LXR linux/arch/hexagon/mm/uaccess.c

   1/*
   2 * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved.
   3 *
   4 * This program is free software; you can redistribute it and/or modify
   5 * it under the terms of the GNU General Public License version 2 and
   6 * only version 2 as published by the Free Software Foundation.
   7 *
   8 * This program is distributed in the hope that it will be useful,
   9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11 * GNU General Public License for more details.
  12 *
  13 * You should have received a copy of the GNU General Public License
  14 * along with this program; if not, write to the Free Software
  15 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  16 * 02110-1301, USA.
  17 */
  18
  19/*
  20 * Support for user memory access from kernel.  This will
  21 * probably be inlined for performance at some point, but
  22 * for ease of debug, and to a lesser degree for code size,
  23 * we implement here as subroutines.
  24 */
  25#include <linux/types.h>
  26#include <asm/uaccess.h>
  27#include <asm/pgtable.h>
  28
  29/*
  30 * For clear_user(), exploit previously defined copy_to_user function
  31 * and the fact that we've got a handy zero page defined in kernel/head.S
  32 *
  33 * dczero here would be even faster.
  34 */
  35__kernel_size_t __clear_user_hexagon(void __user *dest, unsigned long count)
  36{
  37        long uncleared;
  38
  39        while (count > PAGE_SIZE) {
  40                uncleared = __copy_to_user_hexagon(dest, &empty_zero_page,
  41                                                PAGE_SIZE);
  42                if (uncleared)
  43                        return count - (PAGE_SIZE - uncleared);
  44                count -= PAGE_SIZE;
  45                dest += PAGE_SIZE;
  46        }
  47        if (count)
  48                count = __copy_to_user_hexagon(dest, &empty_zero_page, count);
  49
  50        return count;
  51}
  52
  53unsigned long clear_user_hexagon(void __user *dest, unsigned long count)
  54{
  55        if (!access_ok(VERIFY_WRITE, dest, count))
  56                return count;
  57        else
  58                return __clear_user_hexagon(dest, count);
  59}
  60