rust/kernel/miscdevice.rs - pub/scm/fs/xfs/xfs-linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0

 // Copyright (C) 2024 Google LLC.

 //! Miscdevice support.
 //!
 //! C headers: [`include/linux/miscdevice.h`](srctree/include/linux/miscdevice.h).
 //!
 //! Reference: <https://www.kernel.org/doc/html/latest/driver-api/misc_devices.html>

 use crate::{
     bindings,
     error::{to_result, Error, Result, VTABLE_DEFAULT_ERROR},
     prelude::*,
     str::CStr,
     types::{ForeignOwnable, Opaque},
 };
 use core::{
     ffi::{c_int, c_long, c_uint, c_ulong},
     marker::PhantomData,
     mem::MaybeUninit,
     pin::Pin,
 };

 /// Options for creating a misc device.
 #[derive(Copy, Clone)]
 pub struct MiscDeviceOptions {
     /// The name of the miscdevice.
     pub name: &'static CStr,
 }

 impl MiscDeviceOptions {
     /// Create a raw `struct miscdev` ready for registration.
     pub const fn into_raw<T: MiscDevice>(self) -> bindings::miscdevice {
         // SAFETY: All zeros is valid for this C type.
         let mut result: bindings::miscdevice = unsafe { MaybeUninit::zeroed().assume_init() };
         result.minor = bindings::MISC_DYNAMIC_MINOR as _;
         result.name = self.name.as_char_ptr();
         result.fops = create_vtable::<T>();
         result
     }
 }

 /// A registration of a miscdevice.
 ///
 /// # Invariants
 ///
 /// `inner` is a registered misc device.
 #[repr(transparent)]
 #[pin_data(PinnedDrop)]
 pub struct MiscDeviceRegistration<T> {
     #[pin]
     inner: Opaque<bindings::miscdevice>,
     _t: PhantomData<T>,
 }

 // SAFETY: It is allowed to call `misc_deregister` on a different thread from where you called
 // `misc_register`.
 unsafe impl<T> Send for MiscDeviceRegistration<T> {}
 // SAFETY: All `&self` methods on this type are written to ensure that it is safe to call them in
 // parallel.
 unsafe impl<T> Sync for MiscDeviceRegistration<T> {}

 impl<T: MiscDevice> MiscDeviceRegistration<T> {
     /// Register a misc device.
     pub fn register(opts: MiscDeviceOptions) -> impl PinInit<Self, Error> {
         try_pin_init!(Self {
             inner <- Opaque::try_ffi_init(move |slot: *mut bindings::miscdevice| {
                 // SAFETY: The initializer can write to the provided `slot`.
                 unsafe { slot.write(opts.into_raw::<T>()) };

                 // SAFETY: We just wrote the misc device options to the slot. The miscdevice will
                 // get unregistered before `slot` is deallocated because the memory is pinned and
                 // the destructor of this type deallocates the memory.
                 // INVARIANT: If this returns `Ok(())`, then the `slot` will contain a registered
                 // misc device.
                 to_result(unsafe { bindings::misc_register(slot) })
             }),
             _t: PhantomData,
         })
     }

     /// Returns a raw pointer to the misc device.
     pub fn as_raw(&self) -> *mut bindings::miscdevice {
         self.inner.get()
     }
 }

 #[pinned_drop]
 impl<T> PinnedDrop for MiscDeviceRegistration<T> {
     fn drop(self: Pin<&mut Self>) {
         // SAFETY: We know that the device is registered by the type invariants.
         unsafe { bindings::misc_deregister(self.inner.get()) };
     }
 }

 /// Trait implemented by the private data of an open misc device.
 #[vtable]
 pub trait MiscDevice {
     /// What kind of pointer should `Self` be wrapped in.
     type Ptr: ForeignOwnable + Send + Sync;

     /// Called when the misc device is opened.
     ///
     /// The returned pointer will be stored as the private data for the file.
     fn open() -> Result<Self::Ptr>;

     /// Called when the misc device is released.
     fn release(device: Self::Ptr) {
         drop(device);
     }

     /// Handler for ioctls.
     ///
     /// The `cmd` argument is usually manipulated using the utilties in [`kernel::ioctl`].
     ///
     /// [`kernel::ioctl`]: mod@crate::ioctl
     fn ioctl(
         _device: <Self::Ptr as ForeignOwnable>::Borrowed<'_>,
         _cmd: u32,
         _arg: usize,
     ) -> Result<isize> {
         kernel::build_error(VTABLE_DEFAULT_ERROR)
     }

     /// Handler for ioctls.
     ///
     /// Used for 32-bit userspace on 64-bit platforms.
     ///
     /// This method is optional and only needs to be provided if the ioctl relies on structures
     /// that have different layout on 32-bit and 64-bit userspace. If no implementation is
     /// provided, then `compat_ptr_ioctl` will be used instead.
     #[cfg(CONFIG_COMPAT)]
     fn compat_ioctl(
         _device: <Self::Ptr as ForeignOwnable>::Borrowed<'_>,
         _cmd: u32,
         _arg: usize,
     ) -> Result<isize> {
         kernel::build_error(VTABLE_DEFAULT_ERROR)
     }
 }

 const fn create_vtable<T: MiscDevice>() -> &'static bindings::file_operations {
     const fn maybe_fn<T: Copy>(check: bool, func: T) -> Option<T> {
         if check {
             Some(func)
         } else {
             None
         }
     }

     struct VtableHelper<T: MiscDevice> {
         _t: PhantomData<T>,
     }
     impl<T: MiscDevice> VtableHelper<T> {
         const VTABLE: bindings::file_operations = bindings::file_operations {
             open: Some(fops_open::<T>),
             release: Some(fops_release::<T>),
             unlocked_ioctl: maybe_fn(T::HAS_IOCTL, fops_ioctl::<T>),
             #[cfg(CONFIG_COMPAT)]
             compat_ioctl: if T::HAS_COMPAT_IOCTL {
                 Some(fops_compat_ioctl::<T>)
             } else if T::HAS_IOCTL {
                 Some(bindings::compat_ptr_ioctl)
             } else {
                 None
             },
             // SAFETY: All zeros is a valid value for `bindings::file_operations`.
             ..unsafe { MaybeUninit::zeroed().assume_init() }
         };
     }

     &VtableHelper::<T>::VTABLE
 }

 /// # Safety
 ///
 /// `file` and `inode` must be the file and inode for a file that is undergoing initialization.
 /// The file must be associated with a `MiscDeviceRegistration<T>`.
 unsafe extern "C" fn fops_open<T: MiscDevice>(
     inode: *mut bindings::inode,
     file: *mut bindings::file,
 ) -> c_int {
     // SAFETY: The pointers are valid and for a file being opened.
     let ret = unsafe { bindings::generic_file_open(inode, file) };
     if ret != 0 {
         return ret;
     }

     let ptr = match T::open() {
         Ok(ptr) => ptr,
         Err(err) => return err.to_errno(),
     };

     // SAFETY: The open call of a file owns the private data.
     unsafe { (*file).private_data = ptr.into_foreign().cast_mut() };

     0
 }

 /// # Safety
 ///
 /// `file` and `inode` must be the file and inode for a file that is being released. The file must
 /// be associated with a `MiscDeviceRegistration<T>`.
 unsafe extern "C" fn fops_release<T: MiscDevice>(
     _inode: *mut bindings::inode,
     file: *mut bindings::file,
 ) -> c_int {
     // SAFETY: The release call of a file owns the private data.
     let private = unsafe { (*file).private_data };
     // SAFETY: The release call of a file owns the private data.
     let ptr = unsafe { <T::Ptr as ForeignOwnable>::from_foreign(private) };

     T::release(ptr);

     0
 }

 /// # Safety
 ///
 /// `file` must be a valid file that is associated with a `MiscDeviceRegistration<T>`.
 unsafe extern "C" fn fops_ioctl<T: MiscDevice>(
     file: *mut bindings::file,
     cmd: c_uint,
     arg: c_ulong,
 ) -> c_long {
     // SAFETY: The ioctl call of a file can access the private data.
     let private = unsafe { (*file).private_data };
     // SAFETY: Ioctl calls can borrow the private data of the file.
     let device = unsafe { <T::Ptr as ForeignOwnable>::borrow(private) };

     match T::ioctl(device, cmd, arg as usize) {
         Ok(ret) => ret as c_long,
         Err(err) => err.to_errno() as c_long,
     }
 }

 /// # Safety
 ///
 /// `file` must be a valid file that is associated with a `MiscDeviceRegistration<T>`.
 #[cfg(CONFIG_COMPAT)]
 unsafe extern "C" fn fops_compat_ioctl<T: MiscDevice>(
     file: *mut bindings::file,
     cmd: c_uint,
     arg: c_ulong,
 ) -> c_long {
     // SAFETY: The compat ioctl call of a file can access the private data.
     let private = unsafe { (*file).private_data };
     // SAFETY: Ioctl calls can borrow the private data of the file.
     let device = unsafe { <T::Ptr as ForeignOwnable>::borrow(private) };

     match T::compat_ioctl(device, cmd, arg as usize) {
         Ok(ret) => ret as c_long,
         Err(err) => err.to_errno() as c_long,
     }
 }
	// SPDX-License-Identifier: GPL-2.0

	// Copyright (C) 2024 Google LLC.

	//! Miscdevice support.
	//!
	//! C headers: [`include/linux/miscdevice.h`](srctree/include/linux/miscdevice.h).
	//!
	//! Reference: <https://www.kernel.org/doc/html/latest/driver-api/misc_devices.html>

	use crate::{
	bindings,
	error::{to_result, Error, Result, VTABLE_DEFAULT_ERROR},
	prelude::*,
	str::CStr,
	types::{ForeignOwnable, Opaque},
	};
	use core::{
	ffi::{c_int, c_long, c_uint, c_ulong},
	marker::PhantomData,
	mem::MaybeUninit,
	pin::Pin,
	};

	/// Options for creating a misc device.
	#[derive(Copy, Clone)]
	pub struct MiscDeviceOptions {
	/// The name of the miscdevice.
	pub name: &'static CStr,
	}

	impl MiscDeviceOptions {
	/// Create a raw `struct miscdev` ready for registration.
	pub const fn into_raw<T: MiscDevice>(self) -> bindings::miscdevice {
	// SAFETY: All zeros is valid for this C type.
	let mut result: bindings::miscdevice = unsafe { MaybeUninit::zeroed().assume_init() };
	result.minor = bindings::MISC_DYNAMIC_MINOR as _;
	result.name = self.name.as_char_ptr();
	result.fops = create_vtable::<T>();
	result
	}
	}

	/// A registration of a miscdevice.
	///
	/// # Invariants
	///
	/// `inner` is a registered misc device.
	#[repr(transparent)]
	#[pin_data(PinnedDrop)]
	pub struct MiscDeviceRegistration<T> {
	#[pin]
	inner: Opaque<bindings::miscdevice>,
	_t: PhantomData<T>,
	}

	// SAFETY: It is allowed to call `misc_deregister` on a different thread from where you called
	// `misc_register`.
	unsafe impl<T> Send for MiscDeviceRegistration<T> {}
	// SAFETY: All `&self` methods on this type are written to ensure that it is safe to call them in
	// parallel.
	unsafe impl<T> Sync for MiscDeviceRegistration<T> {}

	impl<T: MiscDevice> MiscDeviceRegistration<T> {
	/// Register a misc device.
	pub fn register(opts: MiscDeviceOptions) -> impl PinInit<Self, Error> {
	try_pin_init!(Self {
	inner <- Opaque::try_ffi_init(move \|slot: *mut bindings::miscdevice\| {
	// SAFETY: The initializer can write to the provided `slot`.
	unsafe { slot.write(opts.into_raw::<T>()) };

	// SAFETY: We just wrote the misc device options to the slot. The miscdevice will
	// get unregistered before `slot` is deallocated because the memory is pinned and
	// the destructor of this type deallocates the memory.
	// INVARIANT: If this returns `Ok(())`, then the `slot` will contain a registered
	// misc device.
	to_result(unsafe { bindings::misc_register(slot) })
	}),
	_t: PhantomData,
	})
	}

	/// Returns a raw pointer to the misc device.
	pub fn as_raw(&self) -> *mut bindings::miscdevice {
	self.inner.get()
	}
	}

	#[pinned_drop]
	impl<T> PinnedDrop for MiscDeviceRegistration<T> {
	fn drop(self: Pin<&mut Self>) {
	// SAFETY: We know that the device is registered by the type invariants.
	unsafe { bindings::misc_deregister(self.inner.get()) };
	}
	}

	/// Trait implemented by the private data of an open misc device.
	#[vtable]
	pub trait MiscDevice {
	/// What kind of pointer should `Self` be wrapped in.
	type Ptr: ForeignOwnable + Send + Sync;

	/// Called when the misc device is opened.
	///
	/// The returned pointer will be stored as the private data for the file.
	fn open() -> Result<Self::Ptr>;

	/// Called when the misc device is released.
	fn release(device: Self::Ptr) {
	drop(device);
	}

	/// Handler for ioctls.
	///
	/// The `cmd` argument is usually manipulated using the utilties in [`kernel::ioctl`].
	///
	/// [`kernel::ioctl`]: mod@crate::ioctl
	fn ioctl(
	_device: <Self::Ptr as ForeignOwnable>::Borrowed<'_>,
	_cmd: u32,
	_arg: usize,
	) -> Result<isize> {
	kernel::build_error(VTABLE_DEFAULT_ERROR)
	}

	/// Handler for ioctls.
	///
	/// Used for 32-bit userspace on 64-bit platforms.
	///
	/// This method is optional and only needs to be provided if the ioctl relies on structures
	/// that have different layout on 32-bit and 64-bit userspace. If no implementation is
	/// provided, then `compat_ptr_ioctl` will be used instead.
	#[cfg(CONFIG_COMPAT)]
	fn compat_ioctl(
	_device: <Self::Ptr as ForeignOwnable>::Borrowed<'_>,
	_cmd: u32,
	_arg: usize,
	) -> Result<isize> {
	kernel::build_error(VTABLE_DEFAULT_ERROR)
	}
	}

	const fn create_vtable<T: MiscDevice>() -> &'static bindings::file_operations {
	const fn maybe_fn<T: Copy>(check: bool, func: T) -> Option<T> {
	if check {
	Some(func)
	} else {
	None
	}
	}

	struct VtableHelper<T: MiscDevice> {
	_t: PhantomData<T>,
	}
	impl<T: MiscDevice> VtableHelper<T> {
	const VTABLE: bindings::file_operations = bindings::file_operations {
	open: Some(fops_open::<T>),
	release: Some(fops_release::<T>),
	unlocked_ioctl: maybe_fn(T::HAS_IOCTL, fops_ioctl::<T>),
	#[cfg(CONFIG_COMPAT)]
	compat_ioctl: if T::HAS_COMPAT_IOCTL {
	Some(fops_compat_ioctl::<T>)
	} else if T::HAS_IOCTL {
	Some(bindings::compat_ptr_ioctl)
	} else {
	None
	},
	// SAFETY: All zeros is a valid value for `bindings::file_operations`.
	..unsafe { MaybeUninit::zeroed().assume_init() }
	};
	}

	&VtableHelper::<T>::VTABLE
	}

	/// # Safety
	///
	/// `file` and `inode` must be the file and inode for a file that is undergoing initialization.
	/// The file must be associated with a `MiscDeviceRegistration<T>`.
	unsafe extern "C" fn fops_open<T: MiscDevice>(
	inode: *mut bindings::inode,
	file: *mut bindings::file,
	) -> c_int {
	// SAFETY: The pointers are valid and for a file being opened.
	let ret = unsafe { bindings::generic_file_open(inode, file) };
	if ret != 0 {
	return ret;
	}

	let ptr = match T::open() {
	Ok(ptr) => ptr,
	Err(err) => return err.to_errno(),
	};

	// SAFETY: The open call of a file owns the private data.
	unsafe { (*file).private_data = ptr.into_foreign().cast_mut() };

	0
	}

	/// # Safety
	///
	/// `file` and `inode` must be the file and inode for a file that is being released. The file must
	/// be associated with a `MiscDeviceRegistration<T>`.
	unsafe extern "C" fn fops_release<T: MiscDevice>(
	_inode: *mut bindings::inode,
	file: *mut bindings::file,
	) -> c_int {
	// SAFETY: The release call of a file owns the private data.
	let private = unsafe { (*file).private_data };
	// SAFETY: The release call of a file owns the private data.
	let ptr = unsafe { <T::Ptr as ForeignOwnable>::from_foreign(private) };

	T::release(ptr);

	0
	}

	/// # Safety
	///
	/// `file` must be a valid file that is associated with a `MiscDeviceRegistration<T>`.
	unsafe extern "C" fn fops_ioctl<T: MiscDevice>(
	file: *mut bindings::file,
	cmd: c_uint,
	arg: c_ulong,
	) -> c_long {
	// SAFETY: The ioctl call of a file can access the private data.
	let private = unsafe { (*file).private_data };
	// SAFETY: Ioctl calls can borrow the private data of the file.
	let device = unsafe { <T::Ptr as ForeignOwnable>::borrow(private) };

	match T::ioctl(device, cmd, arg as usize) {
	Ok(ret) => ret as c_long,
	Err(err) => err.to_errno() as c_long,
	}
	}

	/// # Safety
	///
	/// `file` must be a valid file that is associated with a `MiscDeviceRegistration<T>`.
	#[cfg(CONFIG_COMPAT)]
	unsafe extern "C" fn fops_compat_ioctl<T: MiscDevice>(
	file: *mut bindings::file,
	cmd: c_uint,
	arg: c_ulong,
	) -> c_long {
	// SAFETY: The compat ioctl call of a file can access the private data.
	let private = unsafe { (*file).private_data };
	// SAFETY: Ioctl calls can borrow the private data of the file.
	let device = unsafe { <T::Ptr as ForeignOwnable>::borrow(private) };

	match T::compat_ioctl(device, cmd, arg as usize) {
	Ok(ret) => ret as c_long,
	Err(err) => err.to_errno() as c_long,
	}
	}