Re: [PATCH] elf: Add elf checks for main executable

["Fāng-ruì Sòng" <maskray@google.com>]

On Tue, Dec 14, 2021 at 1:03 AM Florian Weimer <fweimer@redhat.com> wrote:
>
> * Fāng-ruì Sòng:
>
> > If the question is: "if upstream glibc implements the diagnostic, will
> > ChromeOS port the patch to their glibc".  My reply is non-authoritative,
> > but if this has not been a problem for more than 3 years now, I do know
> > see large value backporting the feature to their older glibc release.
>
> But if you don't backport, you can teach your toolchain to start
> producing binaries that fail to load on older glibc.  You will have to
> keep creating binaries that lack proper markup.
>
> My concern is that we go through all this trouble to implement a version
> proper handshake, and yet Google binaries will still crash on older
> glibc.

3+ years ago, "still crash on older glibc" was considered an
acceptable compromise as the scenario (cared by some upstream glibc
folks) is simply unsupported (and by many other groups).

Now after 3 years, (while this is unsupported) back porting RELR
executables to less-than-3 year old ChromeOS would still work because
all glibc releases in the past 3 years support RELR. If you consider
symbol versioning, many symbols get new symbols which won't run on
3-year-old glibc anyway.