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 pte_t *get_one_pte_map_nested(struct mm_struct *mm, unsigned long addr)
  26 {
  27         pgd_t *pgd;
  28         pud_t *pud;
  29         pmd_t *pmd;
  30         pte_t *pte = NULL;
  31
  32         pgd = pgd_offset(mm, addr);
  33         if (pgd_none_or_clear_bad(pgd))
  34                 goto end;
  35
  36         pud = pud_offset(pgd, addr);
  37         if (pud_none_or_clear_bad(pud))
  38                 goto end;
  39
  40         pmd = pmd_offset(pud, addr);
  41         if (pmd_none_or_clear_bad(pmd))
  42                 goto end;
  43
  44         pte = pte_offset_map_nested(pmd, addr);
  45         if (pte_none(*pte)) {
  46                 pte_unmap_nested(pte);
  47                 pte = NULL;
  48         }
  49 end:
  50         return pte;
  51 }
  52
  53 static pte_t *get_one_pte_map(struct mm_struct *mm, unsigned long addr)
  54 {
  55         pgd_t *pgd;
  56         pud_t *pud;
  57         pmd_t *pmd;
  58
  59         pgd = pgd_offset(mm, addr);
  60         if (pgd_none_or_clear_bad(pgd))
  61                 return NULL;
  62
  63         pud = pud_offset(pgd, addr);
  64         if (pud_none_or_clear_bad(pud))
  65                 return NULL;
  66
  67         pmd = pmd_offset(pud, addr);
  68         if (pmd_none_or_clear_bad(pmd))
  69                 return NULL;
  70
  71         return pte_offset_map(pmd, addr);
  72 }
  73
  74 static inline pte_t *alloc_one_pte_map(struct mm_struct *mm, unsigned long addr)
  75 {
  76         pgd_t *pgd;
  77         pud_t *pud;
  78         pmd_t *pmd;
  79         pte_t *pte = NULL;
  80
  81         pgd = pgd_offset(mm, addr);
  82
  83         pud = pud_alloc(mm, pgd, addr);
  84         if (!pud)
  85                 return NULL;
  86         pmd = pmd_alloc(mm, pud, addr);
  87         if (pmd)
  88                 pte = pte_alloc_map(mm, pmd, addr);
  89         return pte;
  90 }
  91
  92 static int
  93 move_one_page(struct vm_area_struct *vma, unsigned long old_addr,
  94                 struct vm_area_struct *new_vma, unsigned long new_addr)
  95 {
  96         struct address_space *mapping = NULL;
  97         struct mm_struct *mm = vma->vm_mm;
  98         int error = 0;
  99         pte_t *src, *dst;
 100
 101         if (vma->vm_file) {
 102                 /*
 103                  * Subtle point from Rajesh Venkatasubramanian: before
 104                  * moving file-based ptes, we must lock vmtruncate out,
 105                  * since it might clean the dst vma before the src vma,
 106                  * and we propagate stale pages into the dst afterward.
 107                  */
 108                 mapping = vma->vm_file->f_mapping;
 109                 spin_lock(&mapping->i_mmap_lock);
 110                 if (new_vma->vm_truncate_count &&
 111                     new_vma->vm_truncate_count != vma->vm_truncate_count)
 112                         new_vma->vm_truncate_count = 0;
 113         }
 114         spin_lock(&mm->page_table_lock);
 115
 116         src = get_one_pte_map_nested(mm, old_addr);
 117         if (src) {
 118                 /*
 119                  * Look to see whether alloc_one_pte_map needs to perform a
 120                  * memory allocation.  If it does then we need to drop the
 121                  * atomic kmap
 122                  */
 123                 dst = get_one_pte_map(mm, new_addr);
 124                 if (unlikely(!dst)) {
 125                         pte_unmap_nested(src);
 126                         if (mapping)
 127                                 spin_unlock(&mapping->i_mmap_lock);
 128                         dst = alloc_one_pte_map(mm, new_addr);
 129                         if (mapping && !spin_trylock(&mapping->i_mmap_lock)) {
 130                                 spin_unlock(&mm->page_table_lock);
 131                                 spin_lock(&mapping->i_mmap_lock);
 132                                 spin_lock(&mm->page_table_lock);
 133                         }
 134                         src = get_one_pte_map_nested(mm, old_addr);
 135                 }
 136                 /*
 137                  * Since alloc_one_pte_map can drop and re-acquire
 138                  * page_table_lock, we should re-check the src entry...
 139                  */
 140                 if (src) {
 141                         if (dst) {
 142                                 pte_t pte;
 143                                 pte = ptep_clear_flush(vma, old_addr, src);
 144                                 set_pte_at(mm, new_addr, dst, pte);
 145                         } else
 146                                 error = -ENOMEM;
 147                         pte_unmap_nested(src);
 148                 }
 149                 if (dst)
 150                         pte_unmap(dst);
 151         }
 152         spin_unlock(&mm->page_table_lock);
 153         if (mapping)
 154                 spin_unlock(&mapping->i_mmap_lock);
 155         return error;
 156 }
 157
 158 static unsigned long move_page_tables(struct vm_area_struct *vma,
 159                 unsigned long old_addr, struct vm_area_struct *new_vma,
 160                 unsigned long new_addr, unsigned long len)
 161 {
 162         unsigned long offset;
 163
 164         flush_cache_range(vma, old_addr, old_addr + len);
 165
 166         /*
 167          * This is not the clever way to do this, but we're taking the
 168          * easy way out on the assumption that most remappings will be
 169          * only a few pages.. This also makes error recovery easier.
 170          */
 171         for (offset = 0; offset < len; offset += PAGE_SIZE) {
 172                 if (move_one_page(vma, old_addr + offset,
 173                                 new_vma, new_addr + offset) < 0)
 174                         break;
 175                 cond_resched();
 176         }
 177         return offset;
 178 }
 179
 180 static unsigned long move_vma(struct vm_area_struct *vma,
 181                 unsigned long old_addr, unsigned long old_len,
 182                 unsigned long new_len, unsigned long new_addr)
 183 {
 184         struct mm_struct *mm = vma->vm_mm;
 185         struct vm_area_struct *new_vma;
 186         unsigned long vm_flags = vma->vm_flags;
 187         unsigned long new_pgoff;
 188         unsigned long moved_len;
 189         unsigned long excess = 0;
 190         int split = 0;
 191
 192         /*
 193          * We'd prefer to avoid failure later on in do_munmap:
 194          * which may split one vma into three before unmapping.
 195          */
 196         if (mm->map_count >= sysctl_max_map_count - 3)
 197                 return -ENOMEM;
 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         mm->total_vm += new_len >> PAGE_SHIFT;
 232         __vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
 233
 234         if (do_munmap(mm, old_addr, old_len) < 0) {
 235                 /* OOM: unable to split vma, just get accounts right */
 236                 vm_unacct_memory(excess >> PAGE_SHIFT);
 237                 excess = 0;
 238         }
 239
 240         /* Restore VM_ACCOUNT if one or two pieces of vma left */
 241         if (excess) {
 242                 vma->vm_flags |= VM_ACCOUNT;
 243                 if (split)
 244                         vma->vm_next->vm_flags |= VM_ACCOUNT;
 245         }
 246
 247         if (vm_flags & VM_LOCKED) {
 248                 mm->locked_vm += new_len >> PAGE_SHIFT;
 249                 if (new_len > old_len)
 250                         make_pages_present(new_addr + old_len,
 251                                            new_addr + new_len);
 252         }
 253
 254         return new_addr;
 255 }
 256
 257 /*
 258  * Expand (or shrink) an existing mapping, potentially moving it at the
 259  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
 260  *
 261  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
 262  * This option implies MREMAP_MAYMOVE.
 263  */
 264 unsigned long do_mremap(unsigned long addr,
 265         unsigned long old_len, unsigned long new_len,
 266         unsigned long flags, unsigned long new_addr)
 267 {
 268         struct vm_area_struct *vma;
 269         unsigned long ret = -EINVAL;
 270         unsigned long charged = 0;
 271
 272         if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
 273                 goto out;
 274
 275         if (addr & ~PAGE_MASK)
 276                 goto out;
 277
 278         old_len = PAGE_ALIGN(old_len);
 279         new_len = PAGE_ALIGN(new_len);
 280
 281         /*
 282          * We allow a zero old-len as a special case
 283          * for DOS-emu "duplicate shm area" thing. But
 284          * a zero new-len is nonsensical.
 285          */
 286         if (!new_len)
 287                 goto out;
 288
 289         /* new_addr is only valid if MREMAP_FIXED is specified */
 290         if (flags & MREMAP_FIXED) {
 291                 if (new_addr & ~PAGE_MASK)
 292                         goto out;
 293                 if (!(flags & MREMAP_MAYMOVE))
 294                         goto out;
 295
 296                 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
 297                         goto out;
 298
 299                 /* Check if the location we're moving into overlaps the
 300                  * old location at all, and fail if it does.
 301                  */
 302                 if ((new_addr <= addr) && (new_addr+new_len) > addr)
 303                         goto out;
 304
 305                 if ((addr <= new_addr) && (addr+old_len) > new_addr)
 306                         goto out;
 307
 308                 ret = do_munmap(current->mm, new_addr, new_len);
 309                 if (ret)
 310                         goto out;
 311         }
 312
 313         /*
 314          * Always allow a shrinking remap: that just unmaps
 315          * the unnecessary pages..
 316          * do_munmap does all the needed commit accounting
 317          */
 318         if (old_len >= new_len) {
 319                 ret = do_munmap(current->mm, addr+new_len, old_len - new_len);
 320                 if (ret && old_len != new_len)
 321                         goto out;
 322                 ret = addr;
 323                 if (!(flags & MREMAP_FIXED) || (new_addr == addr))
 324                         goto out;
 325                 old_len = new_len;
 326         }
 327
 328         /*
 329          * Ok, we need to grow..  or relocate.
 330          */
 331         ret = -EFAULT;
 332         vma = find_vma(current->mm, addr);
 333         if (!vma || vma->vm_start > addr)
 334                 goto out;
 335         if (is_vm_hugetlb_page(vma)) {
 336                 ret = -EINVAL;
 337                 goto out;
 338         }
 339         /* We can't remap across vm area boundaries */
 340         if (old_len > vma->vm_end - addr)
 341                 goto out;
 342         if (vma->vm_flags & VM_DONTEXPAND) {
 343                 if (new_len > old_len)
 344                         goto out;
 345         }
 346         if (vma->vm_flags & VM_LOCKED) {
 347                 unsigned long locked, lock_limit;
 348                 locked = current->mm->locked_vm << PAGE_SHIFT;
 349                 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
 350                 locked += new_len - old_len;
 351                 ret = -EAGAIN;
 352                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
 353                         goto out;
 354         }
 355         if (!may_expand_vm(current->mm, (new_len - old_len) >> PAGE_SHIFT)) {
 356                 ret = -ENOMEM;
 357                 goto out;
 358         }
 359
 360         if (vma->vm_flags & VM_ACCOUNT) {
 361                 charged = (new_len - old_len) >> PAGE_SHIFT;
 362                 if (security_vm_enough_memory(charged))
 363                         goto out_nc;
 364         }
 365
 366         /* old_len exactly to the end of the area..
 367          * And we're not relocating the area.
 368          */
 369         if (old_len == vma->vm_end - addr &&
 370             !((flags & MREMAP_FIXED) && (addr != new_addr)) &&
 371             (old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
 372                 unsigned long max_addr = TASK_SIZE;
 373                 if (vma->vm_next)
 374                         max_addr = vma->vm_next->vm_start;
 375                 /* can we just expand the current mapping? */
 376                 if (max_addr - addr >= new_len) {
 377                         int pages = (new_len - old_len) >> PAGE_SHIFT;
 378
 379                         vma_adjust(vma, vma->vm_start,
 380                                 addr + new_len, vma->vm_pgoff, NULL);
 381
 382                         current->mm->total_vm += pages;
 383                         __vm_stat_account(vma->vm_mm, vma->vm_flags,
 384                                                         vma->vm_file, pages);
 385                         if (vma->vm_flags & VM_LOCKED) {
 386                                 current->mm->locked_vm += pages;
 387                                 make_pages_present(addr + old_len,
 388                                                    addr + new_len);
 389                         }
 390                         ret = addr;
 391                         goto out;
 392                 }
 393         }
 394
 395         /*
 396          * We weren't able to just expand or shrink the area,
 397          * we need to create a new one and move it..
 398          */
 399         ret = -ENOMEM;
 400         if (flags & MREMAP_MAYMOVE) {
 401                 if (!(flags & MREMAP_FIXED)) {
 402                         unsigned long map_flags = 0;
 403                         if (vma->vm_flags & VM_MAYSHARE)
 404                                 map_flags |= MAP_SHARED;
 405
 406                         new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
 407                                                 vma->vm_pgoff, map_flags);
 408                         ret = new_addr;
 409                         if (new_addr & ~PAGE_MASK)
 410                                 goto out;
 411                 }
 412                 ret = move_vma(vma, addr, old_len, new_len, new_addr);
 413         }
 414 out:
 415         if (ret & ~PAGE_MASK)
 416                 vm_unacct_memory(charged);
 417 out_nc:
 418         return ret;
 419 }
 420
 421 asmlinkage unsigned long sys_mremap(unsigned long addr,
 422         unsigned long old_len, unsigned long new_len,
 423         unsigned long flags, unsigned long new_addr)
 424 {
 425         unsigned long ret;
 426
 427         down_write(&current->mm->mmap_sem);
 428         ret = do_mremap(addr, old_len, new_len, flags, new_addr);
 429         up_write(&current->mm->mmap_sem);
 430         return ret;
 431 }