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>

5 files changed, 35 insertions, 33 deletions

diff --git a/sysdeps/x86/Makefile b/sysdeps/x86/Makefile
index bf913594c1..4d50b327b5 100644
--- a/sysdeps/x86/Makefile
+++ b/sysdeps/x86/Makefile
@@ -5,7 +5,11 @@ endif
 ifeq ($(subdir),elf)
 sysdep_routines += get-cpuid-feature-leaf
 sysdep-dl-routines += dl-get-cpu-features
-sysdep_headers += sys/platform/x86.h bits/platform/x86.h
+sysdep_headers += \
+  bits/platform/features.h \
+  bits/platform/x86.h \
+  sys/platform/x86.h \
+# sysdep_headers
 
 CFLAGS-dl-get-cpu-features.os += $(rtld-early-cflags)
 CFLAGS-get-cpuid-feature-leaf.o += $(no-stack-protector)
diff --git a/sysdeps/x86/bits/platform/features.h b/sysdeps/x86/bits/platform/features.h
new file mode 100644
index 0000000000..f02489266e
--- /dev/null
+++ b/sysdeps/x86/bits/platform/features.h
@@ -0,0 +1,27 @@
+/* Inline functions for x86 CPU features.
+   This file is part of the GNU C Library.
+   Copyright (C) 2024 Free Software Foundation, Inc.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _SYS_PLATFORM_X86_H
+# error "Never include <bits/platform/features.h> directly; use <sys/platform/x86.h> instead."
+#endif
+
+static __inline__ _Bool
+x86_cpu_cet_active (unsigned int __index)
+{
+  return false;
+}
diff --git a/sysdeps/x86/bits/platform/x86.h b/sysdeps/x86/bits/platform/x86.h
index c31d086194..8b157d99b3 100644
--- a/sysdeps/x86/bits/platform/x86.h
+++ b/sysdeps/x86/bits/platform/x86.h
@@ -337,11 +337,3 @@ enum
   x86_cpu_AVX10_YMM = x86_cpu_index_24_ecx_0_ebx + 17,
   x86_cpu_AVX10_ZMM = x86_cpu_index_24_ecx_0_ebx + 18,
 };
-
-/* Bits in the feature_1 field in TCB.  */
-
-enum
-{
-  x86_feature_1_ibt		= 1U << 0,
-  x86_feature_1_shstk		= 1U << 1
-};
diff --git a/sysdeps/x86/get-cpuid-feature-leaf.c b/sysdeps/x86/get-cpuid-feature-leaf.c
index e6a41cc79c..6f67346081 100644
--- a/sysdeps/x86/get-cpuid-feature-leaf.c
+++ b/sysdeps/x86/get-cpuid-feature-leaf.c
@@ -19,14 +19,6 @@
 #include <tcb-offsets.h>
 #include <ldsodefs.h>
 
-#ifdef __x86_64__
-# ifdef __LP64__
-_Static_assert (FEATURE_1_OFFSET == 72, "FEATURE_1_OFFSET != 72");
-# else
-_Static_assert (FEATURE_1_OFFSET == 40, "FEATURE_1_OFFSET != 40");
-# endif
-#endif
-
 const struct cpuid_feature *
 __x86_get_cpuid_feature_leaf (unsigned int leaf)
 {
diff --git a/sysdeps/x86/sys/platform/x86.h b/sysdeps/x86/sys/platform/x86.h
index 4d77c0991d..b8066ccc9f 100644
--- a/sysdeps/x86/sys/platform/x86.h
+++ b/sysdeps/x86/sys/platform/x86.h
@@ -22,6 +22,7 @@
 #include <features.h>
 #include <stdbool.h>
 #include <bits/platform/x86.h>
+#include <bits/platform/features.h>
 
 __BEGIN_DECLS
 
@@ -46,22 +47,8 @@ static __inline__ _Bool
 x86_cpu_active (unsigned int __index)
 {
   if (__index == x86_cpu_IBT || __index == x86_cpu_SHSTK)
-    {
-#ifdef __x86_64__
-      unsigned int __feature_1;
-# ifdef __LP64__
-      __asm__ ("mov %%fs:72, %0" : "=r" (__feature_1));
-# else
-      __asm__ ("mov %%fs:40, %0" : "=r" (__feature_1));
-# endif
-      if (__index == x86_cpu_IBT)
-	return __feature_1 & x86_feature_1_ibt;
-      else
-	return __feature_1 & x86_feature_1_shstk;
-#else
-      return false;
-#endif
-    }
+    return x86_cpu_cet_active (__index);
+
   const struct cpuid_feature *__ptr = __x86_get_cpuid_feature_leaf
     (__index / (8 * sizeof (unsigned int) * 4));
   unsigned int __reg