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use crate::{alloc::Heap, arch};
use core::{cell::RefCell, marker::PhantomData, ops::DerefMut, ptr::addr_of_mut};
use static_assertions::{assert_eq_size, assert_not_impl_any};
/// The data that is stored in a per-CPU structure.
#[derive(Debug)]
pub struct CPULocals {
/// The index of this CPU.
pub cpu_number: usize,
/// The heap used by this CPU's allocator.
pub heap: RefCell<&'static mut Heap>,
/// A canary for the `CPULocals` being initialized.
canary: usize,
// This ensures that the type is not `Send`.
_phantom: PhantomData<*mut ()>,
}
impl CPULocals {
/// Creates a new instance of the `CPULocals`, using it to initialize this CPU's `CPULocals`.
///
/// # Safety
///
/// - The CPULocals must not have already been initialized.
pub unsafe fn init(cpu_number: usize, heap: &'static mut Heap) {
arch::get_cpu_locals().write(CPULocals {
cpu_number,
heap: RefCell::new(heap),
canary: CANARY,
_phantom: PhantomData,
});
}
/// Returns the instance of the `CPULocals` for this CPU.
pub fn get() -> &'static CPULocals {
let ptr = arch::get_cpu_locals();
// SAFETY: The entrypoint sets this up for hart0, and we allocate this for other harts.
unsafe {
let canary_ptr = addr_of_mut!((*ptr.as_ptr()).canary);
assert_eq!(
*canary_ptr, CANARY,
"CPULocals were not initialized (and we probably just did UB)"
);
ptr.as_ref()
}
}
/// Retrieves a reference to the heap.
///
/// # Panics
///
/// - Panics if the CPU-local heap was already borrowed.
/// - The returned guard will panic on deref if the heap was not initialized.
pub fn heap(&'static self) -> impl DerefMut<Target = &'static mut Heap> {
self.heap.borrow_mut()
}
}
assert_eq_size!(CPULocals, [usize; 4]);
assert_not_impl_any!(CPULocals: Send);
cfg_if::cfg_if! {
if #[cfg(target_pointer_width = "32")] {
const CANARY: usize = usize::from_le_bytes(*b"locl");
} else if #[cfg(target_pointer_width = "64")] {
const CANARY: usize = usize::from_le_bytes(*b"CPULocal");
} else {
compile_error!("unsupported platform");
}
}
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