// SPDX-License-Identifier: GPL-2.0 //! Kernel errors.//!//! C header: [`include/uapi/asm-generic/errno-base.h`](srctree/include/uapi/asm-generic/errno-base.h) use crate::{    alloc::{layout::LayoutError, AllocError},    fmt,    str::CStr,}; use core::num::NonZeroI32;use core::num::TryFromIntError;use core::str::Utf8Error; /// Contains the C-compatible error codes.#[rustfmt::skip]pub mod code {    macro_rules! declare_err {        ($err:tt $(,)? $($doc:expr),+) => {            $(            #[doc = $doc]            )*            pub const $err: super::Error =                match super::Error::try_from_errno(-(crate::bindings::$err as i32)) {                    Some(err) => err,                    None => panic!("Invalid errno in `declare_err!`"),                };        };    }     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, "No child processes.");    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.");    declare_err!(EOVERFLOW, "Value too large for defined data type.");    declare_err!(ETIMEDOUT, "Connection timed out.");    declare_err!(ERESTARTSYS, "Restart the system call.");    declare_err!(ERESTARTNOINTR, "System call was interrupted by a signal and will be restarted.");    declare_err!(ERESTARTNOHAND, "Restart if no handler.");    declare_err!(ENOIOCTLCMD, "No ioctl command.");    declare_err!(ERESTART_RESTARTBLOCK, "Restart by calling sys_restart_syscall.");    declare_err!(EPROBE_DEFER, "Driver requests probe retry.");    declare_err!(EOPENSTALE, "Open found a stale dentry.");    declare_err!(ENOPARAM, "Parameter not supported.");    declare_err!(EBADHANDLE, "Illegal NFS file handle.");    declare_err!(ENOTSYNC, "Update synchronization mismatch.");    declare_err!(EBADCOOKIE, "Cookie is stale.");    declare_err!(ENOTSUPP, "Operation is not supported.");    declare_err!(ETOOSMALL, "Buffer or request is too small.");    declare_err!(ESERVERFAULT, "An untranslatable error occurred.");    declare_err!(EBADTYPE, "Type not supported by server.");    declare_err!(EJUKEBOX, "Request initiated, but will not complete before timeout.");    declare_err!(EIOCBQUEUED, "iocb queued, will get completion event.");    declare_err!(ERECALLCONFLICT, "Conflict with recalled state.");    declare_err!(ENOGRACE, "NFS file lock reclaim refused.");} /// 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(NonZeroI32); 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.    pub fn from_errno(errno: crate::ffi::c_int) -> Error {        if let Some(error) = Self::try_from_errno(errno) {            error        } else {            // TODO: Make it a `WARN_ONCE` once available.            crate::pr_warn!(                "attempted to create `Error` with out of range `errno`: {}\n",                errno            );            code::EINVAL        }    }     /// Creates an [`Error`] from a kernel error code.    ///    /// Returns [`None`] if `errno` is out-of-range.    const fn try_from_errno(errno: crate::ffi::c_int) -> Option<Error> {        if errno < -(bindings::MAX_ERRNO as i32) || errno >= 0 {            return None;        }         // SAFETY: `errno` is checked above to be in a valid range.        Some(unsafe { Error::from_errno_unchecked(errno) })    }     /// Creates an [`Error`] from a kernel error code.    ///    /// # Safety    ///    /// `errno` must be within error code range (i.e. `>= -MAX_ERRNO && < 0`).    const unsafe fn from_errno_unchecked(errno: crate::ffi::c_int) -> Error {        // INVARIANT: The contract ensures the type invariant        // will hold.        // SAFETY: The caller guarantees `errno` is non-zero.        Error(unsafe { NonZeroI32::new_unchecked(errno) })    }     /// Returns the kernel error code.    pub fn to_errno(self) -> crate::ffi::c_int {        self.0.get()    }     #[cfg(CONFIG_BLOCK)]    pub(crate) fn to_blk_status(self) -> bindings::blk_status_t {        // SAFETY: `self.0` is a valid error due to its invariant.        unsafe { bindings::errno_to_blk_status(self.0.get()) }    }     /// Returns the error encoded as a pointer.    pub fn to_ptr<T>(self) -> *mut T {        // SAFETY: `self.0` is a valid error due to its invariant.        unsafe { bindings::ERR_PTR(self.0.get() as crate::ffi::c_long).cast() }    }     /// Returns a string representing the error, if one exists.    #[cfg(not(any(test, testlib)))]    pub fn name(&self) -> Option<&'static CStr> {        // SAFETY: Just an FFI call, there are no extra safety requirements.        let ptr = unsafe { bindings::errname(-self.0.get()) };        if ptr.is_null() {            None        } else {            // SAFETY: The string returned by `errname` is static and `NUL`-terminated.            Some(unsafe { CStr::from_char_ptr(ptr) })        }    }     /// Returns a string representing the error, if one exists.    ///    /// When `testlib` is configured, this always returns `None` to avoid the dependency on a    /// kernel function so that tests that use this (e.g., by calling [`Result::unwrap`]) can still    /// run in userspace.    #[cfg(any(test, testlib))]    pub fn name(&self) -> Option<&'static CStr> {        None    }} impl fmt::Debug for Error {    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {        match self.name() {            // Print out number if no name can be found.            None => f.debug_tuple("Error").field(&-self.0).finish(),            Some(name) => f                .debug_tuple(                    // SAFETY: These strings are ASCII-only.                    unsafe { core::str::from_utf8_unchecked(name.to_bytes()) },                )                .finish(),        }    }} 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<LayoutError> for Error {    fn from(_: LayoutError) -> Error {        code::ENOMEM    }} impl From<fmt::Error> for Error {    fn from(_: 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`].////// Calling a function that returns [`Result`] forces the caller to handle/// the returned [`Result`].////// This can be done "manually" by using [`match`]. Using [`match`] to decode/// the [`Result`] is similar to C where all the return value decoding and the/// error handling is done explicitly by writing handling code for each/// error to cover. Using [`match`] the error and success handling can be/// implemented in all detail as required. For example (inspired by/// [`samples/rust/rust_minimal.rs`]):////// ```/// # #[allow(clippy::single_match)]/// fn example() -> Result {///     let mut numbers = KVec::new();//////     match numbers.push(72, GFP_KERNEL) {///         Err(e) => {///             pr_err!("Error pushing 72: {e:?}");///             return Err(e.into());///         }///         // Do nothing, continue.///         Ok(()) => (),///     }//////     match numbers.push(108, GFP_KERNEL) {///         Err(e) => {///             pr_err!("Error pushing 108: {e:?}");///             return Err(e.into());///         }///         // Do nothing, continue.///         Ok(()) => (),///     }//////     match numbers.push(200, GFP_KERNEL) {///         Err(e) => {///             pr_err!("Error pushing 200: {e:?}");///             return Err(e.into());///         }///         // Do nothing, continue.///         Ok(()) => (),///     }//////     Ok(())/// }/// # example()?;/// # Ok::<(), Error>(())/// ```////// An alternative to be more concise is the [`if let`] syntax:////// ```/// fn example() -> Result {///     let mut numbers = KVec::new();//////     if let Err(e) = numbers.push(72, GFP_KERNEL) {///         pr_err!("Error pushing 72: {e:?}");///         return Err(e.into());///     }//////     if let Err(e) = numbers.push(108, GFP_KERNEL) {///         pr_err!("Error pushing 108: {e:?}");///         return Err(e.into());///     }//////     if let Err(e) = numbers.push(200, GFP_KERNEL) {///         pr_err!("Error pushing 200: {e:?}");///         return Err(e.into());///     }//////     Ok(())/// }/// # example()?;/// # Ok::<(), Error>(())/// ```////// Instead of these verbose [`match`]/[`if let`], the [`?`] operator can/// be used to handle the [`Result`]. Using the [`?`] operator is often/// the best choice to handle [`Result`] in a non-verbose way as done in/// [`samples/rust/rust_minimal.rs`]:////// ```/// fn example() -> Result {///     let mut numbers = KVec::new();//////     numbers.push(72, GFP_KERNEL)?;///     numbers.push(108, GFP_KERNEL)?;///     numbers.push(200, GFP_KERNEL)?;//////     Ok(())/// }/// # example()?;/// # Ok::<(), Error>(())/// ```////// Another possibility is to call [`unwrap()`](Result::unwrap) or/// [`expect()`](Result::expect). However, use of these functions is/// *heavily discouraged* in the kernel because they trigger a Rust/// [`panic!`] if an error happens, which may destabilize the system or/// entirely break it as a result -- just like the C [`BUG()`] macro./// Please see the documentation for the C macro [`BUG()`] for guidance/// on when to use these functions.////// Alternatively, depending on the use case, using [`unwrap_or()`],/// [`unwrap_or_else()`], [`unwrap_or_default()`] or [`unwrap_unchecked()`]/// might be an option, as well.////// For even more details, please see the [Rust documentation].////// [`match`]: https://doc.rust-lang.org/reference/expressions/match-expr.html/// [`samples/rust/rust_minimal.rs`]: srctree/samples/rust/rust_minimal.rs/// [`if let`]: https://doc.rust-lang.org/reference/expressions/if-expr.html#if-let-expressions/// [`?`]: https://doc.rust-lang.org/reference/expressions/operator-expr.html#the-question-mark-operator/// [`unwrap()`]: Result::unwrap/// [`expect()`]: Result::expect/// [`BUG()`]: https://docs.kernel.org/process/deprecated.html#bug-and-bug-on/// [`unwrap_or()`]: Result::unwrap_or/// [`unwrap_or_else()`]: Result::unwrap_or_else/// [`unwrap_or_default()`]: Result::unwrap_or_default/// [`unwrap_unchecked()`]: Result::unwrap_unchecked/// [Rust documentation]: https://doc.rust-lang.org/book/ch09-02-recoverable-errors-with-result.htmlpub type Result<T = (), E = Error> = core::result::Result<T, E>; /// Converts an integer as returned by a C kernel function to an error if it's negative, and/// `Ok(())` otherwise.pub fn to_result(err: crate::ffi::c_int) -> Result {    if err < 0 {        Err(Error::from_errno(err))    } else {        Ok(())    }} /// Transform a kernel "error pointer" to a normal pointer.////// Some kernel C API functions return an "error pointer" which optionally/// embeds an `errno`. Callers are supposed to check the returned pointer/// for errors. This function performs the check and converts the "error pointer"/// to a normal pointer in an idiomatic fashion.////// # Examples////// ```ignore/// # use kernel::from_err_ptr;/// # use kernel::bindings;/// fn devm_platform_ioremap_resource(///     pdev: &mut PlatformDevice,///     index: u32,/// ) -> Result<*mut kernel::ffi::c_void> {///     // SAFETY: `pdev` points to a valid platform device. There are no safety requirements///     // on `index`.///     from_err_ptr(unsafe { bindings::devm_platform_ioremap_resource(pdev.to_ptr(), index) })/// }/// ```pub fn from_err_ptr<T>(ptr: *mut T) -> Result<*mut T> {    // CAST: Casting a pointer to `*const crate::ffi::c_void` is always valid.    let const_ptr: *const crate::ffi::c_void = ptr.cast();    // SAFETY: The FFI function does not deref the pointer.    if unsafe { bindings::IS_ERR(const_ptr) } {        // SAFETY: The FFI function does not deref the pointer.        let err = unsafe { bindings::PTR_ERR(const_ptr) };         #[allow(clippy::unnecessary_cast)]        // CAST: If `IS_ERR()` returns `true`,        // then `PTR_ERR()` is guaranteed to return a        // negative value greater-or-equal to `-bindings::MAX_ERRNO`,        // which always fits in an `i16`, as per the invariant above.        // And an `i16` always fits in an `i32`. So casting `err` to        // an `i32` can never overflow, and is always valid.        //        // SAFETY: `IS_ERR()` ensures `err` is a        // negative value greater-or-equal to `-bindings::MAX_ERRNO`.        return Err(unsafe { Error::from_errno_unchecked(err as crate::ffi::c_int) });    }    Ok(ptr)} /// Calls a closure returning a [`crate::error::Result<T>`] and converts the result to/// a C integer result.////// This is useful when calling Rust functions that return [`crate::error::Result<T>`]/// from inside `extern "C"` functions that need to return an integer error result.////// `T` should be convertible from an `i16` via `From<i16>`.////// # Examples////// ```ignore/// # use kernel::from_result;/// # use kernel::bindings;/// unsafe extern "C" fn probe_callback(///     pdev: *mut bindings::platform_device,/// ) -> kernel::ffi::c_int {///     from_result(|| {///         let ptr = devm_alloc(pdev)?;///         bindings::platform_set_drvdata(pdev, ptr);///         Ok(0)///     })/// }/// ```pub fn from_result<T, F>(f: F) -> Twhere    T: From<i16>,    F: FnOnce() -> Result<T>,{    match f() {        Ok(v) => v,        // NO-OVERFLOW: negative `errno`s are no smaller than `-bindings::MAX_ERRNO`,        // `-bindings::MAX_ERRNO` fits in an `i16` as per invariant above,        // therefore a negative `errno` always fits in an `i16` and will not overflow.        Err(e) => T::from(e.to_errno() as i16),    }} /// Error message for calling a default function of a [`#[vtable]`](macros::vtable) trait.pub const VTABLE_DEFAULT_ERROR: &str =    "This function must not be called, see the #[vtable] documentation.";