Fix panic from extern type KTable introduced by rust-lang/rust#118534

Author: egkoppel

kernel_api/src/bridge.rs

@@ -29,13 +29,18 @@ pub mod hal {
 }
 
 pub mod paging {
+	use core::marker::PhantomData;
 	use core::ops::DerefMut;
 	use crate::memory::{Frame, Page, PhysicalAddress, VirtualAddress};
 	use crate::memory::allocator::{AllocError, BackingAllocator, GlobalAllocator};
 	use crate::sync::RwWriteGuard;
 
+	// FIXME: replace with extern type when alignment can be specified
+	#[repr(align(8))]
+	pub struct KTable((), PhantomData<KTableInner>);
+
 	extern "Rust" {
-		pub type KTable;
+		type KTableInner;
 
 		pub fn __popcorn_paging_ktable_translate_page(this: &KTable, page: Page) -> Option<Frame>;
 		pub fn __popcorn_paging_ktable_translate_address(this: &KTable, addr: VirtualAddress) -> Option<PhysicalAddress>;

kernel_hal/src/arch/amd64/paging2/mod.rs

@@ -34,6 +34,7 @@ pub(crate) unsafe fn construct_tables() -> (Amd64KTable, Amd64TTable) {
 #[derive(Debug)]
 struct KTablePtr(Frame); // points to a [Table<PDPT>; 256]
 
+#[repr(align(8))]
 pub struct Amd64KTable {
 	tables: KTablePtr, // points to a [Table<PDPT>; 256]
 	allocator: &'static dyn BackingAllocator,

kernel_hal/src/lib.rs

@@ -55,6 +55,8 @@ pub unsafe trait Hal {
 	unsafe extern "C" fn switch_thread(from: &mut ThreadControlBlock, to: &ThreadControlBlock);
 }
 
+const _: () = { if core::mem::align_of::<<HalTy as Hal>::KTableTy>() != 8 { panic!("for... reasons... KTables must be 8 byte aligned"); } };
+
 pub trait FormatWriter {
 	fn print(fmt: core::fmt::Arguments);
 }