From 2aac424cb232e7a4a74fce22cf0be3fe5a7659a5 Mon Sep 17 00:00:00 2001
From: David Gow <davidgow@google.com>
Date: Wed, 15 Feb 2023 06:47:35 +0800
Subject: [PATCH] rust: kernel: Mark rust_fmt_argument as extern "C"
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commit c682e4c37d2b8ba3bde1125cbbea4ee88824b4e2 upstream.

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>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Björn Roy Baron <bjorn3_gh@protonmail.com>
Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
[Applied `rustfmt`]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 rust/kernel/print.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/print.rs b/rust/kernel/print.rs
index 30103325696d..8009184bf6d7 100644
--- a/rust/kernel/print.rs
+++ b/rust/kernel/print.rs
@@ -18,7 +18,11 @@ 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()) };