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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Frederic Weisbecker <frederic@kernel.org>
Cc:     LKML <linux-kernel@vger.kernel.org>, x86@kernel.org,
        Steven Rostedt <rostedt@goodmis.org>,
        Brian Gerst <brgerst@gmail.com>,
        Juergen Gross <jgross@suse.com>,
        Alexandre Chartre <alexandre.chartre@oracle.com>
Subject: Re: [patch part-II V2 01/13] context_tracking: Ensure that the critical path cannot be instrumented
In-Reply-To: <20200309142223.GD9615@lenoir>
References: <20200308222359.370649591@linutronix.de> <20200308222609.017810037@linutronix.de> <20200309142223.GD9615@lenoir>
Date:   Mon, 09 Mar 2020 15:40:56 +0100
Message-ID: <87v9nd7frb.fsf@nanos.tec.linutronix.de>
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Frederic Weisbecker <frederic@kernel.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.