page_walker/walkers/
protector.rs

1//! This modules implements the [`PteProtector`] struct which is a helper used to change the
2//! protection flags for a given range of virtual addresses.
3
4use core::marker::PhantomData;
5use core::ops::Range;
6use crate::address_space::PageTableMapper;
7use crate::{PageFormat, PteType};
8use num_traits::{FromPrimitive, PrimInt, Unsigned};
9
10/// The [`PteProtector`] struct is an implementation of a [`crate::walker::PageWalkerMut`] used to
11/// change the protection flags of a given virtual address range. This function is used by the
12/// [`AddressSpace::protect_range`] method.
13///
14/// [`AddressSpace::protect_range`]: `super::super::AddressSpace::protect_range`
15pub struct PteProtector<'a, PTE, Mapper, Error>
16where
17    PTE: FromPrimitive + PrimInt + Unsigned,
18    Mapper: PageTableMapper<PTE, Error>,
19{
20    /// The page table mapper.
21    pub mapper: &'a mut Mapper,
22    /// The protection flags that should be set. The first mask is the mask of bits that should be
23    /// cleared. The second mask is the mask of bits that should be set.
24    pub mask: (PTE, PTE),
25    /// The page format.
26    pub format: &'a PageFormat<'a, PTE>,
27    /// A marker for Error.
28    pub error: PhantomData<Error>,
29}
30
31impl<'a, PTE, Mapper, Error> crate::PageWalkerMut<PTE, Error> for PteProtector<'a, PTE, Mapper, Error>
32where
33    PTE: FromPrimitive + PrimInt + Unsigned,
34    Mapper: PageTableMapper<PTE, Error>,
35{
36    /// Reads the PTE at the given physical address.
37    fn read_pte(&self, phys_addr: PTE) -> Result<PTE, Error> {
38        self.mapper.read_pte(phys_addr)
39    }
40
41    /// Writes the PTE to the given physical address.
42    fn write_pte(&mut self, phys_addr: PTE, value: PTE) -> Result<(), Error> {
43        self.mapper.write_pte(phys_addr, value)
44    }
45
46    /// Checks if the PTE points to a page that is present, and changes the protection flags if so.
47    fn handle_pte(&mut self, pte_type: PteType, _range: Range<usize>, pte: &mut PTE) -> Result<(), Error> {
48        let physical_mask = self.format.physical_mask;
49
50        if let PteType::Page(level) = pte_type {
51            let level = &self.format.levels[level];
52
53            if level.is_present(*pte) {
54                // Ensure the mask does not modify the physical address bits, the huge page bits or the
55                // present bits.
56                let clear_mask = self.mask.0 &
57                    !(physical_mask | level.huge_page_bit.0 | level.present_bit.0);
58                let set_mask   = self.mask.1 &
59                    !(physical_mask | level.huge_page_bit.0 | level.present_bit.0);
60
61                *pte = (*pte & !clear_mask) | set_mask;
62            }
63        }
64
65        Ok(())
66    }
67}
page_walker/walkers/protector.rs

page_walker/walkers/
protector.rs
