Home | History | Annotate | Line # | Download | only in gen 
      1 /*	$NetBSD: makecontext.c,v 1.4 2009/07/30 20:57:17 dsl 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  * Modified from the i386 version for x86_64 by fvdl (at) wasabisystems.com.
     32  *
     33  */
     34 
     35 #include <sys/cdefs.h>
     36 #if defined(LIBC_SCCS) && !defined(lint)
     37 __RCSID("$NetBSD: makecontext.c,v 1.4 2009/07/30 20:57:17 dsl Exp $");
     38 #endif
     39 
     40 #include <inttypes.h>
     41 #include <stddef.h>
     42 #include <ucontext.h>
     43 #include "extern.h"
     44 
     45 #include <stdarg.h>
     46 
     47 void
     48 makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
     49 {
     50 	__greg_t *gr = ucp->uc_mcontext.__gregs;
     51 	uintptr_t *sp;
     52 	va_list ap;
     53 	int stackargs, i;
     54 
     55 	stackargs = argc - 6;
     56 
     57 	/* LINTED __greg_t is safe */
     58 	gr[_REG_RIP] = (__greg_t)func;
     59 
     60 	/* LINTED uintptr_t is safe */
     61 	sp  = (uintptr_t *)
     62 	    ((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
     63 
     64 	/* LINTED uintptr_t is safe */
     65 	sp  = (uintptr_t *)(((uintptr_t)sp & ~15));
     66 	sp--;
     67 	if (stackargs > 0)
     68 		sp -= stackargs;
     69 	/* LINTED __greg_t is safe */
     70 	gr[_REG_RSP] = (__greg_t)sp;
     71 	gr[_REG_RBP] = (__greg_t)0;	/* Wipe out frame pointer. */
     72 
     73 	/* Put return address on top of stack. */
     74 	/* LINTED uintptr_t is safe */
     75 	*sp++ = (uintptr_t)_resumecontext;
     76 
     77 	/*
     78 	 * Construct argument list.
     79 	 * The registers used to pass the first 6 arguments
     80 	 * (rdi, rsi, rdx, rcx, r8, r9) are the first 6 in gregs,
     81 	 * in that order, so those arguments can just be copied to
     82 	 * the gregs array.
     83 	 */
     84 	va_start(ap, argc);
     85 	for (i = 0; i < 6 && argc > 0; i++) {
     86 		argc--;
     87 		/* LINTED __greg_t is safe */
     88 		gr[i] = va_arg(ap, __greg_t);
     89 	}
     90 
     91 	while (stackargs-- > 0) {
     92 		/* LINTED uintptr_t is safe */
     93 		*sp++ = va_arg(ap, uintptr_t);
     94 	}
     95 
     96 	va_end(ap);
     97 }
     98