Enable Intel CET in liblto_plugin.so on Intel CET enabled host

Since ld is Intel CET enabled on Intel CET enabled host, dlopen fails on
liblto_plugin.so if it isn't Intel CET enabled.  Add GCC_CET_HOST_FLAGS
to cet.m4, use it in libiberty and lto-plugin to always enable Intel
CET in liblto_plugin.so on Intel CET enabled host.

On Linux/x86 host, enable Intel CET by default if assembler and compiler
support Intel CET so that the generated liblto_plugin.so can be used on
both CET and non-CET machines.  It is an error to disable Intel CET in
liblto_plugin.so on Intel CET enabled host.

config/

	PR bootstrap/94739
	* cet.m4 (GCC_CET_HOST_FLAGS): New.

libiberty/

	PR bootstrap/94739
	* Makefile.in (COMPILE.c): Add @CET_HOST_FLAGS@.
	(configure_deps): Add $(srcdir)/../config/cet.m4 and
	$(srcdir)/../config/enable.m4.
	* aclocal.m4: Include ../config/cet.m4 and ../config/enable.m4.
	* configure.ac: Add GCC_CET_HOST_FLAGS(CET_HOST_FLAGS) and
	AC_SUBST(CET_HOST_FLAGS).
	* configure: Regenerated.

lto-plugin/

	PR bootstrap/94739
	* Makefile.am (AM_CFLAGS): Add $(CET_HOST_FLAGS).
	* configure.ac: Add GCC_CET_HOST_FLAGS(CET_HOST_FLAGS) and
	AC_SUBST(CET_HOST_FLAGS).
	* Makefile.in: Regenerated.
	* aclocal.m4: Likewise.
	* configure: Likewise.

5 files changed, 165 insertions, 1 deletions

diff --git a/libiberty/ChangeLog b/libiberty/ChangeLog
index 106c107e91a..0c26d455caf 100644
--- a/libiberty/ChangeLog
+++ b/libiberty/ChangeLog
@@ -1,3 +1,14 @@
+2020-04-25  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR bootstrap/94739
+	* Makefile.in (COMPILE.c): Add @CET_HOST_FLAGS@.
+	(configure_deps): Add $(srcdir)/../config/cet.m4 and
+	$(srcdir)/../config/enable.m4.
+	* aclocal.m4: Include ../config/cet.m4 and ../config/enable.m4.
+	* configure.ac: Add GCC_CET_HOST_FLAGS(CET_HOST_FLAGS) and
+	AC_SUBST(CET_HOST_FLAGS).
+	* configure: Regenerated.
+
 2020-03-05  Egeyar Bagcioglu  <egeyar.bagcioglu@oracle.com>
 
 	* simple-object.c (handle_lto_debug_sections): Name
diff --git a/libiberty/Makefile.in b/libiberty/Makefile.in
index fe738d0db43..d6b302e02fd 100644
--- a/libiberty/Makefile.in
+++ b/libiberty/Makefile.in
@@ -112,7 +112,8 @@ installcheck: installcheck-subdir
 INCDIR=$(srcdir)/$(MULTISRCTOP)../include
 
 COMPILE.c = $(CC) -c @DEFS@ $(CFLAGS) $(CPPFLAGS) -I. -I$(INCDIR) \
-               $(HDEFINES) @ac_libiberty_warn_cflags@ -D_GNU_SOURCE
+               $(HDEFINES) @ac_libiberty_warn_cflags@ -D_GNU_SOURCE \
+               @CET_HOST_FLAGS@
 
 # Just to make sure we don't use a built-in rule with VPATH
 .c.$(objext):
@@ -481,6 +482,8 @@ config.status: $(srcdir)/configure
 AUTOCONF = autoconf
 configure_deps = $(srcdir)/aclocal.m4 \
 	$(srcdir)/../config/acx.m4 \
+	$(srcdir)/../config/cet.m4 \
+	$(srcdir)/../config/enable.m4 \
 	$(srcdir)/../config/no-executables.m4 \
 	$(srcdir)/../config/override.m4 \
 	$(srcdir)/../config/picflag.m4 \
diff --git a/libiberty/aclocal.m4 b/libiberty/aclocal.m4
index bf8a907100f..34c0a5bab62 100644
--- a/libiberty/aclocal.m4
+++ b/libiberty/aclocal.m4
@@ -1,4 +1,6 @@
 sinclude(../config/acx.m4)
+sinclude(../config/cet.m4)
+sinclude(../config/enable.m4)
 sinclude(../config/no-executables.m4)
 sinclude(../config/override.m4)
 sinclude(../config/picflag.m4)
diff --git a/libiberty/configure b/libiberty/configure
index d2413f13acf..2b52ce86c89 100755
--- a/libiberty/configure
+++ b/libiberty/configure
@@ -626,6 +626,7 @@ pexecute
 target_header_dir
 CHECK
 LIBOBJS
+CET_HOST_FLAGS
 NOASANFLAG
 PICFLAG
 INSTALL_DATA
@@ -710,6 +711,7 @@ enable_maintainer_mode
 enable_multilib
 enable_install_libiberty
 enable_largefile
+enable_cet
 '
       ac_precious_vars='build_alias
 host_alias
@@ -1337,6 +1339,7 @@ Optional Features:
   --enable-multilib       build many library versions (default)
   --enable-install-libiberty       Install headers and library for end users
   --disable-largefile     omit support for large files
+  --enable-cet            enable Intel CET in host libraries [default=auto]
 
 Optional Packages:
   --with-PACKAGE[=ARG]    use PACKAGE [ARG=yes]
@@ -5264,6 +5267,148 @@ case " ${CFLAGS} " in
 esac
 
 
+ # Check whether --enable-cet was given.
+if test "${enable_cet+set}" = set; then :
+  enableval=$enable_cet;
+      case "$enableval" in
+       yes|no|auto) ;;
+       *) as_fn_error $? "Unknown argument to enable/disable cet" "$LINENO" 5 ;;
+                          esac
+
+else
+  enable_cet=auto
+fi
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for CET support" >&5
+$as_echo_n "checking for CET support... " >&6; }
+
+case "$host" in
+  i[34567]86-*-linux* | x86_64-*-linux*)
+    may_have_cet=yes
+    save_CFLAGS="$CFLAGS"
+    CFLAGS="$CFLAGS -fcf-protection"
+    case "$enable_cet" in
+      auto)
+	# Check if target supports multi-byte NOPs
+	# and if assembler supports CET insn.
+	cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+#if !defined(__SSE2__)
+#error target does not support multi-byte NOPs
+#else
+asm ("setssbsy");
+#endif
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  enable_cet=yes
+else
+  enable_cet=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+	;;
+      yes)
+	# Check if assembler supports CET.
+	cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+asm ("setssbsy");
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+
+else
+  as_fn_error $? "assembler with CET support is required for --enable-cet" "$LINENO" 5
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+	;;
+    esac
+    CFLAGS="$save_CFLAGS"
+    ;;
+  *)
+    may_have_cet=no
+    enable_cet=no
+    ;;
+esac
+
+if test x$may_have_cet = xyes; then
+  save_LDFLAGS="$LDFLAGS"
+  LDFLAGS="$LDFLAGS -Wl,-z,ibt,-z,shstk"
+  if test "$cross_compiling" = yes; then :
+  { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error $? "cannot run test program while cross compiling
+See \`config.log' for more details" "$LINENO" 5; }
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+static void
+foo (void)
+{
+}
+
+static void
+__attribute__ ((noinline, noclone))
+xxx (void (*f) (void))
+{
+  f ();
+}
+
+static void
+__attribute__ ((noinline, noclone))
+bar (void)
+{
+  xxx (foo);
+}
+
+int
+main ()
+{
+  bar ();
+  return 0;
+}
+
+_ACEOF
+if ac_fn_c_try_run "$LINENO"; then :
+  have_cet=no
+else
+  have_cet=yes
+fi
+rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext \
+  conftest.$ac_objext conftest.beam conftest.$ac_ext
+fi
+
+  LDFLAGS="$save_LDFLAGS"
+  if test x$enable_cet = xno -a x$have_cet = xyes; then
+    as_fn_error $? "Intel CET must be enabled on Intel CET enabled host" "$LINENO" 5
+  fi
+fi
+if test x$enable_cet = xyes; then
+  CET_HOST_FLAGS="-fcf-protection"
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
+
 echo "# Warning: this fragment is automatically generated" > temp-frag
 
 if [ -n "${frag}" ] && [ -f "${frag}" ]; then
diff --git a/libiberty/configure.ac b/libiberty/configure.ac
index f1ce76010c9..4e2599c14a8 100644
--- a/libiberty/configure.ac
+++ b/libiberty/configure.ac
@@ -243,6 +243,9 @@ case " ${CFLAGS} " in
 esac
 AC_SUBST(NOASANFLAG)
 
+GCC_CET_HOST_FLAGS(CET_HOST_FLAGS)
+AC_SUBST(CET_HOST_FLAGS)
+
 echo "# Warning: this fragment is automatically generated" > temp-frag
 
 if [[ -n "${frag}" ]] && [[ -f "${frag}" ]]; then