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author | Linus Torvalds <torvalds@linux-foundation.org> | 2023-04-30 11:20:22 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2023-04-30 11:20:22 -0700 |
commit | 310897659cf056016e2c772a028f9b8abc934928 (patch) | |
tree | ca5f122d871a4e54026884bcc98a6309e3fd4069 /rust/kernel/error.rs | |
parent | 825a0714d2b3883d4f8ff64f6933fb73ee3f1834 (diff) | |
parent | ea76e08f4d901a450619831a255e9e0a4c0ed162 (diff) | |
download | linux-stable-310897659cf056016e2c772a028f9b8abc934928.tar.gz linux-stable-310897659cf056016e2c772a028f9b8abc934928.tar.bz2 linux-stable-310897659cf056016e2c772a028f9b8abc934928.zip |
Merge tag 'rust-6.4' of https://github.com/Rust-for-Linux/linux
Pull rust updates from Miguel Ojeda
"More additions to the Rust core. Importantly, this adds the pin-init
API, which will be used by other abstractions, such as the
synchronization ones added here too:
- pin-init API: a solution for the safe pinned initialization
problem.
This allows to reduce the need for 'unsafe' code in the kernel when
dealing with data structures that require a stable address. Commit
90e53c5e70a6 ("rust: add pin-init API core") contains a nice
introduction -- here is an example of how it looks like:
#[pin_data]
struct Example {
#[pin]
value: Mutex<u32>,
#[pin]
value_changed: CondVar,
}
impl Example {
fn new() -> impl PinInit<Self> {
pin_init!(Self {
value <- new_mutex!(0),
value_changed <- new_condvar!(),
})
}
}
// In a `Box`.
let b = Box::pin_init(Example::new())?;
// In the stack.
stack_pin_init!(let s = Example::new());
- 'sync' module:
New types 'LockClassKey' ('struct lock_class_key'), 'Lock',
'Guard', 'Mutex' ('struct mutex'), 'SpinLock' ('spinlock_t'),
'LockedBy' and 'CondVar' (uses 'wait_queue_head_t'), plus macros
such as 'static_lock_class!' and 'new_spinlock!'.
In particular, 'Lock' and 'Guard' are generic implementations that
contain code that is common to all locks. Then, different backends
(the new 'Backend' trait) are implemented and used to define types
like 'Mutex':
type Mutex<T> = Lock<T, MutexBackend>;
In addition, new methods 'assume_init()', 'init_with()' and
'pin_init_with()' for 'UniqueArc<MaybeUninit<T>>' and 'downcast()'
for 'Arc<dyn Any + Send + Sync>'; as well as 'Debug' and 'Display'
implementations for 'Arc' and 'UniqueArc'. Reduced stack usage of
'UniqueArc::try_new_uninit()', too.
- 'types' module:
New trait 'AlwaysRefCounted' and new type 'ARef' (an owned
reference to an always-reference-counted object, meant to be used
in wrappers for C types that have their own ref counting
functions).
Moreover, new associated functions 'raw_get()' and 'ffi_init()' for
'Opaque'.
- New 'task' module with a new type 'Task' ('struct task_struct'),
and a new macro 'current!' to safely get a reference to the current
one.
- New 'ioctl' module with new '_IOC*' const functions (equivalent to
the C macros).
- New 'uapi' crate, intended to be accessible by drivers directly.
- 'macros' crate: new 'quote!' macro (similar to the one provided in
userspace by the 'quote' crate); and the 'module!' macro now allows
specifying multiple module aliases.
- 'error' module:
New associated functions for the 'Error' type, such as
'from_errno()' and new functions such as 'to_result()'.
- 'alloc' crate:
More fallible 'Vec' methods: 'try_resize` and
'try_extend_from_slice' and the infrastructure (imported from the
Rust standard library) they need"
* tag 'rust-6.4' of https://github.com/Rust-for-Linux/linux: (44 commits)
rust: ioctl: Add ioctl number manipulation functions
rust: uapi: Add UAPI crate
rust: sync: introduce `CondVar`
rust: lock: add `Guard::do_unlocked`
rust: sync: introduce `LockedBy`
rust: introduce `current`
rust: add basic `Task`
rust: introduce `ARef`
rust: lock: introduce `SpinLock`
rust: lock: introduce `Mutex`
rust: sync: introduce `Lock` and `Guard`
rust: sync: introduce `LockClassKey`
MAINTAINERS: add Benno Lossin as Rust reviewer
rust: init: broaden the blanket impl of `Init`
rust: sync: add functions for initializing `UniqueArc<MaybeUninit<T>>`
rust: sync: reduce stack usage of `UniqueArc::try_new_uninit`
rust: types: add `Opaque::ffi_init`
rust: prelude: add `pin-init` API items to prelude
rust: init: add `Zeroable` trait and `init::zeroed` function
rust: init: add `stack_pin_init!` macro
...
Diffstat (limited to 'rust/kernel/error.rs')
-rw-r--r-- | rust/kernel/error.rs | 137 |
1 files changed, 136 insertions, 1 deletions
diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs index 5b9751d7ff1d..5f4114b30b94 100644 --- a/rust/kernel/error.rs +++ b/rust/kernel/error.rs @@ -72,10 +72,47 @@ pub mod code { 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_kernel_errno(self) -> core::ffi::c_int { + 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 { @@ -141,3 +178,101 @@ impl From<core::convert::Infallible> for Error { /// it should still be modeled as returning a `Result` rather than /// just an [`Error`]. pub type Result<T = ()> = core::result::Result<T, Error>; + +/// 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), + } +} |