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