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Subject[PATCH] staging: tracing/kprobe: filter kprobe based perf event
Date
From: Jinshan Xiong <jinshan.xiong@gmail.com>

Invoking bpf program only if kprobe based perf_event has been added into
the percpu list. This is essential to make event tracing for cgroup to work
properly.

Signed-off-by: Jinshan Xiong <jinshan.xiong@gmail.com>
---
kernel/trace/trace_kprobe.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 9d483ad9bb6c..40ef0f1945f7 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1171,11 +1171,18 @@ static int
kprobe_perf_func(struct trace_kprobe *tk, struct pt_regs *regs)
{
struct trace_event_call *call = trace_probe_event_call(&tk->tp);
+ struct hlist_head *head = this_cpu_ptr(call->perf_events);
struct kprobe_trace_entry_head *entry;
- struct hlist_head *head;
int size, __size, dsize;
int rctx;

+ /*
+ * If head is empty, the process currently running on this cpu is not
+ * interested by kprobe perf PMU.
+ */
+ if (hlist_empty(head))
+ return 0;
+
if (bpf_prog_array_valid(call)) {
unsigned long orig_ip = instruction_pointer(regs);
int ret;
@@ -1193,10 +1200,6 @@ kprobe_perf_func(struct trace_kprobe *tk, struct pt_regs *regs)
return 0;
}

- head = this_cpu_ptr(call->perf_events);
- if (hlist_empty(head))
- return 0;
-
dsize = __get_data_size(&tk->tp, regs);
__size = sizeof(*entry) + tk->tp.size + dsize;
size = ALIGN(__size + sizeof(u32), sizeof(u64));
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