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Fix a potential race condition during PTE read/write operations

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This commit is contained in:
Chen Chengjun
2025-02-20 20:06:00 +08:00
committed by Tate, Hongliang Tian
parent 3e47a6fdaa
commit 5834f299bc
8 changed files with 89 additions and 16 deletions
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19
ostd/src/mm/page_table/node/mod.rs
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@ -41,8 +41,9 @@ use crate::{
arch::mm::{PageTableEntry, PagingConsts},
mm::{
frame::{inc_frame_ref_count, meta::AnyFrameMeta, Frame},
paddr_to_vaddr, FrameAllocOptions, Infallible, Paddr, PagingConstsTrait, PagingLevel,
VmReader,
paddr_to_vaddr,
page_table::{load_pte, store_pte},
FrameAllocOptions, Infallible, Paddr, PagingConstsTrait, PagingLevel, VmReader,
},
};
@ -309,9 +310,11 @@ where
/// The caller must ensure that the index is within the bound.
unsafe fn read_pte(&self, idx: usize) -> E {
debug_assert!(idx < nr_subpage_per_huge::<C>());
let ptr = paddr_to_vaddr(self.page.start_paddr()) as *const E;
// SAFETY: The index is within the bound and the PTE is plain-old-data.
unsafe { ptr.add(idx).read() }
let ptr = paddr_to_vaddr(self.page.start_paddr()) as *mut E;
// SAFETY:
// - The page table node is alive. The index is inside the bound, so the page table entry is valid.
// - All page table entries are aligned and accessed with atomic operations only.
unsafe { load_pte(ptr.add(idx), Ordering::Relaxed) }
}
/// Writes a page table entry at a given index.
@ -330,8 +333,10 @@ where
unsafe fn write_pte(&mut self, idx: usize, pte: E) {
debug_assert!(idx < nr_subpage_per_huge::<C>());
let ptr = paddr_to_vaddr(self.page.start_paddr()) as *mut E;
// SAFETY: The index is within the bound and the PTE is plain-old-data.
unsafe { ptr.add(idx).write(pte) }
// SAFETY:
// - The page table node is alive. The index is inside the bound, so the page table entry is valid.
// - All page table entries are aligned and accessed with atomic operations only.
unsafe { store_pte(ptr.add(idx), pte, Ordering::Release) }
}
/// Gets the mutable reference to the number of valid PTEs in the node.