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-rw-r--r--rust/kernel/error.rs227
1 files changed, 180 insertions, 47 deletions
diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs
index 4786d3ee1e92..3dee3139fcd4 100644
--- a/rust/kernel/error.rs
+++ b/rust/kernel/error.rs
@@ -4,15 +4,13 @@
//!
//! C header: [`include/uapi/asm-generic/errno-base.h`](srctree/include/uapi/asm-generic/errno-base.h)
-use crate::str::CStr;
-
-use alloc::{
- alloc::{AllocError, LayoutError},
- collections::TryReserveError,
+use crate::{
+ alloc::{layout::LayoutError, AllocError},
+ str::CStr,
};
-use core::convert::From;
use core::fmt;
+use core::num::NonZeroI32;
use core::num::TryFromIntError;
use core::str::Utf8Error;
@@ -24,7 +22,11 @@ pub mod code {
$(
#[doc = $doc]
)*
- pub const $err: super::Error = super::Error(-(crate::bindings::$err as i32));
+ pub const $err: super::Error =
+ match super::Error::try_from_errno(-(crate::bindings::$err as i32)) {
+ Some(err) => err,
+ None => panic!("Invalid errno in `declare_err!`"),
+ };
};
}
@@ -62,6 +64,7 @@ pub mod code {
declare_err!(EPIPE, "Broken pipe.");
declare_err!(EDOM, "Math argument out of domain of func.");
declare_err!(ERANGE, "Math result not representable.");
+ declare_err!(EOVERFLOW, "Value too large for defined data type.");
declare_err!(ERESTARTSYS, "Restart the system call.");
declare_err!(ERESTARTNOINTR, "System call was interrupted by a signal and will be restarted.");
declare_err!(ERESTARTNOHAND, "Restart if no handler.");
@@ -92,26 +95,36 @@ pub mod code {
///
/// The value is a valid `errno` (i.e. `>= -MAX_ERRNO && < 0`).
#[derive(Clone, Copy, PartialEq, Eq)]
-pub struct Error(core::ffi::c_int);
+pub struct Error(NonZeroI32);
impl Error {
/// Creates an [`Error`] from a kernel error code.
///
/// It is a bug to pass an out-of-range `errno`. `EINVAL` would
/// be returned in such a case.
- pub(crate) fn from_errno(errno: core::ffi::c_int) -> Error {
- if errno < -(bindings::MAX_ERRNO as i32) || errno >= 0 {
+ pub fn from_errno(errno: crate::ffi::c_int) -> Error {
+ if let Some(error) = Self::try_from_errno(errno) {
+ error
+ } else {
// TODO: Make it a `WARN_ONCE` once available.
crate::pr_warn!(
- "attempted to create `Error` with out of range `errno`: {}",
+ "attempted to create `Error` with out of range `errno`: {}\n",
errno
);
- return code::EINVAL;
+ code::EINVAL
}
+ }
- // INVARIANT: The check above ensures the type invariant
- // will hold.
- Error(errno)
+ /// Creates an [`Error`] from a kernel error code.
+ ///
+ /// Returns [`None`] if `errno` is out-of-range.
+ const fn try_from_errno(errno: crate::ffi::c_int) -> Option<Error> {
+ if errno < -(bindings::MAX_ERRNO as i32) || errno >= 0 {
+ return None;
+ }
+
+ // SAFETY: `errno` is checked above to be in a valid range.
+ Some(unsafe { Error::from_errno_unchecked(errno) })
}
/// Creates an [`Error`] from a kernel error code.
@@ -119,29 +132,35 @@ impl Error {
/// # Safety
///
/// `errno` must be within error code range (i.e. `>= -MAX_ERRNO && < 0`).
- unsafe fn from_errno_unchecked(errno: core::ffi::c_int) -> Error {
+ const unsafe fn from_errno_unchecked(errno: crate::ffi::c_int) -> Error {
// INVARIANT: The contract ensures the type invariant
// will hold.
- Error(errno)
+ // SAFETY: The caller guarantees `errno` is non-zero.
+ Error(unsafe { NonZeroI32::new_unchecked(errno) })
}
/// Returns the kernel error code.
- pub fn to_errno(self) -> core::ffi::c_int {
- self.0
+ pub fn to_errno(self) -> crate::ffi::c_int {
+ self.0.get()
+ }
+
+ #[cfg(CONFIG_BLOCK)]
+ pub(crate) fn to_blk_status(self) -> bindings::blk_status_t {
+ // SAFETY: `self.0` is a valid error due to its invariant.
+ unsafe { bindings::errno_to_blk_status(self.0.get()) }
}
/// Returns the error encoded as a pointer.
- #[allow(dead_code)]
- pub(crate) fn to_ptr<T>(self) -> *mut T {
+ pub fn to_ptr<T>(self) -> *mut T {
// SAFETY: `self.0` is a valid error due to its invariant.
- unsafe { bindings::ERR_PTR(self.0.into()) as *mut _ }
+ unsafe { bindings::ERR_PTR(self.0.get() as _) as *mut _ }
}
/// Returns a string representing the error, if one exists.
- #[cfg(not(testlib))]
+ #[cfg(not(any(test, testlib)))]
pub fn name(&self) -> Option<&'static CStr> {
// SAFETY: Just an FFI call, there are no extra safety requirements.
- let ptr = unsafe { bindings::errname(-self.0) };
+ let ptr = unsafe { bindings::errname(-self.0.get()) };
if ptr.is_null() {
None
} else {
@@ -155,7 +174,7 @@ impl Error {
/// When `testlib` is configured, this always returns `None` to avoid the dependency on a
/// kernel function so that tests that use this (e.g., by calling [`Result::unwrap`]) can still
/// run in userspace.
- #[cfg(testlib)]
+ #[cfg(any(test, testlib))]
pub fn name(&self) -> Option<&'static CStr> {
None
}
@@ -166,9 +185,11 @@ impl fmt::Debug for Error {
match self.name() {
// Print out number if no name can be found.
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(
+ // SAFETY: These strings are ASCII-only.
+ unsafe { core::str::from_utf8_unchecked(name) },
+ )
.finish(),
}
}
@@ -192,12 +213,6 @@ impl From<Utf8Error> for Error {
}
}
-impl From<TryReserveError> for Error {
- fn from(_: TryReserveError) -> Error {
- code::ENOMEM
- }
-}
-
impl From<LayoutError> for Error {
fn from(_: LayoutError) -> Error {
code::ENOMEM
@@ -234,13 +249,134 @@ impl From<core::convert::Infallible> for Error {
/// [`Error`] as its error type.
///
/// Note that even if a function does not return anything when it succeeds,
-/// it should still be modeled as returning a `Result` rather than
+/// it should still be modeled as returning a [`Result`] rather than
/// just an [`Error`].
+///
+/// Calling a function that returns [`Result`] forces the caller to handle
+/// the returned [`Result`].
+///
+/// This can be done "manually" by using [`match`]. Using [`match`] to decode
+/// the [`Result`] is similar to C where all the return value decoding and the
+/// error handling is done explicitly by writing handling code for each
+/// error to cover. Using [`match`] the error and success handling can be
+/// implemented in all detail as required. For example (inspired by
+/// [`samples/rust/rust_minimal.rs`]):
+///
+/// ```
+/// # #[allow(clippy::single_match)]
+/// fn example() -> Result {
+/// let mut numbers = KVec::new();
+///
+/// match numbers.push(72, GFP_KERNEL) {
+/// Err(e) => {
+/// pr_err!("Error pushing 72: {e:?}");
+/// return Err(e.into());
+/// }
+/// // Do nothing, continue.
+/// Ok(()) => (),
+/// }
+///
+/// match numbers.push(108, GFP_KERNEL) {
+/// Err(e) => {
+/// pr_err!("Error pushing 108: {e:?}");
+/// return Err(e.into());
+/// }
+/// // Do nothing, continue.
+/// Ok(()) => (),
+/// }
+///
+/// match numbers.push(200, GFP_KERNEL) {
+/// Err(e) => {
+/// pr_err!("Error pushing 200: {e:?}");
+/// return Err(e.into());
+/// }
+/// // Do nothing, continue.
+/// Ok(()) => (),
+/// }
+///
+/// Ok(())
+/// }
+/// # example()?;
+/// # Ok::<(), Error>(())
+/// ```
+///
+/// An alternative to be more concise is the [`if let`] syntax:
+///
+/// ```
+/// fn example() -> Result {
+/// let mut numbers = KVec::new();
+///
+/// if let Err(e) = numbers.push(72, GFP_KERNEL) {
+/// pr_err!("Error pushing 72: {e:?}");
+/// return Err(e.into());
+/// }
+///
+/// if let Err(e) = numbers.push(108, GFP_KERNEL) {
+/// pr_err!("Error pushing 108: {e:?}");
+/// return Err(e.into());
+/// }
+///
+/// if let Err(e) = numbers.push(200, GFP_KERNEL) {
+/// pr_err!("Error pushing 200: {e:?}");
+/// return Err(e.into());
+/// }
+///
+/// Ok(())
+/// }
+/// # example()?;
+/// # Ok::<(), Error>(())
+/// ```
+///
+/// Instead of these verbose [`match`]/[`if let`], the [`?`] operator can
+/// be used to handle the [`Result`]. Using the [`?`] operator is often
+/// the best choice to handle [`Result`] in a non-verbose way as done in
+/// [`samples/rust/rust_minimal.rs`]:
+///
+/// ```
+/// fn example() -> Result {
+/// let mut numbers = KVec::new();
+///
+/// numbers.push(72, GFP_KERNEL)?;
+/// numbers.push(108, GFP_KERNEL)?;
+/// numbers.push(200, GFP_KERNEL)?;
+///
+/// Ok(())
+/// }
+/// # example()?;
+/// # Ok::<(), Error>(())
+/// ```
+///
+/// Another possibility is to call [`unwrap()`](Result::unwrap) or
+/// [`expect()`](Result::expect). However, use of these functions is
+/// *heavily discouraged* in the kernel because they trigger a Rust
+/// [`panic!`] if an error happens, which may destabilize the system or
+/// entirely break it as a result -- just like the C [`BUG()`] macro.
+/// Please see the documentation for the C macro [`BUG()`] for guidance
+/// on when to use these functions.
+///
+/// Alternatively, depending on the use case, using [`unwrap_or()`],
+/// [`unwrap_or_else()`], [`unwrap_or_default()`] or [`unwrap_unchecked()`]
+/// might be an option, as well.
+///
+/// For even more details, please see the [Rust documentation].
+///
+/// [`match`]: https://doc.rust-lang.org/reference/expressions/match-expr.html
+/// [`samples/rust/rust_minimal.rs`]: srctree/samples/rust/rust_minimal.rs
+/// [`if let`]: https://doc.rust-lang.org/reference/expressions/if-expr.html#if-let-expressions
+/// [`?`]: https://doc.rust-lang.org/reference/expressions/operator-expr.html#the-question-mark-operator
+/// [`unwrap()`]: Result::unwrap
+/// [`expect()`]: Result::expect
+/// [`BUG()`]: https://docs.kernel.org/process/deprecated.html#bug-and-bug-on
+/// [`unwrap_or()`]: Result::unwrap_or
+/// [`unwrap_or_else()`]: Result::unwrap_or_else
+/// [`unwrap_or_default()`]: Result::unwrap_or_default
+/// [`unwrap_unchecked()`]: Result::unwrap_unchecked
+/// [Rust documentation]: https://doc.rust-lang.org/book/ch09-02-recoverable-errors-with-result.html
pub type Result<T = (), E = Error> = core::result::Result<T, E>;
/// Converts an integer as returned by a C kernel function to an error if it's negative, and
/// `Ok(())` otherwise.
-pub fn to_result(err: core::ffi::c_int) -> Result {
+pub fn to_result(err: crate::ffi::c_int) -> Result {
if err < 0 {
Err(Error::from_errno(err))
} else {
@@ -263,21 +399,21 @@ pub fn to_result(err: core::ffi::c_int) -> Result {
/// fn devm_platform_ioremap_resource(
/// pdev: &mut PlatformDevice,
/// index: u32,
-/// ) -> Result<*mut core::ffi::c_void> {
+/// ) -> Result<*mut kernel::ffi::c_void> {
/// // SAFETY: `pdev` points to a valid platform device. There are no safety requirements
/// // on `index`.
/// from_err_ptr(unsafe { bindings::devm_platform_ioremap_resource(pdev.to_ptr(), index) })
/// }
/// ```
-// TODO: Remove `dead_code` marker once an in-kernel client is available.
-#[allow(dead_code)]
-pub(crate) fn from_err_ptr<T>(ptr: *mut T) -> Result<*mut T> {
- // CAST: Casting a pointer to `*const core::ffi::c_void` is always valid.
- let const_ptr: *const core::ffi::c_void = ptr.cast();
+pub fn from_err_ptr<T>(ptr: *mut T) -> Result<*mut T> {
+ // CAST: Casting a pointer to `*const crate::ffi::c_void` is always valid.
+ let const_ptr: *const crate::ffi::c_void = ptr.cast();
// SAFETY: The FFI function does not deref the pointer.
if unsafe { bindings::IS_ERR(const_ptr) } {
// SAFETY: The FFI function does not deref the pointer.
let err = unsafe { bindings::PTR_ERR(const_ptr) };
+
+ #[allow(clippy::unnecessary_cast)]
// CAST: If `IS_ERR()` returns `true`,
// then `PTR_ERR()` is guaranteed to return a
// negative value greater-or-equal to `-bindings::MAX_ERRNO`,
@@ -287,8 +423,7 @@ pub(crate) fn from_err_ptr<T>(ptr: *mut T) -> Result<*mut T> {
//
// SAFETY: `IS_ERR()` ensures `err` is a
// negative value greater-or-equal to `-bindings::MAX_ERRNO`.
- #[allow(clippy::unnecessary_cast)]
- return Err(unsafe { Error::from_errno_unchecked(err as core::ffi::c_int) });
+ return Err(unsafe { Error::from_errno_unchecked(err as crate::ffi::c_int) });
}
Ok(ptr)
}
@@ -308,7 +443,7 @@ pub(crate) fn from_err_ptr<T>(ptr: *mut T) -> Result<*mut T> {
/// # use kernel::bindings;
/// unsafe extern "C" fn probe_callback(
/// pdev: *mut bindings::platform_device,
-/// ) -> core::ffi::c_int {
+/// ) -> kernel::ffi::c_int {
/// from_result(|| {
/// let ptr = devm_alloc(pdev)?;
/// bindings::platform_set_drvdata(pdev, ptr);
@@ -316,9 +451,7 @@ pub(crate) fn from_err_ptr<T>(ptr: *mut T) -> Result<*mut T> {
/// })
/// }
/// ```
-// TODO: Remove `dead_code` marker once an in-kernel client is available.
-#[allow(dead_code)]
-pub(crate) fn from_result<T, F>(f: F) -> T
+pub fn from_result<T, F>(f: F) -> T
where
T: From<i16>,
F: FnOnce() -> Result<T>,
generated by cgit (git 2.34.1) at 2025-07-01 13:27:38 +0000