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
  53 unsigned 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 }