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 // `krealloc()` is used instead of `kmalloc()` because the latter is
45 // an inline function and cannot be bound to as a result.
46 unsafe { bindings::krealloc(ptr::null(), layout.size(), bindings::GFP_KERNEL) as *mut u8 }
49 unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {
51 bindings::kfree(ptr as *const core::ffi::c_void);
57 static ALLOCATOR: KernelAllocator = KernelAllocator;
59 // `rustc` only generates these for some crate types. Even then, we would need
60 // to extract the object file that has them from the archive. For the moment,
61 // let's generate them ourselves instead.
63 // Note: Although these are *safe* functions, they are called by the compiler
64 // with parameters that obey the same `GlobalAlloc` function safety
65 // requirements: size and align should form a valid layout, and size is
68 // Note that `#[no_mangle]` implies exported too, nowadays.
70 fn __rust_alloc(size: usize, align: usize) -> *mut u8 {
71 // SAFETY: See assumption above.
72 let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
74 // SAFETY: `ptr::null_mut()` is null, per assumption above the size of `layout` is greater
76 unsafe { krealloc_aligned(ptr::null_mut(), layout, bindings::GFP_KERNEL) }
80 fn __rust_dealloc(ptr: *mut u8, _size: usize, _align: usize) {
81 unsafe { bindings::kfree(ptr as *const core::ffi::c_void) };
85 fn __rust_realloc(ptr: *mut u8, _old_size: usize, align: usize, new_size: usize) -> *mut u8 {
86 // SAFETY: See assumption above.
87 let new_layout = unsafe { Layout::from_size_align_unchecked(new_size, align) };
89 // SAFETY: Per assumption above, `ptr` is allocated by `__rust_*` before, and the size of
90 // `new_layout` is greater than 0.
91 unsafe { krealloc_aligned(ptr, new_layout, bindings::GFP_KERNEL) }
95 fn __rust_alloc_zeroed(size: usize, align: usize) -> *mut u8 {
96 // SAFETY: See assumption above.
97 let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
99 // SAFETY: `ptr::null_mut()` is null, per assumption above the size of `layout` is greater
105 bindings::GFP_KERNEL | bindings::__GFP_ZERO,