LXR linux/arch/xtensa/include/asm/asm-uaccess.h

   1/*
   2 * include/asm-xtensa/uaccess.h
   3 *
   4 * User space memory access functions
   5 *
   6 * These routines provide basic accessing functions to the user memory
   7 * space for the kernel. This header file provides functions such as:
   8 *
   9 * This file is subject to the terms and conditions of the GNU General Public
  10 * License.  See the file "COPYING" in the main directory of this archive
  11 * for more details.
  12 *
  13 * Copyright (C) 2001 - 2005 Tensilica Inc.
  14 */
  15
  16#ifndef _XTENSA_ASM_UACCESS_H
  17#define _XTENSA_ASM_UACCESS_H
  18
  19#include <linux/errno.h>
  20#include <asm/types.h>
  21
  22#include <asm/current.h>
  23#include <asm/asm-offsets.h>
  24#include <asm/processor.h>
  25
  26/*
  27 * These assembly macros mirror the C macros in asm/uaccess.h.  They
  28 * should always have identical functionality.  See
  29 * arch/xtensa/kernel/sys.S for usage.
  30 */
  31
  32#define KERNEL_DS       0
  33#define USER_DS         1
  34
  35#define get_ds          (KERNEL_DS)
  36
  37/*
  38 * get_fs reads current->thread.current_ds into a register.
  39 * On Entry:
  40 *      <ad>    anything
  41 *      <sp>    stack
  42 * On Exit:
  43 *      <ad>    contains current->thread.current_ds
  44 */
  45        .macro  get_fs  ad, sp
  46        GET_CURRENT(\ad,\sp)
  47#if THREAD_CURRENT_DS > 1020
  48        addi    \ad, \ad, TASK_THREAD
  49        l32i    \ad, \ad, THREAD_CURRENT_DS - TASK_THREAD
  50#else
  51        l32i    \ad, \ad, THREAD_CURRENT_DS
  52#endif
  53        .endm
  54
  55/*
  56 * set_fs sets current->thread.current_ds to some value.
  57 * On Entry:
  58 *      <at>    anything (temp register)
  59 *      <av>    value to write
  60 *      <sp>    stack
  61 * On Exit:
  62 *      <at>    destroyed (actually, current)
  63 *      <av>    preserved, value to write
  64 */
  65        .macro  set_fs  at, av, sp
  66        GET_CURRENT(\at,\sp)
  67        s32i    \av, \at, THREAD_CURRENT_DS
  68        .endm
  69
  70/*
  71 * kernel_ok determines whether we should bypass addr/size checking.
  72 * See the equivalent C-macro version below for clarity.
  73 * On success, kernel_ok branches to a label indicated by parameter
  74 * <success>.  This implies that the macro falls through to the next
  75 * insruction on an error.
  76 *
  77 * Note that while this macro can be used independently, we designed
  78 * in for optimal use in the access_ok macro below (i.e., we fall
  79 * through on error).
  80 *
  81 * On Entry:
  82 *      <at>            anything (temp register)
  83 *      <success>       label to branch to on success; implies
  84 *                      fall-through macro on error
  85 *      <sp>            stack pointer
  86 * On Exit:
  87 *      <at>            destroyed (actually, current->thread.current_ds)
  88 */
  89
  90#if ((KERNEL_DS != 0) || (USER_DS == 0))
  91# error Assembly macro kernel_ok fails
  92#endif
  93        .macro  kernel_ok  at, sp, success
  94        get_fs  \at, \sp
  95        beqz    \at, \success
  96        .endm
  97
  98/*
  99 * user_ok determines whether the access to user-space memory is allowed.
 100 * See the equivalent C-macro version below for clarity.
 101 *
 102 * On error, user_ok branches to a label indicated by parameter
 103 * <error>.  This implies that the macro falls through to the next
 104 * instruction on success.
 105 *
 106 * Note that while this macro can be used independently, we designed
 107 * in for optimal use in the access_ok macro below (i.e., we fall
 108 * through on success).
 109 *
 110 * On Entry:
 111 *      <aa>    register containing memory address
 112 *      <as>    register containing memory size
 113 *      <at>    temp register
 114 *      <error> label to branch to on error; implies fall-through
 115 *              macro on success
 116 * On Exit:
 117 *      <aa>    preserved
 118 *      <as>    preserved
 119 *      <at>    destroyed (actually, (TASK_SIZE + 1 - size))
 120 */
 121        .macro  user_ok aa, as, at, error
 122        movi    \at, __XTENSA_UL_CONST(TASK_SIZE)
 123        bgeu    \as, \at, \error
 124        sub     \at, \at, \as
 125        bgeu    \aa, \at, \error
 126        .endm
 127
 128/*
 129 * access_ok determines whether a memory access is allowed.  See the
 130 * equivalent C-macro version below for clarity.
 131 *
 132 * On error, access_ok branches to a label indicated by parameter
 133 * <error>.  This implies that the macro falls through to the next
 134 * instruction on success.
 135 *
 136 * Note that we assume success is the common case, and we optimize the
 137 * branch fall-through case on success.
 138 *
 139 * On Entry:
 140 *      <aa>    register containing memory address
 141 *      <as>    register containing memory size
 142 *      <at>    temp register
 143 *      <sp>
 144 *      <error> label to branch to on error; implies fall-through
 145 *              macro on success
 146 * On Exit:
 147 *      <aa>    preserved
 148 *      <as>    preserved
 149 *      <at>    destroyed
 150 */
 151        .macro  access_ok  aa, as, at, sp, error
 152        kernel_ok  \at, \sp, .Laccess_ok_\@
 153        user_ok    \aa, \as, \at, \error
 154.Laccess_ok_\@:
 155        .endm
 156
 157#endif  /* _XTENSA_ASM_UACCESS_H */
 158