linux-kernel - Re: [patch part-II V2 01/13] context_tracking: Ensure that the critical path cannot be instrumented

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Message-ID: <87v9nd7frb.fsf@nanos.tec.linutronix.de>
Date:   Mon, 09 Mar 2020 15:40:56 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Steven Rostedt <rostedt@...dmis.org>,
        Brian Gerst <brgerst@...il.com>,
        Juergen Gross <jgross@...e.com>,
        Alexandre Chartre <alexandre.chartre@...cle.com>
Subject: Re: [patch part-II V2 01/13] context_tracking: Ensure that the critical path cannot be instrumented

Frederic Weisbecker <frederic@...nel.org> writes:
> On Sun, Mar 08, 2020 at 11:24:00PM +0100, Thomas Gleixner wrote:
>> context tracking lacks a few protection mechanisms against instrumentation:
>> 
>>  - While the core functions are marked NOKPROBE they lack protection
>>    against function tracing which is required as the function entry/exit
>>    points can be utilized by BPF.
>
> Just to clarify things up: IIUC, BPF scripts can be called from the
> function graph tracer hooks, and that BPF code uses RCU, right?

At least at the moment.