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makecontext.c revision 1.2 
      1 /*	$NetBSD: makecontext.c,v 1.2 2003/01/18 11:08:11 thorpej Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1999 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  * 3. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *        This product includes software developed by the NetBSD
     21  *        Foundation, Inc. and its contributors.
     22  * 4. Neither the name of The NetBSD Foundation nor the names of its
     23  *    contributors may be used to endorse or promote products derived
     24  *    from this software without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     27  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     28  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     29  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     30  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     31  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     32  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     33  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     34  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     35  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     36  * POSSIBILITY OF SUCH DAMAGE.
     37  */
     38 
     39 #include <sys/cdefs.h>
     40 #if defined(LIBC_SCCS) && !defined(lint)
     41 __RCSID("$NetBSD: makecontext.c,v 1.2 2003/01/18 11:08:11 thorpej Exp $");
     42 #endif
     43 
     44 #include <inttypes.h>
     45 #include <stddef.h>
     46 #include <ucontext.h>
     47 #include "extern.h"
     48 
     49 #if __STDC__
     50 #include <stdarg.h>
     51 #else
     52 #include <varargs.h>
     53 #endif
     54 
     55 
     56 void
     57 #if __STDC__
     58 makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
     59 #else
     60 makecontext(ucp, func, argc, va_alist)
     61 	ucontext_t *ucp;
     62 	void (*func)();
     63 	int argc;
     64 	va_dcl
     65 #endif
     66 {
     67 	__greg_t *gr = ucp->uc_mcontext.__gregs;
     68 	unsigned int *sp;
     69 	va_list ap;
     70 
     71 	/* LINTED __greg_t is safe */
     72 	gr[_REG_EIP] = (__greg_t)func;
     73 
     74 	/* LINTED uintptr_t is safe */
     75 	sp  = (int *)((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
     76 	/* LINTED uintptr_t is safe */
     77 	sp  = (int *)((uintptr_t)sp & ~0x3);	/* Align on word boundary. */
     78 	sp -= argc + 1;			/* Make room for ret and args. */
     79 	/* LINTED __greg_t is safe */
     80 	gr[_REG_UESP] = (__greg_t)sp;
     81 	gr[_REG_EBP] = (__greg_t)0;	/* Wipe out frame pointer. */
     82 
     83 	/* Put return address on top of stack. */
     84 	/* LINTED uintptr_t is safe */
     85 	*sp++ = (uintptr_t)_resumecontext;
     86 
     87 	/* Construct argument list. */
     88 #if __STDC__
     89 	va_start(ap, argc);
     90 #else
     91 	va_start(ap);
     92 #endif
     93 	while (argc-- > 0) {
     94 		/* LINTED uintptr_t is safe */
     95 		*sp++ = va_arg(ap, uintptr_t);
     96 	}
     97 	va_end(ap);
     98 }
     99