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