lib/libc/arch/vax/gen/makecontext.c

   1 /*      $NetBSD: makecontext.c,v 1.4 2012/03/22 17:32:22 christos Exp $ */
   2
   3 /*-
   4  * Copyright (c) 2003 The NetBSD Foundation, Inc.
   5  * All rights reserved.
   6  *
   7  * This code is derived from software contributed to The NetBSD Foundation
   8  * by Matt Thomas.
   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 2012/03/22 17:32:22 christos Exp $");
  35 #endif
  36
  37 #include <stddef.h>
  38 #include <inttypes.h>
  39 #include <ucontext.h>
  40 #include "extern.h"
  41
  42 #include <stdarg.h>
  43
  44 void
  45 makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
  46 {
  47         __greg_t *gr = ucp->uc_mcontext.__gregs;
  48         va_list ap;
  49         int *sp;
  50         int i;
  51
  52         /* Compute and align stack pointer. */
  53         sp = (int *)
  54             (((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size) & ~0x3);
  55
  56         /*
  57          * Allocate necessary stack space for arguments including arg count
  58          * and call frame
  59          */
  60         sp -= argc + 1 + 5;
  61
  62         va_start(ap, argc);
  63         sp[5] = argc;
  64         for (i = 1; argc > 0; argc--, i++)
  65                 sp[5 + i] = va_arg(ap, int);
  66         va_end(ap);
  67
  68         sp[0] = 0;                      /* condition handler is null */
  69         sp[1] = 0x20000000;             /* make this a CALLS frame */
  70         sp[2] = 0;                      /* saved argument pointer */
  71         sp[3] = 0;                      /* saved frame pointer */
  72         sp[4] = (int)(uintptr_t)_resumecontext+2;/* return via trampoline code */
  73
  74         gr[_REG_AP] = (__greg_t)(uintptr_t)(sp + 5);
  75         gr[_REG_SP] = (__greg_t)(uintptr_t)sp;
  76         gr[_REG_FP] = (__greg_t)(uintptr_t)sp;
  77         gr[_REG_PC] = (__greg_t)(uintptr_t)func+2;
  78
  79 }