Re: [PATCH bpf-next v1 0/4] Support bpf trampoline for RV64

[Björn Töpel]

Hi Lehui,

Pu Lehui <pulehui@xxxxxxxxxxxxxxx> writes:

> BPF trampoline is the critical infrastructure of the bpf
> subsystem, acting as a mediator between kernel functions
> and BPF programs. Numerous important features, such as
> using ebpf program for zero overhead kernel introspection,
> rely on this key component. We can't wait to support bpf
> trampoline on RV64. Since RV64 does not support ftrace
> direct call yet, the current RV64 bpf trampoline is only
> used in bpf context.

Thanks a lot for continuing this work. I agree with you that it's
valuable to have BPF trampoline support, even without proper direct call
support (we'll get there soon). The trampoline enables kfunc calls. On
that note; I don't see that you enable "bpf_jit_supports_kfunc_call()"
anywhere in the series.  With BPF trampoline support, the RISC-V BPF
finally can support kfunc calls!

I'd add the following to bpf_jit_comp64.c:

bool bpf_jit_supports_kfunc_call(void)
{
        return true;
}

:-)

I'll do a review ASAP.


Björn