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  * user_ok determines whether the access to user-space memory is allowed.
  28  * See the equivalent C-macro version below for clarity.
  29  *
  30  * On error, user_ok branches to a label indicated by parameter
  31  * <error>.  This implies that the macro falls through to the next
  32  * instruction on success.
  33  *
  34  * Note that while this macro can be used independently, we designed
  35  * in for optimal use in the access_ok macro below (i.e., we fall
  36  * through on success).
  37  *
  38  * On Entry:
  39  *      <aa>    register containing memory address
  40  *      <as>    register containing memory size
  41  *      <at>    temp register
  42  *      <error> label to branch to on error; implies fall-through
  43  *              macro on success
  44  * On Exit:
  45  *      <aa>    preserved
  46  *      <as>    preserved
  47  *      <at>    destroyed (actually, (TASK_SIZE + 1 - size))
  48  */
  49         .macro  user_ok aa, as, at, error
  50         movi    \at, __XTENSA_UL_CONST(TASK_SIZE)
  51         bgeu    \as, \at, \error
  52         sub     \at, \at, \as
  53         bgeu    \aa, \at, \error
  54         .endm
  55
  56 /*
  57  * access_ok determines whether a memory access is allowed.  See the
  58  * equivalent C-macro version below for clarity.
  59  *
  60  * On error, access_ok branches to a label indicated by parameter
  61  * <error>.  This implies that the macro falls through to the next
  62  * instruction on success.
  63  *
  64  * Note that we assume success is the common case, and we optimize the
  65  * branch fall-through case on success.
  66  *
  67  * On Entry:
  68  *      <aa>    register containing memory address
  69  *      <as>    register containing memory size
  70  *      <at>    temp register
  71  *      <sp>
  72  *      <error> label to branch to on error; implies fall-through
  73  *              macro on success
  74  * On Exit:
  75  *      <aa>    preserved
  76  *      <as>    preserved
  77  *      <at>    destroyed
  78  */
  79         .macro  access_ok  aa, as, at, sp, error
  80         user_ok    \aa, \as, \at, \error
  81 .Laccess_ok_\@:
  82         .endm
  83
  84 #endif  /* _XTENSA_ASM_UACCESS_H */