linux/rust/kernel/error.rs
Miguel Ojeda 6551a7fe0a rust: error: Add Error::from_errno{_unchecked}()
Add a function to create `Error` values out of a kernel error return,
which safely upholds the invariant that the error code is well-formed
(negative and greater than -MAX_ERRNO). If a malformed code is passed
in, it will be converted to EINVAL.

Lina: Imported from rust-for-linux/rust as authored by Miguel and Fox
with refactoring from Wedson, renamed from_kernel_errno() to
from_errno().

Co-developed-by: Fox Chen <foxhlchen@gmail.com>
Signed-off-by: Fox Chen <foxhlchen@gmail.com>
Co-developed-by: Wedson Almeida Filho <wedsonaf@gmail.com>
Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Andreas Hindborg <a.hindborg@samsung.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Signed-off-by: Asahi Lina <lina@asahilina.net>
Link: https://lore.kernel.org/r/20230224-rust-error-v3-3-03779bddc02b@asahilina.net
[ Mark the new associated functions as `#[allow(dead_code)]`. ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2023-04-12 18:41:04 +02:00

183 lines
5.7 KiB
Rust

// SPDX-License-Identifier: GPL-2.0
//! Kernel errors.
//!
//! C header: [`include/uapi/asm-generic/errno-base.h`](../../../include/uapi/asm-generic/errno-base.h)
use alloc::{
alloc::{AllocError, LayoutError},
collections::TryReserveError,
};
use core::convert::From;
use core::num::TryFromIntError;
use core::str::Utf8Error;
/// Contains the C-compatible error codes.
pub mod code {
macro_rules! declare_err {
($err:tt $(,)? $($doc:expr),+) => {
$(
#[doc = $doc]
)*
pub const $err: super::Error = super::Error(-(crate::bindings::$err as i32));
};
}
declare_err!(EPERM, "Operation not permitted.");
declare_err!(ENOENT, "No such file or directory.");
declare_err!(ESRCH, "No such process.");
declare_err!(EINTR, "Interrupted system call.");
declare_err!(EIO, "I/O error.");
declare_err!(ENXIO, "No such device or address.");
declare_err!(E2BIG, "Argument list too long.");
declare_err!(ENOEXEC, "Exec format error.");
declare_err!(EBADF, "Bad file number.");
declare_err!(ECHILD, "Exec format error.");
declare_err!(EAGAIN, "Try again.");
declare_err!(ENOMEM, "Out of memory.");
declare_err!(EACCES, "Permission denied.");
declare_err!(EFAULT, "Bad address.");
declare_err!(ENOTBLK, "Block device required.");
declare_err!(EBUSY, "Device or resource busy.");
declare_err!(EEXIST, "File exists.");
declare_err!(EXDEV, "Cross-device link.");
declare_err!(ENODEV, "No such device.");
declare_err!(ENOTDIR, "Not a directory.");
declare_err!(EISDIR, "Is a directory.");
declare_err!(EINVAL, "Invalid argument.");
declare_err!(ENFILE, "File table overflow.");
declare_err!(EMFILE, "Too many open files.");
declare_err!(ENOTTY, "Not a typewriter.");
declare_err!(ETXTBSY, "Text file busy.");
declare_err!(EFBIG, "File too large.");
declare_err!(ENOSPC, "No space left on device.");
declare_err!(ESPIPE, "Illegal seek.");
declare_err!(EROFS, "Read-only file system.");
declare_err!(EMLINK, "Too many links.");
declare_err!(EPIPE, "Broken pipe.");
declare_err!(EDOM, "Math argument out of domain of func.");
declare_err!(ERANGE, "Math result not representable.");
}
/// Generic integer kernel error.
///
/// The kernel defines a set of integer generic error codes based on C and
/// POSIX ones. These codes may have a more specific meaning in some contexts.
///
/// # Invariants
///
/// The value is a valid `errno` (i.e. `>= -MAX_ERRNO && < 0`).
#[derive(Clone, Copy, PartialEq, Eq)]
pub struct Error(core::ffi::c_int);
impl Error {
/// Creates an [`Error`] from a kernel error code.
///
/// It is a bug to pass an out-of-range `errno`. `EINVAL` would
/// be returned in such a case.
#[allow(dead_code)]
pub(crate) fn from_errno(errno: core::ffi::c_int) -> Error {
if errno < -(bindings::MAX_ERRNO as i32) || errno >= 0 {
// TODO: Make it a `WARN_ONCE` once available.
crate::pr_warn!(
"attempted to create `Error` with out of range `errno`: {}",
errno
);
return code::EINVAL;
}
// INVARIANT: The check above ensures the type invariant
// will hold.
Error(errno)
}
/// Creates an [`Error`] from a kernel error code.
///
/// # Safety
///
/// `errno` must be within error code range (i.e. `>= -MAX_ERRNO && < 0`).
#[allow(dead_code)]
unsafe fn from_errno_unchecked(errno: core::ffi::c_int) -> Error {
// INVARIANT: The contract ensures the type invariant
// will hold.
Error(errno)
}
/// Returns the kernel error code.
pub fn to_errno(self) -> core::ffi::c_int {
self.0
}
/// Returns the error encoded as a pointer.
#[allow(dead_code)]
pub(crate) fn to_ptr<T>(self) -> *mut T {
// SAFETY: self.0 is a valid error due to its invariant.
unsafe { bindings::ERR_PTR(self.0.into()) as *mut _ }
}
}
impl From<AllocError> for Error {
fn from(_: AllocError) -> Error {
code::ENOMEM
}
}
impl From<TryFromIntError> for Error {
fn from(_: TryFromIntError) -> Error {
code::EINVAL
}
}
impl From<Utf8Error> for Error {
fn from(_: Utf8Error) -> Error {
code::EINVAL
}
}
impl From<TryReserveError> for Error {
fn from(_: TryReserveError) -> Error {
code::ENOMEM
}
}
impl From<LayoutError> for Error {
fn from(_: LayoutError) -> Error {
code::ENOMEM
}
}
impl From<core::fmt::Error> for Error {
fn from(_: core::fmt::Error) -> Error {
code::EINVAL
}
}
impl From<core::convert::Infallible> for Error {
fn from(e: core::convert::Infallible) -> Error {
match e {}
}
}
/// A [`Result`] with an [`Error`] error type.
///
/// To be used as the return type for functions that may fail.
///
/// # Error codes in C and Rust
///
/// In C, it is common that functions indicate success or failure through
/// their return value; modifying or returning extra data through non-`const`
/// pointer parameters. In particular, in the kernel, functions that may fail
/// typically return an `int` that represents a generic error code. We model
/// those as [`Error`].
///
/// In Rust, it is idiomatic to model functions that may fail as returning
/// a [`Result`]. Since in the kernel many functions return an error code,
/// [`Result`] is a type alias for a [`core::result::Result`] that uses
/// [`Error`] as its error type.
///
/// Note that even if a function does not return anything when it succeeds,
/// it should still be modeled as returning a `Result` rather than
/// just an [`Error`].
pub type Result<T = ()> = core::result::Result<T, Error>;