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From: Peter Zijlstra <peterz@infradead.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Joel Fernandes <joel@joelfernandes.org>,
	Frederic Weisbecker <frederic@kernel.org>,
	Dan Carpenter <dan.carpenter@oracle.com>,
	Josh Poimboeuf <jpoimboe@redhat.com>
Subject: Re: Instrumentation and RCU
Date: Mon, 9 Mar 2020 21:18:42 +0100	[thread overview]
Message-ID: <20200309201842.GL12561@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <87mu8p797b.fsf@nanos.tec.linutronix.de>

On Mon, Mar 09, 2020 at 06:02:32PM +0100, Thomas Gleixner wrote:
> #4 Protecting call chains
> 
>    Our current approach of annotating functions with notrace/noprobe is
>    pretty much broken.
> 
>    Functions which are marked NOPROBE or notrace call out into functions
>    which are not marked and while this might be ok, there are enough
>    places where it is not. But we have no way to verify that.
> 
>    That's just a recipe for disaster. We really cannot request from
>    sysadmins who want to use instrumentation to stare at the code first
>    whether they can place/enable an instrumentation point somewhere.
>    That'd be just a bad joke.
> 
>    I really think we need to have proper text sections which are off
>    limit for any form of instrumentation and have tooling to analyze the
>    calls into other sections. These calls need to be annotated as safe
>    and intentional.

So the only tool I know of that does full callchains is smatch. And in
one of my series I did prod Dan about this.

The alternative is that we bite the bullet and add a vmlinux objtool
pass. This keeps getting mentioned, so maybe it is time :/ I'd hate it,
because it will increase build time at the slowest point, but it'd get
us the coverage we need here.

  parent reply	other threads:[~2020-03-09 20:18 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-09 17:02 Instrumentation and RCU Thomas Gleixner
2020-03-09 18:15 ` Steven Rostedt
2020-03-09 18:42   ` Joel Fernandes
2020-03-09 19:07     ` Steven Rostedt
2020-03-09 19:20       ` Mathieu Desnoyers
2020-03-16 15:02       ` Joel Fernandes
2020-03-09 18:59   ` Thomas Gleixner
2020-03-10  8:09     ` Masami Hiramatsu
2020-03-10 11:43       ` Thomas Gleixner
2020-03-10 15:31         ` Mathieu Desnoyers
2020-03-10 15:46           ` Steven Rostedt
2020-03-10 16:21             ` Mathieu Desnoyers
2020-03-11  0:18               ` Masami Hiramatsu
2020-03-11  0:37                 ` Mathieu Desnoyers
2020-03-11  7:48                   ` Masami Hiramatsu
2020-03-10 16:06         ` Masami Hiramatsu
2020-03-12 13:53         ` Peter Zijlstra
2020-03-10 15:24       ` Mathieu Desnoyers
2020-03-10 17:05       ` Daniel Thompson
2020-03-09 18:37 ` Mathieu Desnoyers
2020-03-09 18:44   ` Steven Rostedt
2020-03-09 18:52     ` Mathieu Desnoyers
2020-03-09 19:09       ` Steven Rostedt
2020-03-09 19:25         ` Mathieu Desnoyers
2020-03-09 19:52   ` Thomas Gleixner
2020-03-10 15:03     ` Mathieu Desnoyers
2020-03-10 16:48       ` Thomas Gleixner
2020-03-10 17:40         ` Mathieu Desnoyers
2020-03-10 18:31           ` Thomas Gleixner
2020-03-10 18:37             ` Mathieu Desnoyers
2020-03-10  1:40   ` Alexei Starovoitov
2020-03-10  8:02     ` Thomas Gleixner
2020-03-10 16:54     ` Paul E. McKenney
2020-03-17 17:56     ` Joel Fernandes
2020-03-09 20:18 ` Peter Zijlstra [this message]
2020-03-09 20:47 ` Paul E. McKenney
2020-03-09 20:58   ` Steven Rostedt
2020-03-09 21:25     ` Paul E. McKenney
2020-03-09 23:52   ` Frederic Weisbecker
2020-03-10  2:26     ` Paul E. McKenney
2020-03-10 15:13   ` Mathieu Desnoyers
2020-03-10 16:49     ` Paul E. McKenney
2020-03-10 17:22       ` Mathieu Desnoyers
2020-03-10 17:26         ` Paul E. McKenney

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