Re: [PATCH v2] ld: Turn on --error-execstack/--error-rwx-segments

["H.J. Lu" <hjl.tools@gmail.com>]

On Sun, Jan 28, 2024 at 11:30 PM Jan Beulich <jbeulich@suse.com> wrote:
>
> On 26.01.2024 22:45, H.J. Lu wrote:
> > --- a/ld/lexsup.c
> > +++ b/ld/lexsup.c
> > @@ -1947,6 +1947,17 @@ parse_args (unsigned argc, char **argv)
> >        && command_line.check_section_addresses < 0)
> >      command_line.check_section_addresses = 0;
> >
> > +  /* Override --no-error-execstack and --no-warn-execstack and turn on
> > +     --error-execstack for --warn-execstack and --error-rwx-segments for
> > +     --warn-rwx-segments if --fatal-warnings is used.  */
> > +  if (config.fatal_warnings)
> > +    {
> > +      if (link_info.warn_execstack)
> > +     link_info.error_execstack = 1;
> > +      if (!link_info.no_warn_rwx_segments)
> > +     link_info.warn_is_error_for_rwx_segments = 1;
> > +    }
> > +
> >    if (export_list)
> >      {
> >        struct bfd_elf_version_expr *head = export_list->head.list;
>
> If I'm not mistaken and if the comment is properly describing things,
> this placement of the addition means --no-* last on the command line
> wouldn't be honored anymore, when later arguments ought to override
> earlier ones.
>

Before my change, we got

[hjl@gnu-cfl-3 ld]$ touch x.s
[hjl@gnu-cfl-3 ld]$ gcc -c x.s
[hjl@gnu-cfl-3 ld]$ ld -shared -z stack-size=0x123400 --fatal-warnings
--warn-execstack --no-error-execstack  x.o
ld: warning: x.o: missing .note.GNU-stack section implies executable stack
ld: NOTE: This behaviour is deprecated and will be removed in a future
version of the linker
[hjl@gnu-cfl-3 ld]$ echo $?
1

The warning is misleading since --fatal-warnings IS position independent
and is always fatal for ANY warning.  My patch changes it to

[hjl@gnu-cfl-3 ld]$ ./ld-new -shared -z stack-size=0x123400
--fatal-warnings --warn-execstack --no-error-execstack  x.o
./ld-new: error: x.o: is triggering the generation of an executable
stack because it does not have a .note.GNU-stack section
./ld-new: failed to set dynamic section sizes: file format not recognized
[hjl@gnu-cfl-3 ld]$

Any other comments to my patch?

Thanks.

-- 
H.J.