mremap.c

   1 /*
   2  *      linux/mm/remap.c
   3  *
   4  *      (C) Copyright 1996 Linus Torvalds
   5  */
   6
   7 #include <linux/slab.h>
   8 #include <linux/smp_lock.h>
   9 #include <linux/shm.h>
  10 #include <linux/mman.h>
  11 #include <linux/swap.h>
  12
  13 #include <asm/uaccess.h>
  14 #include <asm/pgalloc.h>
  15
  16 extern int vm_enough_memory(long pages);
  17
  18 static inline pte_t *get_one_pte(struct mm_struct *mm, unsigned long addr)
  19 {
  20         pgd_t * pgd;
  21         pmd_t * pmd;
  22         pte_t * pte = NULL;
  23
  24         pgd = pgd_offset(mm, addr);
  25         if (pgd_none(*pgd))
  26                 goto end;
  27         if (pgd_bad(*pgd)) {
  28                 pgd_ERROR(*pgd);
  29                 pgd_clear(pgd);
  30                 goto end;
  31         }
  32
  33         pmd = pmd_offset(pgd, addr);
  34         if (pmd_none(*pmd))
  35                 goto end;
  36         if (pmd_bad(*pmd)) {
  37                 pmd_ERROR(*pmd);
  38                 pmd_clear(pmd);
  39                 goto end;
  40         }
  41
  42         pte = pte_offset(pmd, addr);
  43         if (pte_none(*pte))
  44                 pte = NULL;
  45 end:
  46         return pte;
  47 }
  48
  49 static inline pte_t *alloc_one_pte(struct mm_struct *mm, unsigned long addr)
  50 {
  51         pmd_t * pmd;
  52         pte_t * pte = NULL;
  53
  54         pmd = pmd_alloc(mm, pgd_offset(mm, addr), addr);
  55         if (pmd)
  56                 pte = pte_alloc(mm, pmd, addr);
  57         return pte;
  58 }
  59
  60 static inline int copy_one_pte(struct mm_struct *mm, pte_t * src, pte_t * dst)
  61 {
  62         int error = 0;
  63         pte_t pte;
  64
  65         if (!pte_none(*src)) {
  66                 pte = ptep_get_and_clear(src);
  67                 if (!dst) {
  68                         /* No dest?  We must put it back. */
  69                         dst = src;
  70                         error++;
  71                 }
  72                 set_pte(dst, pte);
  73         }
  74         return error;
  75 }
  76
  77 static int move_one_page(struct mm_struct *mm, unsigned long old_addr, unsigned long new_addr)
  78 {
  79         int error = 0;
  80         pte_t * src, * dst;
  81
  82         spin_lock(&mm->page_table_lock);
  83         src = get_one_pte(mm, old_addr);
  84         if (src) {
  85                 dst = alloc_one_pte(mm, new_addr);
  86                 src = get_one_pte(mm, old_addr);
  87                 if (src)
  88                         error = copy_one_pte(mm, src, dst);
  89         }
  90         spin_unlock(&mm->page_table_lock);
  91         return error;
  92 }
  93
  94 static int move_page_tables(struct mm_struct * mm,
  95         unsigned long new_addr, unsigned long old_addr, unsigned long len)
  96 {
  97         unsigned long offset = len;
  98
  99         flush_cache_range(mm, old_addr, old_addr + len);
 100
 101         /*
 102          * This is not the clever way to do this, but we're taking the
 103          * easy way out on the assumption that most remappings will be
 104          * only a few pages.. This also makes error recovery easier.
 105          */
 106         while (offset) {
 107                 offset -= PAGE_SIZE;
 108                 if (move_one_page(mm, old_addr + offset, new_addr + offset))
 109                         goto oops_we_failed;
 110         }
 111         flush_tlb_range(mm, old_addr, old_addr + len);
 112         return 0;
 113
 114         /*
 115          * Ok, the move failed because we didn't have enough pages for
 116          * the new page table tree. This is unlikely, but we have to
 117          * take the possibility into account. In that case we just move
 118          * all the pages back (this will work, because we still have
 119          * the old page tables)
 120          */
 121 oops_we_failed:
 122         flush_cache_range(mm, new_addr, new_addr + len);
 123         while ((offset += PAGE_SIZE) < len)
 124                 move_one_page(mm, new_addr + offset, old_addr + offset);
 125         zap_page_range(mm, new_addr, len);
 126         return -1;
 127 }
 128
 129 static inline unsigned long move_vma(struct vm_area_struct * vma,
 130         unsigned long addr, unsigned long old_len, unsigned long new_len,
 131         unsigned long new_addr)
 132 {
 133         struct mm_struct * mm = vma->vm_mm;
 134         struct vm_area_struct * new_vma, * next, * prev;
 135         int allocated_vma;
 136
 137         new_vma = NULL;
 138         next = find_vma_prev(mm, new_addr, &prev);
 139         if (next) {
 140                 if (prev && prev->vm_end == new_addr &&
 141                     can_vma_merge(prev, vma->vm_flags) && !vma->vm_file && !(vma->vm_flags & VM_SHARED)) {
 142                         spin_lock(&mm->page_table_lock);
 143                         prev->vm_end = new_addr + new_len;
 144                         spin_unlock(&mm->page_table_lock);
 145                         new_vma = prev;
 146                         if (next != prev->vm_next)
 147                                 BUG();
 148                         if (prev->vm_end == next->vm_start && can_vma_merge(next, prev->vm_flags)) {
 149                                 spin_lock(&mm->page_table_lock);
 150                                 prev->vm_end = next->vm_end;
 151                                 __vma_unlink(mm, next, prev);
 152                                 spin_unlock(&mm->page_table_lock);
 153
 154                                 mm->map_count--;
 155                                 kmem_cache_free(vm_area_cachep, next);
 156                         }
 157                 } else if (next->vm_start == new_addr + new_len &&
 158                            can_vma_merge(next, vma->vm_flags) && !vma->vm_file && !(vma->vm_flags & VM_SHARED)) {
 159                         spin_lock(&mm->page_table_lock);
 160                         next->vm_start = new_addr;
 161                         spin_unlock(&mm->page_table_lock);
 162                         new_vma = next;
 163                 }
 164         } else {
 165                 prev = find_vma(mm, new_addr-1);
 166                 if (prev && prev->vm_end == new_addr &&
 167                     can_vma_merge(prev, vma->vm_flags) && !vma->vm_file && !(vma->vm_flags & VM_SHARED)) {
 168                         spin_lock(&mm->page_table_lock);
 169                         prev->vm_end = new_addr + new_len;
 170                         spin_unlock(&mm->page_table_lock);
 171                         new_vma = prev;
 172                 }
 173         }
 174
 175         allocated_vma = 0;
 176         if (!new_vma) {
 177                 new_vma = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
 178                 if (!new_vma)
 179                         goto out;
 180                 allocated_vma = 1;
 181         }
 182
 183         if (!move_page_tables(current->mm, new_addr, addr, old_len)) {
 184                 unsigned long vm_locked = vma->vm_flags & VM_LOCKED;
 185
 186                 if (allocated_vma) {
 187                         *new_vma = *vma;
 188                         new_vma->vm_start = new_addr;
 189                         new_vma->vm_end = new_addr+new_len;
 190                         new_vma->vm_pgoff += (addr-vma->vm_start) >> PAGE_SHIFT;
 191                         new_vma->vm_raend = 0;
 192                         if (new_vma->vm_file)
 193                                 get_file(new_vma->vm_file);
 194                         if (new_vma->vm_ops && new_vma->vm_ops->open)
 195                                 new_vma->vm_ops->open(new_vma);
 196                         insert_vm_struct(current->mm, new_vma);
 197                 }
 198
 199                 /* XXX: possible errors masked, mapping might remain */
 200                 do_munmap(current->mm, addr, old_len);
 201
 202                 current->mm->total_vm += new_len >> PAGE_SHIFT;
 203                 if (vm_locked) {
 204                         current->mm->locked_vm += new_len >> PAGE_SHIFT;
 205                         if (new_len > old_len)
 206                                 make_pages_present(new_addr + old_len,
 207                                                    new_addr + new_len);
 208                 }
 209                 return new_addr;
 210         }
 211         if (allocated_vma)
 212                 kmem_cache_free(vm_area_cachep, new_vma);
 213  out:
 214         return -ENOMEM;
 215 }
 216
 217 /*
 218  * Expand (or shrink) an existing mapping, potentially moving it at the
 219  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
 220  *
 221  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
 222  * This option implies MREMAP_MAYMOVE.
 223  */
 224 unsigned long do_mremap(unsigned long addr,
 225         unsigned long old_len, unsigned long new_len,
 226         unsigned long flags, unsigned long new_addr)
 227 {
 228         struct vm_area_struct *vma;
 229         unsigned long ret = -EINVAL;
 230
 231         if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
 232                 goto out;
 233
 234         if (addr & ~PAGE_MASK)
 235                 goto out;
 236
 237         old_len = PAGE_ALIGN(old_len);
 238         new_len = PAGE_ALIGN(new_len);
 239
 240         if (old_len > TASK_SIZE || addr > TASK_SIZE - old_len)
 241                 goto out;
 242
 243         if (addr >= TASK_SIZE)
 244                 goto out;
 245
 246         /* new_addr is only valid if MREMAP_FIXED is specified */
 247         if (flags & MREMAP_FIXED) {
 248                 if (new_addr & ~PAGE_MASK)
 249                         goto out;
 250                 if (!(flags & MREMAP_MAYMOVE))
 251                         goto out;
 252
 253                 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
 254                         goto out;
 255
 256                 if (new_addr >= TASK_SIZE)
 257                         goto out;
 258
 259                 /*
 260                  * Allow new_len == 0 only if new_addr == addr
 261                  * to preserve truncation in place (that was working
 262                  * safe and some app may depend on it).
 263                  */
 264                 if (unlikely(!new_len && new_addr != addr))
 265                         goto out;
 266
 267                 /* Check if the location we're moving into overlaps the
 268                  * old location at all, and fail if it does.
 269                  */
 270                 if ((new_addr <= addr) && (new_addr+new_len) > addr)
 271                         goto out;
 272
 273                 if ((addr <= new_addr) && (addr+old_len) > new_addr)
 274                         goto out;
 275
 276                 ret = do_munmap(current->mm, new_addr, new_len);
 277                 if (ret && new_len)
 278                         goto out;
 279         }
 280
 281         /*
 282          * Always allow a shrinking remap: that just unmaps
 283          * the unnecessary pages..
 284          */
 285         if (old_len >= new_len) {
 286                 ret = do_munmap(current->mm, addr+new_len, old_len - new_len);
 287                 if (ret && old_len != new_len)
 288                         goto out;
 289                 ret = addr;
 290                 if (!(flags & MREMAP_FIXED) || (new_addr == addr))
 291                         goto out;
 292         }
 293
 294         /*
 295          * Ok, we need to grow..  or relocate.
 296          */
 297         ret = -EFAULT;
 298         vma = find_vma(current->mm, addr);
 299         if (!vma || vma->vm_start > addr)
 300                 goto out;
 301         /* We can't remap across vm area boundaries */
 302         if (old_len > vma->vm_end - addr)
 303                 goto out;
 304         if (vma->vm_flags & VM_DONTEXPAND) {
 305                 if (new_len > old_len)
 306                         goto out;
 307         }
 308         if (vma->vm_flags & VM_LOCKED) {
 309                 unsigned long locked = current->mm->locked_vm << PAGE_SHIFT;
 310                 locked += new_len - old_len;
 311                 ret = -EAGAIN;
 312                 if (locked > current->rlim[RLIMIT_MEMLOCK].rlim_cur)
 313                         goto out;
 314         }
 315         ret = -ENOMEM;
 316         if ((current->mm->total_vm << PAGE_SHIFT) + (new_len - old_len)
 317             > current->rlim[RLIMIT_AS].rlim_cur)
 318                 goto out;
 319         /* Private writable mapping? Check memory availability.. */
 320         if ((vma->vm_flags & (VM_SHARED | VM_WRITE)) == VM_WRITE &&
 321             !(flags & MAP_NORESERVE)                             &&
 322             !vm_enough_memory((new_len - old_len) >> PAGE_SHIFT))
 323                 goto out;
 324
 325         /* old_len exactly to the end of the area..
 326          * And we're not relocating the area.
 327          */
 328         if (old_len == vma->vm_end - addr &&
 329             !((flags & MREMAP_FIXED) && (addr != new_addr)) &&
 330             (old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
 331                 unsigned long max_addr = TASK_SIZE;
 332                 if (vma->vm_next)
 333                         max_addr = vma->vm_next->vm_start;
 334                 /* can we just expand the current mapping? */
 335                 if (max_addr - addr >= new_len) {
 336                         int pages = (new_len - old_len) >> PAGE_SHIFT;
 337                         spin_lock(&vma->vm_mm->page_table_lock);
 338                         vma->vm_end = addr + new_len;
 339                         spin_unlock(&vma->vm_mm->page_table_lock);
 340                         current->mm->total_vm += pages;
 341                         if (vma->vm_flags & VM_LOCKED) {
 342                                 current->mm->locked_vm += pages;
 343                                 make_pages_present(addr + old_len,
 344                                                    addr + new_len);
 345                         }
 346                         ret = addr;
 347                         goto out;
 348                 }
 349         }
 350
 351         /*
 352          * We weren't able to just expand or shrink the area,
 353          * we need to create a new one and move it..
 354          */
 355         ret = -ENOMEM;
 356         if (flags & MREMAP_MAYMOVE) {
 357                 if (!(flags & MREMAP_FIXED)) {
 358                         unsigned long map_flags = 0;
 359                         if (vma->vm_flags & VM_SHARED)
 360                                 map_flags |= MAP_SHARED;
 361
 362                         new_addr = get_unmapped_area(vma->vm_file, 0, new_len, vma->vm_pgoff, map_flags);
 363                         ret = new_addr;
 364                         if (new_addr & ~PAGE_MASK)
 365                                 goto out;
 366                 }
 367                 ret = move_vma(vma, addr, old_len, new_len, new_addr);
 368         }
 369 out:
 370         return ret;
 371 }
 372
 373 asmlinkage unsigned long sys_mremap(unsigned long addr,
 374         unsigned long old_len, unsigned long new_len,
 375         unsigned long flags, unsigned long new_addr)
 376 {
 377         unsigned long ret;
 378
 379         down_write(&current->mm->mmap_sem);
 380         ret = do_mremap(addr, old_len, new_len, flags, new_addr);
 381         up_write(&current->mm->mmap_sem);
 382         return ret;
 383 }