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The C and C++ Include Header Files

/usr/include/x86_64-linux-gnu/bits/platform/features.h


$ cat -n /usr/include/x86_64-linux-gnu/bits/platform/features.h

     1	/* Inline functions for x86 CPU features.
     2	   This file is part of the GNU C Library.
     3	   Copyright (C) 2024 Free Software Foundation, Inc.
     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 _SYS_PLATFORM_X86_H
    20	# error "Never include <bits/platform/features.h> directly; use <sys/platform/x86.h> instead."
    21	#endif
    22	
    23	/* Bits in the feature_1 field in TCB.  */
    24	
    25	enum
    26	{
    27	  x86_feature_1_ibt		= 1U << 0,
    28	  x86_feature_1_shstk		= 1U << 1
    29	};
    30	
    31	static __inline__ _Bool
    32	x86_cpu_cet_active (unsigned int __index)
    33	{
    34	#ifdef __x86_64__
    35	  unsigned int __feature_1;
    36	# ifdef __LP64__
    37	  __asm__ ("mov %%fs:72, %0" : "=r" (__feature_1));
    38	# else
    39	  __asm__ ("mov %%fs:40, %0" : "=r" (__feature_1));
    40	# endif
    41	  if (__index == x86_cpu_IBT)
    42	    return __feature_1 & x86_feature_1_ibt;
    43	  else
    44	    return __feature_1 & x86_feature_1_shstk;
    45	#else
    46	  return false;
    47	#endif
    48	}