Update trace perf output with struct deserialize example

Signed-off-by: Brenden Blanco <[email protected]>

examples/tracing/trace_perf_output.py

@@ -8,20 +8,28 @@
 
 import atexit
 from bcc import BPF
-import ctypes
+import ctypes as ct
+
+class Data(ct.Structure):
+ _fields_ = [("ts", ct.c_ulonglong),
+ ("magic", ct.c_ulonglong)]
 
 counter = 0
 def cb(cpu, data, size):
+ assert size >= ct.sizeof(Data)
+ event = ct.cast(data, ct.POINTER(Data)).contents
+ print("[%0d] %f: %x" % (cpu, float(event.ts) / 1000000, event.magic))
  global counter
  counter += 1
 
 prog = """
 BPF_PERF_OUTPUT(events);
 BPF_TABLE("array", int, u64, counters, 10);
-int kprobe__sys_write(void *ctx) {
+int kprobe__sys_clone(void *ctx) {
  struct {
  u64 ts;
- } data = {bpf_ktime_get_ns()};
+ u64 magic;
+ } data = {bpf_ktime_get_ns(), 0x12345678};
  int rc;
  if ((rc = events.perf_submit(ctx, &data, sizeof(data))) < 0)
  bpf_trace_printk("perf_output failed: %d\\n", rc);
@@ -38,7 +46,7 @@ def cb(cpu, data, size):
 def print_counter():
  global counter
  global b
- print("counter = %d vs %d" % (counter, b["counters"][ctypes.c_int(0)].value))
+ print("counter = %d vs %d" % (counter, b["counters"][ct.c_int(0)].value))
 
 print("Tracing sys_write, try `dd if=/dev/zero of=/dev/null`")
 print("Tracing... Hit Ctrl-C to end.")