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 7 use alloc::collections::TryReserveError; 8 9 /// Contains the C-compatible error codes. 10 pub mod code { 11 macro_rules! declare_err { 12 ($err:tt $(,)? $($doc:expr),+) => { 13 $( 14 #[doc = $doc] 15 )* 16 pub const $err: super::Error = super::Error(-(crate::bindings::$err as i32)); 17 }; 18 } 19 20 declare_err!(ENOMEM, "Out of memory."); 21 } 22 23 /// Generic integer kernel error. 24 /// 25 /// The kernel defines a set of integer generic error codes based on C and 26 /// POSIX ones. These codes may have a more specific meaning in some contexts. 27 /// 28 /// # Invariants 29 /// 30 /// The value is a valid `errno` (i.e. `>= -MAX_ERRNO && < 0`). 31 #[derive(Clone, Copy, PartialEq, Eq)] 32 pub struct Error(core::ffi::c_int); 33 34 impl Error { 35 /// Returns the kernel error code. 36 pub fn to_kernel_errno(self) -> core::ffi::c_int { 37 self.0 38 } 39 } 40 41 impl From<TryReserveError> for Error { 42 fn from(_: TryReserveError) -> Error { 43 code::ENOMEM 44 } 45 } 46 47 /// A [`Result`] with an [`Error`] error type. 48 /// 49 /// To be used as the return type for functions that may fail. 50 /// 51 /// # Error codes in C and Rust 52 /// 53 /// In C, it is common that functions indicate success or failure through 54 /// their return value; modifying or returning extra data through non-`const` 55 /// pointer parameters. In particular, in the kernel, functions that may fail 56 /// typically return an `int` that represents a generic error code. We model 57 /// those as [`Error`]. 58 /// 59 /// In Rust, it is idiomatic to model functions that may fail as returning 60 /// a [`Result`]. Since in the kernel many functions return an error code, 61 /// [`Result`] is a type alias for a [`core::result::Result`] that uses 62 /// [`Error`] as its error type. 63 /// 64 /// Note that even if a function does not return anything when it succeeds, 65 /// it should still be modeled as returning a `Result` rather than 66 /// just an [`Error`]. 67 pub type Result<T = ()> = core::result::Result<T, Error>; 68