mm/mremap.c

   1 /*
   2  *      mm/mremap.c
   3  *
   4  *      (C) Copyright 1996 Linus Torvalds
   5  *
   6  *      Address space accounting code   <alan@redhat.com>
   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/slab.h>
  13 #include <linux/shm.h>
  14 #include <linux/mman.h>
  15 #include <linux/swap.h>
  16 #include <linux/fs.h>
  17 #include <linux/highmem.h>
  18 #include <linux/security.h>
  19 #include <linux/syscalls.h>
  20
  21 #include <asm/uaccess.h>
  22 #include <asm/cacheflush.h>
  23 #include <asm/tlbflush.h>
  24
  25 static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
  26 {
  27         pgd_t *pgd;
  28         pud_t *pud;
  29         pmd_t *pmd;
  30
  31         pgd = pgd_offset(mm, addr);
  32         if (pgd_none_or_clear_bad(pgd))
  33                 return NULL;
  34
  35         pud = pud_offset(pgd, addr);
  36         if (pud_none_or_clear_bad(pud))
  37                 return NULL;
  38
  39         pmd = pmd_offset(pud, addr);
  40         if (pmd_none_or_clear_bad(pmd))
  41                 return NULL;
  42
  43         return pmd;
  44 }
  45
  46 static pmd_t *alloc_new_pmd(struct mm_struct *mm, unsigned long addr)
  47 {
  48         pgd_t *pgd;
  49         pud_t *pud;
  50         pmd_t *pmd;
  51
  52         pgd = pgd_offset(mm, addr);
  53         pud = pud_alloc(mm, pgd, addr);
  54         if (!pud)
  55                 return NULL;
  56
  57         pmd = pmd_alloc(mm, pud, addr);
  58         if (!pmd)
  59                 return NULL;
  60
  61         if (!pmd_present(*pmd) && __pte_alloc(mm, pmd, addr))
  62                 return NULL;
  63
  64         return pmd;
  65 }
  66
  67 static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
  68                 unsigned long old_addr, unsigned long old_end,
  69                 struct vm_area_struct *new_vma, pmd_t *new_pmd,
  70                 unsigned long new_addr)
  71 {
  72         struct address_space *mapping = NULL;
  73         struct mm_struct *mm = vma->vm_mm;
  74         pte_t *old_pte, *new_pte, pte;
  75         spinlock_t *old_ptl;
  76
  77         if (vma->vm_file) {
  78                 /*
  79                  * Subtle point from Rajesh Venkatasubramanian: before
  80                  * moving file-based ptes, we must lock vmtruncate out,
  81                  * since it might clean the dst vma before the src vma,
  82                  * and we propagate stale pages into the dst afterward.
  83                  */
  84                 mapping = vma->vm_file->f_mapping;
  85                 spin_lock(&mapping->i_mmap_lock);
  86                 if (new_vma->vm_truncate_count &&
  87                     new_vma->vm_truncate_count != vma->vm_truncate_count)
  88                         new_vma->vm_truncate_count = 0;
  89         }
  90
  91         old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
  92         new_pte = pte_offset_map_nested(new_pmd, new_addr);
  93
  94         for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
  95                                    new_pte++, new_addr += PAGE_SIZE) {
  96                 if (pte_none(*old_pte))
  97                         continue;
  98                 pte = ptep_clear_flush(vma, old_addr, old_pte);
  99                 /* ZERO_PAGE can be dependant on virtual addr */
 100                 pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
 101                 set_pte_at(mm, new_addr, new_pte, pte);
 102         }
 103
 104         pte_unmap_nested(new_pte - 1);
 105         pte_unmap_unlock(old_pte - 1, old_ptl);
 106         if (mapping)
 107                 spin_unlock(&mapping->i_mmap_lock);
 108 }
 109
 110 #define LATENCY_LIMIT   (64 * PAGE_SIZE)
 111
 112 static unsigned long move_page_tables(struct vm_area_struct *vma,
 113                 unsigned long old_addr, struct vm_area_struct *new_vma,
 114                 unsigned long new_addr, unsigned long len)
 115 {
 116         unsigned long extent, next, old_end;
 117         pmd_t *old_pmd, *new_pmd;
 118
 119         old_end = old_addr + len;
 120         flush_cache_range(vma, old_addr, old_end);
 121
 122         for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
 123                 cond_resched();
 124                 next = (old_addr + PMD_SIZE) & PMD_MASK;
 125                 if (next - 1 > old_end)
 126                         next = old_end;
 127                 extent = next - old_addr;
 128                 old_pmd = get_old_pmd(vma->vm_mm, old_addr);
 129                 if (!old_pmd)
 130                         continue;
 131                 new_pmd = alloc_new_pmd(vma->vm_mm, new_addr);
 132                 if (!new_pmd)
 133                         break;
 134                 next = (new_addr + PMD_SIZE) & PMD_MASK;
 135                 if (extent > next - new_addr)
 136                         extent = next - new_addr;
 137                 if (extent > LATENCY_LIMIT)
 138                         extent = LATENCY_LIMIT;
 139                 move_ptes(vma, old_pmd, old_addr, old_addr + extent,
 140                                 new_vma, new_pmd, new_addr);
 141         }
 142
 143         return len + old_addr - old_end;        /* how much done */
 144 }
 145
 146 static unsigned long move_vma(struct vm_area_struct *vma,
 147                 unsigned long old_addr, unsigned long old_len,
 148                 unsigned long new_len, unsigned long new_addr)
 149 {
 150         struct mm_struct *mm = vma->vm_mm;
 151         struct vm_area_struct *new_vma;
 152         unsigned long vm_flags = vma->vm_flags;
 153         unsigned long new_pgoff;
 154         unsigned long moved_len;
 155         unsigned long excess = 0;
 156         unsigned long hiwater_vm;
 157         int split = 0;
 158
 159         /*
 160          * We'd prefer to avoid failure later on in do_munmap:
 161          * which may split one vma into three before unmapping.
 162          */
 163         if (mm->map_count >= sysctl_max_map_count - 3)
 164                 return -ENOMEM;
 165
 166         new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
 167         new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
 168         if (!new_vma)
 169                 return -ENOMEM;
 170
 171         moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len);
 172         if (moved_len < old_len) {
 173                 /*
 174                  * On error, move entries back from new area to old,
 175                  * which will succeed since page tables still there,
 176                  * and then proceed to unmap new area instead of old.
 177                  */
 178                 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len);
 179                 vma = new_vma;
 180                 old_len = new_len;
 181                 old_addr = new_addr;
 182                 new_addr = -ENOMEM;
 183         }
 184
 185         /* Conceal VM_ACCOUNT so old reservation is not undone */
 186         if (vm_flags & VM_ACCOUNT) {
 187                 vma->vm_flags &= ~VM_ACCOUNT;
 188                 excess = vma->vm_end - vma->vm_start - old_len;
 189                 if (old_addr > vma->vm_start &&
 190                     old_addr + old_len < vma->vm_end)
 191                         split = 1;
 192         }
 193
 194         /*
 195          * If we failed to move page tables we still do total_vm increment
 196          * since do_munmap() will decrement it by old_len == new_len.
 197          *
 198          * Since total_vm is about to be raised artificially high for a
 199          * moment, we need to restore high watermark afterwards: if stats
 200          * are taken meanwhile, total_vm and hiwater_vm appear too high.
 201          * If this were a serious issue, we'd add a flag to do_munmap().
 202          */
 203         hiwater_vm = mm->hiwater_vm;
 204         mm->total_vm += new_len >> PAGE_SHIFT;
 205         vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
 206
 207         if (do_munmap(mm, old_addr, old_len) < 0) {
 208                 /* OOM: unable to split vma, just get accounts right */
 209                 vm_unacct_memory(excess >> PAGE_SHIFT);
 210                 excess = 0;
 211         }
 212         mm->hiwater_vm = hiwater_vm;
 213
 214         /* Restore VM_ACCOUNT if one or two pieces of vma left */
 215         if (excess) {
 216                 vma->vm_flags |= VM_ACCOUNT;
 217                 if (split)
 218                         vma->vm_next->vm_flags |= VM_ACCOUNT;
 219         }
 220
 221         if (vm_flags & VM_LOCKED) {
 222                 mm->locked_vm += new_len >> PAGE_SHIFT;
 223                 if (new_len > old_len)
 224                         make_pages_present(new_addr + old_len,
 225                                            new_addr + new_len);
 226         }
 227
 228         return new_addr;
 229 }
 230
 231 /*
 232  * Expand (or shrink) an existing mapping, potentially moving it at the
 233  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
 234  *
 235  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
 236  * This option implies MREMAP_MAYMOVE.
 237  */
 238 unsigned long do_mremap(unsigned long addr,
 239         unsigned long old_len, unsigned long new_len,
 240         unsigned long flags, unsigned long new_addr)
 241 {
 242         struct mm_struct *mm = current->mm;
 243         struct vm_area_struct *vma;
 244         unsigned long ret = -EINVAL;
 245         unsigned long charged = 0;
 246
 247         if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
 248                 goto out;
 249
 250         if (addr & ~PAGE_MASK)
 251                 goto out;
 252
 253         old_len = PAGE_ALIGN(old_len);
 254         new_len = PAGE_ALIGN(new_len);
 255
 256         /*
 257          * We allow a zero old-len as a special case
 258          * for DOS-emu "duplicate shm area" thing. But
 259          * a zero new-len is nonsensical.
 260          */
 261         if (!new_len)
 262                 goto out;
 263
 264         /* new_addr is only valid if MREMAP_FIXED is specified */
 265         if (flags & MREMAP_FIXED) {
 266                 if (new_addr & ~PAGE_MASK)
 267                         goto out;
 268                 if (!(flags & MREMAP_MAYMOVE))
 269                         goto out;
 270
 271                 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
 272                         goto out;
 273
 274                 /* Check if the location we're moving into overlaps the
 275                  * old location at all, and fail if it does.
 276                  */
 277                 if ((new_addr <= addr) && (new_addr+new_len) > addr)
 278                         goto out;
 279
 280                 if ((addr <= new_addr) && (addr+old_len) > new_addr)
 281                         goto out;
 282
 283                 ret = do_munmap(mm, new_addr, new_len);
 284                 if (ret)
 285                         goto out;
 286         }
 287
 288         /*
 289          * Always allow a shrinking remap: that just unmaps
 290          * the unnecessary pages..
 291          * do_munmap does all the needed commit accounting
 292          */
 293         if (old_len >= new_len) {
 294                 ret = do_munmap(mm, addr+new_len, old_len - new_len);
 295                 if (ret && old_len != new_len)
 296                         goto out;
 297                 ret = addr;
 298                 if (!(flags & MREMAP_FIXED) || (new_addr == addr))
 299                         goto out;
 300                 old_len = new_len;
 301         }
 302
 303         /*
 304          * Ok, we need to grow..  or relocate.
 305          */
 306         ret = -EFAULT;
 307         vma = find_vma(mm, addr);
 308         if (!vma || vma->vm_start > addr)
 309                 goto out;
 310         if (is_vm_hugetlb_page(vma)) {
 311                 ret = -EINVAL;
 312                 goto out;
 313         }
 314         /* We can't remap across vm area boundaries */
 315         if (old_len > vma->vm_end - addr)
 316                 goto out;
 317         if (vma->vm_flags & VM_DONTEXPAND) {
 318                 if (new_len > old_len)
 319                         goto out;
 320         }
 321         if (vma->vm_flags & VM_LOCKED) {
 322                 unsigned long locked, lock_limit;
 323                 locked = mm->locked_vm << PAGE_SHIFT;
 324                 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
 325                 locked += new_len - old_len;
 326                 ret = -EAGAIN;
 327                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
 328                         goto out;
 329         }
 330         if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) {
 331                 ret = -ENOMEM;
 332                 goto out;
 333         }
 334
 335         if (vma->vm_flags & VM_ACCOUNT) {
 336                 charged = (new_len - old_len) >> PAGE_SHIFT;
 337                 if (security_vm_enough_memory(charged))
 338                         goto out_nc;
 339         }
 340
 341         /* old_len exactly to the end of the area..
 342          * And we're not relocating the area.
 343          */
 344         if (old_len == vma->vm_end - addr &&
 345             !((flags & MREMAP_FIXED) && (addr != new_addr)) &&
 346             (old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
 347                 unsigned long max_addr = TASK_SIZE;
 348                 if (vma->vm_next)
 349                         max_addr = vma->vm_next->vm_start;
 350                 /* can we just expand the current mapping? */
 351                 if (max_addr - addr >= new_len) {
 352                         int pages = (new_len - old_len) >> PAGE_SHIFT;
 353
 354                         vma_adjust(vma, vma->vm_start,
 355                                 addr + new_len, vma->vm_pgoff, NULL);
 356
 357                         mm->total_vm += pages;
 358                         vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
 359                         if (vma->vm_flags & VM_LOCKED) {
 360                                 mm->locked_vm += pages;
 361                                 make_pages_present(addr + old_len,
 362                                                    addr + new_len);
 363                         }
 364                         ret = addr;
 365                         goto out;
 366                 }
 367         }
 368
 369         /*
 370          * We weren't able to just expand or shrink the area,
 371          * we need to create a new one and move it..
 372          */
 373         ret = -ENOMEM;
 374         if (flags & MREMAP_MAYMOVE) {
 375                 if (!(flags & MREMAP_FIXED)) {
 376                         unsigned long map_flags = 0;
 377                         if (vma->vm_flags & VM_MAYSHARE)
 378                                 map_flags |= MAP_SHARED;
 379
 380                         new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
 381                                                 vma->vm_pgoff, map_flags);
 382                         ret = new_addr;
 383                         if (new_addr & ~PAGE_MASK)
 384                                 goto out;
 385                 }
 386                 ret = move_vma(vma, addr, old_len, new_len, new_addr);
 387         }
 388 out:
 389         if (ret & ~PAGE_MASK)
 390                 vm_unacct_memory(charged);
 391 out_nc:
 392         return ret;
 393 }
 394
 395 asmlinkage unsigned long sys_mremap(unsigned long addr,
 396         unsigned long old_len, unsigned long new_len,
 397         unsigned long flags, unsigned long new_addr)
 398 {
 399         unsigned long ret;
 400
 401         down_write(&current->mm->mmap_sem);
 402         ret = do_mremap(addr, old_len, new_len, flags, new_addr);
 403         up_write(&current->mm->mmap_sem);
 404         return ret;
 405 }