linux-kernel - Re: [RFC][PATCH] tracing: Warn and notify if tracepoints are not loaded due to module taint

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Message-ID: <188130295.30493.1393375141631.JavaMail.zimbra@efficios.com>
Date:	Wed, 26 Feb 2014 00:39:01 +0000 (UTC)
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [RFC][PATCH] tracing: Warn and notify if tracepoints are not
 loaded due to module taint

----- Original Message -----
> From: "Steven Rostedt" <rostedt@...dmis.org>
> To: "LKML" <linux-kernel@...r.kernel.org>
> Cc: "Ingo Molnar" <mingo@...nel.org>, "Mathieu Desnoyers" <mathieu.desnoyers@...icios.com>, "Rusty Russell"
> <rusty@...tcorp.com.au>, "Frederic Weisbecker" <fweisbec@...il.com>, "Andrew Morton" <akpm@...ux-foundation.org>,
> "Peter Zijlstra" <peterz@...radead.org>
> Sent: Tuesday, February 25, 2014 7:15:05 PM
> Subject: [RFC][PATCH] tracing: Warn and notify if tracepoints are not loaded due to module taint
> 
> [ Posting this as an RFC, but I plan on pushing it as soon as I finish
> testing it ]
> 
> If a module is loaded that is tainted with anything but OOT or CRAP, then
> it will not create the traceoint infrastructure for the module. There should

traceoint -> tracepoint

> be a big warning when this happens instead of exiting silently.
> 
> Fixes: 97e1c18e8d17 "tracing: Kernel Tracepoints"
> Cc: stable@...r.kernel.org
> Cc: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
> ---
>  kernel/tracepoint.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
> index 29f2654..413bc06 100644
> --- a/kernel/tracepoint.c
> +++ b/kernel/tracepoint.c
> @@ -641,7 +641,8 @@ static int tracepoint_module_coming(struct module *mod)
>  	 * module headers (for forced load), to make sure we don't cause a crash.
>  	 * Staging and out-of-tree GPL modules are fine.
>  	 */
> -	if (mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP)))
> +	if (WARN_ONCE(mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP)),
> +		      "Module is tainted, disabling tracepoints"))

Perhaps ever clearer with:

   "Module \"%s\" is tainted, disabling tracepoints", mod->name

?

Other than that, looks good to me!

Thanks,

Mathieu

>  		return 0;
>  	mutex_lock(&tracepoints_mutex);
>  	tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL);
> --
> 1.8.5.3
> 
> 

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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