Re: [PATCH 3/5] v2 seccomp_filters: Enable ftrace-based system call filtering

* Steven Rostedt [off-list ref] wrote:

I'm a bit nervous about the 'active' role of (trace_)events, because of the 
way multiple callbacks can be registered. How would:

	err = event_x();
	if (err == -EACCESS) {

be handled? [...]

The default behavior would be something obvious: to trigger all callbacks and 
use the first non-zero return value.

[...] Would we need a way to prioritize which call back gets the return 
value? One way I guess would be to add a check_event option, where you pass 
in an ENUM of the event you want:

	event_x();
	err = check_event_x(MYEVENT);

If something registered itself as "MYEVENT" to event_x, then you get the 
return code of MYEVENT. If the MYEVENT was not registered, a -ENODEV or 
something could be returned. I'm sure we could even optimize it such a way if 
no active events have been registered to event_x, that check_event_x() will 
return -ENODEV without any branches.

I would keep it simple and extensible - that way we can complicate it when the 
need arises! :)

Thanks,

	Ingo