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 use crate::bindings; 10 11 struct KernelAllocator; 12 13 /// Calls `krealloc` with a proper size to alloc a new object aligned to `new_layout`'s alignment. 14 /// 15 /// # Safety 16 /// 17 /// - `ptr` can be either null or a pointer which has been allocated by this allocator. 18 /// - `new_layout` must have a non-zero size. 19 unsafe fn krealloc_aligned(ptr: *mut u8, new_layout: Layout, flags: Flags) -> *mut u8 { 20 // Customized layouts from `Layout::from_size_align()` can have size < align, so pad first. 21 let layout = new_layout.pad_to_align(); 22 23 let mut size = layout.size(); 24 25 if layout.align() > bindings::ARCH_SLAB_MINALIGN { 26 // The alignment requirement exceeds the slab guarantee, thus try to enlarge the size 27 // to use the "power-of-two" size/alignment guarantee (see comments in `kmalloc()` for 28 // more information). 29 // 30 // Note that `layout.size()` (after padding) is guaranteed to be a multiple of 31 // `layout.align()`, so `next_power_of_two` gives enough alignment guarantee. 32 size = size.next_power_of_two(); 33 } 34 35 // SAFETY: 36 // - `ptr` is either null or a pointer returned from a previous `k{re}alloc()` by the 37 // function safety requirement. 38 // - `size` is greater than 0 since it's either a `layout.size()` (which cannot be zero 39 // according to the function safety requirement) or a result from `next_power_of_two()`. 40 unsafe { bindings::krealloc(ptr as *const core::ffi::c_void, size, flags.0) as *mut u8 } 41 } 42 43 unsafe impl GlobalAlloc for KernelAllocator { 44 unsafe fn alloc(&self, layout: Layout) -> *mut u8 { 45 // SAFETY: `ptr::null_mut()` is null and `layout` has a non-zero size by the function safety 46 // requirement. 47 unsafe { krealloc_aligned(ptr::null_mut(), layout, GFP_KERNEL) } 48 } 49 50 unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) { 51 unsafe { 52 bindings::kfree(ptr as *const core::ffi::c_void); 53 } 54 } 55 56 unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 { 57 // SAFETY: 58 // - `new_size`, when rounded up to the nearest multiple of `layout.align()`, will not 59 // overflow `isize` by the function safety requirement. 60 // - `layout.align()` is a proper alignment (i.e. not zero and must be a power of two). 61 let layout = unsafe { Layout::from_size_align_unchecked(new_size, layout.align()) }; 62 63 // SAFETY: 64 // - `ptr` is either null or a pointer allocated by this allocator by the function safety 65 // requirement. 66 // - the size of `layout` is not zero because `new_size` is not zero by the function safety 67 // requirement. 68 unsafe { krealloc_aligned(ptr, layout, GFP_KERNEL) } 69 } 70 71 unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 { 72 // SAFETY: `ptr::null_mut()` is null and `layout` has a non-zero size by the function safety 73 // requirement. 74 unsafe { krealloc_aligned(ptr::null_mut(), layout, GFP_KERNEL | __GFP_ZERO) } 75 } 76 } 77 78 #[global_allocator] 79 static ALLOCATOR: KernelAllocator = KernelAllocator; 80 81 // See <https://github.com/rust-lang/rust/pull/86844>. 82 #[no_mangle] 83 static __rust_no_alloc_shim_is_unstable: u8 = 0; 84