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
  22#include <asm/uaccess.h>
  23#include <asm/cacheflush.h>
  24#include <asm/tlbflush.h>
  25
  26static 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
  47static 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
  68static 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
 123static 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
 157static 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 */
 249unsigned 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 = do_munmap(mm, new_addr, new_len);
 295                if (ret)
 296                        goto out;
 297        }
 298
 299        /*
 300         * Always allow a shrinking remap: that just unmaps
 301         * the unnecessary pages..
 302         * do_munmap does all the needed commit accounting
 303         */
 304        if (old_len >= new_len) {
 305                ret = do_munmap(mm, addr+new_len, old_len - new_len);
 306                if (ret && old_len != new_len)
 307                        goto out;
 308                ret = addr;
 309                if (!(flags & MREMAP_FIXED) || (new_addr == addr))
 310                        goto out;
 311                old_len = new_len;
 312        }
 313
 314        /*
 315         * Ok, we need to grow..  or relocate.
 316         */
 317        ret = -EFAULT;
 318        vma = find_vma(mm, addr);
 319        if (!vma || vma->vm_start > addr)
 320                goto out;
 321        if (is_vm_hugetlb_page(vma)) {
 322                ret = -EINVAL;
 323                goto out;
 324        }
 325        /* We can't remap across vm area boundaries */
 326        if (old_len > vma->vm_end - addr)
 327                goto out;
 328        if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) {
 329                if (new_len > old_len)
 330                        goto out;
 331        }
 332        if (vma->vm_flags & VM_LOCKED) {
 333                unsigned long locked, lock_limit;
 334                locked = mm->locked_vm << PAGE_SHIFT;
 335                lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
 336                locked += new_len - old_len;
 337                ret = -EAGAIN;
 338                if (locked > lock_limit && !capable(CAP_IPC_LOCK))
 339                        goto out;
 340        }
 341        if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) {
 342                ret = -ENOMEM;
 343                goto out;
 344        }
 345
 346        if (vma->vm_flags & VM_ACCOUNT) {
 347                charged = (new_len - old_len) >> PAGE_SHIFT;
 348                if (security_vm_enough_memory(charged))
 349                        goto out_nc;
 350        }
 351
 352        /* old_len exactly to the end of the area..
 353         * And we're not relocating the area.
 354         */
 355        if (old_len == vma->vm_end - addr &&
 356            !((flags & MREMAP_FIXED) && (addr != new_addr)) &&
 357            (old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
 358                unsigned long max_addr = TASK_SIZE;
 359                if (vma->vm_next)
 360                        max_addr = vma->vm_next->vm_start;
 361                /* can we just expand the current mapping? */
 362                if (max_addr - addr >= new_len) {
 363                        int pages = (new_len - old_len) >> PAGE_SHIFT;
 364
 365                        vma_adjust(vma, vma->vm_start,
 366                                addr + new_len, vma->vm_pgoff, NULL);
 367
 368                        mm->total_vm += pages;
 369                        vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
 370                        if (vma->vm_flags & VM_LOCKED) {
 371                                mm->locked_vm += pages;
 372                                make_pages_present(addr + old_len,
 373                                                   addr + new_len);
 374                        }
 375                        ret = addr;
 376                        goto out;
 377                }
 378        }
 379
 380        /*
 381         * We weren't able to just expand or shrink the area,
 382         * we need to create a new one and move it..
 383         */
 384        ret = -ENOMEM;
 385        if (flags & MREMAP_MAYMOVE) {
 386                if (!(flags & MREMAP_FIXED)) {
 387                        unsigned long map_flags = 0;
 388                        if (vma->vm_flags & VM_MAYSHARE)
 389                                map_flags |= MAP_SHARED;
 390
 391                        new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
 392                                                vma->vm_pgoff, map_flags);
 393                        ret = new_addr;
 394                        if (new_addr & ~PAGE_MASK)
 395                                goto out;
 396                }
 397                ret = move_vma(vma, addr, old_len, new_len, new_addr);
 398        }
 399out:
 400        if (ret & ~PAGE_MASK)
 401                vm_unacct_memory(charged);
 402out_nc:
 403        return ret;
 404}
 405
 406asmlinkage unsigned long sys_mremap(unsigned long addr,
 407        unsigned long old_len, unsigned long new_len,
 408        unsigned long flags, unsigned long new_addr)
 409{
 410        unsigned long ret;
 411
 412        down_write(&current->mm->mmap_sem);
 413        ret = do_mremap(addr, old_len, new_len, flags, new_addr);
 414        up_write(&current->mm->mmap_sem);
 415        return ret;
 416}
 417