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/capability.h>
  17 #include <linux/fs.h>
  18 #include <linux/highmem.h>
  19 #include <linux/security.h>
  20 #include <linux/syscalls.h>
  21 #include <linux/mmu_notifier.h>
  22
  23 #include <asm/uaccess.h>
  24 #include <asm/cacheflush.h>
  25 #include <asm/tlbflush.h>
  26
  27 static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
  28 {
  29         pgd_t *pgd;
  30         pud_t *pud;
  31         pmd_t *pmd;
  32
  33         pgd = pgd_offset(mm, addr);
  34         if (pgd_none_or_clear_bad(pgd))
  35                 return NULL;
  36
  37         pud = pud_offset(pgd, addr);
  38         if (pud_none_or_clear_bad(pud))
  39                 return NULL;
  40
  41         pmd = pmd_offset(pud, addr);
  42         if (pmd_none_or_clear_bad(pmd))
  43                 return NULL;
  44
  45         return pmd;
  46 }
  47
  48 static pmd_t *alloc_new_pmd(struct mm_struct *mm, unsigned long addr)
  49 {
  50         pgd_t *pgd;
  51         pud_t *pud;
  52         pmd_t *pmd;
  53
  54         pgd = pgd_offset(mm, addr);
  55         pud = pud_alloc(mm, pgd, addr);
  56         if (!pud)
  57                 return NULL;
  58
  59         pmd = pmd_alloc(mm, pud, addr);
  60         if (!pmd)
  61                 return NULL;
  62
  63         if (!pmd_present(*pmd) && __pte_alloc(mm, pmd, addr))
  64                 return NULL;
  65
  66         return pmd;
  67 }
  68
  69 static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
  70                 unsigned long old_addr, unsigned long old_end,
  71                 struct vm_area_struct *new_vma, pmd_t *new_pmd,
  72                 unsigned long new_addr)
  73 {
  74         struct address_space *mapping = NULL;
  75         struct mm_struct *mm = vma->vm_mm;
  76         pte_t *old_pte, *new_pte, pte;
  77         spinlock_t *old_ptl, *new_ptl;
  78         unsigned long old_start;
  79
  80         old_start = old_addr;
  81         mmu_notifier_invalidate_range_start(vma->vm_mm,
  82                                             old_start, old_end);
  83         if (vma->vm_file) {
  84                 /*
  85                  * Subtle point from Rajesh Venkatasubramanian: before
  86                  * moving file-based ptes, we must lock vmtruncate out,
  87                  * since it might clean the dst vma before the src vma,
  88                  * and we propagate stale pages into the dst afterward.
  89                  */
  90                 mapping = vma->vm_file->f_mapping;
  91                 spin_lock(&mapping->i_mmap_lock);
  92                 if (new_vma->vm_truncate_count &&
  93                     new_vma->vm_truncate_count != vma->vm_truncate_count)
  94                         new_vma->vm_truncate_count = 0;
  95         }
  96
  97         /*
  98          * We don't have to worry about the ordering of src and dst
  99          * pte locks because exclusive mmap_sem prevents deadlock.
 100          */
 101         old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
 102         new_pte = pte_offset_map_nested(new_pmd, new_addr);
 103         new_ptl = pte_lockptr(mm, new_pmd);
 104         if (new_ptl != old_ptl)
 105                 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
 106         arch_enter_lazy_mmu_mode();
 107
 108         for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
 109                                    new_pte++, new_addr += PAGE_SIZE) {
 110                 if (pte_none(*old_pte))
 111                         continue;
 112                 pte = ptep_clear_flush(vma, old_addr, old_pte);
 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         arch_leave_lazy_mmu_mode();
 118         if (new_ptl != old_ptl)
 119                 spin_unlock(new_ptl);
 120         pte_unmap_nested(new_pte - 1);
 121         pte_unmap_unlock(old_pte - 1, old_ptl);
 122         if (mapping)
 123                 spin_unlock(&mapping->i_mmap_lock);
 124         mmu_notifier_invalidate_range_end(vma->vm_mm, old_start, old_end);
 125 }
 126
 127 #define LATENCY_LIMIT   (64 * PAGE_SIZE)
 128
 129 unsigned long move_page_tables(struct vm_area_struct *vma,
 130                 unsigned long old_addr, struct vm_area_struct *new_vma,
 131                 unsigned long new_addr, unsigned long len)
 132 {
 133         unsigned long extent, next, old_end;
 134         pmd_t *old_pmd, *new_pmd;
 135
 136         old_end = old_addr + len;
 137         flush_cache_range(vma, old_addr, old_end);
 138
 139         for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
 140                 cond_resched();
 141                 next = (old_addr + PMD_SIZE) & PMD_MASK;
 142                 if (next - 1 > old_end)
 143                         next = old_end;
 144                 extent = next - old_addr;
 145                 old_pmd = get_old_pmd(vma->vm_mm, old_addr);
 146                 if (!old_pmd)
 147                         continue;
 148                 new_pmd = alloc_new_pmd(vma->vm_mm, new_addr);
 149                 if (!new_pmd)
 150                         break;
 151                 next = (new_addr + PMD_SIZE) & PMD_MASK;
 152                 if (extent > next - new_addr)
 153                         extent = next - new_addr;
 154                 if (extent > LATENCY_LIMIT)
 155                         extent = LATENCY_LIMIT;
 156                 move_ptes(vma, old_pmd, old_addr, old_addr + extent,
 157                                 new_vma, new_pmd, new_addr);
 158         }
 159
 160         return len + old_addr - old_end;        /* how much done */
 161 }
 162
 163 static unsigned long move_vma(struct vm_area_struct *vma,
 164                 unsigned long old_addr, unsigned long old_len,
 165                 unsigned long new_len, unsigned long new_addr)
 166 {
 167         struct mm_struct *mm = vma->vm_mm;
 168         struct vm_area_struct *new_vma;
 169         unsigned long vm_flags = vma->vm_flags;
 170         unsigned long new_pgoff;
 171         unsigned long moved_len;
 172         unsigned long excess = 0;
 173         unsigned long hiwater_vm;
 174         int split = 0;
 175
 176         /*
 177          * We'd prefer to avoid failure later on in do_munmap:
 178          * which may split one vma into three before unmapping.
 179          */
 180         if (mm->map_count >= sysctl_max_map_count - 3)
 181                 return -ENOMEM;
 182
 183         new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
 184         new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
 185         if (!new_vma)
 186                 return -ENOMEM;
 187
 188         moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len);
 189         if (moved_len < old_len) {
 190                 /*
 191                  * On error, move entries back from new area to old,
 192                  * which will succeed since page tables still there,
 193                  * and then proceed to unmap new area instead of old.
 194                  */
 195                 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len);
 196                 vma = new_vma;
 197                 old_len = new_len;
 198                 old_addr = new_addr;
 199                 new_addr = -ENOMEM;
 200         }
 201
 202         /* Conceal VM_ACCOUNT so old reservation is not undone */
 203         if (vm_flags & VM_ACCOUNT) {
 204                 vma->vm_flags &= ~VM_ACCOUNT;
 205                 excess = vma->vm_end - vma->vm_start - old_len;
 206                 if (old_addr > vma->vm_start &&
 207                     old_addr + old_len < vma->vm_end)
 208                         split = 1;
 209         }
 210
 211         /*
 212          * If we failed to move page tables we still do total_vm increment
 213          * since do_munmap() will decrement it by old_len == new_len.
 214          *
 215          * Since total_vm is about to be raised artificially high for a
 216          * moment, we need to restore high watermark afterwards: if stats
 217          * are taken meanwhile, total_vm and hiwater_vm appear too high.
 218          * If this were a serious issue, we'd add a flag to do_munmap().
 219          */
 220         hiwater_vm = mm->hiwater_vm;
 221         mm->total_vm += new_len >> PAGE_SHIFT;
 222         vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
 223
 224         if (do_munmap(mm, old_addr, old_len) < 0) {
 225                 /* OOM: unable to split vma, just get accounts right */
 226                 vm_unacct_memory(excess >> PAGE_SHIFT);
 227                 excess = 0;
 228         }
 229         mm->hiwater_vm = hiwater_vm;
 230
 231         /* Restore VM_ACCOUNT if one or two pieces of vma left */
 232         if (excess) {
 233                 vma->vm_flags |= VM_ACCOUNT;
 234                 if (split)
 235                         vma->vm_next->vm_flags |= VM_ACCOUNT;
 236         }
 237
 238         if (vm_flags & VM_LOCKED) {
 239                 mm->locked_vm += new_len >> PAGE_SHIFT;
 240                 if (new_len > old_len)
 241                         make_pages_present(new_addr + old_len,
 242                                            new_addr + new_len);
 243         }
 244
 245         return new_addr;
 246 }
 247
 248 /*
 249  * Expand (or shrink) an existing mapping, potentially moving it at the
 250  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
 251  *
 252  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
 253  * This option implies MREMAP_MAYMOVE.
 254  */
 255 unsigned long do_mremap(unsigned long addr,
 256         unsigned long old_len, unsigned long new_len,
 257         unsigned long flags, unsigned long new_addr)
 258 {
 259         struct mm_struct *mm = current->mm;
 260         struct vm_area_struct *vma;
 261         unsigned long ret = -EINVAL;
 262         unsigned long charged = 0;
 263
 264         if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
 265                 goto out;
 266
 267         if (addr & ~PAGE_MASK)
 268                 goto out;
 269
 270         old_len = PAGE_ALIGN(old_len);
 271         new_len = PAGE_ALIGN(new_len);
 272
 273         /*
 274          * We allow a zero old-len as a special case
 275          * for DOS-emu "duplicate shm area" thing. But
 276          * a zero new-len is nonsensical.
 277          */
 278         if (!new_len)
 279                 goto out;
 280
 281         /* new_addr is only valid if MREMAP_FIXED is specified */
 282         if (flags & MREMAP_FIXED) {
 283                 if (new_addr & ~PAGE_MASK)
 284                         goto out;
 285                 if (!(flags & MREMAP_MAYMOVE))
 286                         goto out;
 287
 288                 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
 289                         goto out;
 290
 291                 /* Check if the location we're moving into overlaps the
 292                  * old location at all, and fail if it does.
 293                  */
 294                 if ((new_addr <= addr) && (new_addr+new_len) > addr)
 295                         goto out;
 296
 297                 if ((addr <= new_addr) && (addr+old_len) > new_addr)
 298                         goto out;
 299
 300                 ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
 301                 if (ret)
 302                         goto out;
 303
 304                 ret = do_munmap(mm, new_addr, new_len);
 305                 if (ret)
 306                         goto out;
 307         }
 308
 309         /*
 310          * Always allow a shrinking remap: that just unmaps
 311          * the unnecessary pages..
 312          * do_munmap does all the needed commit accounting
 313          */
 314         if (old_len >= new_len) {
 315                 ret = do_munmap(mm, addr+new_len, old_len - new_len);
 316                 if (ret && old_len != new_len)
 317                         goto out;
 318                 ret = addr;
 319                 if (!(flags & MREMAP_FIXED) || (new_addr == addr))
 320                         goto out;
 321                 old_len = new_len;
 322         }
 323
 324         /*
 325          * Ok, we need to grow..  or relocate.
 326          */
 327         ret = -EFAULT;
 328         vma = find_vma(mm, addr);
 329         if (!vma || vma->vm_start > addr)
 330                 goto out;
 331         if (is_vm_hugetlb_page(vma)) {
 332                 ret = -EINVAL;
 333                 goto out;
 334         }
 335         /* We can't remap across vm area boundaries */
 336         if (old_len > vma->vm_end - addr)
 337                 goto out;
 338         if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) {
 339                 if (new_len > old_len)
 340                         goto out;
 341         }
 342         if (vma->vm_flags & VM_LOCKED) {
 343                 unsigned long locked, lock_limit;
 344                 locked = mm->locked_vm << PAGE_SHIFT;
 345                 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
 346                 locked += new_len - old_len;
 347                 ret = -EAGAIN;
 348                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
 349                         goto out;
 350         }
 351         if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) {
 352                 ret = -ENOMEM;
 353                 goto out;
 354         }
 355
 356         if (vma->vm_flags & VM_ACCOUNT) {
 357                 charged = (new_len - old_len) >> PAGE_SHIFT;
 358                 if (security_vm_enough_memory(charged))
 359                         goto out_nc;
 360         }
 361
 362         /* old_len exactly to the end of the area..
 363          * And we're not relocating the area.
 364          */
 365         if (old_len == vma->vm_end - addr &&
 366             !((flags & MREMAP_FIXED) && (addr != new_addr)) &&
 367             (old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
 368                 unsigned long max_addr = TASK_SIZE;
 369                 if (vma->vm_next)
 370                         max_addr = vma->vm_next->vm_start;
 371                 /* can we just expand the current mapping? */
 372                 if (max_addr - addr >= new_len) {
 373                         int pages = (new_len - old_len) >> PAGE_SHIFT;
 374
 375                         vma_adjust(vma, vma->vm_start,
 376                                 addr + new_len, vma->vm_pgoff, NULL);
 377
 378                         mm->total_vm += pages;
 379                         vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
 380                         if (vma->vm_flags & VM_LOCKED) {
 381                                 mm->locked_vm += pages;
 382                                 make_pages_present(addr + old_len,
 383                                                    addr + new_len);
 384                         }
 385                         ret = addr;
 386                         goto out;
 387                 }
 388         }
 389
 390         /*
 391          * We weren't able to just expand or shrink the area,
 392          * we need to create a new one and move it..
 393          */
 394         ret = -ENOMEM;
 395         if (flags & MREMAP_MAYMOVE) {
 396                 if (!(flags & MREMAP_FIXED)) {
 397                         unsigned long map_flags = 0;
 398                         if (vma->vm_flags & VM_MAYSHARE)
 399                                 map_flags |= MAP_SHARED;
 400
 401                         new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
 402                                                 vma->vm_pgoff, map_flags);
 403                         if (new_addr & ~PAGE_MASK) {
 404                                 ret = new_addr;
 405                                 goto out;
 406                         }
 407
 408                         ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
 409                         if (ret)
 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 }