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Diffstat (limited to 'rust/kernel/alloc/allocator.rs')
-rw-r--r-- | rust/kernel/alloc/allocator.rs | 81 |
1 files changed, 81 insertions, 0 deletions
diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs new file mode 100644 index 000000000000..229642960cd1 --- /dev/null +++ b/rust/kernel/alloc/allocator.rs @@ -0,0 +1,81 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Allocator support. + +use super::{flags::*, Flags}; +use core::alloc::{GlobalAlloc, Layout}; +use core::ptr; + +struct KernelAllocator; + +/// Calls `krealloc` with a proper size to alloc a new object aligned to `new_layout`'s alignment. +/// +/// # Safety +/// +/// - `ptr` can be either null or a pointer which has been allocated by this allocator. +/// - `new_layout` must have a non-zero size. +pub(crate) unsafe fn krealloc_aligned(ptr: *mut u8, new_layout: Layout, flags: Flags) -> *mut u8 { + // Customized layouts from `Layout::from_size_align()` can have size < align, so pad first. + let layout = new_layout.pad_to_align(); + + let mut size = layout.size(); + + if layout.align() > bindings::ARCH_SLAB_MINALIGN { + // The alignment requirement exceeds the slab guarantee, thus try to enlarge the size + // to use the "power-of-two" size/alignment guarantee (see comments in `kmalloc()` for + // more information). + // + // Note that `layout.size()` (after padding) is guaranteed to be a multiple of + // `layout.align()`, so `next_power_of_two` gives enough alignment guarantee. + size = size.next_power_of_two(); + } + + // SAFETY: + // - `ptr` is either null or a pointer returned from a previous `k{re}alloc()` by the + // function safety requirement. + // - `size` is greater than 0 since it's either a `layout.size()` (which cannot be zero + // according to the function safety requirement) or a result from `next_power_of_two()`. + unsafe { bindings::krealloc(ptr as *const core::ffi::c_void, size, flags.0) as *mut u8 } +} + +unsafe impl GlobalAlloc for KernelAllocator { + 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 + // requirement. + unsafe { krealloc_aligned(ptr::null_mut(), layout, GFP_KERNEL) } + } + + unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) { + unsafe { + bindings::kfree(ptr as *const core::ffi::c_void); + } + } + + unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 { + // SAFETY: + // - `new_size`, when rounded up to the nearest multiple of `layout.align()`, will not + // overflow `isize` by the function safety requirement. + // - `layout.align()` is a proper alignment (i.e. not zero and must be a power of two). + let layout = unsafe { Layout::from_size_align_unchecked(new_size, layout.align()) }; + + // SAFETY: + // - `ptr` is either null or a pointer allocated by this allocator by the function safety + // requirement. + // - the size of `layout` is not zero because `new_size` is not zero by the function safety + // requirement. + unsafe { krealloc_aligned(ptr, layout, GFP_KERNEL) } + } + + unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 { + // SAFETY: `ptr::null_mut()` is null and `layout` has a non-zero size by the function safety + // requirement. + unsafe { krealloc_aligned(ptr::null_mut(), layout, GFP_KERNEL | __GFP_ZERO) } + } +} + +#[global_allocator] +static ALLOCATOR: KernelAllocator = KernelAllocator; + +// See <https://github.com/rust-lang/rust/pull/86844>. +#[no_mangle] +static __rust_no_alloc_shim_is_unstable: u8 = 0; |