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 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 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 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 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 } 40 } 41 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 45 // requirement. 46 unsafe { krealloc_aligned(ptr::null_mut(), layout, bindings::GFP_KERNEL) } 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 } 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 } 81 } 82 83 #[global_allocator] 84 static ALLOCATOR: KernelAllocator = KernelAllocator; 85 86 // See <https://github.com/rust-lang/rust/pull/86844>. 87 #[no_mangle] 88 static __rust_no_alloc_shim_is_unstable: u8 = 0; 89