From: Danilo Krummrich dakr@kernel.org
commit a34822d1c4c93085f635b922441a017bd7e959b0 upstream.
Implement `Allocator` for `Kmalloc`, the kernel's default allocator, typically used for objects smaller than page size.
All memory allocations made with `Kmalloc` end up in `krealloc()`.
It serves as allocator for the subsequently introduced types `KBox` and `KVec`.
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/20241004154149.93856-7-dakr@kernel.org Signed-off-by: Miguel Ojeda ojeda@kernel.org --- rust/kernel/alloc/allocator.rs | 31 ++++++++++++++++++++++++++++--- 1 file changed, 28 insertions(+), 3 deletions(-)
diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs index 9ed122401e8a..272c581e24a0 100644 --- a/rust/kernel/alloc/allocator.rs +++ b/rust/kernel/alloc/allocator.rs @@ -13,10 +13,16 @@ use core::ptr; use core::ptr::NonNull;
-use crate::alloc::AllocError; +use crate::alloc::{AllocError, Allocator}; use crate::bindings;
-struct Kmalloc; +/// The contiguous kernel allocator. +/// +/// `Kmalloc` is typically used for physically contiguous allocations up to page size, but also +/// supports larger allocations up to `bindings::KMALLOC_MAX_SIZE`, which is hardware specific. +/// +/// For more details see [self]. +pub struct Kmalloc;
/// Returns a proper size to alloc a new object aligned to `new_layout`'s alignment. fn aligned_size(new_layout: Layout) -> usize { @@ -53,8 +59,10 @@ struct ReallocFunc( unsafe extern "C" fn(*const core::ffi::c_void, usize, u32) -> *mut core::ffi::c_void, );
-#[expect(dead_code)] impl ReallocFunc { + // INVARIANT: `krealloc` satisfies the type invariants. + const KREALLOC: Self = Self(bindings::krealloc); + /// # Safety /// /// This method has the same safety requirements as [`Allocator::realloc`]. @@ -106,6 +114,23 @@ unsafe fn call( } }
+// 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 { + #[inline] + unsafe fn realloc( + ptr: Option<NonNull<u8>>, + layout: Layout, + old_layout: Layout, + flags: Flags, + ) -> Result<NonNull<[u8]>, AllocError> { + // SAFETY: `ReallocFunc::call` has the same safety requirements as `Allocator::realloc`. + unsafe { ReallocFunc::KREALLOC.call(ptr, layout, old_layout, flags) } + } +} + // SAFETY: TODO. unsafe impl GlobalAlloc for Kmalloc { unsafe fn alloc(&self, layout: Layout) -> *mut u8 {