[interrupt-handlers] added IDTR

- made Idtr structure (+ its static mut global var) to house the IDT, and
- made load_idt fxn that uses global_asm's lidt to load the IDT.

Signed-off-by: danbugs <[email protected]>

Author: danbugs

src/hyperlight_guest/src/idtr.rs

@@ -0,0 +1,29 @@
+use core::ptr::addr_of;
+use crate::idt::{IdtEntry, IDT};
+
+#[repr(C, packed)]
+pub struct Idtr {
+    pub limit: u16,
+    pub base: u64,
+}
+
+static mut IDTR: Idtr = Idtr { limit: 0, base: 0 };
+
+impl Idtr {
+    pub unsafe fn init(&mut self, base: u64, size: u16) {
+        self.limit = size - 1;
+        self.base = base;
+    }
+
+    pub unsafe fn load(&self) {
+        core::arch::asm!("lidt [{}]", in(reg) self, options(readonly, nostack, preserves_flags));
+    }
+}
+
+pub(crate) unsafe fn load_idt() {
+    let idt_size = 256 * size_of::<IdtEntry>();
+    let expected_base = addr_of!(IDT) as *const _ as u64;
+
+    IDTR.init(expected_base, idt_size as u16);
+    IDTR.load();
+}

src/hyperlight_guest/src/lib.rs

@@ -54,6 +54,7 @@ pub mod logging;
 pub mod interrupt_entry;
 pub mod interrupt_handlers;
 pub mod idt;
+pub mod idtr;
 
 // Unresolved symbols
 ///cbindgen:ignore