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 alloc::{
  8    alloc::{AllocError, LayoutError},
  9    collections::TryReserveError,
 10};
 11
 12use core::convert::From;
 13use core::num::TryFromIntError;
 14use core::str::Utf8Error;
 15
 16/// Contains the C-compatible error codes.
 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, "Exec format error.");
 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}
 62
 63/// Generic integer kernel error.
 64///
 65/// The kernel defines a set of integer generic error codes based on C and
 66/// POSIX ones. These codes may have a more specific meaning in some contexts.
 67///
 68/// # Invariants
 69///
 70/// The value is a valid `errno` (i.e. `>= -MAX_ERRNO && < 0`).
 71#[derive(Clone, Copy, PartialEq, Eq)]
 72pub struct Error(core::ffi::c_int);
 73
 74impl Error {
 75    /// Returns the kernel error code.
 76    pub fn to_kernel_errno(self) -> core::ffi::c_int {
 77        self.0
 78    }
 79}
 80
 81impl From<AllocError> for Error {
 82    fn from(_: AllocError) -> Error {
 83        code::ENOMEM
 84    }
 85}
 86
 87impl From<TryFromIntError> for Error {
 88    fn from(_: TryFromIntError) -> Error {
 89        code::EINVAL
 90    }
 91}
 92
 93impl From<Utf8Error> for Error {
 94    fn from(_: Utf8Error) -> Error {
 95        code::EINVAL
 96    }
 97}
 98
 99impl From<TryReserveError> for Error {
100    fn from(_: TryReserveError) -> Error {
101        code::ENOMEM
102    }
103}
104
105impl From<LayoutError> for Error {
106    fn from(_: LayoutError) -> Error {
107        code::ENOMEM
108    }
109}
110
111impl From<core::fmt::Error> for Error {
112    fn from(_: core::fmt::Error) -> Error {
113        code::EINVAL
114    }
115}
116
117impl From<core::convert::Infallible> for Error {
118    fn from(e: core::convert::Infallible) -> Error {
119        match e {}
120    }
121}
122
123/// A [`Result`] with an [`Error`] error type.
124///
125/// To be used as the return type for functions that may fail.
126///
127/// # Error codes in C and Rust
128///
129/// In C, it is common that functions indicate success or failure through
130/// their return value; modifying or returning extra data through non-`const`
131/// pointer parameters. In particular, in the kernel, functions that may fail
132/// typically return an `int` that represents a generic error code. We model
133/// those as [`Error`].
134///
135/// In Rust, it is idiomatic to model functions that may fail as returning
136/// a [`Result`]. Since in the kernel many functions return an error code,
137/// [`Result`] is a type alias for a [`core::result::Result`] that uses
138/// [`Error`] as its error type.
139///
140/// Note that even if a function does not return anything when it succeeds,
141/// it should still be modeled as returning a `Result` rather than
142/// just an [`Error`].
143pub type Result<T = ()> = core::result::Result<T, Error>;