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