| Message ID | 20241001150008.183102-7-dakr@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Generic `Allocator` support for Rust | expand |
On 01.10.24 16:59, Danilo Krummrich wrote: > 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`. > > Signed-off-by: Danilo Krummrich <dakr@kernel.org> > --- > rust/kernel/alloc/allocator.rs | 31 ++++++++++++++++++++++++++++--- > 1 file changed, 28 insertions(+), 3 deletions(-) Reviewed-by: Benno Lossin <benno.lossin@proton.me> --- Cheers, Benno
On Tue, 1 Oct 2024 16:59:41 +0200 Danilo Krummrich <dakr@kernel.org> wrote: > 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`. > > Signed-off-by: Danilo Krummrich <dakr@kernel.org> Reviewed-by: Gary Guo <gary@garyguo.net> > --- > 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 1f28b004b447..4f3c3ab7c7a2 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) } > + } > +} > + > unsafe impl GlobalAlloc for Kmalloc { > unsafe fn alloc(&self, layout: Layout) -> *mut u8 { > // SAFETY: `ptr::null_mut()` is null and `layout` has a non-zero size by the function safety
diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs index 1f28b004b447..4f3c3ab7c7a2 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) } + } +} + unsafe impl GlobalAlloc for Kmalloc { unsafe fn alloc(&self, layout: Layout) -> *mut u8 { // SAFETY: `ptr::null_mut()` is null and `layout` has a non-zero size by the function safety
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`. Signed-off-by: Danilo Krummrich <dakr@kernel.org> --- rust/kernel/alloc/allocator.rs | 31 ++++++++++++++++++++++++++++--- 1 file changed, 28 insertions(+), 3 deletions(-)