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