From: Boqun Feng <boqun.feng@gmail.com>
To: linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org
Cc: boqun.feng@gmail.com, ojeda@kernel.org, alex.gaynor@gmail.com,
gary@garyguo.net, bjorn3_gh@protonmail.com,
benno.lossin@proton.me, a.hindborg@samsung.com,
aliceryhl@google.com, tmgross@umich.edu, dakr@kernel.org,
mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
vschneid@redhat.com, pmladek@suse.com, fujita.tomonori@gmail.com,
mingo@kernel.org, tamird@gmail.com
Subject: [PATCH v4 1/2] rust: Introduce file_from_location()
Date: Thu, 19 Jun 2025 08:10:06 -0700 [thread overview]
Message-ID: <20250619151007.61767-2-boqun.feng@gmail.com> (raw)
In-Reply-To: <20250619151007.61767-1-boqun.feng@gmail.com>
Most of kernel debugging facilities take a nul-terminated string for
file names for a callsite (generated from __FILE__), however the Rust
courterpart, Location, would return a Rust string (not nul-terminated)
from method .file(). And such a string cannot be passed to C debugging
function directly.
There is ongoing work to support a Location::file_with_nul() [1], which
returns a nul-terminated string from a Location. Since it's still
working in progress, and it will take some time before the feature
finally gets stabilized and the kernel's minimal rustc version might
also take a while to bump to a version that at least has that feature,
introduce a file_from_location() function, which returns a warning
string if Location::file_with_nul() is not available.
This should work in most cases because as for now the known usage of
Location::file_with_nul() is only in debugging code (e.g. might_sleep())
and there might be other information reported by the debugging code that
could help locate the problematic function, so missing the file name is
fine at the moment.
Link: https://github.com/rust-lang/rust/issues/141727 [1]
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
---
init/Kconfig | 3 +++
rust/kernel/lib.rs | 43 +++++++++++++++++++++++++++++++++++++++++++
2 files changed, 46 insertions(+)
diff --git a/init/Kconfig b/init/Kconfig
index af4c2f085455..6f4ec5633ffa 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -142,6 +142,9 @@ config RUSTC_HAS_SPAN_FILE
config RUSTC_HAS_UNNECESSARY_TRANSMUTES
def_bool RUSTC_VERSION >= 108800
+config RUSTC_HAS_FILE_WITH_NUL
+ def_bool RUSTC_VERSION >= 108900
+
config PAHOLE_VERSION
int
default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE))
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 6b4774b2b1c3..57cff1ca8b90 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -40,6 +40,10 @@
#![cfg_attr(not(CONFIG_RUSTC_HAS_COERCE_POINTEE), feature(coerce_unsized))]
#![cfg_attr(not(CONFIG_RUSTC_HAS_COERCE_POINTEE), feature(dispatch_from_dyn))]
#![cfg_attr(not(CONFIG_RUSTC_HAS_COERCE_POINTEE), feature(unsize))]
+//
+// `feature(file_with_nul)` is expected to become stable. Before Rust 1.89.0, it did not exist, so
+// enable it conditionally.
+#![cfg_attr(CONFIG_RUSTC_HAS_FILE_WITH_NUL, feature(file_with_nul))]
// Ensure conditional compilation based on the kernel configuration works;
// otherwise we may silently break things like initcall handling.
@@ -274,3 +278,42 @@ macro_rules! asm {
::core::arch::asm!( $($asm)*, $($rest)* )
};
}
+
+/// Gets the C string file name of a [`Location`].
+///
+/// If `file_with_nul()` is not available, returns a string that warns about it.
+///
+/// [`Location`]: core::panic::Location
+///
+/// # Examples
+///
+/// ```
+/// # use kernel::file_from_location;
+///
+/// #[track_caller]
+/// fn foo() {
+/// let caller = core::panic::Location::caller();
+///
+/// // Output:
+/// // - A path like "rust/kernel/example.rs" if file_with_nul() available.
+/// // - "<Location::file_with_nul() not supported>" otherwise.
+/// let caller_file = file_from_location(caller);
+///
+/// // Prints out the message with caller's file name.
+/// pr_info!("foo() called in file {caller_file:?}\n");
+///
+/// # if cfg!(CONFIG_RUSTC_HAS_FILE_WITH_NUL) {
+/// # assert_eq!(Ok(caller.file()), caller_file.to_str());
+/// # }
+/// }
+///
+/// # foo();
+/// ```
+#[inline]
+pub fn file_from_location<'a>(_loc: &'a core::panic::Location<'a>) -> &'a core::ffi::CStr {
+ #[cfg(CONFIG_RUSTC_HAS_FILE_WITH_NUL)]
+ { _loc.file_with_nul() }
+
+ #[cfg(not(CONFIG_RUSTC_HAS_FILE_WITH_NUL))]
+ { c"<Location::file_with_nul() not supported>" }
+}
--
2.39.5 (Apple Git-154)
next prev parent reply other threads:[~2025-06-19 15:10 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-19 15:10 [PATCH v4 0/2] Add Rust version of might_sleep() Boqun Feng
2025-06-19 15:10 ` Boqun Feng [this message]
2025-06-19 20:42 ` [PATCH v4 1/2] rust: Introduce file_from_location() Miguel Ojeda
2025-06-19 20:51 ` Boqun Feng
2025-07-03 8:36 ` [tip: sched/core] " tip-bot2 for Boqun Feng
2025-06-19 15:10 ` [PATCH v4 2/2] rust: task: Add Rust version of might_sleep() Boqun Feng
2025-07-03 8:36 ` [tip: sched/core] " tip-bot2 for FUJITA Tomonori
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