projects/linux·blob f24767ca · 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`](../../../include/uapi/asm-generic/errno-base.h)
6
7use crate::str::CStr;
8
9use alloc::{
10 alloc::{AllocError, LayoutError},
11 collections::TryReserveError,
12};
13
14use core::convert::From;
15use core::fmt;
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 $err: super::Error = super::Error(-(crate::bindings::$err as i32));
28 };
29 }
30
31 declare_err!(EPERM, "Operation not permitted.");
32 declare_err!(ENOENT, "No such file or directory.");
33 declare_err!(ESRCH, "No such process.");
34 declare_err!(EINTR, "Interrupted system call.");
35 declare_err!(EIO, "I/O error.");
36 declare_err!(ENXIO, "No such device or address.");
37 declare_err!(E2BIG, "Argument list too long.");
38 declare_err!(ENOEXEC, "Exec format error.");
39 declare_err!(EBADF, "Bad file number.");
40 declare_err!(ECHILD, "Exec format error.");
41 declare_err!(EAGAIN, "Try again.");
42 declare_err!(ENOMEM, "Out of memory.");
43 declare_err!(EACCES, "Permission denied.");
44 declare_err!(EFAULT, "Bad address.");
45 declare_err!(ENOTBLK, "Block device required.");
46 declare_err!(EBUSY, "Device or resource busy.");
47 declare_err!(EEXIST, "File exists.");
48 declare_err!(EXDEV, "Cross-device link.");
49 declare_err!(ENODEV, "No such device.");
50 declare_err!(ENOTDIR, "Not a directory.");
51 declare_err!(EISDIR, "Is a directory.");
52 declare_err!(EINVAL, "Invalid argument.");
53 declare_err!(ENFILE, "File table overflow.");
54 declare_err!(EMFILE, "Too many open files.");
55 declare_err!(ENOTTY, "Not a typewriter.");
56 declare_err!(ETXTBSY, "Text file busy.");
57 declare_err!(EFBIG, "File too large.");
58 declare_err!(ENOSPC, "No space left on device.");
59 declare_err!(ESPIPE, "Illegal seek.");
60 declare_err!(EROFS, "Read-only file system.");
61 declare_err!(EMLINK, "Too many links.");
62 declare_err!(EPIPE, "Broken pipe.");
63 declare_err!(EDOM, "Math argument out of domain of func.");
64 declare_err!(ERANGE, "Math result not representable.");
65 declare_err!(ERESTARTSYS, "Restart the system call.");
66 declare_err!(ERESTARTNOINTR, "System call was interrupted by a signal and will be restarted.");
67 declare_err!(ERESTARTNOHAND, "Restart if no handler.");
68 declare_err!(ENOIOCTLCMD, "No ioctl command.");
69 declare_err!(ERESTART_RESTARTBLOCK, "Restart by calling sys_restart_syscall.");
70 declare_err!(EPROBE_DEFER, "Driver requests probe retry.");
71 declare_err!(EOPENSTALE, "Open found a stale dentry.");
72 declare_err!(ENOPARAM, "Parameter not supported.");
73 declare_err!(EBADHANDLE, "Illegal NFS file handle.");
74 declare_err!(ENOTSYNC, "Update synchronization mismatch.");
75 declare_err!(EBADCOOKIE, "Cookie is stale.");
76 declare_err!(ENOTSUPP, "Operation is not supported.");
77 declare_err!(ETOOSMALL, "Buffer or request is too small.");
78 declare_err!(ESERVERFAULT, "An untranslatable error occurred.");
79 declare_err!(EBADTYPE, "Type not supported by server.");
80 declare_err!(EJUKEBOX, "Request initiated, but will not complete before timeout.");
81 declare_err!(EIOCBQUEUED, "iocb queued, will get completion event.");
82 declare_err!(ERECALLCONFLICT, "Conflict with recalled state.");
83 declare_err!(ENOGRACE, "NFS file lock reclaim refused.");
84}
85
86/// Generic integer kernel error.
87///
88/// The kernel defines a set of integer generic error codes based on C and
89/// POSIX ones. These codes may have a more specific meaning in some contexts.
90///
91/// # Invariants
92///
93/// The value is a valid `errno` (i.e. `>= -MAX_ERRNO && < 0`).
94#[derive(Clone, Copy, PartialEq, Eq)]
95pub struct Error(core::ffi::c_int);
96
97impl Error {
98 /// Creates an [`Error`] from a kernel error code.
99 ///
100 /// It is a bug to pass an out-of-range `errno`. `EINVAL` would
101 /// be returned in such a case.
102 pub(crate) fn from_errno(errno: core::ffi::c_int) -> Error {
103 if errno < -(bindings::MAX_ERRNO as i32) || errno >= 0 {
104 // TODO: Make it a `WARN_ONCE` once available.
105 crate::pr_warn!(
106 "attempted to create `Error` with out of range `errno`: {}",
107 errno
108 );
109 return code::EINVAL;
110 }
111
112 // INVARIANT: The check above ensures the type invariant
113 // will hold.
114 Error(errno)
115 }
116
117 /// Creates an [`Error`] from a kernel error code.
118 ///
119 /// # Safety
120 ///
121 /// `errno` must be within error code range (i.e. `>= -MAX_ERRNO && < 0`).
122 unsafe fn from_errno_unchecked(errno: core::ffi::c_int) -> Error {
123 // INVARIANT: The contract ensures the type invariant
124 // will hold.
125 Error(errno)
126 }
127
128 /// Returns the kernel error code.
129 pub fn to_errno(self) -> core::ffi::c_int {
130 self.0
131 }
132
133 /// Returns the error encoded as a pointer.
134 #[allow(dead_code)]
135 pub(crate) fn to_ptr<T>(self) -> *mut T {
136 // SAFETY: self.0 is a valid error due to its invariant.
137 unsafe { bindings::ERR_PTR(self.0.into()) as *mut _ }
138 }
139
140 /// Returns a string representing the error, if one exists.
141 #[cfg(not(testlib))]
142 pub fn name(&self) -> Option<&'static CStr> {
143 // SAFETY: Just an FFI call, there are no extra safety requirements.
144 let ptr = unsafe { bindings::errname(-self.0) };
145 if ptr.is_null() {
146 None
147 } else {
148 // SAFETY: The string returned by `errname` is static and `NUL`-terminated.
149 Some(unsafe { CStr::from_char_ptr(ptr) })
150 }
151 }
152
153 /// Returns a string representing the error, if one exists.
154 ///
155 /// When `testlib` is configured, this always returns `None` to avoid the dependency on a
156 /// kernel function so that tests that use this (e.g., by calling [`Result::unwrap`]) can still
157 /// run in userspace.
158 #[cfg(testlib)]
159 pub fn name(&self) -> Option<&'static CStr> {
160 None
161 }
162}
163
164impl fmt::Debug for Error {
165 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
166 match self.name() {
167 // Print out number if no name can be found.
168 None => f.debug_tuple("Error").field(&-self.0).finish(),
169 // SAFETY: These strings are ASCII-only.
170 Some(name) => f
171 .debug_tuple(unsafe { core::str::from_utf8_unchecked(name) })
172 .finish(),
173 }
174 }
175}
176
177impl From<AllocError> for Error {
178 fn from(_: AllocError) -> Error {
179 code::ENOMEM
180 }
181}
182
183impl From<TryFromIntError> for Error {
184 fn from(_: TryFromIntError) -> Error {
185 code::EINVAL
186 }
187}
188
189impl From<Utf8Error> for Error {
190 fn from(_: Utf8Error) -> Error {
191 code::EINVAL
192 }
193}
194
195impl From<TryReserveError> for Error {
196 fn from(_: TryReserveError) -> Error {
197 code::ENOMEM
198 }
199}
200
201impl From<LayoutError> for Error {
202 fn from(_: LayoutError) -> Error {
203 code::ENOMEM
204 }
205}
206
207impl From<core::fmt::Error> for Error {
208 fn from(_: core::fmt::Error) -> Error {
209 code::EINVAL
210 }
211}
212
213impl From<core::convert::Infallible> for Error {
214 fn from(e: core::convert::Infallible) -> Error {
215 match e {}
216 }
217}
218
219/// A [`Result`] with an [`Error`] error type.
220///
221/// To be used as the return type for functions that may fail.
222///
223/// # Error codes in C and Rust
224///
225/// In C, it is common that functions indicate success or failure through
226/// their return value; modifying or returning extra data through non-`const`
227/// pointer parameters. In particular, in the kernel, functions that may fail
228/// typically return an `int` that represents a generic error code. We model
229/// those as [`Error`].
230///
231/// In Rust, it is idiomatic to model functions that may fail as returning
232/// a [`Result`]. Since in the kernel many functions return an error code,
233/// [`Result`] is a type alias for a [`core::result::Result`] that uses
234/// [`Error`] as its error type.
235///
236/// Note that even if a function does not return anything when it succeeds,
237/// it should still be modeled as returning a `Result` rather than
238/// just an [`Error`].
239pub type Result<T = (), E = Error> = core::result::Result<T, E>;
240
241/// Converts an integer as returned by a C kernel function to an error if it's negative, and
242/// `Ok(())` otherwise.
243pub fn to_result(err: core::ffi::c_int) -> Result {
244 if err < 0 {
245 Err(Error::from_errno(err))
246 } else {
247 Ok(())
248 }
249}
250
251/// Transform a kernel "error pointer" to a normal pointer.
252///
253/// Some kernel C API functions return an "error pointer" which optionally
254/// embeds an `errno`. Callers are supposed to check the returned pointer
255/// for errors. This function performs the check and converts the "error pointer"
256/// to a normal pointer in an idiomatic fashion.
257///
258/// # Examples
259///
260/// ```ignore
261/// # use kernel::from_err_ptr;
262/// # use kernel::bindings;
263/// fn devm_platform_ioremap_resource(
264/// pdev: &mut PlatformDevice,
265/// index: u32,
266/// ) -> Result<*mut core::ffi::c_void> {
267/// // SAFETY: FFI call.
268/// unsafe {
269/// from_err_ptr(bindings::devm_platform_ioremap_resource(
270/// pdev.to_ptr(),
271/// index,
272/// ))
273/// }
274/// }
275/// ```
276// TODO: Remove `dead_code` marker once an in-kernel client is available.
277#[allow(dead_code)]
278pub(crate) fn from_err_ptr<T>(ptr: *mut T) -> Result<*mut T> {
279 // CAST: Casting a pointer to `*const core::ffi::c_void` is always valid.
280 let const_ptr: *const core::ffi::c_void = ptr.cast();
281 // SAFETY: The FFI function does not deref the pointer.
282 if unsafe { bindings::IS_ERR(const_ptr) } {
283 // SAFETY: The FFI function does not deref the pointer.
284 let err = unsafe { bindings::PTR_ERR(const_ptr) };
285 // CAST: If `IS_ERR()` returns `true`,
286 // then `PTR_ERR()` is guaranteed to return a
287 // negative value greater-or-equal to `-bindings::MAX_ERRNO`,
288 // which always fits in an `i16`, as per the invariant above.
289 // And an `i16` always fits in an `i32`. So casting `err` to
290 // an `i32` can never overflow, and is always valid.
291 //
292 // SAFETY: `IS_ERR()` ensures `err` is a
293 // negative value greater-or-equal to `-bindings::MAX_ERRNO`.
294 #[allow(clippy::unnecessary_cast)]
295 return Err(unsafe { Error::from_errno_unchecked(err as core::ffi::c_int) });
296 }
297 Ok(ptr)
298}
299
300/// Calls a closure returning a [`crate::error::Result<T>`] and converts the result to
301/// a C integer result.
302///
303/// This is useful when calling Rust functions that return [`crate::error::Result<T>`]
304/// from inside `extern "C"` functions that need to return an integer error result.
305///
306/// `T` should be convertible from an `i16` via `From<i16>`.
307///
308/// # Examples
309///
310/// ```ignore
311/// # use kernel::from_result;
312/// # use kernel::bindings;
313/// unsafe extern "C" fn probe_callback(
314/// pdev: *mut bindings::platform_device,
315/// ) -> core::ffi::c_int {
316/// from_result(|| {
317/// let ptr = devm_alloc(pdev)?;
318/// bindings::platform_set_drvdata(pdev, ptr);
319/// Ok(0)
320/// })
321/// }
322/// ```
323// TODO: Remove `dead_code` marker once an in-kernel client is available.
324#[allow(dead_code)]
325pub(crate) fn from_result<T, F>(f: F) -> T
326where
327 T: From<i16>,
328 F: FnOnce() -> Result<T>,
329{
330 match f() {
331 Ok(v) => v,
332 // NO-OVERFLOW: negative `errno`s are no smaller than `-bindings::MAX_ERRNO`,
333 // `-bindings::MAX_ERRNO` fits in an `i16` as per invariant above,
334 // therefore a negative `errno` always fits in an `i16` and will not overflow.
335 Err(e) => T::from(e.to_errno() as i16),
336 }
337}