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