kernel/alloc/allocator/
iter.rs

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

kernel/alloc/allocator/
iter.rs
