75 lines · rust
1// SPDX-License-Identifier: GPL-2.02 3//! Allocator support.4 5use super::{flags::*, Flags};6use core::alloc::{GlobalAlloc, Layout};7use core::ptr;8 9struct KernelAllocator;10 11/// Calls `krealloc` with a proper size to alloc a new object aligned to `new_layout`'s alignment.12///13/// # Safety14///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.17pub(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 aligned23 // 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 the28 // function safety requirement.29 // - `size` is greater than 0 since it's from `layout.size()` (which cannot be zero according30 // to the function safety requirement)31 unsafe { bindings::krealloc(ptr as *const core::ffi::c_void, size, flags.0) as *mut u8 }32}33 34unsafe impl GlobalAlloc for KernelAllocator {35 unsafe fn alloc(&self, layout: Layout) -> *mut u8 {36 // SAFETY: `ptr::null_mut()` is null and `layout` has a non-zero size by the function safety37 // requirement.38 unsafe { krealloc_aligned(ptr::null_mut(), layout, GFP_KERNEL) }39 }40 41 unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {42 unsafe {43 bindings::kfree(ptr as *const core::ffi::c_void);44 }45 }46 47 unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {48 // SAFETY:49 // - `new_size`, when rounded up to the nearest multiple of `layout.align()`, will not50 // overflow `isize` by the function safety requirement.51 // - `layout.align()` is a proper alignment (i.e. not zero and must be a power of two).52 let layout = unsafe { Layout::from_size_align_unchecked(new_size, layout.align()) };53 54 // SAFETY:55 // - `ptr` is either null or a pointer allocated by this allocator by the function safety56 // requirement.57 // - the size of `layout` is not zero because `new_size` is not zero by the function safety58 // requirement.59 unsafe { krealloc_aligned(ptr, layout, GFP_KERNEL) }60 }61 62 unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {63 // SAFETY: `ptr::null_mut()` is null and `layout` has a non-zero size by the function safety64 // requirement.65 unsafe { krealloc_aligned(ptr::null_mut(), layout, GFP_KERNEL | __GFP_ZERO) }66 }67}68 69#[global_allocator]70static ALLOCATOR: KernelAllocator = KernelAllocator;71 72// See <https://github.com/rust-lang/rust/pull/86844>.73#[no_mangle]74static __rust_no_alloc_shim_is_unstable: u8 = 0;75