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/* $NetBSD: makecontext.c,v 1.1 2014/09/19 17:36:25 matt Exp $ */
/*-
* Copyright (c) 2001 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Klaus Klein.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
__RCSID("$NetBSD: makecontext.c,v 1.1 2014/09/19 17:36:25 matt Exp $");
#endif
#include <inttypes.h>
#include <stddef.h>
#include <ucontext.h>
#include "extern.h"
#if __STDC__
#include <stdarg.h>
#else
#include <varargs.h>
#endif
void
makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
{
__greg_t *gr = ucp->uc_mcontext.__gregs;
long *sp;
int i;
va_list ap;
/* LINTED uintptr_t is safe */
sp = (long *)
((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
/* LINTED uintptr_t is safe */
sp -= 1 + (argc > 8 ? argc - 8: 0); /* Make room for call frame. */
sp = (long *) ((uintptr_t)sp & -16L); /* Align on 16byte boundary. */
/*
* Start executing at <func> -- when <func> completes, return to
* <_resumecontext>.
*/
gr[_REG_SP] = (uintptr_t)sp;
gr[_REG_RA] = (uintptr_t)_resumecontext;
gr[_REG_PC] = (uintptr_t)func;
/* Wipe out stack frame backchain pointer. */
*sp = 0;
/* Construct argument list. */
va_start(ap, argc);
/* Up to the first six arguments are passed in x18-x25 */
for (i = 0; i < argc && i < 8; i++)
gr[_REG_A0 + i] = va_arg(ap, int);
/* Pass remaining arguments on the stack above the backchain/lr gap. */
for (sp += 0; i < argc; i++)
*sp++ = va_arg(ap, long);
va_end(ap);
}
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