[PATCH v6 2/4] rust: replace `CStr` with `core::ffi::CStr`

From: Tamir Duberstein
Date: Sun Feb 02 2025 - 07:21:37 EST

`std::ffi::CStr` was moved to `core::ffi::CStr` in Rust 1.64. Replace
`kernel::str::CStr` with `core::ffi::CStr` now that we can.

`kernel::str::CStr::{from,as}_char_ptr` live on as free functions in
`kernel::str` to paper over the difference between `core::ffi::c_char`
and `kernel::ffi::char`; see the code comment on the latter type for
details.

C-String literals were added in Rust 1.77. Opportunistically replace
instances of `kernel::c_str!` with C-String literals where other code
changes were already necessary; the rest will be done in a later commit.

Signed-off-by: Tamir Duberstein <tamird@xxxxxxxxx>
---
drivers/gpu/drm/drm_panic_qr.rs | 2 +-
rust/kernel/device.rs | 5 +-
rust/kernel/error.rs | 4 +-
rust/kernel/firmware.rs | 2 +-
rust/kernel/kunit.rs | 4 +-
rust/kernel/miscdevice.rs | 2 +-
rust/kernel/net/phy.rs | 2 +-
rust/kernel/prelude.rs | 5 +-
rust/kernel/seq_file.rs | 4 +-
rust/kernel/str.rs | 449 ++++++----------------------------------
rust/kernel/sync/condvar.rs | 2 +-
rust/kernel/sync/lock.rs | 2 +-
rust/kernel/sync/lock/global.rs | 2 +-
rust/kernel/workqueue.rs | 2 +-
14 files changed, 88 insertions(+), 399 deletions(-)

diff --git a/drivers/gpu/drm/drm_panic_qr.rs b/drivers/gpu/drm/drm_panic_qr.rs
index bcf248f69252..ef294017888e 100644
--- a/drivers/gpu/drm/drm_panic_qr.rs
+++ b/drivers/gpu/drm/drm_panic_qr.rs
@@ -958,7 +958,7 @@ fn draw_all(&mut self, data: impl Iterator<Item = u8>) {
} else {
// SAFETY: The caller ensures that `url` is a valid pointer to a
// nul-terminated string.
- let url_cstr: &CStr = unsafe { CStr::from_char_ptr(url) };
+ let url_cstr: &CStr = unsafe { kernel::str::from_char_ptr(url) };
let segments = &[
&Segment::Binary(url_cstr.as_bytes()),
&Segment::Numeric(&data_slice[0..data_len]),
diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
index d5e6a19ff6b7..f97c409aaba9 100644
--- a/rust/kernel/device.rs
+++ b/rust/kernel/device.rs
@@ -10,9 +10,6 @@
};
use core::{fmt, ptr};

-#[cfg(CONFIG_PRINTK)]
-use crate::c_str;
-
/// A reference-counted device.
///
/// This structure represents the Rust abstraction for a C `struct device`. This implementation
@@ -175,7 +172,7 @@ unsafe fn printk(&self, klevel: &[u8], msg: fmt::Arguments<'_>) {
bindings::_dev_printk(
klevel as *const _ as *const crate::ffi::c_char,
self.as_raw(),
- c_str!("%pA").as_char_ptr(),
+ crate::str::as_char_ptr(c"%pA"),
&msg as *const _ as *const crate::ffi::c_void,
)
};
diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs
index f6ecf09cb65f..51c5e0f0a0bc 100644
--- a/rust/kernel/error.rs
+++ b/rust/kernel/error.rs
@@ -164,7 +164,7 @@ 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 { crate::str::from_char_ptr(ptr) })
}
}

@@ -187,7 +187,7 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
Some(name) => f
.debug_tuple(
// SAFETY: These strings are ASCII-only.
- unsafe { core::str::from_utf8_unchecked(name) },
+ unsafe { core::str::from_utf8_unchecked(name.to_bytes()) },
)
.finish(),
}
diff --git a/rust/kernel/firmware.rs b/rust/kernel/firmware.rs
index c5162fdc95ff..e75db4d825ce 100644
--- a/rust/kernel/firmware.rs
+++ b/rust/kernel/firmware.rs
@@ -61,7 +61,7 @@ fn request_internal(name: &CStr, dev: &Device, func: FwFunc) -> Result<Self> {

// SAFETY: `pfw` is a valid pointer to a NULL initialized `bindings::firmware` pointer.
// `name` and `dev` are valid as by their type invariants.
- let ret = unsafe { func.0(pfw as _, name.as_char_ptr(), dev.as_raw()) };
+ let ret = unsafe { func.0(pfw as _, crate::str::as_char_ptr(name), dev.as_raw()) };
if ret != 0 {
return Err(Error::from_errno(ret));
}
diff --git a/rust/kernel/kunit.rs b/rust/kernel/kunit.rs
index 630b947c708c..9f40ea744fc2 100644
--- a/rust/kernel/kunit.rs
+++ b/rust/kernel/kunit.rs
@@ -101,12 +101,12 @@ unsafe impl Sync for Location {}
unsafe impl Sync for UnaryAssert {}

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

diff --git a/rust/kernel/miscdevice.rs b/rust/kernel/miscdevice.rs
index b3a6cc50b240..2dd20e981e9b 100644
--- a/rust/kernel/miscdevice.rs
+++ b/rust/kernel/miscdevice.rs
@@ -31,7 +31,7 @@ pub const fn into_raw<T: MiscDevice>(self) -> bindings::miscdevice {
// SAFETY: All zeros is valid for this C type.
let mut result: bindings::miscdevice = unsafe { MaybeUninit::zeroed().assume_init() };
result.minor = bindings::MISC_DYNAMIC_MINOR as _;
- result.name = self.name.as_char_ptr();
+ result.name = crate::str::as_char_ptr(self.name);
result.fops = create_vtable::<T>();
result
}
diff --git a/rust/kernel/net/phy.rs b/rust/kernel/net/phy.rs
index d7da29f95e43..9e410de3c3a3 100644
--- a/rust/kernel/net/phy.rs
+++ b/rust/kernel/net/phy.rs
@@ -504,7 +504,7 @@ 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: crate::str::as_char_ptr(T::NAME),
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 dde2e0649790..96e7029c27da 100644
--- a/rust/kernel/prelude.rs
+++ b/rust/kernel/prelude.rs
@@ -34,7 +34,10 @@

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

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

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

diff --git a/rust/kernel/seq_file.rs b/rust/kernel/seq_file.rs
index 04947c672979..bb3c49fd4ef3 100644
--- a/rust/kernel/seq_file.rs
+++ b/rust/kernel/seq_file.rs
@@ -4,7 +4,7 @@
//!
//! C header: [`include/linux/seq_file.h`](srctree/include/linux/seq_file.h)

-use crate::{bindings, c_str, types::NotThreadSafe, types::Opaque};
+use crate::{bindings, types::NotThreadSafe, types::Opaque};

/// A utility for generating the contents of a seq file.
#[repr(transparent)]
@@ -35,7 +35,7 @@ pub fn call_printf(&self, args: core::fmt::Arguments<'_>) {
unsafe {
bindings::seq_printf(
self.inner.get(),
- c_str!("%pA").as_char_ptr(),
+ crate::str::as_char_ptr(c"%pA"),
&args as *const _ as *const crate::ffi::c_void,
);
}
diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
index 53450c956a6a..2b63cfaaa981 100644
--- a/rust/kernel/str.rs
+++ b/rust/kernel/str.rs
@@ -4,7 +4,7 @@

use crate::alloc::{flags::*, AllocError, KVec};
use core::fmt::{self, Write};
-use core::ops::{self, Deref, DerefMut, Index};
+use core::ops::{Deref, DerefMut};

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

@@ -45,11 +45,11 @@ pub const fn from_bytes(bytes: &[u8]) -> &Self {
/// # use kernel::{fmt, b_str, str::CString};
/// let ascii = b_str!("Hello, BStr!");
/// let s = CString::try_from_fmt(fmt!("{}", ascii.display()))?;
- /// 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.display()))?;
- /// assert_eq!(s.as_bytes(), "\\xf0\\x9f\\xa6\\x80".as_bytes());
+ /// assert_eq!(s.to_bytes(), "\\xf0\\x9f\\xa6\\x80".as_bytes());
/// # Ok::<(), kernel::error::Error>(())
/// ```
#[inline]
@@ -74,11 +74,11 @@ pub fn display(&self) -> Display<'_> {
/// # use kernel::{fmt, b_str, str::CString};
/// let ascii = b_str!("Hello, BStr!");
/// let s = CString::try_from_fmt(fmt!("{}", ascii.display()))?;
-/// 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.display()))?;
-/// assert_eq!(s.as_bytes(), "\\xf0\\x9f\\xa6\\x80".as_bytes());
+/// assert_eq!(s.to_bytes(), "\\xf0\\x9f\\xa6\\x80".as_bytes());
/// # Ok::<(), kernel::error::Error>(())
/// ```
///
@@ -119,11 +119,11 @@ impl fmt::Debug for BStr {
/// // Embedded double quotes are escaped.
/// let ascii = b_str!("Hello, \"BStr\"!");
/// let s = CString::try_from_fmt(fmt!("{:?}", ascii))?;
- /// 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))?;
- /// assert_eq!(s.as_bytes(), "\"\\xf0\\x9f\\x98\\xba\"".as_bytes());
+ /// assert_eq!(s.to_bytes(), "\"\\xf0\\x9f\\x98\\xba\"".as_bytes());
/// # Ok::<(), kernel::error::Error>(())
/// ```
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
@@ -176,254 +176,10 @@ 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,
-
- /// 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 {
- if self.0.is_empty() {
- // 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.
- 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 crate::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) };
- // 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 crate::ffi::c_char {
- self.0.as_ptr()
- }
-
- /// 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")?;
- /// assert_eq!(cstr.to_str(), Ok("foo"));
- /// # Ok::<(), kernel::error::Error>(())
- /// ```
- #[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.
- ///
- /// # 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 {
- // SAFETY: TODO.
- 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)
- }
+pub use core::ffi::CStr;

+/// Extensions to [`CStr`].
+pub trait CStrExt {
/// Returns an object that implements [`Display`] for safely printing a [`CStr`] that may
/// contain non-Unicode data. If you would like an implementation which escapes the [`CStr`]
/// please use [`Debug`] instead.
@@ -439,114 +195,59 @@ pub fn to_ascii_uppercase(&self) -> Result<CString, AllocError> {
/// # use kernel::str::CString;
/// let penguin = c_str!("🐧");
/// let s = CString::try_from_fmt(fmt!("{}", penguin.display()))?;
- /// assert_eq!(s.as_bytes_with_nul(), "\\xf0\\x9f\\x90\\xa7\0".as_bytes());
+ /// assert_eq!(s.to_bytes_with_nul(), "\\xf0\\x9f\\x90\\xa7\0".as_bytes());
///
/// let ascii = c_str!("so \"cool\"");
/// let s = CString::try_from_fmt(fmt!("{}", ascii.display()))?;
- /// assert_eq!(s.as_bytes_with_nul(), "so \"cool\"\0".as_bytes());
+ /// assert_eq!(s.to_bytes_with_nul(), "so \"cool\"\0".as_bytes());
/// # Ok::<(), kernel::error::Error>(())
/// ```
+ fn display(&self) -> Display<'_>;
+}
+
+impl CStrExt for CStr {
#[inline]
- pub fn display(&self) -> Display<'_> {
+ fn display(&self) -> Display<'_> {
Display {
- inner: self,
+ inner: BStr::from_bytes(self.to_bytes()),
escape_common: false,
}
}
}

-impl fmt::Debug for CStr {
- /// Formats printable ASCII characters with a double quote on either end, escaping the rest.
- ///
- /// ```
- /// # use kernel::c_str;
- /// # use kernel::fmt;
- /// # use kernel::str::CString;
- /// let penguin = c_str!("🐧");
- /// let s = CString::try_from_fmt(fmt!("{:?}", penguin))?;
- /// 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))?;
- /// assert_eq!(s.as_bytes_with_nul(), "\"so \\\"cool\\\"\"\0".as_bytes());
- /// # Ok::<(), kernel::error::Error>(())
- /// ```
- 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()
- }
-}
-
-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..]) }
- }
-}
-
-impl Index<ops::RangeFull> for CStr {
- type Output = CStr;
-
- #[inline]
- fn index(&self, _index: ops::RangeFull) -> &Self::Output {
- 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> {}
+/// Wraps a raw C string with a safe C string wrapper.
+///
+/// # Safety
+///
+/// * The memory pointed to by `ptr` must contain a valid nul terminator at the end of the string.
+///
+/// * `ptr` must be [valid] for reads of bytes up to and including the nul terminator. This means in
+/// particular:
+///
+/// * The entire memory range of this `CStr` must be contained within a single allocated object!
+/// * `ptr` must be non-null even for a zero-length cstr.
+///
+/// * The memory referenced by the returned `CStr` must not be mutated for the duration of lifetime
+/// `'a`.
+///
+/// * The nul terminator must be within `isize::MAX` from `ptr`
+// This function exists to paper over the fact that `CStr::from_ptr` takes a `*const
+// core::ffi::c_char` rather than a `*const crate::ffi::c_char`.
+#[inline]
+pub unsafe fn from_char_ptr<'a>(ptr: *const crate::ffi::c_char) -> &'a CStr {
+ // SAFETY: The safety preconditions are the same as for `from_ptr`.
+ unsafe { CStr::from_ptr(ptr.cast()) }
}

-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]
- }
+/// Returns a C pointer to the string.
+// This function exists to paper over the fact that `CStr::as_ptr` returns a `*const
+// core::ffi::c_char` rather than a `*const crate::ffi::c_char`. It is a free function rather than a
+// method on an extension trait because:
+//
+// - error[E0379]: functions in trait impls cannot be declared const
+#[inline]
+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.
@@ -629,25 +330,15 @@ fn test_cstr_to_str_panic() {
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();
- // SAFETY: The contents come from a string literal which contains valid UTF-8.
- 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.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");
+ assert_eq!(format!("{}", c"hello, world!".display()), "hello, world!");
+ assert_eq!(format!("{}", c"\x01\x09\x0a".display()), "\\x01\\x09\\x0a");
+ assert_eq!(format!("{}", c"d\xe9j\xe0 vu".display()), "d\\xe9j\\xe0 vu");
+ assert_eq!(
+ format!("{}", c"\xf0\x9f\xa6\x80".display()),
+ "\\xf0\\x9f\\xa6\\x80"
+ );
}

#[test]
@@ -663,14 +354,13 @@ fn test_cstr_display_all_bytes() {

#[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\"");
+ assert_eq!(format!("{:?}", c"hello, world!"), "\"hello, world!\"");
+ assert_eq!(format!("{:?}", c"\x01\x09\x0a"), "\"\\x01\\t\\n\"");
+ assert_eq!(format!("{:?}", c"d\xe9j\xe0 vu"), "\"d\\xe9j\\xe0 vu\"");
+ assert_eq!(
+ format!("{:?}", c"\xf0\x9f\xa6\x80"),
+ "\"\\xf0\\x9f\\xa6\\x80\""
+ );
}

#[test]
@@ -850,14 +540,14 @@ fn write_str(&mut self, s: &str) -> fmt::Result {
/// # Examples
///
/// ```
-/// use kernel::{str::CString, fmt};
+/// use kernel::{fmt, str::CString};
///
/// let s = CString::try_from_fmt(fmt!("{}{}{}", "abc", 10, 20))?;
-/// 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))?;
-/// 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));
@@ -915,9 +605,8 @@ 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()) }
+ // SAFETY: Properties of `bytes` guaranteed by the safety precondition.
+ unsafe { &mut *(self.buf.as_mut_slice() as *mut [u8] as *mut CStr) }
}
}

@@ -927,7 +616,7 @@ impl<'a> TryFrom<&'a CStr> for CString {
fn try_from(cstr: &'a CStr) -> Result<CString, AllocError> {
let mut buf = KVec::new();

- buf.extend_from_slice(cstr.as_bytes_with_nul(), GFP_KERNEL)?;
+ buf.extend_from_slice(cstr.to_bytes_with_nul(), GFP_KERNEL)?;

// INVARIANT: The `CStr` and `CString` types have the same invariants for
// the string data, and we copied it over without changes.
diff --git a/rust/kernel/sync/condvar.rs b/rust/kernel/sync/condvar.rs
index 7df565038d7d..7bf3df980433 100644
--- a/rust/kernel/sync/condvar.rs
+++ b/rust/kernel/sync/condvar.rs
@@ -107,7 +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, crate::str::as_char_ptr(name), key.as_ptr())
}),
})
}
diff --git a/rust/kernel/sync/lock.rs b/rust/kernel/sync/lock.rs
index 41dcddac69e2..16bf3014f068 100644
--- a/rust/kernel/sync/lock.rs
+++ b/rust/kernel/sync/lock.rs
@@ -128,7 +128,7 @@ 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, crate::str::as_char_ptr(name), key.as_ptr())
}),
})
}
diff --git a/rust/kernel/sync/lock/global.rs b/rust/kernel/sync/lock/global.rs
index 480ee724e3cc..4c4d60a51c1f 100644
--- a/rust/kernel/sync/lock/global.rs
+++ b/rust/kernel/sync/lock/global.rs
@@ -69,7 +69,7 @@ pub unsafe fn init(&'static self) {
unsafe {
B::Backend::init(
self.inner.state.get(),
- B::NAME.as_char_ptr(),
+ crate::str::as_char_ptr(B::NAME),
B::get_lock_class().as_ptr(),
)
}
diff --git a/rust/kernel/workqueue.rs b/rust/kernel/workqueue.rs
index 1dcd53478edd..284b9a739c01 100644
--- a/rust/kernel/workqueue.rs
+++ b/rust/kernel/workqueue.rs
@@ -382,7 +382,7 @@ pub fn new(name: &'static CStr, key: &'static LockClassKey) -> impl PinInit<Self
slot,
Some(T::Pointer::run),
false,
- name.as_char_ptr(),
+ crate::str::as_char_ptr(name),
key.as_ptr(),
)
}

--
2.48.1