1 files changed, 78 insertions, 12 deletions

diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
index aa2dfa9dca4c..08fd31bf72d2 100644
--- a/rust/kernel/alloc/allocator.rs
+++ b/rust/kernel/alloc/allocator.rs
@@ -15,8 +15,14 @@ use core::ptr::NonNull;
 
 use crate::alloc::{AllocError, Allocator};
 use crate::bindings;
+use crate::page;
 use crate::pr_warn;
 
+const ARCH_KMALLOC_MINALIGN: usize = bindings::ARCH_KMALLOC_MINALIGN;
+
+mod iter;
+pub use self::iter::VmallocPageIter;
+
 /// The contiguous kernel allocator.
 ///
 /// `Kmalloc` is typically used for physically contiguous allocations up to page size, but also
@@ -43,17 +49,6 @@ pub struct Vmalloc;
 /// For more details see [self].
 pub struct KVmalloc;
 
-/// Returns a proper size to alloc a new object aligned to `new_layout`'s alignment.
-fn aligned_size(new_layout: Layout) -> usize {
-    // Customized layouts from `Layout::from_size_align()` can have size < align, so pad first.
-    let layout = new_layout.pad_to_align();
-
-    // Note that `layout.size()` (after padding) is guaranteed to be a multiple of `layout.align()`
-    // which together with the slab guarantees means the `krealloc` will return a properly aligned
-    // object (see comments in `kmalloc()` for more information).
-    layout.size()
-}
-
 /// # Invariants
 ///
 /// One of the following: `krealloc`, `vrealloc`, `kvrealloc`.
@@ -88,7 +83,7 @@ impl ReallocFunc {
         old_layout: Layout,
         flags: Flags,
     ) -> Result<NonNull<[u8]>, AllocError> {
-        let size = aligned_size(layout);
+        let size = layout.size();
         let ptr = match ptr {
             Some(ptr) => {
                 if old_layout.size() == 0 {
@@ -123,11 +118,24 @@ impl ReallocFunc {
     }
 }
 
+impl Kmalloc {
+    /// Returns a [`Layout`] that makes [`Kmalloc`] fulfill the requested size and alignment of
+    /// `layout`.
+    pub fn aligned_layout(layout: Layout) -> Layout {
+        // Note that `layout.size()` (after padding) is guaranteed to be a multiple of
+        // `layout.align()` which together with the slab guarantees means that `Kmalloc` will return
+        // a properly aligned object (see comments in `kmalloc()` for more information).
+        layout.pad_to_align()
+    }
+}
+
 // 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,
 // - `realloc` satisfies the guarantees, since `ReallocFunc::call` has the same.
 unsafe impl Allocator for Kmalloc {
+    const MIN_ALIGN: usize = ARCH_KMALLOC_MINALIGN;
+
     #[inline]
     unsafe fn realloc(
         ptr: Option<NonNull<u8>>,
@@ -135,16 +143,68 @@ unsafe impl Allocator for Kmalloc {
         old_layout: Layout,
         flags: Flags,
     ) -> Result<NonNull<[u8]>, AllocError> {
+        let layout = Kmalloc::aligned_layout(layout);
+
         // SAFETY: `ReallocFunc::call` has the same safety requirements as `Allocator::realloc`.
         unsafe { ReallocFunc::KREALLOC.call(ptr, layout, old_layout, flags) }
     }
 }
 
+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,
 // - `realloc` satisfies the guarantees, since `ReallocFunc::call` has the same.
 unsafe impl Allocator for Vmalloc {
+    const MIN_ALIGN: usize = kernel::page::PAGE_SIZE;
+
     #[inline]
     unsafe fn realloc(
         ptr: Option<NonNull<u8>>,
@@ -169,6 +229,8 @@ unsafe impl Allocator for Vmalloc {
 // - passing a pointer to a valid memory allocation is OK,
 // - `realloc` satisfies the guarantees, since `ReallocFunc::call` has the same.
 unsafe impl Allocator for KVmalloc {
+    const MIN_ALIGN: usize = ARCH_KMALLOC_MINALIGN;
+
     #[inline]
     unsafe fn realloc(
         ptr: Option<NonNull<u8>>,
@@ -176,6 +238,10 @@ unsafe impl Allocator for KVmalloc {
         old_layout: Layout,
         flags: Flags,
     ) -> Result<NonNull<[u8]>, AllocError> {
+        // `KVmalloc` may use the `Kmalloc` backend, hence we have to enforce a `Kmalloc`
+        // compatible layout.
+        let layout = Kmalloc::aligned_layout(layout);
+
         // TODO: Support alignments larger than PAGE_SIZE.
         if layout.align() > bindings::PAGE_SIZE {
             pr_warn!("KVmalloc does not support alignments larger than PAGE_SIZE yet.\n");