Re: [RFC PATCH glibc 1/4] glibc: Perform rseq(2) registration at nptl init and thread creation (v4)

Florian Weimer
2019-01-14T18:55:43Z

* Mathieu Desnoyers:

> Therefore, both symbols will end up in
> sysdeps/unix/sysv/linux/Versions.

I'm not sure what you mean by that. The physical location in the
directory tree has little effect on which shared object the symbol is
placed in; that will need other changes.

>> By the way, you could avoid the need for unregistration if you allocated
>> the rseq areas persistently, index by TID. They are quite small, so
>> with the typical PID range, maybe the wasted memory due to changing TIDs
>> would be acceptable?
>
> Would we be able to access those __rseq_abi as normal TLS IE model
> variables ? The overhead of indexing an array matters for a
> fast-path.

No, that wouldn't be possible in this case. You would need another
indirection.

Thanks,
Florian