Miguel Ojeda [off-list ref] writes:

Hi Michael,

On Tue, Mar 23, 2021 at 4:27 AM Michael Ellerman [off-list ref] wrote:

quoted

Hi all,

Here's a first attempt at getting the kernel Rust support building on powerpc.

Thanks a *lot*! It is great to have more architectures rolling.

No worries.

quoted

It's powerpc64le only for now, as that's what I can easily test given the
distros I have installed. Though powerpc and powerpc64 are also Tier 2 platforms

Even if it is just 64-bit, it is very good to have it!

quoted

so in theory should work. Supporting those would require something more
complicated than just pointing rustc at arch/$(ARCH)/rust/target.json.

Yeah, the arch/$(ARCH)/rust/target.json dance is a placeholder -- I
need to figure out how to do that more cleanly, likely generating them
on the fly.

Yeah that's a good idea. That way they can be made to exactly match the
kernel configuration.

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This is based on 832575d934a2 from the Rust-for-Linux tree. Anything newer gives
me errors about symbol name lengths. I figured I'd send this anyway, as it seems
like those errors are probably not powerpc specific.

Sure, feel free to send things even if they don't work completely.

I will take a look at the symbol name lengths -- I increased that
limit to 512 and added support for 2-byte lengths in the tables, but
perhaps something is missing. If I manage to make it work, I can add
ppc64le to our CI! :-)

It would be nice to be in the CI. I was building natively so I haven't
tried cross compiling yet (which we'll need for CI).

quoted

Michael Ellerman (4):
  rust: Export symbols in initialized data section
  rust: Add powerpc64 as a 64-bit target_arch in c_types.rs
  powerpc/rust: Add target.json for ppc64le
  rust: Enable for ppc64le

Regarding the development process: at least until the RFC we are
working with the usual GitHub PR workflow (for several reasons: having
a quick CI setup, getting new Rust developers on-board, having a list
of "issues", cross-reference with the Rust repo, etc.).

I can take patches from the list, of course, but since we are pre-RFC,
do you mind if they get rebased etc. through there?

No I don't mind at all. I just sent patches so other ppc folks could see
what I had, and it's kind of the process I'm used to.

I can send a pull request if that's easiest.

cheers