linux-kernel - Re: [PATCH] kprobes: Print an error if probe is rejected

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Date:   Mon, 21 Jun 2021 15:06:24 +0530
From:   "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>, acme@...nel.org
Subject: Re: [PATCH] kprobes: Print an error if probe is rejected

Hi Masami,

Masami Hiramatsu wrote:
> Hi Naveen,
> 
> On Mon, 14 Jun 2021 21:00:52 +0530
> "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com> wrote:
> 
>> Steven Rostedt wrote:
>> > On Fri, 11 Jun 2021 19:25:38 +0530
>> > "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com> wrote:
>> > 
>> >> We also have perf_event_open() as an interface to add probes, and I 
>> >> don't think it would be helpful to require all tools to utilize the 
>> >> error log from tracefs for this purpose.
>> > 
>> > The there should be a perf interface to read the errors. I agree with
>> > Masami. Let's not have console logs for probe errors.
>> 
>> Ok, understood.
> 
> Will you update this?

Not sure if you are asking about error logging with perf_event_open(), 
or about reading error_log from tracefs.

For perf_event_open(), I think we will just need to return the error 
code, and interpret the return value in userspace. I don't think there 
is any other way to pass error log or strings back from the kernel.

I will update this series to return the correct return value as 
suggested.


Thanks,
Naveen