bcc: Auto-tracepoints similar to auto-kprobes

When a function in the BPF program starts with "tracepoint__", parse
the rest of the name as a tracepoint category and name and attach the
tracepoint automatically. For example:

```
int tracepoint__sched__sched_switch(...)
```

As a result, the sched:sched_switch tracepoint is enabled and the function
is attached to that tracepoint.

src/python/bcc/__init__.py

@@ -608,17 +608,21 @@ def detach_uretprobe(cls, name="", sym="", addr=None):
  del open_uprobes[ev_name]
 
  def _trace_autoload(self):
- # Cater to one-liner case where attach_kprobe is omitted and C function
- # name matches that of the kprobe.
- if len(open_kprobes) == 0:
- for i in range(0, lib.bpf_num_functions(self.module)):
- func_name = lib.bpf_function_name(self.module, i).decode()
- if func_name.startswith("kprobe__"):
- fn = self.load_func(func_name, BPF.KPROBE)
- self.attach_kprobe(event=fn.name[8:], fn_name=fn.name)
- elif func_name.startswith("kretprobe__"):
- fn = self.load_func(func_name, BPF.KPROBE)
- self.attach_kretprobe(event=fn.name[11:], fn_name=fn.name)
+ for i in range(0, lib.bpf_num_functions(self.module)):
+ func_name = lib.bpf_function_name(self.module, i).decode()
+ if func_name.startswith("kprobe__"):
+ fn = self.load_func(func_name, BPF.KPROBE)
+ self.attach_kprobe(event=fn.name[8:], fn_name=fn.name)
+ elif func_name.startswith("kretprobe__"):
+ fn = self.load_func(func_name, BPF.KPROBE)
+ self.attach_kretprobe(event=fn.name[11:], fn_name=fn.name)
+ elif func_name.startswith("tracepoint__"):
+ fn = self.load_func(func_name, BPF.TRACEPOINT)
+ tp = fn.name[len("tracepoint__"):].replace("__", ":")
+ self.attach_tracepoint(tp=tp, fn_name=fn.name)
+ # It would be nice to automatically generate the tracepont
+ # structure here, but once we passed the load of the BPF program,
+ # we can't do that anymore. It will have to go in the clang rewriter.
 
  def trace_open(self, nonblocking=False):
  """trace_open(nonblocking=False)