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Message-ID: <20200420152306.2d45e3c4@gandalf.local.home>
Date: Mon, 20 Apr 2020 15:23:06 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Mark Rutland <mark.rutland@....com>
Cc: Peter Zijlstra <peterz@...radead.org>, Sami Tolvanen
 <samitolvanen@...gle.com>, Will Deacon <will@...nel.org>, Catalin Marinas
 <catalin.marinas@....com>, James Morse <james.morse@....com>, Ard
 Biesheuvel <ard.biesheuvel@...aro.org>, Masahiro Yamada
 <masahiroy@...nel.org>, Michal Marek <michal.lkml@...kovi.net>, Ingo Molnar
 <mingo@...hat.com>, Juri Lelli <juri.lelli@...hat.com>, Vincent Guittot
 <vincent.guittot@...aro.org>, Dave Martin <Dave.Martin@....com>, Kees Cook
 <keescook@...omium.org>, Laura Abbott <labbott@...hat.com>, Marc Zyngier
 <maz@...nel.org>, Masami Hiramatsu <mhiramat@...nel.org>, Nick Desaulniers
 <ndesaulniers@...gle.com>, Jann Horn <jannh@...gle.com>, Miguel Ojeda
 <miguel.ojeda.sandonis@...il.com>, clang-built-linux@...glegroups.com,
 kernel-hardening@...ts.openwall.com, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v11 04/12] scs: disable when function graph tracing is
 enabled

On Fri, 17 Apr 2020 16:46:14 +0100
Mark Rutland <mark.rutland@....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

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