ableos/kernel/src/arch/x86_64/memory.rs

use {
    crate::memory::{MemoryManager, MAX_ORDER},
    core::sync::atomic::AtomicU64,
    limine::{MemmapEntry, MemoryMapEntryType, NonNullPtr},
    spin::{Mutex, Once},
    x86_64::{structures::paging::OffsetPageTable, VirtAddr},
};

pub const PAGE_SIZE: usize = 4096;

pub static MEMORY_MANAGER: Once<Mutex<MemoryManager>> = Once::new();
pub static HHDM_OFFSET: AtomicU64 = AtomicU64::new(0);
static PAGE_TABLE: Once<Mutex<OffsetPageTable>> = Once::new();

/// Initialise page table
pub unsafe fn init_pt(phys_base: VirtAddr) {
    log::debug!("Retrieving page table");
    HHDM_OFFSET.store(phys_base.as_u64(), core::sync::atomic::Ordering::Relaxed);
    PAGE_TABLE.call_once(|| {
        Mutex::new(OffsetPageTable::new(
            &mut *((phys_base
                + x86_64::registers::control::Cr3::read()
                    .0
                    .start_address()
                    .as_u64())
            .as_mut_ptr()),
            phys_base,
        ))
    });
}

/// Initialise memory manager
pub fn initialize(mmap: &'static [NonNullPtr<MemmapEntry>]) {
    let mut memory_manager = MemoryManager::new();

    for entry in mmap {
        if entry.typ != MemoryMapEntryType::Usable {
            continue;
        }

        let alignment = PAGE_SIZE << MAX_ORDER;
        let start_addr_unaligned = entry.base as usize;
        let diff = alignment - start_addr_unaligned % alignment;
        if diff > entry.len as usize {
            continue;
        }
        let start_addr = start_addr_unaligned + diff;
        let page_count = (entry.len as usize - diff) / PAGE_SIZE;

        unsafe {
            memory_manager.add_range(start_addr.into(), page_count);
        }
    }

    MEMORY_MANAGER.call_once(|| Mutex::new(memory_manager));
}