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      1 /*	$NetBSD: makecontext.c,v 1.5 2012/03/17 21:35:06 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 1.5 2012/03/17 21:35:06 martin Exp $");
     35 #endif
     36 
     37 #include <inttypes.h>
     38 #include <stddef.h>
     39 #include <sys/types.h>
     40 #include <ucontext.h>
     41 #include "extern.h"
     42 
     43 #include <stdarg.h>
     44 
     45 void
     46 makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
     47 {
     48 	__greg_t *gr = ucp->uc_mcontext.__gregs;
     49 	int i;
     50 	ulong *sp;
     51 	va_list ap;
     52 
     53 	/*LINTED*/
     54 	sp = (ulong *)((caddr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
     55 	/* Align on quad-word boundary. */
     56 	sp = (ulong *)((ulong)sp & ~0xf);
     57 
     58 	/* Make room for: argx, argd, struct return pointer(?), rwindow. */
     59 	sp -= (argc > 6 ? argc - 6 : 0) + 6 + 8 + 8;
     60 
     61 	va_start(ap, argc);
     62 
     63 	/* Pass up to 6 arguments in %o0-5. */
     64 	for (i = 0; i < argc && i < 6; i++)
     65 		gr[_REG_O0 + i] = sp[i + 16] = va_arg(ap, unsigned long);
     66 
     67 	/* Pass any additional arguments on the stack. */
     68 	for (; i < argc; i++)
     69 		sp[i + 16] = va_arg(ap, unsigned long);
     70 	va_end(ap);
     71 
     72 	sp[14] = (ulong)sp - 2047;
     73 	sp[15] = (ulong)_resumecontext - 8;
     74 
     75 	/*LINTED*/
     76 	sp = (ulong *)((caddr_t)sp - 2047);
     77 
     78 	gr[_REG_O6] = (__greg_t)sp;
     79 	gr[_REG_PC] = (__greg_t)func;
     80 	gr[_REG_nPC] = (__greg_t)func + 4;
     81 	gr[_REG_O7] = (__greg_t)_resumecontext - 8;
     82 
     83 }
     84