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      1 /*	$NetBSD: contextspfunc.S,v 1.1 2025/04/21 02:33:45 riastradh Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2025 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     26  * POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 
     29 #define	_LOCORE
     30 
     31 #include <machine/asm.h>
     32 
     33 RCSID("$NetBSD: contextspfunc.S,v 1.1 2025/04/21 02:33:45 riastradh Exp $")
     34 
     35 /*
     36  * contextspfunc()
     37  *
     38  *	makecontext(3) function.  Store the stack pointer on entry at
     39  *	the global variable contextsp and call contextdone.
     40  */
     41 ENTRY(contextspfunc)
     42 	/*
     43 	 * `The end of the input argument area shall be aligned on a
     44 	 *  [16-byte] boundary.  In other words, the value of (%rsp + 8)
     45 	 *  is always a multiple of 16 when control is transferred to
     46 	 *  the function entry point.'
     47 	 *
     48 	 * To make it convenient for t_signal_and_sp.c, we subtract 8
     49 	 * from %rsp in order to get something congruent to zero modulo
     50 	 * the stack alignemnt.
     51 	 */
     52 	movq	%rsp,_C_LABEL(contextsp)(%rip)
     53 	addq	$-8,_C_LABEL(contextsp)(%rip)
     54 	call	_C_LABEL(contextdone)
     55 END(contextspfunc)
     56