LXR linux-bk/mm/mincore.c

   1/*
   2 *      linux/mm/mincore.c
   3 *
   4 * Copyright (C) 1994-1999  Linus Torvalds
   5 */
   6
   7/*
   8 * The mincore() system call.
   9 */
  10#include <linux/slab.h>
  11#include <linux/pagemap.h>
  12#include <linux/mm.h>
  13#include <linux/mman.h>
  14
  15#include <asm/uaccess.h>
  16#include <asm/pgtable.h>
  17#include <asm/pgalloc.h>
  18
  19/*
  20 * Later we can get more picky about what "in core" means precisely.
  21 * For now, simply check to see if the page is in the page cache,
  22 * and is up to date; i.e. that no page-in operation would be required
  23 * at this time if an application were to map and access this page.
  24 */
  25static unsigned char mincore_page(struct vm_area_struct * vma,
  26        unsigned long pgoff)
  27{
  28        unsigned char present = 0;
  29        struct address_space * as = vma->vm_file->f_dentry->d_inode->i_mapping;
  30        struct page * page;
  31
  32        page = find_get_page(as, pgoff);
  33        if (page) {
  34                present = PageUptodate(page);
  35                page_cache_release(page);
  36        }
  37
  38        return present;
  39}
  40
  41static long mincore_vma(struct vm_area_struct * vma,
  42        unsigned long start, unsigned long end, unsigned char * vec)
  43{
  44        long error, i, remaining;
  45        unsigned char * tmp;
  46
  47        error = -ENOMEM;
  48        if (!vma->vm_file)
  49                return error;
  50
  51        start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
  52        if (end > vma->vm_end)
  53                end = vma->vm_end;
  54        end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
  55
  56        error = -EAGAIN;
  57        tmp = (unsigned char *) __get_free_page(GFP_KERNEL);
  58        if (!tmp)
  59                return error;
  60
  61        /* (end - start) is # of pages, and also # of bytes in "vec */
  62        remaining = (end - start),
  63
  64        error = 0;
  65        for (i = 0; remaining > 0; remaining -= PAGE_SIZE, i++) {
  66                int j = 0;
  67                long thispiece = (remaining < PAGE_SIZE) ?
  68                                                remaining : PAGE_SIZE;
  69
  70                while (j < thispiece)
  71                        tmp[j++] = mincore_page(vma, start++);
  72
  73                if (copy_to_user(vec + PAGE_SIZE * i, tmp, thispiece)) {
  74                        error = -EFAULT;
  75                        break;
  76                }
  77        }
  78
  79        free_page((unsigned long) tmp);
  80        return error;
  81}
  82
  83/*
  84 * The mincore(2) system call.
  85 *
  86 * mincore() returns the memory residency status of the pages in the
  87 * current process's address space specified by [addr, addr + len).
  88 * The status is returned in a vector of bytes.  The least significant
  89 * bit of each byte is 1 if the referenced page is in memory, otherwise
  90 * it is zero.
  91 *
  92 * Because the status of a page can change after mincore() checks it
  93 * but before it returns to the application, the returned vector may
  94 * contain stale information.  Only locked pages are guaranteed to
  95 * remain in memory.
  96 *
  97 * return values:
  98 *  zero    - success
  99 *  -EFAULT - vec points to an illegal address
 100 *  -EINVAL - addr is not a multiple of PAGE_CACHE_SIZE,
 101 *              or len has a nonpositive value
 102 *  -ENOMEM - Addresses in the range [addr, addr + len] are
 103 *              invalid for the address space of this process, or
 104 *              specify one or more pages which are not currently
 105 *              mapped
 106 *  -EAGAIN - A kernel resource was temporarily unavailable.
 107 */
 108asmlinkage long sys_mincore(unsigned long start, size_t len,
 109        unsigned char * vec)
 110{
 111        int index = 0;
 112        unsigned long end;
 113        struct vm_area_struct * vma;
 114        int unmapped_error = 0;
 115        long error = -EINVAL;
 116
 117        down_read(&current->mm->mmap_sem);
 118
 119        if (start & ~PAGE_CACHE_MASK)
 120                goto out;
 121        len = (len + ~PAGE_CACHE_MASK) & PAGE_CACHE_MASK;
 122        end = start + len;
 123        if (end < start)
 124                goto out;
 125
 126        error = -EFAULT;
 127        if (!access_ok(VERIFY_WRITE, (unsigned long) vec, len >> PAGE_SHIFT))
 128                goto out;
 129
 130        error = 0;
 131        if (end == start)
 132                goto out;
 133
 134        /*
 135         * If the interval [start,end) covers some unmapped address
 136         * ranges, just ignore them, but return -ENOMEM at the end.
 137         */
 138        vma = find_vma(current->mm, start);
 139        for (;;) {
 140                /* Still start < end. */
 141                error = -ENOMEM;
 142                if (!vma)
 143                        goto out;
 144
 145                /* Here start < vma->vm_end. */
 146                if (start < vma->vm_start) {
 147                        unmapped_error = -ENOMEM;
 148                        start = vma->vm_start;
 149                }
 150
 151                /* Here vma->vm_start <= start < vma->vm_end. */
 152                if (end <= vma->vm_end) {
 153                        if (start < end) {
 154                                error = mincore_vma(vma, start, end,
 155                                                        &vec[index]);
 156                                if (error)
 157                                        goto out;
 158                        }
 159                        error = unmapped_error;
 160                        goto out;
 161                }
 162
 163                /* Here vma->vm_start <= start < vma->vm_end < end. */
 164                error = mincore_vma(vma, start, vma->vm_end, &vec[index]);
 165                if (error)
 166                        goto out;
 167                index += (vma->vm_end - start) >> PAGE_CACHE_SHIFT;
 168                start = vma->vm_end;
 169                vma = vma->vm_next;
 170        }
 171
 172out:
 173        up_read(&current->mm->mmap_sem);
 174        return error;
 175}
 176