LXR linux/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#include "internal.h"
  28
  29static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
  30{
  31        pgd_t *pgd;
  32        pud_t *pud;
  33        pmd_t *pmd;
  34
  35        pgd = pgd_offset(mm, addr);
  36        if (pgd_none_or_clear_bad(pgd))
  37                return NULL;
  38
  39        pud = pud_offset(pgd, addr);
  40        if (pud_none_or_clear_bad(pud))
  41                return NULL;
  42
  43        pmd = pmd_offset(pud, addr);
  44        if (pmd_none_or_clear_bad(pmd))
  45                return NULL;
  46
  47        return pmd;
  48}
  49
  50static pmd_t *alloc_new_pmd(struct mm_struct *mm, unsigned long addr)
  51{
  52        pgd_t *pgd;
  53        pud_t *pud;
  54        pmd_t *pmd;
  55
  56        pgd = pgd_offset(mm, addr);
  57        pud = pud_alloc(mm, pgd, addr);
  58        if (!pud)
  59                return NULL;
  60
  61        pmd = pmd_alloc(mm, pud, addr);
  62        if (!pmd)
  63                return NULL;
  64
  65        if (!pmd_present(*pmd) && __pte_alloc(mm, pmd, addr))
  66                return NULL;
  67
  68        return pmd;
  69}
  70
  71static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
  72                unsigned long old_addr, unsigned long old_end,
  73                struct vm_area_struct *new_vma, pmd_t *new_pmd,
  74                unsigned long new_addr)
  75{
  76        struct address_space *mapping = NULL;
  77        struct mm_struct *mm = vma->vm_mm;
  78        pte_t *old_pte, *new_pte, pte;
  79        spinlock_t *old_ptl, *new_ptl;
  80        unsigned long old_start;
  81
  82        old_start = old_addr;
  83        mmu_notifier_invalidate_range_start(vma->vm_mm,
  84                                            old_start, old_end);
  85        if (vma->vm_file) {
  86                /*
  87                 * Subtle point from Rajesh Venkatasubramanian: before
  88                 * moving file-based ptes, we must lock vmtruncate out,
  89                 * since it might clean the dst vma before the src vma,
  90                 * and we propagate stale pages into the dst afterward.
  91                 */
  92                mapping = vma->vm_file->f_mapping;
  93                spin_lock(&mapping->i_mmap_lock);
  94                if (new_vma->vm_truncate_count &&
  95                    new_vma->vm_truncate_count != vma->vm_truncate_count)
  96                        new_vma->vm_truncate_count = 0;
  97        }
  98
  99        /*
 100         * We don't have to worry about the ordering of src and dst
 101         * pte locks because exclusive mmap_sem prevents deadlock.
 102         */
 103        old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
 104        new_pte = pte_offset_map_nested(new_pmd, new_addr);
 105        new_ptl = pte_lockptr(mm, new_pmd);
 106        if (new_ptl != old_ptl)
 107                spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
 108        arch_enter_lazy_mmu_mode();
 109
 110        for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
 111                                   new_pte++, new_addr += PAGE_SIZE) {
 112                if (pte_none(*old_pte))
 113                        continue;
 114                pte = ptep_clear_flush(vma, old_addr, old_pte);
 115                pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
 116                set_pte_at(mm, new_addr, new_pte, pte);
 117        }
 118
 119        arch_leave_lazy_mmu_mode();
 120        if (new_ptl != old_ptl)
 121                spin_unlock(new_ptl);
 122        pte_unmap_nested(new_pte - 1);
 123        pte_unmap_unlock(old_pte - 1, old_ptl);
 124        if (mapping)
 125                spin_unlock(&mapping->i_mmap_lock);
 126        mmu_notifier_invalidate_range_end(vma->vm_mm, old_start, old_end);
 127}
 128
 129#define LATENCY_LIMIT   (64 * PAGE_SIZE)
 130
 131unsigned long move_page_tables(struct vm_area_struct *vma,
 132                unsigned long old_addr, struct vm_area_struct *new_vma,
 133                unsigned long new_addr, unsigned long len)
 134{
 135        unsigned long extent, next, old_end;
 136        pmd_t *old_pmd, *new_pmd;
 137
 138        old_end = old_addr + len;
 139        flush_cache_range(vma, old_addr, old_end);
 140
 141        for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
 142                cond_resched();
 143                next = (old_addr + PMD_SIZE) & PMD_MASK;
 144                if (next - 1 > old_end)
 145                        next = old_end;
 146                extent = next - old_addr;
 147                old_pmd = get_old_pmd(vma->vm_mm, old_addr);
 148                if (!old_pmd)
 149                        continue;
 150                new_pmd = alloc_new_pmd(vma->vm_mm, new_addr);
 151                if (!new_pmd)
 152                        break;
 153                next = (new_addr + PMD_SIZE) & PMD_MASK;
 154                if (extent > next - new_addr)
 155                        extent = next - new_addr;
 156                if (extent > LATENCY_LIMIT)
 157                        extent = LATENCY_LIMIT;
 158                move_ptes(vma, old_pmd, old_addr, old_addr + extent,
 159                                new_vma, new_pmd, new_addr);
 160        }
 161
 162        return len + old_addr - old_end;        /* how much done */
 163}
 164
 165static unsigned long move_vma(struct vm_area_struct *vma,
 166                unsigned long old_addr, unsigned long old_len,
 167                unsigned long new_len, unsigned long new_addr)
 168{
 169        struct mm_struct *mm = vma->vm_mm;
 170        struct vm_area_struct *new_vma;
 171        unsigned long vm_flags = vma->vm_flags;
 172        unsigned long new_pgoff;
 173        unsigned long moved_len;
 174        unsigned long excess = 0;
 175        unsigned long hiwater_vm;
 176        int split = 0;
 177
 178        /*
 179         * We'd prefer to avoid failure later on in do_munmap:
 180         * which may split one vma into three before unmapping.
 181         */
 182        if (mm->map_count >= sysctl_max_map_count - 3)
 183                return -ENOMEM;
 184
 185        new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
 186        new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
 187        if (!new_vma)
 188                return -ENOMEM;
 189
 190        moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len);
 191        if (moved_len < old_len) {
 192                /*
 193                 * On error, move entries back from new area to old,
 194                 * which will succeed since page tables still there,
 195                 * and then proceed to unmap new area instead of old.
 196                 */
 197                move_page_tables(new_vma, new_addr, vma, old_addr, moved_len);
 198                vma = new_vma;
 199                old_len = new_len;
 200                old_addr = new_addr;
 201                new_addr = -ENOMEM;
 202        }
 203
 204        /* Conceal VM_ACCOUNT so old reservation is not undone */
 205        if (vm_flags & VM_ACCOUNT) {
 206                vma->vm_flags &= ~VM_ACCOUNT;
 207                excess = vma->vm_end - vma->vm_start - old_len;
 208                if (old_addr > vma->vm_start &&
 209                    old_addr + old_len < vma->vm_end)
 210                        split = 1;
 211        }
 212
 213        /*
 214         * If we failed to move page tables we still do total_vm increment
 215         * since do_munmap() will decrement it by old_len == new_len.
 216         *
 217         * Since total_vm is about to be raised artificially high for a
 218         * moment, we need to restore high watermark afterwards: if stats
 219         * are taken meanwhile, total_vm and hiwater_vm appear too high.
 220         * If this were a serious issue, we'd add a flag to do_munmap().
 221         */
 222        hiwater_vm = mm->hiwater_vm;
 223        mm->total_vm += new_len >> PAGE_SHIFT;
 224        vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
 225
 226        if (do_munmap(mm, old_addr, old_len) < 0) {
 227                /* OOM: unable to split vma, just get accounts right */
 228                vm_unacct_memory(excess >> PAGE_SHIFT);
 229                excess = 0;
 230        }
 231        mm->hiwater_vm = hiwater_vm;
 232
 233        /* Restore VM_ACCOUNT if one or two pieces of vma left */
 234        if (excess) {
 235                vma->vm_flags |= VM_ACCOUNT;
 236                if (split)
 237                        vma->vm_next->vm_flags |= VM_ACCOUNT;
 238        }
 239
 240        if (vm_flags & VM_LOCKED) {
 241                mm->locked_vm += new_len >> PAGE_SHIFT;
 242                if (new_len > old_len)
 243                        mlock_vma_pages_range(new_vma, new_addr + old_len,
 244                                                       new_addr + new_len);
 245        }
 246
 247        return new_addr;
 248}
 249
 250/*
 251 * Expand (or shrink) an existing mapping, potentially moving it at the
 252 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
 253 *
 254 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
 255 * This option implies MREMAP_MAYMOVE.
 256 */
 257unsigned long do_mremap(unsigned long addr,
 258        unsigned long old_len, unsigned long new_len,
 259        unsigned long flags, unsigned long new_addr)
 260{
 261        struct mm_struct *mm = current->mm;
 262        struct vm_area_struct *vma;
 263        unsigned long ret = -EINVAL;
 264        unsigned long charged = 0;
 265
 266        if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
 267                goto out;
 268
 269        if (addr & ~PAGE_MASK)
 270                goto out;
 271
 272        old_len = PAGE_ALIGN(old_len);
 273        new_len = PAGE_ALIGN(new_len);
 274
 275        /*
 276         * We allow a zero old-len as a special case
 277         * for DOS-emu "duplicate shm area" thing. But
 278         * a zero new-len is nonsensical.
 279         */
 280        if (!new_len)
 281                goto out;
 282
 283        /* new_addr is only valid if MREMAP_FIXED is specified */
 284        if (flags & MREMAP_FIXED) {
 285                if (new_addr & ~PAGE_MASK)
 286                        goto out;
 287                if (!(flags & MREMAP_MAYMOVE))
 288                        goto out;
 289
 290                if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
 291                        goto out;
 292
 293                /* Check if the location we're moving into overlaps the
 294                 * old location at all, and fail if it does.
 295                 */
 296                if ((new_addr <= addr) && (new_addr+new_len) > addr)
 297                        goto out;
 298
 299                if ((addr <= new_addr) && (addr+old_len) > new_addr)
 300                        goto out;
 301
 302                ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
 303                if (ret)
 304                        goto out;
 305
 306                ret = do_munmap(mm, new_addr, new_len);
 307                if (ret)
 308                        goto out;
 309        }
 310
 311        /*
 312         * Always allow a shrinking remap: that just unmaps
 313         * the unnecessary pages..
 314         * do_munmap does all the needed commit accounting
 315         */
 316        if (old_len >= new_len) {
 317                ret = do_munmap(mm, addr+new_len, old_len - new_len);
 318                if (ret && old_len != new_len)
 319                        goto out;
 320                ret = addr;
 321                if (!(flags & MREMAP_FIXED) || (new_addr == addr))
 322                        goto out;
 323                old_len = new_len;
 324        }
 325
 326        /*
 327         * Ok, we need to grow..  or relocate.
 328         */
 329        ret = -EFAULT;
 330        vma = find_vma(mm, addr);
 331        if (!vma || vma->vm_start > addr)
 332                goto out;
 333        if (is_vm_hugetlb_page(vma)) {
 334                ret = -EINVAL;
 335                goto out;
 336        }
 337        /* We can't remap across vm area boundaries */
 338        if (old_len > vma->vm_end - addr)
 339                goto out;
 340        if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) {
 341                if (new_len > old_len)
 342                        goto out;
 343        }
 344        if (vma->vm_flags & VM_LOCKED) {
 345                unsigned long locked, lock_limit;
 346                locked = mm->locked_vm << PAGE_SHIFT;
 347                lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
 348                locked += new_len - old_len;
 349                ret = -EAGAIN;
 350                if (locked > lock_limit && !capable(CAP_IPC_LOCK))
 351                        goto out;
 352        }
 353        if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) {
 354                ret = -ENOMEM;
 355                goto out;
 356        }
 357
 358        if (vma->vm_flags & VM_ACCOUNT) {
 359                charged = (new_len - old_len) >> PAGE_SHIFT;
 360                if (security_vm_enough_memory(charged))
 361                        goto out_nc;
 362        }
 363
 364        /* old_len exactly to the end of the area..
 365         * And we're not relocating the area.
 366         */
 367        if (old_len == vma->vm_end - addr &&
 368            !((flags & MREMAP_FIXED) && (addr != new_addr)) &&
 369            (old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
 370                unsigned long max_addr = TASK_SIZE;
 371                if (vma->vm_next)
 372                        max_addr = vma->vm_next->vm_start;
 373                /* can we just expand the current mapping? */
 374                if (max_addr - addr >= new_len) {
 375                        int pages = (new_len - old_len) >> PAGE_SHIFT;
 376
 377                        vma_adjust(vma, vma->vm_start,
 378                                addr + new_len, vma->vm_pgoff, NULL);
 379
 380                        mm->total_vm += pages;
 381                        vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
 382                        if (vma->vm_flags & VM_LOCKED) {
 383                                mm->locked_vm += pages;
 384                                mlock_vma_pages_range(vma, addr + old_len,
 385                                                   addr + new_len);
 386                        }
 387                        ret = addr;
 388                        goto out;
 389                }
 390        }
 391
 392        /*
 393         * We weren't able to just expand or shrink the area,
 394         * we need to create a new one and move it..
 395         */
 396        ret = -ENOMEM;
 397        if (flags & MREMAP_MAYMOVE) {
 398                if (!(flags & MREMAP_FIXED)) {
 399                        unsigned long map_flags = 0;
 400                        if (vma->vm_flags & VM_MAYSHARE)
 401                                map_flags |= MAP_SHARED;
 402
 403                        new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
 404                                                vma->vm_pgoff, map_flags);
 405                        if (new_addr & ~PAGE_MASK) {
 406                                ret = new_addr;
 407                                goto out;
 408                        }
 409
 410                        ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
 411                        if (ret)
 412                                goto out;
 413                }
 414                ret = move_vma(vma, addr, old_len, new_len, new_addr);
 415        }
 416out:
 417        if (ret & ~PAGE_MASK)
 418                vm_unacct_memory(charged);
 419out_nc:
 420        return ret;
 421}
 422
 423SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
 424                unsigned long, new_len, unsigned long, flags,
 425                unsigned long, new_addr)
 426{
 427        unsigned long ret;
 428
 429        down_write(&current->mm->mmap_sem);
 430        ret = do_mremap(addr, old_len, new_len, flags, new_addr);
 431        up_write(&current->mm->mmap_sem);
 432        return ret;
 433}
 434