Re: DT_RELR without libc.so dependency

[Fangrui Song <maskray@google.com>]

On 2022-04-13, H.J. Lu wrote:
>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?

Looks good.