finished initial interrupts implementation

emulator/src/emulator/system/emulator.rs

@@ -212,8 +212,14 @@ pub fn run_emulator(
                 Ok(instruction) => instruction,
                 Err(why) => {
                     let pcx = processor.get(Register::Pcx);
-                    eprintln!("Could not decode instruction at {pcx:x}. Reason: {why}");
-                    continue;
+                    report_err(
+                        state_tx,
+                        &format!(
+                            "Could not decode instruction at {pcx:x}. Reason: {why}"
+                        ),
+                        &mut processor,
+                    );
+                    (pcx, Instruction::Nop)
                 }
             };
 
@@ -228,6 +234,8 @@ pub fn run_emulator(
 }
 
 fn report_err(state_tx: &Sender<StateUpdate>, why: &str, processor: &mut Processor) {
-    processor.begin_interrupt(Interrupt::HardFault);
+    processor
+        .begin_interrupt(Interrupt::HardFault)
+        .expect("What kind of goofy ahh shenanigans did you do with your fault handler? At this point, the emulator can just crash. this is on you.");
     let _ = state_tx.send(StateUpdate::Error(why.to_string()));
 }

emulator/src/emulator/system/processor/mod.rs

@@ -116,15 +116,42 @@ impl Processor {
         *self.reg(Register::Pcx) = self.get(reg) + u32::from(offset);
     }
 
-    pub fn begin_interrupt(&mut self, _int: Interrupt) {
-        // first we get the address of the interrupt descriptor table.
-        todo!();
+    pub fn begin_interrupt(
+        &mut self,
+        interrupt: Interrupt,
+    ) -> Result<(), ProcessorError> {
+        let idt = self.get(Register::Idr);
+
+        let addr = self
+            .memory
+            .read_word(idt + u32::from(interrupt.as_u8()) * 4)?;
+        println!("INFO: Interrupt {interrupt:?} addr: {addr}");
+
+        self.push(self.get(Register::Pcx))?;
+        *self.reg(Register::Pcx) = addr;
+        Ok(())
+    }
+
+    fn push(&mut self, val: u32) -> Result<(), ProcessorError> {
+        *self.reg(Register::Spr) -= 4;
+        let reg = *self.reg(Register::Spr);
+        self.memory.write_word(reg, val)
+    }
+
+    fn pop(&mut self) -> Result<u32, ProcessorError> {
+        let reg = *self.reg(Register::Spr);
+        let val = self.memory.read_word(reg)?;
+        *self.reg(Register::Spr) += 4;
+        Ok(val)
     }
 
     // TODO: remove this once implemented
     #[allow(clippy::needless_pass_by_ref_mut)]
-    fn end_interrupt(&mut self) {
-        todo!();
+    fn end_interrupt(&mut self) -> Result<(), ProcessorError> {
+        let ret = self.pop()?;
+        *self.reg(Register::Ret) = ret;
+        *self.reg(Register::Pcx) = ret;
+        Ok(())
     }
 
     pub fn get_stack(&mut self, n: u32) -> Result<Vec<u8>, ProcessorError> {
@@ -382,12 +409,12 @@ impl Executable for Instruction {
             //      - The return address is saved to the RET register.
             //      - The stack base ptr is set to the kernel stack.
             Self::Interrupt(interrupt_code) => {
-                cpu.begin_interrupt(interrupt_code);
+                cpu.begin_interrupt(interrupt_code)?;
             }
 
             // Returns from an interrupt,
             Self::IntReturn => {
-                cpu.end_interrupt();
+                cpu.end_interrupt()?;
             }
 
             // Halts the processor.