kernel/drm/gem/
mod.rs

1// SPDX-License-Identifier: GPL-2.0 OR MIT
2
3//! DRM GEM API
4//!
5//! C header: [`include/linux/drm/drm_gem.h`](srctree/include/linux/drm/drm_gem.h)
6
7use crate::{
8    alloc::flags::*,
9    bindings, drm,
10    drm::driver::{AllocImpl, AllocOps},
11    error::{to_result, Result},
12    prelude::*,
13    sync::aref::{ARef, AlwaysRefCounted},
14    types::Opaque,
15};
16use core::{mem, ops::Deref, ptr::NonNull};
17
18/// GEM object functions, which must be implemented by drivers.
19pub trait BaseDriverObject<T: BaseObject>: Sync + Send + Sized {
20    /// Create a new driver data object for a GEM object of a given size.
21    fn new(dev: &drm::Device<T::Driver>, size: usize) -> impl PinInit<Self, Error>;
22
23    /// Open a new handle to an existing object, associated with a File.
24    fn open(
25        _obj: &<<T as IntoGEMObject>::Driver as drm::Driver>::Object,
26        _file: &drm::File<<<T as IntoGEMObject>::Driver as drm::Driver>::File>,
27    ) -> Result {
28        Ok(())
29    }
30
31    /// Close a handle to an existing object, associated with a File.
32    fn close(
33        _obj: &<<T as IntoGEMObject>::Driver as drm::Driver>::Object,
34        _file: &drm::File<<<T as IntoGEMObject>::Driver as drm::Driver>::File>,
35    ) {
36    }
37}
38
39/// Trait that represents a GEM object subtype
40pub trait IntoGEMObject: Sized + super::private::Sealed + AlwaysRefCounted {
41    /// Owning driver for this type
42    type Driver: drm::Driver;
43
44    /// Returns a reference to the raw `drm_gem_object` structure, which must be valid as long as
45    /// this owning object is valid.
46    fn as_raw(&self) -> *mut bindings::drm_gem_object;
47
48    /// Converts a pointer to a `struct drm_gem_object` into a reference to `Self`.
49    ///
50    /// # Safety
51    ///
52    /// - `self_ptr` must be a valid pointer to `Self`.
53    /// - The caller promises that holding the immutable reference returned by this function does
54    ///   not violate rust's data aliasing rules and remains valid throughout the lifetime of `'a`.
55    unsafe fn from_raw<'a>(self_ptr: *mut bindings::drm_gem_object) -> &'a Self;
56}
57
58// SAFETY: All gem objects are refcounted.
59unsafe impl<T: IntoGEMObject> AlwaysRefCounted for T {
60    fn inc_ref(&self) {
61        // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
62        unsafe { bindings::drm_gem_object_get(self.as_raw()) };
63    }
64
65    unsafe fn dec_ref(obj: NonNull<Self>) {
66        // SAFETY: We either hold the only refcount on `obj`, or one of many - meaning that no one
67        // else could possibly hold a mutable reference to `obj` and thus this immutable reference
68        // is safe.
69        let obj = unsafe { obj.as_ref() }.as_raw();
70
71        // SAFETY:
72        // - The safety requirements guarantee that the refcount is non-zero.
73        // - We hold no references to `obj` now, making it safe for us to potentially deallocate it.
74        unsafe { bindings::drm_gem_object_put(obj) };
75    }
76}
77
78/// Trait which must be implemented by drivers using base GEM objects.
79pub trait DriverObject: BaseDriverObject<Object<Self>> {
80    /// Parent `Driver` for this object.
81    type Driver: drm::Driver;
82}
83
84extern "C" fn open_callback<T: BaseDriverObject<U>, U: BaseObject>(
85    raw_obj: *mut bindings::drm_gem_object,
86    raw_file: *mut bindings::drm_file,
87) -> core::ffi::c_int {
88    // SAFETY: `open_callback` is only ever called with a valid pointer to a `struct drm_file`.
89    let file = unsafe {
90        drm::File::<<<U as IntoGEMObject>::Driver as drm::Driver>::File>::from_raw(raw_file)
91    };
92    // SAFETY: `open_callback` is specified in the AllocOps structure for `Object<T>`, ensuring that
93    // `raw_obj` is indeed contained within a `Object<T>`.
94    let obj = unsafe {
95        <<<U as IntoGEMObject>::Driver as drm::Driver>::Object as IntoGEMObject>::from_raw(raw_obj)
96    };
97
98    match T::open(obj, file) {
99        Err(e) => e.to_errno(),
100        Ok(()) => 0,
101    }
102}
103
104extern "C" fn close_callback<T: BaseDriverObject<U>, U: BaseObject>(
105    raw_obj: *mut bindings::drm_gem_object,
106    raw_file: *mut bindings::drm_file,
107) {
108    // SAFETY: `open_callback` is only ever called with a valid pointer to a `struct drm_file`.
109    let file = unsafe {
110        drm::File::<<<U as IntoGEMObject>::Driver as drm::Driver>::File>::from_raw(raw_file)
111    };
112    // SAFETY: `close_callback` is specified in the AllocOps structure for `Object<T>`, ensuring
113    // that `raw_obj` is indeed contained within a `Object<T>`.
114    let obj = unsafe {
115        <<<U as IntoGEMObject>::Driver as drm::Driver>::Object as IntoGEMObject>::from_raw(raw_obj)
116    };
117
118    T::close(obj, file);
119}
120
121impl<T: DriverObject> IntoGEMObject for Object<T> {
122    type Driver = T::Driver;
123
124    fn as_raw(&self) -> *mut bindings::drm_gem_object {
125        self.obj.get()
126    }
127
128    unsafe fn from_raw<'a>(self_ptr: *mut bindings::drm_gem_object) -> &'a Self {
129        // SAFETY: `obj` is guaranteed to be in an `Object<T>` via the safety contract of this
130        // function
131        unsafe { &*crate::container_of!(Opaque::cast_from(self_ptr), Object<T>, obj) }
132    }
133}
134
135/// Base operations shared by all GEM object classes
136pub trait BaseObject: IntoGEMObject {
137    /// Returns the size of the object in bytes.
138    fn size(&self) -> usize {
139        // SAFETY: `self.as_raw()` is guaranteed to be a pointer to a valid `struct drm_gem_object`.
140        unsafe { (*self.as_raw()).size }
141    }
142
143    /// Creates a new handle for the object associated with a given `File`
144    /// (or returns an existing one).
145    fn create_handle(
146        &self,
147        file: &drm::File<<<Self as IntoGEMObject>::Driver as drm::Driver>::File>,
148    ) -> Result<u32> {
149        let mut handle: u32 = 0;
150        // SAFETY: The arguments are all valid per the type invariants.
151        to_result(unsafe {
152            bindings::drm_gem_handle_create(file.as_raw().cast(), self.as_raw(), &mut handle)
153        })?;
154        Ok(handle)
155    }
156
157    /// Looks up an object by its handle for a given `File`.
158    fn lookup_handle(
159        file: &drm::File<<<Self as IntoGEMObject>::Driver as drm::Driver>::File>,
160        handle: u32,
161    ) -> Result<ARef<Self>> {
162        // SAFETY: The arguments are all valid per the type invariants.
163        let ptr = unsafe { bindings::drm_gem_object_lookup(file.as_raw().cast(), handle) };
164        if ptr.is_null() {
165            return Err(ENOENT);
166        }
167
168        // SAFETY:
169        // - A `drm::Driver` can only have a single `File` implementation.
170        // - `file` uses the same `drm::Driver` as `Self`.
171        // - Therefore, we're guaranteed that `ptr` must be a gem object embedded within `Self`.
172        // - And we check if the pointer is null befoe calling from_raw(), ensuring that `ptr` is a
173        //   valid pointer to an initialized `Self`.
174        let obj = unsafe { Self::from_raw(ptr) };
175
176        // SAFETY:
177        // - We take ownership of the reference of `drm_gem_object_lookup()`.
178        // - Our `NonNull` comes from an immutable reference, thus ensuring it is a valid pointer to
179        //   `Self`.
180        Ok(unsafe { ARef::from_raw(obj.into()) })
181    }
182
183    /// Creates an mmap offset to map the object from userspace.
184    fn create_mmap_offset(&self) -> Result<u64> {
185        // SAFETY: The arguments are valid per the type invariant.
186        to_result(unsafe { bindings::drm_gem_create_mmap_offset(self.as_raw()) })?;
187
188        // SAFETY: The arguments are valid per the type invariant.
189        Ok(unsafe { bindings::drm_vma_node_offset_addr(&raw mut (*self.as_raw()).vma_node) })
190    }
191}
192
193impl<T: IntoGEMObject> BaseObject for T {}
194
195/// A base GEM object.
196///
197/// Invariants
198///
199/// - `self.obj` is a valid instance of a `struct drm_gem_object`.
200/// - `self.dev` is always a valid pointer to a `struct drm_device`.
201#[repr(C)]
202#[pin_data]
203pub struct Object<T: DriverObject + Send + Sync> {
204    obj: Opaque<bindings::drm_gem_object>,
205    dev: NonNull<drm::Device<T::Driver>>,
206    #[pin]
207    data: T,
208}
209
210impl<T: DriverObject> Object<T> {
211    /// The size of this object's structure.
212    pub const SIZE: usize = mem::size_of::<Self>();
213
214    const OBJECT_FUNCS: bindings::drm_gem_object_funcs = bindings::drm_gem_object_funcs {
215        free: Some(Self::free_callback),
216        open: Some(open_callback::<T, Object<T>>),
217        close: Some(close_callback::<T, Object<T>>),
218        print_info: None,
219        export: None,
220        pin: None,
221        unpin: None,
222        get_sg_table: None,
223        vmap: None,
224        vunmap: None,
225        mmap: None,
226        status: None,
227        vm_ops: core::ptr::null_mut(),
228        evict: None,
229        rss: None,
230    };
231
232    /// Create a new GEM object.
233    pub fn new(dev: &drm::Device<T::Driver>, size: usize) -> Result<ARef<Self>> {
234        let obj: Pin<KBox<Self>> = KBox::pin_init(
235            try_pin_init!(Self {
236                obj: Opaque::new(bindings::drm_gem_object::default()),
237                data <- T::new(dev, size),
238                // INVARIANT: The drm subsystem guarantees that the `struct drm_device` will live
239                // as long as the GEM object lives.
240                dev: dev.into(),
241            }),
242            GFP_KERNEL,
243        )?;
244
245        // SAFETY: `obj.as_raw()` is guaranteed to be valid by the initialization above.
246        unsafe { (*obj.as_raw()).funcs = &Self::OBJECT_FUNCS };
247
248        // SAFETY: The arguments are all valid per the type invariants.
249        to_result(unsafe { bindings::drm_gem_object_init(dev.as_raw(), obj.obj.get(), size) })?;
250
251        // SAFETY: We never move out of `Self`.
252        let ptr = KBox::into_raw(unsafe { Pin::into_inner_unchecked(obj) });
253
254        // SAFETY: `ptr` comes from `KBox::into_raw` and hence can't be NULL.
255        let ptr = unsafe { NonNull::new_unchecked(ptr) };
256
257        // SAFETY: We take over the initial reference count from `drm_gem_object_init()`.
258        Ok(unsafe { ARef::from_raw(ptr) })
259    }
260
261    /// Returns the `Device` that owns this GEM object.
262    pub fn dev(&self) -> &drm::Device<T::Driver> {
263        // SAFETY: The DRM subsystem guarantees that the `struct drm_device` will live as long as
264        // the GEM object lives, hence the pointer must be valid.
265        unsafe { self.dev.as_ref() }
266    }
267
268    fn as_raw(&self) -> *mut bindings::drm_gem_object {
269        self.obj.get()
270    }
271
272    extern "C" fn free_callback(obj: *mut bindings::drm_gem_object) {
273        let ptr: *mut Opaque<bindings::drm_gem_object> = obj.cast();
274
275        // SAFETY: All of our objects are of type `Object<T>`.
276        let this = unsafe { crate::container_of!(ptr, Self, obj) };
277
278        // SAFETY: The C code only ever calls this callback with a valid pointer to a `struct
279        // drm_gem_object`.
280        unsafe { bindings::drm_gem_object_release(obj) };
281
282        // SAFETY: All of our objects are allocated via `KBox`, and we're in the
283        // free callback which guarantees this object has zero remaining references,
284        // so we can drop it.
285        let _ = unsafe { KBox::from_raw(this) };
286    }
287}
288
289impl<T: DriverObject> super::private::Sealed for Object<T> {}
290
291impl<T: DriverObject> Deref for Object<T> {
292    type Target = T;
293
294    fn deref(&self) -> &Self::Target {
295        &self.data
296    }
297}
298
299impl<T: DriverObject> AllocImpl for Object<T> {
300    const ALLOC_OPS: AllocOps = AllocOps {
301        gem_create_object: None,
302        prime_handle_to_fd: None,
303        prime_fd_to_handle: None,
304        gem_prime_import: None,
305        gem_prime_import_sg_table: None,
306        dumb_create: None,
307        dumb_map_offset: None,
308    };
309}
310
311pub(super) const fn create_fops() -> bindings::file_operations {
312    // SAFETY: As by the type invariant, it is safe to initialize `bindings::file_operations`
313    // zeroed.
314    let mut fops: bindings::file_operations = unsafe { core::mem::zeroed() };
315
316    fops.owner = core::ptr::null_mut();
317    fops.open = Some(bindings::drm_open);
318    fops.release = Some(bindings::drm_release);
319    fops.unlocked_ioctl = Some(bindings::drm_ioctl);
320    #[cfg(CONFIG_COMPAT)]
321    {
322        fops.compat_ioctl = Some(bindings::drm_compat_ioctl);
323    }
324    fops.poll = Some(bindings::drm_poll);
325    fops.read = Some(bindings::drm_read);
326    fops.llseek = Some(bindings::noop_llseek);
327    fops.mmap = Some(bindings::drm_gem_mmap);
328    fops.fop_flags = bindings::FOP_UNSIGNED_OFFSET;
329
330    fops
331}
kernel/drm/gem/mod.rs

kernel/drm/gem/
mod.rs
