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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                 pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
 109                 set_pte_at(mm, new_addr, new_pte, pte);
 110         }
 111
 112         arch_leave_lazy_mmu_mode();
 113         if (new_ptl != old_ptl)
 114                 spin_unlock(new_ptl);
 115         pte_unmap_nested(new_pte - 1);
 116         pte_unmap_unlock(old_pte - 1, old_ptl);
 117         if (mapping)
 118                 spin_unlock(&mapping->i_mmap_lock);
 119 }
 120
 121 #define LATENCY_LIMIT   (64 * PAGE_SIZE)
 122
 123 static unsigned long move_page_tables(struct vm_area_struct *vma,
 124                 unsigned long old_addr, struct vm_area_struct *new_vma,
 125                 unsigned long new_addr, unsigned long len)
 126 {
 127         unsigned long extent, next, old_end;
 128         pmd_t *old_pmd, *new_pmd;
 129
 130         old_end = old_addr + len;
 131         flush_cache_range(vma, old_addr, old_end);
 132
 133         for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
 134                 cond_resched();
 135                 next = (old_addr + PMD_SIZE) & PMD_MASK;
 136                 if (next - 1 > old_end)
 137                         next = old_end;
 138                 extent = next - old_addr;
 139                 old_pmd = get_old_pmd(vma->vm_mm, old_addr);
 140                 if (!old_pmd)
 141                         continue;
 142                 new_pmd = alloc_new_pmd(vma->vm_mm, new_addr);
 143                 if (!new_pmd)
 144                         break;
 145                 next = (new_addr + PMD_SIZE) & PMD_MASK;
 146                 if (extent > next - new_addr)
 147                         extent = next - new_addr;
 148                 if (extent > LATENCY_LIMIT)
 149                         extent = LATENCY_LIMIT;
 150                 move_ptes(vma, old_pmd, old_addr, old_addr + extent,
 151                                 new_vma, new_pmd, new_addr);
 152         }
 153
 154         return len + old_addr - old_end;        /* how much done */
 155 }
 156
 157 static unsigned long move_vma(struct vm_area_struct *vma,
 158                 unsigned long old_addr, unsigned long old_len,
 159                 unsigned long new_len, unsigned long new_addr)
 160 {
 161         struct mm_struct *mm = vma->vm_mm;
 162         struct vm_area_struct *new_vma;
 163         unsigned long vm_flags = vma->vm_flags;
 164         unsigned long new_pgoff;
 165         unsigned long moved_len;
 166         unsigned long excess = 0;
 167         unsigned long hiwater_vm;
 168         int split = 0;
 169
 170         /*
 171          * We'd prefer to avoid failure later on in do_munmap:
 172          * which may split one vma into three before unmapping.
 173          */
 174         if (mm->map_count >= sysctl_max_map_count - 3)
 175                 return -ENOMEM;
 176
 177         new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
 178         new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
 179         if (!new_vma)
 180                 return -ENOMEM;
 181
 182         moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len);
 183         if (moved_len < old_len) {
 184                 /*
 185                  * On error, move entries back from new area to old,
 186                  * which will succeed since page tables still there,
 187                  * and then proceed to unmap new area instead of old.
 188                  */
 189                 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len);
 190                 vma = new_vma;
 191                 old_len = new_len;
 192                 old_addr = new_addr;
 193                 new_addr = -ENOMEM;
 194         }
 195
 196         /* Conceal VM_ACCOUNT so old reservation is not undone */
 197         if (vm_flags & VM_ACCOUNT) {
 198                 vma->vm_flags &= ~VM_ACCOUNT;
 199                 excess = vma->vm_end - vma->vm_start - old_len;
 200                 if (old_addr > vma->vm_start &&
 201                     old_addr + old_len < vma->vm_end)
 202                         split = 1;
 203         }
 204
 205         /*
 206          * If we failed to move page tables we still do total_vm increment
 207          * since do_munmap() will decrement it by old_len == new_len.
 208          *
 209          * Since total_vm is about to be raised artificially high for a
 210          * moment, we need to restore high watermark afterwards: if stats
 211          * are taken meanwhile, total_vm and hiwater_vm appear too high.
 212          * If this were a serious issue, we'd add a flag to do_munmap().
 213          */
 214         hiwater_vm = mm->hiwater_vm;
 215         mm->total_vm += new_len >> PAGE_SHIFT;
 216         vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
 217
 218         if (do_munmap(mm, old_addr, old_len) < 0) {
 219                 /* OOM: unable to split vma, just get accounts right */
 220                 vm_unacct_memory(excess >> PAGE_SHIFT);
 221                 excess = 0;
 222         }
 223         mm->hiwater_vm = hiwater_vm;
 224
 225         /* Restore VM_ACCOUNT if one or two pieces of vma left */
 226         if (excess) {
 227                 vma->vm_flags |= VM_ACCOUNT;
 228                 if (split)
 229                         vma->vm_next->vm_flags |= VM_ACCOUNT;
 230         }
 231
 232         if (vm_flags & VM_LOCKED) {
 233                 mm->locked_vm += new_len >> PAGE_SHIFT;
 234                 if (new_len > old_len)
 235                         make_pages_present(new_addr + old_len,
 236                                            new_addr + new_len);
 237         }
 238
 239         return new_addr;
 240 }
 241
 242 /*
 243  * Expand (or shrink) an existing mapping, potentially moving it at the
 244  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
 245  *
 246  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
 247  * This option implies MREMAP_MAYMOVE.
 248  */
 249 unsigned long do_mremap(unsigned long addr,
 250         unsigned long old_len, unsigned long new_len,
 251         unsigned long flags, unsigned long new_addr)
 252 {
 253         struct mm_struct *mm = current->mm;
 254         struct vm_area_struct *vma;
 255         unsigned long ret = -EINVAL;
 256         unsigned long charged = 0;
 257
 258         if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
 259                 goto out;
 260
 261         if (addr & ~PAGE_MASK)
 262                 goto out;
 263
 264         old_len = PAGE_ALIGN(old_len);
 265         new_len = PAGE_ALIGN(new_len);
 266
 267         /*
 268          * We allow a zero old-len as a special case
 269          * for DOS-emu "duplicate shm area" thing. But
 270          * a zero new-len is nonsensical.
 271          */
 272         if (!new_len)
 273                 goto out;
 274
 275         /* new_addr is only valid if MREMAP_FIXED is specified */
 276         if (flags & MREMAP_FIXED) {
 277                 if (new_addr & ~PAGE_MASK)
 278                         goto out;
 279                 if (!(flags & MREMAP_MAYMOVE))
 280                         goto out;
 281
 282                 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
 283                         goto out;
 284
 285                 /* Check if the location we're moving into overlaps the
 286                  * old location at all, and fail if it does.
 287                  */
 288                 if ((new_addr <= addr) && (new_addr+new_len) > addr)
 289                         goto out;
 290
 291                 if ((addr <= new_addr) && (addr+old_len) > new_addr)
 292                         goto out;
 293
 294                 ret = security_file_mmap(0, 0, 0, 0, new_addr, 1);
 295                 if (ret)
 296                         goto out;
 297
 298                 ret = do_munmap(mm, new_addr, new_len);
 299                 if (ret)
 300                         goto out;
 301         }
 302
 303         /*
 304          * Always allow a shrinking remap: that just unmaps
 305          * the unnecessary pages..
 306          * do_munmap does all the needed commit accounting
 307          */
 308         if (old_len >= new_len) {
 309                 ret = do_munmap(mm, addr+new_len, old_len - new_len);
 310                 if (ret && old_len != new_len)
 311                         goto out;
 312                 ret = addr;
 313                 if (!(flags & MREMAP_FIXED) || (new_addr == addr))
 314                         goto out;
 315                 old_len = new_len;
 316         }
 317
 318         /*
 319          * Ok, we need to grow..  or relocate.
 320          */
 321         ret = -EFAULT;
 322         vma = find_vma(mm, addr);
 323         if (!vma || vma->vm_start > addr)
 324                 goto out;
 325         if (is_vm_hugetlb_page(vma)) {
 326                 ret = -EINVAL;
 327                 goto out;
 328         }
 329         /* We can't remap across vm area boundaries */
 330         if (old_len > vma->vm_end - addr)
 331                 goto out;
 332         if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) {
 333                 if (new_len > old_len)
 334                         goto out;
 335         }
 336         if (vma->vm_flags & VM_LOCKED) {
 337                 unsigned long locked, lock_limit;
 338                 locked = mm->locked_vm << PAGE_SHIFT;
 339                 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
 340                 locked += new_len - old_len;
 341                 ret = -EAGAIN;
 342                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
 343                         goto out;
 344         }
 345         if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) {
 346                 ret = -ENOMEM;
 347                 goto out;
 348         }
 349
 350         if (vma->vm_flags & VM_ACCOUNT) {
 351                 charged = (new_len - old_len) >> PAGE_SHIFT;
 352                 if (security_vm_enough_memory(charged))
 353                         goto out_nc;
 354         }
 355
 356         /* old_len exactly to the end of the area..
 357          * And we're not relocating the area.
 358          */
 359         if (old_len == vma->vm_end - addr &&
 360             !((flags & MREMAP_FIXED) && (addr != new_addr)) &&
 361             (old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
 362                 unsigned long max_addr = TASK_SIZE;
 363                 if (vma->vm_next)
 364                         max_addr = vma->vm_next->vm_start;
 365                 /* can we just expand the current mapping? */
 366                 if (max_addr - addr >= new_len) {
 367                         int pages = (new_len - old_len) >> PAGE_SHIFT;
 368
 369                         vma_adjust(vma, vma->vm_start,
 370                                 addr + new_len, vma->vm_pgoff, NULL);
 371
 372                         mm->total_vm += pages;
 373                         vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
 374                         if (vma->vm_flags & VM_LOCKED) {
 375                                 mm->locked_vm += pages;
 376                                 make_pages_present(addr + old_len,
 377                                                    addr + new_len);
 378                         }
 379                         ret = addr;
 380                         goto out;
 381                 }
 382         }
 383
 384         /*
 385          * We weren't able to just expand or shrink the area,
 386          * we need to create a new one and move it..
 387          */
 388         ret = -ENOMEM;
 389         if (flags & MREMAP_MAYMOVE) {
 390                 if (!(flags & MREMAP_FIXED)) {
 391                         unsigned long map_flags = 0;
 392                         if (vma->vm_flags & VM_MAYSHARE)
 393                                 map_flags |= MAP_SHARED;
 394
 395                         new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
 396                                                 vma->vm_pgoff, map_flags);
 397                         if (new_addr & ~PAGE_MASK) {
 398                                 ret = new_addr;
 399                                 goto out;
 400                         }
 401
 402                         ret = security_file_mmap(0, 0, 0, 0, new_addr, 1);
 403                         if (ret)
 404                                 goto out;
 405                 }
 406                 ret = move_vma(vma, addr, old_len, new_len, new_addr);
 407         }
 408 out:
 409         if (ret & ~PAGE_MASK)
 410                 vm_unacct_memory(charged);
 411 out_nc:
 412         return ret;
 413 }
 414
 415 asmlinkage unsigned long sys_mremap(unsigned long addr,
 416         unsigned long old_len, unsigned long new_len,
 417         unsigned long flags, unsigned long new_addr)
 418 {
 419         unsigned long ret;
 420
 421         down_write(&current->mm->mmap_sem);
 422         ret = do_mremap(addr, old_len, new_len, flags, new_addr);
 423         up_write(&current->mm->mmap_sem);
 424         return ret;
 425 }