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

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