freebsd-dev/sys/sparc64/include/wstate.h

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/*-
* 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
* $FreeBSD$
*/
#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_ */