rust: bug: Support DEBUG_BUGVERBOSE_DETAILED option

Make warn_on() support DEBUG_BUGVERBOSE_DETAILED option, which was
introduced by the commit aec58b4 ("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>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260108013350.2880613-1-fujita.tomonori@gmail.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Author: fujita

rust/kernel/bug.rs

@@ -11,9 +11,9 @@
 #[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();
+        const _FILE: &[u8] = $file.as_bytes();
         // Plus one for null-terminator.
         static FILE: [u8; _FILE.len() + 1] = {
             let mut bytes = [0; _FILE.len() + 1];
@@ -50,7 +50,7 @@ macro_rules! warn_flags {
 #[cfg(all(CONFIG_BUG, not(CONFIG_UML), not(CONFIG_LOONGARCH), not(CONFIG_ARM)))]
 #[cfg(not(CONFIG_DEBUG_BUGVERBOSE))]
 macro_rules! warn_flags {
-    ($flags:expr) => {
+    ($file:expr, $flags:expr) => {
         const FLAGS: u32 = $crate::bindings::BUGFLAG_WARNING | $flags;
 
         // SAFETY:
@@ -75,7 +75,7 @@ macro_rules! warn_flags {
 #[doc(hidden)]
 #[cfg(all(CONFIG_BUG, CONFIG_UML))]
 macro_rules! warn_flags {
-    ($flags:expr) => {
+    ($file:expr, $flags:expr) => {
         // SAFETY: It is always safe to call `warn_slowpath_fmt()`
         // with a valid null-terminated string.
         unsafe {
@@ -93,7 +93,7 @@ macro_rules! warn_flags {
 #[doc(hidden)]
 #[cfg(all(CONFIG_BUG, any(CONFIG_LOONGARCH, CONFIG_ARM)))]
 macro_rules! warn_flags {
-    ($flags:expr) => {
+    ($file:expr, $flags:expr) => {
         // SAFETY: It is always safe to call `WARN_ON()`.
         unsafe { $crate::bindings::WARN_ON(true) }
     };
@@ -103,7 +103,7 @@ macro_rules! warn_flags {
 #[doc(hidden)]
 #[cfg(not(CONFIG_BUG))]
 macro_rules! warn_flags {
-    ($flags:expr) => {};
+    ($file:expr, $flags:expr) => {};
 }
 
 #[doc(hidden)]
@@ -116,10 +116,16 @@ pub const fn bugflag_taint(value: u32) -> u32 {
 macro_rules! warn_on {
     ($cond:expr) => {{
         let cond = $cond;
+
+        #[cfg(CONFIG_DEBUG_BUGVERBOSE_DETAILED)]
+        const _COND_STR: &str = concat!("[", stringify!($cond), "] ", file!());
+        #[cfg(not(CONFIG_DEBUG_BUGVERBOSE_DETAILED))]
+        const _COND_STR: &str = file!();
+
         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
     }};