ftrace, perf: Avoid infinite event generation loop
Vince's perf-trinity fuzzer found yet another 'interesting' problem.
When we sample the irq_work_exit tracepoint with period==1 (or
PERF_SAMPLE_PERIOD) and we add an fasync SIGNAL handler we create an
infinite event generation loop:
,-> <IPI>
| irq_work_exit() ->
| trace_irq_work_exit() ->
| ...
| __perf_event_overflow() -> (due to fasync)
| irq_work_queue() -> (irq_work_list must be empty)
'--------- arch_irq_work_raise()
Similar things can happen due to regular poll() wakeups if we exceed
the ring-buffer wakeup watermark, or have an event_limit.
To avoid this, dis-allow sampling this particular tracepoint.
In order to achieve this, create a special perf_perm function pointer
for each event and call this (when set) on trying to create a
tracepoint perf event.
[ roasted: use expr... to allow for ',' in your expression ]
Reported-by: Vince Weaver <vincent.weaver@maine.edu>
Tested-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Dave Jones <davej@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20131114152304.GC5364@laptop.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 9abbe63..8c9b7a1 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -248,6 +248,9 @@
#ifdef CONFIG_PERF_EVENTS
int perf_refcount;
struct hlist_head __percpu *perf_events;
+
+ int (*perf_perm)(struct ftrace_event_call *,
+ struct perf_event *);
#endif
};
@@ -317,6 +320,19 @@
} \
early_initcall(trace_init_flags_##name);
+#define __TRACE_EVENT_PERF_PERM(name, expr...) \
+ static int perf_perm_##name(struct ftrace_event_call *tp_event, \
+ struct perf_event *p_event) \
+ { \
+ return ({ expr; }); \
+ } \
+ static int __init trace_init_perf_perm_##name(void) \
+ { \
+ event_##name.perf_perm = &perf_perm_##name; \
+ return 0; \
+ } \
+ early_initcall(trace_init_perf_perm_##name);
+
#define PERF_MAX_TRACE_SIZE 2048
#define MAX_FILTER_STR_VAL 256 /* Should handle KSYM_SYMBOL_LEN */