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