Commit 721f0c12 authored Mar 07, 2014 by Linus Torvalds

Merge tag 'trace-fixes-v3.14-rc5' of...

Merge tag 'trace-fixes-v3.14-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing fix from Steven Rostedt:
"In the past, I've had lots of reports about trace events not working.
Developers would say they put a trace_printk() before and after the
trace event but when they enable it (and the trace event said it was
enabled) they would see the trace_printks but not the trace event.

I was not able to reproduce this, but that's because I wasn't looking
at the right location. Recently, another bug came up that showed the
issue.

If your kernel supports signed modules but allows for non-signed
modules to be loaded, then when one is, the kernel will silently set
the MODULE_FORCED taint on the module. Although, this taint happens
without the need for insmod --force or anything of the kind, it labels
the module with that taint anyway.

If this tainted module has tracepoints, the tracepoints will be
ignored because of the MODULE_FORCED taint. But no error message will
be displayed. Worse yet, the event infrastructure will still be
created letting users enable the trace event represented by the
tracepoint, although that event will never actually be enabled. This
is because the tracepoint infrastructure allows for non-existing
tracepoints to be enabled for new modules to arrive and have their
tracepoints set.

Although there are several things wrong with the above, this change
only addresses the creation of the trace event files for tracepoints
that are not created when a module is loaded and is tainted. This
change will print an error message about the module being tainted and
not the trace events will not be created, and it does not create the
trace event infrastructure"

* tag 'trace-fixes-v3.14-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
tracing: Do not add event files for modules that fail tracepoints

parents 27ea0f78 45ab2813

include/linux/tracepoint.h

+6 −0

Original line number	Diff line number	Diff line
		@@ -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 {

kernel/trace/trace_events.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -1777,6 +1777,16 @@ static void trace_module_add_events(struct module *mod)
		{
		struct ftrace_event_call call, start, **end;

		if (!mod->num_trace_events)
		return;

		/* Don't add infrastructure for mods without tracepoints */
		if (trace_module_has_bad_taint(mod)) {
		pr_err("%s: module has bad taint, not creating trace events\n",
		mod->name);
		return;
		}

		start = mod->trace_events;
		end = mod->trace_events + mod->num_trace_events;

kernel/tracepoint.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -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);

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