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x86: Add --enable-cet=permissive

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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.
This commit is contained in:
H.J. Lu 2020-04-27 15:44:07 -07:00
parent ce12fc7113
commit 9e38f455a6
10 changed files with 96 additions and 59 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
INSTALL
View File

@ -123,20 +123,24 @@ 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

3
config.h.in
View File

@ -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

12
manual/install.texi
View File

@ -152,20 +152,24 @@ 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

2
sysdeps/unix/sysv/linux/x86/Makefile
View File

@ -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

18
sysdeps/x86/Makefile
View File

@ -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 ($(subdir),elf)
sysdep-dl-routines += dl-cet
@ -42,13 +42,21 @@ CFLAGS-tst-cet-legacy-4.c += -fcf-protection=branch
CFLAGS-tst-cet-legacy-4a.c += -fcf-protection
CFLAGS-tst-cet-legacy-4b.c += -fcf-protection
CFLAGS-tst-cet-legacy-mod-4.c += -fcf-protection=none
CFLAGS-tst-cet-legacy-5a.c += -fcf-protection
CFLAGS-tst-cet-legacy-5b.c += -fcf-protection
CFLAGS-tst-cet-legacy-5a.c += -fcf-protection -mshstk
ifeq ($(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

19
sysdeps/x86/configure vendored
View File

@ -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
if test $libc_cv_x86_cet_available != yes; then
as_fn_error $? "$CC doesn't support CET" "$LINENO" 5
fi
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"

17
sysdeps/x86/configure.ac
View File

@ -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
if test $libc_cv_x86_cet_available != yes; then
AC_MSG_ERROR([$CC doesn't support CET])
fi
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])

4
sysdeps/x86/dl-procruntime.c
View File

@ -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

25
sysdeps/x86/tst-cet-legacy-5.c
View File

@ -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)
{

25
sysdeps/x86/tst-cet-legacy-6.c
View File

@ -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)
{