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add workaround for recursive page tables with recursive index 511 #425

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merged 4 commits into from Jun 19, 2023

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Freax13
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@Freax13 Freax13 commented Jun 14, 2023

This pr adds changes the iterator returned by PageTable::iter{_mut} to a custom iterator that avoids calculating the end pointer of the page table. It also adds a warning against using recursive index 511.

Closes #424

@Freax13 Freax13 requested a review from phil-opp June 14, 2023 19:14
// that address sound, but it avoids some easy to trigger
// miscompilations.
let ptr = self.entries.as_ptr();
(0..512).map(move |i| unsafe { &*ptr.add(i) })
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Have you tried whether self.entries[i] works? This way we might be able to avoid the unsafe..

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This should work for iter, but not iter_mut.

src/structures/paging/mapper/recursive_page_table.rs Outdated Show resolved Hide resolved
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Thanks for the update!

I proposed a small update to the safety comment, otherwise this looks good to me.

src/structures/paging/mapper/recursive_page_table.rs Outdated Show resolved Hide resolved
Co-authored-by: Philipp Oppermann <dev@phil-opp.com>
@Freax13 Freax13 enabled auto-merge June 19, 2023 05:43
@Freax13 Freax13 merged commit 9e0a8d1 into rust-osdev:master Jun 19, 2023
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@Freax13 Freax13 mentioned this pull request Sep 15, 2023
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recursive page table with recursive index 511 is unsound
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