[PATCH v2] nptl: clear the whole rseq area before registration

[Florian Weimer]

* Michael Jeanson:

> Due to the extensible nature of the rseq area we can't explictly
> initialize fields that are not part of the ABI yet. It was agreed with
> upstream that all new fields will be documented as zero initialized by
> userspace. Future kernels configured with CONFIG_DEBUG_RSEQ will
> validate the content of all fields during registration.
>
> Replace the explicit field initialization with a memset of the whole
> rseq area which will cover fields as they are added to future kernels.
>
> Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
> ---
> Changes since v1:
> * Add include of dl-symbol-redir-ifunc.h to dl-tls_init_tp.c to use
>   memset() prior to the full initialization of the TCB.

This version looks okay to me.

Reviewed-by: Florian Weimer <fweimer@redhat.com>

But please wait a week or so with backporting, in case unexpected issues
turn up.

Thanks,
Florian