commit 9e38f455a6c602be86b7b5a8d6523cbdcd7ec051
Author: H.J. Lu <hjl.tools@gmail.com>
Date: Mon Apr 27 15:44:07 2020 -0700
x86: Add --enable-cet=permissive
When CET is enabled, it is an error to dlopen a non CET enabled shared
library in CET enabled application. It may be desirable to make CET
permissive, that is disable CET when dlopening a non CET enabled shared
library. With the new --enable-cet=permissive configure option, CET is
disabled when dlopening a non CET enabled shared library.
Add DEFAULT_DL_X86_CET_CONTROL to config.h.in:
/* The default value of x86 CET control. */
#define DEFAULT_DL_X86_CET_CONTROL cet_elf_property
which enables CET features based on ELF property note.
--enable-cet=permissive it to
/* The default value of x86 CET control. */
#define DEFAULT_DL_X86_CET_CONTROL cet_permissive
which enables CET features permissively.
Update tst-cet-legacy-5a, tst-cet-legacy-5b, tst-cet-legacy-6a and
tst-cet-legacy-6b to check --enable-cet and --enable-cet=permissive.
---
diff --git a/INSTALL b/INSTALL
index d56e102..0655650 100644
--- a/INSTALL
+++ b/INSTALL
@@ -116,20 +116,24 @@ if 'CFLAGS' is specified it must enable optimization. For example:
executables (PIE) by default.
'--enable-cet'
+'--enable-cet=permissive'
Enable Intel Control-flow Enforcement Technology (CET) support.
- When the GNU C Library is built with '--enable-cet', the resulting
- library is protected with indirect branch tracking (IBT) and shadow
- stack (SHSTK). When CET is enabled, the GNU C Library is
- compatible with all existing executables and shared libraries.
- This feature is currently supported on i386, x86_64 and x32 with
- GCC 8 and binutils 2.29 or later. Note that when CET is enabled,
- the GNU C Library requires CPUs capable of multi-byte NOPs, like
- x86-64 processors as well as Intel Pentium Pro or newer.
+ When the GNU C Library is built with '--enable-cet' or
+ '--enable-cet=permissive', the resulting library is protected with
+ indirect branch tracking (IBT) and shadow stack (SHSTK). When CET
+ is enabled, the GNU C Library is compatible with all existing
+ executables and shared libraries. This feature is currently
+ supported on i386, x86_64 and x32 with GCC 8 and binutils 2.29 or
+ later. Note that when CET is enabled, the GNU C Library requires
+ CPUs capable of multi-byte NOPs, like x86-64 processors as well as
+ Intel Pentium Pro or newer. With '--enable-cet', it is an error to
+ dlopen a non CET enabled shared library in CET enabled application.
+ With '--enable-cet=permissive', CET is disabled when dlopening a
+ non CET enabled shared library in CET enabled application.
NOTE: '--enable-cet' has been tested for i686, x86_64 and x32 on
- non-CET processors. '--enable-cet' has been tested for x86_64 and
- x32 on CET SDVs, but Intel CET support hasn't been validated for
- i686.
+ non-CET processors. '--enable-cet' has been tested for i686,
+ x86_64 and x32 on CET processors.
'--disable-profile'
Don't build libraries with profiling information. You may want to
diff --git a/config.h.in b/config.h.in
index f63f6c8..8520b0f 100644
--- a/config.h.in
+++ b/config.h.in
@@ -259,4 +259,7 @@
in i386 6 argument syscall issue). */
#define CAN_USE_REGISTER_ASM_EBP 0
+/* The default value of x86 CET control. */
+#define DEFAULT_DL_X86_CET_CONTROL cet_elf_property
+
#endif
diff --git a/manual/install.texi b/manual/install.texi
index 351d67c..7e9f2be 100644
--- a/manual/install.texi
+++ b/manual/install.texi
@@ -147,20 +147,24 @@ PIE. This option also implies that glibc programs and tests are created
as dynamic position independent executables (PIE) by default.
@item --enable-cet
+@itemx --enable-cet=permissive
Enable Intel Control-flow Enforcement Technology (CET) support. When
-@theglibc{} is built with @option{--enable-cet}, the resulting library
+@theglibc{} is built with @option{--enable-cet} or
+@option{--enable-cet=permissive}, the resulting library
is protected with indirect branch tracking (IBT) and shadow stack
(SHSTK)@. When CET is enabled, @theglibc{} is compatible with all
existing executables and shared libraries. This feature is currently
supported on i386, x86_64 and x32 with GCC 8 and binutils 2.29 or later.
Note that when CET is enabled, @theglibc{} requires CPUs capable of
multi-byte NOPs, like x86-64 processors as well as Intel Pentium Pro or
-newer.
+newer. With @option{--enable-cet}, it is an error to dlopen a non CET
+enabled shared library in CET enabled application. With
+@option{--enable-cet=permissive}, CET is disabled when dlopening a
+non CET enabled shared library in CET enabled application.
NOTE: @option{--enable-cet} has been tested for i686, x86_64 and x32
on non-CET processors. @option{--enable-cet} has been tested for
-x86_64 and x32 on CET SDVs, but Intel CET support hasn't been validated
-for i686.
+i686, x86_64 and x32 on CET processors.
@item --disable-profile
Don't build libraries with profiling information. You may want to use
diff --git a/sysdeps/unix/sysv/linux/x86/Makefile b/sysdeps/unix/sysv/linux/x86/Makefile
index 7dc4e61..8ac2fd4 100644
--- a/sysdeps/unix/sysv/linux/x86/Makefile
+++ b/sysdeps/unix/sysv/linux/x86/Makefile
@@ -24,7 +24,7 @@ ifeq ($(subdir),setjmp)
tests += tst-saved_mask-1
endif
-ifeq ($(enable-cet),yes)
+ifneq ($(enable-cet),no)
ifeq ($(subdir),elf)
tests += tst-cet-property-1 tst-cet-property-2
diff --git a/sysdeps/x86/Makefile b/sysdeps/x86/Makefile
index d9bdf0b..d5f821e 100644
--- a/sysdeps/x86/Makefile
+++ b/sysdeps/x86/Makefile
@@ -14,7 +14,7 @@ gen-as-const-headers += jmp_buf-ssp.sym
sysdep_routines += __longjmp_cancel
endif
-ifeq ($(enable-cet),yes)
+ifneq ($(enable-cet),no)
ifeq ($(subdir),elf)
sysdep-dl-routines += dl-cet
@@ -41,13 +41,21 @@ CFLAGS-tst-cet-legacy-4.c += -fcf-protection=branch
CFLAGS-tst-cet-legacy-4a.c += -fcf-protection
CFLAGS-tst-cet-legacy-4b.c += -fcf-protection
CFLAGS-tst-cet-legacy-mod-4.c += -fcf-protection=none
-CFLAGS-tst-cet-legacy-5a.c += -fcf-protection
-CFLAGS-tst-cet-legacy-5b.c += -fcf-protection
+CFLAGS-tst-cet-legacy-5a.c += -fcf-protection -mshstk
+ifeq ($(enable-cet),permissive)
+CPPFLAGS-tst-cet-legacy-5a.c += -DCET_IS_PERMISSIVE=1
+endif
+CFLAGS-tst-cet-legacy-5b.c += -fcf-protection -mshstk
+CPPFLAGS-tst-cet-legacy-5b.c += -DCET_DISABLED_BY_ENV=1
CFLAGS-tst-cet-legacy-mod-5a.c += -fcf-protection=branch
CFLAGS-tst-cet-legacy-mod-5b.c += -fcf-protection
CFLAGS-tst-cet-legacy-mod-5c.c += -fcf-protection
-CFLAGS-tst-cet-legacy-6a.c += -fcf-protection
-CFLAGS-tst-cet-legacy-6b.c += -fcf-protection
+CFLAGS-tst-cet-legacy-6a.c += -fcf-protection -mshstk
+ifeq ($(enable-cet),permissive)
+CPPFLAGS-tst-cet-legacy-6a.c += -DCET_IS_PERMISSIVE=1
+endif
+CFLAGS-tst-cet-legacy-6b.c += -fcf-protection -mshstk
+CPPFLAGS-tst-cet-legacy-6b.c += -DCET_DISABLED_BY_ENV=1
CFLAGS-tst-cet-legacy-mod-6a.c += -fcf-protection=branch
CFLAGS-tst-cet-legacy-mod-6b.c += -fcf-protection
CFLAGS-tst-cet-legacy-mod-6c.c += -fcf-protection
diff --git a/sysdeps/x86/configure b/sysdeps/x86/configure
index b1ff281..81cc4e8 100644
--- a/sysdeps/x86/configure
+++ b/sysdeps/x86/configure
@@ -1,7 +1,7 @@
# This file is generated from configure.ac by Autoconf. DO NOT EDIT!
# Local configure fragment for sysdeps/x86.
-if test x"$enable_cet" = xyes; then
+if test $enable_cet != no; then
# Check if CET can be enabled.
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether CET can be enabled" >&5
$as_echo_n "checking whether CET can be enabled... " >&6; }
@@ -27,17 +27,11 @@ EOF
fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_x86_cet_available" >&5
$as_echo "$libc_cv_x86_cet_available" >&6; }
- if test $libc_cv_x86_cet_available = yes; then
- enable_cet=yes
- else
- if test x"$enable_cet" = xdefault; then
- enable_cet=no
- else
- as_fn_error $? "$CC doesn't support CET" "$LINENO" 5
- fi
+ if test $libc_cv_x86_cet_available != yes; then
+ as_fn_error $? "$CC doesn't support CET" "$LINENO" 5
fi
fi
-if test $enable_cet = yes; then
+if test $enable_cet != no; then
# Check if assembler supports CET.
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $AS supports CET" >&5
$as_echo_n "checking whether $AS supports CET... " >&6; }
@@ -65,5 +59,12 @@ $as_echo "$libc_cv_x86_cet_as" >&6; }
as_fn_error $? "$AS doesn't support CET" "$LINENO" 5
fi
fi
+if test $enable_cet = yes; then
+ $as_echo "#define DEFAULT_DL_X86_CET_CONTROL cet_elf_property" >>confdefs.h
+
+elif test $enable_cet = permissive; then
+ $as_echo "#define DEFAULT_DL_X86_CET_CONTROL cet_permissive" >>confdefs.h
+
+fi
config_vars="$config_vars
enable-cet = $enable_cet"
diff --git a/sysdeps/x86/configure.ac b/sysdeps/x86/configure.ac
index a909b07..8f3e119 100644
--- a/sysdeps/x86/configure.ac
+++ b/sysdeps/x86/configure.ac
@@ -1,7 +1,7 @@
GLIBC_PROVIDES dnl See aclocal.m4 in the top level source directory.
# Local configure fragment for sysdeps/x86.
-if test x"$enable_cet" = xyes; then
+if test $enable_cet != no; then
# Check if CET can be enabled.
AC_CACHE_CHECK(whether CET can be enabled,
libc_cv_x86_cet_available, [dnl
@@ -16,17 +16,11 @@ EOF
libc_cv_x86_cet_available=no
fi
rm -rf conftest*])
- if test $libc_cv_x86_cet_available = yes; then
- enable_cet=yes
- else
- if test x"$enable_cet" = xdefault; then
- enable_cet=no
- else
- AC_MSG_ERROR([$CC doesn't support CET])
- fi
+ if test $libc_cv_x86_cet_available != yes; then
+ AC_MSG_ERROR([$CC doesn't support CET])
fi
fi
-if test $enable_cet = yes; then
+if test $enable_cet != no; then
# Check if assembler supports CET.
AC_CACHE_CHECK(whether $AS supports CET,
libc_cv_x86_cet_as, [dnl
@@ -43,4 +37,9 @@ EOF
AC_MSG_ERROR([$AS doesn't support CET])
fi
fi
+if test $enable_cet = yes; then
+ AC_DEFINE(DEFAULT_DL_X86_CET_CONTROL, cet_elf_property)
+elif test $enable_cet = permissive; then
+ AC_DEFINE(DEFAULT_DL_X86_CET_CONTROL, cet_permissive)
+fi
LIBC_CONFIG_VAR([enable-cet], [$enable_cet])
diff --git a/sysdeps/x86/dl-procruntime.c b/sysdeps/x86/dl-procruntime.c
index 26b2b39..72b16fa 100644
--- a/sysdeps/x86/dl-procruntime.c
+++ b/sysdeps/x86/dl-procruntime.c
@@ -65,8 +65,8 @@ PROCINFO_CLASS struct dl_x86_feature_control _dl_x86_feature_control
# endif
# ifndef PROCINFO_DECL
= {
- .ibt = cet_elf_property,
- .shstk = cet_elf_property
+ .ibt = DEFAULT_DL_X86_CET_CONTROL,
+ .shstk = DEFAULT_DL_X86_CET_CONTROL,
}
# endif
# if !defined SHARED || defined PROCINFO_DECL
diff --git a/sysdeps/x86/tst-cet-legacy-5.c b/sysdeps/x86/tst-cet-legacy-5.c
index 0a34d37..c578979 100644
--- a/sysdeps/x86/tst-cet-legacy-5.c
+++ b/sysdeps/x86/tst-cet-legacy-5.c
@@ -22,6 +22,14 @@
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
+#include <x86intrin.h>
+#include <support/check.h>
+
+#if defined CET_IS_PERMISSIVE || defined CET_DISABLED_BY_ENV
+# define CET_MAYBE_DISABLED 1
+#else
+# define CET_MAYBE_DISABLED 0
+#endif
static void
do_test_1 (const char *modname, bool fail)
@@ -32,24 +40,25 @@ do_test_1 (const char *modname, bool fail)
h = dlopen (modname, RTLD_LAZY);
if (h == NULL)
{
+ const char *err = dlerror ();
if (fail)
{
- const char *err = dlerror ();
if (strstr (err, "rebuild shared object with SHSTK support enabled")
== NULL)
- {
- printf ("incorrect dlopen '%s' error: %s\n", modname,
- err);
- exit (1);
- }
+ FAIL_EXIT1 ("incorrect dlopen '%s' error: %s\n", modname, err);
return;
}
- printf ("cannot open '%s': %s\n", modname, dlerror ());
- exit (1);
+ FAIL_EXIT1 ("cannot open '%s': %s\n", modname, err);
}
+ /* NB: dlopen should never fail on non-CET platforms. If SHSTK is
+ disabled, assuming IBT is also disabled. */
+ bool cet_enabled = _get_ssp () != 0 && !CET_MAYBE_DISABLED;
+ if (fail && cet_enabled)
+ FAIL_EXIT1 ("dlopen should have failed\n");
+
fp = dlsym (h, "test");
if (fp == NULL)
{
diff --git a/sysdeps/x86/tst-cet-legacy-6.c b/sysdeps/x86/tst-cet-legacy-6.c
index bd45218..78e72ba 100644
--- a/sysdeps/x86/tst-cet-legacy-6.c
+++ b/sysdeps/x86/tst-cet-legacy-6.c
@@ -22,6 +22,14 @@
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
+#include <x86intrin.h>
+#include <support/check.h>
+
+#if defined CET_IS_PERMISSIVE || defined CET_DISABLED_BY_ENV
+# define CET_MAYBE_DISABLED 1
+#else
+# define CET_MAYBE_DISABLED 0
+#endif
static void
do_test_1 (const char *modname, bool fail)
@@ -32,24 +40,25 @@ do_test_1 (const char *modname, bool fail)
h = dlopen (modname, RTLD_LAZY);
if (h == NULL)
{
+ const char *err = dlerror ();
if (fail)
{
- const char *err = dlerror ();
if (strstr (err, "rebuild shared object with SHSTK support enabled")
== NULL)
- {
- printf ("incorrect dlopen '%s' error: %s\n", modname,
- err);
- exit (1);
- }
+ FAIL_EXIT1 ("incorrect dlopen '%s' error: %s\n", modname, err);
return;
}
- printf ("cannot open '%s': %s\n", modname, dlerror ());
- exit (1);
+ FAIL_EXIT1 ("cannot open '%s': %s\n", modname, err);
}
+ /* NB: dlopen should never fail on non-CET platforms. If SHSTK is
+ disabled, assuming IBT is also disabled. */
+ bool cet_enabled = _get_ssp () != 0 && !CET_MAYBE_DISABLED;
+ if (fail && cet_enabled)
+ FAIL_EXIT1 ("dlopen should have failed\n");
+
fp = dlsym (h, "test");
if (fp == NULL)
{