On Mon, Sep 09, 2024 at 08:34:36PM +0200, Oleg Nesterov wrote:

On 09/09, Jiri Olsa wrote:

quoted

On Fri, Sep 06, 2024 at 09:18:15PM +0200, Oleg Nesterov wrote:

quoted

And btw... Can bpftrace attach to the uprobe tp?

	# perf probe -x ./test -a func
	Added new event:
	  probe_test:func      (on func in /root/TTT/test)

	You can now use it in all perf tools, such as:

		perf record -e probe_test:func -aR sleep 1

	# bpftrace -e 'tracepoint:probe_test:func { printf("%d\n", pid); }'
	Attaching 1 probe...
	ioctl(PERF_EVENT_IOC_SET_BPF): Invalid argument
	ERROR: Error attaching probe: tracepoint:probe_test:func

the problem here is that bpftrace assumes BPF_PROG_TYPE_TRACEPOINT type
for bpf program, but that will fail in perf_event_set_bpf_prog where
perf event will be identified as uprobe and demands bpf program type
to be BPF_PROG_TYPE_KPROBE

Yes, thanks, I know,

quoted

I don't think
there's a way to find out the tracepoint subtype (kprobe/uprobe) from
the tracefs record

Hmm, indeed. it seems that it is not possible to derive tp_event->flags
from tracefs...

Perhaps bpftrace could look for probe_test:func in [uk]probe_events?
Or simply retry ioctl(PERF_EVENT_IOC_SET_BPF) with BPF_PROG_TYPE_KPROBE
if BPF_PROG_TYPE_TRACEPOINT returns EINVAL? Ugly, yes.

yep, but will probably work, I created issue https://github.com/bpftrace/bpftrace/issues/3447
so it's not lost

jirka