63 lines
1.6 KiB
Rust
63 lines
1.6 KiB
Rust
//! # Page table entry
|
|
//! Some code borrowed from [Phil Opp's Blog](http://os.phil-opp.com/modifying-page-tables.html)
|
|
|
|
use memory::Frame;
|
|
|
|
use super::PhysicalAddress;
|
|
|
|
/// A page table entry
|
|
pub struct Entry(u64);
|
|
|
|
bitflags! {
|
|
pub flags EntryFlags: u64 {
|
|
const PRESENT = 1 << 0,
|
|
const WRITABLE = 1 << 1,
|
|
const USER_ACCESSIBLE = 1 << 2,
|
|
const WRITE_THROUGH = 1 << 3,
|
|
const NO_CACHE = 1 << 4,
|
|
const ACCESSED = 1 << 5,
|
|
const DIRTY = 1 << 6,
|
|
const HUGE_PAGE = 1 << 7,
|
|
const GLOBAL = 1 << 8,
|
|
const NO_EXECUTE = 1 << 63,
|
|
}
|
|
}
|
|
|
|
pub const ADDRESS_MASK: usize = 0x000f_ffff_ffff_f000;
|
|
|
|
impl Entry {
|
|
/// Is the entry unused?
|
|
pub fn is_unused(&self) -> bool {
|
|
self.0 == 0
|
|
}
|
|
|
|
/// Make the entry unused
|
|
pub fn set_unused(&mut self) {
|
|
self.0 = 0;
|
|
}
|
|
|
|
/// Get the address this page references
|
|
pub fn address(&self) -> PhysicalAddress {
|
|
PhysicalAddress::new(self.0 as usize & ADDRESS_MASK)
|
|
}
|
|
|
|
/// Get the current entry flags
|
|
pub fn flags(&self) -> EntryFlags {
|
|
EntryFlags::from_bits_truncate(self.0)
|
|
}
|
|
|
|
/// Get the associated frame, if available
|
|
pub fn pointed_frame(&self) -> Option<Frame> {
|
|
if self.flags().contains(PRESENT) {
|
|
Some(Frame::containing_address(self.address()))
|
|
} else {
|
|
None
|
|
}
|
|
}
|
|
|
|
pub fn set(&mut self, frame: Frame, flags: EntryFlags) {
|
|
debug_assert!(frame.start_address().get() & !ADDRESS_MASK == 0);
|
|
self.0 = (frame.start_address().get() as u64) | flags.bits();
|
|
}
|
|
}
|