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   1 /*
   2  *      mm/mremap.c
   3  *
   4  *      (C) Copyright 1996 Linus Torvalds
   5  *
   6  *      Address space accounting code   <alan@lxorguk.ukuu.org.uk>
   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/ksm.h>
  15 #include <linux/mman.h>
  16 #include <linux/swap.h>
  17 #include <linux/capability.h>
  18 #include <linux/fs.h>
  19 #include <linux/highmem.h>
  20 #include <linux/security.h>
  21 #include <linux/syscalls.h>
  22 #include <linux/mmu_notifier.h>
  23
  24 #include <asm/uaccess.h>
  25 #include <asm/cacheflush.h>
  26 #include <asm/tlbflush.h>
  27
  28 #include "internal.h"
  29
  30 static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
  31 {
  32         pgd_t *pgd;
  33         pud_t *pud;
  34         pmd_t *pmd;
  35
  36         pgd = pgd_offset(mm, addr);
  37         if (pgd_none_or_clear_bad(pgd))
  38                 return NULL;
  39
  40         pud = pud_offset(pgd, addr);
  41         if (pud_none_or_clear_bad(pud))
  42                 return NULL;
  43
  44         pmd = pmd_offset(pud, addr);
  45         if (pmd_none_or_clear_bad(pmd))
  46                 return NULL;
  47
  48         return pmd;
  49 }
  50
  51 static pmd_t *alloc_new_pmd(struct mm_struct *mm, unsigned long addr)
  52 {
  53         pgd_t *pgd;
  54         pud_t *pud;
  55         pmd_t *pmd;
  56
  57         pgd = pgd_offset(mm, addr);
  58         pud = pud_alloc(mm, pgd, addr);
  59         if (!pud)
  60                 return NULL;
  61
  62         pmd = pmd_alloc(mm, pud, addr);
  63         if (!pmd)
  64                 return NULL;
  65
  66         if (!pmd_present(*pmd) && __pte_alloc(mm, pmd, addr))
  67                 return NULL;
  68
  69         return pmd;
  70 }
  71
  72 static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
  73                 unsigned long old_addr, unsigned long old_end,
  74                 struct vm_area_struct *new_vma, pmd_t *new_pmd,
  75                 unsigned long new_addr)
  76 {
  77         struct address_space *mapping = NULL;
  78         struct mm_struct *mm = vma->vm_mm;
  79         pte_t *old_pte, *new_pte, pte;
  80         spinlock_t *old_ptl, *new_ptl;
  81         unsigned long old_start;
  82
  83         old_start = old_addr;
  84         mmu_notifier_invalidate_range_start(vma->vm_mm,
  85                                             old_start, old_end);
  86         if (vma->vm_file) {
  87                 /*
  88                  * Subtle point from Rajesh Venkatasubramanian: before
  89                  * moving file-based ptes, we must lock truncate_pagecache
  90                  * out, since it might clean the dst vma before the src vma,
  91                  * and we propagate stale pages into the dst afterward.
  92                  */
  93                 mapping = vma->vm_file->f_mapping;
  94                 spin_lock(&mapping->i_mmap_lock);
  95                 if (new_vma->vm_truncate_count &&
  96                     new_vma->vm_truncate_count != vma->vm_truncate_count)
  97                         new_vma->vm_truncate_count = 0;
  98         }
  99
 100         /*
 101          * We don't have to worry about the ordering of src and dst
 102          * pte locks because exclusive mmap_sem prevents deadlock.
 103          */
 104         old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
 105         new_pte = pte_offset_map_nested(new_pmd, new_addr);
 106         new_ptl = pte_lockptr(mm, new_pmd);
 107         if (new_ptl != old_ptl)
 108                 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
 109         arch_enter_lazy_mmu_mode();
 110
 111         for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
 112                                    new_pte++, new_addr += PAGE_SIZE) {
 113                 if (pte_none(*old_pte))
 114                         continue;
 115                 pte = ptep_clear_flush(vma, old_addr, old_pte);
 116                 pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
 117                 set_pte_at(mm, new_addr, new_pte, pte);
 118         }
 119
 120         arch_leave_lazy_mmu_mode();
 121         if (new_ptl != old_ptl)
 122                 spin_unlock(new_ptl);
 123         pte_unmap_nested(new_pte - 1);
 124         pte_unmap_unlock(old_pte - 1, old_ptl);
 125         if (mapping)
 126                 spin_unlock(&mapping->i_mmap_lock);
 127         mmu_notifier_invalidate_range_end(vma->vm_mm, old_start, old_end);
 128 }
 129
 130 #define LATENCY_LIMIT   (64 * PAGE_SIZE)
 131
 132 unsigned long move_page_tables(struct vm_area_struct *vma,
 133                 unsigned long old_addr, struct vm_area_struct *new_vma,
 134                 unsigned long new_addr, unsigned long len)
 135 {
 136         unsigned long extent, next, old_end;
 137         pmd_t *old_pmd, *new_pmd;
 138
 139         old_end = old_addr + len;
 140         flush_cache_range(vma, old_addr, old_end);
 141
 142         for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
 143                 cond_resched();
 144                 next = (old_addr + PMD_SIZE) & PMD_MASK;
 145                 if (next - 1 > old_end)
 146                         next = old_end;
 147                 extent = next - old_addr;
 148                 old_pmd = get_old_pmd(vma->vm_mm, old_addr);
 149                 if (!old_pmd)
 150                         continue;
 151                 new_pmd = alloc_new_pmd(vma->vm_mm, new_addr);
 152                 if (!new_pmd)
 153                         break;
 154                 next = (new_addr + PMD_SIZE) & PMD_MASK;
 155                 if (extent > next - new_addr)
 156                         extent = next - new_addr;
 157                 if (extent > LATENCY_LIMIT)
 158                         extent = LATENCY_LIMIT;
 159                 move_ptes(vma, old_pmd, old_addr, old_addr + extent,
 160                                 new_vma, new_pmd, new_addr);
 161         }
 162
 163         return len + old_addr - old_end;        /* how much done */
 164 }
 165
 166 static unsigned long move_vma(struct vm_area_struct *vma,
 167                 unsigned long old_addr, unsigned long old_len,
 168                 unsigned long new_len, unsigned long new_addr)
 169 {
 170         struct mm_struct *mm = vma->vm_mm;
 171         struct vm_area_struct *new_vma;
 172         unsigned long vm_flags = vma->vm_flags;
 173         unsigned long new_pgoff;
 174         unsigned long moved_len;
 175         unsigned long excess = 0;
 176         unsigned long hiwater_vm;
 177         int split = 0;
 178         int err;
 179
 180         /*
 181          * We'd prefer to avoid failure later on in do_munmap:
 182          * which may split one vma into three before unmapping.
 183          */
 184         if (mm->map_count >= sysctl_max_map_count - 3)
 185                 return -ENOMEM;
 186
 187         /*
 188          * Advise KSM to break any KSM pages in the area to be moved:
 189          * it would be confusing if they were to turn up at the new
 190          * location, where they happen to coincide with different KSM
 191          * pages recently unmapped.  But leave vma->vm_flags as it was,
 192          * so KSM can come around to merge on vma and new_vma afterwards.
 193          */
 194         err = ksm_madvise(vma, old_addr, old_addr + old_len,
 195                                                 MADV_UNMERGEABLE, &vm_flags);
 196         if (err)
 197                 return err;
 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          * Since total_vm is about to be raised artificially high for a
 232          * moment, we need to restore high watermark afterwards: if stats
 233          * are taken meanwhile, total_vm and hiwater_vm appear too high.
 234          * If this were a serious issue, we'd add a flag to do_munmap().
 235          */
 236         hiwater_vm = mm->hiwater_vm;
 237         mm->total_vm += new_len >> PAGE_SHIFT;
 238         vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
 239
 240         if (do_munmap(mm, old_addr, old_len) < 0) {
 241                 /* OOM: unable to split vma, just get accounts right */
 242                 vm_unacct_memory(excess >> PAGE_SHIFT);
 243                 excess = 0;
 244         }
 245         mm->hiwater_vm = hiwater_vm;
 246
 247         /* Restore VM_ACCOUNT if one or two pieces of vma left */
 248         if (excess) {
 249                 vma->vm_flags |= VM_ACCOUNT;
 250                 if (split)
 251                         vma->vm_next->vm_flags |= VM_ACCOUNT;
 252         }
 253
 254         if (vm_flags & VM_LOCKED) {
 255                 mm->locked_vm += new_len >> PAGE_SHIFT;
 256                 if (new_len > old_len)
 257                         mlock_vma_pages_range(new_vma, new_addr + old_len,
 258                                                        new_addr + new_len);
 259         }
 260
 261         return new_addr;
 262 }
 263
 264 static struct vm_area_struct *vma_to_resize(unsigned long addr,
 265         unsigned long old_len, unsigned long new_len, unsigned long *p)
 266 {
 267         struct mm_struct *mm = current->mm;
 268         struct vm_area_struct *vma = find_vma(mm, addr);
 269
 270         if (!vma || vma->vm_start > addr)
 271                 goto Efault;
 272
 273         if (is_vm_hugetlb_page(vma))
 274                 goto Einval;
 275
 276         /* We can't remap across vm area boundaries */
 277         if (old_len > vma->vm_end - addr)
 278                 goto Efault;
 279
 280         if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) {
 281                 if (new_len > old_len)
 282                         goto Efault;
 283         }
 284
 285         if (vma->vm_flags & VM_LOCKED) {
 286                 unsigned long locked, lock_limit;
 287                 locked = mm->locked_vm << PAGE_SHIFT;
 288                 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
 289                 locked += new_len - old_len;
 290                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
 291                         goto Eagain;
 292         }
 293
 294         if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT))
 295                 goto Enomem;
 296
 297         if (vma->vm_flags & VM_ACCOUNT) {
 298                 unsigned long charged = (new_len - old_len) >> PAGE_SHIFT;
 299                 if (security_vm_enough_memory(charged))
 300                         goto Efault;
 301                 *p = charged;
 302         }
 303
 304         return vma;
 305
 306 Efault: /* very odd choice for most of the cases, but... */
 307         return ERR_PTR(-EFAULT);
 308 Einval:
 309         return ERR_PTR(-EINVAL);
 310 Enomem:
 311         return ERR_PTR(-ENOMEM);
 312 Eagain:
 313         return ERR_PTR(-EAGAIN);
 314 }
 315
 316 static unsigned long mremap_to(unsigned long addr,
 317         unsigned long old_len, unsigned long new_addr,
 318         unsigned long new_len)
 319 {
 320         struct mm_struct *mm = current->mm;
 321         struct vm_area_struct *vma;
 322         unsigned long ret = -EINVAL;
 323         unsigned long charged = 0;
 324
 325         if (new_addr & ~PAGE_MASK)
 326                 goto out;
 327
 328         if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
 329                 goto out;
 330
 331         /* Check if the location we're moving into overlaps the
 332          * old location at all, and fail if it does.
 333          */
 334         if ((new_addr <= addr) && (new_addr+new_len) > addr)
 335                 goto out;
 336
 337         if ((addr <= new_addr) && (addr+old_len) > new_addr)
 338                 goto out;
 339
 340         ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
 341         if (ret)
 342                 goto out;
 343
 344         ret = do_munmap(mm, new_addr, new_len);
 345         if (ret)
 346                 goto out;
 347
 348         if (old_len >= new_len) {
 349                 ret = do_munmap(mm, addr+new_len, old_len - new_len);
 350                 if (ret && old_len != new_len)
 351                         goto out;
 352                 old_len = new_len;
 353         }
 354
 355         vma = vma_to_resize(addr, old_len, new_len, &charged);
 356         if (IS_ERR(vma)) {
 357                 ret = PTR_ERR(vma);
 358                 goto out;
 359         }
 360
 361         ret = move_vma(vma, addr, old_len, new_len, new_addr);
 362         if (ret & ~PAGE_MASK)
 363                 vm_unacct_memory(charged);
 364
 365 out:
 366         return ret;
 367 }
 368
 369 static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
 370 {
 371         unsigned long max_addr = TASK_SIZE;
 372         if (vma->vm_next)
 373                 max_addr = vma->vm_next->vm_start;
 374         if (max_addr - vma->vm_end < delta)
 375                 return 0;
 376         /* we need to do arch-specific checks here */
 377         return 1;
 378 }
 379
 380 /*
 381  * Expand (or shrink) an existing mapping, potentially moving it at the
 382  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
 383  *
 384  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
 385  * This option implies MREMAP_MAYMOVE.
 386  */
 387 unsigned long do_mremap(unsigned long addr,
 388         unsigned long old_len, unsigned long new_len,
 389         unsigned long flags, unsigned long new_addr)
 390 {
 391         struct mm_struct *mm = current->mm;
 392         struct vm_area_struct *vma;
 393         unsigned long ret = -EINVAL;
 394         unsigned long charged = 0;
 395
 396         if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
 397                 goto out;
 398
 399         if (addr & ~PAGE_MASK)
 400                 goto out;
 401
 402         old_len = PAGE_ALIGN(old_len);
 403         new_len = PAGE_ALIGN(new_len);
 404
 405         /*
 406          * We allow a zero old-len as a special case
 407          * for DOS-emu "duplicate shm area" thing. But
 408          * a zero new-len is nonsensical.
 409          */
 410         if (!new_len)
 411                 goto out;
 412
 413         if (flags & MREMAP_FIXED) {
 414                 if (flags & MREMAP_MAYMOVE)
 415                         ret = mremap_to(addr, old_len, new_addr, new_len);
 416                 goto out;
 417         }
 418
 419         /*
 420          * Always allow a shrinking remap: that just unmaps
 421          * the unnecessary pages..
 422          * do_munmap does all the needed commit accounting
 423          */
 424         if (old_len >= new_len) {
 425                 ret = do_munmap(mm, addr+new_len, old_len - new_len);
 426                 if (ret && old_len != new_len)
 427                         goto out;
 428                 ret = addr;
 429                 goto out;
 430         }
 431
 432         /*
 433          * Ok, we need to grow..
 434          */
 435         vma = vma_to_resize(addr, old_len, new_len, &charged);
 436         if (IS_ERR(vma)) {
 437                 ret = PTR_ERR(vma);
 438                 goto out;
 439         }
 440
 441         /* old_len exactly to the end of the area..
 442          */
 443         if (old_len == vma->vm_end - addr) {
 444                 /* can we just expand the current mapping? */
 445                 if (vma_expandable(vma, new_len - old_len)) {
 446                         int pages = (new_len - old_len) >> PAGE_SHIFT;
 447
 448                         vma_adjust(vma, vma->vm_start,
 449                                 addr + new_len, vma->vm_pgoff, NULL);
 450
 451                         mm->total_vm += pages;
 452                         vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
 453                         if (vma->vm_flags & VM_LOCKED) {
 454                                 mm->locked_vm += pages;
 455                                 mlock_vma_pages_range(vma, addr + old_len,
 456                                                    addr + new_len);
 457                         }
 458                         ret = addr;
 459                         goto out;
 460                 }
 461         }
 462
 463         /*
 464          * We weren't able to just expand or shrink the area,
 465          * we need to create a new one and move it..
 466          */
 467         ret = -ENOMEM;
 468         if (flags & MREMAP_MAYMOVE) {
 469                 unsigned long map_flags = 0;
 470                 if (vma->vm_flags & VM_MAYSHARE)
 471                         map_flags |= MAP_SHARED;
 472
 473                 new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
 474                                         vma->vm_pgoff, map_flags);
 475                 if (new_addr & ~PAGE_MASK) {
 476                         ret = new_addr;
 477                         goto out;
 478                 }
 479
 480                 ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
 481                 if (ret)
 482                         goto out;
 483                 ret = move_vma(vma, addr, old_len, new_len, new_addr);
 484         }
 485 out:
 486         if (ret & ~PAGE_MASK)
 487                 vm_unacct_memory(charged);
 488         return ret;
 489 }
 490
 491 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
 492                 unsigned long, new_len, unsigned long, flags,
 493                 unsigned long, new_addr)
 494 {
 495         unsigned long ret;
 496
 497         down_write(&current->mm->mmap_sem);
 498         ret = do_mremap(addr, old_len, new_len, flags, new_addr);
 499         up_write(&current->mm->mmap_sem);
 500         return ret;
 501 }