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-rw-r--r--rust/bindings/bindings_helper.h1
-rw-r--r--rust/kernel/lib.rs1
-rw-r--r--rust/kernel/miscdevice.rs241
-rw-r--r--rust/kernel/types.rs16
4 files changed, 259 insertions, 0 deletions
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index ae82e9c941af..84303bf221dd 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -15,6 +15,7 @@
#include <linux/firmware.h>
#include <linux/jiffies.h>
#include <linux/mdio.h>
+#include <linux/miscdevice.h>
#include <linux/phy.h>
#include <linux/refcount.h>
#include <linux/sched.h>
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index b5f4b3ce6b48..8a228bcbbe85 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -39,6 +39,7 @@ pub mod ioctl;
#[cfg(CONFIG_KUNIT)]
pub mod kunit;
pub mod list;
+pub mod miscdevice;
#[cfg(CONFIG_NET)]
pub mod net;
pub mod page;
diff --git a/rust/kernel/miscdevice.rs b/rust/kernel/miscdevice.rs
new file mode 100644
index 000000000000..50885fb511bf
--- /dev/null
+++ b/rust/kernel/miscdevice.rs
@@ -0,0 +1,241 @@
+// 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
+ },
+ ..unsafe { MaybeUninit::zeroed().assume_init() }
+ };
+ }
+
+ &VtableHelper::<T>::VTABLE
+}
+
+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
+}
+
+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
+}
+
+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,
+ }
+}
+
+#[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,
+ }
+}
diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index 9e7ca066355c..070d03152937 100644
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -299,6 +299,22 @@ impl<T> Opaque<T> {
}
}
+ /// Creates a fallible pin-initializer from the given initializer closure.
+ ///
+ /// The returned initializer calls the given closure with the pointer to the inner `T` of this
+ /// `Opaque`. Since this memory is uninitialized, the closure is not allowed to read from it.
+ ///
+ /// This function is safe, because the `T` inside of an `Opaque` is allowed to be
+ /// uninitialized. Additionally, access to the inner `T` requires `unsafe`, so the caller needs
+ /// to verify at that point that the inner value is valid.
+ pub fn try_ffi_init<E>(
+ init_func: impl FnOnce(*mut T) -> Result<(), E>,
+ ) -> impl PinInit<Self, E> {
+ // SAFETY: We contain a `MaybeUninit`, so it is OK for the `init_func` to not fully
+ // initialize the `T`.
+ unsafe { init::pin_init_from_closure::<_, E>(move |slot| init_func(Self::raw_get(slot))) }
+ }
+
/// Returns a raw pointer to the opaque data.
pub const fn get(&self) -> *mut T {
UnsafeCell::get(&self.value).cast::<T>()
generated by cgit v1.2.3 (git 2.39.1) at 2025-01-18 11:17:38 +0100