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- // SPDX-License-Identifier: GPL-2.0
- //! Allocator support.
- use core::alloc::{GlobalAlloc, Layout};
- use core::ptr;
- use crate::bindings;
- 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.
- unsafe fn krealloc_aligned(ptr: *mut u8, new_layout: Layout, flags: bindings::gfp_t) -> *mut u8 {
- // Customized layouts from `Layout::from_size_align()` can have size < align, so pad first.
- let layout = new_layout.pad_to_align();
- let mut size = layout.size();
- if layout.align() > bindings::BINDINGS_ARCH_SLAB_MINALIGN {
- // The alignment requirement exceeds the slab guarantee, thus try to enlarge the size
- // to use the "power-of-two" size/alignment guarantee (see comments in `kmalloc()` for
- // more information).
- //
- // Note that `layout.size()` (after padding) is guaranteed to be a multiple of
- // `layout.align()`, so `next_power_of_two` gives enough alignment guarantee.
- size = size.next_power_of_two();
- }
- // 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 either a `layout.size()` (which cannot be zero
- // according to the function safety requirement) or a result from `next_power_of_two()`.
- unsafe { bindings::krealloc(ptr as *const core::ffi::c_void, size, flags) as *mut u8 }
- }
- unsafe impl GlobalAlloc for KernelAllocator {
- unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
- // `krealloc()` is used instead of `kmalloc()` because the latter is
- // an inline function and cannot be bound to as a result.
- unsafe { bindings::krealloc(ptr::null(), layout.size(), bindings::GFP_KERNEL) as *mut u8 }
- }
- unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {
- unsafe {
- bindings::kfree(ptr as *const core::ffi::c_void);
- }
- }
- }
- #[global_allocator]
- static ALLOCATOR: KernelAllocator = KernelAllocator;
- // `rustc` only generates these for some crate types. Even then, we would need
- // to extract the object file that has them from the archive. For the moment,
- // let's generate them ourselves instead.
- //
- // Note: Although these are *safe* functions, they are called by the compiler
- // with parameters that obey the same `GlobalAlloc` function safety
- // requirements: size and align should form a valid layout, and size is
- // greater than 0.
- //
- // Note that `#[no_mangle]` implies exported too, nowadays.
- #[no_mangle]
- fn __rust_alloc(size: usize, align: usize) -> *mut u8 {
- // SAFETY: See assumption above.
- let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
- // SAFETY: `ptr::null_mut()` is null, per assumption above the size of `layout` is greater
- // than 0.
- unsafe { krealloc_aligned(ptr::null_mut(), layout, bindings::GFP_KERNEL) }
- }
- #[no_mangle]
- fn __rust_dealloc(ptr: *mut u8, _size: usize, _align: usize) {
- unsafe { bindings::kfree(ptr as *const core::ffi::c_void) };
- }
- #[no_mangle]
- fn __rust_realloc(ptr: *mut u8, _old_size: usize, align: usize, new_size: usize) -> *mut u8 {
- // SAFETY: See assumption above.
- let new_layout = unsafe { Layout::from_size_align_unchecked(new_size, align) };
- // SAFETY: Per assumption above, `ptr` is allocated by `__rust_*` before, and the size of
- // `new_layout` is greater than 0.
- unsafe { krealloc_aligned(ptr, new_layout, bindings::GFP_KERNEL) }
- }
- #[no_mangle]
- fn __rust_alloc_zeroed(size: usize, align: usize) -> *mut u8 {
- // SAFETY: See assumption above.
- let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
- // SAFETY: `ptr::null_mut()` is null, per assumption above the size of `layout` is greater
- // than 0.
- unsafe {
- krealloc_aligned(
- ptr::null_mut(),
- layout,
- bindings::GFP_KERNEL | bindings::__GFP_ZERO,
- )
- }
- }
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