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//! Global structures for the allocators.
use crate::arch::{
paging::{PageTable, PageTableEntry, ASID, PAGE_TABLE_BITS, PAGE_TABLE_LEVELS},
MAX_PAGE_SIZE_BITS, PAGE_SIZE, PAGE_SIZE_BITS,
};
use contracts::requires;
use core::ptr::NonNull;
use spin::mutex::FairMutex;
use vernos_alloc_buddy::BuddyAllocator;
use vernos_utils::BelieveMeSend;
/// The global instance of the physical page allocator.
static BUDDY_ALLOCATOR: FairMutex<
Option<BuddyAllocator<PAGE_SIZE, PAGE_SIZE_BITS, { 1 + MAX_PAGE_SIZE_BITS - PAGE_SIZE_BITS }>>,
> = FairMutex::new(None);
/// The global kernel page table.
static KERNEL_PAGE_TABLE: FairMutex<BelieveMeSend<Option<NonNull<PageTable>>>> =
FairMutex::new(BelieveMeSend(None));
/// Initializes the allocator and enables paging.
///
/// # Safety
///
/// - Paging must not have been enabled previously.
/// - The buddy allocator must be valid.
#[requires(BUDDY_ALLOCATOR.lock().is_none())]
#[ensures(BUDDY_ALLOCATOR.lock().is_some())]
#[requires(KERNEL_PAGE_TABLE.lock().is_none())]
#[ensures(KERNEL_PAGE_TABLE.lock().is_some())]
pub unsafe fn init(
mut buddy_allocator: BuddyAllocator<
'static,
PAGE_SIZE,
PAGE_SIZE_BITS,
{ 1 + MAX_PAGE_SIZE_BITS - PAGE_SIZE_BITS },
>,
) {
// Allocate a page to use (for now) as the global kernel page table. Later we'll actually
// replace it with the hart0 initial stack's page, since we'll never free the root page of the
// kernel page table, and we can't return that page to the buddy allocator anyway.
let mut page_table = buddy_allocator
.alloc_zeroed::<PageTable>()
.expect("failed to allocate the kernel page table");
// Create identity mappings for the lower half of memory.
for (i, entry) in page_table
.as_mut()
.iter_mut()
.enumerate()
.take(1 << (PAGE_TABLE_BITS - 1))
{
let addr = (i as u64) << ((PAGE_TABLE_LEVELS - 1) * PAGE_TABLE_BITS + PAGE_SIZE_BITS);
let mut pte = PageTableEntry::default();
pte.set_valid(true).set_rwx(true, true, true).set_addr(addr);
*entry = pte;
}
// Set the page table as the current page table.
page_table.as_mut().make_current(ASID::KERNEL);
// Save the buddy allocator and kernel page table.
*BUDDY_ALLOCATOR.lock() = Some(buddy_allocator);
KERNEL_PAGE_TABLE.lock().0 = Some(page_table);
// Print the page table after this.
vernos_utils::dbg!(page_table.as_mut());
}
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