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Auto merge of #122309 - g-yziquel:issue-122262, r=saethlin

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Use `MAP_PRIVATE` (not unsound-prone `MAP_SHARED`)

Solves https://github.com/rust-lang/rust/issues/122262
This commit is contained in:
bors 2024-03-16 09:19:08 +00:00
commit 774ae599ab
1 changed files with 8 additions and 2 deletions
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10
compiler/rustc_data_structures/src/memmap.rs
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@ -18,8 +18,14 @@ impl Mmap {
/// However in practice most callers do not ensure this, so uses of this function are likely unsound.
#[inline]
pub unsafe fn map(file: File) -> io::Result<Self> {
// Safety: the caller must ensure that this is safe.
unsafe { memmap2::Mmap::map(&file).map(Mmap) }
// By default, memmap2 creates shared mappings, implying that we could see updates to the
// file through the mapping. That would violate our precondition; so by requesting a
// map_copy_read_only we do not lose anything.
// This mapping mode also improves our support for filesystems such as cacheless virtiofs.
// For more details see https://github.com/rust-lang/rust/issues/122262
//
// SAFETY: The caller must ensure that this is safe.
unsafe { memmap2::MmapOptions::new().map_copy_read_only(&file).map(Mmap) }
}
}