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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/capability.h>
  17 #include <linux/fs.h>
  18 #include <linux/highmem.h>
  19 #include <linux/security.h>
  20 #include <linux/syscalls.h>
  21
  22 #include <asm/uaccess.h>
  23 #include <asm/cacheflush.h>
  24 #include <asm/tlbflush.h>
  25
  26 static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
  27 {
  28         pgd_t *pgd;
  29         pud_t *pud;
  30         pmd_t *pmd;
  31
  32         pgd = pgd_offset(mm, addr);
  33         if (pgd_none_or_clear_bad(pgd))
  34                 return NULL;
  35
  36         pud = pud_offset(pgd, addr);
  37         if (pud_none_or_clear_bad(pud))
  38                 return NULL;
  39
  40         pmd = pmd_offset(pud, addr);
  41         if (pmd_none_or_clear_bad(pmd))
  42                 return NULL;
  43
  44         return pmd;
  45 }
  46
  47 static pmd_t *alloc_new_pmd(struct mm_struct *mm, unsigned long addr)
  48 {
  49         pgd_t *pgd;
  50         pud_t *pud;
  51         pmd_t *pmd;
  52
  53         pgd = pgd_offset(mm, addr);
  54         pud = pud_alloc(mm, pgd, addr);
  55         if (!pud)
  56                 return NULL;
  57
  58         pmd = pmd_alloc(mm, pud, addr);
  59         if (!pmd)
  60                 return NULL;
  61
  62         if (!pmd_present(*pmd) && __pte_alloc(mm, pmd, addr))
  63                 return NULL;
  64
  65         return pmd;
  66 }
  67
  68 static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
  69                 unsigned long old_addr, unsigned long old_end,
  70                 struct vm_area_struct *new_vma, pmd_t *new_pmd,
  71                 unsigned long new_addr)
  72 {
  73         struct address_space *mapping = NULL;
  74         struct mm_struct *mm = vma->vm_mm;
  75         pte_t *old_pte, *new_pte, pte;
  76         spinlock_t *old_ptl, *new_ptl;
  77
  78         if (vma->vm_file) {
  79                 /*
  80                  * Subtle point from Rajesh Venkatasubramanian: before
  81                  * moving file-based ptes, we must lock vmtruncate out,
  82                  * since it might clean the dst vma before the src vma,
  83                  * and we propagate stale pages into the dst afterward.
  84                  */
  85                 mapping = vma->vm_file->f_mapping;
  86                 spin_lock(&mapping->i_mmap_lock);
  87                 if (new_vma->vm_truncate_count &&
  88                     new_vma->vm_truncate_count != vma->vm_truncate_count)
  89                         new_vma->vm_truncate_count = 0;
  90         }
  91
  92         /*
  93          * We don't have to worry about the ordering of src and dst
  94          * pte locks because exclusive mmap_sem prevents deadlock.
  95          */
  96         old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
  97         new_pte = pte_offset_map_nested(new_pmd, new_addr);
  98         new_ptl = pte_lockptr(mm, new_pmd);
  99         if (new_ptl != old_ptl)
 100                 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
 101         arch_enter_lazy_mmu_mode();
 102
 103         for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
 104                                    new_pte++, new_addr += PAGE_SIZE) {
 105                 if (pte_none(*old_pte))
 106                         continue;
 107                 pte = ptep_clear_flush(vma, old_addr, old_pte);
 108                 /* ZERO_PAGE can be dependant on virtual addr */
 109                 pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
 110                 set_pte_at(mm, new_addr, new_pte, pte);
 111         }
 112
 113         arch_leave_lazy_mmu_mode();
 114         if (new_ptl != old_ptl)
 115                 spin_unlock(new_ptl);
 116         pte_unmap_nested(new_pte - 1);
 117         pte_unmap_unlock(old_pte - 1, old_ptl);
 118         if (mapping)
 119                 spin_unlock(&mapping->i_mmap_lock);
 120 }
 121
 122 #define LATENCY_LIMIT   (64 * PAGE_SIZE)
 123
 124 static unsigned long move_page_tables(struct vm_area_struct *vma,
 125                 unsigned long old_addr, struct vm_area_struct *new_vma,
 126                 unsigned long new_addr, unsigned long len)
 127 {
 128         unsigned long extent, next, old_end;
 129         pmd_t *old_pmd, *new_pmd;
 130
 131         old_end = old_addr + len;
 132         flush_cache_range(vma, old_addr, old_end);
 133
 134         for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
 135                 cond_resched();
 136                 next = (old_addr + PMD_SIZE) & PMD_MASK;
 137                 if (next - 1 > old_end)
 138                         next = old_end;
 139                 extent = next - old_addr;
 140                 old_pmd = get_old_pmd(vma->vm_mm, old_addr);
 141                 if (!old_pmd)
 142                         continue;
 143                 new_pmd = alloc_new_pmd(vma->vm_mm, new_addr);
 144                 if (!new_pmd)
 145                         break;
 146                 next = (new_addr + PMD_SIZE) & PMD_MASK;
 147                 if (extent > next - new_addr)
 148                         extent = next - new_addr;
 149                 if (extent > LATENCY_LIMIT)
 150                         extent = LATENCY_LIMIT;
 151                 move_ptes(vma, old_pmd, old_addr, old_addr + extent,
 152                                 new_vma, new_pmd, new_addr);
 153         }
 154
 155         return len + old_addr - old_end;        /* how much done */
 156 }
 157
 158 static unsigned long move_vma(struct vm_area_struct *vma,
 159                 unsigned long old_addr, unsigned long old_len,
 160                 unsigned long new_len, unsigned long new_addr)
 161 {
 162         struct mm_struct *mm = vma->vm_mm;
 163         struct vm_area_struct *new_vma;
 164         unsigned long vm_flags = vma->vm_flags;
 165         unsigned long new_pgoff;
 166         unsigned long moved_len;
 167         unsigned long excess = 0;
 168         unsigned long hiwater_vm;
 169         int split = 0;
 170
 171         /*
 172          * We'd prefer to avoid failure later on in do_munmap:
 173          * which may split one vma into three before unmapping.
 174          */
 175         if (mm->map_count >= sysctl_max_map_count - 3)
 176                 return -ENOMEM;
 177
 178         new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
 179         new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
 180         if (!new_vma)
 181                 return -ENOMEM;
 182
 183         moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len);
 184         if (moved_len < old_len) {
 185                 /*
 186                  * On error, move entries back from new area to old,
 187                  * which will succeed since page tables still there,
 188                  * and then proceed to unmap new area instead of old.
 189                  */
 190                 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len);
 191                 vma = new_vma;
 192                 old_len = new_len;
 193                 old_addr = new_addr;
 194                 new_addr = -ENOMEM;
 195         }
 196
 197         /* Conceal VM_ACCOUNT so old reservation is not undone */
 198         if (vm_flags & VM_ACCOUNT) {
 199                 vma->vm_flags &= ~VM_ACCOUNT;
 200                 excess = vma->vm_end - vma->vm_start - old_len;
 201                 if (old_addr > vma->vm_start &&
 202                     old_addr + old_len < vma->vm_end)
 203                         split = 1;
 204         }
 205
 206         /*
 207          * If we failed to move page tables we still do total_vm increment
 208          * since do_munmap() will decrement it by old_len == new_len.
 209          *
 210          * Since total_vm is about to be raised artificially high for a
 211          * moment, we need to restore high watermark afterwards: if stats
 212          * are taken meanwhile, total_vm and hiwater_vm appear too high.
 213          * If this were a serious issue, we'd add a flag to do_munmap().
 214          */
 215         hiwater_vm = mm->hiwater_vm;
 216         mm->total_vm += new_len >> PAGE_SHIFT;
 217         vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
 218
 219         if (do_munmap(mm, old_addr, old_len) < 0) {
 220                 /* OOM: unable to split vma, just get accounts right */
 221                 vm_unacct_memory(excess >> PAGE_SHIFT);
 222                 excess = 0;
 223         }
 224         mm->hiwater_vm = hiwater_vm;
 225
 226         /* Restore VM_ACCOUNT if one or two pieces of vma left */
 227         if (excess) {
 228                 vma->vm_flags |= VM_ACCOUNT;
 229                 if (split)
 230                         vma->vm_next->vm_flags |= VM_ACCOUNT;
 231         }
 232
 233         if (vm_flags & VM_LOCKED) {
 234                 mm->locked_vm += new_len >> PAGE_SHIFT;
 235                 if (new_len > old_len)
 236                         make_pages_present(new_addr + old_len,
 237                                            new_addr + new_len);
 238         }
 239
 240         return new_addr;
 241 }
 242
 243 /*
 244  * Expand (or shrink) an existing mapping, potentially moving it at the
 245  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
 246  *
 247  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
 248  * This option implies MREMAP_MAYMOVE.
 249  */
 250 unsigned long do_mremap(unsigned long addr,
 251         unsigned long old_len, unsigned long new_len,
 252         unsigned long flags, unsigned long new_addr)
 253 {
 254         struct mm_struct *mm = current->mm;
 255         struct vm_area_struct *vma;
 256         unsigned long ret = -EINVAL;
 257         unsigned long charged = 0;
 258
 259         if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
 260                 goto out;
 261
 262         if (addr & ~PAGE_MASK)
 263                 goto out;
 264
 265         old_len = PAGE_ALIGN(old_len);
 266         new_len = PAGE_ALIGN(new_len);
 267
 268         /*
 269          * We allow a zero old-len as a special case
 270          * for DOS-emu "duplicate shm area" thing. But
 271          * a zero new-len is nonsensical.
 272          */
 273         if (!new_len)
 274                 goto out;
 275
 276         /* new_addr is only valid if MREMAP_FIXED is specified */
 277         if (flags & MREMAP_FIXED) {
 278                 if (new_addr & ~PAGE_MASK)
 279                         goto out;
 280                 if (!(flags & MREMAP_MAYMOVE))
 281                         goto out;
 282
 283                 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
 284                         goto out;
 285
 286                 /* Check if the location we're moving into overlaps the
 287                  * old location at all, and fail if it does.
 288                  */
 289                 if ((new_addr <= addr) && (new_addr+new_len) > addr)
 290                         goto out;
 291
 292                 if ((addr <= new_addr) && (addr+old_len) > new_addr)
 293                         goto out;
 294
 295                 ret = do_munmap(mm, new_addr, new_len);
 296                 if (ret)
 297                         goto out;
 298         }
 299
 300         /*
 301          * Always allow a shrinking remap: that just unmaps
 302          * the unnecessary pages..
 303          * do_munmap does all the needed commit accounting
 304          */
 305         if (old_len >= new_len) {
 306                 ret = do_munmap(mm, addr+new_len, old_len - new_len);
 307                 if (ret && old_len != new_len)
 308                         goto out;
 309                 ret = addr;
 310                 if (!(flags & MREMAP_FIXED) || (new_addr == addr))
 311                         goto out;
 312                 old_len = new_len;
 313         }
 314
 315         /*
 316          * Ok, we need to grow..  or relocate.
 317          */
 318         ret = -EFAULT;
 319         vma = find_vma(mm, addr);
 320         if (!vma || vma->vm_start > addr)
 321                 goto out;
 322         if (is_vm_hugetlb_page(vma)) {
 323                 ret = -EINVAL;
 324                 goto out;
 325         }
 326         /* We can't remap across vm area boundaries */
 327         if (old_len > vma->vm_end - addr)
 328                 goto out;
 329         if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) {
 330                 if (new_len > old_len)
 331                         goto out;
 332         }
 333         if (vma->vm_flags & VM_LOCKED) {
 334                 unsigned long locked, lock_limit;
 335                 locked = mm->locked_vm << PAGE_SHIFT;
 336                 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
 337                 locked += new_len - old_len;
 338                 ret = -EAGAIN;
 339                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
 340                         goto out;
 341         }
 342         if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) {
 343                 ret = -ENOMEM;
 344                 goto out;
 345         }
 346
 347         if (vma->vm_flags & VM_ACCOUNT) {
 348                 charged = (new_len - old_len) >> PAGE_SHIFT;
 349                 if (security_vm_enough_memory(charged))
 350                         goto out_nc;
 351         }
 352
 353         /* old_len exactly to the end of the area..
 354          * And we're not relocating the area.
 355          */
 356         if (old_len == vma->vm_end - addr &&
 357             !((flags & MREMAP_FIXED) && (addr != new_addr)) &&
 358             (old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
 359                 unsigned long max_addr = TASK_SIZE;
 360                 if (vma->vm_next)
 361                         max_addr = vma->vm_next->vm_start;
 362                 /* can we just expand the current mapping? */
 363                 if (max_addr - addr >= new_len) {
 364                         int pages = (new_len - old_len) >> PAGE_SHIFT;
 365
 366                         vma_adjust(vma, vma->vm_start,
 367                                 addr + new_len, vma->vm_pgoff, NULL);
 368
 369                         mm->total_vm += pages;
 370                         vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
 371                         if (vma->vm_flags & VM_LOCKED) {
 372                                 mm->locked_vm += pages;
 373                                 make_pages_present(addr + old_len,
 374                                                    addr + new_len);
 375                         }
 376                         ret = addr;
 377                         goto out;
 378                 }
 379         }
 380
 381         /*
 382          * We weren't able to just expand or shrink the area,
 383          * we need to create a new one and move it..
 384          */
 385         ret = -ENOMEM;
 386         if (flags & MREMAP_MAYMOVE) {
 387                 if (!(flags & MREMAP_FIXED)) {
 388                         unsigned long map_flags = 0;
 389                         if (vma->vm_flags & VM_MAYSHARE)
 390                                 map_flags |= MAP_SHARED;
 391
 392                         new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
 393                                                 vma->vm_pgoff, map_flags);
 394                         ret = new_addr;
 395                         if (new_addr & ~PAGE_MASK)
 396                                 goto out;
 397                 }
 398                 ret = move_vma(vma, addr, old_len, new_len, new_addr);
 399         }
 400 out:
 401         if (ret & ~PAGE_MASK)
 402                 vm_unacct_memory(charged);
 403 out_nc:
 404         return ret;
 405 }
 406
 407 asmlinkage unsigned long sys_mremap(unsigned long addr,
 408         unsigned long old_len, unsigned long new_len,
 409         unsigned long flags, unsigned long new_addr)
 410 {
 411         unsigned long ret;
 412
 413         down_write(&current->mm->mmap_sem);
 414         ret = do_mremap(addr, old_len, new_len, flags, new_addr);
 415         up_write(&current->mm->mmap_sem);
 416         return ret;
 417 }