mirror of https://github.com/torvalds/linux.git
103 lines
3.6 KiB
Rust
103 lines
3.6 KiB
Rust
// SPDX-License-Identifier: GPL-2.0
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use super::Vmalloc;
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use crate::page;
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use core::marker::PhantomData;
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use core::ptr::NonNull;
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/// An [`Iterator`] of [`page::BorrowedPage`] items owned by a [`Vmalloc`] allocation.
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///
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/// # Guarantees
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///
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/// The pages iterated by the [`Iterator`] appear in the order as they are mapped in the CPU's
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/// virtual address space ascendingly.
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///
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/// # Invariants
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///
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/// - `buf` is a valid and [`page::PAGE_SIZE`] aligned pointer into a [`Vmalloc`] allocation.
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/// - `size` is the number of bytes from `buf` until the end of the [`Vmalloc`] allocation `buf`
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/// points to.
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pub struct VmallocPageIter<'a> {
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/// The base address of the [`Vmalloc`] buffer.
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buf: NonNull<u8>,
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/// The size of the buffer pointed to by `buf` in bytes.
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size: usize,
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/// The current page index of the [`Iterator`].
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index: usize,
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_p: PhantomData<page::BorrowedPage<'a>>,
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}
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impl<'a> Iterator for VmallocPageIter<'a> {
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type Item = page::BorrowedPage<'a>;
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fn next(&mut self) -> Option<Self::Item> {
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let offset = self.index.checked_mul(page::PAGE_SIZE)?;
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// Even though `self.size()` may be smaller than `Self::page_count() * page::PAGE_SIZE`, it
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// is always a number between `(Self::page_count() - 1) * page::PAGE_SIZE` and
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// `Self::page_count() * page::PAGE_SIZE`, hence the check below is sufficient.
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if offset < self.size() {
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self.index += 1;
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} else {
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return None;
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}
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// TODO: Use `NonNull::add()` instead, once the minimum supported compiler version is
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// bumped to 1.80 or later.
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//
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// SAFETY: `offset` is in the interval `[0, (self.page_count() - 1) * page::PAGE_SIZE]`,
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// hence the resulting pointer is guaranteed to be within the same allocation.
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let ptr = unsafe { self.buf.as_ptr().add(offset) };
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// SAFETY: `ptr` is guaranteed to be non-null given that it is derived from `self.buf`.
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let ptr = unsafe { NonNull::new_unchecked(ptr) };
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// SAFETY:
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// - `ptr` is a valid pointer to a `Vmalloc` allocation.
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// - `ptr` is valid for the duration of `'a`.
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Some(unsafe { Vmalloc::to_page(ptr) })
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}
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fn size_hint(&self) -> (usize, Option<usize>) {
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let remaining = self.page_count().saturating_sub(self.index);
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(remaining, Some(remaining))
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}
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}
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impl<'a> VmallocPageIter<'a> {
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/// Creates a new [`VmallocPageIter`] instance.
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///
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/// # Safety
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///
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/// - `buf` must be a [`page::PAGE_SIZE`] aligned pointer into a [`Vmalloc`] allocation.
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/// - `buf` must be valid for at least the lifetime of `'a`.
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/// - `size` must be the number of bytes from `buf` until the end of the [`Vmalloc`] allocation
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/// `buf` points to.
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pub unsafe fn new(buf: NonNull<u8>, size: usize) -> Self {
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// INVARIANT: By the safety requirements, `buf` is a valid and `page::PAGE_SIZE` aligned
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// pointer into a [`Vmalloc`] allocation.
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Self {
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buf,
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size,
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index: 0,
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_p: PhantomData,
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}
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}
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/// Returns the size of the backing [`Vmalloc`] allocation in bytes.
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///
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/// Note that this is the size the [`Vmalloc`] allocation has been allocated with. Hence, this
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/// number may be smaller than `[`Self::page_count`] * [`page::PAGE_SIZE`]`.
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#[inline]
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pub fn size(&self) -> usize {
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self.size
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}
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/// Returns the number of pages owned by the backing [`Vmalloc`] allocation.
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#[inline]
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pub fn page_count(&self) -> usize {
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self.size().div_ceil(page::PAGE_SIZE)
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}
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}
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