arch/frv/kernel/uaccess.c

   1 /* uaccess.c: userspace access functions
   2  *
   3  * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11
  12 #include <linux/mm.h>
  13 #include <linux/module.h>
  14 #include <linux/uaccess.h>
  15
  16 /*****************************************************************************/
  17 /*
  18  * copy a null terminated string from userspace
  19  */
  20 long strncpy_from_user(char *dst, const char __user *src, long count)
  21 {
  22         unsigned long max;
  23         char *p, ch;
  24         long err = -EFAULT;
  25
  26         BUG_ON(count < 0);
  27
  28         p = dst;
  29
  30 #ifndef CONFIG_MMU
  31         if ((unsigned long) src < memory_start)
  32                 goto error;
  33 #endif
  34
  35         if ((unsigned long) src >= get_addr_limit())
  36                 goto error;
  37
  38         max = get_addr_limit() - (unsigned long) src;
  39         if ((unsigned long) count > max) {
  40                 memset(dst + max, 0, count - max);
  41                 count = max;
  42         }
  43
  44         err = 0;
  45         for (; count > 0; count--, p++, src++) {
  46                 __get_user_asm(err, ch, src, "ub", "=r");
  47                 if (err < 0)
  48                         goto error;
  49                 if (!ch)
  50                         break;
  51                 *p = ch;
  52         }
  53
  54         err = p - dst; /* return length excluding NUL */
  55
  56  error:
  57         if (count > 0)
  58                 memset(p, 0, count); /* clear remainder of buffer [security] */
  59
  60         return err;
  61
  62 } /* end strncpy_from_user() */
  63
  64 EXPORT_SYMBOL(strncpy_from_user);
  65
  66 /*****************************************************************************/
  67 /*
  68  * Return the size of a string (including the ending 0)
  69  *
  70  * Return 0 on exception, a value greater than N if too long
  71  */
  72 long strnlen_user(const char __user *src, long count)
  73 {
  74         const char __user *p;
  75         long err = 0;
  76         char ch;
  77
  78         BUG_ON(count < 0);
  79
  80 #ifndef CONFIG_MMU
  81         if ((unsigned long) src < memory_start)
  82                 return 0;
  83 #endif
  84
  85         if ((unsigned long) src >= get_addr_limit())
  86                 return 0;
  87
  88         for (p = src; count > 0; count--, p++) {
  89                 __get_user_asm(err, ch, p, "ub", "=r");
  90                 if (err < 0)
  91                         return 0;
  92                 if (!ch)
  93                         break;
  94         }
  95
  96         return p - src + 1; /* return length including NUL */
  97
  98 } /* end strnlen_user() */
  99
 100 EXPORT_SYMBOL(strnlen_user);