// src/heap.rs
//! Provides the kernel heap.

use core::arch::asm;

use linked_list_allocator::LockedHeap;

use crate::println;

#[global_allocator]
static ALLOCATOR: LockedHeap = LockedHeap::empty();

/// Initialise the kernel heap.
/// # Safety
/// Must be called at most once.
pub unsafe fn init() {
    let heap_bottom;
    let heap_size;
    // UNSAFE: This is fine, just loading some constants.
    unsafe {
        // using inline assembly is easier to access linker constants
        asm!(
            "la {heap_bottom}, _kernel_heap_bottom",
            "la {heap_size}, _kernel_heap_size",
            heap_bottom = out(reg) heap_bottom,
            heap_size = out(reg) heap_size,
            options(nomem)
        )
    };
    println!(
        "Initialising kernel heap (bottom: {:#x}, size: {:#x})",
        heap_bottom as usize, heap_size
    );
    // UNSAFE: Fine to call at most once.
    unsafe { ALLOCATOR.lock().init(heap_bottom, heap_size) };
}