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From:   Sami Tolvanen <samitolvanen@google.com>
Date:   Mon, 10 Oct 2022 16:15:33 -0700
Message-ID: <CABCJKuenkHXtbWOLZ0_isGewxd19qkM7OcLeE2NzM6dSkXS4mQ@mail.gmail.com>
Subject: Re: [PATCH v10 25/27] x86: enable initial Rust support
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Miguel Ojeda <ojeda@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, patches@lists.linux.dev,
        Jarkko Sakkinen <jarkko@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Wedson Almeida Filho <wedsonaf@google.com>,
        David Gow <davidgow@google.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>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>, linux-doc@vger.kernel.org
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On Fri, Oct 7, 2022 at 10:18 AM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Tue, Sep 27, 2022 at 03:14:56PM +0200, Miguel Ojeda wrote:
> > Note that only x86_64 is covered and not all features nor mitigations
> > are handled, but it is enough as a starting point and showcases
> > the basics needed to add Rust support for a new architecture.
>
> Does it fail the build if required options are missing? Specifically are
> things like kCFI and IBT enabled? Silently not handling those will
> result in an unbootable image.

Rust supports IBT with -Z cf-protection=branch, but I don't see this
option being enabled in the kernel yet. Cross-language CFI is going to
require a lot more work though because the type systems are not quite
compatible:

https://github.com/rust-lang/rfcs/pull/3296

Sami