[PATCH v3 16/16] Add --enable-fortify-source option

["Frédéric Bérat" <fberat@redhat.com>]

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.

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

Updated NEWS and INSTALL.

Adding dedicated x86_64 variant that enables the configuration.
---
 INSTALL                      |  6 +++
 Makeconfig                   |  9 ++++-
 NEWS                         |  7 ++--
 config.make.in               |  1 +
 configure                    | 77 ++++++++++++++++++++++++++++++++++++
 configure.ac                 | 42 ++++++++++++++++++--
 manual/install.texi          |  6 +++
 scripts/build-many-glibcs.py |  4 +-
 8 files changed, 144 insertions(+), 8 deletions(-)

diff --git a/INSTALL b/INSTALL
index 6d51475536..44daf64ebd 100644
--- a/INSTALL
+++ b/INSTALL
@@ -276,6 +276,12 @@ if 'CFLAGS' is specified it must enable optimization.  For example:
      the GNU C Library.  The default value refers to the main
      bug-reporting information for the GNU C Library.
 
+'--enable-fortify-source'
+'--enable-fortify-source=LEVEL'
+     Use -D_FORTIFY_SOURCE='LEVEL' to control code hardening, if not
+     provided, 'LEVEL' defaults to highest possible value for your
+     system, based on the supported 'CC' features.
+
    To build the library and related programs, type 'make'.  This will
 produce a lot of output, some of which may look like errors from 'make'
 but aren't.  Look for error messages from 'make' containing '***'.
diff --git a/Makeconfig b/Makeconfig
index f6396b3e0c..84e5043b14 100644
--- a/Makeconfig
+++ b/Makeconfig
@@ -902,6 +902,11 @@ define elide-stack-protector
 $(if $(filter $(@F),$(patsubst %,%$(1),$(2))), $(no-stack-protector))
 endef
 
+# We might want to compile with fortify-source
+ifneq ($(fortify-source),)
++fortify-source=$(fortify-source)
+endif
+
 # Some routine can't be fortified like the ones used by fortify
 define elide-fortify-source
 $(if $(filter $(@F),$(patsubst %,%$(1),$(2))), $(no-fortify-source))
@@ -973,7 +978,9 @@ endif	# $(+cflags) == ""
 # loader, cannot be fortified. Lastly debug is the fortification routines
 # themselves and they cannot be fortified.
 do-fortify = $(filter-out elf dlfcn csu debug,$(subdir))
-ifneq ($(do-fortify),$(subdir))
+ifeq ($(do-fortify),$(subdir))
++cflags += $(+fortify-source)
+else
 +cflags += $(no-fortify-source)
 endif
 
diff --git a/NEWS b/NEWS
index 027506a44c..b586f0bad5 100644
--- a/NEWS
+++ b/NEWS
@@ -48,6 +48,10 @@ Major new features:
 * The strlcpy and strlcat functions have been added.  They are derived
   from OpenBSD, and are expected to be added to a future POSIX version.
 
+* A new configure option, "--enable-fortify-source", can be used to build GLIBC
+  with _FORTIFY_SOURCE. The level of fortification can either be provided, or
+  is set to the highest value supported by the compiler.
+
 Deprecated and removed features, and other changes affecting compatibility:
 
 * In the Linux kernel for the hppa/parisc architecture some of the
@@ -502,9 +506,6 @@ Major new features:
 * The audit libraries will avoid unnecessary slowdown if it is not required
   PLT tracking (by not implementing the la_pltenter or la_pltexit callbacks).
 
-* Glibc now supports to be built with _FORTIFY_SOURCE. The value is undefined
-  for parts of the library that can't be built with it.
-
 Deprecated and removed features, and other changes affecting compatibility:
 
 * On x86-64, the LD_PREFER_MAP_32BIT_EXEC environment variable support
diff --git a/config.make.in b/config.make.in
index 75ad9765aa..d487a4f4e9 100644
--- a/config.make.in
+++ b/config.make.in
@@ -64,6 +64,7 @@ have-fpie = @libc_cv_fpie@
 have-ssp = @libc_cv_ssp@
 stack-protector = @stack_protector@
 no-stack-protector = @no_stack_protector@
+fortify-source = @fortify_source@
 no-fortify-source = @no_fortify_source@
 have-selinux = @have_selinux@
 have-libaudit = @have_libaudit@
diff --git a/configure b/configure
index 7a15f8d3e6..fa4a1c2346 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
+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 for
+                          your system
 
 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.
@@ -6353,8 +6373,65 @@ $as_echo "#define HAVE_LIBCAP 1" >>confdefs.h
 fi
 
 
+fortify_source=""
 no_fortify_source="-Wp,-U_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
+/* end confdefs.h.  */
+
+int
+main ()
+{
+__builtin_dynamic_object_size("", 0)
+  ;
+  return 0;
+}
+_ACEOF
+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___builtin_dynamic_object_size=no
+         if test "$enable_fortify_source" = yes; then :
+  enable_fortify_source=2
+fi
+fi
+rm -f core conftest.err conftest.$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 "$libc_cv_fortify_source" = yes; then :
+  fortify_source="${no_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
diff --git a/configure.ac b/configure.ac
index ebc04d49e6..ec4de6e551 100644
--- a/configure.ac
+++ b/configure.ac
@@ -466,6 +466,17 @@ AC_ARG_ENABLE([scv],
 
 AS_IF([[test "$use_scv" != "no"]],[AC_DEFINE(USE_PPC_SCV)])
 
+dnl Build glibc with _FORTIFY_SOURCE
+AC_ARG_ENABLE(fortify-source,
+              AS_HELP_STRING([--enable-fortify-source@<:@=1|2|3@:>@],
+                             [Use -D_FORTIFY_SOURCE=[1|2|3] to control code hardening, defaults to highest possible value for your system]),
+              [enable_fortify_source=$enableval],
+              [enable_fortify_source=no])
+case "$enable_fortify_source" in
+1|2|3|no|yes) ;;
+*) AC_MSG_ERROR([Not a valid argument for --enable-fortify-source: "$enable_fortify_source"]);;
+esac
+
 # We keep the original values in `$config_*' and never modify them, so we
 # can write them unchanged into config.make.  Everything else uses
 # $machine, $vendor, and $os, and changes them whenever convenient.
@@ -1559,12 +1570,37 @@ if test "x$have_selinux" = xyes; then
 fi
 AC_SUBST(have_selinux)
 
-dnl Create a variable that can be used to control were _FORTIFY_SOURCE is set.
-dnl This will allow users to enable fortification through FLAGS or compiler
-dnl defaults macro definitions.
+dnl Check if we support the requested _FORTIFY_SOURCE level
+dnl If not, then don't use it.
+dnl Note that _FORTIFY_SOURCE may have been set through FLAGS too.
+dnl _FORTIFY_SOURCE value will be selectively disabled for function that can't
+dnl support it
+fortify_source=""
 no_fortify_source="-Wp,-U_FORTIFY_SOURCE"
 
+AC_CACHE_CHECK([for __builtin_dynamic_object_size], [libc_cv___builtin_dynamic_object_size], [
+    AC_LINK_IFELSE([AC_LANG_PROGRAM([], [__builtin_dynamic_object_size("", 0)])],
+        [libc_cv___builtin_dynamic_object_size=yes
+         AS_IF([test "$enable_fortify_source" = yes], [enable_fortify_source=3])],
+        [libc_cv___builtin_dynamic_object_size=no
+         AS_IF([test "$enable_fortify_source" = yes], [enable_fortify_source=2])])
+])
+
+AS_CASE([$enable_fortify_source],
+        [1|2], [libc_cv_fortify_source=yes],
+        [3], [AS_IF([test "$libc_cv___builtin_dynamic_object_size" = yes],
+                    [libc_cv_fortify_source=yes],
+                    [AC_MSG_ERROR([Compiler doesn't provide necessary support for _FORTIFY_SOURCE=3])])],
+        [libc_cv_fortify_source=no])
+
+AS_IF([test "$libc_cv_fortify_source" = yes],
+      [fortify_source="${no_fortify_source},-D_FORTIFY_SOURCE=${enable_fortify_source}"]
+      )
+
+AC_SUBST(enable_fortify_source)
+AC_SUBST(libc_cv_fortify_source)
 AC_SUBST(no_fortify_source)
+AC_SUBST(fortify_source)
 
 dnl Starting with binutils 2.35, GAS can attach multiple symbol versions
 dnl to one symbol (PR 23840).
diff --git a/manual/install.texi b/manual/install.texi
index a44a552d1f..26b64062a0 100644
--- a/manual/install.texi
+++ b/manual/install.texi
@@ -303,6 +303,12 @@ Specify the URL that users should visit if they wish to report a bug,
 to be included in @option{--help} output from programs installed with
 @theglibc{}.  The default value refers to the main bug-reporting
 information for @theglibc{}.
+
+@item --enable-fortify-source
+@itemx --enable-fortify-source=@var{LEVEL}
+Use -D_FORTIFY_SOURCE=@option{LEVEL} to control code hardening, if not
+provided, @option{LEVEL} defaults to highest possible value for your system,
+based on the supported @code{CC} features.
 @end table
 
 To build the library and related programs, type @code{make}.  This will
diff --git a/scripts/build-many-glibcs.py b/scripts/build-many-glibcs.py
index e022abe284..e4eaec01e3 100755
--- a/scripts/build-many-glibcs.py
+++ b/scripts/build-many-glibcs.py
@@ -464,7 +464,9 @@ class Context(object):
                                       {'arch': 'i486',
                                        'ccopts': '-m32 -march=i486'},
                                       {'arch': 'i586',
-                                       'ccopts': '-m32 -march=i586'}])
+                                       'ccopts': '-m32 -march=i586'},
+                                      {'variant': 'enable-fortify-source',
+                                       'cfg': ['--enable-fortify-source']}])
         self.add_config(arch='x86_64',
                         os_name='gnu',
                         gcc_cfg=['--disable-multilib'])
-- 
2.41.0