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

Frederic Weisbecker
2020-03-09T14:22:31Z

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>