1 // SPDX-License-Identifier: GPL-2.0
5 use core::alloc::{GlobalAlloc, Layout};
10 struct KernelAllocator;
12 /// Calls `krealloc` with a proper size to alloc a new object aligned to `new_layout`'s alignment.
16 /// - `ptr` can be either null or a pointer which has been allocated by this allocator.
17 /// - `new_layout` must have a non-zero size.
18 unsafe fn krealloc_aligned(ptr: *mut u8, new_layout: Layout, flags: bindings::gfp_t) -> *mut u8 {
19 // Customized layouts from `Layout::from_size_align()` can have size < align, so pad first.
20 let layout = new_layout.pad_to_align();
22 let mut size = layout.size();
24 if layout.align() > bindings::BINDINGS_ARCH_SLAB_MINALIGN {
25 // The alignment requirement exceeds the slab guarantee, thus try to enlarge the size
26 // to use the "power-of-two" size/alignment guarantee (see comments in `kmalloc()` for
29 // Note that `layout.size()` (after padding) is guaranteed to be a multiple of
30 // `layout.align()`, so `next_power_of_two` gives enough alignment guarantee.
31 size = size.next_power_of_two();
35 // - `ptr` is either null or a pointer returned from a previous `k{re}alloc()` by the
36 // function safety requirement.
37 // - `size` is greater than 0 since it's either a `layout.size()` (which cannot be zero
38 // according to the function safety requirement) or a result from `next_power_of_two()`.
39 unsafe { bindings::krealloc(ptr as *const core::ffi::c_void, size, flags) as *mut u8 }
42 unsafe impl GlobalAlloc for KernelAllocator {
43 unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
44 // SAFETY: `ptr::null_mut()` is null and `layout` has a non-zero size by the function safety
46 unsafe { krealloc_aligned(ptr::null_mut(), layout, bindings::GFP_KERNEL) }
49 unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {
51 bindings::kfree(ptr as *const core::ffi::c_void);
55 unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
57 // - `new_size`, when rounded up to the nearest multiple of `layout.align()`, will not
58 // overflow `isize` by the function safety requirement.
59 // - `layout.align()` is a proper alignment (i.e. not zero and must be a power of two).
60 let layout = unsafe { Layout::from_size_align_unchecked(new_size, layout.align()) };
63 // - `ptr` is either null or a pointer allocated by this allocator by the function safety
65 // - the size of `layout` is not zero because `new_size` is not zero by the function safety
67 unsafe { krealloc_aligned(ptr, layout, bindings::GFP_KERNEL) }
70 unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {
71 // SAFETY: `ptr::null_mut()` is null and `layout` has a non-zero size by the function safety
77 bindings::GFP_KERNEL | bindings::__GFP_ZERO,
84 static ALLOCATOR: KernelAllocator = KernelAllocator;
86 // See <https://github.com/rust-lang/rust/pull/86844>.
88 static __rust_no_alloc_shim_is_unstable: u8 = 0;