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Diffstat (limited to 'rust/kernel/error.rs')
| -rw-r--r-- | rust/kernel/error.rs | 337 |
1 files changed, 337 insertions, 0 deletions
diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs new file mode 100644 index 000000000..032b64543 --- /dev/null +++ b/rust/kernel/error.rs @@ -0,0 +1,337 @@ +// 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 crate::str::CStr; + +use alloc::{ + alloc::{AllocError, LayoutError}, + collections::TryReserveError, +}; + +use core::convert::From; +use core::fmt; +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 $err: super::Error = super::Error(-(crate::bindings::$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, "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!(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(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. + 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`). + 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 _ } + } + + /// Returns a string representing the error, if one exists. + #[cfg(not(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) }; + 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(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(), + // SAFETY: These strings are ASCII-only. + Some(name) => f + .debug_tuple(unsafe { core::str::from_utf8_unchecked(name) }) + .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<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 = (), 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: core::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 core::ffi::c_void> { +/// // SAFETY: FFI call. +/// unsafe { +/// from_err_ptr(bindings::devm_platform_ioremap_resource( +/// pdev.to_ptr(), +/// index, +/// )) +/// } +/// } +/// ``` +// TODO: Remove `dead_code` marker once an in-kernel client is available. +#[allow(dead_code)] +pub(crate) fn from_err_ptr<T>(ptr: *mut T) -> Result<*mut T> { + // CAST: Casting a pointer to `*const core::ffi::c_void` is always valid. + let const_ptr: *const core::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) }; + // 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`. + #[allow(clippy::unnecessary_cast)] + return Err(unsafe { Error::from_errno_unchecked(err as core::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, +/// ) -> core::ffi::c_int { +/// from_result(|| { +/// let ptr = devm_alloc(pdev)?; +/// bindings::platform_set_drvdata(pdev, ptr); +/// Ok(0) +/// }) +/// } +/// ``` +// TODO: Remove `dead_code` marker once an in-kernel client is available. +#[allow(dead_code)] +pub(crate) fn from_result<T, F>(f: F) -> T +where + 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), + } +} |