1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 
  22 /*
  23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26 
  27 /*      Copyright (c) 1988 AT&T     */
  28 /*        All Rights Reserved   */
  29 
  30 #pragma ident   "%Z%%M% %I%     %E% SMI"
  31 
  32 #pragma weak _makecontext = makecontext
  33 
  34 #include "lint.h"
  35 #include <stdarg.h>
  36 #include <ucontext.h>
  37 #include <sys/stack.h>
  38 
  39 /*
  40  * The ucontext_t that the user passes in must have been primed with a
  41  * call to getcontext(2), have the uc_stack member set to reflect the
  42  * stack which this context will use, and have the uc_link member set
  43  * to the context which should be resumed when this context returns.
  44  * When makecontext() returns, the ucontext_t will be set to run the
  45  * given function with the given parameters on the stack specified by
  46  * uc_stack, and which will return to the ucontext_t specified by uc_link.
  47  */
  48 
  49 static void resumecontext(void);
  50 
  51 void
  52 makecontext(ucontext_t *ucp, void (*func)(), int argc, ...)
  53 {
  54         long *sp;
  55         long *tsp;
  56         va_list ap;
  57         size_t size;
  58 
  59         ucp->uc_mcontext.gregs[EIP] = (greg_t)func;
  60 
  61         size = sizeof (long) * (argc + 1);
  62 
  63         sp = (long *)(((uintptr_t)ucp->uc_stack.ss_sp +
  64             ucp->uc_stack.ss_size - size) & ~(STACK_ALIGN - 1));
  65 
  66         tsp = sp + 1;
  67 
  68         va_start(ap, argc);
  69 
  70         while (argc-- > 0) {
  71                 *tsp++ = va_arg(ap, long);
  72         }
  73 
  74         va_end(ap);
  75 
  76         *sp = (long)resumecontext;              /* return address */
  77 
  78         ucp->uc_mcontext.gregs[UESP] = (greg_t)sp;
  79 }
  80 
  81 
  82 static void
  83 resumecontext(void)
  84 {
  85         ucontext_t uc;
  86 
  87         (void) getcontext(&uc);
  88         (void) setcontext(uc.uc_link);
  89 }