1 /* Definition of __INDIRECT_RETURN. x86 version. 2 Copyright (C) 2018-2021 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 <https://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