kernel/alloc/allocator/
iter.rs

1// SPDX-License-Identifier: GPL-2.0
2
3use super::Vmalloc;
4use crate::page;
5use core::marker::PhantomData;
6use core::ptr::NonNull;
7
8/// An [`Iterator`] of [`page::BorrowedPage`] items owned by a [`Vmalloc`] allocation.
9///
10/// # Guarantees
11///
12/// The pages iterated by the [`Iterator`] appear in the order as they are mapped in the CPU's
13/// virtual address space ascendingly.
14///
15/// # Invariants
16///
17/// - `buf` is a valid and [`page::PAGE_SIZE`] aligned pointer into a [`Vmalloc`] allocation.
18/// - `size` is the number of bytes from `buf` until the end of the [`Vmalloc`] allocation `buf`
19///   points to.
20pub struct VmallocPageIter<'a> {
21    /// The base address of the [`Vmalloc`] buffer.
22    buf: NonNull<u8>,
23    /// The size of the buffer pointed to by `buf` in bytes.
24    size: usize,
25    /// The current page index of the [`Iterator`].
26    index: usize,
27    _p: PhantomData<page::BorrowedPage<'a>>,
28}
29
30impl<'a> Iterator for VmallocPageIter<'a> {
31    type Item = page::BorrowedPage<'a>;
32
33    fn next(&mut self) -> Option<Self::Item> {
34        let offset = self.index.checked_mul(page::PAGE_SIZE)?;
35
36        // Even though `self.size()` may be smaller than `Self::page_count() * page::PAGE_SIZE`, it
37        // is always a number between `(Self::page_count() - 1) * page::PAGE_SIZE` and
38        // `Self::page_count() * page::PAGE_SIZE`, hence the check below is sufficient.
39        if offset < self.size() {
40            self.index += 1;
41        } else {
42            return None;
43        }
44
45        // TODO: Use `NonNull::add()` instead, once the minimum supported compiler version is
46        // bumped to 1.80 or later.
47        //
48        // SAFETY: `offset` is in the interval `[0, (self.page_count() - 1) * page::PAGE_SIZE]`,
49        // hence the resulting pointer is guaranteed to be within the same allocation.
50        let ptr = unsafe { self.buf.as_ptr().add(offset) };
51
52        // SAFETY: `ptr` is guaranteed to be non-null given that it is derived from `self.buf`.
53        let ptr = unsafe { NonNull::new_unchecked(ptr) };
54
55        // SAFETY:
56        // - `ptr` is a valid pointer to a `Vmalloc` allocation.
57        // - `ptr` is valid for the duration of `'a`.
58        Some(unsafe { Vmalloc::to_page(ptr) })
59    }
60
61    fn size_hint(&self) -> (usize, Option<usize>) {
62        let remaining = self.page_count().saturating_sub(self.index);
63
64        (remaining, Some(remaining))
65    }
66}
67
68impl<'a> VmallocPageIter<'a> {
69    /// Creates a new [`VmallocPageIter`] instance.
70    ///
71    /// # Safety
72    ///
73    /// - `buf` must be a [`page::PAGE_SIZE`] aligned pointer into a [`Vmalloc`] allocation.
74    /// - `buf` must be valid for at least the lifetime of `'a`.
75    /// - `size` must be the number of bytes from `buf` until the end of the [`Vmalloc`] allocation
76    ///   `buf` points to.
77    pub unsafe fn new(buf: NonNull<u8>, size: usize) -> Self {
78        // INVARIANT: By the safety requirements, `buf` is a valid and `page::PAGE_SIZE` aligned
79        // pointer into a [`Vmalloc`] allocation.
80        Self {
81            buf,
82            size,
83            index: 0,
84            _p: PhantomData,
85        }
86    }
87
88    /// Returns the size of the backing [`Vmalloc`] allocation in bytes.
89    ///
90    /// Note that this is the size the [`Vmalloc`] allocation has been allocated with. Hence, this
91    /// number may be smaller than `[`Self::page_count`] * [`page::PAGE_SIZE`]`.
92    #[inline]
93    pub fn size(&self) -> usize {
94        self.size
95    }
96
97    /// Returns the number of pages owned by the backing [`Vmalloc`] allocation.
98    #[inline]
99    pub fn page_count(&self) -> usize {
100        self.size().div_ceil(page::PAGE_SIZE)
101    }
102}
kernel/alloc/allocator/iter.rs

kernel/alloc/allocator/
iter.rs
