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makecontext.c revision 1.2 
      1 /*	$NetBSD: makecontext.c,v 1.2 2003/01/18 11:06:24 thorpej 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 1.2 2003/01/18 11:06:24 thorpej Exp $");
     42 #endif
     43 
     44 #include <stddef.h>
     45 #include <inttypes.h>
     46 #include <ucontext.h>
     47 #include "extern.h"
     48 
     49 #include <stdarg.h>
     50 
     51 void
     52 makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
     53 {
     54 	__greg_t *gr = ucp->uc_mcontext.__gregs;
     55 	int i;
     56 	unsigned int *sp;
     57 	va_list ap;
     58 
     59 	/* Compute and align stack pointer. */
     60 	sp = (unsigned int *)
     61 	    (((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size) & ~7);
     62 	/* Allocate necessary stack space for arguments exceeding r0-3. */
     63 	if (argc > 4)
     64 		sp -= argc - 4;
     65 	gr[_REG_SP] = (__greg_t)sp;
     66 	/* Wipe out frame pointer. */
     67 	gr[_REG_FP] = 0;
     68 	/* Arrange for return via the trampoline code. */
     69 	gr[_REG_LR] = (__greg_t)_resumecontext;
     70 	gr[_REG_PC] = (__greg_t)func;
     71 
     72 	va_start(ap, argc);
     73 	/* Pass up to four arguments in r0-3. */
     74 	for (i = 0; i < argc && i < 4; i++)
     75 		gr[_REG_R0 + i] = va_arg(ap, int);
     76 	/* Pass any additional arguments on the stack. */
     77 	for (argc -= i; argc > 0; argc--)
     78 		*sp++ = va_arg(ap, int);
     79 	va_end(ap);
     80 }
     81