linux-kernel - Re: [PATCH] tracing: Kernel access to Ftrace instances

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Message-ID: <a96e884d-534f-65ef-8f82-85cd52953695@oracle.com>
Date:   Wed, 15 May 2019 18:51:23 -0700
From:   Divya Indi <divya.indi@...cle.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
        Joe Jin <joe.jin@...cle.com>
Subject: Re: [PATCH] tracing: Kernel access to Ftrace instances

Hi Masami,

Thanks for pointing it out.

Yes, it should not be static.

On 5/15/19 5:09 PM, Masami Hiramatsu wrote:
> HI Divya,
>
> On Wed, 20 Mar 2019 11:28:51 -0700
> Divya Indi <divya.indi@...cle.com> wrote:
>
>> Ftrace provides the feature “instances” that provides the capability to
>> create multiple Ftrace ring buffers. However, currently these buffers
>> are created/accessed via userspace only. The kernel APIs providing these
>> features are not exported, hence cannot be used by other kernel
>> components.
>>
>> This patch aims to extend this infrastructure to provide the
>> flexibility to create/log/remove/ enable-disable existing trace events
>> to these buffers from within the kernel.
>>
>> Signed-off-by: Divya Indi <divya.indi@...cle.com>
>> Reviewed-by: Joe Jin <joe.jin@...cle.com>
> Would you tested these APIs with your module? Since,
> [...]
>> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
>> index 5b3b0c3..81c038e 100644
>> --- a/kernel/trace/trace_events.c
>> +++ b/kernel/trace/trace_events.c
>> @@ -832,6 +832,7 @@ static int ftrace_set_clr_event(struct trace_array *tr, char *buf, int set)
>>   
>>   	return ret;
>>   }
>> +EXPORT_SYMBOL_GPL(ftrace_set_clr_event);
> I found this exports a static function to module. Did it work?

I had tested the changes with my module. This change to static was added 
in the test patch, but somehow missed it in the final patch that was 
sent out.

Will send a new patch along with a few additional ones to add some NULL 
checks to ensure safe usage by modules and add the APIs to a header file 
that can be used by the modules.

Thanks,

Divya

>
> Thank you,
>