Re: [patch 02/12] rseq: Add fields and constants for time slice extension

Mathieu Desnoyers
2025-09-22T13:57:37Z

On 2025-09-22 01:57, K Prateek Nayak wrote:
> Hello Prakash,
>
> On 9/22/2025 10:58 AM, Prakash Sangappa wrote:
>> With use of a new structure member for slice control, could there be discrepancy
>> with rseq structure size(older version) registered by libc? In that case the application
>> may not be able to use slice extension feature unless Libc’s use of rseq is disabled.
>
> In this case, wouldn't GLIBC's rseq registration fail if presumed
> __rseq_size is smaller than the "struct rseq" size?

The registered rseq size cannot be smaller than 32 bytes, else
registration is refused by the system call (-EINVAL).

The new slice extension fields would fit within those 32 bytes,
so it should always work.

Thanks,

Mathieu

--
Mathieu Desnoyers
EfficiOS Inc.