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      1 /*	$NetBSD: swapcontext.S,v 1.7 2025/05/03 19:56:21 riastradh Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 2003 Wasabi Systems, Inc.
      5  * All rights reserved.
      6  *
      7  * Written by Frank van der Linden for Wasabi Systems, Inc.
      8  *
      9  * Redistribution and use in source and binary forms, with or without
     10  * modification, are permitted provided that the following conditions
     11  * are met:
     12  * 1. Redistributions of source code must retain the above copyright
     13  *    notice, this list of conditions and the following disclaimer.
     14  * 2. Redistributions in binary form must reproduce the above copyright
     15  *    notice, this list of conditions and the following disclaimer in the
     16  *    documentation and/or other materials provided with the distribution.
     17  * 3. All advertising materials mentioning features or use of this software
     18  *    must display the following acknowledgement:
     19  *      This product includes software developed for the NetBSD Project by
     20  *      Wasabi Systems, Inc.
     21  * 4. The name of Wasabi Systems, Inc. may not be used to endorse
     22  *    or promote products derived from this software without specific prior
     23  *    written permission.
     24  *
     25  * THIS SOFTWARE IS PROVIDED BY WASABI SYSTEMS, INC. ``AS IS'' AND
     26  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     27  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     28  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL WASABI SYSTEMS, INC
     29  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     30  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     31  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     32  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     33  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     34  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     35  * POSSIBILITY OF SUCH DAMAGE.
     36  */
     37 
     38 #include <machine/asm.h>
     39 
     40 #if defined(LIBC_SCCS) && !defined(lint)
     41 	RCSID("$NetBSD: swapcontext.S,v 1.7 2025/05/03 19:56:21 riastradh Exp $")
     42 #endif /* LIBC_SCCS && !lint */
     43 
     44 /*
     45  * 56 == offsetof(ucontext_t, uc_mcontext)
     46  * 21 == _REG_RIP
     47  * 24 == _REG_URSP
     48  */
     49 
     50 ENTRY(swapcontext)
     51 	pushq	%rdi				/* preserve oucp */
     52 	pushq	%rsi				/* preserve ucp */
     53 	call	PIC_PLT(_C_LABEL(_getcontext))
     54 	popq	%rsi
     55 	popq	%rdi
     56 	testl	%eax,%eax
     57 	jnz	2f
     58 	movq	0(%rsp),%r11
     59 	movq	%r11,(56 + 21 * 8)(%rdi)
     60 	leaq	8(%rsp),%r11
     61 	movq	%r11,(56 + 24 * 8)(%rdi)
     62 	movq	%rsi,%rdi
     63 	call	PIC_PLT(_C_LABEL(setcontext))
     64 2:
     65 	ret
     66 END(swapcontext)
     67