On Wed, Oct 06, 2021 at 02:05:55PM -0700, Joe Burton wrote:
> > Just to make sure we're on the same patch I'm proposing something like
> > the patch below...
>
> The proposed patch seems reasonable overall:
> + eliminates a lot of boilerplate
> + enables map update filtering
> + minimal perf cost when not tracing maps
> + avoids adding complexity to verifier
> - requires touching every map type's implementation
> - tracing one map implies tracing all maps
right. The single 'if' filter inside attached bpf prog should be fast enough.
> I can rev this RFC with hooks inside the common map types' update() and
> delete() methods.
>
> > Especially for local storage... doing tracing from bpf program itself
> > seems to make the most sense.
>
> I'm a little unclear on how this should work. There's no off-the-shelf
> solution that can do this for us, right?
>
> In particular I think we're looking for an interface like this:
>
> /* This is a BPF program */
> int my_prog(struct bpf_sock *sk) {
> struct MyValue *v = bpf_sk_storage_get(&my_map, sk, ...);
> ...
> bpf_sk_storage_trace(&my_map, sk, v);
> return 0;
> }
>
>
> I.e. we need some way of triggering a tracing hook from a BPF program.
I mean that above can be done as bpf prog.
bpf_sk_storage_trace() can be an empty global function inside a bpf program.
The attach to it is either fentry or even freplace.
