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x86-64/cet: Make CET feature check specific to Linux/x86
CET feature bits in TCB, which are Linux specific, are used to check if CET features are active. Move CET feature check to Linux/x86 directory. Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>
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48
sysdeps/unix/sysv/linux/x86/bits/platform/features.h
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48
sysdeps/unix/sysv/linux/x86/bits/platform/features.h
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@ -0,0 +1,48 @@
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/* Inline functions for x86 CPU features.
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This file is part of the GNU C Library.
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Copyright (C) 2024 Free Software Foundation, Inc.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#ifndef _SYS_PLATFORM_X86_H
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# error "Never include <bits/platform/features.h> directly; use <sys/platform/x86.h> instead."
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#endif
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/* Bits in the feature_1 field in TCB. */
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enum
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{
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x86_feature_1_ibt = 1U << 0,
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x86_feature_1_shstk = 1U << 1
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};
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static __inline__ _Bool
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x86_cpu_cet_active (unsigned int __index)
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{
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#ifdef __x86_64__
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unsigned int __feature_1;
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# ifdef __LP64__
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__asm__ ("mov %%fs:72, %0" : "=r" (__feature_1));
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# else
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__asm__ ("mov %%fs:40, %0" : "=r" (__feature_1));
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# endif
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if (__index == x86_cpu_IBT)
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return __feature_1 & x86_feature_1_ibt;
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else
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return __feature_1 & x86_feature_1_shstk;
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#else
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return false;
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#endif
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}
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@ -54,6 +54,14 @@ dl_cet_get_cet_status (void)
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return status;
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}
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static __always_inline bool
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dl_cet_ibt_enabled (void)
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{
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unsigned int feature_1 = THREAD_GETMEM (THREAD_SELF,
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header.feature_1);
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return (feature_1 & GNU_PROPERTY_X86_FEATURE_1_IBT) != 0;
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}
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/* Enable shadow stack with a macro to avoid shadow stack underflow. */
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#define ENABLE_X86_CET(cet_feature) \
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if ((cet_feature & GNU_PROPERTY_X86_FEATURE_1_SHSTK)) \
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24
sysdeps/unix/sysv/linux/x86_64/get-cpuid-feature-leaf.c
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24
sysdeps/unix/sysv/linux/x86_64/get-cpuid-feature-leaf.c
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@ -0,0 +1,24 @@
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/* Get CPUID feature leaf. Linux/x86-64 version.
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Copyright (C) 2024 Free Software Foundation, Inc.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <sysdeps/x86/get-cpuid-feature-leaf.c>
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#ifdef __LP64__
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_Static_assert (FEATURE_1_OFFSET == 72, "FEATURE_1_OFFSET != 72");
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#else
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_Static_assert (FEATURE_1_OFFSET == 40, "FEATURE_1_OFFSET != 40");
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#endif
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@ -5,7 +5,11 @@ endif
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ifeq ($(subdir),elf)
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sysdep_routines += get-cpuid-feature-leaf
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sysdep-dl-routines += dl-get-cpu-features
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sysdep_headers += sys/platform/x86.h bits/platform/x86.h
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sysdep_headers += \
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bits/platform/features.h \
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bits/platform/x86.h \
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sys/platform/x86.h \
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# sysdep_headers
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CFLAGS-dl-get-cpu-features.os += $(rtld-early-cflags)
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CFLAGS-get-cpuid-feature-leaf.o += $(no-stack-protector)
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27
sysdeps/x86/bits/platform/features.h
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27
sysdeps/x86/bits/platform/features.h
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@ -0,0 +1,27 @@
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/* Inline functions for x86 CPU features.
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This file is part of the GNU C Library.
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Copyright (C) 2024 Free Software Foundation, Inc.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#ifndef _SYS_PLATFORM_X86_H
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# error "Never include <bits/platform/features.h> directly; use <sys/platform/x86.h> instead."
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#endif
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static __inline__ _Bool
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x86_cpu_cet_active (unsigned int __index)
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{
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return false;
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}
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@ -337,11 +337,3 @@ enum
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x86_cpu_AVX10_YMM = x86_cpu_index_24_ecx_0_ebx + 17,
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x86_cpu_AVX10_ZMM = x86_cpu_index_24_ecx_0_ebx + 18,
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};
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/* Bits in the feature_1 field in TCB. */
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enum
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{
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x86_feature_1_ibt = 1U << 0,
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x86_feature_1_shstk = 1U << 1
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};
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@ -19,14 +19,6 @@
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#include <tcb-offsets.h>
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#include <ldsodefs.h>
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#ifdef __x86_64__
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# ifdef __LP64__
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_Static_assert (FEATURE_1_OFFSET == 72, "FEATURE_1_OFFSET != 72");
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# else
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_Static_assert (FEATURE_1_OFFSET == 40, "FEATURE_1_OFFSET != 40");
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# endif
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#endif
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const struct cpuid_feature *
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__x86_get_cpuid_feature_leaf (unsigned int leaf)
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{
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@ -22,6 +22,7 @@
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#include <features.h>
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#include <stdbool.h>
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#include <bits/platform/x86.h>
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#include <bits/platform/features.h>
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__BEGIN_DECLS
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@ -46,22 +47,8 @@ static __inline__ _Bool
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x86_cpu_active (unsigned int __index)
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{
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if (__index == x86_cpu_IBT || __index == x86_cpu_SHSTK)
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{
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#ifdef __x86_64__
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unsigned int __feature_1;
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# ifdef __LP64__
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__asm__ ("mov %%fs:72, %0" : "=r" (__feature_1));
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# else
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__asm__ ("mov %%fs:40, %0" : "=r" (__feature_1));
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# endif
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if (__index == x86_cpu_IBT)
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return __feature_1 & x86_feature_1_ibt;
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else
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return __feature_1 & x86_feature_1_shstk;
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#else
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return false;
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#endif
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}
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return x86_cpu_cet_active (__index);
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const struct cpuid_feature *__ptr = __x86_get_cpuid_feature_leaf
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(__index / (8 * sizeof (unsigned int) * 4));
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unsigned int __reg
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@ -587,10 +587,11 @@ x86_64_rewrite_plt (struct link_map *map, ElfW(Addr) plt_rewrite)
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const ElfW(Rela) *reloc = (const void *) start;
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const ElfW(Rela) *reloc_end = (const void *) (start + size);
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unsigned int feature_1 = THREAD_GETMEM (THREAD_SELF,
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header.feature_1);
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bool ibt_enabled_p
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= (feature_1 & GNU_PROPERTY_X86_FEATURE_1_IBT) != 0;
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# ifdef __CET__
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bool ibt_enabled_p = dl_cet_ibt_enabled ();
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# else
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bool ibt_enabled_p = false;
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# endif
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if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_FILES))
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_dl_debug_printf ("\nchanging PLT in '%s' to direct branch\n",
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