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

Tamir Duberstein
2025-02-28T15:14:23Z

On Fri, Feb 28, 2025 at 7:41 AM Alice Ryhl <aliceryhl@google.com> wrote:
>
> 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

Reviewed-by: Tamir Duberstein <tamird@gmail.com>