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      1 /*	$NetBSD: makecontext.c,v 1.4 2008/04/28 20:22:56 martin 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  *
     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 1.4 2008/04/28 20:22:56 martin Exp $");
     35 #endif
     36 
     37 #include <inttypes.h>
     38 #include <stddef.h>
     39 #include <ucontext.h>
     40 #include "extern.h"
     41 
     42 #if __STDC__
     43 #include <stdarg.h>
     44 #else
     45 #include <varargs.h>
     46 #endif
     47 
     48 
     49 void
     50 #if __STDC__
     51 makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
     52 #else
     53 makecontext(ucp, func, argc, va_alist)
     54 	ucontext_t *ucp;
     55 	void (*func)();
     56 	int argc;
     57 	va_dcl
     58 #endif
     59 {
     60 	__greg_t *gr = ucp->uc_mcontext.__gregs;
     61 	unsigned int *sp;
     62 	va_list ap;
     63 
     64 	/* LINTED __greg_t is safe */
     65 	gr[_REG_EIP] = (__greg_t)func;
     66 
     67 	/* LINTED uintptr_t is safe */
     68 	sp  = (unsigned int *)((uintptr_t)ucp->uc_stack.ss_sp +
     69 	    ucp->uc_stack.ss_size);
     70 	/* Align on word boundary. */
     71 	/* LINTED uintptr_t is safe */
     72 	sp  = (unsigned int *)((uintptr_t)sp & ~0x3);
     73 	sp -= argc + 1;			/* Make room for ret and args. */
     74 	/* LINTED __greg_t is safe */
     75 	gr[_REG_UESP] = (__greg_t)sp;
     76 	gr[_REG_EBP] = (__greg_t)0;	/* Wipe out frame pointer. */
     77 
     78 	/* Put return address on top of stack. */
     79 	/* LINTED uintptr_t is safe */
     80 	*sp++ = (uintptr_t)_resumecontext;
     81 
     82 	/* Construct argument list. */
     83 #if __STDC__
     84 	va_start(ap, argc);
     85 #else
     86 	va_start(ap);
     87 #endif
     88 	while (argc-- > 0) {
     89 		/* LINTED uintptr_t is safe */
     90 		*sp++ = va_arg(ap, uintptr_t);
     91 	}
     92 	va_end(ap);
     93 }
     94