1  /* Definition of __INDIRECT_RETURN.  x86 version.
       2     Copyright (C) 2018-2023 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