On Tue, Jul 16, 2019 at 06:31:17PM -0400, Steven Rostedt wrote: > On Tue, 16 Jul 2019 17:30:50 -0400 > Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> wrote: > > > I don't see why a new bpf node for a trace event is a bad idea, really. > > tracefs is how we deal with trace events on Android. We do it in production > > systems. This is a natural extension to that and fits with the security model > > well. > > What I would like to see is a way to have BPF inject data into the > ftrace ring buffer directly. There's a bpf_trace_printk() that I find a > bit of a hack (especially since it hooks into trace_printk() which is > only for debugging purposes). Have a dedicated bpf ftrace ring > buffer event that can be triggered is what I am looking for. Then comes > the issue of what ring buffer to place it in, as ftrace can have > multiple ring buffer instances. But these instances are defined by the > tracefs instances directory. Having a way to associate a bpf program to > a specific event in a specific tracefs directory could allow for ways to > trigger writing into the correct ftrace buffer. But his problem is with doing the association of a BPF program with tracefs itself. How would you attach a BPF program with tracefs without doing a text based approach? His problem is with the text based approach per his last email. > But looking over the patches, I see what Alexei means that there's no > overlap with ftrace and these patches except for the tracefs directory > itself (which is part of the ftrace infrastructure). And the trace > events are technically part of the ftrace infrastructure too. I see the > tracefs interface being used, but I don't see how the bpf programs > being added affect the ftrace ring buffer or other parts of ftrace. And > I'm guessing that's what is confusing Alexei. In a follow-up patch which I am still writing, I am using the trace ring buffer as temporary storage since I am formatting the trace event into it. This patch you are replying to is just for raw tracepoint and yes, I agree this one does not use the ring buffer, but a future addition to it does. So I don't think the association of this patch series with ftrace is going to be an issue IMO. thanks, - Joel
