Function copy_pagetables

kernel/src/memory.rs:131–170

Copy a set of pagetables

(level_4_table: &PageTable)

/// Copy a set of pagetables
fn copy_pagetables(level_4_table: &PageTable) -> (*mut PageTable, u64) {
    // Create a new level 4 pagetable
    let (table_ptr, table_physaddr) = create_empty_pagetable();
    let table = unsafe {&mut *table_ptr};

    fn copy_pages_rec(physical_memory_offset: VirtAddr,
                      from_table: &PageTable, to_table: &mut PageTable,
                      level: u16) {
        for (i, entry) in from_table.iter().enumerate() {
            if !entry.is_unused() {
                if (level == 1) || entry.flags().contains(PageTableFlags::HUGE_PAGE) {
                    // Maps a frame, not a page table
                    to_table[i].set_addr(entry.addr(), entry.flags());
                } else {
                    // Create a new table at level - 1
                    let (new_table_ptr, new_table_physaddr) = create_empty_pagetable();
                    let to_table_m1 = unsafe {&mut *new_table_ptr};

                    // Point the entry to the new table
                    to_table[i].set_addr(PhysAddr::new(new_table_physaddr),
                                         entry.flags());

                    // Get reference to the input level-1 table
                    let from_table_m1 = {
                        let virt = physical_memory_offset + entry.addr().as_u64();
                        unsafe {& *virt.as_ptr()}
                    };

                    // Copy level-1 entries
                    copy_pages_rec(physical_memory_offset, from_table_m1, to_table_m1, level - 1);
                }
            }
        }
    }

    let memory_info = unsafe {MEMORY_INFO.as_mut().unwrap()};
    copy_pages_rec(memory_info.physical_memory_offset, level_4_table, table, 4);

    return (table_ptr, table_physaddr)
}

/// Creates a PageTable containing only kernel pages
///