From 22ab0641b939967f630d108e33a3582841ad6846 Mon Sep 17 00:00:00 2001 From: Danilo Krummrich Date: Thu, 31 Jul 2025 17:48:07 +0200 Subject: rust: drm: ensure kmalloc() compatible Layout drm::Device is allocated through __drm_dev_alloc() (which uses kmalloc()) and the driver private data, ::Data, is initialized in-place. Due to the order of fields in drm::Device pub struct Device { dev: Opaque, 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") Reviewed-by: Alice Ryhl Link: https://lore.kernel.org/r/20250731154919.4132-3-dakr@kernel.org Signed-off-by: Danilo Krummrich --- rust/kernel/drm/device.rs | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'rust/kernel/drm/device.rs') 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 @@ use crate::{ 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 Device { /// Create a new `drm::Device` for a `drm::Driver`. pub fn new(dev: &device::Device, data: impl PinInit) -> Result> { + // `__drm_dev_alloc` uses `kmalloc()` to allocate memory, hence ensure a `kmalloc()` + // compatible `Layout`. + let layout = Kmalloc::aligned_layout(Layout::new::()); + // 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 @@ impl Device { bindings::__drm_dev_alloc( dev.as_raw(), &Self::VTABLE, - mem::size_of::(), + layout.size(), mem::offset_of!(Self, dev), ) } -- cgit v1.2.3 From 0c04a81c1d0214d5b2025f805ccec1ac37c96b08 Mon Sep 17 00:00:00 2001 From: Danilo Krummrich Date: Thu, 31 Jul 2025 17:48:08 +0200 Subject: rust: drm: remove pin annotations from drm::Device The #[pin_data] and #[pin] annotations are not necessary for drm::Device, since we don't use any pin-init macros, but only __pinned_init() on the impl PinInit argument of drm::Device::new(). Fixes: 1e4b8896c0f3 ("rust: drm: add device abstraction") Reviewed-by: Benno Lossin Link: https://lore.kernel.org/r/20250731154919.4132-4-dakr@kernel.org Signed-off-by: Danilo Krummrich --- rust/kernel/drm/device.rs | 2 -- 1 file changed, 2 deletions(-) (limited to 'rust/kernel/drm/device.rs') diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs index d19410deaf6c..d0a9528121f1 100644 --- a/rust/kernel/drm/device.rs +++ b/rust/kernel/drm/device.rs @@ -54,10 +54,8 @@ macro_rules! drm_legacy_fields { /// /// `self.dev` is a valid instance of a `struct device`. #[repr(C)] -#[pin_data] pub struct Device { dev: Opaque, - #[pin] data: T::Data, } -- cgit v1.2.3 From 360077278ba62e81310080f075a1a3028e778ef9 Mon Sep 17 00:00:00 2001 From: Danilo Krummrich Date: Thu, 31 Jul 2025 17:48:09 +0200 Subject: rust: drm: don't pass the address of drm::Device to drm_dev_put() In drm_dev_put() call in AlwaysRefCounted::dec_ref() we rely on struct drm_device to be the first field in drm::Device, whereas everywhere else we correctly obtain the address of the actual struct drm_device. Analogous to the from_drm_device() helper, provide the into_drm_device() helper in order to address this. Fixes: 1e4b8896c0f3 ("rust: drm: add device abstraction") Reviewed-by: Alice Ryhl Link: https://lore.kernel.org/r/20250731154919.4132-5-dakr@kernel.org Signed-off-by: Danilo Krummrich --- rust/kernel/drm/device.rs | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) (limited to 'rust/kernel/drm/device.rs') diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs index d0a9528121f1..d29c477e89a8 100644 --- a/rust/kernel/drm/device.rs +++ b/rust/kernel/drm/device.rs @@ -120,9 +120,13 @@ impl Device { // - `raw_data` is a valid pointer to uninitialized memory. // - `raw_data` will not move until it is dropped. unsafe { data.__pinned_init(raw_data) }.inspect_err(|_| { - // SAFETY: `__drm_dev_alloc()` was successful, hence `raw_drm` must be valid and the + // SAFETY: `raw_drm` is a valid pointer to `Self`, given that `__drm_dev_alloc` was + // successful. + let drm_dev = unsafe { Self::into_drm_device(raw_drm) }; + + // SAFETY: `__drm_dev_alloc()` was successful, hence `drm_dev` must be valid and the // refcount must be non-zero. - unsafe { bindings::drm_dev_put(ptr::addr_of_mut!((*raw_drm.as_ptr()).dev).cast()) }; + unsafe { bindings::drm_dev_put(drm_dev) }; })?; // SAFETY: The reference count is one, and now we take ownership of that reference as a @@ -143,6 +147,14 @@ impl Device { unsafe { crate::container_of!(Opaque::cast_from(ptr), Self, dev) }.cast_mut() } + /// # Safety + /// + /// `ptr` must be a valid pointer to `Self`. + unsafe fn into_drm_device(ptr: NonNull) -> *mut bindings::drm_device { + // SAFETY: By the safety requirements of this function, `ptr` is a valid pointer to `Self`. + unsafe { &raw mut (*ptr.as_ptr()).dev }.cast() + } + /// Not intended to be called externally, except via declare_drm_ioctls!() /// /// # Safety @@ -192,8 +204,11 @@ unsafe impl AlwaysRefCounted for Device { } unsafe fn dec_ref(obj: NonNull) { + // SAFETY: `obj` is a valid pointer to `Self`. + let drm_dev = unsafe { Self::into_drm_device(obj) }; + // SAFETY: The safety requirements guarantee that the refcount is non-zero. - unsafe { bindings::drm_dev_put(obj.cast().as_ptr()) }; + unsafe { bindings::drm_dev_put(drm_dev) }; } } -- cgit v1.2.3 From f1f2a22b8683d7ac38821d4508d4549a2f0c0a0a Mon Sep 17 00:00:00 2001 From: Shankari Anand Date: Fri, 15 Aug 2025 21:47:06 +0530 Subject: rust: drm: update ARef and AlwaysRefCounted imports from sync::aref Update call sites in drm to import `ARef` and `AlwaysRefCounted` from `sync::aref` instead of `types`. This aligns with the ongoing effort to move `ARef` and `AlwaysRefCounted` to sync. Suggested-by: Benno Lossin Link: https://github.com/Rust-for-Linux/linux/issues/1173 Signed-off-by: Shankari Anand Reviewed-by: Benno Lossin Reviewed-by: Elle Rhumsaa Link: https://lore.kernel.org/r/20250815161706.1324860-1-shankari.ak0208@gmail.com Signed-off-by: Danilo Krummrich --- rust/kernel/drm/device.rs | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'rust/kernel/drm/device.rs') diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs index 3bb7c83966cf..4a62f9fd88b7 100644 --- a/rust/kernel/drm/device.rs +++ b/rust/kernel/drm/device.rs @@ -10,7 +10,8 @@ use crate::{ error::from_err_ptr, error::Result, prelude::*, - types::{ARef, AlwaysRefCounted, Opaque}, + sync::aref::{ARef, AlwaysRefCounted}, + types::Opaque, }; use core::{mem, ops::Deref, ptr, ptr::NonNull}; -- cgit v1.2.3 From c2783c7cfefd55b1a5be781679cbee5191c0fd87 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Wed, 30 Jul 2025 15:07:15 +0200 Subject: rust: drm: fix `srctree/` links These `srctree/` links pointed inside `linux/`, but they are directly under `drm/`. Thus fix them. This cleans a future warning that will check our `srctree/` links. Cc: stable@vger.kernel.org Fixes: a98a73be9ee9 ("rust: drm: file: Add File abstraction") Fixes: c284d3e42338 ("rust: drm: gem: Add GEM object abstraction") Fixes: 07c9016085f9 ("rust: drm: add driver abstractions") Fixes: 1e4b8896c0f3 ("rust: drm: add device abstraction") Fixes: 9a69570682b1 ("rust: drm: ioctl: Add DRM ioctl abstraction") Acked-by: Danilo Krummrich Reviewed-by: Daniel Almeida Signed-off-by: Miguel Ojeda --- rust/kernel/drm/device.rs | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'rust/kernel/drm/device.rs') diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs index d29c477e89a8..f8f1db5eeb0f 100644 --- a/rust/kernel/drm/device.rs +++ b/rust/kernel/drm/device.rs @@ -2,7 +2,7 @@ //! DRM device. //! -//! C header: [`include/linux/drm/drm_device.h`](srctree/include/linux/drm/drm_device.h) +//! C header: [`include/drm/drm_device.h`](srctree/include/drm/drm_device.h) use crate::{ alloc::allocator::Kmalloc, -- cgit v1.2.3 From 23218425cb2f18785539856f9aabfa4a4f47b3c5 Mon Sep 17 00:00:00 2001 From: Tamir Duberstein Date: Wed, 13 Aug 2025 11:41:56 -0400 Subject: rust: drm: use `core::ffi::CStr` method names Prepare for `core::ffi::CStr` taking the place of `kernel::str::CStr` by avoid methods that only exist on the latter. Link: https://github.com/Rust-for-Linux/linux/issues/1075 Acked-by: Greg Kroah-Hartman Reviewed-by: Alice Ryhl Reviewed-by: Benno Lossin Acked-by: Danilo Krummrich Signed-off-by: Tamir Duberstein Signed-off-by: Miguel Ojeda --- rust/kernel/drm/device.rs | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'rust/kernel/drm/device.rs') diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs index f8f1db5eeb0f..0956ba0f64de 100644 --- a/rust/kernel/drm/device.rs +++ b/rust/kernel/drm/device.rs @@ -82,8 +82,8 @@ impl Device { major: T::INFO.major, minor: T::INFO.minor, patchlevel: T::INFO.patchlevel, - name: T::INFO.name.as_char_ptr().cast_mut(), - desc: T::INFO.desc.as_char_ptr().cast_mut(), + name: crate::str::as_char_ptr_in_const_context(T::INFO.name).cast_mut(), + desc: crate::str::as_char_ptr_in_const_context(T::INFO.desc).cast_mut(), driver_features: drm::driver::FEAT_GEM, ioctls: T::IOCTLS.as_ptr(), -- cgit v1.2.3