On Wed, Jul 1, 2026 at 3:40 PM Masami Hiramatsu <[email protected]> wrote: > > On Wed, 01 Jul 2026 11:41:26 -0700 > "Alexei Starovoitov" <[email protected]> wrote: > > > > > Nack. > > I really don't like it. > > There were days in the past when the kernel generating bpf directly was > > appealing. > > These days are gone. Performance improvements for fetchargs is not a good > > reason > > to add all this complexity and bypass verifier checks. > > bpf insns should come from user space. > > Thanks for your comment! > OK, I don't mind because this is a kind of investigation project. And some > people had asked me about the same idea, now I can tell them the result. > > I'm satisfied with the current outcome, as this development process gave me > insight into the implementation of BPF and demonstrated the potential for > optimization via JIT. :) > > And also, as noted in the cover letter, the current performance of fetcharg > is better than I thought, and is good enough for debugging. :) > > BTW, I'm also interested in calling the verifier on this generated code. > Even it it is not merged, I think showing the correct way to implement it > will be useful in the future.
The whole feature you're trying to do is imo reinvention of the wheel. bpf could do that kind of filtering years ago. I don't buy the excuse that embedded environments without any kind of user space needs this facility.
