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

   1 /*      $NetBSD: makecontext.c,v 1.2 2003/01/18 11:06:24 thorpej Exp $  */
   2
   3 /*-
   4  * Copyright (c) 2001 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 1.2 2003/01/18 11:06:24 thorpej 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         int i;
  49         unsigned int *sp;
  50         va_list ap;
  51
  52         /* Compute and align stack pointer. */
  53         sp = (unsigned int *)
  54             (((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size) & ~7);
  55         /* Allocate necessary stack space for arguments exceeding r0-3. */
  56         if (argc > 4)
  57                 sp -= argc - 4;
  58         gr[_REG_SP] = (__greg_t)sp;
  59         /* Wipe out frame pointer. */
  60         gr[_REG_FP] = 0;
  61         /* Arrange for return via the trampoline code. */
  62         gr[_REG_LR] = (__greg_t)_resumecontext;
  63         gr[_REG_PC] = (__greg_t)func;
  64
  65         va_start(ap, argc);
  66         /* Pass up to four arguments in r0-3. */
  67         for (i = 0; i < argc && i < 4; i++)
  68                 gr[_REG_R0 + i] = va_arg(ap, int);
  69         /* Pass any additional arguments on the stack. */
  70         for (argc -= i; argc > 0; argc--)
  71                 *sp++ = va_arg(ap, int);
  72         va_end(ap);
  73 }