linux-kernel - Re: RISC-V: Re-enable GCC+Rust builds

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Message-ID: <b1734c45-42ec-46c7-9d4c-2677044aacab@gmail.com>
Date: Tue, 2 Sep 2025 01:19:42 +0800
From: Asuna <spriteovo@...il.com>
To: Conor Dooley <conor@...nel.org>
Cc: Jason Montleon <jmontleo@...hat.com>, Miguel Ojeda <ojeda@...nel.org>,
 Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>,
 Gary Guo <gary@...yguo.net>, Björn Roy Baron
 <bjorn3_gh@...tonmail.com>, Benno Lossin <lossin@...nel.org>,
 Andreas Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>,
 Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>,
 Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
 <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Alexandre Ghiti <alex@...ti.fr>, rust-for-linux@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org
Subject: Re: RISC-V: Re-enable GCC+Rust builds

> For example, there's a check in the riscv Kconfig menu to see if 
> stack-protector-guard=tls can be used via a cc-option check. If that 
> check passes with gcc as the compiler that option will be passed to 
> the rust side of the build, where llvm might not support it.
If I understand correctly, the `-mstack-protector-guard` option is 
already always filtered out by `bindgen_skip_c_flags` in 
`rust/Makefile`, regardless of architecture. Therefore, we don't need to 
do anything more, right?

> Similarly, turning on an extension like Zacas via a cc-option check 
> could pass for gcc but not be usable when passed to the rust side, 
> causing errors.
That makes sense. I might need to check the version of libclang for each 
extension that passes the cc-option check for GCC to ensure it supports 
them.

> These sorts of things should be prevented via Kconfig, not show up as 
> confusing build errors.
I'm working on a patch, and intend to output an error message in 
`arch/riscv/Makefile` then exit 1 when detecting an incompatible 
gcc+libclang mix in use.