DT_RELR without libc.so dependency

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

On Wed, Apr 13, 2022 at 5:34 PM Alan Modra <amodra@gmail.com> wrote:
>
> On Fri, Apr 08, 2022 at 05:14:12PM -0700, Fangrui Song wrote:
> > HJ's DT_RELR patch series has been upgraded to v7
> > (https://patchwork.sourceware.org/project/glibc/list/?series=8295)
> >
> >   git-pw series apply 8295
> >   # `Add --disable-default-dt-relr` does not apply cleanly
> >
> > If no regressions with default DT_RELR, that will be cool!
>
> I did find one error when testing a build of glibc using Ubuntu gcc-8.
> elf/filter fails with "error while loading shared libraries:
> .../elf/filtmod1.so: DT_RELR without GLIBC_ABI_DT_RELR dependency".
>
> A little analysis shows the problem occurs when filtmod1.so is linked
> with --as-needed and libc.so is not needed.  filtmod1.so ends up with
> no .gnu.version or .gnu.version_r sections, and of course no
> GLIBC_ABI_DT_RELR version.
>
> The error check is not one that belongs in ld.so.  If you have the
> error checking code, then you have DT_RELR support in ld.so and there
> is no reason at all to refuse to run the program!  The check should be
> in the linker, if anywhere.
>

The GLIBC_ABI_DT_RELR dependency is added to avoid the random
crush at run-time with older glibc binaries.   Since it is possible to create
a DSO with DT_RELR, but without the libc.so dependency.   Should ld.so
skip the GLIBC_ABI_DT_RELR check if the DSO doesn't depend on
libc.so?

-- 
H.J.