Date:   Wed, 15 Feb 2023 17:55:03 +0000
To:     David Gow <davidgow@google.com>
From:   =?utf-8?Q?Bj=C3=B6rn_Roy_Baron?= <bjorn3_gh@protonmail.com>
Cc:     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>,
        rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
        stable@vger.kernel.org
Subject: Re: [PATCH] rust: kernel: Mark rust_fmt_argument as extern "C"
Message-ID: <wwIvK-PQ1cuvgLu7VlX_kR2Re7O4IZ_czCWYKQ6BevpEE-rW8OKdXhh5aSpZaZxoAsbMx37508f_7SzbKOd1xEMvYYlsVkNET4fliKbH7ac=@protonmail.com>
In-Reply-To: <20230214224735.264894-1-davidgow@google.com>
References: <20230214224735.264894-1-davidgow@google.com>
Feedback-ID: 27884398:user:proton
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Tuesday, February 14th, 2023 at 23:47, David Gow <davidgow@google.com> w=
rote:

> The rust_fmt_argument function is called from printk() to handle the %pA
> format specifier.
>=20
> Since it's called from C, we should mark it extern "C" to make sure it's
> ABI compatible.
>=20
> Cc: stable@vger.kernel.org
> Fixes: 247b365dc8dc ("rust: add `kernel` crate")
> Signed-off-by: David Gow davidgow@google.com

Reviewed-by: Bj=C3=B6rn Roy Baron <bjorn3_gh@protonmail.com>

>=20
> ---
>=20
> See discussion in:
> https://github.com/Rust-for-Linux/linux/pull/967
> and
> https://github.com/Rust-for-Linux/linux/pull/966
>=20
> ---
>  rust/kernel/print.rs | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>=20
> diff --git a/rust/kernel/print.rs b/rust/kernel/print.rs
> index 30103325696d..ec457f0952fe 100644
> --- a/rust/kernel/print.rs
> +++ b/rust/kernel/print.rs
> @@ -18,7 +18,7 @@ use crate::bindings;
>=20
>  // Called from `vsprintf` with format specifier `%pA`.
>  #[no_mangle]
> -unsafe fn rust_fmt_argument(buf: *mut c_char, end: *mut c_char, ptr: *co=
nst c_void) -> *mut c_char {
> +unsafe extern "C" fn rust_fmt_argument(buf: *mut c_char, end: *mut c_cha=
r, ptr: *const c_void) -> *mut c_char {
>      use fmt::Write;
>      // SAFETY: The C contract guarantees that `buf` is valid if it's les=
s than `end`.
>      let mut w =3D unsafe { RawFormatter::from_ptrs(buf.cast(), end.cast(=
)) };
> --
> 2.39.1.581.gbfd45094c4-goog