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 Kmalloc; 10 11 /// Returns a proper size to alloc a new object aligned to `new_layout`'s alignment. 12 fn aligned_size(new_layout: Layout) -> usize { 13 // Customized layouts from `Layout::from_size_align()` can have size < align, so pad first. 14 let layout = new_layout.pad_to_align(); 15 16 // Note that `layout.size()` (after padding) is guaranteed to be a multiple of `layout.align()` 17 // which together with the slab guarantees means the `krealloc` will return a properly aligned 18 // object (see comments in `kmalloc()` for more information). 19 layout.size() 20 } 21 22 /// Calls `krealloc` with a proper size to alloc a new object aligned to `new_layout`'s alignment. 23 /// 24 /// # Safety 25 /// 26 /// - `ptr` can be either null or a pointer which has been allocated by this allocator. 27 /// - `new_layout` must have a non-zero size. 28 pub(crate) unsafe fn krealloc_aligned(ptr: *mut u8, new_layout: Layout, flags: Flags) -> *mut u8 { 29 let size = aligned_size(new_layout); 30 31 // SAFETY: 32 // - `ptr` is either null or a pointer returned from a previous `k{re}alloc()` by the 33 // function safety requirement. 34 // - `size` is greater than 0 since it's from `layout.size()` (which cannot be zero according 35 // to the function safety requirement) 36 unsafe { bindings::krealloc(ptr as *const core::ffi::c_void, size, flags.0) as *mut u8 } 37 } 38 39 // SAFETY: TODO. 40 unsafe impl GlobalAlloc for Kmalloc { 41 unsafe fn alloc(&self, layout: Layout) -> *mut u8 { 42 // SAFETY: `ptr::null_mut()` is null and `layout` has a non-zero size by the function safety 43 // requirement. 44 unsafe { krealloc_aligned(ptr::null_mut(), layout, GFP_KERNEL) } 45 } 46 47 unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) { 48 // SAFETY: TODO. 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: Kmalloc = Kmalloc; 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