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[PATCH] x86: Assume --enable-cet if GCC defaults to CET [BZ #25225]
- From: Florian Weimer <fweimer at redhat dot com>
- To: libc-alpha at sourceware dot org
- Cc: H.J. Lu <hjl dot tools at gmail dot com>
- Date: Tue, 26 Nov 2019 14:54:43 +0100
- Subject: [PATCH] x86: Assume --enable-cet if GCC defaults to CET [BZ #25225]
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