On 30/7/24 05:01, Andrii Nakryiko wrote: > On Fri, Jul 26, 2024 at 9:04 PM Leon Hwang <hffilwlqm@xxxxxxxxx> wrote: >> >> >> >> On 2024/7/27 08:12, Andrii Nakryiko wrote: >>> On Thu, Jul 25, 2024 at 7:57 PM Leon Hwang <hffilwlqm@xxxxxxxxx> wrote: >>>> >>>> >>>> [...] >>>> >>>> Is it OK to add a tracepoint here? I think tracepoint is more generic >>>> than retsnoop-like way. >>> >>> I personally don't see a problem with adding tracepoint, but how would >>> it look like, given we are talking about vararg printf-style function >>> calls? I'm not sure how that should be represented in such a way as to >>> make it compatible with tracepoints and not cause any runtime >>> overhead. >> >> The tracepoint is not about vararg printf-style function calls. >> >> It is to trace the reason why it fails to bpf_check_attach_target() at >> attach time. >> > > Oh, that changes things. I don't think we can keep adding extra > tracepoints for various potential reasons that BPF prog might be > failing to verify. > > But there is usually no need either. This particular code already > supports emitting extra information into verifier log, you just have > to provide that. This is done by libbpf automatically, can't your > library of choice do the same (if BPF program failed). > > Why go to all this trouble if we already have a facility to debug > issues like this. Note every issue is logged into verifier log, but in > this case it is. > Yeah, it is unnecessary to add tracepoint here, as we are able to trace the log message in bpf_log() arguments with retsnoop. Thanks, Leon
