Re: [RFC][PATCH] kprobes: Remove kprobe::fault_handler

[Alexei Starovoitov]

On Wed, Feb 10, 2021 at 5:57 AM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
>
> Somewhat related.. I had this pending.
>
> ---
> Subject: kprobes: Remove kprobe::fault_handler
> From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Date: Tue Feb 2 10:43:41 CET 2021
>
> The reason for kprobe::fault_handler(), as given by their comment:
>
>  * We come here because instructions in the pre/post
>  * handler caused the page_fault, this could happen
>  * if handler tries to access user space by
>  * copy_from_user(), get_user() etc. Let the
>  * user-specified handler try to fix it first.
>
> If just plain bad. Those other handlers are ran from non-preemptible
> context and had better use _nofault() functions. Also, there is no
> upstream usage of this.

No objections from me.

Since Masami mentioned that systemtap used that you
probably want to give them a courtesy heads-up that it's going away.
Though looking at systemtap source code I couldn't find any
reference to it. So it's likely a nop for them anyway.