xref: /freebsd/lib/libsys/i386/getcontext.S (revision 7899f917b1c0ea178f1d2be0cfb452086d079d23)
1/*-
2 * Copyright (c) 2003 Peter Wemm <peter@FreeBSD.org>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27#include <machine/asm.h>
28#include <SYS.h>
29
30/*
31 * This has to be magic to handle the multiple returns.
32 * Otherwise, the setcontext() syscall will return here and we'll
33 * pop off the return address and go to the *setcontext* call.
34 */
35	WEAK_REFERENCE(__sys_getcontext, _getcontext)
36	WEAK_REFERENCE(__sys_getcontext, getcontext)
37ENTRY(__sys_getcontext)
38	movl	(%esp),%ecx	/* save getcontext return address */
39	_SYSCALL(getcontext)
40	jb	HIDENAME(cerror)
41	addl	$4,%esp		/* remove stale (setcontext) return address */
42	jmp	*%ecx		/* restore return address */
43END(__sys_getcontext)
44
45	.section .note.GNU-stack,"",%progbits
46