Re: [PATCH] rust: kernel: Mark rust_fmt_argument as extern "C"

From: Björn Roy Baron
Date: Wed Feb 15 2023 - 12:55:16 EST


On Tuesday, February 14th, 2023 at 23:47, David Gow <davidgow@xxxxxxxxxx> wrote:

> 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@xxxxxxxxxxxxxxx
> Fixes: 247b365dc8dc ("rust: add `kernel` crate")
> Signed-off-by: David Gow davidgow@xxxxxxxxxx

Reviewed-by: Björn Roy Baron <bjorn3_gh@xxxxxxxxxxxxxx>

>
> ---
>
> See discussion in:
> https://github.com/Rust-for-Linux/linux/pull/967
> and
> https://github.com/Rust-for-Linux/linux/pull/966
>
> ---
> rust/kernel/print.rs | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/rust/kernel/print.rs b/rust/kernel/print.rs
> index 30103325696d..ec457f0952fe 100644
> --- a/rust/kernel/print.rs
> +++ b/rust/kernel/print.rs
> @@ -18,7 +18,7 @@ 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()) };
> --
> 2.39.1.581.gbfd45094c4-goog