drm::Device is allocated through __drm_dev_alloc() (which uses
kmalloc()) and the driver private data, <T as drm::Driver>::Data, is
initialized in-place.
Due to the order of fields in drm::Device
pub struct Device<T: drm::Driver> {
dev: Opaque<bindings::drm_device>,
data: T::Data,
}
even with an arbitrary large alignment requirement of T::Data it can't
happen that the size of Device is smaller than its alignment requirement.
However, let's not rely on this subtle circumstance and create a proper
kmalloc() compatible Layout.
Fixes: 1e4b8896c0f3 ("rust: drm: add device abstraction")
Signed-off-by: Danilo Krummrich <d...@kernel.org>
---
rust/kernel/drm/device.rs | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs
index 3bb7c83966cf..d19410deaf6c 100644
--- a/rust/kernel/drm/device.rs
+++ b/rust/kernel/drm/device.rs
@@ -5,6 +5,7 @@
//! C header:
[`include/linux/drm/drm_device.h`](srctree/include/linux/drm/drm_device.h)
use crate::{
+ alloc::allocator::Kmalloc,
bindings, device, drm,
drm::driver::AllocImpl,
error::from_err_ptr,
@@ -12,7 +13,7 @@
prelude::*,
types::{ARef, AlwaysRefCounted, Opaque},
};
-use core::{mem, ops::Deref, ptr, ptr::NonNull};
+use core::{alloc::Layout, mem, ops::Deref, ptr, ptr::NonNull};
#[cfg(CONFIG_DRM_LEGACY)]
macro_rules! drm_legacy_fields {
@@ -96,6 +97,10 @@ impl<T: drm::Driver> Device<T> {
/// Create a new `drm::Device` for a `drm::Driver`.
pub fn new(dev: &device::Device, data: impl PinInit<T::Data, Error>) ->
Result<ARef<Self>> {
+ // `__drm_dev_alloc` uses `kmalloc()` to allocate memory, hence ensure
a `kmalloc()`
+ // compatible `Layout`.
+ let layout = Kmalloc::aligned_layout(Layout::new::<Self>());
+
// SAFETY:
// - `VTABLE`, as a `const` is pinned to the read-only section of the
compilation,
// - `dev` is valid by its type invarants,
@@ -103,7 +108,7 @@ pub fn new(dev: &device::Device, data: impl
PinInit<T::Data, Error>) -> Result<A
bindings::__drm_dev_alloc(
dev.as_raw(),
&Self::VTABLE,
- mem::size_of::<Self>(),
+ layout.size(),
mem::offset_of!(Self, dev),
)
}
--
2.50.0
