On Sun, Sep 29, 2024 at 10:35:49AM +0800, Yafang Shao wrote: > On Sat, Sep 28, 2024 at 7:14 AM Andrii Nakryiko > <andrii.nakryiko@xxxxxxxxx> wrote: > > > > On Sun, Sep 22, 2024 at 12:59 PM Tyrone Wu <wudevelops@xxxxxxxxx> wrote: > > > > > > Hello, > > > > > > When retrieving bpf_link_info.perf_event kprobe/uprobe/tracepoint > > > data, I noticed that the name_len field always returns 0. After some > > > digging, I see that name_len is never actually populated, which > > > explains the 0 value. > > > > > > I expected it to function similarly to > > > bpf_link_info.raw_tracepoint.tp_name_len, where that field is filled > > > with the length of tp_name. However, I noticed that the selftest > > > explicitly asserts that name_len should be 0. I was wondering if > > > someone could clarify whether it is intended for the > > > bpf_link_info.perf_event name_len field to not be populated. > > > > This sounds like a bug. It should behave consistently with the other > > users of input/output string buffer size fields: on input we get > > maximum buffer size, on output we should put an actual size of the > > string (especially if it was truncated). > > > > Yafang, Jiri, WDYT? > > The reason name_len is 0 is that the user did not set both the buffer > and the length. IOW, this happens when the user buffer is NULL and the > input length is 0. However, we should make this behavior consistent by > returning the actual size to the user if both the buffer and length > are unset. yep, makes sense the same way rawtp does that thanks, jirka
