[PATCH v2 0/9] ld: Implement DT_RELR for x86

[Fangrui Song]

On 2022-01-09, Alexander Monakov wrote:
>On Sat, 8 Jan 2022, Fangrui Song wrote:
>
>> Thank you so much for the heroic work.
>> I cannot think of other items.
>
>I am bummed that Rich Felker's solution for compatibility (sane diagnostic
>for loading a new PIE/DSO with old ld.so) was not accepted:
>https://sourceware.org/pipermail/libc-alpha/2021-November/133313.html
>
>(add just one new relocation to indicate presence of SHT_RELR)
>
>It would have been a nice solution that works the same across all OS'es,
>without requiring changes in ld.so. Was there something wrong with it?
>
>Alexander

Hi Alexander, I think the .gnu.version_r approach is better.
For FreeBSD/musl/etc, there is no version node called GLIBC_2*,
ld.bfd -z pack-relative-relocs will not add anything.

For a relocation approach, every psABI needs to define which relocation
type is used as the available indicator (something like
R_*_GNU_VTENTRY). It's too much work for something only glibc needs.



Now that the ld patch series has landed on
https://sourceware.org/git/?p=binutils-gdb.git, what's the next step for the
glibc patch? The current diff I have is
https://sourceware.org/git/?p=glibc.git;a=shortlog;h=refs/heads/maskray/relr
I think making ld.so/libc.so themselves compatible with DT_RELR can
be separate changes (I personally do not know enough ld.so to contribute
it...)