Re: [PATCH for 5.5 1/2] rseq: Fix: Clarify rseq.h UAPI rseq_cs memory reclaim requirements

[Florian Weimer]

* Mathieu Desnoyers:

> diff --git a/include/uapi/linux/rseq.h b/include/uapi/linux/rseq.h
> index 9a402fdb60e9..6f26b0b148a6 100644
> --- a/include/uapi/linux/rseq.h
> +++ b/include/uapi/linux/rseq.h
> @@ -100,7 +100,9 @@ struct rseq {
>  	 * instruction sequence block, as well as when the kernel detects that
>  	 * it is preempting or delivering a signal outside of the range
>  	 * targeted by the rseq_cs. Also needs to be set to NULL by user-space
> -	 * before reclaiming memory that contains the targeted struct rseq_cs.
> +	 * before reclaiming memory that contains the targeted struct rseq_cs
> +	 * or reclaiming memory that contains the code refered to by the
> +	 * start_ip and post_commit_offset fields of struct rseq_cs.

Maybe mention that it's good practice to clear rseq_cs before
returning from a function that contains a restartable sequence?

That will deal with the dlclose issue because even if the function
calls dlclose itself, unmapping something on call stack for dlclose is
already undefined.