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1// SPDX-License-Identifier: GPL-2.0
2
3//! Kernel errors.
4//!
5//! C header: [`include/uapi/asm-generic/errno-base.h`](srctree/include/uapi/asm-generic/errno-base.h)\
6//! C header: [`include/uapi/asm-generic/errno.h`](srctree/include/uapi/asm-generic/errno.h)\
7//! C header: [`include/linux/errno.h`](srctree/include/linux/errno.h)
8
9use crate::{
10 alloc::{layout::LayoutError, AllocError},
11 fmt,
12 str::CStr,
13};
14
15use core::num::NonZeroI32;
16use core::num::TryFromIntError;
17use core::str::Utf8Error;
18
19/// Contains the C-compatible error codes.
20#[rustfmt::skip]
21pub mod code {
22 macro_rules! declare_err {
23 ($err:tt $(,)? $($doc:expr),+) => {
24 $(
25 #[doc = $doc]
26 )*
27 pub const $err: super::Error =
28 match super::Error::try_from_errno(-(crate::bindings::$err as i32)) {
29 Some(err) => err,
30 None => panic!("Invalid errno in `declare_err!`"),
31 };
32 };
33 }
34
35 declare_err!(EPERM, "Operation not permitted.");
36 declare_err!(ENOENT, "No such file or directory.");
37 declare_err!(ESRCH, "No such process.");
38 declare_err!(EINTR, "Interrupted system call.");
39 declare_err!(EIO, "I/O error.");
40 declare_err!(ENXIO, "No such device or address.");
41 declare_err!(E2BIG, "Argument list too long.");
42 declare_err!(ENOEXEC, "Exec format error.");
43 declare_err!(EBADF, "Bad file number.");
44 declare_err!(ECHILD, "No child processes.");
45 declare_err!(EAGAIN, "Try again.");
46 declare_err!(ENOMEM, "Out of memory.");
47 declare_err!(EACCES, "Permission denied.");
48 declare_err!(EFAULT, "Bad address.");
49 declare_err!(ENOTBLK, "Block device required.");
50 declare_err!(EBUSY, "Device or resource busy.");
51 declare_err!(EEXIST, "File exists.");
52 declare_err!(EXDEV, "Cross-device link.");
53 declare_err!(ENODEV, "No such device.");
54 declare_err!(ENOTDIR, "Not a directory.");
55 declare_err!(EISDIR, "Is a directory.");
56 declare_err!(EINVAL, "Invalid argument.");
57 declare_err!(ENFILE, "File table overflow.");
58 declare_err!(EMFILE, "Too many open files.");
59 declare_err!(ENOTTY, "Not a typewriter.");
60 declare_err!(ETXTBSY, "Text file busy.");
61 declare_err!(EFBIG, "File too large.");
62 declare_err!(ENOSPC, "No space left on device.");
63 declare_err!(ESPIPE, "Illegal seek.");
64 declare_err!(EROFS, "Read-only file system.");
65 declare_err!(EMLINK, "Too many links.");
66 declare_err!(EPIPE, "Broken pipe.");
67 declare_err!(EDOM, "Math argument out of domain of func.");
68 declare_err!(ERANGE, "Math result not representable.");
69 declare_err!(EOVERFLOW, "Value too large for defined data type.");
70 declare_err!(ETIMEDOUT, "Connection timed out.");
71 declare_err!(ERESTARTSYS, "Restart the system call.");
72 declare_err!(ERESTARTNOINTR, "System call was interrupted by a signal and will be restarted.");
73 declare_err!(ERESTARTNOHAND, "Restart if no handler.");
74 declare_err!(ENOIOCTLCMD, "No ioctl command.");
75 declare_err!(ERESTART_RESTARTBLOCK, "Restart by calling sys_restart_syscall.");
76 declare_err!(EPROBE_DEFER, "Driver requests probe retry.");
77 declare_err!(EOPENSTALE, "Open found a stale dentry.");
78 declare_err!(ENOPARAM, "Parameter not supported.");
79 declare_err!(EBADHANDLE, "Illegal NFS file handle.");
80 declare_err!(ENOTSYNC, "Update synchronization mismatch.");
81 declare_err!(EBADCOOKIE, "Cookie is stale.");
82 declare_err!(ENOTSUPP, "Operation is not supported.");
83 declare_err!(ETOOSMALL, "Buffer or request is too small.");
84 declare_err!(ESERVERFAULT, "An untranslatable error occurred.");
85 declare_err!(EBADTYPE, "Type not supported by server.");
86 declare_err!(EJUKEBOX, "Request initiated, but will not complete before timeout.");
87 declare_err!(EIOCBQUEUED, "iocb queued, will get completion event.");
88 declare_err!(ERECALLCONFLICT, "Conflict with recalled state.");
89 declare_err!(ENOGRACE, "NFS file lock reclaim refused.");
90}
91
92/// Generic integer kernel error.
93///
94/// The kernel defines a set of integer generic error codes based on C and
95/// POSIX ones. These codes may have a more specific meaning in some contexts.
96///
97/// # Invariants
98///
99/// The value is a valid `errno` (i.e. `>= -MAX_ERRNO && < 0`).
100#[derive(Clone, Copy, PartialEq, Eq)]
101pub struct Error(NonZeroI32);
102
103impl Error {
104 /// Creates an [`Error`] from a kernel error code.
105 ///
106 /// `errno` must be within error code range (i.e. `>= -MAX_ERRNO && < 0`).
107 ///
108 /// It is a bug to pass an out-of-range `errno`. [`code::EINVAL`] is returned in such a case.
109 ///
110 /// # Examples
111 ///
112 /// ```
113 /// assert_eq!(Error::from_errno(-1), EPERM);
114 /// assert_eq!(Error::from_errno(-2), ENOENT);
115 /// ```
116 ///
117 /// The following calls are considered a bug:
118 ///
119 /// ```
120 /// assert_eq!(Error::from_errno(0), EINVAL);
121 /// assert_eq!(Error::from_errno(-1000000), EINVAL);
122 /// ```
123 pub fn from_errno(errno: crate::ffi::c_int) -> Error {
124 if let Some(error) = Self::try_from_errno(errno) {
125 error
126 } else {
127 // TODO: Make it a `WARN_ONCE` once available.
128 crate::pr_warn!(
129 "attempted to create `Error` with out of range `errno`: {}\n",
130 errno
131 );
132 code::EINVAL
133 }
134 }
135
136 /// Creates an [`Error`] from a kernel error code.
137 ///
138 /// Returns [`None`] if `errno` is out-of-range.
139 const fn try_from_errno(errno: crate::ffi::c_int) -> Option<Error> {
140 if errno < -(bindings::MAX_ERRNO as i32) || errno >= 0 {
141 return None;
142 }
143
144 // SAFETY: `errno` is checked above to be in a valid range.
145 Some(unsafe { Error::from_errno_unchecked(errno) })
146 }
147
148 /// Creates an [`Error`] from a kernel error code.
149 ///
150 /// # Safety
151 ///
152 /// `errno` must be within error code range (i.e. `>= -MAX_ERRNO && < 0`).
153 const unsafe fn from_errno_unchecked(errno: crate::ffi::c_int) -> Error {
154 // INVARIANT: The contract ensures the type invariant
155 // will hold.
156 // SAFETY: The caller guarantees `errno` is non-zero.
157 Error(unsafe { NonZeroI32::new_unchecked(errno) })
158 }
159
160 /// Returns the kernel error code.
161 pub fn to_errno(self) -> crate::ffi::c_int {
162 self.0.get()
163 }
164
165 #[cfg(CONFIG_BLOCK)]
166 pub(crate) fn to_blk_status(self) -> bindings::blk_status_t {
167 // SAFETY: `self.0` is a valid error due to its invariant.
168 unsafe { bindings::errno_to_blk_status(self.0.get()) }
169 }
170
171 /// Returns the error encoded as a pointer.
172 pub fn to_ptr<T>(self) -> *mut T {
173 // SAFETY: `self.0` is a valid error due to its invariant.
174 unsafe { bindings::ERR_PTR(self.0.get() as crate::ffi::c_long).cast() }
175 }
176
177 /// Returns a string representing the error, if one exists.
178 #[cfg(not(testlib))]
179 pub fn name(&self) -> Option<&'static CStr> {
180 // SAFETY: Just an FFI call, there are no extra safety requirements.
181 let ptr = unsafe { bindings::errname(-self.0.get()) };
182 if ptr.is_null() {
183 None
184 } else {
185 use crate::str::CStrExt as _;
186
187 // SAFETY: The string returned by `errname` is static and `NUL`-terminated.
188 Some(unsafe { CStr::from_char_ptr(ptr) })
189 }
190 }
191
192 /// Returns a string representing the error, if one exists.
193 ///
194 /// When `testlib` is configured, this always returns `None` to avoid the dependency on a
195 /// kernel function so that tests that use this (e.g., by calling [`Result::unwrap`]) can still
196 /// run in userspace.
197 #[cfg(testlib)]
198 pub fn name(&self) -> Option<&'static CStr> {
199 None
200 }
201}
202
203impl fmt::Debug for Error {
204 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
205 match self.name() {
206 // Print out number if no name can be found.
207 None => f.debug_tuple("Error").field(&-self.0).finish(),
208 Some(name) => f
209 .debug_tuple(
210 // SAFETY: These strings are ASCII-only.
211 unsafe { core::str::from_utf8_unchecked(name.to_bytes()) },
212 )
213 .finish(),
214 }
215 }
216}
217
218impl From<AllocError> for Error {
219 fn from(_: AllocError) -> Error {
220 code::ENOMEM
221 }
222}
223
224impl From<TryFromIntError> for Error {
225 fn from(_: TryFromIntError) -> Error {
226 code::EINVAL
227 }
228}
229
230impl From<Utf8Error> for Error {
231 fn from(_: Utf8Error) -> Error {
232 code::EINVAL
233 }
234}
235
236impl From<LayoutError> for Error {
237 fn from(_: LayoutError) -> Error {
238 code::ENOMEM
239 }
240}
241
242impl From<fmt::Error> for Error {
243 fn from(_: fmt::Error) -> Error {
244 code::EINVAL
245 }
246}
247
248impl From<core::convert::Infallible> for Error {
249 fn from(e: core::convert::Infallible) -> Error {
250 match e {}
251 }
252}
253
254/// A [`Result`] with an [`Error`] error type.
255///
256/// To be used as the return type for functions that may fail.
257///
258/// # Error codes in C and Rust
259///
260/// In C, it is common that functions indicate success or failure through
261/// their return value; modifying or returning extra data through non-`const`
262/// pointer parameters. In particular, in the kernel, functions that may fail
263/// typically return an `int` that represents a generic error code. We model
264/// those as [`Error`].
265///
266/// In Rust, it is idiomatic to model functions that may fail as returning
267/// a [`Result`]. Since in the kernel many functions return an error code,
268/// [`Result`] is a type alias for a [`core::result::Result`] that uses
269/// [`Error`] as its error type.
270///
271/// Note that even if a function does not return anything when it succeeds,
272/// it should still be modeled as returning a [`Result`] rather than
273/// just an [`Error`].
274///
275/// Calling a function that returns [`Result`] forces the caller to handle
276/// the returned [`Result`].
277///
278/// This can be done "manually" by using [`match`]. Using [`match`] to decode
279/// the [`Result`] is similar to C where all the return value decoding and the
280/// error handling is done explicitly by writing handling code for each
281/// error to cover. Using [`match`] the error and success handling can be
282/// implemented in all detail as required. For example (inspired by
283/// [`samples/rust/rust_minimal.rs`]):
284///
285/// ```
286/// # #[allow(clippy::single_match)]
287/// fn example() -> Result {
288/// let mut numbers = KVec::new();
289///
290/// match numbers.push(72, GFP_KERNEL) {
291/// Err(e) => {
292/// pr_err!("Error pushing 72: {e:?}");
293/// return Err(e.into());
294/// }
295/// // Do nothing, continue.
296/// Ok(()) => (),
297/// }
298///
299/// match numbers.push(108, GFP_KERNEL) {
300/// Err(e) => {
301/// pr_err!("Error pushing 108: {e:?}");
302/// return Err(e.into());
303/// }
304/// // Do nothing, continue.
305/// Ok(()) => (),
306/// }
307///
308/// match numbers.push(200, GFP_KERNEL) {
309/// Err(e) => {
310/// pr_err!("Error pushing 200: {e:?}");
311/// return Err(e.into());
312/// }
313/// // Do nothing, continue.
314/// Ok(()) => (),
315/// }
316///
317/// Ok(())
318/// }
319/// # example()?;
320/// # Ok::<(), Error>(())
321/// ```
322///
323/// An alternative to be more concise is the [`if let`] syntax:
324///
325/// ```
326/// fn example() -> Result {
327/// let mut numbers = KVec::new();
328///
329/// if let Err(e) = numbers.push(72, GFP_KERNEL) {
330/// pr_err!("Error pushing 72: {e:?}");
331/// return Err(e.into());
332/// }
333///
334/// if let Err(e) = numbers.push(108, GFP_KERNEL) {
335/// pr_err!("Error pushing 108: {e:?}");
336/// return Err(e.into());
337/// }
338///
339/// if let Err(e) = numbers.push(200, GFP_KERNEL) {
340/// pr_err!("Error pushing 200: {e:?}");
341/// return Err(e.into());
342/// }
343///
344/// Ok(())
345/// }
346/// # example()?;
347/// # Ok::<(), Error>(())
348/// ```
349///
350/// Instead of these verbose [`match`]/[`if let`], the [`?`] operator can
351/// be used to handle the [`Result`]. Using the [`?`] operator is often
352/// the best choice to handle [`Result`] in a non-verbose way as done in
353/// [`samples/rust/rust_minimal.rs`]:
354///
355/// ```
356/// fn example() -> Result {
357/// let mut numbers = KVec::new();
358///
359/// numbers.push(72, GFP_KERNEL)?;
360/// numbers.push(108, GFP_KERNEL)?;
361/// numbers.push(200, GFP_KERNEL)?;
362///
363/// Ok(())
364/// }
365/// # example()?;
366/// # Ok::<(), Error>(())
367/// ```
368///
369/// Another possibility is to call [`unwrap()`](Result::unwrap) or
370/// [`expect()`](Result::expect). However, use of these functions is
371/// *heavily discouraged* in the kernel because they trigger a Rust
372/// [`panic!`] if an error happens, which may destabilize the system or
373/// entirely break it as a result -- just like the C [`BUG()`] macro.
374/// Please see the documentation for the C macro [`BUG()`] for guidance
375/// on when to use these functions.
376///
377/// Alternatively, depending on the use case, using [`unwrap_or()`],
378/// [`unwrap_or_else()`], [`unwrap_or_default()`] or [`unwrap_unchecked()`]
379/// might be an option, as well.
380///
381/// For even more details, please see the [Rust documentation].
382///
383/// [`match`]: https://doc.rust-lang.org/reference/expressions/match-expr.html
384/// [`samples/rust/rust_minimal.rs`]: srctree/samples/rust/rust_minimal.rs
385/// [`if let`]: https://doc.rust-lang.org/reference/expressions/if-expr.html#if-let-expressions
386/// [`?`]: https://doc.rust-lang.org/reference/expressions/operator-expr.html#the-question-mark-operator
387/// [`unwrap()`]: Result::unwrap
388/// [`expect()`]: Result::expect
389/// [`BUG()`]: https://docs.kernel.org/process/deprecated.html#bug-and-bug-on
390/// [`unwrap_or()`]: Result::unwrap_or
391/// [`unwrap_or_else()`]: Result::unwrap_or_else
392/// [`unwrap_or_default()`]: Result::unwrap_or_default
393/// [`unwrap_unchecked()`]: Result::unwrap_unchecked
394/// [Rust documentation]: https://doc.rust-lang.org/book/ch09-02-recoverable-errors-with-result.html
395pub type Result<T = (), E = Error> = core::result::Result<T, E>;
396
397/// Converts an integer as returned by a C kernel function to a [`Result`].
398///
399/// If the integer is negative, an [`Err`] with an [`Error`] as given by [`Error::from_errno`] is
400/// returned. This means the integer must be `>= -MAX_ERRNO`.
401///
402/// Otherwise, it returns [`Ok`].
403///
404/// It is a bug to pass an out-of-range negative integer. `Err(EINVAL)` is returned in such a case.
405///
406/// # Examples
407///
408/// This function may be used to easily perform early returns with the [`?`] operator when working
409/// with C APIs within Rust abstractions:
410///
411/// ```
412/// # use kernel::error::to_result;
413/// # mod bindings {
414/// # #![expect(clippy::missing_safety_doc)]
415/// # use kernel::prelude::*;
416/// # pub(super) unsafe fn f1() -> c_int { 0 }
417/// # pub(super) unsafe fn f2() -> c_int { EINVAL.to_errno() }
418/// # }
419/// fn f() -> Result {
420/// // SAFETY: ...
421/// to_result(unsafe { bindings::f1() })?;
422///
423/// // SAFETY: ...
424/// to_result(unsafe { bindings::f2() })?;
425///
426/// // ...
427///
428/// Ok(())
429/// }
430/// # assert_eq!(f(), Err(EINVAL));
431/// ```
432///
433/// [`?`]: https://doc.rust-lang.org/reference/expressions/operator-expr.html#the-question-mark-operator
434pub fn to_result(err: crate::ffi::c_int) -> Result {
435 if err < 0 {
436 Err(Error::from_errno(err))
437 } else {
438 Ok(())
439 }
440}
441
442/// Transform a kernel "error pointer" to a normal pointer.
443///
444/// Some kernel C API functions return an "error pointer" which optionally
445/// embeds an `errno`. Callers are supposed to check the returned pointer
446/// for errors. This function performs the check and converts the "error pointer"
447/// to a normal pointer in an idiomatic fashion.
448///
449/// # Examples
450///
451/// ```ignore
452/// # use kernel::from_err_ptr;
453/// # use kernel::bindings;
454/// fn devm_platform_ioremap_resource(
455/// pdev: &mut PlatformDevice,
456/// index: u32,
457/// ) -> Result<*mut kernel::ffi::c_void> {
458/// // SAFETY: `pdev` points to a valid platform device. There are no safety requirements
459/// // on `index`.
460/// from_err_ptr(unsafe { bindings::devm_platform_ioremap_resource(pdev.to_ptr(), index) })
461/// }
462/// ```
463pub fn from_err_ptr<T>(ptr: *mut T) -> Result<*mut T> {
464 // CAST: Casting a pointer to `*const crate::ffi::c_void` is always valid.
465 let const_ptr: *const crate::ffi::c_void = ptr.cast();
466 // SAFETY: The FFI function does not deref the pointer.
467 if unsafe { bindings::IS_ERR(const_ptr) } {
468 // SAFETY: The FFI function does not deref the pointer.
469 let err = unsafe { bindings::PTR_ERR(const_ptr) };
470
471 #[allow(clippy::unnecessary_cast)]
472 // CAST: If `IS_ERR()` returns `true`,
473 // then `PTR_ERR()` is guaranteed to return a
474 // negative value greater-or-equal to `-bindings::MAX_ERRNO`,
475 // which always fits in an `i16`, as per the invariant above.
476 // And an `i16` always fits in an `i32`. So casting `err` to
477 // an `i32` can never overflow, and is always valid.
478 //
479 // SAFETY: `IS_ERR()` ensures `err` is a
480 // negative value greater-or-equal to `-bindings::MAX_ERRNO`.
481 return Err(unsafe { Error::from_errno_unchecked(err as crate::ffi::c_int) });
482 }
483 Ok(ptr)
484}
485
486/// Calls a closure returning a [`crate::error::Result<T>`] and converts the result to
487/// a C integer result.
488///
489/// This is useful when calling Rust functions that return [`crate::error::Result<T>`]
490/// from inside `extern "C"` functions that need to return an integer error result.
491///
492/// `T` should be convertible from an `i16` via `From<i16>`.
493///
494/// # Examples
495///
496/// ```ignore
497/// # use kernel::from_result;
498/// # use kernel::bindings;
499/// unsafe extern "C" fn probe_callback(
500/// pdev: *mut bindings::platform_device,
501/// ) -> kernel::ffi::c_int {
502/// from_result(|| {
503/// let ptr = devm_alloc(pdev)?;
504/// bindings::platform_set_drvdata(pdev, ptr);
505/// Ok(0)
506/// })
507/// }
508/// ```
509pub fn from_result<T, F>(f: F) -> T
510where
511 T: From<i16>,
512 F: FnOnce() -> Result<T>,
513{
514 match f() {
515 Ok(v) => v,
516 // NO-OVERFLOW: negative `errno`s are no smaller than `-bindings::MAX_ERRNO`,
517 // `-bindings::MAX_ERRNO` fits in an `i16` as per invariant above,
518 // therefore a negative `errno` always fits in an `i16` and will not overflow.
519 Err(e) => T::from(e.to_errno() as i16),
520 }
521}
522
523/// Error message for calling a default function of a [`#[vtable]`](macros::vtable) trait.
524pub const VTABLE_DEFAULT_ERROR: &str =
525 "This function must not be called, see the #[vtable] documentation.";