mm/mremap.c

   1 /*
   2  *      mm/mremap.c
   3  *
   4  *      (C) Copyright 1996 Linus Torvalds
   5  *
   6  *      Address space accounting code   <alan@lxorguk.ukuu.org.uk>
   7  *      (C) Copyright 2002 Red Hat Inc, All Rights Reserved
   8  */
   9
  10 #include <linux/mm.h>
  11 #include <linux/hugetlb.h>
  12 #include <linux/shm.h>
  13 #include <linux/ksm.h>
  14 #include <linux/mman.h>
  15 #include <linux/swap.h>
  16 #include <linux/capability.h>
  17 #include <linux/fs.h>
  18 #include <linux/highmem.h>
  19 #include <linux/security.h>
  20 #include <linux/syscalls.h>
  21 #include <linux/mmu_notifier.h>
  22
  23 #include <asm/uaccess.h>
  24 #include <asm/cacheflush.h>
  25 #include <asm/tlbflush.h>
  26
  27 #include "internal.h"
  28
  29 static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
  30 {
  31         pgd_t *pgd;
  32         pud_t *pud;
  33         pmd_t *pmd;
  34
  35         pgd = pgd_offset(mm, addr);
  36         if (pgd_none_or_clear_bad(pgd))
  37                 return NULL;
  38
  39         pud = pud_offset(pgd, addr);
  40         if (pud_none_or_clear_bad(pud))
  41                 return NULL;
  42
  43         pmd = pmd_offset(pud, addr);
  44         if (pmd_none(*pmd))
  45                 return NULL;
  46
  47         return pmd;
  48 }
  49
  50 static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
  51                             unsigned long addr)
  52 {
  53         pgd_t *pgd;
  54         pud_t *pud;
  55         pmd_t *pmd;
  56
  57         pgd = pgd_offset(mm, addr);
  58         pud = pud_alloc(mm, pgd, addr);
  59         if (!pud)
  60                 return NULL;
  61
  62         pmd = pmd_alloc(mm, pud, addr);
  63         if (!pmd)
  64                 return NULL;
  65
  66         VM_BUG_ON(pmd_trans_huge(*pmd));
  67
  68         return pmd;
  69 }
  70
  71 static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
  72                 unsigned long old_addr, unsigned long old_end,
  73                 struct vm_area_struct *new_vma, pmd_t *new_pmd,
  74                 unsigned long new_addr)
  75 {
  76         struct address_space *mapping = NULL;
  77         struct mm_struct *mm = vma->vm_mm;
  78         pte_t *old_pte, *new_pte, pte;
  79         spinlock_t *old_ptl, *new_ptl;
  80
  81         if (vma->vm_file) {
  82                 /*
  83                  * Subtle point from Rajesh Venkatasubramanian: before
  84                  * moving file-based ptes, we must lock truncate_pagecache
  85                  * out, since it might clean the dst vma before the src vma,
  86                  * and we propagate stale pages into the dst afterward.
  87                  */
  88                 mapping = vma->vm_file->f_mapping;
  89                 mutex_lock(&mapping->i_mmap_mutex);
  90         }
  91
  92         /*
  93          * We don't have to worry about the ordering of src and dst
  94          * pte locks because exclusive mmap_sem prevents deadlock.
  95          */
  96         old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
  97         new_pte = pte_offset_map(new_pmd, new_addr);
  98         new_ptl = pte_lockptr(mm, new_pmd);
  99         if (new_ptl != old_ptl)
 100                 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
 101         arch_enter_lazy_mmu_mode();
 102
 103         for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
 104                                    new_pte++, new_addr += PAGE_SIZE) {
 105                 if (pte_none(*old_pte))
 106                         continue;
 107                 pte = ptep_get_and_clear(mm, old_addr, old_pte);
 108                 pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
 109                 set_pte_at(mm, new_addr, new_pte, pte);
 110         }
 111
 112         arch_leave_lazy_mmu_mode();
 113         if (new_ptl != old_ptl)
 114                 spin_unlock(new_ptl);
 115         pte_unmap(new_pte - 1);
 116         pte_unmap_unlock(old_pte - 1, old_ptl);
 117         if (mapping)
 118                 mutex_unlock(&mapping->i_mmap_mutex);
 119 }
 120
 121 #define LATENCY_LIMIT   (64 * PAGE_SIZE)
 122
 123 unsigned long move_page_tables(struct vm_area_struct *vma,
 124                 unsigned long old_addr, struct vm_area_struct *new_vma,
 125                 unsigned long new_addr, unsigned long len)
 126 {
 127         unsigned long extent, next, old_end;
 128         pmd_t *old_pmd, *new_pmd;
 129         bool need_flush = false;
 130
 131         old_end = old_addr + len;
 132         flush_cache_range(vma, old_addr, old_end);
 133
 134         mmu_notifier_invalidate_range_start(vma->vm_mm, old_addr, old_end);
 135
 136         for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
 137                 cond_resched();
 138                 next = (old_addr + PMD_SIZE) & PMD_MASK;
 139                 /* even if next overflowed, extent below will be ok */
 140                 extent = next - old_addr;
 141                 if (extent > old_end - old_addr)
 142                         extent = old_end - old_addr;
 143                 old_pmd = get_old_pmd(vma->vm_mm, old_addr);
 144                 if (!old_pmd)
 145                         continue;
 146                 new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr);
 147                 if (!new_pmd)
 148                         break;
 149                 if (pmd_trans_huge(*old_pmd)) {
 150                         int err = 0;
 151                         if (extent == HPAGE_PMD_SIZE)
 152                                 err = move_huge_pmd(vma, new_vma, old_addr,
 153                                                     new_addr, old_end,
 154                                                     old_pmd, new_pmd);
 155                         if (err > 0) {
 156                                 need_flush = true;
 157                                 continue;
 158                         } else if (!err) {
 159                                 split_huge_page_pmd(vma->vm_mm, old_pmd);
 160                         }
 161                         VM_BUG_ON(pmd_trans_huge(*old_pmd));
 162                 }
 163                 if (pmd_none(*new_pmd) && __pte_alloc(new_vma->vm_mm, new_vma,
 164                                                       new_pmd, new_addr))
 165                         break;
 166                 next = (new_addr + PMD_SIZE) & PMD_MASK;
 167                 if (extent > next - new_addr)
 168                         extent = next - new_addr;
 169                 if (extent > LATENCY_LIMIT)
 170                         extent = LATENCY_LIMIT;
 171                 move_ptes(vma, old_pmd, old_addr, old_addr + extent,
 172                                 new_vma, new_pmd, new_addr);
 173                 need_flush = true;
 174         }
 175         if (likely(need_flush))
 176                 flush_tlb_range(vma, old_end-len, old_addr);
 177
 178         mmu_notifier_invalidate_range_end(vma->vm_mm, old_end-len, old_end);
 179
 180         return len + old_addr - old_end;        /* how much done */
 181 }
 182
 183 static unsigned long move_vma(struct vm_area_struct *vma,
 184                 unsigned long old_addr, unsigned long old_len,
 185                 unsigned long new_len, unsigned long new_addr)
 186 {
 187         struct mm_struct *mm = vma->vm_mm;
 188         struct vm_area_struct *new_vma;
 189         unsigned long vm_flags = vma->vm_flags;
 190         unsigned long new_pgoff;
 191         unsigned long moved_len;
 192         unsigned long excess = 0;
 193         unsigned long hiwater_vm;
 194         int split = 0;
 195         int err;
 196
 197         /*
 198          * We'd prefer to avoid failure later on in do_munmap:
 199          * which may split one vma into three before unmapping.
 200          */
 201         if (mm->map_count >= sysctl_max_map_count - 3)
 202                 return -ENOMEM;
 203
 204         /*
 205          * Advise KSM to break any KSM pages in the area to be moved:
 206          * it would be confusing if they were to turn up at the new
 207          * location, where they happen to coincide with different KSM
 208          * pages recently unmapped.  But leave vma->vm_flags as it was,
 209          * so KSM can come around to merge on vma and new_vma afterwards.
 210          */
 211         err = ksm_madvise(vma, old_addr, old_addr + old_len,
 212                                                 MADV_UNMERGEABLE, &vm_flags);
 213         if (err)
 214                 return err;
 215
 216         new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
 217         new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
 218         if (!new_vma)
 219                 return -ENOMEM;
 220
 221         moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len);
 222         if (moved_len < old_len) {
 223                 /*
 224                  * Before moving the page tables from the new vma to
 225                  * the old vma, we need to be sure the old vma is
 226                  * queued after new vma in the same_anon_vma list to
 227                  * prevent SMP races with rmap_walk (that could lead
 228                  * rmap_walk to miss some page table).
 229                  */
 230                 anon_vma_moveto_tail(vma);
 231
 232                 /*
 233                  * On error, move entries back from new area to old,
 234                  * which will succeed since page tables still there,
 235                  * and then proceed to unmap new area instead of old.
 236                  */
 237                 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len);
 238                 vma = new_vma;
 239                 old_len = new_len;
 240                 old_addr = new_addr;
 241                 new_addr = -ENOMEM;
 242         }
 243
 244         /* Conceal VM_ACCOUNT so old reservation is not undone */
 245         if (vm_flags & VM_ACCOUNT) {
 246                 vma->vm_flags &= ~VM_ACCOUNT;
 247                 excess = vma->vm_end - vma->vm_start - old_len;
 248                 if (old_addr > vma->vm_start &&
 249                     old_addr + old_len < vma->vm_end)
 250                         split = 1;
 251         }
 252
 253         /*
 254          * If we failed to move page tables we still do total_vm increment
 255          * since do_munmap() will decrement it by old_len == new_len.
 256          *
 257          * Since total_vm is about to be raised artificially high for a
 258          * moment, we need to restore high watermark afterwards: if stats
 259          * are taken meanwhile, total_vm and hiwater_vm appear too high.
 260          * If this were a serious issue, we'd add a flag to do_munmap().
 261          */
 262         hiwater_vm = mm->hiwater_vm;
 263         vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
 264
 265         if (do_munmap(mm, old_addr, old_len) < 0) {
 266                 /* OOM: unable to split vma, just get accounts right */
 267                 vm_unacct_memory(excess >> PAGE_SHIFT);
 268                 excess = 0;
 269         }
 270         mm->hiwater_vm = hiwater_vm;
 271
 272         /* Restore VM_ACCOUNT if one or two pieces of vma left */
 273         if (excess) {
 274                 vma->vm_flags |= VM_ACCOUNT;
 275                 if (split)
 276                         vma->vm_next->vm_flags |= VM_ACCOUNT;
 277         }
 278
 279         if (vm_flags & VM_LOCKED) {
 280                 mm->locked_vm += new_len >> PAGE_SHIFT;
 281                 if (new_len > old_len)
 282                         mlock_vma_pages_range(new_vma, new_addr + old_len,
 283                                                        new_addr + new_len);
 284         }
 285
 286         return new_addr;
 287 }
 288
 289 static struct vm_area_struct *vma_to_resize(unsigned long addr,
 290         unsigned long old_len, unsigned long new_len, unsigned long *p)
 291 {
 292         struct mm_struct *mm = current->mm;
 293         struct vm_area_struct *vma = find_vma(mm, addr);
 294
 295         if (!vma || vma->vm_start > addr)
 296                 goto Efault;
 297
 298         if (is_vm_hugetlb_page(vma))
 299                 goto Einval;
 300
 301         /* We can't remap across vm area boundaries */
 302         if (old_len > vma->vm_end - addr)
 303                 goto Efault;
 304
 305         /* Need to be careful about a growing mapping */
 306         if (new_len > old_len) {
 307                 unsigned long pgoff;
 308
 309                 if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
 310                         goto Efault;
 311                 pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
 312                 pgoff += vma->vm_pgoff;
 313                 if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
 314                         goto Einval;
 315         }
 316
 317         if (vma->vm_flags & VM_LOCKED) {
 318                 unsigned long locked, lock_limit;
 319                 locked = mm->locked_vm << PAGE_SHIFT;
 320                 lock_limit = rlimit(RLIMIT_MEMLOCK);
 321                 locked += new_len - old_len;
 322                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
 323                         goto Eagain;
 324         }
 325
 326         if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT))
 327                 goto Enomem;
 328
 329         if (vma->vm_flags & VM_ACCOUNT) {
 330                 unsigned long charged = (new_len - old_len) >> PAGE_SHIFT;
 331                 if (security_vm_enough_memory_mm(mm, charged))
 332                         goto Efault;
 333                 *p = charged;
 334         }
 335
 336         return vma;
 337
 338 Efault: /* very odd choice for most of the cases, but... */
 339         return ERR_PTR(-EFAULT);
 340 Einval:
 341         return ERR_PTR(-EINVAL);
 342 Enomem:
 343         return ERR_PTR(-ENOMEM);
 344 Eagain:
 345         return ERR_PTR(-EAGAIN);
 346 }
 347
 348 static unsigned long mremap_to(unsigned long addr,
 349         unsigned long old_len, unsigned long new_addr,
 350         unsigned long new_len)
 351 {
 352         struct mm_struct *mm = current->mm;
 353         struct vm_area_struct *vma;
 354         unsigned long ret = -EINVAL;
 355         unsigned long charged = 0;
 356         unsigned long map_flags;
 357
 358         if (new_addr & ~PAGE_MASK)
 359                 goto out;
 360
 361         if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
 362                 goto out;
 363
 364         /* Check if the location we're moving into overlaps the
 365          * old location at all, and fail if it does.
 366          */
 367         if ((new_addr <= addr) && (new_addr+new_len) > addr)
 368                 goto out;
 369
 370         if ((addr <= new_addr) && (addr+old_len) > new_addr)
 371                 goto out;
 372
 373         ret = do_munmap(mm, new_addr, new_len);
 374         if (ret)
 375                 goto out;
 376
 377         if (old_len >= new_len) {
 378                 ret = do_munmap(mm, addr+new_len, old_len - new_len);
 379                 if (ret && old_len != new_len)
 380                         goto out;
 381                 old_len = new_len;
 382         }
 383
 384         vma = vma_to_resize(addr, old_len, new_len, &charged);
 385         if (IS_ERR(vma)) {
 386                 ret = PTR_ERR(vma);
 387                 goto out;
 388         }
 389
 390         map_flags = MAP_FIXED;
 391         if (vma->vm_flags & VM_MAYSHARE)
 392                 map_flags |= MAP_SHARED;
 393
 394         ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
 395                                 ((addr - vma->vm_start) >> PAGE_SHIFT),
 396                                 map_flags);
 397         if (ret & ~PAGE_MASK)
 398                 goto out1;
 399
 400         ret = move_vma(vma, addr, old_len, new_len, new_addr);
 401         if (!(ret & ~PAGE_MASK))
 402                 goto out;
 403 out1:
 404         vm_unacct_memory(charged);
 405
 406 out:
 407         return ret;
 408 }
 409
 410 static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
 411 {
 412         unsigned long end = vma->vm_end + delta;
 413         if (end < vma->vm_end) /* overflow */
 414                 return 0;
 415         if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */
 416                 return 0;
 417         if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
 418                               0, MAP_FIXED) & ~PAGE_MASK)
 419                 return 0;
 420         return 1;
 421 }
 422
 423 /*
 424  * Expand (or shrink) an existing mapping, potentially moving it at the
 425  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
 426  *
 427  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
 428  * This option implies MREMAP_MAYMOVE.
 429  */
 430 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
 431                 unsigned long, new_len, unsigned long, flags,
 432                 unsigned long, new_addr)
 433 {
 434         struct mm_struct *mm = current->mm;
 435         struct vm_area_struct *vma;
 436         unsigned long ret = -EINVAL;
 437         unsigned long charged = 0;
 438
 439         down_write(&current->mm->mmap_sem);
 440
 441         if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
 442                 goto out;
 443
 444         if (addr & ~PAGE_MASK)
 445                 goto out;
 446
 447         old_len = PAGE_ALIGN(old_len);
 448         new_len = PAGE_ALIGN(new_len);
 449
 450         /*
 451          * We allow a zero old-len as a special case
 452          * for DOS-emu "duplicate shm area" thing. But
 453          * a zero new-len is nonsensical.
 454          */
 455         if (!new_len)
 456                 goto out;
 457
 458         if (flags & MREMAP_FIXED) {
 459                 if (flags & MREMAP_MAYMOVE)
 460                         ret = mremap_to(addr, old_len, new_addr, new_len);
 461                 goto out;
 462         }
 463
 464         /*
 465          * Always allow a shrinking remap: that just unmaps
 466          * the unnecessary pages..
 467          * do_munmap does all the needed commit accounting
 468          */
 469         if (old_len >= new_len) {
 470                 ret = do_munmap(mm, addr+new_len, old_len - new_len);
 471                 if (ret && old_len != new_len)
 472                         goto out;
 473                 ret = addr;
 474                 goto out;
 475         }
 476
 477         /*
 478          * Ok, we need to grow..
 479          */
 480         vma = vma_to_resize(addr, old_len, new_len, &charged);
 481         if (IS_ERR(vma)) {
 482                 ret = PTR_ERR(vma);
 483                 goto out;
 484         }
 485
 486         /* old_len exactly to the end of the area..
 487          */
 488         if (old_len == vma->vm_end - addr) {
 489                 /* can we just expand the current mapping? */
 490                 if (vma_expandable(vma, new_len - old_len)) {
 491                         int pages = (new_len - old_len) >> PAGE_SHIFT;
 492
 493                         if (vma_adjust(vma, vma->vm_start, addr + new_len,
 494                                        vma->vm_pgoff, NULL)) {
 495                                 ret = -ENOMEM;
 496                                 goto out;
 497                         }
 498
 499                         vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
 500                         if (vma->vm_flags & VM_LOCKED) {
 501                                 mm->locked_vm += pages;
 502                                 mlock_vma_pages_range(vma, addr + old_len,
 503                                                    addr + new_len);
 504                         }
 505                         ret = addr;
 506                         goto out;
 507                 }
 508         }
 509
 510         /*
 511          * We weren't able to just expand or shrink the area,
 512          * we need to create a new one and move it..
 513          */
 514         ret = -ENOMEM;
 515         if (flags & MREMAP_MAYMOVE) {
 516                 unsigned long map_flags = 0;
 517                 if (vma->vm_flags & VM_MAYSHARE)
 518                         map_flags |= MAP_SHARED;
 519
 520                 new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
 521                                         vma->vm_pgoff +
 522                                         ((addr - vma->vm_start) >> PAGE_SHIFT),
 523                                         map_flags);
 524                 if (new_addr & ~PAGE_MASK) {
 525                         ret = new_addr;
 526                         goto out;
 527                 }
 528
 529                 ret = move_vma(vma, addr, old_len, new_len, new_addr);
 530         }
 531 out:
 532         if (ret & ~PAGE_MASK)
 533                 vm_unacct_memory(charged);
 534         up_write(&current->mm->mmap_sem);
 535         return ret;
 536 }