Re: [PATCH 3/3] rust: add tracepoint support

[Peter Zijlstra]

On Thu, Jun 06, 2024 at 12:00:36PM -0700, Boqun Feng wrote:
> On Thu, Jun 06, 2024 at 07:35:44PM +0200, Peter Zijlstra wrote:
> > On Thu, Jun 06, 2024 at 08:49:06AM -0700, Boqun Feng wrote:
> > 
> > > Long-term plan is to 1) compile the C helpers in some IR and 2) inline
> > > the helpers with Rust in IR-level, as what Gary has:
> > > 
> > > 	https://lore.kernel.org/rust-for-linux/20240529202817.3641974-1-gary@xxxxxxxxxxx/
> > 
> > Urgh, that still needs us to maintain that silly list of helpers :-/
> > 
> 
> But it's an improvement from the current stage, right? ;-)

Somewhat, but only marginal.

> > Can't we pretty please have clang parse the actual header files into IR
> > and munge that into rust? So that we don't get to manually duplicate
> > everything+dog.
> 
> That won't always work, because some of our kernel APIs are defined as
> macros, and I don't think it's a trivial job to generate a macro
> definition to a function definition so that it can be translated to
> something in IR. We will have to do the macro -> function mapping
> ourselves somewhere, if we want to inline the API across languages.

We can try and see how far we can get with moving a bunch of stuff into
inlines. There's quite a bit of simple CPP that could be inlines or
const objects I suppose.

Things like the tracepoints are of course glorious CPP abuse and are
never going to work.

But perhaps you can have an explicit 'eval-CPP on this here' construct
or whatnot. If I squit I see this paste! thingy (WTF's up with that !
operator?) to munge function names in the static_call thing. So
something like apply CPP from over there on this here can also be done
:-)