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From: Trevor Gross <tmgross@umich.edu>
Date: Sat, 10 Feb 2024 02:13:06 -0600
Message-ID: <CALNs47sRqAbE=u3=_ciO2oge7Afz-6GBBhW+BwcLRET-TsuxTg@mail.gmail.com>
Subject: Re: [PATCH v1 0/2] RISC-V: enable rust
To: Conor Dooley <conor@kernel.org>
Cc: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>, 
	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, Feb 9, 2024 at 9:18=E2=80=AFAM Conor Dooley <conor@kernel.org> wrot=
e:
>
> On Sat, Jan 27, 2024 at 02:46:38PM +0100, Miguel Ojeda wrote:
> > On Fri, Jan 26, 2024 at 11:01=E2=80=AFPM Conor Dooley <conor@kernel.org=
> wrote:
> > >
> > > Is that even needed? We already have ARCH_SUPPORTS_CFI_CLANG and AFAI=
U
> > > 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?
>
> Well, there's been no reply here. I'll do sa you suggested and add a
> depends on !CFI_CLANG to RUST.
>
> Cheers,
> Conor.
>

I asked on Zulip and it sounds like Ramon may be out [1]. It
_probably_ works, but going with a dependency to not be blocked on
KCFI is probably reasonable for now.

- Trevor

[1]: https://rust-lang.zulipchat.com/#narrow/stream/343119-project-exploit-=
mitigations/topic/KCFI.20on.20RISC-V.20questions