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-rw-r--r--rust/kernel/alloc/allocator.rs81
1 files changed, 81 insertions, 0 deletions
diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
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+// 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();
+
+ let mut size = layout.size();
+
+ if layout.align() > 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.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;