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      1 /*	$NetBSD: makecontext.c,v 1.3 2008/04/28 20:22:56 martin Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2001 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Klaus Klein.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 #include <sys/cdefs.h>
     33 #if defined(LIBC_SCCS) && !defined(lint)
     34 __RCSID("$NetBSD: makecontext.c,v 1.3 2008/04/28 20:22:56 martin Exp $");
     35 #endif
     36 
     37 #include <sys/types.h>
     38 #include <inttypes.h>
     39 #include <ucontext.h>
     40 #include "extern.h"
     41 
     42 #include <stdarg.h>
     43 
     44 void
     45 makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
     46 {
     47 	mcontext_t *mcp = &ucp->uc_mcontext;
     48 	int *sp;
     49 	va_list ap;
     50 
     51 	mcp->__gregs[_REG_PC] = (__greg_t)func;
     52 
     53 	sp  = (int *)((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
     54 	sp  = (int *)((uintptr_t)sp & ~0x3);	/* Align on word boundary. */
     55 	sp -= (argc + 1);		/* Make room for retaddr and args. */
     56 	mcp->__gregs[_REG_A7] = (__greg_t)sp;
     57 	mcp->__gregs[_REG_A6] = 0;		/* Wipe out frame pointer. */
     58 
     59 	*sp++ = (int)_resumecontext;
     60 
     61 	va_start(ap, argc);
     62 	while (argc-- > 0)
     63 		*sp++ = va_arg(ap, int);
     64 	va_end(ap);
     65 }
     66