Re: [PATCH/RFC] Make perf_event_open() propagate errors for use in bpf_perf_event_open()

[Jamal Hadi Salim]

On 2019-01-11 10:55 a.m., Arnaldo Carvalho de Melo wrote:
> Hi Peter,
>
> 	bpf_perf_event_open() already returns a value, but if
> perf_event_output's output_begin (mostly perf_output_begin) fails,
> the only way to know about that is looking before/after the rb->lost,
> right?
>
> 	For ring buffer users that is ok, we'll get a PERF_RECORD_LOST,
> etc, but for BPF programs it would be convenient to get that -ENOSPC and
> do some fallback, whatever makes sense, like in my augmented_syscalls
> stuff for 'perf trace', i.e. don't augment it (i.e. push stuff at the
> end of the normal payload), just don't filter the
> raw_syscalls:sys_enter, 'perf trace' will get the enter syscall enter
> event without the pointer dereference at the end, etc, warn the user but
> don't lose a syscall in the strace-like output.	
>
> 	What do you think? Am I missing something? Probably ;-)
>
> 	Ah, its just test built.

Works as advertised ;->
Tested-by: Jamal Hadi Salim <jhs@xxxxxxxxxxxx>

cheers,
jamal