Date:   Wed, 15 Feb 2023 06:47:35 +0800
Mime-Version: 1.0
Message-ID: <20230214224735.264894-1-davidgow@google.com>
Subject: [PATCH] rust: kernel: Mark rust_fmt_argument as extern "C"
From:   David Gow <davidgow@google.com>
To:     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=20Roy=20Baron?=" <bjorn3_gh@protonmail.com>
Cc:     David Gow <davidgow@google.com>, rust-for-linux@vger.kernel.org,
        linux-kernel@vger.kernel.org, stable@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

The rust_fmt_argument function is called from printk() to handle the %pA
format specifier.

Since it's called from C, we should mark it extern "C" to make sure it's
ABI compatible.

Cc: stable@vger.kernel.org
Fixes: 247b365dc8dc ("rust: add `kernel` crate")
Signed-off-by: David Gow <davidgow@google.com>
---

See discussion in:
https://github.com/Rust-for-Linux/linux/pull/967
and
https://github.com/Rust-for-Linux/linux/pull/966

---
 rust/kernel/print.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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;
 
 // Called from `vsprintf` with format specifier `%pA`.
 #[no_mangle]
-unsafe fn rust_fmt_argument(buf: *mut c_char, end: *mut c_char, ptr: *const c_void) -> *mut c_char {
+unsafe extern "C" fn rust_fmt_argument(buf: *mut c_char, end: *mut c_char, ptr: *const c_void) -> *mut c_char {
     use fmt::Write;
     // SAFETY: The C contract guarantees that `buf` is valid if it's less than `end`.
     let mut w = unsafe { RawFormatter::from_ptrs(buf.cast(), end.cast()) };
-- 
2.39.1.581.gbfd45094c4-goog