[PATCH v2 1/5] rust: fix signature of rust_fmt_argument

Alice Ryhl
2025-02-28T12:40:09Z

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@google.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