FreeBSD/Linux Kernel Cross Reference
sys/sparc64/include/wstate.h

     /*-
      * Copyright (c) 1997 Berkeley Software Design, Inc. All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
      * 1. Redistributions of source code must retain the above copyright
      *    notice, this list of conditions and the following disclaimer.
      * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. Berkeley Software Design Inc's name may not be used to endorse or
     *    promote products derived from this software without specific prior
     *    written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      from: BSDI: wstate.h,v 1.4 1997/09/18 13:05:51 torek Exp
     * $FreeBSD: releng/6.0/sys/sparc64/include/wstate.h 91246 2002-02-25 18:37:17Z jake $
     */
    
    #ifndef _MACHINE_WSTATE_H_
    #define _MACHINE_WSTATE_H_
    
    /*
     * Window state register bits.
     *
     * There really are no bits per se, just the two fields WSTATE.NORMAL
     * and WSTATE.OTHER.  The rest is up to software.
     *
     * We use WSTATE_NORMAL to represent user mode or kernel mode saves
     * (whichever is currently in effect) and WSTATE_OTHER to represent
     * user mode saves (only).
     *
     * We use the low bit to suggest 32-bit mode, with the next bit set
     * once we succeed in saving in some mode.  That is, if the WSTATE_ASSUME
     * bit is set, the spill or fill handler we use will be one that makes
     * an assumption about the proper window-save mode.  If the spill or
     * fill fails with an alignment fault, the spill or fill op should
     * take the `assume' bit away retry the instruction that caused the
     * spill or fill.  This will use the new %wstate, which will test for
     * which mode to use.  The alignment fault code helps us out here by
     * resuming the spill vector at offset +70, where we are allowed to
     * execute two instructions (i.e., write to %wstate and RETRY).
     *
     * If the ASSUME bit is not set when the alignment fault occurs, the
     * given stack pointer is hopelessly wrong (and the spill, if it is a
     * spill, should be done as a sort of "panic spill") -- so those two
     * instructions will be a branch sequence.
     *
     * Note that locore.s assumes this same bit layout (since the translation
     * from "bits" to "{spill,fill}_N_{normal,other}" is done in hardware).
     *
     * The value 0 is preferred for unknown to make it easy to start in
     * unknown state and continue in whichever state unknown succeeds in --
     * a successful "other" save, for instance, can just set %wstate to
     * ASSUMExx << USERSHIFT and thus leave the kernel state "unknown".
     *
     * We also need values for managing the somewhat tricky transition from
     * user to kernel and back, so we use the one remaining free bit to mean
     * "although this looks like kernel mode, the window(s) involved are
     * user windows and should be saved ASI_AIUP".  Everything else is
     * otherwise the same, but we need not bother with assumptions in this
     * mode (we expect it to apply to at most one window spill or fill),
     * i.e., WSTATE_TRANSITION can ignore WSTATE_ASSUME if it likes.
     */
    
    #define WSTATE_NORMAL_MASK      1       /* wstate normal minus transition */
    #define WSTATE_OTHER_SHIFT      3       /* for wstate other / user */
    #define WSTATE_OTHER_MASK               /* wstate other minus nested */ \
            (WSTATE_NORMAL_MASK << WSTATE_OTHER_SHIFT)
    
    #define WSTATE_KERNEL           0       /* normal kernel wstate */
    #define WSTATE_USER_64          0       /* normal 64bit user wstate */
    #define WSTATE_USER_32          1       /* normal 32bit user wstate */
    
    #define WSTATE_TRANSITION       2       /* if set, force user window */
    #define WSTATE_NESTED                   /* if set, spill must not fault */ \
            (WSTATE_TRANSITION << WSTATE_OTHER_SHIFT)
    
    #endif /* !_MACHINE_WSTATE_H_ */

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