LXR linux/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  */
  70unsigned long __copy_from_user_hexagon(void *to, const void __user *from,
  71                                     unsigned long n);
  72unsigned 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
  92extern long __strnlen_user(const char __user *src, long n);
  93
  94static 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.  */
 100static 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
 117