1/* Definition of __INDIRECT_RETURN. x86 version.
2 Copyright (C) 2018-2019 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <http://www.gnu.org/licenses/>. */
18
19#ifndef _UCONTEXT_H
20# error "Never include <bits/indirect-return.h> directly; use <ucontext.h> instead."
21#endif
22
23/* On x86, swapcontext returns via indirect branch when the shadow stack
24 is enabled. Define __INDIRECT_RETURN to indicate whether swapcontext
25 returns via indirect branch. */
26#if defined __CET__ && (__CET__ & 2) != 0
27# if __glibc_has_attribute (__indirect_return__)
28# define __INDIRECT_RETURN __attribute__ ((__indirect_return__))
29# else
30/* Newer compilers provide the indirect_return attribute, but without
31 it we can use returns_twice to affect the optimizer in the same
32 way and avoid unsafe optimizations. */
33# define __INDIRECT_RETURN __attribute__ ((__returns_twice__))
34# endif
35#else
36# define __INDIRECT_RETURN
37#endif
38