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1 | // SPDX-License-Identifier: GPL-2.0 |
2 | ||
3 | //! Allocator support. | |
4 | ||
5 | use core::alloc::{GlobalAlloc, Layout}; | |
6 | use core::ptr; | |
7 | ||
8 | use crate::bindings; | |
9 | ||
10 | struct KernelAllocator; | |
11 | ||
b3d8aa84 BF |
12 | /// Calls `krealloc` with a proper size to alloc a new object aligned to `new_layout`'s alignment. |
13 | /// | |
14 | /// # Safety | |
15 | /// | |
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(); | |
21 | ||
22 | let mut size = layout.size(); | |
23 | ||
74376656 | 24 | if layout.align() > bindings::ARCH_SLAB_MINALIGN { |
b3d8aa84 BF |
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 | |
27 | // more information). | |
28 | // | |
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(); | |
32 | } | |
33 | ||
34 | // SAFETY: | |
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 | |
b6cda913 | 38 | // according to the function safety requirement) or a result from `next_power_of_two()`. |
b3d8aa84 BF |
39 | unsafe { bindings::krealloc(ptr as *const core::ffi::c_void, size, flags) as *mut u8 } |
40 | } | |
41 | ||
247b365d WAF |
42 | unsafe impl GlobalAlloc for KernelAllocator { |
43 | unsafe fn alloc(&self, layout: Layout) -> *mut u8 { | |
f39a97d0 BF |
44 | // SAFETY: `ptr::null_mut()` is null and `layout` has a non-zero size by the function safety |
45 | // requirement. | |
46 | unsafe { krealloc_aligned(ptr::null_mut(), layout, bindings::GFP_KERNEL) } | |
247b365d WAF |
47 | } |
48 | ||
49 | unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) { | |
50 | unsafe { | |
51 | bindings::kfree(ptr as *const core::ffi::c_void); | |
52 | } | |
53 | } | |
0beaf546 BRB |
54 | |
55 | unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 { | |
56 | // SAFETY: | |
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()) }; | |
61 | ||
62 | // SAFETY: | |
63 | // - `ptr` is either null or a pointer allocated by this allocator by the function safety | |
64 | // requirement. | |
65 | // - the size of `layout` is not zero because `new_size` is not zero by the function safety | |
66 | // requirement. | |
67 | unsafe { krealloc_aligned(ptr, layout, bindings::GFP_KERNEL) } | |
68 | } | |
69 | ||
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 | |
72 | // requirement. | |
73 | unsafe { | |
74 | krealloc_aligned( | |
75 | ptr::null_mut(), | |
76 | layout, | |
77 | bindings::GFP_KERNEL | bindings::__GFP_ZERO, | |
78 | ) | |
79 | } | |
80 | } | |
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81 | } |
82 | ||
83 | #[global_allocator] | |
84 | static ALLOCATOR: KernelAllocator = KernelAllocator; | |
85 | ||
89eed1ab | 86 | // See <https://github.com/rust-lang/rust/pull/86844>. |
247b365d | 87 | #[no_mangle] |
89eed1ab | 88 | static __rust_no_alloc_shim_is_unstable: u8 = 0; |