x86: Assume --enable-cet if GCC defaults to CET [BZ #25225]

Message ID 875zj6d9p8.fsf@oldenburg2.str.redhat.com
State New
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Series
  • x86: Assume --enable-cet if GCC defaults to CET [BZ #25225]
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Commit Message

Florian Weimer Nov. 26, 2019, 1:54 p.m.
This links in CET support if GCC defaults to CET.  Otherwise, __CET__
is defined, yet CET functionality is not compiled and linked into the
dynamic loader, resulting in a linker failure due to undefined
references to _dl_cet_check and _dl_open_check.

-----
 configure    | 23 ++++++++++++++++++++++-
 configure.ac |  9 ++++++++-
 2 files changed, 30 insertions(+), 2 deletions(-)

Comments

H.J. Lu Dec. 3, 2019, 5:44 p.m. | #1
On Tue, Nov 26, 2019 at 5:54 AM Florian Weimer <fweimer@redhat.com> wrote:
>

> This links in CET support if GCC defaults to CET.  Otherwise, __CET__

> is defined, yet CET functionality is not compiled and linked into the

> dynamic loader, resulting in a linker failure due to undefined

> references to _dl_cet_check and _dl_open_check.

>

> -----

>  configure    | 23 ++++++++++++++++++++++-

>  configure.ac |  9 ++++++++-

>  2 files changed, 30 insertions(+), 2 deletions(-)

>

> diff --git a/configure b/configure

> index 2f44b66656..b959d2d988 100755

> --- a/configure

> +++ b/configure

> @@ -3777,11 +3777,32 @@ else

>  fi

>

>

> +cat confdefs.h - <<_ACEOF >conftest.$ac_ext

> +/* end confdefs.h.  */

> +

> +int

> +main ()

> +{

> +

> +#ifndef __CET__

> +#error no CET compiler support

> +#endif

> +  ;

> +  return 0;

> +}

> +_ACEOF

> +if ac_fn_c_try_compile "$LINENO"; then :

> +  libc_cv_compiler_default_cet=yes

> +else

> +  libc_cv_compiler_default_cet=no

> +fi

> +rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext

> +

>  # Check whether --enable-cet was given.

>  if test "${enable_cet+set}" = set; then :

>    enableval=$enable_cet; enable_cet=$enableval

>  else

> -  enable_cet=no

> +  enable_cet=$libc_cv_compiler_default_cet

>  fi

>

>

> diff --git a/configure.ac b/configure.ac

> index e69c88c543..49b900c1ed 100644

> --- a/configure.ac

> +++ b/configure.ac

> @@ -473,11 +473,18 @@ AC_ARG_ENABLE([mathvec],

>               [build_mathvec=$enableval],

>               [build_mathvec=notset])

>

> +AC_TRY_COMPILE([], [

> +#ifndef __CET__

> +# error no CET compiler support

> +#endif],

> +              [libc_cv_compiler_default_cet=yes],

> +              [libc_cv_compiler_default_cet=no])

> +

>  AC_ARG_ENABLE([cet],

>               AC_HELP_STRING([--enable-cet],

>                              [enable Intel Control-flow Enforcement Technology (CET), x86 only]),

>               [enable_cet=$enableval],

> -             [enable_cet=no])

> +             [enable_cet=$libc_cv_compiler_default_cet])

>

>  # We keep the original values in `$config_*' and never modify them, so we

>  # can write them unchanged into config.make.  Everything else uses

>


LGTM.

Thanks.

-- 
H.J.

Patch

diff --git a/configure b/configure
index 2f44b66656..b959d2d988 100755
--- a/configure
+++ b/configure
@@ -3777,11 +3777,32 @@  else
 fi
 
 
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+#ifndef __CET__
+#error no CET compiler support
+#endif
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  libc_cv_compiler_default_cet=yes
+else
+  libc_cv_compiler_default_cet=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+
 # Check whether --enable-cet was given.
 if test "${enable_cet+set}" = set; then :
   enableval=$enable_cet; enable_cet=$enableval
 else
-  enable_cet=no
+  enable_cet=$libc_cv_compiler_default_cet
 fi
 
 
diff --git a/configure.ac b/configure.ac
index e69c88c543..49b900c1ed 100644
--- a/configure.ac
+++ b/configure.ac
@@ -473,11 +473,18 @@  AC_ARG_ENABLE([mathvec],
 	      [build_mathvec=$enableval],
 	      [build_mathvec=notset])
 
+AC_TRY_COMPILE([], [
+#ifndef __CET__
+# error no CET compiler support
+#endif],
+	       [libc_cv_compiler_default_cet=yes],
+	       [libc_cv_compiler_default_cet=no])
+
 AC_ARG_ENABLE([cet],
 	      AC_HELP_STRING([--enable-cet],
 			     [enable Intel Control-flow Enforcement Technology (CET), x86 only]),
 	      [enable_cet=$enableval],
-	      [enable_cet=no])
+	      [enable_cet=$libc_cv_compiler_default_cet])
 
 # We keep the original values in `$config_*' and never modify them, so we
 # can write them unchanged into config.make.  Everything else uses