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authorDanilo Krummrich <dakr@kernel.org>2024-10-04 17:41:12 +0200
committerMiguel Ojeda <ojeda@kernel.org>2024-10-15 22:56:59 +0200
commit61c004781d6b928443052e7a6cf84b35d4f61401 (patch)
tree658dcd52aeb70c7bdace12eee020f1acea6682a0 /rust/kernel/alloc/allocator.rs
parent5a888c28e3b4ff6f54a53fca33951537d135e7f1 (diff)
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rust: alloc: implement `Vmalloc` allocator
Implement `Allocator` for `Vmalloc`, the kernel's virtually contiguous allocator, typically used for larger objects, (much) larger than page size. All memory allocations made with `Vmalloc` end up in `vrealloc()`. Reviewed-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Benno Lossin <benno.lossin@proton.me> Reviewed-by: Gary Guo <gary@garyguo.net> Signed-off-by: Danilo Krummrich <dakr@kernel.org> Link: https://lore.kernel.org/r/20241004154149.93856-9-dakr@kernel.org Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Diffstat (limited to 'rust/kernel/alloc/allocator.rs')
-rw-r--r--rust/kernel/alloc/allocator.rs37
1 files changed, 37 insertions, 0 deletions
diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
index 272c581e24a0..ee4c828cbd58 100644
--- a/rust/kernel/alloc/allocator.rs
+++ b/rust/kernel/alloc/allocator.rs
@@ -15,6 +15,7 @@ use core::ptr::NonNull;
use crate::alloc::{AllocError, Allocator};
use crate::bindings;
+use crate::pr_warn;
/// The contiguous kernel allocator.
///
@@ -24,6 +25,15 @@ use crate::bindings;
/// For more details see [self].
pub struct Kmalloc;
+/// The virtually contiguous kernel allocator.
+///
+/// `Vmalloc` allocates pages from the page level allocator and maps them into the contiguous kernel
+/// virtual space. It is typically used for large allocations. The memory allocated with this
+/// allocator is not physically contiguous.
+///
+/// For more details see [self].
+pub struct Vmalloc;
+
/// 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.
@@ -63,6 +73,9 @@ impl ReallocFunc {
// INVARIANT: `krealloc` satisfies the type invariants.
const KREALLOC: Self = Self(bindings::krealloc);
+ // INVARIANT: `vrealloc` satisfies the type invariants.
+ const VREALLOC: Self = Self(bindings::vrealloc);
+
/// # Safety
///
/// This method has the same safety requirements as [`Allocator::realloc`].
@@ -168,6 +181,30 @@ unsafe impl GlobalAlloc for Kmalloc {
}
}
+// 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 {
+ #[inline]
+ unsafe fn realloc(
+ ptr: Option<NonNull<u8>>,
+ layout: Layout,
+ old_layout: Layout,
+ flags: Flags,
+ ) -> Result<NonNull<[u8]>, AllocError> {
+ // TODO: Support alignments larger than PAGE_SIZE.
+ if layout.align() > bindings::PAGE_SIZE {
+ pr_warn!("Vmalloc does not support alignments larger than PAGE_SIZE yet.\n");
+ return Err(AllocError);
+ }
+
+ // SAFETY: If not `None`, `ptr` is guaranteed to point to valid memory, which was previously
+ // allocated with this `Allocator`.
+ unsafe { ReallocFunc::VREALLOC.call(ptr, layout, old_layout, flags) }
+ }
+}
+
#[global_allocator]
static ALLOCATOR: Kmalloc = Kmalloc;