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makecontext.c revision 1.3 
      1 /*	$NetBSD: makecontext.c,v 1.3 2003/10/09 00:17:59 kleink 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  * 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 1.3 2003/10/09 00:17:59 kleink 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 void
     56 makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
     57 {
     58 	__greg_t *gr = ucp->uc_mcontext.__gregs;
     59 	int *sp;
     60 	int i;
     61 	va_list ap;
     62 
     63 	/* LINTED uintptr_t is safe */
     64 	sp  = (int *)
     65 	    ((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
     66 	/* LINTED uintptr_t is safe */
     67 	sp -= 2 + (argc > 8 ? argc - 8: 0); /* Make room for call frame. */
     68 	sp  = (int *)
     69 	    ((uintptr_t)sp & ~0xf);	/* Align on quad-word boundary. */
     70 
     71 	/*
     72 	 * Start executing at <func> -- when <func> completes, return to
     73 	 * <_resumecontext>.
     74 	 */
     75 	gr[_REG_R1]  = (__greg_t)sp;
     76 	gr[_REG_LR] = (__greg_t)_resumecontext;
     77 	gr[_REG_PC] = (__greg_t)func;
     78 
     79 	/* Wipe out stack frame backchain pointer. */
     80 	*sp = 0;
     81 
     82 	/* Construct argument list. */
     83 	va_start(ap, argc);
     84 	/* Up to the first eight arguments are passed in r3-10. */
     85 	for (i = 0; i < argc && i < 8; i++)
     86 		gr[_REG_R3 + i] = va_arg(ap, int);
     87 	/* Pass remaining arguments on the stack above the backchain/lr gap. */
     88 	for (sp += 2; i < argc; i++)
     89 		*sp++ = va_arg(ap, int);
     90 	va_end(ap);
     91 }
     92