Re: [PATCH v1] rust: bug: Support DEBUG_BUGVERBOSE_DETAILED option

[Gary Guo <gary@garyguo.net>]

On Fri,  5 Dec 2025 07:34:05 +0900
FUJITA Tomonori <fujita.tomonori@gmail.com> wrote:

> Make warn_on() support DEBUG_BUGVERBOSE_DETAILED option, which was
> introduced by the commit aec58b48517c ("bugs/core: Extend
> __WARN_FLAGS() with the 'cond_str' parameter").
> 
> When the option is enabled, WARN splats now show the evaluated
> warn_on() condition alongside the file path, e.g.:
> 
> ------------[ cut here ]------------
> WARNING: [val == 1] /linux/samples/rust/rust_minimal.rs:27 at _RNvXCsk7t4azzUqHP_12rust_minimalNtB2_11RustMinimalNtCs8pcx3n4
> Modules linked in: rust_minimal(+)
> 
> Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
> ---
>  rust/kernel/bug.rs | 27 ++++++++++++++++-----------
>  1 file changed, 16 insertions(+), 11 deletions(-)
> 
> diff --git a/rust/kernel/bug.rs b/rust/kernel/bug.rs
> index 36aef43e5ebe..a60db1ef4b48 100644
> --- a/rust/kernel/bug.rs
> +++ b/rust/kernel/bug.rs
> @@ -11,15 +11,14 @@
>  #[cfg(all(CONFIG_BUG, not(CONFIG_UML), not(CONFIG_LOONGARCH), not(CONFIG_ARM)))]
>  #[cfg(CONFIG_DEBUG_BUGVERBOSE)]
>  macro_rules! warn_flags {
> -    ($flags:expr) => {
> +    ($file:expr, $flags:expr) => {
>          const FLAGS: u32 = $crate::bindings::BUGFLAG_WARNING | $flags;
> -        const _FILE: &[u8] = file!().as_bytes();

I think it'll be good to still keep

	const _FILE: &[u8] = $file.as_bytes();


and have the caller just pass in `file!()` or `concat!(...)`. At least the
concat macro doesn't have to expanded multiple times in below.

Best,
Gary

>          // Plus one for null-terminator.
> -        static FILE: [u8; _FILE.len() + 1] = {
> -            let mut bytes = [0; _FILE.len() + 1];
> +        static FILE: [u8; $file.len() + 1] = {
> +            let mut bytes = [0; $file.len() + 1];
>              let mut i = 0;
> -            while i < _FILE.len() {
> -                bytes[i] = _FILE[i];
> +            while i < $file.len() {
> +                bytes[i] = $file[i];
>                  i += 1;
>              }
>              bytes
> @@ -50,7 +49,7 @@ macro_rules! warn_flags {
>  #[cfg(all(CONFIG_BUG, not(CONFIG_UML), not(CONFIG_LOONGARCH), not(CONFIG_ARM)))]
>  #[cfg(not(CONFIG_DEBUG_BUGVERBOSE))]
>  macro_rules! warn_flags {
> -    ($flags:expr) => {
> +    ($file:expr, $flags:expr) => {
>          const FLAGS: u32 = $crate::bindings::BUGFLAG_WARNING | $flags;
>  
>          // SAFETY:
> @@ -75,7 +74,7 @@ macro_rules! warn_flags {
>  #[doc(hidden)]
>  #[cfg(all(CONFIG_BUG, CONFIG_UML))]
>  macro_rules! warn_flags {
> -    ($flags:expr) => {
> +    ($file:expr, $flags:expr) => {
>          // SAFETY: It is always safe to call `warn_slowpath_fmt()`
>          // with a valid null-terminated string.
>          unsafe {
> @@ -93,7 +92,7 @@ macro_rules! warn_flags {
>  #[doc(hidden)]
>  #[cfg(all(CONFIG_BUG, any(CONFIG_LOONGARCH, CONFIG_ARM)))]
>  macro_rules! warn_flags {
> -    ($flags:expr) => {
> +    ($file:expr, $flags:expr) => {
>          // SAFETY: It is always safe to call `WARN_ON()`.
>          unsafe { $crate::bindings::WARN_ON(true) }
>      };
> @@ -103,7 +102,7 @@ macro_rules! warn_flags {
>  #[doc(hidden)]
>  #[cfg(not(CONFIG_BUG))]
>  macro_rules! warn_flags {
> -    ($flags:expr) => {};
> +    ($file:expr, $flags:expr) => {};
>  }
>  
>  #[doc(hidden)]
> @@ -116,10 +115,16 @@ pub const fn bugflag_taint(value: u32) -> u32 {
>  macro_rules! warn_on {
>      ($cond:expr) => {{
>          let cond = $cond;
> +
> +        #[cfg(CONFIG_DEBUG_BUGVERBOSE_DETAILED)]
> +        const _COND_STR: &[u8] = concat!("[", stringify!($cond), "] ", file!()).as_bytes();
> +        #[cfg(not(CONFIG_DEBUG_BUGVERBOSE_DETAILED))]
> +        const _COND_STR: &[u8] = file!().as_bytes();
> +
>          if cond {
>              const WARN_ON_FLAGS: u32 = $crate::bug::bugflag_taint($crate::bindings::TAINT_WARN);
>  
> -            $crate::warn_flags!(WARN_ON_FLAGS);
> +            $crate::warn_flags!(_COND_STR, WARN_ON_FLAGS);
>          }
>          cond
>      }};
> 
> base-commit: 500920fa76819b4909a32081e153bce80ce74824