Allow glibc to be built with _FORTIFY_SOURCE

Add --enable-fortify-source option.

It is now possible to enable fortification through a configure option.
The level may be given as parameter, if none is provided, the configure
script will determine what is the highest level possible that can be set
considering GCC built-ins availability and set it.
If level is explicitly set to 3, configure checks if the compiler
supports the built-in function necessary for it or raise an error if it
isn't.

If the configure option isn't explicitly enabled, it _FORTIFY_SOURCE is
forcibly undefined (and therefore disabled).

The result of the configure checks are new variables, ${fortify_source}
and ${no_fortify_source} that can be used to appropriately populate
CFLAGS.

A dedicated patch will follow to make use of this variable in Makefiles
when necessary.

Updated NEWS and INSTALL.

Adding dedicated x86_64 variant that enables the configuration.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

1 files changed, 65 insertions, 18 deletions

diff --git a/configure b/configure
index f840406..1833a4c 100755
--- a/configure
+++ b/configure
@@ -611,7 +611,10 @@ libc_cv_gcc_unwind_find_fde
 libc_extra_cppflags
 libc_extra_cflags
 libc_cv_cxx_thread_local
-CPPUNDEFS
+fortify_source
+no_fortify_source
+libc_cv_fortify_source
+enable_fortify_source
 have_selinux
 have_libcap
 have_libaudit
@@ -782,6 +785,7 @@ enable_pt_chown
 enable_mathvec
 enable_cet
 enable_scv
+enable_fortify_source
 with_cpu
 '
       ac_precious_vars='build_alias
@@ -1452,6 +1456,10 @@ Optional Features:
                           (CET), x86 only
   --disable-scv           syscalls will not use scv instruction, even if the
                           kernel supports it, powerpc only
+  --enable-fortify-source[=1|2|3]
+                          Use -D_FORTIFY_SOURCE=[1|2|3] to control code
+                          hardening, defaults to highest possible value
+                          supported by the build compiler.
 
 Optional Packages:
   --with-PACKAGE[=ARG]    use PACKAGE [ARG=yes]
@@ -3717,6 +3725,18 @@ if test "$use_scv" != "no"; then :
 
 fi
 
+# Check whether --enable-fortify-source was given.
+if test "${enable_fortify_source+set}" = set; then :
+  enableval=$enable_fortify_source; enable_fortify_source=$enableval
+else
+  enable_fortify_source=no
+fi
+
+case "$enable_fortify_source" in
+1|2|3|no|yes) ;;
+*) as_fn_error $? "Not a valid argument for --enable-fortify-source: \"$enable_fortify_source\"" "$LINENO" 5;;
+esac
+
 # We keep the original values in `$config_*' and never modify them, so we
 # can write them unchanged into config.make.  Everything else uses
 # $machine, $vendor, and $os, and changes them whenever convenient.
@@ -6353,40 +6373,67 @@ $as_echo "#define HAVE_LIBCAP 1" >>confdefs.h
 fi
 
 
-CPPUNDEFS=
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for _FORTIFY_SOURCE predefine" >&5
-$as_echo_n "checking for _FORTIFY_SOURCE predefine... " >&6; }
-if ${libc_cv_predef_fortify_source+:} false; then :
+no_fortify_source="-Wp,-U_FORTIFY_SOURCE"
+fortify_source="${no_fortify_source}"
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for __builtin_dynamic_object_size" >&5
+$as_echo_n "checking for __builtin_dynamic_object_size... " >&6; }
+if ${libc_cv___builtin_dynamic_object_size+:} false; then :
   $as_echo_n "(cached) " >&6
 else
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+
+    cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
 int
 main ()
 {
-
-#ifdef _FORTIFY_SOURCE
-# error bogon
-#endif
+__builtin_dynamic_object_size("", 0)
   ;
   return 0;
 }
 _ACEOF
-if ac_fn_c_try_compile "$LINENO"; then :
-  libc_cv_predef_fortify_source=no
+if ac_fn_c_try_link "$LINENO"; then :
+  libc_cv___builtin_dynamic_object_size=yes
+         if test "$enable_fortify_source" = yes; then :
+  enable_fortify_source=3
+fi
 else
-  libc_cv_predef_fortify_source=yes
+  libc_cv___builtin_dynamic_object_size=no
+         if test "$enable_fortify_source" = yes; then :
+  enable_fortify_source=2
 fi
-rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
 fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_predef_fortify_source" >&5
-$as_echo "$libc_cv_predef_fortify_source" >&6; }
-if test $libc_cv_predef_fortify_source = yes; then
-  CPPUNDEFS="${CPPUNDEFS:+$CPPUNDEFS }-U_FORTIFY_SOURCE"
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv___builtin_dynamic_object_size" >&5
+$as_echo "$libc_cv___builtin_dynamic_object_size" >&6; }
+
+case $enable_fortify_source in #(
+  1|2) :
+    libc_cv_fortify_source=yes ;; #(
+  3) :
+    if test "$libc_cv___builtin_dynamic_object_size" = yes; then :
+  libc_cv_fortify_source=yes
+else
+  as_fn_error $? "Compiler doesn't provide necessary support for _FORTIFY_SOURCE=3" "$LINENO" 5
+fi ;; #(
+  *) :
+    libc_cv_fortify_source=no ;;
+esac
+
+if test "$libc_cv_fortify_source" = yes; then :
+  fortify_source="${fortify_source},-D_FORTIFY_SOURCE=${enable_fortify_source}"
+
 fi
 
 
+
+
+
+
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether the assembler requires one version per symbol" >&5
 $as_echo_n "checking whether the assembler requires one version per symbol... " >&6; }
 if ${libc_cv_symver_needs_alias+:} false; then :