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From: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Date: Sat, 27 Jan 2024 14:46:38 +0100
Message-ID: <CANiq72nu2NXUWYanHZd5EXgX4P_v673EWn6SCRW60Es9naraQQ@mail.gmail.com>
Subject: Re: [PATCH v1 0/2] RISC-V: enable rust
To: Conor Dooley <conor@kernel.org>
Cc: Conor Dooley <conor.dooley@microchip.com>, linux-riscv@lists.infradead.org, 
	Miguel Ojeda <ojeda@kernel.org>, Alex Gaynor <alex.gaynor@gmail.com>, 
	Wedson Almeida Filho <wedsonaf@gmail.com>, Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>, 
	=?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= <bjorn3_gh@protonmail.com>, 
	Jonathan Corbet <corbet@lwn.net>, Paul Walmsley <paul.walmsley@sifive.com>, 
	Palmer Dabbelt <palmer@dabbelt.com>, Nathan Chancellor <nathan@kernel.org>, 
	Nick Desaulniers <ndesaulniers@google.com>, Tom Rix <trix@redhat.com>, 
	rust-for-linux@vger.kernel.org, linux-doc@vger.kernel.org, 
	linux-kernel@vger.kernel.org, llvm@lists.linux.dev, 
	Matthew Maurer <mmaurer@google.com>, Ramon de C Valle <rcvalle@google.com>, 
	Sami Tolvanen <samitolvanen@google.com>
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On Fri, Jan 26, 2024 at 11:01=E2=80=AFPM Conor Dooley <conor@kernel.org> wr=
ote:
>
> Is that even needed? We already have ARCH_SUPPORTS_CFI_CLANG and AFAIU
> rust supports it if clang does, so a second option is superfluous?

From a quick look, I don't see it enabled in any RISC-V built-in
target in `rustc` yet.

It may also still be the case that KCFI needs some tweaks for, say,
RISC-V, before the flag actually works, i.e. we couldn't just test the
flag in that case -- Ramon: how likely is it that RISC-V would work if
KCFI works for aarch64 and x86_64?

> I'm reading back what I wrote, and I must have been trying to get out
> the door or something because none of it really makes that much sense.
> Of course an unknown option should be detectable at build time and not
> be a silent breakage. Maybe I should have written the patch for this
> before sending the mail rather than writing the mail based on what was
> in my head.

No worries, it happens. I probably added to the confusion when I
replied with the "testing the unstable flag".

Cheers,
Miguel