In the future we're going to be introducing more GEM object types in rust then just gem::Object<T>. Since all types of GEM objects have refcounting, let's introduce a macro that we can use in the gem crate in order to copy this boilerplate implementation for each type: impl_aref_for_gem_obj!().

Signed-off-by: Lyude Paul lyude@redhat.com Reviewed-by: Daniel Almeida daniel.almeida@collabora.com Reviewed-by: Janne Grunau j@jananu.net

--- V5: * Move .as_raw() call to `let obj` in dec_ref, to ensure that the reference to object is not live by the time that we call drm_gem_object_put(). * Add missing #[macro_export] annotation V6: * Add missing IntoGEMObject trait bound

rust/kernel/drm/gem/mod.rs | 51 +++++++++++++++++++++++++++----------- 1 file changed, 36 insertions(+), 15 deletions(-)

diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs index d49a9ba026356..94e7c2a7293d0 100644 --- a/rust/kernel/drm/gem/mod.rs +++ b/rust/kernel/drm/gem/mod.rs @@ -15,6 +15,41 @@ }; use core::{ops::Deref, ptr::NonNull};

+/// A macro for implementing [`AlwaysRefCounted`] for any GEM object type. +/// +/// Since all GEM objects use the same refcounting scheme. +#[macro_export] +macro_rules! impl_aref_for_gem_obj { + ( + impl $( <$( $tparam_id:ident ),+> )? for $type:ty + $( + where + $( $bind_param:path : $bind_trait:path ),+ + )? + ) => { + // SAFETY: All gem objects are refcounted + unsafe impl $( <$( $tparam_id ),+> )? $crate::types::AlwaysRefCounted for $type + where + Self: IntoGEMObject, + $( $( $bind_param : $bind_trait ),+ )? + { + fn inc_ref(&self) { + // SAFETY: The existence of a shared reference guarantees that the refcount is + // non-zero. + unsafe { bindings::drm_gem_object_get(self.as_raw()) }; + } + + unsafe fn dec_ref(obj: core::ptr::NonNull<Self>) { + // SAFETY: `obj` is a valid pointer to an `Object<T>`. + let obj = unsafe { obj.as_ref() }.as_raw(); + + // SAFETY: The safety requirements guarantee that the refcount is non-zero. + unsafe { bindings::drm_gem_object_put(obj) }; + } + } + }; +} + /// A type alias for retrieving a [`Driver`]s [`DriverFile`] implementation from its /// [`DriverObject`] implementation. /// @@ -252,21 +287,7 @@ extern "C" fn free_callback(obj: *mut bindings::drm_gem_object) { } }

-// SAFETY: Instances of `Object<T>` are always reference-counted. -unsafe impl<T: DriverObject> crate::sync::aref::AlwaysRefCounted for Object<T> { - fn inc_ref(&self) { - // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero. - unsafe { bindings::drm_gem_object_get(self.as_raw()) }; - } - - unsafe fn dec_ref(obj: NonNull<Self>) { - // SAFETY: `obj` is a valid pointer to an `Object<T>`. - let obj = unsafe { obj.as_ref() }; - - // SAFETY: The safety requirements guarantee that the refcount is non-zero. - unsafe { bindings::drm_gem_object_put(obj.as_raw()) } - } -} +impl_aref_for_gem_obj!(impl<T> for Object<T> where T: DriverObject);

impl<T: DriverObject> super::private::Sealed for Object<T> {}

From: Asahi Lina lina@asahilina.net

This is just for basic usage in the DRM shmem abstractions for implied locking, not intended as a full DMA Reservation abstraction yet.

Signed-off-by: Asahi Lina lina@asahilina.net Signed-off-by: Daniel Almeida daniel.almeida@collabora.com Reviewed-by: Alice Ryhl aliceryhl@google.com Reviewed-by: Janne Grunau j@jananu.net Signed-off-by: Lyude Paul lyude@redhat.com --- rust/bindings/bindings_helper.h | 1 + rust/helpers/dma-resv.c | 13 +++++++++++++ rust/helpers/helpers.c | 1 + 3 files changed, 15 insertions(+) create mode 100644 rust/helpers/dma-resv.c

diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h index 083cc44aa952c..39a8f15603692 100644 --- a/rust/bindings/bindings_helper.h +++ b/rust/bindings/bindings_helper.h @@ -48,6 +48,7 @@ #include <linux/cpumask.h> #include <linux/cred.h> #include <linux/debugfs.h> +#include <linux/dma-resv.h> #include <linux/device/faux.h> #include <linux/dma-direction.h> #include <linux/dma-mapping.h> diff --git a/rust/helpers/dma-resv.c b/rust/helpers/dma-resv.c new file mode 100644 index 0000000000000..05501cb814513 --- /dev/null +++ b/rust/helpers/dma-resv.c @@ -0,0 +1,13 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include <linux/dma-resv.h> + +int rust_helper_dma_resv_lock(struct dma_resv *obj, struct ww_acquire_ctx *ctx) +{ + return dma_resv_lock(obj, ctx); +} + +void rust_helper_dma_resv_unlock(struct dma_resv *obj) +{ + dma_resv_unlock(obj); +} diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c index a3c42e51f00a0..d090e2c7c7ea8 100644 --- a/rust/helpers/helpers.c +++ b/rust/helpers/helpers.c @@ -28,6 +28,7 @@ #include "cred.c" #include "device.c" #include "dma.c" +#include "dma-resv.c" #include "drm.c" #include "err.c" #include "irq.c"

From: Asahi Lina lina@asahilina.net

The DRM shmem helper includes common code useful for drivers which allocate GEM objects as anonymous shmem. Add a Rust abstraction for this. Drivers can choose the raw GEM implementation or the shmem layer, depending on their needs.

Signed-off-by: Asahi Lina lina@asahilina.net Signed-off-by: Daniel Almeida daniel.almeida@collabora.com Reviewed-by: Daniel Almeida daniel.almeida@collabora.com Signed-off-by: Lyude Paul lyude@redhat.com

---

V2: * Use the drm_gem_shmem_init() and drm_gem_shmem_release() that I extracted so we can handle memory allocation in rust, which means we no longer have to handle freeing rust members of the struct by hand and have a closer implementation to the main gem object (this also gets rid of gem_create_object) * Get rid of GemObjectRef and UniqueGemObjectRef, we have ARef<T> at home. * Use Device<T::Driver> in Object<T> * Cleanup Object::<T>::new() a bit: * Cleanup safety comment * Use cast_mut() * Just import container_of!(), we use it all over anyhow * mut_shmem() -> as_shmem(), make it safe (there's no reason for being unsafe) * Remove any *const and *muts in structs, just use NonNull * Get rid of the previously hand-rolled sg_table bindings in shmem, use the bindings from Abdiel's sg_table patch series * Add a TODO at the top about DMA reservation APIs and a desire for WwMutex * Get rid of map_wc() and replace it with a new ObjectConfig struct. While it currently only specifies the map_wc flag, the idea here is that settings like map_wc() and parent_resv_obj() shouldn't be exposed as normal functions since the only place where it's safe to set them is when we're still guaranteed unique access to the GEM object, e.g. before returning it to the caller. Using a struct instead of individual arguments here is mainly because we'll be adding at least one more argument, and there's enough other gem shmem settings that trying to add all of them as individual function arguments in the future would be a bit messy. * Get rid of vm_numa_fields!, Lina didn't like this macro much either and I think that it's fine for us to just specify the #[cfg(…)] attributes by hand since we only need to do it twice. * Set drm_gem_object_funcs.vm_ops directly to drm_gem_shmem_vm_ops, don't export the various shmem funcs. I'm not sure why this wasn't possible before but it seems to work fine now. V4: * Switch from OpaqueObject to a normal Object<T> now that we've removed it * Remove `dev` from Object, it's redundant as drm_gem_object already has a device pointer we can use. * Use &raw instead of addr_of!() V5: * Fix typo in shmem::Object::as_raw() * Add type invariant around `obj` always being a valid `drm_gem_shmem_object` for the duration of the lifetime of `Object`. * Use Opaque::cast_from() instead of unrestricted casts * Use IS_ENABLED() for gem shmem C helpers. V7: * Fix import style * Don't forget to make Object<T> Send/Sync V8: * s/as_shmem()/as_raw_shmem()

rust/bindings/bindings_helper.h | 2 + rust/helpers/drm.c | 56 ++++++- rust/kernel/drm/gem/mod.rs | 5 +- rust/kernel/drm/gem/shmem.rs | 250 ++++++++++++++++++++++++++++++++ 4 files changed, 311 insertions(+), 2 deletions(-) create mode 100644 rust/kernel/drm/gem/shmem.rs

diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h index 39a8f15603692..a343c684e8d06 100644 --- a/rust/bindings/bindings_helper.h +++ b/rust/bindings/bindings_helper.h @@ -33,6 +33,7 @@ #include <drm/drm_drv.h> #include <drm/drm_file.h> #include <drm/drm_gem.h> +#include <drm/drm_gem_shmem_helper.h> #include <drm/drm_ioctl.h> #include <kunit/test.h> #include <linux/auxiliary_bus.h> @@ -62,6 +63,7 @@ #include <linux/interrupt.h> #include <linux/io-pgtable.h> #include <linux/ioport.h> +#include <linux/iosys-map.h> #include <linux/jiffies.h> #include <linux/jump_label.h> #include <linux/mdio.h> diff --git a/rust/helpers/drm.c b/rust/helpers/drm.c index fe226f7b53ef0..a49aff4fb6350 100644 --- a/rust/helpers/drm.c +++ b/rust/helpers/drm.c @@ -1,6 +1,7 @@ // SPDX-License-Identifier: GPL-2.0

#include <drm/drm_gem.h> +#include <drm/drm_gem_shmem_helper.h> #include <drm/drm_vma_manager.h>

#ifdef CONFIG_DRM @@ -21,4 +22,57 @@ rust_helper_drm_vma_node_offset_addr(struct drm_vma_offset_node *node) return drm_vma_node_offset_addr(node); }

-#endif +#if IS_ENABLED(CONFIG_DRM_GEM_SHMEM_HELPER) +__rust_helper void +rust_helper_drm_gem_shmem_object_free(struct drm_gem_object *obj) +{ + return drm_gem_shmem_object_free(obj); +} + +__rust_helper void +rust_helper_drm_gem_shmem_object_print_info(struct drm_printer *p, unsigned int indent, + const struct drm_gem_object *obj) +{ + drm_gem_shmem_object_print_info(p, indent, obj); +} + +__rust_helper int +rust_helper_drm_gem_shmem_object_pin(struct drm_gem_object *obj) +{ + return drm_gem_shmem_object_pin(obj); +} + +__rust_helper void +rust_helper_drm_gem_shmem_object_unpin(struct drm_gem_object *obj) +{ + drm_gem_shmem_object_unpin(obj); +} + +__rust_helper struct sg_table * +rust_helper_drm_gem_shmem_object_get_sg_table(struct drm_gem_object *obj) +{ + return drm_gem_shmem_object_get_sg_table(obj); +} + +__rust_helper int +rust_helper_drm_gem_shmem_object_vmap(struct drm_gem_object *obj, + struct iosys_map *map) +{ + return drm_gem_shmem_object_vmap(obj, map); +} + +__rust_helper void +rust_helper_drm_gem_shmem_object_vunmap(struct drm_gem_object *obj, + struct iosys_map *map) +{ + drm_gem_shmem_object_vunmap(obj, map); +} + +__rust_helper int +rust_helper_drm_gem_shmem_object_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma) +{ + return drm_gem_shmem_object_mmap(obj, vma); +} + +#endif /* CONFIG_DRM_GEM_SHMEM_HELPER */ +#endif /* CONFIG_DRM */ diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs index 68bf33969a7d4..e7ebfb3f6ce6b 100644 --- a/rust/kernel/drm/gem/mod.rs +++ b/rust/kernel/drm/gem/mod.rs @@ -3,6 +3,8 @@ //! DRM GEM API //! //! C header: [`include/drm/drm_gem.h`](srctree/include/drm/drm_gem.h) +#[cfg(CONFIG_DRM_GEM_SHMEM_HELPER)] +pub mod shmem;

use crate::{ alloc::flags::*, @@ -50,6 +52,8 @@ unsafe fn dec_ref(obj: core::ptr::NonNull<Self>) { }; }

+pub(crate) use impl_aref_for_gem_obj; + /// A type alias for retrieving a [`Driver`]s [`DriverFile`] implementation from its /// [`DriverObject`] implementation. /// @@ -205,7 +209,6 @@ fn create_mmap_offset(&self) -> Result<u64> { impl<T: IntoGEMObject> BaseObject for T {}

/// Crate-private base operations shared by all GEM object classes. -#[expect(unused)] pub(crate) trait BaseObjectPrivate: IntoGEMObject { /// Return a pointer to this object's dma_resv. fn raw_dma_resv(&self) -> *mut bindings::dma_resv { diff --git a/rust/kernel/drm/gem/shmem.rs b/rust/kernel/drm/gem/shmem.rs new file mode 100644 index 0000000000000..6c77ace05d30a --- /dev/null +++ b/rust/kernel/drm/gem/shmem.rs @@ -0,0 +1,250 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! DRM GEM shmem helper objects +//! +//! C header: [`include/linux/drm/drm_gem_shmem_helper.h`](srctree/include/linux/drm/drm_gem_shmem_helper.h) + +// TODO: +// - There are a number of spots here that manually acquire/release the DMA reservation lock using +// dma_resv_(un)lock(). In the future we should add support for ww mutex, expose a method to +// acquire a reference to the WwMutex, and then use that directly instead of the C functions here. + +use crate::{ + container_of, + drm::{ + device, + driver, + gem, + private::Sealed, // + }, + error::{ + from_err_ptr, + to_result, // + }, + prelude::*, + scatterlist, + types::{ + ARef, + Opaque, // + }, // +}; +use core::{ + ops::{ + Deref, + DerefMut, // + }, + ptr::NonNull, +}; +use gem::{ + BaseObjectPrivate, + DriverObject, + IntoGEMObject, // +}; + +/// A struct for controlling the creation of shmem-backed GEM objects. +/// +/// This is used with [`Object::new()`] to control various properties that can only be set when +/// initially creating a shmem-backed GEM object. +#[derive(Default)] +pub struct ObjectConfig<'a, T: DriverObject> { + /// Whether to set the write-combine map flag. + pub map_wc: bool, + + /// Reuse the DMA reservation from another GEM object. + /// + /// The newly created [`Object`] will hold an owned refcount to `parent_resv_obj` if specified. + pub parent_resv_obj: Option<&'a Object<T>>, +} + +/// A shmem-backed GEM object. +/// +/// # Invariants +/// +/// `obj` contains a valid initialized `struct drm_gem_shmem_object` for the lifetime of this +/// object. +#[repr(C)] +#[pin_data] +pub struct Object<T: DriverObject> { + #[pin] + obj: Opaquebindings::drm_gem_shmem_object, + // Parent object that owns this object's DMA reservation object + parent_resv_obj: Option<ARef<Object<T>>>, + #[pin] + inner: T, +} + +super::impl_aref_for_gem_obj!(impl<T> for Object<T> where T: DriverObject); + +// SAFETY: All GEM objects are thread-safe. +unsafe impl<T: DriverObject> Send for Object<T> {} + +// SAFETY: All GEM objects are thread-safe. +unsafe impl<T: DriverObject> Sync for Object<T> {} + +impl<T: DriverObject> Object<T> { + /// `drm_gem_object_funcs` vtable suitable for GEM shmem objects. + const VTABLE: bindings::drm_gem_object_funcs = bindings::drm_gem_object_funcs { + free: Some(Self::free_callback), + open: Some(super::open_callback::<T>), + close: Some(super::close_callback::<T>), + print_info: Some(bindings::drm_gem_shmem_object_print_info), + export: None, + pin: Some(bindings::drm_gem_shmem_object_pin), + unpin: Some(bindings::drm_gem_shmem_object_unpin), + get_sg_table: Some(bindings::drm_gem_shmem_object_get_sg_table), + vmap: Some(bindings::drm_gem_shmem_object_vmap), + vunmap: Some(bindings::drm_gem_shmem_object_vunmap), + mmap: Some(bindings::drm_gem_shmem_object_mmap), + status: None, + rss: None, + // SAFETY: `drm_gem_shmem_vm_ops` is static const on the C side, so immutable references are + // safe here and such references shall be valid forever + vm_ops: unsafe { &bindings::drm_gem_shmem_vm_ops }, + evict: None, + }; + + /// Return a raw pointer to the embedded drm_gem_shmem_object. + fn as_raw_shmem(&self) -> *mut bindings::drm_gem_shmem_object { + self.obj.get() + } + + /// Create a new shmem-backed DRM object of the given size. + /// + /// Additional config options can be specified using `config`. + pub fn new( + dev: &device::Device<T::Driver>, + size: usize, + config: ObjectConfig<'_, T>, + args: T::Args, + ) -> Result<ARef<Self>> { + let new: Pin<KBox<Self>> = KBox::try_pin_init( + try_pin_init!(Self { + obj <- Opaque::init_zeroed(), + parent_resv_obj: config.parent_resv_obj.map(|p| p.into()), + inner <- T::new(dev, size, args), + }), + GFP_KERNEL, + )?; + + // SAFETY: `obj.as_raw()` is guaranteed to be valid by the initialization above. + unsafe { (*new.as_raw()).funcs = &Self::VTABLE }; + + // SAFETY: The arguments are all valid via the type invariants. + to_result(unsafe { bindings::drm_gem_shmem_init(dev.as_raw(), new.as_raw_shmem(), size) })?; + + // SAFETY: We never move out of `self`. + let new = KBox::into_raw(unsafe { Pin::into_inner_unchecked(new) }); + + // SAFETY: We're taking over the owned refcount from `drm_gem_shmem_init`. + let obj = unsafe { ARef::from_raw(NonNull::new_unchecked(new)) }; + + // Start filling out values from `config` + if let Some(parent_resv) = config.parent_resv_obj { + // SAFETY: We have yet to expose the new gem object outside of this function, so it is + // safe to modify this field. + unsafe { (*obj.obj.get()).base.resv = parent_resv.raw_dma_resv() }; + } + + // SAFETY: We have yet to expose this object outside of this function, so we're guaranteed + // to have exclusive access - thus making this safe to hold a mutable reference to. + let shmem = unsafe { &mut *obj.as_raw_shmem() }; + shmem.set_map_wc(config.map_wc); + + Ok(obj) + } + + /// Returns the `Device` that owns this GEM object. + pub fn dev(&self) -> &device::Device<T::Driver> { + // SAFETY: `dev` will have been initialized in `Self::new()` by `drm_gem_shmem_init()`. + unsafe { device::Device::from_raw((*self.as_raw()).dev) } + } + + extern "C" fn free_callback(obj: *mut bindings::drm_gem_object) { + // SAFETY: + // - DRM always passes a valid gem object here + // - We used drm_gem_shmem_create() in our create_gem_object callback, so we know that + // `obj` is contained within a drm_gem_shmem_object + let this = unsafe { container_of!(obj, bindings::drm_gem_shmem_object, base) }; + + // SAFETY: + // - We're in free_callback - so this function is safe to call. + // - We won't be using the gem resources on `this` after this call. + unsafe { bindings::drm_gem_shmem_release(this) }; + + // SAFETY: + // - We verified above that `obj` is valid, which makes `this` valid + // - This function is set in AllocOps, so we know that `this` is contained within a + // `Object<T>` + let this = unsafe { container_of!(Opaque::cast_from(this), Self, obj) }.cast_mut(); + + // SAFETY: We're recovering the Kbox<> we created in gem_create_object() + let _ = unsafe { KBox::from_raw(this) }; + } + + /// Creates (if necessary) and returns an immutable reference to a scatter-gather table of DMA + /// pages for this object. + /// + /// This will pin the object in memory. + #[inline] + pub fn sg_table(&self) -> Result<&scatterlist::SGTable> { + // SAFETY: + // - drm_gem_shmem_get_pages_sgt is thread-safe. + // - drm_gem_shmem_get_pages_sgt returns either a valid pointer to a scatterlist, or an + // error pointer. + let sgt = + from_err_ptr(unsafe { bindings::drm_gem_shmem_get_pages_sgt(self.as_raw_shmem()) })?; + + // SAFETY: We checked above that `sgt` is not an error pointer, so it must be a valid + // pointer to a scatterlist + Ok(unsafe { scatterlist::SGTable::from_raw(sgt) }) + } +} + +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> Sealed for Object<T> {} + +impl<T: DriverObject> gem::IntoGEMObject for Object<T> { + fn as_raw(&self) -> *mut bindings::drm_gem_object { + // SAFETY: + // - Our immutable reference is proof that this is safe to dereference. + // - `obj` is always a valid drm_gem_shmem_object via our type invariants. + unsafe { &raw mut (*self.obj.get()).base } + } + + unsafe fn from_raw<'a>(obj: *mut bindings::drm_gem_object) -> &'a Object<T> { + // SAFETY: The safety contract of from_gem_obj() guarantees that `obj` is contained within + // `Self` + unsafe { + let obj = Opaque::cast_from(container_of!(obj, bindings::drm_gem_shmem_object, base)); + + &*container_of!(obj, Object<T>, obj) + } + } +} + +impl<T: DriverObject> driver::AllocImpl for Object<T> { + type Driver = T::Driver; + + const ALLOC_OPS: driver::AllocOps = driver::AllocOps { + gem_create_object: None, + prime_handle_to_fd: None, + prime_fd_to_handle: None, + gem_prime_import: None, + gem_prime_import_sg_table: Some(bindings::drm_gem_shmem_prime_import_sg_table), + dumb_create: Some(bindings::drm_gem_shmem_dumb_create), + dumb_map_offset: None, + }; +}

One of the more obvious use cases for gem shmem objects is the ability to create mappings into their contents. So, let's hook this up in our rust bindings.

Similar to how we handle SGTables, we make sure there's two different types of mappings: owned mappings (kernel::drm::gem::shmem::VMap) and borrowed mappings (kernel::drm::gem::shmem::VMapRef).

Signed-off-by: Lyude Paul lyude@redhat.com

--- V7: * Switch over to the new iosys map bindings that use the Io trait V8: * Get rid of iosys_map bindings for now, only support non-iomem types * s/as_shmem()/as_raw_shmem()

rust/kernel/drm/gem/shmem.rs | 231 ++++++++++++++++++++++++++++++++++- 1 file changed, 230 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/drm/gem/shmem.rs b/rust/kernel/drm/gem/shmem.rs index 3fab5d76c197b..33f46fee87332 100644 --- a/rust/kernel/drm/gem/shmem.rs +++ b/rust/kernel/drm/gem/shmem.rs @@ -21,6 +21,11 @@ from_err_ptr, to_result, // }, + io::{ + Io, + IoCapable, + IoKnownSize, // + }, prelude::*, scatterlist, types::{ @@ -29,13 +34,22 @@ }, // }; use core::{ + ffi::c_void, + mem::{ + self, + MaybeUninit, // + }, ops::{ Deref, DerefMut, // }, - ptr::NonNull, + ptr::{ + self, + NonNull, // + }, }; use gem::{ + BaseObject, BaseObjectPrivate, DriverObject, IntoGEMObject, // @@ -217,6 +231,82 @@ pub fn owned_sg_table(&self) -> Result<SGTable<T>> { _owner: self.into(), }) } + + /// Attempt to create a [`RawIoSysMap`] from the gem object. + fn raw_vmap(&self) -> Result<*mut c_void> { + let mut map: MaybeUninitbindings::iosys_map = MaybeUninit::uninit(); + + // SAFETY: drm_gem_shmem_vmap can be called with the DMA reservation lock held + to_result(unsafe { + // TODO: see top of file + bindings::dma_resv_lock(self.raw_dma_resv(), ptr::null_mut()); + let ret = bindings::drm_gem_shmem_vmap_locked(self.as_raw_shmem(), map.as_mut_ptr()); + bindings::dma_resv_unlock(self.raw_dma_resv()); + ret + })?; + + // SAFETY: The call to drm_gem_shmem_vunmap_locked succeeded above, so we are guaranteed + // that map is properly initialized. + let map = unsafe { map.assume_init() }; + + // XXX: We don't currently support iomem allocations + if map.is_iomem { + // SAFETY: + // - The vmap operation above succeeded, making it safe to call vunmap + // - We checked that this is an iomem allocation, making it safe to read vaddr_iomem + unsafe { self.raw_vunmap(map.__bindgen_anon_1.vaddr_iomem) }; + + Err(ENOTSUPP) + } else { + // SAFETY: We checked that this is not an iomem allocation, making it safe to read vaddr + Ok(unsafe { map.__bindgen_anon_1.vaddr }) + } + } + + /// Unmap a [`RawIoSysMap`] from the gem object. + /// + /// # Safety + /// + /// - The caller promises that addr came from a prior call to [`Self::raw_vmap`] on this gem + /// object. + /// - The caller promises that the memory pointed to by addr will no longer be accesed through + /// this instance. + unsafe fn raw_vunmap(&self, vaddr: *mut c_void) { + let resv = self.raw_dma_resv(); + let mut map = bindings::iosys_map { + is_iomem: false, + __bindgen_anon_1: bindings::iosys_map__bindgen_ty_1 { vaddr }, + }; + + // SAFETY: + // - This function is safe to call with the DMA reservation lock held + // - Our `ARef` is proof that the underlying gem object here is initialized and thus safe to + // dereference. + unsafe { + // TODO: see top of file + bindings::dma_resv_lock(resv, ptr::null_mut()); + bindings::drm_gem_shmem_vunmap_locked(self.as_raw_shmem(), &mut map); + bindings::dma_resv_unlock(resv); + } + } + + /// Creates and returns a virtual kernel memory mapping for this object. + #[inline] + pub fn vmap<const SIZE: usize>(&self) -> Result<VMapRef<'_, T, SIZE>> { + Ok(VMapRef { + addr: self.raw_vmap()?, + owner: self, + }) + } + + /// Creates and returns an owned reference to a virtual kernel memory mapping for this object. + #[inline] + pub fn owned_vmap<const SIZE: usize>(&self) -> Result<VMap<T, SIZE>> { + Ok(VMap { + addr: self.raw_vmap()?, + owner: self.into(), + }) + } }

impl<T: DriverObject> Deref for Object<T> { @@ -268,6 +358,145 @@ impl<T: DriverObject> driver::AllocImpl for Object<T> { }; }

+macro_rules! impl_vmap_io_capable { + ($impl:ident, $ty:ty $(, $lifetime:lifetime )?) => { + impl<$( $lifetime ,)? D: DriverObject, const SIZE: usize> IoCapable<$ty> + for $impl<$( $lifetime ,)? D, SIZE> + { + #[inline(always)] + unsafe fn io_read(&self, address: usize) -> $ty { + let ptr = address as *mut $ty; + + // SAFETY: The safety contract of `io_read` guarantees that address is a valid + // address within the bounds of `Self` of at least the size of $ty, and is properly + // aligned. + unsafe { ptr::read(ptr) } + } + + #[inline(always)] + unsafe fn io_write(&self, value: $ty, address: usize) { + let ptr = address as *mut $ty; + + // SAFETY: The safety contract of `io_write` guarantees that address is a valid + // address within the bounds of `Self` of at least the size of $ty, and is properly + // aligned. + unsafe { ptr::write(ptr, value) } + } + } + }; +} + +// Implement various traits common to both VMap types +macro_rules! impl_vmap_common { + ($impl:ident $(, $lifetime:lifetime )?) => { + impl<$( $lifetime ,)? D, const SIZE: usize> $impl<$( $lifetime ,)? D, SIZE> + where + D: DriverObject, + { + /// Borrows a reference to the object that owns this virtual mapping. + #[inline(always)] + pub fn owner(&self) -> &Object<D> { + &self.owner + } + } + + impl<$( $lifetime ,)? D, const SIZE: usize> Drop for $impl<$( $lifetime ,)? D, SIZE> + where + D: DriverObject, + { + #[inline(always)] + fn drop(&mut self) { + // SAFETY: Our existence is proof that this map was previously created using + // self.owner + unsafe { self.owner.raw_vunmap(self.addr) }; + } + } + + impl<$( $lifetime ,)? D, const SIZE: usize> Io for $impl<$( $lifetime ,)? D, SIZE> + where + D: DriverObject, + { + #[inline(always)] + fn addr(&self) -> usize { + self.addr as usize + } + + #[inline(always)] + fn maxsize(&self) -> usize { + self.owner.size() + } + } + + impl<$( $lifetime ,)? D, const SIZE: usize> IoKnownSize for $impl<$( $lifetime ,)? D, SIZE> + where + D: DriverObject, + { + const MIN_SIZE: usize = SIZE; + } + + impl_vmap_io_capable!($impl, u8 $( , $lifetime )?); + impl_vmap_io_capable!($impl, u16 $( , $lifetime )?); + impl_vmap_io_capable!($impl, u32 $( , $lifetime )?); + #[cfg(CONFIG_64BIT)] + impl_vmap_io_capable!($impl, u64 $( , $lifetime )?); + }; +} + +/// An owned reference to a virtual mapping for a shmem-based GEM object in kernel address space. +/// +/// # Invariants +/// +/// - The size of `owner` is >= SIZE. +/// - The memory pointed to by addr is at least as large as `T`. +/// - The memory pointed to by addr remains valid at least until this object is dropped. +pub struct VMap<D: DriverObject, const SIZE: usize = 0> { + addr: *mut c_void, + owner: ARef<Object<D>>, +} + +impl_vmap_common!(VMap); + +impl<D: DriverObject, const SIZE: usize> Clone for VMap<D, SIZE> { + fn clone(&self) -> Self { + // SAFETY: We have a successful vmap already, so this can't fail + unsafe { self.owner.owned_vmap().unwrap_unchecked() } + } +} + +impl<'a, D: DriverObject, const SIZE: usize> From<VMapRef<'a, D, SIZE>> for VMap<D, SIZE> { + fn from(value: VMapRef<'a, D, SIZE>) -> Self { + let this = Self { + addr: value.addr, + owner: value.owner.into(), + }; + + mem::forget(value); + this + } +} + +// SAFETY: addr is guaranteed to be valid and accessible for the lifetime of VMap, ensuring its +// safe to send across threads. +unsafe impl<D: DriverObject, const SIZE: usize> Send for VMap<D, SIZE> {} +// SAFETY: addr is guaranteed to be valid and accessible for the lifetime of VMap, ensuring its +// safe to send across threads. +unsafe impl<D: DriverObject, const SIZE: usize> Sync for VMap<D, SIZE> {} + +/// A borrowed reference to a virtual mapping for a shmem-based GEM object in kernel address space. +pub struct VMapRef<'a, D: DriverObject, const SIZE: usize = 0> { + addr: *mut c_void, + owner: &'a Object<D>, +} + +impl_vmap_common!(VMapRef, 'a); + +impl<'a, D: DriverObject, const SIZE: usize> Clone for VMapRef<'a, D, SIZE> { + fn clone(&self) -> Self { + // SAFETY: We have a successful vmap already, so this can't fail + unsafe { self.owner.vmap().unwrap_unchecked() } + } +} + /// An owned reference to a scatter-gather table of DMA address spans for a GEM shmem object. /// /// This object holds an owned reference to the underlying GEM shmem object, ensuring that the