134                        tmp = tmp->vm_next;
2135                }
2136        }
2137
2138        /*
2139         * Remove the vma's, and unmap the actual pages
2140         */
2141        detach_vmas_to_be_unmapped(mm, vma, prev, end);
2142        unmap_region(mm, vma, prev, start, end);
2143
2144        /* Fix up all other VM information */
2145        remove_vma_list(mm, vma);
2146
2147        return 0;
2148}
2149
2150int vm_munmap(unsigned long start, size_t len)
2151{
2152        int ret;
2153        struct mm_struct *mm = current->mm;
2154
2155        down_write(&mm->mmap_sem);
2156        ret = do_munmap(mm, start, len);
2157        up_write(&mm->mmap_sem);
2158        return ret;
2159}
2160EXPORT_SYMBOL(vm_munmap);
2161
2162SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
2163{
2164        profile_munmap(addr);
2165        return vm_munmap(addr, len);
2166}
2167
2168static inline void verify_mm_writelocked(struct mm_struct *mm)
2169{
2170#ifdef CONFIG_DEBUG_VM
2171        if (unlikely(down_read_trylock(&mm->mmap_sem))) {
2172                WARN_ON(1);
2173                up_read(&mm->mmap_sem);
2174        }
2175#endif
2176}
2177
2178/*
2179 *  this is really a simplified "do_mmap".  it only handles
2180 *  anonymous maps.  eventually we may be able to do some
2181 *  brk-specific accounting here.
2182 */
2183static unsigned long do_brk(unsigned long addr, unsigned long len)
2184{
2185        struct mm_struct * mm = current->mm;
2186        struct vm_area_struct * vma, * prev;
2187        unsigned long flags;
2188        struct rb_node ** rb_link, * rb_parent;
2189        pgoff_t pgoff = addr >> PAGE_SHIFT;
2190        int error;
2191
2192        len = PAGE_ALIGN(len);
2193        if (!len)
2194                return addr;
2195
2196        flags = VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
2197
2198        error = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
2199        if (error & ~PAGE_MASK)
2200                return error;
2201
2202        /*
2203         * mlock MCL_FUTURE?
2204         */
2205        if (mm->def_flags & VM_LOCKED) {
2206                unsigned long locked, lock_limit;
2207                locked = len >> PAGE_SHIFT;
2208                locked += mm->locked_vm;
2209                lock_limit = rlimit(RLIMIT_MEMLOCK);
2210                lock_limit >>= PAGE_SHIFT;
2211                if (locked > lock_limit && !capable(CAP_IPC_LOCK))
2212                        return -EAGAIN;
2213        }
2214
2215        /*
2216         * mm->mmap_sem is required to protect against another thread
2217         * changing the mappings in case we sleep.
2218         */
2219        verify_mm_writelocked(mm);
2220
2221        /*
2222         * Clear old maps.  this also does some error checking for us
2223         */
2224 munmap_back:
2225        if (find_vma_links(mm, addr, addr + len, &prev, &rb_link, &rb_parent)) {
2226                if (do_munmap(mm, addr, len))
2227                        return -ENOMEM;
2228                goto munmap_back;
2229        }
2230
2231        /* Check against address space limits *after* clearing old maps... */
2232        if (!may_expand_vm(mm, len >> PAGE_SHIFT))
2233                return -ENOMEM;
2234
2235        if (mm->map_count > sysctl_max_map_count)
2236                return -ENOMEM;
2237
2238        if (security_vm_enough_memory_mm(mm, len >> PAGE_SHIFT))
2239                return -ENOMEM;
2240
2241        /* Can we just expand an old private anonymous mapping? */
2242        vma = vma_merge(mm, prev, addr, addr + len, flags,
2243                                        NULL, NULL, pgoff, NULL);
2244        if (vma)
2245                goto out;
2246
2247        /*
2248         * create a vma struct for an anonymous mapping
2249         */
2250        vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
2251        if (!vma) {
2252                vm_unacct_memory(len >> PAGE_SHIFT);
2253                return -ENOMEM;
2254        }
2255
2256        INIT_LIST_HEAD(&vma->anon_vma_chain);
2257        vma->vm_mm = mm;
2258        vma->vm_start = addr;
2259        vma->vm_end = addr + len;
2260        vma->vm_pgoff = pgoff;
2261        vma->vm_flags = flags;
2262        vma->vm_page_prot = vm_get_page_prot(flags);
2263        vma_link(mm, vma, prev, rb_link, rb_parent);
2264out:
2265        perf_event_mmap(vma);
2266        mm->total_vm += len >> PAGE_SHIFT;
2267        if (flags & VM_LOCKED) {
2268                if (!mlock_vma_pages_range(vma, addr, addr + len))
2269                        mm->locked_vm += (len >> PAGE_SHIFT);
2270        }
2271        return addr;
2272}
2273
2274unsigned long vm_brk(unsigned long addr, unsigned long len)
2275{
2276        struct mm_struct *mm = current->mm;
2277        unsigned long ret;
2278
2279        down_write(&mm->mmap_sem);
2280        ret = do_brk(addr, len);
2281        up_write(&mm->mmap_sem);
2282        return ret;
2283}
2284EXPORT_SYMBOL(vm_brk);
2285
2286/* Release all mmaps. */
2287void exit_mmap(struct mm_struct *mm)
2288{
2289        struct mmu_gather tlb;
2290        struct vm_area_struct *vma;
2291        unsigned long nr_accounted = 0;
2292
2293        /* mm's last user has gone, and its about to be pulled down */
2294        mmu_notifier_release(mm);
2295
2296        if (mm->locked_vm) {
2297                vma = mm->mmap;
2298                while (vma) {
2299                        if (vma->vm_flags & VM_LOCKED)
2300                                munlock_vma_pages_all(vma);
2301                        vma = vma->vm_next;
2302                }
2303        }
2304
2305        arch_exit_mmap(mm);
2306
2307        vma = mm->mmap;
2308        if (!vma)       /* Can happen if dup_mmap() received an OOM */
2309                return;
2310
2311        lru_add_drain();
2312        flush_cache_mm(mm);
2313        tlb_gather_mmu(&tlb, mm, 1);
2314        /* update_hiwater_rss(mm) here? but nobody should be looking */
2315        /* Use -1 here to ensure all VMAs in the mm are unmapped */
2316        unmap_vmas(&tlb, vma, 0, -1);
2317
2318        free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, 0);
2319        tlb_finish_mmu(&tlb, 0, -1);
2320
2321        /*
2322         * Walk the list again, actually closing and freeing it,
2323         * with preemption enabled, without holding any MM locks.
2324         */
2325        while (vma) {
2326                if (vma->vm_flags & VM_ACCOUNT)
2327                        nr_accounted += vma_pages(vma);
2328                vma = remove_vma(vma);
2329        }
2330        vm_unacct_memory(nr_accounted);
2331
2332        WARN_ON(mm->nr_ptes > (FIRST_USER_ADDRESS+PMD_SIZE-1)>>PMD_SHIFT);
2333}
2334
2335/* Insert vm structure into process list sorted by address
2336 * and into the inode's i_mmap tree.  If vm_file is non-NULL
2337 * then i_mmap_mutex is taken here.
2338 */
2339int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
2340{
2341        struct vm_area_struct *prev;
2342        struct rb_node **rb_link, *rb_parent;
2343
2344        /*
2345         * The vm_pgoff of a purely anonymous vma should be irrelevant
2346         * until its first write fault, when page's anon_vma and index
2347         * are set.  But now set the vm_pgoff it will almost certainly
2348         * end up with (unless mremap moves it elsewhere before that
2349         * first wfault), so /proc/pid/maps tells a consistent story.
2350         *
2351         * By setting it to reflect the virtual start address of the
2352         * vma, merges and splits can happen in a seamless way, just
2353         * using the existing file pgoff checks and manipulations.
2354         * Similarly in do_mmap_pgoff and in do_brk.
2355         */
2356        if (!vma->vm_file) {
2357                BUG_ON(vma->anon_vma);
2358                vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;
2359        }
2360        if (find_vma_links(mm, vma->vm_start, vma->vm_end,
2361                           &prev, &rb_link, &rb_parent))
2362                return -ENOMEM;
2363        if ((vma->vm_flags & VM_ACCOUNT) &&
2364             security_vm_enough_memory_mm(mm, vma_pages(vma)))
2365                return -ENOMEM;
2366
2367        vma_link(mm, vma, prev, rb_link, rb_parent);
2368        return 0;
2369}
2370
2371/*
2372 * Copy the vma structure to a new location in the same mm,
2373 * prior to moving page table entries, to effect an mremap move.
2374 */
2375struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
2376        unsigned long addr, unsigned long len, pgoff_t pgoff,
2377        bool *need_rmap_locks)
2378{
2379        struct vm_area_struct *vma = *vmap;
2380        unsigned long vma_start = vma->vm_start;
2381        struct mm_struct *mm = vma->vm_mm;
2382        struct vm_area_struct *new_vma, *prev;
2383        struct rb_node **rb_link, *rb_parent;
2384        struct mempolicy *pol;
2385        bool faulted_in_anon_vma = true;
2386
2387        /*
2388         * If anonymous vma has not yet been faulted, update new pgoff
2389         * to match new location, to increase its chance of merging.
2390         */
2391        if (unlikely(!vma->vm_file && !vma->anon_vma)) {
2392                pgoff = addr >> PAGE_SHIFT;
2393                faulted_in_anon_vma = false;
2394        }
2395
2396        if (find_vma_links(mm, addr, addr + len, &prev, &rb_link, &rb_parent))
2397                return NULL;    /* should never get here */
2398        new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags,
2399                        vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma));
2400        if (new_vma) {
2401                /*
2402                 * Source vma may have been merged into new_vma
2403                 */
2404                if (unlikely(vma_start >= new_vma->vm_start &&
2405                             vma_start < new_vma->vm_end)) {
2406                        /*
2407                         * The only way we can get a vma_merge with
2408                         * self during an mremap is if the vma hasn't
2409                         * been faulted in yet and we were allowed to
2410                         * reset the dst vma->vm_pgoff to the
2411                         * destination address of the mremap to allow
2412                         * the merge to happen. mremap must change the
2413                         * vm_pgoff linearity between src and dst vmas
2414                         * (in turn preventing a vma_merge) to be
2415                         * safe. It is only safe to keep the vm_pgoff
2416                         * linear if there are no pages mapped yet.
2417                         */
2418                        VM_BUG_ON(faulted_in_anon_vma);
2419                        *vmap = vma = new_vma;
2420                }
2421                *need_rmap_locks = (new_vma->vm_pgoff <= vma->vm_pgoff);
2422        } else {
2423                new_vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
2424                if (new_vma) {
2425                        *new_vma = *vma;
2426                        new_vma->vm_start = addr;
2427                        new_vma->vm_end = addr + len;
2428                        new_vma->vm_pgoff = pgoff;
2429                        pol = mpol_dup(vma_policy(vma));
2430                        if (IS_ERR(pol))
2431                                goto out_free_vma;
2432                        vma_set_policy(new_vma, pol);
2433                        INIT_LIST_HEAD(&new_vma->anon_vma_chain);
2434                        if (anon_vma_clone(new_vma, vma))
2435                                goto out_free_mempol;
2436                        if (new_vma->vm_file)
2437                                get_file(new_vma->vm_file);
2438                        if (new_vma->vm_ops && new_vma->vm_ops->open)
2439                                new_vma->vm_ops->open(new_vma);
2440                        vma_link(mm, new_vma, prev, rb_link, rb_parent);
2441                        *need_rmap_locks = false;
2442                }
2443        }
2444        return new_vma;
2445
2446 out_free_mempol:
2447        mpol_put(pol);
2448 out_free_vma:
2449        kmem_cache_free(vm_area_cachep, new_vma);
2450        return NULL;
2451}
2452
2453/*
2454 * Return true if the calling process may expand its vm space by the passed
2455 * number of pages
2456 */
2457int may_expand_vm(struct mm_struct *mm, unsigned long npages)
2458{
2459        unsigned long cur = mm->total_vm;       /* pages */
2460        unsigned long lim;
2461
2462        lim = rlimit(RLIMIT_AS) >> PAGE_SHIFT;
2463
2464        if (cur + npages > lim)
2465                return 0;
2466        return 1;
2467}
2468
2469
2470static int special_mapping_fault(struct vm_area_struct *vma,
2471                                struct vm_fault *vmf)
2472{
2473        pgoff_t pgoff;
2474        struct page **pages;
2475
2476        /*
2477         * special mappings have no vm_file, and in that case, the mm
2478         * uses vm_pgoff internally. So we have to subtract it from here.
2479         * We are allowed to do this because we are the mm; do not copy
2480         * this code into drivers!
2481         */
2482        pgoff = vmf->pgoff - vma->vm_pgoff;
2483
2484        for (pages = vma->vm_private_data; pgoff && *pages; ++pages)
2485                pgoff--;
2486
2487        if (*pages) {
2488                struct page *page = *pages;
2489                get_page(page);
2490                vmf->page = page;
2491                return 0;
2492        }
2493
2494        return VM_FAULT_SIGBUS;
2495}
2496
2497/*
2498 * Having a close hook prevents vma merging regardless of flags.
2499 */
2500static void special_mapping_close(struct vm_area_struct *vma)
2501{
2502}
2503
2504static const struct vm_operations_struct special_mapping_vmops = {
2505        .close = special_mapping_close,
2506        .fault = special_mapping_fault,
2507};
2508
2509/*
2510 * Called with mm->mmap_sem held for writing.
2511 * Insert a new vma covering the given region, with the given flags.
2512 * Its pages are supplied by the given array of struct page *.
2513 * The array can be shorter than len >> PAGE_SHIFT if it's null-terminated.
2514 * The region past the last page supplied will always produce SIGBUS.
2515 * The array pointer and the pages it points to are assumed to stay alive
2516 * for as long as this mapping might exist.
2517 */
2518int install_special_mapping(struct mm_struct *mm,
2519                            unsigned long addr, unsigned long len,
2520                            unsigned long vm_flags, struct page **pages)
2521{
2522        int ret;
2523        struct vm_area_struct *vma;
2524
2525        vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
2526        if (unlikely(vma == NULL))
2527                return -ENOMEM;
2528
2529        INIT_LIST_HEAD(&vma->anon_vma_chain);
2530        vma->vm_mm = mm;
2531        vma->vm_start = addr;
2532        vma->vm_end = addr + len;
2533
2534        vma->vm_flags = vm_flags | mm->def_flags | VM_DONTEXPAND;
2535        vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
2536
2537        vma->vm_ops = &special_mapping_vmops;
2538        vma->vm_private_data = pages;
2539
2540        ret = insert_vm_struct(mm, vma);
2541        if (ret)
2542                goto out;
2543
2544        mm->total_vm += len >> PAGE_SHIFT;
2545
2546        perf_event_mmap(vma);
2547
2548        return 0;
2549
2550out:
2551        kmem_cache_free(vm_area_cachep, vma);
2552        return ret;
2553}
2554
2555static DEFINE_MUTEX(mm_all_locks_mutex);
2556
2557static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma)
2558{
2559        if (!test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_node)) {
2560                /*
2561                 * The LSB of head.next can't change from under us
2562                 * because we hold the mm_all_locks_mutex.
2563                 */
2564                mutex_lock_nest_lock(&anon_vma->root->mutex, &mm->mmap_sem);
2565                /*
2566                 * We can safely modify head.next after taking the
2567                 * anon_vma->root->mutex. If some other vma in this mm shares
2568                 * the same anon_vma we won't take it again.
2569                 *
2570                 * No need of atomic instructions here, head.next
2571                 * can't change from under us thanks to the
2572                 * anon_vma->root->mutex.
2573                 */
2574                if (__test_and_set_bit(0, (unsigned long *)
2575                                       &anon_vma->root->rb_root.rb_node))
2576                        BUG();
2577        }
2578}
2579
2580static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping)
2581{
2582        if (!test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
2583                /*
2584                 * AS_MM_ALL_LOCKS can't change from under us because
2585                 * we hold the mm_all_locks_mutex.
2586                 *
2587                 * Operations on ->flags have to be atomic because
2588                 * even if AS_MM_ALL_LOCKS is stable thanks to the
2589                 * mm_all_locks_mutex, there may be other cpus
2590                 * changing other bitflags in parallel to us.
2591                 */
2592                if (test_and_set_bit(AS_MM_ALL_LOCKS, &mapping->flags))
2593                        BUG();
2594                mutex_lock_nest_lock(&mapping->i_mmap_mutex, &mm->mmap_sem);
2595        }
2596}
2597
2598/*
2599 * This operation locks against the VM for all pte/vma/mm related
2600 * operations that could ever happen on a certain mm. This includes
2601 * vmtruncate, try_to_unmap, and all page faults.
2602 *
2603 * The caller must take the mmap_sem in write mode before calling
2604 * mm_take_all_locks(). The caller isn't allowed to release the
2605 * mmap_sem until mm_drop_all_locks() returns.
2606 *
2607 * mmap_sem in write mode is required in order to block all operations
2608 * that could modify pagetables and free pages without need of
2609 * altering the vma layout (for example populate_range() with
2610 * nonlinear vmas). It's also needed in write mode to avoid new
2611 * anon_vmas to be associated with existing vmas.
2612 *
2613 * A single task can't take more than one mm_take_all_locks() in a row
2614 * or it would deadlock.
2615 *
2616 * The LSB in anon_vma->rb_root.rb_node and the AS_MM_ALL_LOCKS bitflag in
2617 * mapping->flags avoid to take the same lock twice, if more than one
2618 * vma in this mm is backed by the same anon_vma or address_space.
2619 *
2620 * We can take all the locks in random order because the VM code
2621 * taking i_mmap_mutex or anon_vma->mutex outside the mmap_sem never
2622 * takes more than one of them in a row. Secondly we're protected
2623 * against a concurrent mm_take_all_locks() by the mm_all_locks_mutex.
2624 *
2625 * mm_take_all_locks() and mm_drop_all_locks are expensive operations
2626 * that may have to take thousand of locks.
2627 *
2628 * mm_take_all_locks() can fail if it's interrupted by signals.
2629 */
2630int mm_take_all_locks(struct mm_struct *mm)
2631{
2632        struct vm_area_struct *vma;
2633        struct anon_vma_chain *avc;
2634
2635        BUG_ON(down_read_trylock(&mm->mmap_sem));
2636
2637        mutex_lock(&mm_all_locks_mutex);
2638
2639        for (vma = mm->mmap; vma; vma = vma->vm_next) {
2640                if (signal_pending(current))
2641                        goto out_unlock;
2642                if (vma->vm_file && vma->vm_file->f_mapping)
2643                        vm_lock_mapping(mm, vma->vm_file->f_mapping);
2644        }
2645
2646        for (vma = mm->mmap; vma; vma = vma->vm_next) {
2647                if (signal_pending(current))
2648                        goto out_unlock;
2649                if (vma->anon_vma)
2650                        list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
2651                                vm_lock_anon_vma(mm, avc->anon_vma);
2652        }
2653
2654        return 0;
2655
2656out_unlock:
2657        mm_drop_all_locks(mm);
2658        return -EINTR;
2659}
2660
2661static void vm_unlock_anon_vma(struct anon_vma *anon_vma)
2662{
2663        if (test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_node)) {
2664                /*
2665                 * The LSB of head.next can't change to 0 from under
2666                 * us because we hold the mm_all_locks_mutex.
2667                 *
2668                 * We must however clear the bitflag before unlocking
2669                 * the vma so the users using the anon_vma->rb_root will
2670                 * never see our bitflag.
2671                 *
2672                 * No need of atomic instructions here, head.next
2673                 * can't change from under us until we release the
2674                 * anon_vma->root->mutex.
2675                 */
2676                if (!__test_and_clear_bit(0, (unsigned long *)
2677                                          &anon_vma->root->rb_root.rb_node))
2678                        BUG();
2679                anon_vma_unlock(anon_vma);
2680        }
2681}
2682
2683static void vm_unlock_mapping(struct address_space *mapping)
2684{
2685        if (test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
2686                /*
2687                 * AS_MM_ALL_LOCKS can't change to 0 from under us
2688                 * because we hold the mm_all_locks_mutex.
2689                 */
2690                mutex_unlock(&mapping->i_mmap_mutex);
2691                if (!test_and_clear_bit(AS_MM_ALL_LOCKS,
2692                                        &mapping->flags))
2693                        BUG();
2694        }
2695}
2696
2697/*
2698 * The mmap_sem cannot be released by the caller until
2699 * mm_drop_all_locks() returns.
2700 */
2701void mm_drop_all_locks(struct mm_struct *mm)
2702{
2703        struct vm_area_struct *vma;
2704        struct anon_vma_chain *avc;
2705
2706        BUG_ON(down_read_trylock(&mm->mmap_sem));
2707        BUG_ON(!mutex_is_locked(&mm_all_locks_mutex));
2708
2709        for (vma = mm->mmap; vma; vma = vma->vm_next) {
2710                if (vma->anon_vma)
2711                        list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
2712                                vm_unlock_anon_vma(avc->anon_vma);
2713                if (vma->vm_file && vma->vm_file->f_mapping)
2714                        vm_unlock_mapping(vma->vm_file->f_mapping);
2715        }
2716
2717        mutex_unlock(&mm_all_locks_mutex);
2718}
2719
2720/*
2721 * initialise the VMA slab
2722 */
2723void __init mmap_init(void)
2724{
2725        int ret;
2726
2727        ret = percpu_counter_init(&vm_committed_as, 0);
2728        VM_BUG_ON(ret);
2729}
2730
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