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

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Message-Id: <20210621215452.0eea52e14dbe5969b66ae149@kernel.org>
Date:   Mon, 21 Jun 2021 21:54:52 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
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

On Mon, 21 Jun 2021 15:06:24 +0530
"Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com> wrote:

> 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.

Yeah, I think that's good idea.

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

OK, then I will update tracefs to interpret the code and put appropriate
error message on error_log.

Thank you!

> 
> 
> Thanks,
> Naveen
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>