Re: [PATCH v6 3/4] rust: replace `kernel::c_str!` with C-Strings
From: Dirk Behme
Date: Sun Feb 02 2025 - 08:10:29 EST
Hi Tamir,
On 02.02.25 13:20, Tamir Duberstein wrote:
> C-String literals were added in Rust 1.77. Replace instances of
> `kernel::c_str!` with C-String literals where possible and rename
> `kernel::c_str!` to `c_str_avoid_literals` to clarify its intended use.
>
> Closes: https://github.com/Rust-for-Linux/linux/issues/1075
> Signed-off-by: Tamir Duberstein <tamird@xxxxxxxxx>
> ---
> drivers/net/phy/ax88796b_rust.rs | 7 +++----
> drivers/net/phy/qt2025.rs | 5 ++---
> rust/kernel/firmware.rs | 4 ++--
> rust/kernel/kunit.rs | 7 ++++---
> rust/kernel/net/phy.rs | 6 ++----
> rust/kernel/str.rs | 37 ++++++++++++++++++++++++-------------
> rust/kernel/sync.rs | 4 ++--
> rust/kernel/sync/lock/global.rs | 3 ++-
> 8 files changed, 41 insertions(+), 32 deletions(-)
Have you checked samples/rust/ [1] as well?
Best regards
Dirk
[1]
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/samples/rust
> diff --git a/drivers/net/phy/ax88796b_rust.rs b/drivers/net/phy/ax88796b_rust.rs
> index 8c7eb009d9fc..b07d36f45a43 100644
> --- a/drivers/net/phy/ax88796b_rust.rs
> +++ b/drivers/net/phy/ax88796b_rust.rs
> @@ -5,7 +5,6 @@
> //!
> //! C version of this driver: [`drivers/net/phy/ax88796b.c`](./ax88796b.c)
> use kernel::{
> - c_str,
> net::phy::{self, reg::C22, DeviceId, Driver},
> prelude::*,
> uapi,
> @@ -41,7 +40,7 @@ fn asix_soft_reset(dev: &mut phy::Device) -> Result {
> #[vtable]
> impl Driver for PhyAX88772A {
> const FLAGS: u32 = phy::flags::IS_INTERNAL;
> - const NAME: &'static CStr = c_str!("Asix Electronics AX88772A");
> + const NAME: &'static CStr = c"Asix Electronics AX88772A";
> const PHY_DEVICE_ID: DeviceId = DeviceId::new_with_exact_mask(0x003b1861);
>
> // AX88772A is not working properly with some old switches (NETGEAR EN 108TP):
> @@ -105,7 +104,7 @@ fn link_change_notify(dev: &mut phy::Device) {
> #[vtable]
> impl Driver for PhyAX88772C {
> const FLAGS: u32 = phy::flags::IS_INTERNAL;
> - const NAME: &'static CStr = c_str!("Asix Electronics AX88772C");
> + const NAME: &'static CStr = c"Asix Electronics AX88772C";
> const PHY_DEVICE_ID: DeviceId = DeviceId::new_with_exact_mask(0x003b1881);
>
> fn suspend(dev: &mut phy::Device) -> Result {
> @@ -125,7 +124,7 @@ fn soft_reset(dev: &mut phy::Device) -> Result {
>
> #[vtable]
> impl Driver for PhyAX88796B {
> - const NAME: &'static CStr = c_str!("Asix Electronics AX88796B");
> + const NAME: &'static CStr = c"Asix Electronics AX88796B";
> const PHY_DEVICE_ID: DeviceId = DeviceId::new_with_model_mask(0x003b1841);
>
> fn soft_reset(dev: &mut phy::Device) -> Result {
> diff --git a/drivers/net/phy/qt2025.rs b/drivers/net/phy/qt2025.rs
> index 1ab065798175..2f4ba85a0d73 100644
> --- a/drivers/net/phy/qt2025.rs
> +++ b/drivers/net/phy/qt2025.rs
> @@ -9,7 +9,6 @@
> //!
> //! The QT2025 PHY integrates an Intel 8051 micro-controller.
>
> -use kernel::c_str;
> use kernel::error::code;
> use kernel::firmware::Firmware;
> use kernel::net::phy::{
> @@ -36,7 +35,7 @@
>
> #[vtable]
> impl Driver for PhyQT2025 {
> - const NAME: &'static CStr = c_str!("QT2025 10Gpbs SFP+");
> + const NAME: &'static CStr = c"QT2025 10Gpbs SFP+";
> const PHY_DEVICE_ID: phy::DeviceId = phy::DeviceId::new_with_exact_mask(0x0043a400);
>
> fn probe(dev: &mut phy::Device) -> Result<()> {
> @@ -69,7 +68,7 @@ fn probe(dev: &mut phy::Device) -> Result<()> {
> // The micro-controller will start running from the boot ROM.
> dev.write(C45::new(Mmd::PCS, 0xe854), 0x00c0)?;
>
> - let fw = Firmware::request(c_str!("qt2025-2.0.3.3.fw"), dev.as_ref())?;
> + let fw = Firmware::request(c"qt2025-2.0.3.3.fw", dev.as_ref())?;
> if fw.data().len() > SZ_16K + SZ_8K {
> return Err(code::EFBIG);
> }
> diff --git a/rust/kernel/firmware.rs b/rust/kernel/firmware.rs
> index e75db4d825ce..93e375e75ca0 100644
> --- a/rust/kernel/firmware.rs
> +++ b/rust/kernel/firmware.rs
> @@ -40,13 +40,13 @@ fn request_nowarn() -> Self {
> /// # Examples
> ///
> /// ```no_run
> -/// # use kernel::{c_str, device::Device, firmware::Firmware};
> +/// # use kernel::{device::Device, firmware::Firmware};
> ///
> /// # fn no_run() -> Result<(), Error> {
> /// # // SAFETY: *NOT* safe, just for the example to get an `ARef<Device>` instance
> /// # let dev = unsafe { Device::get_device(core::ptr::null_mut()) };
> ///
> -/// let fw = Firmware::request(c_str!("path/to/firmware.bin"), &dev)?;
> +/// let fw = Firmware::request(c"path/to/firmware.bin", &dev)?;
> /// let blob = fw.data();
> ///
> /// # Ok(())
> diff --git a/rust/kernel/kunit.rs b/rust/kernel/kunit.rs
> index 9f40ea744fc2..3d812edec057 100644
> --- a/rust/kernel/kunit.rs
> +++ b/rust/kernel/kunit.rs
> @@ -56,10 +56,11 @@ macro_rules! kunit_assert {
> break 'out;
> }
>
> - static NAME: &'static $crate::str::CStr = $crate::c_str!($name);
> - static FILE: &'static $crate::str::CStr = $crate::c_str!($file);
> + static NAME: &'static $crate::str::CStr = $crate::c_str_avoid_literals!($name);
> + static FILE: &'static $crate::str::CStr = $crate::c_str_avoid_literals!($file);
> static LINE: i32 = core::line!() as i32 - $diff;
> - static CONDITION: &'static $crate::str::CStr = $crate::c_str!(stringify!($condition));
> + static CONDITION: &'static $crate::str::CStr =
> + $crate::c_str_avoid_literals!(stringify!($condition));
>
> // SAFETY: FFI call without safety requirements.
> let kunit_test = unsafe { $crate::bindings::kunit_get_current_test() };
> diff --git a/rust/kernel/net/phy.rs b/rust/kernel/net/phy.rs
> index 9e410de3c3a3..5fb9b0e1c9b1 100644
> --- a/rust/kernel/net/phy.rs
> +++ b/rust/kernel/net/phy.rs
> @@ -780,7 +780,6 @@ const fn as_int(&self) -> u32 {
> ///
> /// ```
> /// # mod module_phy_driver_sample {
> -/// use kernel::c_str;
> /// use kernel::net::phy::{self, DeviceId};
> /// use kernel::prelude::*;
> ///
> @@ -799,7 +798,7 @@ const fn as_int(&self) -> u32 {
> ///
> /// #[vtable]
> /// impl phy::Driver for PhySample {
> -/// const NAME: &'static CStr = c_str!("PhySample");
> +/// const NAME: &'static CStr = c"PhySample";
> /// const PHY_DEVICE_ID: phy::DeviceId = phy::DeviceId::new_with_exact_mask(0x00000001);
> /// }
> /// # }
> @@ -808,7 +807,6 @@ const fn as_int(&self) -> u32 {
> /// This expands to the following code:
> ///
> /// ```ignore
> -/// use kernel::c_str;
> /// use kernel::net::phy::{self, DeviceId};
> /// use kernel::prelude::*;
> ///
> @@ -828,7 +826,7 @@ const fn as_int(&self) -> u32 {
> ///
> /// #[vtable]
> /// impl phy::Driver for PhySample {
> -/// const NAME: &'static CStr = c_str!("PhySample");
> +/// const NAME: &'static CStr = c"PhySample";
> /// const PHY_DEVICE_ID: phy::DeviceId = phy::DeviceId::new_with_exact_mask(0x00000001);
> /// }
> ///
> diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
> index 2b63cfaaa981..20d852aa8b3c 100644
> --- a/rust/kernel/str.rs
> +++ b/rust/kernel/str.rs
> @@ -190,14 +190,13 @@ pub trait CStrExt {
> /// # Examples
> ///
> /// ```
> - /// # use kernel::c_str;
> /// # use kernel::fmt;
> /// # use kernel::str::CString;
> - /// let penguin = c_str!("🐧");
> + /// let penguin = c"🐧";
> /// let s = CString::try_from_fmt(fmt!("{}", penguin.display()))?;
> /// assert_eq!(s.to_bytes_with_nul(), "\\xf0\\x9f\\x90\\xa7\0".as_bytes());
> ///
> - /// let ascii = c_str!("so \"cool\"");
> + /// let ascii = c"so \"cool\"";
> /// let s = CString::try_from_fmt(fmt!("{}", ascii.display()))?;
> /// assert_eq!(s.to_bytes_with_nul(), "so \"cool\"\0".as_bytes());
> /// # Ok::<(), kernel::error::Error>(())
> @@ -250,25 +249,37 @@ pub const fn as_char_ptr(c_str: &CStr) -> *const crate::ffi::c_char {
> c_str.as_ptr().cast()
> }
>
> -/// Creates a new [`CStr`] from a string literal.
> +/// Creates a static C string wrapper at compile time.
> ///
> -/// The string literal should not contain any `NUL` bytes.
> +/// Rust supports C string literals since Rust 1.77, and they should be used instead of this macro
> +/// where possible. This macro exists to allow static *non-literal* C strings to be created at
> +/// compile time. This is most often used in other macros.
> +///
> +/// # Panics
> +///
> +/// This macro panics if the operand contains an interior `NUL` byte.
> ///
> /// # Examples
> ///
> /// ```
> -/// # use kernel::c_str;
> +/// # use kernel::c_str_avoid_literals;
> /// # use kernel::str::CStr;
> -/// const MY_CSTR: &CStr = c_str!("My awesome CStr!");
> +/// const MY_CSTR: &CStr = c_str_avoid_literals!(concat!(file!(), ":", line!(), ": My CStr!"));
> /// ```
> #[macro_export]
> -macro_rules! c_str {
> +macro_rules! c_str_avoid_literals {
> + // NB: we could write `($str:lit) => compile_error!("use a C string literal instead");` here but
> + // that would trigger when the literal is at the top of several macro expansions. That would be
> + // too limiting to macro authors, so we rely on the name as a hint instead.
> ($str:expr) => {{
> - const S: &str = concat!($str, "\0");
> - const C: &$crate::str::CStr = match $crate::str::CStr::from_bytes_with_nul(S.as_bytes()) {
> - Ok(v) => v,
> - Err(_) => panic!("string contains interior NUL"),
> - };
> + const S: &'static str = concat!($str, "\0");
> + const C: &'static $crate::str::CStr =
> + match $crate::str::CStr::from_bytes_with_nul(S.as_bytes()) {
> + Ok(v) => v,
> + Err(core::ffi::FromBytesWithNulError { .. }) => {
> + panic!("string contains interior NUL")
> + }
> + };
> C
> }};
> }
> diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs
> index 1eab7ebf25fd..ec7f80a924c3 100644
> --- a/rust/kernel/sync.rs
> +++ b/rust/kernel/sync.rs
> @@ -61,9 +61,9 @@ macro_rules! static_lock_class {
> #[macro_export]
> macro_rules! optional_name {
> () => {
> - $crate::c_str!(::core::concat!(::core::file!(), ":", ::core::line!()))
> + $crate::c_str_avoid_literals!(::core::concat!(::core::file!(), ":", ::core::line!()))
> };
> ($name:literal) => {
> - $crate::c_str!($name)
> + $crate::c_str_avoid_literals!($name)
> };
> }
> diff --git a/rust/kernel/sync/lock/global.rs b/rust/kernel/sync/lock/global.rs
> index 4c4d60a51c1f..732dde45024b 100644
> --- a/rust/kernel/sync/lock/global.rs
> +++ b/rust/kernel/sync/lock/global.rs
> @@ -266,7 +266,8 @@ macro_rules! global_lock {
> $pub enum $name {}
>
> impl $crate::sync::lock::GlobalLockBackend for $name {
> - const NAME: &'static $crate::str::CStr = $crate::c_str!(::core::stringify!($name));
> + const NAME: &'static $crate::str::CStr =
> + $crate::c_str_avoid_literals!(::core::stringify!($name));
> type Item = $valuety;
> type Backend = $crate::global_lock_inner!(backend $kind);
>
>