// SPDX-License-Identifier: GPL-2.0 //! Allocator support. use super::{flags::*, Flags};use core::alloc::{GlobalAlloc, Layout};use core::ptr; struct KernelAllocator; /// Calls `krealloc` with a proper size to alloc a new object aligned to `new_layout`'s alignment.////// # Safety////// - `ptr` can be either null or a pointer which has been allocated by this allocator./// - `new_layout` must have a non-zero size.pub(crate) unsafe fn krealloc_aligned(ptr: *mut u8, new_layout: Layout, flags: Flags) -> *mut u8 {    // Customized layouts from `Layout::from_size_align()` can have size < align, so pad first.    let layout = new_layout.pad_to_align();     // Note that `layout.size()` (after padding) is guaranteed to be a multiple of `layout.align()`    // which together with the slab guarantees means the `krealloc` will return a properly aligned    // object (see comments in `kmalloc()` for more information).    let size = layout.size();     // SAFETY:    // - `ptr` is either null or a pointer returned from a previous `k{re}alloc()` by the    //   function safety requirement.    // - `size` is greater than 0 since it's from `layout.size()` (which cannot be zero according    //   to the function safety requirement)    unsafe { bindings::krealloc(ptr as *const core::ffi::c_void, size, flags.0) as *mut u8 }} unsafe impl GlobalAlloc for KernelAllocator {    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {        // SAFETY: `ptr::null_mut()` is null and `layout` has a non-zero size by the function safety        // requirement.        unsafe { krealloc_aligned(ptr::null_mut(), layout, GFP_KERNEL) }    }     unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {        unsafe {            bindings::kfree(ptr as *const core::ffi::c_void);        }    }     unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {        // SAFETY:        // - `new_size`, when rounded up to the nearest multiple of `layout.align()`, will not        //   overflow `isize` by the function safety requirement.        // - `layout.align()` is a proper alignment (i.e. not zero and must be a power of two).        let layout = unsafe { Layout::from_size_align_unchecked(new_size, layout.align()) };         // SAFETY:        // - `ptr` is either null or a pointer allocated by this allocator by the function safety        //   requirement.        // - the size of `layout` is not zero because `new_size` is not zero by the function safety        //   requirement.        unsafe { krealloc_aligned(ptr, layout, GFP_KERNEL) }    }     unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {        // SAFETY: `ptr::null_mut()` is null and `layout` has a non-zero size by the function safety        // requirement.        unsafe { krealloc_aligned(ptr::null_mut(), layout, GFP_KERNEL | __GFP_ZERO) }    }} #[global_allocator]static ALLOCATOR: KernelAllocator = KernelAllocator; // See <https://github.com/rust-lang/rust/pull/86844>.#[no_mangle]static __rust_no_alloc_shim_is_unstable: u8 = 0;