linux-kernel - Re: [PATCH] selftests/ftrace: Disable multiple

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Date:   Tue, 05 Jan 2021 16:51:50 +0530
From:   "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
        shuah@...nel.org
Subject: Re: [PATCH] selftests/ftrace: Disable multiple_kprobes test on
 powerpc

Masami Hiramatsu wrote:
> On Tue, 5 Jan 2021 19:01:56 +0900
> Masami Hiramatsu <mhiramat@...nel.org> wrote:
> 
>> On Tue,  5 Jan 2021 12:27:30 +0530
>> "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com> wrote:
>> 
>> > Not all symbols are blacklisted on powerpc. Disable multiple_kprobes
>> > test until that is sorted, so that rest of ftrace and kprobe selftests
>> > can be run.
>> 
>> This looks good to me, but could you try to find the functions
>> which should be blocked from kprobes?
>> (Usually, the function which are involved in the sw-breakpoint
>>  handling, including locks etc.)
> 
> Ah, OK. 
> I wonder why CONFIG_KPROBE_EVENTS_ON_NOTRACE=n doesn't help, it
> was ignored if the arch doesn't support CONFIG_KPROBES_ON_FTRACE.

Good point, though we do support CONFIG_KPROBES_ON_FTRACE on powerpc so 
the below patch is unlikely to help. However, since entry code is 
unlikely to be the source of the issue due to 
CONFIG_KPROBE_EVENTS_ON_NOTRACE, I will take another look to see where 
the problem lies.

> 
> Naveen, could you try to run this test case with following patch
> on powerpc?
> 
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index b911e9f6d9f5..241a55313476 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -433,7 +433,7 @@ static int disable_trace_kprobe(struct trace_event_call *call,
>         return 0;
>  }
> 
> -#if defined(CONFIG_KPROBES_ON_FTRACE) && \
> +#if defined(CONFIG_FUNCTION_TRACER) && \
>         !defined(CONFIG_KPROBE_EVENTS_ON_NOTRACE)
>  static bool __within_notrace_func(unsigned long addr)
>  {
> 

This looks like a good change regardless, so if you intend to post this 
separately:
Acked-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>

Thanks,
Naveen