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Paging/Mapper: include active page table flags in translate() result #150

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Paging/Mapper: include active page table flags in translate() result #150

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324c3c4
include active page table flags in translate() result struct
tscs37 Apr 15, 2020
d257e45
reorder fields in TranslateResult to be consistent with usage
tscs37 Apr 18, 2020
297e514
move data definition intro struct declaration
tscs37 Apr 18, 2020
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21 changes: 18 additions & 3 deletions src/structures/paging/mapper/mapped_page_table.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -377,17 +377,27 @@ impl<'a, P: PhysToVirt> MapperAllSizes for MappedPageTable<'a, P> {
Err(PageTableWalkError::NotMapped) => return TranslateResult::PageNotMapped,
Err(PageTableWalkError::MappedToHugePage) => {
let frame = PhysFrame::containing_address(p3[addr.p3_index()].addr());
let flags = p3[addr.p3_index()].flags();
let offset = addr.as_u64() & 0o_777_777_7777;
return TranslateResult::Frame1GiB { frame, offset };
return TranslateResult::Frame1GiB {
frame,
offset,
flags,
};
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Here and elsewhere, if we're making this struct larger, it might make more sense to initialize it like:

TranslateResult::Frame1GiB {
    frame: PhysFrame::containing_address(p3[addr.p3_index()].addr()),
    offset: addr.as_u64() & 0o_777_777_7777,
    flags:  p3[addr.p3_index()].flags(),
}

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I've changed the struct init accordingly, though I've left variables in two places, as it's defined in a match and I feel like that isn't as neat to look at.

}
};
let p1 = match self.page_table_walker.next_table(&p2[addr.p2_index()]) {
Ok(page_table) => page_table,
Err(PageTableWalkError::NotMapped) => return TranslateResult::PageNotMapped,
Err(PageTableWalkError::MappedToHugePage) => {
let frame = PhysFrame::containing_address(p2[addr.p2_index()].addr());
let flags = p2[addr.p2_index()].flags();
let offset = addr.as_u64() & 0o_777_7777;
return TranslateResult::Frame2MiB { frame, offset };
return TranslateResult::Frame2MiB {
frame,
offset,
flags,
};
}
};

Expand All @@ -402,7 +412,12 @@ impl<'a, P: PhysToVirt> MapperAllSizes for MappedPageTable<'a, P> {
Err(()) => return TranslateResult::InvalidFrameAddress(p1_entry.addr()),
};
let offset = u64::from(addr.page_offset());
TranslateResult::Frame4KiB { frame, offset }
let flags = p1_entry.flags();
TranslateResult::Frame4KiB {
frame,
offset,
flags,
}
}
}

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18 changes: 15 additions & 3 deletions src/structures/paging/mapper/mod.rs
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Expand Up @@ -36,9 +36,15 @@ pub trait MapperAllSizes: Mapper<Size4KiB> + Mapper<Size2MiB> + Mapper<Size1GiB>
fn translate_addr(&self, addr: VirtAddr) -> Option<PhysAddr> {
match self.translate(addr) {
TranslateResult::PageNotMapped | TranslateResult::InvalidFrameAddress(_) => None,
TranslateResult::Frame4KiB { frame, offset } => Some(frame.start_address() + offset),
TranslateResult::Frame2MiB { frame, offset } => Some(frame.start_address() + offset),
TranslateResult::Frame1GiB { frame, offset } => Some(frame.start_address() + offset),
TranslateResult::Frame4KiB { frame, offset, .. } => {
Some(frame.start_address() + offset)
}
TranslateResult::Frame2MiB { frame, offset, .. } => {
Some(frame.start_address() + offset)
}
TranslateResult::Frame1GiB { frame, offset, .. } => {
Some(frame.start_address() + offset)
}
}
}
}
Expand All @@ -53,20 +59,26 @@ pub enum TranslateResult {
Frame4KiB {
/// The mapped frame.
frame: PhysFrame<Size4KiB>,
/// Flags in the pagetable for this entry
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Above we use the order (frame, offset, flags), the declaration here should be consistent. Either we should always use (frame, offset, flags) or (frame, flags, offset).

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I've reordered the fields to adhere to (frame, offset, flags), which is think is the neater way to add this field.

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We should clarify here that these are only the flags of the last-level page table entry. (Flags of higher-level page table entries can affect the effective flags for an address too, for example when the WRITABLE flag is not set for a level 3 entry.)

flags: PageTableFlags,
/// The offset whithin the mapped frame.
offset: u64,
},
/// The page is mapped to a physical frame of size 2MiB.
Frame2MiB {
/// The mapped frame.
frame: PhysFrame<Size2MiB>,
/// Flags in the pagetable for this entry
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Same as above.

flags: PageTableFlags,
/// The offset whithin the mapped frame.
offset: u64,
},
/// The page is mapped to a physical frame of size 2MiB.
Frame1GiB {
/// The mapped frame.
frame: PhysFrame<Size1GiB>,
/// Flags in the pagetable for this entry
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Same as above.

flags: PageTableFlags,
/// The offset whithin the mapped frame.
offset: u64,
},
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21 changes: 18 additions & 3 deletions src/structures/paging/mapper/recursive_page_table.rs
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Expand Up @@ -562,8 +562,13 @@ impl<'a> MapperAllSizes for RecursivePageTable<'a> {
}
if p3_entry.flags().contains(PageTableFlags::HUGE_PAGE) {
let frame = PhysFrame::containing_address(p3[addr.p3_index()].addr());
let flags = p3[addr.p3_index()].flags();
let offset = addr.as_u64() & 0o_777_777_7777;
return TranslateResult::Frame1GiB { frame, offset };
return TranslateResult::Frame1GiB {
frame,
offset,
flags,
};
}

let p2 = unsafe { &*(p2_ptr(page, self.recursive_index)) };
Expand All @@ -573,8 +578,13 @@ impl<'a> MapperAllSizes for RecursivePageTable<'a> {
}
if p2_entry.flags().contains(PageTableFlags::HUGE_PAGE) {
let frame = PhysFrame::containing_address(p2[addr.p2_index()].addr());
let flags = p2[addr.p2_index()].flags();
let offset = addr.as_u64() & 0o_777_7777;
return TranslateResult::Frame2MiB { frame, offset };
return TranslateResult::Frame2MiB {
frame,
offset,
flags,
};
}

let p1 = unsafe { &*(p1_ptr(page, self.recursive_index)) };
Expand All @@ -591,7 +601,12 @@ impl<'a> MapperAllSizes for RecursivePageTable<'a> {
Err(()) => return TranslateResult::InvalidFrameAddress(p1_entry.addr()),
};
let offset = u64::from(addr.page_offset());
TranslateResult::Frame4KiB { frame, offset }
let flags = p1_entry.flags();
TranslateResult::Frame4KiB {
frame,
offset,
flags,
}
}
}

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