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Date:   Mon, 20 Apr 2020 15:23:06 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Mark Rutland <mark.rutland@arm.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Sami Tolvanen <samitolvanen@google.com>,
        Will Deacon <will@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        James Morse <james.morse@arm.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Michal Marek <michal.lkml@markovi.net>,
        Ingo Molnar <mingo@redhat.com>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Dave Martin <Dave.Martin@arm.com>,
        Kees Cook <keescook@chromium.org>,
        Laura Abbott <labbott@redhat.com>,
        Marc Zyngier <maz@kernel.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
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        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v11 04/12] scs: disable when function graph tracing is
 enabled
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On Fri, 17 Apr 2020 16:46:14 +0100
Mark Rutland <mark.rutland@arm.com> wrote:

> > > > And doesn't BPF also do stuff like this?  
> > > 
> > > Can BPF mess with return addresses now!?  
> > 
> > At least on x86 I think it does. But what do I know, I can't operate
> > that stuff. Rostedt might know.  
> 
> Sounds like I might need to do some digging...

May want to ping Alexei. It appears that if BPF adds a direct hook to a
function, it will prevent the function graph tracer from tracing it. :-/

-- Steve