[PATCH v5] rust: str: Use `core::CStr`, remove the custom `CStr` implementation

Michal Rostecki
2024-07-17T16:08:15Z

`CStr` became a part of `core` library in Rust 1.75. This change replaces
the custom `CStr` implementation with the one from `core`.

`core::CStr` behaves generally the same as the removed implementation,
with the following differences:

- It does not implement `Display`.
- It does not provide `from_bytes_with_nul_unchecked_mut` method.
- It has `as_ptr()` method instead of `as_char_ptr()`, which also returns
`*const c_char`.

The first two differences are handled by providing the `CStrExt` trait,
with `display()` and `from_bytes_with_nul_unchecked_mut()` methods.
`display()` returns a `CStrDisplay` wrapper, with a custom `Display`
implementation.

`DerefMut` implementation for `CString` is removed here, as it's not
being used anywhere.

Signed-off-by: Michal Rostecki <vadorovsky@gmail.com>
---
v1 -> v2:
- Do not remove `c_str` macro. While it's preferred to use C-string
literals, there are two cases where `c_str` is helpful:
- When working with macros, which already return a Rust string literal
(e.g. `stringify!`).
- When building macros, where we want to take a Rust string literal as an
argument (for caller's convenience), but still use it as a C-string
internally.
- Use Rust literals as arguments in macros (`new_mutex`, `new_condvar`,
`new_mutex`). Use the `c_str` macro to convert these literals to C-string
literals.
- Use `c_str` in kunit.rs for converting the output of `stringify!` to a
`CStr`.
- Remove `DerefMut` implementation for `CString`.

v2 -> v3:
- Fix the commit message.
- Remove redundant braces in `use`, when only one item is imported.

v3 -> v4:
- Provide the `CStrExt` trait with `display()` method, which returns a
`CStrDisplay` wrapper with `Display` implementation. This addresses
the lack of `Display` implementation for `core::ffi::CStr`.
- Provide `from_bytes_with_nul_unchecked_mut()` method in `CStrExt`,
which might be useful and is going to prevent manual, unsafe casts.
- Fix a typo (s/preffered/prefered/).

v4 -> v5:
- Keep the `test_cstr_display*` unit tests.

rust/kernel/error.rs | 7 +-
rust/kernel/kunit.rs | 18 +-
rust/kernel/net/phy.rs | 2 +-
rust/kernel/prelude.rs | 4 +-
rust/kernel/str.rs | 501 ++++++------------------------------
rust/kernel/sync/condvar.rs | 5 +-
rust/kernel/sync/lock.rs | 6 +-
rust/kernel/workqueue.rs | 2 +-
scripts/rustdoc_test_gen.rs | 4 +-
9 files changed, 111 insertions(+), 438 deletions(-)

diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs
index 55280ae9fe40..18808b29604d 100644
--- a/rust/kernel/error.rs
+++ b/rust/kernel/error.rs
@@ -4,10 +4,11 @@
//!
//! C header: [`include/uapi/asm-generic/errno-base.h`](srctree/include/uapi/asm-generic/errno-base.h)

-use crate::{alloc::AllocError, str::CStr};
+use crate::alloc::AllocError;

use alloc::alloc::LayoutError;

+use core::ffi::CStr;
use core::fmt;
use core::num::TryFromIntError;
use core::str::Utf8Error;
@@ -142,7 +143,7 @@ pub fn name(&self) -> Option<&'static CStr> {
None
} else {
// SAFETY: The string returned by `errname` is static and `NUL`-terminated.
- Some(unsafe { CStr::from_char_ptr(ptr) })
+ Some(unsafe { CStr::from_ptr(ptr) })
}
}

@@ -164,7 +165,7 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
None => f.debug_tuple("Error").field(&-self.0).finish(),
// SAFETY: These strings are ASCII-only.
Some(name) => f
- .debug_tuple(unsafe { core::str::from_utf8_unchecked(name) })
+ .debug_tuple(unsafe { core::str::from_utf8_unchecked(name.to_bytes()) })
.finish(),
}
}
diff --git a/rust/kernel/kunit.rs b/rust/kernel/kunit.rs
index 0ba77276ae7e..79a50ab59af0 100644
--- a/rust/kernel/kunit.rs
+++ b/rust/kernel/kunit.rs
@@ -56,13 +56,15 @@ macro_rules! kunit_assert {
break 'out;
}

- static FILE: &'static $crate::str::CStr = $crate::c_str!($file);
+ static FILE: &'static core::ffi::CStr = $file;
static LINE: i32 = core::line!() as i32 - $diff;
- static CONDITION: &'static $crate::str::CStr = $crate::c_str!(stringify!($condition));
+ static CONDITION: &'static core::ffi::CStr = $crate::c_str!(stringify!($condition));

// SAFETY: FFI call without safety requirements.
let kunit_test = unsafe { $crate::bindings::kunit_get_current_test() };
if kunit_test.is_null() {
+ use kernel::str::CStrExt;
+
// The assertion failed but this task is not running a KUnit test, so we cannot call
// KUnit, but at least print an error to the kernel log. This may happen if this
// macro is called from an spawned thread in a test (see
@@ -71,11 +73,13 @@ macro_rules! kunit_assert {
//
// This mimics KUnit's failed assertion format.
$crate::kunit::err(format_args!(
- " # {}: ASSERTION FAILED at {FILE}:{LINE}\n",
- $name
+ " # {}: ASSERTION FAILED at {}:{LINE}\n",
+ $name.display(),
+ FILE.display(),
));
$crate::kunit::err(format_args!(
- " Expected {CONDITION} to be true, but is false\n"
+ " Expected {} to be true, but is false\n",
+ CONDITION.display(),
));
$crate::kunit::err(format_args!(
" Failure not reported to KUnit since this is a non-KUnit task\n"
@@ -98,12 +102,12 @@ unsafe impl Sync for Location {}
unsafe impl Sync for UnaryAssert {}

static LOCATION: Location = Location($crate::bindings::kunit_loc {
- file: FILE.as_char_ptr(),
+ file: FILE.as_ptr(),
line: LINE,
});
static ASSERTION: UnaryAssert = UnaryAssert($crate::bindings::kunit_unary_assert {
assert: $crate::bindings::kunit_assert {},
- condition: CONDITION.as_char_ptr(),
+ condition: CONDITION.as_ptr(),
expected_true: true,
});

diff --git a/rust/kernel/net/phy.rs b/rust/kernel/net/phy.rs
index fd40b703d224..19f45922ec42 100644
--- a/rust/kernel/net/phy.rs
+++ b/rust/kernel/net/phy.rs
@@ -502,7 +502,7 @@ unsafe impl Sync for DriverVTable {}
pub const fn create_phy_driver<T: Driver>() -> DriverVTable {
// INVARIANT: All the fields of `struct phy_driver` are initialized properly.
DriverVTable(Opaque::new(bindings::phy_driver {
- name: T::NAME.as_char_ptr().cast_mut(),
+ name: T::NAME.as_ptr().cast_mut(),
flags: T::FLAGS,
phy_id: T::PHY_DEVICE_ID.id,
phy_id_mask: T::PHY_DEVICE_ID.mask_as_int(),
diff --git a/rust/kernel/prelude.rs b/rust/kernel/prelude.rs
index b37a0b3180fb..b0969ca78f10 100644
--- a/rust/kernel/prelude.rs
+++ b/rust/kernel/prelude.rs
@@ -12,7 +12,7 @@
//! ```

#[doc(no_inline)]
-pub use core::pin::Pin;
+pub use core::{ffi::CStr, pin::Pin};

pub use crate::alloc::{box_ext::BoxExt, flags::*, vec_ext::VecExt};

@@ -35,7 +35,7 @@

pub use super::error::{code::*, Error, Result};

-pub use super::{str::CStr, ThisModule};
+pub use super::ThisModule;

pub use super::init::{InPlaceInit, Init, PinInit};

diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
index bb8d4f41475b..f1acaa377694 100644
--- a/rust/kernel/str.rs
+++ b/rust/kernel/str.rs
@@ -4,8 +4,9 @@

use crate::alloc::{flags::*, vec_ext::VecExt, AllocError};
use alloc::vec::Vec;
+use core::ffi::CStr;
use core::fmt::{self, Write};
-use core::ops::{self, Deref, DerefMut, Index};
+use core::ops::Deref;

use crate::error::{code::*, Error};

@@ -41,11 +42,11 @@ impl fmt::Display for BStr {
/// # use kernel::{fmt, b_str, str::{BStr, CString}};
/// let ascii = b_str!("Hello, BStr!");
/// let s = CString::try_from_fmt(fmt!("{}", ascii)).unwrap();
- /// assert_eq!(s.as_bytes(), "Hello, BStr!".as_bytes());
+ /// assert_eq!(s.to_bytes(), "Hello, BStr!".as_bytes());
///
/// let non_ascii = b_str!("🦀");
/// let s = CString::try_from_fmt(fmt!("{}", non_ascii)).unwrap();
- /// assert_eq!(s.as_bytes(), "\\xf0\\x9f\\xa6\\x80".as_bytes());
+ /// assert_eq!(s.to_bytes(), "\\xf0\\x9f\\xa6\\x80".as_bytes());
/// ```
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
for &b in &self.0 {
@@ -72,11 +73,11 @@ impl fmt::Debug for BStr {
/// // Embedded double quotes are escaped.
/// let ascii = b_str!("Hello, \"BStr\"!");
/// let s = CString::try_from_fmt(fmt!("{:?}", ascii)).unwrap();
- /// assert_eq!(s.as_bytes(), "\"Hello, \\\"BStr\\\"!\"".as_bytes());
+ /// assert_eq!(s.to_bytes(), "\"Hello, \\\"BStr\\\"!\"".as_bytes());
///
/// let non_ascii = b_str!("😺");
/// let s = CString::try_from_fmt(fmt!("{:?}", non_ascii)).unwrap();
- /// assert_eq!(s.as_bytes(), "\"\\xf0\\x9f\\x98\\xba\"".as_bytes());
+ /// assert_eq!(s.to_bytes(), "\"\\xf0\\x9f\\x98\\xba\"".as_bytes());
/// ```
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.write_char('"')?;
@@ -128,271 +129,29 @@ macro_rules! b_str {
}};
}

-/// Possible errors when using conversion functions in [`CStr`].
-#[derive(Debug, Clone, Copy)]
-pub enum CStrConvertError {
- /// Supplied bytes contain an interior `NUL`.
- InteriorNul,
+/// Wrapper around [`CStr`] which implements [`Display`](core::fmt::Display).
+pub struct CStrDisplay<'a>(&'a CStr);

- /// Supplied bytes are not terminated by `NUL`.
- NotNulTerminated,
-}
-
-impl From<CStrConvertError> for Error {
- #[inline]
- fn from(_: CStrConvertError) -> Error {
- EINVAL
- }
-}
-
-/// A string that is guaranteed to have exactly one `NUL` byte, which is at the
-/// end.
-///
-/// Used for interoperability with kernel APIs that take C strings.
-#[repr(transparent)]
-pub struct CStr([u8]);
-
-impl CStr {
- /// Returns the length of this string excluding `NUL`.
- #[inline]
- pub const fn len(&self) -> usize {
- self.len_with_nul() - 1
- }
-
- /// Returns the length of this string with `NUL`.
- #[inline]
- pub const fn len_with_nul(&self) -> usize {
- // SAFETY: This is one of the invariant of `CStr`.
- // We add a `unreachable_unchecked` here to hint the optimizer that
- // the value returned from this function is non-zero.
- if self.0.is_empty() {
- unsafe { core::hint::unreachable_unchecked() };
- }
- self.0.len()
- }
-
- /// Returns `true` if the string only includes `NUL`.
- #[inline]
- pub const fn is_empty(&self) -> bool {
- self.len() == 0
- }
-
- /// Wraps a raw C string pointer.
- ///
- /// # Safety
- ///
- /// `ptr` must be a valid pointer to a `NUL`-terminated C string, and it must
- /// last at least `'a`. When `CStr` is alive, the memory pointed by `ptr`
- /// must not be mutated.
- #[inline]
- pub unsafe fn from_char_ptr<'a>(ptr: *const core::ffi::c_char) -> &'a Self {
- // SAFETY: The safety precondition guarantees `ptr` is a valid pointer
- // to a `NUL`-terminated C string.
- let len = unsafe { bindings::strlen(ptr) } + 1;
- // SAFETY: Lifetime guaranteed by the safety precondition.
- let bytes = unsafe { core::slice::from_raw_parts(ptr as _, len as _) };
- // SAFETY: As `len` is returned by `strlen`, `bytes` does not contain interior `NUL`.
- // As we have added 1 to `len`, the last byte is known to be `NUL`.
- unsafe { Self::from_bytes_with_nul_unchecked(bytes) }
- }
-
- /// Creates a [`CStr`] from a `[u8]`.
- ///
- /// The provided slice must be `NUL`-terminated, does not contain any
- /// interior `NUL` bytes.
- pub const fn from_bytes_with_nul(bytes: &[u8]) -> Result<&Self, CStrConvertError> {
- if bytes.is_empty() {
- return Err(CStrConvertError::NotNulTerminated);
- }
- if bytes[bytes.len() - 1] != 0 {
- return Err(CStrConvertError::NotNulTerminated);
- }
- let mut i = 0;
- // `i + 1 < bytes.len()` allows LLVM to optimize away bounds checking,
- // while it couldn't optimize away bounds checks for `i < bytes.len() - 1`.
- while i + 1 < bytes.len() {
- if bytes[i] == 0 {
- return Err(CStrConvertError::InteriorNul);
- }
- i += 1;
- }
- // SAFETY: We just checked that all properties hold.
- Ok(unsafe { Self::from_bytes_with_nul_unchecked(bytes) })
- }
-
- /// Creates a [`CStr`] from a `[u8]` without performing any additional
- /// checks.
- ///
- /// # Safety
- ///
- /// `bytes` *must* end with a `NUL` byte, and should only have a single
- /// `NUL` byte (or the string will be truncated).
- #[inline]
- pub const unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) -> &CStr {
- // SAFETY: Properties of `bytes` guaranteed by the safety precondition.
- unsafe { core::mem::transmute(bytes) }
- }
-
- /// Creates a mutable [`CStr`] from a `[u8]` without performing any
- /// additional checks.
- ///
- /// # Safety
- ///
- /// `bytes` *must* end with a `NUL` byte, and should only have a single
- /// `NUL` byte (or the string will be truncated).
- #[inline]
- pub unsafe fn from_bytes_with_nul_unchecked_mut(bytes: &mut [u8]) -> &mut CStr {
- // SAFETY: Properties of `bytes` guaranteed by the safety precondition.
- unsafe { &mut *(bytes as *mut [u8] as *mut CStr) }
- }
-
- /// Returns a C pointer to the string.
- #[inline]
- pub const fn as_char_ptr(&self) -> *const core::ffi::c_char {
- self.0.as_ptr() as _
- }
-
- /// Convert the string to a byte slice without the trailing `NUL` byte.
- #[inline]
- pub fn as_bytes(&self) -> &[u8] {
- &self.0[..self.len()]
- }
-
- /// Convert the string to a byte slice containing the trailing `NUL` byte.
- #[inline]
- pub const fn as_bytes_with_nul(&self) -> &[u8] {
- &self.0
- }
-
- /// Yields a [`&str`] slice if the [`CStr`] contains valid UTF-8.
- ///
- /// If the contents of the [`CStr`] are valid UTF-8 data, this
- /// function will return the corresponding [`&str`] slice. Otherwise,
- /// it will return an error with details of where UTF-8 validation failed.
- ///
- /// # Examples
- ///
- /// ```
- /// # use kernel::str::CStr;
- /// let cstr = CStr::from_bytes_with_nul(b"foo\0").unwrap();
- /// assert_eq!(cstr.to_str(), Ok("foo"));
- /// ```
- #[inline]
- pub fn to_str(&self) -> Result<&str, core::str::Utf8Error> {
- core::str::from_utf8(self.as_bytes())
- }
-
- /// Unsafely convert this [`CStr`] into a [`&str`], without checking for
- /// valid UTF-8.
- ///
- /// # Safety
- ///
- /// The contents must be valid UTF-8.
+impl fmt::Display for CStrDisplay<'_> {
+ /// Formats printable ASCII characters, escaping the rest.
///
/// # Examples
///
/// ```
- /// # use kernel::c_str;
- /// # use kernel::str::CStr;
- /// let bar = c_str!("ツ");
- /// // SAFETY: String literals are guaranteed to be valid UTF-8
- /// // by the Rust compiler.
- /// assert_eq!(unsafe { bar.as_str_unchecked() }, "ツ");
- /// ```
- #[inline]
- pub unsafe fn as_str_unchecked(&self) -> &str {
- unsafe { core::str::from_utf8_unchecked(self.as_bytes()) }
- }
-
- /// Convert this [`CStr`] into a [`CString`] by allocating memory and
- /// copying over the string data.
- pub fn to_cstring(&self) -> Result<CString, AllocError> {
- CString::try_from(self)
- }
-
- /// Converts this [`CStr`] to its ASCII lower case equivalent in-place.
- ///
- /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
- /// but non-ASCII letters are unchanged.
- ///
- /// To return a new lowercased value without modifying the existing one, use
- /// [`to_ascii_lowercase()`].
- ///
- /// [`to_ascii_lowercase()`]: #method.to_ascii_lowercase
- pub fn make_ascii_lowercase(&mut self) {
- // INVARIANT: This doesn't introduce or remove NUL bytes in the C
- // string.
- self.0.make_ascii_lowercase();
- }
-
- /// Converts this [`CStr`] to its ASCII upper case equivalent in-place.
- ///
- /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
- /// but non-ASCII letters are unchanged.
- ///
- /// To return a new uppercased value without modifying the existing one, use
- /// [`to_ascii_uppercase()`].
- ///
- /// [`to_ascii_uppercase()`]: #method.to_ascii_uppercase
- pub fn make_ascii_uppercase(&mut self) {
- // INVARIANT: This doesn't introduce or remove NUL bytes in the C
- // string.
- self.0.make_ascii_uppercase();
- }
-
- /// Returns a copy of this [`CString`] where each character is mapped to its
- /// ASCII lower case equivalent.
- ///
- /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
- /// but non-ASCII letters are unchanged.
- ///
- /// To lowercase the value in-place, use [`make_ascii_lowercase`].
- ///
- /// [`make_ascii_lowercase`]: str::make_ascii_lowercase
- pub fn to_ascii_lowercase(&self) -> Result<CString, AllocError> {
- let mut s = self.to_cstring()?;
-
- s.make_ascii_lowercase();
-
- Ok(s)
- }
-
- /// Returns a copy of this [`CString`] where each character is mapped to its
- /// ASCII upper case equivalent.
- ///
- /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
- /// but non-ASCII letters are unchanged.
- ///
- /// To uppercase the value in-place, use [`make_ascii_uppercase`].
- ///
- /// [`make_ascii_uppercase`]: str::make_ascii_uppercase
- pub fn to_ascii_uppercase(&self) -> Result<CString, AllocError> {
- let mut s = self.to_cstring()?;
-
- s.make_ascii_uppercase();
-
- Ok(s)
- }
-}
-
-impl fmt::Display for CStr {
- /// Formats printable ASCII characters, escaping the rest.
- ///
- /// ```
+ /// # use core::ffi::CStr;
/// # use kernel::c_str;
/// # use kernel::fmt;
- /// # use kernel::str::CStr;
- /// # use kernel::str::CString;
- /// let penguin = c_str!("🐧");
- /// let s = CString::try_from_fmt(fmt!("{}", penguin)).unwrap();
- /// assert_eq!(s.as_bytes_with_nul(), "\\xf0\\x9f\\x90\\xa7\0".as_bytes());
- ///
- /// let ascii = c_str!("so \"cool\"");
- /// let s = CString::try_from_fmt(fmt!("{}", ascii)).unwrap();
- /// assert_eq!(s.as_bytes_with_nul(), "so \"cool\"\0".as_bytes());
+ /// # use kernel::str::{CStrExt, CString};
+ /// let penguin = c"🐧";
+ /// let s = CString::try_from_fmt(fmt!("{}", penguin.display())).unwrap();
+ /// assert_eq!(s.to_bytes_with_nul(), "\\xf0\\x9f\\x90\\xa7\0".as_bytes());
+ ///
+ /// let ascii = c"so \"cool\"";
+ /// let s = CString::try_from_fmt(fmt!("{}", ascii.display())).unwrap();
+ /// assert_eq!(s.to_bytes_with_nul(), "so \"cool\"\0".as_bytes());
/// ```
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
- for &c in self.as_bytes() {
+ for &c in self.0.to_bytes() {
if (0x20..0x7f).contains(&c) {
// Printable character.
f.write_char(c as char)?;
@@ -404,116 +163,70 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
}
}

-impl fmt::Debug for CStr {
- /// Formats printable ASCII characters with a double quote on either end, escaping the rest.
+/// Extensions to [`CStr`].
+pub trait CStrExt {
+ /// Returns an object that implements [`Display`](core::fmt::Display) for
+ /// safely printing a [`CStr`] that may contain non-ASCII data, which are
+ /// escaped.
+ ///
+ /// # Examples
///
/// ```
+ /// # use core::ffi::CStr;
/// # use kernel::c_str;
/// # use kernel::fmt;
- /// # use kernel::str::CStr;
- /// # use kernel::str::CString;
- /// let penguin = c_str!("🐧");
- /// let s = CString::try_from_fmt(fmt!("{:?}", penguin)).unwrap();
- /// assert_eq!(s.as_bytes_with_nul(), "\"\\xf0\\x9f\\x90\\xa7\"\0".as_bytes());
- ///
- /// // Embedded double quotes are escaped.
- /// let ascii = c_str!("so \"cool\"");
- /// let s = CString::try_from_fmt(fmt!("{:?}", ascii)).unwrap();
- /// assert_eq!(s.as_bytes_with_nul(), "\"so \\\"cool\\\"\"\0".as_bytes());
+ /// # use kernel::str::{CStrExt, CString};
+ /// let penguin = c"🐧";
+ /// let s = CString::try_from_fmt(fmt!("{}", penguin.display())).unwrap();
+ /// assert_eq!(s.to_bytes_with_nul(), "\\xf0\\x9f\\x90\\xa7\0".as_bytes());
+ ///
+ /// let ascii = c"so \"cool\"";
+ /// let s = CString::try_from_fmt(fmt!("{}", ascii.display())).unwrap();
+ /// assert_eq!(s.to_bytes_with_nul(), "so \"cool\"\0".as_bytes());
/// ```
- fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
- f.write_str("\"")?;
- for &c in self.as_bytes() {
- match c {
- // Printable characters.
- b'\"' => f.write_str("\\\"")?,
- 0x20..=0x7e => f.write_char(c as char)?,
- _ => write!(f, "\\x{:02x}", c)?,
- }
- }
- f.write_str("\"")
- }
-}
-
-impl AsRef<BStr> for CStr {
- #[inline]
- fn as_ref(&self) -> &BStr {
- BStr::from_bytes(self.as_bytes())
- }
-}
-
-impl Deref for CStr {
- type Target = BStr;
-
- #[inline]
- fn deref(&self) -> &Self::Target {
- self.as_ref()
- }
-}
+ fn display(&self) -> CStrDisplay<'_>;

-impl Index<ops::RangeFrom<usize>> for CStr {
- type Output = CStr;
-
- #[inline]
- fn index(&self, index: ops::RangeFrom<usize>) -> &Self::Output {
- // Delegate bounds checking to slice.
- // Assign to _ to mute clippy's unnecessary operation warning.
- let _ = &self.as_bytes()[index.start..];
- // SAFETY: We just checked the bounds.
- unsafe { Self::from_bytes_with_nul_unchecked(&self.0[index.start..]) }
- }
+ /// Creates a mutable [`CStr`] from a `[u8]` without performing any
+ /// additional checks.
+ ///
+ /// # Safety
+ ///
+ /// `bytes` *must* end with a `NUL` byte, and should only have a single
+ /// `NUL` byte (or the string will be truncated).
+ unsafe fn from_bytes_with_nul_unchecked_mut(bytes: &mut [u8]) -> &mut Self;
}

-impl Index<ops::RangeFull> for CStr {
- type Output = CStr;
-
- #[inline]
- fn index(&self, _index: ops::RangeFull) -> &Self::Output {
- self
+impl CStrExt for CStr {
+ fn display(&self) -> CStrDisplay<'_> {
+ CStrDisplay(self)
}
-}
-
-mod private {
- use core::ops;

- // Marker trait for index types that can be forward to `BStr`.
- pub trait CStrIndex {}
-
- impl CStrIndex for usize {}
- impl CStrIndex for ops::Range<usize> {}
- impl CStrIndex for ops::RangeInclusive<usize> {}
- impl CStrIndex for ops::RangeToInclusive<usize> {}
-}
-
-impl<Idx> Index<Idx> for CStr
-where
- Idx: private::CStrIndex,
- BStr: Index<Idx>,
-{
- type Output = <BStr as Index<Idx>>::Output;
-
- #[inline]
- fn index(&self, index: Idx) -> &Self::Output {
- &self.as_ref()[index]
+ unsafe fn from_bytes_with_nul_unchecked_mut(bytes: &mut [u8]) -> &mut Self {
+ // SAFETY: Properties of `bytes` guaranteed by the safety precondition.
+ unsafe { &mut *(bytes as *mut [u8] as *mut CStr) }
}
}

/// Creates a new [`CStr`] from a string literal.
///
-/// The string literal should not contain any `NUL` bytes.
+/// This macro is not needed when C-string literals (`c"hello"` syntax) can be
+/// used directly, but can be used when a C-string version of a standard string
+/// literal is required (often when working with macros).
+///
+/// The string should not contain any `NUL` bytes.
///
/// # Examples
///
/// ```
+/// # use core::ffi::CStr;
/// # use kernel::c_str;
-/// # use kernel::str::CStr;
-/// const MY_CSTR: &CStr = c_str!("My awesome CStr!");
+/// const MY_CSTR: &CStr = c_str!(stringify!(5));
/// ```
#[macro_export]
macro_rules! c_str {
($str:expr) => {{
const S: &str = concat!($str, "\0");
- const C: &$crate::str::CStr = match $crate::str::CStr::from_bytes_with_nul(S.as_bytes()) {
+ const C: &core::ffi::CStr = match core::ffi::CStr::from_bytes_with_nul(S.as_bytes()) {
Ok(v) => v,
Err(_) => panic!("string contains interior NUL"),
};
@@ -540,65 +253,6 @@ mod tests {
\\xe0\\xe1\\xe2\\xe3\\xe4\\xe5\\xe6\\xe7\\xe8\\xe9\\xea\\xeb\\xec\\xed\\xee\\xef\
\\xf0\\xf1\\xf2\\xf3\\xf4\\xf5\\xf6\\xf7\\xf8\\xf9\\xfa\\xfb\\xfc\\xfd\\xfe\\xff";

- #[test]
- fn test_cstr_to_str() {
- let good_bytes = b"\xf0\x9f\xa6\x80\0";
- let checked_cstr = CStr::from_bytes_with_nul(good_bytes).unwrap();
- let checked_str = checked_cstr.to_str().unwrap();
- assert_eq!(checked_str, "🦀");
- }
-
- #[test]
- #[should_panic]
- fn test_cstr_to_str_panic() {
- let bad_bytes = b"\xc3\x28\0";
- let checked_cstr = CStr::from_bytes_with_nul(bad_bytes).unwrap();
- checked_cstr.to_str().unwrap();
- }
-
- #[test]
- fn test_cstr_as_str_unchecked() {
- let good_bytes = b"\xf0\x9f\x90\xA7\0";
- let checked_cstr = CStr::from_bytes_with_nul(good_bytes).unwrap();
- let unchecked_str = unsafe { checked_cstr.as_str_unchecked() };
- assert_eq!(unchecked_str, "🐧");
- }
-
- #[test]
- fn test_cstr_display() {
- let hello_world = CStr::from_bytes_with_nul(b"hello, world!\0").unwrap();
- assert_eq!(format!("{}", hello_world), "hello, world!");
- let non_printables = CStr::from_bytes_with_nul(b"\x01\x09\x0a\0").unwrap();
- assert_eq!(format!("{}", non_printables), "\\x01\\x09\\x0a");
- let non_ascii = CStr::from_bytes_with_nul(b"d\xe9j\xe0 vu\0").unwrap();
- assert_eq!(format!("{}", non_ascii), "d\\xe9j\\xe0 vu");
- let good_bytes = CStr::from_bytes_with_nul(b"\xf0\x9f\xa6\x80\0").unwrap();
- assert_eq!(format!("{}", good_bytes), "\\xf0\\x9f\\xa6\\x80");
- }
-
- #[test]
- fn test_cstr_display_all_bytes() {
- let mut bytes: [u8; 256] = [0; 256];
- // fill `bytes` with [1..=255] + [0]
- for i in u8::MIN..=u8::MAX {
- bytes[i as usize] = i.wrapping_add(1);
- }
- let cstr = CStr::from_bytes_with_nul(&bytes).unwrap();
- assert_eq!(format!("{}", cstr), ALL_ASCII_CHARS);
- }
-
- #[test]
- fn test_cstr_debug() {
- let hello_world = CStr::from_bytes_with_nul(b"hello, world!\0").unwrap();
- assert_eq!(format!("{:?}", hello_world), "\"hello, world!\"");
- let non_printables = CStr::from_bytes_with_nul(b"\x01\x09\x0a\0").unwrap();
- assert_eq!(format!("{:?}", non_printables), "\"\\x01\\x09\\x0a\"");
- let non_ascii = CStr::from_bytes_with_nul(b"d\xe9j\xe0 vu\0").unwrap();
- assert_eq!(format!("{:?}", non_ascii), "\"d\\xe9j\\xe0 vu\"");
- let good_bytes = CStr::from_bytes_with_nul(b"\xf0\x9f\xa6\x80\0").unwrap();
- assert_eq!(format!("{:?}", good_bytes), "\"\\xf0\\x9f\\xa6\\x80\"");
- }
-
#[test]
fn test_bstr_display() {
let hello_world = BStr::from_bytes(b"hello, world!");
@@ -626,6 +280,29 @@ fn test_bstr_debug() {
let good_bytes = BStr::from_bytes(b"\xf0\x9f\xa6\x80");
assert_eq!(format!("{:?}", good_bytes), "\"\\xf0\\x9f\\xa6\\x80\"");
}
+
+ #[test]
+ fn test_cstr_display() {
+ let hello_world = CStr::from_bytes_with_nul(b"hello, world!\0").unwrap();
+ assert_eq!(format!("{}", hello_world.display()), "hello, world!");
+ let non_printables = CStr::from_bytes_with_nul(b"\x01\x09\x0a\0").unwrap();
+ assert_eq!(format!("{}", non_printables.display()), "\\x01\\x09\\x0a");
+ let non_ascii = CStr::from_bytes_with_nul(b"d\xe9j\xe0 vu\0").unwrap();
+ assert_eq!(format!("{}", non_ascii.display()), "d\\xe9j\\xe0 vu");
+ let good_bytes = CStr::from_bytes_with_nul(b"\xf0\x9f\xa6\x80\0").unwrap();
+ assert_eq!(format!("{}", good_bytes.display()), "\\xf0\\x9f\\xa6\\x80");
+ }
+
+ #[test]
+ fn test_cstr_display_all_bytes() {
+ let mut bytes: [u8; 256] = [0; 256];
+ // fill `bytes` with [1..=255] + [0]
+ for i in u8::MIN..=u8::MAX {
+ bytes[i as usize] = i.wrapping_add(1);
+ }
+ let cstr = CStr::from_bytes_with_nul(&bytes).unwrap();
+ assert_eq!(format!("{}", cstr.display()), ALL_ASCII_CHARS);
+ }
}

/// Allows formatting of [`fmt::Arguments`] into a raw buffer.
@@ -779,11 +456,11 @@ fn write_str(&mut self, s: &str) -> fmt::Result {
/// use kernel::{str::CString, fmt};
///
/// let s = CString::try_from_fmt(fmt!("{}{}{}", "abc", 10, 20)).unwrap();
-/// assert_eq!(s.as_bytes_with_nul(), "abc1020\0".as_bytes());
+/// assert_eq!(s.to_bytes_with_nul(), "abc1020\0".as_bytes());
///
/// let tmp = "testing";
/// let s = CString::try_from_fmt(fmt!("{tmp}{}", 123)).unwrap();
-/// assert_eq!(s.as_bytes_with_nul(), "testing123\0".as_bytes());
+/// assert_eq!(s.to_bytes_with_nul(), "testing123\0".as_bytes());
///
/// // This fails because it has an embedded `NUL` byte.
/// let s = CString::try_from_fmt(fmt!("a\0b{}", 123));
@@ -838,21 +515,13 @@ fn deref(&self) -> &Self::Target {
}
}

-impl DerefMut for CString {
- fn deref_mut(&mut self) -> &mut Self::Target {
- // SAFETY: A `CString` is always NUL-terminated and contains no other
- // NUL bytes.
- unsafe { CStr::from_bytes_with_nul_unchecked_mut(self.buf.as_mut_slice()) }
- }
-}
-
impl<'a> TryFrom<&'a CStr> for CString {
type Error = AllocError;

fn try_from(cstr: &'a CStr) -> Result<CString, AllocError> {
let mut buf = Vec::new();

- <Vec<_> as VecExt<_>>::extend_from_slice(&mut buf, cstr.as_bytes_with_nul(), GFP_KERNEL)
+ <Vec<_> as VecExt<_>>::extend_from_slice(&mut buf, cstr.to_bytes_with_nul(), GFP_KERNEL)
.map_err(|_| AllocError)?;

// INVARIANT: The `CStr` and `CString` types have the same invariants for
diff --git a/rust/kernel/sync/condvar.rs b/rust/kernel/sync/condvar.rs
index 2b306afbe56d..16d1a1cb8d00 100644
--- a/rust/kernel/sync/condvar.rs
+++ b/rust/kernel/sync/condvar.rs
@@ -9,12 +9,11 @@
use crate::{
init::PinInit,
pin_init,
- str::CStr,
task::{MAX_SCHEDULE_TIMEOUT, TASK_INTERRUPTIBLE, TASK_NORMAL, TASK_UNINTERRUPTIBLE},
time::Jiffies,
types::Opaque,
};
-use core::ffi::{c_int, c_long};
+use core::ffi::{c_int, c_long, CStr};
use core::marker::PhantomPinned;
use core::ptr;
use macros::pin_data;
@@ -108,7 +107,7 @@ pub fn new(name: &'static CStr, key: &'static LockClassKey) -> impl PinInit<Self
// SAFETY: `slot` is valid while the closure is called and both `name` and `key` have
// static lifetimes so they live indefinitely.
wait_queue_head <- Opaque::ffi_init(|slot| unsafe {
- bindings::__init_waitqueue_head(slot, name.as_char_ptr(), key.as_ptr())
+ bindings::__init_waitqueue_head(slot, name.as_ptr(), key.as_ptr())
}),
})
}
diff --git a/rust/kernel/sync/lock.rs b/rust/kernel/sync/lock.rs
index f6c34ca4d819..318ecb5a5916 100644
--- a/rust/kernel/sync/lock.rs
+++ b/rust/kernel/sync/lock.rs
@@ -6,8 +6,8 @@
//! spinlocks, raw spinlocks) to be provided with minimal effort.

use super::LockClassKey;
-use crate::{init::PinInit, pin_init, str::CStr, types::Opaque, types::ScopeGuard};
-use core::{cell::UnsafeCell, marker::PhantomData, marker::PhantomPinned};
+use crate::{init::PinInit, pin_init, types::Opaque, types::ScopeGuard};
+use core::{cell::UnsafeCell, ffi::CStr, marker::PhantomData, marker::PhantomPinned};
use macros::pin_data;

pub mod mutex;
@@ -113,7 +113,7 @@ pub fn new(t: T, name: &'static CStr, key: &'static LockClassKey) -> impl PinIni
// SAFETY: `slot` is valid while the closure is called and both `name` and `key` have
// static lifetimes so they live indefinitely.
state <- Opaque::ffi_init(|slot| unsafe {
- B::init(slot, name.as_char_ptr(), key.as_ptr())
+ B::init(slot, name.as_ptr(), key.as_ptr())
}),
})
}
diff --git a/rust/kernel/workqueue.rs b/rust/kernel/workqueue.rs
index 553a5cba2adc..a6418873e82e 100644
--- a/rust/kernel/workqueue.rs
+++ b/rust/kernel/workqueue.rs
@@ -380,7 +380,7 @@ pub fn new(name: &'static CStr, key: &'static LockClassKey) -> impl PinInit<Self
slot,
Some(T::Pointer::run),
false,
- name.as_char_ptr(),
+ name.as_ptr(),
key.as_ptr(),
)
}
diff --git a/scripts/rustdoc_test_gen.rs b/scripts/rustdoc_test_gen.rs
index 5ebd42ae4a3f..339991ee6885 100644
--- a/scripts/rustdoc_test_gen.rs
+++ b/scripts/rustdoc_test_gen.rs
@@ -172,7 +172,7 @@ pub extern "C" fn {kunit_name}(__kunit_test: *mut kernel::bindings::kunit) {{
#[allow(unused)]
macro_rules! assert {{
($cond:expr $(,)?) => {{{{
- kernel::kunit_assert!("{kunit_name}", "{real_path}", __DOCTEST_ANCHOR - {line}, $cond);
+ kernel::kunit_assert!(c"{kunit_name}", c"{real_path}", __DOCTEST_ANCHOR - {line}, $cond);
}}}}
}}

@@ -180,7 +180,7 @@ macro_rules! assert {{
#[allow(unused)]
macro_rules! assert_eq {{
($left:expr, $right:expr $(,)?) => {{{{
- kernel::kunit_assert_eq!("{kunit_name}", "{real_path}", __DOCTEST_ANCHOR - {line}, $left, $right);
+ kernel::kunit_assert_eq!(c"{kunit_name}", c"{real_path}", __DOCTEST_ANCHOR - {line}, $left, $right);
}}}}
}}

--
2.45.2