Re: [PATCH v8 2/8] Add rseq extensible ABI support

[Michael Jeanson <mjeanson@efficios.com>]

On 2024-02-16 16 h 17, DJ Delorie wrote:
> 
> Michael Jeanson <mjeanson@efficios.com> writes:
>> When rseq registration is disabled by tunable we still need to allocate
>> an rseq block because application code is allowed to check for the
>> registration status by reading 'rseq->cpu_id'. So in this case we
>> allocate the minimum ABI size of 32.
> 
> Ok, I admit that was confusing ;-)

Yeah, I had to think for a minute to remember that, it should be documented.

> 
>> Internally this is recorded in 'dl_tls_rseq_size' but the application
>> visible '_rseq_size' is left at 0 (this happens in
>> sysdeps/nptl/dl-tls_init_tp.c).
> 
> A comment in sysdeps/nptl/dl-tls_init_tp.c after the if{} noting what
> the variables would be otherwise might be useful.  At least that was one
> of the places I looked at when trying to figure this out.

Ack.

> 
>> I'll try making this more clear with additional comments and finding a
>> name for 'rseq_size' that is not so close to '__rseq_size'.
> 
> Perhaps "rseq_alloc_size" ?

Sounds good.