linux-kernel - [PATCH v2 1/5] rust: fix signature of rust_fmt

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Message-ID: <20250228-export-macro-v2-1-569cc7e8926c@google.com>
Date: Fri, 28 Feb 2025 12:39:30 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Miguel Ojeda <ojeda@...nel.org>
Cc: Petr Mladek <pmladek@...e.com>, Steven Rostedt <rostedt@...dmis.org>, 
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, 
	Rasmus Villemoes <linux@...musvillemoes.dk>, Sergey Senozhatsky <senozhatsky@...omium.org>, 
	Andrew Morton <akpm@...ux-foundation.org>, Boqun Feng <boqun.feng@...il.com>, 
	Gary Guo <gary@...yguo.net>, 
	"Björn Roy Baron" <bjorn3_gh@...tonmail.com>, Benno Lossin <benno.lossin@...ton.me>, 
	Andreas Hindborg <a.hindborg@...nel.org>, Trevor Gross <tmgross@...ch.edu>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
	linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org, 
	dri-devel@...ts.freedesktop.org, Alice Ryhl <aliceryhl@...gle.com>
Subject: [PATCH v2 1/5] rust: fix signature of rust_fmt_argument

Without this change, the rest of this series will emit the following
error message:

error[E0308]: `if` and `else` have incompatible types
  --> <linux>/rust/kernel/print.rs:22:22
   |
21 | #[export]
   | --------- expected because of this
22 | unsafe extern "C" fn rust_fmt_argument(
   |                      ^^^^^^^^^^^^^^^^^ expected `u8`, found `i8`
   |
   = note: expected fn item `unsafe extern "C" fn(*mut u8, *mut u8, *mut c_void) -> *mut u8 {bindings::rust_fmt_argument}`
              found fn item `unsafe extern "C" fn(*mut i8, *mut i8, *const c_void) -> *mut i8 {print::rust_fmt_argument}`

The error may be different depending on the architecture.

To fix this, change the void pointer argument to use a const pointer,
and change the imports to use crate::ffi instead of core::ffi for
integer types.

Fixes: 787983da7718 ("vsprintf: add new `%pA` format specifier")
Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>
---
 lib/vsprintf.c       | 2 +-
 rust/kernel/print.rs | 7 +++----
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 56fe96319292..a8ac4c4fffcf 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -2285,7 +2285,7 @@ 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, void *ptr);
+char *rust_fmt_argument(char *buf, char *end, const void *ptr);
 
 /*
  * Show a '%p' thing.  A kernel extension is that the '%p' is followed
diff --git a/rust/kernel/print.rs b/rust/kernel/print.rs
index b19ee490be58..61ee36c5e5f5 100644
--- a/rust/kernel/print.rs
+++ b/rust/kernel/print.rs
@@ -6,12 +6,11 @@
 //!
 //! Reference: <https://docs.kernel.org/core-api/printk-basics.html>
 
-use core::{
+use crate::{
     ffi::{c_char, c_void},
-    fmt,
+    str::RawFormatter,
 };
-
-use crate::str::RawFormatter;
+use core::fmt;
 
 // Called from `vsprintf` with format specifier `%pA`.
 #[expect(clippy::missing_safety_doc)]

-- 
2.48.1.711.g2feabab25a-goog