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Date:   Mon, 9 Mar 2020 15:22:24 +0100
From:   Frederic Weisbecker <frederic@kernel.org>
To:     Thomas Gleixner <tglx@linutronix.de>
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
Message-ID: <20200309142223.GD9615@lenoir>
References: <20200308222359.370649591@linutronix.de>
 <20200308222609.017810037@linutronix.de>
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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?

> 
>  - static functions invoked from the protected functions need to be marked
>    as well as they can be instrumented otherwise.
> 
>  - using plain inline allows the compiler to emit traceable and probable
>    functions.
> 
> Fix this by adding the missing notrace/NOKPROBE annotations and converting
> the plain inlines to __always_inline.
> 
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Acked-by: Frederic Weisbecker <frederic@kernel.org>