[v4,15/15] 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 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                      |  8 ++++
 Makeconfig                   |  9 ++++-
 NEWS                         |  6 +++
 config.make.in               |  1 +
 configure                    | 77 ++++++++++++++++++++++++++++++++++++
 configure.ac                 | 42 ++++++++++++++++++--
 manual/install.texi          |  8 ++++
 scripts/build-many-glibcs.py |  4 +-
 8 files changed, 150 insertions(+), 5 deletions(-)

On 2023-07-04 12:55, Frédéric Bérat wrote:
> 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 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                      |  8 ++++
>   Makeconfig                   |  9 ++++-
>   NEWS                         |  6 +++
>   config.make.in               |  1 +
>   configure                    | 77 ++++++++++++++++++++++++++++++++++++
>   configure.ac                 | 42 ++++++++++++++++++--
>   manual/install.texi          |  8 ++++
>   scripts/build-many-glibcs.py |  4 +-
>   8 files changed, 150 insertions(+), 5 deletions(-)

Probably best to merge this into 1/15.

> 
> diff --git a/INSTALL b/INSTALL
> index fe591c7dae..873deeccf3 100644
> --- a/INSTALL
> +++ b/INSTALL
> @@ -276,6 +276,14 @@ 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

To be specific, s/control code hardening/control hardening in the GNU C 
Library/

> +     provided, ‘LEVEL’ defaults to highest possible value for your
> +     system, based on the supported ‘CC’ features.
> +
> +     Default is to disable fortification.
> +
>      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 2ec05cfe0f..1286f87159 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -51,6 +51,12 @@ Major new features:
>   * 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.
>   
> +* 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. If not explicitly
> +  enabled, then fortify source is forcibly disabled so to keep original
> +  behavior unchanged.
> +

The old NEWS should be replaced with this.  Also, s/GLIBC/The GNU C Library/

>   Deprecated and removed features, and other changes affecting compatibility:
>   
>   * In the Linux kernel for the hppa/parisc architecture some of the
> 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..daa84f2d35 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

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 $os, and changes them whenever convenient.
> @@ -6354,6 +6374,63 @@ fi
>   
>   
>   no_fortify_source="-Wp,-U_FORTIFY_SOURCE"
> +fortify_source="${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
> +/* 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 "$libc_cv_fortify_source" = yes; then :
> +  fortify_source="${fortify_source},-D_FORTIFY_SOURCE=${enable_fortify_source}"
> +
> +fi
> +
> +
> +
>   
>   
>   
> diff --git a/configure.ac b/configure.ac
> index ebc04d49e6..12493367b1 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -466,6 +466,17 @@ AC_ARG_ENABLE([scv],
>   
>   AS_IF([[test "$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
>   no_fortify_source="-Wp,-U_FORTIFY_SOURCE"
> +fortify_source="${no_fortify_source}"
> +
> +AC_CACHE_CHECK([for __builtin_dynamic_object_size], [libc_cv___builtin_dynamic_object_size], [
> +    AC_LINK_IFELSE([AC_LANG_PROGRAM([], [__builtin_dynamic_object_size("", 0)])],
> +        [libc_cv___builtin_dynamic_object_size=yes
> +         AS_IF([test "$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="${fortify_source},-D_FORTIFY_SOURCE=${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..eb7cb74c2d 100644
> --- a/manual/install.texi
> +++ b/manual/install.texi
> @@ -303,6 +303,14 @@ 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.

Same as above, highest possible value supported by the build compiler.

> +
> +Default is to disable fortification.
>   @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'])