Re: [PATCH] configure: Implement --enable-host-bind-now

[Marek Polacek <polacek@redhat.com>]

On Tue, Jun 27, 2023 at 01:39:16PM +0200, Martin Jambor wrote:
> Hello,
> 
> On Tue, May 16 2023, Marek Polacek via Gcc-patches wrote:
> > As promised in the --enable-host-pie patch, this patch adds another
> > configure option, --enable-host-bind-now, which adds -z now when linking
> > the compiler executables in order to extend hardening.  BIND_NOW with RELRO
> > allows the GOT to be marked RO; this prevents GOT modification attacks.
> >
> > This option does not affect linking of target libraries; you can use
> > LDFLAGS_FOR_TARGET=-Wl,-z,relro,-z,now to enable RELRO/BIND_NOW.
> >
> > With this patch:
> > $ readelf -Wd cc1{,plus} | grep FLAGS
> >  0x000000000000001e (FLAGS)              BIND_NOW
> >  0x000000006ffffffb (FLAGS_1)            Flags: NOW PIE
> >  0x000000000000001e (FLAGS)              BIND_NOW
> >  0x000000006ffffffb (FLAGS_1)            Flags: NOW PIE
> >
> > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> >
> > c++tools/ChangeLog:
> >
> > 	* configure.ac (--enable-host-bind-now): New check.
> > 	* configure: Regenerate.
> >
> > gcc/ChangeLog:
> >
> > 	* configure.ac (--enable-host-bind-now): New check.  Add
> > 	-Wl,-z,now to LD_PICFLAG if --enable-host-bind-now.
> > 	* configure: Regenerate.
> > 	* doc/install.texi: Document --enable-host-bind-now.
> >
> > lto-plugin/ChangeLog:
> >
> > 	* configure.ac (--enable-host-bind-now): New check.  Link with
> > 	-z,now.
> > 	* configure: Regenerate.
> 
> Our reconfiguration checking script complains about a missing hunk in
> lto-plugin/Makefile.in:
> 
> diff --git a/lto-plugin/Makefile.in b/lto-plugin/Makefile.in
> index cb568e1e09f..f6f5b020ff5 100644
> --- a/lto-plugin/Makefile.in
> +++ b/lto-plugin/Makefile.in
> @@ -298,6 +298,7 @@ datadir = @datadir@
>  datarootdir = @datarootdir@
>  docdir = @docdir@
>  dvidir = @dvidir@
> +enable_host_bind_now = @enable_host_bind_now@
>  exec_prefix = @exec_prefix@
>  gcc_build_dir = @gcc_build_dir@
>  get_gcc_base_ver = @get_gcc_base_ver@
> 
> 
> I am somewhat puzzled why the line is not missing in any of the other
> Makefile.in files.  Can you please check whether that is the only thing
> that is missing (assuming it is actually missing)?

Arg, once again, I'm sorry.  I don't know how this happened.  It would
be trivial to fix it but since

commit 4a48a38fa99f067b8f3a3d1a5dc7a1e602db351f
Author: Eric Botcazou <ebotcazou@adacore.com>
Date:   Wed Jun 21 18:19:36 2023 +0200

    ada: Fix build of GNAT tools

the build with Ada included fails with --enable-host-pie.  So that needs
to be fixed first.

Eric, I'm not asking you to fix that, but I'm curious, what did the
commit above fix?  The patch looks correct; I'm just puzzled why I
hadn't seen any build failures.

The --enable-host-pie patch has been a nightmare :(.

Marek