projects/linux·blob 4563243e · refs

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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
7use crate::{alloc::AllocError, str::CStr};
8
9use alloc::alloc::LayoutError;
10
11use core::fmt;
12use core::num::TryFromIntError;
13use core::str::Utf8Error;
14
15/// Contains the C-compatible error codes.
16#[rustfmt::skip]
17pub mod code {
18 macro_rules! declare_err {
19 ($err:tt $(,)? $($doc:expr),+) => {
20 $(
21 #[doc = $doc]
22 )*
23 pub const $err: super::Error = super::Error(-(crate::bindings::$err as i32));
24 };
25 }
26
27 declare_err!(EPERM, "Operation not permitted.");
28 declare_err!(ENOENT, "No such file or directory.");
29 declare_err!(ESRCH, "No such process.");
30 declare_err!(EINTR, "Interrupted system call.");
31 declare_err!(EIO, "I/O error.");
32 declare_err!(ENXIO, "No such device or address.");
33 declare_err!(E2BIG, "Argument list too long.");
34 declare_err!(ENOEXEC, "Exec format error.");
35 declare_err!(EBADF, "Bad file number.");
36 declare_err!(ECHILD, "No child processes.");
37 declare_err!(EAGAIN, "Try again.");
38 declare_err!(ENOMEM, "Out of memory.");
39 declare_err!(EACCES, "Permission denied.");
40 declare_err!(EFAULT, "Bad address.");
41 declare_err!(ENOTBLK, "Block device required.");
42 declare_err!(EBUSY, "Device or resource busy.");
43 declare_err!(EEXIST, "File exists.");
44 declare_err!(EXDEV, "Cross-device link.");
45 declare_err!(ENODEV, "No such device.");
46 declare_err!(ENOTDIR, "Not a directory.");
47 declare_err!(EISDIR, "Is a directory.");
48 declare_err!(EINVAL, "Invalid argument.");
49 declare_err!(ENFILE, "File table overflow.");
50 declare_err!(EMFILE, "Too many open files.");
51 declare_err!(ENOTTY, "Not a typewriter.");
52 declare_err!(ETXTBSY, "Text file busy.");
53 declare_err!(EFBIG, "File too large.");
54 declare_err!(ENOSPC, "No space left on device.");
55 declare_err!(ESPIPE, "Illegal seek.");
56 declare_err!(EROFS, "Read-only file system.");
57 declare_err!(EMLINK, "Too many links.");
58 declare_err!(EPIPE, "Broken pipe.");
59 declare_err!(EDOM, "Math argument out of domain of func.");
60 declare_err!(ERANGE, "Math result not representable.");
61 declare_err!(ERESTARTSYS, "Restart the system call.");
62 declare_err!(ERESTARTNOINTR, "System call was interrupted by a signal and will be restarted.");
63 declare_err!(ERESTARTNOHAND, "Restart if no handler.");
64 declare_err!(ENOIOCTLCMD, "No ioctl command.");
65 declare_err!(ERESTART_RESTARTBLOCK, "Restart by calling sys_restart_syscall.");
66 declare_err!(EPROBE_DEFER, "Driver requests probe retry.");
67 declare_err!(EOPENSTALE, "Open found a stale dentry.");
68 declare_err!(ENOPARAM, "Parameter not supported.");
69 declare_err!(EBADHANDLE, "Illegal NFS file handle.");
70 declare_err!(ENOTSYNC, "Update synchronization mismatch.");
71 declare_err!(EBADCOOKIE, "Cookie is stale.");
72 declare_err!(ENOTSUPP, "Operation is not supported.");
73 declare_err!(ETOOSMALL, "Buffer or request is too small.");
74 declare_err!(ESERVERFAULT, "An untranslatable error occurred.");
75 declare_err!(EBADTYPE, "Type not supported by server.");
76 declare_err!(EJUKEBOX, "Request initiated, but will not complete before timeout.");
77 declare_err!(EIOCBQUEUED, "iocb queued, will get completion event.");
78 declare_err!(ERECALLCONFLICT, "Conflict with recalled state.");
79 declare_err!(ENOGRACE, "NFS file lock reclaim refused.");
80}
81
82/// Generic integer kernel error.
83///
84/// The kernel defines a set of integer generic error codes based on C and
85/// POSIX ones. These codes may have a more specific meaning in some contexts.
86///
87/// # Invariants
88///
89/// The value is a valid `errno` (i.e. `>= -MAX_ERRNO && < 0`).
90#[derive(Clone, Copy, PartialEq, Eq)]
91pub struct Error(core::ffi::c_int);
92
93impl Error {
94 /// Creates an [`Error`] from a kernel error code.
95 ///
96 /// It is a bug to pass an out-of-range `errno`. `EINVAL` would
97 /// be returned in such a case.
98 pub(crate) fn from_errno(errno: core::ffi::c_int) -> Error {
99 if errno < -(bindings::MAX_ERRNO as i32) || errno >= 0 {
100 // TODO: Make it a `WARN_ONCE` once available.
101 crate::pr_warn!(
102 "attempted to create `Error` with out of range `errno`: {}",
103 errno
104 );
105 return code::EINVAL;
106 }
107
108 // INVARIANT: The check above ensures the type invariant
109 // will hold.
110 Error(errno)
111 }
112
113 /// Creates an [`Error`] from a kernel error code.
114 ///
115 /// # Safety
116 ///
117 /// `errno` must be within error code range (i.e. `>= -MAX_ERRNO && < 0`).
118 unsafe fn from_errno_unchecked(errno: core::ffi::c_int) -> Error {
119 // INVARIANT: The contract ensures the type invariant
120 // will hold.
121 Error(errno)
122 }
123
124 /// Returns the kernel error code.
125 pub fn to_errno(self) -> core::ffi::c_int {
126 self.0
127 }
128
129 #[cfg(CONFIG_BLOCK)]
130 pub(crate) fn to_blk_status(self) -> bindings::blk_status_t {
131 // SAFETY: `self.0` is a valid error due to its invariant.
132 unsafe { bindings::errno_to_blk_status(self.0) }
133 }
134
135 /// Returns the error encoded as a pointer.
136 #[allow(dead_code)]
137 pub(crate) fn to_ptr<T>(self) -> *mut T {
138 #[cfg_attr(target_pointer_width = "32", allow(clippy::useless_conversion))]
139 // SAFETY: `self.0` is a valid error due to its invariant.
140 unsafe {
141 bindings::ERR_PTR(self.0.into()) as *mut _
142 }
143 }
144
145 /// Returns a string representing the error, if one exists.
146 #[cfg(not(testlib))]
147 pub fn name(&self) -> Option<&'static CStr> {
148 // SAFETY: Just an FFI call, there are no extra safety requirements.
149 let ptr = unsafe { bindings::errname(-self.0) };
150 if ptr.is_null() {
151 None
152 } else {
153 // SAFETY: The string returned by `errname` is static and `NUL`-terminated.
154 Some(unsafe { CStr::from_char_ptr(ptr) })
155 }
156 }
157
158 /// Returns a string representing the error, if one exists.
159 ///
160 /// When `testlib` is configured, this always returns `None` to avoid the dependency on a
161 /// kernel function so that tests that use this (e.g., by calling [`Result::unwrap`]) can still
162 /// run in userspace.
163 #[cfg(testlib)]
164 pub fn name(&self) -> Option<&'static CStr> {
165 None
166 }
167}
168
169impl fmt::Debug for Error {
170 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
171 match self.name() {
172 // Print out number if no name can be found.
173 None => f.debug_tuple("Error").field(&-self.0).finish(),
174 // SAFETY: These strings are ASCII-only.
175 Some(name) => f
176 .debug_tuple(unsafe { core::str::from_utf8_unchecked(name) })
177 .finish(),
178 }
179 }
180}
181
182impl From<AllocError> for Error {
183 fn from(_: AllocError) -> Error {
184 code::ENOMEM
185 }
186}
187
188impl From<TryFromIntError> for Error {
189 fn from(_: TryFromIntError) -> Error {
190 code::EINVAL
191 }
192}
193
194impl From<Utf8Error> for Error {
195 fn from(_: Utf8Error) -> Error {
196 code::EINVAL
197 }
198}
199
200impl From<LayoutError> for Error {
201 fn from(_: LayoutError) -> Error {
202 code::ENOMEM
203 }
204}
205
206impl From<core::fmt::Error> for Error {
207 fn from(_: core::fmt::Error) -> Error {
208 code::EINVAL
209 }
210}
211
212impl From<core::convert::Infallible> for Error {
213 fn from(e: core::convert::Infallible) -> Error {
214 match e {}
215 }
216}
217
218/// A [`Result`] with an [`Error`] error type.
219///
220/// To be used as the return type for functions that may fail.
221///
222/// # Error codes in C and Rust
223///
224/// In C, it is common that functions indicate success or failure through
225/// their return value; modifying or returning extra data through non-`const`
226/// pointer parameters. In particular, in the kernel, functions that may fail
227/// typically return an `int` that represents a generic error code. We model
228/// those as [`Error`].
229///
230/// In Rust, it is idiomatic to model functions that may fail as returning
231/// a [`Result`]. Since in the kernel many functions return an error code,
232/// [`Result`] is a type alias for a [`core::result::Result`] that uses
233/// [`Error`] as its error type.
234///
235/// Note that even if a function does not return anything when it succeeds,
236/// it should still be modeled as returning a `Result` rather than
237/// just an [`Error`].
238pub type Result<T = (), E = Error> = core::result::Result<T, E>;
239
240/// Converts an integer as returned by a C kernel function to an error if it's negative, and
241/// `Ok(())` otherwise.
242pub fn to_result(err: core::ffi::c_int) -> Result {
243 if err < 0 {
244 Err(Error::from_errno(err))
245 } else {
246 Ok(())
247 }
248}
249
250/// Transform a kernel "error pointer" to a normal pointer.
251///
252/// Some kernel C API functions return an "error pointer" which optionally
253/// embeds an `errno`. Callers are supposed to check the returned pointer
254/// for errors. This function performs the check and converts the "error pointer"
255/// to a normal pointer in an idiomatic fashion.
256///
257/// # Examples
258///
259/// ```ignore
260/// # use kernel::from_err_ptr;
261/// # use kernel::bindings;
262/// fn devm_platform_ioremap_resource(
263/// pdev: &mut PlatformDevice,
264/// index: u32,
265/// ) -> Result<*mut core::ffi::c_void> {
266/// // SAFETY: `pdev` points to a valid platform device. There are no safety requirements
267/// // on `index`.
268/// from_err_ptr(unsafe { bindings::devm_platform_ioremap_resource(pdev.to_ptr(), index) })
269/// }
270/// ```
271// TODO: Remove `dead_code` marker once an in-kernel client is available.
272#[allow(dead_code)]
273pub(crate) fn from_err_ptr<T>(ptr: *mut T) -> Result<*mut T> {
274 // CAST: Casting a pointer to `*const core::ffi::c_void` is always valid.
275 let const_ptr: *const core::ffi::c_void = ptr.cast();
276 // SAFETY: The FFI function does not deref the pointer.
277 if unsafe { bindings::IS_ERR(const_ptr) } {
278 // SAFETY: The FFI function does not deref the pointer.
279 let err = unsafe { bindings::PTR_ERR(const_ptr) };
280 // CAST: If `IS_ERR()` returns `true`,
281 // then `PTR_ERR()` is guaranteed to return a
282 // negative value greater-or-equal to `-bindings::MAX_ERRNO`,
283 // which always fits in an `i16`, as per the invariant above.
284 // And an `i16` always fits in an `i32`. So casting `err` to
285 // an `i32` can never overflow, and is always valid.
286 //
287 // SAFETY: `IS_ERR()` ensures `err` is a
288 // negative value greater-or-equal to `-bindings::MAX_ERRNO`.
289 #[allow(clippy::unnecessary_cast)]
290 return Err(unsafe { Error::from_errno_unchecked(err as core::ffi::c_int) });
291 }
292 Ok(ptr)
293}
294
295/// Calls a closure returning a [`crate::error::Result<T>`] and converts the result to
296/// a C integer result.
297///
298/// This is useful when calling Rust functions that return [`crate::error::Result<T>`]
299/// from inside `extern "C"` functions that need to return an integer error result.
300///
301/// `T` should be convertible from an `i16` via `From<i16>`.
302///
303/// # Examples
304///
305/// ```ignore
306/// # use kernel::from_result;
307/// # use kernel::bindings;
308/// unsafe extern "C" fn probe_callback(
309/// pdev: *mut bindings::platform_device,
310/// ) -> core::ffi::c_int {
311/// from_result(|| {
312/// let ptr = devm_alloc(pdev)?;
313/// bindings::platform_set_drvdata(pdev, ptr);
314/// Ok(0)
315/// })
316/// }
317/// ```
318// TODO: Remove `dead_code` marker once an in-kernel client is available.
319#[allow(dead_code)]
320pub(crate) fn from_result<T, F>(f: F) -> T
321where
322 T: From<i16>,
323 F: FnOnce() -> Result<T>,
324{
325 match f() {
326 Ok(v) => v,
327 // NO-OVERFLOW: negative `errno`s are no smaller than `-bindings::MAX_ERRNO`,
328 // `-bindings::MAX_ERRNO` fits in an `i16` as per invariant above,
329 // therefore a negative `errno` always fits in an `i16` and will not overflow.
330 Err(e) => T::from(e.to_errno() as i16),
331 }
332}
333
334/// Error message for calling a default function of a [`#[vtable]`](macros::vtable) trait.
335pub const VTABLE_DEFAULT_ERROR: &str =
336 "This function must not be called, see the #[vtable] documentation.";