Merge branch 'master' into dcsnoop

docs/tutorial_bcc_python_developer.md

@@ -92,7 +92,7 @@ This is simalar to hello_world.py, and traces new processes via sys_clone() agai
 
 1. ```prog =```: This time we declare the C program as a variable, and later refer to it. This is useful if you want to add some string substitutions based on command line arguments.
 
-1. ```hello()```: Now we're just declaring a C function, instead of the ```kprobe__``` shortcut. We'll refer to this later.
+1. ```hello()```: Now we're just declaring a C function, instead of the ```kprobe__``` shortcut. We'll refer to this later. All C functions declared in the BPF program are expected to be executed on a probe, hence they all need to take a ```pt_reg* ctx``` as first argument. If you need to define some helper function that will not be executed on a probe, they need to be defined as ```static inline``` in order to be inlined by the compiler. Sometimes you would also need to add ```_always_inline``` function attribute to it.
 
 1. ```b.attach_kprobe(event="sys_clone", fn_name="hello")```: Creates a kprobe for the sys_clone() kernel function, which will execute our defined hello() function. You can call attach_kprobe() more than once, and attach your C function to multiple kernel functions.