Function free_pages_rec

kernel/src/memory.rs:649–687

Recursively free all pages and page tables, including the page table at the given table_physaddr.

(physical_memory_offset: VirtAddr,
                  frame_allocator: &mut MultilevelBitmapFrameAllocator,
                  physaddr: PhysAddr,
                  level: u16)

/// Recursively free all pages and page tables, including the page
/// table at the given table_physaddr.
fn free_pages_rec(physical_memory_offset: VirtAddr,
                  frame_allocator: &mut MultilevelBitmapFrameAllocator,
                  physaddr: PhysAddr,
                  level: u16) {

    if level == 0 {
        // A frame, not a table
        frame_allocator.deallocate_frame(
            PhysFrame::containing_address(physaddr));
        return;
    }

    let table = unsafe{&mut *(physical_memory_offset
                              + physaddr.as_u64())
                       .as_mut_ptr() as &mut PageTable};
    for entry in table.iter() {
        if !entry.is_unused() {
            if level == 1 || entry.flags().contains(PageTableFlags::HUGE_PAGE) {
                // Maps a frame, not a page table
                if entry.flags().contains(PageTableFlags::PRESENT |
                                          PageTableFlags::WRITABLE |
                                          PageTableFlags::USER_ACCESSIBLE)  {
                    // A user frame => deallocate
                    frame_allocator.deallocate_frame(
                        entry.frame().unwrap());
                }
            } else {
                // A page table
                free_pages_rec(physical_memory_offset,
                               frame_allocator,
                               entry.addr(),
                               level - 1);
            }
        }
    }
    // Free page table
    frame_allocator.deallocate_frame(
        PhysFrame::from_start_address(physaddr).unwrap());
}

/// Free all user-accessible pages and the page table frames
///