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/*
  36 * get_fs reads current->thread.current_ds into a register.
  37 * On Entry:
  38 *      <ad>    anything
  39 *      <sp>    stack
  40 * On Exit:
  41 *      <ad>    contains current->thread.current_ds
  42 */
  43        .macro  get_fs  ad, sp
  44        GET_CURRENT(\ad,\sp)
  45#if THREAD_CURRENT_DS > 1020
  46        addi    \ad, \ad, TASK_THREAD
  47        l32i    \ad, \ad, THREAD_CURRENT_DS - TASK_THREAD
  48#else
  49        l32i    \ad, \ad, THREAD_CURRENT_DS
  50#endif
  51        .endm
  52
  53/*
  54 * set_fs sets current->thread.current_ds to some value.
  55 * On Entry:
  56 *      <at>    anything (temp register)
  57 *      <av>    value to write
  58 *      <sp>    stack
  59 * On Exit:
  60 *      <at>    destroyed (actually, current)
  61 *      <av>    preserved, value to write
  62 */
  63        .macro  set_fs  at, av, sp
  64        GET_CURRENT(\at,\sp)
  65        s32i    \av, \at, THREAD_CURRENT_DS
  66        .endm
  67
  68/*
  69 * kernel_ok determines whether we should bypass addr/size checking.
  70 * See the equivalent C-macro version below for clarity.
  71 * On success, kernel_ok branches to a label indicated by parameter
  72 * <success>.  This implies that the macro falls through to the next
  73 * insruction on an error.
  74 *
  75 * Note that while this macro can be used independently, we designed
  76 * in for optimal use in the access_ok macro below (i.e., we fall
  77 * through on error).
  78 *
  79 * On Entry:
  80 *      <at>            anything (temp register)
  81 *      <success>       label to branch to on success; implies
  82 *                      fall-through macro on error
  83 *      <sp>            stack pointer
  84 * On Exit:
  85 *      <at>            destroyed (actually, current->thread.current_ds)
  86 */
  87
  88#if ((KERNEL_DS != 0) || (USER_DS == 0))
  89# error Assembly macro kernel_ok fails
  90#endif
  91        .macro  kernel_ok  at, sp, success
  92        get_fs  \at, \sp
  93        beqz    \at, \success
  94        .endm
  95
  96/*
  97 * user_ok determines whether the access to user-space memory is allowed.
  98 * See the equivalent C-macro version below for clarity.
  99 *
 100 * On error, user_ok branches to a label indicated by parameter
 101 * <error>.  This implies that the macro falls through to the next
 102 * instruction on success.
 103 *
 104 * Note that while this macro can be used independently, we designed
 105 * in for optimal use in the access_ok macro below (i.e., we fall
 106 * through on success).
 107 *
 108 * On Entry:
 109 *      <aa>    register containing memory address
 110 *      <as>    register containing memory size
 111 *      <at>    temp register
 112 *      <error> label to branch to on error; implies fall-through
 113 *              macro on success
 114 * On Exit:
 115 *      <aa>    preserved
 116 *      <as>    preserved
 117 *      <at>    destroyed (actually, (TASK_SIZE + 1 - size))
 118 */
 119        .macro  user_ok aa, as, at, error
 120        movi    \at, __XTENSA_UL_CONST(TASK_SIZE)
 121        bgeu    \as, \at, \error
 122        sub     \at, \at, \as
 123        bgeu    \aa, \at, \error
 124        .endm
 125
 126/*
 127 * access_ok determines whether a memory access is allowed.  See the
 128 * equivalent C-macro version below for clarity.
 129 *
 130 * On error, access_ok branches to a label indicated by parameter
 131 * <error>.  This implies that the macro falls through to the next
 132 * instruction on success.
 133 *
 134 * Note that we assume success is the common case, and we optimize the
 135 * branch fall-through case on success.
 136 *
 137 * On Entry:
 138 *      <aa>    register containing memory address
 139 *      <as>    register containing memory size
 140 *      <at>    temp register
 141 *      <sp>
 142 *      <error> label to branch to on error; implies fall-through
 143 *              macro on success
 144 * On Exit:
 145 *      <aa>    preserved
 146 *      <as>    preserved
 147 *      <at>    destroyed
 148 */
 149        .macro  access_ok  aa, as, at, sp, error
 150        kernel_ok  \at, \sp, .Laccess_ok_\@
 151        user_ok    \aa, \as, \at, \error
 152.Laccess_ok_\@:
 153        .endm
 154
 155#endif  /* _XTENSA_ASM_UACCESS_H */
 156