[PATCH 3/4] print: use new #[export] macro for rust_fmt_argument

[Alice Ryhl <aliceryhl@google.com>]

This moves the rust_fmt_argument function over to use the new #[export]
macro, which will verify at compile-time that the function signature
matches what is in the header file.

Signed-off-by: Alice Ryhl <aliceryhl@google.com>
---
I'm not sure which header file to put this in. Any advice?
---
 include/linux/sprintf.h | 3 +++
 lib/vsprintf.c          | 3 ---
 rust/kernel/print.rs    | 3 ++-
 3 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/include/linux/sprintf.h b/include/linux/sprintf.h
index 33dcbec71925..029ad83efd74 100644
--- a/include/linux/sprintf.h
+++ b/include/linux/sprintf.h
@@ -24,4 +24,7 @@ __scanf(2, 0) int vsscanf(const char *, const char *, va_list);
 extern bool no_hash_pointers;
 int no_hash_pointers_enable(char *str);
 
+/* Used for Rust formatting ('%pA'). */
+char *rust_fmt_argument(char *buf, char *end, const void *ptr);
+
 #endif	/* _LINUX_KERNEL_SPRINTF_H */
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index a8ac4c4fffcf..1da61c3e011f 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -2284,9 +2284,6 @@ int __init no_hash_pointers_enable(char *str)
 }
 early_param("no_hash_pointers", no_hash_pointers_enable);
 
-/* Used for Rust formatting ('%pA'). */
-char *rust_fmt_argument(char *buf, char *end, const void *ptr);
-
 /*
  * Show a '%p' thing.  A kernel extension is that the '%p' is followed
  * by an extra set of alphanumeric characters that are extended format
diff --git a/rust/kernel/print.rs b/rust/kernel/print.rs
index 8551631dedf1..e1a5ff3f34a9 100644
--- a/rust/kernel/print.rs
+++ b/rust/kernel/print.rs
@@ -10,12 +10,13 @@
 
 use crate::{
     ffi::{c_char, c_void},
+    prelude::*,
     str::RawFormatter,
 };
 
 // Called from `vsprintf` with format specifier `%pA`.
 #[expect(clippy::missing_safety_doc)]
-#[no_mangle]
+#[export]
 unsafe extern "C" fn rust_fmt_argument(
     buf: *mut c_char,
     end: *mut c_char,

-- 
2.48.1.658.g4767266eb4-goog