Re: [PATCH v2] tracing/uprobe: Add missing PID filter for uretprobe

[Jiri Olsa <olsajiri@gmail.com>]

On Tue, Aug 27, 2024 at 10:19:26PM +0200, Oleg Nesterov wrote:
> Sorry for another reply, I just noticed I missed one part of your email...
> 
> On 08/27, Jiri Olsa wrote:
> >
> >    ->     uretprobe-hit
> >             handle_swbp
> >               uprobe_handle_trampoline
> >                 handle_uretprobe_chain
> >                 {
> >
> >                   for_each_uprobe_consumer {
> >
> >                     // consumer for task 1019
> >                     uretprobe_dispatcher
> >                       uretprobe_perf_func
> >                         -> runs bpf program
> >
> >                     // consumer for task 1018
> >                     uretprobe_dispatcher
> >                       uretprobe_perf_func
> >                         -> runs bpf program
> >
> >                   }
> >                 }
> >
> > and I think the same will happen for perf record in this case where instead of
> > running the program we will execute perf_tp_event
> 
> Hmm. Really? In this case these 2 different consumers will have the different
> trace_event_call's, so
> 
> 	// consumer for task 1019
> 	uretprobe_dispatcher
> 	  uretprobe_perf_func
> 	    __uprobe_perf_func
> 	      perf_tp_event
> 
> won't store the event because this_cpu_ptr(call->perf_events) should be
> hlist_empty() on this CPU, the perf_event for task 1019 wasn't scheduled in
> on this CPU...

I'll double check on that, but because there's no filter for uretprobe
I think it will be stored under 1018 event

> 
> No?
> 
> Ok, looks like I'm totally confused ;)

I'm working on bpf selftests for above (uprobe and uprobe_multi paths)
I plan to send them together with fixes we discussed earlier

I'm hoping this will make it more clear

jirka