diff --git a/drivers/base/base.h b/drivers/base/base.h index 86fa7fbb3548..430cbefbc97f 100644 --- a/drivers/base/base.h +++ b/drivers/base/base.h @@ -85,6 +85,18 @@ struct driver_private { }; #define to_driver(obj) container_of(obj, struct driver_private, kobj) +#ifdef CONFIG_RUST +/** + * struct driver_type - Representation of a Rust driver type. + */ +struct driver_type { + /** + * @id: Representation of core::any::TypeId. + */ + u8 id[16]; +} __packed; +#endif + /** * struct device_private - structure to hold the private to the driver core portions of the device structure. * @@ -100,6 +112,7 @@ struct driver_private { * @async_driver - pointer to device driver awaiting probe via async_probe * @device - pointer back to the struct device that this structure is * associated with. + * @driver_type - The type of the bound Rust driver. * @dead - This device is currently either in the process of or has been * removed from the system. Any asynchronous events scheduled for this * device should exit without taking any action. @@ -116,6 +129,9 @@ struct device_private { const struct device_driver *async_driver; char *deferred_probe_reason; struct device *device; +#ifdef CONFIG_RUST + struct driver_type driver_type; +#endif u8 dead:1; }; #define to_device_private_parent(obj) \ diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h index 2e43c66635a2..a79fd111f886 100644 --- a/rust/bindings/bindings_helper.h +++ b/rust/bindings/bindings_helper.h @@ -85,6 +85,12 @@ #include #include +/* + * The driver-core Rust code needs to know about some C driver-core private + * structures. + */ +#include <../../drivers/base/base.h> + #if defined(CONFIG_DRM_PANIC_SCREEN_QR_CODE) // Used by `#[export]` in `drivers/gpu/drm/drm_panic_qr.rs`. #include diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs index 106aa57a6385..1a307be953c2 100644 --- a/rust/kernel/device.rs +++ b/rust/kernel/device.rs @@ -10,13 +10,16 @@ use crate::{ sync::aref::ARef, types::{ForeignOwnable, Opaque}, }; -use core::{marker::PhantomData, ptr}; +use core::{any::TypeId, marker::PhantomData, ptr}; #[cfg(CONFIG_PRINTK)] use crate::c_str; pub mod property; +// Assert that we can `read()` / `write()` a `TypeId` instance from / into `struct driver_type`. +static_assert!(core::mem::size_of::() >= core::mem::size_of::()); + /// The core representation of a device in the kernel's driver model. /// /// This structure represents the Rust abstraction for a C `struct device`. A [`Device`] can either @@ -198,12 +201,29 @@ impl Device { } impl Device { + fn set_type_id(&self) { + // SAFETY: By the type invariants, `self.as_raw()` is a valid pointer to a `struct device`. + let private = unsafe { (*self.as_raw()).p }; + + // SAFETY: For a bound device (implied by the `CoreInternal` device context), `private` is + // guaranteed to be a valid pointer to a `struct device_private`. + let driver_type = unsafe { &raw mut (*private).driver_type }; + + // SAFETY: `driver_type` is valid for (unaligned) writes of a `TypeId`. + unsafe { + driver_type + .cast::() + .write_unaligned(TypeId::of::()) + }; + } + /// Store a pointer to the bound driver's private data. pub fn set_drvdata(&self, data: impl PinInit) -> Result { let data = KBox::pin_init(data, GFP_KERNEL)?; // SAFETY: By the type invariants, `self.as_raw()` is a valid pointer to a `struct device`. unsafe { bindings::dev_set_drvdata(self.as_raw(), data.into_foreign().cast()) }; + self.set_type_id::(); Ok(()) } @@ -219,6 +239,9 @@ impl Device { // SAFETY: By the type invariants, `self.as_raw()` is a valid pointer to a `struct device`. let ptr = unsafe { bindings::dev_get_drvdata(self.as_raw()) }; + // SAFETY: By the type invariants, `self.as_raw()` is a valid pointer to a `struct device`. + unsafe { bindings::dev_set_drvdata(self.as_raw(), core::ptr::null_mut()) }; + // SAFETY: // - By the safety requirements of this function, `ptr` comes from a previous call to // `into_foreign()`. @@ -235,7 +258,23 @@ impl Device { /// [`Device::drvdata_obtain`]. /// - The type `T` must match the type of the `ForeignOwnable` previously stored by /// [`Device::set_drvdata`]. - pub unsafe fn drvdata_borrow(&self) -> T::Borrowed<'_> { + pub unsafe fn drvdata_borrow(&self) -> Pin<&T> { + // SAFETY: `drvdata_unchecked()` has the exact same safety requirements as the ones + // required by this method. + unsafe { self.drvdata_unchecked() } + } +} + +impl Device { + /// Borrow the driver's private data bound to this [`Device`]. + /// + /// # Safety + /// + /// - Must only be called after a preceding call to [`Device::set_drvdata`] and before + /// [`Device::drvdata_obtain`]. + /// - The type `T` must match the type of the `ForeignOwnable` previously stored by + /// [`Device::set_drvdata`]. + unsafe fn drvdata_unchecked(&self) -> Pin<&T> { // SAFETY: By the type invariants, `self.as_raw()` is a valid pointer to a `struct device`. let ptr = unsafe { bindings::dev_get_drvdata(self.as_raw()) }; @@ -244,7 +283,46 @@ impl Device { // `into_foreign()`. // - `dev_get_drvdata()` guarantees to return the same pointer given to `dev_set_drvdata()` // in `into_foreign()`. - unsafe { T::borrow(ptr.cast()) } + unsafe { Pin::>::borrow(ptr.cast()) } + } + + fn match_type_id(&self) -> Result { + // SAFETY: By the type invariants, `self.as_raw()` is a valid pointer to a `struct device`. + let private = unsafe { (*self.as_raw()).p }; + + // SAFETY: For a bound device, `private` is guaranteed to be a valid pointer to a + // `struct device_private`. + let driver_type = unsafe { &raw mut (*private).driver_type }; + + // SAFETY: + // - `driver_type` is valid for (unaligned) reads of a `TypeId`. + // - A bound device guarantees that `driver_type` contains a valid `TypeId` value. + let type_id = unsafe { driver_type.cast::().read_unaligned() }; + + if type_id != TypeId::of::() { + return Err(EINVAL); + } + + Ok(()) + } + + /// Access a driver's private data. + /// + /// Returns a pinned reference to the driver's private data or [`EINVAL`] if it doesn't match + /// the asserted type `T`. + pub fn drvdata(&self) -> Result> { + // SAFETY: By the type invariants, `self.as_raw()` is a valid pointer to a `struct device`. + if unsafe { bindings::dev_get_drvdata(self.as_raw()) }.is_null() { + return Err(ENOENT); + } + + self.match_type_id::()?; + + // SAFETY: + // - The above check of `dev_get_drvdata()` guarantees that we are called after + // `set_drvdata()` and before `drvdata_obtain()`. + // - We've just checked that the type of the driver's private data is in fact `T`. + Ok(unsafe { self.drvdata_unchecked() }) } }