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Message-Id: <20241007202752.3096472-2-abdiel.janulgue@gmail.com>
Date: Mon, 7 Oct 2024 23:27:50 +0300
From: Abdiel Janulgue <abdiel.janulgue@...il.com>
To: rust-for-linux@...r.kernel.org,
aliceryhl@...gle.com
Cc: dakr@...hat.com,
linux-kernel@...r.kernel.org,
lyude@...hat.com,
airlied@...hat.com,
miguel.ojeda.sandonis@...il.com,
boqun.feng@...il.com
Subject: [PATCH 1/3] rust: page: replace the page pointer wrapper with Opaque
Replace NonNull with Opaque to make it possible to cast to a Page pointer
from a raw struct page pointer.
Signed-off-by: Abdiel Janulgue <abdiel.janulgue@...il.com>
---
rust/kernel/page.rs | 19 +++++++++++++------
1 file changed, 13 insertions(+), 6 deletions(-)
diff --git a/rust/kernel/page.rs b/rust/kernel/page.rs
index 208a006d587c..08ff09a25223 100644
--- a/rust/kernel/page.rs
+++ b/rust/kernel/page.rs
@@ -8,8 +8,9 @@
error::code::*,
error::Result,
uaccess::UserSliceReader,
+ types::Opaque,
};
-use core::ptr::{self, NonNull};
+use core::ptr::{self};
/// A bitwise shift for the page size.
pub const PAGE_SHIFT: usize = bindings::PAGE_SHIFT as usize;
@@ -25,8 +26,9 @@
/// # Invariants
///
/// The pointer is valid, and has ownership over the page.
+#[repr(transparent)]
pub struct Page {
- page: NonNull<bindings::page>,
+ page: Opaque<bindings::page>,
}
// SAFETY: Pages have no logic that relies on them staying on a given thread, so moving them across
@@ -65,15 +67,20 @@ pub fn alloc_page(flags: Flags) -> Result<Self, AllocError> {
// SAFETY: Depending on the value of `gfp_flags`, this call may sleep. Other than that, it
// is always safe to call this method.
let page = unsafe { bindings::alloc_pages(flags.as_raw(), 0) };
- let page = NonNull::new(page).ok_or(AllocError)?;
+ if page.is_null() {
+ return Err(AllocError);
+ }
+ // CAST: Self` is a `repr(transparent)` wrapper around `bindings::page`.
+ let ptr = page.cast::<Self>();
// INVARIANT: We just successfully allocated a page, so we now have ownership of the newly
// allocated page. We transfer that ownership to the new `Page` object.
- Ok(Self { page })
+ // SAFETY: According to invariant above ptr is valid.
+ Ok(unsafe { ptr::read(ptr) })
}
/// Returns a raw pointer to the page.
pub fn as_ptr(&self) -> *mut bindings::page {
- self.page.as_ptr()
+ self.page.get()
}
/// Runs a piece of code with this page mapped to an address.
@@ -245,6 +252,6 @@ pub unsafe fn copy_from_user_slice_raw(
impl Drop for Page {
fn drop(&mut self) {
// SAFETY: By the type invariants, we have ownership of the page and can free it.
- unsafe { bindings::__free_pages(self.page.as_ptr(), 0) };
+ unsafe { bindings::__free_pages(self.page.get(), 0) };
}
}
--
2.34.1
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