lib/libc/arch/i386/gen/makecontext.c

   1 /*      $NetBSD: makecontext.c,v 1.3 2006/05/11 00:34:44 mrg 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 1.3 2006/05/11 00:34:44 mrg 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 }