arch/hexagon/include/asm/uaccess.h

   1 /*
   2  * User memory access support for Hexagon
   3  *
   4  * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 and
   8  * only version 2 as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  18  * 02110-1301, USA.
  19  */
  20
  21 #ifndef _ASM_UACCESS_H
  22 #define _ASM_UACCESS_H
  23 /*
  24  * User space memory access functions
  25  */
  26 #include <linux/sched.h>
  27 #include <linux/mm.h>
  28 #include <asm/segment.h>
  29 #include <asm/sections.h>
  30
  31 /*
  32  * access_ok: - Checks if a user space pointer is valid
  33  * @type: Type of access: %VERIFY_READ or %VERIFY_WRITE.  Note that
  34  *        %VERIFY_WRITE is a superset of %VERIFY_READ - if it is safe
  35  *        to write to a block, it is always safe to read from it.
  36  * @addr: User space pointer to start of block to check
  37  * @size: Size of block to check
  38  *
  39  * Context: User context only.  This function may sleep.
  40  *
  41  * Checks if a pointer to a block of memory in user space is valid.
  42  *
  43  * Returns true (nonzero) if the memory block *may* be valid, false (zero)
  44  * if it is definitely invalid.
  45  *
  46  * User address space in Hexagon, like x86, goes to 0xbfffffff, so the
  47  * simple MSB-based tests used by MIPS won't work.  Some further
  48  * optimization is probably possible here, but for now, keep it
  49  * reasonably simple and not *too* slow.  After all, we've got the
  50  * MMU for backup.
  51  */
  52 #define VERIFY_READ     0
  53 #define VERIFY_WRITE    1
  54
  55 #define __access_ok(addr, size) \
  56         ((get_fs().seg == KERNEL_DS.seg) || \
  57         (((unsigned long)addr < get_fs().seg) && \
  58           (unsigned long)size < (get_fs().seg - (unsigned long)addr)))
  59
  60 /*
  61  * When a kernel-mode page fault is taken, the faulting instruction
  62  * address is checked against a table of exception_table_entries.
  63  * Each entry is a tuple of the address of an instruction that may
  64  * be authorized to fault, and the address at which execution should
  65  * be resumed instead of the faulting instruction, so as to effect
  66  * a workaround.
  67  */
  68
  69 /*  Assembly somewhat optimized copy routines  */
  70 unsigned long __copy_from_user_hexagon(void *to, const void __user *from,
  71                                      unsigned long n);
  72 unsigned long __copy_to_user_hexagon(void __user *to, const void *from,
  73                                    unsigned long n);
  74
  75 #define __copy_from_user(to, from, n) __copy_from_user_hexagon(to, from, n)
  76 #define __copy_to_user(to, from, n) __copy_to_user_hexagon(to, from, n)
  77
  78 /*
  79  * XXX todo: some additonal performance gain is possible by
  80  * implementing __copy_to/from_user_inatomic, which is much
  81  * like __copy_to/from_user, but performs slightly less checking.
  82  */
  83
  84 __kernel_size_t __clear_user_hexagon(void __user *dest, unsigned long count);
  85 #define __clear_user(a, s) __clear_user_hexagon((a), (s))
  86
  87 #define __strncpy_from_user(dst, src, n) hexagon_strncpy_from_user(dst, src, n)
  88
  89 /*  get around the ifndef in asm-generic/uaccess.h  */
  90 #define __strnlen_user __strnlen_user
  91
  92 extern long __strnlen_user(const char __user *src, long n);
  93
  94 static inline long hexagon_strncpy_from_user(char *dst, const char __user *src,
  95                                              long n);
  96
  97 #include <asm-generic/uaccess.h>
  98
  99 /*  Todo:  an actual accelerated version of this.  */
 100 static inline long hexagon_strncpy_from_user(char *dst, const char __user *src,
 101                                              long n)
 102 {
 103         long res = __strnlen_user(src, n);
 104
 105         /* return from strnlen can't be zero -- that would be rubbish. */
 106
 107         if (res > n) {
 108                 copy_from_user(dst, src, n);
 109                 return n;
 110         } else {
 111                 copy_from_user(dst, src, res);
 112                 return res-1;
 113         }
 114 }
 115
 116 #endif