On Thu Jan 23, 2020 at 11:23 PM, Daniel Borkmann wrote: [...] > > Yes, so we've been following this practice for all the BPF helpers no > matter > which program type. Though for tracing it may be up to debate whether it > makes > still sense given there's nothing to be leaked here since you can read > this data > anyway via probe read if you'd wanted to. So we might as well get rid of > the > clearing for all tracing helpers. Right, that makes sense. Do you want me to leave it in for this patchset and then remove all of them in a followup patchset? > > 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. [...] Thanks, Daniel
