Adds a `PhantomPinned` field to `Opaque<T>`. This removes the last Rust
guarantee: the assumption that the type `T` can be freely moved. This is
not the case for many types from the C side (e.g. if they contain a
`struct list_head`). This change removes the need to add a
`PhantomPinned` field manually to Rust structs that contain C structs
which must not be moved.
Signed-off-by: Benno Lossin <[email protected]>
---
This patch depends on the patch that swaps `UnsafeCell` with
`MaybeUninit` inside `Opaque` [1].
[1]: https://lore.kernel.org/rust-for-linux/[email protected]/
---
rust/kernel/types.rs | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)
diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index fb41635f1e1f..e664a2beef30 100644
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -6,7 +6,7 @@
use alloc::boxed::Box;
use core::{
cell::UnsafeCell,
- marker::PhantomData,
+ marker::{PhantomData, PhantomPinned},
mem::MaybeUninit,
ops::{Deref, DerefMut},
ptr::NonNull,
@@ -224,17 +224,26 @@ fn drop(&mut self) {
///
/// This is meant to be used with FFI objects that are never interpreted by Rust code.
#[repr(transparent)]
-pub struct Opaque<T>(UnsafeCell<MaybeUninit<T>>);
+pub struct Opaque<T> {
+ value: UnsafeCell<MaybeUninit<T>>,
+ _pin: PhantomPinned,
+}
impl<T> Opaque<T> {
/// Creates a new opaque value.
pub const fn new(value: T) -> Self {
- Self(UnsafeCell::new(MaybeUninit::new(value)))
+ Self {
+ value: UnsafeCell::new(MaybeUninit::new(value)),
+ _pin: PhantomPinned,
+ }
}
/// Creates an uninitialised value.
pub const fn uninit() -> Self {
- Self(UnsafeCell::new(MaybeUninit::uninit()))
+ Self {
+ value: UnsafeCell::new(MaybeUninit::uninit()),
+ _pin: PhantomPinned,
+ }
}
/// Creates a pin-initializer from the given initializer closure.
@@ -258,7 +267,7 @@ pub fn ffi_init(init_func: impl FnOnce(*mut T)) -> impl PinInit<Self> {
/// Returns a raw pointer to the opaque data.
pub fn get(&self) -> *mut T {
- UnsafeCell::get(&self.0).cast::<T>()
+ UnsafeCell::get(&self.value).cast::<T>()
}
/// Gets the value behind `this`.
--
2.41.0
On 6/30/23 17:03, Benno Lossin wrote:
> Adds a `PhantomPinned` field to `Opaque<T>`. This removes the last Rust
> guarantee: the assumption that the type `T` can be freely moved. This is
> not the case for many types from the C side (e.g. if they contain a
> `struct list_head`). This change removes the need to add a
> `PhantomPinned` field manually to Rust structs that contain C structs
> which must not be moved.
>
> Signed-off-by: Benno Lossin <[email protected]>
Reviewed-by: Alice Ryhl <[email protected]>
On Fri, 30 Jun 2023 15:03:23 +0000
Benno Lossin <[email protected]> wrote:
> Adds a `PhantomPinned` field to `Opaque<T>`. This removes the last Rust
> guarantee: the assumption that the type `T` can be freely moved. This is
> not the case for many types from the C side (e.g. if they contain a
> `struct list_head`). This change removes the need to add a
> `PhantomPinned` field manually to Rust structs that contain C structs
> which must not be moved.
>
> Signed-off-by: Benno Lossin <[email protected]>
Reviewed-by: Gary Guo <[email protected]>
> ---
> This patch depends on the patch that swaps `UnsafeCell` with
> `MaybeUninit` inside `Opaque` [1].
>
> [1]: https://lore.kernel.org/rust-for-linux/[email protected]/
> ---
> rust/kernel/types.rs | 19 ++++++++++++++-----
> 1 file changed, 14 insertions(+), 5 deletions(-)
>
> diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
> index fb41635f1e1f..e664a2beef30 100644
> --- a/rust/kernel/types.rs
> +++ b/rust/kernel/types.rs
> @@ -6,7 +6,7 @@
> use alloc::boxed::Box;
> use core::{
> cell::UnsafeCell,
> - marker::PhantomData,
> + marker::{PhantomData, PhantomPinned},
> mem::MaybeUninit,
> ops::{Deref, DerefMut},
> ptr::NonNull,
> @@ -224,17 +224,26 @@ fn drop(&mut self) {
> ///
> /// This is meant to be used with FFI objects that are never interpreted by Rust code.
> #[repr(transparent)]
> -pub struct Opaque<T>(UnsafeCell<MaybeUninit<T>>);
> +pub struct Opaque<T> {
> + value: UnsafeCell<MaybeUninit<T>>,
> + _pin: PhantomPinned,
> +}
>
> impl<T> Opaque<T> {
> /// Creates a new opaque value.
> pub const fn new(value: T) -> Self {
> - Self(UnsafeCell::new(MaybeUninit::new(value)))
> + Self {
> + value: UnsafeCell::new(MaybeUninit::new(value)),
> + _pin: PhantomPinned,
> + }
> }
>
> /// Creates an uninitialised value.
> pub const fn uninit() -> Self {
> - Self(UnsafeCell::new(MaybeUninit::uninit()))
> + Self {
> + value: UnsafeCell::new(MaybeUninit::uninit()),
> + _pin: PhantomPinned,
> + }
> }
>
> /// Creates a pin-initializer from the given initializer closure.
> @@ -258,7 +267,7 @@ pub fn ffi_init(init_func: impl FnOnce(*mut T)) -> impl PinInit<Self> {
>
> /// Returns a raw pointer to the opaque data.
> pub fn get(&self) -> *mut T {
> - UnsafeCell::get(&self.0).cast::<T>()
> + UnsafeCell::get(&self.value).cast::<T>()
> }
>
> /// Gets the value behind `this`.
Benno Lossin <[email protected]> writes:
> Adds a `PhantomPinned` field to `Opaque<T>`. This removes the last Rust
> guarantee: the assumption that the type `T` can be freely moved. This is
> not the case for many types from the C side (e.g. if they contain a
> `struct list_head`). This change removes the need to add a
> `PhantomPinned` field manually to Rust structs that contain C structs
> which must not be moved.
>
> Signed-off-by: Benno Lossin <[email protected]>
> ---
Reviewed-by: Andreas Hindborg <[email protected]>
> This patch depends on the patch that swaps `UnsafeCell` with
> `MaybeUninit` inside `Opaque` [1].
>
> [1]: https://lore.kernel.org/rust-for-linux/[email protected]/
> ---
> rust/kernel/types.rs | 19 ++++++++++++++-----
> 1 file changed, 14 insertions(+), 5 deletions(-)
>
> diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
> index fb41635f1e1f..e664a2beef30 100644
> --- a/rust/kernel/types.rs
> +++ b/rust/kernel/types.rs
> @@ -6,7 +6,7 @@
> use alloc::boxed::Box;
> use core::{
> cell::UnsafeCell,
> - marker::PhantomData,
> + marker::{PhantomData, PhantomPinned},
> mem::MaybeUninit,
> ops::{Deref, DerefMut},
> ptr::NonNull,
> @@ -224,17 +224,26 @@ fn drop(&mut self) {
> ///
> /// This is meant to be used with FFI objects that are never interpreted by Rust code.
> #[repr(transparent)]
> -pub struct Opaque<T>(UnsafeCell<MaybeUninit<T>>);
> +pub struct Opaque<T> {
> + value: UnsafeCell<MaybeUninit<T>>,
> + _pin: PhantomPinned,
> +}
>
> impl<T> Opaque<T> {
> /// Creates a new opaque value.
> pub const fn new(value: T) -> Self {
> - Self(UnsafeCell::new(MaybeUninit::new(value)))
> + Self {
> + value: UnsafeCell::new(MaybeUninit::new(value)),
> + _pin: PhantomPinned,
> + }
> }
>
> /// Creates an uninitialised value.
> pub const fn uninit() -> Self {
> - Self(UnsafeCell::new(MaybeUninit::uninit()))
> + Self {
> + value: UnsafeCell::new(MaybeUninit::uninit()),
> + _pin: PhantomPinned,
> + }
> }
>
> /// Creates a pin-initializer from the given initializer closure.
> @@ -258,7 +267,7 @@ pub fn ffi_init(init_func: impl FnOnce(*mut T)) -> impl PinInit<Self> {
>
> /// Returns a raw pointer to the opaque data.
> pub fn get(&self) -> *mut T {
> - UnsafeCell::get(&self.0).cast::<T>()
> + UnsafeCell::get(&self.value).cast::<T>()
> }
>
> /// Gets the value behind `this`.
On Fri, Jun 30, 2023 at 5:03 PM Benno Lossin <[email protected]> wrote:
>
> Adds a `PhantomPinned` field to `Opaque<T>`. This removes the last Rust
> guarantee: the assumption that the type `T` can be freely moved. This is
> not the case for many types from the C side (e.g. if they contain a
> `struct list_head`). This change removes the need to add a
> `PhantomPinned` field manually to Rust structs that contain C structs
> which must not be moved.
>
> Signed-off-by: Benno Lossin <[email protected]>
Applied to `rust-next` -- thanks everyone!
Cheers,
Miguel