[PATCH v7 18/23] aarch64: Handle GCS marking

[Yury Khrustalev]

On Tue, Jan 07, 2025 at 02:05:46PM -0300, Adhemerval Zanella Netto wrote:
> 
> > +static void
> > +fail (struct link_map *l, const char *program)
> > +{
> > +  if (program && program[0])
> > +    _dl_fatal_printf ("%s: %s: %s\n", program, l->l_name, N_("not GCS compatible"));
> > +  else if (program)
> > +    _dl_fatal_printf ("%s\n", N_("not GCS compatible"));
> > +  else
> > +    _dl_signal_error (0, l->l_name, "dlopen", N_("not GCS compatible"));
> > +}
> 
> I don't think N_ would make a difference here, it is not support on loader
> and adding on the translation database does not add much without revamping
> how to translation during program loading.

Makes sense, thanks. I'll remove "N_".

> > +static void
> > +check_gcs (struct link_map *l, const char *program)
> > +{
> > +  bool for_dlopen = program == NULL;
> > +  if (!l->l_mach.gcs)
> > +    {
> > +      if (GLRO(dl_aarch64_gcs_policy) == 2 || for_dlopen)
> > +	fail (l, program);
> > +      if (GLRO(dl_aarch64_gcs_policy) == 1)
> > +	GL(dl_aarch64_gcs) = 0;
> > +      else
> > +	unsupported ();
> > +    }
> > +}
> > +
> 
> This requires to update the glibc.cpu.aarch64_gcs_policy entry at 
> manual/tunables.texi with the description of what each value represents.

Right now GCS tunable names are reserved in the manual. When corresponding
Linux kernel functionality has been released, there will be another patch
for Glibc that will add the description of both GCS tunables. At this point
these tunables will become "public". This will likely be after the upcoming
Glibc release.

Thanks,
Yury