x86-64/cet: Make CET feature check specific to Linux/x86
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Commit Message
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.
---
.../sysv/linux/x86/bits/platform/features.h | 48 +++++++++++++++++++
sysdeps/unix/sysv/linux/x86_64/dl-cet.h | 8 ++++
.../linux/x86_64/get-cpuid-feature-leaf.c | 24 ++++++++++
sysdeps/x86/Makefile | 6 ++-
sysdeps/x86/bits/platform/features.h | 27 +++++++++++
sysdeps/x86/bits/platform/x86.h | 8 ----
sysdeps/x86/get-cpuid-feature-leaf.c | 8 ----
sysdeps/x86/sys/platform/x86.h | 19 ++------
sysdeps/x86_64/dl-machine.h | 9 ++--
9 files changed, 120 insertions(+), 37 deletions(-)
create mode 100644 sysdeps/unix/sysv/linux/x86/bits/platform/features.h
create mode 100644 sysdeps/unix/sysv/linux/x86_64/get-cpuid-feature-leaf.c
create mode 100644 sysdeps/x86/bits/platform/features.h
Comments
On Wed, Jan 10, 2024 at 8:49 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> 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.
> ---
> .../sysv/linux/x86/bits/platform/features.h | 48 +++++++++++++++++++
> sysdeps/unix/sysv/linux/x86_64/dl-cet.h | 8 ++++
> .../linux/x86_64/get-cpuid-feature-leaf.c | 24 ++++++++++
> sysdeps/x86/Makefile | 6 ++-
> sysdeps/x86/bits/platform/features.h | 27 +++++++++++
> sysdeps/x86/bits/platform/x86.h | 8 ----
> sysdeps/x86/get-cpuid-feature-leaf.c | 8 ----
> sysdeps/x86/sys/platform/x86.h | 19 ++------
> sysdeps/x86_64/dl-machine.h | 9 ++--
> 9 files changed, 120 insertions(+), 37 deletions(-)
> create mode 100644 sysdeps/unix/sysv/linux/x86/bits/platform/features.h
> create mode 100644 sysdeps/unix/sysv/linux/x86_64/get-cpuid-feature-leaf.c
> create mode 100644 sysdeps/x86/bits/platform/features.h
>
> diff --git a/sysdeps/unix/sysv/linux/x86/bits/platform/features.h b/sysdeps/unix/sysv/linux/x86/bits/platform/features.h
> new file mode 100644
> index 0000000000..7704febe92
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/x86/bits/platform/features.h
> @@ -0,0 +1,48 @@
> +/* 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
> +
> +/* Bits in the feature_1 field in TCB. */
> +
> +enum
> +{
> + x86_feature_1_ibt = 1U << 0,
> + x86_feature_1_shstk = 1U << 1
> +};
> +
> +static __inline__ _Bool
> +x86_cpu_cet_active (unsigned int __index)
> +{
> +#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
> +}
> diff --git a/sysdeps/unix/sysv/linux/x86_64/dl-cet.h b/sysdeps/unix/sysv/linux/x86_64/dl-cet.h
> index a00c7ee662..1fe3133406 100644
> --- a/sysdeps/unix/sysv/linux/x86_64/dl-cet.h
> +++ b/sysdeps/unix/sysv/linux/x86_64/dl-cet.h
> @@ -54,6 +54,14 @@ dl_cet_get_cet_status (void)
> return status;
> }
>
> +static __always_inline bool
> +dl_cet_ibt_enabled (void)
> +{
> + unsigned int feature_1 = THREAD_GETMEM (THREAD_SELF,
> + header.feature_1);
> + return (feature_1 & GNU_PROPERTY_X86_FEATURE_1_IBT) != 0;
> +}
> +
> /* Enable shadow stack with a macro to avoid shadow stack underflow. */
> #define ENABLE_X86_CET(cet_feature) \
> if ((cet_feature & GNU_PROPERTY_X86_FEATURE_1_SHSTK)) \
> diff --git a/sysdeps/unix/sysv/linux/x86_64/get-cpuid-feature-leaf.c b/sysdeps/unix/sysv/linux/x86_64/get-cpuid-feature-leaf.c
> new file mode 100644
> index 0000000000..39b342463c
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/x86_64/get-cpuid-feature-leaf.c
> @@ -0,0 +1,24 @@
> +/* Get CPUID feature leaf. Linux/x86-64 version.
> + 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/>. */
> +
> +#include <sysdeps/x86/get-cpuid-feature-leaf.c>
> +
> +#ifdef __LP64__
> +_Static_assert (FEATURE_1_OFFSET == 72, "FEATURE_1_OFFSET != 72");
> +#else
> +_Static_assert (FEATURE_1_OFFSET == 40, "FEATURE_1_OFFSET != 40");
> +#endif
> 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
> diff --git a/sysdeps/x86_64/dl-machine.h b/sysdeps/x86_64/dl-machine.h
> index 2d2ce503a5..6d605d0d32 100644
> --- a/sysdeps/x86_64/dl-machine.h
> +++ b/sysdeps/x86_64/dl-machine.h
> @@ -587,10 +587,11 @@ x86_64_rewrite_plt (struct link_map *map, ElfW(Addr) plt_rewrite)
> const ElfW(Rela) *reloc = (const void *) start;
> const ElfW(Rela) *reloc_end = (const void *) (start + size);
>
> - unsigned int feature_1 = THREAD_GETMEM (THREAD_SELF,
> - header.feature_1);
> - bool ibt_enabled_p
> - = (feature_1 & GNU_PROPERTY_X86_FEATURE_1_IBT) != 0;
> +# ifdef __CET__
> + bool ibt_enabled_p = dl_cet_ibt_enabled ();
> +# else
> + bool ibt_enabled_p = false;
> +# endif
>
> if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_FILES))
> _dl_debug_printf ("\nchanging PLT in '%s' to direct branch\n",
> --
> 2.43.0
>
LGTM.
Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>
new file mode 100644
@@ -0,0 +1,48 @@
+/* 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
+
+/* Bits in the feature_1 field in TCB. */
+
+enum
+{
+ x86_feature_1_ibt = 1U << 0,
+ x86_feature_1_shstk = 1U << 1
+};
+
+static __inline__ _Bool
+x86_cpu_cet_active (unsigned int __index)
+{
+#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
+}
@@ -54,6 +54,14 @@ dl_cet_get_cet_status (void)
return status;
}
+static __always_inline bool
+dl_cet_ibt_enabled (void)
+{
+ unsigned int feature_1 = THREAD_GETMEM (THREAD_SELF,
+ header.feature_1);
+ return (feature_1 & GNU_PROPERTY_X86_FEATURE_1_IBT) != 0;
+}
+
/* Enable shadow stack with a macro to avoid shadow stack underflow. */
#define ENABLE_X86_CET(cet_feature) \
if ((cet_feature & GNU_PROPERTY_X86_FEATURE_1_SHSTK)) \
new file mode 100644
@@ -0,0 +1,24 @@
+/* Get CPUID feature leaf. Linux/x86-64 version.
+ 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/>. */
+
+#include <sysdeps/x86/get-cpuid-feature-leaf.c>
+
+#ifdef __LP64__
+_Static_assert (FEATURE_1_OFFSET == 72, "FEATURE_1_OFFSET != 72");
+#else
+_Static_assert (FEATURE_1_OFFSET == 40, "FEATURE_1_OFFSET != 40");
+#endif
@@ -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)
new file mode 100644
@@ -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;
+}
@@ -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
-};
@@ -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)
{
@@ -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
@@ -587,10 +587,11 @@ x86_64_rewrite_plt (struct link_map *map, ElfW(Addr) plt_rewrite)
const ElfW(Rela) *reloc = (const void *) start;
const ElfW(Rela) *reloc_end = (const void *) (start + size);
- unsigned int feature_1 = THREAD_GETMEM (THREAD_SELF,
- header.feature_1);
- bool ibt_enabled_p
- = (feature_1 & GNU_PROPERTY_X86_FEATURE_1_IBT) != 0;
+# ifdef __CET__
+ bool ibt_enabled_p = dl_cet_ibt_enabled ();
+# else
+ bool ibt_enabled_p = false;
+# endif
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_FILES))
_dl_debug_printf ("\nchanging PLT in '%s' to direct branch\n",