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makecontext.c revision 1.1 
      1 /*	$NetBSD: makecontext.c,v 1.1 2003/01/30 02:07:31 fvdl 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  * Modified from the i386 version for x86_64 by fvdl (at) wasabisystems.com.
     39  *
     40  */
     41 
     42 #include <sys/cdefs.h>
     43 #if defined(LIBC_SCCS) && !defined(lint)
     44 __RCSID("$NetBSD: makecontext.c,v 1.1 2003/01/30 02:07:31 fvdl Exp $");
     45 #endif
     46 
     47 #include <inttypes.h>
     48 #include <stddef.h>
     49 #include <ucontext.h>
     50 #include "extern.h"
     51 
     52 #include <stdarg.h>
     53 
     54 void
     55 makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
     56 {
     57 	__greg_t *gr = ucp->uc_mcontext.__gregs;
     58 	uintptr_t *sp;
     59 	va_list ap;
     60 	int stackargs, i;
     61 
     62 	stackargs = argc - 6;
     63 
     64 	/* LINTED __greg_t is safe */
     65 	gr[_REG_RIP] = (__greg_t)func;
     66 
     67 	/* LINTED uintptr_t is safe */
     68 	sp  = (uintptr_t *)
     69 	    ((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
     70 
     71 	/* LINTED uintptr_t is safe */
     72 	sp  = (uintptr_t *)(((uintptr_t)sp & ~15) - 8);
     73 	sp--;
     74 	if (stackargs > 0)
     75 		sp -= stackargs;
     76 	/* LINTED __greg_t is safe */
     77 	gr[_REG_URSP] = (__greg_t)sp;
     78 	gr[_REG_RBP] = (__greg_t)0;	/* Wipe out frame pointer. */
     79 
     80 	/* Put return address on top of stack. */
     81 	/* LINTED uintptr_t is safe */
     82 	*sp++ = (uintptr_t)_resumecontext;
     83 
     84 	/*
     85 	 * Construct argument list.
     86 	 * The registers used to pass the first 6 arguments
     87 	 * (rdi, rsi, rdx, rcx, r8, r9) are the first 6 in gregs,
     88 	 * in that order, so those arguments can just be copied to
     89 	 * the gregs array.
     90 	 */
     91 	va_start(ap, argc);
     92 	for (i = 0; i < 6 && argc > 0; i++) {
     93 		argc--;
     94 		/* LINTED __greg_t is safe */
     95 		gr[i] = va_arg(ap, __greg_t);
     96 	}
     97 
     98 	while (stackargs-- > 0) {
     99 		/* LINTED uintptr_t is safe */
    100 		*sp++ = va_arg(ap, uintptr_t);
    101 	}
    102 
    103 	va_end(ap);
    104 }
    105