LXR linux-old/mm/mremap.c

   1/*
   2 *      linux/mm/remap.c
   3 *
   4 *      (C) Copyright 1996 Linus Torvalds
   5 */
   6
   7#include <linux/stat.h>
   8#include <linux/sched.h>
   9#include <linux/kernel.h>
  10#include <linux/mm.h>
  11#include <linux/smp.h>
  12#include <linux/smp_lock.h>
  13#include <linux/shm.h>
  14#include <linux/errno.h>
  15#include <linux/mman.h>
  16#include <linux/string.h>
  17#include <linux/slab.h>
  18#include <linux/swap.h>
  19
  20#include <asm/uaccess.h>
  21#include <asm/system.h>
  22#include <asm/pgtable.h>
  23
  24static inline pte_t *get_one_pte(struct mm_struct *mm, unsigned long addr)
  25{
  26        pgd_t * pgd;
  27        pmd_t * pmd;
  28        pte_t * pte = NULL;
  29
  30        pgd = pgd_offset(mm, addr);
  31        if (pgd_none(*pgd))
  32                goto end;
  33        if (pgd_bad(*pgd)) {
  34                printk("move_one_page: bad source pgd (%08lx)\n", pgd_val(*pgd));
  35                pgd_clear(pgd);
  36                goto end;
  37        }
  38
  39        pmd = pmd_offset(pgd, addr);
  40        if (pmd_none(*pmd))
  41                goto end;
  42        if (pmd_bad(*pmd)) {
  43                printk("move_one_page: bad source pmd (%08lx)\n", pmd_val(*pmd));
  44                pmd_clear(pmd);
  45                goto end;
  46        }
  47
  48        pte = pte_offset(pmd, addr);
  49        if (pte_none(*pte))
  50                pte = NULL;
  51end:
  52        return pte;
  53}
  54
  55static inline pte_t *alloc_one_pte(struct mm_struct *mm, unsigned long addr)
  56{
  57        pmd_t * pmd;
  58        pte_t * pte = NULL;
  59
  60        pmd = pmd_alloc(pgd_offset(mm, addr), addr);
  61        if (pmd)
  62                pte = pte_alloc(pmd, addr);
  63        return pte;
  64}
  65
  66static inline int copy_one_pte(pte_t * src, pte_t * dst)
  67{
  68        int error = 0;
  69        pte_t pte = *src;
  70
  71        if (!pte_none(pte)) {
  72                error++;
  73                if (dst) {
  74                        pte_clear(src);
  75                        set_pte(dst, pte);
  76                        error--;
  77                }
  78        }
  79        return error;
  80}
  81
  82static int move_one_page(struct mm_struct *mm, unsigned long old_addr, unsigned long new_addr)
  83{
  84        int error = 0;
  85        pte_t * src;
  86
  87        src = get_one_pte(mm, old_addr);
  88        if (src)
  89                error = copy_one_pte(src, alloc_one_pte(mm, new_addr));
  90        return error;
  91}
  92
  93static int move_page_tables(struct mm_struct * mm,
  94        unsigned long new_addr, unsigned long old_addr, unsigned long len)
  95{
  96        unsigned long offset = len;
  97
  98        flush_cache_range(mm, old_addr, old_addr + len);
  99        flush_tlb_range(mm, old_addr, old_addr + len);
 100
 101        /*
 102         * This is not the clever way to do this, but we're taking the
 103         * easy way out on the assumption that most remappings will be
 104         * only a few pages.. This also makes error recovery easier.
 105         */
 106        while (offset) {
 107                offset -= PAGE_SIZE;
 108                if (move_one_page(mm, old_addr + offset, new_addr + offset))
 109                        goto oops_we_failed;
 110        }
 111        return 0;
 112
 113        /*
 114         * Ok, the move failed because we didn't have enough pages for
 115         * the new page table tree. This is unlikely, but we have to
 116         * take the possibility into account. In that case we just move
 117         * all the pages back (this will work, because we still have
 118         * the old page tables)
 119         */
 120oops_we_failed:
 121        flush_cache_range(mm, new_addr, new_addr + len);
 122        while ((offset += PAGE_SIZE) < len)
 123                move_one_page(mm, new_addr + offset, old_addr + offset);
 124        zap_page_range(mm, new_addr, new_addr + len);
 125        flush_tlb_range(mm, new_addr, new_addr + len);
 126        return -1;
 127}
 128
 129static inline unsigned long move_vma(struct vm_area_struct * vma,
 130        unsigned long addr, unsigned long old_len, unsigned long new_len)
 131{
 132        struct vm_area_struct * new_vma;
 133
 134        new_vma = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
 135        if (new_vma) {
 136                unsigned long new_addr = get_unmapped_area(addr, new_len);
 137
 138                if (new_addr && !move_page_tables(current->mm, new_addr, addr, old_len)) {
 139                        *new_vma = *vma;
 140                        new_vma->vm_start = new_addr;
 141                        new_vma->vm_end = new_addr+new_len;
 142                        new_vma->vm_offset = vma->vm_offset + (addr - vma->vm_start);
 143                        new_vma->vm_dentry = dget(vma->vm_dentry);
 144                        if (new_vma->vm_ops && new_vma->vm_ops->open)
 145                                new_vma->vm_ops->open(new_vma);
 146                        insert_vm_struct(current->mm, new_vma);
 147                        merge_segments(current->mm, new_vma->vm_start, new_vma->vm_end);
 148                        do_munmap(addr, old_len);
 149                        current->mm->total_vm += new_len >> PAGE_SHIFT;
 150                        return new_addr;
 151                }
 152                kmem_cache_free(vm_area_cachep, new_vma);
 153        }
 154        return -ENOMEM;
 155}
 156
 157/*
 158 * Expand (or shrink) an existing mapping, potentially moving it at the
 159 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
 160 */
 161asmlinkage unsigned long sys_mremap(unsigned long addr,
 162        unsigned long old_len, unsigned long new_len,
 163        unsigned long flags)
 164{
 165        struct vm_area_struct *vma;
 166        unsigned long ret = -EINVAL;
 167
 168        lock_kernel();
 169        if (addr & ~PAGE_MASK)
 170                goto out;
 171        old_len = PAGE_ALIGN(old_len);
 172        new_len = PAGE_ALIGN(new_len);
 173
 174        /*
 175         * Always allow a shrinking remap: that just unmaps
 176         * the unnecessary pages..
 177         */
 178        ret = addr;
 179        if (old_len > new_len) {
 180                do_munmap(addr+new_len, old_len - new_len);
 181                goto out;
 182        }
 183
 184        /*
 185         * Ok, we need to grow..
 186         */
 187        ret = -EFAULT;
 188        vma = find_vma(current->mm, addr);
 189        if (!vma || vma->vm_start > addr)
 190                goto out;
 191        /* We can't remap across vm area boundaries */
 192        if (old_len > vma->vm_end - addr)
 193                goto out;
 194        if (vma->vm_flags & VM_LOCKED) {
 195                unsigned long locked = current->mm->locked_vm << PAGE_SHIFT;
 196                locked += new_len - old_len;
 197                ret = -EAGAIN;
 198                if (locked > current->rlim[RLIMIT_MEMLOCK].rlim_cur)
 199                        goto out;
 200        }
 201        ret = -ENOMEM;
 202        if ((current->mm->total_vm << PAGE_SHIFT) + (new_len - old_len)
 203            > current->rlim[RLIMIT_AS].rlim_cur)
 204                goto out;
 205
 206        /* old_len exactly to the end of the area.. */
 207        if (old_len == vma->vm_end - addr &&
 208            (old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
 209                unsigned long max_addr = TASK_SIZE;
 210                if (vma->vm_next)
 211                        max_addr = vma->vm_next->vm_start;
 212                /* can we just expand the current mapping? */
 213                if (max_addr - addr >= new_len) {
 214                        int pages = (new_len - old_len) >> PAGE_SHIFT;
 215                        vma->vm_end = addr + new_len;
 216                        current->mm->total_vm += pages;
 217                        if (vma->vm_flags & VM_LOCKED)
 218                                current->mm->locked_vm += pages;
 219                        ret = addr;
 220                        goto out;
 221                }
 222        }
 223
 224        /*
 225         * We weren't able to just expand or shrink the area,
 226         * we need to create a new one and move it..
 227         */
 228        if (flags & MREMAP_MAYMOVE)
 229                ret = move_vma(vma, addr, old_len, new_len);
 230        else
 231                ret = -ENOMEM;
 232out:
 233        unlock_kernel();
 234        return ret;
 235}
 236