On Thu Jan 23, 2020 at 11:44 PM, Daniel Borkmann wrote: [...] > >> Different question related to your set. It looks like br_stack is only > >> available > >> on x86, is that correct? For other archs this will always bail out on > >> !br_stack > >> test. Perhaps we should document this fact so users are not surprised > >> why their > >> prog using this helper is not working on !x86. Wdyt? > > > > I think perf_event_open() should fail on !x86 if a user tries to configure > > it with branch stack collection. So there would not be the opportunity for > > the bpf prog to be attached and run. I haven't tested this, though. I'll > > look through the code / install a VM and test it. > > > As far as I can see the prog would still be attachable and runnable, > just that > the helper always will return -EINVAL on these archs. Maybe error code > should be > changed into -ENOENT to avoid confusion wrt whether user provided some > invalid > input args. Ok, will add. > Should this actually bail out with -EINVAL if size is not a > multiple > of sizeof(struct perf_branch_entry) as otherwise we'd end up copying > half broken > branch entry information? Sure, makes sense. > > > Thanks, > Daniel > > > >
