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   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         int split = 0;
 171
 172         /*
 173          * We'd prefer to avoid failure later on in do_munmap:
 174          * which may split one vma into three before unmapping.
 175          */
 176         if (mm->map_count >= sysctl_max_map_count - 3)
 177                 return -ENOMEM;
 178
 179         new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
 180         new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
 181         if (!new_vma)
 182                 return -ENOMEM;
 183
 184         moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len);
 185         if (moved_len < old_len) {
 186                 /*
 187                  * On error, move entries back from new area to old,
 188                  * which will succeed since page tables still there,
 189                  * and then proceed to unmap new area instead of old.
 190                  */
 191                 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len);
 192                 vma = new_vma;
 193                 old_len = new_len;
 194                 old_addr = new_addr;
 195                 new_addr = -ENOMEM;
 196         }
 197
 198         /* Conceal VM_ACCOUNT so old reservation is not undone */
 199         if (vm_flags & VM_ACCOUNT) {
 200                 vma->vm_flags &= ~VM_ACCOUNT;
 201                 excess = vma->vm_end - vma->vm_start - old_len;
 202                 if (old_addr > vma->vm_start &&
 203                     old_addr + old_len < vma->vm_end)
 204                         split = 1;
 205         }
 206
 207         /*
 208          * if we failed to move page tables we still do total_vm increment
 209          * since do_munmap() will decrement it by old_len == new_len
 210          */
 211         mm->total_vm += new_len >> PAGE_SHIFT;
 212         vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
 213
 214         if (do_munmap(mm, old_addr, old_len) < 0) {
 215                 /* OOM: unable to split vma, just get accounts right */
 216                 vm_unacct_memory(excess >> PAGE_SHIFT);
 217                 excess = 0;
 218         }
 219
 220         /* Restore VM_ACCOUNT if one or two pieces of vma left */
 221         if (excess) {
 222                 vma->vm_flags |= VM_ACCOUNT;
 223                 if (split)
 224                         vma->vm_next->vm_flags |= VM_ACCOUNT;
 225         }
 226
 227         if (vm_flags & VM_LOCKED) {
 228                 mm->locked_vm += new_len >> PAGE_SHIFT;
 229                 if (new_len > old_len)
 230                         make_pages_present(new_addr + old_len,
 231                                            new_addr + new_len);
 232         }
 233
 234         return new_addr;
 235 }
 236
 237 /*
 238  * Expand (or shrink) an existing mapping, potentially moving it at the
 239  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
 240  *
 241  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
 242  * This option implies MREMAP_MAYMOVE.
 243  */
 244 unsigned long do_mremap(unsigned long addr,
 245         unsigned long old_len, unsigned long new_len,
 246         unsigned long flags, unsigned long new_addr)
 247 {
 248         struct mm_struct *mm = current->mm;
 249         struct vm_area_struct *vma;
 250         unsigned long ret = -EINVAL;
 251         unsigned long charged = 0;
 252
 253         if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
 254                 goto out;
 255
 256         if (addr & ~PAGE_MASK)
 257                 goto out;
 258
 259         old_len = PAGE_ALIGN(old_len);
 260         new_len = PAGE_ALIGN(new_len);
 261
 262         /*
 263          * We allow a zero old-len as a special case
 264          * for DOS-emu "duplicate shm area" thing. But
 265          * a zero new-len is nonsensical.
 266          */
 267         if (!new_len)
 268                 goto out;
 269
 270         /* new_addr is only valid if MREMAP_FIXED is specified */
 271         if (flags & MREMAP_FIXED) {
 272                 if (new_addr & ~PAGE_MASK)
 273                         goto out;
 274                 if (!(flags & MREMAP_MAYMOVE))
 275                         goto out;
 276
 277                 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
 278                         goto out;
 279
 280                 /* Check if the location we're moving into overlaps the
 281                  * old location at all, and fail if it does.
 282                  */
 283                 if ((new_addr <= addr) && (new_addr+new_len) > addr)
 284                         goto out;
 285
 286                 if ((addr <= new_addr) && (addr+old_len) > new_addr)
 287                         goto out;
 288
 289                 ret = do_munmap(mm, new_addr, new_len);
 290                 if (ret)
 291                         goto out;
 292         }
 293
 294         /*
 295          * Always allow a shrinking remap: that just unmaps
 296          * the unnecessary pages..
 297          * do_munmap does all the needed commit accounting
 298          */
 299         if (old_len >= new_len) {
 300                 ret = do_munmap(mm, addr+new_len, old_len - new_len);
 301                 if (ret && old_len != new_len)
 302                         goto out;
 303                 ret = addr;
 304                 if (!(flags & MREMAP_FIXED) || (new_addr == addr))
 305                         goto out;
 306                 old_len = new_len;
 307         }
 308
 309         /*
 310          * Ok, we need to grow..  or relocate.
 311          */
 312         ret = -EFAULT;
 313         vma = find_vma(mm, addr);
 314         if (!vma || vma->vm_start > addr)
 315                 goto out;
 316         if (is_vm_hugetlb_page(vma)) {
 317                 ret = -EINVAL;
 318                 goto out;
 319         }
 320         /* We can't remap across vm area boundaries */
 321         if (old_len > vma->vm_end - addr)
 322                 goto out;
 323         if (vma->vm_flags & VM_DONTEXPAND) {
 324                 if (new_len > old_len)
 325                         goto out;
 326         }
 327         if (vma->vm_flags & VM_LOCKED) {
 328                 unsigned long locked, lock_limit;
 329                 locked = mm->locked_vm << PAGE_SHIFT;
 330                 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
 331                 locked += new_len - old_len;
 332                 ret = -EAGAIN;
 333                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
 334                         goto out;
 335         }
 336         if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) {
 337                 ret = -ENOMEM;
 338                 goto out;
 339         }
 340
 341         if (vma->vm_flags & VM_ACCOUNT) {
 342                 charged = (new_len - old_len) >> PAGE_SHIFT;
 343                 if (security_vm_enough_memory(charged))
 344                         goto out_nc;
 345         }
 346
 347         /* old_len exactly to the end of the area..
 348          * And we're not relocating the area.
 349          */
 350         if (old_len == vma->vm_end - addr &&
 351             !((flags & MREMAP_FIXED) && (addr != new_addr)) &&
 352             (old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
 353                 unsigned long max_addr = TASK_SIZE;
 354                 if (vma->vm_next)
 355                         max_addr = vma->vm_next->vm_start;
 356                 /* can we just expand the current mapping? */
 357                 if (max_addr - addr >= new_len) {
 358                         int pages = (new_len - old_len) >> PAGE_SHIFT;
 359
 360                         vma_adjust(vma, vma->vm_start,
 361                                 addr + new_len, vma->vm_pgoff, NULL);
 362
 363                         mm->total_vm += pages;
 364                         vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
 365                         if (vma->vm_flags & VM_LOCKED) {
 366                                 mm->locked_vm += pages;
 367                                 make_pages_present(addr + old_len,
 368                                                    addr + new_len);
 369                         }
 370                         ret = addr;
 371                         goto out;
 372                 }
 373         }
 374
 375         /*
 376          * We weren't able to just expand or shrink the area,
 377          * we need to create a new one and move it..
 378          */
 379         ret = -ENOMEM;
 380         if (flags & MREMAP_MAYMOVE) {
 381                 if (!(flags & MREMAP_FIXED)) {
 382                         unsigned long map_flags = 0;
 383                         if (vma->vm_flags & VM_MAYSHARE)
 384                                 map_flags |= MAP_SHARED;
 385
 386                         new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
 387                                                 vma->vm_pgoff, map_flags);
 388                         ret = new_addr;
 389                         if (new_addr & ~PAGE_MASK)
 390                                 goto out;
 391                 }
 392                 ret = move_vma(vma, addr, old_len, new_len, new_addr);
 393         }
 394 out:
 395         if (ret & ~PAGE_MASK)
 396                 vm_unacct_memory(charged);
 397 out_nc:
 398         return ret;
 399 }
 400
 401 asmlinkage unsigned long sys_mremap(unsigned long addr,
 402         unsigned long old_len, unsigned long new_len,
 403         unsigned long flags, unsigned long new_addr)
 404 {
 405         unsigned long ret;
 406
 407         down_write(&current->mm->mmap_sem);
 408         ret = do_mremap(addr, old_len, new_len, flags, new_addr);
 409         up_write(&current->mm->mmap_sem);
 410         return ret;
 411 }