Re: [RFA][PATCH 3/5] tracing: Do not add event files for modules that fail tracepoints

[Mathieu Desnoyers <mathieu.desnoyers@efficios.com>]

----- Original Message -----
> From: "Steven Rostedt" <rostedt@goodmis.org>
> To: linux-kernel@vger.kernel.org
> Cc: "Ingo Molnar" <mingo@kernel.org>, "Andrew Morton" <akpm@linux-foundation.org>, "Peter Zijlstra"
> <peterz@infradead.org>, "Frederic Weisbecker" <fweisbec@gmail.com>, "Mathieu Desnoyers"
> <mathieu.desnoyers@efficios.com>, stable@vger.kernel.org, "Rusty Russell" <rusty@rustcorp.com.au>
> Sent: Thursday, February 27, 2014 10:46:19 AM
> Subject: [RFA][PATCH 3/5] tracing: Do not add event files for modules that fail tracepoints
> 
> [Request for Ack]
> 
> From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>
> 
> If a module fails to add its tracepoints due to module tainting, do not
> create the module event infrastructure in the debugfs directory. As the
> events
> will not work and worse yet, they will silently fail, making the user wonder
> why the events they enable do not display anything.
> 
> Having a warning on module load and the events not visible to the users
> will make the cause of the problem much clearer.

Looks good!

Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

> 
> Fixes: 6d723736e472 "tracing/events: add support for modules to TRACE_EVENT"
> Cc: stable@vger.kernel.org # 2.6.31+
> Cc: Rusty Russell <rusty@rustcorp.com.au>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
> ---
>  include/linux/tracepoint.h  | 6 ++++++
>  kernel/trace/trace_events.c | 4 ++++
>  kernel/tracepoint.c         | 7 ++++++-
>  3 files changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
> index accc497..7159a0a 100644
> --- a/include/linux/tracepoint.h
> +++ b/include/linux/tracepoint.h
> @@ -60,6 +60,12 @@ struct tp_module {
>  	unsigned int num_tracepoints;
>  	struct tracepoint * const *tracepoints_ptrs;
>  };
> +bool trace_module_has_bad_taint(struct module *mod);
> +#else
> +static inline bool trace_module_has_bad_taint(struct module *mod)
> +{
> +	return false;
> +}
>  #endif /* CONFIG_MODULES */
>  
>  struct tracepoint_iter {
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index e71ffd4..b2fee73 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -1777,6 +1777,10 @@ static void trace_module_add_events(struct module
> *mod)
>  {
>  	struct ftrace_event_call **call, **start, **end;
>  
> +	/* Don't add infrastructure for mods without tracepoints */
> +	if (trace_module_has_bad_taint(mod))
> +		return;
> +
>  	start = mod->trace_events;
>  	end = mod->trace_events + mod->num_trace_events;
>  
> diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
> index 29f2654..031cc56 100644
> --- a/kernel/tracepoint.c
> +++ b/kernel/tracepoint.c
> @@ -631,6 +631,11 @@ void tracepoint_iter_reset(struct tracepoint_iter *iter)
>  EXPORT_SYMBOL_GPL(tracepoint_iter_reset);
>  
>  #ifdef CONFIG_MODULES
> +bool trace_module_has_bad_taint(struct module *mod)
> +{
> +	return mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP));
> +}
> +
>  static int tracepoint_module_coming(struct module *mod)
>  {
>  	struct tp_module *tp_mod, *iter;
> @@ -641,7 +646,7 @@ 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 (trace_module_has_bad_taint(mod))
>  		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