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Date: Thu, 6 Jun 2024 21:29:51 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Boqun Feng <boqun.feng@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Alice Ryhl <aliceryhl@google.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Josh Poimboeuf <jpoimboe@kernel.org>,
	Jason Baron <jbaron@akamai.com>, Ard Biesheuvel <ardb@kernel.org>,
	Miguel Ojeda <ojeda@kernel.org>,
	Alex Gaynor <alex.gaynor@gmail.com>,
	Wedson Almeida Filho <wedsonaf@gmail.com>,
	Gary Guo <gary@garyguo.net>,
	=?iso-8859-1?Q?Bj=F6rn?= Roy Baron <bjorn3_gh@protonmail.com>,
	Benno Lossin <benno.lossin@proton.me>,
	Andreas Hindborg <a.hindborg@samsung.com>,
	linux-trace-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/3] rust: add tracepoint support
Message-ID: <20240606192951.GJ8774@noisy.programming.kicks-ass.net>
References: <20240606-tracepoint-v1-0-6551627bf51b@google.com>
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 <389a8c55-a169-47ef-99c0-48f58003b40c@efficios.com>
 <ZmHacqvRwBj7OvWm@boqun-archlinux>
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 <ZmIHVIqEukWWRMgd@boqun-archlinux>
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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@garyguo.net/
> > 
> > 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
:-)