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         /*
  32          * We don't need page_table_lock: we have mmap_sem exclusively.
  33          */
  34         pgd = pgd_offset(mm, addr);
  35         if (pgd_none_or_clear_bad(pgd))
  36                 return NULL;
  37
  38         pud = pud_offset(pgd, addr);
  39         if (pud_none_or_clear_bad(pud))
  40                 return NULL;
  41
  42         pmd = pmd_offset(pud, addr);
  43         if (pmd_none_or_clear_bad(pmd))
  44                 return NULL;
  45
  46         return pmd;
  47 }
  48
  49 static pmd_t *alloc_new_pmd(struct mm_struct *mm, unsigned long addr)
  50 {
  51         pgd_t *pgd;
  52         pud_t *pud;
  53         pmd_t *pmd = NULL;
  54         pte_t *pte;
  55
  56         /*
  57          * We do need page_table_lock: because allocators expect that.
  58          */
  59         spin_lock(&mm->page_table_lock);
  60         pgd = pgd_offset(mm, addr);
  61         pud = pud_alloc(mm, pgd, addr);
  62         if (!pud)
  63                 goto out;
  64
  65         pmd = pmd_alloc(mm, pud, addr);
  66         if (!pmd)
  67                 goto out;
  68
  69         pte = pte_alloc_map(mm, pmd, addr);
  70         if (!pte) {
  71                 pmd = NULL;
  72                 goto out;
  73         }
  74         pte_unmap(pte);
  75 out:
  76         spin_unlock(&mm->page_table_lock);
  77         return pmd;
  78 }
  79
  80 static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
  81                 unsigned long old_addr, unsigned long old_end,
  82                 struct vm_area_struct *new_vma, pmd_t *new_pmd,
  83                 unsigned long new_addr)
  84 {
  85         struct address_space *mapping = NULL;
  86         struct mm_struct *mm = vma->vm_mm;
  87         pte_t *old_pte, *new_pte, pte;
  88
  89         if (vma->vm_file) {
  90                 /*
  91                  * Subtle point from Rajesh Venkatasubramanian: before
  92                  * moving file-based ptes, we must lock vmtruncate out,
  93                  * since it might clean the dst vma before the src vma,
  94                  * and we propagate stale pages into the dst afterward.
  95                  */
  96                 mapping = vma->vm_file->f_mapping;
  97                 spin_lock(&mapping->i_mmap_lock);
  98                 if (new_vma->vm_truncate_count &&
  99                     new_vma->vm_truncate_count != vma->vm_truncate_count)
 100                         new_vma->vm_truncate_count = 0;
 101         }
 102
 103         spin_lock(&mm->page_table_lock);
 104         old_pte = pte_offset_map(old_pmd, old_addr);
 105         new_pte = pte_offset_map_nested(new_pmd, new_addr);
 106
 107         for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
 108                                    new_pte++, new_addr += PAGE_SIZE) {
 109                 if (pte_none(*old_pte))
 110                         continue;
 111                 pte = ptep_clear_flush(vma, old_addr, old_pte);
 112                 /* ZERO_PAGE can be dependant on virtual addr */
 113                 pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
 114                 set_pte_at(mm, new_addr, new_pte, pte);
 115         }
 116
 117         pte_unmap_nested(new_pte - 1);
 118         pte_unmap(old_pte - 1);
 119         spin_unlock(&mm->page_table_lock);
 120         if (mapping)
 121                 spin_unlock(&mapping->i_mmap_lock);
 122 }
 123
 124 #define LATENCY_LIMIT   (64 * PAGE_SIZE)
 125
 126 static unsigned long move_page_tables(struct vm_area_struct *vma,
 127                 unsigned long old_addr, struct vm_area_struct *new_vma,
 128                 unsigned long new_addr, unsigned long len)
 129 {
 130         unsigned long extent, next, old_end;
 131         pmd_t *old_pmd, *new_pmd;
 132
 133         old_end = old_addr + len;
 134         flush_cache_range(vma, 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                 if (next - 1 > old_end)
 140                         next = old_end;
 141                 extent = next - old_addr;
 142                 old_pmd = get_old_pmd(vma->vm_mm, old_addr);
 143                 if (!old_pmd)
 144                         continue;
 145                 new_pmd = alloc_new_pmd(vma->vm_mm, new_addr);
 146                 if (!new_pmd)
 147                         break;
 148                 next = (new_addr + PMD_SIZE) & PMD_MASK;
 149                 if (extent > next - new_addr)
 150                         extent = next - new_addr;
 151                 if (extent > LATENCY_LIMIT)
 152                         extent = LATENCY_LIMIT;
 153                 move_ptes(vma, old_pmd, old_addr, old_addr + extent,
 154                                 new_vma, new_pmd, new_addr);
 155         }
 156
 157         return len + old_addr - old_end;        /* how much done */
 158 }
 159
 160 static unsigned long move_vma(struct vm_area_struct *vma,
 161                 unsigned long old_addr, unsigned long old_len,
 162                 unsigned long new_len, unsigned long new_addr)
 163 {
 164         struct mm_struct *mm = vma->vm_mm;
 165         struct vm_area_struct *new_vma;
 166         unsigned long vm_flags = vma->vm_flags;
 167         unsigned long new_pgoff;
 168         unsigned long moved_len;
 169         unsigned long excess = 0;
 170         unsigned long hiwater_vm;
 171         int split = 0;
 172
 173         /*
 174          * We'd prefer to avoid failure later on in do_munmap:
 175          * which may split one vma into three before unmapping.
 176          */
 177         if (mm->map_count >= sysctl_max_map_count - 3)
 178                 return -ENOMEM;
 179
 180         new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
 181         new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
 182         if (!new_vma)
 183                 return -ENOMEM;
 184
 185         moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len);
 186         if (moved_len < old_len) {
 187                 /*
 188                  * On error, move entries back from new area to old,
 189                  * which will succeed since page tables still there,
 190                  * and then proceed to unmap new area instead of old.
 191                  */
 192                 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len);
 193                 vma = new_vma;
 194                 old_len = new_len;
 195                 old_addr = new_addr;
 196                 new_addr = -ENOMEM;
 197         }
 198
 199         /* Conceal VM_ACCOUNT so old reservation is not undone */
 200         if (vm_flags & VM_ACCOUNT) {
 201                 vma->vm_flags &= ~VM_ACCOUNT;
 202                 excess = vma->vm_end - vma->vm_start - old_len;
 203                 if (old_addr > vma->vm_start &&
 204                     old_addr + old_len < vma->vm_end)
 205                         split = 1;
 206         }
 207
 208         /*
 209          * If we failed to move page tables we still do total_vm increment
 210          * since do_munmap() will decrement it by old_len == new_len.
 211          *
 212          * Since total_vm is about to be raised artificially high for a
 213          * moment, we need to restore high watermark afterwards: if stats
 214          * are taken meanwhile, total_vm and hiwater_vm appear too high.
 215          * If this were a serious issue, we'd add a flag to do_munmap().
 216          */
 217         hiwater_vm = mm->hiwater_vm;
 218         mm->total_vm += new_len >> PAGE_SHIFT;
 219         vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
 220
 221         if (do_munmap(mm, old_addr, old_len) < 0) {
 222                 /* OOM: unable to split vma, just get accounts right */
 223                 vm_unacct_memory(excess >> PAGE_SHIFT);
 224                 excess = 0;
 225         }
 226         mm->hiwater_vm = hiwater_vm;
 227
 228         /* Restore VM_ACCOUNT if one or two pieces of vma left */
 229         if (excess) {
 230                 vma->vm_flags |= VM_ACCOUNT;
 231                 if (split)
 232                         vma->vm_next->vm_flags |= VM_ACCOUNT;
 233         }
 234
 235         if (vm_flags & VM_LOCKED) {
 236                 mm->locked_vm += new_len >> PAGE_SHIFT;
 237                 if (new_len > old_len)
 238                         make_pages_present(new_addr + old_len,
 239                                            new_addr + new_len);
 240         }
 241
 242         return new_addr;
 243 }
 244
 245 /*
 246  * Expand (or shrink) an existing mapping, potentially moving it at the
 247  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
 248  *
 249  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
 250  * This option implies MREMAP_MAYMOVE.
 251  */
 252 unsigned long do_mremap(unsigned long addr,
 253         unsigned long old_len, unsigned long new_len,
 254         unsigned long flags, unsigned long new_addr)
 255 {
 256         struct mm_struct *mm = current->mm;
 257         struct vm_area_struct *vma;
 258         unsigned long ret = -EINVAL;
 259         unsigned long charged = 0;
 260
 261         if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
 262                 goto out;
 263
 264         if (addr & ~PAGE_MASK)
 265                 goto out;
 266
 267         old_len = PAGE_ALIGN(old_len);
 268         new_len = PAGE_ALIGN(new_len);
 269
 270         /*
 271          * We allow a zero old-len as a special case
 272          * for DOS-emu "duplicate shm area" thing. But
 273          * a zero new-len is nonsensical.
 274          */
 275         if (!new_len)
 276                 goto out;
 277
 278         /* new_addr is only valid if MREMAP_FIXED is specified */
 279         if (flags & MREMAP_FIXED) {
 280                 if (new_addr & ~PAGE_MASK)
 281                         goto out;
 282                 if (!(flags & MREMAP_MAYMOVE))
 283                         goto out;
 284
 285                 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
 286                         goto out;
 287
 288                 /* Check if the location we're moving into overlaps the
 289                  * old location at all, and fail if it does.
 290                  */
 291                 if ((new_addr <= addr) && (new_addr+new_len) > addr)
 292                         goto out;
 293
 294                 if ((addr <= new_addr) && (addr+old_len) > new_addr)
 295                         goto out;
 296
 297                 ret = do_munmap(mm, new_addr, new_len);
 298                 if (ret)
 299                         goto out;
 300         }
 301
 302         /*
 303          * Always allow a shrinking remap: that just unmaps
 304          * the unnecessary pages..
 305          * do_munmap does all the needed commit accounting
 306          */
 307         if (old_len >= new_len) {
 308                 ret = do_munmap(mm, addr+new_len, old_len - new_len);
 309                 if (ret && old_len != new_len)
 310                         goto out;
 311                 ret = addr;
 312                 if (!(flags & MREMAP_FIXED) || (new_addr == addr))
 313                         goto out;
 314                 old_len = new_len;
 315         }
 316
 317         /*
 318          * Ok, we need to grow..  or relocate.
 319          */
 320         ret = -EFAULT;
 321         vma = find_vma(mm, addr);
 322         if (!vma || vma->vm_start > addr)
 323                 goto out;
 324         if (is_vm_hugetlb_page(vma)) {
 325                 ret = -EINVAL;
 326                 goto out;
 327         }
 328         /* We can't remap across vm area boundaries */
 329         if (old_len > vma->vm_end - addr)
 330                 goto out;
 331         if (vma->vm_flags & VM_DONTEXPAND) {
 332                 if (new_len > old_len)
 333                         goto out;
 334         }
 335         if (vma->vm_flags & VM_LOCKED) {
 336                 unsigned long locked, lock_limit;
 337                 locked = mm->locked_vm << PAGE_SHIFT;
 338                 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
 339                 locked += new_len - old_len;
 340                 ret = -EAGAIN;
 341                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
 342                         goto out;
 343         }
 344         if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) {
 345                 ret = -ENOMEM;
 346                 goto out;
 347         }
 348
 349         if (vma->vm_flags & VM_ACCOUNT) {
 350                 charged = (new_len - old_len) >> PAGE_SHIFT;
 351                 if (security_vm_enough_memory(charged))
 352                         goto out_nc;
 353         }
 354
 355         /* old_len exactly to the end of the area..
 356          * And we're not relocating the area.
 357          */
 358         if (old_len == vma->vm_end - addr &&
 359             !((flags & MREMAP_FIXED) && (addr != new_addr)) &&
 360             (old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
 361                 unsigned long max_addr = TASK_SIZE;
 362                 if (vma->vm_next)
 363                         max_addr = vma->vm_next->vm_start;
 364                 /* can we just expand the current mapping? */
 365                 if (max_addr - addr >= new_len) {
 366                         int pages = (new_len - old_len) >> PAGE_SHIFT;
 367
 368                         vma_adjust(vma, vma->vm_start,
 369                                 addr + new_len, vma->vm_pgoff, NULL);
 370
 371                         mm->total_vm += pages;
 372                         vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
 373                         if (vma->vm_flags & VM_LOCKED) {
 374                                 mm->locked_vm += pages;
 375                                 make_pages_present(addr + old_len,
 376                                                    addr + new_len);
 377                         }
 378                         ret = addr;
 379                         goto out;
 380                 }
 381         }
 382
 383         /*
 384          * We weren't able to just expand or shrink the area,
 385          * we need to create a new one and move it..
 386          */
 387         ret = -ENOMEM;
 388         if (flags & MREMAP_MAYMOVE) {
 389                 if (!(flags & MREMAP_FIXED)) {
 390                         unsigned long map_flags = 0;
 391                         if (vma->vm_flags & VM_MAYSHARE)
 392                                 map_flags |= MAP_SHARED;
 393
 394                         new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
 395                                                 vma->vm_pgoff, map_flags);
 396                         ret = new_addr;
 397                         if (new_addr & ~PAGE_MASK)
 398                                 goto out;
 399                 }
 400                 ret = move_vma(vma, addr, old_len, new_len, new_addr);
 401         }
 402 out:
 403         if (ret & ~PAGE_MASK)
 404                 vm_unacct_memory(charged);
 405 out_nc:
 406         return ret;
 407 }
 408
 409 asmlinkage unsigned long sys_mremap(unsigned long addr,
 410         unsigned long old_len, unsigned long new_len,
 411         unsigned long flags, unsigned long new_addr)
 412 {
 413         unsigned long ret;
 414
 415         down_write(&current->mm->mmap_sem);
 416         ret = do_mremap(addr, old_len, new_len, flags, new_addr);
 417         up_write(&current->mm->mmap_sem);
 418         return ret;
 419 }