Commit 8e92c990 authored by Danilo Krummrich's avatar Danilo Krummrich
Browse files

rust: alloc: vmalloc: implement Vmalloc::to_page() 



Implement an abstraction of vmalloc_to_page() for subsequent use in the
AsPageIter implementation of VBox and VVec.

Reviewed-by: default avatarAlexandre Courbot <acourbot@nvidia.com>
Tested-by: default avatarAlexandre Courbot <acourbot@nvidia.com>
Reviewed-by: default avatarAlice Ryhl <aliceryhl@google.com>
Reviewed-by: default avatarDaniel Almeida <daniel.almeida@collabora.com>
Link: https://lore.kernel.org/r/20250820145434.94745-3-dakr@kernel.org


Signed-off-by: default avatarDanilo Krummrich <dakr@kernel.org>
parent 467971a9

rust/kernel/alloc/allocator.rs

+49 −0
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ 


use crate::alloc::{AllocError, Allocator};

use crate::bindings;

use crate::page;

use crate::pr_warn;



/// The contiguous kernel allocator.
@@ -140,6 +141,54 @@ unsafe fn realloc( 
    }

}



impl Vmalloc {

    /// Convert a pointer to a [`Vmalloc`] allocation to a [`page::BorrowedPage`].

    ///

    /// # Examples

    ///

    /// ```

    /// # use core::ptr::{NonNull, from_mut};

    /// # use kernel::{page, prelude::*};

    /// use kernel::alloc::allocator::Vmalloc;

    ///

    /// let mut vbox = VBox::<[u8; page::PAGE_SIZE]>::new_uninit(GFP_KERNEL)?;

    ///

    /// {

    ///     // SAFETY: By the type invariant of `Box` the inner pointer of `vbox` is non-null.

    ///     let ptr = unsafe { NonNull::new_unchecked(from_mut(&mut *vbox)) };

    ///

    ///     // SAFETY:

    ///     // `ptr` is a valid pointer to a `Vmalloc` allocation.

    ///     // `ptr` is valid for the entire lifetime of `page`.

    ///     let page = unsafe { Vmalloc::to_page(ptr.cast()) };

    ///

    ///     // SAFETY: There is no concurrent read or write to the same page.

    ///     unsafe { page.fill_zero_raw(0, page::PAGE_SIZE)? };

    /// }

    /// # Ok::<(), Error>(())

    /// ```

    ///

    /// # Safety

    ///

    /// - `ptr` must be a valid pointer to a [`Vmalloc`] allocation.

    /// - `ptr` must remain valid for the entire duration of `'a`.

    pub unsafe fn to_page<'a>(ptr: NonNull<u8>) -> page::BorrowedPage<'a> {

        // SAFETY: `ptr` is a valid pointer to `Vmalloc` memory.

        let page = unsafe { bindings::vmalloc_to_page(ptr.as_ptr().cast()) };



        // SAFETY: `vmalloc_to_page` returns a valid pointer to a `struct page` for a valid pointer

        // to `Vmalloc` memory.

        let page = unsafe { NonNull::new_unchecked(page) };



        // SAFETY:

        // - `page` is a valid pointer to a `struct page`, given that by the safety requirements of

        //   this function `ptr` is a valid pointer to a `Vmalloc` allocation.

        // - By the safety requirements of this function `ptr` is valid for the entire lifetime of

        //   `'a`.

        unsafe { page::BorrowedPage::from_raw(page) }

    }

}



// SAFETY: `realloc` delegates to `ReallocFunc::call`, which guarantees that

// - memory remains valid until it is explicitly freed,

// - passing a pointer to a valid memory allocation is OK,