1 // SPDX-License-Identifier: GPL-2.0
2
3 //! Allocator support.
4
5 use super::{flags::*, Flags};
6 use core::alloc::{GlobalAlloc, Layout};
7 use core::ptr;
8
9 struct KernelAllocator;
10
11 /// Calls `krealloc` with a proper size to alloc a new object aligned to `new_layout`'s alignment.
12 ///
13 /// # Safety
14 ///
15 /// - `ptr` can be either null or a pointer which has been allocated by this allocator.
16 /// - `new_layout` must have a non-zero size.
17 pub(crate) unsafe fn krealloc_aligned(ptr: *mut u8, new_layout: Layout, flags: Flags) -> *mut u8 {
18 // Customized layouts from `Layout::from_size_align()` can have size < align, so pad first.
19 let layout = new_layout.pad_to_align();
20
21 // Note that `layout.size()` (after padding) is guaranteed to be a multiple of `layout.align()`
22 // which together with the slab guarantees means the `krealloc` will return a properly aligned
23 // object (see comments in `kmalloc()` for more information).
24 let size = layout.size();
25
26 // SAFETY:
27 // - `ptr` is either null or a pointer returned from a previous `k{re}alloc()` by the
28 // function safety requirement.
29 // - `size` is greater than 0 since it's from `layout.size()` (which cannot be zero according
30 // to the function safety requirement)
31 unsafe { bindings::krealloc(ptr as *const core::ffi::c_void, size, flags.0) as *mut u8 }
32 }
33
34 unsafe impl GlobalAlloc for KernelAllocator {
35 unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
36 // SAFETY: `ptr::null_mut()` is null and `layout` has a non-zero size by the function safety
37 // requirement.
38 unsafe { krealloc_aligned(ptr::null_mut(), layout, GFP_KERNEL) }
39 }
40
41 unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {
42 unsafe {
43 bindings::kfree(ptr as *const core::ffi::c_void);
44 }
45 }
46
47 unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
48 // SAFETY:
49 // - `new_size`, when rounded up to the nearest multiple of `layout.align()`, will not
50 // overflow `isize` by the function safety requirement.
51 // - `layout.align()` is a proper alignment (i.e. not zero and must be a power of two).
52 let layout = unsafe { Layout::from_size_align_unchecked(new_size, layout.align()) };
53
54 // SAFETY:
55 // - `ptr` is either null or a pointer allocated by this allocator by the function safety
56 // requirement.
57 // - the size of `layout` is not zero because `new_size` is not zero by the function safety
58 // requirement.
59 unsafe { krealloc_aligned(ptr, layout, GFP_KERNEL) }
60 }
61
62 unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {
63 // SAFETY: `ptr::null_mut()` is null and `layout` has a non-zero size by the function safety
64 // requirement.
65 unsafe { krealloc_aligned(ptr::null_mut(), layout, GFP_KERNEL | __GFP_ZERO) }
66 }
67 }
68
69 #[global_allocator]
70 static ALLOCATOR: KernelAllocator = KernelAllocator;
71
72 // See <https://github.com/rust-lang/rust/pull/86844>.
73 #[no_mangle]
74 static __rust_no_alloc_shim_is_unstable: u8 = 0;
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