The DRM GEM subsystem is the DRM memory management subsystem used by most modern drivers. Add a Rust abstraction to allow Rust DRM driver implementations to use it.
Signed-off-by: Asahi Lina lina@asahilina.net --- rust/bindings/bindings_helper.h | 1 + rust/helpers.c | 23 +++ rust/kernel/drm/drv.rs | 4 +- rust/kernel/drm/gem/mod.rs | 374 ++++++++++++++++++++++++++++++++++++++++ rust/kernel/drm/mod.rs | 1 + 5 files changed, 401 insertions(+), 2 deletions(-)
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h index 7d7828faf89c..7183dfe6473f 100644 --- a/rust/bindings/bindings_helper.h +++ b/rust/bindings/bindings_helper.h @@ -9,6 +9,7 @@ #include <drm/drm_device.h> #include <drm/drm_drv.h> #include <drm/drm_file.h> +#include <drm/drm_gem.h> #include <drm/drm_ioctl.h> #include <linux/delay.h> #include <linux/device.h> diff --git a/rust/helpers.c b/rust/helpers.c index 73b2ce607f27..78ec4162b03b 100644 --- a/rust/helpers.c +++ b/rust/helpers.c @@ -18,6 +18,7 @@ * accidentally exposed. */
+#include <drm/drm_gem.h> #include <linux/bug.h> #include <linux/build_bug.h> #include <linux/device.h> @@ -374,6 +375,28 @@ void rust_helper_init_completion(struct completion *c) } EXPORT_SYMBOL_GPL(rust_helper_init_completion);
+#ifdef CONFIG_DRM + +void rust_helper_drm_gem_object_get(struct drm_gem_object *obj) +{ + drm_gem_object_get(obj); +} +EXPORT_SYMBOL_GPL(rust_helper_drm_gem_object_get); + +void rust_helper_drm_gem_object_put(struct drm_gem_object *obj) +{ + drm_gem_object_put(obj); +} +EXPORT_SYMBOL_GPL(rust_helper_drm_gem_object_put); + +__u64 rust_helper_drm_vma_node_offset_addr(struct drm_vma_offset_node *node) +{ + return drm_vma_node_offset_addr(node); +} +EXPORT_SYMBOL_GPL(rust_helper_drm_vma_node_offset_addr); + +#endif + /* * We use `bindgen`'s `--size_t-is-usize` option to bind the C `size_t` type * as the Rust `usize` type, so we can use it in contexts where Rust diff --git a/rust/kernel/drm/drv.rs b/rust/kernel/drm/drv.rs index 1dcb651e1417..c138352cb489 100644 --- a/rust/kernel/drm/drv.rs +++ b/rust/kernel/drm/drv.rs @@ -126,7 +126,7 @@ pub struct AllocOps { }
/// Trait for memory manager implementations. Implemented internally. -pub trait AllocImpl: Sealed { +pub trait AllocImpl: Sealed + drm::gem::IntoGEMObject { /// The C callback operations for this memory manager. const ALLOC_OPS: AllocOps; } @@ -263,7 +263,7 @@ impl<T: Driver> Registration<T> { drm, registered: false, vtable, - fops: Default::default(), // TODO: GEM abstraction + fops: drm::gem::create_fops(), _pin: PhantomPinned, _p: PhantomData, }) diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs new file mode 100644 index 000000000000..8a7d99613718 --- /dev/null +++ b/rust/kernel/drm/gem/mod.rs @@ -0,0 +1,374 @@ +// SPDX-License-Identifier: GPL-2.0 OR MIT + +//! DRM GEM API +//! +//! C header: [`include/linux/drm/drm_gem.h`](../../../../include/linux/drm/drm_gem.h) + +use alloc::boxed::Box; + +use crate::{ + bindings, + drm::{device, drv, file}, + error::{to_result, Result}, + prelude::*, +}; +use core::{mem, mem::ManuallyDrop, ops::Deref, ops::DerefMut}; + +/// GEM object functions, which must be implemented by drivers. +pub trait BaseDriverObject<T: BaseObject>: Sync + Send + Sized { + /// Create a new driver data object for a GEM object of a given size. + fn new(dev: &device::Device<T::Driver>, size: usize) -> Result<Self>; + + /// Open a new handle to an existing object, associated with a File. + fn open( + _obj: &<<T as IntoGEMObject>::Driver as drv::Driver>::Object, + _file: &file::File<<<T as IntoGEMObject>::Driver as drv::Driver>::File>, + ) -> Result { + Ok(()) + } + + /// Close a handle to an existing object, associated with a File. + fn close( + _obj: &<<T as IntoGEMObject>::Driver as drv::Driver>::Object, + _file: &file::File<<<T as IntoGEMObject>::Driver as drv::Driver>::File>, + ) { + } +} + +/// Trait that represents a GEM object subtype +pub trait IntoGEMObject: Sized + crate::private::Sealed { + /// Owning driver for this type + type Driver: drv::Driver; + + /// Returns a pointer to the raw `drm_gem_object` structure, which must be valid as long as + /// this owning object is valid. + fn gem_obj(&self) -> *mut bindings::drm_gem_object; + + /// Returns a reference to the raw `drm_gem_object` structure, which must be valid as long as + /// this owning object is valid. + fn gem_ref(&self) -> &bindings::drm_gem_object { + // SAFETY: gem_obj() must be valid per the above requirement. + unsafe { &*self.gem_obj() } + } + + /// Converts a pointer to a `drm_gem_object` into a pointer to this type. + fn from_gem_obj(obj: *mut bindings::drm_gem_object) -> *mut Self; +} + +/// Trait which must be implemented by drivers using base GEM objects. +pub trait DriverObject: BaseDriverObject<Object<Self>> { + /// Parent `Driver` for this object. + type Driver: drv::Driver; +} + +unsafe extern "C" fn free_callback<T: DriverObject>(obj: *mut bindings::drm_gem_object) { + // SAFETY: All of our objects are Object<T>. + let this = crate::container_of!(obj, Object<T>, obj) as *mut Object<T>; + + // SAFETY: The pointer we got has to be valid + unsafe { bindings::drm_gem_object_release(obj) }; + + // SAFETY: All of our objects are allocated via Box<>, and we're in the + // free callback which guarantees this object has zero remaining references, + // so we can drop it + unsafe { Box::from_raw(this) }; +} + +unsafe extern "C" fn open_callback<T: BaseDriverObject<U>, U: BaseObject>( + raw_obj: *mut bindings::drm_gem_object, + raw_file: *mut bindings::drm_file, +) -> core::ffi::c_int { + // SAFETY: The pointer we got has to be valid. + let file = unsafe { + file::File::<<<U as IntoGEMObject>::Driver as drv::Driver>::File>::from_raw(raw_file) + }; + let obj = + <<<U as IntoGEMObject>::Driver as drv::Driver>::Object as IntoGEMObject>::from_gem_obj( + raw_obj, + ); + + // SAFETY: from_gem_obj() returns a valid pointer as long as the type is + // correct and the raw_obj we got is valid. + match T::open(unsafe { &*obj }, &file) { + Err(e) => e.to_kernel_errno(), + Ok(()) => 0, + } +} + +unsafe extern "C" fn close_callback<T: BaseDriverObject<U>, U: BaseObject>( + raw_obj: *mut bindings::drm_gem_object, + raw_file: *mut bindings::drm_file, +) { + // SAFETY: The pointer we got has to be valid. + let file = unsafe { + file::File::<<<U as IntoGEMObject>::Driver as drv::Driver>::File>::from_raw(raw_file) + }; + let obj = + <<<U as IntoGEMObject>::Driver as drv::Driver>::Object as IntoGEMObject>::from_gem_obj( + raw_obj, + ); + + // SAFETY: from_gem_obj() returns a valid pointer as long as the type is + // correct and the raw_obj we got is valid. + T::close(unsafe { &*obj }, &file); +} + +impl<T: DriverObject> IntoGEMObject for Object<T> { + type Driver = T::Driver; + + fn gem_obj(&self) -> *mut bindings::drm_gem_object { + &self.obj as *const _ as *mut _ + } + + fn from_gem_obj(obj: *mut bindings::drm_gem_object) -> *mut Object<T> { + crate::container_of!(obj, Object<T>, obj) as *mut Object<T> + } +} + +/// Base operations shared by all GEM object classes +pub trait BaseObject: IntoGEMObject { + /// Returns the size of the object in bytes. + fn size(&self) -> usize { + self.gem_ref().size + } + + /// Creates a new reference to the object. + fn reference(&self) -> ObjectRef<Self> { + // SAFETY: Having a reference to an Object implies holding a GEM reference + unsafe { + bindings::drm_gem_object_get(self.gem_obj()); + } + ObjectRef { + ptr: self as *const _, + } + } + + /// Creates a new handle for the object associated with a given `File` + /// (or returns an existing one). + fn create_handle( + &self, + file: &file::File<<<Self as IntoGEMObject>::Driver as drv::Driver>::File>, + ) -> Result<u32> { + let mut handle: u32 = 0; + // SAFETY: The arguments are all valid per the type invariants. + to_result(unsafe { + bindings::drm_gem_handle_create(file.raw() as *mut _, self.gem_obj(), &mut handle) + })?; + Ok(handle) + } + + /// Looks up an object by its handle for a given `File`. + fn lookup_handle( + file: &file::File<<<Self as IntoGEMObject>::Driver as drv::Driver>::File>, + handle: u32, + ) -> Result<ObjectRef<Self>> { + // SAFETY: The arguments are all valid per the type invariants. + let ptr = unsafe { bindings::drm_gem_object_lookup(file.raw() as *mut _, handle) }; + + if ptr.is_null() { + Err(ENOENT) + } else { + Ok(ObjectRef { + ptr: ptr as *const _, + }) + } + } + + /// Creates an mmap offset to map the object from userspace. + fn create_mmap_offset(&self) -> Result<u64> { + // SAFETY: The arguments are valid per the type invariant. + to_result(unsafe { + // TODO: is this threadsafe? + bindings::drm_gem_create_mmap_offset(self.gem_obj()) + })?; + Ok(unsafe { + bindings::drm_vma_node_offset_addr(&self.gem_ref().vma_node as *const _ as *mut _) + }) + } +} + +impl<T: IntoGEMObject> BaseObject for T {} + +/// A base GEM object. +#[repr(C)] +pub struct Object<T: DriverObject> { + obj: bindings::drm_gem_object, + // The DRM core ensures the Device exists as long as its objects exist, so we don't need to + // manage the reference count here. + dev: ManuallyDrop<device::Device<T::Driver>>, + inner: T, +} + +impl<T: DriverObject> Object<T> { + /// The size of this object's structure. + pub const SIZE: usize = mem::size_of::<Self>(); + + const OBJECT_FUNCS: bindings::drm_gem_object_funcs = bindings::drm_gem_object_funcs { + free: Some(free_callback::<T>), + open: Some(open_callback::<T, Object<T>>), + close: Some(close_callback::<T, Object<T>>), + print_info: None, + export: None, + pin: None, + unpin: None, + get_sg_table: None, + vmap: None, + vunmap: None, + mmap: None, + vm_ops: core::ptr::null_mut(), + }; + + /// Create a new GEM object. + pub fn new(dev: &device::Device<T::Driver>, size: usize) -> Result<UniqueObjectRef<Self>> { + let mut obj: Box<Self> = Box::try_new(Self { + // SAFETY: This struct is expected to be zero-initialized + obj: unsafe { mem::zeroed() }, + // SAFETY: The drm subsystem guarantees that the drm_device will live as long as + // the GEM object lives, so we can conjure a reference out of thin air. + dev: ManuallyDrop::new(unsafe { device::Device::from_raw(dev.ptr) }), + inner: T::new(dev, size)?, + })?; + + obj.obj.funcs = &Self::OBJECT_FUNCS; + to_result(unsafe { + bindings::drm_gem_object_init(dev.raw() as *mut _, &mut obj.obj, size) + })?; + + let obj_ref = UniqueObjectRef { + ptr: Box::leak(obj), + }; + + Ok(obj_ref) + } + + /// Returns the `Device` that owns this GEM object. + pub fn dev(&self) -> &device::Device<T::Driver> { + &self.dev + } +} + +impl<T: DriverObject> crate::private::Sealed for Object<T> {} + +impl<T: DriverObject> Deref for Object<T> { + type Target = T; + + fn deref(&self) -> &Self::Target { + &self.inner + } +} + +impl<T: DriverObject> DerefMut for Object<T> { + fn deref_mut(&mut self) -> &mut Self::Target { + &mut self.inner + } +} + +impl<T: DriverObject> drv::AllocImpl for Object<T> { + const ALLOC_OPS: drv::AllocOps = drv::AllocOps { + gem_create_object: None, + prime_handle_to_fd: Some(bindings::drm_gem_prime_handle_to_fd), + prime_fd_to_handle: Some(bindings::drm_gem_prime_fd_to_handle), + gem_prime_import: None, + gem_prime_import_sg_table: None, + gem_prime_mmap: Some(bindings::drm_gem_prime_mmap), + dumb_create: None, + dumb_map_offset: None, + dumb_destroy: None, + }; +} + +/// A reference-counted shared reference to a base GEM object. +pub struct ObjectRef<T: IntoGEMObject> { + // Invariant: the pointer is valid and initialized, and this ObjectRef owns a reference to it. + ptr: *const T, +} + +/// SAFETY: GEM object references are safe to share between threads. +unsafe impl<T: IntoGEMObject> Send for ObjectRef<T> {} +unsafe impl<T: IntoGEMObject> Sync for ObjectRef<T> {} + +impl<T: IntoGEMObject> Clone for ObjectRef<T> { + fn clone(&self) -> Self { + self.reference() + } +} + +impl<T: IntoGEMObject> Drop for ObjectRef<T> { + fn drop(&mut self) { + // SAFETY: Having an ObjectRef implies holding a GEM reference. + // The free callback will take care of deallocation. + unsafe { + bindings::drm_gem_object_put((*self.ptr).gem_obj()); + } + } +} + +impl<T: IntoGEMObject> Deref for ObjectRef<T> { + type Target = T; + + fn deref(&self) -> &Self::Target { + // SAFETY: The pointer is valid per the invariant + unsafe { &*self.ptr } + } +} + +/// A unique reference to a base GEM object. +pub struct UniqueObjectRef<T: IntoGEMObject> { + // Invariant: the pointer is valid and initialized, and this ObjectRef owns the only reference + // to it. + ptr: *mut T, +} + +impl<T: IntoGEMObject> UniqueObjectRef<T> { + /// Downgrade this reference to a shared reference. + pub fn into_ref(self) -> ObjectRef<T> { + let ptr = self.ptr as *const _; + core::mem::forget(self); + + ObjectRef { ptr } + } +} + +impl<T: IntoGEMObject> Drop for UniqueObjectRef<T> { + fn drop(&mut self) { + // SAFETY: Having a UniqueObjectRef implies holding a GEM + // reference. The free callback will take care of deallocation. + unsafe { + bindings::drm_gem_object_put((*self.ptr).gem_obj()); + } + } +} + +impl<T: IntoGEMObject> Deref for UniqueObjectRef<T> { + type Target = T; + + fn deref(&self) -> &Self::Target { + // SAFETY: The pointer is valid per the invariant + unsafe { &*self.ptr } + } +} + +impl<T: IntoGEMObject> DerefMut for UniqueObjectRef<T> { + fn deref_mut(&mut self) -> &mut Self::Target { + // SAFETY: The pointer is valid per the invariant + unsafe { &mut *self.ptr } + } +} + +pub(super) fn create_fops() -> bindings::file_operations { + bindings::file_operations { + owner: core::ptr::null_mut(), + open: Some(bindings::drm_open), + release: Some(bindings::drm_release), + unlocked_ioctl: Some(bindings::drm_ioctl), + #[cfg(CONFIG_COMPAT)] + compat_ioctl: Some(bindings::drm_compat_ioctl), + #[cfg(not(CONFIG_COMPAT))] + compat_ioctl: None, + poll: Some(bindings::drm_poll), + read: Some(bindings::drm_read), + llseek: Some(bindings::noop_llseek), + mmap: Some(bindings::drm_gem_mmap), + ..Default::default() + } +} diff --git a/rust/kernel/drm/mod.rs b/rust/kernel/drm/mod.rs index a767942d0b52..c44760a1332f 100644 --- a/rust/kernel/drm/mod.rs +++ b/rust/kernel/drm/mod.rs @@ -5,4 +5,5 @@ pub mod device; pub mod drv; pub mod file; +pub mod gem; pub mod ioctl;