Re: BPF calls to modules?

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Fri, Jun 18, 2021 at 2:13 AM Alex Ghiti <alex@ghiti.fr> wrote:
>
> Hi guys,
>
> First, pardon my ignorance regarding BPF, the following might be silly.
>
> We were wondering here
> https://patchwork.kernel.org/project/linux-riscv/patch/20210615004928.2d27d2ac@xhacker/
> if BPF programs that now have the capability to call kernel functions
> (https://lwn.net/Articles/856005/) can also call modules function or
> vice-versa?

Not yet, but it was an explicit design consideration and there was
public interest just recently. So I'd say this is going to happen
sooner rather than later.

>
> The underlying important fact is that in riscv, we are limited to 2GB
> offset to call functions and that restricts where we can place modules
> and BPF regions wrt kernel (see Documentation/riscv/vm-layout.rst for
> the current possibly wrong layout).
>
> So should we make sure that modules and BPF lie in the same 2GB region?

Based on the above and what you are explaining about 2GB limits, I'd
say yes?.. Or alternatively those 2GB restrictions might perhaps be
lifted somehow?

>
> Thanks,
>
> Alex