latency tracers(wakeup, wakeup_rt, wakeup_dl, irqsoff) can use the function_graph trace when display_graph trace option is set by user via tracefs. And currently the set_graph_notrace filter is not fully supported in latency tracers, only the graph_ret event can be filtered, the graph_ent events will always be submitted to the trace ring buffer without respecting to the filter.
The issue is that the submitted graph_entry event that matches the filter can be assigned with a negative depth(minuts FTRACE_NOTRACE_DEPTH) which will be used as the array index of fgraph_cpu_data when printing trace entries, as a result, an oops can be hit when accessing the array. Fully supporting the set_graph_notrace filter in latency tracers can avoid this oops and provide a small enhancement for these tracers at the same time. To reproduce the oops: echo 1 > options/display_graph echo schedule > set_graph_notrace echo wakeup > current_tracer cat trace (several times) Signed-off-by: Chunyu Hu <[email protected]> --- kernel/trace/trace_irqsoff.c | 6 ++++++ kernel/trace/trace_sched_wakeup.c | 6 ++++++ 2 files changed, 12 insertions(+) diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c index 03cdff8..a4ed46a 100644 --- a/kernel/trace/trace_irqsoff.c +++ b/kernel/trace/trace_irqsoff.c @@ -175,6 +175,12 @@ static int irqsoff_graph_entry(struct ftrace_graph_ent *trace) int ret; int pc; + if (trace->depth < 0) + return 0; + + if (ftrace_graph_notrace_addr(trace->func)) + return 1; + if (!func_prolog_dec(tr, &data, &flags)) return 0; diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c index 9d4399b..e54fff7 100644 --- a/kernel/trace/trace_sched_wakeup.c +++ b/kernel/trace/trace_sched_wakeup.c @@ -239,6 +239,12 @@ static int wakeup_graph_entry(struct ftrace_graph_ent *trace) unsigned long flags; int pc, ret = 0; + if (trace->depth < 0) + return 0; + + if (ftrace_graph_notrace_addr(trace->func)) + return 1; + if (!func_prolog_preempt_disable(tr, &data, &pc)) return 0; -- 1.8.3.1
